Flyback converter control circuit, control chip and flyback converter

Abstract

The invention relates to the technical field of switching power supplies, and discloses a flyback converter control circuit, a control chip and a flyback converter, and the control circuit comprises a current sampling unit which is configured to obtain a first sampling value based on a primary side switching tube current of the flyback converter, obtaining a second sampling value representing the slope of the first sampling value based on the first sampling value; and the compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to the second sampling value, so that the output power frequency ripple of the flyback converter is suppressed by controlling the peak current of a primary side switching tube. The input side line voltage fluctuation information is reflected by detecting the current sampling slope, so that the current reference or the sampling current can be compensated in time, the power disturbance is avoided, and the output power frequency ripple is inhibited.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular to a control circuit, a control chip and a flyback converter of a flyback converter. Background Art

[0002] In power conversion technology, the flyback converter is widely used due to its simple structure and low cost. Its working principle is based on the process of energy storage and release, and uses the magnetic field of the transformer to achieve voltage conversion and electrical isolation. However, when the flyback converter operates at low voltage and full load, the performance of the flyback converter may be affected by the fluctuation of the input line voltage, resulting in fluctuations in the output power of the flyback converter.

[0003] In order to maintain the stability of the output power, the relevant technology usually generates compensation based on loop compensation to adjust the peak current to maintain the stability of the output voltage. However, the low-frequency filtering link in the loop will introduce a certain response delay, which will cause the compensation adjustment to lag and fail to respond to the rapid changes in the input voltage in time, resulting in a large power frequency ripple in the output voltage, which not only affects the power conversion efficiency, but may also cause unstable operation of other circuit components. Summary of the invention

[0004] The present application provides a control circuit, a control chip and a flyback converter of a flyback converter, which solves the technical problem that the output voltage has power frequency ripple due to the regulation lag in the loop compensation method, and reflects the input side line voltage fluctuation information by detecting the current sampling slope, so that the current reference or the sampling current can be compensated in time, thereby avoiding power disturbance and suppressing the output power frequency ripple.

[0005] In order to achieve the above objectives, the main technical solutions adopted in this application include:

[0006] In a first aspect, an embodiment of the present application provides a control circuit of a flyback converter, the control circuit comprising:

[0007] A current sampling unit, wherein the current sampling unit is configured to obtain a first sampling value based on the primary switch tube current of the flyback converter, and obtain a second sampling value representing a slope of the first sampling value based on the first sampling value;

[0008] A compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to the second sampling value, so as to suppress the output power frequency ripple of the flyback converter by controlling the peak current of the primary switch tube.

[0009] According to the control circuit of the flyback converter proposed in the embodiment of the present application, a first sampling value is obtained by sampling the current of the primary switch tube through a current sampling unit, and a second sampling value representing the slope of the first sampling value is obtained based on the first sampling value, and a compensation control unit generates a compensation signal based on the second sampling value to compensate for one of the first sampling value and the current sampling reference, so as to control the peak current of the primary switch tube to suppress the output power frequency ripple of the flyback converter. Therefore, the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, and improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the disadvantage of the hysteresis effect of the loop compensation, and while realizing the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter.

[0010] Optionally, in some embodiments of the present application, the current sampling unit is further configured to perform sample-holding and difference calculation on the first sampling value within a fixed time to obtain the second sampling value.

[0011] By characterizing the current sampling slope by the change of the first sampling value within a fixed time, and thereby utilizing the correlation between the current sampling slope and the line voltage fluctuation, the line voltage fluctuation information at the input end of the flyback converter can be captured directly on the primary side in a timely manner, thereby simplifying the compensation loop and avoiding the lag effect caused by traditional compensation methods.

[0012] Optionally, in some embodiments of the present application, the compensation control unit is configured to obtain a second sampling average value characterizing an average value of the second sampling value based on the second sampling value, and compensate at least one of the first sampling value and the current sampling reference based on the second sampling value and the second sampling average value.

[0013] In the embodiment of the present application, based on the second sampling value and the second sampling average value, at least one of the first sampling value and the current sampling reference is selected as the compensation object, so that not only the positive superposition of the compensation value can be achieved on the basis of the first sampling value, but also the reverse superposition can be achieved on the basis of the current sampling reference, thereby increasing the flexibility of the compensation mechanism while achieving timely and effective compensation.

[0014] Optionally, in some embodiments of the present application, the compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to a ratio of the second sampling value to the second sampling average value.

[0015] The embodiments of the present application are based on the ratio of the second sampling value to the average value of the second sampling values to reflect the fluctuation trend and amplitude of the line voltage, realize precise compensation control for the change of the line voltage, and contribute to the effective suppression of power frequency ripple.

[0016] Optionally, in some embodiments of the present application, the compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to the difference between the second sampling value and the second sampling average value.

[0017] The embodiments of the present application are based on the difference between the second sampling value and the average value of the second sampling values to reflect the fluctuation trend and amplitude of the line voltage, realize simple and rapid compensation control for the change of the line voltage, and contribute to the effective suppression of power frequency ripple.

[0018] Optionally, in some embodiments of the present application, when the compensation control unit is configured to compensate the current sampling reference according to the second sampling value, the initial compensation signal is also compensated according to the second sampling value to realize the compensation of the current sampling reference;

[0019] Wherein, the initial compensation signal represents the error between the feedback voltage signal and the voltage reference signal, and the feedback voltage signal is used to represent the magnitude of the output voltage of the flyback converter.

[0020] Optionally, in some embodiments of the present application, the compensation control unit is configured to compensate the current sampling reference to obtain a compensated current sampling reference, and generate a control signal according to the compensated current sampling reference and the first sampling value to control the peak current of the primary side switching transistor.

[0021] Optionally, in some embodiments of the present application, the compensation control unit is configured to compensate the first sampling value to obtain a compensated first sampling value, and generate a control signal according to the compensated first sampling value and the current sampling reference to control the peak current of the primary side switching transistor.

[0022] Optionally, the compensation control unit is configured to compensate the current sampling reference to obtain a compensated current sampling reference, and the compensated current sampling reference is determined according to the following formula:

[0023] V COMP1＝ V CSREF *[(1 / K BUS -1)*K1 + 1]

[0024] Wherein, V COMP1 is the compensated current sampling reference, K 1 is the proportional adjustment coefficient, V CSREFis the current sampling reference, K BUS is the ratio of the second sampling value to the second sampling average value.

[0025] Optionally, the compensation control unit is configured to compensate the first sampling value to obtain a compensated first sampling value, and the compensated first sampling value is determined according to the following formula:

[0026] V COMP2＝ V CS *[(1-1 / K BUS )*K1+1]

[0027] Among them, V COMP2 is the first sample value after compensation, K 1 is the proportional adjustment coefficient, V CS is the first sampling value, K BUS is the ratio of the second sampling value to the second sampling average value.

[0028] The embodiments of the present application respectively propose two different compensation mechanisms for two different compensation objects, namely the current sampling reference and the first sampling value, so that not only can the positive superposition of the compensation value be achieved on the basis of the first sampling value, but also the reverse superposition can be achieved on the basis of the current sampling reference. Not only can timely, accurate and effective compensation be achieved, but also the flexibility of the compensation mechanism is increased.

[0029] Optionally, in some embodiments of the present application, the compensation control unit includes a first calculation module and a first compensation module;

[0030] The first calculation module is used to perform mean value calculation, division and ratio adjustment on the second sampling value to obtain a first compensation signal;

[0031] The first compensation module is used to compensate at least one of the first sampling value and the current sampling reference according to the first compensation signal.

