WO2021218271A1

WO2021218271A1 - Power converter starting control method and apparatus, and power converter starting system

Info

Publication number: WO2021218271A1
Application number: PCT/CN2021/075247
Authority: WO
Inventors: 程文峰; 陈勇; 袁金荣; 李秋莲
Original assignee: 珠海格力电器股份有限公司
Priority date: 2020-04-26
Filing date: 2021-02-04
Publication date: 2021-11-04
Also published as: CN111384848A

Abstract

The present disclosure relates to a power converter starting control method and apparatus, and a power converter starting system. Said method comprises: outputting a pulse width modulation signal to a power converter, the pulse width modulation signal being used for driving a power transistor of the power converter; acquiring a working frequency of the power converter; and when the working frequency of the power converter is greater than a set working frequency, gradually reducing the frequency of the pulse width modulation signal, so as to reduce the working frequency of the power converter. When the working frequency of the power converter is greater than the set working frequency, the frequency of the pulse width modulation signal is gradually reduced, so as to reduce the working frequency of the power converter; the power converter is started in a time-domain frequency conversion manner, the starting process does not need switching, and failures such as hardware overcurrent and software overcurrent and overvoltage do not occur, thereby being safe and reliable, and improving the reliability of power converter starting control.

Description

Power converter starting control method, device and power converter starting system

Cross-references to related applications

This application is based on the application whose CN application number is 202010339282.3 and the application date is April 26, 2020, and claims its priority. The disclosure of the CN application is hereby incorporated into this application as a whole.

Technical field

The present disclosure relates to the technical field of power conversion, and in particular to a power converter startup control method, device and power converter startup system.

Background technique

With the development of science and technology and the continuous progress of society, various types of electronic devices are used more and more widely in people's daily work and life. At present, most electronic devices have only power converters. The power converter converts the voltage or current of the connected electronic device to obtain output power suitable for different circuit modules to supply power to different circuit modules of the electronic device.

The starting method of the power converter known to the inventor of the present disclosure is to change the pulse width first and then perform the frequency modulation switch. Although this starting method can start the power converter, it is easy to change the pulse width to the switching point of the frequency modulation during the starting process. Hardware over-current fault occurs. If the fault protection is not timely, it is easy to explode the circuit board and cause great safety hazards. Therefore, the power converter startup method known by the inventor of the present disclosure has the disadvantage of low control reliability.

Summary of the invention

According to one aspect of the present disclosure, there is provided a power converter startup control method, including: outputting a pulse width modulation signal to the power converter, the pulse width modulation signal is used to drive the power tube of the power converter; The operating frequency of the power converter; and when the operating frequency of the power converter is greater than the set operating frequency, the frequency of the pulse width modulation signal is gradually reduced to reduce the operating frequency of the power converter.

In some embodiments, the set operating frequency includes a first set frequency and a second set frequency; when the operating frequency of the power converter is greater than the set operating frequency, the pulse width modulation is gradually reduced The frequency of the signal to reduce the operating frequency of the power converter includes: when the operating frequency of the power converter is greater than the first set frequency, gradually reducing the frequency of the pulse width modulation signal to make the The operating frequency of the power converter is between the first set frequency and the second set frequency; wherein the first set frequency is greater than the second set frequency.

In some embodiments, the stepwise reducing the frequency of the pulse width modulation signal includes: gradually reducing the frequency of the pulse width modulation signal through proportional-integral-derivative PID adjustment control.

In some embodiments, the stepwise reduction of the frequency of the pulse width modulation signal through PID adjustment control includes: updating the PID limit value and/or the register value according to a set update rate to make the pulse width The frequency of the modulation signal gradually becomes smaller and the duty cycle remains unchanged.

In some embodiments, the power converter startup control method further includes: after obtaining the operating frequency of the power converter, when the operating frequency of the power converter is less than or equal to the set operating frequency, obtaining the The output voltage of the power converter; and when the output voltage does not reach the set output voltage, adjust the pulse width change frequency of the pulse width modulation signal according to the difference between the output voltage and the set output voltage, Until the output voltage reaches the set output voltage.

In some embodiments, the step of adjusting the pulse width change frequency of the pulse width modulation signal according to the difference between the output voltage and the set output voltage includes: obtaining the output voltage and the set output after calculating After the voltage difference, the pulse width change frequency of the pulse width modulation signal is adjusted according to the correspondence between the saved output voltage and the set output voltage difference and the pulse width change frequency.

In some embodiments, the power converter startup control method further includes: after obtaining the output voltage of the power converter, when the output voltage reaches the set output voltage, controlling the power converter to perform Synchronous rectification.

In some embodiments, the power converter startup control method further includes: if the operating frequency of the power converter is less than or equal to the set operating frequency, detecting the power conversion before obtaining the output voltage of the power converter Whether the power converter has a fault; and when the fault is not detected, the step of obtaining the output voltage of the power converter is performed.

In some embodiments, the step of detecting whether a power converter has failed includes: comparing the collected output voltage of the power converter with the set output voltage; and when the output voltage is compared with the set output voltage When the voltage difference exceeds the set difference threshold, it is determined that the power converter has a fault, otherwise the power converter does not have a fault.

According to another aspect of the present disclosure, there is provided a power converter startup control device, including: a signal output module for outputting a pulse width modulation signal to the power converter, and the pulse width modulation signal is used to drive the power converter The frequency detection module is used to obtain the operating frequency of the power converter; and the frequency adjustment module is used to gradually reduce the pulse width when the operating frequency of the power converter is greater than the set operating frequency. Modulate the frequency of the signal to reduce the operating frequency of the power converter.

