Abstract: A low-dropout regulator having an output voltage switching circuit is provided. In the low-dropout regulator, a low-dropout linear regulator circuit outputs a regulating signal according to a voltage difference between a second terminal of a transistor and a regulating threshold voltage signal or a reference voltage. In the low-dropout regulator, a switch error amplifier circuit outputs a pull-up control signal according to a voltage difference between the second terminal of the transistor and a voltage pull-up switching signal. When a voltage selector circuit of the low-dropout regulator selects the regulating signal, the transistor operates to regulate an output voltage of the low-dropout regulator according to the regulating signal. When the voltage selector circuit selects the pull-up control signal, a switch component is turned on by the pull-up control signal such that the output voltage of the low-dropout regulator is directly pulled up by an input voltage.

Abstract: A power converter for dynamically adjusting voltage headroom based on a current is provided. The power converter includes a high-side switch, a low-side switch, a sensor circuit, a current source, a mirror circuit, a reference voltage adjusting circuit and a control circuit. The sensor circuit senses a current flowing through a power receiving component to output a sensed current to a first terminal of a first transistor of a current mirror. A first terminal of the second transistor of the current mirror is connected to the current source. The reference voltage adjusting circuit sets a reference voltage according to a current from a node between the first terminal of the second transistor and the current source. The control circuit controls the high-side switch and the low-side switch according to the reference voltage.

Abstract: A power converter having a spectrum spreading control mechanism is provided. In the power converter, a buffer circuit, according to a plurality of energy upper limit values respectively of a plurality of frequency bands falling within a switching frequency range, determines a plurality of buffering ratios corresponding respectively to the plurality of frequency bands. In the power converter, the buffer circuit buffers a voltage signal from an inductor based on one of the plurality of buffering ratios that corresponds to one of the plurality of frequency bands within which a switching frequency of the high-side switch and the low-side switch currently falls. In the power converter, an on-time determining circuit determines an on-time of the high-side switch and an on-time of the low-side switch, according to the buffered voltage signal.

Abstract: A power converter having a stable output voltage is provided. The power converter includes a high-side switch, a low-side switch, an error amplifier, a low-side feedback circuit, a pulse wave signal generator circuit, a control circuit and a driver circuit. The low-side feedback circuit outputs a blank clock signal according to a voltage of a second end of the low-side switch, a low-side drive signal of a control end of the low-side switch and an error amplified signal from the error amplifier. The pulse wave signal generator circuit sets a frequency of a clock signal according to the blank clock signal. The control circuit outputs a control signal according to the clock signal. The driver circuit, according to the control signal, outputs a high-side drive signal to a control end of the high-side switch and outputs the low-side drive signal to the control end of the low-side switch.

Abstract: A motor driver for starting up a motor having any resistance is provided. The motor driver outputs a motor startup signal to the motor according to an initial startup duty cycle, senses a current value of a current signal of the motor multiple times, compares the current value of the motor that is sensed for multiple times with a reference current value and accordingly sets a plurality of pulse waves of a pulse width modulation signal. Then, the motor driver detects duty cycles of the pulse waves of the pulse width modulation signal as startup detection duty cycles. Then, the motor driver outputs a motor startup signal to the motor according to the startup detection duty cycles.

Abstract: A motor rotational speed control system and method having a duty cycle variable modulation mechanism is provided. The motor rotational speed control system is performed by the motor rotational speed control system including a motor rotational speed detector and a motor driver. When a rotational speed of a motor detected by the motor rotational speed detector is larger than or equal to a set rotational speed, the motor driver modulates duty cycles of a plurality of waveforms of an on-time signal, and modulates a duty cycle difference between the duty cycle of each of the plurality of waveforms and the duty cycle of a previous one or every other one of the plurality of waveforms in the on-time signal. The motor driver, according to the on-time signal, drives the motor such that the rotational speed of the motor is limited to be smaller than the set rotational speed.

