Abstract: Transistors are provided that comprise a silicon carbide based semiconductor layer structure, a first current terminal, a second current terminal, a gate terminal, and a minimum gate terminal-to-second current terminal voltage clamp circuit in the semiconductor layer structure that is coupled between the gate terminal and the second current terminal.

Abstract: Power semiconductor devices comprise a gate pad, a gate bus, and a gate resistor that is electrically interposed between the gate pad and the gate bus and comprises a wide band-gap semiconductor material region.

Abstract: A bidirectional power converter includes a first switch circuit coupled to a second switch circuit via a transformer, wherein the first switch circuit is configured to transfer power to the second switch circuit during a charging mode, the second switch circuit is configured to transfer power to the first switch circuit during a discharging mode, and the first switch circuit is configured to operate in a half bridge configuration during a first portion of the charging mode.

Abstract: An AC/DC power converter is coupled between a fluorescent ballast circuit and a set of light emitting diodes (LEDs) forming an LED lamp. The power converter converts an AC output from the ballast circuit to a DC current applied to drive operation of the LEDs. The power converter transforms and rectifies the AC output from the ballast circuit to generate a DC output current. An open load protection circuit is coupled to protect the ballast circuit when the LED lamp is not connected. Current control is provided by a transistor having a source/drain conduction path coupled to shunt the DC output current in response to a control signal having a duty cycle generated as a function of a zero-crossing of the AC output and a sensed value of the DC output current applied to the LED lamp.

Abstract: An AC/DC power converter is coupled between a fluorescent ballast circuit and a set of light emitting diodes (LEDs) forming an LED lamp. The power converter converts an AC output from the ballast circuit to a DC current applied to drive operation of the LEDs. The power converter transforms and rectifies the AC output from the ballast circuit to generate a DC output current. An open load protection circuit is coupled to protect the ballast circuit when the LED lamp is not connected. Current control is provided by a transistor having a source/drain conduction path coupled to shunt the DC output current in response to a control signal having a duty cycle generated as a function of a zero-crossing of the AC output and a sensed value of the DC output current applied to the LED lamp.

Abstract: A line-powered LED driver is operable to provide primary-side regulation of output current supplied to LED circuitry. The circuit includes a feedback loop coupled to a power converter, wherein the feedback loop adds scaled input current to scaled input voltage to produce a control signal. The power converter is responsive to the control signal to adjust input current drawn by the power converter in response to changes in line voltage to provide constant input power. The power converter produces output power for supplying constant output current at the LEDs. The feedback loop may use a reference voltage derived from the LED circuitry so that the output power may be regulated to provide constant LED current for varying LED voltages. When compared to secondary-side current feedback schemes, the LED driver provides increased efficiency and reliability at a reduced cost by implementing primary-side regulation of the output current.

Abstract: A boost circuit is used for power factor correction (PFC). In a low power application, transition mode control is utilized. However, switching frequency varies with different input voltages, and over a wide input voltage range, the switching frequency can become too high to be practical. To address this issue, a boost circuit is provided whose effective inductance changes as a function of input voltage. By changing the inductance, control is exercised over switching frequency.

Abstract: A boost circuit is used for power factor correction (PFC). In a low power application, transition mode control is utilized. However, switching frequency varies with different input voltages, and over a wide input voltage range, the switching frequency can become too high to be practical. To address this issue, a boost circuit is provided whose effective inductance changes as a function of input voltage. By changing the inductance, control is exercised over switching frequency.

Abstract: A system and method for providing a constant current source driver for a light emitting diode string. The converter includes a current sensor that derives feedback signal corresponding to a peak current through the light emitting diode string. The feedback signal is used by a controller to vary a duty cycle of the controller to regulate the average current. The controller is operable to regulate the average current as the number of light emitting diodes is increased and/or decreased.

Abstract: In a method for producing a control signal for regulating a drive current for driving an LED, a current through the LED is sensed, wherein the LED is driven by a power converter output, and wherein an output voltage of the power converter is proportionately controlled by a control signal. Next, a power supply voltage is sensed. The control signal is produced for the power converter, wherein the control signal is proportional to a difference between a reference voltage and the current through the LED. The control signal is then offset in response to the power supply voltage to reduce the current through the LED as the power supply voltage drops.

Abstract: A single-stage integrated circuit drives LED sources in a constant power mode to eliminate the need for LED current sensing, while reshaping the waveform of the inductor current near line zero crossing to achieve high power factor. The integrated circuit achieves substantially constant input power by maintaining a constant voltage at a power factor corrector controller through an input voltage feedforward system. Accordingly, the disclosed circuit provides a high power factor, high efficiency, simple, and cost-effective solution with substantially consistent input power for both isolated and non-isolated offline LED applications.