[0032] Optionally, the first calculation module includes:

[0033] a first mean value calculator, wherein the first mean value calculator is configured to perform mean value calculation on the second sampling value to obtain a first voltage mean value;

[0034] a first divider, wherein the first divider is configured to divide the second sampled value by the first voltage average value, or the first divider is configured to divide the first voltage average value by the second sampled value to obtain a first compensation coefficient;

[0035] A first proportional regulator is configured to proportionally regulate the first compensation coefficient to obtain the first compensation signal.

[0036] The first compensation coefficient is calculated by dividing the second sampling value by the first voltage mean value representing the average value of the second sampling value, so as to reflect the fluctuation trend and amplitude of the line voltage, thereby generating a relatively accurate first compensation signal according to the change of the line voltage, realizing precise compensation control, and contributing to the effective suppression of power frequency ripple.

[0037] Optionally, in some embodiments of the present application, the first compensation module is configured to directly compensate the current sampling reference according to the first compensation signal to obtain a compensated current sampling reference; or,

[0038] The first compensation module is configured to compensate the initial compensation signal according to the first compensation signal, and perform reference parameter conversion on the compensated initial compensation signal to achieve compensation for the current sampling reference and obtain a compensated current sampling reference.

[0039] Optionally, the compensation control unit is configured to compensate the current sampling reference to obtain a compensated current sampling reference, and the compensated current sampling reference is determined according to the following formula:

[0040] V COMP3＝ V CSREF -K 1 (V CS1 -V CSAVG )

[0041] Among them, V COMP3 is the current sampling reference after compensation, K 1 is the proportional adjustment coefficient, V CSREF is the current sampling reference, V CS1 is the second sampling value, V CSAVG Calculate the processed voltage mean for the average value.

[0042] Optionally, in some embodiments of the present application, the compensation control unit is configured to compensate the first sampling value to obtain a compensated first sampling value, and the compensated first sampling value is determined according to the following formula:

[0043] V COMP4＝ V CS +K 1 (V CS1 -V CSAVG )

[0044] Among them, V COMP4 is the first sample value after compensation, K 1 is the proportional adjustment coefficient, VCS is the first sampling value, V CS1 is the second sampling value, V CSAVG Calculate the processed voltage mean for the average value.

[0045] The embodiments of the present application respectively propose two different compensation mechanisms for two different compensation objects, namely the current sampling reference and the first sampling value, so that not only can the positive superposition of the compensation value be achieved on the basis of the first sampling value, but also the reverse superposition can be achieved on the basis of the current sampling reference, which not only can realize fast, simple and effective compensation, but also increases the flexibility of the compensation mechanism.

[0046] Optionally, in some embodiments of the present application, the compensation control unit includes a second calculation module and a second compensation module;

[0047] The second calculation module is used to perform mean value calculation, subtraction and proportional adjustment on the second sampling value to obtain a second compensation signal;

[0048] The second compensation module is used to compensate at least one of the first sampling value and the current sampling reference according to the second compensation signal.

[0049] Optionally, the second calculation module includes:

[0050] a second mean value calculator, the second mean value calculator being configured to perform mean value calculation on the second sampling value to obtain a second voltage mean value;

[0051] a first subtractor, wherein the first subtractor is configured to subtract the second sampled value from the second voltage average value, or the first subtractor is configured to subtract the second voltage average value from the second sampled value to obtain a first difference;

[0052] A second proportional regulator is configured to perform proportional regulation on the first difference to obtain the second compensation signal.

[0053] In some embodiments of the present application, by first performing a subtraction process and then performing a proportional adjustment, the difference between the second sampling value and the second voltage average is used to reflect the fluctuation trend and amplitude of the line voltage, thereby generating a fast compensation signal for the change in the line voltage, which helps to compensate the first sampling value or the current sampling reference in a timely and rapid manner, thereby achieving effective suppression of the power frequency ripple.

[0054] Optionally, the second calculation module includes:

[0055] a third proportional regulator, wherein the third proportional regulator is configured to perform proportional regulation on the second sampling value to obtain a first regulation value;

[0056] a third mean value calculator, the third mean value calculator being configured to perform mean value calculation on the first adjustment value to obtain a third voltage mean value;

[0057] A second subtractor is configured to subtract the first adjustment value from the third voltage average value, or the second subtractor is configured to subtract the third voltage average value from the first adjustment value to obtain the second compensation signal.

[0058] In some embodiments of the present application, by first performing proportional regulation and then performing subtraction processing, the difference between the first adjustment value and the third voltage average is used to reflect the fluctuation trend and amplitude of the line voltage, so that a simple and fast compensation signal can be generated for the fluctuation information of the line voltage, which helps to compensate the first sampling value or the current sampling reference in a timely and fast manner, thereby achieving effective suppression of the power frequency ripple.

[0059] Optionally, in some embodiments of the present application, the second compensation module is configured to directly compensate the current sampling reference according to the second compensation signal to obtain a compensated current sampling reference; or,

[0060] The second compensation module is configured to compensate the initial compensation signal according to the second compensation signal, and perform reference parameter conversion on the compensated initial compensation signal to achieve compensation for the current sampling reference, thereby obtaining a compensated current sampling reference.

[0061] Optionally, in some embodiments of the present application, the compensation control unit is further configured to, when it is determined that the flyback converter operates in a critical conduction mode, compensate at least one of the first sampling value and the current sampling reference.

[0062] In some embodiments of the present application, since the flyback converter is more susceptible to line voltage fluctuations when operating in the critical conduction mode, corresponding compensation operations are performed when it is determined that the flyback converter is operating in the critical conduction mode. This can achieve accurate and effective suppression of the power frequency ripple, while maintaining a stable output power, saving configuration resources related to the control circuit and improving the reliability of the control circuit.

[0063] In a second aspect, an embodiment of the present application provides a control chip for a flyback converter, comprising:

[0064] Current sampling pin;

[0065] Switch tube control pin;

[0066] The control circuit according to the embodiment of the first aspect described above is configured to sample the current of the primary switching transistor of the flyback converter through the current sampling pin, and output a control signal to the primary switching transistor through the switching transistor control pin.

[0067] The control chip provided by the embodiment of the present application directly obtains a first sampling value that can reflect the line voltage fluctuation at the primary switching transistor through the current sampling pin, obtains a second sampling value representing the slope of the first sampling value based on the first sampling value, and generates a compensation signal through the second sampling value to compensate one of the first sampling value and the current sampling reference, so as to control the peak current of the primary switching transistor and suppress the output power frequency ripple of the flyback converter. Therefore, the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the drawback of the lag effect of loop compensation. While achieving the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter.

[0068] In a third aspect, a flyback converter provided by an embodiment of the present application includes:

[0069] The control circuit according to the embodiment of the first aspect described above; or

[0070] The control chip according to the embodiment of the second aspect described above.

