Browse Prior Art Database

Analog Models for Flyback Topology Switching Converter Power Stages in Discontinuous Mode

IP.com Disclosure Number: IPCOM000099545D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 105K

Publishing Venue

IBM

Related People

Kelkar, S: AUTHOR

Abstract

An effective technique for the simulation of switching converter power processors has been disclosed earlier [1] using analog models for the switching portions of the circuit. The models developed earlier were for the continuous mode of operation. Switching converters operating in the discontinuous mode present different modeling problems and form the subject of this disclosure, in which models for the flyback topology are discussed. Flyback topology power processors are often operated in the discontinuous mode to improve stability and the models presented retain all of the advantages of the earlier models viz. ease of use, generality and flexibility. The models can be used in system level simulation of such processors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Analog Models for Flyback Topology Switching Converter Power Stages in Discontinuous Mode

       An effective technique for the simulation of switching
converter power processors has been disclosed earlier [1] using
analog models for the switching portions of the circuit.  The models
developed earlier were for the continuous mode of operation.
Switching converters operating in the discontinuous mode present
different modeling problems and form the subject of this disclosure,
in which models for the flyback topology are discussed. Flyback
topology power processors are often operated in the discontinuous
mode to improve stability and the models presented retain all of the
advantages of the earlier models viz. ease of use, generality and
flexibility.  The models can be used in system level simulation of
such processors.

      Fig. 1 shows the power stage of a typical two output flyback
switching converter.  The coupled inductor stores energy in the
primary winding (Np turns) when the switch is turned on and
discharges into the load and the output capacitor in the interval
that the switch is off.  The two secondary windings (Ns1 and Ns2
turns) thus will carry current only while the switch in the primary
is turned off. The flux in the core of the coupled inductor will
always be greater than zero if the circuit is operated in continuous
mode, while in the discontinuous mode the flux and hence the current
in the secondary windings will be at zero for part of each cycle.
Each cycle is thus composed of three regions -- the ON region when
the switch in the power stage is on, the first OFF region when
current flows in the secondary windings and the reminder when there
is no current in any winding.

      The switching portion of the circuit comprises the transistor,
the coupled inductor and the output diodes and the intention, as in
earlier work, is to develop analog models for this digital part of
the circuit.  The analog model can then be used along with the rest
of the circuit to simulate circuit action; the use of analog models
leads to an efficient technique and avoids convergence, CPU time and
storage problems.

      The state space averaging technique [2] is used to develop an
equivalent nonlinear equation that describes circuit behavior over a
complete cycle.  The key step is the synt...