JP6916481B2 - Device - Google Patents

Description

The present invention relates to a power supply and load connection method using a regulated power supply with little voltage fluctuation.

A power supply is indispensable for operating electronic devices such as audio amplifiers and CD players, and in order to ensure stable operation, a transformer, rectifier and smoothing circuit, and switching power supply are used to convert commercial AC voltage to a predetermined DC voltage. After that, or instead, a battery may be used, but it is common practice to use a regulated power supply circuit for each required voltage as a component circuit of the device. Generally, when using a simple IC-based three-terminal regulator (Fig. 1), when using a DC-DC converter, or when seeking even greater stability, a regulated power supply circuit that combines an operational amplifier and a transistor, etc. (2 stabilized power supply in FIG. 2) may be used.

However, as shown in the examples shown in 2 stabilized power supplies of FIGS. 1 and 2, the output of the conventional stabilized power supply circuit is 101 in the example of FIG. 1 and FIG. 2 because of the stable operation of the power supply circuit itself and the load circuit in the subsequent stage. In the example of, 202 capacitors are connected. This is because the power supply shown in FIGS. 1 and 2 is designed on the premise of a capacitive load because the purpose is to operate a circuit with a bypass capacitor as a load.

FIG. 3 shows only the gain of the board diagram of the operational amplifier in a simplified manner, and the gain characteristic A (broken line) of 30 represents a general operational amplifier, and the operational amplifier 210 used in the example of FIG. You can think about it. Since the connection of the capacitor 202 of FIG. 2 causes a capacitive load even though it is via the transistor 211, the unity gain frequency A of 32 shown in FIG. 3 is generally limited to 33, there is no phase margin, and oscillation is easy. Becoming is a well-known phenomenon. As a method for improving this, it is a well-known method that the phase margin is improved by adding the phase compensation capacitor 201 shown in FIG. 2 to the negative feedback resistor 220 to stabilize the operation of the operational amplifier 210.

However, it is known that the phase compensation capacitor 201 in FIG. 2 limits the maximum gain of the operational amplifier shown in FIG. 3 to a low value as shown by 34.

Therefore, if the characteristic of the original operational amplifier 210 is the gain characteristic A of 30 in FIG. 3, it can be seen that it is limited to the gain characteristic B of 31 by incorporating it into the regulated power supply circuit as shown in FIG. The contents described in paragraphs 0004 and 0005 also apply to the internal description of the 10-three-terminal regulator IC of FIG.

On the other hand, the output impedance is a parameter that indicates the superiority or inferiority of the output characteristics of the power supply circuit, and the lower the impedance, the better the power supply that is resistant to load fluctuations. Specifically, it is required that the operational amplifier 210 described above can obtain a large amount of negative feedback and that the internal impedance of the 202 capacitor shown in FIG. 2 is low.

The load circuit shown in the example in which a 20-load circuit is connected to the voltage output 22 of the 2 regulated power supply circuit in FIG. 2 is a circuit of one operational amplifier, but the power supply terminal of a circuit composed of a plurality of circuits or transistors or the like. But it doesn't matter. A general method of connecting a power supply and a load circuit is to connect a 203 bypass capacitor to the power supply terminal of 23 as close as possible.

Here, the role of the 203 bypass capacitor is that when the 20-load circuit is composed of, for example, an operational amplifier and the gain characteristic of the operational amplifier is as shown in the 30 gain characteristic A of FIG. 3, and there is no 203 bypass capacitor, the power supply impedance is high. It is not low enough, and the voltage of the 23 power supply terminals fluctuates due to the operation of the 20-load circuit. Due to this power supply fluctuation, the characteristics of the 30-load circuit are disturbed in the vicinity of the 32 unity gain frequency A in FIG. 3, the phase margin is reduced, and an abnormal operation state such as oscillation may occur. Therefore, it is an object of connecting a 203 bypass capacitor to lower the impedance, reduce the fluctuation of the power supply voltage, prevent the disturbance of the characteristics of the 20-load circuit, and ensure stable operation.

