Active starting circuit of Boost full-bridge isolation converter and method

Abstract

The invention relates to an active starting circuit of a Boost full-bridge isolation converter and a method. An active switch Q6 and a resistor R constitute a low-loss active starting circuit of the circuit. In the starting process of the converter, the active starting circuit releases energy stored in a boost inductor by turning on the switching device Q6, the problem of inductor energy saturation in the starting process of the converter is thus solved, and the converter can be normally started. The switching device Q6 in the active starting circuit only works in the starting state of the converter. When the converter works in a working steady state, the switching device Q6 is turned off, and the conversion efficiency of the circuit will not be influenced.

Description

technical field [0001] The invention relates to the field of power electronics, in particular to a full-bridge isolated step-up DC conversion circuit and method. Background technique [0002] When the Boost full-bridge isolated converter starts, the output capacitor has no initial voltage. If it works directly in Boost mode, the duty cycle of the control circuit is at the maximum state. When the power switches are all turned on, the power supply voltage is added to the energy storage inductor. The current increases; when the switch tube is turned off, because the output voltage is very low and the power supply voltage is greater than the converted value of the transformer primary side of the output voltage, the current in the inductor continues to increase, that is, the energy stored in the inductor continues to accumulate and cannot be maintained within a cycle Balanced, the circuit will continue to charge the inductance, and the output voltage at this time is very low. Aft...

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Problems solved by technology

[0002] When the Boost full-bridge isolated converter starts, the output capacitor has no initial voltage. If it works directly in Boost mode, the duty cycle of the control circuit is at the maximum state. When the power switches are all turned on, the power supply voltage is added to the energy storage inductor. The current increases; when the switch tube is turned off, because the output voltage is very low and the power supply voltage is greater than the converted value of the transformer primary side of the output voltage, the current in the inductor continues to increase, that is, the energy stored in the inductor continues to accumulate and cannot be maintained within a cycle balance, the circuit will continue to charge the inductance, and the output voltage at this time is very low. After several cycles, the inductance energy cannot be released and will soon be saturated

If no measures are taken, the inrush current of the input inductor will be very large when starting, and even the power switch tube will be broken down.

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