METHOD AND APPARATUSES FOR CONTROLLING THE OUTPUT VOLTAGE OF A VOLTAGE REGULATOR

Abstract

A device includes a voltage regulator, circuits, and a current bus. Each of the circuits includes at least one LED driver. The voltage regulator supplies electrical energy to a plurality of LED groups. Each of the circuits includes a voltage measuring circuit for detecting voltage drops across the LED drivers. The LED drivers set the currents through the LED groups. Each of the circuits includes a local controller. The local controller withdraws a current from the control bus in dependence on the detected voltage drops of the LED drivers included in the circuit. A bias current source injects a bias current into the control bus. The control bus sums the currents in the current bus. The output of the regulator is controlled based on the summed current.

Claims

1. A method for regulating an output voltage of a voltage regulator for supplying a lighting device, wherein the lighting device includes at least two circuits, and each of the at least two circuits includes at least one current source, wherein each of the least one current source in each of the at least two circuits is constructed to supply a respective LED group, the method comprising: generating the output voltage by the voltage regulator; supplying the respective LED group using the output voltage; measuring, by each circuit, a voltage drop of each of the current sources in the respective circuit supplying one of the respective LED groups supplied by the respective circuit; withdrawing, by each circuit, a respective withdrawal current from a control bus based on the measured voltage drop of each of the current sources in the respective circuits; determining a control current based on the withdrawal currents withdrawn from the control bus by each of the circuits; and regulating the output voltage of the voltage regulator based on the control current.

2. The method of claim 1, wherein the at least two circuits include a first circuit and a second circuit, the method further comprising, prior to measuring the voltage drop of each of the current sources: setting of a first LED group current through each of the respective LED groups supplied by the respective current source of the first circuit associated with the respective LED group of the first circuit; and setting of a second LED group current through each of the respective LED groups supplied by the respective current source of the second circuit associated with the respective group of the second circuit.

3. The method of claim 1, further comprising: injecting a bias current into the control bus; wherein the control current based on the withdrawal currents includes summing the bias current and the withdrawal currents.

4. The method of claim 1, wherein withdrawing, by each circuit, the respective withdrawal current from the control bus based on the measured voltage drops of the current sources in the respective circuits includes: detecting a separate voltage drop for each current source; selecting a voltage drop value of one of the current sources as a characteristic voltage drop value of the circuit; and determining the withdrawal current for the circuit based on the characteristic voltage drop value of the circuit.

5. The method of claim 4, wherein, determining the withdrawal current for the circuit based on the characteristic voltage drop value of the circuit includes determining a deviation of the characteristic voltage drop value from a set value.

6. The method of claim 5, wherein the withdrawal current of the respective circuit depends linearly on the deviation of the characteristic voltage drop value from the set value.

7. The method of claim 1, wherein the voltage regulator is a current-controlled voltage regulator.

8. The method of claim 1, wherein the voltage regulator is a voltage-controlled voltage regulator, further comprising: converting the control current to a control voltage; and controlling the voltage regulator based on the control voltage.

9. The method of claim 1, wherein each of the circuits is an integrated circuit.

10. A device for supplying a plurality of LED groups, comprising: a voltage regulator that generates an output voltage, wherein the output voltage supplies electrical energy to each of the plurality of LED groups; a current bus; and at least two circuits, each of the at least two circuits comprising: at least one LED driver; a voltage measuring circuit configured to measure respectively a voltage drop across each of the at least one LED driver in the respective circuit; a controller; and a current driver configured to extract a current from the current bus; wherein: the at least one LED driver of each circuit is coupled to set a current through a respective LED group of the plurality of LED groups; the controller in each circuit is coupled to receive the respective voltage drop of each of the at least one LED driver; and the controller is configured to determine, based on the respective voltage drops of the at least one LED driver, a characteristic voltage drop for the respective circuit; the controller is configured to withdraw, via the current driver, a current from the current bus based on the characteristic voltage drop for the respective circuit; and the voltage regulator is controlled based on a summed current of the current bus.

11. The device according to claim 10, wherein the voltage regulator is a current-controlled voltage regulator.

12. The device according to claim 10, further comprising a current bias circuit coupled to inject a bias current into the current bus.

13. The device according to claim 12, wherein at least one circuit includes the current bias circuit.

14. The device according to claim 10, wherein each of the at least one LED driver in each of the circuits includes a respective current source.

