Continuous load high power flyback converter

Abstract

A continuous load high-power flyback converter includes a first transformer having a first primary winding, a first secondary winding, and a first auxiliary winding, and a second transformer having a second primary winding, a second secondary winding, and a second auxiliary winding. The first primary winding and the second primary winding are connected in parallel between a power source and a transistor. The first secondary winding and the second secondary winding are connected in series to a diode and form an output of the continuous load high-power flyback converter. A load is connected between the output and ground. The first auxiliary winding and the second auxiliary winding are connected in series, and used to generate a control signal for the transistor. Connecting the primary windings in parallel and the secondary windings in series reduces the reflected voltage on the transistor for a given output voltage.

Claims

1. A continuous load high-power flyback converter, comprising: a first transformer having a first primary winding, a first secondary winding and a first auxiliary winding; a second transformer having a second primary winding, a second secondary winding, and a second auxiliary winding; a transistor; and a diode; wherein: the first primary winding and the second primary winding are connected in parallel between a power source and the transistor; the first secondary winding and the second secondary winding are connected in series with the diode to form an output terminal of the continuous load high-power flyback converter for supplying continuous output power to a load; and the first auxiliary winding and the second auxiliary winding are connected in series and used to generate a control signal to control an ON/OFF state of the transistor.

2. The continuous load high-power flyback converter of claim 1, further comprising the load; wherein the load is an LED (Light Emitting Diode) array.

3. The continuous load high-power flyback converter of claim 2, wherein the LED array has a plurality of LEDS.

4. The continuous load high-power flyback converter of claim 1, wherein the continuous load high-power flyback converter is a stepdown converter.

5. The continuous load high-power flyback converter of claim 1, wherein the first transformer has a first magnetic core, and wherein the second transformer has a second magnetic core.

6. The continuous load high-power flyback converter of claim 1, wherein the first and second transformers are configured such that voltage levels on the first and second auxiliary windings respectively correlate to voltage levels on the first and second secondary windings.

7. The continuous load high-power flyback converter of claim 1, wherein the control signal causes the transistor ON/OFF state to alternate between ON and OFF to implement a quasi-resonance control operation of the continuous load high-power flyback converter.

8. A lighting device, comprising: a continuous load high-power flyback converter having an input terminal and an output terminal; and an LED (Light Emitting Diode) array connected to the output terminal; the continuous load high-power flyback converter comprising: a first transformer having a first primary winding, a first secondary winding and a first auxiliary winding; a second transformer having a second primary winding, a second secondary winding, and a second auxiliary winding; a transistor; and a diode; wherein: the first primary winding and the second primary winding are connected in parallel between a power source and the transistor; the first secondary winding and the second secondary winding are connected in series with the diode to form the output terminal; and the first auxiliary winding and the second auxiliary winding are connected in series and used to generate a control signal to control an ON/OFF state of the transistor.

9. The lighting device of claim 8, wherein the LED array has a plurality of LEDS.

10. The lighting device of claim 8, wherein the continuous load high-power flyback converter is a stepdown converter.

11. The lighting device of claim 8, wherein the first transformer has a first magnetic core, and wherein the second transformer has a second magnetic core.

12. The lighting device of claim 8, wherein the first and second transformers are configured such that voltage levels on the first and second auxiliary windings respectively correlate to voltage levels on the first and second secondary windings.

13. The lighting device of claim 8, wherein the control signal causes the transistor ON/OFF state to alternate between ON and OFF to implement a quasi-resonance control operation of the continuous load high-power flyback converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features of the present implementations will be understood better by reading the following detailed description, taken together with the figures herein described. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing.

(2) FIG. 1 is a circuit diagram of an example conventional flyback converter.

(3) FIG. 2 is a circuit diagram of the example conventional flyback converter of FIG. 1, showing the flow of electricity when a transistor forming part of the flyback converter is turned ON.

(4) FIG. 3 is a circuit diagram of the example conventional flyback converter of FIG. 1, showing the flow of electricity when the transistor is turned OFF.

(5) FIG. 4 is a circuit diagram of an example continuous load high-power flyback converter, according to some implementations.

(6) FIG. 5 is a circuit diagram of the example continuous load high-power flyback converter of FIG. 4, showing the flow of electricity when a transistor forming part of the continuous load high-power flyback converter is turned ON.

(7) FIG. 6 is a circuit diagram of the example continuous load high-power flyback converter of FIG. 4, showing the flow of electricity when the transistor is turned OFF.

(8) FIGS. 7 and 8 are circuit diagrams of example continuous load high-power flyback converters, according to some implementations.

(9) FIG. 9 is a functional block diagram of a lighting device having an LED array connected to a continuous load high-power flyback converter, according to some implementations.

DETAILED DESCRIPTION

(10) This disclosure is based, at least in part, on the realization that it would be advantageous to provide a continuous load high-power flyback converter.

