Integrated circuit for non-isolated flyback conversion circuit
By using a non-isolated flyback control integrated circuit, the problem of abnormal conduction of the main power transistor and synchronous rectifier switch in traditional flyback converter circuits is solved, realizing a power supply solution with high power, low loss and high reliability, which is suitable for the home appliance field.
Patent Information
- Application Number
- CN202520148233.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2026-01-16
- Estimated Expiration
- 2035-01-22
AI Technical Summary
In traditional flyback converter circuits, the control circuits of the main power transistor and the synchronous rectifier switch are isolated from each other, which may lead to abnormal conduction and damage under harsh operating conditions. In addition, the Buck circuit cannot meet the requirements when high power is required.
A non-isolated flyback control integrated circuit is used to simultaneously control the main power switch and the secondary synchronous rectifier switch through a single control circuit, avoiding abnormal conduction and optimizing the control of the synchronous rectifier switch under the same ground terminal.
A high-power power supply solution was implemented, reducing losses, improving reliability and anti-interference capabilities, and meeting high power requirements while reducing system complexity.
Smart Images
Figure CN223809707U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to electronic field, specifically but not limited to a kind of non-isolated flyback control integrated circuit and non-isolated flyback conversion circuit of integrated main power switch and secondary side synchronous rectification switch. BACKGROUND
[0002] In air conditioner, refrigerator, washing machine and other white electricity and rice cooker, fan and other small household electrical appliances application field, its auxiliary power supply has many scenes that can adopt non-isolated topology. When power is small, buck circuit (Buck) can be used, and its cost is lower. However, when the power demand of auxiliary power supply is larger, Buck circuit cannot meet the requirements well.
[0003] At the same time, in the field of household appliances, low power consumption and high energy efficiency are also the parameters pursued by the market.
[0004] Flyback conversion circuit is a kind of power supply circuit commonly used in high-power applications. In order to reduce its power consumption, the rectifier tube in the secondary side is preferably used as a synchronous rectification switch. However, in the traditional flyback conversion circuit, the primary side control circuit for controlling the main power tube and the secondary side control circuit for controlling the synchronous rectification switch are isolated from each other, which makes the synchronous rectification switch may work abnormally under adverse conditions such as lightning surge, electrostatic discharge (ESD), etc., causing the main power tube and the synchronous rectification switch to be turned on at the same time or other abnormalities, causing damage to the primary side control circuit or the secondary side control circuit.
[0005] Therefore, it is necessary to provide a new structure or control method to solve at least part of the above problems. UTILITY MODEL CONTENT
[0006] At least for one or more problems in the background art, the utility model proposes a non-isolated flyback control integrated circuit and a non-isolated flyback conversion circuit.
[0007] According to one aspect of the utility model, a kind of non-isolated flyback control integrated circuit, comprising: main power switch, the first end of main power switch is coupled integrated circuit's main power switch pin and the primary winding of transformer, the second end of main power switch is coupled integrated circuit's ground pin or current detection pin, wherein ground pin is coupled to ground terminal outside or current detection pin is coupled to ground terminal outside through detection resistance;Synchronous rectification switch, the first end of synchronous rectification switch is coupled integrated circuit's secondary side switch pin and the first end of the secondary winding of transformer, the second end of synchronous rectification switch is coupled ground pin, wherein the second end of secondary winding provides output voltage as the output terminal of non-isolated flyback converter;And control circuit, control circuit has feedback input, first output, second output and ground input, wherein feedback input is coupled integrated circuit's feedback pin, for receiving the feedback signal indicating output voltage, first output is coupled the control end of main power switch, for controlling the turn-on and turn-off of main power switch, second output is coupled the control end of secondary synchronous rectification switch, for controlling the turn-on and turn-off of synchronous rectification switch, ground input is coupled ground pin.
[0008] Optionally, main power switch includes first MOSFET (Metal Oxide Semiconductor Field Effect Transistor) power device, the gate of first MOSFET power device is coupled the first output of control circuit, the drain of first MOSFET power device is coupled main power switch pin, the source of first MOSFET power device is coupled current detection pin or ground pin;Synchronous rectification switch includes second MOSFET power device, the gate of second MOSFET power device is coupled the second output of control circuit, the drain of second MOSFET power device is coupled secondary side switch pin, the source of second MOSFET power device is coupled ground pin.
