power supply question

Thread Starter

radetonator

Joined Aug 1, 2011
50
Hi. If the circuit needs +5V and +15V power supply from a DC power supply, what is the best way to achieve? Using two voltage regulator or just one?
 

ian123

Joined Aug 24, 2011
73
depends on the circuit i f you need regulation of not and what is the output from the power supply before regulation.

if the power supply is around 15 volts and the 15v circuit doesnt need regulation then one regulator will do for the 5 v
 

tronicsrookie

Joined Aug 22, 2011
14
Why not use the optocoupler design with feedback regulation, that's used in most of the SMPS. Combined with high wattage and clean supply (Deviation less than 100th of output) that's the best you can ask for.

Just visit any computer shop and pick up a faulty one for a few dollars and replace shorted diodes/FETs and use it in your project.

Regds,
TronicRookie.
 

shortbus

Joined Sep 30, 2009
7,613
Why not use the optocoupler design with feedback regulation, that's used in most of the SMPS. Combined with high wattage and clean supply (Deviation less than 100th of output) that's the best you can ask for.

Just visit any computer shop and pick up a faulty one for a few dollars and replace shorted diodes/FETs and use it in your project.

Regds,
TronicRookie.
Where do you find a computer supply with a +15V output?
 

SgtWookie

Joined Jul 17, 2007
22,210
With no current or ripple specifications, it's rather tough to give an accurate recommendation.

If not overly concerned about ripple, you don't mind the bulk, and you can do with +12v instead of +15v an ATX-form-factor PC power supply can be converted to a "bench supply" rather inexpensively.

If your current needs are quite low, you might do with 7815 and 7805 fixed regulators from a ~18v-20v DC supply, but power dissipation in the 7805 regulator will make it very inefficient; ~3/4 of the power in the 5v supply will be wasted as heat.

To help us help you, tell us more about what your current requirements are at 15v and 5v.
 

Thread Starter

radetonator

Joined Aug 1, 2011
50
Thanks.

+5V is for LT1721 and 74AHC08. +15V is for a RF mosfet driver. When Vcc=15V, power supply current of the driver is 10uA.
 

shortbus

Joined Sep 30, 2009
7,613
Thanks.

+5V is for LT1721 and 74AHC08. +15V is for a RF mosfet driver. When Vcc=15V, power supply current of the driver is 10uA.

Most non-logic level Mosfets are fully turned on at 10V gate voltage, so a 12V level for the gate should be more than adequate. Since you don't give your Mosfet number or a data sheet link its hard to answer any better.
 

Thread Starter

radetonator

Joined Aug 1, 2011
50
Most non-logic level Mosfets are fully turned on at 10V gate voltage, so a 12V level for the gate should be more than adequate. Since you don't give your Mosfet number or a data sheet link its hard to answer any better.
I plan to buy a 15V 1.2A switch mode PSU. Should be ok?

Mosfet driver: DEIC420
http://www.ixysrf.com/pdf/driver_ics/deic420.pdf
MOSFET: DE275-501N16A
http://www.ixysrf.com/pdf/switch_mode/de275_501n16a.pdf

I only need to use one pair.
Thanks.:D
 

shortbus

Joined Sep 30, 2009
7,613
You do realize that the components your using are SMD(surface mount device)? If a beginner their not the most friendly to work with.
 

Thread Starter

radetonator

Joined Aug 1, 2011
50
Don't know what specification you're after exactly but how about this?
I think 1A for the whole circuit is enough. Input voltage for the driver is from 9V to 30V. According to the datasheet, the power supply current of the driver is 3mA. LT1721 needs 28mA and SN74AHC08 also does not consume much power.

How you guys think about it?

I found this PSU. looks nice
 
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