This adapter circuit can deliver up to 3A output voltage of 12V. The circuit can be used in cases when a current of more than 3A is required for the controller. IC regulators such high current rating are quite hard to find.
The T1 transformer steps down the voltage of the rectifier bridge 12rms and D1 to produce a rectified voltage. The C1 filters the output of the rectifier produces a DC level. The passage of the series transistor Q1 (2N 3055) is biased by resistor R1 (680Ω). Since D1 is Zener breakdown region of the voltage across it is 12V. So the total output voltage of 12.7 V is constant (in theory). Zener voltage which is the most base emitter voltage of transistor Q1 Q1.Here take out the excess power needed.
Notes.
- If 12V zener is not available ,use the nearest value.
- The transformer T1 can be as 23oV primary;15V/5A secondary step down transformer.
- The capacitors must be rated at least 25V.
- By changing the value of the Zener diode, different output voltages can be obtained from the circuit.
The 2N3055 is a silicon Epitaxial-Base Planar NPN transistor mounted in Jedec TO-3 metal
case. It is intended for power switching circuits, series and shunt regulators, output stages and high fidelity amplifiers.
Maximum Ratings
- Collector-Base Voltage 100 V
- Collector-Emitter Voltage (RBE £ 100W) 70 V
- Collector-Emitter Voltage (IB = 0) 60 V
- Emitter-Base Voltage (IC = 0) 7 V
- Collector Current 15 A
- Base Current 7 A
- Total Dissipation at Tc £ 25 oC 115 W
- Storage Temperature -65 to 200 oC
- Operating Junction Temperature 200 oC
