- 您现在的位置：买卖IC网 > PDF目录20433 > NCV8871SEPGEVB (ON Semiconductor)BOARD EVAL NCV8871SEP BOOST CTLR PDF资料下载
参数资料
| 型号： | NCV8871SEPGEVB |
| 厂商： | ON Semiconductor |
| 文件页数： | 10/12页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL NCV8871SEP BOOST CTLR |
| 设计资源： | NCV8871SEPGEVB Schematic NCV8871SEPGEVB Gerber File NCV8871SEPGEVB Bill Of Materials |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 12V |
| 电流 - 输出： | 2A |
| 输入电压： | 6 V ~ 40 V |
| 稳压器拓扑结构： | 升压 |
| 频率 - 开关： | 170kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | NCV8871 |
| 其它名称： | NCV8871SEPGEVBOS |
NCV8871
D min
w t on(min)
R S +
V OUT
V OUT
V IN(WC) D WC
D I L,max f s
and will shut down when VIN drops below the UVLO
threshold or the part is disabled.
Internal Soft ? Start
To insure moderate inrush current and reduce output
overshoot, the NCV8871 features a soft start which charges a
capacitor with a fixed current to ramp up the reference voltage.
This fixed current is based on the switching frequency, so
that if the NCV8871 is synchronized to twice the default
switching frequency the soft start will last half as long.
VDRV
An internal regulator provides the drive voltage for the
gate driver. Bypass with a ceramic capacitor to ground to
ensure fast turn on times. The capacitor should be between
0.1 m F and 1 m F, depending on switching speed and charge
requirements of the external MOSFET.
APPLICATION INFORMATION
Design Methodology
This section details an overview of the component selection
process for the NCV8871 in continuous conduction mode
boost. It is intended to assist with the design process but does
not remove all engineering design work. Many of the
equations make heavy use of the small ripple approximation.
This process entails the following steps:
1. Define Operational Parameters
2. Select Current Sense Resistor
3. Select Output Inductor
4. Select Output Capacitors
5. Select Input Capacitors
6. Select Feedback Resistors
7. Select Compensator Components
8. Select MOSFET(s)
9. Select Diode
1. Define Operational Parameters
Before beginning the design, define the operating
parameters of the application. These include:
V IN(min) : minimum input voltage [V]
V IN(max): maximum input voltage [V]
V OUT : output voltage [V]
I OUT(max) : maximum output current [A]
I CL : desired typical cycle-by-cycle current limit [A]
From this the ideal minimum and maximum duty cycles
can be calculated as follows:
V IN(max)
D min + 1 *
V IN(min)
D max + 1 *
Both duty cycles will actually be higher due to power loss
in the conversion. The exact duty cycles will depend on
conduction and switching losses. If the maximum input
voltage is higher than the output voltage, the minimum duty
cycle will be negative. This is because a boost converter
cannot have an output lower than the input. In situations
where the input is higher than the output, the output will
follow the input, minus the diode drop of the output diode
and the converter will not attempt to switch.
If the calculated D max is higher the D max of the NCV8871,
the conversion will not be possible. It is important for a boost
converter to have a restricted D max , because while the ideal
conversion ration of a boost converter goes up to infinity as
D approaches 1, a real converter ’s conversion ratio starts to
decrease as losses overtake the increased power transfer. If
the converter is in this range it will not be able to regulate
properly.
If the following equation is not satisfied, the device will
skip pulses at high V IN :
f s
Where: f s : switching frequency [Hz]
t on(min) : minimum on time [s]
2. Select Current Sense Resistor
Current sensing for peak current mode control and current
limit relies on the MOSFET current signal, which is
measured with a ground referenced amplifier. The easiest
method of generating this signal is to use a current sense
resistor from the source of the MOSFET to device ground.
The sense resistor should be selected as follows:
V CL
I CL
Where: R S : sense resistor [ W ]
V CL : current limit threshold voltage [V]
I CL : desire current limit [A]
3. Select Output Inductor
The output inductor controls the current ripple that occurs
over a switching period. A high current ripple will result in
excessive power loss and ripple current requirements. A low
current ripple will result in a poor control signal and a slow
current slew rate in case of load steps. A good starting point
for peak to peak ripple is around 20 ? 40% of the inductor
current at the maximum load at the worst case V IN , but
operation should be verified empirically. The worst case V IN
is half of V OUT , or whatever V IN is closest to half of V OUT .
After choosing a peak current ripple value, calculate the
inductor value as follows:
L +
Where: V IN(WC) : V IN value as close as possible to
half of V OUT [V]
D WC : duty cycle at V IN(WC)
D I L,max : maximum peak to peak ripple [A]
http://onsemi.com
10
相关PDF资料 |
PDF描述 |
|---|---|
| 29SM-K711-00V | MOTOR STEP UNI 71MM DIA 24V |
| K2402GRP | SIDAC 240V DO15 |
| AISM-1812-271K-T | INDUCTOR CHIP 270UH 92MA SMD |
| F911V106MNC | CAP TANT 10UF 35V 20% 2917 |
| SS16-E3/11T | DIODE SCHOTTKY 1A 60V SMA |
相关代理商/技术参数 |
参数描述 |
|---|---|
| NCV887200D1R2G | 制造商:ON Semiconductor 功能描述:IC REG CTRLR BST PWM CM |
| NCV8873 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Automotive Grade Non-Synchronous Boost Controller |
| NCV887300D1R2G | 功能描述:低压差稳压器 - LDO Auto Grade Non-Sync Boost Controller RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| NCV8873LEDBSTGEVB | 制造商:ON Semiconductor 功能描述:NCV8873 EVAL BD - Bulk 制造商:ON Semiconductor 功能描述:BOARD EVAL FOR NCV8873LEDBST |
| NCV8876 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Automotive Grade Start-Stop Non-Synchronous Boost Controller |
发布紧急采购，3分钟左右您将得到回复。