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PDF ACT361 Data sheet ( Hoja de datos )
| Número de pieza | ACT361 | |
| Descripción | High Performance ActivePSR Primary Switching Regulator | |
| Fabricantes | Active-Semi | |
| Logotipo |  |
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ACT361
Rev 8, 14-Nov-12
High Performance ActivePSRTM Primary Switching Regulator
FEATURES
• Patented Primary Side Regulation
Technology
• No Opto-Coupler
• Best-in-Class Constant Voltage, Constant
Current Accuracy
• Low EMI
• Proprietary Fast Startup Circuit
• Built-in Soft-Start Circuit
• Integrated Line and Primary Inductance
Compensation
• Integrated Programmable Output Cord
Resistance Compensation
• Line Under-Voltage, Output Over-Voltage,
Output Short-Circuit and Over-Temperature
Protection
• Complies with all Global Energy Efficiency
and CEC Average Efficiency Standards
• Adjustable power from 2W to 7W
• Minimum External Components
• Tiny SOT23-6 Package
The ACT361 ensures safe operation with complete
protection against all fault conditions. Built-in
protection circuitry is provided for output short-
circuit, output over-voltage, line under-voltage, and
over temperature conditions.
The ACT361 ActivePSRTM is optimized for high
performance, cost-sensitive applications, and
utilizes Active-Semi’s proprietary primary-side
feedback architecture to provide accurate constant
voltage, constant current (CV/CC) regulation
without the need of an opto-coupler or reference
device. Integrated line and primary inductance
compensation circuitry provides accurate constant
current operation despite wide variations in line
voltage and primary inductance. Integrated output
cord resistance compensation further enhances
output accuracy. The ACT361 achieves excellent
regulation and transient response, yet requires less
than 150mW of standby power.
The ACT361 is optimized for 2W to 7W
applications. It is available in space-saving 6 pin
SOT23-6 package.
Figure 1:
Simplified Application Circuit
APPLICATIONS
• Chargers for Cell Phones, PDAs, MP3,
Portable Media Players, DSCs, and Other
Portable Devices and Appliances
• RCC Adapter Replacements
• Linear Adapter Replacements
• Standby and Auxiliary Supplies
GENERAL DESCRIPTION
The ACT361 belongs to the high performance
patented ActivePSRTM Family of Universal-input
AC/DC off-line controllers for battery charger and
adapter applications. It is designed for flyback
topology working in discontinuous conduction mode
(DCM). The ACT361 meets all of the global energy
efficiency regulations (CEC, European Blue Angel,
and US Energy Star standards) while using very
few external components.
INPUT
VDD
BD
ACT361
SW
CS FB
G
OUTPUT
Innovative PowerTM
- 1 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
1 page  
ACT361
Rev 8, 14-Nov-12
FUNCTIONAL DESCRIPTION
As shown in the Functional Block Diagram, to
regulate the output voltage in CV (constant voltage)
mode, the ACT361 compares the feedback voltage
at FB pin to the internal reference and generates an
error signal to the pre-amplifier. The error signal,
after filtering out the switching transients and
compensated with the internal compensation
network, modulates the external NPN transistor
peak current at CS pin with current mode PFWM
(Pulse Frequency and Width Modulation) control.
To regulate the output current in CC (constant
current) mode, the oscillator frequency is modulated
by the output voltage.
SW is a driver output that drives the emitter of an
external high voltage NPN transistor. This base-
emitter-drive method makes the drive circuit the
most efficient.
Fast Startup
VDD is the power supply terminal for the ACT361.
During startup, the ACT361 typically draws only
20μA supply current. The startup resistor from the
rectified high voltage DC rail supplies current to the
base of the NPN transistor. This results in an
amplified emitter current to VDD through the SW
pin via Active-Semi's proprietary fast-startup
circuitry until it exceeds the VDDON threshold 19V. At
this point, the ACT361 enters internal startup mode
with the peak current limit ramping up in 10ms.
