JPH09247855A - Power application circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in signal-to-noise ratio and increase in consumed current with respect to a power application circuit that prevents the production of shock noises at the application of power. SOLUTION: The title power application circuit outputs aural input signals as a voltage of (1/2) VCC at point B, the output end, through an operational amplifier 15, an aural signal processing section 6, and transistors Q10, Q11 at a point of (1/2) VCC relative to a point of supply voltage Vcc. The power application circuit is provided with a voltage monitoring circuit 22 that keeps a transistor Q35 in the on-state and transistors Q17 , Q18 in the off-state until point A reaches the level of a transistor Q33 after the application of power, and thus rings point B at the GND level. Thus the output of raised voltage produced at the point of (1/2)VCC relative to the point of point B, is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power-on circuit that prevents the generation of shock noise when the power is turned on.

[0002]

2. Description of the Related Art In recent years, when power is supplied to a predetermined circuit,
When shock noise occurs, various methods of reducing the shock noise have been considered. Here, in FIG.
The circuit diagram of the conventional audio signal processing circuit is shown. FIG. 3 is a circuit diagram showing an example of a case where shock noise is generated when the power is turned on. In the audio signal processing circuit 11, resistors R ₁ and R _{2 are provided} between the power supply voltage line V _CC and GND (ground). Is connected in series, and the capacitor C ₁ is connected between the connection point of the resistors R ₁ and R ₂ and GND. Further, the PNP type transistor Q _{1 is connected} from the power supply voltage line V _CC through the resistor R _3.
Emitter is connected to the collector of the transistor Q ₁ is connected to the emitters of the transistors Q _2, Q ₃ of the PNP.

The base of the transistor Q ₂ is resistors R ₁ and R
_The collector is connected to the collector of an NPN type transistor Q ₄ . The collector of the transistor Q ₃ is connected to the collector and the base of the NPN type transistor Q ₅ and the base of the transistor Q ₄ . The emitters of the transistors Q ₄ and Q ₅ are connected to GND.

Further, the source voltage line V _CC is connected to the emitter of a PNP type transistor Q ₆ via a resistor R ₄ , and the collector of the transistor Q ₆ is connected to the base of an NPN type transistor Q ₇ . It is connected to the collector of an NPN type transistor Q ₈ . The bases of the transistors Q ₁ and Q ₆ are connected so as to be supplied with a current mirror bias. The base of the transistor Q ₈ is connected to the collector of the transistor Q ₂ , and the emitter is connected to GND.

The collector of the transistor Q ₇ is connected to the power supply voltage line V _CC , and the emitter is the transistor Q ₃
Is connected to the base of the
D is connected. Further, the emitter of the transistor Q ₇ is an input voltage terminal (V _in ), which is audio-inputted through the resistor R _5.
GN via capacitor 13, capacitor C ₂ and AC source 14
It is connected to D as well as to the non-inverting input terminal of the operational amplifier 15. The inverting input terminal of the operational amplifier 15 is connected to the output terminal thereof to form a so-called voltage follower. The output terminal of the operational amplifier 15 is connected to the input end of the audio signal processing unit 16 such as a filter, for example.

On the other hand, the power supply voltage line V_CCMore resistance R₆To
Through PNP type transistor Q₉Connected to the emitter of
The transistor Q₉Is a PNP type transformer
Jista Q_Ten, Q₁₁Connected to their respective emitters.
Transistor Q_TenIs a resistor R₇Voice signal through
The resistor R is connected to the output terminal of the processing unit 16.₈To
Through the transistor Q₇Connected to the emitter.
Also, the transistor Q ₁₁Is a resistor R₉Through the
Transistor Q₇Connected to the emitter of the resistor
R_TenIs connected to a connection point B described later.

The collector of the transistor Q ₁₀ is connected to the collector of an NPN type transistor Q ₁₂ , and the emitter of the transistor Q ₁₂ is connected to GND. The collector of the transistor Q ₁₁ is connected to the collector and base of the NPN transistor Q ₁₃ and the base of the transistor Q ₁₂ , and the emitter of the transistor Q ₁₃ is connected to GND.

