HV9910
Universal High Brightness
LED Driver
Features
►
►
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>90% Efficiency
8V to 450V input range
Constant-current LED driver
Applications from a few mA to more than 1A
Output
►
LED string from one to hundreds of diodes
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PWM Low-Frequency Dimming via Enable pin
►
Input Voltage Surge ratings up to 450V
General Description
The HV9910 is a PWM high-efficiency LED driver control IC.
It allows efficient operation of High Brightness (HB) LEDs
from voltage sources ranging from 8VDC up to 450VDC.
The HV9910 controls an external MOSFET at fixed switching
frequency up to 300kHz. The frequency can be programmed
using a single resistor. The LED string is driven at constant
current rather than constant voltage, thus providing constant
light output and enhanced reliability. The output current can
be programmed between a few milliamps and up to more than
1.0A.
The HV9910 uses a rugged high voltage junction isolated
process that can withstand an input voltage surge of up to
450V. Output current to an LED string can be programmed to
any value between zero and its maximum value by applying
an external control voltage at the linear dimming control input
of the HV9910. The HV9910 provides a low-frequency PWM
dimming input that can accept an external control signal with a
duty ratio of 0-100% and a frequency of up to a few kilohertz.
Applications
►
►
►
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DC/DC or AC/DC LED Driver applications
RGB Backlighting LED Driver
Back Lighting of Flat Panel Displays
General purpose constant current source
Signage and Decorative LED Lighting
Automotive
Chargers
Typical Application
V
IN
V
DD
HV9910
LD
PWMD
R
T
GATE
CS
GND
HV9910
Ordering Information
Device
HV9910
Package Options
SOIC-16
HV9910NG-G
SOIC-8
HV9910LG-G
-G indicates package is RoHS compliant (‘Green’)
Absolute Maximum Ratings
Parameter
V
IN
to GND
CS
LD, PWM_D to GND
GATE to GND
V
DDMAX
Continuous Power Dissipation (T
A
= +25°C) (Note 1)
16-Pin SO (derate 7.5mW/°C above +25°C)
8-Pin SO (derate 6.3mW/°C above +25°C)
Operating temperature range
Junction temperature
Storage temperature range
750mW
630mW
-40°C to +85°C
+125°C
-65°C to +150°C
Pin Configurations
Value
-0.5V to +470V
-0.3V to (V
DD
+ 0.3V)
-0.3V to (V
DD
- 0.3V)
-0.3V to (V
DD
+ 0.3V)
13.5V
V
IN
NC
NC
CS
GND
NC
NC
GATE
NC
NC
R
OSC
LD
V
DD
NC
NC
PWM_D
GATE
V
IN
CS
GND
R
OSC
LD
V
DD
PWM_D
16-Lead SOIC
8-Lead SOIC
Absolute Maximum Ratings are those values beyond which damage to the device may
occur. Functional operation under these conditions is not implied. Continuous operation
of the device at the absolute rating level may affect device reliability. All voltages are
referenced to device ground.
Electrical Characteristics
(Over recommended operating conditions unless otherwise specified - T
A
= 25°C)
Symbol
V
INDC
I
INsd
V
DD
V
DDmax
I
DD(ext)
UVLO
∆UVLO
V
EN(lo)
V
EN(hi)
R
EN
V
CS(hi)
V
GATE(hi)
V
GATE(lo)
f
OSC
D
MAXhf
V
LD
T
BLANK
1
Parameter
Input DC supply voltage range
Shut-down mode supply current
Internally regulated voltage
Maximal pin V
DD
voltage
V
DD
current available for external
circuitry
1
V
DD
undervoltage lockout threshold
V
DD
undervoltage lockout hysteresis
Pin PWM_D input low voltage
Pin PWM_D input high voltage
Pin PWM_D pull-down resistance
Current sense pull-in threshold
voltage
GATE high output voltage
GATE low output voltage
Oscillator frequency
Maximum PWM duty cycle
Linear dimming pin voltage range
Current sense blanking interval
Min
8.0
-
7.0
-
-
6.45
-
-
2.4
50
225
V
DD
-0.3
0
20
80
-
0
150
Typ
0.5
7.5
-
-
6.7
500
-
-
100
250
-
-
25
100
-
-
215
Max
450
1
8.0
13.5
1.0
6.95
-
1.0
-
150
275
V
DD
0.3
30
120
100
250
280
Units
V
mA
V
V
mA
V
mV
V
V
kΩ
mV
V
V
kHz
kHz
%
mV
ns
Conditions
DC input voltage
Pin PWM_D to GND, V
IN
= 8V
V
IN
= 8 – 450V, I
DD(ext)
= 0, pin GATE open
When an external voltage applied to pin V
DD
V
IN
= 8 – 100V
V
IN
rising
V
IN
falling
V
IN
= 8 – 450V
V
IN
= 8 – 450V
V
EN
= 5V
@T
A
= -40°C to +85°C
I
OUT
= 10mA
I
OUT
= -10mA
R
T
= 1.00MΩ
R
T
= 226kΩ
F
PWMhf
= 25kHz, at GATE, CS to GND.
