Texas Instruments | High-Brightness Portable Lighting | Application notes | Texas Instruments High-Brightness Portable Lighting Application notes

Texas Instruments High-Brightness Portable Lighting Application notes
Application Report
SNVA764 – October 2016
High-Brightness Portable Lighting
Travis Eichhorn
ABSTRACT
High-power LED drivers designed for LCD monitors are also good choices for driving LEDs in generalpurpose lighting applications. One such driver is the TPS61199 device, an 8-channel LED boost controller
with integrated current sinks and an 8-V to 30-V input voltage range. The current in each sink can be
programmed for a maximum of 70 mA. The boost-controller topology drives an external N-channel
MOSFET that can handle a wide output-voltage range and inductor-current range. This allows the
TPS61199 to be designed with a wide variety of white LEDs commonly used in general purpose lighting
applications such as:
• 12-V Battery Power Lighting
• 18-V Battery Powered Lighting
• 24-V Battery Powered Lighting
• Marine Ambient Lighting
• Automotive Ambient Lighting
.
1
Application Schematic
Figure 1 shows an applications schematic that drives 8 high-brightness LEDs. The LED current is
controlled in low-side current sinks at IFB1 - IFB8. The maximum current is set via the external current
setting resistor (R6). The design below is set for IFULL_SCALE = 20 mA; however, other full-scale currents can
be programmed up to 70 mA. Dimming is achieved via the PWM input, but in the design PWM is tied to
VDD to force the device fully on.
D1
(Schottky)
L1
(22PH)
71V Max
8V < VIN < 30V
+
C8
(33PF)
R8
(3:)
C1
(10PF)
R21
(20k:)
IN
VDD
R10
(10k:)
S1
R9
(200:)
C3
(2.2PF)
EN
GND
R2
(221k:)
ISNS
C6
(470pF)
PWM
V+
+ C2
(33PF)
+
+ C10
C7
(33PF)
(33PF)
LED1 t LED8
(White LED)
R1
(0.03:)
R3
(10k:)
TPS61199
COMP
R4
(49.9k:)
C4
(47nF)
C11
(2.2PF)
Q1
(NMOS)
GDRV
OVP
C5
(470pF)
IFB1
IFB2
IFB3
FBP
IFB4
R5
(499k:)
IFB5
FSW
IFB6
R7
(162k:)
IFB7
ISET
R6
(121k:)
IFB8
GND
PAD
Figure 1. Applications Schematic
SNVA764 – October 2016
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High-Brightness Portable Lighting
Copyright © 2016, Texas Instruments Incorporated
1
Materials List
2
www.ti.com
Materials List
Table 1. Bill of Materials and Component Description
2
DEVICE
VALUE
DESCRIPTION
PART
NUMBER
SIZE
MANUFACTUR
ER
C1
10 µF
Ceramic, 50V,
X7R, 10%
Standard
1210
Standard
Bypass for IN, keep close to IN
for low inductance connection
C8
33 µF
Electrolytic,
100V, 20%
UPW2A330MP
D6
8 × 11.5 mm
Nichicon
Bulk Bypass for VIN
C2, C7,
C10
33 µF
Electrolytic,
100V, 20%
UPW2A330MP
D6
8 × 11.5 mm
Nichicon
Bulk Bypass for VOUT
C11
2.2 µF
Ceramic,
100V, X7R,
20%
Standard
1206
Standard
High frequency bypass for VOUT.
Keep close to D1 anode and
GND for low inductance
connection
C3
2.2 µF
Ceramic, 10V,
X7R, 20%
Standard
0805
Standard
Bypass capacitor for VDD
C4
47 nF
Ceramic, 25V,
X7R, 10%
Standard
0603
Standard
Compensation capacitor
C5
470 pF
Ceramic, 25V,
X7R, 10%
Standard
0603
Standard
Compensation capacitor
C6
470 pF
Ceramic, 25V,
X7R, 10%
Standard
0603
Standard
Filter capacitor for current sense
input. C6 and R9 filter the current
sense signal developed across
R1
D1
Schottky
Diode
100 V, 5 A
continuous
SSP510
TO-277
Vishay
Boost rectifier diode
L1
22 µH
3.6 A, 43.2 mΩ
CDRH127NP220MC
12.3 mm × 12.3
mm × 8 mm
Sumida
Boost Power Inductor. ISAT = 3.6
A with 25% drop from nominal
Q1
NMOS
Power
Switch
80 V, 6 A, 35
mΩ
SI4480DY-T1E3
SO8
Vishay
Boost Power switch. VOUT_MAX <
80 V
PURPOSE
R1
33 mΩ
1/2 W, 1%
Standard
1812
Standard
Current sense resistor
R2
232 kΩ
1/16 W, 1%
Standard
0603
Standard
R3
10 kΩ
1/16 W, 1%
Standard
0603
Standard
Over Voltage Protection sense
resistive divider. R2, R3 divide
down VOUT to OVP sense input
(2.95 V). VOUT_MAX = (R2/R3 + 1)
× 2.95 V = 71.3 V
R12
10 kΩ
1/16 W, 1%
Standard
0603
Standard
R21
20 kΩ
1/16 W, 1%
Standard
0603
Standard
R10
10 kΩ
1/16 W, 1%
Standard
0603
Standard
Limiting resistor in case S1 is
over voltaged.
