L6564T STMicroelectronics, L6564T Datasheet - Page 25

• Manufacturer Part Number: L6564T
• Description: 10 pin transition-mode PFC controller for outdoor applications
• Manufacturer: STMicroelectronics

L6564T
6.6
Power management/housekeeping functions
A communication line with the control IC of the cascaded DC-DC converter can be
established via the disable function included in the PFC_OK pin (see
details). This line is typically used to allow the PWM controller of the cascaded DC-DC
converter to shut down the L6564T in case of light load and to minimize the no-load input
consumption. Should the residual consumption of the chip be an issue, it is also possible to
cut down the supply voltage. The interface circuits are shown in
this operation assumes that the cascaded DC-DC converter stage works as the master and
the PFC stage as the slave or, in other words, that the DC-DC stage starts first, it powers
both controllers and enables/disables the operation of the PFC stage.
Figure 33. Interface circuits that let DC-DC converter's controller IC disable the
Another function available is the brownout protection which is basically a not-latched
shutdown function that is activated when a condition of mains undervoltage is detected. This
condition may cause overheating of the primary power section due to an excess of RMS
current. Brownout can also cause the PFC pre-regulator to function in open loop and this
may be dangerous to the PFC stage itself and the downstream converter, should the input
voltage return abruptly to its rated value. Another problem is the spurious restarts that may
occur during converter power-down and that cause the output voltage of the converter not to
decay to zero monotonically. For these reasons it is usually preferable to shut down the unit
in case of brownout. The brownout threshold is internally fixed at 0.8 V and is sensed on pin
VFF (5) during the voltage falling and an 80 mV threshold hysteresis prevents rebounding at
input voltage turn-off. In
mentioned working conditions that cause the device to stop operating.
L6564T
Table 5
Doc ID 022671 Rev 1
it is possible to find a summary of all of the above
Figure 32
Application information
Section 6.2
. Needless to say,
for more
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