Abstract: Method and apparatus to control LED brightness are disclosed. An example method includes receiving a dimmer control signal; determining a cutoff point of the dimmer control signal; determining the position of a rising edge signal within the dimmer control signal; determining if the rising edge signal occurred before the cutoff point; and outputting an LED brightness signal indicating full brightness when the rising edge signal occurred before the cutoff point, and indicating a scaled brightness when the rising edge signal did not occur before the cutoff point.

Abstract: Method and apparatus to control LED brightness are disclosed. An example method includes receiving a dimmer control signal; determining a cutoff point of the dimmer control signal; determining the position of a rising edge signal within the dimmer control signal; determining if the rising edge signal occurred before the cutoff point; and outputting an LED brightness signal indicating full brightness when the rising edge signal occurred before the cutoff point, and indicating a scaled brightness when the rising edge signal did not occur before the cutoff point.

Abstract: A DC-DC converter circuit includes a transformer with a resonate filter or snubber connected at a primary side and a switch for controlling operation of the converter. A secondary side of the transformer includes self-driven synchronous rectifiers and an output filter. Transistors are provided at the gates leads of the rectifiers and themselves are provided with a fixed voltage at their gates so as to clamp the peak voltages across to the rectifiers.

Abstract: A DC-DC converter circuit includes a transformer with a resonate filter or snubber connected at a primary side and a switch for controlling operation of the converter. A secondary side of the transformer includes self-driven synchronous rectifiers and an output filter. Transistors are provided at the gates leads of the rectifiers and themselves are provided with a fixed voltage at their gates so as to clamp the peak voltages across to the rectifiers.

Abstract: A DC-DC converter has a main forward converter stage with a snubber at a source side and a sample and hold circuit at a load side. Feedback is provided by a pulse width modulated controller connected at the load side, which feeds an isolation transformer via a differentiating capacitor. The isolation transformer has its output connected to a pulse regenerator which feeds a driver and a volt-time limiter that connects to a main switch at the source side of the forward converter.

Abstract: An electronic ballast having a boot strap capacitor 22 that becomes initially charged at a first rate and a high voltage storage capacitor 23 that becomes charged at a second, faster rate, wherein the boot strap capacitor 22, becoming initially fully charged initiates operation of a PWM driver 18 that in turn causes a power factor corrector and inverter 16 to energize corresponding gas discharge lamps 11. Upon activation of the PWM driver 18 and the corresponding activation of the power factor corrector and inverter 16, a voltage clamp 19 responds to these events by establishing a conductive path 20 between the high voltage storage capacitor 23 and the boot strap capacitor 22, such that continued operation of the PWM driver 18 is ensured. So configured, a relatively small valued capacitor can be utilized for the boot strap capacitor 22, thereby ensuring rapid activation of the lamps 11 without risking subsequent sporadic energization or other operational difficulties.

Abstract: A circuit for powering a fluorescent lamp has a direct current power supply (10). An inverter (12) is coupled to the direct current power supply (10) and provides a lamp current to the fluorescent lamp load (14). The inverter(12) is connected to an inverter control circuit (18). A protection circuit (16) for detecting lamp current is coupled to the inverter control circuit (18) such that the inverter control circuit (18) turns off the inverter (12) whenever the protection circuit detects the absence of lamp current.

Abstract: A switching mode power supply characterized by an output in the forward conversion mode and a separate output in the flyback mode whereby a device having variable power requirements in one aspect of its operation, and a stable power requirement another aspect of its operation may be powered without interference as between the two sources of power. The flyback power output is monitored for voltage regulation, regulation being achieved by a constant-off-time variable-on-time switch. The power supply likewise includes novel protective circuitry to shut it down in the event of excessive voltage or current therein.

Abstract: A phase loss detector for detecting and responding to voltage loss or failure in a polyphase electric power supply to disconnect the load or motor in the event of such loss, which is adapted to serve in conjunction with either a delta or wye power configuration and is characterized by an internally generated AC common line such that a common line of the power source is unnecessary.