Abstract: A coil current detector detects a current component flowing through a coil. A scaling unit scales a drive signal. An induced voltage component extraction unit extracts an induced voltage component by removing the drive signal, scaled by the scaling unit, from the coil current component detected by the current detector. A phase difference detector detects a phase difference between the phase of the drive signal and that of the induced voltage component. A signal adjustment unit adjusts the drive signal so that the phase difference detected by the phase difference detector can be brought close to a target phase difference.

Abstract: The effect of chattering on the measurement of the pulse period is reduced. The pulse period representing the rise interval of target pulses appearing in a pulse signal PI is measured. The pulse signal PI is sampled in synchronization with a measurement clock CLK. Measurement of a designated inhibition period is started in synchronization with the fall of the signal PI. Measurement of the current pulse period is completed and measurement of a new pulse period is started if the inhibition period has elapsed at the rise of the signal PI. Counting of the current pulse period is continued if the inhibition period has not elapsed.

Abstract: A drive-signal-generating circuit includes: a current-detecting unit to detect a current flowing through a three-phase motor; a calculating unit to calculate d- and q-axis currents based on a detection output of the current detecting unit; a reference-signal-output unit to output a reference signal indicating a first-reference value of the q-axis current for rotating the motor at a target-rotational speed; first- and second-control-signal-output units to output first- and second-control signals corresponding to respective errors between current values of the d- and q-axis currents and a second and the first reference values, respectively; a drive-signal-output unit to output such a drive signal that the d- and q-axis currents reach the second and first reference values, respectively; and an adjusting unit to adjust the detection output so that a ripple of the second-control signal become smaller, after a rotational speed of the motor reaches a predetermined rotational speed corresponding to the target-rotatio

Abstract: A differential amplifier detects a coil current Is at the time of steady rotation of a synchronous motor. An application voltage S0 at this time is detected from an output of an ATT circuit and so on. With the use of the coil current Is which is detected, the application voltage S0 at that time, and a predetermined scaling factor As, an induced current Ib is obtained based on Ib=As·S0?Is. The application voltage to the motor is controlled based on the induced current Ib which is obtained.

Abstract: A motor speed controller detects out-of-control reverse rotation of a motor even when the pulse signal obtained from the motor and synchronized with the rotation is of only one kind. A target instruction signal is generated on the basis of a target rotational speed ?T of the motor. A compensation instruction signal is generated on the basis of an error signal Ve that corresponds to a difference between the actual rotational speed ? and ?T. A composite signal is generated by combining above two instruction signals. A state in which the control direction of the composite signal with respect to ? is the reverse of the direction of ?T, and the strength of the composite signal exceeds a designated threshold continues for a designated period, is judged as a state of out-of-control reverse rotation, and restoration to the normal state is performed.

Abstract: A stepping motor includes two coils and has supply currents to the two coils with different phases so that a rotor is rotated by the two coils. During a period where one coil is in a high impedance state, an induced voltage generated at that coil is detected. An output control circuit controls the magnitude of motor drive current supplied to the two coils in accordance with the detected induced voltage state. Then, prior to entering the high impedance state from the drive state, a short-circuit period is provided for short circuiting both terminals of the coil.

Abstract: In a motor speed controller, feedback control is implemented at a gain independent of the target rotational speed ?T while the increase in the circuit size or processing load is reduced. The rotational speed ? of the motor is controlled on the basis of a pulse signal in which a pulse period ?P varies in inverse proportion to ?. A count clock generation circuit varies the clock frequency FC in proportion to ?T. The pulse period measurement section counts the count clock CLK during ?P at the present ? and determines a measured count value C. The feedback filter inputs, as an error signal Ve, the difference between C and a target count value CN that corresponds to ?T, and generates an instruction signal to provide compensation for Ve. The feedback filter scales the instruction signal at a scaling factor that is proportional to ?T.

Abstract: A coil current detector detects a current component flowing through a coil. A scaling unit scales a drive signal. An induced voltage component extraction unit extracts an induced voltage component by removing the drive signal, scaled by the scaling unit, from the coil current component detected by the current detector. A phase difference detector detects a phase difference between the phase of the drive signal and that of the induced voltage component. A signal adjustment unit adjusts the drive signal so that the phase difference detected by the phase difference detector can be brought close to a target phase difference.

Abstract: When a driver unit is in a high impedance state as viewed from a first coil or a second coil, an induced voltage detector detects the voltage across the first coil or that across the second coil so as to detect an induced voltage occurring in the first coil or the second coil. The induced voltage detector includes a differential amplifier circuit for differentially amplifying an electric potential across the first coil or that across the second coil, and an analog-to-digital converter circuit for converting an analog value outputted from the differential amplifier circuit into a digital value and outputting the converted digital value to a control unit. The control unit generates a drive signal based on an input signal set externally and adjusts the drive signal in accordance with the induced voltage detected by the induced voltage detector so as to set the adjusted drive signal in the driver unit.

Abstract: The invention provides an organic EL display device usable for both negative and positive polarity video signals. The organic EL display device of the invention has a polarity switching circuit switching a polarity of a digital video signal. In a case where a display panel is made for a negative polarity video signal, when a negative digital video signal is inputted, this polarity switching circuit lets the negative polarity digital video signal pass therethrough without inverting its polarity. When a positive polarity digital video signal is inputted, this polarity switching circuit inverts a polarity of the positive polarity digital video signal and inverts and switches reference data for a white level and reference data for a black level in order to obtain an accurate inverted image. An output of the polarity switching circuit is converted into an analog video signal through a first D/A converter and outputted to the display panel.