According to another aspect of the present disclosure, there is provided a power converter startup control device, including: a memory; and a processor coupled to the memory, the processor being configured to execute based on instructions stored in the memory The method described earlier.

According to another aspect of the present disclosure, there is provided a power converter starting system, including: a power converter, a drive regulating device, and a controller, the controller is connected to the drive regulating device, and the drive regulating device is connected to the The power converter, the controller is used to control the startup of the power converter according to the aforementioned method.

In some embodiments, the power converter startup system further includes a sampling circuit, and the sampling circuit is connected to the controller and the power converter.

In some embodiments, the power converter includes a first conversion circuit, a transformer, and a second conversion circuit, wherein the primary winding of the transformer is connected to the first conversion circuit, and the secondary winding of the transformer is connected to the The second conversion circuit; the drive adjustment device includes a first drive adjustment circuit and a second drive adjustment circuit, wherein the first drive adjustment circuit is connected to the controller and the first conversion circuit, the second drive The adjustment circuit is connected to the controller and the second conversion circuit.

In some embodiments, the first conversion circuit includes a first power tube, a second power tube, a third power tube, a fourth power tube, and a capacitor, wherein the first power tube and the second power tube , The control ends of the third power tube and the fourth power tube are both connected to the first drive regulating circuit, and the first end of the first power tube is connected to the first end of the third power tube To the positive input, the second end of the first power tube is connected to the first end of the second power tube and one end of the primary winding of the transformer, and the second end of the third power tube is connected to the The first end of the fourth power tube is connected to the other end of the primary winding of the transformer through the capacitor, and the second end of the second power tube and the second end of the fourth power tube are connected to the negative input .

In some embodiments, the first power tube, the second power tube, the third power tube, and the fourth power tube are all metal oxide semiconductor MOS transistors.

In some embodiments, the second conversion circuit includes a fifth power tube, a sixth power tube, a seventh power tube, and an eighth power tube, wherein the fifth power tube, the sixth power tube, and the The control ends of the seventh power tube and the eighth power tube are both connected to the second drive regulation circuit, and the first end of the fifth power tube and the first end of the seventh power tube are connected to the output Positive, the second end of the fifth power tube is connected to the first end of the sixth power tube and one end of the secondary winding of the transformer, and the second end of the seventh power tube is connected to the first end of the transformer. The first end of the eight power tube and the other end of the secondary winding of the transformer, the second end of the sixth power tube and the second end of the eighth power tube are connected to the output negative electrode.

In some embodiments, the fifth power tube, the sixth power tube, the seventh power tube, and the eighth power tube are all MOS tubes.

In some embodiments, the power converter startup system further includes: an oscilloscope connected to the controller.

Description of the drawings

Figure 1 is a flowchart of a power converter startup control method in an embodiment;

Figure 2 is a flowchart of a power converter startup control method in another embodiment;

Figure 3 is a structural block diagram of a power converter startup control device in an embodiment;

Figure 4 is a structural block diagram of a power converter startup control device in another embodiment;

Figure 5 is a structural block diagram of a power converter starting system in an embodiment;

Fig. 6 is a structural block diagram of a power converter starting system in another embodiment;

Fig. 7 is a schematic diagram of a power converter starting system in an embodiment;

Figure 8 is a schematic diagram of complementary PWM waves in an embodiment;

FIG. 9 is a schematic diagram of the adjustment of a single PWM wave in an embodiment;

FIG. 10 is a schematic diagram of the startup of PID adjusting different variables in an embodiment;

FIG. 11 is a schematic diagram of a flow chart of a frequency modulation start of a power converter in an embodiment.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present disclosure clearer, the following further describes the present disclosure in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present disclosure, but not used to limit the present disclosure.

Aiming at the problem of low control reliability of the power converter starting mode known by the inventors of the present disclosure, a power converter starting control method, device and power converter starting system that can improve control reliability are provided.

In one embodiment, a power converter startup control method is provided, which is suitable for the variable frequency startup of LLC (Logical Link Control) frequency modulation converters. As shown in FIG. 1, the method includes:

Step S110: output a pulse width modulation signal to the power converter.

The pulse width modulation (Pulse Width Modulation, PWM) signal is used to drive the power tube of the power converter. Among them, the drive regulation device can be connected to the drive regulation device through the controller, and the drive regulation device is connected to the power tube in the power converter. After the power-on initialization is completed, the controller starts the power converter and prohibits synchronous rectification. The controller outputs the pulse width through the drive regulation device. The modulation signal is sent to the power converter to drive and control the power tube. Specifically, the driving adjustment device outputs the complementary PWM wave to the corresponding power tube, and controls the on and off of the power tube, thereby controlling the operation of the power converter. The frequency of the PWM wave is not unique. Specifically, it can output a high-frequency PWM wave to the corresponding power tube. The high-frequency PWM wave will not generate a large current at the moment when the main circuit of the power converter is connected to electricity, which can effectively avoid the occurrence of faults. The high-frequency PWM wave can be a PWM wave in the range of 300kHz-700kHz. For example, the high-frequency PWM wave can be a PWM wave of 500kHz. In addition, the type of controller is not unique. In this embodiment, the controller may specifically select a microcontroller.

Step S120: Obtain the operating frequency of the power converter.

After the drive regulator outputs the pulse width modulation signal to drive the power tube of the power converter, the working frequency of the power converter can be measured by the oscilloscope, and the oscilloscope sends the measured working frequency to the controller for subsequent timing of the power converter. Domain frequency conversion start control.

