Abstract: A pulse width modulation circuit capable of linearly adjusting duty cycle with voltage, which comprises an input voltage source for generating an input voltage, a regulator for generating a regulated voltage, a first voltage-dividing unit for providing a first divided voltage, a second voltage-dividing unit for providing a second divided voltage, a third voltage-dividing unit for providing a third divided voltage, a voltage adder for adding the first divided voltage and the third divided voltage for generating a high level voltage, a waveform generator for generating an oscillating signal according to the high level voltage and the third divided voltage, and a comparator having a first input terminal coupled to the second voltage-dividing unit, a second terminal coupled to the waveform generator, and an output terminal for comparing the second divided voltage with the oscillating signal to output a pulse width modulation signal through the output terminal.

Abstract: A pulse width modulation circuit capable of linearly adjusting duty cycle with voltage, which comprises an input voltage source for generating an input voltage, a regulator for generating a regulated voltage, a first voltage-dividing unit for providing a first divided voltage, a second voltage-dividing unit for providing a second divided voltage, a third voltage-dividing unit for providing a third divided voltage, a voltage adder for adding the first divided voltage and the third divided voltage for generating a high level voltage, a waveform generator for generating an oscillating signal according to the high level voltage and the third divided voltage, and a comparator having a first input terminal coupled to the second voltage-dividing unit, a second terminal coupled to the waveform generator, and an output terminal for comparing the second divided voltage with the oscillating signal to output a pulse width modulation signal through the output terminal.

Abstract: A pulse width modulation (PWM) structure enabling regulated duty cycle includes a DC power supply unit, a signal generating unit, a voltage-dividing resistor unit, a reference voltage unit, and a comparing unit. When the DC power supply unit supplies a voltage signal to the voltage-dividing resistor unit, the latter receives the voltage signal and sets voltage levels before sending the voltage signal to the signal generating unit, so that a waveform signal generated by the signal generating unit regulates its voltage levels according to the received voltage signal before sending the waveform signal to the comparing unit. The comparing unit receives and compares the signals from the signal generating unit and the reference voltage unit, and outputs a comparison signal for driving a fan motor to operate, so that the finally output signal is substantially linear and smooth.

Abstract: A sensorless method for starting a three-phase brushless direct-current motor includes generating a start-up control signal, a start mode selection signal, and a control signal commutation period; switching to a start mode according to the start mode selection signal; implementing a position aligning procedure according to the start-up control signal and the control signal commutation period; detecting a zero crossing point of back electromotive forces during each control signal commutation period; outputting a sensorless mode selection signal while detecting the zero crossing points of the back electromotive forces during consecutive control signal commutation periods; switching to a sensorless mode according to the sensorless mode selection signal; and detecting a zero crossing point of back electromotive forces in the sensorless mode to determine a starting result of the three-phase brushless direct-current motor.

Abstract: A rotating speed adjustment circuit for a heat dissipation fan includes a first node, a second node, a reception end for receiving a first control signal, a first resistor coupled to a voltage source and the first node, a second resistor coupled to the first node and the second node, a third resistor coupled to the second node and a ground end, a capacitor coupled to the first node and the ground end, a transistor coupled to the reception end, the second node and the ground end, an oscillator for generating an oscillating signal, and a comparator for comparing a signal of the first node and the oscillating signal, so as to output a second control signal to control a rotating speed of the heat dissipation fan.

Abstract: A motor driving circuit for adjusting speed of the motor by changing output voltage is disclosed. One end of the motor is coupled to a variable voltage source. The motor driving circuit includes a motor-driving unit, a control unit and a determining unit. The motor-driving unit includes a first end coupled to another end of the motor, a second end coupled to a ground and a third end, and is utilized for driving the motor. The control unit is utilized for controlling the voltage between the first end and the third end of the motor-driving unit. The determining unit is coupled between the variable voltage source and the control unit, and is utilized for controlling the control unit to adjust the voltage between the first end and the third end of the motor-driving unit according to magnitude of the voltage of the variable voltage source.

