The switching power supply circuit is mainly composed of a fuse, thermistor, the interoperability filter, the bridge rectifier circuit, the filter capacitor, the switch oscillating integrated circuit, the switch transformer, the optical coupling device, and the three -terminal stabilizer.


1. Framer

The fuse in the power circuit is usually installed near the AC 220V input terminal, mainly to ensure the safe operation of the circuit. In the circuit, the fuse is generally cylindrical glass tube. When the circuit has a short circuit and other failures, the current will increase abnormally. At this time, the fuse will increase to a certain size in a certain size. The role of protecting circuit safety.

2. Thermistor


The thermistor resistance has the effect of resisting the circuit. Generally, when the device is turned on, the 220V AC voltage is charged with a capacitor after the fuse, thermistor, and bridge rectification. According to the characteristics of the capacitor, the instant charging current is the maximum, which may generate the surge current. The bridge -type rectifier and fuse in the class circuit cause impact and cause damage. In order to prevent the power from being impacted, the thermistor is usually added after the fuse.

When the resistance value of the armistor is large, the current limit effect is better, but the power consumption of resistance is also large. After working, the power circuit is wasted. In order to achieve a good current limit effect and save power, the negative temperature coefficient thermistor is often used in the power supply circuit for current.


The characteristics of negative temperature coefficient thermal number resistance (NTC) are:


The higher the temperature, the smaller the resistance. At room temperature, the resistance value is relatively large, and the resistance is generally 8-10Ω; when booting, it can play a better current limit; after the power supply is started, the working current passes through the thermoltage resistance, which makes it heated. (About 1-2Ω), the electric energy consumption is minimized after the power supply starts.

Positive temperature coefficient thermistor (PTC) features::

The higher the temperature, the larger the resistance, which is usually used in the compressor startup circuit of the refrigerator.


3. Mutual Filter

The interoperability filter is made of two sets of coils. The role is to eliminate the interference pulses of the external circuit through the interoperability to enters the circuit, and at the same time, the pulse signal in the circuit will not radiate to the grid to interfere with the grid.

4. Bridge rectifier circuit

The bridge rectifier circuit mainly exchange 220V voltage rectification to DC+300V voltage transmission. It is combined by four rectifier diode to form a bridge rectifier circuit according to a certain connection relationship.

In addition, a bridge rectifier pile in some circuits is used as a rectifier device. The pins output DC voltage, the circuit function and principle are the same as the circuit function and principle of the bridge rectifier circuit.

5. Filter capacitor


The filter capacitor is mainly used to filter the 300V DC voltage supplied by the bridge rectifier circuit, and the pulse component in the voltage is filtered, thereby changing the output voltage to a stable DC voltage.

Filter capacitors in power circuits are one of the easiest components to recognize, and it is usually the largest capacitor in the circuit. Negative polar signs are usually marked on the shell of the capacitor, which is convenient to confirm the polarity of the pin.

6. Switch oscillating integrated circuit

When working on a power supply circuit, the switch oscillating integrated circuit mainly provides the driving artery signal for the switch transformer.

The switch oscillating integrated circuit is different according to the different specific structures of the model, such as: some switching oscillating integrated circuit internal integrated switch transistor and oscillation circuit; some mainly include oscillation circuits, which work with external switches transistors.

7. Switch transformer

The switch transformer is a pulse transformer, which has a high operating frequency (1K ~ 50KHz). The winding and switching effect of the transformer (some independent installation, some integrated in the switch oscillating circuit) constitute the oscillation circuit. The second winding group is Obbacking from a winding, the main function is to turn high -frequency and high -voltage pulses into multiple sets of high -frequency low -voltage pulses.

8. Optical coupling device and three -terminal regulator

The main function of the optocoupler is to feedback the error signal of the output voltage of the inverter refrigerator switching power supply to the switch oscillating integrated circuit, and the switch oscillating integrated circuit is controlled according to the signal.

The three -terminal regulator is a DC stabilization integrated circuit with three pins, and the voltage voltage value of the three -terminal stabilizer of different models is also different.