Low-ripple adjustable power supply circuit

Abstract

The utility model discloses a low-ripple adjustable power supply circuit which comprises a power supply module, a first voltage dividing module, a voltage adjusting module, an LDO linear voltage stabilizing module and a differential amplification module. The output end of the voltage regulation module is connected with the first input end of the LDO linear voltage stabilization module, and the output end of the voltage regulation module is further connected with one input end of the first voltage division module. The other input end of the first voltage dividing module is connected with the power supply module; the output end of the differential amplification module is connected with the second input end of the LDO linear voltage stabilization module, the first input end of the differential amplification module is connected with the positive electrode VOUT + of the power supply module to serve as the output positive electrode VOUT1 + of the power supply circuit, and the second input end of the differential amplification module is connected with the output end of the LDO linear voltage stabilization module to serve as the output negative electrode VOUT1-of the power supply circuit. The circuit provided by the utility model has the advantages of obvious ripple suppression effect and low cost, and is particularly suitable for being applied to the fields with wide adjustable output voltage and smaller ripple requirements.

Description

Technical Field

[0001] The utility model relates to the technical field of electrical equipment, and in particular to a power supply circuit with low ripple, low loss and ultra-wide range adjustment. Background Art

[0002] With the rapid development of economy, high-efficiency switching power supplies are more and more widely used, and the adjustable voltage of switching power supplies has become an indispensable requirement in the industry. The traditional adjustable power supply circuit has a large duty cycle range, which leads to a large output ripple at low voltage output. In order to reduce the ripple, the traditional switching power supply will add a linear voltage regulator circuit for ripple suppression, but at this time it cannot meet the requirements of adjustable output voltage, and the voltage loss increases accordingly.

[0003] Therefore, there is an urgent need to propose a power supply circuit with low ripple, low loss and easy-to-implement adjustable output voltage. Utility Model Content

[0004] The utility model aims at the problem that the adjustable output and low ripple voltage of the switching power supply cannot be taken into account at the same time, and proposes a low ripple adjustable power supply circuit. The power supply circuit can achieve the functions of low ripple, low loss and ultra-wide voltage adjustment. The utility model circuit has obvious ripple suppression effect and low cost, and is particularly suitable for application in the field of wide adjustable output voltage and small ripple requirements.

[0005] The technical solution of the utility model to solve the above technical problems is as follows:

[0006] A low ripple adjustable power supply circuit comprises a power supply module for outputting a direct current voltage VOUT+, a first voltage dividing module, a voltage regulating module with adjustable output voltage, an LDO linear voltage regulating module and a differential amplifier module; the output end of the voltage regulating module is connected to the first input end of the LDO linear voltage regulating module, and the voltage regulating module adjusts the output voltage of the LDO linear voltage regulating module by adjusting the output voltage of its output end; the output end of the voltage regulating module is also connected to an input end of the first voltage dividing module; the other input end of the first voltage dividing module is connected to the power supply module; the output end of the differential amplifier module is connected to the second input end of the LDO linear voltage regulating module, the first input end of the differential amplifier module is connected to the positive pole VOUT+ of the power supply module as the output positive pole VOUT1+ of the power supply circuit, and the second input end of the differential amplifier module is connected to the output end of the LDO linear voltage regulating module as the output negative pole VOUT1- of the power supply circuit.

[0007] Furthermore, a filter capacitor C1 is connected between the positive and negative electrodes of the power module, and a filter capacitor C5 is connected between the positive and negative electrodes of the output end of the adjustable circuit.

[0008] The beneficial effect of the above further solution is: suppressing higher frequency power supply ripple and noise, making the output DC more stable.

[0009] Further, the voltage regulation module includes a control voltage VADJ, resistors R9, R10 and R11, the resistors R9 and R10 are connected in series to form a voltage divider circuit, one end of the resistor R9 is connected to the control voltage VADJ, one end of the resistor R10 is grounded, the middle node of the series connection of the resistors R9 and R10 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the first input end of the LDO linear voltage regulator module.

