Control circuit and method for improving output voltage regulation rate

Abstract

The invention provides a control circuit and method for improving an output voltage regulation rate, and relates to the technical field of switching power supply power conversion, and the control circuit comprises an output voltage differential sampling circuit which is used for sampling an output voltage and generating an output voltage sampling signal; the compensation control circuit is used for sampling a load voltage, comparing the load voltage with an output voltage reference and then outputting a compensation signal; the isolation feedback circuit is connected with the output ends of the output voltage differential sampling circuit and the compensation control circuit and is used for superposing the output voltage sampling signal and the compensation signal and generating a feedback signal after isolation; and the primary side control circuit is arranged at the input side of the switching power supply, connected with the output end of the isolation feedback circuit and used for generating a pulse width modulation signal according to the feedback signal so as to control a power switch tube of the switching power supply. Influences brought by isolation operational amplifier transmission precision and digital sampling precision can be eliminated, a high output voltage regulation rate is achieved, and the circuit can be applied to any digital power supply occasion.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of switching power supply power conversion, and in particular to a control circuit and method for improving output voltage regulation. BACKGROUND

[0002] To ensure the safety of power supply, the input and output of the power supply are usually required to be isolated from each other, which requires the use of an isolated converter. When the master chip is on the input side, the output voltage signal needs to be sampled and transmitted to the primary side through an isolated operational amplifier for closed-loop control. However, the transmission accuracy of the isolated operational amplifier is usually only 0.005% due to the influence of temperature and offset voltage, which means that the load regulation is difficult to achieve within 0.005%. On the other hand, with the wide application of digital power supply, the output voltage sampling value is closely related to the sampling time for digital control. Especially in the case of large output voltage ripple, the output voltage sampling value will have a large deviation at different sampling times, which will further affect the load regulation of the converter. SUMMARY

[0003] Therefore, the present application provides a control circuit and method for improving output voltage regulation to eliminate the influence of transmission accuracy of the isolated operational amplifier and digital sampling accuracy, and to achieve a higher output voltage regulation, which can be applied in any digital power supply occasion.

[0004] The present application provides the following technical solutions: a control circuit for improving output voltage regulation, comprising: an output voltage differential sampling circuit connected to an output end of a switching power supply, for sampling an output voltage and generating an output voltage sampling signal; a compensation control circuit connected to a load end, for sampling a voltage across the load and outputting a compensation signal after comparing the load voltage with an output voltage reference; an isolated feedback circuit, a first input end of the isolated feedback circuit being connected to an output end of the output voltage differential sampling circuit, a second input end of the isolated feedback circuit being connected to an output end of the compensation control circuit, for superimposing the output voltage sampling signal and the compensation signal and generating a feedback signal after isolation transmission; a primary side control circuit, the primary side control circuit being arranged on an input side of the switching power supply and connected to an output end of the isolated feedback circuit, for generating a pulse width modulation signal according to the isolated feedback signal to control a power switch tube of the switching power supply.

[0005] According to an embodiment of the present application, the output voltage differential sampling circuit is a differential sampling circuit, comprising a first operational amplifier, a first resistor, a second resistor, a third resistor and a fourth resistor. One end of the first resistor is connected to the positive terminal of the output voltage, and the other end of the first resistor is connected to the inverting input of the first operational amplifier and one end of the second resistor. The other end of the second resistor is connected to the output terminal of the first operational amplifier. One end of the third resistor is connected to the negative terminal of the output voltage, and the other end of the third resistor is connected to the non-inverting input of the first operational amplifier and one end of the fourth resistor. The other end of the fourth resistor is connected to ground.

[0006] According to one embodiment of this application, the compensation circuit includes a second operational amplifier, a seventh resistor, an eighth resistor, and a first capacitor; One end of the seventh resistor is connected to the positive terminal of the power supply load test, and the other end of the seventh resistor is connected to the inverting input of the second operational amplifier and one end of the eighth resistor. The other end of the eighth resistor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the output terminal of the second operational amplifier. One end of the output voltage reference is connected to the non-inverting input of the operational amplifier OP1, and the other end of the output voltage reference is connected to the negative terminal of the power supply load test.

[0007] According to one embodiment of this application, the isolation feedback circuit includes a fifth resistor, a sixth resistor, and an isolation operational amplifier. One end of the fifth resistor is connected to the output terminal of the output voltage differential sampling circuit, one end of the sixth resistor is connected to the output terminal of the compensation circuit, and the other end of the fifth resistor and the other end of the sixth resistor are connected together to the input terminal of the isolation operational amplifier.

