AC Power Supply Low Voltage

This is AC power supply circuit with low voltage output (step down transformer converter). Warning! This project involves the use of dangerous voltages. You must make sure all high-voltage (120 volt household power) conductors are safely insulated from accidental contact. No bare wires should be seen anywhere on the “primary” side of the transformer circuit. Be sure to solder all wire connections so that they’re secure, and use real electrical tape (not duct tape, scotch tape, packing tape, or any other kind!) to insulate your soldered connections.

If you wish to enclose the transformer inside of a box, you may use an electrical “junction” box, obtained from a hardware store or electrical supply house. If the enclosure used is metal rather than plastic, a three-prong plug should be used, with the “ground” prong (the longest one on the plug) connected directly to the metal case for maximum safety.


Before plugging the plug into a wall socket, do a safety check with an ohmmeter. With the line switch in the “on” position, measure resistance between either plug prong and the transformer case. There should be infinite (maximum) resistance. If the meter registers continuity (some resistance value less than infinity), then you have a “short” between one of the power conductors and the case, which is dangerous!

Next, check the transformer windings themselves for continuity. With the line switch in the “on” position, there should be a small amount of resistance between the two plug prongs. When the switch is turned “off,” the resistance indication should increase to infinity (open circuit — no continuity). Measure resistance between pairs of wires on the secondary side. These secondary windings should register much lower resistances than the primary. Why is this?

Plug the cord into a wall socket and turn the switch on. You should be able to measure AC voltage at the secondary side of the transformer, between pairs of terminals. Between two of these terminals, you should measure about 12 volts. Between either of these two terminals and the third terminal, you should measure half that. This third wire is the “center-tap” wire of the secondary winding.

13,8 V Power Supply Using LM338

This is a design circuit for power supply. This circuit produces voltage 13,8 VDC. This circuit is work with based on LM338. Here’s the figure of the power supply circuit.


Maybe we need a supply of relatively strong in the framework we provide a variety of equipment with + 13.8V, as transceivers CB, and others known to use a complete circuit is capable of giving her the inside out, now constantly 5A and 12A peak current operations.

Part Components:
R1=270R 1/4W 2%
C1=10000uF 40V
C2-3=100 nF 100V Polyester
C4-5=10uF 25V
T1=220Vac/15VAC – 8A Mains Transformer
TR1=4k7 (Multiturn)
D1-2=1N4002 (1A/100V)
S1=2 Pole Single Throw Mains Switch
B1=25A Bridge Rectifier
F1=250mA Fuse
IC1=LM338

Source : users.otenet.gr/~ahisrod

APD Bias Supply Circuit

This is design circuit for a high voltage APD bias supply. This circuit is design for current monitor function. This is the figure of the circuit.


This circuit is based on LT1930A switching regulator and L1 form a fly back based boost stage. The fly back events pump a diode-capacitor network tripler, producing a high voltage DC output. Feedback from the output via the R1-R2 combination stabilizes the regulator’s operating point D6 and D7 protect the switch and feedback pins, respectively, from parasitic negative excursions and the 10W resistors prevent excessive switch current. C8 and C9, series connected for high voltage capability, minimize output noise. A 0V to 4.5V programming voltage results in a corresponding 90V to 30V output (3% accuracy) with about 2mA of current capacity. Circuit output noise is quite low. Figure 7, taken with 500mA loading at VOUT = 50V, shows about 200mV ripple and harmonic residue in a 10MHz bandwidth. This is adequate for most APD receivers.

[Circuit’s source design: Linear Technology Notes].

Simple 1,3 Volt Power Supply Circuit

This is the design for a replacement power source for 1.3V mercury cells or other small batteries. This circuit is useful for computer to power a front panel multi adapter which has a digital thermometer. This circuit is a simplest form of the schematic. This is the figure of the circuit.


This circuit takes it power from a PC. The power connectors have color coded wirings, red and black are a 12V supply, black and yellow are a 5V supply. These are extremely high current so absolute care must be taken to avoid short circuits and an inline fuse of 100mA is recommended. The 1.3V is derived from a Red LED. When on and forward biased the LED's voltage drop between anode and cathode is about 1.9V, this is too high for mercury cell powered equipment, but fed in series with a 1N4148 signal diode drops around 0.6V, the supply is then ideal to drive battery powered peripherals. This is not suitable for clocks, because when the computer is turned off the 5V supply is also switched off. It is however ideal for the independent temperature displays often included with PC peripherals such as case mounted usb connectors.

High Voltage Regulator Power Supply

This is a design circuit for a power supply. This circuit is basic for high power supply that is based on LM317 for the regulator IC. This is the figure of the circuit.


How is the circuit work? Zener diode D1 ensures that the LM317H sees only a 5V input-output differential over the entire range of output voltage from 1.2V to 160V. Since high-voltage transistors by necessity have a low β, a Darlington is used to stand off the high voltage. The zener impedance is low enough that no bypass capacitor is required directly at the LM317 input. (In fact, no capacitor should be used here if the circuit is to survive an output short!) R3 limits short circuit current to 50 mA. The RC network on the output improves transient response as does by passing the ADJUST pin, while R4 and D2 protect the ADJUST pin during shorts. [Circuit schematic source: National Semiconductor Notes].

50V 3A Stabilized Power Supply

This is a design for power supply. This is a complete circuit for the stabilized power supply. This is the figure of the circuit.


This circuit can give in his exit + 40V until + 60V 3A, with simultaneous stabilization. The materials that use is very simple and will not exist difficulties in the manufacture, is enough you are careful certain points. For output voltages smaller of + 50V until + 40V, the Q1 is hot enough, so that it needs one big heat sink. This circuit is work using transistor 2N3055.