Switching power supply control device and switching power supply

Abstract

The invention provides a switching power supply control device and a switching power supply. According to the switching power supply control device, a current sensing resistor short circuit protection module is arranged, when the switching tube of the switching power supply is conducted and when the current sensing resistor short circuit protection module detects voltage at two ends of a current sensing resistor of the switching power supply is lower than a predetermined value in a predetermined time period, that is, the current sensing resistor at the moment is short-circuited, the current sensing resistor short circuit protection module generates current sensing resistor short circuit protection signals; and besides, a driving controller controls on and off of the switching tube according to the protection signals, the switching power supply control device is thus closed, burning of the switching power supply is prevented, and error protection does not happen.

Description

technical field [0001] The invention relates to the technical field of power supply control, in particular to a switching power supply control device and a switching power supply. Background technique [0002] figure 1 It is a typical switching power supply circuit. After the AC power is rectified by full wave (diodes D11, D12, D13, D14 form a rectifier bridge), it is converted into high-voltage DC by a π-type filter circuit composed of capacitors C12, C13 and inductor L11. D13 and C11 on the primary side form a secondary rectification and filtering network, which rectifies and filters the voltage on the secondary side of the transformer and then outputs it. The starting circuit composed of R13 and C14 derived from the π-type filter circuit provides the starting voltage for the control chip; the resistors R14 and R15 form a feedback voltage divider network, and the sampling circuit inside the control chip samples the feedback winding Lk through the feedback voltage divider ...

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Problems solved by technology

[0004] In the process of realizing the present invention, the inventors found that there are at least the following problems in the prior art: the scheme of screening out this part of defective products during the test process has low efficiency and high cost; the scheme of limiting the conduction time of the main side inductance is The inductor current is not only related to the conduction time of the switch tube T1, but also related to the current rising slope. When the input voltage is low, the rising slope of the main side inductor current is small. If the main side Ton is set too small, it will easily lead to false protection. When the input When the voltage rises, the rising slope of the inductor current on the main side will increase, and the peak value of the current will also increase within the same period of time. If the Ton setting on the main side is too large, it will also cause bombing, so the solution of fixed on-time is often used in It will fail to protect when the input voltage is low, and it will fail when the input voltage is high

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