JP2002078072A - Portable computer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a portable computer that can realize audio reproduction with sufficiently excellent sound quality without the use of an external speaker system and the need for mounting a large-sized speaker. SOLUTION: The portable computer is provided with a low sound frequency output sub woofer 112 in addition to main speakers 111a, 111b. Thus, the reproduction capability of the low sound frequency can be enhanced more than the case with a single main speaker. Furthermore, a bass boost button 118 is provided to the portable computer to switch an output sound volume level with a low sound frequency from the sub woofer 112, and by operating the bass boost button 118 the output sound volume with the low sound frequency is made to be variable in matching with the preference of a user. In this case, since only a gain with respect to the low frequency component of an input audio signal is switched, the output sound volume level with the low sound frequency can be switched without changing the output sound volume level with medium and high sound frequencies from the sub woofer 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable computer such as a notebook personal computer.
In particular, the present invention relates to a portable computer having a function of reproducing audio data.

[0002]

2. Description of the Related Art In recent years, various portable personal computers of notebook type or laptop type have been developed. In many cases, small-sized monaural speakers are usually mounted on this type of portable computer, but in recent years, stereo speakers have become mainstream along with the use of multimedia in computers.

Further, recently, CD-ROMs and DVDs
For example, it has been required to reproduce audio data stored in such devices as high-quality sound comparable to audio-only devices.
In order to realize high-quality audio reproduction, 1) a sufficient sound pressure level can be obtained, and 2) a reproduction frequency band can be widened and frequency characteristics can be flattened over the entire band. In order to satisfy these conditions, it is necessary to connect an external speaker system to the main body of the portable computer, or to increase the size and performance of the main speakers that are standardly mounted on the main body of the computer.

[0004]

However, since the external speaker system is intended to be used in a state where the "portability" which is a characteristic of the portable computer is sacrificed, it is not sufficient. I can't say that. Also,
If a large-sized, high-performance speaker is installed as standard in the computer itself, it is possible for the computer itself to produce a sufficient sound pressure level from low to high frequency range, but the cost of the computer Will be up. Furthermore, mounting a large speaker requires a large installation area, which leads to problems such as an increase in the size of the computer body.

The present invention has been made in view of the above circumstances, and provides a portable computer capable of realizing sufficiently high-quality audio reproduction without using an external speaker system or mounting a large speaker. The purpose is to do.

[0006]

In order to solve the above-mentioned problems, a portable computer according to the present invention comprises a main speaker, a subwoofer for outputting a low frequency range, and an input audio signal which is amplified and output to the main speaker. A first amplifier circuit, an operation button for switching an output volume level in a low frequency range from the subwoofer, and a second amplifier circuit for amplifying a low frequency component of the input audio signal and outputting the amplified low frequency component to the subwoofer. A second amplifier circuit for switching a gain for a low-frequency component of the input audio signal according to an operation of the operation button without changing a gain for a middle / high-frequency component of the input audio signal. And

In this portable computer, a subwoofer for outputting a low frequency range is provided in addition to the main speaker. This makes it possible to improve the low-frequency range reproduction capability as compared with the case of using only the main speaker alone. Therefore, even when a small main speaker having a low-frequency range reproduction capability is insufficient, 1) sufficient sound can be obtained. Pressure level,
2) Advantages are obtained such that the reproduction frequency band can be widened and the frequency characteristics can be flattened. Further, an operation button for switching the output volume level in the low frequency range from the subwoofer is provided, and by operating the operation button, the output volume in the low frequency range can be changed according to the user's preference. In this case, in the second amplifier circuit, only the gain for the low frequency component of the input audio signal is switched, so that the output volume level of the low frequency range from the subwoofer is not changed without changing the output volume level of the middle / high frequency range. Can switch. Therefore, even when the bass range is emphasized by operating the operation buttons, the volume balance between the main speaker output and the subwoofer output in the middle / treble range does not collapse.

The second amplifier circuit includes an operational amplifier for amplifying and outputting an input audio signal input to an inverting input terminal via an input resistor, and an operational amplifier having an output terminal and an inverting input terminal for the operational amplifier. A feedback resistor connected therebetween, means for changing the value of the feedback resistor in accordance with the operation of the operation button, and connected in parallel with the feedback resistor between an output terminal and an inverting input terminal of the operational amplifier. This can be realized by the capacitance element described above.

