COMMON FAULTS OF POWER BOARD
We are a Power Cord Manufacturers, and our products include 3 Pin Plug Power Cord, etc. Here is a brief introduction to the common faults of power strips.
Blown fuse In general, a blown fuse indicates that there is a problem with the internal circuit of the power supply. Since the power supply works under the condition of high voltage and high current, the fluctuation and surge of the grid voltage will cause the current in the power supply to increase instantaneously and cause the fuse to blow. The key point should be to check the rectifier diodes, high-voltage filter electrolytic capacitors, inverter power switch tubes, etc. at the power input end, and check whether these components have breakdown, open circuit, damage, etc. If the fuse is indeed blown, you should first check the various components on the circuit board to see if the surface of these components is burnt and whether there is electrolyte overflow. . It is necessary to pay special attention: when a component is found to be damaged, it must not be turned on directly after replacement. It is very likely that the replaced component will be damaged because other high-voltage components are still faulty. Be sure to conduct a comprehensive inspection of all high-voltage components of the above circuit. After checking and measuring, the fault of blown fuse can be completely ruled out. No DC voltage output or unstable voltage output If the fuse is in good condition, under load conditions, there will be no DC voltage output at all levels. This situation is mainly caused by the following reasons: open circuit and short circuit in the power supply, overvoltage and overcurrent protection circuit failure, auxiliary power supply failure, oscillation circuit not working, power supply overload, rectifier diode in high frequency rectifier filter circuit Breakdown, leakage of filter capacitors, etc
After measuring the secondary components with a multimeter and ruling out the breakdown of the high-frequency rectifier diode and the short-circuit of the load, if the output is zero at this time, it is certain that the control circuit of the power supply is faulty. If there is some voltage output, it means that the pre-stage circuit is working normally, and the fault is in the high-frequency rectifier filter circuit. The high-frequency filter circuit is mainly composed of a rectifier diode and a low-voltage filter capacitor to form a DC voltage output. The breakdown of the rectifier diode will cause no voltage output in the circuit, and the leakage of the filter capacitor will cause the output voltage to be unstable and other faults. The damaged components can be detected by statically measuring the corresponding components with a multimeter. Example: After a 24V DC motor power supply is powered on, there is no DC 24V output. Remove the power supply case and observe that the fuse is not blown and the circuit board has no obvious burnt or cracked components. Measure the AC input terminal when it is not powered on. The resistance value and the resistance value of the DC output terminal are normal, and the important components such as the switch tube, rectifier bridge, and rectifier tube are normal, so it is judged that there is no possibility of serious internal short circuit, and it is estimated that the protection circuit operates. After checking that this switching power supply adopts U3842 PWM control chip, we found out by looking up relevant information that when the voltage of terminal 3 of U3842 chip is higher than 1V, the internal current-sensitive comparator outputs a high level, and the PWM latch is reset to make the output closure. Power on and measure that the 3-terminal of U3842 is higher than 1 volt, and the 6-terminal has no output. After checking the relevant circuit, it is found that the voltage regulator D2 is broken down, as shown in Figure 3, so PC1 is turned on, causing the 3-terminal of U3842 to be a high level, so 6 There is no output at the terminal, the switch tube does not work, and there is no DC output on the DC side. Replace the voltage regulator tube D2 of the same type, and the fault is removed. Poor load capacity of power supply Poor load capacity of power supply is a common fault, which generally occurs in old-fashioned or long-working power supplies. Should focus on checking whether the Zener diode generates heat and leakage, the rectifier diode is damaged, the high-voltage filter capacitor is damaged, etc.
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We are a Power Cord Manufacturers.Let's take a look at what the power board does and how it works!
As the name suggests, the power board is a main board for power processing. The power processing methods are diversified according to the subsequent circuit requirements, such as:
Input and output types: alternating current (AC), direct current (DC), pulse, high voltage, low voltage, high frequency, low frequency, single channel, multichannel;
Transformation type: step-up, step-down, constant voltage, constant current, linear, nonlinear controllable;
Circuit mode: coil coupling type transformer, electronic device type switching power supply.
2. The working principle of the power board
1. After the power is turned on, the auxiliary power supply starts to work first, and provides a working voltage of positive 5 volts for the microprocessor control system of the main circuit board.
2. After starting up, the auxiliary power supply provides VCC-ON power supply for the PFC power factor correction circuit drive control circuit UCC28051 and the main switching power supply drive giant circuit DLA001, and the main switching power supply starts to work, providing positive 24 volts and positive 12 volts to the load circuit of the main circuit board. two voltages.
3. When the TV is in standby, the VCC-ON power supply of the PFC power factor correction circuit drive control circuit UCC28051 and the main switching power supply drive control circuit DLA00l is cut off, and the main power supply stops working.
3. The role of the power board
The power supply board is a functional circuit used in electronic equipment to convert the input power supply voltage (such as power frequency 220V~) into various levels of working voltage (such as 12V-, 15V-) required by the electronic circuit, and make it on a circuit board. It is called the power board.
Switching power supply is a kind of power conversion circuit. Different from linear power supply, switching power supply has high efficiency, small size and light weight. The average output voltage is adjusted by the on-off time of the switching tube. This power board is called a switching power board.
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