EVL6566A-75WADP Datasheet, PDF (4/8 Pages) STMicroelectronics – 19 V - 75 W laptop adapter with tracking boost PFC pre-regulator, using the L6563 and the L6566A

Light load condition (fold back frequency)
EVL6566A-75WADP
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Light load condition (fold back frequency)
To improve the efficiency at light load, a frequency shifting has been implemented on the
board. Thus, at decreasing load, the frequency also decreases. Figure 4 and Figure 5 below
show the drain and gate fly-back waveforms and the relevant switching frequency with a
load of 0.2 A.
Figure 4. L6566A fly-back stage
waveforms at 115 V-60 Hz 0.2 A
Figure 5. L6566A fly-back stage
waveforms at 230 V-50 Hz full load
CH1: drain 6566A
CH2: gate 6566A
CH1: drain 6566A
CH2: gate 6566A
Table 2 below shows the efficiency when we set the power input with 2.4 or 1.7 W in two
different voltage inputs with the fold back network plugged in.
Table 2.
Standby consumption
Light load condition
Pin
Pout
Efficiency
Vin = 230 V
2.40
1.51
62.9%
1.69
1.06
62.7%
Vin = 115 V
2.41
1.70
70.5%
1.71
1.14
66.7%
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