HV9910LG-G Supertex, HV9910LG-G Datasheet - Page 6

• Manufacturer Part Number: HV9910LG-G
• Description: LED Drivers Universal Hi Bright
• Manufacturer: Supertex

Specifications of HV9910LG-G

• Operating Supply Voltage: 8 V to 450 V
• Maximum Power Dissipation: 630 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Knowing the nominal rectifi ed input voltage V
= 169V, the switching duty ratio can be determined, as:
D = V
Then, given the switching frequency, in this example f
50KHz, the required on-time of the MOSFET transistor can
be calculated:
T
The required value of the inductor is given by:
L = (V
Input Bulk Capacitor
An input fi lter capacitor should be designed to hold the
rectifi ed AC voltage above twice the LED string voltage
throughout the AC line cycle. Assuming 15% relative voltage
ripple across the capacitor, a simplifi ed formula for the
minimum value of the bulk input capacitor is given by:
C
C
A passive PFC circuit at the input requires using two series
connected capacitors at the place of calculated C
these identical capacitors should be rated for ½ of the input
voltage and have twice as much capacitance.
Enable
The HV9910 can be turned off by pulling the PWM_D pin
to ground. When disabled, the HV9910 draws quiescent
current of less than 1mA.
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
Figure 1: Typical Application Circuit
85 - 135VAC
ON
MIN
MIN
AC Input
= D/f
= I
= 22 µF, a value 22µF/250V can be used.
LEDs
IN
LED
- V
OSC
/V
*V
NTC
LEDs
2R
IN
250V
= 3.5 microsecond
LEDs
2A
0.1µF
250V
= 30/169 = 0.177
) * T
*0.06/V
ON
BUSH-2820R5b
/(0.3 * I
Coilcraft
1.0nF
250V
IN
^2
LED
0.1µF
250V
1N4004
) = 4.6mH
0.1µF
250V
LED(s) - a string of HB LEDs, 16 diodes
1N4004
1N4004
1N4004
IN
68µF
160V
= 120V*1.41
1N4004
MIN
Optional for PFC
. Each of
1N4004
68µF
160V
OSC
1N4004
=
6
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 HV9910 may cause excessive voltage stress of
the switching transistor and the rectifi er diode and potential
failure. In this case, the HV9910 can be disabled by pulling
the PMW_D pin to ground when the over voltage condition
is detected.
DC/DC Low Voltage Applications
Buck Converter Operation
The buck power conversion topology can be used when
the LED string voltage is needed to be lower than the input
supply voltage. The design procedure for a buck LED driver
outlined in the previous chapters can be applied to the low
voltage LED drivers as well. However, the designer must
keep in mind that the input voltage must be maintained higher
than 2 times the forward voltage drop across the LEDs. This
limitation is related to the output current instability that may
develop when the HV9910 buck converter operates at a
duty cycle greater than 0.5. This instability reveals itself as
an oscillation of the output current at a sub-harmonic of the
switching frequency.
Flyback (Buck-Boost) Operation
This power conversion topology can be used when the
forward voltage drop of the LED string is higher, equal or
lower than the input supply voltage. For example, the buck-
boost topology can be appropriate when input voltage is
supplied by an automotive battery (12V) and output string
consists of three to six HB LEDs, as the case may be for tail
and break signal lights.
In the buck-boost converter, the energy from the input source
is fi rst stored in the inductor or a Flyback transformer when
1.0μF
10V
V
LD
PWM_D
DD
HV9910
V
IN
GATE
GND
RT
CS
280 kΩ
BYV26B
VN2224
0.2Ω
750μH
HV9910
220nF
400V
LEDs