Primary side control circuit and device

Abstract

The application discloses a primary side control circuit and device, the circuit feeds back the first output voltage of the secondary side of a switching power supply module through an auxiliary winding; the primary side control chip collects the first output voltage, and determines the working mode of the switching power supply module according to the fluctuation value of the first output voltage; the primary side control chip outputs the first secondary side driving signal or the second secondary side driving signal to the isolation driving chip according to the working mode, the first secondary side driving signal is the driving signal suitable for the intermittent conduction mode, and the second secondary side driving signal is the driving signal suitable for the continuous conduction mode; the isolation driving chip drives the synchronous rectifier device according to the first secondary side driving signal or the second secondary side driving signal. The application outputs the first secondary side driving signal suitable for the intermittent conduction mode or the second secondary side driving signal suitable for the continuous conduction mode according to the working mode, and realizes the compatibility of the intermittent conduction mode and the continuous conduction mode in the synchronous rectification technology.

Description

Technical Field

[0001] This invention relates to the field of power management chip technology, and in particular to a primary-side control circuit and device. Background Technology

[0002] Power management chips are widely used in modern electronic products. They are not only used in power circuits, but also in other circuits, such as the backlight circuits of fluorescent lamps and LCD displays.

[0003] Currently, in synchronous rectification technology, existing flyback switching power supply chips require secondary-side driven chips to perform status detection on the secondary side of the synchronous rectification device. This is only applicable to intermittent conduction mode, or outputs a synchronous rectification signal that is complementary to the primary side. This is only applicable to continuous conduction mode and cannot simultaneously support both intermittent and continuous conduction modes.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this invention is to provide a primary-side control circuit and device, which aims to solve the technical problem that existing flyback switching power supply chips in synchronous rectification technology require a secondary-side driven chip to perform state detection of the synchronous rectification device on the secondary side, which is only applicable to intermittent conduction mode, or output a synchronous rectification signal complementary to the primary side, which is only applicable to continuous conduction mode, and cannot simultaneously support both intermittent and continuous conduction modes.

[0006] To achieve the above objectives, the present invention provides a primary-side control circuit, which includes: a primary-side control chip, an isolation driver chip, and a switching power supply module;

[0007] The switching power supply module includes an auxiliary winding and a synchronous rectifier.

[0008] The primary-side control chip is connected to the auxiliary winding and the isolation drive chip respectively, and the isolation drive chip is connected to the control terminal of the synchronous rectifier.

[0009] The auxiliary winding is used to provide feedback on the first output voltage of the secondary side of the switching power supply module;

[0010] The primary-side control chip is used to acquire the first output voltage and determine the operating mode of the switching power supply module based on the fluctuation value of the first output voltage.

[0011] The primary-side control chip is also used to output a first secondary-side drive signal or a second secondary-side drive signal to the isolation drive chip according to the working mode. The first secondary-side drive signal is a drive signal adapted to the intermittent conduction mode, and the second secondary-side drive signal is a drive signal adapted to the continuous conduction mode.

[0012] The isolation driver chip is used to drive the synchronous rectifier according to the first secondary-side drive signal or the second secondary-side drive signal.

[0013] Optionally, the primary-side control chip includes: a first feedback unit and a mode determination unit;

[0014] The first feedback unit is connected to both the auxiliary winding and the mode determination unit.

[0015] The first feedback unit is used to acquire the first output voltage and output the first output voltage to the mode determination unit;

[0016] The mode determination unit is used to compare the first output voltage with the sampled voltage fed back by the auxiliary winding in the previous cycle, determine the difference between the first output voltage and the sampled voltage, and use the difference as the fluctuation value of the first output voltage.

[0017] The mode determination unit is further configured to determine that the working mode is an intermittent conduction mode when the fluctuation value is lower than a preset voltage threshold.

[0018] The mode determination unit is further configured to determine that the operating mode is a continuous conduction mode when the fluctuation value reaches the preset voltage threshold.

[0019] Optionally, the primary-side control chip further includes: a sample-and-hold unit;

[0020] The sampling and holding unit is connected to the first feedback unit and the mode determination unit, respectively.

[0021] The sample-and-hold unit is used to store the first output voltage so that the mode determination unit compares the first output voltage with the voltage of the next cycle fed back by the auxiliary winding.

[0022] Optionally, the sample-and-hold unit includes: first to tenth PMOS transistors, first to fourth NMOS transistors, and a first capacitor;

[0023] The gate of the first PMOS transistor is connected to the bandgap reference, the source of the first PMOS transistor is connected to the power supply terminal, the drain of the first PMOS transistor is connected to the source of the fifth PMOS transistor and the source of the sixth PMOS transistor, the gate of the fifth PMOS transistor is connected to the first feedback unit, the drain of the fifth PMOS transistor is connected to the drain of the first NMOS transistor and the gate of the first NMOS transistor, the gate of the sixth PMOS transistor is connected to the first feedback unit, the drain of the sixth PMOS transistor is connected to the drain of the second NMOS transistor, the gate of the second NMOS transistor is connected to the gate of the first NMOS transistor, and the source of the second NMOS transistor is connected to the source of the first NMOS transistor.

[0024] The gate of the second PMOS transistor is connected to the bandgap reference, the source of the second PMOS transistor is connected to the power supply terminal, the drain of the second PMOS transistor is connected to the gate of the fifth PMOS transistor and the source of the ninth PMOS transistor, the gate of the ninth PMOS transistor is connected to the drain of the sixth PMOS transistor, and the drain of the ninth PMOS transistor is connected to the source of the first NMOS transistor.

[0025] The gate of the third PMOS transistor is connected to the bandgap reference, the source of the third PMOS transistor is connected to the power supply terminal, the drain of the third PMOS transistor is connected to the source of the seventh PMOS transistor and the source of the eighth PMOS transistor, the gate of the seventh PMOS transistor is connected to the output terminal, the drain of the seventh PMOS transistor is connected to the drain of the third NMOS transistor and the gate of the third NMOS transistor, the gate of the eighth PMOS transistor is connected to the first feedback unit and the first terminal of the first capacitor, the second terminal of the first capacitor is connected to the source of the first NMOS transistor, the drain of the eighth PMOS transistor is connected to the drain of the fourth NMOS transistor, the gate of the fourth NMOS transistor is connected to the gate of the third NMOS transistor, and the source of the fourth NMOS transistor is connected to the source of the first NMOS transistor.

[0026] The gate of the fourth PMOS transistor is connected to the bandgap reference, the source of the fourth PMOS transistor is connected to the power supply terminal, the drain of the fourth PMOS transistor is connected to the output terminal and the source of the tenth PMOS transistor, the gate of the tenth PMOS transistor is connected to the drain of the eighth PMOS transistor, and the source of the tenth PMOS transistor is connected to the source of the first NMOS transistor.