On the other hand, it is connected to the emitter of the PNP type transistor Q ₁₄ from the power supply voltage line V _CC through the resistor R _{11 and also} to the emitters of the PNP type transistors Q ₁₅ and Q ₁₆ . The bases of the transistors Q ₉ and Q ₁₄ are connected so that a current mirror bias is supplied. The collector of the transistor Q ₁₄ is connected to the collector and base of the NPN type transistor Q ₁₇ and the base of the NPN type transistor Q ₁₈ . The emitters of the transistors Q _17, Q ₁₈ is connected to GND.

The collector of the transistor Q ₁₅ is connected to the base and the base of the transistor Q ₁₆ and also to the collector of the transistor Q ₁₈ . The collector of the transistor Q ₁₆ is an NPN type transistor Q ₁₉
Of the NPN transistor Q _{20 and} the collector of the NPN transistor Q ₂₀ . The transistor Q ₁₉ is
The base is connected to the collector of the transistor Q ₁₀ ,
The emitter is connected to GND.

Further, it is connected from the power supply voltage line V _CC to the collector of the transistor Q ₂₀ , and the emitter is the current source 17.
Is connected to GND via the transistor, and the connection point between the emitter of this transistor and the current source 17 is B, which is connected to the input terminal of the power amplifier.

Here, FIG. 4 shows a waveform diagram of the rising edge when the power is turned on. In the audio signal processing circuit 11,
The connection point of the resistors R ₁ and R ₂ is A, and the transistor Q
_{The 7th} emitter is set to the (1/2) V _CC point. The capacitor C ₁ has a capacitance of about several tens of μF in order to increase the power supply voltage removal ratio. Therefore, when the power is turned on, the capacitor C
_For the rise of the power supply voltage V _CC due to the capacitance of ₁ ,
As shown in FIG. 4A, the rising of the point A becomes gentle and rises with a delay.

In the waveform timing shown in FIG. 4A, at time t <t ₁ , the currents I ₁ and I ₂ from the constant current sources of the transistors Q ₁ and Q ₆ have risen, but Since Q ₂ is saturated, it is impossible to supply a sufficient base current to the transistor Q ₈ . Therefore, the potential at the point of (1/2) V _CC is
As shown in (B), it _bounces up to V _CC -V _BEQ7 , and this is output from point B via the latter stage of the audio signal processing circuit 11, is transmitted to the power amplifier and the speaker, and shock noise is _generated. Will occur. The same applies to the differential amplifier circuit of the transistors Q ₁₀ and Q _{11 in} the subsequent stage and the amplifier circuit composed of other transistors, and shock noise is generated.

As a means for preventing the occurrence of the shock noise, it is known to connect the transistors constituting the amplifier circuit to Darlington connection. Therefore, FIG. 5 shows a circuit diagram of a conventional noise prevention circuit when the power is turned on. FIG.
(A) shows the resistor R ₃ and the transistor Q ₁ of FIG. 1 as a constant current source 18, and the base of the transistor Q ₂ is PNP.
Type transistor Q ₂₁ is connected to the emitter. In addition, the base of the transistor Q ₃ is a PNP transistor Q _22.
Connect to the emitter of. The collector of the transistor Q ₂₁ is connected to GND, and the base is connected to the connection point A. The collector of the transistor Q ₂₂ is connected to GND,
The base is connected to the (1/2) V _CC point. That is, by adding the transistors Q ₂₁ and Q ₂₂ to the transistors Q ₂ and Q
₃ and Darlington connection, other configurations are the same as in FIG.

Thus, by connecting the transistor Q ₂ to the transistor Q ₂₁ in the Darlington connection, the saturation of the transistor Q ₂ by the current I ₁ can be suppressed, whereby a sufficient base current is supplied to the transistor Q _8. Bounce up (shock noise) as shown in Fig. 4 (B)
Can be prevented.

