Dual-frequency flyback converter with high dynamic response

Abstract

The invention discloses a dual-frequency flyback converter with high dynamic response. The dual-frequency flyback converter comprises a basic flyback converter, a synchronous Buck converter and a diode D2, the basic flyback converter comprises a direct current input source uin, a power switch S1, an excitation inductor Lm, a leakage inductor Lk, a transformer T, a rectifier diode D1 and an output capacitor Co; the synchronous Buck converter comprises an auxiliary capacitor Cvt, a power switch S2, a power switch S3 and an inductor Lvt. The circuit is simple in structure, a traditional flyback converter and the synchronous Buck converter are reasonably connected through the diode D2, the leakage inductance energy utilization rate of the flyback converter is effectively improved, the dynamic response performance of the traditional flyback converter can be effectively improved on the occasion with high output precision, and the reliability of the flyback converter is improved. The overshoot and the adjustment time of the voltage when the load changes are greatly reduced, and the stability of the system is improved.

Description

Technical Field

[0001] The invention relates to a converter, and in particular to a dual-frequency flyback converter with high dynamic response. Background Art

[0002] With the rapid development of cloud servers, big data, and artificial intelligence, the number and scale of data centers are increasing day by day. For the server motherboard of the data center, the power supply voltage regulator (VR) is the most critical component. The VR module needs to adjust the voltage according to the system load fluctuation to maximize energy efficiency and ensure the stability and reliability of the system. The traditional flyback converter circuit is a single switch with simple structure, few components, high conversion efficiency, low loss, no need for isolation of the drive, and low cost. It is widely used in small and medium power occasions. The synchronous Buck converter can provide a stable output voltage, has strong resistance to load changes, can better adapt to output load changes, and has high efficiency. Therefore, it is widely used in step-down occasions.

[0003] However, in traditional flyback converters, for example, the technical solution described in the Chinese patent "A Flyback Switching Power Supply" (application number: 202410264420.4) improves the loop response speed of the system based on peak current control, and the control circuit chip does not use optocouplers, reducing costs. At the same time, a protection circuit is designed in the internal system of the control power chip to keep the chip in a normal working state and improve the reliability of the circuit. However, the use of an RCD clamping circuit to absorb leakage inductance energy and suppress the voltage spike of the power switch tube greatly reduces the efficiency of the converter.

[0004] In the technical solution recorded in the Chinese patent "An Active Clamp Flyback Converter" (application number: 202310177479.5), an active clamp circuit is used to absorb leakage inductance energy, thereby improving the utilization rate of leakage inductance energy. However, since the transformer energy of the flyback converter can only be transmitted to the secondary when the switch is turned off, the system cannot respond quickly when the load fluctuates, and the load fluctuation is large. Summary of the invention

[0005] In order to solve the problems of low utilization rate of leakage inductance energy and insufficient dynamic response performance of traditional flyback converters. The present invention proposes a dual-frequency flyback converter with high dynamic response. The dual-frequency flyback converter has a simple circuit structure, and the traditional flyback converter and the synchronous Buck converter are reasonably connected through the diode D2, which effectively improves the leakage inductance energy utilization rate of the flyback converter. In the case of high output accuracy, it can effectively improve the dynamic response performance of the traditional flyback converter, greatly reduce the voltage overshoot and adjustment time when the load changes, and improve the stability of the system.

[0006] The technical solution adopted by the present invention is:

[0007] A dual-frequency flyback converter with high dynamic response, comprising: a basic flyback converter, a synchronous Buck converter, and a diode D2;

[0008] The basic flyback converter comprises: a DC input source u in , power switch S1, excitation inductance L m , leakage inductance L k , transformer T, rectifier diode D1, output capacitor C o , its connection form is as follows:

[0009] DC input source u in The positive connection leakage inductance L k One end, leakage inductance L k The other end is connected to the excitation inductor L m One end of the primary winding L of the transformer T p one end of

[0010] Excitation inductance L m The other end is connected to the drain of the power switch S1 and the primary winding L of the transformer T. p The other end of

[0011] The source of power switch S1 is connected to the DC input source u in The negative electrode;

[0012] The secondary winding L of the transformer T s The upper end is connected to the anode of the rectifier diode D1, and the cathode of the rectifier diode D1 is connected to the output capacitor C o One end of the secondary winding L of the transformer T s The lower end of the output capacitor C o The other end of

[0013] The synchronous Buck converter comprises: an auxiliary capacitor C vt , power switch S2, power switch S3, inductor L vt , its connection form is as follows:

[0014] The drain of power switch S2 is connected to auxiliary capacitor C vt The source of the power switch S2 is connected to the drain of the power switch S3, the inductor L vt The source of the power switch S3 is connected to the auxiliary capacitor C vt The other end of

[0015] The connection form of the basic flyback converter and the synchronous Buck converter is as follows:

[0016] The drain of the power switch S1 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the auxiliary capacitor C of the synchronous Buck converter. vt One end of the synchronous Buck converter inductor L vt The other end is connected to the cathode of the rectifier diode D1 of the basic flyback converter; the source of the power switch S3 of the synchronous Buck converter is connected to the secondary winding L of the transformer T of the basic flyback converter s The other end of

[0017] Load R o The two ends of the output capacitor C o Connect both ends.

