The present invention relates to a power supply apparatus including a plurality of power supply units connected in parallel with each other.
Such power supply apparatus has been used in such a case that a single power supply unit cannot supply the power required by a load. Such power supply apparatus includes a plurality, for example, two, of power supply units to which a DC voltage is applied from a DC power source. The DC voltage is converted into a high-frequency voltage in inverters of the respective power supply units. The high-frequency voltages are then voltage-transformed in transformers, and rectified in respective rectifiers. The rectified voltages are smoothed by smoothing reactors. The smoothed voltages are developed between output terminals for application to a load. Currents supplied by the respective power supply units to the load are detected by control units of the power supply units, and the inverters are individually controlled by the associated control units in such a manner as to make the load current equal to a predetermined value.
The reactors are used to smooth the outputs of the rectifiers. Also, the reactors absorb a voltage difference between the output voltages of the inverters which would be caused when the inverters are controlled differently from each other. Such reactors each include a core and are large in size, which makes it impossible to downsize power supply apparatuses.
An object of the present invention is to make improvements to a reactor to thereby provide a parallel-type power supply apparatus having a small size.
A power supply apparatus according to the present invention includes at least two power supply units. Each unit includes a DC-to-high-frequency converter which receives a DC voltage and converts the received DC voltage to a high-frequency voltage. A transformer in each power supply unit voltage transforms the high-frequency voltage, and a rectifier rectifies the output voltage of the transformer. A reactor in each unit smoothes the rectifier output. The power supply units have their inputs connected in parallel with each other and connected to a DC source providing the DC voltage, and have their outputs connected in parallel with each other and to a load. The reactors have their windings loosely coupled with each other on a single core.
The core may have a center part, and at least two outer legs which are disposed on opposite sides of the center part and extend along the length of the center part. Each of the outer legs has a gap in it, and reactor windings are wound on the outer legs.
The gaps in the legs can be formed at locations corresponding to substantially the midpoint of the center part. In this case, the core is formed of two like members which are located on opposite sides of a plane passing through the gaps and the center part.
The core may include first, second and third members. Each of the first and second members has a center leg and at least two outer legs. The center legs of the first and second members have the same length. The outer legs of each member are disposed on opposite sides of the center leg, being spaced from the center leg, and have the same length as the center leg. The third member is interposed between the center legs of the first and second members so that the corresponding outer legs of the first and second members can face each other with a spacing disposed between them.
The DC-to-high-frequency converters of the power supply units may be controlled by a common control signal provided by a control unit common to the power supply units.
The common control unit may include detecting means for detecting an output signal coupled to the load, an error detecting means for detecting the difference between the output signal and a predetermined reference signal and develops an error signal representative of the detected difference, and control signal generating means for generating the common control signal based on the error signal. The output signal detecting means may detect current, voltage or power provided for the load. Alternatively, the output signal detecting means may be so arranged as to detect both current and voltage supplied to the load, and the error detecting means may be so arranged as to detect the difference between the detected current and a predetermined reference value and the difference between the detected voltage and a predetermined reference value.
Current detecting means may be used to detect current supplied by each of the DC-to-high-frequency converters to its associated transformer. Comparing means is associated with each current detecting means for comparing the current detected by that current detecting means with a reference signal representative of current to be supplied by that DC-to-high-frequency converter. Interrupting means is used to interrupt the coupling of the common control signal to the DC-to-high-frequency converter which supplies current, as detected by the current detecting means, greater than the reference signal.