L6564D STMicroelectronics, L6564D Datasheet - Page 22

• 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

Application information
6.4
Figure 30. THD optimizer circuit
22/33
THD optimizer circuit
The L6564 is provided with a special circuit that reduces the conduction dead-angle
occurring to the AC input current near the zero-crossings of the line voltage (crossover
distortion). In this way the THD (total harmonic distortion) of the current is considerably
reduced.
A major cause of this distortion is the inability of the system to transfer energy effectively
when the instantaneous line voltage is very low. This effect is magnified by the high-
frequency filter capacitor placed after the bridge rectifier, which retains some residual
voltage that causes the diodes of the bridge rectifier to be reverse-biased and the input
current flow to temporarily stop.
To overcome this issue the device forces the PFC pre-regulator to process more energy
near the line voltage zero-crossings as compared to that commanded by the control loop.
This will result in both minimizing the time interval where energy transfer is lacking and fully
discharging the high-frequency filter capacitor after the bridge.
Figure 30
shows the internal block diagram of the THD optimizer circuit.
Doc ID 16202 Rev 2
L6564