@T
A
= <85°C, V
IN
= 12V
V
CS
= 0.55V
LD
, V
LD
= V
DD
Also limited by package power dissipation limit, whichever is lower.
2
HV9910
Symbol
t
DELAY
t
RISE
t
FALL
Parameter
Delay from CS trip to GATE lo
GATE output rise time
GATE output fall time
Min
-
-
-
Typ
-
30
30
Max
300
50
50
Units
ns
ns
ns
Conditions
V
IN
= 12V, V
LD
= 0.15,
V
CS
= 0 to 0.22V after T
BLANK
C
GATE
= 500pF
C
GATE
= 500pF
Pinout
Pin
V
IN
CS
GND
GATE
PWM_D
SOIC-16
1
4
5
8
9
SOIC-8
1
2
3
4
5
Description
Input voltage 8V to 450V DC
Senses LED string current
Device ground
Drives the gate of the external MOSFET
Low Frequency PWM Dimming pin, also Enable input. Internal
100kΩ pull-down to GND
Internally regulated supply voltage (7.5V nominal). Can supply
up to 1mA for external circuitry. A sufficient storage capacitor is
used to provide storage when the rectified AC input is near the
zero crossings.
Linear dimming by changing the current limit threshold at current
sense comparator
Oscillator control. A resistor connected between this pin and
ground sets the PWM frequency.
V
DD
12
6
LD
R
T
13
14
7
8
No Connects (NC) are not internally connected and may be used for pass-thru PCB traces.
Block Diagram & Typical Applications
V
IN
V
IN
V
DD
REG
7.5V
R
T
OSC
V
DD
250mV
LD
CM
S Q
R
CM
GATE
CS
PWM_D
100k
HV9910
GND
3
HV9910
Application Information
AC/DC Off-Line Applications
The HV9910 is a low-cost off-line buck or boost converter
control IC specifically designed for driving multi-LED stings
or arrays. It can be operated from either universal AC line
or any DC voltage between 8-450V. Optionally, a passive
power factor correction circuit can be used in order to pass
the AC harmonic limits set by EN 61000-3-2 Class C for
lighting equipment having input power less than 25W. The
HV9910 can drive up to hundreds of High-Brightness (HB)
LEDs or multiple strings of HB LEDs. The LED arrays can
be configured as a series or series/parallel connection. The
HV9910 regulates constant current that ensures controlled
brightness and spectrum of the LEDs, and extends their
lifetime. The HV9910 features an enable pin (PWM_D) that
allows PWM control of brightness.
The HV9910 can also control brightness of LEDs by
programming continuous output current of the LED driver
(so-called linear dimming) when a control voltage is applied
to the LD pin.
The HV9910 is offered in a standard 8-pin SOIC package. It
is also available in a high voltage rated SO-16 package for
applications that require V
IN
greater than 250V.
The HV9910 includes an internal high-voltage linear regulator
that powers all internal circuits and can also serve as a bias
supply for low voltage external circuitry.
voltage to the LD pin. When soft start is required, a capacitor
can be connected to the LD pin to allow this voltage to ramp
at a desired rate, therefore, assuring that output current of
the LED ramps gradually.
Optionally, a simple passive power factor correction circuit,
consisting of 3 diodes and 2 capacitors, can be added as
shown in the typical application circuit diagram of Figure 1.
Supply Current
A current of 1mA is needed to start the HV9910. As shown
in the block diagram on page 3, this current is internally
generated in the HV9910 without using bulky startup resistors
typically required in the offline applications. Moreover, in
many applications the HV9910 can be continuously powered
using its internal linear regulator that provides a regulated
voltage of 7.5V for all internal circuits.