(11) FIG. 4 is a circuit diagram of an example continuous load high-power flyback converter 200, according to some implementations. As shown in FIG. 4, in some implementations the continuous load high-power flyback converter 200 has two or more transformers 105.sub.1, 105.sub.2. Although the continuous load high-power flyback converter 200 shown FIG. 4 has only two transformers 105, in some implementations the continuous load high-power flyback converter 200 may have more than two transformers 105, for example as shown in FIG. 8. The first transformer 105.sub.1 has a primary winding 110.sub.1, a secondary winding 115.sub.1, and an auxiliary winding 140.sub.1. The second transformer 105.sub.2 has a primary winding 110.sub.2, a secondary winding 115.sub.2, and an auxiliary winding 140.sub.2. The first and second transformers have separate magnetic cores 145.sub.1, 145.sub.2, respectively. FIG. 4 shows the auxiliary windings 140.sub.1, 140.sub.2, separate from the primary and secondary windings for clarity. FIG. 7 shows the auxiliary windings disposed adjacent the primary and secondary windings as would be implemented in actual electrical components.

(12) The primary winding 110.sub.1 of the first transformer 105.sub.1 and the primary winding 110.sub.2 of the second transformer 105.sub.2 are connected in parallel between the power source 120 and transistor 125. The secondary winding 115.sub.1 of the first transformer 105.sub.1 and the secondary winding 115.sub.2 of the second transformer 105.sub.2 are connected in series, such that an output 150 of the secondary winding 115.sub.2 of the second transformer 105.sub.2 is connected to an input 155 of the secondary winding 115.sub.1 of the first transformer 105.sub.1. The order in which the secondary windings 115.sub.1, 115.sub.2 are series connected may change depending on the implementation. The first secondary winding 115.sub.1 and the second secondary winding 115.sub.2 are connected in series with the diode 130 to form an output terminal V.sub.out of the continuous load high-power flyback converter 200 for supplying continuous output power to a capacitor Co and a load 135.

(13) By connecting the primary windings 110.sub.1, 110.sub.2 in parallel and connecting the secondary windings 115.sub.1, 115.sub.2 in series, each transformer 105.sub.1, 105.sub.2, can be designed to share half the output power that is supplied to load 135. Thus, if the continuous load high-power flyback converter 200 is intended to provide 100 Watts of power to load 135, two 50 Watt transformers 105 can be used instead of one 100 Watt transformer 105. Similarly, if the continuous load high-power flyback converter 200 is intended to provide 75 Watts of power to load 135, one 50 Watt transformer 105 and one 25 Watt transformer 105, or two 40 Watt transformers 105 can be used instead of one 75 Watt transformer 105.

(14) Connecting the primary windings 110.sub.1, 110.sub.2 in parallel between the power source 120 and transistor 125 also reduces the reflected voltage on the transistor 125 when the transistor 125 is in the OFF position. Specifically, the reflected voltage Vref=(NP/NS)*(Vo+Vf)/(number of transformers). For example, where two transformers 105.sub.1, 105.sub.2 are used to implement the continuous load high-power flyback converter 200, it is possible to achieve the same output voltage Vo, while generating only half of the reflected voltage Vref on the transistor 125, as compared to using the single transformer design shown in FIG. 1.

(15) Using two or more transformers 105 also helps to evenly distribute the temperature generated by the continuous load high-power flyback converter 200, since the two or more transformers 105 can be physically separated from each other on the printed circuit board. Further, using two or more transformers enables the continuous load high-power flyback converter 200 to be implemented using smaller magnetics, which may help to design a low profile power supply.

(16) As shown in FIG. 4, in some implementations the auxiliary winding 140.sub.1 of the first transformer 105.sub.1 and the auxiliary winding 140.sub.2 of the second transformer 105.sub.2 are connected in series. Specifically, as shown in FIG. 4, an output 160 of the auxiliary winding 140.sub.2 of the second transformer 105.sub.2 is connected to an input 165 of the auxiliary winding 140.sub.1 of the first transformer 105.sub.1. The order in which the auxiliary windings 140.sub.1, 140.sub.2 are series connected may change depending on the implementation. Depending on the implementation, it is possible for the first transformer 105.sub.1 and the second transformer 105.sub.2 to have different inductances. Further, even if the first transformer 105.sub.1 and the second transformer 105.sub.2 are selected to have approximately the same inductance, due to manufacturing tolerances the two similarly configured transformers 105 may have some inductance variation. These two transformers 105.sub.1, 105.sub.2, accordingly, may take different amounts of time to fully discharge power through load 135. Connecting the auxiliary windings 140.sub.1, 140.sub.2 in series ensures that the zero-crossing detection signal (labeled demagnetization detection in FIG. 4) goes low only after energy from both transformers 105.sub.1, 105.sub.2, has been drained from the secondary windings 115.sub.1, 115.sub.2. In some implementations the continuous load high-power flyback converter 200 is a stepdown converter.

(17) FIG. 5 shows the flow of current in the continuous load high-power flyback converter 200 when the transistor 125 is turned ON. As shown in FIG. 5, when the transistor 125 is turned ON, current flows in parallel through both the primary winding 110.sub.1 of the first transformer 105.sub.1 and the primary winding 110.sub.2 of the second transformer 105.sub.2. This causes both transformers 105.sub.1, 105.sub.2 to be magnetized and store energy. The diode 130 is OFF during this phase due to the negative polarity on the secondary windings 115.sub.1 115.sub.2.

