# Input 24Vac OutPut 40Vdc /1A circuits -issues

Discussion in 'General Electronics Chat' started by selva20, Aug 4, 2014.

1. ### selva20 Thread Starter New Member

Aug 4, 2014
1
0
Dear sir/ madam ,
we use input voltage around 24 Vac and convert into dc by Full wave bridge (IN4007 )diodes with capacitors 2200uF/50v . so the output voltage is around 33vdc. we give this 33vdc to this circuit ,but in no load condition we get voltage but when we on with load condition the input current raise to 2-3A , i want to know how to reduce this input current .The Load we use is COB LED (FLOOD LIGHT) 40Vdc/1A. The Following component are used in this circuit .how solve this issue , we want to reduce the input current

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2. ### AlphaDesign888 New Member

Jul 27, 2014
189
10
I think this one is the good idea ...
Please some expert help us.

3. ### Alec_t AAC Fanatic!

Sep 17, 2013
7,026
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You've posted the same question on the ETO site. Aren't you happy with the answers you got there?

4. ### Papabravo Expert

Feb 24, 2006
11,083
2,159
Something is not making sense to me. The desired power output is 40 Watts. This is 40 Volts times 1 Ampere. To get that 40 Watts on the output would require at least 40 Watts divided by 24 VAC or 1.667 Amperes (RMS). If this were a perfect world and power out was equal to power in then that would be the minimum power input requirement. But we don't live in an ideal world and there will be losses in any power conversion scheme. In your case the efficiency could be as low as 60%.

What does this mean? Glad you asked that, because it means that to get 40 Watts out you need to put 66.667 Watts in. 66.667 Watts in divided by 24 VAC is 2.77 amps. Your numbers seem in line with reality so I don't see any possibility of reducing the input current unless you can improve the efficiency of the conversion process.

Also how about giving us a schematic instead of a nearly worthless datasheet that is so obliterated we can't tell what it is!

5. ### ronv AAC Fanatic!

Nov 12, 2008
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I would expect the input current to be around 2 amps. When you place the load on the supply the ripple voltage will be around 8 volts. So you only have around 25 volts at the input that is usable. So to get from 25 to 40 volts is 1.6 times - with an efficiency of say 80% that is close to 2X. So to get 1 amp out at 40 volts (40 watts) you need about 48 watts in. You can make the 2200 Ufd. cap bigger and that will help a bit, but if I remember correctly the diodes are only 1 amp.

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6. ### ronv AAC Fanatic!

Nov 12, 2008
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Hmm. Great minds and all that.

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7. ### Papabravo Expert

Feb 24, 2006
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Hard to do without a schematic, but we try.