Written Date
2010.05.30
Document No.
Change code
0
File/Reference
Operation Manual.DOC
Page
(12/21)
DONGAH ELECOMM R&D CENTER
All rights are reserved.
6.2.2 Inrush Control Circuit
The Inrush Control circuitry limits large peak currents that occur during module startup, often attributed
to currents pulled directly from the input capacitor.
6.2.3 Power Factor Correction (PFC)
The Active Boost PFC topology controls the duty cycle of the FET so the PFC Inductor pulls sinusoidal
current from the AC Line. The PFC Circuit components include the Inductor, a switching FET, a rectifier
diode, a DC capacitor, and a Control Circuit that feeds back into the gate of the switching FET.
a. PFC Inductor
When the PFC switching FET is on, the current increases in the PFC Inductor. When the FET is off, the
magnetic field collapses and inductor current desreases as it feeds current into the PFC capacitor.
b. PFC FET
The PFC FET controls the current in the PFC Inductor, forming a sinusoidal current based on the duty
cycle changes delivered from the variable PWM signal delivered by the PFC Control Circuit.
c. PFC Diode / Capacitor
The PFC diode allows energy stored in the PFC Inductor to transfer into the PFC DC Bus capacitor.
d. PFC Control Circuit
The PFC Control Circuit feeds a 66KHz PWM gate signal to the PFC FET. The duty cycle of the PWM
6.2.5 Main Switching Circuit
The Main Switching circuit uses a FET-switched DC to transfer power across the main transformer.
The Main Switching Circuit operates as follows:
a. Main FET
The Main FET switches at ~100KHz with a variable duty cycle from the Main Control Circuit, which
regulates the output voltage. As a result, the ~385Vdc PFC Bus voltage is sinusoidal and the energy
is transferred from the Main transformer primary to the secondary windings.
b. Main Transformer
The Main Transformer passes the power from the primary winding over to the magnetically-coupled
secondary during the on-time of the Main FET. The primary-to-secondary windings have a turns ratio
that steps down the voltage on the secondary, which will then be rectified to the desired DC output.
The PFC Circuit operates as follows:
signal is based on comparing the input current/voltage waveforms to the output voltage (~385Vdc).
The Control Circuit includes a protection circuit that will shut down the output of the rectifier when the
output becomes less than 300Vdc due to failure of the feedback loop or other critical circuit elements.
Main PWM Control circui