[0010] The beneficial effect of the above further solution is that the control voltage VADJ is set by software and is controlled by I 2 C bus or SPI bus output, and then the resistors R9 and R10 divide the voltage to obtain the divided voltage value of R10, and use this divided voltage value as the common-phase input voltage of the first operational amplifier U1 and the second operational amplifier U2. As long as the ratio of the resistors is set, the voltage can be adjusted by software, which makes it very convenient to adjust the voltage and simplifies the circuit structure.

[0011] Further, the differential amplification module includes a third operational amplifier U3, resistors R4, R5, R6 and R7, and the resistors R4 and R5 are connected in series to form a voltage-dividing resistor; the output end of the third operational amplifier U3 serves as the output end of the differential amplification module, and the resistor R7 is connected between the output end and the inverting input end of the third operational amplifier U3, the non-inverting input end of the third operational amplifier U3 is connected to the node of the voltage-dividing resistors R4 and R5, the other end of the resistor R4 serves as the first input end of the differential amplification module, the other end of the resistor R5 is grounded, and the inverting input end of the third operational amplifier U3 is connected to the resistor R6 as the second input end of the differential amplification module.

[0012] The beneficial effect of the above further scheme is: the output voltage is differentially sampled and connected in series to form a voltage-dividing resistor through resistors R4 and R5. When working, it is only necessary to control the ratio of R4 and R5 and transmit it to the input end of the LDO linear voltage regulator module and cooperate with the sampling voltage of the in-phase input end of the second operational amplifier U2 to design a linear voltage regulation output.

[0013] Furthermore, the first voltage divider module includes a first operational amplifier U1, and series voltage divider resistors R12 and R13, one end of the resistor R12 is connected to the positive electrode VOUT+ of the power supply module, one end of the resistor R13 is grounded, the middle node of the series voltage divider resistors R12 and R13 is connected to the reverse input terminal of the first operational amplifier U1, the non-inverting input terminal of the first operational amplifier U1 is connected to the voltage regulation module, and the capacitor C7 is connected between the inverting input terminal and the output terminal of the first operational amplifier U1.

[0014] The beneficial effect of the above further scheme is: by controlling the difference between the ratio of the voltage-dividing resistors R12 and R13 and the ratio of the voltage-dividing resistors R4 and R5, the voltage VADJ can be made such that the difference between the input and output of the LDO linear voltage regulator module changes simultaneously with the regulation voltage of the voltage regulation module during voltage regulation, thereby ensuring low output ripple and safe and reliable circuit during the entire voltage regulation process.

[0015] Furthermore, the resistance values ​​of the resistors R4 and R6 are equal, and the resistance values ​​of the resistors R5 and R7 are equal.

[0016] Furthermore, the LDO linear voltage regulator module includes a second operational amplifier U2 and a linear voltage regulator Q1, the output end of the second operational amplifier U2 is connected to the gate of the linear voltage regulator Q1, a resistor R3 is connected between the source and the gate of the linear voltage regulator Q1, the source of the linear voltage regulator Q1 is connected to the negative electrode VOUT- of the power supply module, and the drain of the linear voltage regulator Q1 is connected to the output negative electrode VOUT1- of the power supply circuit; the non-inverting input end of the second operational amplifier U2 is connected to the resistor R1 as the first input end of the LDO linear voltage regulator module, the inverting input end of the second operational amplifier U2 is connected to the resistor R8 as the second input end of the LDO linear voltage regulator module, and the capacitor C3 is connected between the inverting input end and the output end of the second operational amplifier U2.

[0017] The beneficial effect of the above further solution is: the voltage VOUT1- is filtered by the linear voltage regulator Q1, the power ripple is reduced, and the power quality of the output voltage is improved.

[0018] Furthermore, the linear voltage regulator Q1 is an N-channel field effect transistor.

[0019] The beneficial effect of the above further solution is that the N-channel field effect transistor Q1 is easy to select and is not limited by output voltage and power.

