8.7 Switching Frequency
Figure 8-7. Average Switching Frequency vs. Input
at 20-Vo Full Load
Figure 8-8. Maximum switching frequency about
240 kHz (Yellow = PWML, Green = Transformer
Primary Winding Current, Red = Switch Node
Voltage
8.8 Key Switching Waveforms and Operation Mode Load Current
This section shows typical operation modes in
along with typical load currents in this design and with
Vin = 115Vac and Vo = 20V as an example.
• AAM: Adaptive Amplitude Modulation
• ABM: Adaptive Burst Mode
• LPM: Low Power Mode
• SBP1: First Standby Power Mode
• SBP2: Second Standby Power Mode
Table 8-5. Operation Mode and Load Current at 20-V Output and 115Vac Input
Mode
AAM
ABM
LPM
SBP1
SBP2
Survival
Burst Frequency,
f
BUR
Not Applicable
> 25kHz (2 to 9
pulses)
about 25kHz (2
pulses)
8.5kHz to 25kHz (2
pulses)
< 8.5kHz (2
pulses)
about 8 pulses
Typical Load
Current
1.8 A to 3.25 A
0.5 A to 1.8 A
0.2 A to 0.5 A
0.1 A to 0.2 A
< 0.1 A
Not Applicable
Figure 8-9. Typcial Waveform in AAM Operation
Yellow = PWML, Red = PWMH, Green =
Transformer Primary Winding Current (0.2 V/A),
Blue = Switch Node Voltage
Figure 8-10. Typical Waveform in ABM Operation
Yellow = PWML, Red = PWMH, Green =
Transformer Primary Winding Current (0.2 V/A),
Blue = Switch Node Voltage
Performance Data and Typical Characteristic Curves
SLUUBZ3B – MAY 2020 – REVISED AUGUST 2020
Using the UCC28782EVM-030 65-W USB-C PD High-Density Active-Clamp
Flyback Converter
17
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