Flyback switching power supply

Abstract

The invention provides a flyback switching power supply, which comprises a voltage input unit, a first starting resistor, a second starting resistor, a third starting resistor, a first capacitor, a peak current control chip, a primary side current detection circuit, an auxiliary power supply winding, a clamping circuit, a flyback transformer, a main voltage output circuit, a standby voltage output circuit, a first power switching tube and a power limiting unit, wherein one end of the power limiting unit is connected to the voltage input unit through the first starting resistor and the second starting resistor which are connected in series, and the other end of the power limiting unit is connected to a CS pin of the peak current control chip. The flyback switching power supply improves an overload or short-circuit protection ability when high voltage is inputted, devices are prevented from being damaged by overcurrent, and the power consumption of the power limiting unit is reduced.

Description

technical field [0001] The invention relates to the field of circuits, in particular to a flyback switching power supply with improved overload protection capability. Background technique [0002] The flyback switching power supply is widely used in the power supply of electronic products due to its advantages of low cost and small size. In a larger power flyback switching power supply system, a single-tube flyback switching power supply is usually selected and designed to work in a continuous conduction mode. [0003] figure 1 It is a circuit diagram of a flyback switching power supply in continuous current mode in the prior art. The principle of overload or short circuit protection of this circuit is: when overload or short circuit occurs, the current detection pin of the peak current control chip (such as UC2844) detects the primary side When the current reaches the upper limit of 1V, the drive signal of the switch tube is turned off, the rise of the primary current is ...

AI Technical Summary

Problems solved by technology

[0008] The technical problem to be solved by the present invention is to provide a solution for the problem of device damage caused by the inaccurate current limit point of the flyback switching power supply in continuous current mode when overload or short circuit and the problem of large power consumption when adding a power limiting resistor. A flyback switching power supply with a power-limiting unit, which enables the switch to improve the accuracy of the power-limiting point when the high-voltage input is overloaded or short-circuited, prevents the device from being damaged by over-current, and reduces the power consumption of the power-limiting unit

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