AC to DC power supplies are fully integrated into our daily lives. They are the heart of all our electronics, providing energy for the everyday devices that we rely on. A cell phone charger is a power supply, but so are the power electronic circuits embedded inside almost any electronics or appliance connected to the AC line.
This near universal use of power supplies means that although the power that each individual supply draws is small, the cumulative effects are very significant. For this reason it is desirable, and often required by regulation, to control power supply characteristics such as efficiency. AC –DC Power supplies convert electrical energy from their AC line input to provide DC outputs that are:
- Isolated from the dangerous high-voltage, high-capacity AC line.
- Smoothed and low-noise DC voltage.
- Regulated to be largely independent of input voltage changes.
- Current controlled to avoid damage to the load (especially batteries) and to the power supply itself.
Typically, an AC to DC power supply converts the AC line (110 220V 50/60Hz) into low voltage (12, 5, 3V) DC. Power supply designers strive to improve the efficiency of their designs while maintaining specified performance over a range of input and load conditions and complying with demanding international regulations for harmonic current content, standby power, safety and EMC. This application note is intended to assist engineers who design and test power supplies and other equipment connected to the AC line make power related measurements accurately, quickly and safely.