Further, as shown in FIG. 5B instead of FIG. 5A, current sources 19 and 20 are respectively provided between the power supply voltage line V _CC and the emitters of the transistors Q ₂₁ and Q ₂₂ connected in Darlington. Similarly, the saturation of the transistor Q ₂ can be suppressed by connecting with, and shock noise can be prevented.

The differential amplifier circuit composed of the transistors Q _{9 to} Q ₁₃ in the subsequent stage of the audio signal processing circuit 11 of FIG. 3 is provided with the circuits as shown in FIGS. 5A and 5B, respectively. The cause of the generated shock noise can be eliminated.

[0017]

However, as shown in FIG.
In the noise prevention circuit as shown in (B), the flowing current I
₁And transistor Q_Two, Q_{twenty one}(Transistor Q_Three,
Q_{twenty two}), The SN ratio is determined by the base resistance of
Transistor Q_Two(Q_Three), The base current flowing through
Therefore, there is a problem that the SN ratio deteriorates. Also, each
Adding a transistor to the amplifier circuit reduces the current consumption.
There is a problem that it will increase.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a power-on circuit for preventing the deterioration of the SN ratio and the increase of current consumption.

[0019]

In order to solve the above-mentioned problems, in the present invention, the power supply voltage is set to a predetermined voltage at a predetermined circuit position to form a reference voltage, and an input signal is processed based on the reference voltage. In a power-on circuit provided in a circuit that performs an amplification process and outputs a predetermined signal from an output end, the establishment of the reference voltage is monitored from the rise of the power supply voltage at power-on, and the reference voltage is established from the output end. A power-on circuit is provided which is provided with a voltage monitoring means for stopping the output of the.

According to a second aspect of the present invention, in the first aspect, the coupling capacitor is provided for the input signal, and the discharging means is provided for discharging the charge stored in the coupling capacitor when the supply of the power supply voltage is stopped. As described above, according to the first aspect of the invention, the output from the output terminal is stopped from the power-on to the establishment of the reference voltage. This prevents an abnormal increase in the reference voltage at the predetermined circuit position that occurs when the power is turned on, from being output as an output signal, and reduces the drive current of the amplification system by controlling only the state of the output end. It is possible to prevent the deterioration of the SN ratio and the increase of current consumption without the necessity.

According to the second aspect of the present invention, the coupling capacitor is provided for the input signal so that a predetermined amount of charge is operatively accumulated, and the coupling capacitor is charged by the discharging means when the power supply voltage is turned off. Discharge the electric charge that is being stored. As a result, the residual charge of the coupling capacitor is discharged when the power is turned off.Therefore, noise is generated even if the power supply voltage is turned on again within the period when the charge may remain in the coupling capacitor from the power-off state. Can be prevented.

[0022]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 1 shows an audio signal processing circuit 21 similar to FIG. 3 described above, in which a voltage monitoring circuit 22 as a voltage monitoring means and a discharging circuit 23 as a discharging means are provided in a circuit including the power-on circuit of FIG. It is provided. In FIG. 1, circuit parts similar to those in FIG. 3 are denoted by the same reference numerals, and the description of the connection relationship is omitted.

Therefore, the voltage monitoring circuit 22 is connected to the emitters of the PNP type transistors Q ₃₁ and Q ₃₂ from the power supply voltage line V _CC through the current source 24.
The collector of the transistor Q ₃₁ is connected to GND.
Further, the base of the transistor Q ₃₁ has resistors R ₁ and R ₂
Is connected to the connection point A. The collector of the transistor Q ₃₂ is connected to GND via the resistor R ₂₁ .

