Primary side feedback flyback converter constant current control system, method and medium based on primary side sampling resistor

Abstract

The application discloses a primary side feedback flyback converter constant current control system and method based on a primary side sampling resistor, a main topology circuit and a control circuit which constitutes a closed loop with the main topology circuit, the control circuit comprising a current sampling module, a demagnetization time compensation module, an output current calculation module, a PID calculation module and a PWM driving module, the current sampling module being used for filtering, amplifying and digitally or analogically processing the primary side sampling resistor voltage to obtain the average current of the primary side winding; the demagnetization time compensation module being used for voltage discrimination on the auxiliary winding voltage to obtain the demagnetization time of the auxiliary winding; and the output current calculation module outputting the diode average current based on the average current of the primary side winding and the demagnetization time. Compared with the traditional primary side feedback flyback converter, the application adjusts the sampling circuit, greatly reduces the resistance value of the primary side sampling resistor, improves the system conversion efficiency, and improves the precision of the output diode average current.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, and in particular to a primary-side feedback flyback converter constant current control system, method and medium based on a primary-side sampling resistor. BACKGROUND

[0002] With the increasing power consumption of communication systems, the continuous increase of supplier equipment and the continuous emergence of system space problems, the market has put forward requirements for high efficiency, high power density, wide operating temperature and high reliability of communication power supply products. The switching converter power supply greatly reduces the volume of inductors and capacitors through high-frequency switching control, can meet the electrical requirements of communication systems, and has the advantages of small size and high reliability, and is the main form of current communication power supply. The most common one is the primary-side feedback flyback converter.

[0003] The current method for implementing output constant current of the primary-side feedback flyback converter is to control the output diode current to be constant. The main idea is as follows: the average current of the primary winding of the transformer in the conduction stage is obtained through primary-side sampling, the average current of the output winding in the demagnetization stage is obtained according to the principle that the ratio of the primary winding current to the output winding current is equal to the ratio of the number of turns of the primary winding to the number of turns of the secondary winding, and finally the average current of the output diode is obtained based on the average current in the demagnetization stage, the length of time in the demagnetization stage and the switching period. The output diode current is constant, and the load current is constant. The current method can be used in both discontinuous current mode and continuous current mode, and good output voltage accuracy can be obtained.

[0004] However, the current primary-side current sampling method often uses a primary-side sampling resistor to complete sampling while controlling the peak current of the primary winding of the converter through a DAC and a comparator. This sampling method has poor anti-interference ability, and has a large error when the conduction time is small. Moreover, due to the precision limitation of the DAC and the comparator, the resistance value of the sampling resistor cannot be too small, thereby reducing the efficiency of the entire system. Especially when the primary-side current is large, the power loss on the sampling resistor will further increase, increasing the risk of breakdown. SUMMARY

[0005] The present application proposes a primary-side feedback flyback converter constant current control system, method and medium based on a primary-side sampling resistor, which greatly reduces the primary-side sampling resistor, reduces the risk of breakdown and improves the conversion efficiency of the system.

[0006] The technical solution for achieving the purpose of the present application is as follows:

[0007] A constant current control system of a primary side feedback flyback converter based on a primary side sampling resistor, the system comprising a main topology circuit and a control part constituting a closed loop with the main topology circuit; the control part comprising a current sampling module, a demagnetization time compensation module, an output current calculation module, a PID calculation module and a PWM driving module, which combine with the main topology circuit to constitute a closed loop constant current control system;

[0008] Further, the current sampling module comprises a sampling circuit module and a primary side average current calculation module, the sampling circuit module being based on the voltage V Rs on the primary side sampling resistor to obtain the primary side input current Iin, which is processed by the primary side average current calculation module to obtain the accurate primary side average current Ipav, and the Ipav is input to the output current calculation module. The detailed working modes of the sampling circuit module and the primary side average current calculation module are as follows:

[0009] The input signal of the sampling circuit input module is the voltage V Rs on the primary side sampling resistor. Firstly, the high-frequency interference signal generated by the switch tube is filtered out through a first-order RC filter, then the voltage signal V R is amplified through an operational amplifier, and finally the processed voltage signal V pav is input to the primary side average current calculation module.

