An isolated dc-dc boost converter with pull-up active clamping branch and its control method

Abstract

The invention belongs to the field of electrical technology, and relates to an isolated DC-DC boost converter with a pull-up active clamping branch and a control method thereof. On the basis of a single-ended flyback circuit topology, the original transformer A resonant capacitor and a pull-up active clamping branch are connected in parallel, and a high-frequency voltage doubler circuit is cascaded on the secondary side of the transformer. The resonant capacitor connected in parallel resonates with the primary inductance of the transformer, making the original circuit two-way excitation and improving the magnetic core. Utilization, and at the same time improve the voltage gain of the output to input of the isolated converter; the switching period of the auxiliary switching tube of the active clamping branch is the same as that of the main switching tube, but the auxiliary switching tube is only turned on for a short period of time in each switching cycle, and the conduction The pass-through loss is reduced, and both the main switch tube and the auxiliary switch tube can realize soft switching, and there is no through problem; the high-frequency voltage doubler circuit cascaded on the secondary side of the transformer makes effective use of the asymmetrical voltage output by the secondary winding of the transformer, thereby The overall efficiency of the converter is further improved.

Description

Technical field: [0001] The invention belongs to the field of electrical technology, and relates to a new topology of an isolated DC-DC (DC-DC) boost converter and a control method thereof, in particular to an isolated DC-DC with a pull-up active clamping branch Boost converter and its control method. Background technique: [0002] 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 h...

AI Technical Summary

Problems solved by technology

[0002] 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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