LED TUBE DRIVER CIRCUITRY FOR BALLAST AND NON-BALLAST FLUORESCENT TUBE REPLACEMENT

Abstract

An LED lamp tube and driver circuit that is direct replacement for fluorescent tubes with or without ballasts, that works with standard AC high voltage current input, with high frequency pulse current input, or with lower voltage input. The tube is wired to receive the current that is input from any two electrode pins from among the pairs of pins at the ends of the tube, which house the driver circuitry. The input current is converted to DC through a rectifier circuit, is filtered of unwanted frequencies and voltage through a filter circuit, and is controlled with a step-down constant current circuit to drive an LED array within the tube. The circuits comprise current loops having at least one current transformer, at least one transistor, capacitors, inductors, and resistors and interacting with an integrated circuit.

Claims

1. An LED driver circuit for fluorescent tube replacement comprising: a) a tube for enclosing an LED light source, the tube having a first end cap and a second end cap, each of the first and second end caps having respectively a first pair of electrode pins and a second pair of electrode pins; b) a rectifier circuit comprising a first rectifier sub-circuit connected to the first pair of electrode pins and a second rectifier sub-circuit connected to the second pair of the electrode pins, each rectifier circuit having at least a first input diode and a second input diode, each of the input diodes having an input lead connected to one of the electrode pins, and the input diodes having output leads that are connected to provide DC output from the rectifier circuit; in which DC output from the rectifier circuit is conducted to a constant current circuit that converts the DC output from the rectifier circuit into constant DC output for driving the LED light source.

2. The LED driver circuit for fluorescent tube replacement of claim 1, in which the DC output from the rectifier circuit is conducted to the constant current circuit via a filter circuit that filters out surge voltage from the DC output from the rectifier circuit.

3. The LED driver circuit for fluorescent tube replacement of claim 1, in which each of the first and second rectifier sub-circuits has a pair of additional diodes, each pair of additional diodes being looped in parallel with a capacitor connected to the DC output from the rectifier circuit, to provide a stabilizing flyback loop from the DC output of the rectifier circuit back to the input leads of the input diodes.

4. The LED driver circuit for fluorescent tube replacement of claim 1, in which at least three of the input leads each have a fuse in series between the input lead and its respective input diode.

5. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output.

6. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises a temperature-sensitive relay switch that opens if the filter circuit exceeds a safe temperature range for the driver circuit.

7. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises a varistor that grounds excessive voltage spikes in the DC current from the rectifier circuit.

8. The LED driver circuit for fluorescent tube replacement of claim 5, in which the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with a capacitor in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output to ground.

9. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises at least one capacitor in series with DC output from the rectifier circuit to ground.

10. The LED driver circuit for fluorescent tube replacement of claim 1, in which the constant current circuit is a step-down constant current circuit that converts the DC output from the rectifier circuit to DC suitable for driving the LED light source.

11. The LED driver circuit for fluorescent tube replacement of claim 1, further comprising the LED light source, in which the LED light source is an array of LEDs mounted within the tube, the array receiving DC suitable for driving the LED light source from the constant current circuit.

12. The LED driver circuit for fluorescent tube replacement of claim 1, in which the rectifier circuit is on a first PCB located in the first end cap and the constant current circuit is on a second PCB located in the second end cap, with two conductor wires running the length of the tube to connect a first pair of electrode pins on the second end cap to their respective input diodes in the rectifier circuit and two short conductors connecting a second pair of electrode pins on the first end cap to their respective input diodes in the rectifier circuit.

13. The LED driver circuit for fluorescent tube replacement of claim 1, in which current output from the rectifier circuit via two rectifier output wires connected to a first 2-pin connector connected at a first end of an LED array board to two conductors to a second 2-pin connector at an opposite end of the LED array board, second 2-pin connector being connected to an input side of the constant current circuit, and an output side of the constant current circuit being connected by a third 2-pin connection to a positive terminal and a negative terminal for electrical supply to the LED array board.

14. The LED driver circuit for fluorescent tube replacement of claim 10, in which the step-down constant current circuit comprises a positive DC output lead to a positive DC output pin and branch circuits that adjust DC voltage and stabilize DC current for the LED light source across the DC output pin and a negative DC output pin.

15. The LED driver circuit for fluorescent tube replacement of claim 14, comprising an IC that drives the step-down constant current circuit, keeping it in constant on time operation to achieve low switching losses and a high power efficiency.

16. The LED driver circuit for fluorescent tube replacement of claim 15, further comprising a transistor and in which the step-down constant current circuit performs switching to turn output from the transistor on when its input voltage is low.

17. The LED driver circuit for fluorescent tube replacement of claim 15, in which the IC has a current sense pin, a ground pin, a loop compensation pin, an inductor current zero-crossing pin, a power supply pin, and a gate drive pin.

18. The LED driver circuit for fluorescent tube replacement of claim 17, in which a sense resistor is connected across the current sense pin to the ground pin, a resistor-capacitor network driven by the DC output from the rectifier circuit is connected across the loop compensation pin and the ground pin, the inductor current zero-crossing detection pin receives voltage from a resistor divider, the power supply pin receives power for the IC from resistors in series with the DC output from the rectifier circuit.

19. The LED driver circuit for fluorescent tube replacement of claim 18, in which the IC provides output over-voltage protection and line regulation in conjunction with a loop comprising a diode, a resistor, a Zener diode, and a B-side of a DC to DC transformer, on a loop that comprises a resistor to the inductor current zero-crossing detection pin.

20. The LED driver circuit for fluorescent tube replacement of claim 19, in which the gate drive pin is connected to a gate of the transistor via a transistor loop resistor, with feedback current drawn from the sense pin to a ground pin resistor loops also being fed to the transistor loop resistor.

21. The LED driver circuit for fluorescent tube replacement of claim 20, in which a transistor feedback diode receives feedback current from the transistor through a transistor feedback resistor connected by at least one ground resistor to ground in order to assist the transistor to receive a DC supply from the drive pin at consistent levels and to enable the transistor to turn off quickly upon the IC dropping the DC supply from the drive pin.

22. The LED driver circuit for fluorescent tube replacement of claim 19, in which the transistor feeds its current output via two flyback diodes in series, wired in parallel with a series of a flyback capacitor and a flyback resistor to join the positive DC output lead, and also feeds its current output to an A-side input of the DC to DC transformer having it's A-side output connected to a negative output lead for the LED light source.

23. The LED driver circuit for fluorescent tube replacement of claim 22, in which the A-side output of the DC to DC transformer is also connected to an output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor, each of the output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor being bridged in parallel to the positive output pin in order to stabilize output current for the LED light source at a voltage appropriate for the LED array.