[0010] The input signal of the primary side average current calculation module is the voltage signal V pav output by the sampling circuit, and the output value is the value Ipav of the primary side average current; the Ipav can be obtained by processing V pav through an analog or digital processing method:

[0011]

[0012] Ipav_sum(n+1)=Ipav_sum(n)+Iin_dig(n+1)

[0013]

[0014] Wherein, Ipav_dig is the digital quantity of the primary side average current, Counter is a defined counter, n is a count value, f clk is the clock frequency, the Vref is the reference voltage of the A / D conversion unit, and the m is the bit number of the A / D conversion unit.

[0015] Further, the input signal of the demagnetization time compensation module is the voltage signal Vsense after the auxiliary winding voltage division, and the output signal is the actual demagnetization time Tr; the module compares Vsense with zero voltage through a comparator, records the time of each cycle of the comparator being flipped, and finally obtains the actual demagnetization time Tr in each working cycle.

[0016] Furthermore, the input signals of the output current calculation module are the primary-side average current Ipav and the demagnetization time Tr, and the output signal is the calculated average current of the output diode, i.e., the value of the output current Icol; the module calculates the output current of the current cycle using the following formula:

[0017]

[0018] Furthermore, the input signal of the PID calculation module is the digital quantity Icol corresponding to the output current; the output signal is the on-time Ton given to the PWM drive module; the module will perform digital PID calculation on Icol and the given output current to obtain the on-time Ton of the main switch in the next cycle.

[0019] Furthermore, the input signal of the PWM drive module is the on-time Ton of the main switch, and the output signal of the module is the duty cycle drive signal duty of the switch. The module will generate a drive signal according to the on-time Ton of the main switch, and limit the on-time of the main switch in extreme cases to protect the controlled switching power supply system.

[0020] A method for a constant current control system of a primary-side feedback flyback converter based on the aforementioned primary-side sampling resistor includes:

[0021] The voltage of the primary side sampling resistor is filtered, amplified, and digitally or analogly processed by the current sampling module to obtain the average current of the primary winding.

[0022] The demagnetizing time is obtained by voltage discrimination of the voltage division value of the auxiliary winding through the demagnetizing time compensation module;

[0023] Based on the average current of the primary winding and the demagnetization time, the average diode current is output through the output current calculation module and then output to the PID module.

[0024] The on-time Ton of the main switch in the next cycle is determined by the PID module.

[0025] The PWM driver module generates drive signals to control the switching transistors in the main topology circuit.

[0026] Repeat the above steps to perform constant current control of the primary-side feedback flyback converter based on the primary-side sampling resistor.

[0027] A computer storage medium storing an executable program, the executable program being executed by a processor to implement the steps of the method.

[0028] Compared with the prior art, the significant advantages of this invention are:

[0029] 1) By adjusting the primary-side current sampling circuit of the primary-side feedback flyback converter, the primary-side sampling resistance is greatly reduced, further improving the system's conversion efficiency:

[0030] 2) By filtering, amplifying, and digitally or analog processing the voltage of the primary side sampling resistor, the average current of the primary winding is obtained. The demagnetization time is obtained by voltage discrimination of the voltage division value of the auxiliary winding. The accurate value of the average current of the output diode is obtained by comprehensive calculation, which is constant current control.

[0031] 3) This system is applicable to isolated or non-isolated switching power supply circuit structures and can be implemented through analog or digital control methods, possessing advantages such as versatility, reusability, and portability. Attached Figure Description

[0032] Figure 1 This is a system structure block diagram of the control method of the present invention.

[0033] Figure 2 This is the main topology circuit diagram for this example.

[0034] Figure 3(a) is the main topology circuit structure diagram using the traditional sampling method; Figure 3(b) is the relevant key waveform diagram.

[0035] Figure 4 This is a block diagram of the current sampling module in this example.

[0036] Figure 5 shows the relevant waveforms of the demagnetization time compensation module. Figure 5(a) corresponds to the continuous current conduction mode; Figure 5(b) corresponds to the discontinuous current conduction mode.

[0037] Figure 6 These are some key waveforms from the output current calculation process in this example.

