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參數(shù)資料
| 型號： | IRS2540 |
| 廠商： | International Rectifier |
| 英文描述： | IRPLLED1 High Voltage LED Driver using the IRS2540 |
| 中文描述： | IRPLLED1高電壓LED驅(qū)動器采用IRS2540 |
| 文件頁數(shù)： | 12/28頁 |
| 文件大小： | 839K |
| 代理商： | IRS2540 |
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12
RD-0608
www.irf.com
The reverse recovery problem is incurred during the deadtime after the low-side FET has been on and
conducting current. During this deadtime the low-side FET is off, but the body diode is freewheeling
and providing current to the load. Since the body diode is conducting current, carriers are present and
will eventually need to be recombined, leading to reverse recovery. When the high-side FET turns on,
the V
S
node is almost instantly pulled from COM to V
BUS
and the low-side FET or the freewheeling
diode conducts current from V
S
to ground due to the reverse recovery effect, potentially resulting in
large power losses, overheating of the low-side switching component and component stress, as can be
seen in Figs. 17 & 18. Since the power diode has a much shorter reverse recovery time, the diode will
conduct current for a significantly shorter period and have lower power losses. At lower frequency
and lower load current, the long recovery time associated with the FET body diode may not be an
issue. For higher frequency higher current applications, a diode could provide lower power losses with
respect to a FET.
In the evaluation board, the reverse recovery current peaks using a low-side FET would be on the order
of 8 A, which puts a lot of stress on the components, not to mention the increased operating
temperature. By replacing the low-side FET with an appropriate freewheeling diode, the reverse
recovery peaks can be reduced and limited to 4.5 A. The frequency was also selected to keep the diode
reverse recovery associated power losses low.
With the inclusion of a freewheeling diode instead of a low-side FET there is a need for R
S3
and D
VCC
.
Without an initial pulse to come from LO establishing a ground reference for C
BOOT
to charge, an
alternate ground reference must be established. There are two paths that could potentially serve this
role, one is through R
S2
and the other is through the open-circuit components, R
OV1
and R
OV2
. The
most versatile path is through R
OV1
and R
OV2
since there are no constraints along this path tied to the
chip’s turn on threshold. By making these two resistors, that are already serving function to the circuit,
a bit smaller, the capacitor now has a low resistive path for which to charge. R
S3
allows this charging
path to exist without any interference from the chip V
CC
, likewise D
VCC
also allows this path to remain
isolated. As the bus voltage is increased, the path will allow C
BOOT
to fully charge and remain charged
until the chip comes out of UVLO. At which time the self powering feature will take over after the
first pulse from HO, and the ground reference will then be created by the freewheeling diode.
Fig. 17: Using a low-side FET, V
in
= 100 V, I
out
= 1.5 A, V
out
= 17 V
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| IRS25401 | 制造商:IRF 制造商全稱:International Rectifier 功能描述:LED BUCK REGULATOR CONTROL IC |
| IRS25401PBF | 功能描述:LED照明驅(qū)動器 Hysteretic Buck LED Drvr RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| IRS25401PBF | 制造商:International Rectifier 功能描述:IC LED DRVR DIP8 |
| IRS25401SPBF | 功能描述:LED照明驅(qū)動器 200V HALF BRDG DRVR LED BUCK REGULATOR RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| IRS25401STRPBF | 功能描述:LED照明驅(qū)動器 Hysteretic Buck LED Drvr RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
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