[0071] The flyback converter provided by the embodiment of the present application can directly obtain a first sampling value that reflects the line voltage fluctuation at the primary switching transistor through the above control circuit or control chip, obtain a second sampling value representing the slope of the first sampling value based on the first sampling value, and generate a compensation signal through the second sampling value to compensate one of the first sampling value and the current sampling reference, so as to control the peak current of the primary switching transistor and suppress the output power frequency ripple of the flyback converter. Therefore, the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the drawback of the lag effect of loop compensation. While achieving the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter. Description of the Drawings

[0072] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0073] Figure 1 It is a schematic diagram of the circuit structure of a primary-side controlled flyback converter in the related art;

[0074] Figure 2 A schematic diagram of a circuit structure for generating a compensation signal in loop compensation in the related art;

[0075] Figure 3 In the related art, V BUS Schematic diagram of signal waveform for compensating fluctuations;

[0076] Figure 4 A schematic diagram of the structure of a control circuit of a flyback converter proposed in an embodiment of the present application;

[0077] Figure 5 A circuit structure diagram of a current sampling unit proposed in the present application in one embodiment;

[0078] Figure 6 A schematic diagram of sampling values ​​of a current sampling unit in one embodiment of the present application;

[0079] Figure 7 A circuit structure diagram of a current sampling unit proposed in the present application in another embodiment;

[0080] Figure 8 A schematic diagram of sampling values ​​of a current sampling unit proposed in the present application in another embodiment;

[0081] Fig. 9 A logic block diagram of compensation performed by a compensation control unit proposed in the present application in one embodiment;

[0082] Fig.10 Another logic block diagram of compensation performed by the compensation control unit proposed in the present application in one embodiment;

[0083] Fig.11 A logic block diagram of compensation performed by the compensation control unit proposed in the present application in another embodiment;

[0084] Fig.12 Another logic block diagram of the compensation control unit proposed in the present application performing compensation in yet another embodiment;

[0085] Fig.13Schematic diagram of the signal waveform for compensation in an embodiment of the present application;

[0086] Fig.14 Logic block diagram for compensation in an embodiment of the present application;

[0087] Fig.15 Logic block diagram for compensation in another embodiment of the present application;

[0088] Fig.16 Logic block diagram for compensation in yet another embodiment of the present application;

[0089] Fig.17 Logic block diagram for compensation in still another embodiment of the present application;

[0090] Fig.18 Schematic diagram of the circuit structure of the proportional regulator in an embodiment of the present application;

[0091] Fig.19 Schematic diagram of the structure of a control chip in an embodiment of the present application. Detailed implementation manners

[0092] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0093] The flyback converter is a power conversion device widely used in the electronics industry such as switching power supplies. Among them, Figure 1 shows the circuit topology of the primary-side controlled flyback converter in the related art. Its main working principle is based on the energy storage and release of the transformer, and the output voltage is regulated by controlling the on and off of the primary-side switch tube. When the switch tube Q1 is turned on, the input power supply stores energy through the primary winding Np of the transformer. When the switch tube Q1 is turned off, this energy passes through the secondary winding Ns and is released to the output terminal through the diode in sequence. By controlling the on and off time of the switch, the output voltage Vo can be adjusted to supply the load R. L .

[0094] Specifically, at the output end of the AC power supply AC, the alternating current is converted into direct current through a rectifier bridge and a filter in sequence to provide the line voltage V for the primary winding Np. BUSThe auxiliary winding Naux is used to provide the startup voltage VDD for the primary chip U1. The primary chip U1 samples the voltage of the auxiliary winding Naux through the VS pin to obtain the feedback voltage signal, and samples the primary switch tube current I through the CS pin. CS , and output a control signal through the GATE pin to control the on and off of the switch tube Q1.

[0095] The loop compensation method used in related technologies is as follows: Figure 2 As shown, it samples and holds the voltage of the VS pin of the primary chip U1 to obtain the feedback voltage signal FB representing the output voltage of the flyback converter, and uses the error amplifier EA to sample and hold the voltage of the VS pin of the primary chip U1 to obtain the feedback voltage signal FB representing the output voltage of the flyback converter. REF Generate a compensation signal COMP, and then give the compensation signal COMP to the compensation link, so that the compensation signal COMP and the primary switch tube current I sampled based on the CS pin are CS Control the switch tube Q1 to solve the line voltage V BUS The problem of fluctuation affecting the stability of the output voltage of the flyback converter. However, due to the presence of the low-pass filter module in the loop, the compensation signal COMP has a lag, which causes output power fluctuations and results in power frequency ripples in the output voltage.

[0096] Furthermore, if Figure 3 As shown, when V BUS When periodic fluctuations occur, especially in the conduction interval t2 of the rectifier diode, the input voltage suddenly increases, causing the energy stored in Np to increase rapidly. However, due to the response delay time t1 of the loop, the compensation signal COMP cannot respond in time within such a short time as t2, resulting in a large overshoot of the output voltage Vo in the interval t2, causing Vo to have a large power frequency ripple problem.

[0097] In order to solve the above technical problems, the embodiments of the present application propose a control circuit, a control chip and a flyback converter of a flyback converter, which reflect the input side line voltage fluctuation information by detecting the current sampling slope, so that the current reference or sampling current can be compensated in time, thereby avoiding power disturbance and suppressing the output power frequency ripple.

[0098] The output power of the flyback converter in the boundary conduction mode (BCM) is determined by the following formula (1):

[0099]

[0100] Where Pout is the output power, L M is the transformer excitation inductance, I CS is the primary switch current, FS is the switching frequency, V BUS is the line voltage, D ON is the conduction duty cycle of the primary switch tube, and N is the transformer turns ratio.

[0101] From the above formula, we can see that in V BUS When a large disturbance occurs, feedback adjustment is required. CS To achieve the stability of output voltage and output power, the loop regulation hysteresis effect is limited. If the regulation is achieved by increasing the loop bandwidth, it will affect the stability of the system. If the flyback converter is set to work in discontinuous conduction mode (DCM) when the voltage is low and the load is heavy, and the switch tube is not turned on at the bottom of the valley, then in the DCM mode, I CS and F S All need to be strictly determined based on the compensation signal COMP, and its output power is determined by the following formula (2):

[0102]

[0103] Therefore V BUS It will not cause output power fluctuations and no longer require timely adjustment of the compensation signal COMP. However, this solution requires the flyback converter to operate in DCM mode, where the switching frequency is low and the effective current value is large, which will greatly reduce the system efficiency.

[0104] The embodiment of the present application proposes a control circuit of a flyback converter such as Figure 4 As shown, the control circuit 10 can be used in power conversion devices such as low-power power supplies, isolated power supplies, and adapters. The control circuit 10 includes: a current sampling unit 100 and a compensation control unit 200.

[0105] The current sampling unit 100 is configured to obtain a first sampling value based on the primary switch tube current of the flyback converter, and obtain a second sampling value representing the slope of the first sampling value based on the first sampling value.

[0106] In some embodiments of the present application, the current sampling unit 100 can monitor the primary switch tube current I based on the CS pin of the control chip. CS Sampling is performed to obtain the first sampling value V CS Then, further characterize the current sampling slope to target V CS Perform sampling processing to obtain a second sampling value V CS1 It can be seen that the current sampling unit 100 can quickly obtain the second sampling value V that directly reflects the line voltage fluctuation information on the primary side. CS1Compared with the loop compensation method used in related technologies, it overcomes the disadvantage of the hysteresis effect of the loop, can timely and effectively suppress the output power frequency ripple and maintain the power output stability of the flyback converter.

[0107] The compensation control unit 200 is connected to the current sampling unit 100, and is configured to compensate at least one of the first sampling value and the current sampling reference according to the second sampling value, so as to suppress the output power frequency ripple of the flyback converter by controlling the peak current of the primary switch tube Q1.

[0108] In some embodiments of the present application, through the configuration of the above-mentioned compensation control unit 200, it is possible to support two compensation superposition methods based on the first sampling value and based on the current sampling reference, which not only provides the possibility of multiple compensation methods, but also can timely and effectively suppress the output power frequency ripple and maintain the power output stability of the flyback converter.

[0109] To sum up, the control circuit 10 proposed in the embodiment of the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, and improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the disadvantage of the hysteresis effect of the loop compensation. While achieving the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter.

[0110] In some embodiments of the present application, the current sampling unit 100 is further configured to perform sample-holding and difference calculation on the first sampling value within a fixed time to obtain a second sampling value.