[0038] Figure 7 This is the output current waveform diagram of the system in this example under operating conditions. Detailed Implementation

[0039] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0040] This embodiment provides a low-resistance constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor. Compared to traditional primary-side feedback flyback converters, the sampling circuit is adjusted, further improving the system conversion efficiency, and the accuracy of the average current of the output diode is improved through a certain calculation method. This method is fully applicable to flyback converters using clamping circuits with traditional RCD structures or various clamping circuits such as active clamping circuits, and the control method of this system can be implemented through analog control or digital control schemes.

[0041] like Figure 1 As shown, this constant current control system includes a main topology circuit and a control section forming a closed loop. The closed-loop control section includes a current sampling module, a demagnetization time compensation module, an output current calculation module, a PID calculation module, and a PWM drive module. The current sampling module and the demagnetization time compensation module process the primary side sampling resistor voltage VRs and the auxiliary winding voltage Vsense, respectively, to obtain the average value of the input current Iin and the actual demagnetization time Tr, and input them to the output current calculation module. The output current calculation module calculates the output current Icol of the previous cycle based on the input data and inputs it to the PID calculation module. The PID calculation module performs incremental PID calculation based on the error between Icol and the given output current reference value, adjusts the conduction time based on the calculation result, and finally obtains the conduction time Ton of the main tube in the next cycle, which is input to the PWM drive module. The PWM drive module generates PWM drive signals duty1 and duty2 for the main tube and auxiliary tube based on the conduction time Ton of the main tube and outputs them back to the main topology circuit.

[0042] The following section will take a digitally controlled active clamp flyback converter as an example to elaborate on the specific structure of this low-resistance primary-side feedback flyback converter constant current control system based on the primary-side sampling resistor.

[0043] Figure 2 This is a schematic diagram of the main topology of the switching power supply in this system. As shown in the figure, the main topology includes an input capacitor, a primary-side sampling resistor, primary and secondary windings of a transformer, a switching transistor, an auxiliary winding, a clamping circuit, and an output circuit. The input capacitor is connected in parallel at the input terminal, and a small-value primary-side sampling resistor is connected in series in the input circuit. The primary winding is located on the input side, with its same-name terminal connected to the positive terminal of the DC voltage and its opposite-name terminal connected to the drain terminal of the switching transistor. The clamping circuit is an active clamping circuit composed of the switching transistor and the clamping capacitor. The secondary winding is located on the output side and is connected to the output circuit. The auxiliary winding is located on the input side, with voltage divider resistors connected in series at both ends of the auxiliary winding, and the same-name terminal of the auxiliary winding is connected to the input ground.

[0044] This example demonstrates the design of a primary-side feedback DC-DC constant current control power supply based on the proposed patented method, addressing the needs of communication power applications. Its input voltage range is 24–72V, output current is 1.5A, and output voltage is 16–48V.

[0045] In a traditional variable feedback flyback converter scheme, the constant current implementation circuit is shown in Figure 3(a). A sampling resistor is needed to sample the average current of the switching transistor. This current is a linearly changing waveform, as shown in Figure 3(b). To obtain its average value, an ADC or DAC is often needed to sample this current directly or indirectly. To ensure sampling accuracy across the entire load range, this method requires a large sampling resistor to obtain a large current sampling voltage. In this example, the maximum input peak current is approximately 8A. If the sampling resistor has a resistance of 0.25Ω, the peak voltage of the sampling resistor is 2V, and the peak power consumption of the sampling resistor will reach 3.06W. However, using this control system, only a sampling resistor with a resistance of 0.02Ω is needed. Under the same conditions, the power consumption is only 0.245W, which is only 8% of the traditional scheme. This greatly reduces the power loss on the sampling resistor, significantly improves efficiency, and ensures sampling accuracy.

[0046] The following is an introduction to the implementation methods of each module in the closed-loop control section:

[0047] 1) Current Sampling Module. The current sampling module of this system consists of two parts: a current sampling circuit and a primary-side average current calculation module. The following description will use a digital control method as an example to illustrate this module;

[0048] The current sampling circuit structure is as follows: Figure 4 As shown, it includes a filter circuit and an amplifier circuit, and the input is the voltage V across the primary-side sampling resistor. Rs， V Rs First, a first-order RC filter is used to remove the high-frequency interference signal generated by the switching transistor. Then, the signal is amplified by an operational amplifier to obtain the voltage signal V. pav Finally, the amplified voltage signal V pav Input to the primary-side average current calculation module. V pav The relationship between the primary input current Iin and the current is as follows:

[0049] V pav =Iin×Rs×Gain

[0050] Where Rs is the value of the sampling resistor and Gain is the amplification factor of the operational amplifier.

