Main characteristics and circuit description

AN3089

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DocID16493 Rev 2

1.8

Overtemperature protection

The R3 thermistor, connected to the L6566B DIS pin (#8), provides a thermal protection of

the flyback MOSFET (Q1). Therefore, in case of overheating, the flyback converter activity

is latched off. To maintain this state, an internal circuitry of the L6566B monitors the Vcc and

periodically reactivates the HV current source to supply the IC.

1.9

Burst mode operation

The L6566B implements a current mode control, thus it monitors the output power through

the COMP pin, which has a level proportional to the load. Therefore, when the voltage on

the COMP pin falls below an internal threshold, the controller is disabled and its

consumption reduced; normal operation restarts as soon as the COMP voltage rises again.

In this way a low consumption burst mode operation is obtained.