JP3079797B2 - Constant voltage power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant voltage power supply circuit for audio of a CD player.

[0002]

2. Description of the Related Art In recent years, the influence of power supply noise on sound quality has been regarded as a problem in CD players. In particular, noise of a constant voltage power supply circuit of an audio circuit handling an audio signal has a great effect on sound quality.

Hereinafter, a conventional audio constant voltage power supply circuit of a CD player will be described with reference to the drawings.

FIG. 4 is a block diagram showing an example of the configuration of a conventional CD player. In FIG. 4, reference numeral 14 denotes a CD reproducing unit which takes out a digital signal recorded on a CD and reproduces it as an audio signal, 15 denotes an audio circuit which amplifies the audio signal to obtain a line-out output, and 16 denotes an unnecessary shock for the line-out output. Reference numeral 17 denotes a microcomputer for controlling the entire system, 18 denotes an input device for inputting commands such as PLAY and STOP, 19 denotes a power supply circuit, and 20 denotes a constant voltage power supply circuit for audio. As described above, since the noise of the power supply greatly affects the sound quality, the audio circuit power supply is provided with a dedicated audio constant voltage power supply circuit.

FIG. 3 shows an example of the configuration of the simplest conventional constant voltage power supply circuit for audio. 3, reference numeral 3 denotes an input of the constant voltage power supply circuit, 4 denotes an output of the constant voltage power supply circuit, 6 denotes a Zener diode, 8 denotes a resistor, 12 denotes a transistor, 13 denotes a capacitor, and
Power is input between the collector of the transistor and the ground, and a constant voltage is generated with respect to the ground by the Zener diode 6, the resistor 8 and the capacitor 13, and this is applied to the base of the transistor 12, and the output is provided between the emitter of the transistor 12 and the ground. The voltage is taken out. Output voltage V of this configuration
Assuming that V is the voltage between both ends of the Zener diode 6 and VBE is the voltage between the base and the emitter of the transistor 12, VO = VZ-VBE, and since VZ and VBE are almost constant voltages, a constant voltage output is obtained. .

[0006]

However, the above-mentioned conventional constant voltage power supply uses a Zener diode as a reference voltage source for generating a constant voltage with respect to the ground, but the Zener diode generates a large noise. Therefore, there is a problem that there is much noise. That is, in the case of the configuration of FIG. 3, the noise voltage at both ends of the Zener diode is output as it is.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a low-noise CD player audio constant voltage power supply circuit.

[0008]

According to the present invention, there is provided a CD player audio constant voltage power supply circuit comprising: a MOS-FET; a capacitor inserted between the gate of the MOS-FET and ground; A constant voltage source for generating a constant voltage with respect to the ground, the constant voltage source and the MOS
A switch inserted between the gates of the FETs, an input is provided between the drain of the MOS-FET and the ground, an output is provided between the source of the MOS-FET and the ground, and the switch is controlled by the control signal of the microcomputer.
It turns on at the time of P, charges the capacitor inserted between the gate of the MOS-FET and the ground, and turns off the switch at the time of PLAY.

[0009]

According to the present invention, a noise-free capacitor is used as a reference voltage source for generating a constant voltage with respect to the ground, thereby reducing noise in the audio constant-voltage power supply circuit of the CD player. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.
This will be described in detail with reference to FIG.

FIG. 2 is a block diagram showing a configuration of a CD player using a constant voltage power supply circuit according to an embodiment of the present invention. In FIG. 2, reference numeral 14 denotes a CD reproducing unit which takes out a digital signal recorded on a CD and reproduces it as an audio signal, 15 denotes an audio circuit which amplifies the audio signal and obtains a line-out output, and 16 denotes a shock unnecessary for the line-out output. Muting circuit that prevents sound from being emitted, 1
7 is a microcomputer for controlling the entire system, 1
8 is an input device for inputting commands such as PLAY and STOP, 19 is a power supply circuit, 20 is a constant voltage power supply circuit for audio of the present invention, and 5 is a muting signal for controlling the muting circuit 16 by the microcomputer 17. is there. When a PLAY command is input from the input device 18 to the microcomputer 17, the microcomputer 17 sets the muting signal 5 to “L” level,
The muting circuit 16 is released, and a line-out output is output. Except during PLAY, microcomputer 17
Sets the muting signal 5 to the "H" level, operates the muting circuit 16, and prevents noise from being output from the line-out output.

