A discharge lamp lighting device combines one or more discharge lamps and a backswing booster including essentially a power source circuit having a power source connected in series with a ballast and a high voltage generating circuit having an oscillation capacitor and a series circuit of a nonlinear inductor and a switching semiconductor. The supply voltage for the discharge lamp from the power source circuit is established to the extent permissible by the lower limit for sustaining an arc discharge of the lamp so that the terminal voltage of the ballast in the lamp operation is maintained as low as possible. The preferred backswing booster is of small size and an impedance circuit having a capacitor either with or without a bias coil is added to the high voltage generating circuit to produce a momentary high voltage. A leakage transformer or a voltage transformer with a tap or with a supplemental winding may be coupled to the power source circuit to establish a specified potential point from which voltage for the high voltage generating circuit is supplied to reduce the applied voltage during the lamp operation. An economical lighting device for the sequential ignition of two discharge lamps by means of a single high voltage generating circuit is disclosed.
A parallel circuit of a capacitor and a switching element is connected to a hot cathode discharge lamp lighting device using a high frequency and high voltage generating means for permitting the flow of current into the filaments of the hot cathode type discharge lamp only at the lamp starting time. The switching element of the parallel circuit is a current controlled resistance element, such as a switching semiconductor, having a break-over voltage V.sub.BO lower than the capacitor terminal voltage during the initial ignition period and higher than the capacitor terminal voltage during the reignition or operation period, whereby the filament current to the discharge lamp may be used for preheating of the filament in the initial ignition period. The filament current may be stopped or reduced by turning off of the switching element by raising the terminal voltage of the capacitor in the reignition period during normal operation. Thus, the lumen-per-watt efficacy of the lighting device is improved since the filament current is substantially eliminated during the lamp operation. After the initial ignition period it is preferred to use the capacitor of the parallel circuit as an intermittent commutation capacitor in the high frequency and high voltage generating oscillation circuit having an oscillation capacitor, a nonlinear inductor and a thyristor.
A half-bridge converter for operating a discharge lamp utilizes a non-linear coil in series with the discharge lamp. Suitable proportioning ensures an unambiguous relation between the frequency of the lamp current and the lamp power over a comparatively large range of lamp power.
A circuit connected in series with a discharge valve source substantially reducing the current impulse in the course of starting the discharge valve, thereby prolonging its life and reducing the blackening of walls at the ignitor electrodes of the discharge valve.
An electronic ballast (200) includes a rectifier circuit (20), an energy storage inductor (38), a power switch (58), a control circuit (50) for driving the power switch (58), a clamp diode (46), a voltage clamping capacitor (54), a bulk capacitor (34), and an output circuit (70) for providing power to one or more fluorescent lamps (100). In a preferred embodiment, the rectifier circuit (20) includes a full-wave diode bridge (22) and a high frequency filter capacitor (24), and the output circuit (70) has a resonant inductor (72), a resonant capacitor (82), and a dc blocking capacitor (88). The ballast (200) provides power factor correction and high frequency power for fluorescent lamps, but requires only a single power switch (58) and a single energy storage inductor (38).
An energy conserving lighting system is provided wherein a plurality of fluorescent lamps are powered by a poorly regulated voltage source power supply which provides a decreasing supply voltage with increasing arc current so as to generally match the volt-ampere characteristics of the lamps. A transistor ballast and control circuit connected in the arc current path controls the arc current, and hence the light output, in accordance with the total ambient light, i.e., the light produced by the lamps together with whatever further light is produced by other sources such as daylight. In another embodiment, a transistor ballast is utilized in combination with an inductive ballast. The transistor ballast provides current control over a wide dynamic range up to a design current maximum at which maximum the transistor is saturated and the inductive ballast takes over the current limiting function. An operational amplifier is preferably connected in the base biassing circuit of the control transistor of the transistor ballast. In an embodiment wherein two sets of lamps with separate inductive ballasts are provided, the arc currents for the two ballasts are scaled or matched to provide the desired light output.
