A Soft Start Circuit Applied to Charge Pump

Abstract

The invention discloses a soft start circuit applied to a charge pump, comprising a current source, a buffer drive unit, a first control switch, a second control switch and a transistor. The gate and drain of the transistor are connected to each other. In the soft start phase of the charge pump, the second control switch turns off the pull-up function of the driving module, and the driving module is used to drive the gate of the power transistor of the charge pump. When the first control switch is in the open state, the current of the current source flows into the transistor, the gate of the transistor generates a gate voltage, and the gate voltage is sent to the gate of the power transistor through the buffer drive unit to turn on the power transistor. When the first control switch is in the off state, the gate voltage of the transistor is cut off, and the drive module pulls the gate potential of the power transistor to a low potential to turn off the power transistor. The transistors of this circuit receive the current from the current source in the form of a diode connection to generate a gate voltage, which can effectively soft-start the charge pump when the current source current is too small.

Description

technical field [0001] The invention relates to the technical field of charge pump driving, in particular to a soft start circuit applied to a charge pump. Background technique [0002] A charge pump, also known as a switched capacitor voltage converter, is a DC-DC converter that uses a bootstrap capacitor to store energy. The charge pump can increase or decrease the input voltage and can also be used to generate negative voltages. [0003] see figure 1 , wherein the charge pump 3 is a schematic structural diagram of a charge pump in the prior art, including S1, S2, S3 and S4 as four power tubes (switch tubes), and a capacitor Cfly and a capacitor Cout. [0004] Q1 and Q2 are two non-overlapping clock signals, wherein the clock signal Q1 controls the on and off of the power transistors S1 and S3; the clock signal Q2 controls the on and off of the power transistors S2 and S4. [0005] When the clock signal Q1 is high, that is, when Q2 is low, the power transistors S1 and S...

AI Technical Summary

Problems solved by technology

[0012] Aiming at the deficiencies of the prior art, the present invention proposes a soft-start circuit applied to the charge pump, the transistors of the circuit receive the current of the current source in the form of a diode connection, and then generate the current used to control the grid of the power transistor S1 in the charge pump. Gate voltage, the gate voltage is only related to the current in the transistor, which solves the problem that the existing soft-start circuit cannot effectively start the power tube when the current source current is too small

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