15. The device according to claim 14, wherein the respective current sources are current sources to ground.

16. The device of claim 10, further comprising a resistor, wherein: the summed current of the current bus supplies the resistor; and the voltage regulator is controlled based on the voltage drop across the resistor.

17. The device of claim 16, further comprising a voltage-to-current converter, wherein the voltage-to-current converter converts the voltage drop of the across the resistor to a control current, and the voltage regulator is controlled based on the control current.

18. The device of claim 10, wherein the voltage measuring circuit is each circuit is an analog-to-digital converter.

19. The device of claim 10, wherein the controller of each circuit determines the characteristic voltage drop for the respective circuit based on the respective voltage drops of the at least one LED driver based on an algorithm that includes determining a minimum voltage of each of the voltage drops of the at least one LED driver.

20. The device of claim 10, wherein each circuit is an integrated circuit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 shows an exemplary device for regulating a voltage regulator for supplying at least two LED groups.

DESCRIPTION

[0035] The disclosure relates to a method for regulating the output voltage (V.sub.0) at the output (V.sub.out) of a voltage regulator (VREG) for supplying a lighting device with electrical energy, wherein the lighting device comprises several, but at least two, circuits (IC1, IC2) with at least one LED group (LED.sub.1, LED.sub.2, LED.sub.3) and an appropriate current source (LED DRY) per circuit (IC1, IC2).

[0036] The method, shown in FIG. 1, comprises at least the following steps: [0037] First, a supply voltage (V.sub.0) is generated by means of the voltage regulator (VREG) at the output (V.sub.out) of this voltage regulator (VREG). [0038] Next, a respective LED group current (I.sub.LED1, I.sub.LED2, I.sub.LED3) is set by the LED groups (LED.sub.1, LED.sub.2, LED.sub.3) by means of a current source (LED DRV) for each LED group (LED.sub.1, LED.sub.2, LED.sub.3). In the example of FIG. 1, the LED groups (LED.sub.1, LED.sub.2, LED.sub.3) are distributed on two circuits (IC1, IC2). Devices having more than two circuits and more than three LED groups are expressly intended to be included in the claims and to be considered as disclosed herein.

[0039] Next, the detection of the respective voltage drop across respective current sources (LED DRV) of the LED groups (LED1, LED2, LED3) is performed as the respective voltage drop value of this current source (LED DRY). This is preferably done in each of the circuits (IC1, IC2) for preferably each of the current sources (LED DRV).

[0040] Next, in preferably each circuit (IC1, IC2), a voltage drop value of the voltage drop values of the current sources (LED DRV) of this circuit is selected as the characteristic voltage drop value of this circuit from among the voltage drop values determined for this circuit. Thus, one characteristic voltage drop value is preferably obtained for each circuit. It is performed as nothing else than determining a respective voltage drop value of a current source (LED DRV) of each circuit (IC 1, IC2) from the voltage drop values of the current sources (LED DRV) of that respective circuit (IC1, IC2) as a characteristic voltage drop value of that circuit (IC1, IC2). Preferably, the characterizing voltage drop value of this circuit (IC1, IC2) is the minimum voltage drop value of the determined voltage drop values of this circuit (IC1, IC2).

[0041] Next, each of the circuits (IC1, IC2) draws an electric current associated with it, its draw current, from a control bus (RB). This represents a withdrawal of a respective withdrawal current of the respective circuit (IC1, IC2) from a control bus (RB) by each of these circuits (IC1, IC2). The amount of this respective withdrawal current of the respective circuit (ICI, IC2) is to depend thereby on the deviation of its characteristic voltage drop value from a set value. This setpoint is preferably common to all circuits and thus selected or set the same for all circuits (IC1, IC2) within a tolerance interval.

[0042] Preferably, each circuit (IC1, IC2) feeds a substantially constant bias current (bias) into the control bus (RB). However, a single injection is usually sufficient for proper operation. Theoretically, solutions without bias current injection are also conceivable with greater circuitry effort, but are not preferred here.

[0043] By feeding the current into the control bus (RB), all extraction currents and at least one optional constant bias current (I.sub.Bias) are summed up to a common sum current (I.sub.S). Thus is disclosed a low-effort, easy, and inexpensive to implement generation of a common sum current and its subsequent use as a control signal. The output voltage (V.sub.0) of the voltage regulator (VREG) is then regulated at its output (V.sub.out) as in dependence of the sum current (I.sub.S). In the example of FIG. 1, several current-voltage conversions and voltage-current conversions are performed for circuit reasons. Theoretically, however, direct control of the voltage regulator with this current signal is conceivable if the voltage regulator has a current input for controlling its reference value. In the example of FIG. 1, however, a voltage input for the voltage regulator (VREG) is assumed.