[0027] Optionally, the primary-side control chip further includes: a secondary-side duty cycle unit;

[0028] The secondary duty cycle unit is connected to the isolation driver chip;

[0029] The secondary duty cycle unit is used to generate a secondary duty cycle that is proportional to the duty cycle of the primary drive signal when the working mode is the intermittent conduction mode. The primary drive signal is a signal that controls the switching device on or off on the primary side of the switching power supply module.

[0030] The secondary side duty cycle unit is further configured to generate the first secondary side drive signal according to the secondary side duty cycle, and output the first secondary side drive signal to the isolation drive chip.

[0031] Optionally, the secondary duty cycle unit is further configured to generate a second secondary drive signal complementary to the primary drive signal to the isolation drive chip when the operating mode is the continuous conduction mode.

[0032] Optionally, the primary-side control chip further includes: a second feedback unit and a primary-side duty cycle unit;

[0033] The second feedback unit is connected to the auxiliary winding and the primary duty cycle unit respectively, and the primary duty cycle unit is connected to the isolation drive chip;

[0034] The second feedback unit is used to acquire the second output voltage fed back by the auxiliary winding and output the second output voltage to the primary duty cycle unit;

[0035] The primary-side duty cycle unit is used to compare the second output voltage with a preset triangular wave voltage, generate the primary-side drive signal, and output the primary-side drive signal to the isolation drive chip.

[0036] The isolation driver chip is also used to control the switching devices on or off the primary side of the switching power supply module according to the primary side drive signal.

[0037] Optionally, the primary-side control chip further includes a state detection unit;

[0038] The status detection unit is connected to the switching power supply module;

[0039] The status detection unit is used to receive the detection signal input by the switching power supply module and determine whether the detection signal meets the preset ideal conditions.

[0040] The state detection unit is also used to control the primary-side control chip to stop operating when the detection signal does not meet the preset ideal conditions.

[0041] Optionally, the primary side of the switching power supply module includes: the auxiliary winding, the primary winding, the power supply terminal, the first to the seventh resistors, the first diode, the second diode, the second to the fourth capacitors, the sixth capacitor and the seventh capacitor, and the fifth NMOS transistor, which is the switching device of the primary side of the switching power supply module;

[0042] The secondary side of the switching power supply module includes: a secondary winding, an eighth resistor, a fifth capacitor, and a sixth NMOS transistor, wherein the sixth NMOS transistor is the synchronous rectifier.

[0043] The power supply port of the primary-side control chip is connected to the cathode of the first diode, the first end of the first resistor, and the first end of the second capacitor, respectively. The second end of the first resistor is connected to the positive terminal of the power supply port, the negative terminal of the power supply port is grounded, and the second end of the second capacitor is grounded.

[0044] The first feedback port of the primary-side control chip is connected to the first end of the second resistor, the first end of the third resistor, and the first end of the sixth capacitor. The second end of the sixth capacitor is grounded, the second end of the third resistor is grounded, the second end of the second resistor is connected to the anode of the first diode and the first end of the auxiliary winding, and the second end of the auxiliary winding is grounded.

[0045] The second feedback port of the primary-side control chip is connected to the first end of the fourth resistor, the first end of the fifth resistor, and the first end of the seventh capacitor, respectively. The second end of the seventh capacitor is grounded, the second end of the fifth resistor is grounded, and the second end of the fourth resistor is connected to the anode of the first diode and the first end of the auxiliary winding, respectively. The first common ground port of the primary-side control chip is grounded.

[0046] The current detection port of the primary-side control chip is connected to the first terminal of the third capacitor, the first terminal of the sixth resistor, and the source of the fifth NMOS transistor. The drain of the fifth NMOS transistor is connected to the first terminal of the primary winding and the anode of the second diode. The cathode of the second diode is connected to the first terminal of the seventh resistor and the first terminal of the fourth capacitor. The second terminal of the seventh resistor is connected to the second terminal of the primary winding and the positive terminal of the power supply. The second terminal of the fourth capacitor is connected to the second terminal of the primary winding and the positive terminal of the power supply.

[0047] The second common ground port of the primary-side control chip is connected to the second terminal of the third capacitor and the second terminal of the sixth resistor, respectively. The primary-side gate drive signal port of the primary-side control chip is connected to the first input terminal of the isolation drive chip, and the first output terminal of the isolation drive chip is connected to the gate of the fifth NMOS transistor.

[0048] The synchronous rectification drive signal port of the primary-side control chip is connected to the second input terminal of the isolation drive chip. The second output terminal of the isolation drive chip is connected to the gate of the sixth NMOS transistor. The drain of the sixth NMOS transistor is connected to the first terminal of the secondary winding. The source of the sixth NMOS transistor is connected to the first terminal of the fifth capacitor and the first terminal of the eighth resistor. The second terminal of the fifth capacitor is connected to the second terminal of the secondary winding. The second terminal of the eighth resistor is connected to the second terminal of the secondary winding.

[0049] In addition, to achieve the above objectives, the present invention also proposes a primary-side control device, which includes the primary-side control circuit as described above.

[0050] This invention provides a primary-side control circuit and device. The circuit provides feedback on the first output voltage of the secondary side of the switching power supply module through an auxiliary winding. The primary-side control chip acquires the first output voltage and determines the operating mode of the switching power supply module based on the fluctuation value of the first output voltage. The primary-side control chip outputs a first secondary-side drive signal or a second secondary-side drive signal to an isolation drive chip according to the operating mode. The first secondary-side drive signal is a drive signal adapted to the intermittent conduction mode, and the second secondary-side drive signal is a drive signal adapted to the continuous conduction mode. The isolation drive chip drives the synchronous rectifier device according to the first secondary-side drive signal or the second secondary-side drive signal. This invention utilizes a primary-side control chip to output a first secondary-side drive signal adapted to the intermittent conduction mode when the operating mode is intermittent conduction mode, and to output a second secondary-side drive signal adapted to the continuous conduction mode when the operating mode is continuous conduction mode. The first or second secondary-side drive signal is then output to a synchronous rectifier via an isolation drive chip to achieve synchronous rectification. Compared to existing flyback switching power supply chips that are only suitable for one of the intermittent or continuous conduction modes, the primary-side control circuit of this invention is applicable to both intermittent and continuous conduction modes, achieving compatibility with both modes. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the structure of the first embodiment of the primary-side control circuit of the present invention;

[0052] Figure 2 This is a schematic diagram of the structure of the second embodiment of the primary-side control circuit of the present invention;

[0053] Figure 3 This is a circuit diagram of the sample-and-hold unit in the second embodiment of the primary-side control circuit of the present invention;

[0054] Figure 4 This is a schematic diagram of the structure of the third embodiment of the primary-side control circuit of the present invention;

[0055] Figure 5 This is a functional schematic diagram of the primary-side control chip in the third embodiment of the primary-side control circuit of the present invention;

[0056] Figure 6 This is a circuit diagram of the switching power supply module in the third embodiment of the primary-side control circuit of the present invention.

