收藏本站
NCL30000
insulated wire is selected for compliance with safety agency
isolation requirements.
The primary bias winding must supply 10.2 V to maintain
NCL30000 operation. The minimum secondary voltage is
12 V and with 24 turns this means the bias winding needs
20.4 turns. Select 22 turns to meet the minimum.
For maximum primary to secondary coupling, the primary
winding will be split in two equal sections with the
secondary winding placed in between. The bias winding is
wound on top of the second half of the primary winding.
FET Switch
The NCL30000 controller drives an external power FET
controlling the current in the flyback transformer primary.
The demonstration board was designed to accept the surface
mount DPAK or through-hole TO ? 220 power packages. The
17.5 W target application in 50 ? C ambient works well with
a DPAK package. The 800 V 2 A rated SPD02N80C3 was
chosen.
Maximum primary current was calculated as 1.11 A. The
NCL30000 has a 0.5 V over-current protection threshold. To
allow for 25% margin, a minimum sense resistor of 0.348 W
is required. A standard 0.33 W resistor will be selected. The
current sense resistor is placed in the source lead of the
power FET and coupled to the controller with a 100 W
resistor. This resistance in conjunction with the inherent
capacitance of the pin filters high frequency noise. In
addition, a leading edge blanking (LEB) function is included
in the controller. This feature avoids spurious activation of
the over-current protection when the power FET is first
turned on.
On-time Capacitor
Maximum FET switch on-time is controlled by the C t
capacitor. Limiting the maximum on-time reduces
component stress in transient situations. The formula below
establishes the capacitor value based on charging current of
297 m A and maximum voltage threshold of 4.775. The
symbol h ' represents the effective efficiency of the power
transformer stage and secondary losses. It will always be
greater than the measured wall plug efficiency which
includes losses in the EMI filter and primary side compents.
Output Filter
As previously discussed, a high power factor isolated
single-stage converter processes power in a sine squared
manner at twice the line frequency. Energy storage must be
provided on the isolated secondary output just as in normal
flyback converters however significantly more storage
capacity is required due to the sine squared energy transfer
characteristic. Capacitors are used to store energy as the
peak of the 100 or 120 Hz rectified sine wave delivers
maximum power and then releases the stored energy to the
load when the rectified sine wave falls below the target
output power. As the storage capacitor charges and
discharges some ripple current is developed in the LED load.
The magnitude of ripple voltage is controlled by the amount
of filter capacitance and the impedance of the LED string. In
this 350 mA application, two 470 m F capacitors are
sufficient to provide 30% ripple.
High grade electrolytic capacitors should be selected to
match driver lifetime with that of the LEDs. Higher
temperature rated capacitors enhance lifetime for an optimal
solution. To meet ripple requirements in single stage
converters filter capacitance is generally high enough that
capacitor ripple current is well below device ratings.
Secondary Bias
The average mode feedback compensation is
intentionally set to a low frequency as described in the
feedback section. The relatively large feedback
compensation capacitor must charge to normal operating
voltage after initial power up which introduces significant
delay in regulation. Minimizing the required voltage change
on the compensation capacitor allows the feedback loop to
take control of the output quicker therefore reducing
over-current conditions. Maintaining a low bias voltage
reduces the required change in compensation capacitor
voltage. For this example, a bipolar transistor and 5.6 V
zener diode are employed to provide bias voltage of about
5 V. This bias transistor minimizes power loss and allows the
LED driver to operate over a very wide range of output
voltage. This circuit will support as few as 4 LEDs and up
to 15 LEDs.
The secondary bias can be optimized if the application
N @ V out
h @ V pk @ V CT(max)
C t [
C t [
4 @ L pri @ P out @ I charge V pk
2
4 @ 0.00157 @ 17.5 @ 297 m A 2 @ 90
0.95 @ 2 @ 90 @ 4.775 V
@
@ ) 1
2 3.83 @ 50
(eq. 2)
) 1
uses a specific number of LEDs. Fewer components and
better efficiency can be realized by limiting the output
voltage range and adding a secondary bias winding to the
transformer.
Open Load Protection
The LED driver behaves like a current source where the
output voltage is determined by the forward voltage of the
C t [ 740 pF
The C t equation is an approximation for simplification. For
example, V pk assumes no losses through the diode rectifier
bridge and EMI filter. This establishes an initial starting point
LED string. As such, some protection is required to prevent
damage in the event of an open LED situation. Transistor
(Q5) and zener diode (D12) affords the necessary protection.
A 56 V zener is used in this design example.
for the C t capacitor and further optimization may be needed.
For this design, 820 pF was used as the final value.
http://onsemi.com
18
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