Author ：Iflowpower – Portable Power Station Supplier
1. In general, the fuse tube is typically, the fuse tube fuses that there is a short circuit or overcurrent failure of the internal circuit of the battery charger. This is because the charger is working for a long time in a high voltage, a large current, is higher than the failure rate of internal devices.
In addition, the fluctuations of the grid voltage can cause the current to increase the current in the charger and blow the fuse. Maintenance method: First carefully check the various components above the board to see if the appearance of these components is blurred or an electrolyte overflow, and there is no difference. The resistance value of the power input is then measured.
If less than 20ok, the rear end has a local short-circuit phenomenon, and then measures the value of 4 rectifier diode positive, anti-resistance values, and two current limiting resistors. See if there is short circuit or burning The final decreases whether the power filter capacitor can perform normal charge and discharge, the switch power tube breaks down damage, the UC3842 and the surrounding components break through, burn bad, etc. To explain, because of the road measurement, it is possible to make the measurement result is incorrect or false, so the component can be welded to measure.
If there is still not the above situation, measure whether the input power cord and output power cord are short-circuited. In general, in the fuse fuck fault, the rectifier diode, the power supply filter capacitor, the switching power tube, the UC3842 is the loss piece, the probability of damage is more than 95%, and it is easy to inspect these components, it is easy to exclude the fault. 2.
No DC output or voltage output is unstable, if the fuse is intact, under the lanes of the load. This type of failure requires: overpressure, overcurrent protection circuit has an open circuit, short circuit phenomenon; Zhenyi circuit does not work The power supply is overweight, the rectifier diode is broken in the high-frequency rectification filter circuit: filter capacitor leakage, etc. Maintenance method: First, measure whether the components of the high-frequency pulse transformer is damaged by the multimeter: Exclusions high frequency rectifier diode breakdown, the load is short, and then measure the DC voltage of each output, if the output is still zero It can be definitely the control circuit of the power supply out of the fault.
Finally, the high-speed filter circuit is static to measure whether the rectifier diode and the low-voltage filter capacitor are damaged. If the above components are damaged, the new components are replaced, and the general fault can be excluded. However, pay attention to: Output line is broken or soldering, the soldering can also cause this failure, pay attention to this situation during maintenance.
3. There is no DC output, but the insurance silk is intact this phenomenon that the charger does not work, or enters the protection state after work. Maintenance method: First, it should be judged whether or not the changing control chip UC3842 of the charger is in the status of Wangzuo or it has been damaged.
The specific judgment method is to add the 7 foot pair of battery voltages of UC3842. If the 7 foot voltages are normal and 8 feet are + 5 ∨ voltages, 1, 2, 4, 6 feet also have different voltages, then the circuit has Locking, UC3842 is basically normal. If the 7 foot voltage is low, the remaining pin is no voltage, then UC3842 is damaged.
The most common damage is 7 feet to break through, 6, 7 feet breakdown and 1, 7 foot pair. If these few feet are unwaped, the charger still does not start normally, and it is also shown that UC3842 is damaged and should be replaced directly. If it is determined that the chip is not bad, it is checked whether the current limit resistance of the gate is soldered, the solder welding or variable value and the switching power tube itself are poor performance.
In addition, the power output line is disconnected or adversely caused to cause this failure, so it should also be paid attention to during maintenance. 4. DC voltage output excessive failure is often abnormal by the regulated sampling and regulator control circuit, in charge, DC output, sampling resistance, error sampling amplifier, optocoupler, power control chip, etc.
A closed control loop, any problem can result in elevation of voltage. Maintenance method: Since the charger has an overvoltage protection circuit, the output voltage is too high will first make the overvoltage protection circuit action. So this fault, we can disconnect the overvoltage protection circuit, so that this pressure protection circuit is not used, then measures the power main voltage of the power-on instant.
If the measured value is more than 1V higher than the normal value, the reason for excessive output voltage is indeed in the control loop. At this time, it should be heavily detected whether the sample resistance varies or damage, the precision reference voltage source (TL431) or the optocoupler (PC817) is poor performance, deterioration or damage. The precision reference voltage source (TL431) is extremely easily damaged.
We can discriminate the precision stabilizing amplifier by the following method: Connect the reference terminals of the TL431 to its cathode (Cathode), the resistance of the string 1OK, access 5 ∨ voltage. If the anode and the cathode are 2.5V, and the waiters are still 2.
5, it is a good tube, otherwise it is a bad tube.
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