SG1842 データシートの表示（PDF） - Microsemi Corporation

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SG1842

Current Mode PWM Controller

Microsemi Corporation 

Current Mode PWM Controller

IB

VC +

R2

VC1

R1 II R2_

VC

SG1842/43

VC1

7 (11)

C1

R2

6 (10)

R1

VIN

Q1

5 (8)

3 (5)

RS

Figure 19 · Bipolar Transistor Drive

The 1842/43 output stage can provide negative base current to remove base charge of power transistor (Q1)

for faster turn off. This is accomplished by adding a capacitor (C1) in parallel with a resistor (R1). The resistor

(R1) is to limit the base current during turn on.

VCC

VIN

7 (12)

Isolation

Boundary

7 (11)

6 (10)

SG1842/43

5 (8)

3 (5)

R

C

Q1

VGS Waveforms

+

0

_

50% DC

+

_0

RS

NS

NP

25% DC

( ) IPK =

V (PIN 1) – 1.4

3RS

NP

NS

Figure 20 · Isolated MOSFET Drive

Current transformers can be used where isolation is required between PWM and Primary ground. A drive

transformer is then necessary to interface the PWM output with the MOSFET.

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