[0020] This application adopts the above technical solution, which has at least the following beneficial effects:

[0021] The circuit structure of an LDO linear voltage regulator module is added to the output port of the power module, and the output signal of the power module is divided by the voltage divider resistors R4 and R5 to obtain the difference between the voltage V2 and the output signal of the LDO linear voltage regulator module, and the difference is amplified and output to one input end of the LDO linear voltage regulator module, and the first voltage divider module divides the output voltage of the power module by the voltage divider resistors R12 and R13 to obtain V3 and output it to the other input end of the LDO linear voltage regulator module. The output voltage values ​​of voltages V2 and V3 are set by controlling the ratio of R4 and R5 and the difference between the ratio of R12 and R13, and then the voltages V2 and V3 are amplified. The output voltages Vout1 and Vout2 of the third operational amplifier U3 and the first operational amplifier U1 are controlled and adjusted respectively, so that their voltage difference is kept within a certain range. The voltage difference is generally between 0.2V and 1V. As can be seen from the voltages V2 and V3, when the voltage VADJ is adjusted during voltage regulation, the difference between the input and output of the LDO linear voltage regulator module changes simultaneously with the regulated voltage, ensuring that the voltage difference between the DS of the linear voltage regulator Q1 is kept within a certain range. In this way, the loss of the linear voltage regulator Q1 does not change significantly when performing ultra-wide output voltage regulation, which can ensure that the output ripple is low and the circuit is safe and reliable during the entire voltage regulation process.

[0022] Therefore, the circuit of the utility model has obvious effect and low cost, and is particularly suitable for application in fields with wide adjustable output voltage and small ripple requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a power supply circuit diagram of the utility model;

[0024] Figure 2 This is a simulation result diagram of the utility model. DETAILED DESCRIPTION

[0025] Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are merely exemplary, intended to explain the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0026] like Figure 1As shown, a low ripple adjustable power supply circuit includes a power supply module for outputting a DC voltage Vout, a first voltage divider module, a voltage regulating module with adjustable output voltage, an LDO linear voltage regulator module and a differential amplifier module; wherein, the output voltage of the LDO linear voltage regulator module is adjustable, the output end of the voltage regulating module is connected to the first input end of the LDO linear voltage regulator module, and the voltage regulating module adjusts the output voltage of the LDO linear voltage regulator module by adjusting the output voltage of its output end; the output end of the voltage regulating module is also connected to an input end of the first voltage divider module; the other input end of the first voltage divider module is connected to the power supply module; the output end of the differential amplifier module is connected to the second input end of the LDO linear voltage regulator module, the first input end of the differential amplifier module is connected to the positive pole VOUT+ of the power supply module as the output positive pole VOUT1+ of the power supply circuit, and the second input end of the differential amplifier module is connected to the output end of the LDO linear voltage regulator module as the output negative pole VOUT1- of the power supply circuit.

[0027] In order to make the DC output of the power module more stable, a filter capacitor C1 is connected between the positive and negative poles of the power module. In order to suppress higher-frequency power ripple and noise and make the DC output of the power circuit more stable, a filter capacitor C5 is connected between the positive and negative poles of the output end of the adjustable circuit.

[0028] The voltage regulation module of the embodiment of the present application includes a control voltage VADJ, resistors R9, R10 and R11, wherein the resistors R9 and R10 are connected in series to form a voltage divider circuit, one end of the resistor R9 is connected to the control voltage VADJ, one end of the resistor R10 is grounded, the middle node of the series connection of the resistors R9 and R10 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the first input end of the LDO linear voltage regulator module. The control voltage VADJ is set by software and is controlled by I 2 C bus or SPI bus output, and then the resistors R9 and R10 divide the voltage to get the voltage divider value V1 of R10, the calculation formula is: This voltage division value is used as the common-phase input voltage of the first operational amplifier U1 and the second operational amplifier U2. As long as the ratio of the resistors R9 and R10 is set, and the voltage is adjusted by software, it is very convenient to adjust the voltage, reducing the complexity of hardware design.