[0009] Optionally, control circuit further has power input and third input, wherein power input is coupled integrated circuit's power supply pin, for coupling the output terminal of non-isolated flyback converter outside, power input is used to power control circuit;Third input is coupled secondary side switch pin, and control circuit at least based on the voltage of synchronous rectification switch first end controls the turn-off of synchronous rectification switch.
[0010] Optionally, control circuit includes a junction field effect transistor, coupled between main power switch pin and power supply pin.
[0011] Optionally, control circuit includes voltage dividing circuit, the input of voltage dividing circuit is coupled main power switch pin, and the output of voltage dividing circuit provides input voltage feedback signal.
[0012] Optionally, control circuit further has current detection input, for coupling current detection pin or the third end of main power switch.
[0013] Optionally, the main power switch includes a first MOSFET unit and a second MOSFET unit, wherein the drain of the first MOSFET unit and the drain of the second MOSFET unit are coupled to the main power switch pin, the gate of the first MOSFET unit and the gate of the second MOSFET unit are coupled to the first output terminal of the control circuit, the source of the first MOSFET unit is coupled to the ground pin, and the source of the second MOSFET unit is coupled to the current detection input terminal of the control circuit.
[0014] Optionally, the integrated circuit is integrated into an electronic package, and the control circuit is fabricated on the same semiconductor substrate.
[0015] Optionally, the control circuit controls the synchronous rectifier switch to conduct twice in one switching cycle, with the second conduction used to introduce reverse current into the transformer.
[0016] According to another aspect of the present invention, a non-isolated flyback converter circuit is proposed, comprising a rectifier circuit, a transformer, and an integrated circuit as described in any of the above embodiments, wherein the input terminal of the rectifier circuit is coupled to the mains interface, the first output terminal of the rectifier circuit is coupled to the first end of the primary winding, the second output terminal of the rectifier circuit is coupled to the ground terminal, and the second end of the primary winding is coupled to the main power switch pin of the integrated circuit.
[0017] The non-isolated flyback control integrated circuit and non-isolated flyback converter circuit proposed in this utility model have the main power switch and the secondary synchronous rectification switch controlled by a single control circuit. The synchronous rectification can be optimized and can be used to provide high-power power solutions for home appliances. It also features low loss, strong anti-interference ability, and high reliability. Attached Figure Description
[0018] The accompanying drawings are provided to further illustrate the present invention and, together with the description, serve to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:
[0019] Figure 1 A non-isolated flyback converter circuit according to an embodiment of the present invention is shown;
[0020] Figure 2 A circuit diagram showing a specific application of a non-isolated flyback converter circuit according to an embodiment of the present invention is provided.
[0021] Figure 3 A non-isolated flyback control integrated circuit according to another embodiment of the present invention is shown;
[0022] Figure 4 A circuit diagram showing a specific application of a non-isolated flyback converter circuit according to another embodiment of the present invention is shown;
[0023] Figure 5 A working waveform diagram of a non-isolated flyback conversion circuit according to an embodiment of the present application is shown.
[0024] Figure 6 A non-isolated flyback control integrated circuit according to an embodiment of the present application is shown. DETAILED DESCRIPTION
[0025] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with the embodiments, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations to the claims of the present application.
[0026] The description of this part is only for several typical embodiments, and the present application is not limited to the scope described in the embodiments. The combination of different embodiments, the mutual replacement of some technical features in different embodiments, and the mutual replacement of some technical features in the same or similar prior art means and embodiments are also within the scope of the description and protection of the present application.
[0027] In the specification, "coupling" or "connection" includes both direct connection and indirect connection. Indirect connection is the connection through an intermediate medium, such as the connection through an electrically conductive medium such as a conductor, wherein the electrically conductive medium can contain parasitic inductance or parasitic capacitance, or the connection through the intermediate circuit or component described in the embodiments of the specification; indirect connection can also include the connection through other active devices or passive devices on the basis of achieving the same or similar functions, such as the connection through circuits or components such as switches, signal amplification circuits, follower circuits, etc.
