Increasing a Dc Power Supply amperage output

[mohkam]

Hi members!
Got an Adjustable DC Regulated Power Supply Model "Best PS-15014A", with current and voltage indicators and 2 output ranges :
0~15V, 0~1A and
0~7.5V, 0~0.5A
using in particular a 220V~20VDC transformer and a power transistor TIP32A.

Please help as how to convert My power supply into a DC power source outputting 0~10V, 0~1.5A, which I need for repair purpose.

 

[zahwi]

Hi members!
Got an Adjustable DC Regulated Power Supply Model "Best PS-15014A", with current and voltage indicators and 2 output ranges :
0~15V, 0~1A and
0~7.5V, 0~0.5A
using in particular a 220V~20VDC transformer and a power transistor TIP32A.

Please help as how to convert My power supply into a DC power source outputting 0~10V, 0~1.5A, which I need for repair purpose.

Connect the collector of tip32a to the +20V supply. the base to the 0~15V supply and the emitter will give you 0~10V 1.5A

 

[audioguru]

A TIP32 transistor is small. Its datasheet says it can dissipate only 2W without a heatsink and 40W with a perfect heatsink. You cannot buy a perfect heatsink so maybe the dissipation must not exceed 20W with a huge heatsink. If the raw supply is 20VDC and you need 5V at 1.5A then the transistor will dissipate (20V - 5V) x 1.5A= 22.5W of heat which might cause it to melt or smoke.

The TIP32 is a PNP transistor so if you use it as an emitter-follower as said by Zahwi then observe the correct polarity. An emitter-follower at the output of a regulated power supply ruins the voltage regulation.

 

[zahwi]

AG is right, ignore my post.







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I don't use simulators of any kind, I'm happily married.

 

[kinarfi]

https://www.banggood.com/Mini-DC-DC-Converter-Step-Down-Module-Adjustable-Power-Supply-p-920327.html

 

[mohkam]

A TIP32 transistor is small. Its datasheet says it can dissipate only 2W without a heatsink and 40W with a perfect heatsink. You cannot buy a perfect heatsink so maybe the dissipation must not exceed 20W with a huge heatsink. If the raw supply is 20VDC and you need 5V at 1.5A then the transistor will dissipate (20V - 5V) x 1.5A= 22.5W of heat which might cause it to melt or smoke.

The TIP32 is a PNP transistor so if you use it as an emitter-follower as said by Zahwi then observe the correct polarity. An emitter-follower at the output of a regulated power supply ruins the voltage regulation.

hi "audioguru"
Yes indeed, y're right. TIP 32 won't help.
For troubleshooting some circuits, I'll need a supply of 1V/1.5A, so the output transistor has to dissipate
(20V-1V)x1.5A=28.5W say 30W so a transistor with higher Pc is needed.

My DC power supply model "Best PS-15014A" is originally outputting up to 15V/1A through TIP32, which is mounted on the case of the Power supply. So it's actually dissipating up to (20V-1V)x1A= 19W.

Could you P.S suggest any common Transistor to use for the purpose and explain how to connect it on the actual DC power supply to get a variable output of (1V to 10V) with up to 1.5A .

An urgent reply is needed.

 

[audioguru]

The transformer, rectifiers and main filter capacitor will also all be overloaded if you have a load of 1.5A. If they are all upgraded then the TIP32 transistor can be replaced by a TIP2955 transistor that can dissipate up to 90W if the heatsink is big enough.

 

[Tony Stewart]

Since we do not know the limitations of VA of your transformer and diode cap bridge Vdc(min) vs I, suggesting a different regulator is pointless if either of these ratings are short or requirements.

Why not use a PC PSU HDD port connector with 12V out and use a suitable LDO regulator with current limit and voltage adjust?

 

[mohkam]

Since we do not know the limitations of VA of your transformer and diode cap bridge Vdc(min) vs I, suggesting a different regulator is pointless if either of these ratings are short or requirements.

Why not use a PC PSU HDD port connector with 12V out and use a suitable LDO regulator with current limit and voltage adjust?

That will help. Do you suggest any diagram with few components to get it done that way. There are so many schemes on the Net but need a simple one.

 

[kinarfi]

https://www.ti.com/lit/ds/symlink/lm2576.pdf
Using the output of your 20v transformer into a full wave bridge and some large capacitors, you will have an efficient power supply with only a few parts. With LM2576 mounted to a modest heat sink, you will have a 1.23 to 13.5 v powersupply good for 3 amps. When outputting 10 v and 3 amps, you 20v transformer will be outputting about 1.5 amps.
I have a power supply that uses this and I'm very happy with it.

 

[mohkam]

View attachment 96405
https://www.ti.com/lit/ds/symlink/lm2576.pdf
Using the output of your 20v transformer into a full wave bridge and some large capacitors, you will have an efficient power supply with only a few parts. With LM2576 mounted to a modest heat sink, you will have a 1.23 to 13.5 v powersupply good for 3 amps. When outputting 10 v and 3 amps, you 20v transformer will be outputting about 1.5 amps.
I have a power supply that uses this and I'm very happy with it.

Thanks for the link. What I actually need is an adjustable voltage supply with current limiting ability.
The datasheet you link to has fixed current output. Could you suggest any alteration to the scheme to get current limit.

 

[chemelec]

Build a Power Supply using an LM723.
You can create a Supply with Both Voltage and Current Regulation for almost any voltage or current range.

Here is One Example:
http://chemelec.com/Projects/LM723-PS/LM723-PS.htm

 

[zahwi]

Build a Power Supply using an LM723.
You can create a Supply with Both Voltage and Current Regulation for almost any voltage or current range.

Here is One Example:
http://chemelec.com/Projects/LM723-PS/LM723-PS.htm

A resistor of 0.22 ohm is missing from the circuit diagram between the emitter to the output.

 

[kinarfi]

Thanks for the link. What I actually need is an adjustable voltage supply with current limiting ability.
The datasheet you link to has fixed current output. Could you suggest any alteration to the scheme to get current limit.

not fixed, Maximum
One definition of current is voltage applied divided by the load. Generally speaking, you have either voltage control and current is determined by the load with max current being set by the power supply, or current limiting and voltage is controlled by the load with max voltage being set by the power supply.
Because this circuit is a SMPS, the current in is much less than current out, and max current is limited by the LM2576. However, the attached drawing shows how the LM2576 can be used as a constant current device.

 

[kinarfi]

Just for fun, here's a close simulation of my power supply, I can pull 15 amps out it with no problem