Precharging circuit and method for DC-DC boost converter

Abstract

The present invention discloses precharge circuits and methods for DC-DC boost converters. In one embodiment, a precharge method for a DC-DC boost converter having a current mirror circuit that includes a reference transistor and a power transistor, can include: (i) maintaining a reference current flowing through the reference transistor as substantially constant; (ii) maintaining a drain-source voltage of the reference transistor and a drain-source voltage of the power transistor as substantially equal; and (iii) obtaining a substantially constant mirror current by reflecting the reference current through the power transistor to operate as a precharging current of a precharge circuit.

Description

technical field [0001] The invention relates to the technical field of power electronics, and more specifically, to a precharging circuit and a precharging method used in a DC-DC step-up converter. Background technique [0002] The DC-DC boost converter can be applied to a variety of different electronic devices. During the startup process of the DC-DC boost converter, in order to avoid damage to the electronic equipment due to the strong inrush current during startup, it is generally Pre-charge before work, that is, pre-charge to make the output voltage closer to the input voltage. Therefore, in the circuit design of the DC-DC boost converter, the pre-charging circuit is an indispensable link. [0003] refer to Figure 1A , shows a traditional pre-charging circuit, its power transistor PFET and reference transistor P1 form a current mirror circuit, and the drain voltage of the power transistor PFET is used as the output voltage. The voltage is precharged to make it rise t...

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Problems solved by technology

The disadvantage of this circuit is that as the output voltage continues to rise, the drain-source voltage difference of the power transistor PFET will gradually decrease, so the charging current will also decrease, as Figure 1B shown, for Figure 1A The working waveform diagram of the pre-charging circuit shown, the charging current I charge With the output voltage V out decreases with an increase in the output voltage V out close to the input voltage V in , the charging current I charge It will drop to a very low level, even close to zero, which will cause some subsequent larger loads to fail to start, limit the size of the load during the start-up process, and cause a delay in the start-up time of the DC-DC boost converter

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