[0057] Explanation of icon numbers:

[0058]

[0059] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0060] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0061] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0062] It should be noted that the descriptions involving "first," "second," etc., in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" and "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0063] Reference Figure 1 , Figure 1 This is a schematic diagram of the structure of the first embodiment of the primary-side control circuit of the present invention.

[0064] like Figure 1 As shown, the primary-side control circuit in this embodiment includes: a primary-side control chip 100, an isolation driver chip 200, and a switching power supply module 300.

[0065] The switching power supply module 300 includes an auxiliary winding 301 and a synchronous rectifier 302.

[0066] The primary-side control chip 100 is connected to the auxiliary winding 301 and the isolation drive chip 200 respectively, and the isolation drive chip 200 is connected to the control terminal of the synchronous rectifier 302.

[0067] The auxiliary winding 301 is used to provide feedback on the first output voltage of the secondary side of the switching power supply module 300.

[0068] It should be noted that the aforementioned switching power supply module 300 is similar to existing flyback converters or flyback switching power supplies, and is a module that includes a flyback converter. The primary side of the switching power supply module 300 includes a primary winding (coil), and the secondary side of the switching power supply module 300 includes a secondary winding (coil). The primary winding and the secondary winding constitute a transformer. The difference is that the primary side of the aforementioned switching power supply module is also provided with an auxiliary winding 301, which shares a set of windings with the primary winding and the auxiliary winding.

[0069] In a specific implementation, when the primary side of the switching power supply module 300 is turned on, the auxiliary winding 301 can feed back the voltage output by the secondary side of the switching power supply module 300. The voltage fed back by the auxiliary winding is the first output voltage. The relationship between the output voltage and the secondary output voltage can be determined by the turns ratio of the auxiliary winding 301 to the secondary winding. Therefore, the secondary output voltage can be monitored through the auxiliary winding 301.

[0070] It should be understood that in this embodiment, the secondary output voltage can be monitored through the auxiliary winding 301. Compared with the existing flyback switching power supply, there is no need for additional optocouplers or digital isolators to monitor the secondary output voltage, which reduces the peripheral components of the flyback converter, thereby reducing the size of the flyback converter and lowering its cost.

[0071] The primary-side control chip 100 is used to collect the first output voltage and determine the operating mode of the switching power supply module 300 based on the fluctuation value of the first output voltage.

[0072] It should be noted that the above-mentioned operating mode can be the operating mode of the switching power supply module 300 during synchronous rectification, such as intermittent conduction mode or continuous conduction mode.

[0073] In a specific implementation, the primary-side control chip 100 can collect the first output voltage fed back by the auxiliary winding 301 in the current cycle, and compare the collected first output voltage with the voltage fed back by the auxiliary winding 301 in the previous cycle to determine the fluctuation value of the first output voltage. The voltage change of the secondary-side output in the two cycles is determined by the fluctuation value of the first output voltage, thereby determining the working mode of the switching power supply module 300.

[0074] It should be understood that if the aforementioned switching power supply module 300 is in intermittent conduction mode, the voltage fluctuation of the secondary output of the switching power supply module 300 is small. Correspondingly, if it is in continuous conduction mode, the voltage fluctuation of the secondary output of the switching power supply module 300 is large. The voltage of the secondary output can be fed back by the auxiliary winding. Therefore, by collecting the voltage of the auxiliary winding in two cycles before and after, the fluctuation value of the first output voltage can be determined, thereby determining the operating mode of the switching voltage module 300.

[0075] The primary-side control chip 100 is also used to output a first secondary-side drive signal or a second secondary-side drive signal to the isolation drive chip 200 according to the working mode. The first secondary-side drive signal is a drive signal adapted to the intermittent conduction mode, and the second secondary-side drive signal is a drive signal adapted to the continuous conduction mode.

[0076] It should be noted that the intermittent conduction mode mentioned above can be the working mode in which the current output by the switching power supply module 300 drops back to zero within a stable cycle, that is, the non-continuous conduction mode. Correspondingly, the continuous conduction mode mentioned above is the working mode in which the current output by the switching power supply module 300 does not drop back to zero within a stable cycle.

[0077] Understandably, existing flyback converters use a secondary-side driver chip in synchronous rectification technology to monitor the state of the synchronous rectifier on the secondary side. This is only applicable to intermittent conduction mode and cannot be applied to continuous conduction mode. In order to be applicable to continuous conduction mode, a synchronous rectification signal complementary to the primary side can be used. However, this method is only applicable to continuous conduction mode and cannot be applied to intermittent conduction mode. Therefore, existing flyback converters cannot achieve dual operating modes.

[0078] In a specific implementation, the primary-side control chip 100 can output a first secondary-side drive signal when the switching power supply module 300 is in intermittent conduction mode, and output a second secondary-side drive signal when the switching power supply module 300 is in continuous conduction mode, thereby achieving both intermittent and continuous conduction modes.

[0079] The isolation driver chip 200 is used to drive the synchronous rectifier 302 according to the first secondary-side drive signal or the second secondary-side drive signal.

[0080] It should be noted that the aforementioned synchronous rectification device 302 can be a device, such as a MOSFET, located on the secondary side of the switching power supply module 300 to achieve synchronous rectification.

[0081] It is understood that the aforementioned isolation driver chip 200 can be a chip that connects the switching devices on the primary side and the synchronous rectification devices on the secondary side of the switching power supply module 300. The isolation driver chip 200 can isolate the primary and secondary sides of the aforementioned switching power supply module 300 and is independent of the aforementioned primary side control chip 100.

[0082] In a specific implementation, the primary-side control chip 100 does not need to directly output the first secondary-side drive signal or the second secondary-side drive signal to the synchronous rectifier 302. Instead, it outputs the first secondary-side drive signal and the second secondary-side drive signal to the isolation drive chip 200. Only the isolation drive chip 200 outputs the first secondary-side drive signal and the second secondary-side drive signal to the synchronous rectifier 302, thereby reducing the number of drive chips in the switching power supply module 300.

[0083] It should be understood that the aforementioned synchronous rectification device can be a MOSFET, which can effectively reduce the power consumption of the secondary side during synchronous rectification, thereby improving the converter efficiency of the switching power supply module 300.

[0084] In this embodiment, the auxiliary winding provides feedback on the first output voltage of the secondary side of the switching power supply module. The primary-side control chip acquires the first output voltage and determines the operating mode of the switching power supply module based on the fluctuation value of the first output voltage. The primary-side control chip outputs a first secondary-side drive signal or a second secondary-side drive signal to the isolation drive chip according to the operating mode. The first secondary-side drive signal is a drive signal adapted to the intermittent conduction mode, and the second secondary-side drive signal is a drive signal adapted to the continuous conduction mode. The isolation drive chip drives the synchronous rectifier device according to the first secondary-side drive signal or the second secondary-side drive signal. In this embodiment, the primary-side control chip outputs a first secondary-side drive signal adapted to the intermittent conduction mode when the operating mode is intermittent conduction mode, and outputs a second secondary-side drive signal adapted to the continuous conduction mode when the operating mode is continuous conduction mode. The first or second secondary-side drive signal is output to the synchronous rectification device through the isolation drive chip to achieve synchronous rectification. Compared with the existing flyback switching power supply chip, which is only adapted to one of the intermittent conduction mode and continuous conduction mode, the primary-side control circuit in this embodiment is applicable to both intermittent conduction mode and continuous conduction mode, thus achieving compatibility with both intermittent conduction mode and continuous conduction mode.

