Universal High Brightness LED Driver TJ9910

Universal High Brightness LED Driver
TJ9910
FEATURES
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Over 90% Efficiency
10V to 600V Input Range
Constant Current LED Driver
Applications from a few mA to more than 1A output
LED String From One to Hundreds of Diodes
Linear and PWM Dimming Capability
Input Voltage Surge Ratings up to 600V
SOP8 PKG
ORDERING INFORMATION
APPLICATION
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DC/DC or AC/DC LED driver applications
RGB backlighting LED driver
Backlighting of flat panel displays
General-purpose constant current source
Signage and decorative LED lighting
Automotive
Chargers
Device
Package
TJ9910GD
SOP8
DESCRIPTION
The TJ9910 is a PWM high-efficiency LED driver control IC. It allows efficient operation of high-brightness
(HB) LEDs from voltage sources ranging from 10VDC up to 600VDC. TJ9910 controls an external MOSFET
at fixed switching frequencies up to 300 kHz. The frequency can be programmed using a single resistor. The
LED string is driven at a constant current rather than a constant voltage, thus providing a constant light
output and an enhanced reliability. The output current can be programmed between a few milliamps and up
to more than 1.0A. TJ9910 uses a rugged high-voltage junction isolated process that can withstand an input
voltage surge up to 600V. The output current to a 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 TJ9910.
TJ9910 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 kHz.
Absolute Maximum Ratings
CHARACTERISTIC
SYMBOL
MIN.
MAX.
UNIT
Supply voltage to GND
-
-0.5
600
V
CS, LD, PWM_D, GATE to GND
-
-0.3
VDD+0.3
V
Operating Temperature Range
-
-40
85
℃
Junction Temperature
TJOPR
Storage Temperature Range
TSTR
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125
-65
℃
150
℃
HTC
Universal High Brightness LED Driver
TJ9910
Ordering Information
Package
Order No.
SOP8
TJ9910GD
Description
Package Marking
Supplied As
TJ9910G
Reel
LED Driver
PIN CONFIGURATION
SOP8
PIN DESCRIPTION
Pin No.
Pin Name
1
VIN
Input Voltage
2
CS
Senses LED string current
3
GND
Ground
4
GATE
Drives the gate of external MOSFET
5
PWM_D
6
VDD
7
LD
8
ROSC
Jul, 2011_R1.1
Pin Function
Low Frequency PWM Dimming pin, also Enable input. Internal 100kΩ pulldown to GND
Supply Voltage
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
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Universal High Brightness LED Driver
TJ9910
Block Diagram
ELECTRICAL CHARACTERISTICS
(TA = 25℃ unless otherwise specified)
PARAMETER
SYMBOL
Input DC supply voltage range
VINDC
Shut-down mode supply current
IINSD
Internally regulated voltage
Load regulation of VDD
1
VDD
ΔVDD,
load
TEST CONDITION
MIN.
TYP.
MAX.
UNIT
DC Input Voltage
10
600
V
Pin PWM_D to GND, VIN = 8V
0.5
1
mA
VIN = 10 to 600V, IDD(ext)=0,
pin Gate open
IDD(ext) = 0 to 1.0mA,
500pF at GATE
ROSC = 226kΩ,
PWM_D = VDD
7.0
7.5
8.0
V
0
-
100
mV
Maximal pin VDD voltage
VDD,max
When an external voltage is
applied to pin VDD
10.0
V
VDD current available for external
circuitry
IDD(ext)
VIN = 10 to 100V
0.7
mA
VDD undervoltage lockout
threshold
UVLO
VIN rising
6.95
V
ΔUVLO
VIN falling
Pin PWM_D input low voltage
VEN(lo)
VIN = 10 to 600V
Pin PWM_D input high voltage
VEN(hi)
VIN = 10 to 600V
2.0
Pin PWM_D pull-down resistance
REN
VEN = 5V
50
100
150
kΩ
Current sense pull-in threshold
VCS(hi)
TA = -40C to +85C
225
250
275
mV
VDD undervoltage lockout
hysteresis
Jul, 2011_R1.1
6.45
3/9
6.7
500
mV
0.8
V
V
HTC
Universal High Brightness LED Driver
TJ9910
voltage
GATE high output voltage
VGATE(hi)
IOUT = 10mA
VDD-0.3
VDD
V
GATE low output voltage
VGATE(lo)
IOUT = -10mA
0
0.3
V
Oscillator frequency
fOSC
ROSC = 1.00MΩ
20
25
30
ROSC = 226kΩ
80
100
120
Maximum Oscillator PWM
Duty Cycle
Pin LD (Linear Dimming) voltage
DMAX hf
FPWM
hf
= 25kHz, at GATE, CS
to GND
VLD
TA = <85C, VIN = 12V
Current sense blanking interval
TBLANK
VCS = 0.55VLD, VLD = VDD
Delay from CS to GATE lo
tDELAY
GATE output rise time
GATE output fall time
tRISE
tFALL
range
VIN = 12V, VLD = 0.15,
VCS = 0 to 0.22V after TBLANK
CGATE = 500pF, VDD = 7.5V
CGATE = 500pF, VDD = 7.5V
0
150
30
30
215
kHz
100
%
250
mV
280
ns
300
ns
50
50
ns
ns
Note 1. Also limited by package power dissipation limit, whichever is lower.
