PWM feedforward control circuit and device based on CCM mode flyback circuit

Abstract

The invention provides a PWM feedforward control circuit and device based on a CCM mode flyback circuit. The PWM feedforward control circuit comprises a differential amplification circuit, a feedforward control circuit, a drive circuit, a PI feedback circuit and a CCM continuous flyback circuit. The differential amplification circuit and the CCM continuous flyback circuit are connected with an input voltage Vin, the feedforward control circuit is connected with the differential amplification circuit, the driving circuit and the PI feedback circuit are both connected with the CCM continuous flyback circuit, and the driving circuit is connected with the differential amplification circuit. According to the invention, by combining feedforward and feedback control strategies, the performance, including dynamic response and application output stability, of equipment is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a PWM feedforward control circuit and device based on a CCM mode flyback circuit. Background Art

[0002] Many new energy products use batteries as energy storage devices to provide power output for the load. The battery output voltage will change within a large voltage range as the battery power or dynamic large load changes. Usually, the back-end electrical appliances need a stable voltage source. The flyback circuit is widely used in low-power voltage stabilization applications due to its high efficiency and simple topology.

[0003] However, due to the existence of the right half plane zero point, the traditional CCM mode flyback circuit has a slow response speed and poor output stability when dealing with load changes and input voltage fluctuations. The input voltage feedforward control technology in the present invention can quickly respond to changes in input voltage, ensure output voltage stability, and can be applied to high voltage fields and products with input voltage fluctuations.

[0004] Patent application document CN106849655A discloses a feedforward circuit for a DC-DC converter with a digital voltage control loop, which is used to receive a first clock signal; receive a digital duty cycle value; use the first clock signal and the digital duty cycle value to generate a digital pulse width modulation (DPWM) signal with multiple discrete steps to control the switch of a switch mode power supply; and use a voltage control circuit to modify the duration of each of the multiple discrete steps of the DPWM signal, wherein the voltage control circuit is configured to receive an analog voltage input. This patent only uses a digital pulse width modulation signal to control the switch operation and does not give the relationship between the subsequent output voltage and the modulation signal.

[0005] Patent document CN105720824B discloses a system and method for zero voltage switching of a continuous conduction mode (CCM) flyback converter, which can achieve zero voltage switching in a continuous conduction mode (CCM) flyback converter by reducing the voltage difference across the primary winding immediately before the primary circuit changes from an off state to an on state. In one example, the voltage difference is reduced to the extent that the polarity across the primary winding is reversed. In another example, the voltage difference across the primary winding is significantly reduced, but not to the extent of polarity reversal. Reducing the voltage difference across the primary winding can reduce the voltage potential across the current path of the switching transistor (e.g., the source-drain in a FET transistor), and the switching transistor is used to change the primary circuit from an off state to an on state, and when the switching transistor is activated (closed), it can reduce parasitic power loss. Although the patent uses a system and method for zero voltage switching of a continuous conduction mode (CCM) flyback converter, the present application combines a feedforward control circuit to make the patent respond faster when regulating voltage. Summary of the invention

[0006] In view of the defects in the prior art, an object of the present invention is to provide a PWM feedforward control circuit and device based on a CCM mode flyback circuit.

[0007] The PWM feedforward control circuit based on the CCM mode flyback circuit provided by the present invention comprises: a differential amplifier circuit, a feedforward control circuit, a drive circuit, a PI feedback circuit and a CCM continuous flyback circuit;

[0008] The differential amplifier circuit and the CCM continuous flyback circuit are connected to the input voltage Vin, the feedforward control circuit is connected to the differential amplifier circuit, the drive circuit and the PI feedback circuit are both connected to the CCM continuous flyback circuit, and the drive circuit is connected to the differential amplifier circuit;

[0009] The differential amplifier circuit is applied in a preset high voltage field or when the input voltage variation range exceeds a preset threshold value, including being used to monitor the input voltage of the power supply and amplify the signal output by the sensor;

[0010] The feedforward control circuit includes a hysteresis comparison circuit N1, a triangle wave generating circuit N2 and a PWM comparison circuit N3, which are used to adjust the upper limit of the triangle wave signal, generate a corresponding PWM duty cycle control signal through the PWM comparator chopping, and control the on and off of the main power switch tube through the driving circuit;

