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
(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
200
V
V
100
100
DC-INPUT
DC-INPUT
0
0
10
10
V
V
5
5
BYPASS
BYPASS
0
0
400
400
200
200
V
V
DRAIN
DRAIN
0
0
1
2
0
1
2
0
Time (ms)
Time (ms)
Figure 11. Power Up Without Optional External UV Resistor
Connected to EN/UV Pin.
Figure 10. Power Up with Optional External UV Resistor (4 MΩ)
Connected to EN/UV Pin.
200
200
V
V
100
0
100
0
DC-INPUT
DC-INPUT
400
300
400
300
V
V
200
100
0
200
100
0
DRAIN
DRAIN
2.5
5
0
.5
1
0
Time (s)
Time (s)
Figure 13. Slow Power Down Timing with Optional External (4 MΩ) UV Resistor
Figure 12. Normal Power Down Timing (without UV).
Connected to EN/UV Pin.
6
Rev. I 01/09
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