Cellphone chargers typically sit plugged in and unused most of the time. Yet they still draw power from the grid, wasting energy and the consumer’s money. A problem facing design engineers is how to reduce standby power in these devices, thereby saving energy, meeting government regulations and saving the consumer money.
To help designers meet this challenge, Fairchild Semiconductor developed the FAN302HL PWM controller for low standby power charger applications. Incorporating mWSaver technology, the device features patented technologies that allow it to minimise standby input power consumption to <10 mW at 230 V a.c.
The device provides several features to enhance the performance of general flyback converters. Integrating a 500 V JFET, it can cut off the current path after the device is turned on, reducing start-up losses. The patented constant current control topology enables simplified circuit design without secondary constant current feedback circuitry – especially important in battery charger applications.
The FAN302HL also provides several protection features. These include cycle-to-cycle current limiting to ensure a fixed peak current limit level, even if a short circuit occurs. Additionally, the gate output is clamped at 15 V to protect the power MOSFET from high gate-source voltage damage. The IC does not require an external secondary-side over-voltage protection (OVP) circuit. If either VS pin OVP or internal over-temperature protection is triggered, the device enters latch mode until AC power is removed, saving secondary-side OVP components and tightening VO protection (<6 V).
Primary side regulation control for constant current and no secondary-side current sensing provides lower losses and improved efficiency. Proprietary burst mode operation, with lower operation current, minimises standby power consumption. Additionally, the FAN302HL uses secondary-side regulation for constant voltage with good dynamic response, meeting USB 2.0 specifications.
In addition to cellphone chargers, the device is suitable for applications such as smart phones, cordless phones, DVD/set-top boxes, power over Ethernet and small appliances.
For more information contact Marian Ledgerwood, Future Electronics, +27 (0)21 421 8292, [email protected], www.futureelectronics.com
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