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

LED Drivers Universal Hi Bright

HV9910LG-G

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

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.
ON
MIN
MIN
= D/f
= I
= 22 µF, a value 22µF/250V can be used.
LEDs
IN
LED
- V
OSC
/V
*V
LEDs
IN
= 3.5 microsecond
LEDs
= 30/169 = 0.177
) * T
*0.06/V
ON
/(0.3 * I
IN
^2
LED
) = 4.6mH
IN
= 120V*1.41
MIN
. Each of
OSC
=
6
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
against an open circuit condition in the LED string. Open LED
connection means no switching and can be continuous.
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.
HV9910

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