A switching power supply circuit

Abstract

An embodiment of the present invention discloses a switching power supply circuit, which includes: a BUCK power supply converter and an output voltage regulation circuit, wherein the output end of the BUCK power supply converter is grounded, and the ground of the switching power supply circuit is used as the output end to output a negative voltage; the output voltage regulation circuit includes a digital-to-analog converter and a common-phase operational amplifier circuit, and the output voltage regulation circuit is used to implement digital regulation of the negative voltage output by the switching power supply circuit according to the first control signal received by the digital-to-analog converter. The circuit structure of the present invention is simple, the space occupied is small, and the cost is relatively low; at the same time, the risks brought by a single dedicated chip supplier can be avoided. And unlike dedicated chips, it will not be affected by the selection of devices, and the output power is limited.

Description

Technical Field

[0001] The present invention relates to the field of display screen testing, and more specifically, to a switching power supply circuit for display screen testing. Background Art

[0002] In the detection equipment of display screens such as LCD modules, a negative power supply voltage needs to be provided to the LCD module. Depending on the LCD module, the required negative voltage is different, and the power will also vary greatly. Often, the larger the size of the module, the greater the power of the negative voltage required; and modules of different specifications may require different negative power supply voltage values, so the negative voltage needs to be made digitally adjustable. Providing a negative power supply voltage to the LCD module usually includes the following methods:

[0003] 1: Under normal circumstances, if a negative power supply is required, an isolated switching power supply solution can be provided by reversing the output voltage;

[0004] 2: If the power required by the module is different, that is, the load current is very small, a linear regulator (LDO) with negative voltage input and negative voltage output can be used to provide it;

[0005] 3: The power chip supplier provides a proprietary non-isolated inverting converter switching power supply chip solution that can output negative voltage.

[0006] The first method is a way for the switching power supply to output negative voltage, but this isolated switching power supply requires the introduction of an isolation transformer. The circuit structure of the power supply solution is complicated, the volume is relatively large, the efficiency of the power supply is not high, and the cost will be higher. The second method uses a negative voltage LDO. First, a negative voltage source must be provided to the negative voltage LDO. Then, due to the power consumption problem of the LDO, it is destined to not be able to provide a large current load, especially when the output voltage is adjustable. The limitations are greater. The third method is a dedicated chip provided by a power chip supplier. Because it is dedicated, the price of the chip is relatively high, and a dual-winding inductor with a small current is required. There are not many manufacturers that can provide such inductors, and the overall cost of this solution will be relatively high. Summary of the invention

[0007] The object of the present invention is to provide a switching power supply circuit to solve at least one of the problems existing in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a switching power supply circuit, which includes: a BUCK power converter and an output voltage regulation circuit, wherein

[0010] The output terminal of the BUCK power converter is grounded, and the ground of the switching power circuit is used as the output terminal to output a negative voltage;

[0011] The output voltage regulation circuit comprises a digital-to-analog converter and a common-mode operational amplifier circuit, and the output voltage regulation circuit is used to digitally regulate the negative voltage output by the switching power supply circuit according to a first control signal received by the digital-to-analog converter.

[0012] In a specific embodiment, the output voltage regulation circuit further includes

[0013] A first resistor connected between an output terminal and a feedback terminal of the BUCK power converter;

[0014] a second resistor connected between the feedback terminal of the BUCK power converter and the output terminal of the switching power circuit; and

[0015] A third resistor is connected between the output terminal of the non-inverting operational amplifier circuit and the feedback terminal of the BUCK power converter.

[0016] In a specific embodiment, the in-phase operational amplifier circuit includes: an operational amplifier, a fourth resistor, and a fifth resistor;

[0017] The non-inverting input terminal of the operational amplifier is connected to the digital-to-analog converter, and the inverting input terminal of the operational amplifier is connected to the second end of the fourth resistor and the first end of the fifth resistor;

[0018] The first end of the fourth resistor is connected to the output end of the operational amplifier;

[0019] The second end of the fifth resistor is grounded;

[0020] The output terminal of the operational amplifier is connected to the second terminal of the third resistor.

