Electricity: electrical systems and devices – Safety and protection of systems and devices – Voltage regulator protective circuits
Patent
1986-06-30
1987-09-22
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Voltage regulator protective circuits
323222, H02H 710
Patent
active
046954139
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention relates to a protective circuit for a hacker type D.C. converter in which a series circuit including a coil, a diode and a capacitor is connected to the poles of a supply voltage source, and in which a connection point between the coil and the diode is connected to the end of the capacitor facing away from the diode via a controllable switching element which is adapted for periodically changing between open and closed states.
BACKGROUND
A converter of the kind mention above is illustrated, for example, in German Pat. No. DE 2,644,715 in FIG. 25. Large power losses occur in such a converter, particularly when converting high voltages and at high power take-off. The losses occur particularly in the diode, through which a reverse current occurs each time the switching element closes. Losses in the double also occur when it is in on-state condition in the forward direction. These so-called on-state losses dominate at comparatively low switching frequencies for example at the supply frequency (50-60 Hz). On the other hand, the switching-off losses of the diode dominate when hacking at high frequency, e.g. 20 kHz, particularly in conjunction with high voltages, e.g. 400 volts, and high current strengths. Apart from the disadvantages which the losses intrinsically are, they also result, together with the heavy voltage and current variations occurring in the converter, in that the diode and switch are subjected to large stresses and are easily damaged. The current variations also give rise to radio interference, which can disturb the apparatus in which the converter is included and other apparatus as well.
The known converter according to the above has been provided with a protective circuit for decreasing the power losses and high voltages at the switch. However, it has been found difficult to get a circuit of this kind to function satisfactorily. Furthermore, the losses are increased due to energy that has been preciously stored in coils capacitors, being subsequently consumed in resistors.
SUMMARY OF INVENTION
An object of the present invention is to provide a protective circuit for D.C. converter of the kind mentioned above, with the aid of which power losses as well as rapid voltage and current variations can be reduced considerably. This is achieved in principle by two suitably selected inductive elements being inserted in series with the diode, and in that a second diode is connected in parallel with these inductive elements and the diode.
To achieve the above and other objects of the invention, there is provided a hacker type D.C. converter circuit having protective circuit features. The converter circuit comprises a supply voltage source, and a series circuit including a first coil, a first diode and a first capacitor. The series circuit is connected to the supply voltage source.
In addition, there is included a controllable switching arrangement, a connection junction between the first coil and first diode, and a further diode coupling across the switching arrangement.
The first capacitor includes a first terminal remote from said further diode and a second terminal proximate the further diode. The connection junction is connected to the first terminal of the first capacitor remote from the further diode across the controllable switching arrangement which periodically alternates between open and closed states.
The series between the connection junction and the first diode further includes an inductor and a second coil which is inductively connected to the first coil. A second diode is connected in a parallel circuit from the connection junction mentioned above and across the first diode of the first capacitor.
Other features of the invention include that a resistor is connected in the above-mentioned parallel circuit in series with the second diode and that the first diode has a lower threshhold voltage than the second diode. Another feature is that the first capacitor is connected in parallel with a second capacitor which from an impedance aspect is a shorter dist
REFERENCES:
patent: 3265956 (1966-08-01), Schlabach
patent: 4131843 (1978-12-01), Koyama et al.
patent: 4346431 (1982-08-01), Steigerwald
patent: 4363067 (1982-12-01), Kadomski
patent: 4566051 (1986-01-01), Komulainen
Ekelund Folke J. B.
Lilja Per O.
Stahl Matts F.
Wald Roland J. E.
Pellinen A. D.
Telefonaktiebolaget LM Ericsson
Wysocki A. Jonathan
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