A power supply circuit

Abstract

The present invention discloses a power supply circuit. The power supply circuit includes a DC-DC module, an LDO module, a first voltage divider circuit, a voltage-controlled constant current source, and an amplifier circuit. The output end of the DC-DC module is connected to the input end of the LDO module, the input end of the first voltage divider circuit is connected to the output end of the DC-DC module, the output end of the first voltage divider circuit is connected to the feedback input end of the DC-DC module, and the first voltage divider circuit divides the voltage at the input end and outputs it from the output end. The input end of the amplifier circuit inputs a first set voltage, and the output end of the amplifier circuit is connected to the output voltage control end of the LDO module. The first end of the voltage-controlled constant current source inputs a second set voltage, and the second end of the voltage-controlled constant current source is connected to the output end of the first voltage divider circuit. The voltage-controlled constant current source controls the current at its second end according to the voltage at its first end. By adjusting the input signals of the voltage-controlled constant current source and the amplifier circuit, the input and output of the LDO module are controlled to have a stable voltage difference, thereby outputting a voltage signal with low power consumption and low ripple noise.

Description

Technical Field

[0001] The embodiments of the present invention relate to a display module testing technology, and in particular to a power supply circuit. Background Art

[0002] Currently, the power supply for display modules (such as liquid crystal modules) is required to have low ripple noise, output voltage adjustable from 0V and other output characteristics to meet the detection requirements of liquid crystal modules.

[0003] Current power supply designs typically utilize a DC / DC buck power supply solution. However, due to their inherent high-frequency switching characteristics, DC / DC buck power supplies exhibit relatively high output ripple noise, making them difficult to meet low ripple noise requirements. While LDO power supplies can ideally control output ripple noise, a certain voltage difference between the LDO's input voltage and its output voltage is required to ensure a normal voltage output. If this voltage difference increases, the LDO's power consumption increases, leading to increased heat generation. When this heat exceeds the LDO's maximum junction temperature, the LDO will be damaged.

[0004] It can be seen that both the DC / DC buck power supply solution and the sampling LDO power supply have defects and cannot meet the power output requirements of the LCD module during the testing process. Summary of the Invention

[0005] The present invention provides a power supply circuit, which can reliably output a stable voltage and a voltage signal with low ripple noise, thereby reducing interference to a liquid crystal display module.

[0006] An embodiment of the present invention provides a power supply circuit, including a DC-DC module, an LDO module, a first voltage divider circuit, a voltage-controlled constant current source, and an amplifier circuit;

[0007] The output end of the DC-DC module is connected to the input end of the LDO module, the input end of the first voltage divider circuit is connected to the output end of the DC-DC module, the output end of the first voltage divider circuit is connected to the feedback input end of the DC-DC module, and the first voltage divider circuit divides the voltage of the input end and outputs it from the output end;

[0008] The input end of the amplifier circuit inputs a first set voltage, and the output end of the amplifier circuit is connected to the output voltage control end of the LDO module;

[0009] The first end of the voltage-controlled constant current source inputs a second set voltage, the second end of the voltage-controlled constant current source is connected to the output end of the first voltage divider circuit, and the voltage-controlled constant current source controls the current at the second end according to the voltage at the first end.

[0010] Optionally, the voltage-controlled constant current source includes a first resistor, a second resistor, a first transistor and a first operational amplifier;

[0011] The inverting input terminal of the first operational amplifier is grounded via the first resistor, the non-inverting input terminal of the first operational amplifier inputs a second set voltage, and the output terminal of the first operational amplifier is connected to the base of the first transistor via the second resistor;

[0012] The emitter of the first transistor is connected to the inverting input terminal of the first operational amplifier, and the collector of the first transistor is connected to the output terminal of the first voltage divider circuit.

[0013] Optionally, the first voltage divider circuit includes a third resistor and a fourth resistor;

[0014] The first end and the second end of the third resistor serve as the input end and the output end of the first voltage divider circuit respectively. The first end of the fourth resistor is connected to the second end of the third resistor, and the second end of the fourth resistor is grounded.

[0015] Optionally, a second voltage divider circuit is further included, wherein the input end of the second voltage divider circuit is connected to the input end of the amplifier circuit, and the output end of the second voltage divider circuit is connected to the first end of the voltage-controlled constant current source; the second voltage divider circuit divides the voltage of the input end and outputs it from the output end.

[0016] Optionally, it further includes a digital-to-analog conversion circuit and a controller; the input end of the digital-to-analog conversion circuit is connected to the controller, and the output end of the digital-to-analog conversion circuit is connected to the input end of the second voltage divider circuit.

[0017] Optionally, the second voltage divider circuit includes a fifth resistor and a sixth resistor;

[0018] The first end and the second end of the fifth resistor serve as the input end and the output end of the second voltage divider circuit respectively. The first end of the sixth resistor is connected to the second end of the sixth resistor, and the second end of the sixth resistor is grounded.

[0019] Optionally, the amplifying circuit includes a second operational amplifier.

[0020] Optionally, a load current source is further included, and the load current source is connected to the output end of the power supply circuit.

[0021] Optionally, the load current source includes a second transistor and a seventh resistor; the collector of the second transistor is connected to the output end of the power supply circuit, the emitter of the second transistor is connected to the voltage source through the seventh circuit, and the base of the second transistor is grounded.

[0022] Optionally, the emitter of the second transistor is connected to a voltage source that outputs a negative voltage.

[0023] The present invention provides a voltage-controlled constant current source, which extracts current from the feedback input terminal of the DC-DC module. The voltage-controlled constant current source regulates the current entering the feedback input terminal of the DC-DC module, thereby adjusting the output voltage of the DC-DC module, that is, adjusting the input voltage of the LDO module. A first voltage divider circuit is provided, which feeds back the output voltage of the DC-DC module to the feedback input terminal of the DC-DC module, thereby automatically adjusting the output voltage of the DC-DC module when the input voltage of the voltage-controlled constant current source remains unchanged, controlling the DC-DC module to output a stable voltage, that is, providing a stable input voltage for the LDO module when the input voltage remains unchanged. The technical solution provided in this embodiment regulates the output voltage of the DC-DC module through a voltage-controlled constant current source, and by simultaneously regulating the input signals of the voltage-controlled constant current source and the amplifier circuit, ensures that the output voltage of the LDO module has a stable voltage difference with the output voltage of the DC-DC module, thereby ensuring that the LDO module can operate normally. The invention solves the problems of large output voltage ripple noise when using DC-DC power supply and high power consumption when using LDO power supply in the prior art, and provides a stable power supply circuit capable of outputting low ripple noise and low power consumption voltage for liquid crystal display modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of a power supply circuit provided by an embodiment of the present invention;

[0025] Figure 2 is a structural diagram of another power supply circuit provided by an embodiment of the present invention;

[0026] Figure 3 is a structural diagram of another power supply circuit provided by an embodiment of the present invention;

[0027] Figure 4 is a structural diagram of another power supply circuit provided by an embodiment of the present invention;

[0028] Figure 5 It is a structural diagram of another power supply circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0030] Figure 1This is a schematic diagram of a power supply circuit provided by an embodiment of the present invention. This embodiment can be applied to provide power for liquid crystal module detection equipment to minimize the output ripple of the power supply and reduce the power consumption of the power supply. Figure 1 As shown, the power supply circuit includes: a DC-DC module 10, an LDO module 20, a first voltage divider circuit 30, a voltage-controlled constant current source 40 and an amplifier circuit 50;

[0031] The output end of the DC-DC module 10 is connected to the input end of the LDO module 20, the input end of the first voltage divider circuit 30 is connected to the output end of the DC-DC module 10, and the output end of the first voltage divider circuit 30 is connected to the feedback input end FB of the DC-DC module 10. The first voltage divider circuit 30 divides the voltage at the input end and outputs it from the output end;

[0032] The input terminal of the amplifier circuit 50 inputs the first set voltage V1, and the output terminal of the amplifier circuit 50 is connected to the output voltage control terminal Iset of the LDO module 20;

[0033] The first end of the voltage-controlled constant current source 40 inputs the second set voltage V2, and the second end of the voltage-controlled constant current source 40 is connected to the output end of the first voltage divider circuit 30. The voltage-controlled constant current source 40 controls the current at its second end according to the voltage at its first end.

