收藏本站
NCL30000
ZCD Detection Block
A dedicated circuit block is necessary to implement the
zero current detection . The NCL30000 provides a separate
input pin to signal the controller to turn the power switch
back on just after the flyback transformer discharges all the
stored energy to the secondary winding. When the output
winding current reaches zero the winding voltage will
reverse. Since all windings of the transformer reflect the
same voltage characteristic this voltage reversal appears on
the primary bias winding. Coupling the winding voltage to
the ZCD input of the NCL30000 allows the controller to start
the next switching cycle at the precise time. To avoid
inadvertent false triggering, the ZCD input has a dual
comparator input structure to arm the latch when the ZCD
detect voltage rises above 1.4 V (nominal) thus setting the
latch. When the voltage on ZCD falls below 0.7 V (nominal)
a zero current event is detected and a signal is asserted which
initiates the next switching cycle. This is illustrated in
Figure 27. The input of the ZCD has an internal circuit
which clamps the positive and negative voltage excursions
on this pin. The current into or out of the ZCD pin must be
limited to ? 10 mA with an external resistor.
V arm
V trig
N ZCD
+
?
S
Q
Reset
Demag
V ZCD(ARM)
+
DRIVE
Dominant
Latch
R Q
?
V ZCD(TRIG)
Bias Winding Voltage
R ZCD
ZCD
ZCD Clamp
Figure 27. ZCD Operation
At startup, there is no energy in the ZCD winding and no
voltage signal to activate the ZCD comparators. To enable
the controller to start under these conditions, an internal
watchdog timer is provided which initiates a switching cycle
in the event that the output drive has been off for more than
180 m s (nominal).
The timer is deactivated only under an OVP or UVP fault
DRV
R sense
CS
optional
LEB
+
?
V ILIM
OCP
condition which will be discussed in the next section.
I SW(peak) +
V ILIM
R sense
Overcurrent Protection (OCP)
The dedicated CS pin of the NCL30000 senses the current
through the MOSFET switch and the primary side of the
transformer. This provides an additional level of protection
in the event of a fault. If the voltage of the CS pin exceeds
V ILIM , the internal comparator will detect the event and turn
off the MOSFET. The peak switch current is calculated
using Equation 1:
(eq. 1)
To avoid the probability of false switching, the
NCL30000 incorporated a built in leading edge blanking
circuit (LEB) which masks the CS signal for a nominal time
of 190 ns. If required, an optional RC filter can be added
Figure 28. OCP Circuitry with Optional
External RC Filter
MFP Input
The multi-function pin is connected to the input of the
transconductance amplifier, the undervoltage and
overvoltage protection comparators. This allows this pin to
perform several functions. To place the device in standby,
the MFP pin should be pulled below the V uvp threshold. This
is illustrated in Figure 29. Additionally, raising the MFP pin
above V ovp will also suspend switching activity but not place
the controller in the standby mode. This can be used
implement overvoltage monitoring on the bias winding and
add an additional layer of fault protection.
between R sense and CS to provide additional filtering. This
is illustrated below.
http://onsemi.com
14
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
NCL30051LEDGEVB BOARD EVAL NCL30051 LED DRIVER
NCL30100ASLDGEVB BOARD DEMO SGL LAYER PWM DIM LED
NCL30105GEVB BOARD EVAL 80V 350 FOR LED DRV
NCP1013LEDGEVB BOARD EVAL 5W UNIV LED DRIVER
NCP1028LEDGEVB EVAL BOARD FOR NCP1028LEDG
NCP1216AFORWGEVB BOARD EVAL NCP1216A 35W
NCP1351LEDGEVB EVAL BOARD FOR NCP1351LEDG
NCP3065BBGEVB BOARD EVAL NCP3065 MR16 BOOST
相关代理商/技术参数
NCL30001 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:High-Efficiency Single Stage Power Factor Correction and Step-Down Offline LED Driver
NCL30001DR2G 功能描述:LED照明驱动器 ANA PFC CONTROLLER RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
NCL30001DR2G-CUT TAPE 制造商:ON 功能描述:NCL30001 Series 11.3 V Isolated Step-Down Single Stage Power Factor - SOIC-16
NCL30001LEDGEVB 功能描述:LED 照明开发工具 Programmers Development RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装:
NCL30002 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Power Factor Corrected Buck LED Driver
NCL30002DIM1GEVB 制造商:ON Semiconductor 功能描述:120V DIMMABLE HPF BUCK - Bulk
NCL30002DIM2GEVB 制造商:ON Semiconductor 功能描述:230V DIMMABLE HPF BUCK - Bulk
NCL30002DR2G 功能描述:LED照明驱动器 Power Factor Offline Buck LED Driver RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N