top209 Power Integrations, Inc., top209 Datasheet - Page 6

• Manufacturer Part Number: top209
• Description: Three-terminal Off-line Pwm Switch
• Manufacturer: Power Integrations, Inc.

2
General Circuit Description
Figure 7 shows a low-cost, DC input, flyback switching power
supply using the TOP210 integrated circuit. This 5 V, 4 W
power supply operates from a DC voltage derived from rectified
and filtered AC mains voltage of 85 to 265 VAC. The 5 V
output is indirectly sensed via the primary bias winding. The
output voltage is determined by the TOPSwitch CONTROL pin
shunt regulator voltage (V
and D3, and the turns ratio between the bias winding and output
winding of T1. Other output voltages are also possible by
adjusting the transformer turns ratios.
The high voltage DC bus is applied to the primary winding of
T1. Capacitor C1 filters the high voltage supply, and is only
Figure 7. Schematic Diagram of a Minimum Parts Count 5 V, 4 W Bias Supply Using the TOP210.
6
TOP209/210
A
8/97
INPUT
DC
+
-
400 V
10 nF
C1
C
), the voltage drops of rectifiers D2
TOPSwitch
UF4005
D
S
D1
TOP210
CONTROL
U1
BZY97-
120 V
C120
VR1
C
1
2
necessary if the connections between the high voltage DC
supply and the TOP210 are long. The other side of the
transformer primary is driven by the integrated high-voltage
MOSFET within the TOP210. D1 and VR1 clamp the voltage
spike caused by transformer leakage inductance to a safe value
and reduce ringing at the DRAIN of U1. The power secondary
winding is rectified and filtered by D2, C2, L1, and C3 to create
the 5V output voltage. The bias winding is rectified and filtered
by D3, R1 and C5 to create a bias voltage to the TOP210. C5
also filters internal MOSFET gate drive charge current spikes
on the CONTROL pin, determines the auto-restart frequency,
and together with R1, compensates the control loop.
T1
TRD1
47 F
10 V
C5
8
5
4
3
1N5822
D2
330 F
10 V
1N4148
C2
D3
3.3 H
CIRCUIT PERFORMANCE:
15
L1
R1
Line Regulation - –1.5%
Ripple Voltage –25 mV
Load Regulation - –5%
100 F
10 V
(104-370 VDC)
C3
(10-100%)
PI-2045-041798
+5 V
RTN