Low voltage ballast circuit for a high brightness discharge light source

A low voltage DC input ballast circuit for a discharge lamp comprising:

• a power converter circuit having an input filter stage receptive of said low voltage DC input and having as an output thereof, a filtered DC signal, said power converter circuit further including a boost converter stage receptive of said filtered DC signal, said boost converter stage being effective so as to produce a run signal from said filtered DC signal, said run signal having a predetermined amplitude and frequency selected so as to operate said discharge lamp between a warm-up condition and a steady state condition, said amplitude and said frequency of said run signal being determined as a function of a control signal coupled to said boost converter stage;
• control circuit means coupled to said discharge lamp for receiving a sample of at least one of a voltage and a current operating characteristic of said discharge lamp and developing said control signal as a function thereof;
• output coupling circuit having said run signal coupled as an input thereto, said output coupling circuit being connected to said discharge lamp so that said run signal is fed to said discharge lamp as a voltage during such steady state operating conditions;
• starting means connected to said output coupling circuit effective prior to such lamp warm-up condition for developing a high voltage pulse across said output coupling circuit, said high voltage pulse being effective to cause ionization of the ingredients of said discharge lamp and thus the starting thereof;
• and;
• said control circuit means including timer means for sensing a time period for which power to said discharge lamp has been removed and adjusting said run signal so as to achieve a warm-up power level higher than the power level to said discharge lamp during steady-state operation, said timer means being effective for adjusting such warm-up power level according to how long power to said discharge lamp has been removed, said timer means further including a timer circuit having an output coupled to a high impedance device such that said timer circuit discharges in an exponential manner even during power off conditions.

A ballast circuit arrangement for a discharge lamp comprising:

• an input power conditioning circuit receptive of input power and effective for producing a conditioned power signal therefrom;
• boost converter circuit receptive of said conditioned power signal and effective for developing therefrom, a run signal for driving said discharge lamp to a discharge state, said boost converter circuit developing said run signal to at least one level of magnitude and frequency as a function of a control signal coupled to said boost converter circuit;
• control circuit means coupled to said discharge lamp so as to receive a sample of at least one of a voltage and a current operating characteristic of said discharge lamp and develop said control signal as a function thereof;
• output coupling circuit having said run signal connected as an input thereto, said output coupling circuit being connected to said discharge lamp so as to couple said run signal thereto, said output coupling circuit coupling said run signal to said discharge lamp in a voltage fed manner;
• and
• wherein said control circuit means includes a fade circuit effective, upon detection of a drop in said input power below a predetermined level, for clamping the current supplied to said discharge lamp to a predetermined value.

A ballast circuit arrangement for a discharge lamp comprising:

• an input power conditioning circuit receptive of input power and effective for producing a conditioned power signal therefrom;
• boost converter circuit receptive of said conditioned power signal and effective for developing therefrom, a run signal for driving said discharge lamp to a discharge state, said boost converter circuit developing said run signal to at least one level of magnitude and frequency as a function of a control signal coupled to said boost converter circuit;
• control circuit means coupled to said discharge lamp so as to receive a sample of at least one of a voltage and a current operating characteristic of said discharge lamp and develop said control signal as a function thereof;
• output coupling circuit having said run signal connected as an input thereto, said output coupling circuit being connected to said discharge lamp so as to couple said run signal thereto;
• wherein said control circuit means includes a time-out circuit arrangement whereby, during periods immediately following removal of said input power conditioning circuit, a warm-up power level of a magnitude greater than power to said discharge lamp during steady state conditions, is applied to said discharge lamp for a duration variable as a function of the period of time for which steady state power to said discharge lamp was removed;
• and
• wherein said time-out circuit arrangement includes a logic device having a high impedance input and a resistor, capacitor tuning circuit connected to said high impedance input of said logic device such that, in the event input power to said ballast circuit arrangement is removed, said resistor, capacitor tuning circuit continues to time out in an exponentially decreasing manner.