[0029] In the voltage regulating module, the set reference voltage VADJ is output through software configuration, and then the voltage is divided by resistors R9 and R10, so that the output voltage VOUT1- can be accurately configured. The voltage regulating module can adopt a circuit structure of adjustable resistor voltage division, and the adjustable resistor adjusts the output voltage of the voltage regulating module by adjusting the voltage division; the voltage regulating module can also use a DAC digital analog converter to control the output voltage of the voltage regulating module, and the DAC digital analog converter can use AD5683R. The structure of the voltage regulating module is not limited to the above two types.

[0030] The differential amplifier module of the embodiment of the present application includes a third operational amplifier U3, resistors R4, R5, R6 and R7. In order to balance the resistance of the entire circuit, the resistance values ​​of the resistors R4 and R6 are equal, and the resistance values ​​of the resistors R5 and R7 are equal. The resistors R4 and R5 are connected in series to form a voltage-dividing resistor; the output end of the third operational amplifier U3 serves as the output end of the differential amplifier module, the resistor R7 is connected between the output end and the inverting input end of the third operational amplifier U3, the in-phase input end of the third operational amplifier U3 is connected to the node of the voltage-dividing resistors R4 and R5, the other end of the resistor R4 serves as the first input end of the differential amplifier module, the other end of the resistor R5 is grounded, and the inverting input end of the third operational amplifier U3 is connected to the resistor R6 as the second input end of the differential amplifier module. In this embodiment, the output voltage of the power supply module is divided by the voltage-dividing resistors R4 and R5 to obtain V2, which is transmitted to the in-phase end of the operational amplifier. The calculation formula is: When working, it is only necessary to control the ratio of R4 and R5 and transmit it to the input end of the LDO linear voltage regulator module and cooperate with the sampling voltage of the in-phase input end of the second operational amplifier U2 to design the linear voltage regulator output.

[0031] In this embodiment, the first voltage divider module includes a first operational amplifier U1, and series voltage divider resistors R12 and R13, one end of the resistor R12 is connected to the positive electrode VOUT+ of the power module, and one end of the resistor R13 is grounded. The series voltage divider resistors R12 and R13 divide the output voltage of the power module to obtain V3 and transmit it to the reverse input terminal of the first operational amplifier U1. The calculation formula is:

[0032] From the formula of V2 and V3, we know that they are connected to the voltage VOUT+ together. Therefore, by controlling the ratio of the voltage-dividing resistors R12 and R13 and the difference between the ratios of the voltage-dividing resistors R4 and R5, the voltage VADJ can be adjusted so that the difference between the input and output of the LDO linear voltage regulator module changes simultaneously with the control voltage of the voltage regulation module, which can ensure low output ripple and safe and reliable circuit during the entire voltage regulation process.

[0033] Specifically, in the embodiment of the present application, the non-inverting input terminal of the first operational amplifier U1 is connected to the voltage regulation module, and the capacitor C7 is connected between the inverting input terminal and the output terminal of the first operational amplifier U1.

[0034] In this embodiment, the LDO linear voltage regulator module includes a second operational amplifier U2 and a linear voltage regulator Q1, the output end of the second operational amplifier U2 is connected to the gate of the linear voltage regulator Q1, a resistor R3 is connected between the source and the gate of the linear voltage regulator Q1, the source of the linear voltage regulator Q1 is connected to the negative electrode VOUT- of the power supply module, and the drain of the linear voltage regulator Q1 is connected to the output negative electrode VOUT1- of the power supply circuit; the non-inverting input end of the second operational amplifier U2 is connected to the resistor R1 as the first input end of the LDO linear voltage regulator module, the inverting input end of the second operational amplifier U2 is connected to the resistor R8 as the second input end of the LDO linear voltage regulator module, and the capacitor C3 is connected between the inverting input end and the output end of the second operational amplifier U2.

