CN102469666A - Feedback voltage stabilizing circuit - Google Patents

Abstract

The invention provides a feedback voltage stabilizing circuit which provides voltage stabilization to a multi-voltage output circuit and outputs a plurality of output voltages. The feedback voltage stabilizing circuit comprises a voltage control unit which is coupled with the output voltages, generates a first voltage according to the output voltages and outputs a voltage control signal accordingly. The feedback voltage stabilizing circuit further comprises a reference voltage generator which is coupled to the voltage control unit, receives the voltage control signal and generates a reference voltage for feeding back to the multi-voltage output circuit.

Description

Feedback Regulator Circuit

technical field

The present invention relates to a monitor circuit, in particular to an efficiency optimization and fault detection circuit of an LED driving system.

Background technique

In view of many advantages of light-emitting diodes (LEDs), such as small size, short response time, low power consumption, high reliability, and high feasibility of mass production, light-emitting diodes are widely used as light sources in electronic devices. For example, light-emitting diodes are used as the backlight of liquid crystal displays (LCDs) to replace traditional fluorescent tubes.

The schematic diagram of FIG. 1 shows a traditional LED driving system, which mainly includes a plurality of LED strings (LED string) 10, a boost controller 14 and a boost power stage circuit 16.

For the traditional LED drive system shown in Figure 1, even if each LED string 10 uses the same voltage source V-- _DC and the same number of LEDs 100, however, due to the incomplete matching between the LEDs 100, thus making The voltage of each input pad (input pad) 11 is different. In order to reduce the power consumption of the LED string 10, in the circuit design, a predetermined voltage value, for example, 1 volt, will be fed into the boost controller 14, as the reference of the control voltage source V _DC , and then controlled by the boost The feedback circuit of the converter 14 and the boost power stage circuit 16 is designed to control the voltage source V _DC so that the voltage of the input pad 11 can be stabilized at the predetermined voltage value of 1 volt.

However, the above-mentioned designs cannot achieve the required accuracy. Therefore, it is often impossible to optimize the efficiency of the LED driving system. In addition, the conventional LED driving system lacks a mechanism to monitor the fault of the LED string 10 , such as a faulty short circuit or open circuit of the LED 100 . Therefore, when serious failure of the LED 100 occurs, the boost controller 14 and the boost power stage circuit 16 of the conventional LED driving system cannot optimize the efficiency of the LED 100 .

Therefore, it is urgent to propose a novel efficiency optimization and error detection mechanism to effectively monitor the LED driving system and improve its luminous efficiency.

Contents of the invention

In view of the above, the embodiment of the present invention discloses a feedback regulator circuit, which is applicable to the LED driving system, and can not only reduce the power consumption of the LED driving system, but also monitor its abnormal failure.

According to an embodiment of the present invention, the feedback regulator circuit provides regulation in a multi-voltage output circuit, which outputs a plurality of output voltages. The feedback regulator circuit includes a voltage control unit and a reference voltage generator. Wherein, the voltage control unit is coupled to these output voltages, generates a first voltage according to these output voltages, and outputs a voltage control signal accordingly. The reference voltage generator is coupled to the voltage control unit and receives the voltage control signal to generate a reference voltage for feeding back to the multi-voltage output circuit.

Description of drawings

FIG. 1 is a schematic diagram showing a conventional LED driving system.

FIG. 2 is a schematic diagram showing a feedback regulator circuit according to an embodiment of the present invention.

Figure 3 shows a detailed circuit diagram of the block-to-digital voltage converter (ADC) of Figure 2.

FIG. 4 shows a detailed circuit diagram of the low-pass filter of the embodiment of the present invention.

FIG. 5 shows a detailed circuit diagram of a boost controller and a boost power stage circuit according to an embodiment of the present invention.

Description of main component symbols

10 LED strings

100 LEDs

11 input pad

14 Boost controller

16 Boost power stage circuit

2 module circuit

20 Multi-voltage output circuit

21 Module to Digital Voltage Converter (ADC)

210 multiplexer

212 module to digital voltage conversion (ADC) unit

22 Voltage control unit

220 logic units

23 reference voltage generator

232 signal generator

234 low pass filter (LPF)

24 boost controller

26 Boost power stage circuit

V _DC voltage source

_IS current source

R1/R2 voltage divider resistor

R _LPF resistance

C _LPF capacitance

L inductance

C capacitance

SW switching transistor

Detailed ways

FIG. 2 is a schematic diagram showing a feedback regulator circuit according to an embodiment of the present invention, which can provide voltage regulation in a multi-voltage output circuit 20, which can output multiple output voltages. In this embodiment, the multi-voltage output circuit 20 includes multiple LED strings 10, the brightness of which is controlled by multiple current sources I _S respectively. Each LED string 10 includes a plurality of LEDs 100 connected in series, the anodes of the outermost LEDs 100 of the LED strings 10 are connected to the voltage source V _DC , and the cathodes of the outermost LEDs 100 of the LED strings 10 are connected to Input pad 11 of module circuit 2 . The multi-voltage output circuit 20 can be applied to a LED driving system, such as a backlight module of a liquid crystal display, but not limited thereto.

