CN212231334U

CN212231334U - Power supply circuit

Info

Publication number: CN212231334U
Application number: CN202020280582.4U
Authority: CN
Inventors: 樊定
Original assignee: Suzhou HYC Technology Co Ltd
Current assignee: Suzhou HYC Technology Co Ltd
Priority date: 2020-03-09
Filing date: 2020-03-09
Publication date: 2020-12-25
Anticipated expiration: 2030-03-09

Abstract

The utility model discloses a power supply circuit. The power supply circuit comprises a DC-DC module, an LDO module, a first voltage division circuit, a voltage-controlled constant current source and an amplifying circuit; the output end of the DC-DC module is connected with the input end of the LDO module, the input end of the first voltage division circuit is connected with the output end of the DC-DC module, the output end of the first voltage division circuit is connected with the feedback input end of the DC-DC module, and the first voltage division circuit divides the voltage of the input end and outputs the voltage from the output end; the input end of the amplifying circuit inputs a first set voltage, and the output end of the amplifying circuit is connected with the output voltage control end of the LDO module; 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 with the output end of the first voltage division circuit, and the voltage-controlled constant current source controls the current of the second end according to the voltage of the first end. The input and output of the LDO module are controlled to have stable voltage difference by adjusting the input signals of the voltage-controlled constant current source and the amplifying circuit, so that a voltage signal with low power consumption and low ripple noise is output.

Description

Power supply circuit

Technical Field

The embodiment of the utility model provides a relate to display module assembly test technique, especially relate to a power supply circuit.

Background

Currently, a power supply for supplying power to a display module (e.g., a liquid crystal module) requires output characteristics such as low ripple noise and 0V start-up of output voltage, so as to meet the detection requirements of the liquid crystal module.

In the existing power supply design, a DC/DC BUCK power supply scheme is generally adopted, but the DC/DC BUCK power supply has relatively large output ripple noise due to the high-frequency switching characteristic of the DC/DC BUCK power supply, and the DC/DC BUCK power supply cannot meet the requirement of low ripple noise. If the LDO power supply is adopted, although the output ripple noise can be controlled more ideally, the input voltage of the LDO power supply must have a certain voltage difference with the output voltage thereof to ensure that the LDO power supply has a normal voltage output.

Therefore, the DC/DC BUCK power supply scheme or the LDO power supply sampling scheme has defects, and the output requirement of the liquid crystal module on the power supply in the detection process cannot be met.

SUMMERY OF THE UTILITY MODEL

The utility model provides a power supply circuit, this power supply circuit can reliably export steady voltage to can export the voltage signal of low ripple noise, reduce the interference to the liquid crystal display module assembly.

The embodiment of the utility model provides a power supply circuit, including DC-DC module, LDO module, first voltage division circuit, voltage-controlled constant current source and amplifier circuit;

the output end of the DC-DC module is connected with the input end of the LDO module, the input end of the first voltage division circuit is connected with the output end of the DC-DC module, the output end of the first voltage division circuit is connected with the feedback input end of the DC-DC module, and the first voltage division circuit divides the voltage of the input end and outputs the voltage from the output end;

a first set voltage is input to the input end of the amplifying circuit, and the output end of the amplifying circuit is connected with the output voltage control end of the LDO module;

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 with the output end of the first voltage division circuit, and the current of the second end of the voltage-controlled constant current source is controlled according to the voltage of the first end of the voltage-controlled constant current source.

Optionally, the voltage-controlled constant current source includes a first resistor, a second resistor, a first triode, and a first operational amplifier;

the inverting input end of the first operational amplifier is grounded through the first resistor, the non-inverting input end of the first operational amplifier inputs a second set voltage, and the output end of the first operational amplifier is connected with the base electrode of the first triode through the second resistor;

and the emitter of the first triode is connected with the inverting input end of the first operational amplifier, and the collector of the first triode is connected with the output end of the first voltage division circuit.

Optionally, the first voltage dividing circuit includes a third resistor and a fourth resistor;

the first end and the second end of the third resistor are respectively used as the input end and the output end of the first voltage division circuit, the first end of the fourth resistor is connected with the second end of the third resistor, and the second end of the fourth resistor is grounded.