[0051] Primary-side average current calculation module. It includes two parts: A / D conversion and digital calculation. Its input is the voltage signal V amplified by the sampling circuit mentioned above. pav The output is the primary-side average current Ipav. This example uses a digital control method to implement the module's function. In this example, the sampling resistor Rs is 0.02Ω, the operational amplifier gain Gain is 50, the ADC reference voltage Vref is 5.2V, and the bit depth is 8 bits. Therefore, the relationship between Iin_dig and the primary-side input current Iin can be calculated as follows:

[0052]

[0053] Define a counter, Counter, which counts during each duty cycle of the converter, based on the converter's operating frequency f and the control system's clock frequency f. clk The maximum value of Counter can be obtained (as shown in Equation 1). When Counter is less than this maximum value, Ipav_sum is defined to accumulate Iin_dig within the current working cycle (as shown in Equation 2). When Counter equals the maximum value, the average value of Ipav_sum is calculated to obtain Ipav_dig (as shown in Equation 3), and Ipav_sum is cleared to zero. Finally, Ipav_dig is transmitted to the output current calculation module.

[0054]

[0055] Ipav_sum(n+1)=Ipav_sum(n)+Iin_dig(n+1) (Formula 2)

[0056]

[0057] 3) The demagnetization time compensation module calculates the actual demagnetization time of the converter based on the voltage signal on the auxiliary winding. This function is typically implemented using a comparator. It determines the actual demagnetization time Tr by analyzing the voltage signal Vsense after the auxiliary winding is divided. Specifically, Vsense is used as the positive input of the comparator, and zero voltage is used as the inverting input. The actual demagnetization time Tr for each working cycle is obtained by timing the flipping time of the comparator output signal in each cycle and transmitted to the output current calculation module. In continuous current conduction mode, the comparator flips only once after the main conductor is turned off; the flipping time is the demagnetization time Tr, as shown in Figure 5(a). In discontinuous current conduction mode, due to the influence of transformer leakage inductance and the parasitic capacitance of the switching transistor, the Vsense signal resonates. Therefore, the comparator flips multiple times after the main conductor is turned off. In this case, the total duration of the comparator output being high within one cycle is taken as Tr, as shown in Figure 5(b).

[0058] 4) Output Current Calculation Module. This example uses a digital control method. Its input signals are the digital quantity of the primary side average current Ipav_dig, the demagnetization time Tr, and the main conductor conduction time Ton. The output signal is the calculated output current value I. col The module calculates the output current for the current cycle. Finally, it calculates the output current I. col The data is then transferred to the PID calculation module. The specific calculation method is as follows:

[0059] like Figure 6 The primary input current Iin and the primary winding current I of the transformer are... p The waveform of the primary-side average current Ipav is shown below. The primary-side average current Ipav is obtained by processing the primary-side input current Iin using the sampling module; therefore, Ipav is equal to the average value of the primary-side input current Iin. The primary-side input current ultimately flows into the primary winding of the transformer; therefore, the value of the primary-side average current Ipav is related to the transformer primary winding current Iin. p The average value is also the same throughout the entire period, as shown in the following formula:

[0060]

[0061] Where Ts represents the total duration of each work cycle, and after the supervisor shuts down, I p It is 0, and I p The increase is linear during the conduction phase, therefore the above equation can be simplified to:

[0062]

[0063] Among them I p (T on / 2) When I is at the midpoint of the main conduction time p The value of I, because I p It increases linearly during the conduction phase, therefore this value is equal to the conduction phase I. p The average value, referred to below as Replace this value. Therefore, during the time the main conductor is on in each working cycle, Impav and the primary winding current I... p average The following relationship exists:

[0064]

[0065] At the transformer output terminal, the output winding current I s The current flows to the output load through the output rectifier diode; therefore, the value of the output current is related to the transformer secondary winding current I. s The average value is also the same throughout the entire period, as shown in the following formula:

