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參數(shù)資料
| 型號(hào)： | SG1540Y/883B |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | OFF-LINE START-UP CONTROLLER |
| 中文描述： | 0.2 A SWITCHING CONTROLLER, 400 kHz SWITCHING FREQ-MAX, CDIP8 |
| 封裝： | HERMETIC SEALED, CERAMIC, DIP-8 |
| 文件頁(yè)數(shù)： | 4/6頁(yè) |
| 文件大?。?/td> | 98K |
| 代理商： | SG1540Y/883B |
Rev 1.1a
Copyright
1994
11861 Western Avenue
∞
∞ Garden Grove, CA 92841
4
(714) 898-8121
∞
∞ FAX: (714) 893-2570
SG1540/SG2540/SG3540
APPLICATION INFORMATION
FIGURE 3 - EFFICIENT PRIMARY SIDE START-UP
PRIMARY SIDE START-UP
When the design goal is efficient start-up for a control PWM referenced to the primary side of the power transformer, the configuration
in Figure 3 is recommended. An energy storage capacitor C
START is trickle-charged from the 300-400 Volt DC bus by resistor RSTART.
The value of R
START is chosen to provide a constant 1mA charging current, allowing the use of a watt resistor. As the voltage on
C
START ramps up from zero, the only load current is the standby current of the SG1540 and that of the divider network R1-R3. (Connecting
the TIMING pin to +V
IN disables the internal power oscillator and forces the circuitry into a micropower standby model. Since the input
bias current at the START pin is 1A maximum, a divider current of 100A is adequate).
When the voltage at the START pin reaches +2.5 Volts, the hysteresis transistor turns off, overdriving the START pin. The V
OUT pin
is switched to the HIGH state, providing power to the PWM control circuit. As energy flows out of the START capacitor, its voltage
decays; but it remains connected to the PWM circuit until the dropout voltage is reached (V
START - VHYSTERESIS). The bootstrap winding
on the power transformer and rectifier diode D5 prevent this from happening. As the PWM control circuit becomes active, the power
transistor begins to switch, providing operating current to the PWM circuit through the SG1540.
RESISTOR CALCULATIONS
Given that V
START and VDROPOUT have been chosen, and that the divider current at start-up is 100A, then the values for R1 through R3
are calculated as follows:
1. For simplification, let X =
and Y =
V
DROPOUT -2.5
2.5
2. Then,R1 = 2.5 x 104 * X
[1]
R2 = R1/Y
[2]
and
R3 =
[3]
R1 * R2
X * R2 - R1
DESIGN EXAMPLE
Suppose we have a power MOSFET device, and so want to start at +18 volts and drop out at +12 volts.
Then
X = 6.20
and Y = 3.80
Therefore
R1 = 2.5 x 104 * 6.2 = 155K
(Choose 150K)
R2 = 1.5 x 105/3.8 = 39.5K
(Choose 39K)
R3 =
= 63.7K
(Choose 62K)
1.5 x 105 * 3.9 x 104
6.2 * 3.9 x 104 - 1.5 x 105
V
START - 2.5
2.5
O
B
SO
LETE
PRO
D
UCT
NOT
RECOMMENDED
FOR
NEW
DESIGNS
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SG1543 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:POWER SUPPLY OUTPUT SUPERVISORY CIRCUIT |
| SG1543_1 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:POWER SUPPLY OUTPUT SUPERVISORY CIRCUIT |
| SG1543J | 制造商:Microsemi Corporation 功能描述:SG1543J - Bulk |
| SG1543J/883B | 制造商:Silicon General 功能描述:_ 制造商: 功能描述: 制造商:undefined 功能描述: |
| SG1543J/DESC | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:POWER SUPPLY OUTPUT SUPERVISORY CIRCUIT |
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