LED lamp drive power failure exclusion approach

If you want to learn to rule out switching power supply LED fluorescent tube failure, we have to its working principle and which components are easily damaged there was an understanding . When the mains input from the input terminal , the first component reaches the capacitor and inductor L -type or π -type filter circuit for filtering to eliminate surges in the mains voltage and the interference signal to improve power quality . Meanwhile, in the mains input is also connected in series with fuse, short circuit fault occurs when the power when the fuse blows, to avoid malfunction magnification. And now most of the switching power supply input and have also varistor . Such resistance when the voltage is normal , the resistance is infinite, does not affect the operation of the circuit . Once the voltage is too high , the varistor will be short , so that the current increases through the fuse , fuse blows, to avoid damage due to hypertension caused by other components .LED TUBE LIGHTS
After filtering the AC by a diode bridge rectifier circuit and a high-voltage large -capacity capacitor filter , the resulting high voltage of 300V DC voltage, after which the voltage via a resistor and a simple buck regulator into the oscillation control circuit to generate an oscillation signal , generated oscillation signal amplified by the power oscillating tube , with high frequency transformer, will be transformed into low-voltage AC voltage , low voltage AC voltage rectified and filtered once again after , you can generate a variety of available devices use a low-voltage DC . In addition, the primary voltage output , also has a feedback voltage sampling circuit , the current voltage feedback loop oscillation control circuit , once the main voltage due to load changes resulting voltage drift , the oscillation control circuit will change the oscillation pulse width in order to ensure that the output voltage stability. Meanwhile , when the load is shorted, sampled feedback signal will promptly notify the oscillation control circuit , the output voltage is stopped to avoid damage due to overload power .LED TUBE LIGHTS
So how do we detect it ?
The switching power supply have a basic understanding, we take a look fault detection and maintenance methods.
The first should observe the power fuse is damaged. If the fuse is damaged, can not rush to replace , you must first check whether there is a short circuit power supply . Methods: The electrical barrier test with a multimeter after AC power fuse terminal ( test point a ) , its normal resistance should be in the tens of kilohms or more, such as the resistance is zero , then there is AC power supply short circuit . In addition , we should focus on checking the power supply AC filter capacitor is damaged ; while if varistor , then you should also check the resistance .
If the above test result is normal , then we should detect power four rectifier diodes ( test point two ) . In the normal state, the diode forward resistance amounting to k ( with a multimeter × 1k block test ) , reverse resistance approaches infinity . If the test results are not normally found , replace . Along the investigation down, next thing is to test the power of the DC resistance of the parts ( test point three ) , its normal resistance is also number k, such as resistance is zero, then there is no DC short circuit. DC short circuit caused by more reasons , such as short-circuit damage to the filter capacitor , the power oscillation tube is damaged , the oscillation partially damaged manifold and external circuit may cause a short circuit phenomenon . At this point, should be noted that the replacement power oscillating tube , you must determine the oscillation manifold and external circuit is normal, otherwise it will cause damage to the power tube again .LED TUBE LIGHTS
So ruled out switching power above problems, mostly the fault exists in the oscillation control circuit , sampling feedback circuit or load. At this time, we should first check whether the power supply circuit oscillation Manifold normal ( test point four ) , its normal voltage should be about 10V ( Special note: The test voltage shall be conducted in the case of power , and there is high voltage power supply board electricity, so pay special attention to personal safety , do not attempt to directly touch any part of the power supply ) . If the point of no voltage or low voltage, a dropping resistor should first check whether the damage ; followed by re-examine the oscillation manifold and its external power supply circuit is normal. If the external circuit is not found fault , the proposed replacement oscillating manifold . Sometimes, the power supply does not have the output voltage may be due to load short-circuit caused by the power protection . For this power , we only need to disconnect the output line , check the output voltage is normal ( test point five ) , you can determine the fault location . Preceding troubleshooting , the final should also check the feedback circuit, generally focused on this part of the fault and its optocoupler amplifier circuit , we should pay special attention.LED TUBE LIGHTS