JP2865042B2 - Constant current source 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 current source circuit, and more particularly to a constant current source circuit having a function of controlling the supply of a power supply current according to the magnitude of an input signal to an external signal processing circuit to which the power supply current is to be supplied. The present invention relates to a constant current source circuit having a current supply amount control function.

[0002]

2. Description of the Related Art FIG. 4 shows a circuit diagram of an example of a general constant current source circuit. Referring to FIG. 4, the constant current source circuit shown in FIG. 4 includes a plus power supply line (voltage = V _cc ) 1 and a minus power supply line (voltage = V _EE ) 2. Then, one end of a resistor R ₂ connected to positive power line 1, a collector electrode connected to the same time base electrode when connected to the other end of the resistor R _2, an npn type bipolar transistor Q ₂ of diode-connected , The collector electrode is connected to the emitter electrode of transistor Q _{2, and} the emitter electrode is connected to negative power supply line 2.
_3, a collector electrode connected to the positive power line 1, the base electrode is connected to the base electrode of the transistor Q _2, an npn type bipolar transistor Q ₄ whose emitter electrode is connected to the base electrode of the transistor Q _3, transistor Q ₄ and the resistor R ₃ connected between the emitter electrode and the negative power line 2, the base electrode is an npn bipolar transistor is connected to a connection node between the collector electrodes of the emitter electrode and the transistor Q ₃ of the transistor Q ₂ Q ₁
Is the is composed of a connected and a resistor R ₁ between the emitter electrode and the negative power line 2 of the transistor Q _1, the collector electrode of the transistor Q ₁ is a current supply terminal 3 to an external signal processing circuit ing.

The above-described constant current source circuit is configured to supply a constant power supply current regardless of the presence or absence of an input signal to an external signal processing circuit (not shown). Therefore, it is not suitable for use as a constant current source circuit in a semiconductor integrated circuit or the like, which consumes a large amount of current and has recently been strongly demanded to reduce power consumption. Therefore, a constant current source circuit has been proposed in which the amount of current supplied to the signal processing circuit is controlled according to the magnitude of an input signal to the signal processing circuit. FIG. 5 shows a circuit diagram of an amplifier circuit using such a constant current source circuit with a current supply amount control function. The circuit shown in this figure is an amplifying circuit disclosed in Japanese Patent Application Laid-Open No. 4-111506, in which a constant current source circuit for determining an operating current of a main amplifier is provided with the above-described current supply amount control function. Referring to FIG. 5, the constant current source used in this amplifier circuit includes a first current source 7 for supplying a constant current to main amplifier 6 and a magnitude of input signal S _in to main amplifier 6. It has a parallel configuration with the second current source 8 whose current value changes. Therefore,
Total amount of current supplied to the main amplifier 6, when the input signal S _in is absolutely not determined by the supply amount of the first current source 7, when the input signal S _in is present varies by the supply amount of the second current source 8 .

The amount of current supplied from the second current source 8 is controlled by the output signal S ₉ of the full-wave rectifier circuit 9. When the signal S _in having the voltage waveform shown in FIG. 6A is input to the main amplifier 6, the full-wave rectifier circuit 9 performs full-wave rectification on the input signal S _in and supplies the input signal S _in to the second current source 8. Therefore, the second current source 8
As in the current waveform shown in (b), when the input signal S _in is had large supplies a large current, when the signal S _in is small and so to supply a small current, the magnitude of the input signal S _in The current supply amount to the main amplifier 6 is changed accordingly.
Thus, the operating current of the main amplifier 6 is controlled, and power consumption is reduced.

[0005]

In the conventional constant current source circuit having a current supply amount control function shown in FIG.
It changes according to the magnitude of the input signal to the signal processing circuit (in this case, the main amplifier 6). Therefore, if this constant current source circuit is used for an amplifier, for example, the main amplifier 6
Is changed by the input signal S _in . When the amplifier 6 is used open, for example, FIG.
When you try to amplify the input signal S _in voltage waveform (a), the output signal S _out is distorted as the voltage waveform shown in FIG. 7 (b). In order to avoid such distortion of the output signal, the amplifier 6 is usually used by applying feedback, but at this time, the amplification factor must be set to an amplification factor that is not affected even if the open gain changes. , Circuit design,
The configuration becomes complicated.

In the constant current source having the configuration shown in FIG.
Since the first current source 7 continues to supply current even when there is no input signal Sin as _{in the} current waveform shown in (b), the current needs to be further reduced.