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Universal High Brightness LED Driver
TJ9910
Application Circuit
Typical LED Driver
CIN
1
VIN
ROSC
8
VDD
GATE
COUT
L1
RT
TJ9910
6
D1
4
Q1
7
LD
CS
2
CDD
5
PWM_D
GND
3
RCS
AC/DC Off-Line LED driver
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Universal High Brightness LED Driver
TJ9910
APPLICATION INFORMATION
The TJ9910 is designed for wide range for lighting applications. When the gate signal enhances the external
power MOSFET, the LED driver stores the input energy in an inductor and, 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.
The gate drive is enabled when VDD is higher than UVLO threshold (6.7V, typical). The output current is then
controlled by limiting the peak current in the external power MOSFET. This is done by a current sense resistor
connected in series with the source terminal of the MOSFET. The voltage from the sense resistor is applied to the
CS pin of the TJ9910. When the voltage at CS pin exceeds the threshold voltage, the gate drive terminates to turn
off the power MOSFET. This threshold voltage is internally set to 250mV, or it can be programmed externally by
applying voltage to the LD pin.
Supply Current
A current of 1mA is required to start TJ9910, as shown in block diagram. In many cases, the TJ9910 can be
continuously powered using its internal linear regulator which provides a regulated voltage of 7.5V, typical.
Setting Light Output
The peak CS voltage is a good representation of the average current in LED. However, since there is difference
between peak and average current, so such an error should be taken into account while selecting the value of this
current sense resistor. 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
Dimming
Dimming can be accomplished by two ways, Linear or PWM dimming. The linear dimming is by changing the
LED current linearly or by switching the current ON and OFF while maintaining it constant. PWM dimming controls
the LED brightness by varying the duty ratio of the output current.
The linear dimming can be achieved 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. However, applying a control voltage higher than 250mV at the LD pin will not change the output
current setting.
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Universal High Brightness LED Driver
TJ9910
The PWM dimming can be achieved by an external PWM signal to the PWM_D pin. The PWM signal 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.
By using the PWM control method, 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.
Inductor Selection
For the given assumptions, the ideal inductor is calculated as
L=
(VIN - VLEDS ) • TON
0.3 • I LED
Where
VIN = 110V x 1.414 = 155.5V, for the normal rectified input voltage, and,
ILED is 350mA as a typical current level of normal LED’s, and
VLED is 3.0V as typical forward voltage of normal LED’s, and
TON is defined:
TON =
Duty
f OSC
And Duty is defined as:
Duty =
VLEDs
30V
=
= 19.3%
VIN
155V
Then
TON =
0.193
= 3.86us
50K
Then
L=
(VIN - VLEDS ) • TON (155V - 30V) • 3.86us
= 4.59mH
=
0.3 • I LED
0.3 • 350mA
Input Bulk Capacitor
An input filter capacitor is required to hold the rectified AC voltage above twice the LED string voltage throughout
the AC line cycle. Assuming 15% relative voltage ripple across the capacitor, a simplified formula for the minimum
value of the bulk input capacitor is given by:
C MIN =
I LED • VLED • 0.06
VIN
2
C MIN = 22uF, a value 22uF/250V can be used.
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Universal High Brightness LED Driver
TJ9910
Enable
The TJ9910 can be turned off by pulling the PWM_D pin to ground. When disabled, the product draws quiescent
current of less than 1mA.
Oscillator
The TJ9910 operates in a constant frequency mode. Setting the oscillator frequency is achieved by connecting an
external resistor between Rosc and GND. In general, switching frequency selection is based on the inductor size,
controller power dissipation, and the input filter capacitor. The typical off-line LED driver switching frequency,
frequency is between 30kHz and 120kHz. This operating range gives designers a reasonable compromise
between switching losses and inductor size. The internal RC oscillator has a frequency accuracy of ±20%.
Output Open Circuit Protection
When the buck topology is used, and the LED is connected in series with the inductor, there is no need for any
protection against an open circuit condition in the LED string. Open LED connection means no switching and can
be continuous. However, in the case of the buck-boost or the Flyback topology the TJ9910 may cause excessive
voltage stress of the switching transistor and the rectifier diode and potential failure. In this case, the TJ9910 can
be disabled by pulling the PMW_D pin to ground when the over voltage condition is detected.
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Universal High Brightness LED Driver
TJ9910
REVISION NOTICE
The information in this datasheet can be revised without any notice to describe proper electrical characteristics.
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HTC