TNY274-280
PI-2381-1030801
200
V
EN
100
0
10
V
DC-INPUT
CLOCK
DC
MAX
5
0
V
BYPASS
I DRAIN
400
200
0
0
1
2
V
DRAIN
Time (ms)
V DRAIN
Figure 11. Power-Up Without Optional External UV Resistor
Connected to EN/UV Pin.
PI-2661-082305
PI-2348-030801
Figure 9. Operation at Very Light Load.
200
100
V
DC-INPUT
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.
PI-2383-030801
0
400
300
200
100
0
0
.5
1
V
DRAIN
Time (s)
Figure 12. Normal Power-Down Timing (without UV).
PI-2395-030801
200
100
0
10
5
0
400
200
0
0
1
V
DRAIN
V
BYPASS
V
DC-INPUT
200
100
0
400
300
200
100
0
V
DRAIN
V
DC-INPUT
2
0
2.5
5
Time (ms)
Time (s)
Figure 10. Power-Up with Optional External UV Resistor (4 MΩ)
Connected to EN/UV Pin.
Figure 13. Slow Power-Down Timing with Optional External
(4 MΩ) UV Resistor Connected to EN/UV Pin.
6
E
2/06
POWERINT [ POWER INTEGRATIONS, INC. ]
