Short-circuit protective circuit

A short-circuit protection circuit and short-circuit protection technology, which is applied to emergency protection circuit devices, circuit devices, emergency protection devices with automatic disconnection, etc., can solve problems such as low reliability, manual reset, and large short-circuit loss of switching power supplies, and achieve Effects of improving reliability, reducing operating current and loss

Inactive Publication Date: 2003-07-16
ZTE CORP
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  • Abstract
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Problems solved by technology

Since this solution only limits the current peak value of the main circuit, it has been frequently protected and restored in the short-circuit state, and the working current of the main circuit is still very large. There are problems such as high residual voltage of the short-circuit output of the switching power supply, large loss, and low reliability.
[0003] U.S. Patent US5,400,206 "Short circuit and overload protection circuit which allows a predetermined number of reconnection attempts" uses a short circuit

Method used

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[0014] Combine below figure 1 , 2 To further explain the present invention:

[0015] by figure 2 The parallel branch composed of the first capacitor C1 and resistor R2 is connected across the cathode of the diode VD1 and the ground to form the delay circuit 101; the parallel branch composed of the second capacitor C2 and the resistor R4 is connected in series with the resistor R5 The threshold setting circuit 102 is formed across the VREF power terminal and the ground; the hysteresis circuit 104 can be realized by the resistor R3; the short circuit overcurrent detection circuit 103 can be realized by the comparator D1;

[0016] The VCC port supplies power to the comparator D1 and provides a pull-up level. D1 is an open-collector comparator. It is connected to the VCC port through a pull-up resistor R1. If a comparator or operational amplifier that is not an open collector is used, the pull-up resistor R1 Can be removed

[0017] VREF is a stable DC voltage used to supply power to ...

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Abstract

A short-circuit protecting circuit is composed of a time delay circuit for holding the sampled output current level of power unit for PWM switching power supply for a certain time and slowly lowering it to become a continuous signal, a short-circuit current threshold setting-up circuit for generating threshold level, an over-current detecting circuit for comparing the output of time delay circuit with the said threshold level and making judgement, and a lagging circuit for forming window comparactor, elongating short-circuit protecting signal, feeding the short-circuit protecting signal back to threshold setting up circuit, and improving the anti-interference power of over-current detecting circuit.

Description

technical field [0001] The invention relates to the field of switching power supplies, in particular to a current-type pulse width modulation (PWM) switching power supply. Background technique [0002] At present, the application of switching power supply is more and more extensive. In the protection function of switching power supply, a short circuit protection circuit is generally required to prevent the switching power supply from damaging the power supply and load due to excessive operating current when it is short-circuited. The performance of the short-circuit protection circuit directly affects the reliability of the entire power supply. At present, most of the short-circuit protection circuits in switching power supplies use the current peak limit circuit inside the pulse width modulation chip to detect the working current of the primary side of the transformer, and limit its peak value to achieve the function of short-circuit protection. Because this solution only ...

Claims

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Application Information

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IPC IPC(8): H02H3/06H02H3/093
Inventor 甘旭王满堂
Owner ZTE CORP
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