[0008] According to one embodiment of this application, the primary-side control circuit includes a controller, the ADC sampling terminal of the controller is connected to the output terminal of the isolation feedback circuit, for sampling the feedback signal, and outputting the pulse width modulation signal by executing a control algorithm.

[0009] According to one embodiment of this application, the controller is an analog controller built from an analog control chip.

[0010] According to one embodiment of this application, the controller is a digital controller built from a digital control chip.

[0011] The present invention also provides a control method for the control circuit as described above, the method comprising: Acquire the output voltage sampling signal of the switching power supply; Obtain the sampled values ​​of the load voltage across the load terminals; The load voltage sample value is compared with the output voltage reference, and a compensation signal is generated through the first control loop. The output voltage sampling signal and the compensation signal are superimposed and electrically isolated to generate a feedback signal that is transmitted to the input side of the switching power supply. On the input side of the switching power supply, a pulse width modulation signal is generated through a second control loop based on the isolated feedback signal to control the power switching transistor of the switching power supply.

[0012] According to one embodiment of this application, the bandwidth of the first control loop is lower than the bandwidth of the second control loop.

[0013] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least: 1. The control circuit and method for improving output voltage regulation proposed in this invention can effectively eliminate the errors caused by temperature drift of the isolation feedback operational amplifier and different sampling times of the ADC, improve the output voltage regulation of the power supply, and the loop of the compensation circuit is relatively slow, so it does not affect the original control loop and dynamic performance.

[0014] 2. The control circuit proposed in this invention for improving output voltage regulation has a simple structure and low cost. The compensation circuit can be connected to the load root, also serving as a remote compensation function, and the range of remote compensation can be flexibly adjusted by simply setting a resistor.

[0015] 3. The control method for improving output voltage regulation proposed in this invention is applicable to both digital and analog control, and can be widely used in various types of switching power supplies, thus having significant practical value. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a control circuit structure for improving output voltage regulation according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a digital control method for improving output voltage regulation according to an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0019] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] An embodiment of the present invention provides a control circuit for improving output voltage regulation, comprising: The output voltage differential sampling circuit is connected to the output terminal of the switching power supply and is used to sample the output voltage and generate an output voltage sampling signal. The compensation control circuit is connected to the load terminal to sample the voltage across the load and compare the load voltage with the output voltage reference before outputting a compensation signal. An isolation feedback circuit is provided, wherein the first input terminal of the isolation feedback circuit is connected to the output terminal of the output voltage differential sampling circuit, and the second input terminal of the isolation feedback circuit is connected to the output terminal of the compensation control circuit. The circuit is used to superimpose the output voltage sampling signal and the compensation signal, and generate a feedback signal after isolated transmission. The primary-side control circuit is located on the input side of the switching power supply and connected to the output of the isolation feedback circuit. It is used to generate a pulse width modulation signal based on the isolated feedback signal to control the power switching transistor of the switching power supply.

[0021] The control method of the control circuit of the present invention includes: acquiring an output voltage sampling signal of a switching power supply; acquiring a load voltage sampling value at both ends of a load; comparing the load voltage sampling value with an output voltage reference, and generating a compensation signal through a first control loop; superimposing the output voltage sampling signal and the compensation signal, and generating a feedback signal after electrical isolation, which is then transmitted to the input side of the switching power supply; and generating a pulse width modulation signal through a second control loop on the input side of the switching power supply based on the isolated feedback signal, so as to control the power switching transistor of the switching power supply.

[0022] This invention proposes a control circuit and method for effectively improving power supply load regulation, which can be implemented using both digital and analog control. The implementation method is simple and can be quickly extended to various power supply applications.

[0023] In some embodiments, the output voltage differential sampling circuit comprises an operational amplifier. OP 1. First resistor R 1. Second resistor R 2. Third resistor R 3. Fourth resistor R 4 components. First resistor R One end of 1 is connected to the output voltage V o Connect the positive terminal to the first resistor. R The other end of 1 is connected to the operational amplifier. OP The inverting input of 1 and the second resistor R Connect one end of 2, and the third resistor R The other end of 2 is connected to the operational amplifier. OP The output terminal of 1, the third resistor R One end of 3 is connected to the output voltage. V o Connect the negative terminal to the third resistor. R The other end of 3 is connected to the operational amplifier. OP The non-inverting input of 1 and the fourth resistor R Connect one end of 4 to the fourth resistor. R The other end of 4 is connected to the ground.