On the other hand, if the signal passing through the 30-load circuit in the above does not have a band of about 32 unity gain or more in FIG. 3, the 30-load circuit can maintain normal operation even without the 203 bypass capacitor.

Here, FIG. 4 shows the internal impedance characteristics of the capacitor. As a general capacitor value, if 202 in FIG. 2 is several hundred uF and 203 is 1 uF or less, it can be considered that they correspond to 40 and 41 in FIG. 4, respectively. As shown in 40 impedance characteristic 1 of FIG. 4, the one with a large capacitance has a peak with a low impedance on the low frequency side, and the one with a low capacitance has a peak with a low impedance in a higher frequency region than 40 as in 41 impedance characteristic 2. Exists. Moreover, the peak of 41 has a higher impedance than that of 40, and the internal impedance characteristic of the capacitor common to 40 and 41 is characterized by having a V-shaped characteristic with respect to the frequency. These are different in the structure of the capacitor, for example, ceramic capacitor, film capacitor, chemical capacitor, etc., although there is a difference in internal impedance, this V-shaped feature is common.

Therefore, FIG. 5 shows the output impedance of the voltage output 22 of FIG. Originally, it is necessary to consider the impedance due to the wiring from the voltage output 22 to the power supply terminal and the influence of the load circuit 20, but it may be omitted from the gist of the present invention and is omitted here. Here, the output impedance of the voltage output 22 is composed of a 210 operational amplifier, a 211 transistor, a 212 voltage reference, a 220, and a 221 resistor, and the value obtained by dividing the voltage output 22 by the resistors 220 and 221 is compared with the reference voltage of the voltage reference 212. The circuit that feeds back the difference and stabilizes the voltage output 22 is equipped with 201 and 202 capacitors. The characteristic is that the 2 stabilized power supply of FIG. 2 having the 31 gain B characteristic shown in FIG. 3 and the bypass capacitor of 203 are added. .. Therefore, the impedance of the voltage output 22 has the 50 impedance characteristic A of FIG.

As is clear from the impedance characteristic A, the impedance in the low frequency range is low to some extent due to the function of the feedback circuit of the 210 operational amplifier in FIG. 2, but the impedance characteristic with respect to the overall frequency depends on the characteristic of the capacitor. Conventionally, for the purpose of further reducing the impedance at each frequency, it has been possible to contribute to the purpose to some extent by connecting a plurality of capacitors characterized by low internal impedance and capacitors having different capacities. However, installation space and cost are also issues, and there is naturally a limit to mounting multiple capacitors. Further, it cannot be avoided that it depends on the impedance characteristics of the capacitor described above, and there is a drawback that the power supply circuit is not uniform depending on the frequency.

In the explanation so far, we have not touched on the DC-DC converter, but since it is a circuit that generates switching noise in the first place, a capacitor is connected to the output to eliminate switching noise, and the output impedance is inside the capacitor. Since it is clear that it depends on impedance to some extent, detailed description thereof will be omitted.

By the way, not only the sound quality of the audio amplifier, but also the operating performance of the device that is the load of the power supply largely depends on the stability of the power supply, and it largely depends on the characteristics of the regulated power supply and the characteristics of the output capacitor of the regulated power supply. As described above, the characteristics of the regulated power supply itself also deteriorate due to the output capacitors. There was no way to avoid this with the conventional circuit method.

As a remedy for this, it is provided a method of not connecting any capacitor such as a bypass capacitor in the connection path from the output of the regulated power supply circuit to the load circuit. Although there is an invention according to Japanese Patent Application Laid-Open No. 2012-104014 in the prior art, it is an invention of a power output stabilizing circuit corresponding to a high-speed pulse change due to a digital circuit load, and the method and purpose are different from the present invention described below.