Optionally, the voltage-controlled constant current source further comprises a second voltage-dividing circuit, an input end of the second voltage-dividing circuit is connected with an input end of the amplifying circuit, and an output end of the second voltage-dividing circuit is connected with the first end of the voltage-controlled constant current source; and the second voltage division circuit divides the voltage of the input end and outputs the voltage from the output end.

Optionally, the system further comprises a digital-to-analog conversion circuit and a controller; the input end of the digital-to-analog conversion circuit is connected with the controller, and the output end of the digital-to-analog conversion circuit is connected with the input end of the second voltage division circuit.

Optionally, the second voltage dividing circuit includes a fifth resistor and a sixth resistor;

a first end and a second end of the fifth resistor are respectively used as an input end and an output end of the second voltage division circuit, the first end of the sixth resistor is connected with the second end of the sixth resistor, and the second end of the sixth resistor is grounded.

Optionally, the amplifying circuit comprises a second operational amplifier.

Optionally, the power supply further comprises a load current source, and the load current source is connected with the output end of the power supply circuit.

Optionally, the load current source includes a second triode and a seventh resistor; and the collector of the second triode is connected with the output end of the power circuit, the emitter of the second triode is connected with a voltage source through the seventh resistor, and the base of the second triode is grounded.

Optionally, an emitter of the second triode is connected to a voltage source outputting a negative voltage.

The embodiment of the utility model provides a through setting up voltage-controlled constant current source, draw the electric current from the feedback input end of DC-DC module by voltage-controlled constant current source to adjust the electric current that gets into DC-DC module feedback input end through voltage-controlled constant current source, realize adjusting the output voltage of DC-DC module, realized adjusting the input voltage of LDO module promptly; by arranging the first voltage division circuit, the output voltage of the DC-DC module is fed back to the feedback input end of the DC-DC module by the first voltage division circuit, so that the output voltage of the DC-DC module is automatically regulated when the input voltage of the voltage-controlled constant current source is unchanged, the DC-DC module is controlled to output stable voltage, and stable input voltage is provided for the LDO module when the input voltage is unchanged. According to the technical scheme provided by the embodiment, the output voltage of the DC-DC module is regulated by the voltage-controlled constant current source, and the voltage-controlled constant current source and the input signal of the amplifying circuit are regulated simultaneously, so that a stable voltage difference is ensured between the output voltage of the LDO module and the output voltage of the DC-DC module, and the LDO module can work normally. The problem of output voltage ripple noise when using DC-DC power among the prior art big and the big consumption when using the LDO power is solved, the power supply circuit of the stable work that can export low ripple noise and low-power consumption voltage is provided for the liquid crystal display module.

Drawings

Fig. 1 is a schematic structural diagram of a power supply circuit according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention;

fig. 4 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention;

fig. 5 is a schematic structural diagram of another power circuit according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 1 is the embodiment of the utility model provides a pair of power supply circuit's schematic structure diagram, this embodiment is applicable to and provides the power for liquid crystal module check out test set to control the output ripple of power to the minimum, and reduce the consumption of power. As shown in fig. 1, the power supply circuit includes: the voltage-controlled constant current source circuit comprises a DC-DC module 10, an LDO module 20, a first voltage division circuit 30, a voltage-controlled constant current source 40 and an amplifying circuit 50;

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, the output end of the first voltage divider circuit 30 is connected to the feedback input end FB of the DC-DC module 10, and the first voltage divider circuit 30 divides the voltage at the input end and outputs the divided voltage from the output end;

the input end of the amplifying circuit 50 inputs a first set voltage V1, and the output end of the amplifying circuit 50 is connected with the output voltage control end Iset of the LDO module 20;

the first end of the voltage-controlled constant current source 40 inputs the second setting voltage V2, the second end of the voltage-controlled constant current source 40 is connected to the output end of the first voltage-dividing circuit 30, and the voltage-controlled constant current source 40 controls the current at the second end according to the voltage at the first end.

The input end of the first voltage dividing circuit 30 is connected to the output end of the DC-DC module 10, the output end of the first voltage dividing circuit 30 is connected to the feedback input end FB of the DC-DC module 10, and the output voltage Vout1 of the DC-DC module 10 is adjusted by the first voltage dividing circuit 30, so as to ensure that the DC-DC module 10 outputs a stable voltage. Since the output terminal of DC-DC module 10 is connected to the input terminal of LDO module 20, the input voltage of LDO module 20 is stabilized by first voltage divider circuit 30.

