Electronic ballasts

A thermionic lighting system comprising:

• a high intensity discharge lamp,
• an electronic ballast having a regulated alternating current power output,
• a joint operating circuit included in and between the ballast and the lamp,
• the ballast having a variable frequency generator which is arranged to vary a frequency of the ballast output over a range of frequencies, with a minimum frequency of 400 kHz,
• the circuit having a reactance such that the circuit is arranged to be resonant to provide a staring voltage for the lamp at or above the minimum frequency,
• wherein the reactance comprises a series arrangement of an inductance and a capacitor where the output frequency and the value of the reactance is arranged so that the output frequency is above a resonant frequency of the reactance, and
• the output power is arranged to pass through a capacitor in series with the lamp, the value of capacitance being sufficiently small to limit a current flow, through the lamp at a frequency of the electrical power input to the ballast, to less than 30 mA.

A thermionic lighting system comprising:

• a high intensity discharge lamp,
• an electronic ballast having a regulated alternating current power output,
• a joint operating circuit included in and between the ballast and the lamp,
• the ballast having a variable frequency generator which is arranged to vary a frequency of the ballast output over a range of frequencies, with a minimum frequency of 400 kHz,
• the circuit having a reactance such that the circuit is arranged to be resonant to provide a starting voltage for the lamp at or above the minimum frequency,
• wherein a connection to the lamp is arranged so that the lamp can be replaced, and a capacitance is placed in a parallel current path to the lamp, the capacitance being arranged such that disconnection of the lamp from the ballast output disconnects the capacitance from the ballast, the variable frequency generator being so arranged to sweep over a pre-determined range of frequencies to produce by means of a resonant circuit including the said capacitor a specific high frequency high voltage output to ignite the lamp.

A thermionic lighting system comprising:

• a high intensity discharge lamp,
• an electronic ballast having a regulated alternating current power sinusoidal waveform output,
• a joint operating circuit included in and between the ballast and the lamp,
• the ballast having a variable frequency generator which is arranged to vary a frequency of ballast output over a range of frequencies, with a minimum frequency of 400 kHz,
• the circuit having a reactance such that the circuit is arranged to be resonant to provide a starting voltage for the lamp at or above the minimum frequency.