Quasi-resonant current mode static power conversion method and apparatus
First Claim
1. Quasi-resonant current mode power conversion apparatus comprising:
- (a) a resonant circuit having a resonant inductor and a resonant capacitor connected in a parallel configuration with respect to each other;
(b) a filter capacitor connected in series with the resonant inductor and having substantially greater capacitance than the resonant capacitor, the output voltage across the filter capacitor being the output voltage of the power conversion apparatus;
(c) a switching circuit including at least two switching devices, which are controllable to be turned on and off, connected together at a node to which the resonant inductor and capacitor are connected;
(d) control means for switching the switching devices to cause a stable resonant oscillation in the resonant circuit when the switching circuit is provided with a supply voltage such that a high frequency AC resonant voltage oscillation is maintained across the resonant circuit and a lower frequency sinusoidal oscillation is maintained across the filter capacitor, the control means switching the switching devices on and off when the inductor current reaches selected minimum and maximum envelope values such that the average value of the inductor current yields a desired waveform which is at a substantially lower frequency than the frequency of switching of the switching devices.
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Accused Products
Abstract
An inverter has a resonant circuit composed of a parallel connected inductor and capacitor and a filter capacitor connected in series with the inductor which has a capacitance substantially greater than the resonant capacitor. A half bridge or full bridge switching circuit formed of pairs of gate controlled switching devices is connected to a DC power supply and to the resonant circuit and filter capacitor, with the switching devices being switched to provide a relatively high frequency, e.g., 20 KHz or higher, resonant current in the resonant circuit. The filter capacitor is of a size such that the high frequency component of the current flowing in the resonant circuit does not result in a substantial voltage at the switching frequency appearing across the filter capacitor. In addition to the high frequency switching current in the resonant circuit, the switching frequency and the duration of switching is adjusted in a controlled manner such that a lower frequency AC component appears in the current flowing in the resonant circuit and through the filter capacitor such that a voltage at the lower frequency component appears across the filter capacitor.
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Citations
17 Claims
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1. Quasi-resonant current mode power conversion apparatus comprising:
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(a) a resonant circuit having a resonant inductor and a resonant capacitor connected in a parallel configuration with respect to each other; (b) a filter capacitor connected in series with the resonant inductor and having substantially greater capacitance than the resonant capacitor, the output voltage across the filter capacitor being the output voltage of the power conversion apparatus; (c) a switching circuit including at least two switching devices, which are controllable to be turned on and off, connected together at a node to which the resonant inductor and capacitor are connected; (d) control means for switching the switching devices to cause a stable resonant oscillation in the resonant circuit when the switching circuit is provided with a supply voltage such that a high frequency AC resonant voltage oscillation is maintained across the resonant circuit and a lower frequency sinusoidal oscillation is maintained across the filter capacitor, the control means switching the switching devices on and off when the inductor current reaches selected minimum and maximum envelope values such that the average value of the inductor current yields a desired waveform which is at a substantially lower frequency than the frequency of switching of the switching devices. - View Dependent Claims (3, 4, 5, 6, 11, 12, 14, 15)
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2. Quasi-resonant current mode power conversion apparatus comprising:
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(a) power supply means for supplying DC output power; (b) a resonant circuit having an inductor and at least one capacitor connected in a parallel configuration with respect to each other; (c) a filter capacitor connected in series with the resonant inductor and having substantially greater capacitance than the resonant capacitor, the output voltage across the filter capacitor being the output voltage of the power conversion apparatus; (d)a switching circuit including at least one pair of switching devices connected together which are controllable to be turned on and off, and connected to the power supply means and to the resonant circuit; (e) control means for switching the switching devices at the proper times to cause the resonant circuit to oscillate at a high frequency which is filtered out by the filter capacitor and does not substantially appear as a voltage across the filter capacitor and to also oscillate at a second lower frequency which appears as an alternating voltage across the filter capacitor, the control means switching the switching devices on and off when the inductor current reaches selected minimum and maximum envelope values such that the average value of the inductor current yields a desired waveform which is at a substantially lower frequency than the frequency of switching of the switching devices. - View Dependent Claims (7, 8, 9, 10, 13)
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16. A method for converting a DC supply voltage from a DC power source to an AC voltage,
utilizing a resonant circuit comprised of a resonant inductor and a resonant capacitor connected in parallel, and a filter capacitor connected in series with the resonant inductor which is substantially larger in capacitance than the resonant capacitor, comprising the steps of: -
(a) applying the DC supply voltage across the series connected resonant inductor and filter capacitor at a first polarity for a time sufficient to build up a desired current level in the inductor; (b) then removing the supply voltage from the series connected inductor and filter capacitor to cause the current in the inductor to flow into the resonant capacitor until the voltage across the resonant inductor and filter capacitor is equal to the supply voltage at the opposite polarity; (c) then applying the DC supply voltage to the resonant conductor and filter capacitor at the opposite polarity which matches the polarity of the voltage across the resonant circuit and filter capacitor at the time for a time sufficient to build up a selected current level in the inductor; (d) then removing the supply voltage from the resonant inductor and filter capacitor to cause the current in the inductor to flow through the resonant capacitor until the voltage across the resonant inductor and filter capacitor is equal to the supply voltage of opposite polarity; and (e) then repeating steps (a) through (d) above; wherein steps (a) through (e) are carried out such that the time of application of the supply voltage in each polarity to the resonant inductor and filter capacitor and the frequency of switching from one polarity to he other are selected to result in a time varying voltage appearing across the filter capacitor at a frequency substantially lower than the frequency of switching between the two polarities of the power supply voltage, and such that substantially no voltage varying at the switching frequency appears across the filter capacitor. - View Dependent Claims (17)
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Specification