Variable Power Supply Using LM723

Using LM723 regulator can be designed a very simple variable power supply circuit which can provide a maximum current up to 2A and a variable voltage between 2 and 25 volts.This 25v variable power supply is designed using a LM723 regulator and a few common electronic components.Input voltage must be between 28 and 37 volts. Mj3000 transistor must be mounted on a radiator for heat dissipation.

LM723 Variable Power Supply Circuit diagram

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High Current Power Supply

Since my page was first posted, I have received a number of emails asking about a high current power supply. I looked around, but couldnt find one that was suitable. So, I designed this. It is a linear supply, which might have a few of you rolling your eyes, but it takes very few parts, is simple to build and can supply huge currents

High Current Power Supply Circuit diagram :

Parts Table :

Part	Total Qty	Description
R1	1	680 Ohm 1/4 Watt Resistor
C1	1	20,000 - 50,000uF 20-40 Volt Capacitor
C2, C3	2	100uF 50 Volt Capacitor
C4	1	0.1uF 50 Volt Capacitor
C5	1	0.01uF 50 Volt Capacitor
D1	1	Zener Diode (See Notes)
Q1	1	2N3055 Or Other (See Notes)
T1	1	Transformer (See Notes)
BR1	1	Bridge Rectifier (See Notes)
S1	1	SPST 250 VAC 10 A Switch
MISC	1	Case, Line Cord, Heatsink For Q1, Binding Posts For Output

Notes :

1. D1 should be rated at about one volt higher than then desired output of the supply. A half watt diode will do.
2. Q1 can be a transistor similar to the 2N3055. I chose the 2N3055 for its availability and power handling (150 watts).
3. T1 should be about 5 volts higher than the desired output of the supply, and rated for about one amp more of current. The voltage overhead is required by the regulator section. The extra current is to keep the transformer from over heating.
4. The choice of BR1 will depend on the voltage and current of your transformer. The rectifier should be rated for 50 volts more than the transformer, and 5 amps more than the transformer.
5. The value of R1 will be smaller when supplying high currents. Expiriment until you get what you need.
6. Heatsink and fans are absolutely necessary!

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Floating 9V Supply For DVM Modules

Most commercial DVM modules with an LCD readout are 9-V powered and based on an ICL7106 or similar A-D converter chip. These modules are typically used in laboratory power supplies and other test and measurement equipment where a drop-in solution needs to be found to realize a voltmeter readout. Particularly in power supply units, the LCD module will need to ‘float’ relative to the PSU supply rails, and this inevitably requires a separate 9-volt power supply. In some cases, batteries may be used but these have distinct advantages. The alternative, a 9-V converter effectively powered by the PSU and yet floating, is shown here.


It is built from the ubiquitous TLC555, LMC555 or 7555) timer IC acting in astable multivibrator configuration producing a 70-kHz square wave fed into a simple rectifier. In essence, capacitors C5 and C6 afford the above mentioned electrical isolation between the PSU supply rails and the LCD module. The old, bipolar NE555 IC should not be used here because it presents a too heavy loads on the converter’s own supply voltage. Depending on the exact type and brand of the CMOS 555 you’re using, resistor R6 may need to be redimensioned a bit to ensure a supply voltage of about 10 volts at pins 8 and 4 of the chip. At an output voltage of 9.5 V, the maximum output current of the converter s about 1 mA.

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3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM

3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM

A 5V DC regulated output from 2 cells 3V DC batteries. The output current of the circuit is limited to 50mA. However, it still able to supply many microcontroller circuits. 3009 and 560R Resistor provide the 5V DC output, make up a voltage divider network.

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Add this Short Circuit Protection to Your Power Supply

A power supply unit is an indispensable unit for every electronic enthusiast and engineers working in the relevant field. Though today all of us use hi-tech power supply units having built-in protection, there are folks who still rely on ordinary types of power supply units with no protection facility.


The biggest enemy of all power supply units is a possible short circuit that might occur at its output terminals due to an accidental connection or due to the fault with the connected load.

There are various electronic circuits that might be employed with a power supply unit for checking this problem, however these circuits sometimes themselves are at risk of getting damaged due to the limitations with many electrical parameters.

A very innovative way of rectifying this problem has been shown in this article. A single relay is used for sensing as well as tripping the output from the involved malfunction.

Referring the circuit diagram, we see that a relay is connected directly to the output of the power supply DC output, however the connection is made through the N/O contacts of the relay. These contacts are also terminated as the output of the unit.

N/O means normally open, that means the contacts are open initially, which in turn keeps the output disconnected from the positive of the power supply.

Now when the shown push button is momentarily pushed, the N/O contacts are bypassed allowing the current to flow across the relay coil.

The relay coil energizes, closing the N/O contacts, which in turn latches and sticks to the position even after the push button is released.

The relay latch maintains this latched position as long as the output is used under normal conditions, but when a short is made or happens across the output terminals of the supply, voltage drops rapidly across the relay coil and it immediately trips, cutting OFF the supply to the output and in the course switches OFF the latch preventing the short hazard conditions.  

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Power Supply Failure Alarm

Most of the circuit power supply failure alarm circuits require additional or external power supply. However, this circuit requires no additional power supply. The circuit uses a voltage of 5 volts to 15 volts. To adjust the voltage of this circuit, first connect the power source (5 to 15V) and change the position of potentiometer VR1 until the buzzer buzzer On to Off position.

