Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
243 words
A discharge lamp driving circuit, comprising: a DC voltage source; a discharge lamp; a current limiting inductor inserted in series between the voltage source and the lamp; means connected to the DC voltage for operating the lamp at a low frequency AC voltage while repetitively interrupting, at a high frequency, the voltage component to be applied to the lamp, said means comprising a bridge invertor having at least one pair of switching elements controlled to alternately reverse the DC voltage at the low frequency so as to apply the resulting AC voltage to the lamp at the low frequency, and switching means for repetitively interrupting, at the high frequency, the voltage component to be applied to the lamp; control means for providing an all-off period during which the switching elements of the bridge invertor are simultaneously off for a predetermined time interval at the polarity reversal of the AC voltage being applied to the lamp in order to prevent the power source from being short circuited through the circuit of the bridge invertor; a bypass capacitor connected in parallel with the lamp for bypassing the high frequency component resulting from the high frequency interrupting operation of the switching means; and an oscillation-including inductor connected in series with the lamp and in parallel relation with the bypass capacitor, said oscillation-inducing inductor forming, with said bypass capacitor, a series oscillating circuit which causes an alternating current to flow through the lamp during the all-off period.
Claim 2
Dependent Claim
243 words
A discharge lamp driving circuit, comprising: a DC voltage source; a discharge lamp; a current limiting inductor inserted in series between the voltage source and the lamp; means connected to the DC voltage for operating the lamp at a low frequency AC voltage while repetitively interrupting, at a high frequency, the voltage component to be applied to the lamp, said means comprising a bridge invertor having at least one pair of switching elements controlled to alternately reverse the DC voltage at the low frequency so as to apply the resulting AC voltage to the lamp at the low frequency, and switching means for repetitively interrupting, at the high frequency, the voltage component to be applied to the lamp; control means for providing an all-off period during which the switching elements of the bridge invertor are simultaneously off for a predetermined time interval at the polarity reversal of the AC voltage being applied to the lamp in order to prevent the power source from being short circuited through the circuit of the bridge invertor; a bypass capacitor connected in parallel with the lamp for bypassing the high frequency component resulting from the high frequency interrupting operation of the switching means; and an oscillation-including inductor connected in series with the lamp and in parallel relation with the bypass capacitor, said oscillation-inducing inductor forming, with said bypass capacitor, a series oscillating circuit which causes an alternating current to flow through the lamp during the all-off period.
Claim 3
Dependent Claim
76 words
A circuit as set forth in claim 1, wherein said oscillation-inducing inductor is selected to have an inductive value such that said all-off period terminates at a moment when the voltage appearing across the bypass capacitor by the operation of the oscillating circuit is in a subtractive relation to the voltage to be applied across the same capacitor in the subsequent operation of turning on the switching means with respect to the polarity of the voltage.
Claim 4
Dependent Claim
77 words
A circuit as set forth in claim 1, further including a starting circuit connected in series with the lamp, said starting circuit comprising: a pulse transformer having a primary winding and a secondary winding, the secondary winding defining itself said oscillation-inducing inductor forming the oscillating circuit; and pulse generating means connected to the primary winding of the pulse transformer whereby the pulse transformer produces a high open circuit ignition voltage across the lamp over said bypass capacitor.
Claim 5
Dependent Claim
82 words
A circuit as set forth in claim 1, wherein said bridge inverter comprises two pairs of switching transistors which are arranged in a bridge circuit and define said switching elements, the one pair of said switching transistor being operated at the low frequency so as to reverse the interrupted DC voltage for applying the AC voltage to the lamp, and the other pair of the switching transistors being operated at the high frequency so as to be utilized as said switching means.
Claim 6
Dependent Claim
61 words
A circuit as set forth in claim 1, wherein said inverter circuit comprises two pairs of switching transistor arranged in a bridge circuit to define said switching elements operated at the low frequency, and including another switching transistor defining said switching means operating at the high frequency, the latter switching transistor being connected between the DC voltage source and the inverter.