Datasheet LYTSwitch-6 (Power Integrations) - 5

LYTSwitch-6
The second was included to ensure that if communication is lost, the primary tries to restart again. Although this should never be the case in normal operation, this can be useful in the case of system ESD P: Primary Chip S: Secondary Chip events for example where a loss of communication due to noise Start disturbing the secondary control er, the issue is resolved when the P: Powered Up, Switching S: Powering Up primary restarts after an auto-restart off time. The very first auto-restart off-time is short. This short auto-restart timer is to provide a quick recovery under fast reset conditions. The P: Auto-Restart short auto-restart off-time al ows the control er to quickly check to S: Powering Up determine whether the auto-restart condition is maintained beyond t . If so will resort to full auto-restart off timing. AR(OFF)SH 2s The auto-restart is reset as soon as an AC reset occurs.
SOA Protection
S: Has powered No P: Goes to Auto-Restart Off up within t S: Bypass Discharging In the event there are two consecutive cycles where the ILIM is AR reached within the blanking time and current limit delay time (~500 ns), the control er will skip approximately 2.5 cycles or ~25 ms Yes 64 ms (based on full frequency of 100 kHz). This provides sufficient time for reset of the transformer during start-up into large capacitive loads P: Switching without extending the start-up time. S: Sends Handshaking Pulses
Input Line Voltage Monitoring
The INPUT OVERVOLTAGE

pin is used for input overvoltage sensing and protection. P: Has Received No P: Continuous Switching A 4 MΩ resistor is tied between the high-voltage DC bulk capacitor Handshaking S: Doesn’t Take Control Pulses after the bridge (or to the AC side of the bridge rectifier for fast AC reset) and the INPUT OVERVOLTAGE

pin to enable this functionality. Yes This pin functionality can be disabled by shorting INPUT OVERVOLTAGE pin to primary Source. P: Stops Switching, Hands Over Control to Secondary
Primary/Secondary-Side Handshake
At start-up, the primary-side initial y switches without any feedback information (this is very similar to the operation of a standard TOPSwitch™, TinySwitch™ or LinkSwitch™ control ers). S: Has Taken No P: Not Switching If no feedback signals are received during the auto-restart on-time Control? S: Doesn’t Take Control (t ), the primary goes into auto-restart mode. Under normal AR conditions, the secondary control er will power-up via the FORWARD Yes pin or from OUTPUT VOLTAGE pin and take over control. From this point onwards the secondary controls switching. End of Handshaking, If the primary stops switching or does not respond to cycle requests Secondary Control Mode from the secondary during normal operation (when the secondary PI-8437-092017 has control), the handshake protocol is initiated to ensure that the secondary is ready to assume control once the primary begins to switch again. An additional handshake is also triggered if the Figure 7. Primary-Secondary Handshake Flow Chart. secondary detects that the primary is providing more cycles than were requested. second handshake sequence. This provides additional protection The most likely event that could require an additional handshake is against cross-conduction of SF FET while the primary is switching. when the primary stops switching as the result of a momentary line This protection mode also prevents an output overvoltage condition brown-out event. When the primary resumes operation, it will default in the event that the primary is reset while the secondary is still in into a start-up condition and attempt to detect handshake pulses control. from the secondary.
Wait and Listen
If the secondary does not detect that the primary responds to When the primary resumes switching after initial power-up recovery switching requests for 8 consecutive cycles, or if the secondary from input line voltage fault or an auto-restart event, it will assume detects that the primary is switching without cycle requests for 4 control and require a successful handshake to relinquish control to or more consecutive cycles, the secondary control er will initiate a the secondary control er.
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Rev. E 02/18 www.power.com Document Outline Product Highlights Description Output Power Table Pin Functional Description LYTSwitch-6 Functional Description Primary Controller Secondary Controller Application Example Key Applications Design Considerations Primary-Side Components of LYTSwitch-6 Secondary-Side Components of f LYTSwitch-6 Recommendations for Circuit Board Layout Recommended Position of InSOP-24D Package with Respect to Transformer Quick Design Checklist Other Applications Design Example PCB Layout Example Absolute Maximum Ratings Thermal Resistance Key Electrical Characteristics Typical Performance Curves InSOP-24D Package Drawing MSL Table ESD and Latch-Up Table Part Ordering Information