[0085] refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of the second embodiment of the primary-side control circuit of the present invention.

[0086] Based on the first embodiment described above, in this embodiment, the primary-side control chip 100 includes: a first feedback unit 101 and a mode determination unit 102.

[0087] The first feedback unit 101 is connected to the auxiliary winding 301 and the mode determination unit 102 respectively.

[0088] The first feedback unit 101 is used to acquire the first output voltage and output the first output voltage to the mode determination unit 102.

[0089] In a specific implementation, the first feedback unit 101 can be connected to the auxiliary winding 301 to collect the first output voltage fed back by the auxiliary winding 301 in each cycle of the switching power supply module 300, and output the collected first output voltage to the mode determination unit 102.

[0090] The mode determination unit 102 is used to compare the first output voltage with the sampled voltage fed back by the auxiliary winding 301 in the previous cycle, determine the difference between the first output voltage and the sampled voltage, and use the difference as the fluctuation value of the first output voltage.

[0091] It should be noted that the above-mentioned sampling voltage can be the voltage fed back by the auxiliary winding 301 in the previous cycle of the current cycle, that is, the sampling voltage can be the first output voltage of the previous cycle.

[0092] In a specific implementation, the above-mentioned mode determination unit can compare the first output voltage with the above-mentioned sampling voltage. Since the sampling voltage is the first output voltage of the previous cycle, by comparing the first output voltage of the current cycle with the first output voltage of the previous cycle, the difference between the two can be the difference between the first output voltage and the voltage of the previous cycle. This difference can be the fluctuation value of the first output voltage.

[0093] The mode determination unit 102 is further configured to determine that the working mode is an intermittent conduction mode when the fluctuation value is lower than a preset voltage threshold.

[0094] It should be noted that the aforementioned preset voltage threshold can be used to determine whether the fluctuation of the first output voltage is in a continuous conduction mode, and the specific value can be set according to the requirements.

[0095] In a specific implementation, the mode determination unit 102 can compare the fluctuation value of the first output voltage with a preset voltage threshold to determine whether the fluctuation value reaches the preset voltage threshold. If the fluctuation value is lower than the preset voltage threshold, it indicates that the fluctuation value of the first output voltage is small, and the working mode of the switching power supply module 300 is determined to be the intermittent conduction mode.

[0096] The mode determination unit 102 is further configured to determine that the working mode is a continuous conduction mode when the fluctuation value reaches the preset voltage threshold.

[0097] In a specific implementation, when the mode determination unit 102 determines that the fluctuation value reaches the preset voltage threshold, it indicates that the fluctuation of the first output voltage is large at this time, and determines that the working mode of the switching power supply module 300 is the continuous conduction mode.

[0098] Furthermore, such as Figure 2 As shown, in this embodiment, the primary-side control chip 100 further includes a sample-and-hold unit 103.

[0099] The sampling and holding unit 103 is connected to the first feedback unit 101 and the mode determination unit 102, respectively.

[0100] The sample-and-hold unit 103 is used to store the first output voltage so that the mode determination unit 102 compares the first output voltage with the voltage of the next cycle fed back by the auxiliary winding 301.

[0101] It should be noted that in order for the mode determination unit 102 to compare the first output voltage of the current cycle fed back by the auxiliary winding 301 with the sampled voltage of the previous cycle fed back by the auxiliary winding 301, the sampled voltage of the previous cycle needs to be saved. Therefore, the above-mentioned sample and hold unit is proposed.

[0102] For ease of understanding, please refer to Figure 3 This explanation does not limit the scope of this solution. Figure 3 This is a circuit diagram of the sample-and-hold unit in the second embodiment of the primary-side control circuit of the present invention. Figure 3 In the sample-and-hold unit 103, the first to tenth PMOS transistors M1 to M10, the first to fourth NMOS transistors M1 to M4, and the first capacitor C1 are included.

[0103] The gate of the first PMOS transistor M1 is connected to the bandgap reference, the source of the first PMOS transistor M1 is connected to the power supply terminal, the drain of the first PMOS transistor M1 is connected to the source of the fifth PMOS transistor M5 and the source of the sixth PMOS transistor M6, the gate of the fifth PMOS transistor M5 is connected to the first feedback unit 101, the drain of the fifth PMOS transistor M5 is connected to the drain of the first NMOS transistor M11 and the gate of the first NMOS transistor M11, the gate of the sixth PMOS transistor M6 is connected to the first feedback unit 101, and the drain of the sixth PMOS transistor M6 is connected to the drain of the second NMOS transistor M12. The gate of the second NMOS transistor M12 is connected to the gate of the first NMOS transistor M11, and the source of the second NMOS transistor M12 is connected to the source of the first NMOS transistor M11. The gate of the second PMOS transistor M2 is connected to the bandgap reference, the source of the second PMOS transistor M2 is connected to the power supply terminal, and the drain of the second PMOS transistor M2 is connected to the gate of the fifth PMOS transistor M5 and the source of the ninth PMOS transistor M9. The gate of the ninth PMOS transistor M9 is connected to the drain of the sixth PMOS transistor M6, and the drain of the ninth PMOS transistor M9 is connected to the source of the first NMOS transistor M11. The gate of the third PMOS transistor M3 is connected to the bandgap reference. The third PMOS transistor M3 is connected to the power supply terminal. The drain of the third PMOS transistor M3 is connected to the source of the seventh PMOS transistor M7 and the source of the eighth PMOS transistor M8. The gate of the seventh PMOS transistor M7 is connected to the output terminal. The drain of the seventh PMOS transistor M7 is connected to the drain of the third NMOS transistor M13 and the gate of the third NMOS transistor M13. The gate of the eighth PMOS transistor M8 is connected to the first feedback unit 101 and the first terminal of the first capacitor C1. The second terminal of the first capacitor C1 is connected to the source of the first NMOS transistor M11. The drain of the eighth PMOS transistor M8 is connected to the fourth NMOS transistor M11. The drain of MOS transistor M14 is connected, the gate of the fourth NMOS transistor M14 is connected to the gate of the third NMOS transistor M13, and the source of the fourth NMOS transistor M14 is connected to the source of the first NMOS transistor M11; the gate of the fourth PMOS transistor M4 is connected to the bandgap reference, the source of the fourth PMOS transistor M4 is connected to the power supply terminal, the drain of the fourth PMOS transistor M4 is connected to the output terminal and the source of the tenth PMOS transistor M10, the gate of the tenth PMOS transistor M10 is connected to the drain of the eighth PMOS transistor M8, and the source of the tenth PMOS transistor M10 is connected to the source of the first NMOS transistor M11.