Step S130: When the working frequency of the power converter is greater than the set working frequency, gradually reduce the frequency of the pulse width modulation signal to reduce the working frequency of the power converter.

For example, the set operating frequency is related to the circuit structure of the power converter. The set operating frequency can be determined and saved in advance according to the structure of the power converter. After the controller receives the operating frequency measured by the oscilloscope, it compares the set operating frequency with For the measured operating frequency, when the operating frequency of the power converter is greater than the set operating frequency, the frequency of the pulse width modulation signal is gradually reduced to reduce the operating frequency of the power converter.

In some embodiments, the way in which the controller performs frequency reduction control is not unique. The amplitude of frequency reduction of the pulse width modulation signal by the controller can also be selected according to actual conditions, and the frequency reduction amplitude may be the same or different each time. By gradually reducing the frequency of the pulse width modulation signal, the range of the operating frequency is forcibly reduced in each cycle, so that the operating frequency is forcibly reduced, avoiding the power tube heating and causing failure when the power tube is driven by the high-frequency PWM wave. The way to gradually reduce the frequency of the pulse width modulation signal is not the only way. Taking the PID (Proportion Integral Derivative, proportional-integral-derivative) adjustment method for time-domain frequency modulation control as an example, it can be modified to set the internal register value of the controller. It can also continuously modify and update the PID limiter value, or it can also perform frequency modulation control from two aspects at the same time to ensure that the operating frequency of the power converter can be forcibly reduced.

The power converter startup control method described above monitors the working frequency of the power converter after outputting a pulse width modulation signal to drive the power tube of the power converter, and gradually reduces the pulse width modulation when the working frequency of the power converter is greater than the set working frequency The frequency of the signal is to reduce the working frequency of the power converter, and the power converter is started by the time domain frequency conversion method. The startup process does not need to switch, and will not cause hardware overcurrent, software overcurrent and overvoltage faults, safe and reliable, and improves the power supply. The control reliability of the converter startup.

In one embodiment, the set operating frequency includes a first set frequency and a second set frequency, and step S130 includes: when the operating frequency of the power converter is greater than the first set frequency, gradually reducing the frequency of the pulse width modulation signal , So that the operating frequency of the power converter is between the first set frequency and the second set frequency; wherein, the first set frequency is greater than the second set frequency.

Specifically, taking the LLC power converter as an example, during the circuit design of the LLC power converter, the first resonant frequency and the second resonant frequency of the LLC power converter are determined, and these are fixed after the circuit is designed. The first resonant frequency and the second resonant frequency of the power converter can be calculated using formulas according to the circuit structure of the LLC power converter, and they are stored as the first set frequency f1 and the second set frequency f2, respectively. The LLC power converter has 3 normal working states, namely, the working frequency is greater than the first set frequency f1, the working frequency is equal to the first set frequency f1, and the working frequency is greater than the second set frequency f2 and less than the first set frequency f1. , LLC power converter works between the first set frequency f1 and the second set frequency f2, can achieve zero voltage turn-on and zero current turn-off, can effectively improve the efficiency of the power converter, and give full play to the advantages of the LLC power converter. When the LLC power converter does not work between the first set frequency f1 and the second set frequency f2, in order to achieve zero voltage turn-on and zero current turn-off, additional circuit adjustment devices need to be added, which increases the hardware cost.

When it is detected that the working frequency of the power converter is greater than the first set frequency f1, the time-domain frequency modulation control is performed to gradually reduce the frequency of the pulse width modulation signal, thereby forcibly reducing the working frequency of the power converter, and avoiding starting the power converter When the frequency of the driven PWM wave is very high, the power tube heats up seriously. At the same time, by reducing the working frequency of the power converter to make the power converter work between the first resonant frequency and the second resonant frequency, zero voltage turn-on and zero current turn-off can be achieved without additional circuit adjustment devices, which can effectively improve the power supply. The efficiency of the converter.

In one embodiment, gradually reducing the frequency of the pulse width modulation signal in step S130 includes: gradually reducing the frequency of the pulse width modulation signal through PID adjustment control. The controller adopts the PID adjustment method to gradually reduce the frequency of the pulse width modulation signal, and the control is simple and reliable. Specifically, in this embodiment, the frequency of the pulse width modulation signal is gradually reduced by PID adjustment control, including: updating the PID limit value and/or register value according to the set update rate, so that the pulse width modulation signal The frequency gradually becomes smaller and the duty cycle remains unchanged.

For example, the update rate can be selected according to actual needs and saved in advance. The controller cyclically updates the PID limiter value and/or internal register value according to the saved update rate, so as to perform PWM wave down-frequency adjustment to forcibly reduce the work of the power converter frequency. Specifically, the controller updates the PID limiting value and the internal register value each time, so that the frequency of the PWM wave is gradually reduced, and the duty cycle remains unchanged at 50%. Keep the duty cycle constant during down-frequency adjustment, which facilitates PWM wave adjustment and ensures that the output complementary PWM wave can drive the power tube normally and avoid malfunctions.

In one embodiment, as shown in FIG. 2, after step S120, when the operating frequency of the power converter is less than or equal to the set operating frequency, the method further includes step S150 and step S160.

Step S150: Obtain the output voltage of the power converter. Specifically, the output voltage of the power converter can be detected by the sampling circuit, and the detected output voltage is sent to the controller.

Step S160: When the output voltage does not reach the set output voltage, adjust the pulse width change frequency of the pulse width modulation signal according to the difference between the output voltage and the set output voltage until the output voltage reaches the set output voltage.