[0011] The driving circuit includes a PNP tube and an NPN tube, which alternately provide current and absorb current from the connected load to provide high power to the load;

[0012] The PI feedback circuit feeds back all the output voltage to the input end to achieve control and regulation of the output voltage, and includes an amplifier and a feedback network, wherein the amplifier is used to amplify the input signal, and the feedback network is used to feed back part or all of the output signal to the input end;

[0013] The CCM continuous flyback circuit converts the input voltage into an isolated output voltage through a built-in inductor.

[0014] Preferably, the input voltage Vin is reduced by K times to Vin1 through a differential amplifier circuit. The calculation of the K value is determined by the input voltage. The circuit voltage withstand range after the differential amplifier circuit is 9-16V. In the differential signal, the signal size is determined by the voltage difference between the positive and negative electrodes.

[0015] Preferably, the hysteresis comparison circuit N1 adopts a comparator whose output terminal is in a high-impedance cut-off state when the output is high level. When the input voltage Vin changes, the proportionally changing Vin1 and the reference voltage Vref are superimposed on each other through a feedforward control circuit and given to the in-phase input terminal N1+ of the hysteresis comparison chip, so that the difference between the upper limit voltage of the hysteresis comparison interval and the reference voltage Vref changes in proportion to the Vin input voltage, thereby playing a feedforward role of the input voltage.

[0016] Preferably, the triangular wave generating circuit N2 adjusts the RC value according to the actual application to obtain the required frequency, the upper limit voltage value of the triangular wave is automatically adjusted with the input voltage, the triangular wave signal is given to the inverting end of the hysteresis comparator N1, and the triangular wave signal is also given to the inverting end of the PWM comparison circuit N3, which is compared with the reference voltage Vref and chopped to obtain the duty cycle control signal of the main power switch tube.

[0017] Preferably, during normal operation, the difference between the peak value of the triangle wave signal and the reference voltage Vref is proportional to the input voltage Vin.

[0018] Preferably, the feedforward control circuit adopts a comparator whose output terminal is in a high-impedance cut-off state when the output is high level, the non-inverting input terminal of the hysteresis comparator is connected to the Vin1 input signal and the reference source through an external resistor divider, and the inverting input terminal receives a triangular wave; when the triangular wave voltage rises and exceeds the non-inverting input terminal of the operational amplifier, the hysteresis comparator output is close to 0V; when the triangular wave signal drops and is lower than the non-inverting input terminal of the operational amplifier, the hysteresis comparator output is in a high-impedance cut-off state; due to the existence of positive feedback, the hysteresis upper limit of the hysteresis comparator automatically adjusts following the change of the input power supply Vin, so that the difference between the peak value of the triangular wave and the reference voltage Vref changes in direct proportion to the Vin input voltage, and the triangular wave is used as a carrier signal for the CCM mode flyback circuit to drive PWM.

[0019] Preferably, the reference source ensures that when Vin in the circuit changes, the reference voltage Vref remains unchanged. Z1 and Z2 are used as reference sources in the circuit to obtain the reference voltage Vref through resistor voltage division; the reference voltage Vref obtained by voltage division of Z1 is input to N3+ for PWM chopping to ensure that the on-time Ton of the switch tube remains unchanged when Vin changes; at the same time, Z1 determines the lower limit voltage of the hysteresis interval of the hysteresis comparator of N2 outputting the triangular wave and N1-; at the same time, Z1 makes the hysteresis upper limit voltage = reference voltage Vref + k*Vin, ensuring that when Vin changes, it only changes in the same proportion as the off-time Toff of the switch tube.

[0020] Preferably, the PWM comparison circuit N3 includes: a fixed reference voltage Vref value at the non-phase end of the PWM comparator is equal to the reference voltage Vref, a triangular wave signal is input to the inverting end of the PWM comparator and the reference voltage Vref at the non-phase end of the PWM comparator for chopping to perform open-loop control, or chopped with the output closed-loop feedback voltage signal of the flyback circuit to form a duty cycle control signal of the drive circuit, driving the main power switch tube of the CCM continuous flyback circuit, and as the peak value of the triangular wave changes, the duty cycle of the drive signal changes in the same proportion as Vin1, so that the output voltage Vout of the CCM continuous flyback circuit is not affected by the change of Vin.

[0021] Preferably, when the flyback circuit operates in CCM mode, the relationship between the input voltage Vin and the output voltage Vout satisfies: Among them, Ton is the switch on time, Toff is the switch off time, and n is the turns ratio of the primary winding to the secondary winding. When the switch tube of the drive circuit is turned on, the primary winding stores energy, and the secondary winding is not turned on due to the cut-off of the rectifier diode. When the switch tube is turned off, the energy in the primary winding is released through the secondary winding. At this time, the secondary winding is turned on to provide energy to the load.

[0022] According to the present invention, the PWM feedforward control device based on the CCM mode flyback circuit includes the PWM feedforward control circuit based on the CCM mode flyback circuit.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a PWM feedforward control circuit based on a CCM mode flyback circuit, which significantly improves the performance of the device, including dynamic response and output stability, by combining feedforward and feedback control strategies; and significantly broadens the applicable scenarios of the device by combining a differential amplifier circuit and a feedforward control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0026] Figure 1 The schematic diagram of the overall circuit is shown below;

[0027] Figure 2 This is the structural frame schematic diagram;

[0028] Figure 3 It is an input voltage feedforward hysteresis comparison circuit;

[0029] Figure 4 It is a triangle wave generating circuit;

[0030] Figure 5is the relationship between hysteresis comparators N1+ and N1-;

[0031] Figure 6 This is the relationship diagram between the triangular wave output waveform and the power switch PWM wave. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0033] Example

[0034] The present invention provides a PWM feedforward control method based on a CCM mode flyback circuit, comprising the following steps:

[0035] Step 1: The input power Vin is collected by a differential amplifier circuit and converted into a low voltage signal Vin1;

[0036] Step 2: Vin1 and the reference voltage Vref are superimposed and given to the non-inverting terminal of the hysteresis comparator, so that the hysteresis upper limit of the hysteresis comparator is automatically adjusted as the input power supply Vin changes;

[0037] Step 3: Due to the characteristics of LM193, the hysteresis upper limit of the hysteresis comparator is equal to the voltage upper limit of the triangle wave;

[0038] Step 4: By adjusting the ratio of the peripheral resistors of the hysteresis comparator, the change ratio of the upper limit amplitude of the triangle wave and the relationship between Vin and Vout of the flyback circuit are automatically satisfied to ensure the stability of the output Vout voltage.

[0039] The present invention provides a PWM feedforward control circuit based on a CCM mode flyback circuit, comprising:

[0040] Input voltage differential amplifier acquisition circuit, input voltage feedforward control circuit, drive circuit, output voltage feedback circuit and CCM mode flyback circuit. The input voltage feedforward control circuit includes a hysteresis comparator circuit N1, a triangle wave generating circuit N2, and a PWM comparator circuit N3, wherein the hysteresis comparator N1 needs to use a comparator similar to LM193 (when the output is high level, the output end is in a high impedance cutoff state, rather than outputting a fixed level).