In this embodiment, the feedback regulator circuit mainly includes a voltage control unit 22 and a reference voltage generator 23 . Wherein, the voltage control unit 22 is coupled to these output voltages, generates a first voltage according to these output voltages, and outputs a voltage control signal accordingly. In addition, the reference voltage generator 23 is coupled to the voltage control unit 22 and receives the voltage control signal to generate a reference voltage for feeding back to the multi-voltage output circuit 20 . The above-mentioned voltage control unit 22 can generally be integrated in the module circuit 2 , while the reference voltage generator 23 is made outside the module circuit 2 . However, whether the above-mentioned constituent blocks are fabricated in the same module circuit depends on various application occasions.

In addition, the feedback regulator circuit of this embodiment may further include a module-to-digital voltage converter (ADC) 21 connected to the multi-voltage output circuit 20 and converting these (module) output voltages into multi-digital voltages. These multiple voltages are fed to the voltage control unit 22, which selects one of these digital voltages as the above-mentioned first voltage. FIG. 3 shows a detailed circuit diagram of a module-to-digital converter (ADC) 21 according to an embodiment of the present invention. In this embodiment, the module-to-digital voltage converter (ADC) 21 includes a multiplexer 210 and a module-to-digital voltage conversion (ADC) unit 212 . Wherein, the multiplexer 210 receives the output voltages of the multi-input pads 11 , and selects (or samples) one of them at each time to feed to the ADC unit 212 . The ADC unit 212 converts the output voltage selected by the multiplexer 210 into a digital voltage.

In this embodiment, the voltage control unit 22 includes a logic unit 220 . Wherein, the logic unit 220 selects one of these digital voltages as the above-mentioned first voltage according to a preset rule, and outputs a corresponding voltage control signal. In different embodiments, different preset rules may be adopted according to different requirements. For example, in this embodiment, in order to improve the efficiency of the multi-voltage output circuit 20, the circuit can be designed to take the minimum output voltage to minimize the power consumed by the multi-voltage output circuit. Therefore, the logic unit 220 selects the minimum voltage of these digital voltages as the first voltage. The logic unit 220 may generally be implemented using hardware technology, software technology or a combination thereof.

The reference voltage generator 23 is connected to the logic unit 220 . The reference voltage generator 23 includes a signal generator 232 for generating a waveform according to the voltage control signal generated by the first voltage. In this embodiment, the signal generator 232 is a pulse width modulation signal generator, which generates different pulse widths according to the voltage control signal. In one embodiment, the logic unit 220 compares the first voltage with a target voltage, and generates a voltage control signal based on the difference between the two to enable the signal generator 232 to adjust the pulse width. In detail, the signal generator 232 can adjust the pulse width in proportion to the ratio of the difference to the target voltage. When the feedback system reaches a steady state, the target voltage is adjusted to approach the first voltage. In one embodiment of the present invention, the voltage control unit 22 adjusts the value of the first voltage, and then the reference voltage generator 23 generates a reference voltage, so that the target voltage is adjusted according to the change of the first voltage. In this way, the voltage source connected to the multi-output circuit is also adjusted to reach the system preset or ideal value.

The reference voltage generator 23 of this embodiment further includes a low-pass filter (LPF) 234 for extracting a part of the DC voltage from the modulated waveform output by the signal generator 232 as the reference voltage. FIG. 4 shows a detailed circuit diagram of a low-pass filter (LPF) 234 according to an embodiment of the present invention, which mainly includes a resistor R _LPF and a capacitor C _LPF . Wherein, the resistor R _LPF is connected to the output terminal of the signal generator 232 , and the capacitor C _LPF is connected between the resistor R _LPF and the ground.

The reference voltage generator 23 is controlled by the voltage control signal. By adjusting the duty cycle, the output reference voltage is also adjusted accordingly, and then the voltage source of the multi-voltage output circuit is adjusted, so that the minimum voltage among the multi-output voltages able to stabilize at the target voltage.