24. An LED driver circuit for fluorescent tube replacement comprising: a) a tube for enclosing an LED light source, the tube having a first end cap and a second end cap, each of the first and second end caps having a pair of electrode pins; b) each of the pairs of electrode pins being wired to a respective first rectifier circuit and a second rectifier circuit; c) each of the first rectifier circuit and the second rectifier circuit having a pair of input diodes, each input diode having an input side that is wired to one of the electrode pins; d) a first input capacitor connecting a first electrode pin connected to a first input diode in the first rectifier circuit to a first electrode pin connected to a first input diode in the second rectifier circuit, and a second input capacitor connecting a second electrode pin connected to a second input diode in the first rectifier circuit to a second electrode pin connection to a second input diode in the second rectifier circuit; e) each input diode having an output lead, the output leads being connected to provide a combined DC output from the first rectifier circuit and the second rectifier circuit; in which DC output from the rectifier circuit is conducted to filter circuit that filters to ground unwanted frequencies of electrical current and filters to ground harmful surges in voltage and in which filter circuit output is conducted to a step-down constant current circuit that converts the DC output from the rectifier circuit into constant DC output for driving the LED light source.

25. The LED driver circuit for fluorescent tube replacement of claim 24, in which the step-down constant current circuit operates with ON time determined by an IC that increases with current to the rectifier circuit increasing to a minimum preselected level, up to a maximum preset ON time for output current when a full load for the LED light source is reached, at which time OFF time for the output current is dictated by the IC.

26. The LED driver circuit for fluorescent tube replacement of claim 2, in which: a) the rectifier circuit has two pairs of additional diodes, each pair of additional diodes being looped in parallel with a capacitor connected to the DC output from the rectifier circuit, to provide a stabilizing flyback loop from the DC output of the rectifier circuit back to the input leads of the input diodes; b) at least three of the input leads each have a fuse in series between the input lead and its respective input diode; c) the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output; d) the filter circuit comprises a temperature-sensitive relay switch that opens if the filter circuit exceeds a safe temperature range for the driver circuit; e) the filter circuit comprises a varistor that grounds excessive voltage spikes in the DC current from the rectifier circuit; f) the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with a capacitor in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output to ground; g) the filter circuit comprises at least one capacitor in series with DC output from the rectifier circuit to ground.

27. The LED driver circuit for fluorescent tube replacement of claim 2, in which: a) the constant current circuit is a step-down constant current circuit that converts the DC output from the rectifier circuit to DC suitable for driving the LED light source; b) an LED light source which is an array of LEDs mounted within the tube, the array receiving DC suitable for driving the LED light source from the constant current circuit; c) the step-down constant current circuit comprises a positive DC output lead to a positive DC output pin and branch circuits that adjust DC voltage and stabilize DC current for the LED light source across the DC output pin and a negative DC output pin; d) an IC drives the step-down constant current, keeping it in constant on-time operation to achieve low switching losses and a high power efficiency; e) a transistor, the step-down constant current circuit performing switching to turn on output from the transistor when its input voltage is low;

28. The LED driver circuit for fluorescent tube replacement of claim 27, in which: a) the IC has a current sense pin, a ground pin, a loop compensation pin, an inductor current zero-crossing pin, a power supply pin, and a gate drive pin; b) a sense resistor is connected across the current sense pin to the ground pin, a resistor-capacitor network driven by the DC output from the rectifier circuit is connected across the loop compensation pin and the ground pin, the inductor current zero-crossing detection pin receives voltage from a resistor divider, the power supply pin receives power for the IC from resistors in series with the DC output from the rectifier circuit; c) the IC provides output over-voltage protection and line regulation in conjunction with a loop comprising a diode, a resistor a Zener diode, and a B-side of a DC to DC transformer, on a loop that comprises a resistor to the inductor current zero-crossing detection pin; d) the gate drive pin is connected to a gate of the transistor via a transistor loop resistor, with feedback current drawn from the sense pin to a ground pin resistor loops also being fed to the transistor loop resistor; e) a transistor feedback diode receives feedback current from the transistor through a transistor feedback resistor connected by at least one ground resistor to ground in order to assist the transistor to receive a DC supply from the drive pin at consistent levels and to enable the transistor to turn off quickly upon the IC dropping the DC supply from the drive pin.

29. The LED driver circuit for fluorescent tube replacement of claim 28 in which: a) the transistor feeds its current output via two flyback diodes in series, wired in parallel with a series of a flyback capacitor and a flyback resistor to join the positive DC output lead, and also feeds its current output to an A-side input of the DC to DC transformer having it's a-side output connected to a negative output lead for the LED light source; b) the A-side output of the DC to DC transformer is also connected to an output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor, each of the output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor being bridged in parallel to the positive output pin in order to stabilize output current for the LED light source at a voltage appropriate for the LED array.

30. The LED driver circuit for fluorescent tube replacement of claim 25, in which: a) the rectifier circuit is on a first PCB located in the first end cap and the constant current circuit is on a second PCB located in the second end cap, with two conductor wires running the length of the tube to connect a first pair of electrode pins on the second end cap to their respective input diodes in the rectifier circuit and two short conductors connecting a second pair of electrode pins on the first end cap to their respective input diodes in the rectifier circuit; b) current output from the rectifier circuit via two rectifier output wires connected to a first 2-pin connector connected at a first end of an LED array board to two conductors to a second 2-pin connector at an opposite end of the LED array board, second 2-pin connector being connected to an input side of the constant current circuit, and an output side of the constant current circuit being connected by a third 2-pin connection to a positive terminal and a negative terminal for electrical supply to the LED array board.

31. The LED driver circuit for fluorescent tube replacement of claim 1, in which a sub-driver circuit comprising capacitors on input leads to the rectifier circuit passes current via a transformer to a transistor connected to a VCC lead of an IC and connected via a Zener diode to a DRV output lead of the IC.

32. The LED driver circuit for fluorescent tube replacement of claim 15, in which: a) the step-down constant current circuit performs switching to turn output from a first transistor on when the first transistor's input voltage is low; b) the IC provides output over-voltage protection and line regulation in conjunction with a loop comprising a diode, a resistor, and a B-side of a first DC to DC transformer; c) a sub-driver circuit comprising capacitors on input leads to the rectifier circuit's, in which output current from the capacitors is transformed through a second transformer to a second transistor connected to a VCC lead of an IC and connected via a Zener diode to a DRV output lead of the IC.

33. The LED driver circuit for fluorescent tube replacement of claim 32, in which the sub-drive circuit has at least one transistor feedback diode that receives feedback current from the second transistor through a transistor feedback resistor connected by at least one ground resistor to ground in order to assist the second transistor to receive input current at consistent levels and to enable the second transistor to turn off quickly.

34. The LED driver circuit for fluorescent tube replacement of claim 33, further comprising: a) a tube for enclosing an LED light source, the tube having a first end cap and a second end cap, each of the first and second end caps having a pair of electrode pins; b) each of the pairs of electrode pins being wired to a respective first rectifier circuit and a second rectifier circuit; c) each of the first rectifier circuit and the second rectifier circuit having a pair of input diodes, each input diode having an input side that is wired to one of the electrode pins; d) a first input capacitor connecting a first electrode pin connected to a first input diode in the first rectifier circuit to a first electrode pin connected to a first input diode in the second rectifier circuit, and a second input capacitor connecting a second electrode pin connected to a second input diode in the first rectifier circuit to a second electrode pin connection to a second input diode in the second rectifier circuit; e) each input diode having an output lead, the output leads being connected to provide a combined DC output from the first rectifier circuit and the second rectifier circuit; in which DC output from the rectifier circuit is conducted to filter circuit that filters to ground unwanted frequencies of electrical current and filters to ground harmful surges in voltage and in which filter circuit output is conducted to a step-down constant current circuit that converts the DC output from the rectifier circuit into constant DC output for driving the LED light source.

