Abstract: An EL lamp characterized by non-linear brightness decay is driven to constant brightness for the life of the lamp by an inverter controlled by a microprocessor. The microprocessor controls the inverter in accordance with a table containing data which is the inverse function of the non-linear brightness decay. The microprocessor tracks the total on-time of the EL lamp and selects the appropriate data from the table for driving the lamp. Control can be analog or digital. If control is analog, the selected data is coupled to a D/A converter which is coupled to the inverter. If control is digital, the selected data is coupled to a counter driving a pulse width modulator which is coupled to the inverter. In accordance with another aspect of the invention, an EL lamp is dimmed a precise amount based upon the data in the table and the EL lamp can be dimmed in unison with other lamp types, each lamp type having a table containing data for dimming.

Abstract: An electronic watch, either digital or analog, includes an EL lamp powered by a split chip inverter having a low voltage portion incorporated into a first semiconductor chip and a high voltage portion incorporated in a second semiconductor chip. The first semiconductor chip preferably includes all the other low voltage circuitry of the watch, e.g. timer/divider circuitry and logic for driving a display.

Abstract: A power supply for an electroluminescent lamp includes a pair of inverters for alternately powering the EL lamp from a low voltage DC source. A first inverter is connected to a first electrode of the EL lamp and a transistor is connected between the first electrode and electrical ground. A second inverter is connected to a second electrode of the EL lamp and a second transistor is connected between the second electrode and electrical ground. A pulse generator connected to the inverters and the transistors operates the inverters and transistors to power the EL lamp alternately from one inverter and then the other. In one embodiment of the invention, the voltage across the EL lamp is referenced to ground and, in another embodiment, the voltage across the EL lamp is referenced to the voltage of the DC source.

Abstract: DC bias does not accumulate on an EL lamp connected in series with a switch circuit including, in one embodiment, two, asymmetric, parallel current paths, one current path for each half cycle of the AC. The first current path includes a first diode for preventing DC bias on the lamp, the first diode is in series with a first transistor between a first terminal and a second terminal. The second current path includes a second diode in series with the base-collector junction of a second transistor between the first terminal and the second terminal. The base of the first transistor is connected to the emitter of the second transistor and to a control terminal. The first transistor and the second transistor are opposite conductivity types. The second current path takes advantage of the fact that the current through an electroluminescent lamp is small and uses the control terminal as a source of current for the lamp.

Abstract: An inverter for powering an electroluminescent lamp has a direct current supply terminal, a ground terminal, and a single output terminal. A high frequency pumping circuit stores electrical energy in an inductor having a first terminal and a second terminal. A switching circuit alternately connects the first and second terminals of the inductor to the output terminal at a low frequency. The output from the inverter is a high voltage, low frequency, alternating current.