how does Power-On Delay and Low Voltage Protector works?

Question

Its a project. If anybody knows, please help me with this also list the advantages and disadvantages of this project. thank you

Answer 1

Power on delay is used to prevent a large in-rush of current when you first turn on an electronic device. This is implemented in 2 ways.

The first, is where you slowly ramp up the voltage from 0 to 100% over time. Take a light bulb. When you initially present full voltage to it, it is actually displaying an almost full short, and current will be very high. As the light begins to glow, the resistance of the light drops, and the current decreases. This inital in-rush of current is damaging to the filament of the light.

The second is stepping the component power on sequence, withing a device to lower the initial in-rush of current. The best example I can use for this is a tube type amplifier (AKA Linear Amplifier). If you switch on the filament and high voltage levels at the same time, there will be a very large initial current surge. If you step the filament first, and then the high voltage supply, you are dividing this by time. Also, the tube is more suseptible to damage if high voltage is applied when it's cold, so the delay can increase failure time.

Now the large in-rush of current can actually be damaging to other components in a device. The power on is not a clean power on pulse, but a messy give and take struggle. Transients are produced by this initial surge, that can damage components.

A low voltage protector simply turns off the device, when a lower voltage threshold is reached. As the voltage lowers on many devices, the current increases to make up for the voltage loss. Devices have voltage and current limits that must be adhered to.