After switching starts, the output voltage begins to
rise. The VDD bypass capacitor must supply the
ACT361 internal circuitry and the NPN base drive
until the output voltage is high enough to sustain
VDD through the auxiliary winding. The VDDOFF
threshold is 5.5V; therefore, the voltage on the VDD
capacitor must remain above 5.5V while the output
is charging up.
Constant Voltage (CV) Mode Operation
In constant voltage operation, the ACT361 captures
the auxiliary flyback signal at FB pin through a
resistor divider network R8 and R9 in Figure 6. The
signal at FB pin is pre-amplified against the internal
reference voltage, and the secondary side output
voltage is extracted based on Active-Semi's
proprietary filter architecture.
This error signal is then amplified by the internal
error amplifier. When the secondary output voltage
is above regulation, the error amplifier output
voltage decreases to reduce the switch current.
When the secondary output voltage is below
regulation, the error amplifier output voltage
increases to ramp up the switch current to bring the
secondary output back to regulation. The output
regulation voltage is determined by the following
relationship:
VOUTCV
=
2.20V
×
⎜⎜⎝⎛1
+
RFB1
RFB 2
⎟⎟⎠⎞
×
NS
NA
− VD
(1)
where RFB1 (R8) and RFB2 (R9) are top and bottom
feedback resistor, NS and NA are numbers of
transformer secondary and auxiliary turns, and VD
is the rectifier diode forward drop voltage at
approximately 0.1A bias.
Standby (No Load) Mode
In no load standby mode, the ACT361 oscillator
frequency is further reduced to a minimum
frequency while the current pulse is reduced to a
minimum level to minimize standby power. The
actual minimum switching frequency is
programmable with an output preload resistor.
Loop Compensation
The ACT361 integrates loop compensation circuitry
for simplified application design, optimized transient
response, and minimal external components.
Output Cable Resistance Compensation
The ACT361 provides programmable output cable
resistance compensation during constant voltage
regulation, monotonically adding an output voltage
correction up to predetermined percentage at full
power. There are four levels to program the output
cable compensation by connecting a resistor (R4 in
Figure 6) from the SW pin to VDD pin. The
percentage at full power is programmable to be 3%,
6%, 9% or 12%, and by using a resistor value of
300k, 150k, 75k or 33k respectively. If there is no
resistor connection, there is no cord compensation.
This feature allows for better output voltage
accuracy by compensating for the output voltage
droop due to the output cable resistance.
Constant Current (CC) Mode Operation
When the secondary output current reaches a level
set by the internal current limiting circuit, the
ACT361 enters current limit condition and causes
the secondary output voltage to drop. As the output
voltage decreases, so does the flyback voltage in a
proportional manner. An internal current shaping
circuitry adjusts the switching frequency based on
the flyback voltage so that the transferred power
remains proportional to the output voltage, resulting
Innovative PowerTM
- 5 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
5 Page 
ACT361
Rev 8, 14-Nov-12
TYPICAL PERFORMANCE CHARACTERISTICS CONT’D
(Circuit of Figure 6, unless otherwise specified.)
VDD ON/OFF Voltage vs. Temperature
20.5
18.5
16.5
VDDON
14.5
12.5
10.5
8.5
6.5 VDDOFF
4.5
0
25 50 75
Temperature (°C)
Start Up Supply Current vs. Temperature
28
26
24
22
20
18
16
14
0
25 50 75
Temperature (°C)
2.25
2.20
2.15
2.10
2.05
2.00
0
FB Voltage vs. Temperature
25 50
Temperature (°C)
75
Normalized ILIM vs. Temperature
1.02
1.01
1.00
0.99
0.98
0.97
0.96
0.95
0
25 50
Temperature (°C)
75
Max. Switching Frequency vs. Temperature
50.6
49.8
49.0
48.2
47.4
46.6
45.8
45.0
0
25 50
Temperature (°C)
75
Internal MOSFET RON vs. Temperature
2.4
2.0
1.6
1.2
0.8
0.4
0.0
0
25 50
Temperature (°C)
75
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet ACT361.PDF ] | |
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