InnoSwitch5-Pro This algorithm enables the most efficient use of the primary switch A sense resistor is tied between the high-voltage DC bulk capacitor with the benefit that this algorithm responds to digital feedback after the bridge (or to the AC side of the bridge rectifier for fast AC information immediately when a feedback switching cycle request is reset) and the UNDER/OVER INPUT VOLTAGE pin to enable this received. functionality. This function can be disabled by shorting the UNDER/ OVER INPUT VOLTAGE pin to primary GND. At full load, switching cycles have a maximum current approaching 100% I . This gradual y reduces to 30% of the full current limit as At power-up, after the primary bypass capacitor is charged and the LIMIT load decreases. Once 30% current limit is reached, there is no ILIM state is latched, and prior to switching, the state of the UNDER/ further reduction in current limit (since this is low enough to avoid OVER INPUT VOLTAGE pin is checked to confirm that it is above the audible noise). The time between switching cycles will continue to brown-in and below the overvoltage shutdown thresholds. increase as load reduces. In normal operation, if the UNDER/OVER INPUT VOLTAGE pin current Jitter falls below the brown-out threshold and remains below brown-out for The normalized current limit is modulated between 100% and 95% at longer than t , the control er enters auto-restart. Switching will only a modulation frequency of f this results in a frequency jitter of ~7 kHz UV- M resume once the UNDER/OVER INPUT VOLTAGE pin current is above with average frequency of ~100 kHz. the brown-in threshold. Auto-Restart In the event that the UNDER/OVER INPUT VOLTAGE pin current is In the event a fault condition occurs (such as an output overload, above the overvoltage threshold, the control er will also enter output short-circuit, or external component/pin fault), the InnoSwitch5-Pro auto-restart. Again, switching will only resume once the UNDER/ enters auto-restart (AR) or latches off. The latching condition is reset OVER INPUT VOLTAGE pin current has returned to within its normal by bringing the PRIMARY BYPASS pin below V or by going BPP(RESET) operating range. below the UNDER/OVER INPUT VOLTAGE pin UV (I ) threshold. UV- The input line UV/OV function makes use of a internal high-voltage In auto-restart, switching of the power switch is disabled for t . AR(OFF) MOSFET on the UNDER/OVER INPUT VOLTAGE pin to reduce power There are 2 ways to enter auto-restart: consumption. If the cycle off-time t is greater than 50 ms, the OFF 1. Continuous secondary requests at above the overload detection internal high-voltage MOSFET will disconnect the external sense frequency f for longer than 82 ms (t ). resistor from the internal IC to eliminate current drawn through the OVL AR 2. No requests for switching cycles from the secondary for > t . sense resistor. The line sensing function will activate again at the AR(SK) beginning of the next switching cycle. The second is included to ensure that if communication is lost, the primary tries to restart. Although this should never be the case in Primary-Secondary Handshake normal operation, it can be useful when system ESD events (for At start-up, the primary-side initial y switches without any feedback example) causes a loss of communication due to noise disturbing the information (this is very similar to the operation of a standard secondary control er. The issue is resolved when the primary restarts TOPSwitch™, TinySwitch™ or LinkSwitch™ controllers). after an auto-restart off-time. If no feedback signals are received during the auto-restart on-time The auto-restart is reset as soon as an AC reset occurs. (t ), the primary goes into auto-restart mode. Under normal AR conditions, the secondary control er will power-up via the FORWARD SOA Protection pin or from the OUTPUT VOLTAGE pin and take over control. From In the event that there are two consecutive cycles where 110% I LIMIT this point onwards the secondary controls switching. is reached within ~500 ns (the blanking time + current limit delay time), the control er will skip 2.5 cycles or ~25 ms. This provides If the primary control er stops switching or does not respond to cycle sufficient time for the transformer to reset with large capacitive loads requests from the secondary during normal operation (when the without extending the start-up time. secondary has control), the handshake protocol is initiated to ensure that the secondary is ready to assume control once the primary Input Line Voltage Monitoring begins to switch again. An additional handshake is also triggered if The UNDER/OVER INPUT VOLTAGE pin is used for input undervoltage the secondary detects that the primary is providing more cycles than and overvoltage sensing and protection. were requested. 5 Rev. C 01/24 www.power.com
