Abstract: A motor control device including a preprocessing portion calculating a counter electromotive force using an analog operation is provided. The motor control device may include an offset compensation portion and a counter electromotive force measuring portion. The offset compensation portion receives a three-phase current signal from the motor and compensates an offset of the three-phase current signal. The counter electromotive force measuring portion receives the compensated current signal and a three-phase voltage signal from the motor and calculates the received current signal and the received voltage signal using an analog operation to provide the calculated result.

Abstract: Provided is a sensorless BLDC motor system. The sensorless BLDC motor system includes a BLDC motor, a comparator, a motor controller, a three-phase inverter, and a mode selector. The BLDC motor includes first to third coils. The comparator compares a voltage of a specific coil of the first to third coils with a neutral-point voltage to output the compared result. The voltage of the specific coil becomes equal to the neutral-point voltage and a specific time elapses, and then the motor controller generates first and second coil control signals based on the compared result. The three-phase inverter supplies a source voltage or ground voltage to the specific coil, or floats the specific coil, in response to the first and second coil control signals. The mode selector selects a driving mode of the BLDC motor by adjusting the specific time.

Abstract: A phase-locked loop (PLL) circuit including a voltage-controlled oscillator (VCO) with a variable gain is provided. A phase frequency detector (PFD) detects a phase difference between a reference signal and a PLL feedback signal. A charge pump and a loop filter sequentially process an output signal of the PFD. A VCO has different gains according to a mode transition. A control voltage applied to the VCO is selected from an output signal of the loop filter and an additional control signal according to the mode transition.

Abstract: Provided is a transformer-based oscillator which is suited to oscillate frequencies in multiple bands. An oscillator includes a transformer resonance unit and a plurality of complementary transistors. The transformer resonance unit includes a primary coil and a secondary coil corresponding to the primary coil. The plurality of complementary transistors have gates and drains between which both ends of the transformer resonance unit are respectively connected. Thus, the oscillator may operate in a differential mode or common mode according to the phase of the transformer resonance unit. Also, a complementary transistor constituting a multiband oscillation loop may be independently connected to both ends of the transformer resonance unit, and an oscillation loop of at least one band may be selected out of a multiband oscillation loop using a switch unit. Thus, the oscillator may be suited to oscillate resonance frequencies in multiple bands.

Abstract: An LC voltage-controlled oscillator (VCO) is provided. The LC VCO includes an LC resonant circuit including at least one inductor whose both terminals are connected to output nodes and at least one capacitor connected in parallel with the inductor, and an amplifier circuit including at least one pair of switching transistors. Here, drains of the pair of switching transistors are connected to the output nodes respectively, and gates of the switching transistors are connected with the drains through a variable capacitance block exhibiting different characteristics according to an input signal.

Abstract: Provided is a spread spectrum clock generating circuit. The spread spectrum clock generating circuit includes: a phase detector receiving a reference frequency signal from the external and detecting a phase difference between the reference frequency signal and a frequency-divided signal; a voltage controlled oscillator outputting an oscillation signal corresponding to a detection result of the phase detector; a main divider generating the frequency-divided signal by dividing a frequency of the oscillation signal by a main dividing ratio; and a dividing ratio controller generating a variable count value, generating a sub dividing ratio by performing delta-sigma modulation according to the count value, and adjusting the main dividing ratio according to the sub dividing ratio.

Abstract: Provided is a PLL circuit including automatic frequency control circuit and an operating method thereof. The voltage controlled oscillator is primarily controlled by an automatic frequency control circuit, and is secondarily controlled by a loop filter. The voltage controlled oscillator outputs a coarsely-tuned oscillation signal when primarily controlled, and outputs a finely-tuned oscillation signal when secondarily controlled. The PLL circuit can have a quick frequency fixing time, and output the oscillation signal having a broad and stable frequency. Moreover, the noise characteristic of the PLL circuit is enhanced.

Abstract: Provided is a ring oscillator having an extended range of oscillation frequency by varactors coupled to delay cells even in a simple structure. The wide frequency range results from simply varying an oscillation frequency by control signals applied to the varactors. Since additional switches connected to the delay cells contribute to increase or decrease of the oscillation frequency range, the ring oscillator can conveniently be employed in various types of oscillation systems.

Abstract: Provided are a lock detection circuit and a lock detecting method. The lock detection circuit includes two delay devices, four flip-flops and two logic gates, and can accurately detect a lock state of a phase locked loop (PLL) circuit. Therefore, the lock detection circuit can be implemented in a simple structure, and as a result, the lock detection circuit can be compact in size and can consume less electric power. Also, the lock detecting method enables lock detection process to be simpler, so that a lock state can be detected within a short time period.

