Device and method for improving auxiliary circuit voltage precision of multi-output flyback converter

Abstract

The invention provides a device and a method for improving the auxiliary voltage precision of a multi-output flyback converter. The device comprises a sampling module, a comparator, a PI controller, a modulation module, a NOT gate, a delay module, an AND gate and a first driving circuit, the sampling module is used for secondary output voltage; the comparator is used for obtaining an error signal; the PI controller is used for obtaining an error signal after PI adjustment; the modulation module is used for obtaining an initial driving signal of a secondary MOSFET on the secondary side; the driving module is also used for obtaining an initial driving signal of the secondary side main path MOSFET; the NOT gate is used for obtaining a driving signal after NOT operation; the time delay module is used for obtaining a synchronous rectification driving signal; the AND gate is used for obtaining a final driving signal of the secondary MOSFET on the secondary side; the driving module is also used for obtaining a final driving signal of the secondary side main path MOSFET; the first driving circuit is used for driving the secondary side auxiliary MOSFET according to the final driving signal of the secondary side auxiliary MOSFET; and the driving module is also used for driving the secondary side main path MOSFET according to the final driving signal of the secondary side main path MOSFET.

Description

Technical Field

[0001] The present invention relates to the technical field of flyback converters, and in particular to a device and method for improving the accuracy of a secondary circuit voltage of a multi-output flyback converter. Background Art

[0002] Flyback converters are widely used in single-input, multi-output and low-power situations. For multi-output flyback converters, the output voltage is controlled by the duty cycle of the primary MOSFET. The traditional method is to sample one of the output voltages, and the output voltages of the other outputs are not sampled. The output voltages of the outputs without voltage sampling are distributed by the transformer windings. For an ideal transformer without leakage inductance, this method can generate accurate voltages.

[0003] However, due to the existence of actual transformer leakage inductance, there will be voltage deviation in the output path without voltage sampling, which is not suitable for application scenarios with strict requirements on output voltage accuracy. Summary of the invention

[0004] The present invention provides a device and method for improving the voltage accuracy of a secondary circuit of a multi-output flyback converter, which solves the technical problem of low output voltage accuracy of a secondary circuit of a flyback converter in the prior art.

[0005] According to one aspect of the present invention, there is provided a device for improving the accuracy of the secondary voltage of a multi-output flyback converter, the device comprising a sampling module, a comparator, a PI controller, a modulation module, a NOT gate, a delay module, an AND gate and a first drive circuit;

[0006] The sampling module is used to collect the secondary output voltage of the flyback converter;

[0007] The comparator is used to perform a difference between the voltage reference and the secondary output voltage to obtain an error signal;

[0008] The PI controller is used to perform PI regulation on the error signal to obtain a PI-regulated error signal;

[0009] The modulation module is used to obtain an initial drive signal of the secondary side secondary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side secondary MOSFET; and is also used to take the inverse of the error signal after PI adjustment, and obtain the initial drive signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET;

[0010] The NOT gate is used to perform a NOT operation on the driving signal of the primary-side MOSFET to obtain a driving signal after the NOT operation;

[0011] The delay module is used to delay the non-operated driving signal to obtain a synchronous rectification driving signal;

[0012] The AND gate is used to perform an AND operation on the initial drive signal of the secondary MOSFET and the synchronous rectification drive signal of the secondary MOSFET to obtain the final drive signal of the secondary MOSFET; and is also used to perform an AND operation on the initial drive signal of the secondary MOSFET and the synchronous rectification drive signal of the main MOSFET to obtain the final drive signal of the secondary MOSFET;

[0013] The first driving circuit is used to drive the secondary side auxiliary MOSFET according to the final driving signal of the secondary side auxiliary MOSFET; and is also used to drive the secondary side main MOSFET according to the final driving signal of the secondary side main MOSFET.

[0014] Preferably, the device further comprises a second driving circuit, and the second driving circuit is used to adjust the duty cycle of the driving signal of the primary-side MOSFET according to the main output voltage.

