What should be checked when the adjustable DC stabilized power supply is damaged?
With the popularity of personal smart mobile devices, it has become one of the most important daily necessities for people. What are the main reasons for the damage of the adjustable DC regulated power supply in daily use? Today we will take a look at the solutions to the problems encountered by most engineers.
1. Line failure
Line faults, such as damaged power cords, failure to connect to the power supply, oxidation of contact terminals or poor contact. Focus on checking that the input and output lines are open. If a line fault occurs, it can be repaired by replacing the power cord.
2. The output voltage is too low
The main causes of low output voltage are:
1. Adjustable DC stabilized power supply load short circuit fault (especially DC/DC converter short circuit or poor performance) At this time, you can first disconnect and adjust all loads of the adjustable DC stabilized power supply circuit. Make sure the DC stabilized voltage is correct. Is the circuit disconnected or is the load circuit disconnected? If the load circuit is disconnected and the voltage output is normal, it means that the load is too heavy. If it is still abnormal, it means that the adjustable DC circuit is faulty.
2. The fault of the filter capacitor or rectifier diode on the output voltage side can be determined by the exchange method.
3. The performance of the arc extinguishing chamber decreases, the arc extinguishing chamber cannot work normally, the internal resistance of the power supply increases, and the load capacity decreases.
4. A bad switching transformer will not only reduce the output voltage, but also cause insufficient excitation of the arc extinguishing chamber, thus damaging the arc extinguishing chamber.
5. The 300V filter capacitor is defective, which will reduce the load capacity and output voltage of the power supply when the load is connected.
3. The output voltage is too high
Excessive output voltage is usually caused by a voltage-stabilized sensing circuit and a voltage-stabilized control circuit. In a closed loop consisting of a DC output, a sense resistor, an error sense amplifier such as the TL431, an optocoupler, a power control chip, and other circuitry, one of the components increases the output voltage. The fuse is OK and there is no output voltage. If the fuse is normal and there is no output voltage, it means that the adjustable DC stabilized power supply does not work or has entered a protection state. The first step is to check the startup voltage value of the startup pin of the power control chip. If there is no starting voltage or the starting voltage is too low, check whether the external components of the starting pin and the starting resistor are leaking. If the power control chip is normal, the above monitoring will help you find the fault quickly. If the start-up voltage is applied, it will be measured whether there is a high or low level transition at the output of the control chip when it is turned on. If there is no jump, it means that the control chip is damaged, the components of the peripheral oscillator circuit are damaged, or the protection circuit is faulty. Check the peripheral components by replacing the control chip. If replaced, most of the switch tubes are damaged or damaged.
4. Insurance burnt or blown up
Mainly look for bridge rectifiers, diodes, interrupters and large 300 volt filter capacitors. The fuse may be burned or blackened, or it may be due to a problem with the anti-jamming circuit. In particular, it should be noted that the failure of the arc extinguishing chamber will blow the fuse, thereby burning the adjustable DC power supply control chip and the current detection resistor. Even with insurance, a thermistor can easily burn out.