[0111] Specifically, the current sampling unit 100 can sense the primary switch tube current I based on the CS pin. CS Sampling is performed to obtain the first sampling value V CS =I CS *R CS , and then the first sampling value V CS The sampling is held, and the difference between the sampling value at the beginning and the end of the sampling is taken as the second sampling value V CS1 .

[0112] This application samples the current signal slope of the primary switch tube to characterize the line voltage V BUS The fluctuation information of V BUS and I CS The relationship between is shown in the following formula (3):

[0113]

[0114] Where, T ON is the conduction time of the primary switch tube, L M is the transformer excitation inductance. From formula (3), we can see that V CS With V BUS The current sampling slope can indicate the change of V BUS Fluctuation information.

[0115] Further, Figure 5 FIG. 2 shows a circuit structure of a current sampling unit 100 in an embodiment. Figure 5 and Figure 6 As shown, the input end of the current sampling unit 100 is connected to the GATE pin of the control chip to receive the control signal GON output by the GATE pin. The control signal GON is sent to the first input end of the AND gate 120 after passing through the first delay module 110 and the inverter. At the same time, the control signal GON is also sent to the second input end of the AND gate 120. When the first input end and the second input end of the AND gate 120 are both at a high level, the output end of the AND gate 120 outputs a trigger signal TREF1 for turning on the switch Q2. At the same time, the switch Q2 is connected to the CS pin of the control chip, thereby completing the V CSA In addition, the trigger signal TREF1 is connected to the S input terminal of the SR trigger 150 through the inverter and the pulse generator 130, and the control signal GON is connected to the R input terminal of the SR trigger 150 through the pulse generator 140. When both the S input terminal and the R input terminal receive a high level, the Q output terminal of the SR trigger 150 outputs a trigger signal that turns on the switch Q3, thereby obtaining V from the start of sampling to the moment when the trigger signal TREF1 is generated. CS The change of the second sampling value V CS1 , and the second sample value V CS1 Input into the compensation control unit 200.

[0116] exist Figure 5 Based on the current sampling unit 100 shown in FIG. Figure 6 As shown, because the current sampling unit 100 starts sampling and holding, V CS is zero, so the sample value V when TREF1 is triggered SCA The current sampling slope can be characterized and V SCA As the second sample value V CS1 .

[0117] Figure 7 FIG. 2 shows a circuit structure of the current sampling unit 100 in another embodiment. Figure 7 It can be seen that Figure 5Compared with the circuit structure of the current sampling unit 100 shown in FIG. Figure 7 The circuit structure of the current sampling unit 100 shown has two sampling paths. Specifically, the input end of the current sampling unit 100 is connected to the GATE pin of the control chip to receive the control signal GON output by the GATE pin. The control signal GON is sent to the first input end of the AND gate 120 after passing through the first delay module 110 and the inverter. At the same time, the control signal GON is also sent to the second input end of the AND gate 120. When the first input end and the second input end of the AND gate 120 are both high level, the output end of the AND gate 120 outputs the trigger signal TREF1 that turns on the switch Q4. At the same time, the switch Q4 is connected to the CS pin of the control chip, thereby completing the V CSA The control signal GON is sent to the first input terminal of the AND gate 170 after passing through the second delay module 160 and the inverter. At the same time, the control signal GON is also directly sent to the second input terminal of the AND gate 170. When the first input terminal and the second input terminal of the AND gate 170 are both at a high level, the output terminal of the AND gate 170 outputs a trigger signal TREF2 that turns on the switch Q5. At the same time, the switch Q5 is connected to the CS pin of the control chip, thereby completing V by using the sampling resistor R3 and the capacitor C4. CSB The subtractor 180 obtains V CSB With V CSA The difference between the two times when the trigger signal TREF1 is generated and the trigger signal TREF2 is generated is obtained. CS In addition, the control signal GON is connected to the S input terminal and the R input terminal of the SR trigger 150 through the pulse generator 130 and the pulse generator 140 respectively. When the S input terminal and the R input terminal both receive a high level, the Q output terminal of the SR trigger 150 outputs a trigger signal to turn on the switch Q6, thereby turning V CSB With V CSA The difference is taken as the second sampling value V CS1 Input into the compensation control unit 200.

[0118] exist Figure 7 Based on the current sampling unit 100 shown in FIG. Figure 8 As shown, the sampling value V when TREF2 is triggered SCB The sample value V when TRER1 is triggered SCA The difference is used to represent the current sampling slope, and this difference is used as the second sampling value V CS1 .

[0119] It can be seen therefrom that the change of the first sampling value within a fixed time is used to achieve the purpose of characterizing the current sampling slope. Thus, by utilizing the correlation between the current sampling slope and the line voltage fluctuation, the line voltage fluctuation information at the primary side of the flyback converter can be directly captured in a timely manner, which helps to generate an accurately adjusted compensation signal in a timely manner subsequently and can avoid the hysteresis effect brought by the traditional loop compensation method.

[0120] In some embodiments of the present application, the compensation control unit 200 is configured to obtain a second sampling average value representing the average value of the second sampling value according to the second sampling value, and compensate at least one of the first sampling value and the current sampling reference according to the second sampling value and the second sampling average value.

[0121] Among them, the embodiments of the present application provide two compensation methods for compensating according to the second sampling value and the second sampling average value. On the one hand, the compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to the ratio of the second sampling value to the second sampling average value. Here, the ratio can be the ratio obtained by dividing the second sampling value by the second sampling average value, or the ratio obtained by dividing the second sampling average value by the second sampling value. On the other hand, the compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to the difference between the second sampling value and the second sampling average value. Here, the difference can be the difference obtained by subtracting the second sampling average value from the second sampling value, or the difference obtained by subtracting the second sampling from the second sampling average value.

[0122] Some embodiments of the present application are given below for the above configuration of the compensation control unit and are specifically described.

[0123] In some embodiments of the present application, the compensation control unit 200 includes a first calculation module 210 and a first compensation module 220;

[0124] Among them, the first calculation module 210 is used to perform filtering processing, division processing, and proportional adjustment on the second sampling value to obtain a first compensation signal;

[0125] The first compensation module 220 is used to compensate at least one of the first sampling value and the current sampling reference according to the first compensation signal.

[0126] Further, the first calculation module 210 includes: a first mean value calculator 211, a first divider 212 and a first proportional regulator 213. The first mean value calculator 211 is configured to perform an average value calculation on the second sampled value to obtain a first voltage mean value, the first divider 212 is configured to divide the second sampled value by the first voltage mean value, or the first divider 212 is configured to divide the first voltage mean value by the second sampled value to obtain a first compensation coefficient, and the first proportional regulator 213 is configured to perform proportional regulation on the first compensation coefficient to obtain a first compensation signal.

[0127] In some embodiments of the present application, the averaging processing method of the first mean value calculator 211 includes but is not limited to performing low-pass filtering on the second sampling value to obtain the average value of the second sampling value.

[0128] The first compensation coefficient is calculated by dividing the second sampling value by the first voltage mean value, so as to reflect the fluctuation trend and amplitude of the line voltage, thereby generating a relatively accurate compensation signal for the change of the line voltage, realizing precise compensation control, and contributing to the effective suppression of the power frequency ripple.

[0129] Specifically, Fig. 9 The logic block diagram of the compensation control unit 200 for accurate compensation is shown. Fig. 9 In the logic block diagram shown in FIG. 1 , a second sampling value V representing the current sampling slope is obtained by sampling within a fixed time T0. CS1 The second sampling value V is output to the compensation control unit 200 through the output terminal of the current sampling unit 100. CS1 First, the first mean value calculator 211 obtains the second sampling mean value representing the mean value of the second sampling value, and records it as the first voltage mean value V CSAVG , and then the first compensation coefficient K is calculated by the first divider 212 BUS =V CS1 / V CSAVG , or the first compensation coefficient K BUS =V CSAVG / V CS1 Then, the first compensation coefficient is proportionally adjusted by the first proportional regulator 213 to obtain a first compensation signal [(1 / K BUS -1])*K 1 +1].

