As the module power supply is widely used in various fields of electronic equipment, it is inevitable that there will be overcurrent, overvoltage or short circuit phenomenon in the use process due to other factors. In order to protect the product performance, the power module will be designed with overcurrent and short circuit protection functions. The following is a brief discussion of several ways of overcurrent protection.

Type I: Rated current droop type

Burp type, self - recovery. The principle is to check the circuit to see if there is any flow, and then feedback to the control circuit to close the output, after a certain period of time if the flow is also checked, feedback control, until the flow disappeared.

Second: constant current type

The product maintains a constant current value, and since the current value is greater than the full load, the design power margin is greater than the nominal.

The third type: constant power type

When an overcurrent occurs, the output power remains constant and the current increases, which is protected by reducing the output voltage.

Overcurrent protection is the protection of module power supply or load in case of short circuit or overload of output. The principle of overcurrent protection is that when a phase-to-phase short-circuit fault occurs in the power grid, the current will suddenly increase and the voltage will suddenly drop. According to the requirement of line selectivity, the operating current of the current relay will be adjusted. When the fault current in the line reaches the action value of the current relay, the action of the current relay shall selectively cut off the fault line according to the requirements of selectivity of the protection device.

For current passing current protection, the general control method is turn-off or current-limiting, and the overcurrent circuit is generally fusing current limiting protection or sampling resistance to obtain circuit signals. Current-limiting fuse protection is widely used in switching power supply, power supply module circuit, the fuse has since the recovery and irreversible, PPTC is a kind of irreversible, when an exception occurs, the operation principle of the fuse is current when power increases to a certain strength, current leads to temperature overheat blown fuse, input circuit disconnection.

Sampling the acquisition current-limiting resistance protection, pictured above is the LM317 current limiting protection circuit, 2 p connector to load, in which R is the sampling resistor, once too much electricity, capacitance charging MC1, triode charging more than 9013 conduction voltage, output voltage of the LM317 fall below its reference voltage, also can is about 1.25 V, thus protecting the load.

Overcurrent protection mainly includes short circuit protection and overload protection. Short circuit protection is characterized by large setting current and instantaneous action. Electromagnetic current tripping devices, relays and fuses are commonly used as short-circuit protection elements. Overload protection is characterized by low setting current and inverse time - limit action. Thermal relays and delay electromagnetic current relays are commonly used as overload protection elements.