The feedback regulator circuit in an embodiment of the present invention may further include a boost controller 24 and a boost power stage circuit 26 . FIG. 5 shows a detailed circuit diagram of the boost controller 24 and the boost power stage circuit 26 according to an embodiment of the present invention. The boost controller 24 is used for comparing the reference voltage output from the reference voltage generator 23 and the voltage of a voltage division point of the adjustable voltage source V _DC of the multi-voltage output circuit, and accordingly outputs a feedback control signal to the boost power stage circuit 26. The boost power stage circuit 26 makes the voltage of the voltage division point of the voltage source V _DC close to the reference voltage according to the feedback control signal, and then adjusts the voltage value of the adjustable voltage source V _DC . The step-up power stage circuit 26 of the present embodiment includes a switching power supply (switching power supply), which mainly includes an N-type metal oxide semiconductor (NMOS) switching transistor SW, and is composed of an inductor L and/or a capacitor C energy storage circuit. The NMOS switching transistor SW is controlled by a voltage control signal to switch the power supply.

In addition to achieving the purpose of feedback voltage regulation, this embodiment can also be used for error detection. For example, when one or more LEDs 100 of a certain LED string 10 fail and short circuit, a certain voltage of the output voltage of the corresponding input pad 11 will increase abnormally. The logic unit 220 can detect the short circuit of a certain LED string 10 by monitoring the voltage of the corresponding input pad 11 of each LED string 10 . In another example, when one or more LEDs 100 of a certain LED string 10 fail to open, the voltage of the corresponding input pad 11 will drop abnormally, and the logic unit 220 can monitor the LED string 10 The corresponding input pad 11 voltage detects the fail open circuit of the LED string 10 . The detected faulty short circuit or open circuit can be further provided to other units of the system for further treatment.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention; all other equivalent changes or modifications that do not deviate from the spirit disclosed by the invention should be included in the claims within a limited range.

Claims (12)

1. A feedback voltage stabilizing circuit, which provides voltage stabilization in a multi-voltage output circuit, and the multi-voltage output circuit outputs a plurality of output voltages, and the feedback voltage stabilizing circuit includes: A voltage control unit, coupled to the output voltages, generates a first voltage according to the output voltages and outputs a voltage control signal accordingly; and A reference voltage generator, coupled to the voltage control unit, receives the voltage control signal and generates a reference voltage for feeding back to the multi-voltage output circuit. 2. The feedback regulator circuit according to claim 1, further comprising: A module-to-digital voltage converter is connected to the multi-voltage output circuit and converts the output voltages into a plurality of digital voltages; wherein the voltage control unit selects one of the digital voltages as the first voltage. 3. The feedback regulator circuit according to claim 1 or 2, wherein the voltage control unit comprises: A logic unit selects one of the digital voltages as the first voltage according to a preset rule and generates the voltage control signal according to the first voltage. 4. The feedback regulator circuit according to claim 3, wherein the reference voltage generator comprises a signal generator, receives the voltage control signal and generates a corresponding output signal, wherein the signal generator is a pulse The width modulation signal generator adjusts a pulse width of the output signal according to the voltage control signal. 5. The feedback regulator circuit as claimed in claim 4, wherein the logic unit compares the first voltage with a target voltage to generate the voltage control signal, and the signal generator adjusts the pulse width accordingly. 6. The feedback regulator circuit as claimed in claim 5, wherein the logic unit generates the voltage control signal according to a difference between the first voltage and the target voltage for the signal generator to adjust the pulse width. 7. The feedback regulator circuit as claimed in claim 6, wherein the logic unit selects a minimum voltage among the digital voltages as the first voltage. 8. The feedback regulator circuit according to claim 6, wherein the logic unit generates the voltage control signal in proportion to the ratio of the difference to the target voltage, and the signal generator adjusts the pulse width accordingly. 9. The feedback voltage stabilizing circuit according to claim 4, wherein said reference voltage generator further comprises: A low-pass filter extracts a DC voltage part from the output signal as the reference voltage. 10. The feedback regulator circuit as claimed in claim 3, wherein the logic unit monitors the output voltages to detect the state of the multi-voltage output circuit. 11. The feedback regulator circuit according to claim 2, wherein the above-mentioned module-to-digital voltage converter comprises: a multiplexer that receives the output voltages and selects one of them at a time; and A module-to-digital voltage conversion unit converts the selected output voltage into a corresponding digital voltage. 12. The feedback regulator circuit according to claim 1, further comprising: a boost controller that compares the reference voltage with a divided voltage of an adjustable voltage source of the multi-voltage output circuit and generates a feedback control signal; and A step-up power stage circuit receives the feedback control signal to make the voltage at the voltage dividing point close to the reference voltage, so as to provide the corresponding adjustable voltage source.

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