48 VOLT PHANTOM POWER SUPPLY By TL783C


48 VOLT PHANTOM POWER SUPPLY By TL783C

This is a simple 48 V regulated linear power supply design that will provide up to 60 mA of current. This circuit is based on the Texas Instruments TL783C high voltage adjustable linear regulator IC, because this device will provide short circuit protection for an input to output differential voltage of up to 125 V. An LM317T can also be used in this circuit, but a short on the output will destroy the regulator IC. Protective diodes are included in this design to provide a discharge path around the regulator in case of an accidental reverse bias condition.

Capacitors C1 – C4 are used to filter the unregulated voltage. Multiple capacitors in parallel, as shown, will help to reduce the overall ESR of the filter section, but a single large value capacitor can also be used. Since the TL783C needs to pass a minimum of 15 mA to maintain regulation, R1 should be 82 Ohms, and R3 must be have a power rating of at least 1 Watt. The internal reference voltage of the regulator IC can vary in range of 1.2 V to 1.3 V from one device to the next. Given this range of reference voltage variation, the combined value of R2 + R3 can range from 2950 Ohms to 3200 Ohms. Assigning a standard value of 2.7K Ohms to R3 and making R2 a 1K Ohm trimmer potentiometer permits precise adjustment of the desired output voltage of 48 Volts.

A power transformer with a 6 VA power rating and a 40 V secondary voltage has been selected to minimize the physical size of the power supply, and to minimize the amount of power dissipated by the regulator IC, thus requiring little or no heatsink. Operating at 15 mA, the unregulated voltage reaches approximately 70 V, and the regulator dissipates 0.33 W. When this circuit is operating at its full capacity of 60 mA, the regulator dissipates less than 0.75 W, which is safely below the device’s free air dissipation rating.

C1
220 uF 100 V
C2
220 uF 100 V
C3
220 uF 100 V
C4
220 uF 100 V
C5
10 uF 100 V
C6
10 uF 100 V
D1
1N4002
D2
1N4002
D3
1N4002
D4
1N4002
D5
1N4002
D6
1N4002
R1
82 OHM 1/4 W
R2
1 K OHM TRIMMER
R3
2.7K OHM 1 W
T1
40 V at 0.15 A (6 VA)
U1
TL783C

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