Switching power supply failure check

The principle of the switching power supply is roughly the same HP3748 printer supporting voltage output switching power supply manufacturer, for example, where the works of friends troubleshooting method to explain the switching power supply. Understand the working principle If you want to learn to rule out the failure of the switching power supply, we must first understand the working principle of the switching power supply, and which components are easily damaged. When the mains input from the input, first to the capacitance and inductance L-type or -type filter circuit for filtering, to eliminate the surge in the mains voltage and interference signals, improve power quality.
The same time, in the mains input is also connected in series with the fuse when the power supply short circuit fault, the fuse blows, to avoid failure expansion. And now most of the switching power supply input and a varistor. This resistance when the voltage is normal, resistance is infinite, does not affect circuit operation. Once the voltage is too high, the varistor will short-circuit, so that the current increases through the fuse, the fuse fuse, to avoid damage due to high pressure caused by other components.
After the filtered alternating current through the diode bridge rectifier circuit and the high-voltage large-capacity capacitor filter to generate 300V high-voltage DC voltage, the voltage by the resistance of the step-down and simple regulator into the oscillation control circuit to generate the oscillation signal generated oscillation signal by the amplification of the power oscillating tube with high-frequency transformer, will be transformed into low-voltage AC voltage, low-voltage AC voltage to a rectifier filter, you can generate a variety of available devices use low-voltage DC. In addition, the output of the main voltage with voltage sampling feedback circuit, the current voltage is fed back to the oscillation control circuit, once the main voltage due to load changes and voltage drift, the oscillation control circuit will change the oscillation pulse width to ensure that the output voltage stability. Meanwhile, when the load short-circuit, sampling the feedback signal will promptly notify the oscillation control circuit to stop the output of the voltage, to avoid power overload and damage. Fault detection method With a basic understanding of the switching power supply, we take a look at the method of fault detection and repair. Should first be observed that the power supply fuse is damaged. If the fuse is damaged, can not rush to replace, you must first check the power supply if there are short-circuited. :
Multimeter electrical AC-side barrier test power fuse (test point), its normal resistance should be more than tens of kilohms, such as resistance to zero, then the power supply to the existence of exchange short circuit. In addition, we should focus on examination of power AC filter capacitor is damaged; varistor should also check this resistance. If the test is normal, we shall then detect power four rectifier diodes (test point). In the normal state, the forward resistance of the diode number k (with multimeter 1k block test) and reverse resistance approaches infinity. If the test results are not normal, you need to be replaced. Down the investigation down, and then have to do is to test the power of the DC resistance of this part (test point), its normal resistance is also the number of k, such as the resistance is zero, indicating the presence of a DC short circuit. The reason for the DC short circuit is more like a filter capacitor short-circuit damage, the power oscillation tube damage, the oscillation Manifold and the peripheral circuit part damage may cause a short circuit phenomenon. In this note is to replace the power oscillation tube, you must determine the oscillation Manifold and the external circuit, otherwise it will cause the power tubes damaged again. Exclude the above-mentioned problems of the switching power supply, indicating a fault exists in most of the oscillation control circuit, sampling the feedback circuit or load. At this time, we should first check the power supply circuit of the oscillation Manifold normal (test point), its normal voltage should be around 10V (to remind: the test voltage in the power case, the power supply board with high pressure the mains, so pay special attention to personal safety, and not attempt to directly touch any part of the power). Such as the point of no voltage or voltage is very low, we must first check the dropping resistor is not damaged; check the the oscillation Manifold and its external power supply circuit. No fault found, such as peripheral circuits, the proposed replacement of the oscillation Manifold. Of course, sometimes the power can not be the normal output voltage may be due to the load short-circuit power protection caused. This power, we only need to disconnect the output line, check the output voltage is normal (test point), you can determine the fault position. Front of troubleshooting, the final should also check the feedback circuit section, in general, this part of the fault is mainly concentrated in the optocoupler and amplifier, with particular attention.
Summary Of course, the above method can not solve all the problems of the power supply, but is effective for switching power supply daily are more prone to some problems. Hope that through this presentation, can play a valuable role to help solve the minor problems encountered in switching power supply More information about Fiber Optic Connector and sensor supplier in cpbay.