InnoSwitch3-EP
FEEDBACK Pin Short Detection
SECONDARY BYPASS Pin Overvoltage Protection
The InnoSwitch3-EP secondary controller features a SECONDARY
BYPASS pin OV feature similar to the PRIMARY BYPASS pin OV
feature. When the secondary is in control, in the event that the
SECONDARY BYPASS pin current exceeds IBPS(SD) (~7 mA) the
secondary will send a command to the primary to initiate an
auto-restart off-time (tAR(OFF)).
If the sensed FEEDBACK pin voltage is below VFB(OFF) at start-up, the
secondary controller will complete the handshake to take control of
the primary complete tSS(RAMP) and will stop requesting cycles to initiate
auto-restart (no cycle requests made to primary for longer than tAR(SK)
second triggers auto-restart).
During normal operation, the secondary will stop requesting pulses
from the primary to initiate an auto-restart cycle when the FEEDBACK
pin voltage falls below the VFB(OFF) threshold. The deglitch filter on the
protection mode is on for less than ~10 ms. By this mechanism, the
secondary will relinquish control after detecting that the FEEDBACK
pin is shorted to ground.
Output Constant Current and Constant Power Regulation
The InnoSwitch3-EP regulates the output current through an external
current sense resistor between the ISENSE and SECONDARY
GROUND pins and also controls output power in conjunction with the
output voltage sensed on the OUTPUT VOLTAGE pin. If constant
current regulation is not required, the ISENSE pin must be tied to the
SECONDARY GROUND pin. The InnoSwitch3-EP has constant current
regulation below the VPK threshold, and a constant output power
profile above the VPK threshold. The transition between CP and CC is
set by the VPK threshold and the set constant current is programmed
by the resistor between the ISENSE and SECONDARY GROUND pins.
Auto-Restart Thresholds
The OUTPUT VOLTAGE pin includes a comparator to detect when the
output voltage falls below VFB(AR) or VVO(AR), for a duration exceeding
tFB(AR) or tVO(AR)respectively. The secondary controller will relinquish
control when this fault condition is detected. This threshold is meant
to limit the range of constant current (CC) operation and is included
to support high power charger applications.
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Figure 8. Intelligent Quasi-Resonant Mode Switching.
7
Rev. D 08/18
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