The controller can pre-set the set output voltage of the power converter. After receiving the output voltage of the power converter detected by the sampling circuit, it compares the set output voltage with the collected output voltage. If the output voltage has not reached the set output voltage. For a fixed output voltage, the pulse width change frequency of the pulse width modulation signal is adjusted according to the difference between the output voltage and the set output voltage until the output voltage reaches the set output voltage. It can be understood that when the output voltage reaches the set output voltage, the controller can control the power converter to turn on the synchronous rectification function.

Specifically, the corresponding relationship between the difference between the output voltage and the set output voltage and the pulse width change frequency can be established in advance, and the corresponding relationship between the two can be a linear relationship or a non-linear relationship. After the controller calculates the difference between the output voltage and the set output voltage, it adjusts the pulse width change frequency of the pulse width modulation signal according to the saved correspondence relationship. For example, if the difference between the output voltage and the set output voltage is large, Increasing the pulse width change frequency can increase the output voltage value and reduce the start-up time; on the contrary, reduce the pulse width change frequency.

In this embodiment, according to the difference between the output voltage and the set output voltage, the pulse width change frequency of the pulse width modulation signal is adjusted, which can make the output voltage curve change when the power converter starts more smoothly, and improve the startup of the power converter. reliability.

Further, in an embodiment, after step S150, the method further includes step S170.

Step S170: When the output voltage reaches the set output voltage, control the power converter to perform synchronous rectification.

Specifically, when the output voltage of the power converter reaches the set output voltage, the controller controls the power converter to turn on the synchronous rectification function by driving the adjustment device. The DC output voltage is obtained by rectification and output.

In addition, after the power converter performs synchronous rectification, the input voltage of the power converter can also be collected through the sampling circuit, and the controller performs logical control of the operation of the power converter according to the relationship between the collected input voltage and the reference input voltage. Specifically, the controller uses the input voltage as one of the judgment conditions to determine under what conditions the synchronous rectification is turned on or off. For example, the controller can control the power converter to turn on the synchronous rectification when the input voltage is greater than the reference input voltage, and turn off the synchronous rectification when the input voltage is lower than the reference input voltage.

In one embodiment, referring to FIG. 2 continuously, if the working frequency of the power converter is less than or equal to the set working frequency, before step S150, the method further includes step S140.

Step S140: Detect whether the power converter fails. When no failure is detected, step S150 is performed.

There is no unique way to detect whether the power converter has a fault. Specifically, the output voltage of the power converter can also be detected through a sampling circuit, and the detected output voltage can be sent to the controller. The controller can compare the collected output voltage with the set output voltage. When the difference between the collected output voltage and the set output voltage exceeds the set difference threshold, it can be considered that the power converter is malfunctioning; otherwise, it does not appear. Fault. When no failure is detected, step S150 is performed. If a fault is detected, the controller can start the fault processing logic and cut off the output of the power converter to avoid safety accidents. When the fault is eliminated, the process is restarted, power-on initialization is performed and the synchronous rectification of the power converter is disabled, and step S110 is entered.

In one embodiment, a power converter startup control device is also provided, which is suitable for frequency conversion startup of LLC FM converters. As shown in FIG. 3, the device includes a signal output module 110, a frequency detection module 120, and a frequency adjustment module. 130. The signal output module 110 is used to output a pulse width modulation signal to the power converter, and the pulse width modulation signal is used to drive the power tube of the power converter. The frequency detection module 120 is used to obtain the operating frequency of the power converter. The frequency adjustment module 130 is used for gradually reducing the frequency of the pulse width modulation signal when the working frequency of the power converter is greater than the set working frequency, so as to reduce the working frequency of the power converter.

In one embodiment, the set operating frequency includes a first set frequency and a second set frequency, and the frequency adjustment module 130 gradually reduces the frequency of the pulse width modulation signal when the operating frequency of the power converter is greater than the first set frequency. , So that the operating frequency of the power converter is between the first set frequency and the second set frequency; wherein, the first set frequency is greater than the second set frequency.

In one embodiment, the frequency adjustment module 130 gradually reduces the frequency of the pulse width modulation signal through PID adjustment control.

In one embodiment, the frequency adjustment module 130 updates the PID limit value and/or the register value according to the set update rate, so that the frequency of the pulse width modulation signal gradually decreases and the duty cycle remains unchanged.

In one embodiment, as shown in FIG. 4, the power converter startup control device further includes a voltage adjustment module 150. The voltage regulation module 150 is used to obtain the output voltage of the power converter when the operating frequency of the power converter is less than or equal to the set operating frequency after the frequency detection module 120 obtains the operating frequency of the power converter; when the output voltage does not reach the set operating frequency, When the output voltage is set, adjust the pulse width change frequency of the pulse width modulation signal according to the difference between the output voltage and the set output voltage until the output voltage reaches the set output voltage.

Further, in one embodiment, the voltage regulation module 150 also controls the power converter to perform synchronous rectification when the output voltage reaches the set output voltage.

In an embodiment, the power converter startup control device further includes a fault detection module 140. The fault detection module 140 is used to detect whether the power converter has a fault after the working frequency of the power converter is less than or equal to the set working frequency and before the voltage regulation module 150 obtains the output voltage of the power converter; when no fault is detected, The control voltage adjustment module 150 obtains the output voltage of the power converter. In addition, if a fault is detected, the fault detection module 140 can also be used to cut off the output of the power converter to avoid a safety accident.