Specifically, when the output voltage Vout1 of the DC-DC module 10 decreases, the output voltage of the first voltage dividing circuit 30 decreases, and accordingly, the input voltage of the feedback input terminal FB of the DC-DC module 10 decreases, and according to the output voltage regulation characteristic of the DC-DC module 10, at this time, the output voltage Vout1 of the DC-DC module 10 becomes large; in contrast, when the output voltage Vout1 of the DC-DC module 10 increases, the output voltage of the first voltage dividing circuit 30 increases, and accordingly, the input voltage of the feedback input terminal FB of the DC-DC module 10 increases, and at this time, the output voltage Vout1 of the DC-DC module 10 becomes smaller according to the regulation characteristic of the output voltage of the DC-DC module 10. It can be seen that, through the first voltage dividing circuit 30, the output voltage Vout1 of the DC-DC module 10 can be automatically adjusted, and the DC-DC module 10 is guaranteed to output a stable voltage, because the output terminal of the DC-DC module 10 is connected to the input terminal of the LDO module 20, therefore, through the first voltage dividing circuit 30, the purpose of providing a stable input voltage for the LDO module 20 is achieved. Alternatively, the DC-DC module 10 may employ a DC-DC type BUCK power supply.

The input end of the amplifying circuit 50 inputs the first setting voltage V1, and the output end of the amplifying circuit 50 is connected to the output voltage control end Iset of the LDO module 20, so that the output voltage Vout2 of the LDO module 20 can be adjusted by adjusting the first setting voltage V1, and the output voltage of the power circuit is output by the LDO module 20. Since the LDO module 20 can adjust the magnitude of the output voltage according to the output voltage control terminal Iset, the output terminal of the amplifying circuit 20 outputs a voltage corresponding to the first setting voltage V1 by inputting the first setting voltage V1 to the input terminal of the amplifying circuit 50; furthermore, the output voltage of LDO module 20 is adjusted by changing first setting voltage V1, so that the range of the output voltage of LDO module 20 can be adjusted to meet the power supply requirement. In an embodiment, the LDO module 20 selects an LT3083 chip capable of outputting a voltage of 0V, an output voltage of the LT3083 chip is determined by a voltage of an SET pin, and the SET pin supports an external resistor through a current source of an internal 50uA to form a voltage reference source, so that the LDO module 20 is controlled to output a voltage within a preset range by directly supplying a voltage signal to the SET pin.

The first end of the voltage-controlled constant current source 40 inputs the second setting voltage V2, the second end of the voltage-controlled constant current source 40 is connected to the output end of the first voltage-dividing circuit 30, and the voltage-controlled constant current source 40 controls the current at the second end according to the voltage at the first end. Specifically, when the second setting voltage V2 increases, the current drawn by the second terminal of the voltage-controlled constant current source 40 from the feedback input terminal FB of the DC-DC module 10 increases, and 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 setting voltage V2 decreases, the current drawn by the second terminal of the voltage-controlled constant current source 40 from the feedback input terminal FB of the DC-DC module 10 decreases, so that the output voltage Vout1 of the DC-DC module 10 decreases, i.e., the input voltage of the LDO module 20 decreases. It can be seen that, under the action of the voltage-controlled constant current source 40, the output voltage Vout1 of the DC-DC module 10 can be adjusted by adjusting the second setting voltage, and then the input voltage of the LDO module 20 is adjusted, so that the input voltage of the LDO module 20 can be adjusted.

According to the above analysis, the first setting voltage V1 and the second setting voltage V2 respectively determine the input voltage and the output voltage of the LDO module 20, so that the input voltage and the output voltage of the LDO module 20 can be controlled to maintain a stable voltage difference by adjusting the voltage distribution of the first setting voltage V1 and the second setting voltage V2, so that the power consumption of the LDO module 20 can still be controlled within a setting range under the condition that the load current increases, thereby solving the problem of power consumption increase caused by the increase of the voltage difference when the LDO power supply is used alone, and ensuring that the LDO module 20 can normally operate. For example, the input and output voltage difference of LDO module 20 may be controlled to be 0.6V, 0.8V, or 1V. In an embodiment of the present invention, the first setting voltage V1 and the second setting voltage V1 are the same voltage.