[0024] In some embodiments, the compensation control circuit comprises an operational amplifier. OP 2. The seventh resistor R 7. The eighth resistor R 8 and the first capacitor C 1. Composition. Seventh resistor. R One end of resistor 7 is connected to the positive terminal Sense+ of the power supply load. The seventh resistor... R The other end of 7 is connected to the operational amplifier. OP The inverting input of 2 and the eighth resistor R Connect one end of 8 to the eighth resistor. R The other end of 8 is connected to the first capacitor. C One end of 1, the first capacitor C The other end of 1 is connected to the operational amplifier. OP 2. Output terminal, output voltage reference. V sense_ref One end is connected to the operational amplifier OP Connect the non-inverting input of 1 to the output voltage reference. V sense_ref The other end is connected to the negative terminal Sense- of the power supply load.

[0025] In some embodiments, the isolation feedback circuit consists of a fifth resistor. R 5. Sixth resistor RThe fifth resistor consists of 6 and the isolation operational amplifier N1. R One end of 5 is connected to the operational amplifier. OP The output terminal of 1, the fifth resistor R The other end of 5 is connected to the sixth resistor. R One end of resistor 6 is connected to the input terminal of isolation operational amplifier N1. (The sixth resistor...) R The other end of 6 is connected to the operational amplifier. OP 2 is the output terminal.

[0026] In some embodiments, the primary-side control circuit consists of an input-side control chip and its peripheral circuitry. Optionally, it can be an analog control circuit built with analog control chips such as UC3843 or UC3825; alternatively, it can be a digital control circuit built with digital control chips such as STM32. Taking a digital control chip as an example, the output of the isolation operational amplifier N1 is connected to the ADC sampling terminal of the digital control chip MCU as a sampling signal for the internal digital voltage loop. After processing, a PWM wave is output through a timer to control the switching transistors of the converter.

[0027] like Figure 1 As shown, Figure 1 This invention provides a control circuit for improving output voltage regulation. It should be noted that this embodiment is only for illustrating the working principle; for simplicity, the specific implementations of some circuits, such as the sampling circuit, modulation circuit, driving circuit, and main power circuit, are omitted.

[0028] This embodiment of a control circuit for improving output voltage regulation includes: an output voltage differential sampling circuit, a compensation control circuit, an isolation feedback circuit, and a primary-side control circuit.

[0029] The output voltage differential sampling circuit consists of an operational amplifier. OP 1. First resistor R 1. Second resistor R 2. Third resistor R 3. Fourth resistor R 4 components. First resistor R One end of 1 is connected to the output voltage V o Connect the positive terminal to the first resistor. R The other end of 1 is connected to the operational amplifier. OP The inverting input of 1 and the second resistor R Connect one end of 2, and the third resistor R The other end of 2 is connected to the operational amplifier. OP The output terminal of 1, the third resistor R One end of 3 is connected to the output voltage. V o Connect the negative terminal to the third resistor. RThe other end of 3 is connected to the operational amplifier. OP The non-inverting input of 1 and the fourth resistor R Connect one end of 4 to the fourth resistor. R The other end of 4 is connected to ground. Assume the first resistor... R 1 and the third resistor R The resistance values ​​of all three resistors are r1 and the second resistor. R 2 and the fourth resistor R The resistance values ​​of 4 are all r2. Based on the virtual short and virtual open of the op-amp, the operational amplifier can be obtained. OP Output of 1 V os The expression is: .

[0030] The compensation control circuit consists of an operational amplifier. OP 2. The seventh resistor R 7. The eighth resistor R 8 and the first capacitor C 1. Composition. Seventh resistor. R One end of resistor 7 is connected to the positive terminal Sense+ of the power supply load. The seventh resistor... R The other end of 7 is connected to the operational amplifier. OP The inverting input of 2 and the eighth resistor R Connect one end of 8 to the eighth resistor. R The other end of 8 is connected to the first capacitor. C One end of 1, the first capacitor C The other end of 1 is connected to the operational amplifier. OP 2. Output terminal, output voltage reference. V o_ref One end is connected to the operational amplifier OP Connect the non-inverting input of 1 to the output voltage reference. V sense_ref The other end is connected to the negative terminal Sense- of the power supply load. This is because the output voltage reference... V sense_ref The reference ground is Sense-, and the load output voltage (the difference between Sense+ and Sense-) can be controlled by the regulator, ultimately relating to... V o_ref They are equal. That is: Operational amplifier OP Output of 2 V comp This is the remote compensation voltage.

