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參數(shù)資料
| 型號(hào)： | MC44608 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | Few External Components Reliable Flexible GreenLine Very High Voltage PWM Controller |
| 中文描述： | 很少的外部元件的可靠靈活二七二三六七六七高電壓PWM控制器 |
| 文件頁(yè)數(shù)： | 8/16頁(yè) |
| 文件大?。?/td> | 266K |
| 代理商： | MC44608 |
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MC44608
http://onsemi.com
8
2. Overload
In the hiccup mode the 3 distinct phases are described as
follows (refer to Figure 6):
The SWITCHING PHASE: The SMPS output is low and
the regulation block reacts by increasing the ON time (dmax
= 80%). The OC is reached at the end of every switching
cycle. The LW latch (Figure 7) is reset before the VPWM
signal appears. The SMPS output voltage is low. The VCC
voltage cannot be maintained at a normal level as the
auxiliary winding provides a voltage which is also reduced
in a ratio similar to the one on the output (i.e. Vout nominal
/ Vout short–circuit). Consequently the VCC voltage is
reduced at an operating rate given by the combination VCC
capacitor value together with the ICC working consumption
(3.2mA) according to the equation 2. When VCC crosses
10V the WORKING PHASE gets terminated. The LW latch
remains in the reset status.
The LATCHED–OFF PHASE: The VCC capacitor
voltage continues to drop. When it reaches 6.5V this phase
is terminated. Its duration is governed by equation 3.
The START–UP PHASE is reinitiated. The high voltage
start–up current source (–ICC1 = 9mA) is activated and the
MODE latch is reset. The VCC voltage ramps up according
to the equation 1. When it reaches 13V, the IC enters into the
SWITCHING PHASE.
The NEXT SWITCHING PHASE: The high voltage
current source is inhibited, the MODE latch (Q=0) activates
the NORMAL mode of operation. Figure 2 shows that no
current is injected out pin 2. The over current sense level
corresponds to 1V.
As long as the overload is present, this sequence repeats.
The SWITCHING PHASE duty cycle is in the range of 10%.
3. Transition from Normal to Pulsed Mode
In this sequence the secondary side is reconfigured (refer
to the typical application schematic on page 13). The high
voltage output value becomes lower than the NORMAL
mode regulated value. The TL431 shunt regulator is fully
OFF. In the SMPS stand–by mode all the SMPS outputs are
lowered except for the low voltage output that supply the
wake–up circuit located at the isolated side of the power
supply. In that mode the secondary regulation is performed
by the zener diode connected in parallel to the TL431.
The secondary reconfiguration status can be detected on
the SMPS primary side by measuring the voltage level
present on the auxiliary winding Laux. (Refer to the
Demagnetization Section). In the reconfigured status, the
Laux voltage is also reduced. The VCC self–powering is no
longer possible thus the SMPS enters in a hiccup mode
similar to the one described under the Overload condition.
In the SMPS stand–by mode the 3 distinct phases are:
The SWITCHING PHASE: Similar to the Overload
mode. The current sense clamping level is reduced
according to the equation of the current sense section, page
5. The C.S. clamping level depends on the power to be
delivered to the load during the SMPS stand–by mode.
Every switching sequence ON/OFF is terminated by an OC
as long as the secondary Zener diode voltage has not been
reached. When the Zener voltage is reached the ON cycle is
terminated by a true PWM action. The proper SWITCHING
PHASE termination must correspond to a NOC condition.
The LW latch stores this NOC status.
The LATCHED OFF PHASE: The MODE latch is set.
The START–UP PHASE is similar to the Overload Mode.
The MODE latch remains in its set status (Q=1).
The SWITCHING PHASE: The Stand–by signal is
validated and the 200
μ
A is sourced out of the Current Sense
pin 2.
4. Transition from Stand–by to Normal
The secondary reconfiguration is removed. The
regulation on the low voltage secondary rail can no longer
be achieved, thus at the end of the SWITCHING PHASE, no
PWM condition can be encountered. The LW latch is reset.
At the next WORKING PHASE a NORMAL mode status
takes place.
In order to become independent of the recovery time
constant on the secondary side of the SMPS an additional
reset input R2 is provided on the MODE latch. The condition
Idemag<24
μ
A corresponds to the activation of the
secondary reconfiguration status. The R2 reset insures a
return into the NORMAL mode following the first
START–UP PHASE.
Pulsed Mode Duty Cycle Control
During the sleep mode of the SMPS the switch S3 is
closed and the control input pin 3 is connected to a 4.6V
voltage source thru a 500 resistor. The discharge rate of the
VCC capacitor is given by ICC–latch (device consumption
during the LATCHED OFF phase) in addition to the current
drawn out of the pin 3. Connecting a resistor between the Pin
3 and GND (RDPULSED) a programmable current is drawn
from the VCC through pin 3. The duration of the LATCHED
OFF phase is impacted by the presence of the resistor
RDPULSED. The equation 3 shows the relation to the pin 3
current.
Pulsed Mode Phases
Equations 1 through 8 define and predict the effective
behavior during the PULSED MODE operation. The
equations 6, 7, and 8 contain K, Y, and D factors. These
factors are combinations of measured parameters. They
appear in the parameter section “Kfactors for pulsed mode
operation” page 4. In equations 3 through 8 the pin 3 current
is the current defined in the above section “Pulsed Mode
Duty Cycle Control”.
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相關(guān)代理商/技術(shù)參數(shù) |
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| MC44608_06 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Few External Components Reliable and Flexible SMPS Controller |
| MC44608P100 | 功能描述:IC REG CTRLR FLYBK ISO PWM 8-DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MC44608P40 | 功能描述:電壓模式 PWM 控制器 40KHz High Voltage RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| MC44608P40G | 功能描述:電壓模式 PWM 控制器 40KHz High Voltage SMPS PWM RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| MC44608P75 | 功能描述:電壓模式 PWM 控制器 75KHz High Voltage RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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