[0015] Preferably, obtaining the initial driving signal of the secondary side secondary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side secondary MOSFET comprises:

[0016] The error signal after PI regulation is compared with the carrier of the secondary MOSFET on the secondary side;

[0017] When the error signal after PI adjustment is greater than the carrier of the secondary MOSFET, the initial driving signal of the secondary MOSFET is high level.

[0018] When the error signal after PI adjustment is less than or equal to the carrier of the secondary-side auxiliary MOSFET, the initial driving signal of the secondary-side auxiliary MOSFET is at a low level.

[0019] Preferably, obtaining the initial drive signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET includes:

[0020] Compare the inverse of the PI-regulated error signal with the carrier of the secondary-side main MOSFET;

[0021] When the inverse number of the error signal after PI adjustment is greater than the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is high level;

[0022] When the inverse of the error signal after PI adjustment is less than or equal to the carrier of the secondary-side main MOSFET, the initial driving signal of the secondary-side main MOSFET is at a low level.

[0023] Preferably, the flyback converter comprises a transformer, a primary-side MOSFET, a secondary-side main MOSFET, a secondary-side secondary MOSFET, a primary-side capacitor, a secondary-side main capacitor and a secondary-side secondary capacitor;

[0024] The same-name end of the primary winding of the transformer is connected to the drain of the primary MOSFET, and the other end is connected to one end of the primary capacitor and the positive electrode of the input voltage; the source of the primary MOSFET is connected to the other end of the primary capacitor and the negative electrode of the input voltage, and the gate is connected to the second drive circuit;

[0025] The same-name end of the secondary-side main winding of the transformer is connected to the source of the secondary-side main MOSFET, and the other end is connected to one end of the secondary-side main capacitor, the negative electrode of the main output voltage and the same-name end of the secondary-side secondary winding of the transformer; the drain of the secondary-side main MOSFET is connected to the other end of the secondary-side main capacitor and the positive electrode of the main output voltage, and the gate is connected to the first drive circuit;

[0026] The same-name end of the secondary winding on the secondary side of the transformer is connected to one end of the secondary side secondary capacitor and the positive electrode of the secondary output voltage, and the other end is connected to the drain of the secondary side secondary MOSFET; the source of the secondary side secondary MOSFET is connected to the other end of the secondary side secondary capacitor and the negative electrode of the secondary output voltage, and the gate is connected to the first drive circuit.

[0027] According to another aspect of the present invention, a method for improving the secondary voltage accuracy of a multi-output flyback converter is provided, the method comprising:

[0028] The sampling module samples the secondary output voltage of the flyback converter;

[0029] The comparator makes a difference between the voltage reference and the secondary output voltage to obtain an error signal;

[0030] The PI controller performs PI regulation on the error signal to obtain a PI-regulated error signal;

[0031] The modulation module obtains an initial driving signal of the secondary side auxiliary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side auxiliary MOSFET;

[0032] The modulation module takes the inverse of the error signal after PI adjustment, and obtains the initial driving signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET;

[0033] Input the driving signal of the primary MOSFET into the NOT gate to obtain the driving signal after the NOT operation;

[0034] The non-operated driving signal is input into the delay module to obtain a synchronous rectification driving signal;

[0035] Inputting an initial driving signal of the secondary MOSFET on the secondary side, an initial driving signal of the main MOSFET on the secondary side, and a synchronous rectification driving signal into an AND gate, performing an AND operation on the initial driving signal of the secondary MOSFET on the secondary side and the synchronous rectification driving signal to obtain a final driving signal of the secondary MOSFET on the secondary side, performing an AND operation on the initial driving signal of the main MOSFET on the secondary side and the synchronous rectification driving signal to obtain a final driving signal of the main MOSFET on the secondary side;

[0036] The first driving circuit drives the secondary side auxiliary MOSFET according to the final driving signal of the secondary side auxiliary MOSFET, and drives the secondary side main MOSFET according to the final driving signal of the secondary side main MOSFET.

[0037] Preferably, the method further comprises: the second driving circuit adjusts the duty cycle of the driving signal of the primary-side MOSFET according to the main output voltage.