[0018] When the auxiliary capacitor C vt Before the voltage reaches the target value:

[0019] When the power switch S1 is turned on, the rectifier diode D1, diode D2, power switch S2, and power switch S3 are turned off, and the excitation inductor L m , leakage inductance L k The current rises linearly, the transformer energy storage increases, and the output capacitor C o For load R o powered by;

[0020] When the power switch S1 is turned off, the rectifier diode D1 and the diode D2 are turned on, the power switch S2 and the power switch S3 are turned off, and the excitation inductor L m Energy passes through the primary winding L of transformer T p Transmitted to the secondary winding L of transformer T s , through the rectifier diode D1 to the output capacitor C o 、Load R o Power supply, leakage inductance L k The current flows through diode D2 to capacitor C vt Charge to leakage inductance L k The current is 0.

[0021] When the auxiliary capacitor C vt After the voltage reaches the target value:

[0022] When the power switch S1 is turned on, the rectifier diode D1, diode D2, and power switch S2 are turned off, and the excitation inductor L m , leakage inductance L k The current rises linearly, the transformer energy storage increases, the power switch S3 is turned on, and the inductor L vt , output capacitor C o For load R o powered by;

[0023] When the power switch S1 is turned off, the rectifier diode D1 and the diode D2 are turned on, the power switch S3 is turned off, and the leakage inductance Lk The current flows through diode D2 to capacitor C vt Charge to leakage inductance L k After the current is 0, the power switch S2 is turned on and the capacitor C vt The voltage drop across the inductor L vt With load R o Power supply, excitation inductance L m Energy passes through the primary winding L of transformer T p Transferred to the secondary winding L of transformer T s , through the rectifier diode D1 to the output capacitor C o 、Load R o powered by.

[0024] When diode D2 is turned on, auxiliary capacitor C vt Absorption leakage inductance L k Energy is stored and the excess energy is supplied to the load through the synchronous Buck converter, and the auxiliary capacitor C vt The power switch S1 can be clamped to reduce the voltage spike when it is turned off. The clamping voltage is set to 1.3 to 1.5 times the voltage stress of the power switch tube, and the following relationship is obtained:

[0025] The voltage stress of power switch S1 is: s1 =u vt =(1.3~1.5)i[(u o +u don )iN+u in ];

[0026] The voltage stress of the rectifier diode D1 is:

[0027] Where: u s1 is the voltage stress of power switch S1, u vt is the capacitance C vt Voltage across the terminals, u o is the output voltage, u don is the conduction voltage of the rectifier diode D1, u d1 is the voltage stress of the rectifier diode D1, u in is the input voltage, and N is the ratio of the number of turns of the primary winding to the number of turns of the secondary winding of the transformer.

[0028] When the load R o When the synchronous Buck converter changes, the capacitor C vt Energy to load R o transfer, reducing the load R o The voltage fluctuation caused by the change can achieve high dynamic response. According to the volt-second balance characteristics of the inductor, the following relationship can be obtained: The input and output voltage relationship is: o =Dbuck ·u vt

[0029] The voltage stress of power switch tube S2 is: s2 =u vt

[0030] The voltage stress of power switch tube S3 is: s3 =u vt

[0031] Where: u vt is the capacitance C vt Voltage across the board, D buck is the synchronous Buck converter duty cycle.

[0032] The present invention provides a dual-frequency flyback converter with high dynamic response, and the technical effects are as follows:

[0033] 1) The dual-frequency flyback converter circuit uses an auxiliary capacitor as the input of the synchronous Buck converter, which effectively suppresses the voltage spike of the power switch tube S1 and solves the problem of low leakage inductance energy utilization in the traditional flyback circuit.

[0034] 2) The dual-frequency flyback converter circuit has a simple topology. During normal operation, the flyback converter is the main power circuit that efficiently realizes energy conversion. When the load fluctuates, the synchronous Buck converter responds quickly to load changes, achieves high dynamic response, greatly reduces the output voltage regulation overshoot, and reduces the regulation time during load fluctuations.