Setting Light Output
When the buck converter topology of Figure 2 is selected,
the peak CS voltage is a good representation of the average
current in the LED. However, there is a certain error
associated with this current sensing method that needs to
be accounted for. This error is introduced by the difference
between the peak and the average current in the inductor.
For example if the peak-to-peak ripple current in the inductor
is 150mA, to get a 500mA LED current, the sense resistor
should be 250mV/(500mA+ 0.5*150mA) = 0.43Ω.
LED Driver Operation
The HV9910 can control all basic types of converters, isolated
or non-isolated, operating in continuous or discontinuous
conduction mode. When the gate signal enhances the external
power MOSFET, the LED driver stores the input energy in an
inductor or in the primary inductance of a transformer and,
depending on the converter type, may partially deliver the
energy directly to LEDs The energy stored in the magnetic
component is further delivered to the output during the off-
cycle of the power MOSFET producing current through the
string of LEDs (Flyback mode of operation).
When the voltage at the V
DD
pin exceeds the UVLO threshold
the gate drive is enabled. The output current is controlled
by means of limiting peak current in the external power
MOSFET. A current sense resistor is connected in series
with the source terminal of the MOSFET. The voltage from
the sense resistor is applied to the CS pin of the HV9910.
When the voltage at CS pin exceeds a peak current sense
voltage threshold, the gate drive signal terminates, and the
power MOSFET turns off. The threshold is internally set
to 250mV, or it can be programmed externally by applying
Dimming
Dimming can be accomplished in two ways, separately or
combined, depending on the application. Light output of the
LED can be controlled either by linear change of its current,
or by switching the current on and off while maintaining it
constant. The second dimming method (so-called PWM
dimming) controls the LED brightness by varying the duty
ratio of the output current.
The linear dimming can be implemented by applying a
control voltage from 0 to 250mV to the LD pin. This control
voltage overrides the internally set 250mV threshold level
of the CS pin and programs the output current accordingly.
For example, a potentiometer connected between V
DD
and
ground can program the control voltage at the CS pin.
Applying a control voltage higher than 250mV will not change
the output current setting. When higher current is desired,
select a smaller sense resistor.
The PWM dimming scheme can be implemented by applying
an external PWM signal to the PWM_D pin. The PWM signal
4
HV9910
can be generated by a microcontroller or a pulse generator
with a duty cycle proportional to the amount of desired
light output. This signal enables and disables the converter
modulating the LED current in the PWM fashion. In this
mode, LED current can be in one of the two states: zero or
the nominal current set by the current sense resistor. It is not
possible to use this method to achieve average brightness
levels higher than the one set by the current sense threshold
level of the HV9910. By using the PWM control method of
the HV9910, the light output can be adjusted between zero
and 100%. The accuracy of the PWM dimming method is
limited only by the minimum gate pulse width, which is a
fraction of a percent of the low frequency duty cycle.
Some of the typical waveforms illustrating the PWM dimming
method used with the application circuit on page 7 are given
below. CH
1
shows the MOSFET Drain voltage, CH
2
is the
PWM signal to pin PWM_D and CH
4
is the current in the
LED string.
0.4% PWM Ratio at 500Hz Dimming
Programming Operating Frequency
The operating frequency of the oscillator is programmed
between 25 and 300kHz using an external resistor connected
to the R
T
pin:
F
OSC
= 25000/(R
T
[kΩ] + 22) [kHz]
Power Factor Correction
When the input power to the LED driver does not exceed
25W, a simple passive power factor correction circuit can be
added to the HV9910 typical application circuit on page 7 in
order to pass the AC line harmonic limits of the EN61000-
3-2 standard for Class C equipment. The typical application
circuit diagram shows how this can be done without affecting
the rest of the circuit significantly. A simple circuit consisting
of 3 diodes and 2 capacitors is added across the rectified AC
line input to improve the line current harmonic distortion and
to achieve a power factor greater than 0.85.
33% PWM Ratio at 500Hz Dimming
Inductor Design
Referring to the typical application circuit on page 7 the
value can be calculated from the desired peak-to-peak LED
ripple current in the inductor. Typically, such ripple current
is selected to be 30% of the nominal LED current. In the
example given here, the nominal current I
LED
is 350mA.
The next step is determining the total voltage drop across
the LED string. For example, when the string consists of 10
High-Brightness LEDs and each diode has a forward voltage
drop of 3.0V at its nominal current; the total LED voltage
V
LEDS
is 30V.
95% PWM Ratio at 500Hz Dimming
5
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