Abstract: A phase-locked loop (PLL) circuit including a voltage-controlled oscillator (VCO) with a variable gain is provided. A phase frequency detector (PFD) detects a phase difference between a reference signal and a PLL feedback signal. A charge pump and a loop filter sequentially process an output signal of the PFD. A VCO has different gains according to a mode transition. A control voltage applied to the VCO is selected from an output signal of the loop filter and an additional control signal according to the mode transition.

Abstract: An LC voltage-controlled oscillator (VCO) is provided. The LC VCO includes an LC resonant circuit including at least one inductor whose both terminals are connected to output nodes and at least one capacitor connected in parallel with the inductor, and an amplifier circuit including at least one pair of switching transistors. Here, drains of the pair of switching transistors are connected to the output nodes respectively, and gates of the switching transistors are connected with the drains through a variable capacitance block exhibiting different characteristics according to an input signal.

Abstract: Provided is a low voltage frequency synthesizer using a boosting method for a power supply voltage of a charge pump. The low voltage frequency synthesizer includes a phase/frequency detector (PFD) that receives and compares a reference frequency and a feedback frequency to output a comparison signal, a charge pump that receives the comparison signal to output a current corresponding to the comparison signal, a low-pass filter (LPF) that generates a voltage corresponding to the output current of the charge pump, a voltage controlled oscillator (VCO) that receives the voltage of the LPF, amplifies the voltage to generate a boosting voltage, and outputs a frequency corresponding to the received voltage, and a DC converter that receives the boosting voltage of the VCO, converts the boosting voltage into a DC voltage, and applies the DC voltage as a power supply voltage of the charge pump.

Abstract: An LC voltage-controlled oscillator (VCO) is provided. According to the LC voltage-controlled oscillator (VCO), the amplitude of an oscillation signal is improved by increasing the impedance value of an amplifier circuit seen from an output node in an LC voltage-controlled oscillator (VCO), and phase noise is also improved.

Abstract: Provided is a transformer-based oscillator which is suited to oscillate frequencies in multiple bands. An oscillator includes a transformer resonance unit and a plurality of complementary transistors. The transformer resonance unit includes a primary coil and a secondary coil corresponding to the primary coil. The plurality of complementary transistors have gates and drains between which both ends of the transformer resonance unit are respectively connected. Thus, the oscillator may operate in a differential mode or common mode according to the phase of the transformer resonance unit. Also, a complementary transistor constituting a multiband oscillation loop may be independently connected to both ends of the transformer resonance unit, and an oscillation loop of at least one band may be selected out of a multiband oscillation loop using a switch unit. Thus, the oscillator may be suited to oscillate resonance frequencies in multiple bands.

Abstract: Provided is a low voltage frequency synthesizer using a boosting method for a power supply voltage of a charge pump. The low voltage frequency synthesizer includes a phase/frequency detector (PFD) that receives and compares a reference frequency and a feedback frequency to output a comparison signal, a charge pump that receives the comparison signal to output a current corresponding to the comparison signal, a low-pass filter (LPF) that generates a voltage corresponding to the output current of the charge pump, a voltage controlled oscillator (VCO) that receives the voltage of the LPF, amplifies the voltage to generate a boosting voltage, and outputs a frequency corresponding to the received voltage, and a DC converter that receives the boosting voltage of the VCO, converts the boosting voltage into a DC voltage, and applies the DC voltage as a power supply voltage of the charge pump.

Abstract: Provided is a ring oscillator having an extended range of oscillation frequency by varactors coupled to delay cells even in a simple structure. The wide frequency range results from simply varying an oscillation frequency by control signals applied to the varactors. Since additional switches connected to the delay cells contribute to increase or decrease of the oscillation frequency range, the ring oscillator can conveniently be employed in various types of oscillation systems.

Abstract: Provided are a lock detection circuit and a lock detecting method. The lock detection circuit includes two delay devices, four flip-flops and two logic gates, and can accurately detect a lock state of a phase locked loop (PLL) circuit. Therefore, the lock detection circuit can be implemented in a simple structure, and as a result, the lock detection circuit can be compact in size and can consume less electric power. Also, the lock detecting method enables lock detection process to be simpler, so that a lock state can be detected within a short time period.

Abstract: Provided is a voltage-controlled oscillator with a wide oscillation frequency range and linear characteristics, which can linearly change an oscillation frequency versus control voltage due to a variable capacitance range increased by several MOS transistors additionally connected to an LC resonant circuit, and can control the oscillation frequency range by adjusting numbers, widths, lengths and operation regions of the MOS transistors. Thus, the voltage-controlled oscillator with a wide oscillation frequency range and linear control voltage-oscillation frequency characteristics without using a switching device can be implemented.