Electronic ballast with load-independent and self-oscillating inverter topology
First Claim
1. An inverter comprising:
- first and second switching elements arranged in a half-bridge configuration;
a resonant circuit having a primary winding of a resonant inductor coupled on a first end to a node between the first and second switching elements and a resonant capacitor coupled between a second end of the resonant inductor and a negative terminal for the inverter;
a load circuit comprising a secondary winding of the resonant inductor effective to drive a load when an output voltage is generated across the primary winding of the resonant inductor;
a diode having its anode coupled to a node between the resonant capacitor and the primary winding of the resonant inductor and its cathode coupled to a positive terminal of the inverter, the diode effective to clamp the voltage across the resonant capacitor to a predetermined maximum value wherein an output voltage during a steady-state operation across the primary winding and thereby the secondary winding of the resonant inductor is a quasi-square waveform with a fixed amplitude; and
a starting circuit having at least a second secondary winding of the resonant inductor and effective to cause self-oscillation of the first and second switching elements, the starting circuit further effective to fix the operating frequency of self-oscillation in the first and second switching elements equal to the natural resonant frequency of the resonant circuit regardless of a load condition.
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Accused Products
Abstract
A self-oscillating inverter provides an output voltage with fixed operating frequency and amplitude independently of a load. First and second switching elements are arranged in a half-bridge configuration. A resonant circuit having a primary winding of a resonant inductor and a resonant capacitor is coupled between the switching elements. A clamping circuit limits the voltage across the resonant capacitor to a predetermined maximum value, and along with the resonant capacitor defines a capacitance compensation circuit having an equivalent capacitance greater than that of the resonant capacitor alone, wherein the actual resonant frequency of the inverter is less than the natural frequency of the resonant circuit such that soft-switching is assured. An output voltage across the resonant inductor during steady-state operation is a quasi-square waveform with a fixed amplitude, wherein a load voltage across a secondary winding of the inductor is also a quasi-square waveform with a fixed amplitude.
30 Citations
11 Claims
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1. An inverter comprising:
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first and second switching elements arranged in a half-bridge configuration; a resonant circuit having a primary winding of a resonant inductor coupled on a first end to a node between the first and second switching elements and a resonant capacitor coupled between a second end of the resonant inductor and a negative terminal for the inverter; a load circuit comprising a secondary winding of the resonant inductor effective to drive a load when an output voltage is generated across the primary winding of the resonant inductor; a diode having its anode coupled to a node between the resonant capacitor and the primary winding of the resonant inductor and its cathode coupled to a positive terminal of the inverter, the diode effective to clamp the voltage across the resonant capacitor to a predetermined maximum value wherein an output voltage during a steady-state operation across the primary winding and thereby the secondary winding of the resonant inductor is a quasi-square waveform with a fixed amplitude; and a starting circuit having at least a second secondary winding of the resonant inductor and effective to cause self-oscillation of the first and second switching elements, the starting circuit further effective to fix the operating frequency of self-oscillation in the first and second switching elements equal to the natural resonant frequency of the resonant circuit regardless of a load condition. - View Dependent Claims (2, 3, 4, 5)
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6. An inverter comprising:
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first and second switching elements arranged in a half-bridge configuration between positive and negative inverter terminals; a resonant circuit having a primary winding of a resonant inductor coupled on a first end to a node between the first and second switching elements and a resonant capacitor coupled between a second end of the resonant inductor and the negative inverter terminal; a load circuit comprising a secondary winding of the resonant inductor effective to drive a load when an output voltage is generated across the primary winding of the resonant inductor; a clamping circuit further comprising a first diode having its anode coupled to a node between the resonant capacitor and the primary winding of the resonant inductor and its cathode coupled to the positive inverter terminal, and a second diode having its cathode coupled to said node and its anode coupled to the negative terminal; and a starting circuit having at least a second secondary winding of the resonant inductor and effective to cause self-oscillation of the first and second switching elements. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification