AccuSwitch PWM controllers remove the need for optocouplers

The household appliance market is growing at 3.8% annually and will reach 430 million units by 2017. The company’s iW1818 and iW1830 digital controllers are designed for use in dishwashers, refrigerators, cooking ranges, microwaves and other high volume appliance applications.

Most appliances today use secondary-side control to maintain the tight output voltage regulation for stable operation in multi-rail systems. For example, a 5V output for the system MCU needs ±5% voltage accuracy, while 12V to 16V rails for motor or relay control require ±10% accuracy. However, secondary-side designs require optocouplers, which have significantly worse failure rates compared to other components in the power supply.

The AccuSwitch PWM controllers use Dialog’s PrimAccurate primary-side control to eliminate the need for optocouplers, the weakest link in achieving the high reliability and long operating lifetime for appliances. The elimination of a secondary-side regulator and optocoupler means reduced BOM costs and fewer solder joints for potential failure, inherently increasing reliability. The company’s patented intelligent digital control loop technology provides accurate voltage cross-regulation between the multiple power rails in the system.

“The common notion is that primary-side regulation in white goods applications may eliminate the optocoupler, but comes at the expense of voltage cross-regulation accuracy,” said Davin Lee, Senior Vice President and General Manager, Power Conversion Business Group, Dialog Semiconductor. “Leveraging Dialog’s proven expertise in digital control, the iW1818 and iW1830 provide the best of both worlds, higher reliability of primary-side design and accurate cross regulation for lower cost, longer lifetime appliance designs.”

The iW1818 and iW1830 simplify appliance power supply designs by integrating a high-voltage power switch, and support high capacitance loads of up to 6,000µF at up to 12V.

The adaptive multi-mode PWM/PFM control in the devices dynamically changes the switching frequency to optimise the system for high efficiency even at light loads. They provide greater than 80% active average efficiency, maintain high efficiency at loads as light as 10% and achieve less than 50mW no-load standby power with fast standby recovery time. This helps white goods designers meet global energy efficiency regulations, including the European Ecodesign Directive and the U.S. Department of Energy energy conservation standards.

Both parts come in a thermally efficient, small footprint, easy-to-use PDIP-7 package that ensures excellent thermal performance using a single-layer PC board. In addition to built-in over-temperature protection, they offer full protection from fault conditions, such as output short-circuit, over-voltage and over-current.