Isolated DC-DC boost converter with pull-down active clamping branch circuits

Abstract

The invention belongs to the technical field of electricity, and relates to an isolated DC-DC boost converter with pull-down active clamping branch circuits. On the basis of a single-ended flyback type circuit topology, a resonant capacitor is connected in parallel on the primary side of a transformer, the pull-down active clamping branch circuits are in parallel connection at two ends of a drain source of a main switch tube; a high-frequency voltage doubling circuit is in cascade connection on the secondary side of the transformer; resonance oscillation is carried out on the resonant capacitor and an inductor on the primary side of the transformer which are in parallel connection, so that an original circuit becomes into bidirectional excitation, the utilization rate of a magnetic core is improved, and the voltage gain of isolated converter output for input is improved; the switching period of an auxiliary switch tube is the same as that of a main switch tube in the active clamping branch circuits, but each switching period of the auxiliary switch tube is a small period of time for conduction, the conduction loss is greatly reduced, the main switch tube and the auxiliary switch tube can realize soft switching, and a direct connection problem does not exist; asymmetrical voltage output by a secondary side winding of the transformer is effectively utilized through the high-frequency voltage doubling circuit in cascade connection on the secondary side of the transformer, so that the overall efficiency of the converter is improved.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of electricity, and relates to an isolated direct current-direct current (DC-DC) boost converter, in particular to an isolated DC-DC boost converter with a pull-down active clamping branch. [0003] Background technique: [0004] The traditional isolated DC-DC boost converter topology circuit has five forms: forward type, flyback type, half-bridge type, full-bridge type, and push-pull type. Among them, the structure of the forward type and flyback type circuits is simple, Low cost and easy to control, but there are disadvantages such as one-way excitation of the transformer, easy saturation of the magnetic core, low utilization rate of the magnetic core, difficulty in increasing the power, and difficulty in realizing soft switching control; the two-way excitation of the transformer in the half-bridge and full-bridge circuits, The utilization rate of the magnetic core is high, and the power can be incr...

AI Technical Summary

Problems solved by technology

[0004] The traditional isolated DC-DC boost converter topology circuit has five forms: forward type, flyback type, half-bridge type, full-bridge type, and push-pull type. Among them, the structure of the forward type and flyback type circuits is simple, Low cost and easy to control, but there are disadvantages such as one-way excitation of the transformer, easy saturation of the magnetic core, low utilization rate of the magnetic core, difficulty in increasing the power, and difficulty in realizing soft switching control; the two-way excitation of the transformer in the half-bridge and full-bridge circuits, The utilization rate of the magnetic core is high, and the power can be increased, but there is a bias problem, and the upper and lower bridge arms are easy to pass through, the circuit control is relatively difficult, and the reliability is low; the transformer of the push-pull circuit is also bidirectionally excited, and there is no direct connection between the upper and lower bridge arms problem, but there is still a magnetic bias problem, and the transformer needs to be tapped, the design is difficult, and soft switching cannot be realized

In recent years, a new circuit topology of the isolated DC-DC boost converter has emerged, that is, the active clamp flyback circuit topology. This topology circuit can realize soft switching through resonance, and has a simple circuit structure and no shoot-through problem. , low cost, easy control, etc., have been applied to the front-end circuit of solar micro-inverters, but this new topology still has one-way excitation, the magnetic core is easy to saturate, the utilization rate of the magnetic core is low, and the power is difficult to increase, etc. problem, and the auxiliary switch tube of the active clamp branch is complementary to the main switch tube, and the conduction loss of the auxiliary switch tube is relatively large, which restricts its further popularization and application

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