Switching control circuit and method for providing additional base drive

Abstract

The present invention relates generally to switch mode power converters (SMPCs), and methods for providing additional base drive to bipolar transistors of SMPCs, and more particularly to switching control circuits for SMPCs having: inductive components , the inductive component connected to receive power from an input to the SMPC; a bipolar transistor connected to control current flow in the inductive component; an auxiliary power rail; a charge storage device, said charge storage means for supplying power via said auxiliary rail to a switching control circuit for driving said bipolar transistor; and a steering circuit for discharging current from an input to said bipolar transistor, thereby thereby providing amplified current to said charge storage device, said switching control circuit comprising: a base current line for connection to the base terminal of said bipolar transistor; an emitter current line for said an emitter current line for connection to the emitter terminal of the bipolar transistor; an auxiliary line for connection to the auxiliary power rail; and at least one reference line for connection to to a reference voltage; a base current switch configured to controllably connect a base current source to the base current line; an emitter current switch configured to configured to controllably connect said emitter current line to said reference line; a pilot element for discharging current from said emitter current line to said auxiliary line, said pilot element also for blocking said current according to a current or voltage bias; a base discharge switch configured to discharge current from said base current line to said reference line in a controllable manner; and an additional base drive line for connection to a series circuit comprising an additional base drive resistor and a current control element connected in series, the series circuit for releasing from the input current to the base terminal, the current steering element is used to block current flow from the steering circuit to the additional base drive resistor.

Description

technical field [0001] The present invention relates generally to switch mode power converters (SMPCs), and methods for providing additional base drive to bipolar transistors of SMPCs, and more particularly to switching control circuits for SMPCs. Background technique [0002] A low-cost bipolar junction transistor (BJT) is ideal for the main switch in off-line power converters because it offers high breakdown voltage and low on-state voltage. However, bipolar junction transistors generally require relatively high drive currents, and this can cause disadvantages, eg with regard to power dissipation. [0003] There is therefore still a need for improved drive schemes for main switches such as BJTs, for example in converters that are off-line and / or with main-side sensing. Such needs may relate specifically to cost, converter output power capability / rating and / or reliability, preferably in drive schemes addressing a wide range of bipolar transistors and the like. Additionall...

AI Technical Summary

Problems solved by technology

While this problem arises for MOSFET based converters, it is significantly exacerbated by the high current required by the BJT

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