BP9916B datasheet(6/8 Pages) BPS

6 / 8 page

BP9916B

Non-isolated Buck Offline LED Driver

BP9916B_EN _DS_Rev.1.0

www.bpsemi.com

BPS Confidential – Customer Use Only

晶丰明源半导体

600

()



Where, RCS is the current sense resistor value.

The current in LED can be calculated by the

equation:

LED 

Where, IPK is the peak current of the inductor.

Inductor Selection

The BP9916B works under inductor current critical

conduction mode. When the power MOFET is

switched on, the current in the inductor rises up from

zero, the on time of the MOSFET can be calculated

by the equation:

LED







Where,

L is the inductance value

VIN is the DC bus voltage after the rectifier bridge

VLED is the voltage on the LED

After the power MOSFET is switched off, the

current in the inductor decreases. When the inductor

current reaches zero, the power MOSFET is turned

on again by IC internal logic. The off time of the

MOSFET is given by:

LED

off





The inductance can be calculated by the equation:

LED

)

(









The f is the system switching frequency, which is

proportional to the input voltage. So the minimum

switching frequency is set at lowest input voltage,

and the maximum switching frequency is set at

highest input voltage.

The minimum and maximum off time of BP9916B is

set at 2.5us and 300us, respectively. Referring to the

equation of tOFF calculation, if the inductance is too

small, the tOFF may be smaller than the minimum off

time,

system

will

operate

discontinuous

conduction mode and the output current will be

smaller than the designed value. If the inductance is

too large, the tOFF may be larger than the maximum

off time, the system will operate in continuous

conduction mode and the output current will be

higher than the designed value. So it is important to

choose a proper inductance.

Protection Function

The BP9916B offers rich protection functions to

improve the system reliability, including LED short

protection, VCC under voltage protection, thermal

regulation.

When the LED short circuit is detected, the system

works at low frequency (3kHz), so the system power

consumption is very low.

Thermal Regulation

The BP9916B integrates thermal regulation function.

When the system is over temperature, the output

current is gradually reduced; the output power and

thermal dissipation are also reduced. The system

temperature is regulated and the system reliability is

improved. The thermal regulation temperature is set

to 140℃ internally.

PCB Layout

The following rules should be followed in BP9916B

PCB layout:

Bypass Capacitor

The bypass capacitor on VCC pin should be as close

as possible to the VCC Pin.

CS Resister

BP9916B Datasheet(PDF) 6 Page - Bright Power Semiconductor Co., Ltd.

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