公开(公告)号：JPH11145747A

公开(公告)日：1999-05-28

申请号：JP30218497

申请日：1997-11-04

Applicant: YAMAHA CORP

Inventor： KISHII TATSUYA ,  NORO MASAO

IPC: H03G3/12

Abstract: PROBLEM TO BE SOLVED: To provide a gain control circuit which causes no error to an expected value of gain and can secure its stable operation, even for a low level of power voltage. SOLUTION: A current operational amplifier 12 outputs currents IOUT1 and IOUT2 , which are proportional to an input signal VIN. An adder circuit 20 adds together both currents IOUT1 and IOUT2 and outputs a signal VOUT that is accordant with the addition result. The amplifier 12 contains plural FETs which output the currents IOUT1 and IOUT2 , a current mirror which supplies a gate voltage to the FETs to acquire the currents IOUT1 and IOUT2 , and a switching control means, which supplies a gate voltage in place of the gate voltage to the FET that outputs the current IOUT1 to turn off the FET, in response to a switching signal CON.

公开(公告)号：JPH0955634A

公开(公告)日：1997-02-25

申请号：JP20605395

申请日：1995-08-11

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: G11B20/10 ,  H03G5/02

Abstract: PROBLEM TO BE SOLVED: To reproduce an audio signal full of natural sense by recovering a high frequency spectrum lost from the audio signal in the case of transmission or recording to an original state. SOLUTION: A harmonic signal is added to a music signal by giving the music signal obtained via a DAC 1 and a low-pass filter 2 to a nonlinear circuit 3. Then a band-pass filter 4 is used to select signals at a prescribed frequency band with higher frequencies than the band of the frequency of the audio signal from an output signal of the nonlinear circuit 3 and an adder 5 adds the selected signal and the original audio signal to obtain the audio signal whose lost harmonics are recovered.

公开(公告)号：JPH08307224A

公开(公告)日：1996-11-22

申请号：JP13482795

申请日：1995-05-08

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H03K17/16 ,  H03F3/30 ,  H03F3/34 ,  H03F3/42 ,  H03F3/45 ,  H03K17/687 ,  H03K19/0948

Abstract: PURPOSE: To provide an operational amplifier circuit in which an output stage is in push-pull operation and a stability function of an output stage current is provided. CONSTITUTION: A 1st differential amplifier circuit 1 having n-channel differential MOS TR pairs Q1, Q3 and a 2nd differential amplifier circuit 2 having p-channel differential MOS TR pairs Q2, Q4 are provided to an input stage. A complementary output circuit 5 is configured by a p-channel MOS TR Q15 and an n- channel MOS TR Q16 whose gates are controlled by an output of the circuits 1, 2. A current of the output stage MOS TRs Q15, Q16 is detected respectively by 1st and 2nd current detection circuits 6, 7. A reference current source circuit 8 providing a common reference current to current mirror circuits 3, 4 providing an active load current of the differential amplifier circuits 1, 2 is controlled by the detected current to apply negative feedback to suppress fluctuation in a through-current of the complementary output circuit 5.

公开(公告)号：JPH07162311A

公开(公告)日：1995-06-23

申请号：JP34006493

申请日：1993-12-07

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H03M1/68

Abstract: PURPOSE:To provide a D/A converter circuit obtained by simply extending the number of bits without expanding its size. CONSTITUTION:Upper ten bits out of digital data consisting of eleven bits are inputted to a 1st D/A converter 1 and the least significant bit(LSB) is inputted to a 2nd D/A converter 2. An adder circuit 3 to be used also as a voltage follower for an output from the 1st D/A converter 1 is constituted of an operational amplifier OP for supplying the output of the 1st D/A converter 1 to its non-inverted input terminal and supplying the output of the 2nd D/A converter 2 to its inverted input terminal through an input resistor R1 and a feedback resistor R2 connected between the inverted input terminal and an output terminal. The output of the 2nd D/A converter 2 is reduced by a voltage dividing ratio determined by the resistors R1, R2 and the reduced voltage is added to the output of the 1st D/A converter 1.

公开(公告)号：JPH07123005A

公开(公告)日：1995-05-12

申请号：JP28862493

申请日：1993-10-25

Applicant: YAMAHA CORP

Inventor： KADAKA TAKAYUKI ,  NORO MASAO

IPC: H03M1/10 ,  H03M1/18 ,  H03M1/38

Abstract: PURPOSE:To improve the S/N and to enhance the conversion of precision a very small signal by amplifying an input analog signal with a gain A prior to A/D conversion and attenuating an output of the A/D conversion by 1/A. CONSTITUTION:An analog amplifier 12 amplifies an input analog signal with a gain of the unity or over and the amplified signal is given to an A/D conversion unit 10. The unit 10 converts the intermediate analog signal from the amplifier 12 into an intermediate digital signal with an attenuation of the unity or lower. A digital attenuator 13 attenuates the intermediate digital signal from the unit 10 to obtain a final digital signal. An analog comparator 11 implements discrimination of the input analog signal whose level is divided into three levels. The gain of the amplifier 12 and the attenuation of the attenuator 13 have a relation that the product of them is always '1'. When the effect of noise on A/D conversion in the unit 10 of the post stage is too small, the comparator 11 controls the gain of the amplifier 12 with respect to the input signal to make it larger than the unity.