Abstract: An inrush voltage clamping circuit for an electronic device for clamping an inrush voltage induced by hot plugging is disclosed. The clamp circuit includes a buffer unit and a clamp unit. The buffer unit is coupled to an input power end for receiving an inrush current of the inrush voltage. The clamp unit is coupled to the input power end and the buffer unit for controlling the buffer unit to receive the inrush current according to an input voltage of the input power end.

Abstract: A driving circuit includes a power supply, an input capacitor, a Hall sensor, a first amplifier, a second amplifier, a full-bridge driver circuit, and a first operational amplifier. The input capacitor is coupled to the power supply. The input end of the first amplifier and the second amplifier is coupled to the output end of the Hall sensor. The control end of the full-bridge driver circuit is coupled to the output end of the first amplifier and the output end of the second amplifier. The first operational amplifier includes a first input end for receiving a first reference voltage and a second input end coupled to the first output end of the full-bridge driver circuit.

Abstract: The present invention relates to a pulse width modulation switching direct voltage circuit. The PWM circuit comprises a first passive device, a second passive device and a third passive device connected in series between a power supply and a ground such that the first passive device is connected to the second passive device and the second passive device is connected to the third passive device, and a fourth passive device which is connected in-parallel between an output end and a point between the first passive device and the second passive device, wherein the rated value of the fourth passive device is at least three times more than the rated value of the first passive device. Herewith, the voltage-cycle relationship of the PWM circuit becomes linear. Under such a state, the PWM circuit is enabled with good work efficiency.

Abstract: A pulse width modulation (PWM) structure enabling regulated duty cycle includes a DC power supply unit, a signal generating unit, a voltage-dividing resistor unit, a reference voltage unit, and a comparing unit. When the DC power supply unit supplies a voltage signal to the voltage-dividing resistor unit, the latter receives the voltage signal and sets voltage levels before sending the voltage signal to the signal generating unit, so that a waveform signal generated by the signal generating unit regulates its voltage levels according to the received voltage signal before sending the waveform signal to the comparing unit. The comparing unit receives and compares the signals from the signal generating unit and the reference voltage unit, and outputs a comparison signal for driving a fan motor to operate, so that the finally output signal is substantially linear and smooth.

Abstract: Avibration-reduction an driving circuit is applicable to a fan that operates according to a current signal sent thereto, and is characterized in a current buffer unit connected to a drive current supplied from a power source and having a relatively large magnitude of change in current. The current buffer unit divides the original drive current into multiple continuously changing drive currents that have a relatively small magnitude of change in current, so that electric current supplied to the fan is regulated and output fractionally to achieve the purpose of reducing the vibration of fan caused by a large magnitude of change in current.

Abstract: A driving circuit for switching DC power includes a DC power generator, a bridge circuit, a control signal generator, and a clamping module. The bridge circuit includes a plurality of legs each including an up-bridge switch and a down-bridge switch. The clamping circuit is coupled to each up-bridge switch of the bridge circuit for clamping voltage of an input end of the up-bridge switch.

Abstract: A motor protection device includes a detection unit for detecting an operating state of a motor and outputting a detection signal; a reference unit for generating a variable reference signal; a discriminating unit for comparing the detection signal with the variable reference signal to discriminate whether the motor is in an abnormal condition; and a protection unit that receives a result of discrimination from the discriminating unit and limits a driving current for the motor when the motor is in an abnormal condition. The motor protection device is characterized in that the reference unit adjusts the variable reference signal according to a motor rotation detection signal, so that the motor rotation detection signal and the detection signal are used synchronously in discriminating whether the motor is in an abnormal condition, and the motor in an abnormal condition may be doubly protected.

Abstract: A power cutter, an oscillator, a counter, a S-R latch, and a Hall bias are further disposed inside a DC motor driving circuit so that current consumption of the DC motor driving circuit is reduced significantly under a standby mode. When the counter detects that a received pulse width modulation signal stays at a low electrical level over a predetermined time, the counter triggers the S-R latch so as to activate a disabling signal of the power cutter for shutting down most elements until the pulse width modulation signal returns to a high electrical level. With the aid of the built-in Hall bias, space for externally coupling the Hall bias is saved, and moreover, a Hall sensor retrieves a dynamically-adjusted power and currents so that remarkable current consumption is saved under a standby mode.

Abstract: The present invention relates to a pulse width modulation switching direct voltage circuit. The PWM circuit comprises a first passive device, a second passive device and a third passive device which they are connected orderly in series, and a fourth passive device which is connected in parallel between the first passive device and the second passive device, wherein the rated value of the fourth passive device is at least three times more than the rated value of the first passive device. Herewith, the voltage-cycle relationship of the PWM circuit becomes linear. Under such a state, the PWM circuit is enabled with good work efficiency.

Abstract: A driving level control structure eliminating electric noise from motor includes a drive control unit, a sensing unit, a setting unit, a first comparing unit, and a frequency control unit. The first comparing unit generates a first discriminating signal based on a reference level signal provided by the sensing unit and a preset level signal provided by the setting unit. The frequency control unit generates a second discriminating signal based on the first discriminating signal. The second discriminating signal is set to a specific frequency fallen out of a human ear perceptible frequency range before being sent to the drive control unit for controlling a motor coil unit to on or off as a current limiting operation, so that electric noise from a motor during the current limiting operation thereof is eliminated.

Abstract: A power cutter, an oscillator, a counter, a S-R latch, and a Hall bias are further disposed inside a DC motor driving circuit so that current consumption of the DC motor driving circuit is reduced significantly under a standby mode. When the counter detects that a received pulse width modulation signal stays at a low electrical level over a predetermined time, the counter triggers the S-R latch so as to activate a disabling signal of the power cutter for shutting down most elements until the pulse width modulation signal returns to a high electrical level. With the aid of the built-in Hall bias, space for externally coupling the Hall bias is saved, and moreover, a Hall sensor retrieves a dynamically-adjusted power and currents so that remarkable current consumption is saved under a standby mode.

Abstract: A full bridge circuit includes a first switch, a second switch, a third switch, a fourth switch, a first controller, a second controller, a first operational amplifier, a first multiplexer, a second operational amplifier, and a second multiplexer. The first controller includes a first output coupled to the first switch. The second controller includes a first output coupled to the third switch. The first operational amplifier includes a first input coupled to the first switch and the second switch, and a second input for receiving a first reference voltage. The second operational amplifier includes a first input coupled to the third switch and the fourth switch, and a second input for receiving a second reference voltage. The first multiplexer is coupled to the first operational amplifier, the first controller, and the second switch. The second multiplexer is coupled to the second operational amplifier, the second controller, and the fourth switch.

Abstract: A driving circuit for switching DC power includes a DC power generator, a bridge circuit, a control signal generator, and a clamping module. The bridge circuit includes a plurality of legs each including an up-bridge switch and a down-bridge switch. The clamping circuit is coupled to each up-bridge switch of the bridge circuit for clamping voltage of an input end of the up-bridge switch.

Abstract: A full bridge circuit includes a first switch, a second switch, a third switch, a fourth switch, a first controller, a second controller, a first operational amplifier, a first multiplexer, a second operational amplifier, and a second multiplexer. The first controller includes a first output coupled to the first switch. The second controller includes a first output coupled to the third switch. The first operational amplifier includes a first input coupled to the first switch and the second switch, and a second input for receiving a first reference voltage. The second operational amplifier includes a first input coupled to the third switch and the fourth switch, and a second input for receiving a second reference voltage. The first multiplexer is coupled to the first operational amplifier, the first controller, and the second switch. The second multiplexer is coupled to the second operational amplifier, the second controller, and the fourth switch.