Download based discontinuous conduction mode (DCM) detection technique

Digital DCM Detection and Mixed Conduction Mode
Control for Boost PFC Converters
ABSTRACT
This paper presents a control technique and DSP-PIC based DCM
detection method to provide simple MCM control of the boost PFC converter. By
using integrated high-speed comparators so the need for a costly auxiliary winding
to detect zero inductor current is eliminated, as well as providing detection of
DCM operation without knowledge of the power converter component values.
This paper presents a novel mixed conduction mode (MCM) digital
controller with a digital signal processor (DSP-PIC) based discontinuous
conduction mode (DCM) detection technique to realize total harmonic distortion
(THD) and power factor improvements in boost power factor correction (PFC)
converters operating in both continuous conduction mode (CCM) and DCM
during a single ac line half-cycle. By using DSP-PIC simple and cost-reductions
over existing DCM and zero-current detection methods are made possible.
Additionally, performance improvements over a conventional CCM digital control
technique are possible with simple software modification, and can be extended to
existing boost PFC converter designs provided a compatible DSP-PIC is present.
Existing System
 Digital feed forward control.
 MCM boost converter by using an auxiliary winding.
 Voltage comparator to measure the length of the DCM period.
Drawbacks of Existing System

Need of auxiliary windings to detect zero inductor current.
 Need more cost to install an additional winding to the boost inductor.
 Feedforward control technique is the need for comparison and computation
of two separate feedforward terms.
 Required more components.
Proposed System
 DSP PIC-based DCM detection method to provide MCM control of the
boost PFC converter.
Advantages of Proposed System
 It can detect DCM without knowledge of the power converter component
values.

The need for a costly auxiliary winding to detect zero inductor current is
eliminated.

It consists of high speed comparators.

The proposed control method requires only simple modification to existing
control software.

Total Harmonic distortion is reduced.
Applications

Constant frequency control.

This technique is applicable for any converter operating in DCM including
power factor correctors (PFC).

The DSP PIC-based control can achieve a power factor higher than 0.99 in
the entire line range.

Applicable for a flyback converter operating in discontinuous conduction
mode (DCM).

DC-DC Buck-Boost converter.