Abstract: A positive hysteresis elimination comparison circuit and a motor driver having a positive hysteresis elimination comparison circuit are provided. The motor driver includes a comparator and a hysteresis switching circuit. The comparator compares a voltage of a first voltage signal received by a first input terminal of the comparator with a voltage of a second voltage signal received by a second input terminal of the comparator to output a comparing signal within a comparison time. When the voltage of the first voltage signal is lower than the voltage of the second voltage signal, the comparison time is delayed. When the voltage of the first voltage signal is higher than the voltage of the second voltage signal and a positive hysteresis elimination signal is received by a first control terminal of the comparator, the comparison time is not delayed.

Abstract: An adaptive voltage modulation circuit is provided. The adaptive voltage modulation circuit includes a plurality of driver circuits and a voltage control circuit. A first one of the driver circuits outputs a feedback signal to a next one of the driver circuits according to data of a load connected thereto. Each of the driver circuits, except for the first one and a last one of the driver circuits, according to the data of the load connected thereto and the feedback signal from a previous one of the driver circuits, outputs a next feedback signal to a next one of the driver circuits. The last one of the driver circuits, according to the data of the load connected thereto and the feedback signal from a previous one of the driver circuits, instructs the voltage control circuit to supply a common modulation power signal to each of the loads.

Abstract: A power converter having a multi-mode switching mechanism is provided. The power converter includes a first switch, a second switch, a low-side switch, an output calculating circuit and a control circuit. A first terminal of the first switch is connected to a first terminal of an inductor. A second terminal of the inductor is connected to an input power source. A first terminal of the second switch is connected to a second terminal of the first switch. A second terminal of the second switch is connected to the output calculating circuit. A first terminal of the low-side switch is connected to the first terminal of the first switch. A control circuit is connected to a control terminal of the first switch, a control terminal of the second switch, a control terminal of the low-side switch and the output calculating circuit.

Abstract: A power conversion system having spread spectrum and phase shifting mechanisms is provided. Each of a plurality of power converters of the power conversion system includes a spread spectrum instructing circuit, a synchronization signal detecting circuit, an oscillator circuit and a phase shifting circuit. The oscillator circuit outputs an oscillation signal according to a spread spectrum instruction parameter from the spread spectrum instructing circuit or a synchronization detected signal from the synchronization signal detecting circuit. The phase shifting circuit shifts phases of a plurality of waveforms of the oscillation signal to generate a clock signal. The phase shifting circuit of each of the plurality of power converters outputs the clock signal to a next one of the plurality of power converters. The synchronization signal detecting circuit of each of the power converters detects the clock signal to output the synchronization detected signal.

Abstract: A motor starting circuit having a dead time setting mechanism is provided. The motor starting circuit includes a rotational speed detection circuit, a start-up commutation selector circuit, a control circuit, a driver circuit and an output stage circuit. The rotational speed detection circuit detects a rotational speed of a motor. The start-up commutation selector circuit determines whether or not to set a dead time within a motor start-up time interval to output a commutation instructing signal according to the rotational speed of the motor. The control circuit controls the driver circuit to drive the output stage circuit so as to start up the motor according to the commutation instructing signal.

Abstract: A motor driver for adjusting power based on a common voltage is provided. The motor driver includes a common voltage difference calculation circuit, a duty cycle determination circuit, a signal generator circuit, a control circuit, a driver circuit and an output stage circuit. The common voltage difference calculation circuit calculates a difference between the common voltage received by the output stage circuit and a threshold. The duty cycle determination circuit determines a duty cycle adjustment value according to the difference. The signal generator circuit adjusts a plurality of waveform signals according to the duty cycle adjustment value. The control circuit outputs control signals according to the plurality of waveform signals. The driver circuit outputs driving signals according to the control signals. The output stage circuit operates to drive the motor according to the common voltage and the driving signals.

Abstract: A detector circuit having a current conversion mechanism for a power converter is provided. An output terminal of the power converter is connected to a first terminal of an inductor. The detector circuit detects a current flowing through the inductor as a detected current, and converts the detected current into a detected voltage. The detector circuit compares the detected voltage with a reference voltage to generate a comparison signal. Each time when a level of the comparison signal reaches a reference level, the detector circuit counts a count value.