The current source 25 is connected to the power source voltage line V _CC.
Is connected to the base of the transistor Q ₃₂ through, it is connected to the collector and base of the NPN-type transistor Q _33. The emitter of the transistor Q ₃₃ is GND
Connected to. Further, it is connected to the collector of the NPN transistor Q ₃₅ from the power supply voltage line V _CC via the current source 26 and to the base of the NPN transistor Q ₃₅ . The base of the transistor Q ₃₄ is connected to the collector of the transistor Q ₃₂ , and the emitter is connected to GND.

Transistor Q₃₅Of the emitter is connected to GND
And the collector is transistor Q ₁₄Connect to the collector
Is done. On the other hand, the discharge circuit 23 includes a transistor Q₇No
(1/2) V which is a mitter_CCPNP type transition from the point
Star Q₃₆Connected to the emitter of the transistor Q₃₆of
The collector is an NPN type transistor Q₃₇Connect to the base of
And the resistance R_{twenty two}Is connected to GND via.
Transistor Q₃₇The emitter of is connected to GND and
The input voltage terminal (V_in) 13 is connected.

Further, the power supply voltage line V _CC is connected to the emitter of a PNP type transistor Q ₃₈ , and the collector of the transistor Q ₃₈ has its own base and the transistor Q _36.
Is connected to the base of the
It is connected to D. Here, in the audio signal processing circuit 21, as described above, the connection point (1/2) V
_CC is a circuit position where the reference voltage appears, and in this embodiment, it is set to 1/2 of the power supply voltage V _CC as shown.
Further, the connection point A is a transistor Q due to the delay due to the capacitor C ₁ from the rise of the power supply voltage V _{CC from} the power-on.
₂ is operated from the on state to the off state and transistor Q
_This is a point representing (1/2) V _CC at the emitter of ₇ . Further, the connection point B is an output end that outputs an output signal, and is connected to, for example, the input end of a power amplifier.

The operational amplifier 15 has an output terminal and an inverting input terminal connected to each other, and constitutes a so-called voltage follower. That is, this voltage follower receives an input voltage with a high input impedance and outputs the voltage as it is to the output of a low output impedance circuit.
The audio signal processing unit 16, for example formed by a circuit such as a filter, the audio signal transistor Q ₁₀ to Q ₁₃
Transistors Q ₁₉ , Q ₂₀
Is output from the output end (connection point B) to the speaker (not shown) via the power amplifier.

Therefore, the power source of the audio signal processing circuit 21.
The operation at the time of turning on will be described. When the power is turned on, A
The point is the transistor Q of the voltage monitoring circuit 22.₃₃V_BENo level
Transistor Q until reaching₃₁Is turned on
Transistor Q_{twenty two}, Q_{twenty four}Is off and the transistor
TA Q₃₅Turns on. Therefore, the transistor
Q ₁₇, Q₁₈Turns off and the current mirror
Transistor Q₁₃, Q₁₄Turn off the transistor
Q₁₆Turns off. Therefore, the output point B is GND level.
Keep the bell.

At this time, the connection point (1
/ 2) Even if the voltage of V _CC jumps up as shown in FIG. 4B, since the point B is at the GND level, the jumping is not output to the power amplifier and is not transmitted to the speaker. The shock noise is prevented from occurring.
In this case, since the transistor Q ₁ does not have the Darlington connection as shown in FIG. 5, the base resistance is minimum, and the deterioration of the SN ratio can be prevented. Further, the transistor Q ₃₅ can prevent the transistors Q ₁₇ , Q _{18 from} being deteriorated. Since the drive circuit is driven, it is possible to prevent an increase in current consumption without affecting the amplification stage.

[0030] Incidentally, the point A reaches the level of the transistor Q ₃₃ of the voltage monitoring circuit 22, transistor Q ₃₁ is the transistor Q ₃₅ is turned off in the OFF state, the transistor Q _17, Q ₁₈ in an on state . Therefore, the audio signal from the audio signal processing unit 16 is output from the output terminal B to the power amplifier and the speaker.