[0028] Figure 1The utility model discloses a non -isolated flyback conversion circuit according to an embodiment of the utility model. The non -isolated flyback conversion circuit can be used in the field of home appliance. It can provide larger power, and has smaller loss and higher reliability. The non -isolated flyback conversion circuit includes transformer T and integrated circuit 10 for non -isolated flyback control. Integrated circuit 10 includes main power switch Q1, synchronous rectification switch Q2 and control circuit 100, wherein the first end of main power switch Q1 is coupled with the main power switch pin PDS of integrated circuit 10 and is used for coupling with the primary winding L1 of transformer T externally, and the other end of primary winding L1 receives input voltage Vin. Preferably, the input voltage Vin is the line voltage after rectification and filtering of the mains alternating current, the second end of main power switch Q1 is coupled with the current detection pin CS of integrated circuit 10, and the current detection pin CS is used for coupling with the ground terminal externally through detection resistor Rcs. The first end of synchronous rectification switch Q2 is coupled with the secondary side switch pin SDS of integrated circuit 10 and is used for coupling with the first end of secondary winding L2 of transformer T externally, and the second end of synchronous rectification switch Q2 is coupled with ground pin GND. The ground pin GND is used for coupling with the ground terminal externally. The second end of secondary winding L2 provides output voltage Vout as the output terminal of the non -isolated flyback conversion circuit. The non -isolated flyback conversion circuit can further include: rectification circuit and input capacitor, for converting the mains alternating current into input voltage Vin after rectification and filtering; the non -isolated flyback conversion circuit can further include output capacitor, coupled with the output terminal of the non -isolated flyback conversion circuit; and diode and energy storage capacitor, for storing energy based on output voltage Vout to power control circuit 100. Control circuit 100 has feedback input terminal, first output terminal, second output terminal and ground input terminal, wherein the feedback input terminal is coupled with the feedback pin FB of integrated circuit 10, for receiving feedback signal representing output voltage Vout, the first output terminal of control circuit 100 is coupled with the control end of main power switch Q1, for controlling the conduction and turn-off of main power switch Q1, the second output terminal of control circuit 100 is coupled with the control end of secondary synchronous rectification switch Q2, for controlling the conduction and turn-off of synchronous rectification switch Q2, and the ground input terminal of control circuit 100 is coupled with ground pin GND. Control circuit 100 controls main power switch Q1 and synchronous rectification switch Q2 under the same ground terminal, which can conveniently control main power switch Q1 and synchronous rectification switch Q2 not to conduct at the same time, reduce control complexity and reliability. Control circuit 100 can further have power input terminal and third input terminal, wherein the power input terminal is coupled with the power supply pin VDD of integrated circuit 10, for coupling with the output terminal of the non -isolated flyback conversion circuit externally, and the power input terminal is used for powering control circuit 100. Specifically, the output terminal of the flyback conversion circuit can power the power supply pin VDD through the diode, and stabilize the voltage on the power supply pin VDD through the power supply capacitor.A third input of the control circuit 100 is coupled to the secondary side switch pin SDS, and the control circuit 100 controls the turn-off of the synchronous rectification switch based on at least the voltage at the first terminal of the synchronous rectification switch Q2. In the illustrated embodiment, the main power switch Ql and the synchronous rectification switch Q2 each comprise a MOSFET power device. The main power switch Ql comprises a first MOSFET power device, the gate of the first MOSFET power device is coupled to the first output of the control circuit 100, the drain of the first MOSFET power device is coupled to the main power switch pin PDS, and the source of the first MOSFET power device is coupled to the current sense pin CS. The synchronous rectification switch Q2 comprises a second MOSFET power device, the gate of the second MOSFET power device is coupled to the second output of the control circuit 100, the drain of the second MOSFET power device is coupled to the secondary side switch pin SDS, and the source of the second MOSFET power device is coupled to the ground pin GND. In other embodiments, the main power switch Ql and the synchronous rectification switch Q2 can comprise other types of power switching devices. The main power switch Ql and the synchronous rectification