In this configuration, the gain of the operational amplifier is determined by the ratio of the value of the feedback impedance given by the combined impedance of the feedback resistor and the capacitor connected in parallel to the value of the input impedance due to the input resistance. . For an input signal in a low frequency range, since the impedance of the capacitive element is high, the feedback impedance is determined only by the feedback resistance, and the gain of the operational amplifier is given by the impedance ratio between the feedback resistance and the input resistance. Therefore, in the low frequency range, the gain of the operational amplifier in the low frequency range can be variably set by changing the value of the feedback resistance. On the other hand, for input signals in the middle and treble range, the impedance of the capacitive element is low, so that the feedback impedance is dominated by the impedance of the capacitive element. It is determined only by the ratio between the impedance of the element and the impedance of the input resistance. Therefore, it is possible to vary only a desired low-frequency gain with a very simplified circuit configuration in which the amplification stage for varying the subwoofer output and the amplification stage for the low-pass filter are configured with the same operational amplifier. It is possible to realize an optimal system for a portable computer.

Further, it is desirable to provide a bass reflex opening for outputting sound on the back side of the subwoofer on the front face of the computer main body. This makes it possible to efficiently emit a low-frequency sound pressure level from the front of the computer main body. Also, since the size of the bass reflex opening is generally smaller than the diameter of the subwoofer, even a thin computer body can be provided on the front surface thereof.

It is preferable that the subwoofer is disposed so that the front surface thereof faces the bottom surface side, not the top surface side of the computer main body. Thus, even when a relatively large subwoofer is used, it is possible to prevent the operation space on the upper surface of the computer main body from being occupied by the subwoofer. Since the bass reflex is provided, a sufficient sound pressure level can be obtained even if the subwoofer is arranged facing the bottom surface.

It is desirable that the above-mentioned operation button for switching the output sound volume level of the bass range from the subwoofer is provided at a predetermined position on the upper surface of the computer main body which can be operated even when the display unit is in the closed position. Thereby, even when playing a music CD or the like with the display unit closed,
Since the operation buttons can be operated, the output volume level of the bass range can be switched. Such an arrangement of the operation buttons is particularly suitable for a portable computer having an audio reproduction mode in which a disk drive device incorporated in the computer main body is driven to reproduce audio data even when the computer main body is turned off. It is.

When two main speakers for left and right for stereo output are provided, the L-channel input audio signal and the R-channel input audio signal are amplified and
A third amplifier that adds an L-channel input audio signal and an R-channel input audio signal, amplifies a low-frequency component of the added signal, and outputs the amplified signal to a subwoofer, in addition to the first and second amplifier circuits that output to the main speakers. An amplifier circuit is provided, and the third amplifier circuit is configured to switch the gain for the low-frequency component of the addition signal without changing the gain for the middle / high-frequency component of the addition signal according to the operation of the operation button. Is preferred.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, a basic structure of a portable notebook personal computer according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front view of the computer with the display unit opened, and FIG. 2 is a front view of the computer with the display unit closed.

The computer comprises a computer body 11
And a display unit 12.
The display unit 12 incorporates a display screen 121 composed of an LCD. The display unit 12 is attached to the computer main body 11 so as to be rotatable between an open position and a closed position. The computer main body 11 has a thin box-shaped housing, on which a keyboard, a pointing stick, and the like are arranged. A stereo speaker 111a for the L channel and a stereo speaker 11
1b are arranged separately on the left and right. These stereo speakers 111a and 111b function as main speakers of the computer, and are mainly used for reproducing a middle / high frequency range. The L-channel stereo speaker 111a is arranged so that a part thereof reaches the left side of the computer main body 11, and the R-channel stereo speaker 111b partially reaches the right side of the computer main body 11. Are arranged as follows.
This is to allow sound from the stereo speakers 111a and 111b to be transmitted to the outside even when the display unit 12 is closed at the closed position.

The computer main body 11 is provided with a subwoofer 112 for outputting a low frequency range. With this subwoofer 112, it is possible to enhance the low-frequency reproduction performance in which sufficient reproduction is difficult with the main speakers (stereo speakers 111a and 111b). Subwoofer 112
Is disposed in the housing of the computer main body 11 such that the front surface faces the bottom side of the computer main body 11. As shown, a bass reflex opening 113 is provided on the front surface of the computer main body 11 at both left and right sides of a receiving portion of the display latch 122. The bass reflex opening 113 is used for outputting sound on the back side of the subwoofer 112. The sound on the back side of the subwoofer 112 is transmitted through the bass reflex opening 113 to the computer main body 1.
1 Directly emitted from the front to the user side.