[0044] The corresponding device for supplying several, but at least two LED groups (LED.sub.1, LED.sub.2, LED.sub.3) with electrical energy therefore preferably comprises a voltage regulator (VREG), at least two circuits (IC1, IC2), a voltage-to-current converter (VC-C), a control bus (RB), a resistor (R.sub.GPIO) and a resistor network (R1, R2). Each of the circuits (IC1, IC2) preferably has at least one LED connection (LED0, LED1) for at least one LED group (LED.sub.1, LED.sub.2, LED.sub.3), at least one LED driver (LED DRV) per LED group (LED.sub.1, LED.sub.2, LED.sub.3) for supplying power to this LED group (LED.sub.1, LED.sub.2, LED.sub.3) via an LED connection (LED0, LED1) associated with this LED group (LED.sub.1, LED.sub.2, LED.sub.3) and at least one measuring means (ADC) of this circuit (IC1, IC2) for detecting the voltage differences between the potentials of LED connections (LED0, LED1) of this circuit (IC1, IC2) and a reference potential (GND). Furthermore, each of the circuits (IC1, IC2) has a local controller (VR) which, by means of at least one driver (DRV), draws a current from the control bus (RB) depending on the voltage differences detected by its measuring means (ADC). One or more bias current sources (IQ) inject one or more bias currents (I.sub.Bias) into the control bus (RB) in the form of a sum current of the injected bias currents (I.sub.Bias) in order to set the operating point correctly. The resistor (R.sub.GPIO) performs a current-to-voltage conversion of the sum current (I.sub.S) into a control voltage (V.sub.R). The voltage-to-current converter (VC-C) converts the control voltage (V.sub.R) into a current of a voltage control signal (VCTR). The resistor network (R1, R2) converts the current of the voltage control signal (VCTR) into a voltage value (V.sub.ADJ). The output voltage (V.sub.0) of the voltage regulator (VREG) depends on the voltage value (V.sub.ADJ), so that this then closes the control loop. Preferably, the dependencies are linear.

[0045] The control chain of FIG. 1 can be massively shortened.

[0046] The corresponding device simplified in a first step for supplying several, but at least two LED groups (LED.sub.1, LED.sub.2, LED.sub.3) with electrical energy therefore preferably comprises a voltage regulator (VREG), at least two circuits (IC1, IC2), a control bus (RB), and a resistor (R.sub.GPIO). Each of the circuits (IC1, IC2) preferably has at least one LED connection (LED0, LED1) for at least one LED group (LED.sub.1, LED.sub.2, LED.sub.3), at least one LED driver (LED DRY) per LED group (LED.sub.1, LED.sub.2, LED.sub.3) for supplying power to this LED group (LED.sub.1, LED.sub.2, LED.sub.3) via the LED connection (LED0, LED1) associated with this LED group (LED.sub.1, LED.sub.2, LED.sub.3) and at least one measuring means (ADC) of this circuit (IC1, IC2) for detecting the voltage differences between the potentials of LED connections (LED0, LED1) of this circuit (ICI, IC2) and a reference potential (GND). Furthermore, each of the circuits (IC1, IC2) has a local controller (VR) which, by means of at least one driver (DRV), draws a current from the control bus (RB) depending on the voltage differences detected by its measuring means (ADC). One or more bias current sources (IQ) inject one or more bias currents (I.sub.Bias) into the control bus (RB) in the form of a sum current of the injected bias currents (I.sub.Bias) in order to set the operating point correctly. The resistor (R.sub.GPOP) performs a current-voltage conversion of the sum current (I.sub.S) into a control voltage (V.sub.R). The output voltage (V.sub.0) of the voltage regulator (VREG) depends on the voltage value of the control voltage (V.sub.R), so that this then closes the control loop. Preferably, the dependencies are linear.

[0047] This control chain can be further shortened.

