STMicroelectronics L6563H 100 W TM PFC demonstration board EVL6563H-100W EVL6563H-100W Data Sheet
Product codes
EVL6563H-100W
AN3063
Test results and significant waveforms
Doc ID 16261 Rev 3
23/33
4.6
TBO (tracking boost option)
To use the TBO function on L6563H, a dedicated input of the multiplier is available on pin #6
(TBO). The function can be implemented by simply connecting a resistor (RT) between the
TBO pin and ground.
(TBO). The function can be implemented by simply connecting a resistor (RT) between the
TBO pin and ground.
Usually, in traditional PFC stages, the DC output voltage is regulated at a fixed value
(typically 400 volt) but in some applications, it may be advantageous to regulate the PFC
output voltage with the "tracking boost" or "follower boost" approach. In this way the circuit
with the TBO function provides better efficiency and, thanks to the lower differential voltage
across the boost inductor, the value of L2 can be reduced as compared to the same circuit
without the TBO function.
(typically 400 volt) but in some applications, it may be advantageous to regulate the PFC
output voltage with the "tracking boost" or "follower boost" approach. In this way the circuit
with the TBO function provides better efficiency and, thanks to the lower differential voltage
across the boost inductor, the value of L2 can be reduced as compared to the same circuit
without the TBO function.
The TBO pin presents a DC level equal to the peak of the MULT pin voltage and is
representative of the mains RMS voltage. The resistor defines a current, equal to
V(TBO)/RT, that is internally 1:1 mirrored and sunk from pin INV (pin 1) input of the error
amplifier. In this way, when the mains voltage increases, the voltage at the TBO pin
increases also as well as the current flowing through the resistor connected between TBO
and GND. Then a larger current will be sunk by the INV pin and the output voltage of the
PFC pre-regulator will be forced to go higher. Obviously, the output voltage will move in the
opposite direction if the input voltage decreases.
representative of the mains RMS voltage. The resistor defines a current, equal to
V(TBO)/RT, that is internally 1:1 mirrored and sunk from pin INV (pin 1) input of the error
amplifier. In this way, when the mains voltage increases, the voltage at the TBO pin
increases also as well as the current flowing through the resistor connected between TBO
and GND. Then a larger current will be sunk by the INV pin and the output voltage of the
PFC pre-regulator will be forced to go higher. Obviously, the output voltage will move in the
opposite direction if the input voltage decreases.
To avoid an undesired output voltage rise should the mains voltage exceed the maximum
specified value, the voltage at the TBO pin is clamped at 3 V. By properly selecting the
multiplier bias it is possible to set the maximum input voltage above which input-to-output
tracking ends and the output voltage becomes constant. If this application is not used, leave
the pin open. The device will regulate at a fixed output voltage.
specified value, the voltage at the TBO pin is clamped at 3 V. By properly selecting the
multiplier bias it is possible to set the maximum input voltage above which input-to-output
tracking ends and the output voltage becomes constant. If this application is not used, leave
the pin open. The device will regulate at a fixed output voltage.
4.7
Power management and housekeeping functions
A special feature of the L6563H is that it facilitates the implementation of the
"housekeeping" circuitry needed to coordinate the operation of the PFC stage to that of the
cascaded DC-DC converter. The functions implemented by the housekeeping circuitry
ensure that transient conditions like power-up or power-down sequencing or failures of
either power stage are properly handled. The L6563H provides pins to do that.
"housekeeping" circuitry needed to coordinate the operation of the PFC stage to that of the
cascaded DC-DC converter. The functions implemented by the housekeeping circuitry
ensure that transient conditions like power-up or power-down sequencing or failures of
either power stage are properly handled. The L6563H provides pins to do that.
As already mentioned, one communication line between the L6563H and the PWM
controller of the cascaded DC-DC converter is the PWM_LATCH (pin #8), which is normally
open when the PFC works properly. It goes high if the L6563H loses control of the output
voltage (because of a failure of the control loop), with the aim of latching off the PWM
controller of the cascaded DC-DC converter as well.
controller of the cascaded DC-DC converter is the PWM_LATCH (pin #8), which is normally
open when the PFC works properly. It goes high if the L6563H loses control of the output
voltage (because of a failure of the control loop), with the aim of latching off the PWM
controller of the cascaded DC-DC converter as well.
A second communication line can be established via the disable function included in the
RUN pin. Typically, this line is used to allow the PWM controller of the cascaded DC-DC
converter to shut down the L6563H in case of light load, in order to minimize the no-load
input consumption of the power supply.
RUN pin. Typically, this line is used to allow the PWM controller of the cascaded DC-DC
converter to shut down the L6563H in case of light load, in order to minimize the no-load
input consumption of the power supply.