Osram Sylvania Inc.

Osram Gmbh

Afroz M Imam

Sivakumar Thangavelu

Mustansir Kheraluwala

Biju Antony

Techniques and corresponding circuitry and drivers are disclosed for improving power factor (PF) and total harmonic distortion (THD) of a flyback power factor correction (PFC) topology operating in transition-mode. In one or more embodiments, the PF and THD are improved by correcting the on-time of the switching element of the flyback PFC topology to actively shape the wave of the PFC input current. In some embodiments, the on-time is corrected using a phase-lock-loop module that synchronizes with the rectified input line voltage signal and a output regulator module that corrects the switch on-time. The control may be implemented using a digital or an analog controller.

Flyback AC-to-DC converter

Methods of protecting an electrical device, such as a ballast, from damage due to an inrush current, and devices incorporating such methods, are disclosed. A loss of input power received by the ballast is detected. In response, the ballast is entered into a standby mode. The ballast is able to remain in the standby mode for a standby period of time. The input power is monitored during the standby period of time to measure a start time. Measurement of the start time is triggered by the ballast receiving input power again. The ballast is entered into an active mode when the measured start time exceeds a protection time. The protection time corresponds to an amount of time needed for an inrush current to dissipate following input power again being received by the ballast, protecting the ballast from possible damage due to the inrush current.

Inrush current protection

A driver circuit includes a plurality of switches, forming two switching legs, each of at least two switches and connected between two DC voltage buses. The switches are matched to form diagonal pairs. The driver circuit also includes a load circuit connecting the legs, with a first inductor connected between one leg's switches, and a second inductor connected between the other leg's switches, and lamp terminals between the inductors and in series with the second inductor. The driver circuit also includes a capacitor in parallel with the series-connected lamp terminals and the second inductor, and a control circuit connected to the plurality of switches. During a commutation period, a diagonal pair operates in a non-conductive state and the other in a conductive state, until a current through the first inductor reaches a predefined value. Then the other operates in a non-conductive state until the current through the first inductor reaches zero.

Transition mode commutation for inverter

A control circuit for a lamp. The control circuit is used in conjunction with an alternating current (AC) variable voltage power source to energize the lamp. The control circuit includes a voltage sensing component for sensing the voltage of an voltage input signal from the power source for energizing the lamp. The control circuit includes a controller configured to estimate a delay angle as a linear function of the sensed voltage. The control circuit includes an AC converter for modifying the voltage input signal according to the estimated delay angle to generate an AC voltage output signal having a constant root mean square voltage for energizing the lamp.

AC delay angle control for energizing a lamp

A ballast including an H-bridge type inverter for driving a lamp and a filter circuit that includes a buck inductor is disclosed. The buck inductor is a primary winding of a transformer, and a secondary winding of the transformer provides power to a controller of the ballast. The controller operates the inverter in various pre-ignition modes of operation such that prior to ignition, the open circuit voltage (OCV) (i.e., voltage across the lamp) and buck inductor current are controlled to transfer sufficient power from the primary of the transformer to the secondary winding of the transformer to power the controller. No switches of the inverter are turned on while there is a non-zero current through the filter circuit.

Growing community of inventors

Peabody, MA, United States of America

Afroz M Imam