In addition to audio amplifiers, there has been a demand for higher stabilization quality of regulated power supplies.

Japanese Unexamined Patent Publication No. 2012-104014

Shigeru Tanimoto, "Practical Technology for Operational Amplifiers", published by Seibundo Shinkosha, 1980

The problem to be solved is that the output impedance characteristic of the regulated power supply circuit is affected by the capacitor connected to the output and the bypass capacitor (capacitive load) connected to the load circuit.

The present invention is to operate a regulated power supply circuit that eliminates an output capacitor and a load circuit that eliminates a bypass capacitor in combination.

For example, when the circuit of the present invention is used for an audio amplifier, stable voltage supply in a wide band with extremely little power fluctuation than before enables stable signal amplification operation in a wide band, and is high over the entire audible band from bass to treble. Sound quality reproduction is possible.

FIG. 1 is an explanatory diagram showing a circuit of a three-terminal regulator IC. FIG. 2 is an explanatory diagram showing a connection between a general regulated power supply and a load circuit. FIG. 3 is an explanatory diagram showing the gain in the Bode diagram of the operational amplifier characteristics. FIG. 4 is an explanatory diagram showing the internal impedance characteristics of the capacitor. FIG. 5 is an explanatory diagram showing the output impedance characteristics of the regulated power supply circuits of FIGS. 2 and 6. FIG. 6 is an explanatory diagram showing a method of connecting the stabilized power supply and the load circuit of the present invention.

This was achieved by combining an existing commercially available component with a stabilized power supply circuit that eliminates the output capacitor and a load circuit that eliminates the bypass capacitor.

FIG. 6 is a circuit diagram of an embodiment of the circuit of the present invention, showing a case where the load circuit 60 has a positive and negative power supply.

As shown in FIG. 3, the operational amplifier 610 employs an amplifier whose 35-fold point frequency B is equal to or exceeds the audio band, as shown in FIG. The operational amplifier 610, together with the resistors 620 and 621, produces a positive voltage V3. The reference voltage Vr of the voltage reference 612 is connected to the non-inverting input to obtain a voltage of V3 = (1 + R2 / R1) · Vr. At this time, the power supply voltage connected to the power supply terminal of the operational amplifier 610 is V1> V3> V2, and it is a condition that the output is not saturated in the operation of the operational amplifier 610.

Similarly, the operational amplifier 611 employs an amplifier whose 35-fold point frequency B is equal to or exceeds the audio band, as shown in the 36 gain characteristic C shown in FIG. The operational amplifier 611 generates a negative voltage V6 together with the resistors 622 and 623. The reference voltage Vr of the voltage reference 612 is connected to the side opposite to the operational amplifier input side of the inverting amplifier input resistance 622 to obtain a voltage of V6 = − (R4 / R3) · Vr. At this time, the power supply voltage connected to the power supply terminals 602 and 603 of the operational amplifier 611 is V4> V6> V5, and it is a condition that the output is not saturated in the operation of the operational amplifier 611.

Although the load circuit 60 shows a circuit of one operational amplifier in FIG. 6, it may be a circuit composed of a plurality of circuits, transistors, or the like.

Further, the maximum current consumption of the load circuit 60 must be equal to or less than the maximum output current of the operational amplifiers 610 and 611.

Further, the operable frequency of the load circuit 60 must be approximately unity gain B or less of the regulated power supply circuits 66 and 67 (37 in FIG. 3). In order to satisfy this condition, the low-pass filter 65 may be inserted before the load circuit 60 to satisfy this condition.

After satisfying the design procedures and conditions of paragraphs 0026 to 0030, the output of the regulated power supply circuit 66 is bypassed to the power supply terminal 61 of the load circuit 60, and the output of the regulated power supply circuit 67 is bypassed to the power supply terminal 62 of the load circuit 60. By connecting without adding any capacitors, a combined operation circuit of a regulated power supply circuit that eliminates the output capacitor of the present invention and a load circuit that eliminates the bypass capacitor is realized.

