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Resonant power processing at a fixed frequency using a controllable inductance

Citation

Vollin, Jeffrey Lance (1994) Resonant power processing at a fixed frequency using a controllable inductance. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-06212005-102928

Abstract

Power processing at high frequencies often involves the use of resonant conversion techniques. Most of these techniques require the use of a variable switching frequency to provide control over the output voltage or current. In many applications this variable switching frequency is not tolerable and another method of regulation is required. A novel device called a magnetic regulator can be used in conjunction with a resonant DC-to-DC converter to provide regulation of the output voltage or current at a fixed switching frequency. This device resembles an ordinary transformer except with an additional winding which provides control over the input-output conversion ratio.

Prior to the use of the magnetic regulator, suitable resonant DC-to-DC converters are identified and partitioned into a resonant inverter which converts the incoming DC energy into high frequency AC energy and into a rectifier circuit which converts the AC back to DC. The candidate inverters used include the Class E and Class D Zero-Voltage-Switched circuits. Since the rectifier circuit must be compatible with the choice of the inverter, the design details of such a rectifier are presented.

The magnetic regulator is modeled using the reluctance concept exposing the true nature of the regulation mechanism. The control current changes the permeability of a portion of the core of the device which results in a current-controlled leakage inductance.

The magnetic regulator may be inserted into the forward power path of a resonant DC-to-DC converter. In the process, it is possible to integrate the resonant inductor and a matching inductor into the basic structure of the magnetic regulator. The result is a high frequency, resonant converter with only one or two magnetic components which can be controlled by a low-level control signal without resorting to a variable switching frequency.

The inclusion of a variable inductance poses special problems in the design and modeling of the control loop which regulates this family of converters. The small-signal model of the magnetic regulator is derived and verified with experimental results. This model is then incorporated into a model for the DC-to-DC converter. The converter model is presented with three levels of complexity beginning with a very simple model which exposes the contribution of the magnetic regulator to the overall response of the converter. The model is further refined to include a bilateral model for a resonant rectifier with a final bilateral model for the inverter.

The model of the complete DC-to-DC converter is compared against simulated data from the computer program SPICE and also against measured data on a typical converter. The model is shown to contain low frequency dynamics dominated by the input and output filters on the converter, and high frequency dynamics associated with the resonant circuit elements. The models developed are continuous-time average models which are conveniently represented using equivalent circuits.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Cuk, Slobodan (advisor)
  • Middlebrook, Robert David (co-advisor)
Thesis Committee:
  • Unknown, Unknown
Defense Date:6 October 1993
Record Number:CaltechETD:etd-06212005-102928
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-06212005-102928
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2670
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:24 Jun 2005
Last Modified:26 Dec 2012 02:53

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