35. The LED driver circuit for fluorescent tube replacement of claim 34, in which the step-down constant current circuit operates with ON time determined by an IC that increases with current to the rectifier circuit increasing to a minimum preselected level, up to a maximum preset ON time for output current when a full load for the LED light source is reached, at which time OFF time for the output current is dictated by the IC.

36. The LED driver circuit for fluorescent tube replacement of claim 35, in which: a) the rectifier circuit has two pairs of additional diodes, each pair of additional diodes being looped in parallel with a capacitor connected to the DC output from the rectifier circuit, to provide a stabilizing flyback loop from the DC output of the rectifier circuit back to the input leads of the input diodes; b) at least three of the input leads each have a fuse in series between the input lead and its respective input diode; c) the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output; d) the filter circuit comprises a varistor that grounds excessive voltage spikes in the DC current from the rectifier circuit; e) the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with a capacitor in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output to ground; f) the filter circuit comprises at least one capacitor in series with DC output from the rectifier circuit to ground.

37. The LED driver circuit for fluorescent tube replacement of claim 36, in which: a) the constant current circuit is a step-down constant current circuit that converts the DC output from the rectifier circuit to DC suitable for driving the LED light source; b) an LED light source which is an array of LEDs mounted within the tube, the array receiving DC suitable for driving the LED light source from the constant current circuit; c) the step-down constant current circuit comprises a positive DC output lead to a positive DC output pin and branch circuits that adjust DC voltage and stabilize DC current for the LED light source across the DC output pin and a negative DC output pin; d) an IC drives the step-down constant current, keeping it in constant on-time operation to achieve low switching losses and a high power efficiency.

38. The LED driver circuit for fluorescent tube replacement of claim 37, in which: a) the IC has a current sense pin, a ground pin, a loop compensation pin, an inductor current zero-crossing pin, a power supply pin, and a gate drive pin; b) a sense resistor is connected across the current sense pin to the ground pin, a resistor-capacitor network driven by the DC output from the rectifier circuit is connected across the loop compensation pin and the ground pin, the inductor current zero-crossing detection pin receives voltage from a resistor divider, the power supply pin receives power for the IC from resistors in series with the DC output from the rectifier circuit; c) the gate drive pin is connected to a gate of the first transistor via a transistor loop resistor, with feedback current drawn from the sense pin to a ground pin resistor loops also being fed to the transistor loop resistor; d) a transistor feedback diode receives feedback current from the first transistor through a transistor feedback resistor connected by at least one ground resistor to ground in order to assist the first transistor to receive a DC supply from the drive pin at consistent levels and to enable the first transistor to turn off quickly upon the IC dropping the DC supply from the drive pin.

39. The LED driver circuit for fluorescent tube replacement of claim 38 in which: a) the first transistor feeds its current output via two flyback diodes in series, wired in parallel with a series of a flyback capacitor and a flyback resistor to join the positive DC output lead, and also feeds its current output to an A-side input of the first DC to DC transformer having it's a-side output connected to a negative output lead for the LED light source; b) the A-side output of the DC to DC transformer is also connected to an output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor, each of the output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor being bridged in parallel to the positive output pin in order to stabilize output current for the LED light source at a voltage appropriate for the LED array.

40. The LED driver circuit for fluorescent tube replacement of claim 39, in which: a) the rectifier circuit is on a first PCB located in the first end cap and the constant current circuit is on a second PCB located in the second end cap, with two conductor wires running the length of the tube to connect a first pair of electrode pins on the second end cap to their respective input diodes in the rectifier circuit and two short conductors connecting a second pair of electrode pins on the first end cap to their respective input diodes in the rectifier circuit; b) current output from the rectifier circuit via two rectifier output wires connected to a first 2-pin connector connected at a first end of an LED array board to two conductors to a second 2-pin connector at an opposite end of the LED array board, second 2-pin connector being connected to an input side of the constant current circuit, and an output side of the constant current circuit being connected by a third 2-pin connection to a positive terminal and a negative terminal for electrical supply to the LED array board.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows an external perspective view of an LED driver circuit for fluorescent tube replacement, with its driver circuitry split onto two PCBs, with wiring for connecting the lamp's electrode pins to the driver circuitry PCB, and with an LED array.

[0025] FIG. 2 shows an electronic schematic of the power management circuitry of the LED driver circuit for fluorescent tube replacement.

[0026] FIG. 3 shows an exploded isometric view of external and internal elements of the LED driver circuit for fluorescent tube replacement together with a tube to hold its LED array.

[0027] FIG. 4 shows a side view of a fluorescent compatible LED tube lamp assembled with the LED driver circuit and a transparent tube to hold its LED array.

DETAILED DESCRIPTION

[0028] Referring to FIG. 1, the main sections of the driver circuitry are arranged on two separate PCBs. A rectifier circuit and a filter circuit are on a rectifier and filter circuit PCB 18 shown on the left, and a step-down constant current circuit is on PCB 19 shown on the right. To the rectifier and filter circuit PCB 18 are mounted various diodes, a varistor, capacitors, and conductors, all of which that are identified on the schematic of FIG. 2 described below. Again referring to FIG. 1, on the PCB 19 is mounted an integrated circuit (IC), a transistor, a DC to DC converter (transformer), flyback diodes, a electrolytic polarized capacitor, and conductors, all of which are also identified on schematic of FIG. 2 described below. Again referring to FIG. 1, long insulated wires 81 and 82 between the remote (lower right) pair of end cap electrode pins 30 and 32 and the rectifier and filter circuit PCB 18 will conduct, directly to the rectifier circuit, electrical current supply (if any) that may be input from either or both of the electrode pins 30 and 32 located adjacent to PCB 19. The other (upper right) end cap electrode pins34 and 36 on PCB 18 are also wired directly to the (their adjacent) rectifier circuit (as also shown in FIG. 2 described below) and will conduct, directly to the rectifier circuit, electrical current supply (if any) that may be input from either or both of the electrode pins 34 and 36. The (possibly AC) power supply from any combination of (typically from only two of the pins simultaneously of) the four electrode pins 30, 32, 34, 36 is thus connected for processing through the rectifier circuit and the filter circuit mounted on PCB 18 into filtered DC before being passed to the step-down constant current circuit on PCB 19. The filtered DC output from PCB 18 is conducted via wires 83 and 84 through their 2-pin connector 85 on the LED array PCB on long conductors (not shown) layered within that PCB that terminate at two of the four pins at 4-pin connector 88. Wires 89 and 90 then conduct the PCB 18 output to the input side of the step-down constant current circuit on PCB 19. After the step-down constant current circuit processes the DC current as described below regarding FIG. 2, the processed DC current is output from the step-down constant current circuit to the LED array PCB on the other two wires 91 and 92 of the 4-pin connector 88.

