Need and efficient circuit to obtain 12v 5a dc

[rajdarshan]

I have a laptop,its getting real hot i need a circuit that can power 3 fans and 6 leds. The problem is that i cannot find a diode that can give me 5amps . The fans that i am using here are pc power case fans,and the question here is that do i need a regulated stuff or an ordinary is ok.are there any ic that convert 12vac into 12vdc?

 

[logicon]

I am wondering why you will need 5A to power just 3 fans and 6 leds. If they are PC power case fans, you don't need that much. Apart from the speed control, fans motors are generally friendly to dc ripples once you rectified your incoming 12VAC. I suggest you use a 2A ratings bridge rectifier with a filter for your power needs. A parallell rectifier configuration will also work for you. Please mark the post as helpful. If you need more help, provide more specification or post a document of what you are trying to accomplish.

 

[rajudp]

for laptop a small attachment is available with inbuilt fan powered from usb port, there is no need of additional power supply,
if you want to your own if you want it to carry better go for smps type and there is no need of 5A supply, maxim 1A will do for 3 fans( it takes 12V around .15A for one)

 

[rajdarshan]

2a is enough , but what about the LED's i tried connecting the 3 fans and 12 LEDs in parallel (3fans one bunch and 12 leds in other bunch both bunches in parallel) after few seconds burnt up 8 of them (rechecked 3 times before connecting them). what do you think the problem would be .should i go for a SMPS or a normal AC to Dc, the circuit will be runing 10 hours a day.please suggest. waiting for your reply.

 

[rajudp]

12 led's in parallel with 12v?
try connect 6 led's in series and add a resistor in series with it then connect to 12v you can add the other 6 in the same way

 

[rajdarshan]

why not 6 +6 LEDs?

 

[betwixt]

LEDs are constant voltage devices with a Vf of 1.5V to 3.5V depending on color and make. If you connect them directly across 12V they WILL draw far too much current and burn out - guaranteed!

Fans draw less than 0.2A so with 3 you need 0.6A at most, LEDs generally draw around 0.02A so 12 should draw no more than 0.24A, therefore a 1A supply should be more than adequate. You MUST add series resistors to the LEDs though or they will burn out.

Brian.

 

[rajudp]

Brain , i agree with you