Browse Prior Art Database

A High Efficiency Power Factor Correction (PFC) Circuit For AC/DC Adapters

IP.com Disclosure Number: IPCOM000014633D
Original Publication Date: 2000-Sep-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Abstract

A High Efficiency Power Factor Correction (PFC) Circuit For AC/DC Adapters Problem: The ac -dc adapters required for mobile products require very high efficiency and small size. The ac -dc adapter so far has not required any power factor correction. However, there is a trend to require power factor correction for these low power ac -dc adapters. Also. the existing methods for power factor correction are not suitable because of the size limitation.

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A High Efficiency Power Factor Correction (PFC) Circuit For AC/DC Adapters Problem:

The ac -dc adapters required for mobile products require very high efficiency and small size. The ac -dc adapter so far has not required any power factor correction. However, there is a trend to require power factor correction for these low power ac -dc adapters. Also. the existing methods for power factor correction are not suitable because of the size limitation.

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3

1

3

Q1

Q2

22PWM 2

2PWM 1

3

11 D14

C1

+

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Error
Amp

Figure 1. A Boost and Chop Circuit for Power factor correction.

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2

4

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Q3

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Driver

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Square wave
Oscillator

Boost
Controller

R4

Figure 2. A PFC Circuit for AC/DC adapters

1

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Problem Solved:

The present invention uses an open loop Zero Volt Switching (ZVS) chopper operating at 1 MHz and a Zero Current Switching (ZCS) Boost operating close to 500 kHz. The high frequency is important to achieve the smallest size possible because of EMC filter requirement. Also there is no high voltage electrolytic capacitor required on the primary side of the switching regulator and no inrush current limitation circuitry needed. As the boost stage components operate at low voltage, low Rds(on) MOSFET and SCHOTTKY diodes can be used for the application to achieve high efficiency .

Description:

Figure 1 sh...