[0029] FIG. 2 is an electronic schematic of the power management circuitry of the Fluorescent Compatible LED Tube Lamp 10 of FIGS. 1 and 2, showing how power can be supplied through either or both pairs of electrode pins, 30-32, or 34-36. Incoming AC power is rectified by parallel DC converter 38a and 38b, which then filtered by a filter circuit 40, and finally managed by a step-down constant current control circuit 40. The resulting current, at a required, appropriate voltage for the LED array is then allowed to reach the LED array via output pins 23 and 25, supplying the LED array 20 with power for illumination.

Rectifier Circuits

[0030] Following the schematic of FIG. 2 from the left, power would be supplied from external fluorescent fixtures to the first pair of electrode pins 30 and 32, to the second pair of electrode pins 34 and 36, or to a combination of pins of both pairs. The power, whether arriving at the electrodes as AC or DC is passed through the respective first rectifier circuit 38a and/or second rectifier circuit 38b. The purpose of the rectifier circuits is to convert AC supply, which periodically reverses direction, to direct current (DC), which flows in only one direction. The driver circuitry is configured to handle AC which is present at the sockets of a fluorescent fixture into which the Fluorescent Compatible LED Tube Lamp 10 is plugged, and convert it into DC current in order to operate the rest of the driver circuitry, which in turn supplies the LED array of the Fluorescent Compatible LED Tube Lamp 10. The driver circuitry is also configured to handle DC current directly from the sockets in case the fixture, into which Fluorescent Compatible LED Tube Lamp 10 may is inserted, has been previously re-wired for LED tube conversion and supplies DC current from its sockets.

[0031] Each rectifier circuit is protected by fuses. Power arriving and leaving via any particular subset of the four electrodes is fed through one or two of fuses FU1, FU2, FU3. Having one of the leads (in the schematic, the lead from electrode pin 32) without a fuse suffices as there must be at least one other electrode pin involved as a positive or negative electrode to complete the circuit of electrical current. Each of the first and second rectifier circuits 38a and 38b has four diodes, which each pass electrical current in only one direction. The first and second rectifier circuits are connected in parallel as shown. Any AC current arriving via electrode pins 30 and 32 is converted to DC by diodes D7 and D8 alternately. If AC current arrives via electrode pins 34 and 36 the current is converted to DC by diodes D13 and D14 alternately. Either way the converted DC current arrives at the input terminus of resistor R1 and inductor L1 of filter circuit 40. The electrode pins 34 and 30 are bridged with capacitor C30 and the electrode pins 32 and 36 are bridged with capacitor C31. The DC output (whether converted from AC or received as DC from any of the electrode pins 30, 32, 34, 36) of the first and second (paralleled) rectifier circuits is bridged with capacitor C0 to draw out high frequencies to the grounding branch of the filter circuit 40, with the positive side of the rectifier output being received at the positive input terminus of resistor R1 paralleled with inductor L1 of filter circuit 40, and the negative side of the DC output from the rectifier circuit being connected to the input terminus of resistor R2 paralleled with inductor L2 of filter circuit 40. The opposite terminus of R2 and L2 is grounded.

[0032] Either end of the Fluorescent Compatible LED Tube Lamp 10 can be plugged into either end of a fluorescent fixture having a tube to be replaced. The driver circuit is versatile in handling a variety of electrical current conditions present among various fluorescent lamp fixtures. It doesn't matter to the driver circuit shown in FIG. 2 whether the socket is shunted or Non-shunted. It also does not matter to the driver circuit shown in FIG. 2 whether any particular one of the various fluorescent lamp fixtures into which the Fluorescent Compatible LED Tube Lamp 10 might be plugged, has a ballast delivering modified AC current to the socket, whether there is bare line voltage (e.g. 110V AC) present at the socket, or whether there is an AC-DC transformer already wired into the fixture for a previous LED conversion. The arrangement of eight diodes D7 to D14 of the rectifier circuits 38a and 38b ensures that when power is input from any two of the electrode pins, four of the eight diodes will operate to pass DC current to the filter circuit 40, whether it is DC or AC power that is input from the electrode pins. The arrangement of eight diodes of the rectifier circuit, as shown in FIG. 2, allows that the electrode pins from which the input power is received can be any two of the tube's four electrode pins, that is, the input power can be from an electrode pin on one end of the tube in conjunction with another pin on the other end of the tube completing the input power circuit, or input power can be from an electrode pin on one end of the tube and with the other pin of the pair on the same end of the tube completing the input power circuit.

Filter Circuit

[0033] The driver circuit has a filter circuit 40 that protects against surge voltage. At the positive input side of filter circuit 40, the positive DC after being filtered through R1 and L2 in parallel is sent through a temperature-sensitive relay switch (RO) 46. If the circuitry including the temperature-sensitive relay switch 46 becomes too hot, it opens, the driver circuit is broken and the Fluorescent Compatible LED Tube Lamp 10 would turn off for safety reasons. When temperature-sensitive relay switch 46 is again in a safe temperature range, it closes, and the DC current proceeds to be filtered by the filter circuit 40. The filter circuit has a varistor RV that connects the output of the temperature-sensitive relay switch 46 to ground. Capacitor C1 is wired in parallel with varistor RV to ground. A varistor is an electronic component with diode-like but nonlinear current-voltage characteristics. At low voltage it has high resistance to current, and at high voltage it changes and becomes low resistance to current. The varistor is thus a voltage-dependent variable resistor. The varistor RV is used to protect the circuit against excessive transient voltages by inserting it as shown so that, when triggered, it will shunt to ground voltage and current levels that would otherwise be harmful to the sensitive components of the step-down constant current circuit 42 shown in FIG. 2 and described below.

Step-Down Constant Current Circuit

[0034] After the useful DC current makes its way through the filter circuit 40, it is directed to a step-down constant current circuit 42. The positive DC output lead 70 goes directly to the positive DC output pin 23. The other branches from the positive DC output lead 70 conduct current away from positive DC output lead 70 through a number of paths that together have the effect of adjusting the DC voltage and stabilizing the DC current drawn by the LED array across positive DC output pin 23 and negative DC output pin 25.

