Voltage Inverter Using Switch Mode Regulator

This circuit uses a step-up switch-mode regulator, which is usually used to produce a positive supply, to generate a regulated negative output voltage. The device used here is the MIC4680 from Micrel (www.micrel.com), but the idea would of course work with similar regulators from other manufacturers. Because of coil L1, which performs the voltage conversion by the intermediate storage of energy in the form of a magnetic field, the output is effectively isolated from the input. We can therefore connect the right-hand side of L1 to ground rather than to the positive output without causing a large current to flow. Then we connect the ground pin of the regulator IC and all the components connected to it as the negative voltage output, isolated from ground.

The components on the output side of the regulator are connected as usual: flywheel diode D1, coil L1 and the voltage divider formed by R1 and R2. These last two components set the output voltage, according to a formula given in the data sheet. Example component values for the MIC4680 used here are given in the table. The input voltage should lie within the permitted range for the regulator used, and must in any case be at least as great in magnitude as the desired output voltage (here +5 V or +12 V), so that the step-down regulation technique can wor.

It is important to take care when building this circuit to mount the regulator using an insulator, since generally the GND pin of the device is connected to the heatsink tab. Also, the ON/OFF control input cannot be driven using a normal logic signal, since the regulator’s ground reference is the output voltage rather than ground itself. If the ON/OFF function is required, a level shifter or optocoupler must be used.

Source: http://www.ecircuitslab.com/2011/06/voltage-inverter-using-switch-mode.html 

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Regulator current Source Circuit Diagram

The circuit powers the load via the regulator`s input instead of its output. Because the regulator`s output sees constant dummy load R1, it tries to consume a constant amount of current, no matter what the voltage across the actual load really is. Hence, the regulator`s input serves as a constant-current source for the actual load. 

Power the circuit with any one of the commonly available ± 15 or ±12 V supplies. The voltage dropped across the regulator and dummy load decreased the total compliance voltage of the~circuit. You set the load`s current with Rl. The current equals 1.25 A/`J x Rl.

Regulator current Source Circuit Diagram

Regulator current Source Circuit Diagram

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PRECISION POWER REGULATOR ELECTRONIC DIAGRAM

PRECISION POWER REGULATOR ELECTRONIC DIAGRAM

A precision voltage source is quite easy, except when the voltage should be consistent over wide range of ambient temperature. This requirement might be needed in high precision measurement system environment. For example, to provide reference voltage in analog to digital conversion.

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High Current Low Dropout Voltage Regulator

This circuit was designed to allow a laptop computer to be powered from a solar power setup. The computer requires 12V at 3.3A. The circuit is a linear regulator with Mosfet Q4 as the series pass device. A 100kO resistor provides Q4 with a positive gate-source voltage. Any tendency for the output voltage to exceed ZD1s voltage causes Q2 to turn on. This turns on Q3 which reduces Q4s gate voltage and thus reduces the output voltage. Note that Q2s base-emitter voltage stabilizes at about 0.35V. This combined with the zener voltage gives an output of 12.4V. If a more precise output is required, first select ZD1 so that its voltage rating is at least 0.4V less than the required output voltage.

You can then "trim" to the required output voltage by installing a resistor in series with ZD1. Q2s base-emitter voltage and the 680W base resistor set the current through ZD1 to 0.5mA. This means that the output voltage will be boosted by 0.1V for each 200O of resistance in series with ZD1. Zener diode ZD2 ensures that Q4s maximum rated gate-source voltage is not exceeded. Mosfet Q1 provides reverse polarity protection. Note that Q4 requires a heatsink since it will dissipate about 10W under worst-case conditions. No heatsink is required for Q1. At 3.3A, the regulator reduces the output voltage by just 0.2V. This can be further reduced by paralleling Q1 & Q4 with additional Mosfets.

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Adjustable Switching Regulator Circuit with LM2576

The Adjustable Switching Regulator Circuit with LM2576 are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving 3A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V, and an adjustable output version.

LM2576 IC Package

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixed-frequency oscillator. The Adjustable Switching Regulator Circuit with LM2576 offers a high-efficiency replacement for popular three-terminal linear regulators. It substantially reduces the size of the heat sink, and in some cases no heat sink is required.

IC Switching Regulator Circuit with LM2576

A standard Adjustable Switching Regulator Circuit with LM2576 of inductors optimized for use with the LM2576 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies.

Other features include a guaranteed ±4% tolerance on output voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring 50 μA (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions.

Features Adjustable Switching Regulator Circuit with LM2576 :
- 3.3V, 5V, 12V, 15V, and adjustable output versions
- Adjustable version output voltage range,1.23V to 37V
- Guaranteed 3A output current
- Wide input voltage range, 40V up to 60V for HV version
- Requires only 4 external components
- 52 kHz fixed frequency internal oscillator
- TTL shutdown capability, low power standby mode
- High efficiency
- Uses readily available standard inductors
- Thermal shutdown and current limit protection
- P+ Product Enhancement tested

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