ACT30
Active- Semi
Rev 5, 05-Jun-09
FUNCTIONAL BLOCK DIAGRAM
2
DRV1
DRV2
VDD
REGULATOR
+
3.6V (ACT30A/C)
4.6V (ACT30B/D)
BIAS
& UVLO
9k
HICCUP
CONTROL
OSC &
RAMP
CURRENT
PFWM
SWITCHING
CONTROL
LOGIC
1
SLEW
20k
FREQ
1X
56X
56X
200k
ERROR
COMP
ILIM VC
40
GENERATOR
20k
4.75V
10µA/V
GND
GND
c: FREQ terminal wire-bonded to VDD in ACT30C/D (TO-92)
d: DRV2 terminal wire-bonded to DRV1 in ACT30B/D (TO-92)
Startup Sequence
FUNCTIONAL DESCRIPTION
Figure 1 shows a Simplified Application Circuit for
the ACT30. Initially, the small current through
resistor R1 charges up the capacitor C1, and the
BJT acts as a follower to bring up the DRV1
voltage. An internal regulator generates a VVDD
As seen in the Functional Block Diagram, the main
components include switching control logic, two on-
chip medium-voltage power-MOSFETs with parallel
current sensor, driver, oscillator and ramp
generator, current limit VC generator, error
comparator, hiccup control, bias and under voltage-
lockout, and regulator circuitry.
voltage equal to VDRV1 – 3.6V for ACT30A (VDRV1
–
4.6V for ACT30B) but limits it to 5.5V max. As VVDD
crosses 5V, the regulator sourcing function stops
and VVDD begins to drop due to its current
consumption. As VVDD voltage decreases below
4.75V, the IC starts to operate with increasing driver
current. When the output voltage reaches regulation
point, the optocoupler feedback circuit stops VVDD
from decreasing further. The switching action also
allows the auxiliary windings to take over in
supplying the C1 capacitor. Figure 2 shows a
typical startup sequence for the ACT30.
As seen in the Functional Block Diagram, the
design has six internal terminals. VVDD is the power
supply terminal. DRV1 and DRV2 are linear driver
outputs that can drive the emitter of an external
high voltage NPN transistor or N-channel MOSFET.
This emitter-drive method takes advantage of the
high VCBO of the transistor, allowing a low cost
transistor such as ‘13003 (VCBO = 700V) or ‘13002
(VCBO = 600V) to be used for a wide AC input range.
The slew-rate limited driver coupled with the turn-off
characteristics of an external NPN transitor result in
lower EMI.
To limit the auxiliary voltage, use a 12V zener diode
for ACT30A or a 13V zener diode for ACT30B (D1
diode in Figure 1).
The driver peak current is designed to have a
negative voltage coefficient with respect to supply
Even though up to 2Mꢀ startup resistor (R1) can be
used due to the very low startup current, the actual
R1 value should be chosen as a compromise
between standby power and startup time delay.
voltage VVDD
,
so that lower supply voltage
automatically results in higher DRV1 peak current.
This way, the optocoupler can control VVDD directly
to affect driver current.
Innovative PowerTM
ActiveSwitcherTM is a trademark of Active-Semi.
- 4 -
www.active-semi.com
Copyright © 2009 Active-Semi, Inc.
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