On the upper surface of the computer main body 11, a power button 114 serving as a power switch of the computer main body is provided.
, A system indicator 115, a mode control switch 116, an A / V control button 117,
A bass boost button 118 is provided. As shown in FIG. 2, the system indicator 115, the mode control switch 116, the A / V control button 117, and the bass boost button 118 are arranged so as to be exposed to the outside even when the display panel 12 is closed. . In this example, the display panel 1
2 There is a notch between the left and right hinges at the bottom,
Thus, even when the display panel 12 is closed, the rear region on the upper surface of the computer main body 11 is configured to be exposed to the outside.

The system indicator 115 has a plurality of LEs.
D lamps are included, and when these lamps are turned on, various statuses such as a power ON / OFF state, an HDD access state, and the presence or absence of an AC adapter connection are displayed. The mode control switch 116 is connected to the display panel 1 while the computer main body 11 is turned off.
Built-in CD-ROM drive / DV even when 2 is closed
This is a switch for switching to a mode (audio playback mode) in which audio playback can be realized using the D drive. By turning on the mode control switch 116, a CD-ROM drive / DVD drive,
And power is supplied to the minimum devices required for audio playback. Therefore, audio reproduction from the CD-ROM drive / DVD drive can be performed without starting the operating system.

The A / V control button 117 is
An operation button for controlling audio / video reproduction from the ROM drive / DVD drive.
It includes a button, a "stop" button, a "forward" button, and a "reverse" button. The bass boost button 118 is an operation button for switching the output volume level in the low range from the subwoofer. Bass boost button 118
Is turned on, it is possible to increase the output volume level of the bass range from the subwoofer 112 (bass enhancement). That is, in the present embodiment, a function of variably setting the output volume level in the low frequency range according to the operation of the bass boost button 118 (hereinafter referred to as bass boost) is provided, and when the bass boost function is turned on, , The output volume level of the low frequency range from the subwoofer 112 can be increased as compared with the case where the bass boost function is turned off. In this case, what is increased is the subwoofer 1
Only the output volume level of the low frequency range from the subwoofer 112 is unchanged, and the output volume level of the middle / high frequency range from the subwoofer 112 does not change. This means that the main speakers (stereo speakers 111a and 111b) can be used even when the bass boost is on.
This is to prevent the balance between the output volume of the middle / high range from the subwoofer 112 and the output volume of the middle / high range from the subwoofer 112.

A volume switch 119 is provided on the left side of the computer main body 11. The volume switch 119 is connected to a main speaker (stereo speaker 1).
11a, 111b) and the subwoofer 112 are used to adjust the output volume of the entire composite speaker system.

FIG. 3 is a view of the computer main body 11 viewed from the bottom side. As illustrated, a number of openings 131 are provided on the bottom surface 13 at positions corresponding to the front surface of the subwoofer 112. The opening 131 has a role as an air hole for vibrating the cone of the subwoofer 112 with good responsiveness. Of course, there is also an action of outputting the sound on the front of the subwoofer 112 to the outside.

FIG. 4 schematically shows the structure of the subwoofer 112. The subwoofer 112 is a box-type speaker, for example, and has a cone 112a and a hollow bass reflex duct 112b. Cone 112
As shown in the figure, a has a front surface in contact with the bottom surface of the computer main body 11. Bass reflex duct 112b
Extends from the back side of the cone 112a, and is connected to the above-described bass reflex opening 113. Cone 11
Since the sound on the back side of 2a is in a state where the phase is inverted by 180 degrees, the sound is output after the phase is further inverted by 180 degrees through the bass reflex duct 112b.

FIG. 5 shows the system configuration of the computer. As shown in the figure,
CPU 201, main memory 202, sound controller 203, CD-ROM drive 204, volume circuit 205, L-channel main speaker amplifier 206a,
An R-channel main speaker amplifier 206b, a subwoofer amplifier 207, and the like are provided. In the audio reproduction mode, in addition to the CD-ROM drive 204, the sound controller 203 and the volume circuit 20
5. Power is supplied to the L-channel main speaker amplifier 206a, the R-channel main speaker amplifier 206b, and the subwoofer amplifier 207, and no power is supplied to other parts.