In the technical scheme of this embodiment, by setting the voltage-controlled constant current source 40, the voltage-controlled constant current source 40 extracts 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 adjusted by the voltage-controlled constant current source 40, and the output voltage Vout1 of the DC-DC module 10 is adjusted, that is, the input voltage of the LDO module 20 is adjusted; by arranging the first voltage dividing circuit 30, the output voltage Vout1 of the DC-DC module 10 is fed back to the feedback input terminal FB of the DC-DC module 10 by the first voltage dividing circuit 30, so that the output voltage Vout1 of the DC-DC module 10 is automatically adjusted when the input of the voltage-controlled constant current source 40 is unchanged, and the DC-DC module 10 is controlled to output a stable voltage. In the technical scheme provided by this embodiment, the output voltage Vout1 of the DC-DC module 10 is adjusted by a voltage-controlled constant current source 40, and the input signals of the voltage-controlled constant current source 40 and the amplifying circuit 50 are adjusted at the same time, so that 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 that the LDO module 20 can work normally. The problem of output voltage ripple noise when using DC-DC power among the prior art big and the big consumption when using the LDO power is solved, the power supply circuit of the stable work that can export low ripple noise and low-power consumption voltage is provided for the liquid crystal display module.

Optionally, fig. 2 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention. On the basis of the above embodiment, as shown in fig. 2, 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;

the inverting input end of the first operational amplifier U1 is grounded through a first resistor R1, the non-inverting input end of the first operational amplifier U1 inputs a second set voltage V2, and the output end of the first operational amplifier U1 is connected with the base of a first triode Q1 through a second resistor R2;

an emitter of the first transistor Q1 is connected to an inverting input of the first operational amplifier U1, and a collector of the first transistor Q1 is connected to an output of the first voltage divider circuit 30.

Wherein the second setting voltage V2 is applied to the first resistor R1. The first resistor R1 is a current-limiting resistor, and adjusts the current of the first resistor R1 by adjusting the voltage of the second set voltage V2, and then adjusts the collector current of the first transistor Q1, i.e., the current value drawn by the collector of the first transistor Q1 from the feedback input terminal FB of the DC-DC module 10.

The base of the first triode Q1 is communicated with the output end of the first operational amplifier U1, so that the first operational amplifier U1 controls the base current of the first triode Q1, and further, under the action of the first triode Q1, the collector current of the first triode Q1 is controlled, and therefore the collector current of the first triode Q1 is controlled through the first operational amplifier U1. Since the non-inverting input terminal of the first operational amplifier U1 is connected to the second setting voltage V2, the adjustment of the second setting voltage V2 realizes the following adjustment of the collector current of the first transistor Q1 under the action of the operational amplifier. According to the above analysis, the collector current of the first transistor Q1 is the extracted current of the feedback input terminal FB of the DC-DC module 10, so that the following regulation of the voltage of the feedback input terminal FB of the DC-DC module 10, i.e. the following regulation of the input voltage of the LDO module 20, is substantially realized by regulating the second setting voltage V2.

After the second setting voltage V2 is set, the current of the collector of the first transistor Q1 can be maintained constant by the action of the first operational amplifier U1 and the first transistor Q1, that is, at a certain time of the second setting voltage V2, the voltage-controlled constant current source 40 composed of 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 be maintained constant, that is, the input voltage of the LDO module 20 to be maintained constant. Optionally, the first transistor Q1 is an NPN transistor.

With continued reference to fig. 2, in one embodiment, the first voltage divider circuit 30 includes a third resistor R3 and a fourth resistor R4;

a first terminal and a second terminal of the third resistor R3 are respectively used as an input terminal and an output terminal of the first voltage divider circuit 30, a first terminal of the fourth resistor R4 is connected to a second terminal of the third resistor R3, and a second terminal of the fourth resistor R4 is grounded.

The third resistor R3 and the fourth resistor R4 form a voltage divider network, and automatically adjust 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, so that the output voltage of the first voltage dividing circuit 30 decreases, so that the voltage of the feedback input terminal FB of the DC-DC module 10 decreases, and at this time, the output voltage Vout1 of the DC-DC module 10 increases according to the operating characteristics of the DC-DC module 10. In contrast, 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, so that the output voltage of the first voltage dividing circuit 30 increases, resulting in an increase in the voltage of the feedback input terminal FB of the DC-DC module 10, at which time the output voltage Vout1 of the DC-DC module 10 decreases according to the operating characteristics of the DC-DC module 10. Therefore, the DC-DC module 10 keeps the output of the output terminal outputting a stable voltage through the voltage dividing network formed by the third resistor R3 and the fourth resistor R4, and provides a stable input voltage for the LDO module 20. The voltage dividing network formed by the third resistor R3 and the fourth resistor R4 determines the minimum output voltage of the DC-DC module 10.

