A resonant drive circuit and its operating method

Abstract

The present invention provides a resonant drive circuit, comprising a positive and negative rectangular wave power supply, a nonlinear resonant inductor, a primary winding, a secondary winding, and a MOS switch. The positive and negative rectangular wave power supply, the nonlinear resonant inductor, and the primary winding are connected in series, one end of the secondary winding is connected to the gate of the MOS switch, and the other end of the secondary winding is connected to the source of the MOS switch. The primary winding and the secondary winding are wound on the same magnetic core to form a transformer. The present invention has the following beneficial effects: it improves the traditional sinusoidal wave resonant drive. Because of the resonant drive, most of the drive energy is returned to the power supply, so the drive efficiency is high; at the same time, because the resonant current is very low for most of the time in a resonant cycle, the conduction loss of the drive circuit is small; and the resonant frequency is very high when the inductor is saturated, so the drive voltage rise rate is faster than that of the traditional sinusoidal wave resonant drive, thereby improving the effective duty cycle and thus improving the efficiency of the power converter.

Description

Technical field

[0001] The present invention relates to the field of switching power supplies, and in particular to a resonant drive circuit and an operating method thereof. [Background Technology]

[0002] With the development of switching power supply technology, high frequency and high power density are the development trends of power converters. The switching frequency reaches the MHz level. The traditional rectangular wave drive circuit has large driving loss, which seriously affects the efficiency of the power converter. It is necessary to adopt low-loss resonant drive. The traditional resonant drive circuit generates a sinusoidal voltage through a resonant capacitor and a resonant inductor. The sine wave frequency is the resonant frequency. Since the driving voltage of this drive circuit is a sine wave, the effective duty cycle is low, which affects the efficiency of the converter. In addition, the switching frequency needs to match the resonant frequency of the drive circuit. When the resonant circuit components deviate from the typical values, the resonant frequency deviates from the switching frequency, which leads to increased power consumption of the drive circuit. [Summary of the invention]

[0003] The present invention aims to solve the above-mentioned problems existing in the traditional rectangular wave driving circuit and to provide a resonant driving circuit and an operating method thereof.

[0004] The present invention is achieved through the following technical solution: a resonant drive circuit, including a positive and negative rectangular wave power supply, a nonlinear resonant inductor, a primary winding, a secondary winding, and a switching tube MOS, wherein the positive and negative rectangular wave power supply, the nonlinear resonant inductor and the primary winding are connected in series, one end of the secondary winding is connected to the gate of the switching tube MOS, and the other end of the secondary winding is connected to the source of the switching tube MOS, and the primary winding and the secondary winding are wound on the same magnetic core to form a transformer.

[0005] Furthermore, the positive and negative rectangular wave power supplies are implemented through a full-bridge topology, a half-bridge topology, a push-pull topology or an active clamp forward topology.

[0006] Furthermore, the duty cycle of the positive and negative rectangular waves of the positive and negative rectangular wave power supply is a fixed duty cycle or an adjustable duty cycle.

[0007] Furthermore, the nonlinear resonant inductor is a fast saturation inductor, the saturation current of the nonlinear resonant inductor is less than 1.571A, and the typical inductance before saturation is 2.718 times or more of the typical inductance after saturation.

[0008] Furthermore, the transformer has two or more secondary windings.

[0009] Furthermore, the driving voltage of the switching tube MOS is an approximate positive and negative square wave composed of resonant waveforms.

[0010] A method for operating a resonant drive circuit comprises: a voltage source outputting positive and negative square waves to provide resonant energy; a nonlinear inductor having a low saturation current; and when the saturation current is reached, the inductor rapidly decreases and resonates with the capacitor Ciss of the MOS switch and the distributed capacitance of the circuit. This resonant frequency is high, causing the gate voltage of the MOS switch to rise rapidly until it is turned on, forming a rising edge when the MOS switch is turned on. When the inductor resonant current decreases below the saturation current, the nonlinear inductor exits saturation, the inductance recovers to a certain value, and continues to resonate with the capacitor Ciss of the MOS switch and the distributed capacitance of the circuit. At this time, the resonant frequency is low and the drive loop current is small, forming the time when the MOS switch is turned on. When the resonant current reaches the inductor saturation current value in the reverse direction, the inductor rapidly decreases and resonates with the capacitor Ciss of the MOS switch and the distributed capacitance of the circuit. This resonant frequency is high, causing the gate voltage of the MOS switch to drop rapidly until it is turned off, forming a falling edge when the MOS switch is turned off.

[0011] The beneficial effects of the present invention are as follows: it improves the traditional sinusoidal wave resonant drive. Because of the resonant drive, most of the driving energy is returned to the power supply, so the driving efficiency is high; at the same time, since the resonant current is very low most of the time in a resonant cycle, the conduction loss of the driving circuit is small; and the resonant frequency is very high when the inductor is saturated, so that the driving voltage rise rate is faster than that of the traditional sinusoidal wave resonant drive, thereby increasing the effective duty cycle and thus improving the efficiency of the power converter.