By the way, the power supply voltage V_CCOnce stop the power supply
It may be restarted immediately after being stopped. Here, FIG.
FIG. 3 shows a waveform diagram for explaining the re-turn-on of power. example
If. In the audio signal processing circuit 21, the discharging circuit 23
If not connected, the power supply voltage V_CCOnce
When the power supply is turned off (power supply is stopped), input voltage terminal
(V _in) Coupling capacitor C connected to 13_Two
The power supply is charged before the electric charge that has been charged to the
Pressure V_CCIs turned on again (t = t in FIG. 2)_Three), B
Shock noise occurs as shown in FIG. 2 at the point.

That is, the power supply voltage V_CCIs off period (t_Two
<T <t_Three), (1/2) V_CCFor point and B point
Coupling capacitor C_TwoDue to the residual charge of
Will occur (t in FIG. 2)_TwoThe rise from
Power supply voltage V in this state _CCIs turned on again at point B
The generated voltage is the transistor Q₃₅Turned on and suddenly
To the GND level, and shock noise from the output point B
Will be output as.

Therefore, in the discharge circuit 23 shown in FIG. 1, the voltage is lowered by the operation of stopping the supply of the power supply voltage V _CC , and when the power supply voltage V _CC becomes (1/2) V _CC , the transistor Q ₃₆
Is turned on, and the transistor Q ₃₇ is turned on. As a result, the residual charge of the coupling capacitor C ₂ is discharged via the transistor Q ₃₇ . That is,
During the off period (t ₂ <t <t ₃ ) of the power supply voltage V _CC , (1 /
2) The voltage is prevented from being generated at the V _CC point and the B point.

If the power-supply voltage V _CC is off for a long time when the power is turned on again and the residual charge of the coupling capacitor C ₂ is discharged, the discharge circuit 23
Is unnecessary. In the above embodiment, the audio signal processing circuit 21
Although the case where the present invention is applied is shown in the above, the present invention is not limited to this, and the present invention can be applied to all circuits that can be used by replacing the audio signal processing unit 16 as necessary.

[0035]

As described above, according to the invention of claim 1,
By stopping the output from the output terminal from power-on to the establishment of the reference voltage, it is possible to prevent an abnormal rise in the reference voltage at the specified circuit position that occurs when the power is turned on, as an output signal. Since only the end state is controlled, it is not necessary to reduce the drive current of the amplification system, and it is possible to prevent deterioration of the SN ratio and increase of current consumption.

According to the second aspect of the present invention, the coupling capacitor is provided for the input signal so that a predetermined amount of charge is operatively accumulated, and the coupling capacitor is discharged by the discharging means when the power supply voltage is turned off. Since the residual charge of the coupling capacitor is discharged when the power is turned off by discharging the electric charge that has been charged to the power supply, the power supply voltage It is possible to prevent noise from being generated even if the power is turned on again.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining power-on again.

FIG. 3 is a circuit diagram of a conventional audio signal processing circuit.

FIG. 4 is a waveform chart of rising when the power is turned on.

FIG. 5 is a circuit diagram of a conventional noise prevention circuit when the power is turned on.

[Explanation of symbols]

 13 input voltage terminal 15 operational amplifier 16 audio signal processing unit 21 audio signal processing circuit 22 voltage monitoring circuit 23 discharge circuit

Claims (2)

[Claims] 1. A circuit for outputting a predetermined signal from an output end by subjecting a power supply voltage to a predetermined voltage at a predetermined circuit position as a reference voltage, subjecting an input signal to signal processing and amplification processing based on the reference voltage. In the power-on circuit, a voltage monitoring means is provided for monitoring the establishment of the reference voltage from the rise of the power supply voltage when the power is turned on, and for stopping the output from the output terminal until the reference voltage is established. Power on circuit 2. The coupling capacitor according to claim 1, wherein a coupling capacitor is provided for the input signal, and discharging means is provided for discharging the charge charged in the coupling capacitor when the supply of the power supply voltage is stopped. Power-on circuit.