[0041] refer to Figure 1As shown, the overall circuit schematic diagram of the prior art is illustrated. The system includes the following circuits: an input voltage differential amplifier acquisition circuit, an input voltage feedforward control circuit, a drive circuit, an output voltage feedback circuit and a CCM mode flyback circuit. The input voltage feedforward control circuit includes a hysteresis comparator circuit (N1), a triangular wave generating circuit (N2), and a PWM comparator circuit (N3). The input voltage Vin is reduced by K times by a differential amplifier acquisition circuit to become Vin1. Vin1 and Z1 (6V voltage regulator tube) are input to the non-inverting end of the hysteresis comparator after resistance voltage division and superposition to form a hysteresis upper limit voltage, thereby generating input voltage feedforward. When the voltage on the non-inverting input end (N1+) side of the hysteresis comparator is greater than the voltage on the inverting input end (N1-), the output end (N1out) of the hysteresis comparator is in a high-resistance cut-off state, S1 is turned on, and the triangular wave generator N2 outputs a triangular wave rising voltage until the triangular wave rising voltage is greater than the N1+ hysteresis upper limit, N1out outputs a low level, and the triangular wave voltage output by N2 decreases until it is less than the N1+ hysteresis lower limit, and this process is repeated to obtain a complete output triangular wave (N2out). When the input voltage Vin increases, Vin1 increases in proportion, so the superimposed hysteresis upper limit voltage also increases according to a specific rule and is input to the non-inverting terminal (N1+) of the hysteresis comparator. At the same time, the triangular wave (N2out) is also connected to the inverting terminal of the PWM comparison circuit N3 and compared with the reference level N3+. At this time, due to the increase in the upper limit value of the triangular wave, the Toff of the driving circuit becomes longer, resulting in a decrease in the PWM duty cycle D input to the driving circuit, and making Vin and Toff change in the same proportion, so the output voltage remains unchanged. Similarly, when VIN becomes smaller, the PWM duty cycle D becomes larger to ensure that the output voltage remains unchanged. The hysteresis comparator N1 diagram includes two voltage stabilization application methods of the present invention, one is an open-loop reference control circuit as shown in the schematic diagram, using a fixed reference voltage Vref as the chopping signal of the PWM comparator to obtain the duty cycle; the other is a closed-loop feedback circuit, which needs to sample the flyback output voltage Vout PI and feed it back (N6) to replace the reference signal as the chopping signal of the PWM comparator to obtain the duty cycle. The input voltage feedforward hysteresis comparator automatically adjusts the upper limit of the triangle wave signal N2out, and generates a corresponding PWM duty cycle control signal through the PWM comparator chopping, which is used to control the on and off of the main power switch tube through the drive circuit.

[0042] refer to Figure 2As shown, the structural framework principle diagram of the technology is illustrated. When Vin fluctuates, Vin1 increases at a certain scaling ratio, and the Vin1 voltage and the voltage regulator tube (Z1) are superimposed on the feedforward resistors on both sides and are given to the hysteresis comparator (N1+). At this time, when the voltage on the non-inverting input side (N1+) of the hysteresis comparator is greater than the voltage on the inverting input side (N1-), the output end (N1out) of the hysteresis comparator is cut off in a high impedance state, and S1 is turned on; when the N2out output triangular wave voltage rises until it is equal to the upper limit voltage of the N1+ hysteresis interval, N1out is disconnected, S1 is turned off, and the N2out output triangular wave voltage drops until it is less than the lower limit voltage of the N1+ hysteresis interval, and a complete output triangular wave (N2out) is obtained. The other end of N2out is connected to N3- in the comparison circuit, and N3- is compared with the reference level N3+. At this time, due to the increase in the upper limit value of the triangular wave, the Toff and Vin of the driving circuit change in proportion.

[0043] refer to Figure 3 As shown in the figure, the input voltage feedforward hysteresis comparator circuit of the technology is demonstrated. Vin1 is divided and superimposed by resistors R2, R3, R4 and the voltage regulator Z1 to positively feedback to the non-inverting input terminal of N1. Among them, R2, R3, and R4 need to calculate specific proportions according to different practical applications to meet the effect of stable output voltage Vout. The hysteresis comparator N1 needs to use a comparator similar to LM193 (the output terminal is in a high-impedance cut-off state when the output is high level, rather than outputting a fixed high level); the feedforward circuit characteristics and the hysteresis comparator circuit characteristics are combined, so that the "difference between the upper limit voltage of the hysteresis comparison interval and the reference voltage Vref" and the Vin input voltage change in proportion, thereby obtaining that the upper limit value of the triangular wave changes with the change of the input voltage. And the hysteresis comparator needs to use a comparator similar to LM193 (the output terminal is in a high-impedance cut-off state when the output is high level, rather than outputting a fixed high level), the non-inverting input terminal of the hysteresis comparator is connected to the Vin1 input signal and the reference source (voltage regulator) through an external resistor divider, and the inverting input terminal receives the triangular wave. When the triangle wave voltage rises and exceeds the non-inverting input terminal of the operational amplifier, the hysteresis comparator output is close to 0V; when the triangle wave signal drops and is lower than the non-inverting input terminal of the operational amplifier, the hysteresis comparator output is cut off in a high impedance state. Due to the existence of positive feedback, the hysteresis upper limit of the hysteresis comparator automatically adjusts as the input power supply Vin changes, so that the "difference between the triangle wave peak value and the reference voltage Vref" changes in direct proportion to the Vin input voltage, and the triangle wave is used as the carrier signal of the CCM mode flyback circuit to drive the PWM.

[0044] refer to Figure 4 , 5As shown, the triangular wave generating circuit of the present invention is demonstrated, N2+ is connected to a 3V voltage regulator as a reference voltage, N2out is connected to N2- through a negative feedback capacitor, N2- is connected to the output end of the feedforward hysteresis comparator through a charge and discharge resistor R8 and a NOT gate, when the output end of the hysteresis comparator N1 is cut off, S1 is turned on, the capacitor C1 is discharged, and N2out outputs a rising voltage; when the hysteresis comparator N1 outputs a low level, S1 is cut off, VZ2 charges the capacitor C1, and N2out outputs a falling voltage, and the values ​​of R8 and the capacitor C can be adjusted according to actual conditions to obtain the required triangular wave frequency.

[0045] refer to Figure 6 As shown, combined with the waveform diagram of the input voltage Vin1 before and after the two states, the working mechanism of the present invention is demonstrated, which mainly includes a triangular wave waveform, an upper limit and a lower limit of the hysteresis interval, a reference voltage Vref value, and a PWM duty cycle signal. The triangular wave amplitude changes at the reverse input terminal of N3 due to the change of the input voltage Vin, where the ordinate is the voltage value and the abscissa is the time.

[0046] according to Figure 6 Example quantitative calculation:

[0047] 3V means that Z1 inputs 3V through two 2K ​​resistors;

[0048] 4.5V means that the 6V voltage of N3+ is divided by a 1:3 resistor to obtain 4.5V;

[0049] 7.5V means when Vin1 is 12V, when N1->N2+, N1out is cut off, the feedforward circuit calculates the upper limit voltage of the hysteresis comparator by the superposition principle.

[0050] Vz1 represents the voltage output after comparison by the hysteresis comparator;

[0051] Therefore, when the input voltage is rated at 12V, the hysteresis range of the hysteresis comparator is 3V-7.5V.

[0052] 8.5V means that when Vin1 changes to Vin1'16V, N1->N2+, N1out is cut off, and the feedforward circuit calculates the upper limit voltage of the hysteresis comparator through the superposition principle.

[0053] Vin1′ indicates when Vin1 changes from 12V to 16V.

[0054] Therefore, when Vin1 becomes 16V, the hysteresis range of the hysteresis comparator is 3V-8.5V.

[0055] When Vin1 is 12V, when N1+>N1-, the output terminal N1out outputs a high level, S1 is turned on, the C1 capacitor is charged, and N2out outputs a triangular wave rising edge; when the N1- voltage is greater than the upper limit of the hysteresis interval 7.5V, the output terminal N1out is cut off, the C1 capacitor is discharged, and N2out outputs a triangular wave falling edge.

[0056] In the example, the triangle wave of N2out is compared with 4.5V. When the Vin voltage is 12V, the Vin1 after differential amplification is also 12V. The transformer primary-secondary turns ratio (n) is 1:2 (the specific turns ratio can be adjusted according to the actual application). When Vout needs to output 12V, the PWM should be about 33%;

[0057] By the formula:

[0058]

[0059] D represents the time of the whole cycle occupied by the high duty cycle;

[0060] have to Therefore, the PWM to control the power tube to turn off should be 33%;

[0061] Comparing the waveform of N2out with 4.5V, the PWM should be around 27% when the VIN voltage is 16V.

[0062] By the formula:

[0063]

[0064] Vout′ represents the actual voltage output after the driving circuit;

[0065] Vin′ represents the actual input voltage;

[0066] have to Therefore, the PWM value obtained by controlling the power tube to shut down should be 27%, and finally the CCM mode flyback circuit outputs a stable 12V.

