Switching Regulator Efficiency - Minimize Power Consumption in Battery-Operated Systems

A switching voltage regulator converts input DC voltage into a desired output DC voltage. This month, Stuart delves into the factors that influence the efficiency of switching regulators, and why they are crucial for embedded applications. From understanding the role of inductors and transistors to exploring practical examples, this article offers valuable knowledge for anyone interested in optimizing power supply designs.

- Stuart Ball

In a lot of embedded applications, you will use a single power supply, either from the AC line or from batteries. But in some cases, you will have an application that needs more than one voltage. For example, you might have a battery-operated system that needs a 9V or 12V supply voltage for an op amp that is sensing something from a sensor. Or you might need to illuminate an LCD backlight using a voltage that is higher than the supply voltage. You might have a device that operates from a 6V battery (such as four AAA cells), but that has to power a 3.3V MCU.

In all these cases, you need a voltage regulator—a device that produces a constant output voltage to power an electronic circuit. In each instance, you can use a switching power supply to generate the needed voltage. A switching regulator, whether step-down or step-up, uses switching techniques to produce a regulated output voltage. But, especially in battery-operated equipment, you want the power supply to be as efficient as possible, so as to minimize the power it uses.

In my column on “Voltage Regulators” (Circuit Cellar #387, October 2022) [1], I looked at voltage regulators, power, and efficiency, and I touched on switching regulators. This month, I want to narrow specifically to the things that affect the efficiency of switching regulators.

SWITCHING SUPPLY TYPES

Switching supplies come in three basic configurations:

• AC-to-DC converters change AC input to a DC output. An example is the power supply in a desktop computer. I won't be covering those here.

• Step-up or boost converters change a DC input voltage to a higher output voltage. An example would be the aforementioned switcher that converts the 3.3V MCU supply voltage to 6V to power an LCD backlight.