[0104] In a specific implementation, the first to tenth PMOS transistors M1 to M10, the first to fourth NMOS transistors M1 to M4, and the first capacitor C1 constitute the circuit of the sample and hold unit 103. The aforementioned bandgap reference can be a reference source inside the primary-side control chip 100. The bandgap reference can output a reference signal to the gates of the first to fourth PMOS transistors M1 to M4. The aforementioned power supply terminal can be a power supply terminal that increases the operating voltage of the primary-side control chip 100. Correspondingly, the power supply terminal can also output a power supply voltage to the source of the first to fourth PMOS transistors M1 to M4. The aforementioned first feedback unit 101 can input the sampling voltage collected by the aforementioned auxiliary winding 301 in the previous cycle to the gate of the aforementioned fifth PMOS transistor M5, the gate of the sixth PMOS transistor M6, and the gate of the aforementioned eighth PMOS transistor M8 as the input of the sample-and-hold unit 103. The aforementioned output terminal can be the aforementioned mode determination unit 102. When the aforementioned mode determination unit 102 determines the fluctuation value of the first output voltage, the aforementioned sampling voltage is output to the aforementioned mode determination unit 102 through the drain of the aforementioned eighth PMOS transistor and the drain of the aforementioned fourth PMOS transistor M4 to determine the fluctuation value of the first output voltage.

[0105] It should be understood that after the fluctuation value of the first output voltage in the current cycle is determined, the sample and hold unit 103 can also save the first output voltage so that when the next cycle arrives, the mode determination unit 102 can determine the voltage fluctuation value of the next cycle based on the first output voltage.

[0106] Furthermore, such as Figure 2 As shown, in this embodiment, the primary-side control chip 100 further includes a secondary-side duty cycle unit 104.

[0107] The secondary duty cycle unit 104 is connected to the isolation driver chip 200.

[0108] The secondary duty cycle unit 104 is used to generate a secondary duty cycle that is proportional to the duty cycle of the primary drive signal when the working mode is the intermittent conduction mode. The primary drive signal is a signal that controls the switching device on or off on the primary side of the switching power supply module.

[0109] In a specific implementation, the secondary-side duty cycle unit 104 can output the secondary-side drive signal that drives the synchronous rectifier to the isolation drive chip 200 in real time, and can detect the determination result of the mode determination unit 102. When the determination result is that the working mode is the intermittent conduction mode, the secondary-side duty cycle of the synchronous secondary-side drive signal is a number of times that of the primary-side drive signal, such as half, so that the output secondary-side determination signal adapts to the intermittent conduction mode.

[0110] The secondary side duty cycle unit 104 is further configured to generate the first secondary side drive signal according to the secondary side duty cycle, and output the first secondary side drive signal to the isolation drive chip 200.

[0111] In a specific implementation, the secondary duty cycle unit 104 can determine a first secondary drive signal adapted to the intermittent conduction mode based on the synchronized secondary duty cycle, and output the first secondary drive signal to the isolation drive chip 200, so that the isolation drive chip 200 drives the synchronous rectifier according to the first secondary drive signal.

[0112] Accordingly, in this embodiment, the secondary duty cycle unit 104 is also used to generate a second secondary drive signal complementary to the primary drive signal to the isolation drive chip 200 when the working mode is the continuous conduction mode.

[0113] In a specific implementation, when the secondary duty cycle unit 104 detects that the working mode determined by the mode determination unit 102 is the continuous conduction mode, it synchronizes the secondary drive signal to be complementary to the primary drive signal. The secondary drive signal that is complementary to the primary drive signal is the second secondary drive signal adapted to the continuous conduction mode.

[0114] Furthermore, such as Figure 2 As shown, in this embodiment, the primary-side control chip further includes: a second feedback unit 105 and a primary-side duty cycle unit 106.

[0115] The second feedback unit 105 is connected to the auxiliary winding 301 and the primary duty cycle unit 106, respectively. The primary duty cycle unit is connected to the isolation drive chip 200.

[0116] The second feedback unit 105 is used to collect the second output voltage fed back by the auxiliary winding 301 and output the second output voltage to the primary duty cycle unit 106.

[0117] It should be noted that the second output voltage is also the voltage output from the secondary side of the switching power supply module 300 fed back by the auxiliary winding 301, but the value of the second output voltage is different from the value of the first output voltage. The first output voltage is used to determine the duty cycle of the secondary side of the switching power supply module 300, and the second output voltage is used to determine the duty cycle of the primary side of the switching power supply module 300.

[0118] In a specific implementation, the resistance value between the second feedback unit 105 and the auxiliary winding 301 can be set to be different from the resistance value between the first feedback unit 101 and the auxiliary winding 301, so that the magnitudes of the first output voltage and the second output voltage are not equal, thereby separating the drive signal output to the primary side of the switching power supply module 300 and reducing the interference between the primary side drive signal and the secondary side drive signal.

[0119] The primary-side duty cycle unit 106 is used to compare the second output voltage with a preset triangular wave voltage, generate the primary-side drive signal, and output the primary-side drive signal to the isolation drive chip 200.

[0120] It should be noted that the aforementioned preset triangular wave voltage can be the preset voltage for generating the primary-side drive signal.

[0121] In a specific implementation, the primary-side duty cycle unit 106 can compare the second output voltage input to the second feedback unit 105 with a preset triangular wave voltage to generate a primary-side drive signal with a certain duty cycle.

[0122] The isolation driver chip 200 is also used to control the switching devices on or off the primary side of the switching power supply module 300 according to the primary side drive signal.

[0123] It should be noted that the aforementioned switching device can be a switching device in the primary side of the switching power supply module 300, such as a MOSFET. When the switching device is turned on, the primary side of the switching power supply module 300 is turned on; conversely, when the switching device is turned off, the primary side of the switching power supply module 300 is turned off.

[0124] In a specific implementation, the isolation driver chip 200 drives the switching device according to the primary-side drive signal input with a primary-side duty cycle of 106. When the switching device receives the primary-side drive signal, it turns on or off according to the high or low level of the primary-side drive signal.

[0125] It should be understood that by using the aforementioned isolation driver chip 200 to drive the switching devices on the primary side and the synchronous rectifier devices on the secondary side of the switching power supply module 300, the number of driver chips in the switching power supply module 300 is effectively reduced, and the driving efficiency is improved.

[0126] refer to Figure 4 , Figure 4 This is a schematic diagram of the third embodiment of the primary-side control circuit of the present invention.

[0127] Based on the second embodiment described above, in this embodiment, the primary-side control chip 100 further includes a state detection unit 107.

[0128] The status detection unit 107 is connected to the switching power supply module 300.

[0129] The state detection unit 107 is used to receive the detection signal input by the switching power supply module 300 and determine whether the detection signal meets the preset ideal conditions.

