Abstract: A circuit for powering of a Light Emitting Diode (LED) string has a switching power converter. A brightness control circuit is coupled to the switching power converter to allow a duration of a conductive state of the power converter to exceed a duration of a conductive state of the LED string for maintaining a current magnitude in the LED string constant.

Abstract: A driver circuit has a Light Emitting Diode (LED) driver having an input and output. A switching device is coupled to an output of the LED driver. An edge detector is coupled to the LED driver. A timing device is coupled to the edge detector. A latch is coupled to the edge detector, the timing device and the switching device.

Abstract: A power supply circuit for powering a load at constant current has a rectifier stage for receiving an AC voltage input and for producing a first substantially DC voltage. A first capacitor is attached to the load. A charge-pump is attached to an output of the rectifier stage and to the load for providing power factor correction and for converting the first substantially DC voltage to a second substantially DC voltage at the first capacitor. The charge pump is prevented from conducting energy back into the output of the rectifier stage. The charge pump delivers energy to a charge pump output, the energy being delivered directly instead of being stored. A converter stage is attached to the load and the first capacitor. The converter stage is used for converting voltages at the first capacitor and the charge pump to an output DC current. The converter stage has a switch for periodically connecting a first series-coupled circuit of the charge pump to the output of the rectifier stage.

Abstract: A method of controlling an output current of a power supply circuit comprising a first converter stage for receiving an input voltage, a second converter stage delivering a regulated output current, a controlled switch for conducting the input current and the output current, the method comprising: detecting a portion of the input current conducted by the controlled switch; detecting a current in the controlled switch; deriving a difference between the current in the controlled switch and the portion of the input current conducted by the controlled switch; and maintaining the difference at a reference level.

Abstract: A current driver for powering a string of LEDs has a boost converter coupled to an input voltage source. A voltage multiplier circuit is coupled to the boost converter and to the string of LEDs. A latch is provided having an output coupled to the boost converter. A current sense element is coupled to the boost converter. A current comparator is provided having an output coupled to a first input of the latch, a first input coupled to the current sense element, and a second input coupled to a reference current. A zero-volt detector circuit is provided having an output coupled to a second input of the latch and an input coupled to the boost converter and the voltage multiplier circuit.

Abstract: A switching power converter has an input voltage source. An output load is coupled to the input voltage source. An inductive element is coupled to the load. A switch is coupled to the inductive element. A current reference input is provided. A control circuit is coupled to the switch and the current reference input for activating and deactivating the switch. The inductive element receives power from the input voltage source when the switch is activated and conducting continuous current. The control circuit deactivates the switch after a controlled delay time when the current in the inductive element and the switch exceeds the current reference input so that an average current in the inductive element is determined by a magnitude of the current reference input.

Abstract: A circuit for powering of a Light Emitting Diode (LED) string has a switching power converter. A brightness control circuit is coupled to the switching power converter to allow a duration of a conductive state of the power converter to exceed a duration of a conductive state of the LED string for maintaining a current magnitude in the LED string constant.

Abstract: A dimming circuit for driving a string of LEDs at constant current has a power converter. A control circuit is coupled to the power converter. A plurality of shunt switches is provided. An individual shut switch is coupled to each LED. Each LED can be shunted individually by the individual shunt switch. The control circuit corrects an internal DC state based on a feedback signal VO so that the output current of the power converter remains unchanged when at least one LED is shunted.

Abstract: A power supply circuit for powering a load at constant current has a rectifier stage for receiving an AC voltage input and for producing a first substantially DC voltage. A first capacitor is attached to the load. A charge-pump is attached to an output of the rectifier stage and to the load for providing power factor correction and for converting the first substantially DC voltage to a second substantially DC voltage at the first capacitor. The charge pump is prevented from conducting energy back into the output of the rectifier stage. The charge pump delivers energy to a charge pump output, the energy being delivered directly instead of being stored. A converter stage is attached to the load and the first capacitor. The converter stage is used for converting voltages at the first capacitor and the charge pump to an output DC current. The converter stage has a switch for periodically connecting a first series-coupled circuit of the charge pump to the output of the rectifier stage.

Abstract: A switching power converter has an input voltage source. An output load is coupled to the input voltage source. An inductive element is coupled to the load. A switch is coupled to the inductive element. A current reference input is provided. A control circuit is coupled to the switch and the current reference input for activating and deactivating the switch. The inductive element receives power from the input voltage source when the switch is activated and conducting continuous current. The control circuit deactivates the switch after a controlled delay time when the current in the inductive element and the switch exceeds the current reference input so that an average current in the inductive element is determined by a magnitude of the current reference input.