[0035] Preferably, in the embodiment of the present application, the linear voltage regulator Q1 adopts an N-channel field effect transistor, which functions as a voltage switch. In the embodiment of the present application, the linear voltage regulator Q1 works in the variable resistance area to control the voltage of the output voltage VOUT1-. By using an N-channel field effect transistor, the circuit structure can be simpler and the performance can be better. The selection of the N-channel field effect transistor is convenient and is not limited by the output voltage and power. When the linear voltage regulator Q1 is an NMOS tube, the source S of the linear voltage regulator Q1 is connected to the output end of the power module, the gate G of the linear voltage regulator Q1 is connected to the output end of the second operational amplifier U2, and the drain D of the linear voltage regulator Q1 outputs the voltage VOUT1-.

[0036] The working principle of the LDO linear voltage regulator module of the embodiment of the present application is as follows: the linear voltage regulator Q1 and the second operational amplifier U2 form a negative feedback circuit. When the negative feedback circuit works stably, the negative feedback balance characteristic of the second operational amplifier U2 is utilized. The second operational amplifier U2 outputs an adaptively adjustable voltage value when the circuit is stable. The working state of the linear voltage regulator Q1 is controlled by the voltage value, so that the linear voltage regulator Q1 works in a variable resistance area, also known as a non-saturation area. When the voltage difference UGS between the gate and the source of the linear voltage regulator Q1 remains unchanged, the drain current ID is linearly related to the gate and drain voltage of the linear voltage regulator Q1, and the area is approximately a straight line. At this time, the drain and gate of the linear voltage regulator Q1 are equivalent to a variable resistor controlled by the voltage UGS, thereby filtering the voltage VOUT1-, reducing the power supply ripple, and improving the power supply quality.

[0037] In this embodiment, the power module unit may be LM5117, and the first operational amplifier U1, the second operational amplifier U2 and the third operational amplifier U3 may be OPA2188.

[0038] In the adjustable power supply circuit capable of reducing power supply ripple in the embodiment of the present application, by setting the output voltage values ​​of V2 and V3, the output voltages Vout1 and Vout2 of the third operational amplifier U3 and the first operational amplifier U1 are controlled and adjusted respectively, so that their voltage difference is kept within a certain range. This voltage difference is generally between 0.2V and 1V. As can be seen from the foregoing, for V2 and V3, it is only necessary to control the ratio of R4 and R5 and the difference between the ratios of R12 and R13. When the voltage VADJ is performing voltage regulation, the difference between the input and output of the LDO linear voltage regulator module changes simultaneously with the regulation voltage, ensuring that the voltage difference between the DS of the linear voltage regulator Q1 is maintained within a certain range. In this way, the loss of the linear voltage regulator Q1 does not change significantly when performing ultra-wide output voltage regulation, which can ensure that the output ripple is low and the circuit is safe and reliable during the entire voltage regulation process. Of course, in practical applications, it is necessary to set and adjust according to the actual circuit parameters and specification requirements. By reasonably setting the voltage difference value according to the actual application situation, not only can the negative feedback loop of the subsequent stage work stably and suppress ripple to the maximum effect, but also the heat dissipation of the linear voltage regulator Q1 can be controlled to reduce the power consumption in the circuit.

[0039] like Figure 2 As shown, the circuit simulation result of the utility model regulating the voltage so that the voltage difference across the linear voltage regulator module is 2V: VOUT+ DC voltage 200V, an AC ripple with a frequency of 200kHz and a peak-to-peak value of 2V is superimposed on the input voltage, and after passing through the ripple suppression circuit, the VOUT1 DC voltage is 198V, and the peak-to-peak value of the voltage ripple is 9.03mV; by applying this circuit, it can be concluded that when the output voltage is adjustable, the voltage ripple is absorbed by the low-loss linear voltage regulator circuit, and the peak-to-peak value of the output voltage ripple is also reduced to 1 / 220 of the peak-to-peak value of the input voltage ripple of the linear voltage regulator circuit.