[0130] It should be noted that the above detection signal can be the signal output by the switching power supply module 300 on the primary side, including the operating voltage input to the primary control chip 100 and the loop current flowing through the switching devices on the primary side of the switching power supply module 300.

[0131] Understandably, the aforementioned preset ideal conditions can be conditions where the switching power supply module 300 is within a reasonable voltage range, current range, or temperature range.

[0132] In a specific implementation, the aforementioned state detection unit 107 can detect the operating voltage input from the switching power supply module 300 to the primary-side control chip 100 and the loop current flowing into the switching power supply module 300 through the switching device, and compare the operating voltage and loop current with a preset reference value, thereby realizing the monitoring and judgment of non-ideal states.

[0133] It should be understood that the aforementioned non-ideal condition monitoring includes conditions that exceed reasonable ranges, such as overvoltage monitoring, undervoltage monitoring, overcurrent monitoring, overtemperature monitoring, and output short-circuit protection.

[0134] The state detection unit 107 is also used to control the primary-side control chip 100 to stop operating when the detection signal does not meet the preset ideal conditions.

[0135] In a specific implementation, when the state detection unit 107 compares the detection signal with the reference value and determines that the detection signal does not meet the preset ideal conditions, it indicates that the switching power supply module 300 is in an unreasonable state. The preset output enable signal controls the primary-side control chip 100 to stop running and no longer outputs the primary-side drive signal and the secondary-side drive signal to the isolation drive chip 200, thereby protecting the switching power supply module 300.

[0136] For ease of understanding, please refer to Figure 5 This explanation does not limit the scope of this solution. Figure 5 This is a functional schematic diagram of the primary-side control chip in the third embodiment of the primary-side control circuit of the present invention. Figure 5In the diagram, VDD is the power supply port of the primary-side control chip 100, INV is the first feedback port of the primary-side control chip 100, DEM is the second feedback port of the primary-side control chip 100, GATE1 is the primary-side gate drive signal port of the primary-side control chip 100, GATE2 is the synchronous rectification drive signal port of the primary-side control chip 100, GED is the common ground port of the primary-side control chip 100, and CS is the current detection port of the primary-side control chip 100.

[0137] It should be noted that the aforementioned power port VDD can be a port for receiving the operating voltage input to the switching power supply module 300. The primary-side control chip 100 uses this operating voltage to perform overvoltage detection, undervoltage detection, output of various reference sources, and voltage clamping. This voltage port VDD can also be a port connecting the aforementioned status detection unit to the switching power supply module 300.

[0138] Understandably, the aforementioned current detection port CS can be a port for receiving the loop current flowing through the switching devices on the primary side of the switching power supply module 300. The primary side control chip 100 implements current detection protection and current detection functions based on this loop current. This current detection port CS can also be another port connecting the aforementioned status detection unit to the switching power supply module 300.

[0139] It should be noted that the aforementioned first feedback port INV can be the port for acquiring the first output voltage fed back from the auxiliary winding 301, that is, the port where the aforementioned first feedback unit 101 is connected to the auxiliary winding 301. After acquiring the aforementioned first output voltage through the first feedback port INV, the primary-side control chip 100 performs operations such as current control, sample and hold, analog-to-digital conversion, signal decoding, and secondary-side duty cycle determination. For the determination of the secondary-side duty cycle, please refer to the relevant descriptions of the aforementioned first feedback unit 101 and secondary-side duty cycle unit 102, which will not be repeated here.

[0140] It is understood that the aforementioned second feedback port DEM can be the port for collecting the second output voltage fed back from the auxiliary winding 301, that is, the port where the aforementioned second feedback unit 105 is connected to the auxiliary winding 301. After the primary-side control chip 100 collects the aforementioned second output voltage through the second feedback port DEM, it performs operations such as output voltage feedback and primary-side duty cycle determination. For the determination of the primary-side duty cycle, please refer to the relevant descriptions of the aforementioned second feedback unit 105 and primary-side duty cycle unit 106, which will not be repeated here.

[0141] It should be noted that the primary-side gate drive signal port GATE1 can be a port connected to the isolation drive chip 200 and outputting the primary-side drive signal. This primary-side gate drive signal port does not have driving capability, but the isolation drive chip 200 drives the switching devices on the primary side of the switching power supply module 300.

[0142] It is understood that the aforementioned synchronous rectification drive signal port GATE2 can be a port connected to the aforementioned isolation drive chip 200 and outputting the aforementioned first secondary drive signal and the aforementioned second secondary drive signal. This synchronous rectification drive signal port does not have driving capability, but is driven by the isolation drive chip 200 to drive the synchronous rectification device on the secondary side of the switching power supply module 300.

[0143] It should be noted that the aforementioned common ground port GND is used to connect the reference ground of the primary-side control chip 100 to the external ground to achieve potential matching.

[0144] Understandably, the primary-side control chip 100 also includes logic control and soft-start functions. The logic control function is used to control the priority of each control logic in the primary-side control chip 100 and to judge the outputs. The soft-start function is used to adjust the duty cycle of the output drive signal step by step during the startup process of the primary-side control chip 100, so that the output voltage rises steadily and thus the output voltage does not overshoot.

[0145] For ease of understanding, please refer to Figure 6 This explanation does not limit the scope of this solution. Figure 6 This is a circuit schematic diagram of the switching power supply module in the third embodiment of the primary-side control circuit of the present invention. Figure 6 In the switching power supply module 300, the primary side includes: the auxiliary winding N3, the primary winding N1, the power supply terminal VCC, the first to seventh resistors R1 to R7, the first diode D1, the second diode D2, the second to fourth capacitors C2 to C4, the sixth capacitor C6 and the seventh capacitor C7, and the fifth NMOS transistor M15, which is the switching device of the primary side of the switching power supply module 300.

[0146] The secondary side of the switching power supply module 300 includes: a secondary winding N2, an eighth resistor R8, a fifth capacitor C6, and a sixth NMOS transistor M16, wherein the sixth NMOS transistor M16 is the synchronous rectifier.

