Switching power supplies go green

Today’s rising energy crisis and abnormal climate changes have made eco-friendliness and energy efficiency the top priorities among electronic manufacturers. Companies are coming up with products that are recyclable and power-efficient without compromising performance.

The electronic industries play a crucial role in the conservation of energy. Manufacturers are trying to help save power by optimizing the overall energy efficiency of their products. One way to achieve this is through minimizing power loss, especially when electronic devices are in standby mode. FOCUS ON LOSSES

In designing switching power supplies, achieving a high level of overall efficiency is a top priority. This can be done by developing and incorporating improved circuit topologies and component characteristics, circuit optimization by software enhancements, and advanced IC controls. Moreover, the designer must focus on power losses to optimize the device’s overall power efficiency. Minimizing losses can be achieved in two ways: by reducing the switching loss, and by reducing the conduction loss.

Several factors can contribute to conduction loss. The turn on resistance (R_DS(ON)) of the power MOSFET and the forward voltage dropout of the rectified diode are just some of these factors. For example, power loss in the output of a Schottky diode is common in traditional designs and needs to be addressed immediately. Thankfully, Schottky diodes are now being replaced with MOSFETs that feature dedicated current sensing and control circuit. This kind of synchronous rectifier controller can improve the device’s overall power efficiency by up to 2 percent, which is noteworthy in high power applications with high current output.

Switching loss, meanwhile, can be reduced by using a dedicated electronic controller that has intelligent and sophisticated control algorithms. The Zero Voltage Switching (ZVS) is a promising control technique. Losses in the power MOSFET and the snubber circuit can be reduced by either ON or OFF at the moment when the voltage (current) of the MOSFET reaches its minimum level.

The BCT8210S controller from BlueChips Technology is a zero voltage switching controller for half bridge topologies. It monitors the drain voltage of the MOSFET via an auxiliary winding that detects the near zero voltage, enabling high efficiency switching in every cycle.

GREEN-MODE PWM CONTROLLER

Electronic devices and appliances such as DVD recorders and televisions, even when not in use, continue to consume power when plugged into a wall socket. The International Energy Agency (IEA) estimates that 1 to 5 percent of household electricity consumption is wasted by appliances in standby mode. These losses can be significantly minimized by reducing the switching frequency.

BlueChips’ BCT8320 is a green-mode PWM controller that features a switching frequency of up to 30 times (1.5kHz) lower than the normal (~75kHz) rate to reduce switching loss. This green-mode function enables the power supply to meet numerous industry power conservation requirements, such as Energy Star and Blue Angel.

The PWM controller’s passive components include isolated transformers, chokes and capacitors. The controller’s performance and electrical characteristics are continuously improved by the latest manufacturing technologies. BCT8320 features good electrical characteristics by using chokes and capacitors in SMT size. In addition, fringing and leakage flux losses of the power transformer are greatly reduced by computer modeling and optimization programs.