If the power supply fails, resistor R2 will bias the transistor and the base will turn on the buzzer. Here is a picture series of power supply failure alarm :

 Power Supply Failure Alarm  Circuit

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Low Cost Dual Power Supply

This circuit shows how to symmetrically split a supply voltage using a minimum of parts - one LM380 power amplifier plus two 10µF capacitors. It was originally published in National Semiconductors AN69 and provides more output power than a conventional general-purpose op amp split power supply. Unlike the normal power zener diode technique, the LM380 circuit does not require a high standby current to maintain regulation. In addition, with a 20V input voltage (ie, for ± 10V outputs), the circuit exhibits a change in output voltage of only about 2% per 100mA of unbalanced load change. Any balanced load change will reflect only the regulation of the source voltage, Vin.

Circuit diagram:

Low-Cost Dual Power Supply Circuit Diagram

The theoretical plus and minus output tracking ability is 100% since the device will provide an output voltage at one-half of the instantaneous supply voltage in the absence of a capacitor on the bypass terminal. The actual error in tracking will be directly proportional to the unbalance in the quiescent output voltage. An optional 1MO potentiometer may be installed with its wiper connected to pin 1 of the LM380 IC to null any output offset. The unbalanced current output is limited by the power dissipation of the package.

In the case of sustained unbalanced excess loads, the device will go into thermal limiting as the internal temperature sensing circuit begins to function. And for instantaneous high current loads or short circuits, the device limits the output current to approximately 1.3A until thermal shutdown takes over or the fault is removed. For maximum output power (2.5W), all ground pins (3-5 & 10-12) should be soldered to a large copper area (the LM380 data sheet contains more details).

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Adjustable Stabilized Power Supply 0 15V 5A

Adjustable Stabilized Power Supply 0-15V / 5A

This
adapted ability accumulation can be adapted amid a few volts and 15V
with P1 and with P2 acclimatize the high absolute ( 15.0V ). R6 amount
is 0.7V / Imax area Imax is the best current. At Imax = 5A, R6 is
0.14Ω

T1 and T2 charge accept
heatsinks because ability losses are abundant at a low achievement
voltage and a Imax according accepted but you can affix the lamp L to
abate this losses.

I’ve body
this adjustable ability accumulation and works great! I achievement
you’ll adore it too and accept fun body this abundant counterbalanced
ability supply.

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5 to 15V Regulated Power Supply Rise

Regulated Power Supply

This project is a normal DC regulated power supply that is a variable DC voltage range from 5V to 15V. It can supply current up to  400mA to power the various circuits for your electronic projects. The voltage output is varied by using the potentiometer V.R1. In this circuit, the input line power supply is designed for 240V.A.C. If 110VAC input is used, alter the ratings of the varistor to 150VAC & the transformer ratio to 110V/12V. 

Fuse F1 is used as a protection in case theres any short circuit in the circuit. Varistor V1 is connected in parallel to the input of the line voltage to clamp the surge voltage from the line to a reasonable level that helps to protect the transformer & other circuitry. One time the voltage level surge to a high level beyond the ability of the varistor to absorb it, fuse F1 or varistor V1 or both will burn. If this circuit failed after a period of operation, check that the fuse & the varistor are still in nice condition or else replace them.

Diodes D1, D2, D3 and D4 are used to rectify the 12V.A.C voltage to DC voltage. Electrolytic capacitor E1 is used as a smoothing capacitor to reduce the ripple of the DC voltage. The DC voltage is fed in to the input of 7805 regulator where the output DC voltage is obtained. Changing the worth of VR1 will alter the output of the DC voltage. Capacitor C1 is used to filter out high frequency part from the power supply.

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Computer Power Supply for Battery Charger

Some workbenches can’t help ending up looking like a rats nest of cables and equipment, so its always an advantage if a piece of mains equipment can be removed from somewhere to free up an extra mains socket. Here we are using the ubiquitous PC as a battery charger. An unused serial interface port can supply enough current to charge (or trickle charge) low-capacity Nickel Cadmium (NiCd) batteries. You could for example, use the batteries in a radio and charge them during use.

The three serial port connections TxD, DTR, and RTS, when not in use, are at –10 V and can supply a current of around 10 to 20mA (they are short-circuit protected). The circuit shown supplies a charging current of approximately 30mA. If it is necessary to alter the polarity of the charging circuit then it is a simple job to reverse the diodes and using software, switch the port signals +10 V. Those interested could also write a software routine to automatically recharge the batteries.

Source : www.extremecircuits.net

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35 Ampere Power Supply

To make 12Volt 35 Amp Power Supply such as those titles can using LM7812 voltage regulator as the regulator 12 Volt DC and as a power supply can use transistor  TIP2955 .

Series Power Supply 12Volt 35 Amp uses 6 units TIP2955 type power regulator transistors. I use a type MJ2955 TIP2955 not because packaging TIP2955 easier to install heatsink. The series 12Volt 35 Amp Power Supply can be loaded up to 35A depending on the travo which we attach. The series 12Volt 35 Amp Power Supply is very simple, because the voltage regulators make use of IC7812 which will leave a power regulator alone. For more details, series 12Volt 35 Amp Power Supply can be seen in thethe following figure .

12Volt 35Ampere schematic

If want the maximum currents up to 35A not only reduced the live circuit TIP2955nya power regulator, no need to 6 levels as seen in the image series 35 Ampere Power Supply 12Volt above.

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