For the specific definition of the power converter startup control device, please refer to the above definition of the power converter startup control method, which will not be repeated here. Each module in the power converter startup control device described above can be implemented in whole or in part by software, hardware, and a combination thereof. The above-mentioned modules may be embedded in the form of hardware or independent of the processor in the computer equipment, or may be stored in the memory of the computer equipment in the form of software, so that the processor can call and execute the operations corresponding to the above-mentioned modules.

In some embodiments of the present disclosure, a power converter startup control device is also provided. The power converter startup control device includes: a memory; and a processor coupled to the memory, and the processor is configured to execute the aforementioned method based on instructions stored in the memory (for example, as shown in FIG. 1 and / Or the method shown in Figure 2).

The power converter startup control device described above monitors the working frequency of the power converter after outputting a pulse width modulation signal to drive the power tube of the power converter, and gradually reduces the pulse width modulation when the working frequency of the power converter is greater than the set working frequency The frequency of the signal is to reduce the working frequency of the power converter, and the power converter is started by the time domain frequency conversion method. The startup process does not need to switch, and will not cause hardware overcurrent, software overcurrent and overvoltage faults, safe and reliable, and improves the power supply. The control reliability of the converter startup.

In one embodiment, a power converter startup system is also provided, as shown in FIG. 5, including a controller 210, a drive regulating device 220, and a power converter 230. The controller 210 is connected to the drive regulating device 220, and the drive regulating device 220 is connected to the power converter 230, and the controller 210 is used for starting control of the power converter according to the above method. In addition, the power converter startup system also includes an oscilloscope connected to the controller 210.

In one embodiment, as shown in FIG. 6, the power converter startup system further includes a sampling circuit 240, and the sampling circuit 240 is connected to the controller 210 and the power converter 230.

Specifically, in one embodiment, as shown in FIG. 7, the power converter 230 includes a first conversion circuit 232, a transformer T, and a second conversion circuit 234, and the drive adjustment device 220 includes a first drive adjustment circuit 222 and a second drive In the regulating circuit 224, the primary winding of the transformer T is connected to the first conversion circuit 232, the secondary winding of the transformer T is connected to the second conversion circuit 234, the first drive regulation circuit 222 is connected to the controller 210 and the first conversion circuit 232, and the second drive regulation The circuit 224 connects the controller 210 and the second conversion circuit 234. In this embodiment, the controller 210 is a microcontroller 212.

In some embodiments, the first conversion circuit 232 includes a first power tube Q1, a second power tube Q2, a third power tube Q3, a fourth power tube Q4, and a capacitor C. The control ends of the first power tube Q1, the second power tube Q2, the third power tube Q3, and the fourth power tube Q4 are all connected to the first drive regulating circuit 222. The first end of the first power tube Q1 and the first end of the third power tube Q3 are connected to the input positive Vin+. The second end of the first power tube Q1 is connected to the first end of the second power tube Q2 and one end of the primary winding of the transformer T. The second end of the third power tube Q3 is connected to the first end of the fourth power tube Q4, and is connected to the other end of the primary winding of the transformer T through a capacitor C. The second end of the second power tube Q2 and the second end of the fourth power tube Q4 are connected to the input negative Vin-. The sampling circuit 240 is connected to the positive input Vin+ and the positive input Vin+.

In some embodiments, the first power tube Q1, the second power tube Q2, the third power tube Q3, and the fourth power tube Q4 may specifically be triodes or MOS (Metal Oxide Semiconductor) transistors. For example, in this embodiment, the first power tube Q1, the second power tube Q2, the third power tube Q3, and the fourth power tube Q4 are all MOS tubes. The microcontroller 212 outputs the complementary PWM wave to the corresponding power tube in the first conversion circuit 232 through the first drive adjustment circuit 222, and down-regulates the PWM wave according to the operating frequency collected by the oscilloscope to reduce the work of the power converter frequency. Each power tube in the first conversion circuit 232 performs on-off switching according to the PWM wave received by the control terminal, so that the first conversion circuit 232 converts the connected DC power to obtain AC power and transmit it to the transformer T.

In some embodiments, the second conversion circuit 234 includes a fifth power tube Q5, a sixth power tube Q6, a seventh power tube Q7, and an eighth power tube Q8. The control ends of the fifth power tube Q5, the sixth power tube Q6, the seventh power tube Q7, and the eighth power tube Q8 are all connected to the second drive regulation circuit 224. The first end of the fifth power tube Q5 and the first end of the seventh power tube Q7 are connected to the output anode Vout+. The second end of the fifth power tube Q5 is connected to the first end of the sixth power tube Q6 and one end of the secondary winding of the transformer T. The second end of the seventh power tube Q7 is connected to the first end of the eighth power tube Q8 and the other end of the secondary winding of the transformer T. The second end of the sixth power tube Q6 and the second end of the eighth power tube Q8 are connected to the output negative Vout-. The sampling circuit 240 is connected to the output positive Vout+ and the output negative Vout-.

In some embodiments, the fifth power tube Q5, the sixth power tube Q6, the seventh power tube Q7, and the eighth power tube Q8 may specifically be transistors or MOS tubes. For example, in this embodiment, the fifth power tube Q5, the sixth power tube Q6, the seventh power tube Q7, and the eighth power tube Q8 are all MOS tubes. After the output voltage collected by the sampling circuit 240 reaches the set output voltage, the microcontroller 212 controls the second drive adjustment circuit 224 to output a PWM signal to drive the corresponding power tube in the second conversion circuit 234, so that the second conversion circuit 234 is connected to the transformer The alternating current output by the secondary winding of T is synchronously sorted to obtain a direct current voltage output.