[0035] 3) The two basic topologies of the dual-frequency flyback converter circuit are decoupled from each other and can work independently, with a simple control strategy and easy maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with the accompanying drawings and examples:

[0037] Figure 1 This is the schematic diagram of a traditional flyback converter.

[0038] Figure 2 This is the schematic diagram of a traditional active clamp flyback converter.

[0039] Figure 3 It is a circuit schematic diagram of the present invention.

[0040] Figure 4 This is the dynamic response curve of the traditional active clamp flyback converter when the load fluctuates.

[0041] Figure 5 It is the dynamic response curve of the circuit of the present invention when the load fluctuates. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0043] like Figure 1 As shown, the basic flyback converter includes a DC input source u in , power switch S1, excitation inductance L m , leakage inductance L k , transformer T, rectifier diode D1, output capacitor C o , its connection form is as follows:

[0044] DC input source u in The positive connection leakage inductance L k left end;

[0045] Leakage inductance L k The right end of each is connected to the excitation inductor L m The upper end of the primary winding L of the transformer T p The upper end of

[0046] The drain of the power switch S1 is connected to the excitation inductor L m The lower end of the primary winding L of the transformer T p The lower end of

[0047] The source of power switch S1 is connected to the DC input source u in The negative electrode;

[0048] The secondary winding L of the transformer T s The lower end is connected to the anode of the rectifier diode D1;

[0049] The cathode of the rectifier diode D1 is connected to the output capacitor C o The upper end of

[0050] The secondary winding L of the transformer T s The lower end of the output capacitor C o The lower end.

[0051] like Figure 2 As shown, the conventional active clamp flyback converter includes a basic flyback converter, a power switch S c , absorption capacitor C c , the connection method is as follows:

[0052] Absorption capacitor C c The upper end is connected to the DC input source u in The positive electrode;

[0053] Power switch S c The drain connection absorption capacitor C c The lower end of

[0054] Power switch S cThe source of is connected to the drain of the power switch S1 of the basic flyback converter;

[0055] When the power switch S1 is turned on, the rectifier diode D1 and the power switch S c Disconnect, excitation inductance L m , leakage inductance L k The current rises linearly, the transformer energy storage increases, and the output capacitor C o For load R o powered by;

[0056] When the power switch S1 is turned off, the rectifier diode D1 and the power switch S c conduction, absorption capacitor C c Absorbs leakage inductance energy and feeds the energy back to the DC input source u in , magnetizing inductance L m Energy passes through the primary winding L of transformer T p Transmitted to the secondary winding L of transformer T s , through the rectifier diode D1 to the output capacitor C o 、Load R o powered by.

[0057] like Figure 3 As shown, a dual-frequency flyback converter with high dynamic response, the dual-frequency flyback converter circuit includes: the circuit includes a basic flyback converter, a synchronous Buck converter, and a diode D2, and the connection form thereof is as follows:

[0058] The drain of the power switch S1 is connected to the anode of the diode D2;

[0059] The cathode of diode D2 is connected to the auxiliary capacitor C of the synchronous Buck converter. vt The upper end of

[0060] Inductor L of synchronous Buck converter vt The right side is connected to the cathode of the rectifier diode D1 of the basic flyback converter;

[0061] The source of the power switch S3 of the synchronous Buck converter is connected to the secondary winding L of the transformer T of the basic flyback converter. s The lower end.

[0062] When diode D2 is turned on, auxiliary capacitor C vt Absorption leakage inductance L k Energy is stored and the excess energy is supplied to the load through the synchronous Buck converter, and the auxiliary capacitor C vt The power switch S1 can be clamped to reduce the voltage spike when it is turned off. The clamping voltage is usually set to 1.3 to 1.5 times the voltage stress of the power switch tube.

[0063] When the load R o When the synchronous Buck converter changes, the capacitor C vt Energy to load R o transfer, reducing the load R o The voltage fluctuation caused by the change can achieve high dynamic response and greatly reduce the output voltage regulation overshoot.

[0064] Figure 4 This is the load regulation fluctuation curve of the traditional active clamp flyback converter PID closed-loop system. It can be seen that the fluctuation overshoot is large and the regulation time is long.

[0065] Figure 5 The load regulation fluctuation curve of the present invention greatly reduces the overshoot when the load fluctuates, and shortens the regulation time.