[0038] Preferably, obtaining the initial driving signal of the secondary side secondary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side secondary MOSFET comprises:

[0039] The error signal after PI regulation is compared with the carrier of the secondary MOSFET on the secondary side;

[0040] When the error signal after PI adjustment is greater than the carrier of the secondary MOSFET, the initial driving signal of the secondary MOSFET is high level.

[0041] When the error signal after PI adjustment is less than or equal to the carrier of the secondary-side auxiliary MOSFET, the initial driving signal of the secondary-side auxiliary MOSFET is at a low level.

[0042] Preferably, obtaining the initial drive signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET includes:

[0043] Compare the inverse of the PI-regulated error signal with the carrier of the secondary-side main MOSFET;

[0044] When the inverse number of the error signal after PI adjustment is greater than the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is high level;

[0045] When the inverse of the error signal after PI adjustment is less than or equal to the carrier of the secondary-side main MOSFET, the initial driving signal of the secondary-side main MOSFET is at a low level.

[0046] Preferably, the flyback converter comprises a transformer, a primary-side MOSFET, a secondary-side main MOSFET, a secondary-side secondary MOSFET, a primary-side capacitor, a secondary-side main capacitor and a secondary-side secondary capacitor;

[0047] The same-name end of the primary winding of the transformer is connected to the drain of the primary MOSFET, and the other end is connected to one end of the primary capacitor and the positive electrode of the input voltage; the source of the primary MOSFET is connected to the other end of the primary capacitor and the negative electrode of the input voltage, and the gate is connected to the second drive circuit;

[0048] The same-name end of the secondary-side main winding of the transformer is connected to the source of the secondary-side main MOSFET, and the other end is connected to one end of the secondary-side main capacitor, the negative electrode of the main output voltage and the same-name end of the secondary-side secondary winding of the transformer; the drain of the secondary-side main MOSFET is connected to the other end of the secondary-side main capacitor and the positive electrode of the main output voltage, and the gate is connected to the first drive circuit;

[0049] The same-name end of the secondary winding on the secondary side of the transformer is connected to one end of the secondary side secondary capacitor and the positive electrode of the secondary output voltage, and the other end is connected to the drain of the secondary side secondary MOSFET; the source of the secondary side secondary MOSFET is connected to the other end of the secondary side secondary capacitor and the negative electrode of the secondary output voltage, and the gate is connected to the first drive circuit.

[0050] By applying the technical solution of the present invention, according to the different voltage drops of the MOSFET on the secondary side of the flyback converter when it is turned on and off, the MOSFET on the secondary side of the flyback converter is controlled to be turned on and off by the final driving signal, thereby changing the voltage drop of the MOSFET on the secondary side of the flyback converter, improving the output voltage accuracy of the secondary circuit, and compensating for the voltage deviation caused by the leakage inductance. The method of the present invention is applicable to a flyback converter with dual or multi-channel outputs. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0052] Figure 1A schematic diagram of the structure of a device for improving the secondary voltage accuracy of a multi-output flyback converter provided according to an embodiment of the present invention is shown;

[0053] Figure 2 A modulation schematic diagram provided according to an embodiment of the present invention is shown;

[0054] Figure 3 Another modulation schematic diagram provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0055] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0057] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0058] like Figure 1As shown, the present invention provides a device for improving the accuracy of the secondary voltage of a multi-output flyback converter, the device comprising a sampling module, a comparator, a PI controller, a modulation module, a NOT gate, a delay module, an AND gate and a first driving circuit;

[0059] The sampling module is used to collect the secondary output voltage of the flyback converter;

[0060] The comparator is used to perform a difference between the voltage reference and the secondary output voltage to obtain an error signal;

[0061] The PI controller is used to perform PI regulation on the error signal to obtain a PI-regulated error signal;

[0062] The modulation module is used to obtain an initial drive signal of the secondary side secondary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side secondary MOSFET; and is also used to take the inverse of the error signal after PI adjustment, and obtain the initial drive signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET;

[0063] The NOT gate is used to perform a NOT operation on the driving signal of the primary-side MOSFET to obtain a driving signal after the NOT operation;

[0064] The delay module is used to delay the non-operated driving signal to obtain a synchronous rectification driving signal;

[0065] The AND gate is used to perform an AND operation on the initial drive signal of the secondary MOSFET and the synchronous rectification drive signal of the secondary MOSFET to obtain the final drive signal of the secondary MOSFET; and is also used to perform an AND operation on the initial drive signal of the secondary MOSFET and the synchronous rectification drive signal of the main MOSFET to obtain the final drive signal of the secondary MOSFET;

[0066] The first driving circuit is used to drive the secondary side auxiliary MOSFET according to the final driving signal of the secondary side auxiliary MOSFET; and is also used to drive the secondary side main MOSFET according to the final driving signal of the secondary side main MOSFET.

[0067] The present invention also provides a method for improving the secondary voltage accuracy of a multi-output flyback converter, the method comprising:

[0068] The sampling module samples the secondary output voltage of the flyback converter;

[0069] The comparator makes a difference between the voltage reference and the secondary output voltage to obtain an error signal;

[0070] The PI controller performs PI regulation on the error signal to obtain a PI-regulated error signal;

[0071] The modulation module obtains an initial driving signal of the secondary side auxiliary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side auxiliary MOSFET;

[0072] The modulation module takes the inverse of the error signal after PI adjustment, and obtains the initial driving signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET;

[0073] Input the driving signal of the primary MOSFET into the NOT gate to obtain the driving signal after the NOT operation;

[0074] The non-operated driving signal is input into the delay module to obtain a synchronous rectification driving signal;

[0075] Inputting an initial driving signal of the secondary MOSFET on the secondary side, an initial driving signal of the main MOSFET on the secondary side, and a synchronous rectification driving signal into an AND gate, performing an AND operation on the initial driving signal of the secondary MOSFET on the secondary side and the synchronous rectification driving signal to obtain a final driving signal of the secondary MOSFET on the secondary side, performing an AND operation on the initial driving signal of the main MOSFET on the secondary side and the synchronous rectification driving signal to obtain a final driving signal of the main MOSFET on the secondary side;

[0076] The first driving circuit drives the secondary side auxiliary MOSFET according to the final driving signal of the secondary side auxiliary MOSFET, and drives the secondary side main MOSFET according to the final driving signal of the secondary side main MOSFET.

[0077] The present invention controls the turning on and off of the MOSFET on the secondary side of the flyback converter by a final driving signal according to the different voltage drops when the MOSFET on the secondary side of the flyback converter is turned on and off, thereby changing the voltage drop of the MOSFET on the secondary side of the flyback converter, improving the output voltage accuracy of the secondary circuit, and compensating for the voltage deviation caused by the leakage inductance. The method of the present invention is applicable to a flyback converter with dual or multi-channel outputs.

[0078] In the present invention, the device further comprises a second driving circuit, and the second driving circuit is used to adjust the duty cycle of the driving signal of the primary side MOSFET according to the main output voltage. The adjustment process is prior art and will not be described in detail in the present invention.

[0079] In the present invention, the flyback converter includes a transformer, a primary side MOSFET, a secondary side main MOSFET, a secondary side secondary MOSFET, a primary side capacitor, a secondary side main capacitor and a secondary side secondary capacitor;

[0080] The same-name end of the primary winding of the transformer is connected to the drain of the primary MOSFET, and the other end is connected to one end of the primary capacitor and the positive electrode of the input voltage; the source of the primary MOSFET is connected to the other end of the primary capacitor and the negative electrode of the input voltage, and the gate is connected to the second drive circuit;

[0081] The same-name end of the secondary-side main winding of the transformer is connected to the source of the secondary-side main MOSFET, and the other end is connected to one end of the secondary-side main capacitor, the negative electrode of the main output voltage and the same-name end of the secondary-side secondary winding of the transformer; the drain of the secondary-side main MOSFET is connected to the other end of the secondary-side main capacitor and the positive electrode of the main output voltage, and the gate is connected to the first drive circuit;

[0082] The same-name end of the secondary winding on the secondary side of the transformer is connected to one end of the secondary side secondary capacitor and the positive electrode of the secondary output voltage, and the other end is connected to the drain of the secondary side secondary MOSFET; the source of the secondary side secondary MOSFET is connected to the other end of the secondary side secondary capacitor and the negative electrode of the secondary output voltage, and the gate is connected to the first drive circuit.

