Abstract: An embodiment is an apparatus that includes an energy-storage circuit and a rectifying circuit. The energy-storage circuit is configured to generate a current that flows in a direction, and the rectifying circuit is configured to substantially block the current from flowing in a reverse direction in response to the current. Such an apparatus may be configured to block a reverse current before it begins to flow. For example, such an apparatus may include a transistor disposed in the path of the current, and may be configured to deactivate the transistor while a forward current is still flowing. Furthermore, by being configured to block the current from flowing in a reverse direction in response to the current itself, such an apparatus may better block a reverse current than an apparatus that blocks a reverse current in another manner, such as in response to a voltage across a rectifying transistor.

Abstract: An embodiment is an apparatus that includes an energy-storage circuit and a rectifying circuit. The energy-storage circuit is configured to generate a current that flows in a direction, and the rectifying circuit is configured to substantially block the current from flowing in a reverse direction in response to the current. Such an apparatus may be configured to block a reverse current before it begins to flow. For example, such an apparatus may include a transistor disposed in the path of the current, and may be configured to deactivate the transistor while a forward current is still flowing. Furthermore, by being configured to block the current from flowing in a reverse direction in response to the current itself, such an apparatus may better block a reverse current than an apparatus that blocks a reverse current in another manner, such as in response to a voltage across a rectifying transistor.

Abstract: An LED driver with open loop dimming including a full wave rectifier circuit, a DC/DC converter, and an oscillator circuit. The rectifier is configured to receive an input voltage in the form of an AC conductive angle modulated voltage and to provide a rectified voltage. The DC/DC converter converts the rectified voltage to an output voltage and an output current, where the output current has a magnitude which varies proportionately with a square of a quadratic mean of the input voltage. The oscillator circuit controls switching of the DC/DC converter with constant frequency and constant duty cycle. The DC/DC converter may be a flyback converter and may include a transformer operated in DCM. The driver may include output voltage and/or output current limit. The output current may be limited when the input voltage is within normal operating range of an AC line voltage from which the input voltage is derived.

Abstract: Disclosed are full-bridge power converters providing DC output power at increased conversion efficiencies, and methods of operating full-bridge power converters providing DC output power at increased conversion efficiencies. In disclosed embodiments, the switches of the full-bridge are operated to reduce conduction losses and to provide for zero-voltage switching.

Abstract: Disclosed are full-bridge power converters providing DC output power at increased conversion efficiencies, and methods of operating full-bridge power converters providing DC output power at increased conversion efficiencies. In disclosed embodiments, the switches of the full-bridge are operated to reduce conduction losses and to provide for zero-voltage switching.

Abstract: A DC/DC voltage converter includes a transformer having a primary side and a secondary side. Primary side circuitry is connected to the primary side and includes a first pair of switching transistors controlled responsive to first control signals from the primary side of the transformer and receiving an input voltage. Secondary side circuitry is connected to the secondary side and includes a second pair of switching transistors controlled responsive to second control signals from the secondary side of the transformer and providing an output voltage. Driver circuitry generates the second control signals responsive to drain and source voltages at each of the second pair of switching transistors and a first and second PWM control signals. Signal shaping circuitry provides the first and second PWM control signals responsive to a drain voltage of each of the second pair of switching transistors.

Abstract: Disclosed are full-bridge power converters providing DC output power at increased conversion efficiencies, and methods of operating full-bridge power converters providing DC output power at increased conversion efficiencies. In disclosed embodiments, the switches of the full-bridge are operated to reduce conduction losses and to provide for zero-voltage switching.

Abstract: A dimming control circuit for dimming light emitting diodes receives an AC input voltage signal from a dimming circuit. The control circuit includes a power stage and a current control loop coupled to the power stage. An AC detector is operable to detect an instantaneous value of the AC input voltage signal and to generate a signal indicating whether the AC input voltage signal is present or absent. A current control circuit is operable responsive to the signal to adjust the operation of the current control loop and to control current through the light emitting diodes to achieve the desired dimming, and to prevent inrush current on the AC input voltage signal.

Abstract: A drive circuit supplies a drive current to a plurality of light emitting diodes. The drive circuit includes a voltage converter circuit having a particular topology and including at least one inductive element and at least one switching element. The drive circuit senses a current through one of the inductive and switching elements and generates a feedback signal from the sensed current. The feedback signal has a value indicating the drive current being supplied to the light emitting diodes and the drive circuit controls the operation of the voltage converter responsive to the feedback signal.

Abstract: A connector-less charging circuit includes a transformer having a primary side associated with a secondary side. A primary switch is responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle, and disconnecting the transformer from ground during the second portion of the duty cycle. An active clamp circuit connects to the primary side of the transformer for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle. A PWM controller generates the control signal to both the active clamp circuit and the primary switch.

Abstract: A dimming control circuit for dimming light emitting diodes receives an AC input voltage signal from a dimming circuit. The control circuit includes a power stage and a current control loop coupled to the power stage. An AC detector is operable to detect an instantaneous value of the AC input voltage signal and to generate a signal indicating whether the AC input voltage signal is present or absent. A current control circuit is operable responsive to the signal to adjust the operation of the current control loop and to control current through the light emitting diodes to achieve the desired dimming, and to prevent inrush current on the AC input voltage signal.

Abstract: A drive circuit supplies a drive current to a plurality of light emitting diodes. The drive circuit includes a voltage converter circuit having a particular topology and including at least one inductive element and at least one switching element. The drive circuit senses a current through one of the inductive and switching elements and generates a feedback signal from the sensed current. The feedback signal has a value indicating the drive current being supplied to the light emitting diodes and the drive circuit controls the operation of the voltage converter responsive to the feedback signal.

Abstract: A connector-less charging circuit includes a transformer having a primary side associated with a secondary side. A primary switch is responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle, and disconnecting the transformer from ground during the second portion of the duty cycle. An active clamp circuit connects to the primary side of the transformer for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle. A PWM controller generates the control signal to both the active clamp circuit and the primary switch.

Abstract: A current averaging circuit for averaging a piecewise linear switching current waveform of a PWM power converter including first, second and third sample and hold circuits and a sample averaging circuit. The first sample and hold circuit samples a short duration of the current waveform for each PWM cycle and provides corresponding short samples. The second sample and hold circuit samples a long duration of each PWM cycle and provides corresponding long samples. The sample averaging circuit is coupled to the first and second sample and hold circuits, averages corresponding ones of the short and long samples and provides corresponding average values. The third sample and hold circuit samples each average value and provides a current average signal. The waveform may include ramp-on-a-step voltage pulses representing switching current. The current average signal is updated after each current pulse.

Abstract: A DC-DC power converter including a bridge converter, a switching controller, a current sensing device, a current amplifier, and a PWM generator. The switching controller controls switching of the bridge converter based on a PWM signal. The current sensing device provides an average current signal indicative of an average output current of the bridge converter. The current amplifier compares the average current signal with a current reference signal and outputs an overload signal indicative thereof. The PWM generator generates the PWM signal and modifies the duty cycle of the PWM signal when the overload signal indicates an overload condition. The bridge converter may be implemented as either a half-bridge or a full-bridge converter. The current is sensed at the output or at the transformer primary. The sensed current may be processed to provide a signal proportional to average output current.