[0034] The input end of the first voltage divider circuit 30 is connected to the output end of the DC-DC module 10, and the output end of the first voltage divider circuit 30 is connected to the feedback input end FB of the DC-DC module 10. The first voltage divider circuit 30 is used to adjust the output voltage Vout1 of the DC-DC module 10 to ensure that the DC-DC module 10 outputs a stable voltage. Because the output end of the DC-DC module 10 is connected to the input end of the LDO module 20, the first voltage divider circuit 30 ensures the stability of the input voltage of the LDO module 20.

[0035] Specifically, when the output voltage Vout1 of the DC-DC module 10 decreases, the output voltage of the first voltage divider circuit 30 decreases. Accordingly, the input voltage of the feedback input terminal FB of the DC-DC module 10 decreases. Based on the output voltage regulation characteristics of the DC-DC module 10, the output voltage Vout1 of the DC-DC module 10 increases. Conversely, when the output voltage Vout1 of the DC-DC module 10 increases, the output voltage of the first voltage divider circuit 30 increases. Accordingly, the input voltage of the feedback input terminal FB of the DC-DC module 10 increases. Based on the output voltage regulation characteristics of the DC-DC module 10, the output voltage Vout1 of the DC-DC module 10 decreases. Thus, the first voltage divider circuit 30 automatically regulates the output voltage Vout1 of the DC-DC module 10, ensuring a stable output voltage from the DC-DC module 10. Because the output terminal of the DC-DC module 10 is connected to the input terminal of the LDO module 20, the first voltage divider circuit 30 provides a stable input voltage for the LDO module 20. Optionally, the DC-DC module 10 may adopt a DC-DC BUCK power supply.

[0036] The input of the amplifier circuit 50 receives a first set voltage V1, and the output of the amplifier circuit 50 is connected to the output voltage control terminal Iset of the LDO module 20. Adjusting the first set voltage V1 adjusts the output voltage Vout2 of the LDO module 20, and the LDO module 20 outputs the output voltage of the power supply circuit. Because the LDO module 20 can adjust the output voltage based on the output voltage control terminal Iset, by inputting the first set voltage V1 to the input of the amplifier circuit 50, the output of the amplifier circuit 50 outputs a voltage corresponding to the first set voltage V1. Furthermore, by adjusting the first set voltage V1, the output voltage of the LDO module 20 can be adjusted to meet power supply requirements. In one embodiment, the LDO module 20 uses the LT3083 chip, which can output 0V. The output voltage of the LT3083 chip is determined by the voltage of its SET pin. This SET pin uses an internal 50uA current source and supports an external resistor to form a voltage reference source. Therefore, by directly supplying a voltage signal to the SET pin, the LDO module 20 can be controlled to output a voltage within a preset range.

[0037] The first terminal of the voltage-controlled constant current source 40 inputs a second set voltage V2, and the second terminal of the voltage-controlled constant current source 40 is connected to the output terminal of the first voltage divider circuit 30. The voltage-controlled constant current source 40 controls the current at its second terminal based on the voltage at its first terminal. Specifically, when the second set voltage V2 increases, the current drawn from the feedback input terminal FB of the DC-DC module 10 by the second terminal of the voltage-controlled constant current source 40 increases. According to the above analysis, the output voltage Vout1 of the DC-DC module 10 increases, that is, the input voltage of the LDO module 20 increases. Conversely, if the second set voltage V2 decreases, the current drawn from the feedback input terminal FB of the DC-DC module 10 by the second terminal of the voltage-controlled constant current source 40 decreases, thereby decreasing the output voltage Vout1 of the DC-DC module 10, that is, decreasing the input voltage of the LDO module 20. It can be seen that under the action of the voltage-controlled constant current source 40, by adjusting the second set voltage, the output voltage Vout1 of the DC-DC module 10 can be adjusted, and then the input voltage of the LDO module 20 can be adjusted, thereby achieving adjustable input voltage of the LDO module 20.

