Discharge lamp lighting circuit
AssigneeKoito Manufacturing Co., Ltd.
InventorsHiroki Ishibashi, Masayasu Ito
Life of this patent
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Abstract
A discharge lamp lighting circuit includes an emission acceleration controller for detecting a voltage for a discharge lamp and for supplying power exceeding a rated value when the discharge lamp is initially lighted, and thereafter gradually reducing the power to shift the discharge lamp to a steady state. While the value of the power supplied when the lighting of the discharge lamp is started is employed as the maximum, the power supplied to the discharge lamp is controlled. Thus, the speed at which the power is reduced during a period of transition to the steady state is increased in consonance with an increase in the discharge lamp voltage.
Claims20
A discharge lamp lighting circuit comprising:
- an emission acceleration controller that detects a voltage of a discharge lamp having one of no mercury and a substantially small amount of mercury, wherein said emission acceleration controller supplies power in an amount greater than a rated value when the discharge lamp is initially lighted and thereafter gradually reduces the supplied power to shift the discharge lamp to a steady state,
- wherein the emission acceleration controller controls the power of the discharge lamp, so that the speed at which, during a period of transition to the steady state, the power is reduced increases as the voltage of the discharge lamp increases.
The discharge lamp lighting circuit according to 1, wherein an upper limit value for the power supplied is reduced when an elapsed time period beginning at the start of the lighting of the discharge lamp is extended.
A circuit for lighting a discharge lamp, comprising:
- a direct-current (DC) power source coupled to a DC-DC power converter that adjusts a voltage received from said DC power source to generate an output DC voltage;
- a DC-AC converter coupled to said DC-DC power converter, said DC-AC power converter receiving and converting said output DC voltage into an AC voltage to be supplied to said discharge lamp;
- a starting circuit coupled between said DC-AC converter and said discharge lamp, for providing a start pulse to activate said discharge lamp;
- a detector that is coupled between said DC-DC converter and said AC-AC converter, and detects said output DC voltage to generate a detection signal;
- and
- a controller that receives said detection signal and controls said DC output voltage in accordance with said detection signal processed by an emission accelerator controller in said controller,
- wherein said discharge lamp contains substantially no mercury.
A method of controlling lighting of a discharge lamp, comprising:
- initializing a control circuit in response to an instruction for starting said lighting of said discharge lamp;
- detecting a voltage and a current of said discharge lamp;
- determining whether said control circuit is in a normal operational state or an abnormal operational state;
- when said control circuit is in a normal operational state, controlling power input to said discharge lamp during a steady state and a transition state by supplying power above a prescribed level during said transition state, and reducing said supplied power to shift said discharge lamp to said steady state, in accordance with said voltage level of said discharge lamp, in response to a control signal generated by said control circuit.
Dependencies are inferred from the claim text.