Switch IC. BF1501 Datasheet

BF1501 IC. Datasheet pdf. Equivalent

BYD Microelectronics BF1501
BYD Microelectronics Co., Ltd.
BF1501 Series
Off Line AC/DC Switcher IC
General Description
The THC0X switcher ICs cost effectively replace all
power supplies up to 5W output power based on
unregulated isolated linear transformer (50/60HZ).
Unlike conventional PWM (pulse width modulation)
controllers, it regulates the output voltage in a new
method of off-time modulation control. The controller
consists of a VCO (voltage control oscillator), Sense
and logic circuit, VDD pin, under-voltage lockout
circuit, over-voltage protection, current limited circuit,
leading edge blanking, over load protection and fault
condition auto-restart. They are ideal low power
AC/DC adapter/charger for cell phones.
„ AC/DC adapter/charger for cell/cordless phones,
digital cameras, MP3/portable audio devices etc
„ LED Lighting
„ Replacements for linear transformers and RCC
z Low start-up current
„ Typ.15 µA
„ Max.25 µA
z Low operating current
„ Typ.2 mA
„ Max.5 mA
z UVLO(under voltage lockout)
„ Typ.12V start-up
„ Typ.6V shut-down
z LEB(leading edge blanking)
„ Typ.300ns
z OVP(over voltage protection)
„ Typ.28 V
z Operation Frequency
„ Typ.50KHZ
z Output Driver Ability
„ Typ.15 mA
z OLP(over load protection)
z Universal AC input range
z Constant voltage and constant
z Small SOT-23-6 Package
Typical Application Circuits
ES-BYD-WDZCE01D-045 Rev.A/0
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BF1501 Datasheet
Recommendation BF1501 Datasheet
Part BF1501
Description Off Line AC/DC Switch IC
Feature BF1501; BYD Microelectronics Co., Ltd. BF1501 Series Off Line AC/DC Switcher IC General Description The TH.
Manufacture BYD Microelectronics
Download BF1501 Datasheet

BYD Microelectronics BF1501
BYD Microelectronics Co., Ltd.
Block Diagram
BF1501 series
Package Type
2 SOT-26 5
Pin Description
Pin number
Pin name
Not connected
Current sensor, it senses the voltage via a sensed resistor
Not connected
Gate drive output for the external power BJT switch
Power Supply
ES-BYD-WDZCE01D-045 Rev.A/0
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BYD Microelectronics BF1501
BYD Microelectronics Co., Ltd.
BF1501 series
Function Description
1. Under Voltage Lockout
The turn-on and turn-off thresholds of the THC01 are fixed internally at 12V/6V. During start-up, the hold-up capacitor
must be charger to 12V through the start-up resistor, so that the THC01 can be enabled. The hold-up capacitor will
continue to supply VDD until power can be delivered from the auxiliary winding of the main transformer, When VDD drop
below 6V, IC will be shut-down, and have to start-up again. This UVLO hysteretic window ensures that THC01 can
start-up very well.
2. Leading Edge Blanking
When the power BJT is switched on, a voltage spike will inevitably occur at the sense pin. To avoid premature
termination of the switching pulse, a 350 ns leading-edge blanking time is built in THC01. Conventional RC filtering can
be omitted. During this blanking period, the current-limit comparator is disabled and it cannot switch off the gate driver.
3. Voltage Control Oscillator
The sense circuit of THC0X series will sense the voltage of VDD pin (also the power pin of THC01) and then control the
frequency of the oscillator. The max frequency of THC0X is set to the rated output power point and for THC01 is 50 KHZ.
Two signals are generated from the oscillator: the maximum duty cycle signal (DC max) and the clock signal that
indicates the beginning of each switching cycle.
4. Sense Circuit
A resistor voltage divided circuit is connected between the VDD and GND pin in order to sample the feedback voltage at
VDD pin. When the voltage of VDD pin exceeds 20V, IC will come into constant voltage control mode, shut down the
output pin and start a bypass current. This bypass current is linearly controlled by the feedback voltage. When the
voltage of VDD pin falls below 20V, the off-time linearly increases in order to have a constant current output.
5. Gate Output
Unlike other chips, THC01 used a constant current circuit to drive the output BJT. The output current is fixed at 15mA,
select the appropriate hFE of BJT could have a different output power.
6. Fault Condition Auto-restart
In the event of a fault condition such as output over-load or short circuit, THC0X enter into auto-restart operation. It is
using the turn-on and turn-off threshold again. THC0X is working in start mode to protect the system from damage
caused by the fault condition.
7. Current Limit
The current limit circuit detecets the current through the power BJT. This current flow through the sense-resistor and
makes the voltage on Vsense pin ramp up. When this voltage exceeds the internal threshold (Vlimit), the power BJT is
turned off immediately.
ES-BYD-WDZCE01D-045 Rev.A/0
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