[0031] The isolation feedback circuit consists of a fifth resistor. R 5. Sixth resistor R The fifth resistor consists of 6 and the isolation operational amplifier N1. R One end of 5 is connected to the operational amplifier.OP The output terminal of 1, the fifth resistor R The other end of 5 is connected to the sixth resistor. R One end of resistor 6 is connected to the input terminal of isolation operational amplifier N1. (The sixth resistor...) R The other end of 6 is connected to the operational amplifier. OP The output terminal of 2. According to the superposition theorem, the signal fed into the isolation operational amplifier N1 can be obtained. V fb The expression is: Since the output voltage range of the operational amplifier is from zero to the supply voltage, it can be adjusted... R 5 and R The proportional relationship between 6 and 6 can limit the voltage regulation range of remote compensation.

[0032] The primary-side control circuit consists of an input-side control chip and its peripheral circuitry. Optionally, it can be an analog control circuit built with analog control chips such as UC3843 or UC3825; alternatively, it can be a digital control circuit built with digital control chips such as STM32. Taking a digital control chip as an example, the output of the isolation operational amplifier N1 is connected to the ADC sampling terminal of the digital control chip MCU as a sampling signal for the internal digital voltage loop. After processing, a PWM wave is output through a timer to control the switching transistors of the power electronic converter.

[0033] This embodiment provides a digital control method for improving output voltage regulation, as follows: Figure 2 As shown, the output voltage V o After sampling, the data is sent to the secondary MCU for compensation loop calculation, and the loop calculation result is output through the DAC, which is then compared with the output voltage sample. V sense After proportional superposition, the voltage is transmitted to the primary-side MCU via an isolation operational amplifier. The primary-side MCU performs the final voltage loop calculation and sends the result to a timer unit to generate a PWM wave to control the switching transistors of the power electronic converter. The following analyzes the adjustment process of the compensation loop. If the isolation operational amplifier has an accuracy error, causing a certain deviation between the output voltage and the set steady-state value (lower than the actual set value), the secondary-side MCU can directly sample the voltage across the load. V sense Therefore, it is not affected by the isolation operational amplifier, and its voltage is related to the reference voltage. V sense_ref Comparison via secondary MCU V sense The voltage loop adjusts the output to reduce the DAC, thereby reducing... V fb The primary side receives the signal output from the isolation operational amplifier. V fb After reduction, through Vfb The voltage loop increases the converter's duty cycle, thereby increasing the output voltage until the secondary output voltage... V sense With reference voltage V sense_ref They are equal, thus effectively improving the output voltage regulation of the power supply. It is worth noting that here... V sense The loop bandwidth of the voltage loop needs to be set to a ratio V fb The voltage loop has a much lower loop bandwidth and only adjusts slowly in steady state, so it does not affect the original loop and dynamic performance.

[0034] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control circuit for improving the line regulation of an output voltage, characterized by The application relates to a switching power supply compensation control method and device. The output voltage differential sampling circuit is a differential sampling circuit and comprises a first operational amplifier, a first resistor, a second resistor, a third resistor and a fourth resistor. The compensation circuit comprises a second operational amplifier, a seventh resistor, an eighth resistor and a first capacitor. The isolation feedback circuit comprises a fifth resistor, a sixth resistor and an isolation operational amplifier. The primary side control circuit comprises a controller, an ADC sampling end of the controller is connected to the output end of the isolation feedback circuit, the feedback signal is sampled, and the pulse width modulation signal is output by executing a control algorithm.

2. The control circuit for improving the regulation of the output voltage according to claim 1, characterized in that, The controller is an analog controller built by an analog control chip. The controller is a digital controller built by a digital control chip.

3. The control circuit for improving the regulation of the output voltage according to claim 1, wherein, The method comprises the following steps: an output voltage sampling signal of a switching power supply is acquired; 4. The control circuit for improving the regulation of the output voltage according to claim 1, wherein, a load voltage sampling value of both ends of a load is acquired; 5. The control circuit for improving the regulation of the output voltage according to claim 1, wherein, ​ 6. The control circuit for improving the regulation of the output voltage according to claim 5, wherein, ​ 7. The control circuit for improving the regulation of the output voltage according to claim 5, wherein, ​ 8. A control method of a control circuit according to any one of claims 1 to 7, characterized by, ​ ​ ​ The load voltage sampling value is compared with an output voltage reference benchmark, and a compensation signal is generated through a first control loop; The output voltage sampling signal is superimposed with the compensation signal, and after electrical isolation, a feedback signal is generated and transmitted to the input side of the switching power supply; At the input side of the switching power supply, according to the isolated feedback signal, a pulse width modulation signal is generated through a second control loop to control the power switch tube of the switching power supply.

9. The control method according to claim 8, characterized by, The bandwidth of the first control loop is lower than that of the second control loop.

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