L6564D STMicroelectronics, L6564D Datasheet - Page 23

• Manufacturer Part Number: L6564D
• Description: IC PFC CTRLR TRANSITION 10SSOP
• Manufacturer: STMicroelectronics

Specifications of L6564D

• Mode: Discontinuous (Transition)
• Frequency - Switching: 1MHz
• Current - Startup: 90µA
• Voltage - Supply: 10.3 V ~ 22.5 V
• Operating Temperature: -25°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: L6564; L6564

L6564
Figure 31. THD optimization: standard TM PFC controller (left side) and L6564 (right side)
6.5
Essentially, the circuit artificially increases the ON-time of the power switch with a positive
offset added to the output of the multiplier in the proximity of the line voltage zero-crossings.
This offset is reduced as the instantaneous line voltage increases, so that it becomes
negligible as the line voltage moves toward the top of the sinusoid. Furthermore the offset is
modulated by the voltage on the VFF pin (see “Voltage Feedforward” section) so as to have
little offset at low line, where energy transfer at zero crossings is typically quite good, and a
larger offset at high line where the energy transfer gets worse.
The effect of the circuit is shown in
PFC controller are compared to those of this chip.
To take maximum benefit from the THD optimizer circuit, the high-frequency filter capacitor
after the bridge rectifier should be minimized, compatibly with EMI filtering needs. A large
capacitance, in fact, introduces a conduction dead-angle of the AC input current in itself -
even with an ideal energy transfer by the PFC pre-regulator - thus reducing the effectiveness
of the optimizer circuit.
Inductor saturation detection
Boost inductor's hard saturation may be a fatal event for a PFC pre-regulator: the current up-
slope becomes so large (50-100 times steeper, see
propagation delay the current may reach abnormally high values. The voltage drop caused
by this abnormal current on the sense resistor reduces the gate-to-source voltage, so that
the MOSFET may work in the active region and dissipate a huge amount of power, which
leads to a catastrophic failure after few switching cycles.
Input current
Imains
Rectified mains voltage
Input current
MOSFET's drain voltage
Vdrain
Doc ID 16202 Rev 2
Figure 31
Input current
Imains
, where the key waveforms of a standard TM
Figure 32
Rectified mains voltage
) that during the current sense
MOSFET's drain voltage
Input current
Application information
Vdrain
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