[0038] Based on the above analysis, the first set voltage V1 and the second set voltage V2 determine the input voltage and output voltage of the LDO module 20, respectively. Therefore, by adjusting the voltage distribution between the first set voltage V1 and the second set voltage V2, the input voltage and output voltage of the LDO module 20 can be controlled to maintain a stable voltage difference. This allows the power consumption of the LDO module 20 to remain within the set range even when the load current increases. This solves the problem of increased power consumption caused by the increased voltage difference when using a single LDO power supply, and ensures the normal operation of the LDO module 20. For example, the input and output voltage difference of the LDO module 20 can be controlled to 0.6V, 0.8V, or 1V. In one embodiment provided in an embodiment of the present invention, the first set voltage V1 and the second set voltage V1 are the same voltage.

[0039] The technical solution of this embodiment is to provide a voltage-controlled constant current source 40, which draws current from the feedback input terminal FB of the DC-DC module 10, so that the current entering the feedback input terminal FB of the DC-DC module 10 is regulated by the voltage-controlled constant current source 40, thereby adjusting the output voltage Vout1 of the DC-DC module 10, that is, adjusting the input voltage of the LDO module 20; and to provide a first voltage divider circuit 30, which feeds back the output voltage Vout1 of the DC-DC module 10 to the feedback input terminal FB of the DC-DC module 10, thereby automatically adjusting the output voltage Vout1 of the DC-DC module 10 when the input of the voltage-controlled constant current source 40 remains unchanged, thereby controlling the DC-DC module 10 to output a stable voltage. The technical solution provided by this embodiment uses a voltage-controlled constant current source 40 to regulate the output voltage Vout1 of the DC-DC module 10. By simultaneously adjusting the input signals of the voltage-controlled constant current source 40 and the amplifier circuit 50, a stable voltage difference is ensured between the output voltage Vout2 of the LDO module 20 and the output voltage Vout1 of the DC-DC module 10, thereby ensuring the normal operation of the LDO module 20. This solves the problems of high output voltage ripple noise when using a DC-DC power supply and high power consumption when using an LDO power supply in the prior art, providing a stable power supply circuit for liquid crystal display modules that can output low ripple noise and low power consumption.

[0040] Optional, Figure 2 This is a schematic diagram of another power supply circuit provided by an embodiment of the present invention. Figure 2 As shown, the voltage-controlled constant current source 40 includes a first resistor R1, a second resistor R2, a first transistor Q1 and a first operational amplifier U1;

[0041] The inverting input terminal of the first operational amplifier U1 is grounded via the first resistor R1, the non-inverting input terminal of the first operational amplifier U1 inputs the second set voltage V2, and the output terminal of the first operational amplifier U1 is connected to the base of the first transistor Q1 via the second resistor R2;

[0042] The emitter of the first transistor Q1 is connected to the inverting input terminal of the first operational amplifier U1 , and the collector of the first transistor Q1 is connected to the output terminal of the first voltage divider circuit 30 .

[0043] The second set voltage V2 is applied to the first resistor R1. The first resistor R1 is a current-limiting resistor. By adjusting the voltage of the second set voltage V2, the current in the first resistor R1 is adjusted, and then the collector current of the first transistor Q1 is adjusted. In other words, the current value drawn by the collector of the first transistor Q1 from the feedback input terminal FB of the DC-DC module 10 is adjusted.

[0044] The base of the first transistor Q1 is connected to the output of the first operational amplifier U1, allowing the first operational amplifier U1 to control the base current of the first transistor Q1. This, in turn, controls the collector current of the first transistor Q1 under the action of the first transistor Q1, thereby achieving control of the collector current of the first transistor Q1 through the first operational amplifier U1. Because the non-inverting input of the first operational amplifier U1 is connected to the second set voltage V2, the operational amplifier adjusts the second set voltage V2 to achieve tracking regulation of the collector current of the first transistor Q1. Based on the above analysis, the collector current of the first transistor Q1 is the current extracted from the feedback input terminal FB of the DC-DC module 10. Therefore, adjusting the second set voltage V2 effectively achieves tracking regulation of the voltage at the feedback input terminal FB of the DC-DC module 10, thereby adjusting the input voltage of the LDO module 20.

[0045] After the second set voltage V2 is set, the collector current of the first transistor Q1 can be maintained constant through the action of the first operational amplifier U1 and the first transistor Q1. That is, when the second set voltage V2 is constant, the voltage-controlled constant current source 40 formed by the first operational amplifier U1 and the first transistor Q1 can control the current drawn from the feedback input terminal FB of the DC-DC module 10 to remain constant, that is, control the input voltage of the LDO module 20 to remain constant. Optionally, the first transistor Q1 is an NPN transistor.