[0067] refer to Figure 6 As shown, the change in the amplitude of the triangle wave at the reverse input terminal of N3 due to the change in input voltage is demonstrated. According to the image, the following formula can be obtained:

[0068] Vin*Ton=Vout*Toff (1)

[0069] Vin ′ *Ton ′ =Vout′*Toff′ (2)

[0070] Ton represents the time when the N3- voltage is less than the N3+ voltage when the input voltage is 12V;

[0071] Toff represents the time when the N3- voltage is greater than the N3+ voltage when the input voltage is 16V;

[0072] Ton′ represents the time when the voltage of N3- is less than the voltage of N3+ when the input voltage is 12V;

[0073] Toff′ represents the time when the voltage of N3- is greater than the voltage of N3+ when the input voltage is 16V;

[0074] Vout′ represents the actual output voltage of the driving circuit;

[0075] Because the voltage amplitude and slope remain unchanged below 4.5V, Ton=Ton'.

[0076] Comparing formula (1) and (2) we get formula (3):

[0077]

[0078] Depend on Figure 6 As shown, formula (4) can be obtained:

[0079]

[0080] Substituting formula (4) into formula (3) yields formula (5):

[0081] Vout=Vout′ (5)

[0082] V1 represents the difference between the output upper limit voltage of the hysteresis comparator and 4.5V when the input voltage is 12V;

[0083] V1′ represents the difference between the output upper limit voltage of the hysteresis comparator and 4.5V when the input voltage is 16V;

[0084] Conclusion: Therefore, when Vin' changes, Toff' and Vin' change in equal proportion, resulting in the final output Vout = Vout' not changing.

[0085] in The part that controls the amplitude change;

[0086] and This value must be equal to the reference voltage Vref value of the in-phase input terminal of N3 or the output voltage closed-loop feedback value, so that when Vin changes, the present invention can ensure that the switch tube Ton remains unchanged and only allows Toff to change in proportion to Vin.

[0087] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0088] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0089] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A PWM feedforward control circuit based on a CCM mode flyback circuit, characterized in that: include: Differential amplifier circuit, feedforward control circuit, drive circuit, PI feedback circuit and CCM continuous flyback circuit; The differential amplifier circuit and the CCM continuous flyback circuit are connected to the input voltage Vin, the feedforward control circuit is connected to the differential amplifier circuit, the drive circuit and the PI feedback circuit are both connected to the CCM continuous flyback circuit, and the drive circuit is connected to the differential amplifier circuit; The differential amplifier circuit is applied in a preset high voltage field or when the input voltage variation range exceeds a preset threshold value, including being used to monitor the input voltage of the power supply and amplify the signal output by the sensor; The feedforward control circuit includes a hysteresis comparison circuit N1, a triangle wave generating circuit N2 and a PWM comparison circuit N3, which are used to adjust the upper limit of the triangle wave signal, generate a corresponding PWM duty cycle control signal through the PWM comparator chopping, and control the on and off of the main power switch tube through the driving circuit; The driving circuit includes a PNP tube and an NPN tube, which alternately provide current and absorb current from the connected load to provide high power to the load; The PI feedback circuit feeds back all the output voltage to the input end to achieve control and regulation of the output voltage, and includes an amplifier and a feedback network, wherein the amplifier is used to amplify the input signal, and the feedback network is used to feed back part or all of the output signal to the input end; The CCM continuous flyback circuit converts the input voltage into an isolated output voltage through a built-in inductor.

2. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 1, characterized in that: The input voltage Vin is reduced by K times through the differential amplifier circuit to become Vin1. The calculation of the K value is determined by the input voltage. The voltage withstand range of the circuit after the differential amplifier circuit is 9-16V. In the differential signal, the signal size is determined by the voltage difference between the positive and negative electrodes.

3. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 2, characterized in that: The hysteresis comparison circuit N1 adopts a comparator whose output terminal is in a high-impedance cut-off state when the output is high level. When the input voltage Vin changes, the proportionally changing Vin1 and the reference voltage Vref are superimposed on each other through the feedforward control circuit and given to the in-phase input terminal N1+ of the hysteresis comparison chip, so that the difference between the upper limit voltage of the hysteresis comparison interval and the reference voltage Vref changes in proportion to the Vin input voltage, thereby playing a feedforward role of the input voltage.

4. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 3, characterized in that: The triangular wave generating circuit N2 adjusts the RC value according to the actual application to obtain the required frequency, and the upper limit voltage value of the triangular wave is automatically adjusted with the input voltage. The triangular wave signal is given to the inverting end of the hysteresis comparator N1, and the triangular wave signal is also given to the inverting end of the PWM comparison circuit N3, which is compared with the reference voltage Vref and chopped to obtain the duty cycle control signal of the main power switch tube.

5. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 4, characterized in that: During normal operation, the difference between the peak value of the triangle wave signal and the reference voltage Vref is proportional to the input voltage Vin.

6. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 5, characterized in that: The feedforward control circuit adopts a comparator whose output end is in a high-impedance cut-off state when the output is high level, the non-inverting input end of the hysteresis comparator is connected to the Vin1 input signal and the reference source through an external resistor divider, and the inverting input end receives a triangular wave; when the triangular wave voltage rises and exceeds the non-inverting input end of the operational amplifier, the hysteresis comparator output is close to 0V; when the triangular wave signal drops and is lower than the non-inverting input end of the operational amplifier, the hysteresis comparator output is in a high-impedance cut-off state; due to the existence of positive feedback, the hysteresis upper limit of the hysteresis comparator is automatically adjusted following the change of the input power supply Vin, so that the difference between the triangular wave peak value and the reference voltage Vref changes in direct proportion to the Vin input voltage, and at the same time, the triangular wave is used as a carrier signal for the CCM mode flyback circuit to drive PWM.

7. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 6, characterized in that: The reference source ensures that when Vin in the circuit changes, the reference voltage Vref remains unchanged. Z1 and Z2 are used as reference sources in the circuit to obtain the reference voltage Vref through resistor voltage division; Z1 obtains the reference voltage Vref through voltage division and inputs it into N3+ for PWM chopping to ensure that when Vin changes, the on-time Ton of the switch tube remains unchanged; at the same time, Z1 determines the lower limit voltage of the hysteresis interval of the hysteresis comparator of N2 outputting the triangular wave and N1-; at the same time, Z1 makes the hysteresis upper limit voltage = reference voltage Vref + k*Vin, ensuring that when Vin changes, it only changes in the same proportion as the off-time Toff of the switch tube.

8. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 7, characterized in that: The PWM comparison circuit N3 includes: a fixed reference voltage Vref value at the non-phase end of the PWM comparator is equal to the reference voltage Vref, a triangular wave signal is input to the inverting end of the PWM comparator and chopped with the reference voltage Vref at the non-phase end of the PWM comparator for open-loop control, or chopped with the output closed-loop feedback voltage signal of the flyback circuit to form a duty cycle control signal of the drive circuit, driving the main power switch tube of the CCM continuous flyback circuit, and as the peak value of the triangular wave changes, the duty cycle of the drive signal changes in the same proportion as Vin1, so that the output voltage Vout of the CCM continuous flyback circuit is not affected by the change of Vin.

9. The PWM feedforward control circuit based on the CCM mode flyback circuit according to claim 8, characterized in that: When the flyback circuit works in CCM mode, the relationship between the input voltage Vin and the output voltage Vout satisfies: Among them, Ton is the switch on time, Toff is the switch off time, and n is the turns ratio of the primary winding to the secondary winding. When the switch tube of the drive circuit is turned on, the primary winding stores energy, and the secondary winding is not turned on due to the cut-off of the rectifier diode. When the switch tube is turned off, the energy in the primary winding is released through the secondary winding. At this time, the secondary winding is turned on to provide energy to the load.

10. A PWM feedforward control device based on a CCM mode flyback circuit, characterized in that: A PWM feedforward control circuit based on a CCM mode flyback circuit comprising any one of claims 1 to 9.

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