Renesas Critical Conduction Mode PFC IC R2A20113 April 2010 Features (1)AC (1)AC high high voltage voltage line line less less Simple External Circuit Best for Small Power Supplies (3) Reduce recovery diode loss • AC sense line less • ZCD line less No open/short detector, No turn-on at inrush • Feedback loop detection • High efficiency by Zero current switching • Low radiation noise • Small package: SOP8/DIP8 390V (2) ZCD line less 19V Specification Vcc Maximum Tj operation Drive peak current FB ＶＣＣ ＣＯＭＰ OUT ＲＴ GND VREF OCP R2A2012X 24V -40 to 150deg. +/-0.9A Applications R2A20113 Best support for power supplies of 1-phase operating products that require low noise and downsizing due to the power factor regulation for flat-screen TV, HDD recorder and AV home electronics. 1. ZCD Line Less Getting ZCD signal pulse from the current sense resistor, therefore ZCD auxiliary winding is unneeded. External open short detection circuit is unneeded 390V + Unneeded! Unneeded! OCP comp. Open/Short Detector CS ZCD comp. R2A20113 Turn-on of MOSFET at inrush timing is prevented ZCD Vth Out put Voltage GND Input Current OUT Previous 2. Improvement of Load Reg. Adopting gmAMP In case of adopting gmAMP adopted, there is no feedback current flow, and load regulation becomes good. Conventional VOUT R2A20113 VOUT R2A20113 3．Dynamic OVP The R2A20113 has “Dynamic” and “Static” OVP. Dynamic OVP is doing discharge error AMP voltage before reaching Static OVP voltage. Therefore peak current is limited. As the result, reduce over voltage cause “No coil vibration”. Acoustic Acoustic noise noise isis reduced. reduced. 200ms/div Error AMP R2 R2 FB Error Amp Block Error AMP Feedback input VEO R1 R1 VREF OVP Dynamic OVP VREF 4. Feedback Loop Detector Feedback loop absence detect function can stop output pulse. Therefore Renesas PFC IC prevents the breakings of bulk capacitor and MOSFET. Conventional R2A20113 PFC out voltage In case of feedback loop down, bulk voltage is going up abnormal voltage. Then capacitor is broken. FB Convention IC (Without the function) PFC out voltage Detect the feedback loop disconnection, and stop the pulse!! cut Prevent from the breakings of Bulk capacitor & Power MOS!!! FB Vout COMP ILm 20ms/div Dynamic OVP 5. Principle Power Loss Reduction Continue conduction mode Recovery Loss of Boost diode by ZCS Basically, no recovery diode In CCM case, switching loss and radiation noise are large. loss by zero current switching too. Critical conduction mode FET current Drain voltage R2A20113 In CRM case, switching loss and radiation noise are small due to zero current and zero voltage switching. Renesas Electronics URL http://www.renesas.com/pfcic ©2010. Renesas Electronics Corporation, All rights reserved.