Abstract: A differential amplifier detects a coil current Is at the time of steady rotation of a synchronous motor. An application voltage S0 at this time is detected from an output of an ATT circuit and so on. With the use of the coil current Is which is detected, the application voltage S0 at that time, and a predetermined scaling factor As, an induced current Ib is obtained based on Ib=As·S0?Is. The application voltage to the motor is controlled based on the induced current Ib which is obtained.

Abstract: A stepping motor includes two coils and has supply currents to the two coils with different phases so that a rotor is rotated by the two coils. During a period where one coil is in a high impedance state, an induced voltage generated at that coil is detected. An output control circuit controls the magnitude of motor drive current supplied to the two coils in accordance with the detected induced voltage state. Then, prior to entering the high impedance state from the drive state, a short-circuit period is provided for short circuiting both terminals of the coil.

Abstract: An amount of a motor drive current is controlled to an appropriate value. Two coils are provided, and a rotor is rotated by the coils by setting different phases for the supplied currents to the two coils. During a phase where one of the coils is in a high-impedance state, an induced voltage generated in the coil is detected. According to the state of the induced voltage, an output control circuit controls the amounts of the motor drive currents supplied to the two coils.

Abstract: A motor speed controller detects out-of-control reverse rotation of a motor even when the pulse signal obtained from the motor and synchronized with the rotation is of only one kind. A target instruction signal is generated on the basis of a target rotational speed ?T of the motor. A compensation instruction signal is generated on the basis of an error signal Ve that corresponds to a difference between the actual rotational speed ? and ?T. A composite signal is generated by combining above two instruction signals. A state in which the control direction of the composite signal with respect to ? is the reverse of the direction of ?T, and the strength of the composite signal exceeds a designated threshold continues for a designated period, is judged as a state of out-of-control reverse rotation, and restoration to the normal state is performed.

Abstract: In a motor speed controller, feedback control is implemented at a gain independent of the target rotational speed ?T while the increase in the circuit size or processing load is reduced. The rotational speed ? of the motor is controlled on the basis of a pulse signal in which a pulse period ?P varies in inverse proportion to ?. A count clock generation circuit varies the clock frequency FC in proportion to ?T. The pulse period measurement section counts the count clock CLK during ?P at the present ? and determines a measured count value C. The feedback filter inputs, as an error signal Ve, the difference between C and a target count value CN that corresponds to ?T, and generates an instruction signal to provide compensation for Ve. The feedback filter scales the instruction signal at a scaling factor that is proportional to ?T.

Abstract: The effect of chattering on the measurement of the pulse period is reduced. The pulse period representing the rise interval of target pulses appearing in a pulse signal PI is measured. The pulse signal PI is sampled in synchronization with a measurement clock CLK. Measurement of a designated inhibition period is started in synchronization with the fall of the signal PI. Measurement of the current pulse period is completed and measurement of a new pulse period is started if the inhibition period has elapsed at the rise of the signal PI. Counting of the current pulse period is continued if the inhibition period has not elapsed.

Abstract: This invention provides a drive system of a display device preventing an uneven display caused by output current values of current conversion circuits. A drive system of a display device of the invention has a plurality of pixels disposed in a matrix of m rows and n columns and having current drive elements, n pieces of current conversion circuits converting digital display signals inputted from outside into analog signals corresponding to the digital display signals, a first selector circuit selectively supplying the digital display signals to the n pieces of the current conversion circuits, and a second selector circuit selectively supplying current outputs of n pieces of the current conversion circuits to pixel groups divided in columns.

Abstract: This invention provides a clock switching circuit that can switch clocks without causing a hazard or a distortion of a duty ratio of the clocks. The clock switching circuit of this invention includes a first synchronization circuit that synchronizes a clock selection signal with a first clock, a second synchronization circuit that synchronizes with a second clock the clock selection signal that has been synchronized with the first clock by the first synchronization circuit and a clock selection circuit that outputs “1”, that is a high level, in synchronization with the clock selection signal that has been synchronized with the first clock by the first synchronization circuit and after that selects the second clock in synchronization with the clock selection signal that has been synchronized with the second clock by the second synchronization circuit.

Abstract: In a display device performing multiple gray level display using a sub-field drive method, an operation rate of a scan driver and a data driver is reduced and power consumption in the circuits are reduced. When 28 levels of gray level display is performed with 8 bits of video data, one field is equally divided by 8 into eight sub-fields to generate a first sub-field SF0 through an eighth sub-field SF7. Each of the sub-fields SF0 through SF7 has an equal length of sub-field period to each other. And a line-sequential addressing is adopted in addressing pixels so that each line of video data is written-in collectively. Addressing operation of the pixels and light emitting operation of the pixels are performed in parallel. Each of addressing periods AP0 through AP7 in each of the sub-fields is approximately equal to the sub-field period, that is a period of one field divided by 8.

Abstract: This invention provides a clock switching circuit that can switch clocks without causing a hazard or a distortion of a duty ratio of the clocks. The clock switching circuit of this invention includes a first synchronization circuit that synchronizes a clock selection signal with a first clock, a second synchronization circuit that synchronizes with a second clock the clock selection signal that has been synchronized with the first clock by the first synchronization circuit and a clock selection circuit that outputs “1”, that is a high level, in synchronization with the clock selection signal that has been synchronized with the first clock by the first synchronization circuit and after that selects the second clock in synchronization with the clock selection signal that has been synchronized with the second clock by the second synchronization circuit.