Abstract: A multiple output regulating charge pump includes a load current regulator to balance currents in multiple branches of at least one load, such as light emitting diodes in a parallel configuration. The load current regulator includes current mirror circuits to provide substantially identical currents to the respective light emitting diodes, thereby producing uniform light from each of the light emitting diodes. The multiple output charge pump includes a charge storage component that is alternately charged during a charge cycle and discharged during a discharge cycle. The charge pump provides current to a second load during the charge cycle and to a first load during a discharge cycle.

Abstract: A linear voltage regulator, such as a low-dropout regulator, supplies power to one or more digital circuits within a computer system. The low-dropout regulator provides a substantially constant output voltage independent of loading conditions. The low-dropout regulator is biased at a relatively low operating current for steady-state operation to improve power efficiency of the low-dropout regulator. During a loading condition change, an adaptive biasing circuit senses the loading condition change and provides additional biasing current to momentarily increase the operating current of the low-dropout regulator to improve transient response.

Abstract: A charge pump receives a direct current input voltage at a first level and provides a substantially constant direct current output voltage at a second level. Variations of the input voltage level above and below the output voltage level are handled seamlessly by a continuous mode control scheme that controls a charging current of the charge pump. The charge pump includes an error amplifier which produces a control signal based on a comparison of a feedback voltage proportional to the output voltage and a reference voltage. The control signal controls a variable current source to regulate the charging current provided to a charge storage component.

Abstract: An efficient power conversion circuit for driving a fluorescent lamp uses a minimum pulse generator circuit to control the minimum on-time of a time modulated signal to increase the dimming range of the fluorescent lamp operating over a wide range of temperature and supply voltage. A minimum number of lamp current cycles with respective amplitudes above a preset threshold is typically required to avoid flickering or shimmering during minimum brightness. The minimum pulse generator circuit counts the lamp current cycles and adjusts the on-time accordingly to guarantee the minimum number of cycles with respective amplitudes above a preset threshold under all operating conditions.

Abstract: An improved class D power amplifier is disclosed. Instead of using prior art triangle waves a ramp signal having a first state of about 90% or greater is used and a second state for the remainder of the cycle. Further, the amplifier includes flip-flops and amplifiers with hysteresis to reduce switching noise. Also, level shifting circuitry is provided for shifting the level of the input signal in response to both DC and AC variations in the power supply and to provide power supply rejection. Still further, multiple channels may be used with all of the channels synchronized to the same timing source.

Abstract: A transient recovery circuit in a switching regulator responds to relatively quick changes in load currents to suppress output voltage overshoots or undershoots. The transient recovery circuit operates independently of a regular feedback circuit and overrides a control voltage from the regular feedback circuit to control the duty cycle of a pulse-width modulation circuit in the switching regulator during transient conditions. The transient recovery circuit is inactive during non-transient conditions. The transient recovery circuit can be used in a single phase or a multiphase switching regulator.

Abstract: All efficient power conversion circuit for driving a fluorescent lamp uses a minimum pulse generator circuit to control the minimum on-time of a time modulated signal to increase the dimming range of the fluorescent lamp operating over a wide range of temperature and supply voltage. A minimum number of lamp current cycles with respective amplitudes above a preset threshold is typically required to avoid flickering or shimmering during minimum brightness. The minimum pulse generator circuit counts the lamp current cycles and adjusts the on-time accordingly to guarantee the minimum number of cycles with respective amplitudes above a preset threshold under all operating conditions.

Abstract: An efficient multiphase switching regulator uses sensed voltages to achieve accurate forced current sharing and programmable current sharing. The voltage waveforms at the input of respective inductors are low-pass filtered to produce sensed voltages which are proportional to the duty cycles of the respective voltage waveforms. The sensed voltages are compared. The comparisons are used to adjust PWM circuits which control the duty cycles of the voltage waveforms of the respective inductors. Substantially identical sensed voltages at the inputs of identical inductors result in substantially identical output currents from respective inductors. The ratio of the output currents from respective inductors can be changed by adjusting a variable resistor that changes the fractions of respective sensed voltages being compared.

Abstract: An efficient multiphase switching regulator uses sensed voltages to achieve accurate forced current sharing and programmable current sharing. The voltage waveforms at the input of respective inductors are low-pass filtered to produce sensed voltages which are proportional to the duty cycles of the respective voltage waveforms. The sensed voltages are compared. The comparisons are used to adjust PWM circuits which control the duty cycles of the voltage waveforms of the respective inductors. Substantially identical sensed voltages at the inputs of identical inductors result in substantially identical output currents from respective inductors. The ratio of the output currents from respective inductors can be changed by adjusting a variable resistor that changes the fractions of respective sensed voltages being compared.