switch Q2 can comprise silicon-based power devices such as a Si MOSFET, silicon carbide power devices such as a SiC MOSFET, or gallium nitride power devices such as a GaN MOSFET. The control circuit 100 controls the turn-on and turn-off of the main power switch Ql based on the output voltage feedback signal at the feedback pin FB. Preferably, the main power switch Ql is turned on with zero voltage. The control circuit 100 controls the duration of the turn-on of the main power switch Ql based on the feedback signal. In one embodiment, the control circuit 100 controls the turn-on of the synchronous rectification switch Q2 when the main power switch Ql is turned off. Of course, the control circuit 100 can also control the turn-on of the synchronous rectification switch Q2 based on the voltage at the drain of the synchronous rectification switch Q2 as in the control of an isolated flyback converter. In one embodiment, the control circuit 100 controls the turn-off of the synchronous rectification switch Q2 when the control circuit detects the end of the freewheeling current in the secondary winding based on the voltage at the drain of the synchronous rectification switch Q2, i.e., the voltage at the secondary side switch pin SDS. In one embodiment, the control circuit 100 comprises a peak current control circuit that controls the turn-off of the main power switch Ql when the current through the main power switch Ql reaches a peak reference value. The peak reference value is generated based on a compensation signal of the signal at the feedback pin FB, and the compensation signal can be generated based on the error signal of the signal at the feedback pin FB and a reference voltage value. When the feedback signal is low, the peak reference value is increased to extend the turn-on time of the main power switch Ql. In one embodiment, the control circuit 100 controls the turn-on of the main power switch Ql when the voltage at the main power switch pin PDS drops to zero voltage after the turn-off of the synchronous rectification switch Q2.
[0029] Preferably, the integrated circuit 10 is integrated in an electronic package. The integrated circuit 10 can have six pins exposed outside the electronic package, as shown in Figure 1 The control circuit 100 is fabricated on the same semiconductor substrate to form an electric chip for simultaneously controlling the main power switch Q1 and the synchronous rectification switch Q2 in the non-isolated flyback converter. By sharing the ground terminal for the main power switch Q1 and the synchronous rectification switch Q2, the control circuit 100 can control the synchronous rectification switch Q2 based on the state of the main power switch Q1, completely avoiding the common phenomenon of false triggering of the synchronous rectification switch under abnormal conditions, thus greatly improving the application reliability of the system while improving the power supply capability and reducing the power loss of the system.
[0030] Figure 2 A specific application circuit diagram of the non-isolated flyback converter according to an embodiment of the present application is shown. The non-isolated flyback converter includes a rectifier circuit 21, a transformer T, and an integrated circuit 20. The integrated circuit 20 can use the integrated circuit 10 shown in Figure 1 The integrated circuit 20 has six pins, which are a first pin PDS, i.e., a main power switch pin, a second pin SDS, i.e., a secondary switch pin, a third pin VDD, i.e., a power supply pin, a fourth pin GND, i.e., a ground pin, a fifth pin CS, i.e., a current detection pin, and a sixth pin FB, i.e., a feedback pin. The input end of the rectifier circuit 21 is coupled to a power interface for receiving an AC power signal AC IN, and an EMI filter circuit can be further included before the rectifier circuit 21. The first output end of the rectifier circuit 21 is coupled to the first end of the primary winding of the transformer T, and the second output end of the rectifier circuit 21 is coupled to the ground terminal GND. The second end of the primary winding is coupled to the main power switch pin PDS of the integrated circuit 20. The first end of the secondary winding of the transformer T is coupled to the secondary switch pin SDS of the integrated circuit 20, and the second end of the secondary winding provides an output voltage Vout as the output end of the non-isolated flyback converter. The non-isolated flyback converter can further include filter elements such as input capacitors Ci and output capacitors Co, and can further include diodes and energy storage capacitors Cd for storing energy based on the output voltage Vout to supply power to the control circuit in the integrated circuit 20. In the illustrated embodiment, the positive output end of the non-isolated flyback converter is coupled to a voltage dividing circuit composed of resistors R1 and R2 for obtaining a feedback signal proportional to the output voltage Vout, and the feedback signal is transmitted to the integrated circuit 20 through the feedback pin FB.