[0048] The corresponding device simplified in a second step for supplying electrical energy to several, but at least two LED groups (LED.sub.1), LED.sub.2, LED.sub.3) preferably comprises a voltage regulator (VREG), at least two circuits (IC1, IC2), and a control bus (RB). Each of the circuits (IC1, IC2) preferably has at least one LED connection (LED0, LED1) for at least one LED group (LED.sub.1, LED.sub.2, LED.sub.3), at least one LED driver (LED DRV) per LED group (LED.sub.1, LED.sub.2, LED.sub.3) for supplying power to this LED group (LED.sub.1, LED.sub.2, LED.sub.3) via the LED connection (LED0, LED1) associated with this LED group (LED.sub.1, LED.sub.2, LED.sub.3) and at least one measuring means (ADC) of this circuit (IC1, IC2) for detecting the voltage differences between the potentials of LED connections (LED0, LED1) of this circuit (IC1, IC2) and a reference potential (GND). Furthermore, each of the circuits (IC1, IC2) has a local controller (VR) which, by means of at least one driver (DRV), draws a current from the control bus (RB) depending on the voltage differences detected by its measuring means (ADC). One or more bias current sources (IQ) feed one or more bias currents (I.sub.Bias) in the form of a sum current (I.sub.S) of the fed bias currents (I.sub.Bias) into the control bus (RB) in order to set the operating point correctly. The output voltage (V.sub.0) of the voltage regulator (VREG) depends on the current value of the sum current (I.sub.S), so that this then closes the control loop. Preferably, the dependencies are linear. A current-controlled voltage regulator is required here.

[0049] A device according to the disclosure allows a regulation of the voltage regulator (VREG) in a simple manner in order to supply more complex LED arrangements supplied with electrical energy from several circuits. It was recognized that this is particularly easy with a current-controlled voltage regulator. Here, the total current (I.sub.S) is the actual value signal and the input of the voltage-to-current converter (VC-C) is the exemplary input of a current controlled voltage regulator advanced by a said component (VREG, R1, R2, VC-C). In contrast to the state of the art, the construction is particularly robust against EMC radiation and potential offset due to the current-controlled signal.

LIST OF REFERENCES

[0050] ADC analog-to-digital converter, also known as measuring equipment [0051] ADJ Control input of the voltage regulator (VREG) for the voltage control signal (VCTR) [0052] I.sub.ADJ additional current [0053] I.sub.Bias Constant current of the respective bias current source (IQ), which is supplied via the control bus connection of the respective integrated circuit (IC1, IC2) is fed into the control bus (RB). The bias current is preferably a current that is constant over time for setting the operating point of the proposed device. [0054] IC1 first integrated circuit [0055] IC2 second integrated circuit [0056] IQ bias current source of an integrated circuit (IC1, IC2) [0057] I.sub.S sum current of the fed bias currents (I.sub.Bias) of all integrated circuits (IC) connected to the control bus (RB) [0058] GND reference potential [0059] GPIO control bus connection of the associated integrated circuit (IC1, IC2) [0060] OP1 amplifier [0061] LED.sub.1 first LED; first group of LEDs [0062] LED.sub.2 second LED; second group of LEDs [0063] LED.sub.3 third LED; third group of LEDs [0064] LED.sub.3a first LED of the third LED group (LED.sub.3) [0065] LED.sub.3b second LED of the third LED group (LED.sub.3) [0066] LED0 first LED connection [0067] LED1 second LED connection [0068] LED DRV LED driver [0069] R1 first resistance [0070] R2 second resistance [0071] R3 third resistor [0072] RB control bus [0073] R.sub.i internal control signal [0074] RS control signal [0075] R.sub.GPIO resistance to convert the sum current (I.sub.S) into a voltage [0076] T1 first transistor [0077] V.sub.0 Output voltage of the voltage regulator (VREG) at his voltage regulator output (V.sub.out) against the reference potential (GND) [0078] V.sub.ADJ Voltage value of the voltage control signal (VCTR) against a reference potential (GND) [0079] VC-C voltage-to-current converter (external voltage to current converter), which is preferably not part of the integrated circuits (IC1, IC2) and/or of the voltage regulator (VREG) and which can consist, for example, of a first transistor (T1), an amplifier (OP1) and a third resistor (R3).

[0080] VCTR voltage control signal [0081] V.sub.R Control voltage at the resistor (R.sub.GPIO) [0082] VR local controller of an associated integrated circuit (IC1, IC2) [0083] VREG voltage regulator [0084] V.sub.out voltage regulator output of the voltage regulator (VREG)

LIST OF CITED DOCUMENTS

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