InnoSwitch-CH
InnoSwitch-CH Operation
required. If the InnoSwitch-CH is appropriately chosen for the power
level, the current in the calculated inductance will ramp up to current
limit before the DCMAX limit is reached.
InnoSwitch-CH devices operate in the current limit mode. When
enabled, the oscillator turns the power MOSFET on at the beginning
of each cycle. The MOSFET is turned off when the current ramps up
to the current limit or when the DCMAX limit is reached. Since the
highest current limit level and frequency of a InnoSwitch-CH design
are constant, the power delivered to the load is proportional to the
primary inductance of the transformer and peak primary current
squared. Hence, designing the supply involves calculating the primary
inductance of the transformer for the maximum output power
InnoSwitch-CH senses the output voltage on the FEEDBACK pin using
a resistive voltage divider to determine whether or not to proceed
with the next switching cycle. The sequence of cycles is used to
determine the current limit. Once a cycle is started, it always
completes the cycle. This operation results in a power supply in
which the output voltage ripple is determined by the output capacitor,
and the amount of energy per switch cycle.
CꢅꢆCꢇ
ꢁꢈꢃꢉ
CꢅꢆCꢇ
ꢁꢈꢃꢉ
IꢁꢂꢃIꢄ
IꢁꢂꢃIꢄ
ꢀꢁꢂꢃIꢄ
ꢀꢁꢂꢃIꢄ
ꢀꢁꢂ70ꢃ0ꢂ10101ꢃ
PI-7041-101014
Figure 8. Operation at Near Maximum Loading.
Figure 9. Operation at Moderately Heavy Loading.
CꢅꢆCꢇ
ꢁꢈꢃꢉ
CꢅꢆCꢇ
ꢁCꢈꢃꢉ
IꢁꢂꢃIꢄ
IꢁꢂꢃIꢄ
ꢀꢁꢂꢃIꢄ
ꢀꢁꢂꢃIꢄ
ꢀꢁꢂ70ꢃꢄꢂ10101ꢅ
ꢀꢁꢂ70ꢃꢄꢂ10101ꢅ
Figure 11. Operation at Very Light Load.
Figure 10. Operation at Medium Loading.
6
Rev. J 10/17
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