JP2000222055A - Serial control type regulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a serial control type regulator capable of eliminating noise superposed upon an output voltage even when voltage of a direct current source being an input voltage falls below the neighborhood of a set output voltage and does not exist in a normal operation area and also eliminating the noise of the input voltage more than in the conventional practice even when the input voltage becomes higher than the output voltage and exists in a normal operation area. SOLUTION: A reference voltage generation circuit 4 generates voltage that is slightly higher than an output voltage VOUT, and the voltage is inputted to a voltage follower circuit through a lowpass filter. When the circuit 4 is in a normal operation area and stabilization is performed, noise superimposed on an input voltage VIN can be eliminated by its operation and the working of the lowpass filter, and when it does not exist in the normal operation area, the noise superimposed on the voltage VIN can be eliminated by the working of the lowpass filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a series control type regulator capable of removing noise superimposed on a direct current source even when its voltage decreases.

[0002]

2. Description of the Related Art As a power source for electronic equipment, a DC source obtained by rectifying a commercial power source or a DC source using a battery and a DC source stabilized by various converters such as a series control type regulator and a switching regulator are used. However, various noises are superimposed on the output of such a converter. For example, when there is a motor or the like that easily generates noise as a nearby electronic device, the noise is likely to be superimposed on the output of the converter serving as the power supply of another electronic device.
This is due to the fact that noise superimposed on the DC source input to the converter cannot be removed by the converter. In particular,
Since the series control type regulator is stabilized by making the output voltage lower than the DC source voltage, when the DC source voltage drops below the vicinity of the set output voltage, the operation for stabilization is performed normally. It simply operates as an amplifier circuit for the input voltage. Therefore, the noise of the DC source appears as it is superimposed on the output voltage as it is. In a portable audio device or the like, this noise becomes annoying or affects the rotation speed of the motor. Also, when the DC source is a battery, these shorten the usable time of the battery, which is not desirable.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to reduce noise superimposed on an output voltage even when the voltage of a DC source serving as an input voltage falls below a set output voltage and is not in a normal operation region. It is an object of the present invention to provide a series control type regulator which can eliminate the noise of the input voltage even when the input voltage is in a normal operation region where the input voltage is higher than the output voltage.

[0004]

SUMMARY OF THE INVENTION A series-controlled regulator according to the present invention comprises a transistor connected in series between an input terminal to which an input voltage is supplied and an output terminal to obtain an output voltage. A reference voltage generating circuit that generates a slightly higher voltage, a series circuit of a resistor and a constant current source that generates almost the same voltage as the output voltage by lowering the voltage of the reference voltage generating circuit, at the connection point, And a voltage follower circuit that controls the transistor using the voltage at the connection point as a reference voltage.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A series control type regulator of the present invention generates a voltage slightly higher than an output voltage by a reference voltage generation circuit, and uses the voltage as an input to a voltage follower circuit through a low-pass filter. is there. When the reference voltage generation circuit is in the normal operation area and the output is stabilized, the operation is performed by the operation of the low-pass filter. Noise can be eliminated.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of a series control type regulator according to the present invention.
In FIG. 1, a PNP transistor Q1 is connected in series between an input terminal 1 and an output terminal 2 of a series control type regulator. A reference voltage generating circuit 4 is connected to the input terminal 1, 6 is its input terminal, and 7 is its output terminal. A series circuit is formed by the resistor R1 and the constant current source S1, and one end of the resistor R1 is connected to the output terminal 7 of the reference voltage generation circuit 4. One end of a capacitor C1 is connected to a connection point P1 between the resistor R1 and the constant current source S1. The other end of the capacitor C1 and one end of the constant current source S1 are grounded. As a result, the resistance R is higher than the voltage of the output terminal 7 of the reference voltage generation circuit 4.
A voltage lower by the voltage between both ends is obtained at the connection point P1 as a reference voltage.

