Maker Pro
Maker Pro

Why does DVD power supply "pulse"?

microbe

Aug 24, 2011
1
Joined
Aug 24, 2011
Messages
1
Hey folks,

I am trying to learn about electronics mucking around, pulling things apart playing with arduino - a bit of everything.

When a DVD player died I thought "Aha, a cheap DC power supply", but what I have found is that it seems to put out brief (.1 sec?) bursts of power every .5 second or so rather than a continuous supply.

Why would they do something like that in a DVD player?

Thanks in advance.
 

Resqueline

Jul 31, 2009
2,848
Joined
Jul 31, 2009
Messages
2,848
I'd figure that the DVD-player died for a reason, namely that the PSU went bust..
What you're seeing there is a short-circuit protection circuit in action.
Most likely there's a shorted diode in the secondary side.
 

jackorocko

Apr 4, 2010
1,284
Joined
Apr 4, 2010
Messages
1,284
Your not talking about PWM are you? Are you testing out the new PSU, I take it this is a linear supply?
 

davelectronic

Dec 13, 2010
1,087
Joined
Dec 13, 2010
Messages
1,087
DVD psu

Hi there.
Some units need a load on the supply rails, ive tried rescuing a DVD psu and had no luck, more than once, i think the main DVD board sends signals back to the psu for its demands, a theory. Dave. PS oh a dream cast game console i had and pulled apart working did exactly the same, again an optical drive load. :)
 

JoeyAVR

Aug 25, 2011
16
Joined
Aug 25, 2011
Messages
16
Dave's right. Some 'intelligent' PSUs send out pulses to decide if there's a load to drive or not. If it detects open circuit, it saves power by doing nothing. If it detects a short, it obviously avoids damaging itself by not switching on. If the load is as expected during the pulse, it switches to supplying continuous power. Try putting a 10-20ohm power resistor across the output and see if it gives a steady voltage.

Many phone chargers are a good source of well-regulated 5V for small projects.
 
Top