[0130] It should be noted that the operation logic in the first calculation module 210 proposed in the embodiment of the present application can have many variations, including but not limited to Fig. 9 The logic block diagram is shown.

[0131] For example, Fig.10 Shown for Fig. 9A logical transformation of Fig.10 In the logic block diagram shown in FIG. 1 , a second sampling value V representing the current sampling slope is obtained by sampling within a fixed time T0. CS1 The second sampling value V is output to the compensation control unit 200 through the output terminal of the current sampling unit 100. CS1 First, the first mean value calculator 211 obtains the second sampling mean value representing the mean value of the second sampling value, and records it as the first voltage mean value V CSAVG , and then the third subtractor 214 calculates V CSAVG -V CS1 Then the first divider 212 calculates (V CSAVG -V CS1 ) / V CS1 , where K BUS =V CS1 / V CSAVG Then, the first proportional regulator 213 performs proportional adjustment to obtain a first compensation signal [(V CSAVG -V CS1 ) / V CS1 ]*K 1 +1, that is, [(1 / K BUS -1])*K 1 +1].

[0132] In the embodiment of the present application, you can choose to perform reverse superposition compensation on the current sampling reference, or you can choose to perform forward superposition compensation on the first sampling value. These two compensation methods are specifically described below.

[0133] In the case of compensating the current sampling reference, the compensation control unit 200 is configured to compensate the current sampling reference to obtain a compensated current sampling reference, and generate a control signal based on the compensated current sampling reference and the first sampling value to control the peak current of the primary side switch tube.

[0134] The compensation control unit 200 is configured to compensate the current sampling reference to obtain a compensated current sampling reference, and the compensated current sampling reference is determined according to the following formula:

[0135] V COMP1＝ V CSREF *[(1 / K BUS -1])*K1+1]

[0136] Among them, V COMP1 K is the current sampling reference after compensation, 1 is the proportional adjustment coefficient, V CSREF is the current sampling reference, K BUS is the ratio of the second sampling value to the second sampling average value.

[0137] It should be noted that the embodiment of the present application takes into account that the duty cycle of the primary switch tube of the flyback converter is close to 50% when the primary switch tube is turned off. BUS The fluctuation will not affect the operation of the flyback converter, that is, the change of duty cycle can suppress nearly half of V BUS fluctuations, while the other half of V BUS The fluctuation can be suppressed based on the configuration of the current sampling unit 100 and the compensation control unit 200. Therefore, the embodiment of the present application can preferably set the proportional adjustment coefficient K 1 =0.5.

[0138] In some embodiments of the present application, the first compensation module 220 is configured to directly compensate the current sampling reference according to the first compensation signal to obtain the compensated current sampling reference. Fig. 9 and Fig.10 As shown, the initial compensation signal COMP is obtained by the feedback compensation module 221, and the reference parameter conversion module 222 determines the current sampling reference V according to the initial compensation signal COMP. CSREF And sent to the compensation unit 223, which is a multiplier in the embodiment of the present application. Finally, the compensation unit 223 calculates the current sampling reference V CSREF The product of the first compensation signal and the first compensation signal is used to obtain the first compensation value, that is, the first compensation value is V COMP1＝ V CSREF *[(1 / K BUS -1])*K1+1].

[0139] In some other embodiments of the present application, the first compensation module 220 is further configured to compensate the initial compensation signal according to the second sampling value to achieve compensation for the current sampling reference;

[0140] The initial compensation signal represents the error between the feedback voltage signal and the voltage reference signal, and the feedback voltage signal is used to represent the output voltage of the flyback converter.

[0141] like Fig.11 As shown, the first compensation module 220 is configured to compensate the initial compensation signal COMP by the compensation unit 223 according to the first compensation signal, and convert the reference parameter of the compensated initial compensation signal to achieve compensation for the current sampling reference, and obtain the compensated current sampling reference. In the embodiment of the present application, the compensation unit 223 is a multiplier. That is, Fig.11 Another compensation logic is shown, which performs compensation based on the initial compensation signal COMP, and then generates a compensated current sampling reference through the reference parameter conversion module 222.

[0142] In addition, it should be noted that in some embodiments of the present application, Figures 9 to 11 It can be seen that the compensation control unit 200 is further configured to compensate the current sampling reference when it is determined that the flyback converter operates in the critical conduction mode BCM.

[0143] That is to say, the control circuit proposed in the embodiment of the present application further sets a selection module 224 in the compensation control unit 200, and the selection module 224 is used to receive V COMP1 and V CSREF , and the mode discrimination module determines whether the flyback converter is running in the BCM mode. If it is determined to be in the BCM mode, the mode discrimination module displays a BCM signal, and the selection module 224 selects the output V according to the BCM signal. COMP1 The peak current control module 207 performs compensation control, while the flyback converter does not need compensation when operating in the DCM mode.

[0144] The peak current control module 225 is based on the first compensation value V COMP1 and the first sample value V CS , generating a control signal GON to control the peak current of the primary switch tube Q1.

[0145] For the case of compensating the first sampling value, the compensation control unit 200 is also configured to compensate the first sampling value according to the first compensation signal to obtain the compensated first sampling value, and generate a control signal according to the compensated first sampling value and the current sampling reference to control the peak current of the primary side switching tube.

[0146] The first sample value after compensation is determined according to the following formula:

[0147] V COMP2＝ V CS *[(1-1 / K BUS )*K1+1]

[0148] Among them, V COMP2 is the first sampling value after compensation, K 1 is the proportional adjustment coefficient, V CS is the first sampling value, K BUS is the ratio of the second sampling value to the second sampling average value.

[0149] Specifically, Fig.12 As shown, K BUS The first proportional regulator 213 is input for adjustment, and the proportional adjustment coefficient is K 1 The corresponding first compensation signal is [(1-1 / K BUS )*K1+1].

[0150] Depend on Fig.12 It can be seen that the compensation unit 223 is based on the first sampling value V CS The product of the first compensation signal is obtained by multiplying the first sampled value V after compensation. COMP2 The feedback compensation module 221 then generates a COMP signal, and the reference parameter conversion module 222 determines the current sampling reference V according to the COMP signal. CSREF And sent to the peak current control module 225.

[0151] In some embodiments of the present application, Fig.12 It can be seen that the compensation control unit 200 is further configured to compensate the first sampling value according to the compensation signal when it is determined that the flyback converter operates in the critical conduction mode BCM.

[0152] Depend on Fig.10 It can be seen that the compensation control unit 200 is also configured with a selection module 224 for determining whether the flyback converter outputs the second compensation value V when operating in the BCM mode. COMP2 To the peak current control module 225 for compensation control, while the flyback converter does not need compensation when operating in the DCM mode.

[0153] The peak current control module 225 is based on the compensated first sampling value V COMP2 and current sampling reference V CSREF , generating a control signal GON to control the peak current of the primary switch tube Q1.

[0154] The embodiments of the present application respectively propose two different precise compensation mechanisms for two different compensation objects, namely the current sampling reference and the first sampling value, so that not only can the positive superposition of the compensation value be achieved on the basis of the first sampling value, but also the reverse superposition can be achieved on the basis of the current sampling reference. Not only can timely, accurate and effective compensation be achieved, but also the flexibility of the compensation mechanism is increased.