[0035] The IC 28 drives the step-down constant current circuit, keeping it in constant on time operation to achieve low switching losses and a high power efficiency. The step-down constant current circuit performs switching, that is, turn-on of the transistor Q1, when the voltage to it is at or near a minimum, that is, when a valley in the voltage value is detected. The valley turn-on of the transistor Q1 minimizes the hard switching effect that would occur at higher voltages and cause extra heat as well as electromagnetic interference. Valley switching is also known a quasi-resonant switching mode. The IC 28 works with, for example, a 0.3V current sense reference voltage which leads to a low sense resistance and a low conduction loss of energy from the current to heat ((which should be dissipated away from the LED array). Current as low as 15 μA can start the IC driver, which then operates with current sourcing in a useful range of 1A sourcing and 2A sinking. A 6-pin IC 28 suffices. As shown in the schematic of FIG. 2, a sense resistor R11 is connected across current sense (ISEN) pin 1 and the ground (GND) pin 2. A resistor-capacitor circuit (RC circuit or RC filter or RC network) of resistors and capacitors driven by the voltage or current source as shown is connected across loop compensation (COMP) pin 3 and (GND) pin 2 (via the two ground points for those respective pins). An inductor current zero-crossing detection pin 4 receives voltage from a resistor divider (R13 and R15) as shown and detects an inductor current zero cross point, providing both voltage protection and line regulation. If the voltage on the inductor current zero-crossing detection (ZCS) pin 4 rises above a programmed value, the IC 28 enters a voltage protection mode. Line regulation can be adjusted by changing the upper resistor R13 of the resistor divider. Power supply (VIN) pin 5 receives power to the IC 28 via resistors R5 and R8 and also provides output over-voltage protection in conjunction with the loop comprising diode D5, resistor R9, Zener diode Z1, and the B side of transformer T1, on the loop also comprising resistor R13 to the inductor current zero-crossing detection pin 4. The Zener diode allows current to flow in the forward direction in the same manner as a simple diode, but also permits it to flow in the reverse direction when the voltage is above a certain value (known as the breakdown voltage). The transformer T1 operates as a DC to DC converter that can produce different output voltages depending on input voltages. The step-down constant current converter generally reduces (steps down) the input DC voltage to an output DC voltage selected for the desired current flow to the LEDs, but with appropriate values of for components is capable of a range from an output voltage much larger than the input voltage, down to an output voltage of almost zero. See the value table farther below for an example of component selection.

[0036] The gate drive (DRV) pin 6 is connected to the gate of the transistor Q1 via resistor R7, with feedback current drawn from the sense pin 1 to ground pin 2 R10/R11 loops also being fed to R7. The transistor Q1 is preferably a metal-oxide-semiconductor field-effect transistor (MOSFET), a four-terminal device that has source (S), gate (G), drain (D), and body (B) terminals available, but with the S and B terminals short-circuited internally, making it a three-terminal device as shown in the schematic like other field-effect transistors. The current output from Q1 drives the remaining components of step-down constant current circuit 42. The diode D4 receiving feedback current through R12 and having R16 and R10 assists Q1 to receive its on or off DC supply signal at consistent levels from DRV pin 6 and makes transistor Q1 turn off very soon after DRV pin 6 drops its output to an “off” condition.

[0037] Valley turn-on of Q1, a MOSFET, known as quasi-resonant switching, is termed “valley” because it is done at a low point in drain voltage. Each switching cycle of control by the integrated circuit (IC) 28 consists of tracking a current rising, current falling, and a switching-on time. The start-up current of the IC 28 is very low, and standby power loss is kept correspondingly low. The switching frequency of the step-down constant current circuit can be limited to, for example, 200 kHz by programming the IC, which limits switching losses and improves EMI performance during light load conditions for this sub-circuit. The IC also monitors for short circuit conditions in the output to the LED array and protects the device by shutting down current supply via Q1 accordingly.

[0038] Q1 feeds its current output via the two diodes D6 in parallel with the series of capacitor C12 and resistor R20 to join the positive DC output lead 70 from the filter circuit 40. On the other hand the positive current output from Q1 provides the required output for the LED array via the A-side of DC to DC transformer T1 to the negative DC lead 71. An electrolytic capacitor will achieve a larger capacitance per unit volume than other types of capacitors. The polarized aspect of capacitor E3 requires its marked positive side must be joined to the positive DC output lead (if it were wired the opposite way, its electro-chemical reaction would work in reverse, eating away at the thin insulating layer inside the capacitor and leading to a short between the two pins). A final current stabilizing component for the step-down constant current circuit 42 is R21 which bridges the positive DC output lead 70 to the negative DC output lead 71. R21 has high resistance but allows some low current flow from the positive DC output lead 70 to the negative DC output lead 71. The potential drop in voltage in absolute magnitude between that at positive output pin 23 and that at negative output pin 25 provides the voltage required by the LED array to draw the appropriate flow of electrical current for its rating and the resulting level of illumination. The two diodes D6 in series, wired in parallel with the series C12, R20 are free-wheeling (or flyback) diodes, and work in combination with the inductance of the rest of the final output circuitry T1 A, C9, E3 and R21. The transistor Q1 feeds its current output via the two flyback diodes D6 in series, wired in parallel with a series of a flyback capacitor C9 and a flyback resistor R21 to join the positive DC output lead, and also feeds its current output to an A-side input of the DC to DC transformer having its A-side output connected to a negative output lead for the LED light source. The A-side output of the DC to DC transformer is also connected to the output pin capacitor C9, the polarized electrolytic capacitor E3, and an LED output bridging resistor R21. Each of the output pin capacitor C9, the polarized electrolytic capacitor E3, and the LED output bridging resistor R21 are bridged in parallel across the negative lead 71 and its negative output pin 25 to the positive output pin 23 in order to stabilize output current for the LED light source at a voltage appropriate for the LED array, to provide a smooth current for the load of the LED array 20 to which output leads 23 and 25 are connected.

[0039] To summarize, when the electrode pins 30, 32, 34, and/or 36 are fed either AC supply or DC supply, either or both of the first rectifier circuit 38a and the second rectifier circuit 38b convert the AC or DC supply to DC. The DC current is then filtered of unwanted high voltage in filter circuit 40. The power from AC input to DC (or from direct input DC from the electrode pins) as filtered by the filter circuit is then converted by the step-down constant current ciruit 42 into output current at a desired level for the selected LED array.

[0040] When the lighting fixture for the replacement tube is switched off with a remote pre-existing switch (typically a hand-operated wall-mounted switch), the voltage arriving at the IC 28 will drop to a level at which the IC will shut off. Capacitors (C0 to C31) are used throughout the drive circuit to store electricity and provide a smooth shutdown of the system as they discharge upon electrical supply to the driver being shut off. A like shutdown will occur if the output voltage spikes to a large transient value that exceeds a programmed maximum, whether due to a null load or otherwise, as the IC 28 will be triggered into over-voltage protection and will discharge the output voltage to ground. To protect against an exceedingly large spike, a varistor RV is used in the filter circuit 40. If a short-circuit is detected by the IC 28, it drops the output voltage of the step-down constant current circuit to 0. The IC's own power can be made to concomitantly shut off by having the voltage powering the IC proportional to its output via auxiliary winding. If the cause of the over-voltage or short-circuit is removed, the system will self-start again automatically with the valley turn-on from within-range AC or DC input to the rectifier circuits 38a and 38b.

[0041] Once started via valley-turn of the MOSFET Q1 by the IC 28, the step-down constant current circuit 42 operates in a constant ON time mode, that is, the ON time determined by the IC increases with the input AC (or DC) to the rectifiers increasing to a minimum preselected level, up to a maximum preset ON time for output current when a full load for device is reached. However, when the input voltage for the step-down constant current circuit 42 reaches a preselected maximum, OFF time for the output current is dictated by the IC. The ON and OFF determinations are made to reduce switching frequency, with benefits of less heat to be dissipated, less EMI, and less strain on the electronic components. However, the electronic components are preferably solid state and would last a very long time in any event in most typical ambient conditions.

