Starting circuit for switching power supply

Abstract

The invention discloses a starting circuit for a high-voltage and wide-input range switching power supply. The starting circuit comprises a voltage-sharing part, a voltage stabilizing part, a current source part and an output circuit, wherein the voltage-sharing part consists of at least two stages of voltage-sharing circuits which are connected in series; the voltage stabilizing part is formed by connecting at least two stages of voltage stabilizing circuits in series; the current source part is formed by connecting at least two stages of current source circuits in series; an input source voltage is connected to the two ends of each of the voltage-sharing part and the voltage-stabilizing part which have the same stage; voltage-sharing points at which every two stages of voltage-sharing circuits are connected in series are connected with series-connection points of the voltage stabilizing circuits of the corresponding stages; the input end of the current source part is connected with the anode of the input source voltage; the control ends of each stage of current source circuits are connected with the voltage stabilizing output ends of the voltage stabilizing circuits of the corresponding stages; the output end of the current source part is connected with the input end of the output circuit; the output end of the output circuit is the output end of the starting circuit; after the input source voltage passes through the voltage-sharing part, shared voltages are output are input into each stage of current source circuits by the voltage stabilizing part to control the input source voltage sharing of each stage of current source circuits; or a switching-off circuit can be connected to switch the starting circuit off when the switching power supply works normally, so loss is reduced.

Description

technical field [0001] The invention relates to a start-up circuit applied to a switch power supply, in particular to a start-up circuit for a high-voltage, wide-range input switch power supply. Background technique [0002] In photovoltaic inverters and ultra-high-voltage direct current transmission systems, the voltage range is very wide, as low as one or two hundred volts and as high as more than two thousand volts, so it is difficult to design the auxiliary power supply of the system, especially the design of the high-voltage start-up circuit. On the one hand, it is necessary to find electronic components that can withstand high voltage. On the other hand, in terms of reliability, it is necessary to reduce the circuit loss of the startup part to prevent heat damage to key components. [0003] Currently commonly used switching power supply starting circuits (such as figure 1 As shown), including power resistors, capacitors, Zener diodes, auxiliary windings and diodes, it...

AI Technical Summary

Problems solved by technology

However, when the switching power supply works at high voltage input, the switching tube Q2 needs to withstand high voltage, and it is difficult to find a device that can withstand high voltage on the market. cargo risk

[0005] Therefore, the start-up circuit of the above-mentioned switching power supply is not suitable for high-voltage and wide-range input occasions due to its high loss and high cost.

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