Optionally, fig. 3 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 3, the power supply circuit further includes: a second voltage dividing circuit 60, an input end of the second voltage dividing circuit 60 is connected with an input end of the amplifying circuit 50, and an output end of the second voltage dividing circuit 60 is connected with a first end of the voltage-controlled constant current source 40; the second voltage dividing circuit 60 divides the voltage at the input terminal and outputs the divided voltage from the output terminal.

Wherein, the output end of the second voltage dividing circuit 60 outputs a voltage V4, the input end of the second voltage dividing circuit 60 inputs a voltage V3, so that the voltage distribution of the input voltages of the voltage-controlled constant current source 40 and the amplifying circuit 50 is completed by the second voltage dividing circuit 60, the voltage V3 is output to the voltage-controlled constant current source and the amplifying circuit according to the set proportion by adjusting the voltage dividing proportion of the second voltage dividing circuit 60, so that the voltage V3 is changed under a voltage control signal (voltage V3), and simultaneously the voltage V4 and the voltage output by the amplifying circuit 50 are changed, and then the output voltage Vout1 of the DC-DC module 10 and the voltage output by the LDO module 20 are changed, that is, the output of the DC-DC module 10 and the LDO module 20 is adjusted by adjusting the magnitude of the voltage V3, and the voltage difference between the two power modules is ensured to be always consistent when different output voltages are set, the voltage difference between the input voltage and the output voltage of the LDO module 20 is controlled to be stable, the regulated voltage is output by the LDO module 20 according to the setting requirement, the power consumption of the power supply is reduced, and the low ripple voltage output is realized. In one embodiment, the ripple of the output voltage can be controlled within 10mV by properly configuring the parameters of the voltage-controlled constant current source 40, the first voltage-dividing circuit 30, and the second voltage-dividing circuit 60.

Optionally, fig. 4 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 4, the power supply circuit further includes a digital-to-analog conversion circuit 80 and a controller 70; an input terminal of the digital-to-analog conversion circuit 80 is connected to the controller 70, and an output terminal of the digital-to-analog conversion circuit 80 is connected to an input terminal of the second voltage division circuit 60.

The controller 70 is configured to output a voltage V3 through the digital-to-analog conversion circuit 80, wherein the voltage V3 is used as the input voltage of the amplifying circuit 50 and is used as the input voltage of the second voltage dividing circuit 60. In this embodiment, the controller 70 and the digital-to-analog conversion circuit 80 are arranged to output a voltage signal, which is used as an input voltage source of the DC-DC module 10 and an input voltage source of the LDO module 20, so that the output voltage of the power circuit is adjusted from 0V under the control of a voltage signal, thereby reducing the power consumption of the power supply and realizing low ripple voltage output.

With continued reference to fig. 4, in one embodiment, the second voltage divider circuit 60 employs a resistive voltage divider circuit, and in particular, the second voltage divider circuit 60 includes a fifth resistor R5 and a sixth resistor R6;

a first terminal and a second terminal of the fifth resistor R5 are respectively used as an input terminal and an output terminal of the second voltage-dividing circuit 60, a first terminal of the sixth resistor R6 is connected to a second terminal of the sixth resistor R6, and a second terminal of the sixth resistor R6 is grounded.

The second voltage dividing circuit 60 outputs the divided voltage value of the sixth resistor R6 as a voltage V4. Meanwhile, under the action of the second voltage dividing circuit 60 composed of the fifth resistor R5 and the sixth resistor R6, the input voltage of the voltage-controlled constant current source 40 is smaller than the voltage of the feedback input terminal FB of the DC-DC module 10 when the digital-to-analog conversion circuit 80 outputs the maximum voltage.