Layout

[0042] To reduce heat buildup that could be to the detriment of components, and concomitantly to reduce consumption of energy that is not transformed into light energy by the LEDs, and finally to avoid or minimize unwanted resistance effects from conductors themselves, the length of the conducting loops of the driver should be minimized. It is particularly effective in this regard to keep the conductor loop from the source pin to the current sample resistor to the GND pin 2 as short as is feasible. Likewise the resistor divider network connected to the inductor current zero-crossing detection pin 4 should be looped adjacent to the IC 28.

[0043] In contrast and in keeping with general electronic principles to avoid interference effects, it is best to insulate or keep separate the control circuit from the power circuit loop—this too can be done within the spatial constraints of the overall device. In a preferred embodiment, the first rectifier block and the second rectifier block 38b are physically located in one end cap, adjacent the power supply input electrode pins for one rectifier circuit, with tube-length wires connecting the other rectifier circuit to its (remote) input pins mounted on the opposite end cap. The filter circuit 40 can likewise be mounted with the rectifier circuits in their end cap. Wires running the length of the tube then connect these circuits in one end cap to the rest of the driver circuit, including the step-down constant current circuit 42 which contains low-voltage, sensitive electronic components such as the IC 28, is physically located in the opposite end cap away from the rectifier circuitry.

[0044] The driver circuit as presented in the schematic and with sample values for the components such as given below, results in circuitry that can be fitted into the end caps for the tube, the end caps being no larger than will fit into standard fluorescent fixtures with sockets to receive the electrode pins. The driver circuitry need not extend into the translucent tube into which the LED array is mounted, except for connecting wires to connect sections of the driver circuitry mounted in opposite end caps of the tube to each other.

EXAMPLES

[0045] A preferred implementation of the Fluorescent Compatible LED Tube Lamp will now be described in detail—an T8 fluorescent tube replacement with an 18 Watt LED array, putting out 140 lumens per watt (which is more power efficient than the T8 fluorescent tube being replaced) in which an array of 120 LEDs (HL-A-2835H431 W-S1-08-HR3_3000k_R80_0.2 W_3.3V_RO) would be driven with the following component Ids/sources/values for the electronic parts of the driver circuit disclosed on FIG. 2:

TABLE-US-00001 FU1-FU3 2 A_350 V_3.6*10 mm_RO RV 10D561_10_7.5 mmRO C0 CL21_630 V_100 nF_10%_10 mm_RO C1 CL21_630 V_100 nF_10%_10 mm_RO (C2 omitted for 18 Watt version) L1 2.0 mH_Φ0.15_Φ6*8_RO L2 2.0 mH_Φ0.15_Φ6*8_RO E3 80 V_82 UF_105° C._20%_10*16 mm_10000 h_RO R0 80_5% _15*7.3*3.9 mm_RO Q1 COOL MOS_5N70_T0-251_700 V_5 A_0.9Ω_150°_RO T1 Ferrite core, magnet wire 2 UEW 0.2, dual inductor coils with 2 Ts mylar layer tape CT-280 ( L-16HD-T08A1-V1.0-EFD15_RO from Jinhu Electronics Co., Ltd Jimei, Xiamen, China) IC IC_SO-6_SY5824A_150°_RO (Silergy Corp., A1501, Technology Mansion, Eastern Software Park, No. 90 Wensan Road, Hangzhou, Zhejiang, China) R1 0805_1KΩ_5%_RO R2 0805_1KΩ_5%_RO R5 1206_330KΩ_5%_RO R7 0805_100Ω_5%_RO R8 1206_330KΩ_5%_RO R9 0805_100Ω_5%_RO R10 1206_0.75Ω_1%_RO R11 1206_6.8Ω1%_RO R12 0805_10Ω_5%_RO R13 0805_120KΩ_5%_RO R14 0805_1KΩ_5%_RO R15 0805_10KΩ_5%_RO R16 0805_10KΩ_5%_RO R17 0805_7.5KΩ_5%_RO R18 1206_220KΩ_5%_RO R19 1206_220KΩ_5%_RO R20 0805_68Ω_5%_RO R21 1206_100KΩ_5%_RO C6 1206_25 V_10 uF_10%_X7R_RO C8 0805_25 V_1 uF_10%_X7R_RO C9 1206_100 V_10 nF_10%_X7R_RO C10 0805_25 V_1 uF_10%_X7R_RO C12 1206_1000 V_68 pF_5%_NPO_RO C30 1206_1000 V_470 pF_5%_NPO_RO C31 1206_1000 V_470 pF_5%_NPO_RO Z1 SOD-123_16 V_0.5 W_150°_RO D4 1N4148W_SOD-123_75 V_150 mA_150°_RO D5 E1D_SOD-123FL_200 V_1 A_35 nS_150°_RO D6 ES2J_SMB_600 V_2 A_35 nS_150°_RO D7-D14 US1M_SMA_1000 V_1 A_75 nS_150°_RO.

[0046] Another preferred implementation is a T8 fluorescent tube replacement with a 10 Watt LED array, putting out 140 lumens per watt (which is more power efficient than a T8 fluorescent tube) having an array of 60 LEDs (HL-A-2835H431 W-S1-08-HR3_3000 k_R80_0.2 W_3.3V_RO—the only change in the LEDs used being the “color” or hot/cool range value of 3000K rather than 4000K example given above for the 18Watt version—the particular range selected for the LEDs does not affect the values appropriate for the driver circuit), in which the LED array would be driven with the above component values for the electronic parts of the circuit disclosed on FIG. 2, except for the following changes: [0047] C1 would be paralleled with a C2 CL21_630V_150 nF_10%_10 mm_8.1 mmRO [0048] E3 (the polarized electrolytic capacitor) would be changed to [0049] 80V_56UF_105° C._20%_10*16 mm_10000 h_RO. [0050] There is no R10 (1206_0.75Ω_1%_RO in the 18 W example) [0051] but R11 would be changed to 1206_1.08Ω_1%_RO
to accommodate the lower wattage rating of the LEDs. Other wattage examples would have corresponding changes to the above-noted components to a like fit and working effect.

