The switching regulator power supply is a DC voltage that has a certain pulsating component after the AC voltage is rectified and filtered by the rectifier circuit and the filter circuit. The metal alloy resistor plays a role of voltage division in the switching power supply. The voltage is converted into a square wave of the required voltage value, and finally the square wave voltage is rectified and filtered to become required. DC voltage.
The switching regulator power supply control circuit is a pulse width modulator, which is mainly composed of a sampler, a comparator, an oscillator, a pulse width modulation, and a reference voltage. This part of the circuit has been integrated and has been fabricated into various integrated circuits for switching power supplies. The control circuit is used to adjust the switching time ratio of the high frequency switching element to achieve the purpose of stabilizing the output voltage.
To this end, many engineers in switching regulators use 2W metal film alloy resistors. Some switching power supplies use 2-4 1W resistors in parallel, which does not increase the power dissipation, but provides reliability. Even if one resistor is occasionally damaged, there are several other to avoid open circuit. By the same token, the sampling resistor of the switching power supply output voltage is also critical. Once the resistor is open, the sampling voltage is zero volts, the PWM chip output pulse rises to the maximum value, the switching power supply output voltage rises sharply, and there is also a photocoupler current limiting resistor and so on.