Further, the resistor R1 and the capacitor C1 are used to
A pass filter is formed. Operational amplifier 3 and transformer
The transistor Q1 forms a voltage follower circuit.
Connection point P1 to the inverting input terminal of the operational amplifier 3,
The output terminal 2 is connected to the input terminal, and the transistor Q1 is connected to the output side.
Source connects. The input terminal 1 has a DC source E1
Is connected, and an electronic device is connected to output terminal 2 as a load.
It is. FIG. 2 shows a specific circuit of the reference voltage generation circuit 4 of FIG.
It is a partial circuit diagram showing an example of a road. Reference voltage in FIG.
The pressure generating circuit 4 has a PNP-type transistor between the input terminal 6 and the output terminal 7.
The transistor Q2 is connected. Between output terminal 7 and ground.
Anti-R2 and resistor R3 are connected in series, and the connection point is
Connect to the non-inverting input terminal of circuit 5. The error amplifier 5
The input terminal and the output side are a DC source E2 and a transistor.
The base of Q2 connects. In this reference voltage generating circuit 4,
Means that the voltage at the output terminal 7 is divided by the resistors R2 and R3.
Is detected and compared with the voltage of the DC source E2 by the error amplifier circuit 5.
Is done. Then, the output of the error amplifier 5
The star Q2 is controlled and the output voltage V _OUT Slightly higher than
A desired voltage is obtained at the output terminal 7. DC input 6
Input voltage V of source E1_INIs added. That is, the base of FIG.
The quasi-voltage generation circuit 4 is also composed of a series control type regulator.
Have been. FIG. 3 shows the voltage follower shown in FIG.
FIG. 3 is a partial circuit diagram showing an example of a specific circuit of the circuit,
The pair amplifier 3 is an NPN type transistor Q3, Q5, Q
6. PNP transistor Q4 and constant current source S2
Formed from The collector and base of transistor Q3 are
Connected to the emitter of the transistor Q1 and the connection point P1, respectively.
And the emitter is connected to the base of transistor Q4.
With the base of the transistor Q5 via the constant current source S2.
Connected to the collector of transistor Q6. Transis
The emitter and collector of the transistor Q4 are the collectors of the transistor Q1.
And the base of the transistor Q6. G
The collector of transistor Q5 is the base of transistor Q1.
And the emitters of the transistors Q5 and Q6 are grounded.
Is done.

Next, the operation of the series control type regulator shown in FIG. 1 will be described. For example, the resistance value of the resistor R1 is 200K
Assuming that the current of the constant current source S1 is 1 .mu.A, the voltage across the resistor R1 is 200 mV, and a reference voltage 200 mV lower than the voltage of the output terminal 7 of the reference voltage generating circuit 4 is obtained at the connection point P1. The output voltage V _OUT of the output terminal 2 is equal to the connection point P.
The transistor Q1 is controlled by the operational amplifier 3 so as to be the same as the reference voltage of the first transistor Q1. Assuming that the output voltage V _OUT is set to 3.0 V and the voltage at the output terminal 7 of the reference voltage generating circuit 4 is set to 3.2 V to obtain the output voltage V _OUT , the reference voltage generating circuit 4 In the case of a series control type regulator as shown in FIG.
If the input voltage V _IN by the DC source E1 connected to the terminal is 3.5 V or more, the stabilizing operation of the normal operation area is performed and the output terminal 7
The voltage of 3.2V set in is obtained. The reference voltage at the connection point P1 is 3.0V, and the output voltage V _{OUT of} 3.0V is applied to the output terminal 7.
Is obtained.