[0031] Figure 3 A non-isolated flyback control integrated circuit 30 according to an embodiment of the present application is shown. And Figure 1Compared with the integrated circuit 10, the main power switch Q1 in the integrated circuit 30 includes a first MOSFET unit Q11 and a second MOSFET unit Q12, and the integrated circuit 30 has only five pins, i.e., a first pin PDS, a main power switch pin, a second pin SDS, a secondary side switch pin, a third pin VDD, a power supply pin, a fourth pin GND, a ground pin, and a fifth pin FB, a feedback pin. The integrated circuit 30 does not include a current detection pin, but the control circuit 300 has a current detection input end Vcs for coupling the source of the second MOSFET unit Q12, and the source of Q12 can be regarded as the third end of the main power switch Q1. The drain of the first MOSFET unit Q11 and the drain of the second MOSFET unit Q12 are coupled to the main power switch pin PDS, the gate of the first MOSFET unit Q11 and the gate of the second MOSFET unit Q12 are coupled to the first output end of the control circuit 300, the control circuit 300 controls the first MOSFET unit Q11 and the second MOSFET unit Q12 to be turned on and turned off at the same time, the source of the first MOSFET unit Q11 is coupled to the ground pin GND, and the first MOSFET unit Q11 is used as the main power switch, the source of the second MOSFET unit Q12 is coupled to the current detection input end Vcs of the control circuit 300, and the control circuit 300 is used for providing a current detection signal reflecting the current flowing through the main power switch Q1. The control circuit 300 includes a first control module and a second control module, wherein the first control module provides a switching control signal Vgate for controlling the main power switch Q1 based on the feedback signal of the feedback pin FB and the current detection signal received by the current detection end Vcs, and controls the main power switch Q1 to be turned off when the current detection signal rises to a current peak reference value. In an embodiment, the current peak reference value can be generated based on the feedback signal FB. In an embodiment, the first control module controls the turn-on of the main power switch Q1 based on the freewheeling end state of the synchronous rectification switch Q2. In an embodiment, the first control module controls the turn-off of the synchronous rectification switch Q2 and the turn-on of the main power switch Q1 when the feedback signal on the feedback pin FB is lower than a set threshold. In an embodiment, the first control module can be further coupled to the main power switch pin PDS for realizing the turn-on of the main power switch Q1 when the drain voltage of the main power switch Q1 drops to zero voltage after the synchronous rectification switch Q2 is turned off. The second control module generates a rectification control signal SRGate for controlling the synchronous rectification switch Q2 based on the switching control signal Vgate and the voltage on the secondary side switch pin SDS.
[0032] Figure 4 A specific application circuit diagram of a non-isolated flyback conversion circuit according to an embodiment of the present application is shown. The non-isolated flyback conversion circuit includes a rectification circuit, a transformer, and an integrated circuit 40. The integrated circuit 40 can adopt Figure 3The integrated circuit 40 is shown in FIG. 4. The integrated circuit 40 has five pins, which are a first pin PDS, a second pin SDS, a third pin VDD, a fourth pin GND, and a fifth pin FB.
