TOP101AI POWERINT [Power Integrations, Inc.], TOP101AI Datasheet - Page 6
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TOP101AI
Manufacturer Part Number
TOP101AI
Description
Three-terminal Off-line PWM Switch
Manufacturer
POWERINT [Power Integrations, Inc.]
Datasheet
1.TOP101AI.pdf
(20 pages)
General Circuit Operation
Primary Feedback Regulation
The circuit shown in Figure 7 is a simple
5 V, 5 W bias supply using the TOP100.
This flyback power supply employs
primary-side regulation from a
transformer bias winding. This approach
is best for low-cost applications requiring
isolation and operation within a narrow
range of load variation. Line and load
regulation of
achieved from 10% to 100% of rated
load.
Voltage feedback is obtained from the
transformer (T1) bias winding, which
eliminates the need for optocoupler and
secondary-referenced error amplifier.
High-voltage DC is applied to the
primary winding of T1. The other side
of the transformer primary is driven by
Figure 7. Schematic Diagram of a Minimum Parts Count 5 V, 5 W Bias Supply Utilizing the TOP100.
6
TOP100-4
E
7/96
INPUT
DC
5% or better can be
CONTROL
SOURCE
DRAIN
TOP100YAI
U1
the integrated high-voltage MOSFET
transistor within the TOP100 (U1). The
circuit operates at a switching frequency
of 100 kHz, set by the internal oscillator
of the TOP100. The clamp circuit
implemented by VR1 and D1 limits the
leading-edge voltage spike caused by
transformer leakage inductance to a safe
value. The 5 V power secondary winding
is rectified and filtered by D2, C2, C3,
and L1 to create the 5 V output voltage.
The output of the T1 bias winding is
rectified and filtered by D3, R1, and C5.
The voltage across C5 is regulated by
U1, and is determined by the 5.7 V
internal shunt regulator at the
CONTROL pin of U1.
rectified bias voltage on C5 begins to
exceed the shunt regulator voltage,
P6KE91
UF4004
VR1
47 F
D1
C5
T1
When the
22
R1
1N5822
D2
1N4148
330 F
D3
25 V
C2
current will flow into the control pin.
Increasing control pin current decreases
the duty cycle until a stable operating
point is reached. The output voltage is
proportional to the bias voltage by the
turns ratio of the output to bias windings.
C5 is used to bypass the CONTROL pin.
C5 also provides loop compensation for
the power supply by shunting AC
currents around the CONTROL pin
dynamic impedance, and also determines
the auto-restart frequency during start-
up and auto-restart conditions. See DN-
8 for more information regarding bias
supplies.
(Bead)
CIRCUIT PERFORMANCE:
L1
Line Regulation - ±1.5%
150 F
Ripple Voltage ±25 mV
Load Regulation - ±4%
25 V
C3
95 to 185 V DC
(10% to 100%)
PI-1767-020296
5 V
RTN