BP3122

High Precision PSR Constant Current LED Driver

Description Features
The BP3122 is a high precision primary-side feedback  Built-in 650V Power MOSFET
and regulation controller for LED lighting, it operates  Constant current control without secondary sense
in constant current control mode and is designed to and feedback circuit.
work in inductor current discontinuous conduction  No Auxiliary winding for sensing and supplying
 Ultra low operating current to improve efficiency
mode and especially suitable for flyback convertor
 Universal input voltage
under universal input. The output power of system is
 ±5% LED current accuracy
recommended to less than 5W.  LED short and open circuit protection
 CS resistor short circuit protection
The BP3122 integrates 650V power MOSFET. Since
 VCC under-voltage protection
adopting primary sense and feedback control
 Over temperature protection
technology, the secondary sense and feedback circuit
 Available in SOP8 package
is eliminated. The loop compensation components are
also removed while maintaining stability overall Applications
operating conditions. It uses patent pending source  GU10/E27 LED bulb, spot light
driver architecture and demagnetization sensing  Other LED lighting
technology, the operating current is very low, and it
doesn’t need the auxiliary winding for sensing the
output current and supplying the chip. The low
component counts and small system size are realized.

Since using the proprietary high accurate current sense

method, the BP3122 realizes ±5% accuracy of LED
current along with excellent line and load regulation.

The BP3122 offers rich protection functions including

LED open/short circuit protection, CS resistor short
circuit protection, over-temperature protection, VCC
under voltage protection.

Typical Application
NP NS

AC BP3122
4 OUT NC 8

3 VCC NC 7

1 CS DRAIN 6

2 GND DRAIN 5

Figure 1. Typical application circuit for BP3122

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High Precision PSR Constant Current LED Driver

Ordering Information
Part Number Package Operating Packing Method Marking
Temperature
BP3122
Tape
BP3122 SOP8 -40℃ to 105℃ XXXXXY
4,000 Piece/Reel
WXYY

Pin Configuration and Marking Information

CS NC
XXXXXY XXXXXY: Lot Code
GND BP3122 NC W: Sign
WXYY

X: Year
VCC DRAIN YY: Week

OUT DRAIN

Figure 2. Pin configuration

Pin Definition
Pin No. Name Description
Current sense. This pin connects a current sense resistor to GND to detect
1 CS
the primary current of transformer.
2 GND Ground

3 VCC Power supply

4 OUT Internal high voltage MOSFET Source

5,6 DRAIN Internal high voltage MOSFET Drain

7,8 NC No connection, must be floated

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High Precision PSR Constant Current LED Driver

Absolute Maximum Ratings (note1)

Symbol Parameters Range Units

ICC_max VCC pin maximum sink current 5 mA

DRAIN Internal HV MOSFET drain voltage -0.3~650 V

CS Current sense pin input voltage -0.3~6 V

OUT Internal HV MOSFET Source voltage -0.3~18 V

PDMAX Power dissipation (note2) 0.45 W

θJA Thermal resistance (Junction to Ambient) 145 ℃/W

TJ Operating junction temperature -40 to 150 ℃

TSTG Storage temperature range -55 to 150 ℃

ESD (note3) 2 kV
Note 1: Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Under “recommended operating

conditions” the device operation is assured, but some particular parameter may not be achieved. The electrical characteristics table defines the operation

range of the device, the electrical characteristics is assured on DC and AC voltage by test program. For the parameters without minimum and maximum

value in the EC table, the typical value defines the operation range, the accuracy is not guaranteed by spec.

Note 2: The maximum power dissipation decrease if temperature rise, it is decided by TJMAX, θJA, and environment temperature (TA). The maximum power

dissipation is the lower one between PDMAX = (TJMAX - TA)/ θJA and the number listed in the maximum table.

Note 3: Human Body mode, 100pF capacitor discharge on 1.5kΩ resistor

Recommended Operation Conditions

Symbol Parameter Range Unit

POUT1 Output power (input voltage 230V±15%) <6 W

POUT2 Output power (input voltage 85V～265V) <5 W

FOP System operating frequency 65~70 kHz

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High Precision PSR Constant Current LED Driver

Electrical Characteristics (Notes 4, 5) (Unless otherwise specified, VCC=14V and TA =25 ℃)

Symbol Parameter Conditions Min. Typ. Max. Units
Supply Voltage Section
VCC_Clamp VCC clamp voltage 1mA 15 17 V
VCC_ON Turn on threshold voltage VCC rising 13.8 V
V CC_UVLO Turn off threshold voltage VCC falling 9 V
IST VCC startup current VCC= VCC_ON - 1V 60 100 uA
IOP VCC operating current FOP=70KHz 150 250 uA
Current Sense Section
Threshold voltage for
VCS_TH 485 500 515 mV
peak current limit
Leading edge blanking
TLEB 500 ns
time for current sense
TDELAY Switch off delay time 200 ns
Switching Frequency
Minimum working
FMIN 5 kHz
frequency
LED open circuit
FOVP protection switching 90 kHz
frequency
Maximum Duty Cycle
DMAX Maximum duty cycle 42 %
MOSFET Section
Static drain-source
RDS_ON VGS=14V/IDS=0.5A 15 Ω
on-resistance
Drain-source breakdown
BVDSS VGS=0V/IDS=250uA 650 V
voltage
Drain-source leakage
IDSS VGS=0V/VDS=650V 10 uA
current
Over Temperature Protection
Thermal shutdown
TSD 150 ℃
threshold
Thermal shutdown
TSD_HYS 25 ℃
hysteresis
Note 4: production testing of the chip is performed at 25°C.

Note 5: the maximum and minimum parameters specified are guaranteed by test, the typical value are guaranteed by design, characterization and statistical

analysis

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High Precision PSR Constant Current LED Driver

Typical Performance Characteristics

Turn on threshold VS. Temperature Turn off threshold VS. Temperature

Start-up current VS. Temperature Operation current VS. Temperature

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High Precision PSR Constant Current LED Driver

Internal Block Diagram

VCC DRAIN

15V VCC 650V

MOSFET
9.0V 13.8V
OTP
+
-
-

OUT

OCP
CC &
UVLO OVP Logic Control

RESET
LEB

CS
+
Current
Sense
-
500mV

GND

Figure 3. BP3122 Internal Block Diagram

Cycle-by-Cycle current sense is adopted in BP3122,
Function Description the CS is connected to the current sense comparator,
The BP3122 is a high performance power switch and the voltage on CS will be compared with the
specially designed for LED lighting, with patent internal 500mV reference voltage, the MOSFET will
constant current control technology. The BP3122 be switched off when the voltage on CS reaches the
integrates a 650V power MOSFET. The accurate threshold. The output of the comparator includes a
LED current can be realized without opto-coupler, 500ns leading edge blanking time.
TL431 feedback circuit and auxiliary winding while
The primary peak current is given by:
minimizing the external component count, lowering
the total bill of material cost. 500
I P_PK  (mA)
RCS
Start Up

The start-up current in BP3122 is designed to as low The current in LED can be calculated by the
as 60uA. The VCC capacitor will be charged through equation:
the start-up resistor when the system is powered on.
I P_PK NP
Once the VCC voltage reaches the start-up threshold, I OUT  
the BP3122 will start to switch. The BP3122 4 NS
integrates a 15V zener for VCC clamping. Due to the Where,
ultra-low operating current, the auxiliary winding is NP: primary winding turns of transformer
not needed to supply the IC. NS: secondary winding turns of transformer
IP_PK: peak current in MOSFET
Constant Current Control Power MOSFET

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High Precision PSR Constant Current LED Driver
The BP3122 integrates a 650V power N-MOSFET. It After the system enters into fault latch condition, the
can minimize the external component count and VCC voltage will fall until it reaches UVLO threshold.
reduce the BOM cost and PCB size. Then the system will re-start again. If the fault
condition is removed, the system will recover to
The BP3122 uses SOP-8 package. The recommended
normal operation.
system output power is below 5W in universal input
(85Vac~265Vac) application. The thermal shutdown circuitry in the BP3122
senses the die temperature after start up, and the
Operating Switching Frequency
thermal protection threshold is set to 150℃ with a
The BP3122 is designed to work in discontinuous 25℃ hysteresis. When the temperature on die of
conduction mode and no external loop compensation BP3122 rises and reaches the threshold, the power
component is required while maintaining stability. MOSFET will be shut down immediately and
The maximum duty cycle is limited to 42%. The maintained switch off until the temperature on die
maximum switching frequency at normal operation falls 25 ℃ from thermal protection trigger point.
is suggested to set around 65kHz~70kHz. If the
PCB Layout
maximum frequency is set too high, it will affect the
number of maximum series LED lamps. If set too The following rules should be followed in BP3122
low, the LED open circuit voltage will be too high. PCB layout:

The maximum and minimum switching frequency is Bypass Capacitor

limited in BP3122 to ensure the stability of system. The bypass capacitor on VCC should be as close as
The switching frequency can be set by the formula: possible to the VCC pin and GND pin.

Np 2  VLED Ground Path

f 
8  Ns 2  Lp  I LED The power ground path for current sense should be
short, and the power ground path should be separated
Where, LP is the primary winding inductance of
from small signal ground path before the negative of
transformer.
the bulk capacitor.
Protection Function
The Area of Power Loop
The BP3122 has integrated rich protection functions,
The area of main current loop should be as small as
LED open/short protection, CS resistor short circuit
possible to reduce EMI radiation, such as the
protection, VCC under voltage protection, over
primary current loop, the snubber circuit and the
temperature protection, and so on. When the LED is
secondary rectifying loop.
open circuit, it will trigger over-voltage protection
logic and latch, the system stops switching NC Pin
immediately. The NC pin must be left floating to satisfy the
When the LED short circuit is detected, the system requirement of creepage distance.
works at low frequency (Fop=5kHz), so the power Drain pin
consumption is low. At some catastrophic fault
To increase the copper area of drain for thermal
condition, such as shorted CS resistor or flyback
consideration.
transformer saturation, the internal fast fault
detection circuit will trigger and latch, the system
stops switching immediately.

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High Precision PSR Constant Current LED Driver

Physical Dimensions

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