Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With bootstrap circuit
Reexamination Certificate
1999-04-28
2001-05-01
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With bootstrap circuit
C327S390000, C326S088000
Reexamination Certificate
active
06225862
ABSTRACT:
BACKGROUND OF THE INVENTION
Series resonant circuits are widely used in conjunction with electronic switching devices to perform DC/DC power conversion.
Such circuits are generally called “series resonant converters” and are susceptible to destruction in case of overloads or short circuits, particularly when operating at their resonant frequency.
SUMMARY OF THE INVENTION
To summarize, according to the present invention, a series resonant circuit including a power source, an inductor and a capacitance is provided. The resonant capacitance includes two capacitors, connected to form a voltage doubler.
Two rectifiers clamp the resonant capacitors' voltage to the output voltage, so the voltage on the resonant capacitors is limited under overload conditions.
Under a short circuit, the amplitude of the voltage on the resonant capacitors is zero. The capacitors are effectively eliminated from the circuit and the output current is limited to a value determined by the input voltage, switching frequency and the resonant inductor. Thus, short circuit protection is achieved.
Briefly described, in a first aspect, the present invention includes a voltage doubler circuit which has an input and a pair of series circuits connected across first and second nodes of the input. Each series circuit includes a series connected first rectifier and capacitor. Second rectifiers are connected across each of the capacitors in the first series circuits.
As an enhancement, the first rectifiers may be of opposite polarity with respect to each other. Further, the second rectifier of each series circuit may be of opposite polarity to its corresponding first rectifier within the series circuit. As an example, the rectifiers may be diodes.
As further enhancements, each of the capacitors of the pair of series circuits is connected to the first node of the input, while each of the first rectifiers is connected to the second node of the input. The output of the circuit may be taken between the junctions of the capacitor and first rectifier within each series circuit.
The circuit of the present invention may include a filter capacitor across its output and may be used in combination with, for example, an alternating current power source and an inductor in series with it.
According to further aspects and enhancements of the present invention, the power supply may operate at substantially the resonant frequency of the circuit. The frequency of the power supply may also be varied to achieve different results. For example, a current passing through the circuit may be monitored, and the frequency may be varied in accordance with the monitored current to achieve a desired output current.
REFERENCES:
patent: 3851182 (1974-11-01), Wallace
patent: 4780805 (1988-10-01), Chewuk et al.
patent: 5047913 (1991-09-01), De Doncker et al.
patent: 5119283 (1992-06-01), Steigerwald et al.
patent: 5134344 (1992-07-01), Vos et al.
patent: 5898278 (1999-04-01), Muessli
Lamda Electronics Inc.
Luu An T.
Wells Kenneth B.
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