Socket power failure troubleshooting method(2)


4. Overhaul of output ripple If the power outlet fails […]

4. Overhaul of output ripple
If the power outlet fails periodically, the problem is often too much loss in the outlet. If the snubber circuit has been used, check whether it works normally. The working principle of this buffer circuit: when the transistor is turned off, the voltage of the C pole increases, which turns on the diode, and shunts a part of the off current on the C pole. When the transistor is turned on again, the capacitor is charged through the resistor and the transistor, and the snubber circuit does not extend the on time of the transistor. The resistor should be wire-wound, and its small inductance will help charge the retarder before the transistor turns on.
5. Overhaul method of output socket with spike signal
When it is found that the socket spike signal in the output is too high, first check whether the ground wire of the power supply has a good low impedance. The socket power supply filter capacitor used is generally an electrolytic capacitor. Filter capacitors should have low equivalent series resistance (ESR) to effectively filter out the high frequency (fs) portion of the current ripple and filter out the spikes in the socket. Any replacement filter capacitor should be of low ESR type. If the output switching spike or ripple becomes severe over time, then one of the filter capacitors (probably the output filter capacitor) is defective. If the socket spike signal is higher than the desired value, juxtaposing a good polystyrene capacitor or mica capacitor on the output filter capacitor will control the spike signal.
6.Excessive EMI noise overhaul method
Excessive EMI from the power output of the socket of this machine will cause serious interference to other devices (such as televisions) in the same power circuit. The converter has the worst interference if it has a pulsating input current. The series type, polarity reversal type, and all the converters derived from them, such as push-pull type, are easily affected by the conducted EM1. The solution is to make the impedance of the input filter lower than the input impedance of the power supply. It should be noted that the output impedance of the input filter must be lower than the effective input impedance of the power supply, otherwise the power supply's stable torque and output impedance will be affected. The voltage regulation performance will deteriorate, and the output impedance of the power supply will increase.
7. Inspection method of oscillation
The oscillation of the socket power supply may damage the digital integrated circuit when it is subject to changes in the route or load, and make the role of the analog circuit load meaningless. In general, this situation is caused by the attenuation of a certain power filter being inappropriate. The inductance or capacitance of a power filter must have low series resistance to filter well and keep losses to a minimum, which means that if excited, they will oscillate at certain frequencies for at least a short period of time. If the oscillation is reflected in the output, you should check the filter attenuation circuit to see if the component is working properly; if there is no attenuation, install it,