Abstract: A line-powered LED driver is operable to provide primary-side regulation of output current supplied to LED circuitry. The circuit includes a feedback loop coupled to a power converter, wherein the feedback loop adds scaled input current to scaled input voltage to produce a control signal. The power converter is responsive to the control signal to adjust input current drawn by the power converter in response to changes in line voltage to provide constant input power. The power converter produces output power for supplying constant output current at the LEDs. The feedback loop may use a reference voltage derived from the LED circuitry so that the output power may be regulated to provide constant LED current for varying LED voltages. When compared to secondary-side current feedback schemes, the LED driver provides increased efficiency and reliability at a reduced cost by implementing primary-side regulation of the output current.

Abstract: A boost circuit is used for power factor correction (PFC). In a low power application, transition mode control is utilized. However, switching frequency varies with different input voltages, and over a wide input voltage range, the switching frequency can become too high to be practical. To address this issue, a boost circuit is provided whose effective inductance changes as a function of input voltage. By changing the inductance, control is exercised over switching frequency.

Abstract: A single-stage integrated circuit drives LED sources in a constant power mode to eliminate the need for LED current sensing, while reshaping the waveform of the inductor current near line zero crossing to achieve high power factor. The integrated circuit achieves substantially constant input power my maintaining a constant voltage at a power factor corrector controller through an input voltage feedforward system. Accordingly, the disclosed circuit provides a high power factor, high efficiency, simple, and cost-effective solution with substantially consistent input power for both isolated and non-isolated offline LED applications.

Abstract: A system and method for providing a constant current source driver for a light emitting diode string. The converter includes a current sensor that derives feedback signal corresponding to a peak current through the light emitting diode string. The feedback signal is used by a controller to vary a duty cycle of the controller to regulate the average current. The controller is operable to regulate the average current as the number of light emitting diodes is increased and/or decreased.

Abstract: In a method for producing a control signal for regulating a drive current for driving an LED, a current through the LED is sensed, wherein the LED is driven by a power converter output, and wherein an output voltage of the power converter is proportionately controlled by a control signal. Next, a power supply voltage is sensed. The control signal is produced for the power converter, wherein the control signal is proportional to a difference between a reference voltage and the current through the LED. The control signal is then offset in response to the power supply voltage to reduce the current through the LED as the power supply voltage drops.

Abstract: In a method for producing a control signal for regulating a drive current for driving an LED, a current through the LED is sensed, wherein the LED is driven by a power converter output, and wherein an output voltage of the power converter is proportionately controlled by a control signal. Next, a power supply voltage is sensed. The control signal is produced for the power converter, wherein the control signal is proportional to a difference between a reference voltage and the current through the LED. The control signal is then offset in response to the power supply voltage to reduce the current through the LED as the power supply voltage drops.

Abstract: A prior art direct back EMF detection method synchronously sampled motor back EMF during PWM “off” time without the need to sense or re-construct the motor neutral in a sensorless brushless DC (BLDC) motor drive system. Since this direct back EMF sensing scheme requires a minimum PWM “off” time to sample the back EMF signal, the duty cycle cannot reach 100%. Also in some applications, for example, high inductance motors, the long settling time of a parasitic resonant between the motor inductance and the parasitic capacitance of power devices can cause false zero crossing detection of back EMF. An improved direct back EMF detection scheme samples the motor back EMF synchronously during PWM “on” time at high speed. In the final system the motor back EMF can be detected during PWM “off” time at low speed, and it is detected during PWM “on” time at high speed.

Abstract: A device and method that determine a freewheeling rotation of an electric motor. The method includes steps of measuring first and second signals from respective first and second windings of an unenergized motor, and determining from the first and second signals whether the unenergized motor is rotating. The method may also include determining from the first and second signals the direction of rotation if the unenergized motor is rotating. The method may further include measuring a third signal from a third winding of the unenergized motor, and determining whether the motor is rotating may include determining that the motor is not rotating if the first, second, and third signals are equal. The first and second signals may each include a respective back voltage.

Abstract: A circuit and method provide a back EMF signal that represents a back EMF voltage induced in a coil of a brushless motor. In one embodiment of the invention, the circuit includes an input node operable to receive a tap voltage from the coil, and a network coupled to the input node and operable to generate the back EMF signal by removing a predetermined offset voltage from the tap voltage. Such a circuit provides a signal that more accurately indicates a zero crossing than existing circuits for controlling a sensorless brushless motor.