[0021] In a specific embodiment, the switching power supply circuit further includes an enabling circuit, wherein the enabling circuit enables the BUCK power converter based on receiving a second control signal.

[0022] In a specific embodiment, the enabling circuit includes a first transistor, a second transistor and a sixth resistor, the first end and the second end of the first transistor are respectively connected to the input end and the enabling end of the BUCK power converter, and the third end is coupled to the first end through the sixth resistor; the first end of the second transistor serves as the input end for receiving the second control signal, the second end is coupled to the third end of the first transistor, and the third end is grounded.

[0023] In a specific embodiment, the enabling circuit further includes a seventh resistor connected to the enabling terminal of the BUCK power converter and the output terminal of the switching power circuit.

[0024] In a specific embodiment, the switching power supply circuit further includes a capacitor, one end of which is connected to the input end of the BUCK power converter, and the other end of which is connected to the output end of the BUCK power converter and is grounded.

[0025] In a specific embodiment, the switching power supply circuit further includes a diode coupled between the output terminal of the switching power supply circuit and ground.

[0026] In a specific embodiment, the negative voltage output by the switching power supply circuit is:

[0027]

[0028] Wherein, Vref is the reference voltage of the FB pin of the BUCK power converter; Vdac is the output voltage of the in-phase operational amplifier circuit; R1 is the resistance value of the first resistor; R2 is the resistance value of the second resistor; and R3 is the resistance value of the third resistor.

[0029] The beneficial effects of the present invention are as follows:

[0030] The present invention discloses a switching power supply circuit. By grounding the voltage output terminal of a common BUCK (step-down converter) power supply structure, a negative voltage output can be achieved. By utilizing the control signal output by a microprocessor MCU and a voltage regulating circuit including a digital-to-analog converter DAC and a common-phase proportional amplifier, a switching power supply circuit with a digitally adjustable function of a negative power supply output voltage is achieved. The circuit structure of the present invention is simple, the space occupied is small, and the cost is relatively low. At the same time, the risks brought by a single dedicated chip supplier can be avoided. Due to the use of the BUCK power supply topology, the output power of the power supply can be relatively large, and it will not be affected by the selection of devices like a dedicated chip, and the output power is not limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 A schematic diagram showing a conventional BUCK type converter.

[0033] Figure 2 It is a structural schematic diagram of a switching power supply circuit provided by an embodiment of the present invention.

[0034] Figure 3 is another structural schematic diagram of a switching power supply circuit provided by an embodiment of the present invention.

[0035] Figure 4 is another structural schematic diagram of a switching power supply circuit provided by an embodiment of the present invention.

[0036] Figure 5 is another structural schematic diagram of a switching power supply circuit provided by an embodiment of the present invention.

[0037] Figure 6 is another structural schematic diagram of a switching power supply circuit provided by an embodiment of the present invention.

[0038] Figure 7 is another structural schematic diagram of a switching power supply circuit provided by an embodiment of the present invention.

[0039] Description of reference numerals: 110 : enabling circuit, 120 : output voltage regulating circuit. DETAILED DESCRIPTION

[0040] In order to make the technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. Those skilled in the art should understand that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0041] like Figure 1 As shown, a conventional BUCK type converter for connecting to a power supply device includes a BUCK power converter U1, a first resistor R1, a second resistor R2 and a sixth resistor R6. The input terminal VIN of the BUCK power converter U1 is connected to the enable terminal EN through the sixth resistor, the feedback terminal FB is connected to the ground (also called ground potential, GND) of the device power supply through the second resistor, and the output terminal VOUT is connected to the feedback terminal through the first resistor. The BUCK power converter is connected to the power supply device, the input terminal receives the input voltage from the power supply device, and the output terminal outputs a positive voltage Vout.

[0042] like Figure 2 As shown, a switching power supply circuit including a BUCK power converter according to an embodiment of the present invention is disclosed, which is used to connect to a device power supply to output a negative voltage with a digitally adjustable voltage. Figure 1 The voltage output pin VOUT shown is grounded, and the ground of the device power supply is inverted to achieve reverse connection and serve as the output end of the switching power supply circuit, thereby outputting a negative voltage that is inverted relative to the input voltage.

