Rohm Co., Ltd.

Teac Corporation

Norio Fujii

Kenji Otani

Motoyasu Yoshino

Takahiro Sakaguchi

Toshiya Suzuki

Indirect detection of current using a current mirror circuit is performed with good accuracy, with a small sized circuit. In a current detection circuit, a current detection current mirror circuit includes an output current transistor which supplies an output current, and a current detection transistor which supplies a detection current proportional to the output current. A compensation current mirror circuit is connected to a current supply side of the current detection current mirror circuit, so as to make a collector voltage of the output current transistor and a collector voltage of the current detection transistor equal. A current detector detects the detection current, to indirectly detect the output current.

Current detecting circuit

The invention provides a differential current output unit that has a least number of capacitors and a minimized chip area on one hand, and on the other hand that is capable of providing a smoothly varying output current across a zero-crossing point in accord with an inputted difference input voltage. To do this, the differential current output unit is entirely formed of differential circuits and current mirror circuits having predetermined current mirror ratios. Thus, the unit has a stable output current characteristic. The unit has an inflow output transistor circuit and an outflow output transistor circuit that are operably separated by a delivery circuit. Thus, no penetration current will flow through the inflow- and outflow-output transistor circuits.

Differential current output unit

A rotor of a sensor-less motor has a multiplicity of magnetic poles, with one magnetic pole giving a smaller magnetic flux than other the magnetic poles. A coil is provided at a predetermined position external to the rotor. An induction signal is generated in the coil as the magnetic flux through it is changed by the rotation of the rotor. An index signal indicative of the reference rotational position of the rotor is generated based on the change in the induction signal. Thus, the reference rotational position of the disk of an information recording-reproducing unit, for example, can be detected without utilizing any Hall elements.

Rotational position detector and recording-reproducing unit utilizing the same

A motor drive device of the invention has means for producing a pulse signal having a fixed amplitude by comparing a drive signal that is a sinusoidal signal synchronous with the rotation of a motor with a predetermined high-frequency signal, and the switching of a switching device connected between a power source and the motor is controlled by the pulse signal. This prevents the lowering of the switching speed of the switching device connected between the power source and the motor near the zero-cross points of the sinusoidal drive signal. This helps minimize switching loss and enhance power efficiency. Moreover, the phase current that flows through the motor comes to have a sinusoidal waveform. This helps enhance rotation characteristics.

Motor drive device

A first current mirror circuit for driving a first output stage transistor to flow out current to a coil in a motor is disposed between a power source voltage line and a reference voltage line, and a second current mirror circuit for driving a second output stage transistor to receive a current flowing out from the coil of the motor is disposed between a reference voltage line and a ground line.

Motor control circuit and motor drive system using the same

A reference period generating circuit is provided which generates a pulse having a width corresponding/to a reference period T.sub.1 in response to the input of a trigger pulse. A switch, a first resistor and a second resistor are connected in series between the first and second reference voltages. The node between the first and second resistors is connected to an inverting terminal of an operational amplifier. A non-inverting terminal thereof is connected to a third reference voltage. A clamping circuit is provided to clamp the output voltage of the operational amplifier to a predetermined value. By comparing the output voltage with a predetermined reference value by means of a comparator, a pulse representative of a timing period is generated.

Timing signal generating circuit

An IIL circuit includes a current mirror circuit that receives a constant current as an incoming signal and which inverts and amplifies the constant current to produce an outgoing inverted current. The current mirror circuit adds the incoming constant current to the inverted current and supplies the sum of those currents as an injector current to the respective injectors of a plurality of IIL gates.

IIL circuit and integrated circuit having the same

A flexible disk drive device includes an adjusting circuit which sets termination timing of outputting of an index signal in response to the rotating speed of a motor by adjusting charge or discharge time constant of a capacitor; a reference voltage generating circuit which includes a plurality of resistors connected in series between the power source line and the ground line and generates the reference voltage at one of the nodes of the resistor chain; and a reference voltage switching circuit which switches the reference voltage to another reference voltage upon receipt of a speed selection signal which represents a different rotating speed from a predetermined rotating speed, wherein the other reference voltage is so set that the pulse width of the index signal corresponds to a predetermined rotating angle of the motor.

Flexible disk drive device

A motor control circuit which controls the speed of a motor so as to settle at a predetermined reference rotational speed based upon a detection signal dependent upon the rotating speed of the motor, and outputs to external devices a ready signal representing that the rotating speed of the motor has stabilized within a predetermined allowable range with respect to the reference rotational speed, includes a window pulse generating circuit which generates a window pulse having a width dependent upon a range of the generating period of the detection pulse generated in correspondence with the rotating speed within the allowable range; and a detection circuit which compares the window pulse and a detection pulse generated from the detection signal, detects either the window pulse or the detection pulse when the period of the detection pulse falls within a range of the period represented by the window of the window pulse and outputs the ready signal when the detection continues consecutively a plurality of times.

A motor control circuit, in which the motor is driven to rotate by a driving current according to a torque control signal and the motor rotation is stopped by generating a torque on the motor in the reversing direction when a stop signal for stopping the motor is received, further being provided with a level inverting circuit disposed between a torque control signal generating circuit and a drive circuit for inverting the level of the torque control signal with respect to a predetermined reference level, a level inverted torque control signal by the level inverting circuit is outputted to the drive circuit when the stop signal is received, and further provided with a reference signal generating circuit generating a reference signal corresponding to a reference rotational speed of the motor as well as generating another reference signal corresponding to a rotational speed lower than that of the reference rotational speed when the stop signal is received.

Growing community of inventors

Kyoto, Japan

Norio Fujii