The sound controller 203 is a CD-R
Audio signal C read from OM drive 204
An input signal from a D-direct or a microphone (MIC), or various sound data supplied through the CPU 201 is input, and an L-channel audio signal (Audio L channel) and an R-channel audio signal (Audio R) are correspondingly input. cha
nnel) is output. The L-channel audio signal and the R-channel audio signal are supplied to a line-out (LINE OUT) terminal for connecting an external audio device, and the L-channel main speaker amplifier 206a and the R-channel main speaker amplifier through the volume circuit 205. 206b and the subwoofer amplifier 207.

The volume circuit 205 is a main speaker 1
This is a circuit for adjusting the output volume from the sub-woofers 112a and 111b, and increases and decreases the signal levels of the L-channel audio signal and the R-channel audio signal according to the volume control signal from the volume switch 119 described above.

L channel main speaker amplifier 206
a is for driving the L-side stereo speaker 111a, amplifies the L-channel audio signal input via the volume circuit 205, and outputs the amplified signal to the stereo speaker 111a. The R-channel main speaker amplifier 206b is for driving the R-side stereo speaker 111b, and amplifies the R-channel audio signal input via the volume circuit 205 and outputs the amplified signal to the stereo speaker 111b.

The subwoofer amplifier 207 is for driving the subwoofer 112, and has a built-in low-pass filter for reproducing only a low frequency range from the subwoofer amplifier 207. This subwoofer amplifier 2
07, both the L-channel audio signal and the R-channel audio signal are input via the volume circuit 205. In the subwoofer amplifier 207, the L-channel audio signal and the R-channel audio signal are added, and the added signal is amplified to be added to the subwoofer 112.
Is output to

The subwoofer amplifier 207 includes:
A gain adjustment mechanism for switching the output volume level in the low-frequency range from the subwoofer 112 in accordance with the bass boost control signal from the bass boost button 118 is incorporated. This gain adjustment mechanism is configured to change only the gain of the input signal in the low frequency range, and not to change the gain in the middle / high frequency range of the input signal regardless of whether the bass boost is on or off. This is because if a configuration that merely changes the gain of the subwoofer amplifier 207 is used, the entire frequency characteristic of the low-pass filter is increased, and not only the volume change in the low frequency range originally intended, but also the medium・ This is because the volume of the high frequency range changes together. In this case, a change in the gain of the subwoofer output causes an imbalance in the volume balance between the main speaker output and the subwoofer output in the middle and treble ranges.

Next, a specific circuit configuration of the subwoofer amplifier 207 will be described with reference to FIG. The subwoofer amplifier 207 has a two-stage amplifier circuit 20 as shown in the figure.
7a and 207b.

The first-stage amplifier circuit 207a includes an operational amplifier (operational amplifier) 301, resistors Ra1, Ra2, Rb1, Rb2, a capacitor C, and an analog switch (Analog SW) 302, as shown in FIG. ing. The resistors Ra1 and Ra2 are input resistors that supply the L-channel audio signal (IN1) and the R-channel audio signal (IN2) to the inverting input terminal (-) of the operational amplifier 115, respectively. Resistance Ra1
And connecting the resistor Ra2 as shown in FIG.
An added signal of the L channel audio signal (IN1) and the R channel audio signal (IN2) is an operational amplifier 301.
Will be amplified.

The non-inverting input terminal (+) of the operational amplifier 301 is grounded in this example. The resistor Rb1, the resistor Rb2, and the capacitor C function as feedback impedances of the operational amplifier 301, respectively.
Are connected in parallel as shown in the figure between the output terminal and the inverting input terminal (-). The resistor Rb1 and the capacitor C are directly connected between the output terminal of the operational amplifier 301 and the inverting input terminal (−), respectively. However, the resistor Rb2 and the analog switch 30 are connected to the resistor Rb2.
2 is connected between the output terminal of the operational amplifier 301 and the inverting input terminal (−).

The analog switch 302 has a resistor Rb
This is provided to variably set the value of the negative feedback resistor formed by connecting the resistor 1 and the resistor Rb2 in parallel, and is turned on / off according to a bass boost control signal. When the bus burst is on, the analog switch 302 is controlled to the open state by the bus boost control signal.
When turned off, the analog switch 302 is controlled to a closed state by a bass boost control signal.