Therefore, the present invention is a constant current source circuit having a current supply amount control function, wherein the current supply amount is controlled according to the magnitude of an input signal to a signal processing circuit to which a power supply current is to be supplied. An object of the present invention is to provide a constant current source circuit in which a supply amount at the time of supply is constant regardless of the magnitude of an input signal to a signal processing circuit, and does not change its open gain even when applied to, for example, an amplifier. Things.

It is another object of the present invention to provide a constant current source circuit having lower power consumption than a conventional constant current source circuit having a current supply amount control function.

[0009]

A constant current source circuit according to the present invention comprises a power supply required for an external signal processing circuit to operate the circuit.
Current source transformer configured to provide a constant current
The control electrode of the transistor and the transistor of the current source.
Analog switch provided in the bias current supply path
A current source unit including a switch, and an input signal to the signal processing circuit.
A rectifying / smoothing circuit for taking in and converting to direct current;
Ratio between the output voltage of the smoothing circuit and the given voltage
And a comparator for converting the comparison result into a binary signal.
Opening and closing the analog switch,
It is controlled by the binary signal output from the comparator.
In the constant current source circuit, the current source section
Are a first power supply line of a first potential and a second power supply line of a second potential
A first terminal connected to the first power supply line at one end.
A resistor and a collector electrode connected to the other end of the first resistor;
The first bipolar transistor and the collector electrode
A contact is made with the emitter electrode of the first bipolar transistor.
And the emitter electrode is connected to the second power line.
A second bipolar transistor and a collector electrode
A base electrode connected to the first power supply line;
Connected to the base electrode of the polar transistor, the emitter
An electrode is a base electrode of the second bipolar transistor;
A third bipolar transistor connected to the
3. The emitter electrode of the third bipolar transistor and the second
A second resistor connected between the power supply line and a base electrode;
Are connected to the emitter electrode of the first bipolar transistor.
A collector electrode of the second bipolar transistor;
Fourth bipolar transistor connected to a connection node
And an emitter electrode of the fourth bipolar transistor
A third resistor connected between the first power supply line and the second power supply line;
The collector electrode and the base of the first bipolar transistor
MO connected to the source electrode to form a current path
An S-type field effect transistor;
The comparator is connected to the gate electrode of
Inputting the output binary signal of the fourth bipolar transistor
From the collector electrode of the transistor to the external signal processing circuit
The power supply current is supplied .

A constant current source circuit according to the present invention comprises a current source transistor configured to constantly supply a power supply current required for the operation of the circuit to an external signal processing circuit and a control electrode of the current source transistor. A current source unit including an analog switch provided in a bias current supply path; a rectifying / smoothing circuit which takes in an input signal to the signal processing circuit and converts the signal into a direct current; and a predetermined voltage given an output voltage of the rectifying / smoothing circuit. And a comparator for comparing the magnitude of the analog switch with the voltage of the analog switch and converting the comparison result into a binary signal. The opening and closing of the analog switch is controlled by the output binary signal of the comparator. That is, the magnitude of the input signal to the signal processing circuit is converted into a binary value that is larger or smaller than a predetermined voltage, and the power supply current to the signal processing circuit is supplied or stopped depending on the binary state. . The current source unit is configured to supply a constant current when supplying current. Therefore, a constant power supply current is supplied to the signal processing circuit when the input signal is large, and is not supplied when the input signal is small. Thus, even if the constant current source circuit of the present invention is applied to an amplifier, the open gain does not change. In addition, the current supply is stopped when there is no input signal to the signal processing circuit, so that the power consumption is further reduced as compared with the conventional constant current source circuit.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a signal processing system including a constant current source circuit 10 according to an embodiment of the present invention, and a circuit diagram of an example of a current source unit 11 and a rectifying and smoothing circuit 12 used in the constant current source circuit. It is. Referring to FIG. 1, a constant current source circuit 10 of the present invention includes a rectifying / smoothing circuit 12 for half-wave rectifying and smoothing an input signal S _in to a signal processing circuit 20, and a DC output voltage V of the rectifying / smoothing circuit 12.
A comparator 13 that compares the magnitude of ₀ with a voltage provided by a reference voltage source 21 and converts the comparison result into a binary signal S ₁₃ , and a current source unit 11 that supplies a current to the signal processing circuit 20.
It consists of The current source unit 11 is configured so that the supply amount at the time of current supply is constant, and the signal processing circuit 2
Whether to supply a current to 0, the output signal S ₁₃ of the comparator 13, is controlled.

