HID Lamp power supply

In a control system for a high intensity discharge lamp, the combination of, a source of alternating current, means including at least a pair of silicon controlled rectifiers for supplying power to the lamp from said AC source, means for controlling the firing point of said controlled rectifiers, and means controlled by said firing point control means for applying lamp strike pulses to the lamp a predetermined time interval after said controlled rectifier firing point and when the voltage across the lamp has reached a substantial value, thereby to cause the formation of an arc within the lamp.

In a lamp strike circuit for initiating an arc in a high intensity discharge lamp, the combination of, a pulse transformer having a primary winding and a secondary winding, means connecting said secondary winding in circuit with the lamp, a series circuit comprising said primary winding, a capacitor, a saturable reactor and a silicon controlled rectifier, means for charging said capacitor to a predetermined voltage level, and means for applying a gate pulse to the gate electrode of said silicon controlled rectifier, said saturable reactor having an inductance many times larger than the inductance of said primary, thereby to limit current flow in said series circuit for a predetermined time interval which is sufficient to permit said silicon controlled rectifier to become fully conductive.

A control circuit for a high intensity discharge lamp which reduces warm-up time of the lamp, comprising a source of alternating current, control means connected in series with said lamp, the series combination of said lamp and said control means being connected across said source of alternating current, a first resistor for developing a voltage proportional to the current flow through the lamp, a second resistor for developing a voltage proportional to the voltage across the lamp, the values of said first and second resistors being chosen so that a predetermined voltage is developed across said first resistor when the lamp is short circuited which predetermined voltage is equal to the voltage developed across said second resistor when the lamp is open circuited, means for developing a reference signal, and means jointly controlled by said reference signal and the voltages developed across said first and second resistors for controlling said control means to maintain the sum of the voltages developed across said first and second resistors equal to said predetermined voltage as the lamp warms up from an initially cold condition.

A control circuit for a high intensity discharge lamp which reduces warm-up time of the lamp, comprising a source of alternating current, control means connected in series with said lamp, the series combination of said lamp and said control means being connected across said source of alternating current, means for sensing the current flowing through the lamp and the voltage developed across the lamp, and means responsive to said current and voltage sensing means for controlling said control means so that the lamp is operated along a linear current-voltage load line as the lamp warms up from a cold condition, said current-voltage load line extending from a first point on the current axis corresponding to a short circuit current through the lamp to a second point on the voltage axis corresponding to the open circuit voltage across the lamp when no current is flowing therethrough.

The combination of claim 38, wherein said current and voltage sensing means comprise first and second resistive means for producing control voltages proportional respectively to the current flow through and voltage across the lamp, the values of said first and second resistive means being chosen so that the voltage developed across said first resistive means under a short circuit condition of the lamp is equal to the voltage developed across said second resistive means under an open circuit condition of the lamp.

A control circuit for a high intensity discharge lamp which reduces warm-up time for the lamp, comprising a source of alternating current, energy storage inductance means, first and second pairs of controlled rectifiers, each of said pairs being connected in series with said energy storage inductance means so that current flows through said inductance means in the same direction upon conduction of either of said pairs of rectifiers, means for connecting said energy storage inductance means in series with the lamp across said AC source, means for developing AC control signals proportional to the flow of AC current through the lamp and the AC voltage across the lamp, and means controlled by said control signals for varying the firing point of each of said pairs of controlled rectifiers so that the current flow through the lamp is initially limited to maximum predetermined value when the lamp is cold and said current flow is proportionately decreased in response to an increase in the voltage developed across the lamp as the lamp warms up.