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
21/33
voltage exceeds a preset value (V
OVP
), usually larger than the maximum Vout that can be
expected, also including worst-case load/line transients.
●
For the EVL6563H-100W we have:
–
V
O
= 400 V
–
V
OVP
= 434 V
–
Select: R3+R4+R11 = 8.8 M
Ω
then:
–
R15 = 8.8 M
Ω ·2.5/(434-2.5) = 51 kΩ
Once this function is triggered, the gate drive activity is immediately stopped until the
voltage on the pin PFC_OK drops below 2.4 V. An example is given in
voltage on the pin PFC_OK drops below 2.4 V. An example is given in
Notice that both feedback dividers connected to L6563H V_INV (pin #1) and PFC_OK (pin
#7) can be selected without any constraints. The unique criterion is that both dividers have
to sink a current from the output bus which needs to be significantly higher than the current
biasing the error amplifier and PFC_OK comparator.
#7) can be selected without any constraints. The unique criterion is that both dividers have
to sink a current from the output bus which needs to be significantly higher than the current
biasing the error amplifier and PFC_OK comparator.
The OVP function described above is able to handle "normal" overvoltage conditions, i.e.
those resulting from an abrupt load/line change or occurring at startup. In case the
overvoltage is generated by a feedback disconnection, for instance, when one of the upper
resistors of the output divider fails open, an additional circuitry detects the voltage drop of
pin INV. If the voltage on pin INV is lower than 1.66 V and at the same time OVP is active, a
feedback failure is assumed. Thus, the gate drive activity is immediately stopped, the device
is shut down, its quiescent consumption is reduced below 180 µA and the condition is
latched as long as the supply voltage of the IC is above the UVLO threshold. To restart the
system, it is necessary to recycle the input power so that the Vcc voltage of the L6563H
goes below 6 V and that one of the PWM controllers goes below its UVLO threshold.
those resulting from an abrupt load/line change or occurring at startup. In case the
overvoltage is generated by a feedback disconnection, for instance, when one of the upper
resistors of the output divider fails open, an additional circuitry detects the voltage drop of
pin INV. If the voltage on pin INV is lower than 1.66 V and at the same time OVP is active, a
feedback failure is assumed. Thus, the gate drive activity is immediately stopped, the device
is shut down, its quiescent consumption is reduced below 180 µA and the condition is
latched as long as the supply voltage of the IC is above the UVLO threshold. To restart the
system, it is necessary to recycle the input power so that the Vcc voltage of the L6563H
goes below 6 V and that one of the PWM controllers goes below its UVLO threshold.
Note that this function offers a complete protection against not only feedback loop failures or
erroneous settings, but also against a failure of the protection itself. Either resistor of the
PFC_OK divider failing short or open or a PFC_OK pin floating results in shutting down the
IC and stopping the pre-regulator.
erroneous settings, but also against a failure of the protection itself. Either resistor of the
PFC_OK divider failing short or open or a PFC_OK pin floating results in shutting down the
IC and stopping the pre-regulator.
Moreover, the pin PFC_OK doubles its function as a non-latched IC disable. A voltage below
0.23 V shuts down the IC, reducing its consumption below 2 mA. To restart the IC, simply let
the voltage at the pin go above 0.27 V.
0.23 V shuts down the IC, reducing its consumption below 2 mA. To restart the IC, simply let
the voltage at the pin go above 0.27 V.