[0046] Continue to refer Figure 2 In one embodiment, the first voltage divider circuit 30 includes a third resistor R3 and a fourth resistor R4;

[0047] The first end and the second end of the third resistor R3 serve as the input end and the output end of the first voltage divider circuit 30 respectively. The first end of the fourth resistor R4 is connected to the second end of the third resistor R3 , and the second end of the fourth resistor R4 is grounded.

[0048] The third resistor R3 and the fourth resistor R4 form a voltage divider network that automatically adjusts the output voltage Vout1 of the DC-DC module 10. For example, when the output voltage Vout1 of the DC-DC module 10 decreases, the current flowing through the third resistor R3 and the fourth resistor R4 decreases, thereby reducing the output voltage of the first voltage divider circuit 30 and, consequently, the voltage at the feedback input terminal FB of the DC-DC module 10. Based on the operating characteristics of the DC-DC module 10, the output voltage Vout1 of the DC-DC module 10 increases. Conversely, when the output voltage Vout1 of the DC-DC module 10 increases, the current flowing through the third resistor R3 and the fourth resistor R4 increases, thereby increasing the output voltage of the first voltage divider circuit 30 and causing the voltage at the feedback input terminal FB of the DC-DC module 10 to increase. Based on the operating characteristics of the DC-DC module 10, the output voltage Vout1 of the DC-DC module 10 decreases. Thus, the voltage divider network formed by the third resistor R3 and the fourth resistor R4 maintains a stable output voltage at the output terminal of the DC-DC module 10, providing a stable input voltage for the LDO module 20. The voltage divider network formed by the third resistor R3 and the fourth resistor R4 determines the minimum output voltage of the DC-DC module 10 .

[0049] Optional, Figure 3 This is a schematic diagram of another power supply circuit provided by an embodiment of the present invention. Figure 3 The power supply circuit also includes: a second voltage divider circuit 60, the input end of the second voltage divider circuit 60 is connected to the input end of the amplifier circuit 50, and the output end of the second voltage divider circuit 60 is connected to the first end of the voltage-controlled constant current source 40; the second voltage divider circuit 60 divides the voltage of the input end and outputs it from the output end.

[0050] The output terminal of the second voltage divider circuit 60 outputs a voltage V4, and the input terminal of the second voltage divider circuit 60 receives a voltage V3. Thus, the second voltage divider circuit 60 distributes the input voltages of the voltage-controlled constant current source 40 and the amplifier circuit 50. By adjusting the voltage divider ratio of the second voltage divider circuit 60, the voltage V3 is output to the voltage-controlled constant current source and the amplifier circuit according to a set ratio. Consequently, under a voltage control signal (voltage V3), while the voltage of voltage V3 changes, the voltage of voltage V4 and the voltage output of the amplifier circuit 50 are also changed, thereby changing the output voltage Vout1 of the DC-DC module 10 and the output voltage of the LDO module 20. Specifically, by adjusting the magnitude of voltage V3, the outputs of the DC-DC module 10 and the LDO module 20 are simultaneously adjusted, and the voltage difference between the two power modules is ensured to remain consistent at different output voltage settings. Specifically, the voltage difference between the input and output voltages of the LDO module 20 is stabilized, so that the LDO module 20 outputs the start-up voltage according to the set requirements, thereby reducing the power consumption of the power supply and achieving a low ripple voltage output. In one embodiment, by properly configuring the parameters of the voltage-controlled constant current source 40 , the first voltage divider circuit 30 , and the second voltage divider circuit 60 , the ripple of the output voltage can be controlled within 10 mV.

[0051] Optional, Figure 4 This is a schematic diagram of another power supply circuit provided by an embodiment of the present invention. Figure 4 The power supply circuit further includes a digital-to-analog conversion circuit 80 and a controller 70 ; the input end of the digital-to-analog conversion circuit 80 is connected to the controller 70 , and the output end of the digital-to-analog conversion circuit 80 is connected to the input end of the second voltage divider circuit 60 .

