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HV9921 の電気的特性と機能

HV9921のメーカーはMicrochipです、この部品の機能は「3-Pin Switch-Mode LED Lamp Driver ICs」です。


製品の詳細 ( Datasheet PDF )

部品番号 HV9921
部品説明 3-Pin Switch-Mode LED Lamp Driver ICs
メーカ Microchip
ロゴ Microchip ロゴ 




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HV9921 Datasheet, HV9921 PDF,ピン配置, 機能
HV9921/HV9922/HV9923
3-Pin Switch-Mode LED Lamp Driver ICs
Features
• Constant output current:
- HV9921 – 20mA
- HV9922 – 50mA
- HV9923 – 30mA
• Universal 85 - 264VAC operation
• Fixed off-time buck converter
• Internal 475V power MOSFET
Applications
• Decorative lighting
• Low power lighting fixtures
Description
HV9921/HV9922/HV9923 are pulse-width modulated
(PWM), high-efficiency, LED driver control ICs. They
allow efficient operation of LED strings from voltage
sources ranging up to 400VDC. HV9921/22/23 include
an internal high voltage switching MOSFET controlled
with fixed off-time (TOFF) of approximately 10μs. The
LED string is driven at constant current, thus providing
constant light output and enhanced reliability. The out-
put current is internally fixed at 20mA for HV9921,
50mA for HV992, and 30mA for HV9923. The peak cur-
rent control scheme provides good regulation of the
output current throughout the universal AC line voltage
range of 85 to 264VAC or DC input voltage of 20 to
400V.
2014 Microchip Technology Inc.
DS20005311A-page 1

1 Page





HV9921 pdf, ピン配列
PIN DIAGRAM
HV9921/HV9922/HV9923
1
2
3
TO-243AA
(SOT-89)
See Table 2-1 for Pin information.
TYPICAL APPLICATION CIRCUIT
123
TO-92
AC
HV9921/22/23
3 VDD
DRAIN 1
GND
2
LED1
-
LEDn
2014 Microchip Technology Inc.
DS20005311A-page 3


3Pages


HV9921 電子部品, 半導体
HV9921/HV9922/HV9923
2.0 PIN DESCRIPTION
See Pin Diagram on page 3 for the figures.
TABLE 2-1: PIN DESCRIPTION
Pin #
Name Description
1 Drain Drain terminal of the output switching MOSFET and a linear regulator input
2 GND Common connection for all circuits
3
VDD
Power Supply pin for all control circuits. By pass this pin with a 0.1 μF low-impedance
capacitor
3.0 FUNCTIONAL DESCRIPTION
The HV9921/22/23 are PWM peak current controllers
designed to control a buck converter topology in contin-
uous conduction mode (CCM). The output current is
internally preset at 20mA for HV9921, 50mA for
HV992, and 30mA for HV9923.
When the input voltage of 20 to 400V appears at the
DRAIN pin, the internal high-voltage linear regulator
seeks to maintain a voltage of 7.5VDC at the VDD pin.
Until this voltage exceeds the internally programmed
under-voltage threshold, the output switching MOSFET
is non-conductive. When the threshold is exceeded,
the MOSFET turns on. The input current begins to flow
into the DRAIN pin. Hysteresis is provided in the under-
voltage comparator to prevent oscillation.
When the input current exceeds the internal preset
level, a current sense comparator resets an RS flip-
flop, and the MOSFET turns off. At the same time, a
one-shot circuit is activated that determines the dura-
tion of the off-state (10.5μs typical). As soon as this
time is over, the flip-flop sets again. The new switching
cycle begins.
A “blanking” delay of 300ns is provided that prevents
false triggering of the current sense comparator due to
the leading edge spike caused by circuit parasitics.
4.0 APPLICATION INFORMATION
HV9921/22/23 are low-cost off-line buck converter ICs
specifically designed for driving multi-LED strings.
They can be operated from either universal AC line
range of 85 to 264VAC, or 20 to 400VDC, and drive up
to tens of high-brightness LEDs. All LEDs can be run in
series, and the HV9921/22/23 regulate at constant cur-
rent, yielding uniform illumination. HV9921/22/23 are
compatible with triac dimmers. The output current is
internally fixed at 20mA for HV9921, 50mA for HV9922,
and 30mA for HV9923. These parts are available in
space saving TO-92 and SOT-89 packages.
4.1 Selecting L1 and D1
There is a certain trade-off to be considered between
optimal sizing of the output inductor L1 and the toler-
ated output current ripple. The required value of L1 is
inversely proportional to the ripple current IO in it.
L1= V-----O----------IT--O--O-----F----F--
VO is the forward voltage of the LED string. TOFF is the
off-time of HV9921/22/23. The output current in the
LED string (IO) is calculated then as:
IO= ITH12--  IO
where ITH is the current sense comparator threshold.
The ripple current introduces a peak-to-average error
in the output current setting that needs to be accounted
for. Due to the constant off-time control technique used
in HV9921/22/23, the ripple current is independent of
the input AC or DC line voltage variation. Therefore, the
output current will remain unaffected by the varying
input voltage.
Adding a filter capacitor across the LED string can
reduce the output current ripple even further, thus per-
mitting a reduced value of L1. However, keep in mind
that the peak-to-average current error is affected by the
variation of TOFF. Therefore, the initial output current
accuracy might be sacrificed at large ripple current in
L1.
Another important aspect of designing an LED driver
with the HV9921/22/23 is related to certain parasitic
elements of the circuit, including distributed coil capac-
itance of L1, junction capacitance and reverse recovery
of the rectifier diode D1, capacitance of the printed cir-
cuit board traces CPCB and output capacitance CDRAIN
of the controller itself. These parasitic elements affect
the efficiency of the switching converter and could
potentially cause false triggering of the current sense
comparator if not properly managed. Minimizing these
parasitics is essential for efficient and reliable operation
of the HV9921/22/23.
DS20005311A-page 6
2014 Microchip Technology Inc.

6 Page



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共有リンク

Link :


部品番号部品説明メーカ
HV9921

3-Pin Switch-Mode LED Lamp Driver ICs

Microchip
Microchip
HV9921

3-Pin Switch-Mode LED Lamp Driver IC

Supertex
Supertex
HV9922

3-Pin Switch-Mode LED Lamp Driver ICs

Microchip
Microchip
HV9922

(HV9921 - HV9923) 3-Pin Switch-Mode LED Lamp Driver ICs

Supertex
Supertex


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