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Showing posts with label supply. Show all posts

Thursday, December 26, 2013

Simple Multivoltage Power Supply Circuit Diagram

This dual-polarity, multivoltage power supply circuit diagram can be built for a very small investment. The circuit is built around 78XX and 79XX series i-A voltage regulators, four 3-A diodes, a 24-30-V 2-6-A transformer, and eight filter capacitors.

Multivoltage Power Supply Circuit Diagram

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Wednesday, December 25, 2013

Simple UPS Power Supply

This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply.

Basic UPS Power Supply-1

Notes:

This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit.

TR1 has a primary matched to the local electrical supply which is 240 Volts in the UK. The secondary winding should be rated at least 12 Volts at 2 amp, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and output voltage is maintained by the battery. The circuit below simulates a working circuit with mains power applied:

Basic UPS Power Supply-2

Note that in all cases the 5 Volt regulated supply is maintained constantly, whilst the unregulated supply will vary a few volts.

Basic UPS Power Supply-3

Standby Capacity

The ability to maintain the regulated supply with no electrical supply depends on the load taken from the UPS and also the Ampere hour capacity of the battery. If you were using a 7A/h 12 Volt battery and load from the 5 Volt regulator was 0.5 Amp (and no load from the unregulated supply) then the regulated supply would be maintained for around 14 hours. Greater A/h capacity batteries would provide a longer standby time, and vice versa.

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Sunday, December 22, 2013

Preregulator for Power Supply Circuit Diagram

This SCR pre-regulator keeps the filter capacitor Vc, in a variable output power supply, a few volts above the output voltage V0. The benefits include: less heat dissipated by the pass transistor and therefore small heatsink, cooler operation and higher efficiency, especially at low output voltages. Ql, Rl, R2, Dl and D2 form a constant current source for zener Zl, so that the contribution to the output current is always a few mA (2-3 mA). The Darlington pair Q2, Q3 keeps the SCR off.

Preregulator for Power Supply Circuit Diagram

The voltage Vc decreases until Vc = V0 = V at which point the Darlington pair fires the SCR, charging the filter capacitor to a higher voltage VC1 in less than half the period of the input voltage. The component values, shown are for a 0 - 250-V, 3-A power supply.

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Power Supply Balance Indicator Circuit Diagram

This circuit uses two comparator pairs from an LM339N quad comparator; one pair drives the yellow positive (+)and negative (-)indicators, the other jointly drives the red warn LED3. The circuit draws its power from the unregulated portion of the power supply. The four comparators get their switching inputs from two parallel resistor-divider strings. Both~strings have their ends tied between the power supply`s positive and negative output terminals.

The first string, consisting of R4, R5, and R6, divides the input voltage in half, with output taps at 0.5%. The other string, made up of R7, R8, and R9, also divides the input voltage in half, with taps at + lO%. The 0.5% R4/R5/R6 string drives the two comparators controlling the positive and negative indicators (LEDl and LED2). Their inputs are crossed so that LED2 does not fire until the positive supply is at least 0.5% higher than the negative; the positive indicator does not go off until the negative supply is at least 0.5% higher than the positive-in relative levels.

That overlap permits both LEDs to be on when the two supplies are in 1 % or better balance. The +lOT R7/R8/R9 string drives the other two comparators, which control the warn indicator. If either side of the supply is lO% or more higher than the other, one of the two comparators will switch its output low and light the redLED3the LM339N has opened-collector outputs, allowing such wired OR connections. The inputs are not crossed, as with the other comparator pair, so there is a band in the middle where neither comparators output is low and the LED remains off.

Power Supply Balance Indicator Circuit Diagram

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Friday, December 20, 2013

Simple Efficient Supply Splitter Circuit Diagram

Simple Efficient Supply Splitter Circuit Diagram. In this application, the Vl-7660 is connected as a voltage splitter. Note that the normal output pin is connected to ground and the normal ground pin is used as the output. The switches that allow the charge pumping are bidirectional; therefore, charge transfer can be performed in reverse.

The 1-MO resistor is used to avoid start-up problems by forcing the internal regulator on. An application for this circuit would be driving low-voltage, Â± 7.5 Vdc, circuits from Â± 15 Vdc supplies, or low-voltage logic from 9 to 12 V batteries.

Efficient Supply Splitter Circuit Diagram

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Wednesday, April 10, 2013

High Current Regulated Supply Circuit Using LM317

The high current regulator circuit is built uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency. For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage. The operation of this circuit is explained like this.

The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage. The LM317 will provide over 1 amp of current to drive the bases of the pass transistors and assumption a gain of 10 the combination should deliver 15 amps or more.

The LM317 always operates with a voltage difference of 1.2 between the output terminal and adjustment terminal and requires a minimum load of 10mA, so a 75 ohm resistor was chosen which will draw (1.2/75 = 16mA). This same current flows through the emitter resistor of the 2N3904 which produces about a 1 volt drop across the 62 ohm resistor and 1.7 volts at the base. The output voltage is set with the voltage divider (1K/560) so that 1.7 volts is applied to the 3904 base when the output is 5 volts. For 13 volt operation, the 1K resistor could be adjusted to around 3.6K. The regulator has no output short circuit protection so the output probably should be fused.

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