[0155] Fig.13 The signal waveform is shown in FIG. 1 , which is an example of compensating the current sampling reference. Fig.13 It can be seen that the line voltage V BUS The average line voltage V BUSAVG The output voltage Vo of the flyback converter is kept stable by using the configuration of the current sampling unit 100 and the compensation control unit 200, which effectively suppresses the generation of power frequency ripple and eliminates the influence of line voltage fluctuation on the output power of the flyback converter. In addition, since the first compensation coefficient is used to timely reflect the V BUS The corresponding compensation amount is added to the current sampling reference V CSREFThat is, the line voltage fluctuation of the primary side of the transformer has been compensated in the current sampling link of the control chip, so there is no need to use COMP to adjust the reference value I of the primary side switch tube current. CSREF .

[0156] It is understandable that the above is an accurate absolute compensation for the power change with VBUS, using the proportional relationship between the second sampling value and the first voltage average. It is also possible to consider using the difference between the sampling value of the CS pin and the sampling average to make a fast relative compensation. Figures 14 to 17 The logic block diagram of the compensation control unit for fast compensation is shown. The compensation accuracy may be slightly lower than Figures 9 to 12 The compensation logic shown in the figure is simpler than the division operation, and can quickly achieve the ripple suppression requirements that do not require high compensation accuracy.

[0157] In some embodiments of the present application, the compensation control unit 200 includes a second calculation module 230 and a second compensation module 240;

[0158] The second calculation module 230 performs mean value calculation, subtraction and ratio adjustment on the second sampling value to obtain a second compensation signal;

[0159] The second compensation module 240 is used to compensate at least one of the first sampling value and the current sampling reference according to the second compensation signal.

[0160] Among them, Fig.14 or Fig.15 As shown, the second calculation module 230 includes: a second mean value calculator 231, a first subtractor 232 and a second proportional regulator 233. The second mean value calculator 231 is configured to perform mean value calculation on the second sampled value to obtain a second voltage mean value, the first subtractor 232 is configured to subtract the second sampled value from the second voltage mean value, or the first subtractor is configured to subtract the second voltage mean value from the second sampled value to obtain a first difference value, and the second proportional regulator 233 is configured to perform proportional regulation on the first difference value to obtain a second compensation signal.

[0161] In some embodiments of the present application, the averaging processing method of the second mean value calculator 231 includes but is not limited to performing low-pass filtering on the second sampling values ​​to obtain the average value of the second sampling values.

[0162] By first performing subtraction processing and then performing proportional adjustment, the difference between the second sampling value and the second voltage average is used to reflect the fluctuation trend and amplitude of the line voltage, thereby generating a fast compensation signal for the change of the line voltage, which helps to compensate the first sampling value or the current sampling reference in a timely and rapid manner, thereby achieving effective suppression of the power frequency ripple.

[0163] Specifically, if Fig.14 or Fig.15 As shown, a second sampling value V representing the current sampling slope is obtained by sampling within a fixed time T0. CS1 The second sampling value V is output to the compensation control unit 200 through the output terminal of the current sampling unit 100. CS1 First, the second voltage mean value V is obtained by the second mean value calculator 231. CSAVG , and then the first difference V is obtained through the first subtractor 232 CS1 -V CSAVG , and then the second compensation signal K is obtained through the adjustment of the second proportional regulator 210 1 (V CS1 -V CSAVG ).

[0164] Similarly, the present application may choose to perform reverse superposition compensation on the current sampling reference, or may choose to perform forward superposition compensation on the first sampling value. These two compensation methods are specifically described below.

[0165] In the case of compensating the current sampling reference, the compensation control unit 200 is also configured to compensate the current sampling reference according to the second compensation signal to obtain a compensated current sampling reference, and generate a control signal according to the compensated current sampling reference and the first sampling value to control the peak current of the primary side switching tube.

[0166] Among them, the current sampling reference after compensation is determined according to the following formula:

[0167] V COMP3＝ V CSREF -K 1 (V CS1 -V CSAVG )

[0168] Among them, V COMP3 K is the current sampling reference after compensation. 1 is the proportional adjustment coefficient, V CSREF is the current sampling reference, V CS1 is the second sampling value, V CSAVG Calculate the processed voltage mean for the average value.

[0169] In some embodiments of the present application, the second compensation module 240 is configured to directly compensate the current sampling reference according to the second compensation signal to obtain the compensated current sampling reference. Fig.14 As shown, the feedback compensation module 241 generates a COMP signal and generates a current sampling reference V through the reference parameter conversion module 242. CSREF , the compensation module 243 is based on V CSREF Calculate the current sampling reference VCSREF The difference between the second compensation signal and the current sampling reference V after compensation COMP3 , that is, in the embodiment of the present application, the compensation module 243 is a subtractor.

[0170] In some other embodiments of the present application, the second compensation module 240 is further configured to compensate the initial compensation signal according to the second sampling value to achieve compensation for the current sampling reference;

[0171] The initial compensation signal represents the error between the feedback voltage signal and the voltage reference signal, and the feedback voltage signal is used to represent the output voltage of the flyback converter.

[0172] Specifically, the second compensation module 240 is configured to compensate the initial compensation signal according to the second compensation signal, and perform reference parameter conversion on the compensated initial compensation signal to achieve compensation for the current sampling reference, thereby obtaining the compensated current sampling reference. The compensation logic can be referred to Fig.11 The compensation logic of the first compensation module 220 is shown and will not be described in detail here.

[0173] Similarly, the control circuit proposed in the embodiment of the present application further provides a selection module 244 in the compensation control unit 200 for determining the output compensation current sampling reference V of the flyback converter when operating in the BCM mode. COMP3 The peak current control module 245 performs compensation control, while the flyback converter does not need compensation when operating in the DCM mode. The peak current control module 245 samples the reference voltage V after compensation. COMP3 and the first sample value V CS , generating a control signal GON to control the peak current of the primary switch tube Q1.

[0174] For the case of compensating the first sampling value, the compensation control unit 200 is also configured to compensate the first sampling value according to the second compensation signal to obtain the compensated first sampling value, and generate a control signal according to the compensated first sampling value and the current sampling reference to control the peak current of the primary side switching tube.

[0175] The first sample value after compensation is determined according to the following formula:

[0176] V COMP4＝ V CS +K 1 (V CS1 -V CSAVG )

[0177] Among them, V COMP4 is the first sampling value after compensation, K 1 is the proportional adjustment coefficient, V CSis the first sampling value, V CS1 is the second sampling value, V CSAVG Calculate the processed voltage mean for the average value.

[0178] Specifically, Fig.15 As shown, the compensation module 243 calculates the first sampling value V CS The sum of the second compensation signal and the fourth compensation value V COMP4 , that is, in the embodiment of the present application, the compensation module 243 is an adder. The feedback compensation module 241 generates a COMP signal and generates a current sampling reference V through the reference parameter conversion module 242. CSREF , and the current sampling reference V CSREF The control circuit proposed in the embodiment of the present application also sets a selection module 244 in the compensation control unit 200 for determining whether the flyback converter outputs the compensated first sampling value V when operating in the BCM mode. COMP4 The peak current control module 245 performs compensation control, while the flyback converter does not need compensation when operating in the DCM mode. The peak current control module 245 performs compensation control based on the first sampled value V COMP4 and current sampling reference V CSREF , generating a control signal GON to control the peak current of the primary switch tube Q1.

[0179] In other embodiments of the present application, Fig.16 or Fig.17 As shown, the second calculation module 230200 includes: a third proportional regulator 234, a third mean calculator 235, and a second subtractor 236. The third proportional regulator 234 is configured to perform proportional regulation on the second sampling value to obtain a first regulated value, the third mean calculator 235 is configured to perform average value calculation on the first regulated value to obtain a third voltage mean, and the second subtractor 236 is configured to subtract the first regulated value from the third voltage mean to obtain a second compensation signal.