Abstract: A current driver for powering a string of LEDs has a boost converter coupled to an input voltage source. A voltage multiplier circuit is coupled to the boost converter and to the string of LEDs. A latch is provided having an output coupled to the boost converter. A current sense element is coupled to the boost converter. A current comparator is provided having an output coupled to a first input of the latch, a first input coupled to the current sense element, and a second input coupled to a reference current. A zero-volt detector circuit is provided having an output coupled to a second input of the latch and an input coupled to the boost converter and the voltage multiplier circuit.

Abstract: A Pulse Width Modulation (PWM) dimming circuit for individually controlling brightness of series connected Light Emitting Diodes (LEDS) operated at constant current has a first plurality of switching devices, a signal switching device of the first plurality coupled to an individual LED of series connected LEDS to control a brightness of the individual LED by periodically shunting the individual LED. A power converter supplies a constant output current to the series connected LEDs. Control circuitry is coupled to the power converter, wherein the control circuit corrects an internal DC state based on a feedback signal VO so that the output current of the power supply remains unchanged when at least one LEDs is shunted.

Abstract: A system and method for delivering regulated power and current to an output load has a flyback transformer having a primary winding and a secondary winding. The secondary winding delivers stored energy to the output load. An oscillator circuit is provided for generating a periodical signal. A switching circuit is coupled to the flyback transformer and the oscillator circuit for energizing the primary winding to a reference current level each cycle of the oscillator circuit. The oscillator circuit has an integrator for deriving a time integral of a voltage at the primary winding. The oscillator circuit has a peak detector coupled to the integrator for holding a peak value of the time integral. The oscillator circuit further has a ramp generator for producing a ramp signal. A comparator is provided for comparing the peak value with the ramp signal and generating the periodical signal whenever the ramp signal exceeds the peak value.

Abstract: A circuit and a method for controlling output current of cascaded switching power converters having a buck type output stage are disclosed. The circuit comprises two comparators for sensing input and output current, a logic gate for processing the output states of the comparators, and a pulse width modulator circuit for receiving the output of the logic gate and for controlling a switching power converter in accordance with this output. The method comprises simultaneous monitoring current in the stages of the converter, comparing the currents to the corresponding reference levels, generating the corresponding error signals, and controlling a pulse-width modulator circuit of a switching converter in accordance with these error signals.

Abstract: A dimming circuit for driving a string of LEDs at constant current has a power converter. A control circuit is coupled to the power converter. A plurality of shunt switches is provided. An individual shut switch is coupled to each LED. Each LED can be shunted individually by the individual shunt switch. The control circuit corrects an internal DC state based on a feedback signal VO so that the output current of the power converter remains unchanged when at least one LED is shunted.

Abstract: A system and method for delivering regulated power and current to an output load has a flyback transformer having a primary winding and a secondary winding. The secondary winding delivers stored energy to the output load. An oscillator circuit is provided for generating a periodical signal. A switching circuit is coupled to the flyback transformer and the oscillator circuit for energizing the primary winding to a reference current level each cycle of the oscillator circuit. The oscillator circuit has an integrator for deriving a time integral of a voltage at the primary winding. The oscillator circuit has a peak detector coupled to the integrator for holding a peak value of the time integral. The oscillator circuit further has a ramp generator for producing a ramp signal. A comparator is provided for comparing the peak value with the ramp signal and generating the periodical signal whenever the ramp signal exceeds the peak value.

Abstract: A circuit and a method for controlling output current of cascaded switching power converters having a buck type output stage are disclosed. The circuit comprises two comparators for sensing input and output current, a logic gate for processing the output states of the comparators, and a pulse width modulator circuit for receiving the output of the logic gate and for controlling a switching power converter in accordance with this output. The method comprises simultaneous monitoring current in the stages of the converter, comparing the currents to the corresponding reference levels, generating the corresponding error signals, and controlling a pulse-width modulator circuit of a switching converter in accordance with these error signals.

Abstract: A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. An integrator generates a voltage that represents flux within a magnetic element by integrating a primary-side winding voltage. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to zero energy level in the power magnetic element. The integrator voltage is stored at the end of the half-cycle and is used to determine a sampling point prior to or equal to the start of post-conduction resonance in a subsequent switching cycle of the power converter. The primary-side winding voltage is then sampled at the sampling point, providing an indication of the output voltage of the power converter by which the output voltage of the converter can be controlled.

Abstract: A switch state controller generating a pulse train is used in a power converter utilizing a plurality of converter stages all simultaneously controlled by a single switch controlled by said pulse train. On time of the pulse train is controlled according to an input or interim node characteristic of the supply and period is controlled by a characteristic of the output of the converter. This allows development of AC-to-DC converters, including power-factor-correction converters, and DC to DC converters with high conversion ratio with minimal parts count & high reliability.

Abstract: A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. The power converter has improved immunity to parasitic phenomena and other variations within the power converter components. An integrator is used to generate a voltage analog that represents magnetic flux within a power magnetic element via an integration of a voltage on a primary-side winding of the power magnetic element. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to the energy level in the power magnetic element reaching zero.