When the input voltage V _IN falls below 3.2 V, which is the voltage set by the reference voltage generating circuit 4, the normal operation of the stabilizing operation in the operating region is not performed, and the voltage at the output terminal 7 is reduced to the input terminal 1 and the input terminal. It becomes the same as the voltage V _{IN of the} terminal 6. For example,
When the input voltage V _IN is 3.2 V, 3.0 V, and 2.5 V, respectively, the voltage at the output terminal 7 is the same, but the reference voltage at the connection point P1 is 200 m
V Low 3.0V, 2.8V and 2.3V respectively. The output voltage V _OUT of the output terminal 2 becomes the same as the voltage of the connection point P 1, and the output voltage V of 3.0 V from which noise has been removed by the reference voltage generation circuit 4.
_OUT cannot be obtained. When the reference voltage generating circuit 4 is in a normal operating region, noise superimposed on the input voltage V _IN is removed if the difference between the voltages whose amplitude is obtained at the output terminal 7 and the input voltage V _IN. Even if noise that does not fall within the difference remains in the voltage at the output terminal 7 and is superimposed, a considerable noise is added to the input voltage V _IN because the noise removal effect by the low-pass filter of the resistor R1 and the capacitor C1 is added. Is obtained at the output terminal 2 from which the noise is removed even if the output voltage V _OUT is superimposed.

When the reference voltage generation circuit 4 is not in a normal operation region, noise superimposed on the input voltage V _IN is superimposed on the voltage at the output terminal 7 as it is. However, since the low-pass filter is always present, the output voltage V _OUT from which noise has been removed by the low-pass filter is obtained at the output terminal 2. As described above, the output voltage V _OUT of the output terminal 2 is lower by 200 mV than the voltage obtained at the output terminal 7 of the reference voltage generating circuit 4. The value of the resistor R1 of the low-pass filter can be determined in consideration of the magnitude of noise superimposed on the input voltage V _IN . Since a large current does not flow through the resistor R1, the loss is small. Further, since the reference voltage generating circuit 4 only obtains a voltage near the reference voltage and almost no current flows to the output terminal 7, the transistor connected to the output terminal 7, for example, the transistor Q2 in FIG. A smaller current capacity can be used. Note that even if noise is superimposed on the emitter of the transistor Q1, the operational amplifier 3 is not affected. This is because a voltage from which noise is removed is applied from the connection point P1 to the inverting input terminal of the operational amplifier 3, for example, the base of the transistor Q3 in FIG.

FIG. 4 shows a series control type regulator of the present invention.
FIG. 5 is a characteristic diagram showing how noise is removed, and the horizontal axis represents the input voltage.
Pressure V_IN, The vertical axis is the input voltage V_INOutput of noise superimposed on
Voltage V _OUT Represents the amount of attenuation at. Input voltage V_IN
Is the output voltage V_OUT Is larger than
When the voltage generation circuit 4 is in a normal operation area, the reference voltage generation
Noise reduction of 40dB of raw circuit 4 and 40dB of low pass filter
The effect is added and the output voltage V_OUT Now 80dB noise attenuation
The amount is obtained. Input voltage V_INIs the set output voltage V
_OUT If it is smaller than the neighborhood, that is, the reference voltage generation circuit 4
Is not in the normal operating range.
The output voltage V is the amount of attenuation due to the noise reduction effect of the filter of 40 dB.
_OUT Is obtained.

FIG. 6 is a characteristic diagram showing how a conventional series control type regulator removes noise. When the input voltage V _IN is larger than the output voltage V _OUT, the output voltage V _OUT that has been removed of noise by the noise elimination effect of 60dB series control type regulator is obtained at the output terminal. However, when the input voltage V _IN is smaller than the vicinity of the set output voltage V _OUT , the noise removal effect of the series control type regulator becomes 0 dB, so that the noise of the input voltage V _IN is superimposed on the output voltage V _OUT as it is. Will be.

FIG. 5 is a circuit diagram of a multi-channel series control type regulator according to the present invention. In FIG. 5, three outputs are obtained. A transistor is connected in series between the common input terminal 1 and the output terminals 21, 22, and 23 for each channel, and a transistor is connected for each channel by the operational amplifier and the transistor. A voltage follower circuit is formed. The channel CH1 forms a voltage follower circuit by the transistor Q11 and the operational amplifier 11, the channel CH2 comprises the transistor Q12 and the operational amplifier 12, and the channel CH3 comprises the transistor Q13 and the operational amplifier 13. Resistor R1 and DC source S
One series circuit and a capacitor C1 having one end connected to the connection point P1 are commonly connected to each voltage follower circuit. A connection point P1 is connected to the input side of each voltage follower circuit. Then, one end of the resistor R1 is connected to the output terminal 7 of the common reference voltage generation circuit 4. The input terminal 6 of the constant voltage generation circuit 4 is connected to the input terminal 1.

