Electric power conversion systems – Current conversion – Using semiconductor-type converter
Patent
1999-03-18
2000-05-23
Riley, Shawn
Electric power conversion systems
Current conversion
Using semiconductor-type converter
363127, H02M 75387
Patent
active
060672439
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an AC/AC converter having the function of converting voltage/current of electrical energy, that is widely used in various electronic devices, domestic appliances, personal power generators, various industrial installations, and power generators etc.
Technical Background
A transformer such as that shown in FIG. 21, for example, is generally used as an AC transformer, which is a conventional AC/AC converter. However, this type of transformer has an output voltage regulated by a turns ratio of a primary winding to a secondary winding, which means that it is difficult to obtain an arbitrary voltage. Moreover, there is also a problem that because the main materials for such a transformer are iron and copper, it becomes extremely heavy and large in size.
On the other hand, there have been various suggestions for AC control devices having AC input and AC output that use semiconductor elements, but the devices shown in FIG. 22 and FIG. 23 are known.
In FIG. 22, reference numeral 11 is a rectifier, reference numeral 12 is a smoothing circuit, reference numeral 13 is an inverter, reference numeral 14 is a high frequency filter, and reference numeral 15 is a step-up transformer. In a device having such a structure, an AC input is rectified to DC by the rectifier 11, ripple components are removed by the smoothing circuit 12, output from the smoothing circuit 12 is subjected to high speed switching processing in the inverter 13 using well known PWM (pulse width modulation) control, turned back into low frequency AC by the high frequency filter 14, and converted as necessary to a desired voltage by the step-up transformer 15.
Also, in the device of FIG. 23, an AC input is rectified by a rectifier 11, an output of a smoothing circuit 12 is input to a power amplifier 16 and made into AC of a desired power, and converted to a desired voltage as required by the step-up transformer 15.
Such AC control devices enable high speed control, for example, for an input fluctuation of .+-.20% in a 100V AC input, an output of 100V .+-.0.1% is possible.
However, because input AC is temporarily converted to DC and then re-converted to AC, the circuit structure is complicated, re-converted AC becomes less reliable and conversion efficiency is bad. Also, because the step-up transformer 15 is a low frequency transformer, it becomes heavy and large in size, and there is a problem that it is difficult to reduce the size or weight of a device.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a high reliability AC/AC converter that is small in size and light in weight.
The present invention provides an AC-AC/DC converter in which an AC input or an AC input voltage-divided by a capacitor is converted into a high frequency AC by a control unit which turns on and off AC switches operable bi-directionally in the forward and reverse directions. The high frequency AC is applied to a primary winding of a high frequency transformer including primary and secondary windings. The high frequency AC induced at the secondary winding is demodulated into an AC output or is rectified into a DC output by turning on and off the bi-directional AC switches under the control of the control unit. The demodulated AC output or rectified DC output is supplied to a load via a high frequency filter.
The control unit can sequentially control a voltage of an AC or DC output to have a value in a range from a maximum value of a positive phase or polarity, passing through zero, to a maximum value of a negative phase or polarity, using a pulse phase modulation control technique in which a phase of a driving pulse at a demodulation side switch is varied in accordance with a phase of a driving pulse of AC switches for modulating the AC input into a high frequency AC.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a circuit diagram showing the basic structure of an AC/AC converter of a first embodiment of the present invention.
FIG. 1B is a drawing showing waveforms at each of points N1-N4 in FIG.
REFERENCES:
patent: 3517300 (1970-06-01), McMurray
patent: 3564390 (1971-02-01), Stratton
patent: 5255174 (1993-10-01), Murugan
patent: 5570279 (1996-10-01), Venkataramanan
Sugawara Isao
Suzuki Yasunobu
Chiyoda Corporation
I-Hits Laboratory Corporation
Riley Shawn
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