[0052] FIG. 3 shows an exploded isometric view of external and internal elements of the invention including a fluorescent compatible LED tube lamp 10. In addition to elements listed previously, housing bolts 24 are shown which are inserted into holes 26 and 27 to secure the PCB housings (14 & 16) to threaded holes in each end of the LED holder 22. The rectifier and filter printed circuit board (PCB) 18 and the step-down constant current PCB 19 are each to be enclosed by a PCB Housing (14 or 16). The rectifier portion of the driver circuit is on PCB 18 and would receives power from any two (or more) individual electrode pins from among the first pair of electrode pins 30 and 32 at one end of the fluorescent compatible led tube lamp 10 and the second pair of electrode pins 34 and 36 at the other end of the fluorescent compatible LED tube lamp 10 (via the wiring shown in FIG. 1). One pair of the electrode pins is connected (through a fuse or fuses as indicated in FIG. 2) directly to the rectifier circuit. The other two electrode pins located at the other end of the tube 10 are also connected to the rectifier but with wires (81 and 82 in FIG. 1) that would run the length of the inside of the tube 10, behind the LED array (so as not to obscure the light emitted). The rectifier passes DC if it is input from the pins, and converts AC to DC when AC is input from any of the electrode pins. In a preferred embodiment, the filter circuit of the driver circuitry is mounted adjacent to the rectifier circuit on PCB 18. The DC output of the rectifier circuit may thus be passed to the filter circuit by conductors PCB 18. Referring back to FIG. 1 again, the output of the filter circuit is however to be passed from PCB 18 by a pair of wires that fit into a 2-pin wire connector and thereby make contact with a pair of conductors on the LED array PCB that run its length to 2 terminals of a 4-pin connector at the other end of the LED array PCB. The filter circuit's DC power output is thereby passed to the step-down constant current circuit of the driver circuitry by 2 of the 4 wires that connect of the step-down constant current circuit to the 4-pin connector of the LED array PCB. The filtered DC power is modified by the step-down constant current circuit of the driver circuitry to supply DC power at a voltage and current level that will drive the LED array 20 to illuminate in accordance with its capabilities. The other two of the 4 wires that connect of the step-down constant current circuit to the 4-pin connector of the LED array PCB are output wires for the constant DC thereby created to arrive at the LED array. Referring again to FIG. 3, the LED array 20 is supported inside the tube 12 by means of the LED holder 22 with ridges 44 for longitudinal strength. The LED holder can be made of plastic or alternatively of metal in which case the ridges 44 function as cooling fins to help dissipate heat away from individual LED's in the LED array 20. The channels 45 inside tube end 16 (and like channels in the other tube end) receive and hold flanged LED array holder 22 with its ridges 44.

[0053] FIG. 4 shows a side view of an assembled fluorescent compatible LED tube lamp 10 (containing an LED array and the LED driver circuitry of the present invention) comprising of a cylindrical translucent or transparent tube 12, enclosed at the left end by a left PCB housing 14 with a first pair of electrode pin 30 and 32 and on the right end by a right PCB housing 16 with a second pair of electrode pins 34 and 36. The PCB housings function as end caps for the tube 12. Each pair of electrode pins is sized to seat into existing fluorescent tube fixture sockets.

[0054] As can be seen from the Figures and the foregoing description, the LED driver circuit for fluorescent tube replacement of the present invention can be summarized as:

a) a tube for enclosing an LED light source, the tube having a first end cap and a second end cap, each of the first and second end caps having a pair of electrode pins;
b) each of the pairs of electrode pins being wired to a respective first rectifier circuit and a second rectifier circuit;
c) each of the first rectifier circuit and the second rectifier circuit having a pair of input diodes, each input diode having an input side that is wired to one of the electrode pins;
d) a first input capacitor connecting a first electrode pin connected to a first input diode in the first rectifier circuit to a first electrode pin connected to a first input diode in the second rectifier circuit, and a second input capacitor connecting a second electrode pin connected to a second input diode in the first rectifier circuit to a second electrode pin connection to a second input diode in the second rectifier circuit;
e) each input diode having an output lead, the output leads being connected to provide a combined DC output from the first rectifier circuit and the second rectifier circuit.
in which DC output from the rectifier circuit is conducted to filter circuit that filters to ground unwanted frequencies of electrical current and filters to ground harmful surges in voltage and in which filter circuit output is conducted to a step-down constant current circuit that converts the DC output from the rectifier circuit into constant DC output for driving the LED light source.

[0055] The LED lamp tube and driver circuit with the electronic parts values specified in the examples above would be a direct replacement for T8 fluorescent tubes in lamp systems with or without ballasts. With a different diameter and electrode pin gap the LED lamp tube would also fit in sockets designed for other kinds of fluorescent tubes, and with different values for the parts in the driver circuit to handle different electrical supply values, the LED lamp tube and driver circuit would be a direct replacement for other fluorescent tubes in other lamp systems, regardless of whether those systems had ballasts present or previously removed.

[0056] The LED Tube Driver Circuitry for Ballast and Non-ballast Fluorescent Tube Replacement allows direct replacement of fluorescent tubes while using available power from ballasted or non-ballasted fixtures, as well as shunted or non-shunted sockets. The invention is a self-ballasted LED array replacement device for previously installed, formerly fluorescent tube fixtures.

[0057] The foregoing was disclosed in the Canadian patent application 2,861,789 filed Aug. 28, 2014 and claimed for priority in the present application.

Supplementary Disclosure/Continuation

[0058] The following shows another example of the driver circuitry for use with the present invention.

Summary of the Supplementary Disclosure/Continuation

[0059] A sub-driver circuit comprising capacitors on the rectifier circuit′ input leads that feed current via a second transformer to a second transistor connected to the VCC lead of the IC of the step-down circuit and connected via the Zener diode to the DRV output of the IC, provides enhanced stability of both electrical output and operational temperatures of the driver circuitry, obviating the need for a temperature-sensitive relay such as was included in the driver example of FIG. 2.

BRIEF DESCRIPTION OF THE SUPPLEMENTARY DRAWING

[0060] FIG. 5 shows an alternate electronic schematic of the power management circuitry of the LED driver circuit for fluorescent tube replacement.

DETAILED SUPPLEMENTARY DESCRIPTION

[0061] Referring to FIG. 5, when AC current flows through any combination of (typically from only two of the pins simultaneously of) the four electrode pins 30, 32, 34, 36 through the respective fuse(s)—for example FU3—the current is purified by rectifier D7-D10, filtered by capacitors C0, C2, C1 and inductor L1, L2 and ends up as a stable DC current. At this point, DC input will charge the capacitor C6 through resistors R5 R8. When the voltage of C6 reaches the rated voltage of the IC 28, it starts functioning. A voltage with square shape sine wave will come out from the IC 28's DRV pin 6, and control the opening and closing of Q1 through R7. When Q1 is open, the DC current goes through the LEDs and also charges the electrolytic capacitor E3, passing the first transformer T1's T1A side, Q1, R11, R10 to the ground. When Q1 is closed, T1A reserves energy and charges E3 through D6 and supplies power to the LED at the same time. Meanwhile, T1B will copy the voltage from T1A and charge C6 through D5 and R9 which limits the current.

[0062] Since the frequency of AC city power is low, typically only 50-60 Hz, the resistance of C11, C12, C13, C14 is huge and cuts the current to the second transformer T2's T2A. Because the B-side (T2B) of transformer T2 in sub-driver circuit 80 is copying the voltage from T2A, there is no current going through T2B, the second transistor Q2 does not work, and D16 is not connected. This occurs whether the driver circuitry is connected to AC city power via adjacent electrode pins (e.g. 30 and 32) on one side of the LED tube or from opposite sides of the tube (e.g. 30 and 34) as the driver is designed to work with any combination of two of the four electrode pins 30, 32, 34, 36.

