HV9910P データシートの表示（PDF） - Supertex Inc
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HV9910P Datasheet PDF : 11 Pages
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HV9910
Inductor Design
Referring to the Typical Application Circuit below
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 ILED 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 VLEDS is 30V.
Knowing the nominal rectified input voltage
VIN=120V*1.41=169V, the switching duty ratio can
be determined, as:
D= VLEDs /VIN=30/169=0.177
Then, given the switching frequency, in this
example fosc=50KHz, the required on-time of the
MOSFET transistor can be calculated:
Ton=D/fosc=3.5 microsecond
Figure 1: Typical Application Circuit
The required value of the inductor is given by:
L = (Vin - VLEDs) * Ton/(0.3 * ILED) = 4.6mH
Input Bulk Capacitor
An input filter capacitor should be designed 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:
Cmin = ILED*VLEDs*0.06/VIN^2
Cmin = 22 µF, a value 22uF/250V can be used.
A passive PFC circuit at the input requires using
two series connected capacitors at the place of
calculated CMIN. Each of 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.
AC Input
85-135V AC
2A,
250 V
0.1µ F,
250 V
2R
NTC
coilcraft
BUSH-2820R5B
1N4004
1n F,
250 V
0.1µ F,
250 V
1n F,
250 V
1N4004
1N4004
68µ F,
160 V
1N4004
1N4004
1N4004
1µF,
10V
68µ F,
160 V
optional for PFC
LED(s) – a string of HB LEDs , 16 diodes
VDD
VIN
RT
HV9910
GATE
LD
CS
BYV26B
280 kΩ
PW M_D
GND
750µΗ ,
LEDs
VN2224
220nF,
400 V
0.2 Ω
6
C110504
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