(18) FIG. 6 shows the flow of current in the continuous load high-power flyback converter 200 when the transistor 125 is turned OFF. As shown in FIG. 6, when the transistor 125 is turned OFF, the output diode 130 starts to conduct due to the reversal of polarity on the secondary winding 115.sub.1 of the first transformer 105.sub.1 and the secondary winding 115.sub.2 of the second transformer 105.sub.2.

(19) After the power stored in the first and second transformer 105.sub.1, 105.sub.2 has been transferred to the load 135, the current on the secondary windings 115.sub.1, 115.sub.2 will start to approach zero. The first and second auxiliary windings 140.sub.1, 140.sub.2 reflect the voltage of the secondary windings 115.sub.1, 115.sub.2, respectively. Because the auxiliary windings 140.sub.1, 140.sub.2 are connected in series, the demagnetization detection signal will remain high until both secondary windings 115.sub.1, 115.sub.2 have discharged to the point where the voltage across both of the secondary winding 115.sub.1, 115.sub.2 approaches zero. At that point, the auxiliary windings 140.sub.1, 140.sub.2 will start ringing, caused by resonance between the primary inductance of the transformers 105.sub.1, 105.sub.2 and parasitic lumped capacitance. This ringing can be used to detect demagnetization of the transformers 105.sub.1, 105.sub.2 to cause the transistor 125 to be turned ON again.

(20) FIG. 7 is a circuit diagram showing a continuous load high-power flyback converter 200 according to some implementations. As shown in FIG. 7, in some implementations each transformer 105.sub.1, 105.sub.2, is implemented as a separate electrical component with a separate magnetic core 145.sub.1, 145.sub.2. For example, if the continuous load high-power flyback converter 200 is to be designed to output 100 Watts of power to load 135, two separate 50 Watt transformers 105 may be used to implement transformers 105.sub.1, 105.sub.2.

(21) FIG. 8 is a circuit diagram showing a continuous load high-power flyback converter 200 according to some implementations. As shown in FIG. 8, multiple transformers 105.sub.1, 105.sub.2, 105.sub.3, 105.sub.4 can be connected such that the primary winding 110 of each transformer 105.sub.1, 105.sub.2, 105.sub.3, 105.sub.4 is connected in parallel between power source 120 and transistor 125, and such that the secondary windings 115.sub.1, 115.sub.2, 115.sub.3, 115.sub.4 (collectively 115) of each transformer 105.sub.1, 105.sub.2, 105.sub.3, 105.sub.4 is connected in series between output V.sub.out and ground. Although four transformers 105.sub.1, 105.sub.2, 105.sub.3, 105.sub.4 are shown in FIG. 8, other numbers of transformers 105 may be connected in this manner. Further, as shown in FIG. 8, the auxiliary windings 140.sub.1, 140.sub.2, 140.sub.3, and 140.sub.4 of each of the multiple transformers 105.sub.1, 105.sub.2, 105.sub.3, 105.sub.4 are connected in series to ensure that the transistor 125 is turned ON only after the power has dissipated from each of the secondary windings 115.sub.1, 115.sub.2, 115.sub.3, 115.sub.4.

(22) By using multiple transformers 105 having parallel connected primary windings 110 and series connected secondary windings 115, it is possible to create a continuous load high-power flyback converter 200 that has higher efficiency and which exhibits lower reflected voltage on the transistor 125, as compared to a flyback converter 100 designed to provide the same output power but using only one transformer 105. This enables the continuous load high-power flyback converter 200 to scale to higher output power while using multiple smaller magnetic cores 145. While the continuous load high-power flyback converter 200 does require a larger number of transformers, which may occupy a larger amount of space on a printed circuit board, the use of multiple transformers 105 enables heat generated by the transformers 105 to be more evenly distributed across the printed circuit board used to implement the continuous load high-power flyback converter 200. The use of multiple smaller transformers can also enable the continuous load high-power flyback converter 200 to have a lower profile, which is advantageous in certain applications.

(23) FIG. 9 is a functional block diagram of a lighting device 300 having an LED (Light Emitting Diode) array 305 implemented as a load 135 connected to an output V.sub.out of a continuous load high-power flyback converter 200, according to some implementations. As shown in FIG. 9, in some implementations the lighting device 300 has an LED array 305 having multiple LEDS 310 connected to the output V.sub.out of a continuous load high-power flyback converter 200 as load 135.

(24) Throughout the entirety of the present disclosure, use of the articles “a” and/or “an” and/or “the” to modify a noun may be understood to be used for convenience and to include one, or more than one, of the modified noun, unless otherwise specifically stated. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

(25) Although the methods and systems have been described relative to specific implementations thereof, they are not so limited. Many modifications and variations may become apparent in light of the above teachings. Many additional changes in the details, materials, and arrangement of parts, herein described and illustrated, may be made by those skilled in the art. A number of implementations have been described. Nevertheless, it will be understood that additional modifications may be made without departing from the scope of the inventive concepts described herein, and, accordingly, other implementations are within the scope of the following claims.