Switch power supply circuit with output short circuit protection function

Abstract

A switching power supply circuit with an output short-circuit protection function, including a power manager, an optocoupler isolation transmission circuit, an error amplifier circuit, etc. The power manager is composed of a charging circuit, a low-voltage protection circuit, an oscillator, a sawtooth wave generator, and a PWM signal The control and driving circuit are integrated into a power management chip, which is characterized by: It also includes a forced start circuit, which is connected between the oscillator and the PWM signal control and driving circuit, and is used for the control circuit power supply VDD output by the low-voltage protection circuit During the starting process of the voltage from low to high, a number of switching pulses with a set duty ratio are generated to start the system. After the system is started, the circuit is closed, and the feedback loop of the system controls and adjusts the switching pulse width. to make the system work properly. When a short circuit occurs in the output of the switching power supply, the present invention reduces the output power consumption of the system, saves energy, and more importantly, can avoid the occurrence of circuit device burnout events, eliminate potential safety hazards, and play a protective role.

Description

technical field [0001] The invention relates to a switching power supply circuit with output short-circuit protection function. Background technique [0002] With the rapid development of science and technology, various electronic products are more and more used in people's daily life. For the power supply of various electronic products, the consumption of low-power AC-DC power supply is rising rapidly. In the case of low-power AC-DC power supply (adapter), flyback switching power supply is the most common one. At present, the typical circuit structure of the flyback switching power supply is as follows: figure 1 As shown, it includes: AC input rectification filter circuit 1, primary coil and switch circuit 2, power manager 100, power supply capacitor 5, auxiliary coil and output rectification circuit 6, optocoupler isolation transmission circuit 10, secondary coil and rectification filter circuit 11. An error sampling circuit 12 and an error amplifier circuit 13 are compo...

AI Technical Summary

Problems solved by technology

[0005] An obvious disadvantage of the above circuit is: when the output is short-circuited, the output voltage is lower than the normal voltage, and the voltage feedback loop maximizes the PWM duty cycle in order to stabilize the voltage. The maximum duty cycle will cause the transformer to transmit more energy to the output

This may cause diode D2, transformer T1 and other devices to burn out, which will bring potential safety hazards

And there is no protection when the output is short-circuited

Images