Precharging circuit and method for DC-DC boost converter

Abstract

The invention discloses a precharging circuit and method for a DC-DC boost converter. The reference current flowing through a reference transistor is adjusted to be kept unchanged; the drain voltage of the reference transistor is controlled to change along with the drainage voltage of a power transistor, so that the reference transistor and the power transistor from a current mirror circuit in the precharging process, and a constant mirror image current is used as a precharging current through a mirror image of the power transistor to the reference transistor, and thus the precharging current of the precharging current is kept unchanged. According the precharging circuit and method disclosed by the invention, the output voltage can be boosted by the precharging, and the precharging current can be kept unchanged in the precharging process, and thus the requirement of rapid load boost is met. Furthermore, according to the technical scheme, the precharging current is controlled to low in boost circuit and long in maintenance time by a precharging control technology, and therefore the precharging circuit has lower circuit loss and higher stability.

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...

AI Technical Summary

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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