ZXLD1374(2010) Просмотр технического описания (PDF) - Diodes Incorporated.

Номер в каталоге

Компоненты Описание

производитель

ZXLD1374
(Rev.:2010)

60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST LED DRIVER CONVERTER

Diodes Incorporated. 

A Product Line of

Diodes Incorporated

Applications Information (Continued)

ZXLD1374

When the ADJ pin is directly connected to the REF pin, this becomes:

Rs =

RGI1 225mV

(RGI1 + RGI2) ILED

Note that the average LED current for a Boost or Buck-boost converter is always less than the average sense resistor

current. For the ZXLD1374, the recommended potential divider ratio is given by:

0.2 ≤

RGI1

≤ 0.50

(RGI1 + RGI2 )

It is possible to use a different combination of GI pin voltages and sense resistor values to set the LED current.

In general the design procedure to follow is:

- Define input conditions in terms of VIN and IIN

- Set output conditions in terms of LED current and the number of LEDs

- Define controller topology – Buck, Boost or Buck-boost

Calculate the maximum duty-cycle as:

Buck mode

DMAX

=

VLEDs

VINMIN

Boost mode

DMAX

=

VLEDS − VIN MIN

VLEDS

Buck-boost mode

DMAX

=

VLEDS

VLEDS + VIN MIN

Set the appropriate GIRATIO according to the circuit duty and the max switch current admissible limitations

GIRATIO

=

VGI

VADJ

=

RGI1

(RGI1 + RGI2)

≤

1− DMAX

- Set RGI1 as:

10kΩ ≤ RGI1 ≤ 200kΩ

- Calculate RGI2 as:

R GI2

≈ DMAX

1− DMAX

x RGI1

- Calculate the sense resistor as:

Rs =

RGI1 225mV

(RGI1 + RGI2) ILED

If the potential divider ratio is greater than 0.64, the device detects that Buck-mode operation is desired and the output

current will deviate from the desired value.

ZXLD1374

Document number: DS35032 Rev. 1 - 2

Page 16 of 35

www.diodes.com

October 2010

© Diodes Incorporated

Share Link: