Supertex inc.
HV9911DB1
High Brightness Boost LED Driver Demoboard
with 1:3000 Dimming Ratio and Excellent Current Regulation
General Description
The HV9911DB1 is an LED driver capable of driving up to 20
one-watt LEDs in series from an input of 21 - 27VDC. The
demoboard uses Supertex’s HV9911 in a boost topology.
The converter has a very good initial regulation (+/-5%) and
excellent line and load regulation over the entire input and
output voltage range (<+/- 1%). The full load efficiency of the
converter is typically greater than 90%.
The HV9911DB1 is also protected against open LED and
output short circuit conditions. It is also protected under
input undervoltage conditions by limiting the input current.
It has an excellent PWM dimming response, with typical rise
and fall times less than 2.0μs, which will allow high PWM
dimming ratios.
The switching frequency of the HV9911DB1 can be
synchronized to other HV9911 boards or to an external
200kHz clock by connecting the clock to the SYNC pin of the
HV9911DB1.
The HV9911DB1 includes and RC filter to prevent false
triggering of the short circuit protection during PWM dimming,
which was noticed with the HV9911DB1. This improvement
makes the HV9911DB1 immune to turn-on current spikes
in most cases. For a detailed explanation of the origin of
the turn-on spike and the effect of the RC filter on the short
circuit response time, please refer to the HV9911 datasheet.
Specifications
Parameter
Input voltage (steady state):
Output LED string voltage:
Output current:
Output current ripple:
Switching frequency:
Full Load efficiency:
Open LED protection:
Output short circuit protection:
Input under voltage protection:
PWM dimming:
Value
21V – 27VDC
35V min - 80V max
350mA +/-5%
10% typical
200kHz
93% (at 24V input)
Shuts down at 92V
Included
Included
1:3000 dimming ratio
at 200Hz
Board Layout and Connection Diagram
V
IN
+
-
+
4
3
2
1
Actual size: 64mm x 34.5mm
Connections:
I
nput -
The input is connected between the terminals of
connector J1 as shown in the Connection Diagram.
Output -
The output is connected between the terminals of
connector J2 as shown.
Enable/PWM Dimming -
To just enable the board, short pins
PWMD and V
DD
of connector J3 as shown by the dashed
lines. To PWM dim the board, connect the external push-
pull waveform source between terminals PWMD and GND
of connector J3 as shown by the solid lines.
SYNC -
To synchronize two or more boards, connect the
SYNC pins of all the boards together. To synchronize the
HV9911DB1 to an external 200kHz clock, connect the clock
between the SYNC and GND pins of terminal J3.
Note:
During PWM dimming, pin 2 of connector J3 should be left
open. Also, the PWM signal must have the proper polarity
with the positive connected to pin 3 of J3. Note that pin 4
of J3 is internally connected to the return path of the input
voltage.
Doc.# DSDB-HV9911DB1
A032713
Supertex inc.
www.supertex.com
HV9911DB1
Testing The Demoboard:
Normal Operation:
Connect the input source and the output
LEDs as shown in the Connection Diagram and enable the
board. The LEDs will glow with a steady intensity. Connecting
an ammeter in series with the LEDs will allow measurement
of the LED current. The current will be 350mA +/- 5%.
Current Regulation:
With the input power to the converter
disconnected, change the LED string voltage within
the specifications mentioned. The current output of the
HV9911DB1 will remain very steady over the entire load
range. Vary the input voltage while the circuit is operational.
The current will be regulated over the entire line range.
Open LED test:
Connect a voltmeter across the output
terminals of the HV9911DB1. Start the demoboard normally
and once the LED current reaches steady state, unplug
one end of the LED string from the demoboard. The output
voltage will rise to about 92V and then the HV9911DB1
will shut down. To restart the converter, disconnect and
reconnect the input voltage (recycle the power to the board).
Short Circuit Test:
When the HV9911DB1 is operating in
steady state, connect a jumper across the terminals of the
LED string. Notice that the output current will immediately
go to zero and the converter will shut down. To restart the
HV9911DB1, recycle the input power to the demoboard.
PWM Dimming:
With the input voltage to the board
disconnected, apply a TTL compatible, push-pull square wave
signal between PWMD and GND terminals of connector J3
as shown in the Connection Diagram. Turn the input voltage
back on and adjust the duty cycle and / or frequency of the
PWM dimming signal. The output current will track the PWM
dimming signal. Note that although the converter operates
perfectly well at 1.0kHz PWM dimming frequency, the widest
PWM dimming ratio can be obtained at lower frequencies
like 100 or 200Hz.
