EVL6564-100W STMicroelectronics, EVL6564-100W Datasheet - Page 21

• Manufacturer Part Number: EVL6564-100W
• Description: BOARD EVAL PFC FOR L6564D
• Manufacturer: STMicroelectronics
• Type: Power Factor Correctionr

Specifications of EVL6564-100W

• Main Purpose: AC/DC, Primary Side
• Outputs And Type: 1, Non-Isolated
• Power - Output: 100W
• Voltage - Output: 400V
• Voltage - Input: 90 ~ 265VAC
• Regulator Topology: Boost
• Frequency - Switching: 40kHz
• Board Type: Fully Populated
• Utilized Ic / Part: L6564
• Input Voltage: 90 V to 265 V
• Output Voltage: 400 V
• Dimensions: 90 mm x 83 mm
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free by exemption / RoHS compliant by exemption
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: L6564
• Other names: 497-10164

AN3022
3.4
PFC_OK pin and feedback failure (open loop) protection
During normal operation, the voltage control loop provides for the output voltage (Vout) of
the PFC pre-regulator close to its nominal value, set by the resistors ratio of the feedback
output divider. In the L6564, a pin of the device (PFC_OK, pin #6) has been dedicated to
monitor the output voltage with a separate resistor divider composed of R3, R4, R11 (high)
and R15 (low), see
2.5 V if the output voltage exceeds a preset value (Vovp), usually larger than the maximum
Vout that can be expected, also including worst-case load/line transients.
For the EVL6564-100W we have:
Vo = 400 V, Vovp = 434 V.
Select: R3+R4+R11=8.8MW;
then: R15 = 8.8 MΩ · 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, see an example in
Notice that both feedback dividers connected to L6564 pin #1 (INV) and pin #6 (PFC_OK)
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 behind the pin PFC_OK
detects the voltage gap with respect to pin INV. If the voltage gap is greater than 40 mV and
the OVP is active, the feedback failure protection is triggered. 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 L6564 goes below 6 V and that one of the PWM controller 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.
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.
Figure
1. This divider is selected so that the voltage at the pin reaches
Doc ID 16106 Rev 1
Test results and significant waveforms
Figure
29.
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