[0180] By first performing proportional regulation and then performing subtraction processing, the difference between the sampling value and the average value is used to reflect the fluctuation trend and amplitude of the line voltage, thereby generating a relatively simple and fast compensation signal for the change of the line voltage, which helps to compensate the first sampling value or the current sampling reference in a timely and fast manner, thereby achieving effective suppression of the power frequency ripple.

[0181] Similarly, the embodiment of the present application may choose to perform reverse superposition compensation on the current sampling reference, or may choose to perform forward superposition compensation on the first sampling value.

[0182] In some embodiments of the present application, Fig.16Figure 1 is a schematic diagram of the compensation logic structure for compensating the current sampling reference. Fig.16 As shown, a second sampling value V representing the current sampling slope is obtained by sampling within a fixed time T0. CS1 The second sampling value V is output to the compensation control unit 200 through the output terminal of the current sampling unit 100. CS1 First, the first adjustment value K is obtained by the third proportional regulator 234 1 *V CS1 , and then the third voltage mean value K is obtained by the third mean value calculator 235 1 *V CSAVG , and then processed by the second subtractor 236 to obtain the second compensation signal K 1 *V CS1 -K 1 *V CSAVG The compensation logic of the second compensation module 240 is Fig.14 The compensation logic shown is the same, and the compensation control unit 200 is also configured with a selection module 244 for determining the output of the compensated current sampling reference V when the flyback converter is running in the BCM mode. COMP3 The peak current control module 245 performs compensation control, while the flyback converter does not need compensation when operating in the DCM mode. The peak current control module 245 samples the reference voltage V after compensation. COMP3 and the first sample value V CS , generating a control signal GON to control the peak current of the primary switch tube Q1.

[0183] Depend on Fig.14 and Fig.16 It can be seen that the difference between the two embodiments lies in the configuration order of the compensation control unit performing average value calculation processing, subtraction processing and proportional adjustment on the second sampling value, wherein Fig.14 The embodiment shown is to first calculate the average value, then perform subtraction, and finally perform proportional adjustment. Fig.16 The embodiment shown is to first perform proportional adjustment, then perform filtering, and finally perform subtraction. The second compensation signals finally generated by the two are substantially the same, and the effects of suppressing the power frequency ripple at the output end are also the same.

[0184] In some embodiments of the present application, Fig.17 FIG. 1 is a schematic diagram of a compensation logic structure for compensating the first sampling value. Fig.17 As shown, a second sampling value V representing the current sampling slope is obtained by sampling within a fixed time T0. CS1 The second sampling value V is output to the compensation control unit 200 through the output terminal of the current sampling unit 100. CS1 First, the first adjustment value K is obtained by the third proportional regulator 234 1*V CS1 , and then the third voltage mean value K is obtained by the third mean value calculator 235 1 *V CSAVG , and then processed by the second subtractor 236 to obtain the second compensation signal K 1 *V CS1 -K 1 *V CSAVG The compensation logic of the second compensation module 240 is Fig.15 The compensation logic shown is the same, and the compensation control unit 200 is also configured with a selection module 244 for determining the output of the compensated first sampling value V when the flyback converter is running in the BCM mode. COMP4 The peak current control module 245 performs compensation control, while the flyback converter does not need compensation when operating in the DCM mode. The peak current control module 245 performs compensation control based on the first sampled value V COMP4 and current sampling reference V CSREF , generating a control signal GON to control the peak current of the primary switch tube Q1.

[0185] Depend on Fig.15 and Fig.17 It can be seen that the difference between the two embodiments also lies in the configuration order of the compensation control unit performing average value calculation processing, subtraction processing and proportional adjustment on the second sampling value, wherein Fig.15 The embodiment shown is to first calculate the average value, then perform subtraction, and finally perform proportional adjustment. Fig.17 The embodiment shown is to first perform proportional adjustment, then perform filtering, and finally perform subtraction. The second compensation signals finally generated by the two are substantially the same, and the effects of suppressing the power frequency ripple at the output end are also the same.

[0186] In some embodiments of the present application, the specific circuit structures of the first proportional regulator 213, the second proportional regulator 233 and the third proportional regulator 234 may be the same. Fig.18 As shown in FIG. 1 , the proportional regulator includes an error amplifier EA1, a MOSFET switch, a resistor R4 and a resistor R5. The error amplifier receives a signal at the input end and forms a feedback circuit through the resistor R4 and the resistor R5 to set the proportional regulation coefficient K. 1 At the same time, VA is connected to the drain of the MOSFET switch as the power supply, and the source of the MOSFET switch is connected to the output end, so that the voltage ratio between the input end and the output end can be accurately controlled through the MOSFET switch.

[0187] In summary, the control circuit of the flyback converter proposed in the embodiment of the present application samples the current of the primary switch tube by a current sampling unit to obtain a first sampling value, obtains a second sampling value representing the current sampling slope based on the first sampling value, and generates a compensation signal based on the second sampling value by a compensation control unit to compensate for one of the first sampling value and the current sampling reference, thereby controlling the peak current of the primary switch tube to suppress the output power frequency ripple of the flyback converter. Therefore, the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, and improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the disadvantage of the hysteresis effect of the loop compensation, and while realizing the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter.

[0188] Accordingly, please refer to Fig.19 The embodiment of the present application also provides a control chip 1 of a flyback converter, including: a current sampling pin CS, a switch tube control pin GATE and the control circuit 10 described in the above embodiment, wherein the control circuit 10 is configured to sample the primary switch tube current of the flyback converter through the current sampling pin CS, and output a control signal to the primary switch tube Q1 through the switch tube control pin GATE.

[0189] The control chip in this embodiment refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and a memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0190] The specific configuration and further functional description of the control circuit 10 in this embodiment are the same as those in the above embodiment and will not be repeated here.

[0191] The control chip proposed in the embodiment of the present application directly obtains a first sampling value that can reflect the line voltage fluctuation at the primary switch tube through a current sampling pin, and obtains a second sampling value that characterizes the current sampling slope based on the first sampling value, and generates a compensation signal through the second sampling value to compensate for one of the first sampling value and the current sampling reference, thereby controlling the peak current of the primary switch tube to suppress the output power frequency ripple of the flyback converter. Therefore, the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, and improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the disadvantage of the hysteresis effect of the loop compensation, and while achieving the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter.

[0192] Accordingly, an embodiment of the present application further provides a flyback converter, which may include the control circuit 10 described in the above embodiment or the control chip 1 described in the above embodiment.

[0193] The flyback converter proposed in the embodiment of the present application can directly obtain the first sampling value reflecting the line voltage fluctuation at the primary switch tube through the above-mentioned control circuit or control chip, and obtain the second sampling value representing the current sampling slope based on the first sampling value, and generate a compensation signal through the second sampling value to compensate for one of the first sampling value and the current sampling reference, so as to control the peak current of the primary switch tube to suppress the output power frequency ripple of the flyback converter. Therefore, the present application can timely reflect the line voltage fluctuation information according to the current sampling slope, quickly suppress the output power fluctuation caused by the line voltage fluctuation through compensation, and improve the output voltage power frequency ripple of the flyback converter. Compared with the loop compensation method used in the related art, it can overcome the disadvantage of the hysteresis effect of the loop compensation, and while realizing the suppression of the power frequency ripple and reducing the output power disturbance, it also improves the flexibility and diversity of the power frequency ripple suppression method for the flyback converter, and greatly improves the power conversion efficiency of the flyback converter.

