Power Electronics

PFC Controllers Reduce Heat Dissipation

The latest generation of power factor correction (PFC) controllers offers new features that reduce their power consumption and ease thermal management requirements for these ICs. Two recently introduced controller chips from Renesas Technology America and Fairchild Semiconductor exemplify this trend.

From Renesas, the R2A20112 critical-conduction-mode (CRM) PFC controller for ac-dc power supplies implements interleaved operation. The power conversion efficiency of this IC is better by 5% or more than Renesas' previous products. As a result, heatsinks can be smaller and the overall dissipation of the power supply can be reduced enough to make a cooling fan unnecessary.

The device uses various techniques that enable system simplification. For example, a zero-current switching (ZCS) function causes the power MOSFET to switch at the exact instant at which no current is flowing. This reduces the device's heat emission and allows a smaller heatsink. Also, the combination of ZCS and interleaved operation prevents the flow of redundant currents such as stepup diode-recovery current. AC-DC power supplies have typically used simple choke input rectification or similar voltage conversion techniques that suffer power losses due to waveform mismatches and timing variations between the voltage and current waveforms.

The device is available with the SOP-16 package option as the R2A20112SP, or the DILP-16 package as the R2A20112DD. The sample pricing for each is $1.00, and both devices will be available in Q1 of 2007.

Fairchild’s FAN7529 and FAN7530 utilize an internal voltage-mode pulse-width modulation (PWM) method, compared with conventional current-mode controllers requiring rectified ac line-voltage information, even when the PFC IC does not operate. As a result, these CRM PFC controllers reduce overall power loss by approximately 200 mW. Moreover, these controllers offer a disable function to further reduce power consumption during standby mode, and their current-type error amplifiers enable these devices to use a higher output-voltage-sensing resistor (RFB), resulting in reduced power loss (80 mW when RFB = 2 MΩ).

The FAN7529 and FAN7530 are offered separately as pin-out options for meeting specific requirements and design preferences. Both are available in DIP-8 and SOP-8 packages. The 1000-piece pricing is $0.70 for the FAN7529 and $0.64 for the FAN7530.

For more information on recently developed PFC controllers, see “PFC Controller ICs Continue to Advance” in the September 2006 issue of Power Electronics Technology.

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