- 您現(xiàn)在的位置：買(mǎi)賣(mài)IC網(wǎng) > PDF目錄380065 > CS3842A (ON SEMICONDUCTOR) Current Mode PWM IC(電流模式的脈寬調(diào)制芯片) PDF資料下載
參數(shù)資料
| 型號(hào)： | CS3842A |
| 廠(chǎng)商： | ON SEMICONDUCTOR |
| 英文描述： | Current Mode PWM IC(電流模式的脈寬調(diào)制芯片) |
| 中文描述： | 電流模式PWM IC（電流模式的脈寬調(diào)制芯片） |
| 文件頁(yè)數(shù)： | 1/12頁(yè) |
| 文件大小： | 177K |
| 代理商： | CS3842A |
1
C
Single CS3842A Provides Control
for 500W/200kHz
Current-Mode Power Supply
CS3842A
Application Note
With the introduction of the CS3842A PWM IC, current-
mode is possible for power supplies of a wide range of
output power levels. It’s low cost makes the CS3842A par-
ticularly attractive in low power DC to DC converter
applications. But because this IC can provide a high out-
put current (1A peak, 200mA average), it is also capable of
driving large power MOSFETS which can switch high
amounts of power.
In a switching power supply, the output voltage is con-
trolled by varying the conduction duty cycle of the power
switch(es). Traditionally duty cycle control was done by
comparing the amplified difference of the output voltage
feedback signal and a fixed stable reference to the saw-
tooth waveform derived from an oscillator. This consti-
tutes the basic voltage mode control (VMC) scheme.
VMC was later improved by allowing a sample of the
input voltage to vary the slope of the sawtooth waveform.
This feed forward scheme provided excellent line regula-
tion in most of the popular circuit topologies. However,
the task of compensating voltage mode converters has not
been simple due to its resonant peak and 40dB/decade roll
off associated with the output LC filter.
In current mode control, (CMC) the control signal repre-
sents the peak inductor current and forms a second loop
in the circuit (Figure 1). The advantages of current mode
control are:
Instantaneous correction to line voltage variations; the
inductor current slope varies with input voltage.
Stable power supply designs; the pole associated with
the inductor is eliminated.
Equal current sharing in paralleled power stages when
both share the same control signal and have the same
current sense circuits.
No current limit amplifier is needed.
Flux balancing exists in push-pull circuits.
Disadvantages:
Slope compensation is required for peak versus average
inductor current error and for compensating instabili-
ties associated with load disturbances in single ended
topologies operating at greater than 50% duty cycle.
Premature shutdown due to the turn on current spike
caused by the reverse diode recovery of the output free
wheeling diode.
Runaway conditions when half bridge topology is oper-
ated in current-mode control.
If the current sense signal is properly filtered, noise
induced problems including the turn on spike can be
avoided. By deliberately adding more slope to the current
sense signal, or subtracting it from the control voltage sig-
nal, the instability due to greater than 50% duty cycle
operation can be overcome. Slope compensation aids in
reducing uncertainty at the point of trigger in the PWM
comparator when shallow current ramps are involved. It
also helps the peak current appear higher than the turn-on
spike. This eliminates premature shutdown.
Figure 2a illustrates how peak current detection in current
mode control produces a change in the average current by
relying on the feed forward property of current mode to
compensate for line voltage variations. If a slope equal to
one-half the negative going inductor current slope is
added to the current sense signal, or subtracted from the
control signal, this error is corrected(Figure 2b).
Introduction
Current-Mode vs. V oltage-Mode Control
Figure 1. Basic Circuit using Current-Mode Control
-
COMP
+
S
LATCH
R
Q
ERROR
CLOCK
R
T
/C
T
V
REF
V
OUT
V
IN
I
S
Rev. 2/ 10/ 95
ON Semiconductor
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885–3600 Fax: (401)885–5786
N. American Technical Support: 800-282-9855
Web Site: www.cherry–semi.com
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| CS3972 | 1.25A High Efficiency Switching Regulator(1.25A,75V輸出,高效率開(kāi)關(guān)穩(wěn)壓器) |
| CS4103 | IEEE P1394a Physical Layer Device |
| CS4103VHG | IEEE P1394a Physical Layer Device |
| CS4121EDWF20G | Low Voltage Precision Air-Core Tach/Speedo Driver |
| CS4122 | Triple Air-Core Gauge Driver with Serial Input Bus |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| CS-3842A | 制造商:未知廠(chǎng)家 制造商全稱(chēng):未知廠(chǎng)家 功能描述: |
| CS3842AGD14 | 制造商:CHERRY 制造商全稱(chēng):CHERRY 功能描述:Off-Line Current Mode PWM Control Circuit with Undervoltage Lockout |
| CS3842AGD8 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| CS3842AGDR14 | 制造商:CHERRY 制造商全稱(chēng):CHERRY 功能描述:Off-Line Current Mode PWM Control Circuit with Undervoltage Lockout |
| CS3842AGDR8 | 制造商:CHERRY 制造商全稱(chēng):CHERRY 功能描述:Off-Line Current Mode PWM Control Circuit with Undervoltage Lockout |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。