Philips Electronics North America Corporation

O2micro International Limited

Other

Micro International Limited

John Chou

Yung-Lin Lin

Yongping Xia

Yung Lin Lin

Kwang H Liu

Arnel Dela Cruz

Xing-Xing Lu

Ching-Chuan Kuo

Feng Chang Hu

A lamp driving system that includes a first impedance and a second impedance coupled to the secondary side of a transformer, where the second impedance has a phase shifted value compared to the first impedance. Two lamp loads are connected in series together, and in parallel to the first and second impedances and to the transformer. The phase shift between the impedances ensures that the transformer need not supply double the striking voltage to strike the series-connected lamps. A difference in the resistance between the first and second impedances ensures that the lamps ignite in a specified sequence.

Lamp driving topology

An electronic ballast for lamps or tubes is provided. In one embodiment the present invention includes a ballast controller that includes filament heating circuitry and dimming circuitry. The filament heating circuitry may include preheat dimming circuits which preheat the filaments for a predetermined time period prior to striking the lamp, and steady-state heating circuitry that continually heats the filaments during steady state operation of the lamp. The steady state heating circuitry may be adapted to heat the filaments inversely proportional to the dim desired value of the lamp. The dimming circuitry may include conventional analog dimming and/or burst mode dimming to define a wide range of dimming characteristics for the lamp.

Integrated circuit for lamp heating and dimming control

A lamp load control system that includes a lamp controller comprising an inverter generating an AC signal from a DC signal, a load coupled to the inverter, and a feedback circuit coupled to the load generating a feedback signal indicative of power supplied to the load. In one exemplary embodiment, the system also includes a command signal generator generating a command signal indicative of a preferred power output of the inverter; wherein the command signal is combined with the feedback signal to cause the controller to temporarily reduce power delivered to the load. In another exemplary embodiment, the system includes a command signal generator generating a command signal indicative of a preferred power output of said inverter; wherein the controller receives the feedback signal and the command signal and temporarily reduces power delivered to the load based on the value of the feedback signal or the command signal.

Inverter operably controlled to reduce electromagnetic interference

The present invention provides a CCFL driving circuit having a parallel-arranged transformer system and a feedback loop positioned to sense the current in one of the lamps in the system. Each CCFL in the system is driven by the secondary side an individual transformer. Based on the current sensed in the feedback loop, a controller supplies the appropriate driving voltage to the primary side of the transformers, which in turn powers each CCFL. Since the primary sides of the transformers are arranged in parallel, and since each CCFL is connected at a common node, it is ensured that each transformer receives identical voltage, and the current in each CCFL loop is balanced.

Balanced power supply circuit for multiple cold-cathode fluorescent lamps

An electrical circuit for simultaneously energizing at least a pair of CCFLs that are connected in series. The circuit also includes a transformer having a primary winding adapted to receive an alternating current. A secondary winding is coupled in series with the CCFLs to energize their operation. A shunt capacitor, connected in parallel across one CCFL, significantly reduces the peak voltage that must be applied across the CCFLs. Usually, the circuit also includes an isolation capacitor connected in series between the CCFLs and the secondary winding of the transformer. The isolation capacitor provides both DC blocking and electrical isolation between the secondary winding and the CCFLs.

Circuit for energizing cold-cathode fluorescent lamps

An electronic ballast for driving a fluorescent lamp includes an electromagnetic interference (EMI) filter and power circuit, a preconditioner coupled to the EMI filter and power circuit and an inverter circuit coupled to the preconditioner for energizing the fluorescent lamp. The preconditioner includes an active power factor controller and a boost circuit which is controlled at least in part by the active power factor controller. The active power factor controller has a reference voltage input to which is applied a reference voltage. At start up, the inverter provides a time varying signal which is rectified. At least a portion of the rectified signal is fed back to the reference voltage input of the active power factor controller to boost the reference voltage to a level above normal so that the active power factor controller will cause greater current to flow through the boost circuit, causing the boost circuit to generate a direct current (DC) rail voltage more rapidly, which rail voltage is provided to the inverter circuit to ignite and operate the fluorescent lamp.

Instant start for an electronic ballast preconditioner having an active

A programmed electronic ballast circuit including a voltage maintenance circuit to ensure that the integrated circuit continues to oscillate and drive the half-bridge inverter until the DC bus voltage falls to a level insufficient to permit the fluorescent bulbs at the output to ignite. Additionally, the voltage maintenance circuit drives the voltage of the integrated circuit down to a level whereby proper resetting of the integrated circuit and proper preheating of the florescent bulb filaments is assured.

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Monterey Park, CA, United States of America

John Chou