Boost full bridge isolation type converter and composite active clamping circuit thereof

Abstract

The invention provides a Boost full bridge isolation type converter and a composite active clamping circuit thereof. The composite active clamping circuit is applied to a full bridge and boost type topological circuit with an isolation function; the primary side oscillation voltage of a high frequency transformer is suppressed effectively, so that danger of breakdown of a switching tube is lowered, and working reliability of the system is improved; in addition, the energy absorbed by a capacitor is transferred to the output end in a no-loss manner; compared with an RCD buffer circuit, the switching power supply efficiency is improved; compared with a passive no-loss absorption circuit, the voltage stress of the switching tube is lowered, and the circuit can be suitable for power electronicproducts, such as a switching power supply and the like used in occasions with relatively high switching frequency; and the Boost full bridge isolation type converter can realize no loss of energy and is also suitable for occasions with relatively high switching frequency.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a Boost full-bridge isolated converter and a composite active clamping circuit thereof. Background technique [0002] Boost (boost) full-bridge isolated converter is a DC-DC conversion topology that can achieve both a large boost ratio and electrical isolation. It is used in electric vehicle systems, battery energy storage systems, renewable energy power generation and superconducting There are broad application prospects in the field of energy storage systems. Compared with other topologies, this type of topology has the characteristics of overcurrent and short circuit protection because the inductance of the energy storage transformer can limit the current when the load is overloaded or even short circuited, and the switching tube of the main circuit is easy to realize soft switching. It is widely used in the field of power electronic products such as switching power...

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Problems solved by technology

[0006] But this kind of topology also has a serious defect: the actual circuit is not ideal, there is always stray inductance in the circuit, the junction capacitance of the power switch tube, the leakage inductance of the isolation transformer, and the leakage inductance of the primary winding of the high-frequency transformer T Sense L lk When the switch tube of the bridge arm switches from the straight-through state to the conduction state of the opposite arm, because there is no release circuit, the energy in the inductance cannot flow into the primary side of the transformer instantaneously, and the junction capacitance of the switch tube will resonate with the leakage inductance of the primary side of the transformer , so a high surge voltage will be generated at both ends of the switch tube. If it is not suppressed, the voltage stress of the power switch tube may exceed the safe operating range of the device when the circuit is working, and each switch tube will be damaged due to overvoltage. breakdown, reducing circuit reliability

Although the RCD snubber circuit has a simple structure and low price, due to the existence of stray inductance and capacitance in the circuit, high voltage spikes will still be generated, and the energy absorbed by the capacitor will be consumed by the resistor, which will reduce the efficiency of the entire system, so Only suitable for occasions that do not require high conversion efficiency

[0009] The second type: passive lossless absorption technology, such as Figure 5 As shown, in the current source type, especially the full-bridge boost topology with isolation function, the buffer circuit can effectively suppress the oscillation voltage of the primary side of the high-frequency transformer, and at the same time, the energy of the leakage inductance of the transformer is fed back to the power supply without loss. , but the large LC resonance at high frequency increases the voltage stress and conduction loss of the power switch tube, which can only be applied to occasions where the switching frequency is lower than tens of kHz to ensure high conversion efficiency

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