San Jose, Calif.—Renesas Technology's R2A20112 is a critical-conduction mode (CCM) power factor correction (PFC) control IC for AC/DC power supplies, which the company says is the first device of its type to implement interleaved operation. As such it enables design of small, thin, low-noise, high-efficiency AC/DC power supplies for consumer and office automation products.
Traditional AC/DC power supplies use choke-input rectifiers or similar voltage conversion techniques, with consequent inefficiency due to waveform mismatches and timing variations between the voltage and current waveforms. Power-factor-control ICs using the so-called continuous-current-conduction mode have largely replaced the basic topologies. The R2A20112 adds interleaved operation to further boost efficiency and shrink the size of the power supply, both from the standpoint of reducing component size as well as often eliminating the need for a cooling fan.
The R2A20112 uses two signals (master and slave) for control, allowing critical mode PFC control with interleaved operation that reduces variations in operating timing. The slave control circuit allows highly precise current distribution, making it possible to reduce the size of components such as the input filter, step-up coil, and input/output capacitors.
In addition, the chip implements ZCS (zero-current switching) circuitry, thus reducing heat to allow a smaller, less complex heat sink. The combination of
ZCS and interleaved operation, says the company, prevents the flow of redundant currents (e.g., step-up-diode recovery current). It also controls the flow of appropriate currents and reduces the power supply line noise and ripple current. Consequently, EMI is reduced, allowing the designer to simplify the AC input filter and noise shielding. In total, these design advances for reducing switching, recovery, and conduction losses boost the IC's power conversion efficiency by at least 5 percent over the company's previous generation products (i.e., HA16174, R2A20111).
Contact the company directly for the product datasheet.
The R2A20112SP, in a SOP-16, and R2A20112DD, in a DILP-16, are priced at $1 each. They'll be available in 1Q.
Renesas Technology, 1-408-382-7407,
•Critical-conduction mode (CCM): A mode in which an external power MOSFET is switched after detection of a zero step-up coil current.
•Power factor correction (PFC): A means of regulating a higher harmonic wave (a sine wave that is an integral multiple of the 50 or 60 Hz of a commercial power supply) that accounts for the time lag (phase lag) between the voltage waveform and current waveform. The output of a simple choke (inductor) input stage, on the other hand, is a pulse.
•Interleaved operation: A method whereby a number of switching elements (MOSFETs) are operated alternately. While single switching performed by one control signal is normally used, interleaved operation provides for the use of a separate complementary switching line between switching operations.
•Zero current switching (ZCS): A method whereby a MOSFET is switched when the current through it is zero.