Claims

1. A dual-frequency flyback converter with high dynamic response, characterized in that include: Flyback converter, synchronous Buck converter, diode D2; The flyback converter comprises: a DC input source u in , power switch S1, excitation inductance L m , leakage inductance L k , transformer T, rectifier diode D1, output capacitor C o , its connection form is as follows: DC input source u in The positive connection leakage inductance L k One end of the leakage inductance L k The other end is connected to the excitation inductor L m One end of the primary winding L of the transformer T p one end of Excitation inductance L m The other end is connected to the drain of the power switch S1 and the primary winding L of the transformer T. p The other end of The source of power switch S1 is connected to the DC input source u in The negative electrode; The secondary winding L of the transformer T s The upper end is connected to the anode of the rectifier diode D1, and the cathode of the rectifier diode D1 is connected to the output capacitor C o One end of the secondary winding L of the transformer T s The lower end of the output capacitor C o The other end of The synchronous Buck converter comprises: an auxiliary capacitor C vt , power switch S2, power switch S3, inductor L vt , its connection form is as follows: The drain of power switch S2 is connected to auxiliary capacitor C vt The source of the power switch S2 is connected to the drain of the power switch S3, the inductor L vt The source of the power switch S3 is connected to the auxiliary capacitor C vt The other end of The connection between the flyback converter and the synchronous Buck converter is as follows: The drain of the power switch S1 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the auxiliary capacitor C of the synchronous Buck converter. vt One end of the synchronous Buck converter inductor L vt The other end is connected to the cathode of the rectifier diode D1 of the flyback converter; the source of the power switch S3 of the synchronous Buck converter is connected to the secondary winding L of the transformer T of the flyback converter s The other end of Load R o The two ends of the output capacitor C o Connect both ends.

2. A dual-frequency flyback converter with high dynamic response according to claim 1, characterized in that: When the auxiliary capacitor C vt Before the voltage reaches the target value: When the power switch S1 is turned on, the rectifier diode D1, diode D2, power switch S2, and power switch S3 are turned off, and the excitation inductor L m , leakage inductance L k The current rises linearly, the transformer energy storage increases, and the output capacitor C o For load R o powered by; When the power switch S1 is turned off, the rectifier diode D1 and the diode D2 are turned on, the power switch S2 and the power switch S3 are turned off, and the excitation inductor L m Energy passes through the primary winding L of transformer T p Transmitted to the secondary winding L of transformer T s , through the rectifier diode D1 to the output capacitor C o 、Load R o Power supply, leakage inductance L k The current flows through diode D2 to capacitor C vt Charge to leakage inductance L k The current is 0; When the auxiliary capacitor C vt After the voltage reaches the target value: When the power switch S1 is turned on, the rectifier diode D1, diode D2, and power switch S2 are turned off, and the excitation inductor L m , leakage inductance L k The current rises linearly, the transformer energy storage increases, the power switch S3 is turned on, and the inductor L vt , output capacitor C o For load R o powered by; When the power switch S1 is turned off, the rectifier diode D1 and the diode D2 are turned on, the power switch S3 is turned off, and the leakage inductance L k The current flows through diode D2 to capacitor C vt Charge to leakage inductance L k After the current is 0, the power switch S2 is turned on and the capacitor C vt The voltage drop across the inductor L vt With load R o Power supply, excitation inductance L m Energy passes through the primary winding L of transformer T p Transmitted to the secondary winding L of transformer T s , through the rectifier diode D1 to the output capacitor C o 、Load R o powered by.

3. A dual-frequency flyback converter with high dynamic response according to claim 1, characterized in that: When diode D2 is turned on, the auxiliary capacitor C vt Absorption leakage inductance L k Energy is stored and the excess energy is supplied to the load through the synchronous Buck converter, and the auxiliary capacitor C vt The power switch S1 can be clamped to reduce the voltage spike when it is turned off. The clamping voltage is set to 1.3 to 1.5 times the voltage stress of the power switch tube, and the following relationship is obtained: The voltage stress of power switch S1 is: s1 =u vt =(1.3~1.5)i[(u o +u don )iN+u in ]; The voltage stress of the rectifier diode D1 is: Where: u s1 is the voltage stress of power switch S1, u vt is the capacitance C vt Voltage across the terminals, u o is the output voltage, u don is the conduction voltage of the rectifier diode D1, u d1 is the voltage stress of the rectifier diode D1, u in is the input voltage, N is the ratio of the number of turns of the primary winding to the number of turns of the secondary winding of the transformer; When the load R o When the synchronous Buck converter changes, the capacitor C vt Energy to load R o transfer, reducing the load R o To achieve high dynamic response, the voltage fluctuation caused by the change can be obtained according to the volt-second balance characteristics of the inductor: The relationship between input and output voltage is: o =D buck ·u vt ; The voltage stress of power switch tube S2 is: s2 =u vt ; The voltage stress of power switch tube S3 is: s3 =u vt ; Where: u vt is the capacitance C vt Voltage across the board, D buck is the synchronous Buck converter duty cycle.

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