In one embodiment, the amplification circuit 50 includes a second operational amplifier. The second operational amplifier linearly amplifies the input voltage V3, and the voltage V3 can be set according to the requirement of the output voltage of LDO module 20, that is, by adjusting the voltage V3, LDO module 20 can be controlled to output a voltage signal meeting the requirement. For example, in one embodiment, by adjusting voltage V3, the output voltage Vout2 of LDO module 20 is 0V 15V.

Optionally, fig. 5 is a schematic structural diagram of another power circuit provided in an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 5, the power circuit further includes a load current source 90, and the load current source 90 is connected to the output terminal of the power circuit.

Load current source 90 can provide a fixed load for LDO module 20 to ensure that LDO module 20 can operate normally, regardless of the voltage output by LDO module 20. Especially, when the output of LDO module 20 is idle, load current source 90 provides load current for LDO module 20, so that LDO module 20 can operate stably. Because LDO module 20 is intended to operate stably, there is a requirement that a load current of 1mA must be applied to the output of the LDO when the output is idle. Since the output voltage of 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, and a fixed load current source 90 is added to the output of LDO module 20, so that it is ensured that there is a fixed load to ensure the normal operation of LDO regardless of the output voltage of LDO module 20,

with continued reference to fig. 5, in one embodiment, the load current source 90 includes a second transistor Q2 and a seventh resistor R7; the collector of the second triode Q2 is connected with the output end of the power circuit, the emitter of the second triode Q2 is connected with the voltage source through the seventh resistor, and the base of the second triode Q2 is grounded.

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

With continued reference to fig. 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, and the-5V voltage source controls the emitter current of the second transistor Q2 through the seventh resistor R7, so as to control the collector current of the second transistor Q2, and provide a fixed load current for the LDO module 20.

The embodiment of the utility model provides a through providing a power supply circuit, this power supply circuit adopts the DC-DC module to provide input voltage for the LDO module, and the output voltage of LDO module is as this power supply circuit's output voltage. The digital-to-analog conversion circuit is arranged to output a voltage control signal (voltage V3), and the voltage V3 control signal is used for providing output voltage for the DC-DC module and the LDO module, so that the input voltage and the output voltage of the LDO module can be regulated by regulating the voltage control signal; when the voltage control signal is stable, the voltage-controlled constant current source is used for stably extracting current from the feedback input end of the DC-DC module, and then the first voltage division circuit is used for controlling the DC-DC module to output stable voltage, so that when the voltage control signal is stable, stable input voltage and output voltage are provided for the LDO module, namely, the voltage difference stability of the LDO module is controlled, and the power consumption of the power supply is reduced; the output voltage of the DC-DC module and the LDO module is adjusted by adjusting the voltage V3 at the input end of the amplifying circuit, the output voltage of the LDO module can be adjusted from 0V, the output of the LDO module has a voltage signal with low ripple noise, and a power supply circuit capable of outputting the stable work of the low ripple noise and the low power consumption voltage is provided for the liquid crystal display module.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims

1. A power supply circuit is characterized by comprising a DC-DC module, an LDO module, a first voltage division circuit, a voltage-controlled constant current source and an amplifying circuit;

2. The power supply circuit according to claim 1, wherein the voltage-controlled constant current source comprises a first resistor, a second resistor, a first triode, and a first operational amplifier;

3. The power supply circuit according to claim 1, wherein the first voltage dividing circuit includes a third resistor and a fourth resistor;

4. The power supply circuit according to claim 1, further comprising a second voltage divider circuit, an input terminal of the second voltage divider circuit being connected to an input terminal of the amplifier circuit, an output terminal of the second voltage divider circuit being connected to the first terminal of the voltage-controlled constant current source; and the second voltage division circuit divides the voltage of the input end and outputs the voltage from the output end.

5. The power supply circuit of claim 4, further comprising a digital-to-analog conversion circuit and a controller; the input end of the digital-to-analog conversion circuit is connected with the controller, and the output end of the digital-to-analog conversion circuit is connected with the input end of the second voltage division circuit.

6. The power supply circuit according to claim 4, wherein the second voltage dividing circuit includes a fifth resistor and a sixth resistor;

7. The power supply circuit according to claim 1, wherein the amplification circuit comprises a second operational amplifier.

8. The power supply circuit of claim 1, further comprising a load current source connected to an output of the power supply circuit.

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

10. The power supply circuit of claim 9, wherein an emitter of the second transistor is coupled to a voltage source that outputs a negative voltage.