AN3119

Main characteristics and circuit description

Doc ID 16849 Rev 2

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and R28 resistor divider, providing a voltage level for brown-out (AC mains under voltage)

protection. A voltage on the RUN pin below 0.8 V shuts down (not latched) the IC and brings

its consumption to a considerably lower level. The L6563S restarts as the voltage at the pin

rises above 0.88 V.

The R21, R25, R26 and R33 dividers provide the information regarding the output voltage

level to the L6563S pin #7 (PFC_OK). It is required by the L6563S output voltage monitoring

and disable functions used for PFC protection purposes.

If the voltage on pin #7 exceeds 2.5 V the IC stops switching and restarts as the voltage on

the pin falls below 2.4 V, realizing the so-called dynamic OVP, preventing the output voltage

becoming excessive in case of transient, due to the slow response of the error amplifier.

However, if contemporaneously the voltage of the INV pin falls below 1.66 V (typ.), a

feedback failure is assumed. In this case the device is latched off. Normal operation can be

resumed only by cycling Vcc, bringing its value lower than 6 V, before moving up to turn-on

the threshold.

Additionally, if the voltage on pin #7 (PFC_OK) is tied below 0.23 V, the L6563S is shut

down. To restart the L6563S operation the voltage on pin #7 (PFC_OK) must increase

above 0.27 V. This function can be used as a remote on/off control input.

To allow the interfacing of the board with a D2D converter the J3 connector allows the

powering of the L6563S with an external Vcc. It also gives the opportunity to manage failure

or abnormal conditions via the PWM_LATCH (#8) and PWM_STOP (#9) pins. The L6563S

operation can also be disabled or enabled to properly manage light load or failure conditions

by the D2D via the PFC_OK pin (#7), still available at pin #5 of J3 (on/off). For further details

please see Section 4.7.