Needless to say, the wiring length between the output of the regulated power supply circuits 66 and 67 and the power supply terminals 61 and 62 of the load circuit 60 is as short as possible in order to prevent an increase in the power supply impedance.

Further, although FIG. 6 shows a case where the load circuit 60 has a plus and minus two power supplies, it does not matter even if it is a single power supply circuit, and the circuit can be easily considered, so the description of the single power supply connection will be omitted.

Further, although the regulated power supply circuit 66 has been described as a non-inverting circuit and 67 as an inverting circuit, the inverting circuit, the non-inverting circuit, the buffer circuit connection, etc. are not particularly particular, although it depends on the output voltage of the voltage reference of 612.

Similarly, there is no particular preference regarding the circuit format of the 612 voltage reference.

For example, when an audio amplifier is applied as a load, an operational amplifier whose 35-fold point frequency B exceeds the maximum frequency of the audio band is used as a regulated power supply circuit as shown in 36 gain characteristic C in FIG. 3, and its output is used as a load circuit. It takes the form of connecting directly to the power supply terminal of. Here, the load circuit may be a circuit with one operational amplifier, a circuit composed of a plurality of circuits, transistors, or the like. At this time, no capacitor is connected to the connection path from the output of the operational amplifier used as the regulated power supply circuit to the power supply terminal of the load circuit. In addition, the maximum output current capacity of the operational amplifier used for the power supply is equal to or greater than the maximum current consumption assumed for the load circuit. Similarly, the unity gain frequency of the operational amplifier used for the regulated power supply should be equal to or higher than the unity gain frequency of the amplifier used for the load circuit. At this time, if the passing signal is band-limited by something like a low-pass filter, the unity gain frequency of the operational amplifier used for the regulated power supply should be the upper limit of the frequency band passing through the load circuit or higher. As a result, the regulated power supply circuit and load circuit operate stably, and the regulated power supply output impedance is lower than that of the conventional regulated power supply, at least in the audio band, regardless of the characteristics of the capacitor, and there is no unevenness of impedance due to frequency. A stable power supply and power supply method can be constructed.

An amplifier having a band equal to or higher than the pass signal band of the circuit that is a load with respect to the controllable band of the regulated power supply circuit is used for the regulated power supply circuit. Alternatively, it can be realized by limiting the band of the passing signal with a low-pass filter or the like so that it is within the controllable band of the regulated power supply circuit.

60 Load circuit 65 Low-pass filter 66 Positive side regulated power supply 67 Negative side regulated power supply 612 Voltage reference

Claims (1)

A first including an error amplifier that outputs an output voltage obtained by converting a DC voltage by a dropper method.
A regulated power supply circuit including a semiconductor device, wherein the error amplifier has a predetermined reference voltage.
And the output voltage fed by the negative feedback circuit are compared, and the reference voltage and the output voltage are compared with each other.
A regulated power supply that outputs the output voltage by adjusting the output voltage so as to eliminate the comparison error of
Road and
The second half of the load circuit of the regulated power supply circuit, which includes an operational amplifier, a transistor, and the like.
With a load circuit including an amplifier circuit with a conductor device,
The regulated power supply circuit is a connection for connecting the first semiconductor device and the second semiconductor device.
It is a connection form that supplies power to the load circuit without providing a bypass capacitor in the system.
When the gain characteristics of the error amplifier are shown in the Bode diagram, the gain on the low frequency side is a constant value.
The first line shown and the first line showing that the gain on the high frequency side decreases monotonically as the frequency increases.
The folding point frequency at the intersection of the two lines exceeds the maximum frequency of the audio band,
The unity gain frequency of the error amplifier is the unity gain frequency of the amplifier circuit.
Has frequency characteristics equal to or higher than the upper limit
A device characterized by that.

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