top209 Power Integrations, Inc., top209 Datasheet - Page 5

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

Figure 6. Typical Waveforms for (1) Normal Operation, (2) Auto-restart.
Shutdown/Auto-restart
To minimize TOPSwitch power dissipation, the shutdown/
auto-restart circuit turns the power supply on and off at a duty
cycle of typically 5% if an out of regulation condition persists.
Loss of regulation interrupts the external current into the
CONTROL pin. V
hysteretic auto-restart mode described above. When the fault
condition is removed, the power supply output becomes
regulated, V
operation of the power supply resumes.
Hysteretic Overtemperature Protection
Temperature protection is provided by a precision analog
circuit that turns the output MOSFET off when the junction
temperature exceeds the thermal shutdown temperature
C
regulation returns to shunt mode, and normal
C
regulation changes from shunt mode to the
DRAIN
V OUT
I OUT
V IN
V C
I C
V IN
0
0
0
0
0
1
1
1
2
2
• • •
• • •
(typically 145 C). When the junction temperature cools past
the hysteresis temperature, normal operation resumes. V
regulated in hysteretic mode while the power supply is turned
off.
High-voltage Bias Current Source
This current source biases TOPSwitch from the DRAIN pin and
charges the CONTROL pin external capacitance (C
start-up or hysteretic operation. The current source is switched
on and off with an effective duty cycle of approximately 35%.
This duty cycle is determined by the ratio of CONTROL pin
charge (I
source is turned off during normal operation when the output
MOSFET is switching.
8
8
1
1
2
C
) and discharge currents (I
2
2
• • •
• • •
8
8
1
1
1
CD1
TOP209/210
and I
CD2
). This current
PI-1742-011796
8/97
T
A
) during
5
C
is