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| Renesas Continuous Conduction Mode PFC IC R2A20115 Features with High Accurate Constant Power Limiter Rev.6.0 April 2010 * No reference voltage adjustment resistor is needed with higher accurate built-in circuit (+/-1.6%) than previous products (+/-2%). * No margin for inductor design is needed with higher accuracy of detect level of the built-in over current protection circuit. (Previously, the margin can not be omitted for its lower accuracy) * Prevention of "coil vibration" at starting-up or over current period by the function of VCC OUT power limiter. (Previously, it's not supported) SS GND DIP16 * The function of power limiter cuts down unnecessary power supplied to the next EO DELAY stage. (Previously, the higher AC input voltage is applied, the higher power can be FB CGND or supplied to the next stage, of which power supply might be heavily loaded unnecessarily.) IAC CAI * Prevention of overshoot on output voltage by dynamic OVP function without specific VREF SOP16 PFC-ON Pins. (Previously, this function is not supported or partly supported using specific Pins) CT CAO * Power dissipation is cut down by 35% of comparable products. RT CLIMIT * Easy system design by using calculation sheet in Excel format provided for customers. 1-1. Introduction of Constant Power Limiter Using Current Monitoring and Setting Pins Separately Conventional R2A20115 Voltage amplifier FB Constant power limiter EO CAI VREF CLIMIT Over-current limiter "Coil vibration" is prevented by gradual/steady control when over current occurs. Multiplier 1-2. Introduction of Constant Power Limiter and Reduction of Needless Device Margin by the Improvement of it's Accuracy Input Ef f ectiv e Power v s Input AC Voltage Input Effective Power [W] 6000 5000 4000 3000 2000 1000 0 0 50 100 Constant power limiter is effectively working independently of input voltage R2A20115 [W] (R2A20115) [W] Using only Over Current Limiter (calculated) [W] () Multiplier CS Current amplifier Over-current limiter Current amplifier 150 200 250 Input AC v oltage [V] 300 1-3. Reduction of Maximum Current in Boost Inductor by Improved Accuracy of Power Limiter and Current Limiter Input AC Current Current limiter accuracy Power Limiter accuracy R2A20111 Current Limiter Vcl=+/-78mv Input AC Current R2A20115 Current Limiter Cut the extra margin by minimizing the peak current distribution of inductor due to high accuracy power limiter and current limiter function. Vcl=+/-15mv Power Limiter Power Limiter Inductor Input AC Voltage Inductor Input AC Voltage 2. Improvement of Load Regulation by Utilizing gm AMP in Feedback Loop In case voltage amplifier is feedback type, the current via feedback resister influences load regulation. By using gm amplifier, there is no current path in the circuit. So that, load regulation can be improved. Additionally, contributed by the improvement in accuracy of circuit (2% to 1.6%), the resister to adjust the reference voltage becomes unnecessary. VOUT VEO 3. Hold Function at Brownout Brownout AC Input Detection level Detection level Brownout Hold Counter PFC Output voltage Competitor's VOUT VOUT R2A20115 Hold time can be adjusted. 1.6% 2% FET OUT (R2A20115) R2 R1 Error AMP VEO VREF R2 R1 FB Error AMP Final adjustment of resister Final adjustment of resister is not needed. is not needed. VEO Io VREF 5 4 3 2 1 By hold function, the IC keeps working if the duration of brownout is shorter than the preset hold time. So that it can recover rapidly. The IC restarts safely with soft-start mode if the duration of brownout is longer than the preset hold time. 4. Prevention of "Coil Vibration" and Overshooting Contributed by Dynamic OVP The IC newly integrates Dynamic OVP circuit, which limits peak current by making the width of OUT pulse narrower gradually and then prevents over voltage, when over voltage is detected, in addition to Static OVP circuit, which stops the output pulse. Even if overshooting occurs in transition period, such as the period of start-up or sudden variation of load, Dynamic OVP keeps the output pulse on, so that, "coil vibration" can be prevented. Error Amp Block Operations just after sudden variation of load <0.1A-1.3A> Dynamic OVP With Dynamic OVP (c)2010. Renesas Electronics Corporation, All rights reserved. Without Dynamic OVP Renesas Electronics URL http://www.renesas.com/pfcic |
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