[0052] The controller 70 is configured to output a voltage V3 through the digital-to-analog conversion circuit 80. This voltage V3 serves as the input voltage of the amplifier circuit 50 and the input voltage of the second voltage divider circuit 60. This embodiment, by providing the controller 70 and the digital-to-analog conversion circuit 80, outputs a voltage signal that serves as both the input voltage source for the DC-DC module 10 and the input voltage source for the LDO module 20. This allows the output voltage of the power supply circuit to be adjusted from 0V under the control of a single voltage signal, thereby reducing power consumption and achieving low ripple voltage output.

[0053] Continue to refer Figure 4 In one embodiment, the second voltage divider circuit 60 adopts a resistor voltage divider circuit. Specifically, the second voltage divider circuit 60 includes a fifth resistor R5 and a sixth resistor R6;

[0054] The first and second ends of the fifth resistor R5 serve as the input and output ends of the second voltage divider circuit 60 respectively. The first end of the sixth resistor R6 is connected to the second end of the sixth resistor R6 , and the second end of the sixth resistor R6 is grounded.

[0055] The second voltage divider circuit 60 outputs the divided voltage of the sixth resistor R6 as a voltage V4. Furthermore, under the action of the second voltage divider circuit 60 composed of the fifth resistor R5 and the sixth resistor R6, when the digital-to-analog converter 80 outputs a maximum voltage, the input voltage of the voltage-controlled constant current source 40 is always lower than the voltage at the feedback input terminal FB of the DC-DC module 10.

[0056] In one embodiment, the amplifier circuit 50 includes a second operational amplifier. The second operational amplifier linearly amplifies the input voltage V3. This voltage V3 can be set based on the output voltage requirements of the LDO module 20. Specifically, by adjusting the magnitude of voltage V3, the LDO module 20 can be controlled to output a voltage signal that meets the requirements. For example, in one embodiment, by adjusting voltage V3, the output voltage Vout2 of the LDO module 20 can be set to 0V to 15V.

[0057] Optional, Figure 5 This is a schematic diagram of another power supply circuit provided by an embodiment of the present invention. Figure 5 The power supply circuit further includes a load current source 90, which is connected to the output end of the power supply circuit.

[0058] Among them, the load current source 90 can ensure that no matter what the voltage output by the LDO module 20 is, a fixed load can be provided for the LDO module 20 to ensure that the LDO module 20 can work normally. Especially when the output end of the LDO module 20 is unloaded, the load current source 90 provides a load current for the LDO module 20, allowing the LDO module 20 to work stably. Because in order for the LDO module 20 to work stably, there is a requirement that when the output is unloaded, a load current of 1mA must be added to the output of this LDO. Because the output voltage of the LDO module 20 is required to be digitally adjustable from 0V, it is not possible to simply add a resistor to set the load current. A fixed load current source 90 is added to the output end of the LDO module 20, so that no matter what the voltage output by the LDO module 20 is, there will be a fixed load to ensure the normal operation of the LDO.

[0059] Continue to refer Figure 5 In one embodiment, the load current source 90 includes a second transistor Q2 and a seventh resistor R7; the collector of the second transistor Q2 is connected to the output end of the power supply circuit, the emitter of the second transistor Q2 is connected to the voltage source through the seventh circuit, and the base of the second transistor Q2 is grounded.

[0060] The resistance of the seventh resistor R7 determines the current value drawn from the output voltage Vout2 of the LDO module 20. This current value serves as the fixed load current of the LDO module 20 to ensure that the LDO module 20 can operate normally when no load is connected. Optionally, the second transistor Q2 is an NPN transistor.

[0061] Continue to refer Figure 5 In one embodiment, the emitter of the second transistor Q2 is connected to a voltage source Vcc that outputs a negative voltage. For example, a -5V voltage source is connected to the emitter of the second transistor Q2. The -5V voltage source controls the emitter current of the second transistor Q2 through the seventh resistor R7, thereby controlling the collector current of the second transistor Q2 and providing a fixed load current for the LDO module 20.

