InnoSwitch3-CP
The first auto-restart off-time is short (tAR(OFF)SH). This short auto-
restart time is to provide quick recovery under fast reset conditions.
The short auto-restart off-time allows the controller to quickly check to
determine whether the auto-restart condition is maintained beyond
tAR(OFF)SH. If so, it will resort to a full auto-restart off-time.
ꢖꢉ ꢖꢎꢑꢅꢋꢎꢟ ꢜꢓꢑꢌ
ꢈꢉ ꢈeꢗꢇꢔꢏꢋꢎꢟ ꢜꢓꢑꢌ
ꢈꢒꢋꢎꢒ
ꢖꢉ ꢖꢇꢍeꢎeꢏ ꢦꢌꢝ ꢈꢍꢑꢒꢗꢓꢑꢔꢙ
ꢈꢉ ꢖꢇꢍeꢎꢑꢔꢙ ꢦꢌ
The auto-restart is reset as soon as an AC reset occurs.
SOA Protection
In the event that there are two consecutive cycles where the ILIM is
reached within ~500 ns (the blanking time + current limit delay time),
the controller will skip 2.5 cycles or ~25 ms (based on full frequency
of 100 kHz). This provides sufficient time for the transformer to reset
with large capacitive loads without extending the start-up time.
ꢖꢉ ꢢꢐꢒꢇꢣReꢁꢒꢋꢎꢒ
ꢈꢉ ꢖꢇꢍeꢎꢑꢔꢙ ꢦꢌ
ꢂꢁ
ꢈꢉ ꢊꢋꢁ ꢌꢇꢍeꢎeꢏ
ꢐꢌ ꢍꢑꢒꢓꢑꢔ ꢃꢄ ꢅꢁꢕ
ꢆꢇ
ꢆꢇ
ꢆꢇ
Secondary Rectifier/SR MOSFET Short Protection (SRS)
In the event that the output diode or SR FET is short-circuited before
or during the primary conduction cycle, the drain current (prior to the
end of the leading edge blanking time) can be much higher than the
maximum current limit threshold. If the controller turns the high-
voltage power MOSFET off, the resulting peak drain voltage could
exceed the rated BVDSS of the device, resulting in catastrophic failure
even with minimum on-time.
ꢖꢉ ꢡꢇeꢁ ꢒꢇ ꢢꢐꢒꢇꢣReꢁꢒꢋꢎꢒ ꢞꢤꢤ
ꢈꢉ ꢥꢟꢌꢋꢁꢁ Dꢑꢁꢗꢓꢋꢎꢙꢑꢔꢙ
ꢀeꢁ
ꢃꢄ ꢅꢁ
ꢖꢉ ꢈꢍꢑꢒꢗꢓꢑꢔꢙ
ꢈꢉ ꢈeꢔꢏꢁ ꢊꢋꢔꢏꢁꢓꢋꢘꢑꢔꢙ ꢖꢐꢚꢁeꢁ
To address this issue, the controller features a circuit that reacts
when the drain current exceeds the maximum current limit threshold
prior to the end of leading-edge blanking time. If the leading-edge
current exceeds current limit within a cycle (200 ns), the primary
controller will trigger a 30 ms off-time event. SOA mode is triggered if
there are two consecutive cycles above current limit within tLES
(~500 ns). SRS mode also triggers ~200 ms off-time, if the current
limit is reached within 200 ns after a 30 ms off-time.
ꢖꢉ ꢊꢋꢁ Reꢗeꢑveꢏ
ꢊꢋꢔꢏꢁꢓꢋꢘꢑꢔꢙ
ꢖꢐꢚꢁeꢁ
ꢖꢉ ꢜꢇꢔꢒꢑꢔꢐꢇꢐꢁ ꢈꢍꢑꢒꢗꢓꢑꢔꢙ
ꢈꢉ Dꢇeꢁꢔꢠꢒ ꢛꢋꢘe ꢜꢇꢔꢒꢎꢇꢚ
ꢀeꢁ
ꢖꢉ ꢈꢒꢇꢌꢁ ꢈꢍꢑꢒꢗꢓꢑꢔꢙꢝ ꢊꢋꢔꢏꢁ
ꢞveꢎ ꢜꢇꢔꢒꢎꢇꢚ ꢒꢇ ꢈeꢗꢇꢔꢏꢋꢎꢟ
Input Line Voltage Monitoring
The UNDER/OVER INPUT VOLTAGE pin is used for input undervoltage
and overvoltage sensing and protection.
ꢈꢉ ꢊꢋꢁ ꢛꢋꢘeꢔ
ꢜꢇꢔꢒꢎꢇꢚꢕ
A 4 MΩ resistor is tied between the high-voltage DC bulk capacitor
after the bridge (or to the AC side of the bridge rectifier for fast AC
reset) and the UNDER/OVER INPUT VOLTAGE pin to enable this
functionality. This function can be disabled by shorting the UNDER/
OVER INPUT VOLTAGE pin to SOURCE pin.
ꢖꢉ ꢆꢇꢒ ꢈꢍꢑꢒꢗꢓꢑꢔꢙ
ꢈꢉ Dꢇeꢁꢔꢠꢒ ꢛꢋꢘe ꢜꢇꢔꢒꢎꢇꢚ
ꢀeꢁ
ꢧꢔꢏ ꢇꢤ ꢊꢋꢔꢏꢁꢓꢋꢘꢑꢔꢙꢝ
ꢈeꢗꢇꢔꢏꢋꢎꢟ ꢜꢇꢔꢒꢎꢇꢚ ꢨꢇꢏe
At power-up, after the primary bypass capacitor is charged and the
ILIM state is latched, and prior to switching, the state of the UNDER/
OVER INPUT VOLTAGE pin is checked to confirm that it is above the
brown-in and below the overvoltage shutdown thresholds.
ꢖꢩꢣꢪꢄ1ꢃꢣ10ꢂ81ꢄ
Figure 8. Primary-Secondary Handshake Flowchart.
In normal operation, if the UNDER/OVER INPUT VOLTAGE pin current
falls below the brown-out threshold and remains below brown-in for
longer than tUV-, the controller enters auto-restart. Switching will only
resume once the UNDER/OVER INPUT VOLTAGE pin current is above
the brown-in threshold.
Primary-Secondary Handshake
At start-up, the primary-side initially switches without any feedback
information (this is very similar to the operation of a standard
TOPSwitch™, TinySwitch™ or LinkSwitch™ controllers).
In the event that the UNDER/OVER INPUT VOLTAGE pin current is
above the overvoltage threshold, the controller will also enter
auto-restart. Again, switching will only resume once the UNDER/
OVER INPUT VOLTAGE pin current has returned to within its normal
operating range.
If no feedback signals are received during the auto-restart on-time
(tAR), the primary goes into auto-restart mode. Under normal
conditions, the secondary controller will power-up via the FORWARD
pin or from the OUTPUT VOLTAGE pin and take over control. From
this point onwards the secondary controls switching.
The input line UV/OV function makes use of an internal high-voltage
MOSFET on the UNDER/OVER INPUT VOLTAGE pin to reduce power
consumption. If the cycle off-time tOFF is greater than 50 ms, the
internal high-voltage MOSFET will disconnect the external 4 MΩ
resistor from the internal IC to eliminate current drawn through the
4 MΩ resistor. The line sensing function will activate again at the
beginning of the next switching cycle.
If the primary controller stops switching or does not respond to cycle
requests from the secondary during normal operation (when the
secondary 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 secondary detects that the primary is providing more cycles than
were requested.
5
Rev. D 08/18
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