The second-stage amplifier circuit 207b is provided to improve the frequency cutoff characteristic of the subwoofer amplifier 207. As shown in the figure, an operational amplifier 401, an input resistor Ra, and an operational amplifier 401 are provided. It comprises a feedback resistor Rb and a capacitor C connected in parallel between the output terminal and the inverting input terminal (-).

The subwoofer amplifier 207 functions as an active low-pass filter, amplifies and outputs signals in the low frequency range up to the cutoff frequency (fc), but outputs signals in the middle and high frequency ranges above the cutoff frequency. Decay. Hereinafter, the operation of the subwoofer amplifier 207 will be specifically described. The second-stage amplifier circuit 2
07b is provided to improve the frequency cutoff characteristic as described above, and therefore, the operation of the first-stage amplifier circuit 207a will be mainly described below.

The gain (G) of the operational amplifier 301 is equal to the resistance Rb for the L-channel audio signal (IN1).
1, determined by the ratio between the feedback impedance of the resistor Rb2 and the capacitor C and the input resistance Ra1, and the R channel audio signal (IN2) is determined by the ratio between the feedback impedance of the resistors Rb1, Rb2 and the capacitor C and the input resistance Ra2. It is determined. Input resistance Ra1, Ra
If the resistance value of 2 is Ra and the feedback impedance is Z,
For both the L-channel audio signal (IN1) and the R-channel audio signal (IN2), the gain (G) is G = Z / Ra.

1. The gain in the low range (cutoff frequency fc or lower) when the burst is on is set by the analog switch 3.
02 is opened. Analog switch 30
2, the path of the resistor Rb2 is opened. In the low frequency range, the impedance Zc of the capacitor C (= | 1
/ 2πfc |) is very large and the value of C is selected so that the path of the capacitor C is also opened.
The resistor R functions substantially as a feedback impedance.
b1 only. Therefore, the gain (G) of the operational amplifier 301 at this time is represented by G = Rb1 / Ra.

2. Further, the gain in the low tone range (cutoff frequency fc or lower) at the time of burst off is realized with the analog switch 302 closed. When the analog switch 302 is closed, the path of the resistor Rb2 becomes effective, so that the combined resistance of the parallel connection of the resistor Rb1 and the resistor Rb2 becomes the feedback impedance. Therefore, the gain (G) of the operational amplifier 301 at this time is represented by G = (Rb1 // Rb2) / Ra. Here, (Rb1 // Rb2) is the resistance Rb
1 shows a combined resistance of 1 and the resistor Rb2.

3. The gain in the middle and treble range is resistance Rb
1. Considering the impedance Zc of the capacitor C connected in parallel with the resistor Rb2, G = (| Rb1 // Rb2 // Zc |) / Ra. Since the impedance is small and most of the signals are fed back to the inverting input terminal (-) through the capacitor C, the impedance Zc
Becomes dominant and G = Zc / Ra.
Therefore, regardless of the on / off state of the analog switch 302, the gain G in the middle / high range becomes extremely low, and the output signal can be cut off.

FIG. 7 shows the transition of the feedback impedance. 1. As described above. (In the case of bass boost ON), the feedback impedance Rb1 is equal to 2. (When the bass boost is off), the feedback impedance Rb1
// Rb2, the output volume of the subwoofer 112 can be increased in the low-tone range. Since the feedback impedance is represented by the impedance Zc of the capacitor C in the middle / high range above the cutoff frequency, the output volume of the subwoofer 112 in the middle / high range even if the bass boost is switched on / off. Does not change. This is shown in FIG.

FIG. 8 shows the frequency characteristics of the subwoofer output volume and the main speaker output volume. FIG. 8 (a)
FIG. 8 shows a case where a conventional gain adjustment circuit is used.
(B) shows a case where the subwoofer amplifier 207 of the present embodiment is used.

As shown in FIG. 8A, in the conventional circuit, since the entire frequency range is gained up by turning on the bass boost, the crossover characteristic between the subwoofer output and the main speaker output is reduced by the bass boost. It will be different from when it is off. On the other hand, as shown in FIG. 8B, when the subwoofer amplifier 207 of the present embodiment is used, only the bass gain is changed without changing the mid / treble gain, and the bass boost Since it can be changed by turning on / off, even if the bass region is emphasized by turning on the bass boost, no change occurs in the crossover characteristic between the subwoofer output and the main speaker output.

