Common Fault Analysis and Troubleshooting of DC Stabilized Power Supply
Brief working principle of DC regulated power supply
DC regulated power supply is divided according to the principle of voltage regulation, and generally includes two categories: series regulated power supply and switching regulated power supply. The two types of DC regulated power supplies have their own advantages and disadvantages: the series regulated power supply circuit is simple, the ripple is small, but the efficiency is low. The switching regulated power supply has high efficiency and small size, but the circuit is complex and has a great impact on the surrounding electronic systems. At present, the application of switching regulated power supply is more and more extensive.
1 Basic principle of series DC regulated power supply
The circuit forms of the series DC regulated power supply are various, but they all have similarities in essence. Composition block diagram of a general series DC regulated power supply
In general, the output voltage of the DC stabilized power supply is low, and the AC input voltage is generally about 220 V of the mains. Therefore, a power frequency transformer with a power that meets the requirements is first required to reduce the 220 V voltage to an appropriate level, and then The bridge circuit composed of a rectifier bridge or a rectifier diode is used for rectification, then filtered by a capacitor, and finally stabilized by an integrated voltage stabilizer or a series voltage regulator circuit composed of transistors and other circuits to obtain the required DC output voltage.
Fault Analysis and Troubleshooting Methods of DC Stabilized Power Supply
1) Fault 1: No output voltage, that is, the output voltage is 0 V
The output voltage of the circuit is zero, which means that the circuit has no output. It can be easily seen from the analysis of the input end of the circuit to the output end that if any of the following conditions exists in the circuit, the circuit will have no output voltage.
①The power cord and output wire are faulty or poorly connected,
②The fuse is blown or open circuit,
③transformer open circuit, ④bridge rectifier circuit open circuit,
⑤ capacitor short circuit,
⑥resistor open circuit, ⑦transistor open circuit,
⑧ The voltage regulator tube is open.
How to judge where
A cause? It can be tested according to the following steps. If a fault is found, it can be repaired. If the fault is eliminated, it is not necessary to proceed to the next step:
Step 1: Check whether the plugs and interfaces of the power cord and output wires are loose, check whether the wire body is damaged, use a multimeter to measure whether the voltage at the interface is consistent with the voltage on the socket, and measure their continuity. If there is a fault, you can directly adjust and replace the wire manually.
Step 2: Take out the fuse to see if it is blown, or there is a phenomenon of poor contact. If the fuse is blown, just replace the fuse with corresponding parameters.
Step 3: Open the machine cover and observe whether there are components burnt out, wires are disconnected, and whether the circuit board is open-circuited or disconnected. If there is no visual fault, use a multimeter to further measure the continuity between the units and find that After a failure, replace the component or re-weld or re-wire the open circuit.
2) Fault 2: The output voltage is inaccurate, that is, the voltage is higher or lower than the normal voltage, and it is not adjustable
When the circuit output is not punctual, we can use a multimeter or an oscilloscope to test the performance of each unit circuit. If a problem is found, we can test whether the independent components in the unit circuit are charged or not. Common faults mainly have the following reasons.