[0066]

[0067] And the output winding current I s The non-zero time is the demagnetization time Tr, therefore the formula can be simplified to:

[0068]

[0069] in, During the demagnetization period of each working cycle, the secondary winding current I... S The average value can be obtained from this. With output current I col Relationship:

[0070]

[0071] However, within one working cycle, the transformer... and The ratio is equal to the inverse ratio of the number of turns ns on the primary side of the transformer to the number of turns np on the secondary side, as shown in the following formula:

[0072]

[0073] Based on the above relationships, the formula for calculating the converter output current can be obtained:

[0074]

[0075] Where nps is the turns ratio of the primary and secondary windings of the transformer in the system, Ton is the conduction time of the main conductor, and the relationship between the average primary current Ipav and its digital value Ipav_dig is as follows:

[0076]

[0077] 5) PID Calculation Module. The PID calculation module of this system performs digital PID calculations based on the output current and a given reference value to obtain the main conduction time for the next cycle. The specific calculation formula is as follows:

[0078] t on (n)-t on (n-1)=kp×[e(n)-e(n-1)]+ki×e(n)

[0079] Where t on (n) represents the calculation amount of conduction time in this cycle, t on (n-1) represents the calculated conduction time of the previous cycle, e(n) represents the error in the current calculation of the current cycle, and e(n-1) represents the error in the current calculation of the previous cycle. This error is achieved by adjusting k. p With k i The parameter values ​​are used to perform the entire calculation. Finally, the conduction time Ton of the next cycle is obtained and transmitted to the PWM drive module and the output current calculation module.

[0080] 6) PWM Drive Module. Its input signal is the on-time Ton provided by the PID calculation module, and its output signals are the drive signals duty1 and duty2 of the switching transistors. The waveform is described as follows: at the beginning of a cycle, the main drive signal duty1 is set to a high level "1". After the main on-time equals Ton, the main drive signal duty1 is set to a low level "0". Subsequently, the auxiliary transistor drive signal duty2 is set to a high level "1" for a certain period of time, both after the main drive signal duty1 is set to a high level "1" and before the end of the current cycle. Finally, the drive signals duty1 and duty2 are transmitted back to the main circuit topology.

[0081] A method for a constant current control system of a primary-side feedback flyback converter based on the aforementioned primary-side sampling resistor includes:

[0082] The voltage of the primary side sampling resistor is filtered, amplified, and digitally or analogly processed by the current sampling module to obtain the average current of the primary winding.

[0083] The demagnetizing time is obtained by voltage discrimination of the voltage division value of the auxiliary winding through the demagnetizing time compensation module;

[0084] Based on the average current of the primary winding and the demagnetization time, the average diode current is output through the output current calculation module and then output to the PID module.

[0085] The on-time Ton of the main switch in the next cycle is determined by the PID module.

[0086] The PWM driver module generates drive signals to control the switching transistors in the main topology circuit.

[0087] By repeating the above sampling, output current calculation, demagnetization time compensation, PID calculation, and switching mode control, the system can achieve good sampling accuracy and conversion efficiency.

[0088] The method includes the technical features of a constant current control system for a primary-side feedback flyback converter based on the primary-side sampling resistor, which will not be elaborated here.

[0089] Figure 7 The output waveform is shown in the constant current output mode of 1.5A, with a 40VDC DC input and the load switching from 32Ω to 16Ω. When the load is 32Ω, the system output voltage is 1.48A, and when the load is 16Ω, the system output voltage is 1.51A. The output error is controlled within 1.3%, which shows that the system can achieve good output accuracy.

[0090] In this embodiment, the average current of the primary winding is obtained by processing and calculating the voltage of the primary sampling resistor. The demagnetization time is obtained by voltage discrimination of the voltage division value of the auxiliary winding. The accurate value of the average current of the output diode is obtained by comprehensive calculation. Moreover, this method is applicable to active clamp flyback converters or RCD clamped flyback circuit structures, etc., and has the advantages of versatility, reusability and portability. It can be implemented by analog control or digital control methods.