[0194] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or physical circuits, or by products with certain functions.

[0195] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0196] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0197] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0198] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0199] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A control circuit for a flyback converter, characterized in that: The control circuit comprises: A current sampling unit, wherein the current sampling unit is configured to obtain a first sampling value based on the primary switch tube current of the flyback converter, and obtain a second sampling value representing a slope of the first sampling value based on the first sampling value; A compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to the second sampling value, so as to suppress the output power frequency ripple of the flyback converter by controlling the peak current of the primary switch tube.

2. The control circuit according to claim 1, characterized in that: The current sampling unit is further configured to perform sampling and holding and difference calculation on the first sampling value within a fixed time to obtain the second sampling value.

3. The control circuit according to claim 1, characterized in that: The compensation control unit is configured to obtain a second sampling average value representing an average value of the second sampling value according to the second sampling value, and compensate at least one of the first sampling value and the current sampling reference according to the second sampling value and the second sampling average value.

4. The control circuit according to claim 3, characterized in that: The compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to a ratio of the second sampling value to the second sampling average value.

5. The control circuit according to claim 3, characterized in that: The compensation control unit is configured to compensate at least one of the first sampling value and the current sampling reference according to a difference between the second sampling value and the second sampling average value.

6. The control circuit according to any one of claims 1 to 5, characterized in that: In a case where the compensation control unit is configured to compensate the current sampling reference according to the second sampling value, the initial compensation signal is also compensated according to the second sampling value to achieve compensation for the current sampling reference; The initial compensation signal represents the error between the feedback voltage signal and the voltage reference signal, and the feedback voltage signal is used to represent the output voltage of the flyback converter.

7. The control circuit according to any one of claims 1 to 5, characterized in that: The compensation control unit is configured to compensate the current sampling reference to obtain a compensated current sampling reference, and generate a control signal according to the compensated current sampling reference and the first sampling value to control the peak current of the primary switch tube.

8. The control circuit according to any one of claims 1 to 5, characterized in that: The compensation control unit is configured to compensate the first sampling value to obtain a compensated first sampling value, and generate a control signal according to the compensated first sampling value and the current sampling reference to control the peak current of the primary switch tube.

9. The control circuit according to claim 4, characterized in that: The compensation control unit is configured to compensate the current sampling reference to obtain a compensated current sampling reference, wherein the compensated current sampling reference is determined according to the following formula: V COMP1＝ V CSREF *[(1 / K BUS -1])*K1+1] Among them, V COMP1 is the current sampling reference after compensation, K1 is the proportional adjustment coefficient, V CSREF is the current sampling reference, K BUS is the ratio of the second sampling value to the second sampling average value.

10. The control circuit according to claim 4, characterized in that: The compensation control unit is configured to compensate the first sampling value to obtain a compensated first sampling value, and the compensated first sampling value is determined according to the following formula: V COMP2＝ V CS *[(1-1 / K BUS )*K1+1] Among them, V COMP2 is the first sampling value after compensation, K1 is the proportional adjustment coefficient, V CS is the first sampling value, K BUS is the ratio of the second sampling value to the second sampling average value.

11. The control circuit according to any one of claims 4, 9 or 10, characterized in that: The compensation control unit includes a first calculation module and a first compensation module; The first calculation module is used to perform mean value calculation, division and ratio adjustment on the second sampling value to obtain a first compensation signal; The first compensation module is used to compensate at least one of the first sampling value and the current sampling reference according to the first compensation signal.

12. The control circuit according to claim 11, characterized in that: The first calculation module includes: a first mean value calculator, wherein the first mean value calculator is configured to perform mean value calculation on the second sampling value to obtain a first voltage mean value; a first divider, wherein the first divider is configured to divide the second sampled value by the first voltage average value, or the first divider is configured to divide the first voltage average value by the second sampled value to obtain a first compensation coefficient; A first proportional regulator is configured to proportionally regulate the first compensation coefficient to obtain the first compensation signal.

13. The control circuit according to claim 11, characterized in that: The first compensation module is configured to directly compensate the current sampling reference according to the first compensation signal to obtain a compensated current sampling reference; or, The first compensation module is configured to compensate the initial compensation signal according to the first compensation signal, and perform reference parameter conversion on the compensated initial compensation signal to achieve compensation for the current sampling reference and obtain a compensated current sampling reference.

14. The control circuit according to claim 5, characterized in that: The compensation control unit is configured to compensate the current sampling reference to obtain a compensated current sampling reference, wherein the compensated current sampling reference is determined according to the following formula: V COMP3＝ V CSREF -K1(V CS1 -V CSAVG ) Among them, V COMP3 is the current sampling reference after compensation, K1 is the proportional adjustment coefficient, V CSREF is the current sampling reference, V CS1 is the second sampling value, V CSAVG Calculate the processed voltage mean for the average value.

15. The control circuit according to claim 5, characterized in that: The compensation control unit is configured to compensate the first sampling value to obtain a compensated first sampling value, and the compensated first sampling value is determined according to the following formula: V COMP4＝ V CS +K1(V CS1 -V CSAVG ) Among them, V COMP4 is the first sampling value after compensation, K1 is the proportional adjustment coefficient, V CS is the first sampling value, V CS1 is the second sampling value, V CSAVG Calculate the processed voltage mean for the average value.

16. The control circuit according to any one of claims 5, 13 or 14, characterized in that: The compensation control unit includes a second calculation module and a second compensation module; The second calculation module is used to perform mean value calculation, subtraction and proportional adjustment on the second sampling value to obtain a second compensation signal; The second compensation module is used to compensate at least one of the first sampling value and the current sampling reference according to the second compensation signal.

17. The control circuit according to claim 16, characterized in that: The second calculation module includes: a second mean value calculator, the second mean value calculator being configured to perform mean value calculation on the second sampling value to obtain a second voltage mean value; a first subtractor, wherein the first subtractor is configured to subtract the second sampled value from the second voltage average value, or the first subtractor is configured to subtract the second voltage average value from the second sampled value to obtain a first difference; A second proportional regulator is configured to perform proportional regulation on the first difference to obtain the second compensation signal.

18. The control circuit according to claim 16, characterized in that: The second calculation module includes: a third proportional regulator, wherein the third proportional regulator is configured to perform proportional regulation on the second sampling value to obtain a first regulation value; a third mean value calculator, the third mean value calculator being configured to perform mean value calculation on the first adjustment value to obtain a third voltage mean value; A second subtractor is configured to subtract the first adjustment value from the third voltage average value, or the second subtractor is configured to subtract the third voltage average value from the first adjustment value to obtain the second compensation signal.

19. The control circuit according to claim 16, characterized in that: The second compensation module is configured to directly compensate the current sampling reference according to the second compensation signal to obtain a compensated current sampling reference; or, The second compensation module is configured to compensate the initial compensation signal according to the second compensation signal, and perform reference parameter conversion on the compensated initial compensation signal to achieve compensation for the current sampling reference, thereby obtaining a compensated current sampling reference.

20. The control circuit according to claim 1, characterized in that: The compensation control unit is further configured to, when it is determined that the flyback converter operates in a critical conduction mode, compensate at least one of the first sampling value and a current sampling reference.

21. A control chip for a flyback converter, characterized in that: include: Current sampling pin; Switch tube control pin; According to any one of claims 1-20, the control circuit is configured to sample the primary switch tube current of the flyback converter through the current sampling pin, and output a control signal to the primary switch tube through the switch tube control pin.

22. A flyback converter, characterized in that: include: A control circuit according to any one of claims 1 to 20; or A control chip according to claim 21.

Images