- 您现在的位置：买卖IC网 > Sheet目录996 > NCP1351LEDGEVB (ON Semiconductor)EVAL BOARD FOR NCP1351LEDG
NCP1351
Current Sense Resistor
Current Sense Pin
Figure 8. The Voltage on the Current Sense Pin
Below are a few recommendations concerning the wiring
and the PCB layout:
? A small 22 pF capacitor can be placed between the CS
pin and the controller ground. Place it as close as
possible to the controller.
? Do not place the offset resistor in the vicinity of the
sense element, but put it close to the controller as well.
? Regulation by frequency
? The power a flyback converter can deliver relates to the
energy stored in the primary inductance L p and obeys
the following formulae:
Figure 9. The Voltage Across the Sense
Resistor
in this NCP1351 for simplicity and ease of implementation.
Thus, once the peak current has been selected, the feedback
loop automatically reacts to satisfy Equations 5 and 6. The
external capacitor that you connect between pin 2 and
ground (again, place it close to the controller pins) sets the
maximum frequency you authorize the converter to operate
up to. Normalized values for this timing capacitor are
270 pF (65 kHz) and 180 pF (100 kHz). Of course, different
combinations can be tried to design at higher or lower
frequencies. Please note that changing the capacitor value
does not affect the operating frequency at nominal line and
load conditions. Again, the operating frequency is selected
Pout_DCM +
1
2
LP Ipeak2 FSW h
(eq. 5)
by the feedback loop to cope with Equations 5 and 6
definitions.
Pout_CCM + 12 LP(Ipeak2 * Ivalley2)FSW h
(eq. 6)
The feedback current controls the frequency by changing
the timing capacitor end of charge voltage, as illustrated by
V C + 45 k (I FB * 40u) ) 500m (eq. 7)
Where:
h (eta) is the converter efficiency
I peak is the peak inductor current reached at the on time
termination
I valley represents the current at the end of the off time. It
equals zero in DCM.
F SW is the operating frequency.
Thus, to control the delivered power, we can either play on
the peak current setpoint (classical peak current mode
control) or adjust the switching frequency by keeping the
peak current constant. We have chosen the second scheme
Figure 10.
The timing capacitor ending voltage can be precisely
computed using the following formula:
t
Where I FB represents the injected current inside the FB
pin (pin 1). The 40u term corresponds to a 40 mA offset
current purposely placed to force a minimum current
injection when the loop is closed. This allows the controller
to detect a short-circuit condition as the feedback current
drops to zero in that condition.
http://onsemi.com
11
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
NCP3065BBGEVB
BOARD EVAL NCP3065 MR16 BOOST
NCP3066SCBCKGEVB
EVAL BOARD FOR NCP3066SCBCKG
NCP5005GEVB
EVAL BOARD FOR NCP5005G
NCP5006EVB
EVAL BOARD FOR NCP5006
NCP5030MTTXGEVB
EVAL BOARD FOR NCP5030MTTXG
NCP5602EVB
EVAL BOARD FOR NCP5602
NCP5603GEVB
EVAL BOARD FOR NCP5603G HI FREQ
NCP5604AAGEVB
EVAL BOARD FOR NCP5604AAG
相关代理商/技术参数
NCP1351PRINTGEVB
功能描述:电源管理IC开发工具 NCP1351 40 W PRINTER EVB
RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V
NCP1377
制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:PWM Current-Mode Controller for Free-Running Quasi-Resonant Operation
NCP1377/D
制造商:未知厂家 制造商全称:未知厂家 功能描述:PWM Current -Mode Controller
NCP1377_06
制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:PWM Current−Mode Controller for Free−Running Quasi−Resonant Operation
NCP1377_11
制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:PWM Current-Mode Controller for Free-Running Quasi-Resonant Operation
NCP1377B
制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:PWM Current-Mode Controller for Free-Running Quasi-Resonant Operation
NCP1377BD1R2G
功能描述:电流型 PWM 控制器 ANA PWM CURRNT MODE CNTR RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
NCP1377BDR2
功能描述:电流型 PWM 控制器 Quasi Resonant RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14