Overcurrent protection circuit and switching power supply

Abstract

According to the overcurrent protection circuit, when the absolute value of a voltage signal V1 representing the magnitude of the output current of the switching power supply is larger than a first set value and smaller than or equal to a second set value, the overcurrent protection circuit is switched on and off when the absolute value of the voltage signal V1 represents the magnitude of the output current of the switching power supply; when a timing time set value is reached, a constant-current control signal V8 is output to control the switching power supply to perform constant-current output at a first current value; when the absolute value of the voltage signal V1 is greater than a second set value, the constant current control signal V8 immediately controls the switching power supply to output at a second current value in a constant current manner, and when a timing time set value is reached, the constant current control signal V8 is output to control the switching power supply to output at a first current value in a constant current manner; the switching power supply applying the over-current protection circuit not only can meet the output capability during transient over-power, but also can control the working time of the switching power supply exceeding rated current to prevent overheating damage; meanwhile, the output current of the switching power supply is not greater than the rated current value of an internal device to cause over-current breakdown of the device.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a protection circuit when the switching power supply is overcurrent. Background technique [0002] With the rapid development of power electronics technology, the application of switching power supply is more and more extensive, especially the demand for switching power supply with high power, high power density, low cost and high reliability is increasing. When the load of switching power supply is relay, motor drive When the system or the load is in the state of frequent start and stop, the current value (also called transient current value, transient overpower current value) required during the load start-up process is often greater than the current value during normal operation (also known as It is called the rated steady-state current value, rated current value), and even reached 2 to 3 times. [0003] When selecting a switching power supply, if the switchi...

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Problems solved by technology

[0003] When selecting a switching power supply, if the switching power supply is selected based on the power when the load is started, the volume and cost of the switching power supply will increase greatly. Risk, so in order to meet the transient high current output demand, most switching power supplies will add over-current protection function in the control

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