FIG. 1B is a circuit diagram of an example of the current source section 11. Compared FIG 1 (b) and FIG. 4, the current source 11 in the present embodiment, the conventional constant current source circuit, the structure of the transistor Q ₂ is doing. That is,
Transistor Q ₂ is, conventionally, while the base and collector electrodes have been short-circuited, in this embodiment, between the collector electrode and the base electrode, n-channel MOS transistor Q ₅ forms a current path Connected. Then, the gate electrode of the transistor Q _5, the signal S ₁₃ from the comparator 13 is input. In the present embodiment, by controlling the output signal S ₁₃ at the transistor Q ₅ of the on and off states of the comparators 13, the current can be controlled on-off flow to the signal processing circuit 20. That is, when the signal S ₁₃ is high level, the transistor Q
₅ is turned on, and the constant current source 11 operates to supply a constant current to the signal processing circuit 20. On the other hand, when the signal S ₁₃ is at the low level, the transistor Q ₅ is so turned off the constant current source unit 11 does not operate, the signal processing circuit 20 supply current does not flow.

FIG. 1C is a circuit diagram showing an example of the rectifying / smoothing circuit 12 in FIG. 1A. Referring to FIG.
The circuit 12 includes a rectifier circuit section 14 for half-wave rectifying the input signal S _in to the signal processing circuit 20 and a smoothing circuit section 15 for smoothing the output of the rectifier circuit section 14. Rectifier circuit 1
4 is a diode D between the input terminal 16 and the ground line 5.
₁ and a resistor R ₇ in this order, a diode D ₁ is a configuration connected in series such that the forward direction to this direction. Output point of the rectifier circuit 14 is connected the node N ₁ between the cathode electrode of the diode D ₁ and a resistor R _7. On the other hand, the smoothing circuit section 15 is a circuit having a configuration in which a resistor R ₈ and a capacitor C ₁ are connected in series in this order between the output point N ₁ of the rectifier circuit section 14 and the ground line 5. The smoothing circuit section 15 includes a resistor R
A connection node N ₂ between the capacitor ₈ and the capacitor C ₁ is set as an output point
Here to output a voltage V _0.

The circuit of this embodiment shown in FIG. 1 operates as follows. Referring to the circuit diagram shown in FIG. 1 and FIG. 2 showing signal waveforms at the time of operation of each node of this circuit, FIG.
When the input signal S _in having the voltage waveform shown in FIG. 7A is input to the signal processing circuit 20, the same input signal S _in is taken _in by the rectifying and smoothing circuit 12 at the same time. Rectifying smoothing circuit 1
In FIG. 2, half-wave rectification is performed by the rectifier circuit unit 14 as shown in the voltage waveform in FIG.
5, the DC signal V having the voltage waveform shown in FIG.
₀ is obtained.

The output DC signal V _{0 of the} above-mentioned smoothing circuit section 15
Is input to the comparator 13, and the level of the voltage is compared with a reference voltage provided by the reference voltage source 21. When the output voltage V ₀ of the smoothing circuit unit 15 is higher than the reference voltage, the comparator 13 outputs a high-level signal S ₁₃ and turns on the MOS transistor Q ₅ in the current source unit 11. As a result, FIG.
A constant current like the current waveform shown in FIG. On the other hand, when the output voltage V ₀ of the smoothing circuit section 15 is lower than the reference voltage, the output signal S ₁₃ of the comparator 13 becomes low level, and the MOS transistor Q ₅ in the current source section 11 is turned off. As a result, no current flows through the signal processing circuit 20.

As described above, the constant current source circuit according to the present embodiment allows a constant current to flow through the signal processing circuit 20 when the input signal S _in to the signal processing circuit 20 exceeds a certain reference, and the reference current exceeds the reference. As long as it continues to flow the same current. Therefore, unlike the conventional constant current source circuit shown in FIG.
Even if an amplifier is used as the
No distortion is caused as shown in FIG. On the other hand, if the input signal to the signal processing circuit 20 is equal to or less than the reference, the power supply current does not flow through the signal processing circuit 20. Therefore, the signal processing circuit 2
0 does not work and does not consume power. As described above, since the current source unit is turned on / off depending on the magnitude of the input signal to the signal processing circuit, the current consumption can be reduced.

