收藏本站
IR2277S/IR2177S (PbF)
This method has the advantage of being simple and
low cost but may force some limitations on duty-
cycle and on-time since they are limited by the
requirement to refresh the charge in the bootstrap
capacitor.
Proper capacitor choice can reduce drastically
these limitations.
Bootstrap capacitor sizing
Given the maximum admitted voltage drop for V BS ,
namely ? V BS , the influencing factors contributing to
V BS decrease are:
? Floating section quiescent current ( I QBS );
? Floating section leakage current ( I LK )
? Bootstrap diode leakage current ( I LK_DIODE );
? Charge required by the internal level shifters
( Q LS ); typical 20nC
? Bootstrap capacitor leakage current ( I LK_CAP );
? High side on time ( T HON ).
I LK_CAP is only relevant when using an electrolytic
capacitor and can be ignored if other types of
capacitors are used. It is strongly recommend using
at least one low ESR ceramic capacitor (paralleling
electrolytic and low ESR ceramic may result in an
efficient solution).
Then we have:
Q TOT = Q LS + ( I QBS + + I LK + I LK _ DIODE + I LK _ CAP ) ? T HON
The minimum size of bootstrap capacitor is then:
high side freewheeling diode get forwarded
biased
I LOAD = 0; the IGBT is not loaded while being
on and V CE can be neglected
V BS = V CC ? V F
I LOAD > 0; the load current flows through the
freewheeling diode
V BS = V CC ? V F + V FP
In this case we have the highest value for V BS .
Turning on the high side IGBT, I LOAD flows into it
and V S is pulled up.
b) Bootstrap Resistor
A resistor (R boot ) is placed in series with the
bootstrap diode (see Figure 20) to limit the current
when the bootstrap capacitor is initially charged. We
suggest not exceeding some Ohms (typically 5,
maximum 10 Ohms) to avoid increasing the V BS
time-constant. The minimum on time for charging
the bootstrap capacitor or for refreshing its charge
must be verified against this time-constant.
c) Bootstrap Capacitor
For high T HON designs where an electrolytic tank
capacitor is used, its ESR must be considered. This
parasitic resistance develops a voltage divider with
R boot generating a voltage step on V BS at the first
charge of bootstrap capacitor. The voltage step and
the related speed (dV BS /dt) should be limited. As a
general rule, ESR should meet the following
C BOOT min =
Q TOT
? V BS
constraint:
ESR
ESR + R BOOT
? V CC ≤ 3 V
Some important considerations
a) Voltage ripple
There are three different cases making the
bootstrap circuit get conductive (see Figure 20)
I LOAD < 0; the load current flows in the low side
IGBT displaying relevant V CEon
V BS = V CC ? V F ? V CEon
In this case we have the lowest value for V BS .
This represents the worst case for the bootstrap
capacitor sizing. When the IGBT is turned off the
Vs node is pushed up by the load current until the
18
Parallel combination of small ceramic and large
electrolytic capacitors is normally the best
compromise, the first acting as fast charge tank for
the gate charge only and limiting the dV BS /dt by
reducing the equivalent resistance while the second
keeps the V BS voltage drop inside the desired ? V BS .
d) Bootstrap Diode
The diode must have a BV> 600V (or 1200V
depending on application) and a fast recovery time
(t rr < 100 ns) to minimize the amount of charge fed
back from the bootstrap capacitor to V CC supply.
www.irf.com
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
IRDC2085S-DF BOARD EVAL CONV DC BUS W/IRF6603
IRDC3038 KIT W/IRU3038 PWM CTRL DDR 14-PI
IRDC3039 BOARD EVAL CTRLR PWM W/IRU3039
IRDC3046 KIT W/IRU3046 DUAL PWM LDO CTRLR
IRDC3048 KIT W/IRU3048 DUAL PWM LDO CTRLR
IRDC3055 KIT W/IRU3055 5BIT 3PH BUCK CTRL
IRDC3073 PWM CONTROLLER DESIGN KIT
IRDC3137 KIT REFERENCE DESIGN W/IRU3137
相关代理商/技术参数
IRCW0805LF031002BR1 制造商:TT Electronics / IRC 功能描述:
IRCW0805R033482BR1 制造商:TT Electronics / IRC 功能描述:
IRCW1206R031210BR1 制造商:TT Electronics / IRC 功能描述:
IRCWCR0603000ZPI 制造商:MAJOR 功能描述:
IRCZ24 制造商:IRF 制造商全称:International Rectifier 功能描述:Power MOSFET(Vdss=55V, Rds(on)=0.040ohm, Id=26A)
IRCZ24-007 制造商:未知厂家 制造商全称:未知厂家 功能描述:TRANSISTOR | MOSFET | N-CHANNEL | 60V V(BR)DSS | 16A I(D) | TO-220VAR
IRCZ24-008 制造商:未知厂家 制造商全称:未知厂家 功能描述:TRANSISTOR | MOSFET | N-CHANNEL | 60V V(BR)DSS | 16A I(D) | TO-220VAR
IRCZ24PBF 功能描述:MOSFET N-Chan 55V 26 Amp RoHS:否 制造商:STMicroelectronics 晶体管极性:N-Channel 汲极/源极击穿电压:650 V 闸/源击穿电压:25 V 漏极连续电流:130 A 电阻汲极/源极 RDS（导通）:0.014 Ohms 配置:Single 最大工作温度: 安装风格:Through Hole 封装 / 箱体:Max247 封装:Tube