Abstract: An improved class D power amplifier is disclosed. Instead of using prior art triangle waves, a ramp signal having a first state of about 90% or greater is used and a second state for the remainder of the cycle. Further, the amplifier includes flip-flops and amplifiers with hysteresis to reduce switching noise. Also, level shifting circuitry is provided for shifting the level of the input signal in response to both DC and AC variations in the power supply and to provide power supply rejection. Still further, multiple channels may be used with all of the channels synchronized to the same timing source.

Abstract: A dimmable, backlight system provides increased light output at low temperatures and provides a full range of dimming. Both current amplitude control and current duty cycle control are used to more precisely adjust the lamp light output. During low temperatures, the lamp is overdriven using a high amplitude current source. The increased current provides increased light output at low temperatures. When the lamp temperature increases, the amount of current flowing to the lamp is reduced to prevent damage from occurring to the lamp. The lamp may be dimmed throughout the entire temperature range by adjusting the duty cycle of the current source. By dimming using the duty cycle, the light output of the lamp may be more precisely controlled. The amplitude and duty cycle may be controlled using either an analog or digital control signal.

Abstract: A power conversion circuit drives a cold cathode fluorescent lamp (CCFL) while requiring minimal number of external components. The circuit includes a controller, a direct drive network responsive to control inputs from the controller and coupled to receive a power signal, and a secondary network coupled to the CCFL. The direct drive network is low Q circuit comprising a plurality of switching transistors and a primary winding of a transformer such that an impedance of the direct drive network consists essentially of an inductance of the primary winding and capacitance of the direct drive network consists essentially of parasitic capacitance reflected from the secondary winding. The Q of the direct drive network is less than about 0.5 so that a square wave voltage signal is provided across the primary winding of the transformer. However, the inductance of the transformer is sufficiently high such that the voltage across a secondary winding of the transformer is sinusoidal.

Abstract: A power conversion circuit drives a cold cathode fluorescent lamp (CCFL) while requiring minimal number of external components. The circuit includes a controller, a direct drive network responsive to control inputs from the controller and coupled to receive a power signal, and a secondary network coupled to the CCFL. The direct drive network is low Q circuit comprising a plurality of switching transistors and a primary winding of a transformer such that an impedance of the direct drive network consists essentially of an inductance of the primary winding and capacitance of the direct drive network consists essentially of parasitic capacitance reflected from the secondary winding. The Q of the direct drive network is less than about 0.5 so that a square wave voltage signal is provided across the primary winding of the transformer. However, the inductance of the transformer is sufficiently high such that the voltage across a secondary winding of the transformer is sinusoidal.

Abstract: A method for sensing motor commutation pulses during motor braking without creating negative voltages, which some junction isolated technologies substantially cannot tolerate. For instance, a commutation pulse sensing circuit containing junction isolated technology may only be able to detect commutation pulses intermittently. An H-bridge motor drive configuration is used to drive and brake a motor. High side clamp diodes are coupled between the motor terminals and a high potential source for high side braking of the motor. As an alternative to high side clamp diodes, any other suitable device may be used, including operating the pair of transistors in the upper portion of the H-bridge in an inverse mode. A commutation pulse sensing circuit is coupled to a terminal of the motor. The use of the high side brake clamp diodes avoids generating negative voltages at the motor terminals.

Abstract: A power converter circuit provides low conversion losses, low generated noise and output power controllability. The circuit includes a controller, at least two transistors and an output network that provides impedance matching and operating point stabilization functions. The output network also enables zero voltage switching of the transistors, thus reducing radiated noise and minimizing (and possibly eliminating almost completely) switching losses. The controller circuitry includes an oscillator which is capable of self synchronizing to the resonant frequency of the components of the output network. Power modulation (e.g., for dimming of a lamp) is accomplished simply by desynchronizing and increasing the oscillator frequency. Thus, the control architecture allows the use of external parts of lower precision and cost while providing dimming capability in a single stage.

Abstract: An improved low voltage dropout regulation circuit is provided. The internal compensating capacitance coupled to the regulated output port is coupled to a virtual ground and the virtual ground is current buffered for coupling to the control electrode of the path element. For additional frequency compensation, particularly when the path element has a large capacitance, an additional internal compensating capacitance is coupled between the input of the dropout circuit and an output of a transconductance amplifier, which is responsive to the voltage at the regulated output port.

Abstract: An improved low voltage dropout regulation circuit is provided. The internal compensating capacitance coupled to the regulated output port is coupled to a virtual ground and the virtual ground is current buffered for coupling to the control electrode of the path element.