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Quasi-Resonant type AC/DC converter IC
BM1Q0XX series Quasi-Resonant converter Technical Design
This application note describes the design of Quasi-Resonant converters using ROHM’s AC/DC converter IC BM1Q0xx series
devices. It explains the selection of external components and provides PCB layout guidelines. Please note that all performance
characteristics have to be verified. They are not guaranteed by the PCB layout shown here.
● Description
The BM1Q0xx series of ICs are AC/DC converters for Quasi-Resonant switching, incorporating a built-in starter circuit having
withstanding voltage of 650V. Use of external switching MOSFET and current detection resistors, provides a higher degree of
design freedom. Power efficiency is improved by the built-in starter circuit and the reduction of switching frequency under light
load conditions.
● Key features
Quasi-resonant method
Built-in 650V tolerate start circuit
Low power when load is light (Burst operation)
Maximum frequency control (120kHz)
Frequency reduction function
AC voltage correction function
VCC pin : under voltage protection
VCC pin : overvoltage protection
Over-current protection (cycle-by-cycle)
OUT pin : H voltage 12V clamp
Soft start
ZT trigger mask function
ZT Over voltage protection
FB Over Load protection [Auto-restart]
CS pin open protection [Auto-restart]
● Basic specifications
Operating power supply voltage range(VCC) : 8.9V to 26.0V
VH voltage range(VH pin) : up to 600V
Operating current : Normal mode 0.60 mA (Typ.)
: Burst mode 0.35 mA (Typ.)
Maximum frequency : 120 KHz (Typ.)
Operating temperature range : -40°C to +85°C
● BM1Q0xx Series line-up
Product Package VCC OVP ZT OVP
BM1Q001FJ Auto restart None
BM1Q002FJ
SOP-J8
Latch stop Latch stop
● Applications
AC adapters, TVs, household appliances (vacuum cleaners, humidifiers, air filters, air conditioners, refrigerators,
induction heating cookers, rice cookers, etc.)
A
pplication Note
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2014.08 - Rev.
A
© 2014 ROHM Co., Ltd. All rights reserved.
BM1Q0XX series Quasi-Resonant converter Technical Design
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PC817
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1. Design Example of Isolated Type Quasi-Resonant Converter
Quasi-Resonant Converters become DCM (Discontinuous Conduction Mode) under light load, and switching frequency
increases with the load increasing. When the load increased further, Quasi-Resonant Converters become BCM (Boundary
Conduction Mode), and switching frequency decreases with the load increasing.
Figure 1-1.Isolated Type Quasi-Resonant Converter Circuit Example
Figure 1-2.Switching Frequency – Output Load Characteristics
Figure 1-3.Switching waveform (MOSFET Vds,Ids)
DCM
BCM
IC detects Bottom and controls a timing o
f
switching turn ON.