A 2KW high frequency switching power supply circuit design

In recent years, with the development of electronic technology, postal and telecommunications, transportation facilities, instrumentation, industrial facilities, household appliances, etc. are increasingly using switching power supplies. With the continuous advancement of science and technology, the demand for high-power power supplies is also increasing. getting bigger.

At the same time, a large number of electronic communication devices such as integrated circuits and ultra-large-scale integrated circuits are increasing, and the development trend of power supplies is required to be miniaturized and lightweight. In this paper, the volume and weight of the filter inductor, capacitor and transformer are relatively large. Therefore, a design scheme of 2KW high-frequency switching Power Supply circuit is proposed. Through the design method of the power supply circuit in the scheme, the volume is reduced to reduce their volume. Miniaturization and weight reduction.

0 Preface

We can increase the operating frequency by reducing the winding turns of the transformer and reducing the core size by gold. However, while increasing the switching frequency, the switching loss will increase and the circuit efficiency will be seriously degraded. A soft-switching technology has emerged for these problems. It uses the auxiliary commutation method based on resonance to solve the switching loss and switching noise problem in the circuit, so that the switching power supply can operate at high frequency and efficiently, since the 1970s. The high-frequency soft-switching technology has been continuously studied since the beginning, and it is relatively mature. The following is an example of a 2KW power supply in the scheme.

1 Design content and method

1.1 The choice of the main circuit type

The type of the conversion circuit is mainly selected according to the technical requirements of the load requirement and the given power supply voltage. In several commonly used conversion circuits, since the voltage of the half-bridge and full-bridge conversion circuit power switching tube is twice as low as that of the push-pull conversion circuit, since the commercial power voltage is high, the push-pull conversion circuit is not selected. When the half-bridge conversion circuit and the full-bridge conversion circuit output the same power, the power switch tube of the half-bridge conversion circuit is subjected to twice the working current, and it is difficult to select the tube, and the output power is smaller than the full bridge, so a full-bridge conversion circuit is adopted.

The traditional full-bridge conversion circuit switching element is turned on or off under the control of the gate under the condition of high voltage or large current. During the switching process, the voltage and current are not zero, and overlap occurs, resulting in switching loss. The switching loss rises sharply as the switching frequency increases, which reduces the efficiency of the circuit and hinders the increase of the switching frequency. On the basis of the phase shift control technology, the output capacitor of the power tube and the leakage inductance of the output transformer are used as the resonant components, so that the four switching tubes of the full bridge converter are turned on at zero voltage in sequence to realize constant frequency soft switching. Due to the reduced switching process losses, the conversion efficiency can reach 80%-90%, and the switching stress does not occur too much. Therefore, the phase shift control full bridge type zero voltage switching pulse width modulation (PSC FB ZVS-PWM) conversion circuit is selected.

Phase shift control Full-bridge conversion circuit is one of the most widely used soft-switching circuits. It is characterized by simple circuit. Compared with traditional hard-switching circuits, it does not add components such as auxiliary switches. The principle is shown in Figure 1. It consists mainly of four identical power tubes and a high frequency transformer. E is the input DC voltage, T1~T4 are the switch tubes, D1~D4 are the body diodes, and C1 ~C4 are the output capacitors of the switch. Taking the first bridge arm as an example, using the transformer leakage inductance and the power output capacitor C1 to resonate, the leakage sense energy is released to the capacitor C1, the voltage on the capacitor is gradually reduced to zero, and the body diode D1 is turned on, creating T1. ZVS condition.

Figure 1 Schematic diagram of phase shift control full bridge conversion circuit

Figure 1 Schematic diagram of phase shift control full bridge conversion circuit

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