Datasheet InnoSwitch-CP (Power Integrations) - 7

InnoSwitch-CP InnoSwitch-CP Operation ON/OFF Operation with Current Limit State Machine
The internal clock of the InnoSwitch-CP runs all the time. At the InnoSwitch-CP devices operate in the current limit mode. When beginning of each clock cycle, the voltage comparator on the enabled, the oscillator turns the power MOSFET on at the beginning FEEDBACK pin decides whether or not to implement a switch cycle, of each cycle. The MOSFET is turned off when the current ramps up and based on the sequence of samples over multiple cycles, it to the current limit or when the DC limit is reached. Since the MAX determines the appropriate current limit. At high loads, the state highest current limit level and frequency of a InnoSwitch-CP design machine sets the current limit to its highest value. At lighter loads, are constant, the power delivered to the load is proportional to the the state machine sets the current limit to reduced values. primary inductance of the transformer and peak primary current squared. Hence, designing the supply involves calculating the At near maximum load, InnoSwitch-CP will conduct during nearly primary inductance of the transformer for the maximum output power al of its clock cycles (Figure 9). At slightly lower load, it will “skip” required. If the InnoSwitch-CP is appropriately chosen for the power additional cycles in order to maintain voltage regulation at the power level, the current in the calculated inductance will ramp up to current supply output (Figure 10). At medium loads, cycles will be skipped limit before the DC limit is reached. and the current limit will be reduced (Figure 11). At very light loads, MAX the current limit will be reduced even further (Figure 12). Only a smal InnoSwitch-CP senses the output voltage on the FEEDBACK pin using percentage of cycles will occur to satisfy the power consumption of a resistive voltage divider to determine whether or not to proceed the power supply. with the next switching cycle. The sequence of cycles is used to determine the current limit. Once a cycle is started, it always The response time of the ON/OFF control scheme is very fast completes the cycle. This operation results in a power supply in compared to PWM control. This provides accurate regulation and which the output voltage ripple is determined by the output capacitor, excel ent transient response. and the amount of energy per switch cycle. 200 100
VDC-INPUT
200 -7042-053013 PI
PI-2395-101014
0 100
VDC-INPUT
10 0 5
VBPP
400 0 300 400 200
VDRAIN
200
VDRAIN
100 0 0 0 1 2 0 2.5 5
Time (ms) Time (s)
Figure 13. Power-Up. Figure 14. Normal Power-Down Timing.
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Rev. F 09/17 www.power.com Document Outline Product Highlights Highly Integrated, Compact Footprint EcoSmart - Energy Efficient Advanced Protection / Safety Features Full Safety and Regulatory Compliance Green Package Applications Description Output Power Table Pin Functional Description InnoSwitch-CP Functional Description InnoSwitch-CP Operation Applications Example Key application Considerations Selection of Components Recommendations for Circuit Board Layout Recommendations for EMI Reduction Recommendations for Audible Noise Suppression Recommendations for Transformer Design Quick Design Checklist Absolute Maximum Ratings Thermal Resistance Key Electrical Characteristics NOTES Typical Performance Characteristics eSOP-R16B Package Package Marking MSL Table ESD and Latch-Up Table Part Ordering Information