BP3125 データシートの表示（PDF） - Unspecified
部品番号
コンポーネント説明
メーカー
BP3125 Datasheet PDF : 10 Pages
| |||
BP3125
High Precision PSR Constant Current LED Driver
I OUT
I P_PK
4
NP
NS
Where,
NP: primary winding turns of transformer
NS: secondary winding turns of transformer
IP_PK: peak current in MOSFET
Feedback Network
Protection Function
The BP3125 has several protection functions. The
internal MOSFET will be shut down immediately
when the voltage on VCC reaches the threshold of
OVP and the device will not recover until the
protection condition is removed. A 19V zener diode
is designed in the BP3125 to prevent the chip
damage from the abnormal situation.
The BP3125 senses the output information through
the feedback network and the FB threshold voltage is
set to 1V. The ratio of FB upper resistor to lower
resistor is recommended to about 4.0. The FB upper
resistor can be set to 300KΩ~750KΩ to improve
efficiency of convertor.
The upper resistor on FB is also used for line
compensation.
The ratio of line compensation can be calculated by
the equation:
VCS
1.1106 VAUX
RFBH
mV
Where, RFBH is the upper resistor of the feedback
network.
Operation Switching Frequency
The BP3125 is designed to work in discontinuous
conduction mode and no external loop compensation
component is required while maintaining stability.
The maximum duty cycle is limited to 42%. The
maximum switching frequency should be set to less
than 100KHz and the minimum switching frequency
should be set to more than 20KHz. The maximum
and minimum switching frequency is limited in
BP3125 to ensure the stability of system.
The switching frequency can be set by the formula:
f
8
Np2 VLED
Ns2 Lp ILED
Where, LP is the primary winding inductance of
transformer.
The thermal shutdown circuitry in the BP3125
senses the die temperature after start up, and the
thermal protection threshold is set to 150℃ with a
20℃ hysteresis. When the temperature on die of
BP3125 rises and reaches the threshold, the power
MOSFET will be shut down immediately and
maintained switch off until the temperature on die
falls 20 ℃ from thermal protection trigger point.
The system will work in low consumption mode
when the output LED short circuit or open circuit is
detected, while the BP3125 continuous to detect
output status until the LED recover to normal
condition, and then the device will be operate in
normal mode.
PCB Layout
The following rules should be followed in BP3125
PCB layout:
Bypass Capacitor
The bypass capacitor on VCC should be as close as
possible to the VCC pin
Ground Path
The power ground path for current sense should be
short, and the power ground path should be separated
from small signal ground path before the negative of
the bulk capacitor.
The Area of Power Loop
The area of main current loop should be as small as
possible to reduce EMI radiation, such as the
primary current loop, the snubber circuit and the
secondary rectifying loop.
BP3125_EN_DS_Rev.1.0
www.bpsemi.com
8
Bright Power Semiconductor Co. Confidential – Customer Use Only
Share Link: 