R4
49.9 kΩ
1/16 W, 1%
Standard
0603
Standard
Compensation resistor
R5
499 kΩ
1/16 W, 1%
Standard
0603
Standard
LED short protection threshold
setting resistor. VLED_SHORT =
R5/R6 × 1.229 V = 5.08 V
R6
121 kΩ
1/16 W, 1%
Standard
0603
Standard
ILED max current setting resistor.
ILEDX = 1.229 V/R6 × 1990 =
20.2 mA per LED
R7
162 kΩ
1/16 W, 1%
Standard
0603
Standard
Boost frequency setting resistor.
fSW = 80,000/R7 (kΩ)
R8
3Ω
1/16 W, 1%
Standard
0603
Standard
Gate drive filter resistor. R3 and
CG of Q1 form a low pass filter
for the gate drive signal.
R9
200 Ω
1/16 W, 1%
Standard
0603
Standard
Filter for current sense signal. R9
and C6 filter the current sense
signal developed across R1
High-Brightness Portable Lighting
Resistive divider from VIN to
SW1, divides down VIN. The
divided down voltage is used to
turn the device on when S1 is
toggled. V+ = VIN × (R10/(R10 +
R21) = (10V to 2.66V)
SNVA764 – October 2016
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Modifications to Existing TPS61199EVM
www.ti.com
Table 1. Bill of Materials and Component Description (continued)
3
DESCRIPTION
PART
NUMBER
SIZE
MANUFACTUR
ER
Switch
Various
Various
Various
Various
U1
White LED
Driver
White LED
Driver + Boost
Controller
TPS61199PW
P
20-pin HTSSOP
Texas
Instruments
8-Channel Boost WLED Driver.
See TPS61199 data sheet and
SLVU421 for more information.
LED1LED8
White LED
VF = 68 V
max, IF = 20
mA, TA = 25°C,
180 lumens
SAW0LH0A
5 mm × 5 mm
Seoul
Semiconductor
High brightness LED (total 1440
Lumens)
DEVICE
VALUE
S1
PURPOSE
Typical switch. Low current
Modifications to Existing TPS61199EVM
The TPS61199 high-brightness LED lighting circuit is very similar to the TPS61199EVM. Some minor
modifications have been made:
1. Added C11 to reduce the switching noise at the circuits output. This (ceramic) capacitor must be place
close to the Schottky diodes output (D1) and the GND return of the TPS61199. This reduces noise that
can be conducted through the LEDs.
2. Adjusted the overvoltage protection threshold from 59.3 V to 71.3 V in order to accommodate the
forward voltage of the SAW0LH0A (VF_MAX = 68 V).
3. Adjusted the maximum current down to 20 mA.
4. Connected the PWM input directly to VDD in order to force the LED currents to 20 mA as soon as S1
is switched to V+.
4
Circuit Efficiency
Table 2 shows the measured efficiency with the specified components of Table 1.
Table 2. Typical Efficiency
VIN
ILED (per LED, 8 Total)
VOUT
INPUT CURRENT
EFFICIENCY
8V
21.63 mA
64.74 V
1.55 A
90.3 %
10 V
21.53 mA
64.87 V
1.229 A
91 %
12 V
21.44 mA
64.87 V
1.019A
91 %
14 V
21.25 mA
64.77 V
0.865 A
90.9 %
16 V
21.13 mA
64.77 V
0.756 A
90.5 %
18 V
21.0 mA
64.77 V
0.669 A
90.4 %
20 V
20.99 mA
64.67 V
0.6026 A
90.1 %
22 V
20.88 mA
64.65 V
0.543 A
90.4 %
24 V
20.81 mA
64.61 V
0.489 A
91.7 %
26 V
20.63 mA
64.59 V
0.456 A
90 %
28 V
20.54 mA
64.58 V
0 4237 A
89.4 %
30 V
20.48 mA
64.57 V
0.392 A
90 %
SNVA764 – October 2016
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High-Brightness Portable Lighting
Copyright © 2016, Texas Instruments Incorporated
3
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