[0033] Figure 5 A working waveform diagram of the non-isolated flyback converter circuit according to an embodiment of the present application is shown. The signals from top to bottom are a switch control signal Vgate output by the control circuit for controlling the main power switch, a main power switch drain-source voltage Vds, a transformer excitation inductor current Ilm, and a rectifier control signal SR Gate output by the control circuit for controlling the synchronous rectifier switch. At time t0, the switch control signal Vgate is high, the main power switch is turned on, the main power switch drain-source voltage Vds is zero, the excitation inductor current Ilm rises, and the synchronous rectifier switch remains off. At time t1, the switch control signal Vgate is low, the main power switch is turned off, the main power switch drain-source voltage Vds rises, and the excitation inductor current Ilm begins to drop. Then, the secondary side switch control signal SR Gate is high, the synchronous rectifier switch is turned on, the voltage difference across the synchronous rectifier switch is reduced, and the power loss is reduced. In an embodiment, the condition for the switch control signal Vgate being low is that the current flowing through the main power switch rises to a peak reference value, i.e., the signal obtained by the current detection pin CS or the current detection input of the control circuit is greater than the peak current reference signal, wherein the peak current reference signal can be generated based on the feedback signal obtained from the feedback pin FB. At time t2, the current flowing through the secondary winding and the excitation inductor current Ilm drop to zero, the freewheeling ends, the control circuit controls the secondary side switch control signal SR Gate to be low, and the synchronous rectifier switch is turned off. The main power switch drain-source voltage Vds begins to oscillate. In an embodiment, the detection of the end of the freewheeling can be achieved by detecting that the voltage on the secondary side switch pin rises to be greater than a preset reference value. At time t3, in the same switching period, the control circuit controls the secondary side switch control signal SR Gate to be high again, and the synchronous rectifier switch is turned on again, so that the current flowing through the transformer secondary winding and the excitation inductor current both have a reverse current, the parasitic oscillation of the flyback converter circuit is strengthened, the main power switch drain-source voltage Vds drops rapidly, and the drain voltage of the main power switch reaches or approaches zero voltage turn-on condition. When the voltage Vds approaches or reaches zero, the control circuit controls the switch control signal Vgate to be high, the main power switch is turned on, and the next switching period is entered. In this way, through the two turn-ons of the synchronous rectifier switch in the same switching period, the main power switch can reliably achieve zero voltage turn-on, and the power loss can be further reduced, and the power efficiency can be improved.
[0034] Figure 6The non-isolated flyback control integrated circuit 60 according to an embodiment of the present application is shown. The integrated circuit 60 comprises a main power switch Q1, a synchronous rectification switch Q2 and a control circuit 600. The control circuit 600 comprises a junction field effect transistor J1 coupled between a main power switch pin PDS and a power supply pin VDD for supplying power to the control circuit 600 in a starting stage. When the voltage on the power supply pin VDD is low, the control circuit 600 controls the junction field effect transistor J1 to selectively conduct when the main power switch Q1 is off, for charging an external power supply capacitor connected to the power supply pin VDD with the voltage on the main power switch pin PDS, i.e. the drain voltage of the main power switch Q1, to supply power to the control circuit 600, without adding extra pins to the integrated circuit 60. In this way, the control circuit 600 is powered by the primary side circuit of the non-isolated flyback converter in the starting stage, and by the output voltage of the non-isolated flyback converter in the normal working stage, and the power supply path is simple and reliable. In the illustrated embodiment, the control circuit 600 can further comprise a resistance voltage dividing circuit comprising resistors R3 and R4, the input of the voltage dividing circuit is coupled to the main power switch pin PDS, the series coupled resistors R3 and R4 are coupled between the main power switch pin PDS and a ground pin GND, and the output of the voltage dividing circuit (the coupling point of the resistors R3 and R4) is used to obtain a voltage representing the drain terminal of the main power switch Q1. When the main power switch Q1 is off, the voltage on the drain terminal of the main power switch Q1 reflects the input voltage, and thus the signal obtained by the voltage dividing circuit can be used for input overvoltage protection or input undervoltage protection. The voltage can also be used to determine whether the drain voltage of the main power switch Q1 reaches or approaches zero, for zero voltage conduction control of the main power switch Q1.
[0035] The description and application of the present application are illustrative, and are not intended to limit the scope of the present application to the embodiments described. The effects or advantages related to the description in the specification may not be achieved in actual experimental examples due to uncertainty of specific conditions or other factors, and the effects or advantages related to the description are not used to limit the scope of the present application. Variations and changes of the embodiments disclosed herein are possible, and various components of the embodiments are known to those skilled in the art. It should be clear to those skilled in the art that the present application can be realized in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential characteristics of the present application. Other variations and changes of the embodiments disclosed herein can be made without departing from the scope and spirit of the present application.
Claims
1. A non-isolated flyback control integrated circuit, characterized in that, The integrated circuit comprises: a main power switch, a first end of the main power switch being coupled to a main power switch pin of the integrated circuit and a primary winding of a transformer, a second end of the main power switch being coupled to a ground pin or a current sense pin of the integrated circuit, wherein the ground pin is externally coupled to a ground terminal or the current sense pin is externally coupled to the ground terminal through a sense resistor; a synchronous rectification switch, a first end of the synchronous rectification switch being coupled to a secondary switch pin of the integrated circuit and a first end of a secondary winding of the transformer, a second end of the synchronous rectification switch being coupled to the ground pin, wherein a second end of the secondary winding provides an output voltage as an output terminal of the non-isolated flyback converter circuit; and a control circuit having a feedback input terminal, a first output terminal, a second output terminal and a ground input terminal, wherein the feedback input terminal is coupled to a feedback pin of the integrated circuit for receiving a feedback signal indicative of the output voltage, the first output terminal is coupled to a control terminal of the main power switch for controlling turn-on and turn-off of the main power switch, the second output terminal is coupled to a control terminal of the synchronous rectification switch for controlling turn-on and turn-off of the synchronous rectification switch, and the ground input terminal is coupled to the ground pin.
2. The integrated circuit of claim 1, wherein, The main power switch comprises a first MOSFET power device, a gate of the first MOSFET power device being coupled to the first output terminal of the control circuit, a drain of the first MOSFET power device being coupled to the main power switch pin, and a source of the first MOSFET power device being coupled to the ground pin or the current sense pin. The synchronous rectification switch comprises a second MOSFET power device, a gate of the second MOSFET power device being coupled to the second output terminal of the control circuit, a drain of the second MOSFET power device being coupled to the secondary switch pin, and a source of the second MOSFET power device being coupled to the ground pin.
3. The integrated circuit of claim 1, wherein, The control circuit further has a power supply input terminal and a third input terminal, wherein the power supply input terminal is coupled to a power supply pin of the integrated circuit for externally coupling to the output terminal of the non-isolated flyback converter circuit for supplying power to the control circuit; the third input terminal is coupled to the secondary switch pin, and the control circuit controls turn-off of the synchronous rectification switch based on at least a voltage at the first end of the synchronous rectification switch.
4. The integrated circuit of claim 3, wherein, The control circuit comprises a junction field effect transistor coupled between the main power switch pin and the power supply pin.
5. The integrated circuit of claim 4, wherein, The control circuit comprises a voltage dividing circuit, an input terminal of the voltage dividing circuit being coupled to the main power switch pin, and an output terminal of the voltage dividing circuit providing the input voltage feedback signal.
6. The integrated circuit of claim 1, wherein, The control circuit further has a current sense input terminal for coupling to the current sense pin or a third end of the main power switch.
7. The integrated circuit of claim 1, wherein, The main power switch comprises a first MOSFET unit and a second MOSFET unit, wherein a drain of the first MOSFET unit and a drain of the second MOSFET unit are coupled to the main power switch pin, a gate of the first MOSFET unit and a gate of the second MOSFET unit are coupled to the first output terminal of the control circuit, a source of the first MOSFET unit is coupled to the ground pin, and a source of the second MOSFET unit is coupled to the current sense input terminal of the control circuit.
8. The integrated circuit of claim 1, wherein, The integrated circuit is integrated in one electronic package, and the control circuit is fabricated on the same semiconductor substrate.
9. The integrated circuit of claim 1, wherein, The control circuit controls the synchronous rectification switch to be turned on twice in a switching period, the second time for introducing a reverse current in the transformer.
10. A non-isolated flyback conversion circuit comprising a rectification circuit, a transformer and the integrated circuit according to any one of claims 1-9, wherein an input of the rectification circuit is coupled to a mains interface, a first output of the rectification circuit is coupled to a first end of a primary winding, a second output of the rectification circuit is coupled to a ground terminal, and a second end of the primary winding is coupled to a main power switch pin of the integrated circuit.