[0147] The power supply port VDD of the primary-side control chip U1 is connected to the cathode of the first diode D1, the first terminal of the first resistor R1, and the first terminal of the second capacitor C1. The second terminal of the first resistor R1 is connected to the positive terminal of the power supply VCC, the negative terminal of the power supply VCC is grounded, and the second terminal of the second capacitor C2 is grounded. The first feedback port INV of the primary-side control chip U1 is connected to the first terminal of the second resistor R2, the first terminal of the third resistor R3, and the first terminal of the sixth capacitor C6. The second terminal of the sixth capacitor C6 is grounded, the second terminal of the third resistor R3 is grounded, and the second terminal of the second resistor R2 is connected to the anode of the first diode D1 and the first terminal of the auxiliary winding N3. The second terminal of the auxiliary winding N3 is grounded. The second feedback port DEM of the primary-side control chip U1 is connected to the first terminal of the fourth resistor R4, the first terminal of the fifth resistor R5, and the first terminal of the seventh capacitor C7. The second terminal of the seventh capacitor C7 is grounded, the second terminal of the fifth resistor R5 is grounded, and the second terminal of the fourth resistor R4 is connected to the anode of the first diode D1 and the first terminal of the auxiliary winding N3. The first common ground port GND1 of the primary-side control chip U1 is grounded; the current detection port CS of the primary-side control chip U1 is connected to the first terminal of the third capacitor C3, the first terminal of the sixth resistor R6, and the source of the fifth NMOS transistor M15, respectively; the drain of the fifth NMOS transistor M15 is connected to the first terminal of the primary winding N1 and the anode of the second diode D2, respectively; the cathode of the second diode D2 is connected to the first terminal of the seventh resistor R7 and the first terminal of the fourth capacitor C4, respectively; and the second terminal of the seventh resistor R7 is connected to the primary winding N1. The second terminal of the primary winding N1 is connected to the positive terminal of the power supply VCC. The second terminal of the fourth capacitor C4 is connected to the second terminal of the primary winding N1 and the positive terminal of the power supply VCC. The second common ground port GND2 of the primary-side control chip U1 is connected to the second terminal of the third capacitor C3 and the second terminal of the sixth resistor R6. The primary-side gate drive signal port GATE1 of the primary-side control chip U1 is connected to the first input terminal I1 of the isolation drive chip U2. The first output terminal V1 of the isolation drive chip U2 is connected to the gate of the fifth NMOS transistor M15.The synchronous rectification drive signal port GATE2 of the primary-side control chip U1 is connected to the second input terminal I2 of the isolation drive chip U2. The second output terminal V2 of the isolation drive chip U2 is connected to the gate of the sixth NMOS transistor M16. The drain of the sixth NMOS transistor M16 is connected to the first terminal of the secondary winding N2. The source of the sixth NMOS transistor M16 is connected to the first terminal of the fifth capacitor C5 and the first terminal of the eighth resistor R8. The second terminal of the fifth capacitor C5 is connected to the second terminal of the secondary winding N2. The second terminal of the eighth resistor R8 is connected to the second terminal of the secondary winding N2.

[0148] It should be noted that the resistance values ​​of the fourth resistor R4 and the fifth resistor R5 are different from those of the third resistor R3 and the second resistor R2. This results in the first output voltage collected by the first feedback port INV being different from the second output voltage collected by the second feedback port DER. This achieves the separation of the primary-side drive signal and the secondary-side drive signal, reducing the mutual interference between the primary-side drive signal and the secondary-side drive signal.

[0149] It is understandable that the primary winding N1, secondary winding N2 and auxiliary winding N3 share a common set of windings, and the auxiliary winding N3 can provide feedback on the voltage output by the secondary winding N2.

[0150] It should be noted that the aforementioned fifth NMOS transistor M15 is a switching power supply device on the primary side of the switching power supply module 300. The first input terminal I1 of the aforementioned isolation drive chip U2 is connected to the primary side gate drive signal port GATE1 of the primary side control chip U1 to receive the primary side drive signal output from the primary side gate drive signal port GATE1, and control the gate of the fifth NMOS transistor M15 according to the primary side drive signal, thereby realizing the control of the opening and closing of the primary side of the switching power supply module 300.

[0151] Understandably, the aforementioned sixth NMOS transistor M16 is a synchronous rectification device on the secondary side of the switching power supply module 300. The first input terminal I1 of the aforementioned isolation drive chip U2 is connected to the synchronous rectification drive signal port GATE2 of the primary side control chip U1 to receive the first secondary side drive signal or the second secondary side drive signal output by the synchronous rectification drive signal port GATE2, and control the gate of the sixth NMOS transistor M16 according to the first secondary side drive signal or the second secondary side drive signal, thereby realizing synchronous rectification on the secondary side of the switching power supply module 300, and thus achieving both intermittent conduction mode and continuous conduction mode.

[0152] In addition, to achieve the above objectives, the present invention also proposes a primary-side control device, which includes the primary-side control circuit as described above.

[0153] Other embodiments or specific implementations of the primary-side control device of the present invention can be referred to the embodiments of the primary-side control circuit described above, and will not be repeated here.

[0154] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0155] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0156] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A primary-side control circuit, characterized in that, The primary-side control circuit includes: a primary-side control chip, an isolation driver chip, and a switching power supply module; The switching power supply module includes an auxiliary winding and a synchronous rectifier. The primary-side control chip is connected to the auxiliary winding and the isolation drive chip respectively, and the isolation drive chip is connected to the control terminal of the synchronous rectifier. The auxiliary winding is used to provide feedback on the first output voltage of the secondary side of the switching power supply module; The primary-side control chip is used to acquire the first output voltage and determine the operating mode of the switching power supply module based on the fluctuation value of the first output voltage. The primary-side control chip is also used to output a first secondary-side drive signal or a second secondary-side drive signal to the isolation drive chip according to the working mode. The first secondary-side drive signal is a drive signal adapted to the intermittent conduction mode, and the second secondary-side drive signal is a drive signal adapted to the continuous conduction mode. The isolation driver chip is used to drive the synchronous rectifier according to the first secondary-side drive signal or the second secondary-side drive signal; The primary-side control chip includes: a first feedback unit and a mode determination unit; The first feedback unit is connected to both the auxiliary winding and the mode determination unit. The first feedback unit is used to acquire the first output voltage and output the first output voltage to the mode determination unit; The mode determination unit is used to compare the first output voltage with the sampled voltage fed back by the auxiliary winding in the previous cycle, determine the difference between the first output voltage and the sampled voltage, and use the difference as the fluctuation value of the first output voltage. The mode determination unit is further configured to determine that the working mode is an intermittent conduction mode when the fluctuation value is lower than a preset voltage threshold. The mode determination unit is further configured to determine that the operating mode is a continuous conduction mode when the fluctuation value reaches the preset voltage threshold.

2. The primary-side control circuit as described in claim 1, characterized in that, The primary-side control chip further includes: a sample-and-hold unit; The sampling and holding unit is connected to the first feedback unit and the mode determination unit, respectively. The sample-and-hold unit is used to store the first output voltage so that the mode determination unit compares the first output voltage with the voltage of the next cycle fed back by the auxiliary winding.

