Switch IC. BF1501-DA Datasheet

BF1501-DA IC. Datasheet pdf. Equivalent


BYD Microelectronics BF1501-DA
BYD Microelectronics Co., Ltd.
BF1501-DA
Off Line AC/DC Switch IC
General Description
The BF1501-DA 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, they regulate 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, protection for
over-voltage, current limited circuit, leading edge
blanking, over load protection and fault condition
auto-restart. They are ideal low power AC/DC
adapter/charger solution for portable devices.
Applications
„ AC/DC adapter/charger for cell/cordless
phones, digital cameras, MP3/portable audio
devices etc
„ LED Lighting
„ Replacements for linear transformers and
RCC SMTPS
Features
„ Low start-up current
z Typ.15 µA
z Max.25 µA
„ Low operating current
z Typ.2 mA
z Max.5 mA
„ UVLO(under voltage lockout)
z Typ.12V start-up
z Typ.6V shut-down
„ LEB(leading edge blanking)
z Typ.300ns
„ OVP(over voltage protection)
z Typ.28 V
„ Operation Frequency
z Typ.50KHZ(VDD=21V)
„ Output Driver Ability
z Typ.15 mA
„ OLP(over load protection)
„ Universal AC input range
„ Constant voltage and constant current
„ Small SOT-23-6 Package
Typical application
Datasheet
TS-POM-PD-0003 Rev.A/1
Page 1 of 8


BF1501-DA Datasheet
Recommendation BF1501-DA Datasheet
Part BF1501-DA
Description Off Line AC/DC Switch IC
Feature BF1501-DA; BYD Microelectronics Co., Ltd. BF1501-DA Off Line AC/DC Switch IC General Description The BF1501-D.
Manufacture BYD Microelectronics
Datasheet
Download BF1501-DA Datasheet




BYD Microelectronics BF1501-DA
BYD Microelectronics Co., Ltd.
Block Diagram
VDD
12V
6V
0.5V
UVLO
OLP
Internal Ref
& Bias
OSC
GND
FB
1V
Package Type
BF1501-DA Sep-16-10
OVP
28V
S SET
R CLR
LEB
Driver
VOUT
OCP
0.5V
Sense
Pin Description
Pin number
1
2
3
4
5
6
Pin name
NC
GND
Sense
NC
Vout
VDD
Description
Not connected
Ground
Current sensor, it senses the voltage via a sensed resistor
Not connected
Gate drive output for the external power BJT switch
Power Supply
Datasheet
TS-POM-PD-0003 Rev.A/1
Page 2 of 8



BYD Microelectronics BF1501-DA
BYD Microelectronics Co., Ltd.
BF1501-DA Sep-16-10
Function Description
1 Under Voltage Lockout
The turn-on and turn-off thresholds of the BF1501-DA 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 BF1501-DA 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 BF1501-DA 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 300 ns leading-edge blanking time is built in BF1501-DA.
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 BF1501-DA will sense the voltage of VDD pin (also the power pin of BF1501-DA)
and then control the frequency of the oscillator. The max frequency of BF1501-DA is set to the rated
output power point, and the BF1501-DA is set to 50KHZ. 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 pin and GND pin in order to sample the
feed-back voltage at VDD pin. When the voltage of VDD pin exceeds 21.3V, IC will come into constant
voltage control mode, shut- down the output pin and start a bypass circuit. This bypass circuit is linearly
controlled by the feedback voltage. When the voltage of VDD pin falls below 21.3V, the off-time linearly
increases in order to have a constant current output.
5 Gate Output
Unlike other chips, BF1501-DA 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, the BF1501-DA enters into
auto-restart operation. It is using the turn-on and turn-off threshold again. The BF1501-DA is working in
start mode to protect the system from damage caused by the fault condition.
7 Current Limit
The current through the power BJT is detected by the current limit circuit. Then the current flows through
the sense-resistor and makes the voltage on Sense pin ramp up. And when this voltage exceeds the
internal threshold (Vlimit), the power BJT is turned off immediately.
Datasheet
TS-POM-PD-0003 Rev.A/1
Page 3 of 8







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