The subwoofer amplifier 207 has a very simplified circuit configuration in which an amplification stage for varying the output of the subwoofer 112 and an amplification stage for a low-pass filter are constituted by the same operational amplifier 301. It is suitable for mounting on equipment. In addition, since the feedback impedance is changed by turning on / off the analog switch 302, it is not necessary to use a variable resistance element or the like.

Although a case has been described above in which the gain is adjusted in two stages of bass boost on / off, the gain can be adjusted in multiple stages of three or more in accordance with the operation of the bass boost button 118. FIG. 9 shows a configuration example of the amplifier circuit 207a necessary for this.

The amplifying circuit 207a of FIG. 9 is for adjusting the gain in four stages in accordance with the operation of the bass boost button 118. Compared with the circuit configuration of FIG.
And an analog switch 303 is added. The resistor Rb3 and the analog switch 303 are connected in series between the output terminal of the operational amplifier 301 and the inverting input terminal (-) as shown. By making the resistance values of the resistors Rb3 and Rb2 different, 1) the analog switches 302 and 303 are both open, 2) the analog switch 302 is open, and 303 is closed, 3).
Analog switch 302 is closed, 303 is open,
4) The gain can be adjusted in four stages when both the analog switches 302 and 303 are closed (bass boost = off). As the bass boost button 118, a multi-stage open switch that can generate a 2-bit bass boost control signal may be used.

FIG. 10 shows a circuit configuration of an active high-pass filter constructed on the same principle as the subwoofer amplifier 207 of FIG. This active
Contrary to the subwoofer amplifier 207, the high-pass filter is configured to be able to change only the gain in the high frequency range without changing the gain in the low / middle frequency range. Speaker amplifier 20
6a and 206b, or can be used for driving a tweeter for outputting a high frequency range.

That is, the high-pass filter shown in FIG.
An operational amplifier (operational amplifier) 501, a capacitor C, a resistor Ra1, a resistor Ra2, an analog switch (Analog)
SW) 502 and a resistor Rb.
The capacitor C and the resistors Ra1 and Ra2 are connected to the operational amplifier 21.
1 functions as an input impedance. The resistor Ra2 is connected in parallel to the resistor Ra1 via the analog switch 502. This analog switch 502 includes a resistor Ra
This is provided to variably set the value of the input resistance formed by connecting the resistor 1 and the resistor Ra2 in parallel, and is turned on / off in accordance with a boost control signal for emphasizing high frequencies. The analog switch 502 is controlled to be in a closed state when the boost is on for performing the gain increase in the high frequency range, and is controlled to be in an open state when the boost is off.

The input audio signal IN is supplied to a capacitor C
Is input to the inverting input terminal (−) of the operational amplifier 501 via a series circuit of the input and an input resistor (a parallel circuit of the resistors Ra1 and Ra2). Non-inverting input terminal (+) of this operational amplifier 501
Are grounded as shown. The resistor Rb functions as a feedback impedance of the operational amplifier 501, and is negatively connected between the output terminal and the inverting input terminal (-) of the operational amplifier 501 as illustrated.

This high-pass filter amplifies and outputs a signal in a high frequency range above the cutoff frequency (fc).
The signal output in the low / mid frequency range below the cutoff frequency is attenuated. Hereinafter, the operation of the high-pass filter will be specifically described.

The gain (G) of the operational amplifier 501 is determined by the ratio between the feedback impedance of the resistor Rb and the input impedance of the capacitor C and the resistors Ra1 and Ra2.

1. The gain in the high frequency range (at or above the cutoff frequency) when the boost is on is controlled by the analog switch 502.
Is realized in a closed state. By closing the analog switch 502, a parallel circuit is formed by the resistors Ra1 and Ra2, and the impedance Zc of the capacitor C in a high frequency range.
Is very low, the gain (G) of the operational amplifier 501 at this time is represented by G = Rb / (Ra1 // Ra2). (Ra1 // Ra2) is the resistance Ra1 and Ra
2 is a combined resistance due to the parallel connection of the two.