FIG. 1 shows the configuration of an audio constant voltage power supply circuit according to an embodiment of the present invention. In FIG. 1, 1 is a MOS-FET, 2 is a capacitor, 3 is an input of a constant voltage power circuit, 4 is an output of the constant voltage power circuit, 5 is a muting signal from the microcomputer 17, 6 is a Zener diode, 7 is Relays, 8-10 are resistors, 1
1 is a transistor.

The operation of the constant voltage power supply circuit configured as described above will be described below. First, during the STOP, the muting signal 5 from the microcomputer 17 is at “H” level, and the transistor 11 is turned on.
Then, the relay 7 is turned on. As a result, the capacitor 2 is charged to a constant voltage generated by the Zener diode 6, and a voltage is output to the output 4. Next, when the state changes to PLAY, the muting signal 5 from the microcomputer 17 becomes “L” level, and the transistor 11 is turned off.
It becomes F, and the relay 7 is turned off. Even if the relay 7 is turned off, since the gate leak current of the MOS-FET 1 is extremely small, the capacitor 2 keeps the charged voltage up to that point and keeps outputting the voltage from the output 4.

That is, in this embodiment, the gate of the MOS-FET 1 is driven using the capacitor 2 charged with a constant voltage generated by the Zener diode 6 as a reference voltage source. Therefore, if the voltage between both ends of the capacitor 2 is VK and the voltage between the gate and the source of the MOS-FET 1 is VGS, the output voltage VO becomes VO = VK-VGS. Here, assuming that the voltage of the Zener diode 6 is VZ, VK = VZ, so that a constant voltage output is obtained. Since the capacitor does not generate noise, output noise can be significantly reduced.

When used as a constant voltage power supply circuit for audio of a CD player, the maximum playing time of the CD player is about 80 minutes. Therefore, if the capacitor 2 can hold the charged voltage for 80 minutes. good. That is, at the time of PLAY, the muting signal 5 from the microcomputer 17 is set to "L" level, the relay is turned off, and the capacitor 2 is used as a reference voltage source. The muting signal 5 may be set to “H” level, the relay may be turned on, and the capacitor 2 may be charged. As described above, in the case of a CD player, since the maximum playing time is determined, the charging of the capacitor 2 can be controlled by the muting signal 5, so that the charging timing is detected or a timing signal is generated. No circuit is needed.

[0016]

As described above, since the constant voltage power supply circuit of the present invention uses a capacitor having no noise as a reference voltage source, a constant voltage power supply for audio of a CD player with low noise can be realized. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a constant voltage power supply circuit according to one embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a CD player using a constant voltage power supply circuit according to one embodiment of the present invention.

FIG. 3 is a diagram showing the configuration of a conventional simplest constant voltage power supply circuit.

FIG. 4 is a block diagram showing a configuration of a CD player using a conventional constant voltage power supply circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 MOS-FET 2 Capacitor 3 Input 4 Output 5 Muting signal 6 Zener diode 7 Relay 8 Resistance 9 Resistance 10 Resistance 11 Transistor 12 Transistor 13 Capacitor 14 CD reproduction part 15 Audio circuit 16 Muting circuit 17 Microcomputer 18 Input device 19 Power supply Circuit 20 Constant voltage power supply circuit for audio

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05F 1 / 445,1 / 56 G05F 1 / 613,1 / 618 G11B 19/00

Claims (1)

(57) [Claims] A MOS-FET having an input between a drain and a ground and an output between a source and a ground;
-A capacitor inserted between the gate of the FET and ground;
A constant voltage source for generating a constant voltage with respect to the ground; and a switch inserted between the constant voltage source and the gate of the MOS-FET. Charges the capacitor inserted between the grounds and turns off the switch during PLAY
A constant-voltage power supply circuit for audio of a CD player.