Maintenance Methods For Common Failures Of AUTOMATIVE BATTERY CHARGER
Maintenance methods for common failures of AUTOMATIVE BATTERY CHARGER
Because the input circuit of AUTOMATIVE BATTERY CHARGER works in high voltage and too current, the failure rate is highest. Such as high voltage high current rectifier triode, filter capacitor, switch power tube, etc. The second most vulnerable is the rectifying diode, protective diode, filter capacitance and current-limiting resistance of the output rectifier. Again, the feedback part of the pulse width modulation controller and the protective circuit part.
1. Fuse of fuse
In general, the internal circuit of the AUTOMATIVE BATTERY CHARGER is faulty or short-circuited. This is because the AUTOMATIVE BATTERY CHARGER is working in high voltage and high current condition, the failure rate of internal devices is high. In addition, the voltage fluctuation of the power grid will cause the electric current of the AUTOMATIVE BATTERY CHARGER to increase instantly and fuse the fuse.
Method of repair: first, check all the components on the circuit board to see whether the appearance of these elements is burnt or that there is an electrolyte overflow. To measure the power input end resistance, if less than 20 ok Ω, illustrate the back-end to have local short circuit phenomenon, then measured 4 rectifier diode is only, the resistance value and two current limiting resistor value, the presence of short circuit or burn out; Finally, it is necessary to measure whether the power filter capacitor can carry out normal charging and discharge, whether the switching power tube is damaged, the UC3842 and the surrounding components are punctured or burnt. It is important to note that because it is in the road measurement, it is possible to make the measurement result wrong or to cause misjudgment, so that the components can be welded and measured when necessary. If this is not the case, then measure the internal short circuit of the input power line and the output power line. Generally, in the fuse fusing failure, rectifier diode, the power filter capacitor, switch power tube, UC3842 is wearing parts, the probability of damage can reach more than 95%, to inspect these components, it is easy to troubleshoot.
2. No dc voltage output or voltage output instability
If the fuse is in good condition, in the condition of the load, the reason for this type of failure is: overpressure, overcurrent protection circuit to open circuit, short circuit phenomenon; The consumption circuit is not working; The power load is too heavy, and the rectifier diode in the high frequency rectifier filter circuit is punctured: the filter capacitor leakage and so on.
Maintenance methods: first, AUTOMATIVE BATTERY CHARGER the various components of high frequency pulse transformer is measured with a multimeter for damage: ruled out high-frequency rectifier diode breakdown, load short circuit, and then measure the dc voltage at the output, if the output is zero at this moment, is to be sure there is something wrong with the power of control circuit, and finally in the high frequency filter circuit is measured with a multimeter static rectifier diode and low pressure filter capacitance is damaged, if the components are damaged, replace the new components, general fault can be ruled out. However, it is important to note that this kind of fault can be caused by wire breakage or welding and virtual welding, which should be paid attention to during maintenance.
3. No dc voltage output, but the insurance silk is intact
This phenomenon indicates that the AUTOMATIVE BATTERY CHARGER is not working, or has entered protective status after work.
Repair method: the first step should be to determine whether the AUTOMATIVE BATTERY CHARGER's variable control chip UC3842 is in the king's state or has been damaged. Specific judgment method is: add 7 feet of voltage, electric logging UC3842 7 voltage normal feet a + 5 and 8 feet ∨ voltage, 1, 2, 4, 6 feet will have different version for different voltage, the circuit has rev vibration, UC3842. If the power of the foot is low and the rest of the tube has no voltage, the UC3842 has been damaged. The most common damage is 7 feet to the ground, 6, 7 feet to the ground and 1, 7 to the ground breakdown. If these feet are not worn, and the AUTOMATIVE BATTERY CHARGER cannot be started properly, it also indicates that UC3842 has been damaged and should be replaced directly. If the chips are not bad, check to see if the limit resistance of the grid is not soldering, virtual or variable, and whether the power tube of the switch is not performing well. In addition, the power output line breaking or poor contact can also cause this failure, so should be noticed during maintenance.