[0063] When the present device is connected to an electronic ballast in a formerly fluorescent fixture, since the output voltage is high frequency high voltage (usually frequency is over 20 KHz), the resistance of C11 C12 C13 C14 will become very small. The high frequency current will go through T2A. T2B will copy the current and charge E4 when the current passes diode D15. When the voltage of E4 reaches a certain level, the voltage will be divided by resistor R26 R27 and supply the power to the second transistor Q2. When Q2 is functioning, the voltage of VCC will be limited to 0.7V according to Q2's specifications. Thus, the voltage of C6 will never reach the start-up voltage of 17.6V required by the IC 28, so it will not operate under that condition. Since the voltage of T2B remains at 9.5V, diode D16 will be operating. The current will be limited by R28 and Q1 will remain working at all times under this condition. So, the current will be purified by D7-D14, and filtered by capacitor C0 C2 C1 and inductor L1 L2 to LED chip, and go through T1A Q1 R11 R10 to the ground. The sub-drive circuit thus has its own feedback loop that assists its transistor to receive input at consistent levels and enables it to turn off quickly.

[0064] Thus in case of either city power AC or ballast DC being supplied to the driver circuitry of FIG. 5, current at a required, appropriate voltage for the LED array 20 is then allowed to reach the LED array via output pins 23 and 25, supplying the LED array 20 with power for illumination.

[0065] When compared to FIG. 2, it can be seen that the driver example of FIG. 5 has moved Z1 of the step-down constant current circuit 42 of FIG. 2 into the sub-driver circuit 80 of FIG. 5 to operate with the second transistor Q2 in a bridge from the inputs to rectifier sub-circuits 38A and 39B via capacitors C11, C12, C13 and C14 through the sides T2A and T2B of the second transformer T2 to the step-down constant current circuit 42 via the VCC and the DRV connections shown in both the sub-driver circuit 80 and in the step-down constant current circuit 42.

[0066] The use of R18, R19, R17 and C10 in the driver circuitry is to improve the power factor (PF), that is, the ratio of the real power used to do the work of illumination to the apparent power that is supplied to the driver circuit.

[0067] For an 18 Watt Fluorescent Compatible LED Tube Lamp (such as an HL-A-2835D46 W-S1-08-HR), appropriate component Ids/sources/values for the electronic parts of the driver circuit disclosed on FIG. 5 would be:

TABLE-US-00002 Fuses FU1-FU3 0.47Ω_1 WS_with heat shrink tube_350 V_RO VDR RV 10D561_¢0_7.5 mmRO Film capacitors C1 C0 C2 CL21_630 V_100 nF_10%_10 mm_RO Capacitors L1 L2 2.0 mH_Φ0.18_Φ8*10_RO Electrolytic Capacitor E2 35 V_47 UF_105° C._20%_5*11 mm_8000 h_RO Electrolytic Capacitors E3 E4 100 V_33 UF_105° C._20%_8*12 mm_8000 h_RO MOS Q1 4N65_TO-251_4 A_650 V_150°_RO T1 L-36HD-T08JR-V1.0-EE13 T2 L-38HD-T08JR-V1.0-EE8.3-6-6 PCB Board D-91HD-SY24-JRT8-B-V1.2_1.0 mm_CEM-1_CTI > 175_94 V-0_RO SMD Resistors R1 R2 1206_1.5KΩ_5%_RO SMD Resistors R5 R8 1206_330KΩ_5%_RO SMD Resistor R7 1206_100Ω_5%_RO SMD Resistor R9 0805_10Ω_5%_RO SMD Resistor R10 0805_2.0Ω_1%_RO SMD Resistor R11 1206_1.1Ω_1%_RO SMD Resistor R13 0603_100KΩ_5%_RO SMD Resistor R14 0603_1.0KΩ_5%_RO SMD Resistor R15 0603_10KΩ_5%_RO SMD Resistor R16 0603_10KΩ_5%_RO SMD Resistor R17 0603_7.5KΩ_5%_RO SMD Resistors R18 R19 1206_1MΩ_5%_RO SMD Resistor R20 0805_47Ω_5%_RO SMD Resistor R21 0805_100KΩ_5%_RO SMD Resistor R22-R25 1206_390KΩ_5%_RO SMD Resistor R26 0603_15KΩ_5%_RO SMD Resistor R27 0603_10KΩ_5%_RO SMD Resistor R28 1206_47Ω_5%_RO SMD Capacitor C3 1206_1 KV_68 PF_10%_NPO_RO SMD Capacitor C6 1206_25 V_10 uF_10%_X7R_RO SMD Capacitors C8 C10 0603_25 V_1 uF_10%_X7R_RO SMD Capacitors C9 C11-C14 1206 _500 V_10 nF_10%_X7R_RO SMD Capacitor C15 0603_25 V_2.2 uF_10%_X7R_RO SMD Zener Diode Z1 SOD-123_15 V_0.5 W_150°_RO SMD Diodes D5 D15 E1D_SOD-123FL_200 V_1 A_35 nS_150°_RO SMD Diode D6 ES2J_SMB_600 V_2 A_35 nS_150°_RO SMD Diode D16 1N4148W_SOD-123_75 V_150 mA_150°_RO SMD Diodes D7-D14 US1M_SMA_1000 V_1 A_75 nS_150°_RO SMD Transistor Q2 MMBT4401_SOT-23 SMD IC 28 IC_SO-6_SY5824A_150°_RO

[0068] For a 10 Watt Fluorescent Compatible LED Tube Lamp, appropriate component Ids/sources/values for the electronic parts of the driver circuit disclosed on FIG. 5 would be the same as for the 18 Watt version as noted above, except for the below-noted component changes:

TABLE-US-00003 Electrolytic Capacitors E3 E4 80 V_56 UF_105° C._20%_8*12 mm_8000 h_ROT1 L-37HD-T08JR-V1.0-EE13 T2 L-39HD-T08JR-V1.0-EE8.3-6-6 PCB Board D-91HD-SY24-JRT8-A-V2.0_1.0 mm_FR-4_CTI > 175_94 V-0_RO SMD Resistor R10 0805_4.7Ω_1%_RO SMD Resistor R11 1206_1.0Ω_1%_RO

[0069] Other wattage examples would have comparable changes to the above-noted components for a corresponding working effect.

[0070] The driver of FIG. 5 will work, for example, with a (recommended) DC power input of 24 Volts-36 Volts from an electronic ballast with its secondary side having a Hertz rating in a (typical) range of 20,000 Hz-40,000 Hz. It will also work up to 120 Volts DC although it is recommended not to approach such a high level of input due to heat building up in the driver and adversely affecting longevity of the components. It is recommended to use wire with a 600 Volt rating in Type AWM Class I, Class II, or Class I/II, Group A with this invention.

[0071] The foregoing description of the preferred and alternate apparatus and arrangement of installation and use should be considered as illustrative only, and not limiting. Other forming techniques and other materials may be employed towards similar ends. Various changes and modifications will occur to those skilled in the art, without departing from the true scope of the invention as defined in the above disclosure, and the following general claims.