How to solve common problems in switching power supply applications?
In daily life with home appliances and other electrical equipment, to the utility power supply on the line. But many instrumentation equipment with the power supply is not to the utility as a standard, but with low-voltage DC power, so the utility can not work and switching power supply can be a good solution. To the switching power supply into the mains, the output can output a stable DC power, convenient and safe. Common is also the easiest to see is the switching power supply output voltage abnormality or even no output, seemingly simple failure phenomenon, the cause of the failure and complex.
The basic circuit of the switching power supply, rectifier filter circuit, start-up circuit, AC/DC or DC/DC conversion circuit, switching drive pulse oscillation generation circuit, output voltage
Sampling ratio circuit, pulse adjustment circuit and various protection circuits.
Failure of any of these circuits will result in abnormal output voltage or even no output.
Rectifier filter circuit failure, the failure phenomenon may burn the fuse may also be grating distortion. Burn fuse, rectifier diode or filter capacitor breakdown. Grating distortion Curve, rectifier diode open circuit over the filter capacitor capacity becomes small, do not burn the fuse, but the performance of the grating distortion. Start-up circuit failure, fault phenomenon of switching power supply no output, not burn fuse. No output from switching power supply, no fuse burning. May be open resistance, may start capacitor leakage may also be switching power supply can not oscillate.
Switching drive pulse oscillation generation circuit failure, the phenomenon of fuse burning or no output or not burn the fuse but no output. The base of the switching tube may not be driving pulse generation and stop oscillation. AC/DC or DC/DC circuit failure, the phenomenon of no output, burn fuse. Switching oscillator breakdown is more common. Phenomenon of no output, no grating, pulse change poor contact with the pins of the voltage or internal coil breakage or local short circuit, there is a switching tube components burned. Phenomenon of no output without burning fuse, may be rectifier diode breakdown or filter capacitor breakdown. wear or filter capacitor breakdown.
Output voltage sampling than circuit failure, the phenomenon of no output. Sampling comparison link failure, causing the output voltage deviation from the normal value, the output is too high over-voltage protection circuit protection, no output. No output. Pulse width adjustment circuit failure, if there is no output, may be the integrated block is damaged, because the pulse width adjustment circuit is used to control the integrated block. Burning fuse Tube, common demagnetisation resistance is bad or filter capacitor breakdown or switching tube breakdown. No grating, power indicator does not light. Check the DC voltage, check the switching tube, check the start-up circuit, and check the voltage protection. Check the start-up circuit, check the voltage protection circuit.
As the intuitive phenomenon of switching power supply is anomalous output or no output, but the occurrence of the fault site is uncertain. Therefore, specific problems have to be specifically analysed.