2. The gain in the high frequency range (at or above the cutoff frequency) at the time of boost-off is realized with the analog switch 502 opened. By opening the analog switch 502, the path of the resistor Ra2 is opened, and the impedance Zc of the capacitor C is very low in a high frequency range, so that the gain (G) of the operational amplifier 501 at this time.
Is represented by G = Rb / Ra1.

3. The gain in the low / mid range is the resistance Ra
G = Rb / | (Ra1 // Ra2) + Zc | in consideration of the impedance Zc of the capacitor C connected in series to the parallel circuit of Ra1 and Ra2. C
, The impedance Zc of the capacitor C becomes dominant, and G = Rb / | Zc |. Therefore, the analog switch 502
Irrespective of the on / off state, the gain G in the low / middle tone range becomes extremely low, and the output signal can be cut off.

FIG. 11 shows the transition of the input impedance. 1. As described above. (When boost is on)
Is the input impedance Ra1 // Ra2 of 2.
Input impedance (when boost is off)
Since it is smaller than 1, it is possible to increase the output sound volume in a high tone range. In the low / middle frequency range below the cutoff frequency, the input impedance is represented by the impedance Zc of the capacitor C. Therefore, even if the boost is switched on / off, the output volume in the low / middle frequency range does not change. This is shown in FIG.

FIG. 12 shows the frequency characteristic of the high-pass filter. As illustrated, when the high-pass filter of the present embodiment is used, only the gain in the high frequency range can be changed by turning on / off the boost without changing the gain in the low / mid frequency range. Therefore, the high-pass filter circuit in FIG. 10 can be used as a tweeter amplifier for driving a tweeter for outputting a high-frequency range. In this case, in addition to the main speakers 111a and 111b of FIG. 1 or the main speakers 111a and 111b and the subwoofer 112 of FIG.
It is driven by a 0 high-pass filter. This enables application as an equalizer for improving high-frequency reproduction characteristics.

The present invention is not limited to the above embodiment, and can be variously modified at the stage of implementation without departing from the scope of the invention. Further, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effects described in the column of the effect of the invention can be solved. If you get
A configuration from which this configuration requirement is deleted can be extracted as an invention.

[0056]

As described in detail above, according to the present invention, without using an external speaker system or mounting a large speaker,
Audio reproduction with sufficiently high sound quality can be realized on a portable computer.

[Brief description of the drawings]

FIG. 1 is an exemplary view showing an appearance of a computer according to an embodiment of the present invention when a display is opened.

FIG. 2 is an exemplary view showing the appearance of the computer according to the embodiment in a display closed state.

FIG. 3 is an exemplary view of the appearance of the computer according to the embodiment in a display closed state as viewed from the back side;

FIG. 4 is an exemplary view schematically showing a mounting structure of a subwoofer in the computer of the embodiment.

FIG. 5 is an exemplary block diagram showing the system configuration of the computer according to the embodiment;

FIG. 6 is an exemplary view showing a circuit configuration of a subwoofer amplifier provided in the computer of the embodiment.

FIG. 7 is a diagram showing a state of transition of a feedback impedance of the subwoofer amplifier of FIG. 6;

FIG. 8 is a diagram showing output characteristics of the subwoofer amplifier in FIG. 6;

FIG. 9 is an exemplary view showing another configuration example of the subwoofer amplifier provided in the computer of the embodiment.

FIG. 10 is an exemplary view showing a configuration of a high-pass filter applied to the computer of the embodiment.

FIG. 11 is a diagram showing a state of transition of a feedback impedance of the high-pass filter of FIG. 10;

FIG. 12 is a diagram showing output characteristics of the high-pass filter of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Computer main body 12 ... Display unit 111a ... Main speaker for L channel 111b ... Main speaker for R channel 112 ... Subwoofer 113 ... Opening for bass reflex 116 ... Mode control switch 117 ... A / V control button 118 ... Bass boost button 203 ... Sound Controller 204 CD-ROM drive 205 Volume control circuit 206a L-channel main speaker amplifier 206b R-channel main speaker amplifier 207 Subwoofer amplifier 301, 401 Op-amp 302, 303 Analog switch Ra1, Ra2, Ra Input resistance Rb1, Rb2, Rb ... feedback resistance C ... capacitor

Claims (12)

