TNY274-280
At near maximum load, TinySwitch-III will conduct during nearly
all of its clock cycles (Figure 6). At slightly lower load, it will
“skip” additional cycles in order to maintain voltage regulation at
the power supply output (Figure 7). At medium loads, cycles
will be skipped and the current limit will be reduced (Figure 8).
At very light loads, the current limit will be reduced even further
200
100
0
10
5
0
400
200
0
0
1
2
V
DRAIN
V
BYPASS
V
DC-INPUT
(Figure 9). Only a small percentage of cycles will occur to satisfy
the power consumption of the power supply.
The response time of the ON/OFF control scheme is very fast
compared to PWM control. This provides tight regulation and
excellent transient response.
200
100
0
10
5
0
400
200
0
0
1
2
V
DRAIN
V
BYPASS
V
DC-INPUT
PI-2383-030801
Time (ms)
Figure 10. Power Up with Optional External UV Resistor (4 MΩ)
Connected to EN/UV Pin.
Time (ms)
Figure 11. Power Up Without Optional External UV Resistor
Connected to EN/UV Pin.
PI-2348-030801
200
100
0
400
300
200
100
0
0
.5
V
DRAIN
V
DC-INPUT
200
100
0
400
300
200
100
0
V
DRAIN
V
DC-INPUT
1
0
2.5
5
Time (s)
Figure 12. Normal Power Down Timing (without UV).
Time (s)
Figure 13. Slow Power Down Timing with Optional External (4 MΩ) UV Resistor
Connected to EN/UV Pin.
6
Rev. I 01/09
www.powerint.com
PI-2395-030801
PI-2381-1030801
POWERINT [ POWER INTEGRATIONS, INC. ]
