Soft startup circuit of switch power supply and its startup method

Abstract

The invention is concerned with the soft-start circuit of the switch power and its method, which is generating the second power with the first power. It includes: the controlling unit, which generates the impulse signal, the switch control signal and the first off-set signal, according to the exterior clock and the soft-start active signal; the off-set circuit, generates the first prearranged electric potential with the first power accordingly to make the electric potential of the switch control signal migrates to the first prearranged electric potential; the pressure drop control unit, according to the impulse signal and the first off-set signal to make the electric potential of the switch control signal migrates to the second prearranged electric potential from the first prearranged electric potential; and the switch unit, generates the second power according to the switch control signal and the first power. The inventions keeps the voltage of the switch control signal descends steadily, and makes the output second power of the switch ascends, which prevents the biggish peak current appearing in the process of soft-start.

Description

Technical field [0001] The invention relates to a switching power supply, in particular to a switching power supply supporting soft start operation. Background technique [0002] A switching power supply is used to convert power from one power supply to another. For example, a personal computer can supply power to external devices such as memory cards and digital players through the switching power supply. figure 1 Shown is a schematic diagram of a switching power supply in the prior art. Such as figure 1 As shown, the switching power supply 100 is used to convert a local power supply VPP into an external power supply VPPO to supply power to external devices. The switching power supply 100 includes a control unit 101, a switching unit PSD, and inverters INV1 and INV2. The control unit 101 outputs a clock signal 102 and a switch control signal VG according to an external clock CLK and a soft start enable signal EN. After the soft start operation ends, the control unit 101 stabil...

AI Technical Summary

Problems solved by technology

Correspondingly, the external power supply VPPO output by the switch unit PSD rises sharply to a high potential according to the switch control signal VG, and will generate a huge peak current due to the connection of devices that consume a large load current

Images