3. The primary-side control circuit as described in claim 2, characterized in that, The sample-and-hold unit includes: first to tenth PMOS transistors, first to fourth NMOS transistors, and a first capacitor; The gate of the first PMOS transistor is connected to the bandgap reference, the source of the first PMOS transistor is connected to the power supply terminal, the drain of the first PMOS transistor is connected to the source of the fifth PMOS transistor and the source of the sixth PMOS transistor, the gate of the fifth PMOS transistor is connected to the first feedback unit, the drain of the fifth PMOS transistor is connected to the drain of the first NMOS transistor and the gate of the first NMOS transistor, the gate of the sixth PMOS transistor is connected to the first feedback unit, the drain of the sixth PMOS transistor is connected to the drain of the second NMOS transistor, the gate of the second NMOS transistor is connected to the gate of the first NMOS transistor, and the source of the second NMOS transistor is connected to the source of the first NMOS transistor. The gate of the second PMOS transistor is connected to the bandgap reference, the source of the second PMOS transistor is connected to the power supply terminal, the drain of the second PMOS transistor is connected to the gate of the fifth PMOS transistor and the source of the ninth PMOS transistor, the gate of the ninth PMOS transistor is connected to the drain of the sixth PMOS transistor, and the drain of the ninth PMOS transistor is connected to the source of the first NMOS transistor. The gate of the third PMOS transistor is connected to the bandgap reference, the source of the third PMOS transistor is connected to the power supply terminal, the drain of the third PMOS transistor is connected to the source of the seventh PMOS transistor and the source of the eighth PMOS transistor, the gate of the seventh PMOS transistor is connected to the output terminal, the drain of the seventh PMOS transistor is connected to the drain of the third NMOS transistor and the gate of the third NMOS transistor, the gate of the eighth PMOS transistor is connected to the first feedback unit and the first terminal of the first capacitor, the second terminal of the first capacitor is connected to the source of the first NMOS transistor, the drain of the eighth PMOS transistor is connected to the drain of the fourth NMOS transistor, the gate of the fourth NMOS transistor is connected to the gate of the third NMOS transistor, and the source of the fourth NMOS transistor is connected to the source of the first NMOS transistor. The gate of the fourth PMOS transistor is connected to the bandgap reference, the source of the fourth PMOS transistor is connected to the power supply terminal, the drain of the fourth PMOS transistor is connected to the output terminal and the source of the tenth PMOS transistor, the gate of the tenth PMOS transistor is connected to the drain of the eighth PMOS transistor, and the source of the tenth PMOS transistor is connected to the source of the first NMOS transistor.

4. The primary-side control circuit as described in claim 3, characterized in that, The primary-side control chip also includes: a secondary-side duty cycle unit; The secondary duty cycle unit is connected to the isolation driver chip; The secondary duty cycle unit is used to generate a secondary duty cycle that is proportional to the duty cycle of the primary drive signal when the working mode is the intermittent conduction mode. The primary drive signal is a signal that controls the switching device on or off on the primary side of the switching power supply module. The secondary side duty cycle unit is further configured to generate the first secondary side drive signal according to the secondary side duty cycle, and output the first secondary side drive signal to the isolation drive chip.

5. The primary-side control circuit as described in claim 4, characterized in that, The secondary duty cycle unit is further configured to generate a second secondary drive signal complementary to the primary drive signal to the isolation drive chip when the operating mode is the continuous conduction mode.

6. The primary-side control circuit as described in claim 5, characterized in that, The primary-side control chip further includes: a second feedback unit and a primary-side duty cycle unit; The second feedback unit is connected to the auxiliary winding and the primary duty cycle unit respectively, and the primary duty cycle unit is connected to the isolation drive chip; The second feedback unit is used to acquire the second output voltage fed back by the auxiliary winding and output the second output voltage to the primary duty cycle unit; The primary-side duty cycle unit is used to compare the second output voltage with a preset triangular wave voltage, generate the primary-side drive signal, and output the primary-side drive signal to the isolation drive chip. The isolation driver chip is also used to control the switching devices on or off the primary side of the switching power supply module according to the primary-side drive signal.

7. The primary-side control circuit as described in claim 6, characterized in that, The primary-side control chip also includes a state detection unit; The status detection unit is connected to the switching power supply module; The status detection unit is used to receive the detection signal input by the switching power supply module and determine whether the detection signal meets the preset ideal conditions. The state detection unit is also used to control the primary-side control chip to stop operating when the detection signal does not meet the preset ideal conditions.

8. The primary-side control circuit as described in claim 7, characterized in that, The primary side of the switching power supply module includes: the auxiliary winding, the primary winding, the power supply terminal, the first to the seventh resistors, the first diode, the second diode, the second to the fourth capacitors, the sixth capacitor and the seventh capacitor, and the fifth NMOS transistor, which is the switching device of the primary side of the switching power supply module. The secondary side of the switching power supply module includes: a secondary winding, an eighth resistor, a fifth capacitor, and a sixth NMOS transistor, wherein the sixth NMOS transistor is the synchronous rectifier. The power supply port of the primary-side control chip is connected to the cathode of the first diode, the first end of the first resistor, and the first end of the second capacitor, respectively. The second end of the first resistor is connected to the positive terminal of the power supply port, the negative terminal of the power supply port is grounded, and the second end of the second capacitor is grounded. The first feedback port of the primary-side control chip is connected to the first end of the second resistor, the first end of the third resistor, and the first end of the sixth capacitor. The second end of the sixth capacitor is grounded, the second end of the third resistor is grounded, the second end of the second resistor is connected to the anode of the first diode and the first end of the auxiliary winding, and the second end of the auxiliary winding is grounded. The second feedback port of the primary-side control chip is connected to the first end of the fourth resistor, the first end of the fifth resistor, and the first end of the seventh capacitor, respectively. The second end of the seventh capacitor is grounded, the second end of the fifth resistor is grounded, and the second end of the fourth resistor is connected to the anode of the first diode and the first end of the auxiliary winding, respectively. The first common ground port of the primary-side control chip is grounded. The current detection port of the primary-side control chip is connected to the first terminal of the third capacitor, the first terminal of the sixth resistor, and the source of the fifth NMOS transistor. The drain of the fifth NMOS transistor is connected to the first terminal of the primary winding and the anode of the second diode. The cathode of the second diode is connected to the first terminal of the seventh resistor and the first terminal of the fourth capacitor. The second terminal of the seventh resistor is connected to the second terminal of the primary winding and the positive terminal of the power supply. The second terminal of the fourth capacitor is connected to the second terminal of the primary winding and the positive terminal of the power supply. The second common ground port of the primary-side control chip is connected to the second terminal of the third capacitor and the second terminal of the sixth resistor, respectively. The primary-side gate drive signal port of the primary-side control chip is connected to the first input terminal of the isolation drive chip, and the first output terminal of the isolation drive chip is connected to the gate of the fifth NMOS transistor. The synchronous rectification drive signal port of the primary-side control chip is connected to the second input terminal of the isolation drive chip. The second output terminal of the isolation drive chip is connected to the gate of the sixth NMOS transistor. The drain of the sixth NMOS transistor is connected to the first terminal of the secondary winding. The source of the sixth NMOS transistor is connected to the first terminal of the fifth capacitor and the first terminal of the eighth resistor. The second terminal of the fifth capacitor is connected to the second terminal of the secondary winding. The second terminal of the eighth resistor is connected to the second terminal of the secondary winding.

9. A primary-side control device, characterized in that, The primary-side control device includes the primary-side control circuit as described in any one of claims 1 to 8.

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