[0043] The switching power supply circuit according to the present invention includes a BUCK power converter U1 and an output voltage regulating circuit. The BUCK power converter is, for example, a power chip connected to a device power supply, including a voltage input pin VIN, a voltage output pin VOUT, an enable pin EN, and a feedback pin FB. In the embodiment of the present invention, the voltage output pin VOUT is grounded, and the output terminal nVOUT of the switching power supply circuit is connected to the ground potential of the device power supply for outputting a negative voltage.

[0044] The VIN pin of the BUCK power converter receives a positive input voltage, the input end of the output voltage regulation circuit receives a voltage regulation control signal from the single-chip computer MCU, and the output end of the output voltage regulation circuit is connected to the VOUT pin and the FB pin of the BUCK power converter.

[0045] The output voltage regulation circuit includes a digital-to-analog converter DAC and a common-phase operational amplifier circuit connected in series. The digital-to-analog converter DAC receives a voltage regulation control signal from the single-chip microcomputer MCU. The common-phase operational amplifier circuit amplifies the voltage output by the digital-to-analog converter DAC and outputs it to the feedback pin FB of the BUCK power converter through a resistor, thereby realizing digital regulation of the negative voltage nVout output by the switching power supply circuit.

[0046] The invention discloses a switching power supply circuit. By grounding the voltage output terminal of a common BUCK power supply structure, the output of a negative voltage can be realized. By utilizing a control signal output by a microprocessor MCU and a voltage regulating circuit including a digital-to-analog converter DAC and a common-phase proportional amplifier, a switching power supply circuit with a digitally adjustable function of a negative power supply output voltage is realized.

[0047] Optional, Figure 3 Another structural diagram of a switching power supply circuit provided by an embodiment of the present invention is shown in FIG. Figure 3 As shown, the output voltage regulation circuit includes a digital-to-analog converter DAC U2, a non-inverting operational amplifier circuit, and first to third resistors R1 to R3. In the non-inverting operational amplifier circuit, the output end of the operational amplifier U3 is connected to the inverting input end through the fourth resistor R4, and the non-inverting input end is connected to the digital-to-analog converter DAC to amplify the received signal, and the amplified signal is output to the feedback pin FB through the third resistor R3. The inverting input end is further grounded through the fifth resistor R5.

[0048] More specifically, the digital-to-analog converter outputs an analog voltage under the control of the single-chip microcomputer MCU; the non-inverting input terminal of the operational amplifier receives the analog voltage; the inverting input terminal of the operational amplifier is connected to the second end of the fourth resistor and the first end of the fifth resistor; the first end of the fourth resistor is connected to the output terminal of the operational amplifier; the second end of the fifth resistor is grounded. The output terminal of the operational amplifier is connected to the second end of the third resistor; the first end of the first resistor R1 is connected to the VOUT pin of the BUCK power converter and grounded; the second end of the first resistor, the first end of the second resistor R2 and the first end of the third resistor are connected to the FB pin of the BUCK power converter.

[0049] In this example, the present invention realizes the digital adjustable function of the negative power supply output voltage through the single-chip microcomputer MCU controlling the digital-to-analog converter through the in-phase operational amplifier circuit. Specifically, the process of realizing the digital adjustable output negative voltage includes: the single-chip microcomputer MCU controls the digital-to-analog converter to output an analog voltage of 0 to 2.048V, and the in-phase operational amplifier circuit amplifies the analog voltage proportionally to obtain the gain voltage value Vdac of the in-phase proportional amplifier, which is connected to the output voltage feedback pin FB of the BUCK power converter through the third resistor R3. Using the upper voltage divider resistor R1, the lower voltage divider resistor R2 of the output voltage feedback pin FB, and the operational amplifier output series resistor R3, the values ​​of the three resistors can be obtained through mathematical operations. The negative voltage output by the switching power supply circuit is:

[0050]

[0051] Wherein, Vref is the reference voltage of the FB pin of the BUCK power converter; Vdac is the output voltage of the in-phase operational amplifier circuit; R1 is the resistance value of the first resistor; R2 is the resistance value of the second resistor; and R3 is the resistance value of the third resistor.

