Increasing the DC 5V 250 mA adopter volt & amp.

**crazybuoy** · 19-09-10, 11:54

I want transformerless power supply with 24V 2 Amp and I think any existing cell phone battery adopter can do it for me. I have an DC adopter (5V 250 mA) and want some changes in the circuit to get my desired volt & amp. You can review the circuit of any of your adopter, as most peoples has such a adopters.
You may also suggest any other circuit that can provides me transformerless power supply with DC 24V 2 Amp.

**xaccto** · 20-09-10, 01:03

have you even opened one of those mains DC adapters ? many parts are surrounded in glue. If you spend enough time
you might identify the feedback resistor divider network and alter the values for a different output voltage.
But there is no way you will at the same time increase the current rating.
5V @ 250ma is 1.25Watts, you can't magically make such a supply deliver 24V@2amps = 48Watts.
None of the components in it will be rated for that power capability.

**spectrum17** · 20-09-10, 04:51

Originally Posted by crazybuoy

I want transformerless power supply with 24V 2 Amp and I think any existing cell phone battery adopter can do it for me. I have an DC adopter (5V 250 mA) and want some changes in the circuit to get my desired volt & amp. You can review the circuit of any of your adopter, as most peoples has such a adopters.
You may also suggest any other circuit that can provides me transformerless power supply with DC 24V 2 Amp.

chargers have a transformer w/c is a switching transformer,you can only achieve 24V with 2A using flyback topology SMPS using an input of AC mains(offline).main advantage of this topology is isolated,the input is not connected with output because of switching transformer.you can use link below for reference.

http://www.fairchildsemi.com/an/AN/AN-4137.pdf

but if you still want an offline power supply but without transformer,you can use non-isolated but this is not a high current output but this can be use to power-up low power devices such as microncontroller.link below for references.

http://ww1.microchip.com/downloads/e...tes/00954A.pdf

regards,

spectrum17

**crazybuoy** · 22-09-10, 09:56

How about to use big resistor to drop the 220v AC to 24v AC then use bridge rectifier to convert it to DC?

**spectrum17** · 23-09-10, 02:47

Originally Posted by crazybuoy

How about to use big resistor to drop the 220v AC to 24v AC then use bridge rectifier to convert it to DC?

this is acceptable,however it is only applicable for low power applications,but it is not efficient and not isolated.with step-down transformer is always a good design and safe to use.

regards,

spectrum17

**qa majid** · 24-09-10, 13:18

my project is 48v to 12 v buck converter in continuous conduction mode using matlab simulink.but it is difficult to me to make a simulink model of PWM which hass as out put duty cycle 0.12.can some body help me plz?

**spectrum17** · 06-10-10, 06:57

Originally Posted by qa majid

my project is 48v to 12 v buck converter in continuous conduction mode using matlab simulink.but it is difficult to me to make a simulink model of PWM which hass as out put duty cycle 0.12.can some body help me plz?

maybe you can use SIMetrix from Catena and PSIM to simulate buck converters to tailor your compensation needs.

Analog Circuit Simulation Software from SIMetrix Technologies - SPICE
PSIM Software by Powersim Inc

**abhityagi85** · 09-11-10, 18:11

Why do u want to use the DC adaptor anyway.

Use power electronic converters if u wish to directly convert AC to DC.
Advantage will be that the circuit will be small in size and will not be too much complex.
Read about thyristor (SCR) and the related devices in family.

browse journals for design specific for your requirement. u can also
refer to this:
http://www.nxp.com/documents/applica...te/APPCHP6.pdf

**Qube** · 11-11-10, 18:44

Originally Posted by crazybuoy

How about to use big resistor to drop the 220v AC to 24v AC then use bridge rectifier to convert it to DC?

I think the resistor may get very heated up,it may need high watt rated resistor for this purpose...wat do u think??
And it's also not that much safe when compared to transformer...u can't use it for a long time..

**qayyoum** · 26-11-10, 20:38

hi ( xaccto ) you are right that supply not able to provide 48 watt(2 amp)
please must be see this link you understand how to convert smps volt complite technical information
(Smps Voltaj)

**war4one** · 01-12-10, 07:25

Originally Posted by crazybuoy

How about to use big resistor to drop the 220v AC to 24v AC

You can use big resistor or big capacitor to drop 220 V to 24 V AC, but he must dissipate (220V - 24V)*2A = 392 Watt of heat.
If you want use transformerless power supply, you can get about 0.1 A maximum (from this transformerless circuit, replace VD3 to 24 V 0.5 W zener diode).
If you find cheapest solution for 24 V 2 A hobby power supply, you can use this SMPS circuit, after replace T1 to POL24020 and D1 to TOP226 (use radiator for D1 and VD5).

**grittinjames** · 01-12-10, 07:52

Hi,

Please visit Powerint.com
You will get many usefull circuit
Grittin

**S.Ali** · 17-02-11, 06:51

Please visit Powerint.com

this is good website for more details

**sswalia** · 13-03-11, 09:07

Originally Posted by crazybuoy

I want transformerless power supply with 24V 2 Amp and I think any existing cell phone battery adopter can do it for me. I have an DC adopter (5V 250 mA) and want some changes in the circuit to get my desired volt & amp. You can review the circuit of any of your adopter, as most peoples has such a adopters.
You may also suggest any other circuit that can provides me transformerless power supply with DC 24V 2 Amp.

24V/250ma adapter is designed for 6 watt and you want 24V and 2 amp which is 48 watt. So there is a big deference. This is not possible use the same adapter for your purpose. you need a new design altogether.

**Jigar 4 Electronics** · 29-07-12, 09:34

Originally Posted by war4one

You can use big resistor or big capacitor to drop 220 V to 24 V AC, but he must dissipate (220V - 24V)*2A = 392 Watt of heat.
If you want use transformerless power supply, you can get about 0.1 A maximum (from this transformerless circuit, replace VD3 to 24 V 0.5 W zener diode).
If you find cheapest solution for 24 V 2 A hobby power supply, you can use this SMPS circuit, after replace T1 to POL24020 and D1 to TOP226 (use radiator for D1 and VD5).

Can you tell me which value of the resistor and capacitor I should use to do this.
I wanna make that without transformer for my very small circuit which is also a low power circuit.
I have 220V AC 50Hz and want 5 V DC.
But better you tell me how to calculate the value of R & C to get XYZ Volt DC o/p.

**lucy1** · 30-07-12, 03:07

Originally Posted by crazybuoy

I want transformerless power supply with 24V 2 Amp and I think any existing cell phone battery adopter can do it for me. I have an DC adopter (5V 250 mA) and want some changes in the circuit to get my desired volt & amp. You can review the circuit of any of your adopter, as most peoples has such a adopters.
You may also suggest any other circuit that can provides me transformerless power supply with DC 24V 2 Amp.

HI,How about the power module converter for the electronic parts?

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