公开(公告)号：JPH05176532A

公开(公告)日：1993-07-13

申请号：JP27314591

申请日：1991-09-25

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H02M3/28

Abstract: PURPOSE:To realize stabilization of output by a simple construction in a power circuit wherein all switching operations are executed by a zero voltage or a zero current by utilizing current and voltage resonance operations alternately. CONSTITUTION:By turning a switching element S1 ON and OFF, parallel resonance is executed by the primary self-inductance of a transformer T1 and a capacitor C1 and series resonance is executed by leakage inductances L2 between the primary and secondary sides and by capacitors C2a to C2c. Thereby zero-voltage ON and zero-current OFF are realized. Constant-voltage circuits composed of switching elements S3a to S3c, inductances L4a to L4c, diodes D3a to D3c and capacitors C6a to C6c are connected to the capacitors C2a to C2c and thereby constant voltages are attained.

公开(公告)号：JPH0591740A

公开(公告)日：1993-04-09

申请号：JP27314491

申请日：1991-09-25

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H02M3/28 ,  H02M3/337

Abstract: PURPOSE:To reduce a current flowing to a switching element and to prevent generation of heat in a power source circuit in which all switching operations are conducted by a zero voltage or a zero current by alternately utilizing current and voltage resonance operations. CONSTITUTION:A transformer has a primary winding 10 with a center tap. Two switching elements S1, S2 are connected in series between both ends of the winding 10. A DC power source 1 is connected to a point between the connecting point P of the elements S1, S2 and the center tap Q of the primary winding. The elements S1, S2 are alternately turned ON, OFF to perform a parallel resonance by a primary self-inductance L1 of a transformer and a capacitor C1 and to achieve a series resonance by leakage inductance L2 between primary and secondary windings and the capacitor C2. Thus, a zero- voltage ON, a zero-voltage OFF are realized. Since the switching is of a push- pull type, currents flowing to the elements S1, S2 are reduced by half as compared with a half-bridge type.

公开(公告)号：JPH0591736A

公开(公告)日：1993-04-09

申请号：JP27196391

申请日：1991-09-24

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H02M3/155 ,  H02M3/28 ,  H02M3/338

Abstract: PURPOSE:To simplify a circuit configuration by realizing a power source circuit for conducting all switching operations with a zero-voltage or a zero-current by alternately utilizing current and voltage resonance operations by one power source. CONSTITUTION:When a switching element S1 is turned ON, a sine wavelike resonance current flows to series resonance circuit 4, thereby charging a smoothing capacitor 3 of DC output means 3. Since the current, if a half wave of the resonance current is elapsed, tends to be reversed, a rectifying diode D1 is reversely biased, a resonance route is interrupted, and the resonance current is automatically eliminated. Even if parallel resonance means 5 suppresses resonance during the ON period of the S1, it excites L1 and stores charge in C1. When the S1 is turned OFF during the following current zero period, the zero-current is tuned OFF. When the S1 is turned OFF, the resonance of the means 5 is started. The zero voltage is turned ON by turning ON S1 at a timing when the voltage of the means 5 is returned to a power source voltage V.

公开(公告)号：JPH0564451A

公开(公告)日：1993-03-12

申请号：JP25302191

申请日：1991-09-04

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H02M3/155 ,  H02M7/06 ,  H02M7/12 ,  H02M7/48

Abstract: PURPOSE:To improve the power factor of power by providing the power input part of a load device with it additionally without changing the power source itself of the load device consisting of electronic equipment constituted for commercial power source. CONSTITUTION:Input terminals T1 and T2 are connected with rectifying circuits 1, and these rectifying circuits are connected with an active filter 2, which makes input current waves into sine waves by switching input AC voltage several times per half a cycle so as to take out power. For the active filter 2, the output is supplied to a PWM inverter 3 as power source power, and the PWM inverter 3 is driven by the AC input at input ends T1 and T2. The waveform of the output of the PWM inverter 3 is faired by a filter 4, and the output is output from the output terminals T3 and T4. Since the power factor can be improved as an AC-AC inverter, the power factor can be improved by inserting it between the AC plug socket of a commercial power source and the electronic equipment being a load device.

公开(公告)号：JPH04356896A

公开(公告)日：1992-12-10

申请号：JP7381491

申请日：1991-03-13

Applicant: YAMAHA CORP

Inventor： NORO MASAO

IPC: H04Q9/00

Abstract: PURPOSE:To prevent the malfunction of an equipment by effectively removing noise in a band at a remote control signal repeating device such as a repeater or the like. CONSTITUTION:A remote control photodetected signal 36 extracted for the required band at a band pass filter is inputted to an input terminal 34. This remote control photodetected signal is guided to an output terminal 40, supplied to a light emitter and emitted again after receiving level slice by the variable bias of a C-class bias amplifier circuit 38. A smoothing circuit 42 smoothes the remote control photodetected signal 36 at a prescribed time constant. A bias control circuit 44 variably controls the depth of the C-class bias corresponding to the smoothed output, when the smoothed output is large, the C-class bias is made deep and when the smoothed output is small, the C-class bias is made shallow. Thus, since the C-class bias is made deep, continuous noise is cut and since the C-class bias is made shallow, the remote control signal as an intermittent pulse can be passed. Then, the continuous noise can be effectively cut off.