Short-circuit protection circuit for switching power supply of frequency converter

Abstract

The invention relates to a short-circuit protection circuit for switching power supply of a frequency converter, comprising a main power circuit. The main power circuit is respectively connected to an RCD absorbing circuit, a PWM controller and an output rectification circuit. A feedback circuit is respectively connected with the PWM controller and the output rectification circuit. The short-circuit protection circuit further comprises an overvoltage protection circuit connected with the PWM controller and the feedback circuit. In the +5V rectification output circuit of the output rectification circuit, a restorable fuse is serially connected between a 5V rectifier diode and a resistor. The beneficial effects of the invention are that the invention protects the output of any circuit and has perfect protection function; when short circuit appears, on-the-job accident of the frequency converter is not caused and failure of elements is not caused.

Description

technical field [0001] The invention relates to a frequency converter switching power supply, in particular to a short circuit protection circuit of the frequency converter switching power supply. Background technique [0002] Depend on figure 1 , figure 2 It can be seen that the working principle of the short-circuit protection circuit of the existing switching power supply of the inverter is as follows: when the ±15V, +24V, and four-way +25V IGBT drive power supply short-circuits, the feedback voltage +V5F is far lower than 5V, and the PWM chip is fully Due to the sharp increase of the output current of the short-circuit winding, most of the energy provided by the primary side of the transformer is consumed, and the voltage of other windings also drops. Since the PWM chip requires a working current of about 10mA, by adjusting the resistance of R5, the auxiliary winding voltage VCC can drop below the minimum voltage of the PWM chip, and then the switching power supply en...

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Problems solved by technology

[0003] However, the above circuit structure has the following defects: when +5V is short-circuited, the +5V output power supply only outputs a lower voltage (about 3V), which is far from the feedback voltage (5V). At this time, the PWM chip outputs with a full duty cycle. input energy increase

Due to the low output voltage of this channel, although a short circuit occurs, the energy consumed is less than the energy increased due to the full PWM duty cycle, so the output voltages of other channels have risen, and the "hiccup" protection cannot be realized

The consequences are as follows: the rectifier diode of +5V output will be burnt out, and the driving voltage of +25V IGBT will rise, resulting in the gate and source voltage V acting on the IGBT. GE Rise may lead to damage of IGBT; rise of ±15V and +24V voltage may lead to failure of chips and other components

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