Electric power conversion systems – Current conversion – Using semiconductor-type converter
Patent
1993-06-21
1994-12-06
Stephan, Steven L.
Electric power conversion systems
Current conversion
Using semiconductor-type converter
315209R, H02M 75387, H05B 3702
Patent
active
053716680
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to inverters.
More particularly, the invention relates to inverters of the kind comprising a resonant circuit including a capacitor and an inductor, a first main switching device arranged to conduct current from a d.c. source in one direction through the capacitor and inductor, a second main switching device arranged to conduct current from the d.c. source through the capacitor and inductor in the opposite direction, and drive means for causing the switching devices to conduct alternately, the drive means comprising a transformer having a primary winding in series with the capacitor and inductor and two secondary windings arranged to provide drive signals to the respective main switching devices.
2. Description of Related Art
An inverter of this kind is described in published European patent application EP-A-0 121 917. The described inverter operates at the resonant frequency of the resonant circuit, the main switching devices being switched at the zero crossing points of the oscillatory current in the resonant circuit, and there is no means of controlling the power output of the inverter.
A paper by Sebastian et al, entitled "Regulating Self-Oscillating Resonant Converters", 2nd European Conference on Power Electronics and Applications held at Grenoble, France, on 22-24 Sep., 1987 describes an inverter in which switching of the field-effect transistors forming the main switching devices is effected by two saturable transformers with primaries connected in the resonant circuit and secondaries connected to the gates of the field-effect transistors, so that the drive to each transistor is removed when the associated transformer saturates. Each transformer has an additional winding through which a variable controlled d.c. current is fed, to control the point at which the transformer saturates. The switching of the transistors can thereby be controlled to control the phase difference between the voltage and current in the resonant circuit so as to control the power output of the inverter. However, the described inverter is relatively complex.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved inverter.
In accordance with this invention, an inverter of the kind set forth is provided with control means fop controlling the switching of the main switching devices, the control means comprising means for sensing reversal of current in the resonant circuit after one of the main switching devices has been turned on, means for turning off the switching device a predetermined time after current reversal, and means for varying the predetermined time.
Preferably, the means for sensing reversal of current comprises an additional transformer having a primary winding connected in the resonant circuit and a secondary winding connected to timing means operable to provide a signal for turning off the main switching device after the predetermined time.
In one form of the invention, the means for turning off the main switching device comprises a secondary switching device connected across the associated secondary winding of the drive transformer so as to remove the drive from the main switching device when the secondary switching device is turned on by the signal from the timing means.
Preferably, the drive transformer has a core of magnetisable material with a square hysteresis loop characteristic, so that following turning off of the said main switching device a predetermined time after current reversal, the other main switching device is turned off by saturation of the drive transformer after a period of time from the next current reversal equal to the said predetermined time.
In one form of the invention, the first and second main switching devices are connected in series across the d.c. source, two capacitors are connected in series across the d.c. source, and the capacitor and inductor of the resonant circuit are connected in series between the junction of the said two capacitors and the junction of the main switc
REFERENCES:
patent: 4346332 (1982-08-01), Walden
patent: 4857806 (1989-08-01), Nilssen
patent: 4952845 (1990-08-01), Veldman
patent: 5032782 (1991-07-01), Nilssen
patent: 5039919 (1991-08-01), Nilssen
patent: 5062031 (1991-10-01), Flachenecker et al.
Gurwicz David
Morris Paul
Nada Electronics Limited
Nguyen Matthew
Stephan Steven L.
LandOfFree
Resonant inverter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Resonant inverter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resonant inverter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-219018