95
Efficiency (%)
94
93
92
91
90
35
40
45
50
55
60
65
70
75
80
Output Voltage (V)
Fig. 1. Efficiency vs. Output Voltage
95
Efficiency (%)
94
93
92
91
90
20
22
24
26
28
Input Voltage (V)
Fig. 2. Efficiency vs. Input Voltage
Output Current (A)
0.354
0.352
0.35
0.348
0.346
35
40
45
50
55
60
65
70
75
80
Output Voltage (V)
Fig. 3. Output Current vs. Output Voltage
Output Current (A)
0.354
0.352
0.350
0.348
0.346
20
22
24
26
28
Typical Results:
1. Efficiency:
The efficiency of the
converter at various LED
string voltages are shown in Fig.1 (measured at the nominal
input voltage of 24V). Fig.2 shows the full load efficiency
of the converter at varying input voltages. The minimum ef-
ficiency of 93% for the converter occurs at 21V input and full
load output.
2. Current Regulation:
Figs. 3 and 4 show the output cur-
rent regulation vs. output voltage and input voltage respec-
tively. The total current regulation (line and load combined)
is found to be less than 1%.
Input Voltage (V)
Fig. 4. Output Current vs. Input Voltage
Doc.# DSDB-HV9911DB1
A032713
2
Supertex inc.
www.supertex.com
HV9911DB1
3. Input Under Voltage Protection:
Input under voltage
protection is provided by limiting the input current at low in-
put voltages. Fig. 5 shows the output and input currents at
voltages less than the minimum rated voltage. The LED cur-
rent will decrease as the input voltage falls and the input
current limits to about 1.4A. Note that the input current limit
is not a hard limit as the slope compensation added to the
peak current sense signal will allow a small change in the
input current with a decrease in the input voltage.
0.4
1.6
5. Output Short Circuit Protection:
Fig. 7 shows the
waveforms for output short circuit condition. The disconnect
FET is turned off in less than 300ns. The rise in the output
current will depend on the input voltage and the value of
inductor L1. The same protection will also help in protecting
the LEDs in case the output voltage increases beyond the
LED string voltage.
Output Current (A)
Input Current (A)
0.3
1.4
Output Voltage
0.2
1.2
Output Current
0.1
25
20
15
10
1.0
Input Voltage (V), Sweep
Input Current
Output Current
Fig. 5. Input Under Voltage Behavior
4. Open LED Protection:
Open LED protection for the cir-
cuit is set at 92V. The waveforms in Fig. 6 show the output
voltage, drain voltage and output current during an open
LED condition. The time taken for the over voltage protec-
tion to shut the IC down will depend on the size of the output
capacitor.
Fig. 7:Output Short Circuit Protection
(500ns/div)
Output Voltage
LED Current
Drain Voltage of Q1
Fig. 6: Open LED Protection
(20 s/div)
Doc.# DSDB-HV9911DB1
A032713
3
Supertex inc.
www.supertex.com
HV9911DB1
6. PWM Dimming:
The rise and fall transitions of the LED
current during PWM dimming are shown in Figs. 8 and 9, at
output voltages of 80 and 40V respectively. The timescale
for all waveforms is set at 5.0μs/div. The rise and fall times
PWM dimming input
Output Voltage
are less than 1.0μs in each case. Thus, a PWM dimming
ratio of 1:3000 is achievable at a PWM dimming frequency
of 200Hz.
PWM dimming input
Output Voltage
LED Current
LED Current
Fig. 8a: Rise time of LED Current at
80V output (5 s/div)
Fig. 8b: Fall time of LED Current at
80V output (5 s/div)
PWM dimming input
PWM dimming input
Output Voltage
Output Voltage
LED Current
LED Current
Fig. 9a: Rise time of LED Current at
40V output (5 s/div)
Fig. 9b: Fall time of LED Current at
40V output (5 s/div)
Silk Screen:
Doc.# DSDB-HV9911DB1
A032713
4
Supertex inc.
www.supertex.com
Doc.# DSDB-HV9911DB1
A032713
Circuit Schematic:
J1B
C1
2.2 F
25V
C1
2.2 F
25V
220 H
(CDRH127/LDNP-221MC)
2
J3B
R2
453k
2
R4
8
OPEN
10
1
R5
1.0k
3
5
Q2
FDS 3692
D1
B1100-13
C4
1.0 F
100V
C9
1.0 F
100V
1
2
L1
1
R1
82.5k
J1A
1
J2A
J3A
SYNC
REF
IREF
CS
11
12
C5
1.0 F
16V
R3
1.13k
C11
10nF
C6
0.1 F
16V
REF
VDD VIN
HV9911
GATE
R6
0.15
1/2W
RT
7
REF
16.2k
16
R12
15
2
J2B
Q1
TN251DN8
5
FDBK
COMP
CLIM
OVP
PWM SC GND
13
R8
R9
7.87k
17.4k
R11
49.9k
6
4
C7
2.2nF
9
R7
20k
R13
14
8.66k
I
O_
SNS
FAULT
REF
J3C
J3D
J6
J7
C8
6.8nF
I
O_
SNS
R14
C10
470pF
1k
J4
J5
Specifications:
Input: 21 - 27VDC
Output Voltage: 40 - 80V
Output Current: 350mA
Overvoltage: 92V
Short Circuit Protection Included
R10
1.24
1/4W
Supertex inc.
HV9911DB1
www.supertex.com
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