[0083] exist Figure 1 In the figure, Vin is the input voltage of the flyback converter, Vo1 is the main output voltage, Vo2 is the secondary output voltage, Q1 is the primary MOSFET, S1 and S2 are the secondary main MOSFET and the secondary secondary MOSFET respectively, C1 is the primary capacitor, C2 and C3 are the secondary main capacitor and the secondary secondary capacitor respectively.

[0084] According to an embodiment of the present invention, obtaining an initial driving signal of the secondary side secondary MOSFET according to the PI-adjusted error signal and the carrier of the secondary side secondary MOSFET includes:

[0085] The error signal after PI regulation is compared with the carrier of the secondary MOSFET on the secondary side;

[0086] When the error signal after PI adjustment is greater than the carrier of the secondary MOSFET, the initial driving signal of the secondary MOSFET is high level.

[0087] When the error signal after PI adjustment is less than or equal to the carrier of the secondary-side auxiliary MOSFET, the initial driving signal of the secondary-side auxiliary MOSFET is at a low level.

[0088] According to an embodiment of the present invention, obtaining the initial driving signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET includes:

[0089] Compare the inverse of the PI-regulated error signal with the carrier of the secondary-side main MOSFET;

[0090] When the inverse number of the error signal after PI adjustment is greater than the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is high level;

[0091] When the inverse of the error signal after PI adjustment is less than or equal to the carrier of the secondary-side main MOSFET, the initial driving signal of the secondary-side main MOSFET is at a low level.

[0092] Figure 2 and Figure 3 The initial drive signal of the secondary side MOSFET and the initial drive signal of the secondary side main MOSFET obtained by the error signal after PI adjustment of different sizes are shown. Figure 2 and Figure 3 In the figure, the carrier waveforms of S1 and S2 are both sawtooth waves, and Vx represents the error signal after PI adjustment.

[0093] Through the above settings, when the Vo2 voltage is small, Vx is positive, S1 is not conducting, the parasitic anti-parallel diode is turned on, S2 is turned on, PWM control is performed to keep the voltage stable. When Vo2 is large, Vx is negative, S2 is not conducting, the parasitic anti-parallel diode is turned on, S1 is turned on, and PWM control is performed.

[0094] In this embodiment, the working principle of the flyback converter is as follows:

[0095] When the flyback converter is working, Q1 on the primary side is turned on, S1 and S2 are in the off state, and energy is stored in the transformer. When Q1 is turned off, if S1 and S2 are not driven, the current will flow through the parasitic anti-parallel diodes of S1 and S2, thereby turning on. Compared with the voltage drop of the parasitic anti-parallel diode of MOSFET, the voltage drop of MOSFET is lower when MOSFET is turned on. The main voltage sampling samples Vo1 to adjust the duty cycle of the drive signal of Q1 on the primary side. When the driver S1 is turned on, the voltage drop Vs1 of S1 decreases, and the main sampling circuit detects the voltage rise. The duty cycle of the drive signal of Q1 on the primary side is adjusted through the loop to reduce it, and the secondary output voltage Vo2 is reduced; when the driver S2 is turned on, the voltage drop Vs2 of S2 is reduced, and the secondary output voltage Vo2 is increased. When Q1 is turned off, the control of S1 and S2 on and off can adjust the secondary output voltage.

[0096] The driving signal of Q1 is inverted and used as the enabling signal of the secondary side S1 and S2. In order to prevent the direct inversion from being unsafe, the present invention uses a delay module to delay the signal to ensure that S1 and S2 have a chance to turn on again after Q1 is completely turned off.

[0097] In summary, the present invention provides a device and method for improving the voltage accuracy of the secondary circuit of a multi-output flyback converter. According to the different voltage drops of the MOSFET on the secondary side of the flyback converter when it is turned on and off, the MOSFET on the secondary side of the flyback converter is controlled to be turned on and off by the final drive signal, thereby changing the voltage drop of the MOSFET on the secondary side of the flyback converter, improving the output voltage accuracy of the secondary circuit, and compensating for the voltage deviation caused by leakage inductance. The method of the present invention is applicable to a flyback converter with dual or multiple outputs.

[0098] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0099] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for improving the accuracy of the secondary voltage of a multi-output flyback converter, characterized in that: The device comprises a sampling module, a comparator, a PI controller, a modulation module, a NOT gate, a delay module, an AND gate and a first driving circuit; The sampling module is used to collect the secondary output voltage of the flyback converter; The comparator is used to perform a difference between the voltage reference and the secondary output voltage to obtain an error signal; The PI controller is used to perform PI regulation on the error signal to obtain a PI-regulated error signal; The modulation module is used to obtain an initial driving signal of the secondary side secondary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side secondary MOSFET; It is also used to take the inverse of the error signal after PI adjustment, and obtain the initial driving signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET; The NOT gate is used to perform a NOT operation on the driving signal of the primary-side MOSFET to obtain a driving signal after the NOT operation; The delay module is used to delay the non-operated driving signal to obtain a synchronous rectification driving signal; The AND gate is used to perform an AND operation on the initial driving signal of the secondary MOSFET and the synchronous rectification driving signal to obtain a final driving signal of the secondary MOSFET; It is also used to perform AND operation on the initial drive signal of the secondary side main MOSFET and the synchronous rectification drive signal to obtain the final drive signal of the secondary side main MOSFET; The first driving circuit is used to drive the secondary side secondary MOSFET according to the final driving signal of the secondary side secondary MOSFET; It is also used to drive the secondary side main MOSFET according to the final driving signal of the secondary side main MOSFET.

2. The device according to claim 1, characterized in that The device also includes a second driving circuit, which is used to adjust the duty cycle of the driving signal of the primary-side MOSFET according to the main output voltage.

3. The device according to claim 1 or 2, characterized in that: Obtaining an initial driving signal of the secondary side auxiliary MOSFET according to the PI-regulated error signal and the carrier of the secondary side auxiliary MOSFET includes: comparing the PI-regulated error signal with the carrier of the secondary side auxiliary MOSFET; When the error signal after PI adjustment is greater than the carrier of the secondary MOSFET, the initial driving signal of the secondary MOSFET is high level. When the error signal after PI adjustment is less than or equal to the carrier of the secondary-side auxiliary MOSFET, the initial driving signal of the secondary-side auxiliary MOSFET is at a low level.

4. The device according to claim 1 or 2, characterized in that: According to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is obtained, including: Compare the inverse of the PI-regulated error signal with the carrier of the secondary-side main MOSFET; When the inverse number of the error signal after PI adjustment is greater than the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is high level; When the inverse of the error signal after PI adjustment is less than or equal to the carrier of the secondary-side main MOSFET, the initial driving signal of the secondary-side main MOSFET is at a low level.

5. The device according to any one of claims 1 to 4, characterized in that: The flyback converter includes a transformer, a primary-side MOSFET, a secondary-side main MOSFET, a secondary-side secondary MOSFET, a primary-side capacitor, a secondary-side main capacitor and a secondary-side secondary capacitor; The same-name end of the primary winding of the transformer is connected to the drain of the primary MOSFET, and the other end is connected to one end of the primary capacitor and the positive electrode of the input voltage; the source of the primary MOSFET is connected to the other end of the primary capacitor and the negative electrode of the input voltage, and the gate is connected to the second drive circuit; The same-name end of the secondary-side main winding of the transformer is connected to the source of the secondary-side main MOSFET, and the other end is connected to one end of the secondary-side main capacitor, the negative electrode of the main output voltage and the same-name end of the secondary winding of the transformer; The drain of the secondary side main MOSFET is connected to the other end of the secondary side main capacitor and the positive electrode of the main output voltage, and the gate is connected to the first drive circuit; The same-name end of the secondary winding of the transformer secondary side is connected to one end of the secondary capacitor and the positive electrode of the secondary output voltage, and the other end is connected to the drain of the secondary MOSFET; The source of the secondary-side secondary MOSFET is connected to the other end of the secondary-side secondary capacitor and the negative electrode of the secondary output voltage, and the gate is connected to the first drive circuit.

