Soft start device and method for switching power supply

Abstract

The invention relates to the technical field of a server and provides a switching power supply soft start device and method. The soft start device comprises a control chip, an MOSFET A and an MOSFET B. A pin 1 of the control chip is connected with the grid electrode of the MOSFET A, and the pin 2 is connected with the grid electrode of the MOSFET B; the drain electrodes of the MOSFET A and the MOSFET B are connected with the positive electrode of a DC power supply; the source electrodes of the MOSFET A and the MOSFET B are connected with a back-end capacitor C2; the positive and negative electrodes of the DC power supply are connected in parallel with a filter capacitor C1; and the control chip is used for starting the MOSFET A, and starting the MOSFET B according to the voltage value detected by a voltage detection circuit, and generating a Power good signal, so that in the board card starting or hot plug process, large instantaneous impact current is not caused, and MOSFET work safety is ensured effectively.

Description

technical field [0001] The invention belongs to the technical field of servers, and in particular relates to a soft start device and method for a switching power supply. Background technique [0002] With the development of the server, the power consumption of the board is increasing, and there are more and more filter capacitors at the input end of the switching power supply on the board, and the capacitance value is getting larger and larger. When the PSU is turned on or the board is hot-swapped, since the initial voltage on the capacitor is zero, a large instantaneous inrush current will be formed. Such a large instantaneous inrush current will often lead to PSU protection or even loss. In order to reduce the instantaneous inrush current, especially for boards that need to be hot-swapped, it is necessary to add a soft-start switch on the front end of the board to make the output voltage rise slowly. [0003] A soft-start switch is generally composed of a controller and a...

AI Technical Summary

Problems solved by technology

During the slow start of the soft-start switch, the MOSFET works in the saturation region, that is, the source and drain terminals of the MOSFET bear a large voltage, and the MOSFET also passes a certain starting current. At this time, the power loss on the MOSFET is relatively large, and it is easy to lose the MOSFET

Therefore, for the case where there are many filter capacitors on the board and the load current is large, the common practice is to connect multiple MOSFETs in parallel, but it is easy to cause uneven current among MOSFETs, and even a single MOSFET is still working at certain moments.

[0004] At the same time, as the power consumption of the board increases, the current passing through the soft-start switch is getting larger and larger. To obtain lower conduction loss, the MOSFET is required to have a lower resistance Rds(On), which is limited by the existing MOSFET technology. , to obtain low Rds(On) can only be achieved by reducing the thickness of the MOSFET drift region, and the impact is to reduce the withstand voltage value of the MOSFET. For the MOSFET participating in the soft start, the reduction in the withstand voltage value will seriously affect the safety.

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