Question What causes a "locked" power supply ?

[bfdalton]

I have experienced the following many times with computers as well as consumer electronics.

After some disturbance on the AC feed to a power supply, the device will not turn on. However, unplugging the AC, pressing the power switch and returning AC to the device alleviates the problem.

I assume that performing these steps effectively discharges some capacitor that is remaining charged, but can someone provide an electrical engineering explanation as to what is going on here?

 

[Ralston18]

Make and model PSU?

Wattage, age, condition?

History of heavy use for gaming, video editing, or even bit-mining?

Are there any other devices in the power path - for example: UPS, surge protector, power strip, wall switch, extension cord?

 

[Zerk2012]

I have experienced the following many times with computers as well as consumer electronics.

After some disturbance on the AC feed to a power supply, the device will not turn on. However, unplugging the AC, pressing the power switch and returning AC to the device alleviates the problem.

I assume that performing these steps effectively discharges some capacitor that is remaining charged, but can someone provide an electrical engineering explanation as to what is going on here?

When a safety gets triped it has to be cut off and back on to reset the safety.

 

[bfdalton]

This is a general question. I have experienced this issue many times with many different types of equipment, PCs, stereos, displays, etc. It is generally preceded by an electrical storm or some random power outage. The device will simply not turn on by a normal press of a power switch. Unplugging and re-plugging the device does not correct the problem... However, unplug AC, press the power switch then re-plug AC and voila, the device turns on. I am curious what the power event is that causes the behavior: voltage spike, voltage sag, noise, etc., and what the electronic mechanism is that results.

 

[COLGeek]

This is a general question. I have experienced this issue many times with many different types of equipment, PCs, stereos, displays, etc. It is generally preceded by an electrical storm or some random power outage. The device will simply not turn on by a normal press of a power switch. Unplugging and re-plugging the device does not correct the problem... However, unplug AC, press the power switch then re-plug AC and voila, the device turns on. I am curious what the power event is that causes the behavior: voltage spike, voltage sag, noise, etc., and what the electronic mechanism is that results.

What you are describing is a sort of "reset" function.

In the context of PC power supplies, this often temporarily resets a failing/defective PSU.

In other devices, I suppose it would depend on the design/function of the device.

 

[Eximo]

The engineering explanation is quite simple. The PSU has a POST (Power On Self Test) circuit, as well as several fail safes. If those failsafes get tripped, such as over current protection, over voltage protection they get flagged. Until the power is completely drained, those failsafes are present and prevent the PSU from powering. It is a safety feature.

 

[Eximo]

I should add that most electronic devices that take in AC power directly have some sort of POST system.

Televisions, radios, home theatre stuff, etc. Which will be what happens to your other devices after a storm.