Even in such a multi-channel series control type regulator, since the noise of the input voltage V _IN is removed by the common reference voltage generating circuit 4 and the low-pass filter of each channel, the output voltage V _OUT of each channel is reduced. Has almost no noise. Although the reference voltage generation circuit 4 is formed using a series control type regulator in the embodiment, another circuit such as a switching regulator or a simple circuit for dividing the voltage of a Zener diode by resistance may be used. In any converter, the noise of the input voltage is not removed in a region other than the normal operation region where the output stabilization operation is performed, but the noise can be removed by the low-pass filter outside the normal operation region. Therefore, a DC source having a low input voltage can be used.

[0015]

As described above, the DC control type regulator of the present invention generates a voltage slightly higher than the output voltage by the reference voltage generation circuit, and supplies the voltage to the input of the voltage follower circuit through the low-pass filter. Is what you do. When the reference voltage generation circuit is in the normal operation area and the output is stabilized, the operation is performed by the operation of the low-pass filter. Noise can be eliminated. As a result, noise can be removed not only when the input voltage is lower than the set output voltage but also when the input voltage is lower than the normal operation range. This also has the advantage that the use time can be extended since the input voltage can be used even at a low input voltage, particularly when supplied from a battery.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a series control type regulator of the present invention.

FIG. 2 is a partial circuit diagram of FIG.

FIG. 3 is a partial circuit diagram of FIG. 1;

FIG. 4 is a characteristic diagram showing how noise is removed in FIG.

FIG. 5 is a circuit diagram showing an embodiment of a multi-channel series control type regulator of the present invention.

FIG. 6 is a characteristic diagram of a conventional series control type regulator.

[Explanation of symbols]

 4 Reference voltage generating circuit R1 Resistance C1 Capacitor 3 Operational amplifier 5 Error amplifier circuit

Claims (4)

[Claims] A transistor connected in series between an input terminal to which an input voltage is supplied and an output terminal for obtaining an output voltage; a reference voltage generation circuit connected to the input terminal for generating a voltage slightly higher than the output voltage; A series circuit of a resistor and a constant current source that generates substantially the same voltage as the output voltage by dropping the output of the reference voltage generating circuit at a connection point between the two, a capacitor having one end connected to the connection point, and the connection point And a voltage follower circuit for controlling the transistor using the reference voltage as a reference voltage. 2. A transistor connected in series between an input terminal to which an input voltage is supplied and an output terminal for obtaining an output voltage, and a reference voltage having an input terminal connected to the input terminal and generating a voltage slightly higher than the output voltage. A series circuit consisting of a generator, a resistor having one end connected to the output terminal of the reference voltage generation circuit, and a constant current source connected to the other end, a capacitor having one end connected to a connection point between the resistor and the constant current source, and the connection point A voltage follower circuit having an input connected to the input terminal and an output connected to the transistor. 3. A voltage follower circuit is connected between a common input terminal and an output terminal of each channel for each channel, and a voltage follower circuit is formed for each channel by the operational amplifier and the transistor. On the input side, a connection point between the resistor and the constant current source of a series circuit composed of a resistor and a constant current source and one end of a capacitor are commonly connected, and the input terminal is connected to the input terminal and the output terminal is A multi-channel series controlled regulator, wherein one end of the resistor is connected to the output terminal of a reference voltage generation circuit that generates a voltage slightly higher than the output voltage of the channel. 4. The series control type regulator according to claim 1, wherein the reference voltage generation circuit is formed by a series control type regulator.