[0052] Optional, Figure 4 Another structural diagram of a switching power supply circuit provided by an embodiment of the present invention. Figure 4 The switch power supply circuit also includes an enabling circuit, which enables the BUCK power converter based on receiving a second control signal. The reference voltage of the enabling pin EN of the present invention is the output voltage nVout. The single-chip microcomputer MCU outputs an enabling signal, and controls the enabling pin of the BUCK power converter through the enabling circuit, so that the BUCK power chip has a negative voltage output only when the enabling control signal is at a high level.

[0053] In this example, when the DAC outputs 0V, the negative voltage of the power supply output is the lowest value, and when the DAC outputs 2.048V, the negative voltage of the power supply output is the highest value; when the device is just powered on, the DAC outputs 0V, and the output voltage of the negative power supply is the lowest value, such as -16V. If the output voltage is the lowest value when the device is just powered on, it is very likely to cause damage to the customer's product. In order to avoid misoperation, it is necessary to ensure that the output voltage of the negative power supply is the highest value when the DAC has not yet configured the output; for example, -1V. In addition, because the reference voltage of the EN pin of the BUCK power converter is the output voltage nVout, not the system ground, the voltage of the EN pin when the power is turned on will be affected. Applying a digital signal-controlled level converter to the EN pin, that is, using the microcontroller MCU to output an enable signal, and controlling the enable pin of the BUCK power converter through the enable circuit, can solve these problems well.

[0054] Optional, Figure 5 Another structural diagram of a switching power supply circuit provided by an embodiment of the present invention is shown in FIG. Figure 5 As shown, the enabling circuit includes: a first transistor Q1, a second transistor Q2, a sixth resistor R6 and a seventh resistor R7. The base of the transistor Q2 receives the enabling signal output by the single-chip microcomputer MCU; the emitter of the transistor Q2 is grounded; the collector of the transistor Q2 is connected to the base of the transistor Q1 and the first end of the sixth resistor; the second end of the sixth resistor and the emitter of the transistor Q1 are connected to the VIN pin of the BUCK power converter; the collector of the transistor Q1 is connected to the EN pin of the BUCK power converter; the first end of the seventh resistor is connected to the EN pin of the BUCK power converter; the second end of the seventh resistor is connected to the second end of the second resistor and the output end of the switching power supply circuit. In this example, the transistor Q1 is a PNP transistor, and the transistor Q2 is an NPN transistor.

[0055] The present invention outputs an enable signal through a single-chip microcomputer MCU, and uses an enable circuit to control the enable pin of the BUCK power converter. When the digital-to-analog converter DAC is configured to have a voltage output and reaches the required negative power output voltage value, the enable pin is enabled to ensure the negative power output voltage value, thereby solving the problem that the output voltage is the lowest value when the device is just powered on, which is very likely to cause damage to customer products.

[0056] Optional, Figure 6 Another structural diagram of a switching power supply circuit provided by an embodiment of the present invention. Figure 6The switching power supply circuit also includes a capacitor, a first end of the capacitor is connected to the VIN pin of the BUCK power converter, and a second end is connected to the VOUT pin of the BUCK power converter and the first end of the first resistor and grounded. Preferably, a capacitor with a larger capacity can be used. The present invention adds an input power supply capacitor to the switching power supply circuit, which can help suppress high-frequency noise that may be coupled to the circuit and keep the system stable. Specifically, the voltage of the capacitor needs to meet the stress of the entire voltage range.

