Switching regulators

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Electronic projects often need stable, constant power supply voltages. The traditional way for hobbyists to do this has been using a LM78xx series linear regulator, because they're cheap and easy to use. They're also usually very inefficient, wasting a minimum of 30% of the input power (efficiency decreases further as the difference between the input and output voltage increases: with a 5V output and a 12V input, the loss is 60%). In addition to efficiency concerns, linear regulators can only step voltage down; they cannot raise or invert an input voltage.

The solution to these problems is a switching regulator. Purpose-designed regulators can be as much as 95% efficient, although for hobby purposes they usually end up closer to 80-90%. Switching regulators have their own problems of course. From the hobbyist perspective, the largest problem is the design and construction. The process requires balancing a number of different constraints against each other, and frequently has to be redone when components are unavailable in small quantities. Circuit board layout is important, and can mean the difference between a highly efficient stable regulator and one that oscillates or just doesn't work.

Fortunately, a number of easy to use modules have recently become available for cheap. Some have fixed outputs, and some have adjustable outputs set by a resistor. Some require capacitors on the input or output - check the data sheet. This table is only a guide. Check the data sheet to make sure that a part is suitable for your purpose. Also, manufacturers typically have a large range of modules with varying input/output voltage and current capabilities. Check the manufacturer's web site to see if there's something that might be better-suited to your application.

In the hobby RC world, these modules are known as Battery Eliminator Circuits (BEC). Traditionally an RC vehicle would have two batteries, one to power the drive motor (usually higher voltage and high capacity) and one to power the receiver and steering servos (usually 4.8-6V and lower capacity). A BEC powers the receiver and servos from the larger battery, providing clean regulated power at the correct voltage for the sensitive digital electronics.

Voltage Regulators
Part # Manufacturer Function Input V Output V Dropout V Output Imax Output Pmax Package
PTH08080 TI Step-down 4.5V - 18V 0.9V - 5.5V higher of Vo + 1.1V or 4.5V 2.25A 12W 5-pin non-standard module
PTR08060W TI Step-down 4.5V - 14V 0.6V - 5.5V higher of Vo/0.83 or 4.5V 6A 5-pin inline 0.067" spacing
78xxSR Murata Step-down 7.5V, 7.5V, 15V 3.3V, 5V, 12V 0.5A 3-SIP, 78xx compatible lots of 78xx-compatible regulators - google for "switching 78xx"
PTN04050C TI Step-up 2.95V - 5.5V 5V - 15V  ? 12W 4-pin non-standard module
MintyBoost AdaFruit Step-up 3V 5V 400mA altoids-gum-tin-shaped meant for charging portable devices over USB
VPack PCB SparkFun Step-up 1V - 4V 5V 300mA PCB also available attached to 1xAA case or 2xAA case.
NCP1400-5V SparkFun Step-up 1V - 4V 5V 100mA PCB, holes on 0.1" spacing
NCP1400-3.3V SparkFun Step-up 1V - 3V 3.3V 100mA PCB, holes on 0.1" spacing

Other sources:

There are also switching current regulators, essential for driving >1W LEDs like Luxeons from a battery. BuckPuck, BoostPuck, TaskLED, others.

All switching regulators will be more expensive than linear regulators. In a wall-powered device, the extra cost may not be worth it. In battery-powered devices they will probably pay back due to less frequent battery replacement/recharging, smaller size for high power uses (since a heat sink is not needed), or the ability to use lower capacity batteries.