[Claims] 1. A main speaker, a subwoofer for bass output, a first amplifier circuit for amplifying an input audio signal and outputting the amplified signal to the main speaker, and for switching an output volume level of a bass from the subwoofer. And a second amplification circuit that amplifies a low-frequency component of the input audio signal and outputs the amplified low-frequency component to the subwoofer.
A second amplifier circuit for switching a gain for a low-frequency component of the input audio signal without a change in a gain for a high-frequency component. 2. An operational amplifier for amplifying and outputting an input audio signal input to an inverting input terminal via an input resistor, and an output terminal of the operational amplifier and an inverting input terminal. A feedback resistor connected therebetween, means for changing the value of the feedback resistor in accordance with the operation of the operation button, and connected in parallel with the feedback resistor between an output terminal and an inverting input terminal of the operational amplifier. 2. The portable computer according to claim 1, further comprising: a capacitive element. 3. The means for changing the value of the feedback resistor,
A switch circuit connected in series to the feedback resistor, wherein the switch circuit is turned on / off in response to operation of the operation button.
The portable computer according to claim 2, wherein the portable computer is turned off. 4. The apparatus according to claim 1, wherein the second amplifier circuit variably sets a gain for a low-frequency component of the input audio signal in at least three or more stages according to an operation of the operation button. Item 6. The portable computer according to Item 1. 5. The operational amplifier according to claim 1, wherein the second amplifier circuit includes an operational amplifier that amplifies and outputs an input audio signal input to an inverting input terminal via an input resistor, and a feedback resistor and a switch circuit. A plurality of series circuits respectively connected between the output terminal and the inverting input terminal of
A capacitor connected between the output terminal and the inverting input terminal of the operational amplifier in parallel with the plurality of series circuits; a switch circuit in each of the series circuits being individually operated in accordance with an operation of the operation button; The portable computer according to claim 4, wherein the portable computer is on / off controlled. 6. A volume operation button for adjusting an output volume level from the main speaker and the subwoofer; and a first and second amplifying circuit provided before the first and second amplifying circuits. 2. The portable computer according to claim 1, further comprising: a sound volume adjusting unit that increases or decreases the value of the input audio signal input to the controller according to an operation of the volume operation button. 7. The portable computer according to claim 1, wherein a bass reflex opening for outputting a sound on the back side of the subwoofer is provided on a front surface of the computer main body of the portable computer. 8. The subwoofer is arranged such that the front surface faces the bottom surface side of the computer main body, and an opening is provided at a position on the bottom surface of the computer main body corresponding to the front surface of the subwoofer. The portable computer according to claim 7. 9. The portable computer includes the computer main body, and a display unit rotatably attached to the computer main body between an open position and a closed position. The portable computer according to claim 1, wherein the display unit is provided at a predetermined position on the upper surface of the computer main body that can be operated even when the display unit is in the closed position. 10. The computer main body has a built-in disk drive device capable of driving a storage medium storing audio data, and the portable computer has a computer main body even when the computer main body is turned off. An audio reproduction mode for driving a disk drive device incorporated in the device to reproduce audio data, wherein the disk drive device is operated in response to an operation of a mode operation switch for indicating a transition to the audio reproduction mode. 10. The portable computer according to claim 9, wherein the portable computer is configured to supply power to some devices in the computer main body related to audio reproduction. 11. A left and right main speaker for stereo output, a subwoofer for bass output, and an L channel input audio signal and an R channel input audio signal which are respectively amplified and output to the two main speakers. A first and a second amplifier circuit, an operation button for switching an output volume level in a low frequency range from the subwoofer, a sum of the L-channel input audio signal and the R-channel input audio signal, and a low range of the sum signal A third amplifier circuit for amplifying a component and outputting the amplified signal to the subwoofer, wherein a low-frequency component of the addition signal is changed without a change in a gain with respect to a middle / high-frequency component of the addition signal in response to an operation of the operation button. A third amplifying circuit for switching a gain with respect to the portable computer. Data. 12. The third amplifier circuit comprises: an operational amplifier; first and second input resistors for guiding the L-channel input audio signal and the R-channel input audio signal to inverting input terminals of the operational amplifier, respectively. A feedback resistor connected between the output terminal and the inverting input terminal of the operational amplifier, means for changing the value of the feedback resistor according to the operation of the operation button, and an output terminal of the operational amplifier and an inverting input terminal. 12. The portable computer according to claim 11, further comprising a capacitor connected in parallel with the feedback resistor and the terminal.