Abstract: A circuit to modulate the power supply to track input or output voltages provided to or output by a plurality of amplifiers to reduce power dissipation is provided. The circuit may include a peak detection circuit configured to receive a plurality of voltages respectively corresponding to the plurality of amplifiers, and to detect and output information regarding a maximum instantaneous voltage from the received plurality of voltages, and a summing circuit configured to output a sum of the information regarding the maximum instantaneous voltage and an amplifier headroom voltage. A reference voltage may be provided for the supply voltage responsive to the output sum. The circuit may also include a scaling circuit configured to scale the output sum, and the reference voltage may be a scaled reference voltage output by the scaling circuit.

Abstract: A circuit to modulate the power supply to track input or output voltages provided to or output by a plurality of amplifiers to reduce power dissipation is provided. The circuit may include a peak detection circuit configured to receive a plurality of voltages respectively corresponding to the plurality of amplifiers, and to detect and output information regarding a maximum instantaneous voltage from the received plurality of voltages, and a summing circuit configured to output a sum of the information regarding the maximum instantaneous voltage and an amplifier headroom voltage. A reference voltage may be provided for the supply voltage responsive to the output sum. The circuit may also include a scaling circuit configured to scale the output sum, and the reference voltage may be a scaled reference voltage output by the scaling circuit.

Abstract: An apparatus and method for reducing an output voltage ripple of a converter are provided. The apparatus may include a controller for controlling a converter, wherein the controller may include a clock generating circuit that generates a periodic clock signal containing periodic clock pulses, and a control circuit that causes the clock generating circuit to asynchronously initiate a clock pulse based on a difference between a feedback voltage of the converter and a reference voltage. The apparatus may also include an on-time modulation circuit which modulates the on-time based on the difference between the reference voltage and the sampled output voltage.

Abstract: An apparatus and method for reducing an output voltage ripple of a converter are provided. The apparatus may include a controller for controlling a converter, wherein the controller may include a clock generating circuit that generates a periodic clock signal containing periodic clock pulses, and a control circuit that causes the clock generating circuit to asynchronously initiate a clock pulse based on a difference between a feedback voltage of the converter and a reference voltage. The apparatus may also include an on-time modulation circuit which modulates the on-time based on the difference between the reference voltage and the sampled output voltage.

Abstract: A high power-factor buck-boost converter having a rectified low-frequency AC line voltage input and a DC output is provided. The converter may include a magnetic element, a controlled switch having a gate terminal and a drain terminal that is coupled to the magnetic element, a rectifier diode coupled to the magnetic element, an output smoothing capacitor coupled to the rectifier diode, and a control circuit having an output coupled to the gate terminal of the controlled switch for repeatedly turning the controlled switch off for a first time duration and on for a second time duration. The second time duration may be determined as a function of the first time duration immediately preceding the second time duration.

Abstract: A high power-factor buck-boost converter having a rectified low-frequency AC line voltage input and a DC output is provided. The converter may include a magnetic element, a controlled switch having a gate terminal and a drain terminal that is coupled to the magnetic element, a rectifier diode coupled to the magnetic element, an output smoothing capacitor coupled to the rectifier diode, and a control circuit having an output coupled to the gate terminal of the controlled switch for repeatedly turning the controlled switch off for a first time duration and on for a second time duration. The second time duration may be determined as a function of the first time duration immediately preceding the second time duration.

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

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 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 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: 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 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) 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.

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.