[0091] The above descriptions are merely preferred embodiments of this application, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor, comprising a main topology circuit and a control circuit forming a closed loop therewith, characterized in that: The control circuit includes a current sampling module, a demagnetizing time compensation module, an output current calculation module, a PID calculation module, and a PWM drive module. The current sampling module is used to filter, amplify, and perform digital or analog processing on the voltage of the primary-side sampling resistor to obtain the average current of the primary winding. The demagnetizing time compensation module is used to determine the demagnetizing time by voltage discrimination of the voltage division value of the auxiliary winding. The output current calculation module outputs the average current of the diode based on the average current of the primary winding and the demagnetizing time. The PID calculation module is used to determine the on-time Ton of the main switch in the next cycle. The PWM drive module is used to generate drive signals to control the switches in the main topology circuit. The current sampling module includes a sampling circuit module and a primary-side average current calculation module; the sampling circuit module includes a filtering circuit and an amplification circuit; the filtering circuit is used to calculate the voltage V across the primary-side sampling resistor. Rs The filter removes interference signals and outputs them to the amplifier circuit, which amplifies the input DC voltage and outputs the amplified voltage signal V. pav The data is processed by the primary-side average current calculation module to obtain the primary-side average current Ipav, and then Ipav is input to the output current calculation module. The primary-side average current calculation module uses digital processing of voltage signal V. pav It includes an A / D conversion unit and a digital calculation unit. The A / D conversion unit is used for analog-to-digital conversion, and the digital calculation unit is used for calculating the primary-side average current.

2. The constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor according to claim 1, characterized in that: The primary-side average current output by the digital computing unit is: Ipav_sum(n+1)=Ipav_sum(n)+Iin_dig(n+1) Where Ipav_dig is the digital value of the primary side average current, Counter is the defined counter, n is the count value, and f clk Where is the clock frequency, Vref is the reference voltage of the A / D conversion unit, and m is the number of bits in the A / D conversion unit.

3. The constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor according to claim 1, characterized in that: The demagnetization time compensation module uses a comparator to compare Vsense with a small voltage or zero voltage, and records the flip time of the comparator in each cycle to calculate the actual demagnetization time Tr in each working cycle.

4. The constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor according to claim 1, characterized in that: The average diode current output by the output current calculation module is: Where nps is the turns ratio of the primary and secondary windings of the transformer, and Ton is the on-time of the main switch in the current cycle.

5. The constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor according to claim 1, characterized in that: The method for determining the on-time Ton of the main switch in the next cycle is as follows: t on (n)-t on (n-1)=kp×[e(n)-e(n-1)]+ki×e(n) Among them, t on (n) represents the calculation amount of conduction time in this cycle, t on (n-1) represents the calculated conduction time of the previous cycle, e(n) represents the error in the current calculation of the current cycle, and e(n-1) represents the error in the current calculation of the previous cycle. This error is achieved by adjusting the PID parameter k. p With k i The parameter values ​​are used to perform the entire calculation, and the conduction time Ton for the next cycle is obtained.

6. The constant current control system for a primary-side feedback flyback converter based on a primary-side sampling resistor according to claim 1, characterized in that: The PWM drive module is used to generate drive signals by: setting the main drive signal duty1 to a high level 1 at the beginning of a cycle; setting the main drive signal duty1 to a low level 0 after the main drive conduction time equals Ton; and then setting the auxiliary tube drive signal duty2 to a high level 1 after the main drive signal duty1 is set to a high level 1 and before the end of the cycle.

7. A method for a constant current control system of a primary-side feedback flyback converter based on the primary-side sampling resistor as described in any one of claims 1-6, characterized in that: include: The voltage of the primary side sampling resistor is filtered, amplified, and digitally or analogly processed by the current sampling module to obtain the average current of the primary winding. The demagnetizing time is obtained by voltage discrimination of the voltage division value of the auxiliary winding through the demagnetizing time compensation module; Based on the average current of the primary winding and the demagnetization time, the average diode current is output through the output current calculation module and then output to the PID module. The on-time Ton of the main switch in the next cycle is determined by the PID module. The PWM driver module generates drive signals to control the switching transistors in the main topology circuit. Repeat the above steps to perform constant current control of the primary-side feedback flyback converter based on the primary-side sampling resistor.

8. A computer storage medium, characterized in that, The computer storage medium stores an executable program, which is executed by a processor to implement the steps of the method of claim 7.

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