Brief Description of the Drawings

[0012] Figure 1 This is a schematic diagram of a two-way resonant drive structure with capacitance matching in a resonant drive circuit of the present invention;

[0013] Figure 2 A schematic diagram of a full-bridge drive structure of a resonant drive circuit of the present invention;

[0014] Figure 3 A schematic diagram of a half-bridge drive structure of a resonant drive circuit of the present invention;

[0015] Figure 4 This is a schematic diagram of a two-way resonant drive structure of a resonant drive circuit of the present invention;

[0016] Figure 5 A schematic diagram of a resonant driving structure of multiple switching devices in a resonant driving circuit of the present invention;

[0017] Figure numerals: 1. positive and negative rectangular wave power supply; 2. nonlinear resonant inductor; 3. primary winding; 4. secondary winding; 5. MOS switch; 6. magnetic core; 7. transformer. [Specific implementation method]

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0019] like Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 As shown, a resonant drive circuit includes a positive and negative rectangular wave power supply 1, a nonlinear resonant inductor 2, a primary winding 3, a secondary winding 4, and a switching tube MOS5. The positive and negative rectangular wave power supply 1, the nonlinear resonant inductor 2 and the primary winding 3 are connected in series, one end of the secondary winding 4 is connected to the gate of the switching tube MOS5, and the other end of the secondary winding 4 is connected to the source of the switching tube MOS5. The primary winding 3 and the secondary winding 4 are wound on the same magnetic core 6 to form a transformer 7.

[0020] Preferably, the positive and negative rectangular wave power supply 1 is implemented by a full-bridge topology, a half-bridge topology, a push-pull topology or an active clamp forward topology.

[0021] Preferably, the duty cycle of the positive and negative rectangular waves of the positive and negative rectangular wave power supply 1 is a fixed duty cycle or an adjustable duty cycle.

[0022] Preferably, the nonlinear resonant inductor 2 is a fast saturation inductor, the saturation current of the nonlinear resonant inductor 2 is less than 1.571A, and the typical inductance before saturation is 2.718 times or more of the typical inductance after saturation.

[0023] Preferably, the transformer 7 has two or more secondary windings 4 .

[0024] Preferably, the driving voltage of the switch tube MOS5 is an approximately positive and negative square wave composed of resonant waveforms.

[0025] A method for operating a resonant drive circuit comprises: a voltage source outputting positive and negative square waves to provide resonant energy; a nonlinear inductor having a low saturation current; and when the saturation current is reached, the inductor rapidly decreases and resonates with the capacitor Ciss of the MOS switch and the distributed capacitance of the circuit. This resonant frequency is high, causing the gate voltage of the MOS switch to rise rapidly until it is turned on, forming a rising edge when the MOS switch is turned on. When the inductor resonant current decreases below the saturation current, the nonlinear inductor exits saturation, the inductance recovers to a certain value, and continues to resonate with the capacitor Ciss of the MOS switch and the distributed capacitance of the circuit. At this time, the resonant frequency is low and the drive loop current is small, forming the time when the MOS switch is turned on. When the resonant current reaches the inductor saturation current value in the reverse direction, the inductor rapidly decreases and resonates with the capacitor Ciss of the MOS switch and the distributed capacitance of the circuit. This resonant frequency is high, causing the gate voltage of the MOS switch to drop rapidly until it is turned off, forming a falling edge when the MOS switch is turned off.

[0026] Based on the disclosure and teachings of the above description, those skilled in the art may also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and any modifications and variations of the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although certain specific terms are used in this description, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A resonant drive circuit and an operating method thereof, characterized in that: The resonant drive circuit includes a positive and negative rectangular wave power supply, a nonlinear resonant inductor, a primary winding, a secondary winding, and a MOS switch. The positive and negative rectangular wave power supply, the nonlinear resonant inductor, and the primary winding are connected in series. One end of the secondary winding is connected to the gate of the MOS switch, and the other end of the secondary winding is connected to the source of the MOS switch. The primary and secondary windings are wound on the same magnetic core to form a transformer. The positive and negative rectangular wave power supply is realized by a full-bridge topology, a half-bridge topology, a push-pull topology or an active clamp forward topology, and the duty cycle of the positive and negative rectangular waves of the positive and negative rectangular wave power supply is a fixed duty cycle or an adjustable duty cycle; The nonlinear resonant inductor is a fast saturation inductor, the saturation current of the nonlinear resonant inductor is less than 1.571A, and the typical inductance before saturation is 2.718 times or more of the typical inductance after saturation; The driving voltage of the switching tube MOS is an approximately positive and negative square wave composed of resonant waveforms; The operation method of the resonant drive circuit is as follows: the voltage source outputs positive and negative square waves to provide resonant energy. The saturation current of the nonlinear inductor is low. When the saturation current is reached, the inductor inductance decreases rapidly and resonates with the capacitance Ciss of the MOS switch and the distributed capacitance of the circuit. This resonant frequency is high, causing the gate voltage of the MOS switch to rise rapidly to turn on, forming the rising edge of the MOS switch turn-on. When the inductor resonant current decreases below the saturation current, the nonlinear inductor exits saturation, the inductance recovers to a certain value, and continues to resonate with the capacitance Ciss of the MOS switch and the distributed capacitance of the circuit. At this time, the resonant frequency is low and the drive loop current is small, which constitutes the time when the MOS switch is turned on. When the resonant current reaches the inductor saturation current value in the reverse direction, the inductor inductance decreases rapidly and resonates with the capacitance Ciss of the MOS switch and the distributed capacitance of the circuit. This resonant frequency is high, causing the gate voltage of the MOS switch to drop rapidly to turn off, forming the falling edge of the MOS switch turn-off.

2. A resonant drive circuit and operating method thereof according to claim 1, characterized in that: The transformer has two or more secondary windings.

Images