6. A method for improving the secondary voltage accuracy of a multi-output flyback converter, characterized in that: The method comprises: The sampling module samples the secondary output voltage of the flyback converter; The comparator makes a difference between the voltage reference and the secondary output voltage to obtain an error signal; The PI controller performs PI regulation on the error signal to obtain a PI-regulated error signal; The modulation module obtains an initial driving signal of the secondary side auxiliary MOSFET according to the error signal after PI adjustment and the carrier of the secondary side auxiliary MOSFET; The modulation module takes the inverse of the error signal after PI adjustment, and obtains the initial driving signal of the secondary side main MOSFET according to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET; Input the driving signal of the primary MOSFET into the NOT gate to obtain the driving signal after the NOT operation; The non-operated driving signal is input into the delay module to obtain a synchronous rectification driving signal; Inputting an initial driving signal of the secondary MOSFET on the secondary side, an initial driving signal of the main MOSFET on the secondary side, and a synchronous rectification driving signal into an AND gate, performing an AND operation on the initial driving signal of the secondary MOSFET on the secondary side and the synchronous rectification driving signal to obtain a final driving signal of the secondary MOSFET on the secondary side, performing an AND operation on the initial driving signal of the main MOSFET on the secondary side and the synchronous rectification driving signal to obtain a final driving signal of the main MOSFET on the secondary side; The first driving circuit drives the secondary side auxiliary MOSFET according to the final driving signal of the secondary side auxiliary MOSFET, and drives the secondary side main MOSFET according to the final driving signal of the secondary side main MOSFET.

7. The method according to claim 6, characterized in that The method further includes: the second driving circuit adjusts the duty cycle of the driving signal of the primary-side MOSFET according to the main output voltage.

8. The method according to claim 6 or 7, characterized in that: Obtaining an initial driving signal of the secondary side auxiliary MOSFET according to the PI-regulated error signal and the carrier of the secondary side auxiliary MOSFET includes: comparing the PI-regulated error signal with the carrier of the secondary side auxiliary MOSFET; When the error signal after PI adjustment is greater than the carrier of the secondary MOSFET, the initial driving signal of the secondary MOSFET is high level. When the error signal after PI adjustment is less than or equal to the carrier of the secondary-side auxiliary MOSFET, the initial driving signal of the secondary-side auxiliary MOSFET is at a low level.

9. The method according to claim 6 or 7, characterized in that: According to the inverse of the error signal after PI adjustment and the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is obtained, including: Compare the inverse of the PI-regulated error signal with the carrier of the secondary-side main MOSFET; When the inverse number of the error signal after PI adjustment is greater than the carrier of the secondary side main MOSFET, the initial driving signal of the secondary side main MOSFET is high level; When the inverse of the error signal after PI adjustment is less than or equal to the carrier of the secondary-side main MOSFET, the initial driving signal of the secondary-side main MOSFET is at a low level.

10. The method according to claim 6, characterized in that The flyback converter includes a transformer, a primary side MOSFET, a secondary side main MOSFET, a secondary side secondary MOSFET, a primary side capacitor, a secondary side main capacitor and a secondary side secondary capacitor; The same-name end of the primary winding of the transformer is connected to the drain of the primary MOSFET, and the other end is connected to one end of the primary capacitor and the positive electrode of the input voltage; the source of the primary MOSFET is connected to the other end of the primary capacitor and the negative electrode of the input voltage, and the gate is connected to the second drive circuit; The same-name end of the secondary-side main winding of the transformer is connected to the source of the secondary-side main MOSFET, and the other end is connected to one end of the secondary-side main capacitor, the negative electrode of the main output voltage and the same-name end of the secondary winding of the transformer; The drain of the secondary side main MOSFET is connected to the other end of the secondary side main capacitor and the positive electrode of the main output voltage, and the gate is connected to the first drive circuit; The same-name end of the secondary winding of the transformer secondary side is connected to one end of the secondary capacitor and the positive electrode of the secondary output voltage, and the other end is connected to the drain of the secondary MOSFET; The source of the secondary side secondary MOSFET is connected to the other end of the secondary side secondary capacitor and the negative electrode of the secondary output voltage, and the gate is connected to the first drive circuit.

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