[0062] An embodiment of the present invention provides a power supply circuit. The power supply circuit adopts a DC-DC module to provide an input voltage for an LDO module, and the output voltage of the LDO module serves as the output voltage of the power supply circuit. By setting a digital-to-analog conversion circuit to output a voltage control signal (voltage V3), and using the voltage V3 control signal to provide an output voltage for the DC-DC module and the LDO module, the input voltage and output voltage of the LDO module are adjusted by adjusting the voltage control signal. When the voltage control signal is stable, a voltage-controlled constant current source is used to stably draw current from the feedback input terminal of the DC-DC module. Then, a first voltage divider circuit is used to control the DC-DC module to output a stable voltage. When the voltage control signal is stable, stable input voltage and output voltage are provided to the LDO module, that is, the voltage difference of the LDO module is controlled to be stable, thereby reducing the power consumption of the power supply. By adjusting the voltage V3 at the input terminal of the amplifier circuit, the output voltage of the DC-DC module and the LDO module are adjusted, so that the output voltage of the LDO module can be adjusted from 0V. Finally, the output of the LDO module has a voltage signal with low ripple noise, providing a stable power supply circuit for the liquid crystal display module that can output low ripple noise and low power consumption.

[0063] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A power supply circuit, characterized in that: It includes a DC-DC module, an LDO module, a first voltage divider circuit, a voltage-controlled constant current source and an amplifier circuit; The output end of the DC-DC module is connected to the input end of the LDO module, the input end of the first voltage divider circuit is connected to the output end of the DC-DC module, the output end of the first voltage divider circuit is connected to the feedback input end of the DC-DC module, and the first voltage divider circuit divides the voltage of the input end and outputs it from the output end; The input end of the amplifier circuit inputs a first set voltage, and the output end of the amplifier circuit is connected to the output voltage control end of the LDO module; A second set voltage is input to the first end of the voltage-controlled constant current source, and a second end of the voltage-controlled constant current source is connected to the output end of the first voltage divider circuit, and the voltage-controlled constant current source controls the current at the second end according to the voltage at the first end; It also includes a second voltage divider circuit, the input end of the second voltage divider circuit is connected to the input end of the amplifier circuit, and the output end of the second voltage divider circuit is connected to the first end of the voltage-controlled constant current source; the second voltage divider circuit divides the voltage of the input end and outputs it from the output end.

2. The power supply circuit according to claim 1, wherein: The voltage-controlled constant current source includes a first resistor, a second resistor, a first transistor and a first operational amplifier; The inverting input terminal of the first operational amplifier is grounded via the first resistor, the non-inverting input terminal of the first operational amplifier inputs a second set voltage, and the output terminal of the first operational amplifier is connected to the base of the first transistor via the second resistor; The emitter of the first transistor is connected to the inverting input terminal of the first operational amplifier, and the collector of the first transistor is connected to the output terminal of the first voltage divider circuit.

3. The power supply circuit according to claim 1, wherein: The first voltage divider circuit includes a third resistor and a fourth resistor; The first end and the second end of the third resistor serve as the input end and the output end of the first voltage divider circuit respectively. The first end of the fourth resistor is connected to the second end of the third resistor, and the second end of the fourth resistor is grounded.

4. The power supply circuit according to claim 1, wherein: It also includes a digital-to-analog conversion circuit and a controller; the input end of the digital-to-analog conversion circuit is connected to the controller, and the output end of the digital-to-analog conversion circuit is connected to the input end of the second voltage divider circuit.

5. The power supply circuit according to claim 1, wherein: The second voltage divider circuit includes a fifth resistor and a sixth resistor; The first end and the second end of the fifth resistor serve as the input end and the output end of the second voltage divider circuit respectively. The first end of the sixth resistor is connected to the second end of the sixth resistor, and the second end of the sixth resistor is grounded.

6. The power supply circuit according to claim 1, wherein: The amplifying circuit includes a second operational amplifier.

7. The power supply circuit according to claim 1, wherein: It also includes a load current source, which is connected to the output end of the power supply circuit.

8. The power supply circuit according to claim 7, wherein: The load current source includes a second transistor and a seventh resistor; the collector of the second transistor is connected to the output end of the power supply circuit, the emitter of the second transistor is connected to the voltage source through the seventh resistor, and the base of the second transistor is grounded.

9. The power supply circuit according to claim 8, wherein: The emitter of the second transistor is connected to a voltage source that outputs a negative voltage.

Images