HV9803 데이터 시트보기 (PDF) - Supertex Inc
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HV9803 Datasheet PDF : 7 Pages
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Functional Block Diagram
VDD
LD
+
UVLO1 -
VLD
Auto-REF
xAV(LD)
i
IRT(LIM)
+
-
Reset
UVLO2
-
+
250mV
6.0mV
POR
SKIP
HV9803
UVLO
Average-Mode
CS
L/E
Blanking
Control Logic
IN
OUT
GATE
GND
+
VLIM
-
SKIP Q S
HV9803
R
Reset
RQ
SQ
TOFF
Timer
i
Current
Mirror
PWMD
RT
Functional Description
General
Peak-current control of a buck converter is the most
economical and simple way to regulate its output current.
However, it suffers accuracy and regulation problems that
arise from the peak-to-average current error, contributed
to by the current ripple in the output inductor and the
propagation delay in the current sense comparator. The full
inductor current signal is unavailable for direct sensing at the
ground potential in a buck converter when the control switch
is referenced to the same ground potential. While it is very
simple to detect the peak current in the switch, controlling
the average inductor current is usually implemented by
level-translating the current sense signal from the positive
input supply rail. While this is practical for relatively low input
voltage, this type of average-current control may become
excessively complex and expensive in the case of input
voltage in excess of 100V.
The HV9803 employs Supertex’ patented control scheme,
achieving fast and very accurate control of average current
in the buck inductor through sensing the switch current only.
No compensation of the current control loop is required.
The inductor current ripple amplitude does not affect this
control scheme significantly, and therefore, the LED current
is independent of the variation in inductance, switching
frequency or output voltage. Constant off-time control of the
buck converter is used for stability and to improve the LED
current regulation over a wide range of input voltages. The
IC features excellent PWM dimming response.
Doc.# DSFP-HV9803
NR012313
Supertex inc.
4
www.supertex.com
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