Switch power supply circuit with output short circuit protection function

Abstract

The switching power supply circuit with protection for output short circuit comprises a source manager composed of a charge circuit, a low-voltage protection circuit, a vibrator, a sawtooth generator, source management chip integrated with PWM signal control and drive circuit, light-coupling isolating transmission circuit, and error amplifier circuit; wherein, there is also a forced starting circuit connected between vibrator and the PWM circuit to generate some switch pulse with determined duty rate to start system during the VDD varies from small to large and shut the circuit after system starts, then the feedback loop controls and adjusts switch pulse width to keep system running. This invention decreases output power consumption, saves energy, and prevents burn to eliminate hidden danger.

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 output and rectification filter circuit 11. An error sampling circuit 12 and an error amplifier circuit 13 are com...

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

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