参数资料
| 型号： | MIC2171BU TR |
| 厂商： | Micrel Inc |
| 文件页数： | 8/12页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG 2.5A TO263-5 |
| 标准包装： | 750 |
| 类型： | 降压（降压），升压（升压），反相，Cuk |
| 输出数： | 1 |
| 输入电压： | 3 V ~ 40 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz |
| 电流 - 输出： | 2.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | TO-263-6，D²Pak（5 引线+接片），TO-263BA |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | TO-263-5 |
| 其它名称： | MIC2171BUTR MIC2171BUTR-ND |
( 4.178 × 0.662 ) 2
I L1(peak) =
V IN T ON
I L1(peak) =
2P OUT
(
)
Micrel, Inc.
where:
P OUT = 12 × 0.25 = 3W
f SW = 1×105Hz (100kHz)
For our practical example:
L1 ≥
2 × 3.0 × 1 × 10 5
L1 ≥ 12.4μH (use 15μH)
Equation (3) solves for L1’s maximum current value.
(3)
L1
where:
T ON = δ / fSW = 6.62×10-6 sec
4.178 × 6.62 × 10 ? 6
15 × 10 ? 6
I L1(peak) = 1.84A
Use a 15μH inductor with a peak current rating of at
least 2A.
Flyback Conversion
Flyback converter topology may be used in low power
applications where voltage isolation is required or
whenever the input voltage can be less than or greater
MIC2171
solutions to be connected to circuit ground, although a
more conventional technique of connecting the
components from the error amplifier output to its
inverting input is also possible.
Voltage Clipper
Care must be taken to minimize T1’s leakage
inductance, otherwise it may be necessary to
incorporate the voltage clipper consisting of D1, R4, and
C3 to avoid second breakdown (failure) of the
MIC2171’s internal power switch.
Discontinuous Mode Design
When designing a discontinuous flyback converter, first
determine whether the device can safely handle the
peak primary current demand placed on it by the output
power. Equation (8) finds the maximum duty cycle
required for a given input voltage and output power. If
the duty cycle is greater than 0.8, discontinuous
operation cannot be used.
(8) δ ≥
I CL V IN(min) ? VSW
For a practical example let: (see Figure 2)
P OUT = 5.0V × 0.5A = 2.5W
V IN = 4.0V to 6.0V
than the output voltage. As with the step-up converter
the inductor (transformer primary) current can be
continuous or discontinuous. Discontinuous operation is
recommended.
then:
I CL = 2.5A when δ < 50%
1.67 (2 – δ ) when δ ≥ 50%
Figure 2 shows a practical flyback converter design
using the MIC2171.
Switch Operation
During Q1’s on time (Q1 is the internal NPN transistor—
see block diagrams), energy is stored in T1’s primary
inductance. During Q1’s off time, stored energy is
partially discharged into C4 (output filter capacitor).
Careful selection of a low ESR capacitor for C4 may
provide satisfactory output ripple voltage making
additional filter stages unnecessary.
V IN(min) = V IN – (I CL × R SW
V IN(min) = 4 – 0.78V
V IN(min) = 3.22V
δ ≥ 0.74 (74%), less than 0.8 so discontinuous is
permitted.
A few iterations of equation (8) may be required if the
duty cycle is found to be greater than 50%.
Calculate the maximum transformer turns ratio a, or
N PRI /N SEC , that will guarantee safe operation of the
MIC2171 power switch.
C1 (input capacitor) may be reduced or eliminated if the
MIC2171 is located near a low impedance voltage
source.
(9)
a ≤
V CE F CE ? V IN(max)
V SEC
Output Diode
The output diode allows T1 to store energy in its primary
inductance (D2 non-conducting) and release energy into
C4 (D2 conducting). The low forward voltage drop of a
Schottky diode minimizes power loss in D2.
Frequency Compensation
A simple frequency compensation network consisting of
R3 and C2 prevents output oscillations.
High impedance output stages (transconductance type)
in the MIC2171 often permit simplified loop-stability
May 2007
8
where:
a = transformer maximum turns ratio
V CE = power switch collector to emitter maximum
voltage
F CE = safety derating factor (0.8 for most
commercial and industrial applications)
V IN(max) = maximum input voltage
V SEC = transformer secondary voltage (V OUT +
V F )
M9999-051107
相关PDF资料 |
PDF描述 |
|---|---|
| MIC2174-1YMM TR | IC REG CTRLR BUCK PWM 10-MSOP |
| MIC2176-3YMM TR | IC REG CTRLR BUCK PWM 10-MSOP |
| MIC2177BWM TR | IC REG BUCK SYNC ADJ 2.5A 20SOIC |
| MIC2178BWM TR | IC REG BUCK SYNC ADJ 2.5A 20SOIC |
| MIC2179BSM TR | IC REG BUCK SYNC ADJ 1.5A 20SSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2171WT | 功能描述:直流/直流开关调节器 2.5A 100kHz Switching Regulator (ROHS Compliant) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC2171WU | 功能描述:直流/直流开关调节器 2.5A 100kHz Switching Regulator (ROHS Compliant) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC2171WU TR | 功能描述:直流/直流开关调节器 2.5A 100kHz Switching Regulator (ROHS Compliant) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC2171WU-TR | 功能描述:Buck, Boost, Cuk, Flyback, Forward Converter Switching Regulator IC Positive or Negative, Isolation Capable Adjustable 1 Output 2.5A (Switch) TO-263-6, D2Pak (5 Leads + Tab), TO-263BA 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:有效 功能:升压，降压，升压/降压 输出配置:正或负，可提供隔离 拓扑:降压，升压，Cuk，反激，正激转换器 输出类型:可调式 输出数:1 电压 - 输入（最小值）:3V 电压 - 输入（最大值）:40V 电压 - 输出（最小值/固定）:- 电压 - 输出（最大值）:65V（开关） 电流 - 输出:2.5A（开关） 频率 - 开关:100kHz 同步整流器:无 工作温度:-40°C ~ 85°C（TA） 安装类型:表面贴装 封装/外壳:TO-263-6，D2Pak（5 引线+接片），TO-263BA 供应商器件封装:TO-263-5 标准包装:1 |
| MIC2172 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:100kHz 1.25A Switching Regulators |
发布紧急采购，3分钟左右您将得到回复。