Active-Semi
APPLICATIONS INFORMATION
External Power Transistor
The ACT30 allows a low-cost high voltage power
NPN transistor such as ‘13003 or ‘13002 to be used
safely in a flyback configuration. The required
collector voltage rating for V
AC
= 265V with full
output load is at least 600V to 700V. As seen in
Figure 4, the breakdown voltage of an NPN is
significantly improved when it is driven at its emitter.
Thus, the ACT30 and ’13002 or ‘13003 combination
meet the necessary breakdown safety requirement
even though RCC circuits using ‘13002 or ‘13003
do not. Table 1 lists the breakdown voltage of some
transistors appropriate for use with the ACT30.
Table 1:
Recommended Power Transistor List
DEVICE
MJE13002
I
C
Rev 5, 05-Jun-09
Figure 4:
NPN Reverse Bias Safe Operation Area
ACT30
Base-Drive
Safe Region
(RCC)
Emitter-Drive
Safe Region
(ACT30)
V
CEO
V
CBO
V
C
V
CBO
V
CEO
I
C
h
FEMIN
PACKAGE
8
8
8
TO-126
TO-126
TO-92
600V 300V 1.5A
MJE13003,
700V 400V 1.5A
KSE13003
STX13003
700V 400V
1A
The power dissipated in the NPN transistor is equal
to the collector current times the collector-emitter
voltage. As a result, the transistor must always be
in saturation when turned on to prevent excessive
power dissipation. Select an NPN transistor with
sufficiently high current gain (h
FEMIN
> 8) and a base
drive resistor (R2 in Figure 1) low enough to ensure
that the transistor easily saturates.
Figure 5:
A 3.75W Charger Using ACT30A in Combination with TL431
F1
AC1
D4
D1
L1
R1
D3
AC2
C1
C2
R2A
D2
R2B
C4
R3
R6
D5
C19
C7
IC2A
Opto
R13
C8
T1
EE-16
C10
R18
L2
5V/750mA
D8
R9
R10
R11
C9
D6
R5
D7
R7
Z1
Q2
IC3
TL431
R12
R16
R15
GND
IC2B Opto
R14
1
IC1
3
ACT30A
2
R8
C3
C5
C6
C20
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TM
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TM
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