Demonstration board: high-efficiency switching LED driver for
high-current LEDs based on the L6726A
Features
■ Input voltage Vin: 8 V to 18 V
■ Output voltage (with Vin = 18 V): 2.5 V to 14 V
■ Output current I
■ Analog dimming (with I
■ Low level PWM signal: 0 V
■ High level PWM signal: 2.8 V to 3.8 V
(typ: 3.3 V)
■ Duty cycle (at fdim = 200 Hz): 0% to 99 %
■ Efficiency (with Vin = 18 V and Vout = 12.6 V):
94.8 %
Description
Rapid advances in LED technology has led to
increases in their output current capabilities in
recent years. 0.350 A LEDs, for example, were
soon followed by 0.7 A LEDs, and then 1 A
devices appeared shortly thereafter. Currently,
LEDs with currents as high as several amps are
present on the market. However, these high
currents increase the requirements of the driving
circuitry of the LEDs, particularly in terms of
efficiency.
: 1 A / 1.5 A / 2.8 A
LED
= 0 A): 0 V to 2.5 V
LED
STEVAL-ILL023V1
Data Brief
STEVAL-ILL023V1
The STEVAL-ILL023V1 demonstration board is
based on the L6726A single phase PWM
controller, with two external MOSFETS for
synchronous rectification. Designed for 2.8 A
LEDs (1-3 in a series string), the main benefit of
the solution is its exceptional efficiency. Ease of
dimming and scalability to even higher currents
are additional advantages of the design.
The solution is also much safer with regard to
border conditions, since the current limit is based
solely on the selection of the MOSFETS.
February 2009 Rev 1 1/4
For further information contact your local STMicroelectronics sales office.
www.st.com
4
Circuit schematic STEVAL-ILL023V1
oo
GN
70
0n
00n
GN
06
0n
cc
oo
OU
OU
OU
1 Circuit schematic
Figure 1. STEVAL-ILL023V1 schematic diagram
T
6
5
4
3
2
OU
3
2
1
P1
T-A
OU
L1
4.7uF
C8
1
0R3
R16
0R3
R15
R14
0R56
T-K
0R56
R10
OU
R9
0R56
22uF
C9
10uH
Inductor
D3
STPS1L30M
7
8
Q1
2
D2
6V
Vcc
1
AC
OUT
D
GN
IN
U1 L78L06
3
22uF
C1
Vcc18V
2
3
1
CN1
8-18V
STS8DNH3LL
Ugate
R7
F
100n
C7
10R
R6
t
Boo
2
1
t
1N4148
Boo
Ugate
Vcc
5
FB
U2 L6726A
F
C6
100n
C4
10uF
2
K375A
7
6
FB
R4
4k7
6
3
5
1
4
Lgate
Phase
R8
2R2
8
4
Lgate
Phase
GNGND
COMP
Comp
R3
4k7
R1
3
PWM
2R2
3
1k1
R2
C3
82nF
pF
470
C2
R5
6k8
F
C5
100n
TS821
D1
Vref
62k
D
GN
PWM
2
1
2/4
STEVAL-ILL023V1 Revision history
2 Revision history
Table 1. Document revision history
Date Revision Changes
26-Feb-2009 1 Initial release.
3/4
STEVAL-ILL023V1
y
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