In the embodiments described above, the transistors constituting the current source section 11 (see FIG. 1B) are npn-type bipolar transistors and n-channel type MO transistors.
Although S transistors are used, as shown in FIG. 3, these transistors may be replaced with pnp bipolar transistors and p-channel MOS transistors and the polarities of the power supply lines 1 and 2 may be reversed. In the constant current source unit shown in FIG. 3, when the low level signal is input to the gate electrode of the p-channel type MOS transistor Q _10, the constant current source unit transistor Q ₁₀ is turned on operates, the high level When a signal is input transistor Q ₁₀ is turned off, the constant current source unit to an inactive state.

[0018]

As described above, according to the present invention, a constant current source circuit receives a signal input to an external signal processing circuit to which a power supply current is to be supplied, and rectifies the input signal to obtain a direct current. According to the magnitude of the voltage, a constant power supply current is supplied to an external signal processing circuit or the supply thereof is stopped. Thus, according to the present invention, when the input signal to the signal processing circuit is below a certain reference, the current supply to the signal processing circuit is completely stopped. The current consumption can be further reduced as compared with the circuit.

When the input signal to the signal processing circuit exceeds a certain reference, a constant current flows during the time when the signal exceeds the certain reference. Therefore, even when an amplifier is used as the signal processing circuit, the open gain is reduced. No change, no need to apply feedback.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a signal waveform at each node in one embodiment during operation.

FIG. 3 is a circuit diagram of another example of the current source unit according to the embodiment;

FIG. 4 is a circuit diagram of an example of a conventional constant current source circuit having no current supply amount control function.

FIG. 5 is a circuit diagram of an example of a conventional constant current source circuit having a current supply amount control function.

6 is a diagram showing a signal waveform of each node during operation of the constant current source circuit shown in FIG. 5;

FIG. 7 is an input / output signal waveform diagram for describing distortion of an output signal in the constant current source circuit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive power supply line 2 Negative power supply line 3 Current supply terminal 5 Grounding line 6 Main amplifier 7 First current source 8 Second current source 9 Full-wave rectifier circuit 10 Constant current source circuit 11 Current source unit 12 Rectifying smoothing circuit 13 Comparator 14 Rectification Circuit part 15 Smoothing circuit part 16 Input terminal 20 Signal processing circuit 21 Reference voltage source

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03F 1/00-3/72 H03G 1/00-3/34 H04B 1/06-1/30 G05F 1 / 00-3/30

Claims (2)

(57) [Claims] An external signal processing circuit is provided for controlling the operation of the circuit.
A current configured to provide a constant supply current
Source transistor and control of the current source transistor
An electrode provided in the bias current supply path to the electrode
A current source unit including a log switch;
A rectifying / smoothing circuit that takes in an input signal and converts it to DC;
The output voltage of the rectifying and smoothing circuit and a given predetermined voltage;
A comparator that compares the magnitudes of
Opening and closing the analog switch
Is controlled by the output binary signal of the comparator.
In the constant current source circuit , the current source unit includes a first power supply line having a first potential and a second power supply line having a second potential, and one end of the first power supply line has the first power supply line. Connect to wire
A first bipolar transistor having a collector electrode connected to the other end of the first resistor, a collector electrode connected to an emitter electrode of the first bipolar transistor, and an emitter electrode connected to the first bipolar transistor. A second bipolar transistor connected to a second power supply line; a collector electrode connected to the first power supply line; a base electrode connected to a base electrode of the first bipolar transistor; and an emitter electrode connected to the second bipolar transistor. A third bipolar transistor connected to the base electrode of the second bipolar transistor, a second resistor connected between the emitter electrode of the third bipolar transistor and the second power supply line, and a base electrode connected to the third bipolar transistor. Connection between the emitter electrode of the first bipolar transistor and the collector electrode of the second bipolar transistor A fourth bipolar transistor connected to a point, a third resistor connected between the emitter electrode of the fourth bipolar transistor and the second power supply line, and a collector electrode of the first bipolar transistor And a MOS field-effect transistor connected to form a current path between the MOS field-effect transistor and a base electrode. The output binary signal of the comparator is input to a gate electrode of the MOS field-effect transistor, 4. A constant current source circuit, wherein a power supply current is supplied from a collector electrode of the bipolar transistor to the external signal processing circuit. 2. The constant current source circuit according to claim 1 ,
The rectification in the rectification smoothing circuit is half-wave rectification, wherein the constant current source circuit is provided.