The above power converter startup system monitors the operating frequency of the power converter after outputting a pulse width modulation signal to drive the power tube of the power converter, and gradually reduces the pulse width modulation signal when the operating frequency of the power converter is greater than the set operating frequency The frequency of the power converter is to reduce the working frequency of the power converter, and the time domain frequency conversion method is used to start the power converter. There is no need to switch during the startup process, and there will be no hardware over-current, software over-current and over-voltage faults. It is safe and reliable, and improves the power conversion. Control reliability of the start-up of the device.

In order to facilitate a better understanding of the above-mentioned power converter startup control method, device and power converter startup system, the following takes the frequency conversion startup control of the LLC frequency modulation converter as an example for detailed explanation.

The traditional starting method of FM LLC power converter is to change the pulse width first and then perform FM switching. Although this starting method can start the LLC power converter, it has the following shortcomings:

①During the startup process, the switching point from changing the pulse width to the frequency modulation is prone to hardware over-current faults. When the fault protection is not in time, it is easy to blow up the circuit board, causing great safety hazards;

② It is necessary to set the switching conditions, the conditions are not set properly, and the power converter is difficult to start, which means that it takes a lot of time and energy to debug and find suitable conditions, which increases the project cycle;

③The setting curve of the output voltage at start-up does not change smoothly.

Based on this, the present disclosure provides a time-domain frequency conversion start control scheme. By adopting the time-domain frequency conversion start control method, it can effectively solve the problem of the LLC frequency conversion power converter during the startup process, which causes the circuit board to burn out and the output voltage curve is not smooth. And other problems, and can reduce the startup and debugging time of the power board, and reduce the project cycle.

As shown in FIG. 7, the power converter startup system includes a microcontroller 212, a first drive regulation circuit 222, a second drive regulation circuit 224, a power converter and a sampling circuit 240. The power converter includes a first conversion circuit 232, a transformer T and the second conversion circuit 234. The microcontroller 212 outputs a PWM wave, and controls the operation of the power tube in the power converter via the first drive regulation circuit 222 and the second drive regulation circuit 224.

As shown in FIG. 8, the microcontroller 212 outputs a complementary PWM wave, where DB is the dead time and does not change, and the frequency of the PWM wave is constantly changing. During the startup of the LLC power converter, the microcontroller 212 will first output high-frequency PWM waves (such as 500kHz PWM waves), and output high-frequency PWM waves at the moment of startup, which will not cause the LLC power converter to malfunction or burn. Bad circuit board. Then enter the time domain FM control link, and debug according to the needs to select the appropriate amplitude for frequency reduction. The conversion process of the PWM wave is shown in Figure 8. The frequency of p1 to p3 gradually decreases, but the duty cycle remains unchanged at 50%.

Figure 9 shows a schematic diagram of the change of a single PWM wave during frequency modulation control. For example, at time t _a , the frequency of the PWM wave is f _a , and its corresponding pulse width is h, and the frequency of the PWM wave _{at time t b} f _a becomes frequency f _b , and the pulse width increases by d _h .

Figure 10 shows the schematic diagram of PID adjusting different variables to start, a and b are the start curves of different variable adjustments respectively _{, the output voltage of curve a reaches the set output voltage Vset at time t a} , and curve b is at time t _b The set output voltage Vset is reached. The main factors affecting the startup curve are: PID parameters, PID limiting value and the size of dh/dt. Among them, dh/dt (that is, the pulse width change frequency of the pulse width modulation signal) is used to measure the pulse width during the change of the PWM wave. The speed of h changes. When the dh/dt changes greatly, the start-up curve in Figure 10 becomes steep, otherwise it will become flat.

Different loads have different requirements for the establishment of the output voltage of the power converter. When the output voltage is established faster or slower, it may cause the load to malfunction. The appropriate PID parameters can be selected according to the actual needs, and the PID limit value is updated. When selecting the appropriate update rate. In addition, dh/dt is related to the difference between the output voltage and the set output voltage, and the two can be set to a linear relationship or a non-linear relationship.

Fig. 11 is a program flow chart of the frequency conversion start of the LLC FM converter. First, the LLC power converter performs initialization work at the moment of power-on, such as the bias calibration of the sampling circuit 240, the configuration of the PWM register, the ADC register, and so on. After the microcontroller 212 determines that the power converter can work normally according to the initialization logic, it outputs the complementary PWM wave to the corresponding power tube, starts to start the power converter and prohibits synchronous rectification. Because the synchronous rectification is performed during startup, it will fail, and in serious cases, the power tube will be blown up, and the power converter will be burned out. As shown in Figure 7, the first power tube Q1 and the fourth power tube Q4 are driven by the same PWM wave, the second power tube Q2 and the third power tube Q3 are driven by the same PWM wave; the first power tube Q1 and the second power tube Q3 are driven by the same PWM wave. The power tube Q2 is driven by complementary PWM waves. As shown in Figure 8, there is a dead zone DB between PWM wave drives, and the dead zone time remains unchanged. Similarly, the third power tube Q3 and the fourth power tube Q4 are driven by complementary PWM waves with dead zones.

The microcontroller 212 controls the first driving adjustment circuit 222 to output a high-frequency PWM wave, and selects the high-frequency PWM wave for driving, which will not generate a large current at the moment when the main circuit of the power converter is powered on, and can effectively avoid the occurrence of faults. However, after the high-frequency PWM wave is started, if you do not perform forced frequency reduction and rely solely on PID to adjust the output, the output voltage can still reach the set voltage value, but the frequency of driving the PWM wave is very high at this time, which causes the power tube to heat up extremely seriously and does not meet the requirements. LLC power converter has shortcomings such as circuit characteristics, so software is required to forcefully reduce its operating frequency.