[0057] Optional, Figure 7 Another structural diagram of a switching power supply circuit provided by an embodiment of the present invention. Figure 7 , the switching power supply circuit also includes a diode. Considering that the capacitor from VIN to nVOUT inside the BUCK power converter will introduce an AC path, when VIN is applied to the circuit, the dV / dt across the bypass capacitor will generate a current, which must return to the ground GND of the device power supply to complete the loop. This current may flow through the body diode and inductor of the low-end MOSFET (metal-oxide semiconductor field effect transistor) inside the BUCK power converter to return to the ground GND of the device power supply. Therefore, in this example, the diode D1 is coupled between the output end of the switching power supply circuit and the ground. Specifically, the anode of the diode is connected to the output end of the circuit, and the cathode of the diode is grounded. Preferably, the diode is a Schottky diode.

[0058] The present invention discloses a switching power supply circuit. By grounding the voltage output terminal of a common BUCK power supply structure, the output of a negative voltage can be realized. By utilizing the control signal output by a microprocessor MCU and a voltage regulating circuit including a digital-to-analog converter DAC and a common-phase proportional amplifier, a switching power supply circuit with a digitally adjustable function of a negative power supply output voltage is realized. The circuit structure of the present invention is simple, the space occupied is small, and the cost is relatively low; at the same time, the risks brought by a single dedicated chip supplier can be avoided. Due to the use of the BUCK power supply topology structure, the output power of the power supply can be relatively large, and it will not be affected by the selection of devices like a dedicated chip, and the output power is not limited.

[0059] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A switching power supply circuit, characterized in that: The switching power supply circuit includes: a BUCK power converter and an output voltage regulation circuit, wherein The output terminal of the BUCK power converter is grounded, and the ground of the switching power circuit is used as the output terminal to output a negative voltage; The output voltage regulation circuit comprises a digital-to-analog converter and a common-phase operational amplifier circuit, and the output voltage regulation circuit is used to implement digital regulation of the negative voltage output by the switching power supply circuit according to the first control signal received by the digital-to-analog converter; The output voltage regulation circuit further comprises A first resistor connected between an output terminal and a feedback terminal of the BUCK power converter; a second resistor connected between the feedback terminal of the BUCK power converter and the output terminal of the switching power circuit; and a third resistor connected between the output terminal of the in-phase operational amplifier circuit and the feedback terminal of the BUCK power converter; The in-phase operational amplifier circuit comprises: an operational amplifier, a fourth resistor and a fifth resistor; The non-inverting input terminal of the operational amplifier is connected to the digital-to-analog converter, and the inverting input terminal of the operational amplifier is connected to the second end of the fourth resistor and the first end of the fifth resistor; The first end of the fourth resistor is connected to the output end of the operational amplifier; The second end of the fifth resistor is grounded; The output terminal of the operational amplifier is connected to the second terminal of the third resistor.

2. The switching power supply circuit according to claim 1, characterized in that: The switching power supply circuit further includes an enabling circuit, which enables the BUCK power converter based on receiving a second control signal.

3. The switching power supply circuit according to claim 2, characterized in that: The enabling circuit includes a first transistor, a second transistor and a sixth resistor, wherein the first end and the second end of the first transistor are respectively connected to the input end and the enabling end of the BUCK power converter, and the third end is coupled to the first end through the sixth resistor; the first end of the second transistor serves as the input end for receiving the second control signal, the second end is coupled to the third end of the first transistor, and the third end is grounded.

4. The switching power supply circuit according to claim 3, characterized in that: The enabling circuit further includes a seventh resistor connected to the enabling terminal of the BUCK power converter and the output terminal of the switching power circuit.

5. The switching power supply circuit according to claim 1, characterized in that: The switch power circuit further includes a capacitor, one end of which is connected to the input end of the BUCK power converter, and the other end of which is connected to the output end of the BUCK power converter and is grounded.

6. The switching power supply circuit according to claim 1, characterized in that: The switching power supply circuit further includes a diode coupled between the output terminal of the switching power supply circuit and ground.

7. The switching power supply circuit according to claim 1, characterized in that: The negative voltage output by the switching power supply circuit is: Wherein, Vref is the reference voltage of the FB pin of the BUCK power converter; Vdac is the output voltage of the in-phase operational amplifier circuit; R1 is the resistance value of the first resistor; R2 is the resistance value of the second resistor; and R3 is the resistance value of the third resistor.

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