STEVAL-ISF001V1 STMicroelectronics, STEVAL-ISF001V1 Datasheet - Page 21

• Manufacturer Part Number: STEVAL-ISF001V1
• Description: BOARD EVAL FOR L6563/STW55NM60N
• Manufacturer: STMicroelectronics
• Type: MOSFET & Power Driverr

Specifications of STEVAL-ISF001V1

• Main Purpose: Power Management, Power Factor Correction
• Embedded: No
• Utilized Ic / Part: L6563
• Primary Attributes: 3 kW, 400 V Out, FOT(Fixed Off Time Control), 240 VAC (185 ~ 265 Vrms)
• Secondary Attributes: Iout Max 7.5 A
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: STW55NM60N
• Other names: 497-8850

L6563 - L6563A
6.4
THD optimizer circuit
The L6563/A 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 37 shows the internal block diagram of the THD optimizer circuit.
Figure 37. THD optimizer circuit
@ Vac1
@ Vac1
@ Vac2 > Vac1
@ Vac2 > Vac1
MULT
MULT
t
t
t
t
VFF
VFF
1 / V
1 / V
1 / V
GENERATOR
GENERATOR
GENERATOR
2
2
2
MULTIPLIER
MULTIPLIER
MULTIPLIER
OFFSET
OFFSET
OFFSET
COMP
COMP
t
t
+
+
+
+
t
t
comparator
comparator
Application information
to PWM
to PWM
t
t
t
t
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