ICL5101_16 Datasheet, PDF (15/44 Pages) Infineon Technologies AG – Resonant controller IC with PFC for LED driver

2.2
Detection Stage
ICL5101
Functional Description
2.2.1
Detection of Over Temperature
Force a shut-off of the IC due to over temperature by using a PTC to GND on pin 13. In the event of an over
temperature of the system (in run mode), the current out of the OTP pin 13 I_OTP3 = - 21.3 µA charges up a
capacitor. If the voltage at the OTP pin 13 exceeds the V_OTP3 = 3.2V threshold, the controller detects an over
temperature and stops the gate drives after a delay of t = 620µs set by an internal timer. The system restarts
automatically. The possibility of a latch of the system is happen when it cools down and heat up within 200ms.
When system is too hot before startup, the system prevents a power up.
2.2.2
Detection of Output Overvoltage
Overvoltage is detected by measuring the peak levels of the voltage at the AUX winding via an AC current fed
into the OVP pin 12. If the sensed AC current exceeds 210 µA_PP for longer than 620 µs, the status of
overvoltage is detected. The OVP fault results in a latched power-down mode (after trying a single restart). The
controller continuously monitors the status until the overvoltage status changes.
2.2.3
Detection of Capacitive Mode Operation
RESONANT converter designs should avoid working in capacitive mode operation – not even under abnormal
conditions. ICL5101 provides capacitive mode operation detection and latch-off of the system after a single
restart for error verification. Resonant converters work in capacitive mode when their switching frequency falls
below a critical value. This depends on the loading condition and the input-to-output ratio. They are especially
prone to enter capacitive mode when the input voltage is lower than the minimum specified and/or the output is
overloaded or shorted. In order to prevent a malfunction in the area of capacitive load during run mode due to
certain deviations from the normal load, the IC senses only via the LSCS pin 2.
Capacitive load operation is detected if the voltage at the LSCS pin drops below a first threshold of V_LSCSCap1 = –
50 mV directly before the high-side MOSFET is turned on or exceeds a second threshold of V_LSCSCap2 = 2.0 V
during ON switching of the high-side MOSFET (Figure 8). If this overcurrent is present for longer than 620 µs,
the IC results a latched power-down mode after trying a single restart.
Figure 8 Capacitive Mode Operation
Datasheet
15
Rev. 1.3, 2016-01-15