Dual Output Adjustable Linear Power Supply +/-1.2V to +/-12V @ 250mA

Rajkumar Sharma
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SKU: EL113051
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This project is a solution to power up most devices or projects requiring dual (+/-) adjustable power. The circuit consists of a stepdown transformer, bridge rectifier, DC filter capacitors, LM317 positive and LM337 negative adjustable voltage regulators, 2 x trimmer pot for independent output voltage adjust, and power LEDs.

Parts Explanation

Connector CN1 : 230V/115V AC Input
Jumper J2 : 230V Selection
Jumper J1 & J3 : 115V Selection
Transformer T1 : Step Down Transformer 12V-0-12VAC Output, 230V/115V AC Input
Bridge Rectifier BR1 : Rectifier Converts DC in to AC Supply
Capacitors C3, C5 : DC Filter Capacitors
LED D1 : +V PWR LED
LED D2 : -V PWR LED
Resistor R1, R2 : Current Limiting Resistors For LEDs D1 and D2
Regulator U1 : +V Adjustable Regulator
Regulator U2 : -V Adjustable Regulator
Trimmer Pot PR1 : +V Output Adjust +1.2V to +12V
Trimmer Pot PR2 : -V Output Adjust -1.2V to -12V
Capacitor C1, C2, C4, C6 : DC Filter Capacitors
Connector CN2 : Adjustable DC Output

Note1: This power supply supports 230V AC or 115V AC input, Jumpers are located under PCB for input voltage selection, remove input power cable while changing Jumper selection.

Note 2: This power supply contains hazardous voltage at the input, PCB must be installed in an encloser that prevents accidental contact. Use Plastic screws to mount the PCB

Note 3: Heatsink is a must for regulators U1 and U2 @ full load, the heatsink should be mounted with plastic screws and should not touch the ground plane of the PCB.

Note 4: It is advisable to set the output voltage using PR1 and PR2 before connecting the output to the load.

Input Voltage Selection

For 230V AC Input: Close Jumper J2, Jumper J1, and J3 Open
For 115V AC Input: Close Jumper J1 and J3, Jumper J2 Open

Other Similar AC to DC Power Supplies

Features

Input 230V or 115V AC (Use Jumpers to Select 230V or 115V AC)
Output +/-1.2V to 12V DC (Dual Output)
Output Ripple Approx. 5mV
Maximum Load Current 500mA (250mA + 250mA)
2 X Power LEDs, for +V and -V
Screw Terminal for AC Input
Screw Terminal for Regulated DC Output
PCB Dimensions 91.76 x 43.82 mm

Schematic

Parts List

NO	QNTY.	REF.	DESC.	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	1	BR1	BRIDGE RECTIFIER W10M	MICRO COMM	DIGIKEY	W10M-BPMS-ND
2	1	CN1	3 PIN SCREW TERMINAL PITCH 5.08MM	PHOENINX	DIGIKEY	277-1248-ND
3	1	CN2	3 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1248-ND
4	2	C1,C6	10uF/25V SMD SIZE 1206	MURATA/YAGEO	DIGIKEY
5	2	C2,C4	0.1uF/50V SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
6	2	C3,C5	1000uF/25V OR 2200/25V	PANASONIC	DIGIKEY	P13121-ND
7	1	D1	RED LED SMD SIZE 0805	LITE ON	DIGIKEY	160-1427-1-ND
8	1	D2	GREEN LED SMD SIZE 0805	DIALIGHT	DIGIKEY	350-2044-1-ND
9	3	J1,J2,J3	JUMPER(PCB SOLDER) USE SMD 0-OHM RESISTOR SIZE 1206		DIGIKEY	PCB JUMPERS
10	2	PR1,PR2	5K TRIMMER POT	BOURNS	DIGIKEY	3362H-502LF-ND
11	2	R1,R2	1.5K 5% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
12	2	R3,R4	220E 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
13	1	T1	TRANSFORMER 3FD-424	TAMURA	DIGIKEY	MT2115-ND
14	1	U1	LM317-ADJ TO 220	ST	DIGIKEY	497-1575-5-ND
15	1	U2	LM337-ADJ TO 220	ST	DIGIKEY	497-1585-5-ND
16	2		HEATSINK -TO220	AVID	DIGIKEY	HS106-ND
17	2		M3 X 10MM SCREW AND NUT FOR TO220 HEATSINK/REGULATOR	IO AUDIO	DIGIKEY	1937-IO-M3X10/M3HN-50-ND