Abstract: A constant-current controller with square wave input current shaping for driving a series of light emitting diodes (LEDs) is provided. The controller may include a sample and hold circuit that samples a current sense voltage, a first multiplier circuit that multiplies an output of the sample and hold circuit, an error detector circuit that compares an output of the multiplier circuit with a reference voltage, an error amplifier that amplifies an output of the error detector circuit, a second multiplier circuit that multiplies an output of the error amplifier by a coefficient, and an output circuit that outputs a pulse-width modulated control signal based on an output of the second multiplier circuit. The coefficient may vary depending on whether the constant-current LED driver controller is used with a boost converter or a buck-boost converter.

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 communication method and apparatus that uses modulation of post-conduction oscillation frequency in switching converters is provided. The apparatus may include a converter having a magnetic element having a primary winding and a secondary winding, a first switch, a control circuit configured to repeatedly activate the first switch to couple an input voltage source to the primary winding to store electrical energy in the magnetic element, and a diode coupled to the secondary winding, said diode configured to couple the secondary winding to a load to deliver the electrical energy stored in the magnetic element, and a communication apparatus having a second switch, a first modulator capacitor coupled to the secondary winding, a first transmitter configured to activate the second switch in accordance with a first input signal, and a first receiver configured to detect a post-conduction oscillation frequency of a voltage signal at the primary or secondary windings.

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 control circuit is coupled to the switch and the inductive element for activating and deactivating the switch, the control circuit activating and deactivating the switch based on a negative voltage drop across a resistive element of the control circuit.

Abstract: The invention relates to methods for supplying current to an auxiliary power supply, where the auxiliary supply is connected in parallel to a first switch of a switching regulator and the parallel connection of the auxiliary supply comprises a diode and a second switch.

Abstract: A comparator sense input is disconnected from a current sense resistor for the duration of a switching transition in an adjacent channel(s). Instead, the sense input receives a signal of the magnitude and the slew rate sampled prior to the transition.

Abstract: A circuit and method are provided detecting a persistent short circuit in a power MOSFET for the purpose of protecting a load from over-current.

Abstract: The invention comprises a dimming switch for use with a string of light emitting diodes (LEDs). The dimming switch comprises a bipolar junction transistor (BJT) driven in a cascode scheme. The dimming switch also comprises circuitry to offset the current that drives the base of the BJT to provide a controlled amount of current to the LEDs when the dimming input signal is high.

Abstract: A ballast circuit for a Light Emitting Diode (LED) has a regulator element coupled to the LED and to an input voltage source. A control circuit is coupled to the LED and to an input voltage source. A first switching device is coupled in series with the regulator element. A second switching device is coupled to the input voltage and the control 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 control circuit is coupled to the switch and the inductive element for activating and deactivating the switch, the control circuit activating and deactivating the switch based on a negative voltage drop across a resistive element of the control circuit.

Abstract: The invention relates to auxiliary power supplies.

Abstract: A circuit for flicker suppression in a Light Emitting Diode (LED) has a latch. The latch has a first state set with a trailing edge of Pulse Width Modulated Dimming (PWMD) pulse, and a second state set delayed with respect to the PWMD trailing edge. A trigger circuit is coupled to the latch. The trigger circuit sends a signal to the latch to change to the second state when a decision point occurs during a time following a duty limit Dmax of a gate of a LED driver circuit.

Abstract: An electronic circuit and method for sampling negative coil current in a power converter includes a zero crossing detector and a sample-and-hold circuit. A switch determines whether a charging or discharging current is flowing through a coil.

Abstract: A Light Emitting Diode (LED) driver circuit for driving an LED string has a switch-mode power supply coupled to the LED string. A control circuit is provided and has a first terminal coupled to a pulse width modulated input and a second terminal coupled to the switch mode power supply. A disconnect switch is coupled to a third terminal of the control circuit and the LED string.

Abstract: A ballast circuit for a Light Emitting Diode (LED) has a regulator element coupled to the LED and to an input voltage source. A control circuit is coupled to the LED and to an input voltage source. A first switching device is coupled in series with the regulator element. A second switching device is coupled to the input voltage and the control circuit.

Abstract: A circuit for flicker suppression in a Light Emitting Diode (LED) has a latch. The latch has a first state set with a trailing edge of Pulse Width Modulated Dimming (PWMD) pulse, and a second state set delayed with respect to the PWMD trailing edge. A trigger circuit is coupled to the latch. The trigger circuit sends a signal to the latch to change to the second state when a decision point occurs during a time following a duty limit Dmax of a gate of a LED driver circuit.

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 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 Light Emitting Diode (LED) lighting circuit has a passive valley-fill type power factor correction (PFC) circuit. A boost converter stage is coupled to the PFC circuit.

Abstract: A Light Emitting Diode (LED) driver for preventing shorting has an LED driver circuit. A protection circuit is coupled to the LED driver to detect a fault condition by monitoring a cathode of an LED string of the LED driver, an LED current sense voltage of the LED driver, an LED current feedback error voltage of the LED driver circuit, and a state of a dimming switch of the LED driver.