Abstract: A power converter having a current limit protection mechanism is provided. An error amplifier of the power converter multiples a difference between (a divided voltage of) an output voltage of the power converter and a reference voltage by a gain to output an error amplified signal. A comparator of the power converter compares the error amplified signal with a ramp signal to output an on-time signal. A current limiting circuit of the power converter detects data related to a high-side switch and a low-side switch of the power converter. The current limiting circuit of the power converter compares working periods and non-working periods of the on-time signal with blanking times to output a current limiting signal. A control circuit of the power converter, according to the current limiting signal, determines whether to control the high-side switch and the low-side switch according to the detected data.

Abstract: A compensation circuit of realizing equivalent capacitance amplification is provided. The compensation circuit includes an error amplifier, a resistor and a capacitor. A first terminal of the resistor is connected to a first output terminal of the error amplifier. A second terminal of the resistor is connected to a second output terminal of the error amplifier and the capacitor. An amplified error current signal outputted from the first output terminal of the error amplifier flows through the resistor, and is then divided into a capacitor charging signal and an error amplified reverse current signal. The capacitor charging signal flows to the capacitor. The error amplified reverse current signal flows through the second output terminal of the error amplifier into the error amplifier. The error amplified reverse current signal is larger than the capacitor charging signal.

Abstract: A buck converter using an ultra-low working current is provided. An error amplifier amplifies a difference between a voltage of an output terminal of the buck converter and a reference voltage to output an error amplified signal. A comparator compares a voltage of the error amplified signal with a ramp voltage to output a comparison signal. A control circuit controls a driver circuit to drive a high-side switch and a low-side switch according to the comparison signal. When the buck converter does not enter an ultra-low current mode, a low current controller circuit controls a system circuit to obtain an input current from an input power source. When the buck converter enters the ultra-low current mode, the low current controller circuit controls the system circuit to stop obtaining the input current from the input power source.

Abstract: A driver circuit for adaptively switching a light-emitting diode current is provided. The driver circuit at least includes a first transistor, a first switching component, a second transistor, a third transistor and an operational amplifier. A first terminal of the first transistor is connected to a first input terminal of the operational amplifier. A first terminal of the first switching component is connected to a control terminal of the first transistor. A control terminal of the second transistor is connected to a second terminal of the first switching component. A first terminal of the third transistor is connected to one or more light-emitting diodes. A second terminal of the third transistor is connected to a first terminal of the second transistor and a second input terminal of the operational amplifier. An output terminal of the operational amplifier is connected to a control terminal of the third transistor.

Abstract: A multi-fan control system is provided. A controller, within each of a plurality of time intervals, outputs a control signal including a reading command to one of a plurality of fans, and outputs a control signal including a writing command to another of the plurality of fans. The controller, within each of the plurality of time intervals, only reads operation state data of the one of the plurality of fans that receives the control signal including the reading command, and writes operation control commands respectively into the plurality of fans.

Abstract: A power converter having an overvoltage protection mechanism is provided. A node between a second terminal of the high-side switch and a first terminal of a low-side switch is connected to an inductor. When an output current or an output voltage of the power converter must be released, the output current of the power converter flows to the input power source sequentially through the inductor, the high-side switch being turned on. Under this condition, when an overvoltage protecting circuit determines that a current or a voltage of the inductor or a current or a voltage of the input power source is larger than a threshold, the output current of the power converter flows to a ground through the overvoltage protecting circuit.

Abstract: A power-saving supply controller circuit of supplying power based on electrical specifications is provided. The power-saving supply controller circuit includes a first switch component, a second switch component and a control circuit. A first terminal of the first switch component and a first terminal of a capacitor are connected to a first terminal of a power supply device. Second terminals of the first and second switch components are connected to a second terminal of the power supply device. A first terminal of the second switch component is connected to a second terminal of the capacitor. When a current is supplied from the first terminal of the power supply device, the control circuit controls the first and second switch components such that a current flowing back to the second terminal of the power supply device is not smaller than a specified current.