Skip to main content

Variable Power Supply with Transistor

electronic circuit diagram


Component parts list:

P1____________500R Linear Potentiometer
P2_____________10K Log. Potentiometer

R1,R2___________2K2 1/2W Resistors
R3____________330R 1/4W Resistor
R4____________150R 1/4W Resistor
R5______________1R 5W Resistor

C1___________3300µF 35V Electrolytic Capacitor (see Notes)
C2______________1µF 63V Polyester Capacitor

D1,D2________1N5402 200V 3A Diodes
D3_____________5mm. Red LED

Q1____________BC182 50V 100mA NPN Transistor
Q2____________BD139 80V 1.5A NPN Transistor
Q3____________BC212 50V 100mA PNP Transistor
Q4 __________2N3055 60V 15A NPN Transistor

T1_____________220V Primary, 36V Center-tapped Secondary
50VA Mains transformer

PL1____________Male Mains plug

SW1____________SPST Mains switch

Notes:
  • P1 sets the maximum output current you want to be delivered by the power supply at a given output voltage.
  • P2 sets the output voltage and must be a logarithmic taper type, in order to obtain a more linear scale voltage indication.
  • You can choose the Transformer on the grounds of maximum voltage and current output needed. Best choices are: 36, 40 or 48V center-tapped and 50, 75, 80 or 100VA.

Comments

Anonymous said…
i want to increase the amerage of a common ac adapter from 350mA to any amount under 3000mA without changing the voltage. can i simply remove a capacitor and use a smaller one?
no, the value of output electric current is not depended on capacitor value... if you replace the capacitor with smaller value then you will see the different output wave (if you are using osciloscope). AC to DC conversion will be worse..

Popular posts from this blog

LM317T Voltage Regulator Circuit with Pass Transistor

This is the schematic diagram of voltage regulator circuit with pass transostor. The regulator is based regulator IC of LM317T. The LM317T output current can be raised by utilizing an additional power transistor (on circuit, it is 2N2955) to share a portion of the total current. The amount of current sharing is established with a resistor placed in series with the LM317 input and a resistor placed in series with the emitter of the pass transistor. In the above scheme design , the pass transistor will start conducting when the LM317 current reaches about 1 ampere, due to the voltage drop across the 0.7 ohm resistor. Current limiting happens at about 2 amperes for the LM317 which will drop about 1.4 volts across the 0.7 ohm resistor and make a 700 millivolt drop across the 0.3 ohm emitter resistor. Thus the total current is limited to about 2+ (.7/.3) = 4.3 amperes.

Sealed Lead Acid (SLA) 12V Battery Charger with Current Limiting

This is the circuit design of Smart Sealed Lead Acid (SLA) 12V Battery Charger featuretwith Current Limiting. The charger uses a two step process for charging SLA batteries – a current limited ‘fast’ mode followed by a constant voltage ‘float’ mode. Maximum charging current is 1A. An onboard LED indicates when the charger is in ‘fast’ mode. When the LED goes out the battery is charged and the charger has switched to ‘float’ mode.

5V to Isolated 5V Converter Circuit

This is the circuit diagram of 5V to Isolated 5V Converter, rated at 20mA electric current. In this converter circuit, a negative output voltage dc to dc converter generates a -5V output at pin A. In order to generate -5V at point A. the primary of the transformer must fly back to a diode drop more negative than -5V. If the transformer has a tightly coupled I : 1 turns ratio. there will be a 5 V plus a diode drop across the secondary. The IN5817 rectifies this secondary voltage to generate an isolated 5V output. The isolated output is not fully regulated since only the -5V at point A is sensed by the MAX635.