AC/DC converter using resonant network for high input power factor

DETAILED DESCRIPTION In FIG.
1 there is shown an AC to DC converter comprising: (a) an input transformer, generally designated 1, for connection to a single phase, high frequency, sinusoidal wave form, AC voltage source 2, the transformer 1, in operation, providing an output matching voltage for, and isolating, the AC voltage source 2, (b) a resonant network, generally designated 4, for converting the single phase, high frequency, sinusoidal wave form AC voltage to a sinusoidal, high frequency bi-directional current output, (c) a current controller, generally designated 6, connected in parallel to the resonant network 4 to receive the sinusoidal high frequency current output therefrom and provide the desired output current from the converter, (d) a diode rectifier, generally designated 8, connected in parallel with the current controller 6 and for converting the bi-directional current into a unidirectional current output, and (e) an output filter, generally designated 10, connected to the rectifier 8 to provide an essentially ripple free, substantially constant voltage, DC output to a load 11.
As shown in FIG.
2, in some embodiments of the present invention the resonant network comprises an inductor 16 and a capacitor 18, with the capacitor 18 connected in series to the output of the inductor 16.
The current controller 6 is a thyristorized, bi-directional switch comprising two anti-parallel, thyristor switches 20 and 22.
The diode rectifier comprises four diodes 24 to 27.
The output filter 10 comprises a capacitor.
In operation a single phase, high frequency, sinusoidal wave form, AC voltage from source 2 is applied to the primary winding 12 of the transformer 1 and the secondary winding 14 providing a matching output voltage for, and isolates the remaining circuit from, the source 2.
The matching output from the secondary winding 14 of the transformer 1 is fed to the inductor 16.
Both of the series components of the resonant network 4, that is, the inductor 16 and the capacitor 18 are tuned closely to the operating frequency of the input from the single phase, high frequency, sinusoidal wave form, AC voltage source 2, so that these components offer close to zero impedance for fundamental current and very high impedance to harmonic currents to keep the total harmonic current distortion of the input current to a minimum