[0040] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low ripple adjustable power supply circuit, characterized in that: It includes a power supply module for outputting a direct current voltage VOUT+, a first voltage divider module, a voltage regulating module with adjustable output voltage, an LDO linear voltage regulator module and a differential amplifier module; the output end of the voltage regulating module is connected to the first input end of the LDO linear voltage regulator module, and the voltage regulating module adjusts the output voltage of the LDO linear voltage regulator module by adjusting the output voltage of its output end; the output end of the voltage regulating module is also connected to an input end of the first voltage divider module; the other input end of the first voltage divider module is connected to the power supply module; the output end of the differential amplifier module is connected to the second input end of the LDO linear voltage regulator module, the first input end of the differential amplifier module is connected to the positive pole VOUT+ of the power supply module as the output positive pole VOUT1+ of the power supply circuit, and the second input end of the differential amplifier module is connected to the output end of the LDO linear voltage regulator module as the output negative pole VOUT1- of the power supply circuit.

2. The low ripple adjustable power supply circuit according to claim 1, characterized in that: A filter capacitor C1 is connected between the positive and negative electrodes of the power module, and a filter capacitor C5 is connected between the positive and negative electrodes of the output end of the adjustable circuit.

3. The low ripple adjustable power supply circuit according to claim 1, characterized in that: The voltage regulation module includes a control voltage VADJ, resistors R9, R10 and R11, the resistors R9 and R10 are connected in series to form a voltage divider circuit, one end of the resistor R9 is connected to the control voltage VADJ, one end of the resistor R10 is grounded, the middle node of the series connection of the resistors R9 and R10 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the first input end of the LDO linear voltage regulator module.

4. The low ripple adjustable power supply circuit according to claim 1, characterized in that: The differential amplifier module includes a third operational amplifier U3, resistors R4, R5, R6 and R7, and the resistors R4 and R5 are connected in series to form a voltage-dividing resistor; the output end of the third operational amplifier U3 serves as the output end of the differential amplifier module, and the resistor R7 is connected between the output end and the inverting input end of the third operational amplifier U3. The in-phase input end of the third operational amplifier U3 is connected to the node of the voltage-dividing resistors R4 and R5. The other end of the resistor R4 serves as the first input end of the differential amplifier module, and the other end of the resistor R5 is grounded. The inverting input end of the third operational amplifier U3 is connected to the resistor R6 as the second input end of the differential amplifier module.

5. The low ripple adjustable power supply circuit according to claim 4, characterized in that: The first voltage divider module includes a first operational amplifier U1, and series voltage divider resistors R12 and R13, one end of the resistor R12 is connected to the positive electrode VOUT+ of the power module, one end of the resistor R13 is grounded, the middle node of the series voltage divider resistors R12 and R13 is connected to the reverse input terminal of the first operational amplifier U1, the non-inverting input terminal of the first operational amplifier U1 is connected to the voltage regulation module, and the capacitor C7 is connected between the inverting input terminal and the output terminal of the first operational amplifier U1.

6. The low ripple adjustable power supply circuit according to claim 4, characterized in that: The resistance values ​​of the resistors R4 and R6 are equal, and the resistance values ​​of the resistors R5 and R7 are equal.

7. The low ripple adjustable power supply circuit according to claim 1, characterized in that: The LDO linear voltage regulator module includes a second operational amplifier U2 and a linear voltage regulator Q1, wherein the output end of the second operational amplifier U2 is connected to the gate of the linear voltage regulator Q1, a resistor R3 is connected between the source and the gate of the linear voltage regulator Q1, the source of the linear voltage regulator Q1 is connected to the negative electrode VOUT- of the power supply module, and the drain of the linear voltage regulator Q1 is connected to the output negative electrode VOUT1- of the power supply circuit; the non-inverting input end of the second operational amplifier U2 is connected to the resistor R1 as the first input end of the LDO linear voltage regulator module, the inverting input end of the second operational amplifier U2 is connected to the resistor R8 as the second input end of the LDO linear voltage regulator module, and a capacitor C3 is connected between the inverting input end and the output end of the second operational amplifier U2.

8. The low ripple adjustable power supply circuit according to claim 7, characterized in that: The linear voltage regulator Q1 is an N-channel field effect transistor.

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