InnoSwitch-CH
ON/OFF Operation with Current Limit State Machine
The internal clock of the InnoSwitch-CH runs all the time. At the
beginning of each clock cycle, the voltage comparator on the
FEEDBACK pin decides whether or not to implement a switch cycle,
and based on the sequence of samples over multiple cycles, it
determines the appropriate current limit. At high loads, the state
machine sets the current limit to its highest value. At lighter loads,
the state machine sets the current limit to reduced values.
supply output (Figure 9). At medium loads, cycles will be skipped and
the current limit will be reduced (Figure 10). At very light loads, the
current limit will be reduced even further (Figure 11). 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 accurate regulation and excellent
transient response.
At near maximum load, InnoSwitch-CH will conduct during nearly
all of its clock cycles (Figure 8). At slightly lower load, it will “skip”
additional cycles in order to maintain voltage regulation at the power
ꢄ00
ꢆꢇC-Iꢈꢉꢊꢀ
100
0
ꢃ00
100
0
ꢆꢇC-Iꢈꢉꢊꢀ
10
ꢆꢋꢉꢉ
ꢅ
0
ꢇ00
ꢄ00
ꢆꢇꢋꢌIꢈ
ꢃ00
ꢄ00
0
ꢃ00
100
0
ꢆꢇꢌꢍIꢈ
1
ꢄ
ꢃ.ꢆ
ꢆ
0
0
ꢀiꢁꢂ ꢃꢁꢄꢅ
ꢀiꢁꢂ ꢃꢄꢅ
Figure 12. Power-Up Timing.
Figure 13. Normal Power-Down Timing.
7
Rev. J 10/17
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