- 您现在的位置：买卖IC网 > Sheet目录1233 > NCP1650EVB (ON Semiconductor)BOARD EVAL NCP1650 PFC CTLR
NCP1650
converter to stabilize the units operation when the duty cycle
is greater than 50%.
The amount of compensation required is dependent on
several variables, including the boost inductor value, and the
desires of the designer. The value should be based on the
falling di/dt of the inductor current. For a boost inductor with
a variable input voltage, this will vary over the AC input
cycle, and with changes in the input line. A di/dt chart is
included in the design spreadsheet that is available for the
NCP1650.
This pin is a buffered output of the oscillator, which
provides a voltage equal to the ramp on the oscillator C T pin.
A resistor from this pin to ground, programs a current that
is transformed via a current mirror to the non--inverting
input of the PWM comparator.
The ramp voltage due to the inductor di/dt at the input to
the PWM comparator is the current shunt voltage at pin 11
multiplied by 15, which is the gain of the current amplifier
output that feeds the PWM.
pin with a saturated transistor. A hysteretic comparator
monitors that ramp signal and is used to switch between the
current source and discharge transistor. While the cap is
charging, the comparator has a reference voltage of
4.0 volts. When the ramp reaches that voltage, the
comparator switches from the charging circuit to the
discharge circuit, and its reference changes from 4.0
to ~ 0.5 volts (overshoot and delays will allow the valley
voltage to reach 0 volts).
The relationship between the frequency and timing
capacitor is:
CT = 47, 000 ∕ f
Where C T is in pF and f is in kHz.
It is important not to load the capacitor on this pin, since
this could affect the accuracy of the frequency as well as that
of the multipliers which use the ramp signal. Any use of this
signal should incorporate a high impedance buffer.
Due to the required accuracy of the peak and valley ramp
voltages, the NCP1650 is not designed to be synchronized
Current
Sense
Amp
AC Ref
Buffer
to the frequency of another oscillator.
Average Current Compensation
Oscillator
+
--
i
1.6 i
16 k
+
--
PWM
Comparator
The Peak Current Compensation circuit adjusts the
maximum current that can occur before the controller limits
the current. This allows for higher levels of current under
low line conditions than at high line.
The input signal to this amplifier is the input fullwave
rectified sinewave. The amplifier is a unity gain amplifier,
with a voltage divider on the output that attenuates the signal
by a factor of 0.75. This scaled down fullwave rectified
13
Ramp Compensation
R RC
sinewave is summed with the low frequency current signal
out of the current sense amplifier.
The sum of these signals must equal the signal at the
inverting input to the AC error amplifier, which is the output
of the reference multiplier. Since there is a hard limit of
Figure 36. Ramp Compensation Circuit
The current mirror is designed with a 1:1.6 current ratio.
The ramp signal injected can be calculated by the following
formula:
4.5 volts at the inverting input, the sum of the line voltage
plus the current cannot exceed this level.
A typical universal input design operates from 85 to
265 vac, which is a range of 3.1:1. The output of the Average
Current Compensation amplifier will change by this amount
= 102
VRcomp =
1.6 Voscpk 16 k
RRC
RRC
to allow the maximum current to vary inversely to the line
voltage.
Where:
V Rcomp = Peak injected ramp signal (v)
R RC = Ramp compensation resistor (k Ω )
Oscillator
The oscillator generates the sawtooth ramp signal that sets
the switching frequency, as well as sets the gain for the
multipliers. Both the frequency and the peak--to--peak
amplitude are important parameters.
The oscillator uses a current source for charging the
capacitor on the C T pin. The charge rate is approximately
200 m A and is trimmed to maintain an accurate, repeatable
frequency. Discharge is accomplished by grounding the C T
Driver
The output driver can be used to directly drive a FET, for
low and medium power applications, or a larger driver for
high power applications.
It is a complementary MOS, totem pole design, and is
capable of sourcing and sinking over 1.5 amps, with typical
rise and fall times of 30 ns with a 1.0 nF load. The totem pole
output has been optimized to minimize cross conduction
current during high speed operation.
Additional internal circuitry has been added to keep the
Driver in its low state whenever the Undervoltage Lockout
is active. This characteristic eliminates the need for an
external gate pulldown resistor.
http://onsemi.com
19
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
NCP1652L48VGEVB
BOARD EVAL 100W 48V NCP1652 PFC
NCP1653EVB
BOARD EVAL FOR NCP1653
NCP2993FCT2GEVB
BOARD EVAL NCP2993 AUDIO PWR AMP
NCP345SNT1G
IC DETECTOR OVER VOLTAGE 5TSOP
NCP346SN2T1G
IC DETECTOR OVER VOLTAGE 5TSOP
NCP347MTAITBG
IC OVERVOLTAGE PROT CTRLR 10WDFN
NCP348AEMUTBG
IC MOSFET DRIVER DUAL 12V 10LLGA
NCP360MUTXG
IC CTLR USB POS OVP FET 6-UDFN
相关代理商/技术参数
NCP1651DR2
功能描述:功率因数校正 IC Single Stage PFC RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
NCP1651DR2G
功能描述:功率因数校正 IC Single Stage PFC RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
NCP1652ADR2G
功能描述:功率因数校正 IC ANA PFC CONTROLLER RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
NCP1652DR2G
功能描述:功率因数校正 IC ANA PFC CONTROLLER RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
NCP1652DWR2G
功能描述:功率因数校正 IC ANA PFC CONTROLLER RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
NCP1652L48VGEVB
功能描述:电源管理IC开发工具 100W PFC 48V FIXED VOLTAGE
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
NCP1653ADR2
功能描述:功率因数校正 IC Fixed Frequency RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
NCP1653ADR2G
功能描述:功率因数校正 IC Fixed Frequency Current Mode PFC RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel