Supertex inc.
HV9911DB4
High Brightness SEPIC LED Driver Demoboard
with High Dimming Ratio and Excellent Current Regulation
General Description
The HV9911DB4 is an LED driver dempboard capable of
driving one to six three-watt LEDs in series from an input of 9.0
- 16VDC. The demoboard uses Supertex’s HV9911 in a SEPIC
topology to drive LED string voltages higher or lower than the
input voltage. 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 85%.
The HV9911DB4 is also protected against open LED and
output short circuit conditions. It is protected against over load
conditions by limiting the input current. It has an excellent PWM
dimming response. The switching frequency of the HV9911DB4
can be synchronized to other HV9911 boards or to an external
350kHz clock by connecting the clock to the SYNC pin of the
HV9911DB4.
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:
Dimensions
Value
9.0 - 16VDC
3V min - 24V max
700mA +/-5%
5% typical
350kHz
87% (at 13V input)
Shuts down at 30V
Included
56.0mm x 38.2mm
Board Layout and Connection Diagram
V
IN
J1
J2
J3
Actual Size: 56.0mm x 38.2mm
Connections:
Input -
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 enable the board, short pins
PWMD and V
DD
of connector J3 as shown. To use the PWM
dimming feature of the board, connect an external push-pull
square wave source between terminal PWMD and GND of
connector J3 as shown by the dotted lines.
SYNC:
To synchronize two or more boards, connect the
SYNC pins of all the boards. To synchronize the HV9911DB4
to an external 350kHz clock, connect the clock between
SYNC and GND pins of terminal J3.
Note:
During PWM dimming, V
DD
of connector J3 should be left
open. Also, the PWM signal must have the proper polarity
with the positive connected to PWMD of J3. Note that
GND of J3 is internally connected to the return path of the
input voltage.
Doc.# DSDB-HV9911DB4
A032713
Supertex inc.
www.supertex.com
HV9911DB4
Demoboard Testing:
Fig.1 Efficiency vs. Output Voltage
90
Efficiency (%)
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 700mA +/- 5%.
Current Regulation:
With the input power to the converter
disconnected, change the input voltage or the LED string
voltage within the specifications mentioned. The current
output of the HV9911DB4 will remain very steady over the
entire line range.
Efficiency vs. Load Voltage (V
IN
= 13.5V)
85
80
75
70
65
3
8
13
18
23
Output Voltage (V)
Fig.2 Efficiency vs. Input Voltage
Full Load Efficiency vs. Input Voltage
88
Efficiency (%)
With the supply turned off, change the LED string voltage
within the specified limits and turn the power supply back on.
The current will still be regulated at around 700mA.
Open LED test:
Connect a voltmeter across the output
terminals of the HV9911DB4. Start the demoboard normally
and once the LED current reaches a steady state, unplug
one end of the LED string from the demoboard. The output
voltage will rise to about 30V and the HV9911DB4 will shut
down. To restart the converter, disconnect and reconnect the
input voltage (recycle the power to the board).
Short Circuit Test:
When the HV9911DB4 is operating in a
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
HV9911DB4, 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 1kHz PWM dimming
frequency, the best PWM dimming ratio can be obtained at
lower frequencies, like 100Hz or 200Hz.
87
86
85
84
83
82
9
11
13
15
Input Voltage (V)
2. Current Regulation:
Fig.3 and Fig.4 show the output
current regulation vs. load voltage and input voltage
respectively. The total current regulation (line and load
combined) is less than 1%.
Fig.3 Output Current vs. Output Voltage
Output Current (A)
0.710
0.705
0.700
0.695
0.690
Load Regulation (V
IN
= 13.5V)
3
8
13
18
23
Output Voltage (V)
Fig.4 Output Current vs. Input Voltage
Output Current (A)
0.710
0.705
0.700
0.695
0.690
9
11
13
15
Line Regulation (V
O
= 24V)
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
efficiency of 68% for the converter occurs at minimum load
voltage.
Input Voltage (V)
Doc.# DSDB-HV9911DB4
A032713
2
Supertex inc.
www.supertex.com
HV9911DB4
3. Normal Operation:
The drain voltage of the switching FET
and the output current are shown in Fig.5. It can be seen that
the converter is switching at 350kHz, and the output current
ripple is about 16% (peak to peak).
Fig.5. Switching waveforms for the HV9911DB4
6. PWM Dimming:
Typical PWM dimming response is
shown in Fig.8. Fig.9a shows the rise and Fig.9b shows the
fall of the LED current on an expanded time scale.
Fig.8: Typical PWM Dimming Waveforms
PWM Dimming Input
Output Current
Drain voltage
LED Current
4. Open LED Protection:
Open LED protection for the
circuit is set at 30V. 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 protection
to shut the IC down will depend on the size of the output
capacitor.
Fig.6. Open LED Protection
Fig.9a. Rise Time
(10µs/div)
PWM Dimming Signal
Output Voltage
LED Current
LED Current
Fig.9b. Fall Time
(10µs/div)
Drain Voltage of Q1
PWM Dimming Signal
5. Output Short Circuit Protection:
Fig.7 shows the
waveforms for output short circuit condition. The disconnect
FET is turned off in about 300ns. The rise in the output
current will depend on the output voltage and the energy
stored in the output capacitor.
LED Current
Doc.# DSDB-HV9911DB4
A032713
3
Supertex inc.
www.supertex.com
HV9911DB4
7. Input Audio Susceptibility:
Fig.10 shows the response
of the converter for a step change in the input voltage from
10 to 16V. The current overshoots by 30% and comes back
into regulation in 7ms.
8. Input Current Ripple:
Fig.10 shows the input current
ripple of the converter at full load and 13.5V input. The ripple
current is about 4% (peak to peak).
Fig. 10. Response of the HV9911DB4
to an input voltage change
(Time Scale: 1ms/div)
Input Voltage
LED Current
Silk Screen
Doc.# DSDB-HV9911DB4
A032713
4
Supertex inc.
www.supertex.com
Doc.# DSDB-HV9911DB4
A032713
J1B
C2
2.2 F
25V
33 H
D1
SK38-TP
C4
2.2 F
50V
1
L2
100 H
2
C9
2.2 F
50V
C3
1.0 F
50V
C10
1.0 F
50V
J3B
C5
1.0 F
16V
R2
261k
U1
VDD
SYNC
REF
IREF
FDBK
COMP
CLIM
PWM
SC
GND
OVP
FAULT
GATE
RT
VIN
L1
1
2
D2
1N4148
1
Circuit Schematic:
J2A
R1
56.2k
2
J1A
C1
2.2 F
25V
1
J3A
R4
open
499
R6
0.1
1W
R5
Q1
FDS3692
C11
1.0 F
50V
R3
2.43k
C13
1.0nF
50V
REF
5
C6
0.1 F
16V
R12
2
J2B
REF
Io_SNS
R13
CS
19.1k
HV9911
6.81k C7
0.1 F
16V
Q2
ZXMN6A11G
Io_SNS
C12
470pF
50V
R14
1k
R10
0.47
0.5W
C8
open
R8
17.4k
J3D
R11
36k
J3C
R7
open
REF
R9
8.66k
Supertex inc.
HV9911DB4
www.supertex.com
能源基础设施
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