Specifically, the operating frequency of the LLC power converter circuit will completely enter the discontinuous mode between the first resonant frequency and the second resonant frequency. At this time, zero voltage turn-on and zero current turn-off can be achieved, which can effectively improve the power converter. Efficiency, give full play to the advantages of LLC power converter circuit. Among them, after the power converter is designed, the first resonant frequency and the second resonant frequency are both fixed, which can be calculated using formulas based on the structure of the LLC power converter. The LLC power converter has 3 normal working states, namely, the working frequency is greater than the first resonant frequency, the working frequency is equal to the first resonant frequency, and the working frequency is greater than the second resonant frequency and less than the first resonant frequency, but the LLC power converter works in Between the first resonant frequency and the second resonant frequency, zero voltage turn-on and zero current turn-off can be achieved, and the LLC power converter has high efficiency.

The first resonant frequency and the second resonant frequency are respectively used as the first set frequency f1 and the second set frequency f2. When the circuit is working, the operating frequency of the LLC power converter can be measured with an oscilloscope. When it is detected that the operating frequency is higher than When the frequency f1 is first set, the working frequency of the power tubes Q1-Q4 is forced to be reduced. In each cycle, the operating frequency range of the LLC power converter is forcibly reduced, so that the operating frequency is forcibly reduced. The amount of each reduction can be selected according to actual needs to reduce the upper limit of the operating frequency. The forced reduction of the operating frequency is mainly achieved through two aspects. On the one hand, the internal register value of the microcontroller 212 is continuously modified and set, and on the other hand, the limit value of the PID is continuously modified and updated. This ensures that the forced reduction can be achieved from two aspects. The operating frequency is such that the operating frequency of the LLC power converter circuit is between the first resonant frequency and the second resonant frequency. As shown in Figure 11, if it is detected that the operating frequency is lower than the first resonance frequency, the operation of updating the PID limit value and internal register value to reduce the operating frequency can no longer be performed, and the fault detection process is entered.

When outputting different frequencies of PWM waves to drive the power tube, the main circuit of the LLC power converter generates voltage and current, and the output voltage value continues to increase, which can effectively solve problems such as failures and burnout of circuit boards during the traditional startup process. For the sake of safety and insurance, fault detection and processing are still carried out.

The sampling circuit 240 and the external interrupt circuit can be used to determine whether the power converter is faulty. For example, the designed power converter needs to stabilize the output voltage of 400V, but due to some factors, the output voltage of the power converter reaches 450V, then the sampling circuit 240 The high voltage of 450V will be sampled and compared with the set safe value (for example, the set safe value is 405V), if 450V>405V, then the microcontroller 212 will take measures to cut off the voltage output to avoid safety accidents. Alternatively, an interruption method may also be adopted. When the external voltage exceeds 405V, an interruption is triggered, and the microcontroller 212 takes measures to cut off the voltage output.

When no fault occurs, ADC sampling is performed by the sampling circuit 240 to obtain the current output voltage value. From a macro point of view, the voltage value continues to rise until it is the same as the set voltage value. When the output voltage is the same as the set value, the LLC power converter starts the synchronous rectification and enters the normal operation logic. Otherwise, as shown in Figure 11, it needs Adjust the start-up time of LLC power converter. When the difference between the detected voltage and the set voltage is large, increase dh/dt, which can be linear or non-linear, by increasing the pulse width change of the PWM wave Frequency, pull up the output voltage value, reduce the start-up time; vice versa.

If a cycle does not enter the normal operation logic, it will enter the cycle again until the sampled output voltage reaches the set output voltage, and the synchronous rectification is turned on, and the normal operation logic is entered; if the startup process enters the fault logic, the fault is removed and restored, and then restarted. Start the startup process.

After the synchronous rectification is turned on and the normal operation logic is entered, the microcontroller 212 uses the input voltage collected by the sampling circuit 240 as one of the judgment conditions to determine under what conditions the synchronous rectification is turned on or off. For example, when the input voltage is greater than 380V, the synchronous rectification is turned on. In actual operation, the microcontroller 212 will turn on the synchronous rectification when the input voltage is greater than 380V, and turn off the synchronous rectification when the input voltage is lower than 380V.

The time-domain variable frequency start control scheme provided by the present disclosure has the following beneficial effects:

① The power tube changes regularly, and no hardware over-current, software over-current, over-voltage and other faults will occur during the startup process, which is safe and reliable, and improves the service life of the power converter;

②There is no switching during the startup process, smooth adjustment, no need to spend time looking for switching conditions, reducing development time;

③In the whole process, the output voltage establishes a curve and changes smoothly.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several implementation manners of the present disclosure, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several modifications and improvements can be made, and these all fall within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the appended claims.

Claims

A power converter startup control method includes:

Outputting a pulse width modulation signal to the power converter, where the pulse width modulation signal is used to drive the power tube of the power converter;

Obtaining the operating frequency of the power converter; and

When the operating frequency of the power converter is greater than the set operating frequency, the frequency of the pulse width modulation signal is gradually reduced to reduce the operating frequency of the power converter.
The power converter startup control method according to claim 1, wherein the set operating frequency includes a first set frequency and a second set frequency;

When the operating frequency of the power converter is greater than the set operating frequency, gradually reducing the frequency of the pulse width modulation signal to reduce the operating frequency of the power converter includes:

When the operating frequency of the power converter is greater than the first set frequency, the frequency of the pulse width modulation signal is gradually reduced, so that the operating frequency of the power converter is at the first set frequency and the first set frequency. Between the second set frequency; wherein, the first set frequency is greater than the second set frequency.
The power converter startup control method according to claim 1, wherein the stepwise reducing the frequency of the pulse width modulation signal comprises: making the frequency of the pulse width modulation signal step by step through proportional-integral-derivative PID adjustment control Become smaller.
The power converter startup control method according to claim 3, wherein the stepwise reduction of the frequency of the pulse width modulation signal through PID adjustment control comprises: updating the PID limit value and/or according to a set update rate Or register value, so that the frequency of the pulse width modulation signal gradually becomes smaller and the duty cycle remains unchanged.
The power converter startup control method according to claim 1, further comprising:

After obtaining the operating frequency of the power converter, when the operating frequency of the power converter is less than or equal to the set operating frequency, obtaining the output voltage of the power converter; and

When the output voltage does not reach the set output voltage, adjust the pulse width change frequency of the pulse width modulation signal according to the difference between the output voltage and the set output voltage until the output voltage reaches the set The output voltage.
The power converter startup control method according to claim 5, wherein the step of adjusting the pulse width change frequency of the pulse width modulation signal according to the difference between the output voltage and the set output voltage comprises:

After the difference between the output voltage and the set output voltage is calculated, the difference between the saved output voltage and the set output voltage and the corresponding relationship between the pulse width change frequency is calculated on the pulse width modulation signal The pulse width change frequency is adjusted.
The power converter startup control method according to claim 5, further comprising:

After obtaining the output voltage of the power converter, when the output voltage reaches the set output voltage, the power converter is controlled to perform synchronous rectification.
The power converter startup control method according to claim 5, further comprising:

If the working frequency of the power converter is less than or equal to the set working frequency, before obtaining the output voltage of the power converter, detect whether the power converter is malfunctioning; and

When no fault is detected, the step of obtaining the output voltage of the power converter is performed.
8. The start-up control method of a power converter according to claim 8, wherein the step of detecting whether the power converter is malfunctioning comprises:

Comparing the collected output voltage of the power converter with the set output voltage; and

When the difference between the output voltage and the set output voltage exceeds the set difference threshold, it is determined that the power converter has a fault, otherwise the power converter does not have a fault.
A power converter startup control device, including:

A signal output module for outputting a pulse width modulation signal to the power converter, and the pulse width modulation signal is used to drive the power tube of the power converter;

A frequency detection module for obtaining the operating frequency of the power converter; and

The frequency adjustment module is used for gradually reducing the frequency of the pulse width modulation signal when the working frequency of the power converter is greater than the set working frequency, so as to reduce the working frequency of the power converter.
A power converter startup control device, including:

Memory; and

A processor coupled to the memory, the processor being configured to execute the method according to any one of claims 1 to 9 based on instructions stored in the memory.
A power converter starting system, comprising: a power converter, a drive regulating device and a controller, the controller is connected to the drive regulating device, the drive regulating device is connected to the power converter, and the controller is used for The method according to any one of claims 1-9 performs start-up control of the power converter.
The power converter starting system according to claim 12, further comprising: a sampling circuit connected to the controller and the power converter.
The power converter starting system according to claim 12, wherein:

The power converter includes a first conversion circuit, a transformer, and a second conversion circuit, wherein a primary winding of the transformer is connected to the first conversion circuit, and a secondary winding of the transformer is connected to the second conversion circuit;

The drive regulation device includes a first drive regulation circuit and a second drive regulation circuit, wherein the first drive regulation circuit is connected to the controller and the first conversion circuit, and the second drive regulation circuit is connected to the A controller and the second conversion circuit.
The power converter starting system according to claim 14, wherein:

The first conversion circuit includes a first power tube, a second power tube, a third power tube, a fourth power tube, and a capacitor,

Wherein, the control ends of the first power tube, the second power tube, the third power tube, and the fourth power tube are all connected to the first drive regulation circuit, and the control ends of the first power tube The first end and the first end of the third power tube are connected to the input anode, and the second end of the first power tube is connected to the first end of the second power tube and one end of the primary winding of the transformer , The second end of the third power tube is connected to the first end of the fourth power tube, and the other end of the primary winding of the transformer is connected through the capacitor, and the second end of the second power tube And the second end of the fourth power tube is connected to the input negative electrode.
The power converter starting system according to claim 15, wherein:

The first power tube, the second power tube, the third power tube, and the fourth power tube are all metal oxide semiconductor MOS transistors.
The power converter starting system according to claim 14, wherein:

The second conversion circuit includes a fifth power tube, a sixth power tube, a seventh power tube, and an eighth power tube,

Wherein, the control ends of the fifth power tube, the sixth power tube, the seventh power tube, and the eighth power tube are all connected to the second drive regulation circuit, and the fifth power tube The first end and the first end of the seventh power tube are connected to the output anode, and the second end of the fifth power tube is connected to the first end of the sixth power tube and the secondary winding of the transformer. One end, the second end of the seventh power tube is connected to the first end of the eighth power tube and the other end of the secondary winding of the transformer, and the second end of the sixth power tube is connected to the second end of the transformer. The second end of the eight power tube is connected to the output negative pole.
The power converter starting system according to claim 17, wherein:

The fifth power tube, the sixth power tube, the seventh power tube, and the eighth power tube are all MOS tubes.
The power converter starting system according to claim 12, further comprising: an oscilloscope connected to the controller.