DVD player SMPS

[Ziddik]

DVD player SMPS..HELP!!

hi..
My dvd player's powersupply is SMPS and it is fried last week while i was watching a movie so i opened the player and tested the entire circuits and found that SMPS's tiny transformer is fried. I cant find that transformer in any shop at my area, the dvd control circuit needs a 12v+,-12v,GND,+5.
so my question is can i use a regulated powersupply instead of the SMPS? i think a dual supply for 12V and 7805 for +5v? Is it possible guys? Or will the control circuit fry? Thanx

 

[alec_t]

It may be possible. The regulated supply will have to handle properly any signal being fed back by the control circuit to the SMPS to adjust the volts/current supplied.
Could you just rewind the transformer?

 

[Ziddik]

but i want to use an ordinary" 12-0-12V" 5amperes" transformer with some regulated iCs ie.7805,7812 and 7912,instead of the SMPS, so the output may be "-12v,+12v,+5v,GND" (Pls see post #1). I get +16volts from the transformer after rectification so i think the 7812 will work properly.. So can i use it to power my DVD Player or should i buy a new SMPS?

 

[alec_t]

but i want to use an ordinary" 12-0-12V" 5amperes" transformer with some regulated iCs

What you want to do and what is possible may not be the same thing!
Does the control circuit (or other part of the dvd) provide any feedback signal to the SMPS?
Is the transformer rewindable?

 

[Ziddik]

What you want to do and what is possible may not be the same thing!
Does the control circuit (or other part of the dvd) provide any feedback signal to the SMPS?

No

Is the transformer rewindable?

i think it cant be rewindable as it looks very tiny
and
ther are 4 outputs to the control circuit from SMPS [1.+12V,2.-12V,3.GND,4.+5V] so all i want to do is remove the SMPS from the DVD player and use an ordinary 12.0.12v transformer and regulate the output voltages of the transformer as shown above with regulate iCs, any idea?

What i meant with the "control circuit" is the "Mother board" of DVD PLAYER..

Hope u understand it

 

[unclejed613]

it should work, but you are going to probably need more current for the +5V supply than a regular 7805 can provide. standard 7805 regulators are rated between 1 and 1.5A. you are likely going to need closer to 2 or 3A for the +5V supply, so you should use a 7805CK, or a standard 7805 in a current boosted configuration (i'll try to find the NS app note on this) using a 7805 driving a pass transistor.

 

[Ziddik]

it should work, but you are going to probably need more current for the +5V supply than a regular 7805 can provide. standard 7805 regulators are rated between 1 and 1.5A. you are likely going to need closer to 2 or 3A for the +5V supply, so you should use a 7805CK, or a standard 7805 in a current boosted configuration (i'll try to find the NS app note on this) using a 7805 driving a pass transistor.

thanx unclejed.and can u please post a circuit schematic to use 7805ck?

 

[Ziddik]

does anyone have any comments about this topic?

 

[unclejed613]

the 7805ck is actually a regular 7805 with a TO-3 case, and can be used (with adequate heat sinking) up to about 2A. the pins are in and out, and the case is ground.

i'll take a whack at doing a current boosted regulator schematic (it's not in the data sheet, so i'm doing it from memory...)

forgive the crude paint image, but you see how it works. the 7805 has it's ground lifted 0.7Vdc by the 1N4004, which compensates for the 0.7V drop across the B-E junction of the transistor resulting in a regulated +5V at the emitter. your load is the "emitter resistor". the transistor should be heat sinked, and remember the transistor tab is at +16V, NOT ground, so the heat sink should be isolated from ground.

i made one error in the drawing, and it is that the input to the circuit should be connected to the +16V rail, before the 7812, not to the output of the 7812.

 

[Ziddik]

thanx for the circuit unclejed.. It works perfectly