JP2006295415A - Power supply circuit and amplifying device provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit capable of detecting saturation of a power supply circuit without affecting a path between an amplifier and a transistor. <P>SOLUTION: The power supply circuit is provided with a control part 1 for applying an output voltage Vout to an output load 20 by controlling a power supply voltage +Vcc, a saturation prevention circuit 5 for detecting a state that the power supply voltage +Vcc is below a reference voltage Vs1, and a multiplication circuit 6 for multiplying a control voltage Pc for controlling the control part 1 by output of the saturation prevention circuit 5 and for inputting it to the control part 1. The saturation of the control part 1 can be prevented by reducing a voltage outputted to the control part 1 after multiplying the control voltage for controlling the output voltage of the control part 1 by the output voltage of the saturation prevention circuit 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply circuit, and more particularly to a power supply circuit having a function of detecting saturation by comparing a power supply voltage of the power supply circuit with a reference voltage from the outside when the power supply circuit is saturated, and preventing saturation of the power supply circuit. .

Conventionally, this type of power supply circuit is configured as in (Patent Document 1).
This power supply circuit shown in FIG. 6 includes an amplifier 13 that amplifies the reference voltage D, a transistor 15 that is connected to the output of the amplifier 13 via a resistor 14, and a differential amplifier 16 that detects a voltage difference between both ends of the resistor 14. And a comparator 17 that compares the output voltage of the differential amplifier 16 with the reference voltage E. With this configuration, saturation of the transistor 15 can be prevented by detecting a voltage difference across the resistor 14.
JP-A-5-191179

  The conventional power supply circuit has a configuration in which a resistor 14 is inserted between the amplifier 13 and the transistor 15 in order to detect saturation of the power supply circuit. Therefore, even if the resistor 14 has a low resistance, there is a problem in that the resistance value causes a voltage drop, a delay, and a narrow band.

  It is an object of the present invention to provide a power supply circuit that can prevent saturation of the power supply circuit without affecting the path between the amplifier and the transistor.

  According to a first aspect of the present invention, there is provided a power supply circuit that controls a power supply voltage to apply an output voltage to an output load, a saturation prevention circuit that detects that the power supply voltage is equal to or lower than a reference voltage, and the control A multiplication circuit that multiplies a control voltage for controlling the unit and an output of the saturation prevention circuit and inputs the multiplication result to the control unit, and prevents saturation of the control unit when a power supply voltage becomes a reference voltage or lower. The saturation prevention circuit is configured to control the output voltage of the multiplication circuit.

  According to a second aspect of the present invention, there is provided the power supply circuit according to the first aspect, wherein the control unit that changes the output voltage in proportion to the control voltage supplied via the multiplication circuit is provided between the power supply output and the output load. A transistor having an output circuit connected in series, a feedback circuit that attenuates and outputs the output of the transistor, an output voltage of the multiplier circuit is applied to one input terminal, and an output of the feedback circuit is applied to the other input terminal It is characterized by comprising an operational amplifier having a voltage applied and an output terminal connected to the control input of the transistor.

  A power supply circuit according to a third aspect of the present invention is the power supply circuit according to the first aspect, wherein the saturation prevention circuit includes a comparison circuit that compares a power supply voltage with a reference voltage from the outside, a power supply voltage according to an output of the comparison circuit, A division circuit for dividing an external reference voltage is provided, and the output of the division circuit is used as an output signal to the multiplication circuit.

  A power supply circuit according to a fourth aspect of the present invention is the power supply circuit according to the first aspect, wherein the saturation prevention circuit is multiplied by a comparison circuit that compares a power supply voltage with an external reference voltage and a control voltage that controls the control unit. A multiplication circuit, a comparison circuit for comparing the output voltage of the multiplication circuit and the output voltage of the control unit, and a division for dividing a power supply voltage and an external reference voltage in accordance with the output of the comparison circuit and the output of the comparison circuit And an output of the divider circuit as an output signal to the multiplier circuit.

  The power supply circuit of the present invention provides a voltage that saturates when the control unit falls below this voltage as the reference voltage, and detects the voltage difference between the power supply voltage and the reference voltage with the saturation prevention circuit when the power supply voltage falls below the reference voltage. Since the multiplication circuit disposed on the input side of the control unit is controlled, it is possible to determine and control whether the power supply circuit is saturated without affecting the control unit 1.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(Embodiment 1)
1 and 2 show (Embodiment 1) of the present invention.

  The power supply circuit of FIG. 1 that controls the power supply voltage according to the control voltage and supplies power to the output load 20 includes the control unit 1 that controls the power supply voltage + Vcc and applies the output voltage Vout to the output load 20, and A saturation prevention circuit 5 for detecting that the reference voltage Vs1 has been reduced or less; a multiplication circuit 6 for multiplying the control voltage Pc for controlling the control unit 1 by the output of the saturation prevention circuit 5 and inputting the result to the control unit 1; The saturation prevention circuit 5 controls the output voltage of the multiplication circuit 6 so as to prevent the control unit 1 from being saturated when the power supply voltage + Vcc becomes equal to or lower than the reference voltage Vs1.

  Specifically, the saturation prevention circuit 5 compares the power supply voltage + Vcc with the reference voltage Vs1, and when detecting that the power supply voltage + Vcc has dropped to the reference voltage Vs1, the multiplication circuit 6 applies a voltage corresponding to the voltage drop. Output to. The multiplication circuit 6 multiplies the control voltage Pc and the output voltage from the saturation prevention circuit 5 and outputs the multiplied voltage to the control unit 1.

  As shown in FIG. 2, the control unit 1 includes an operational amplifier 2, a transistor 3, and a feedback circuit 4 including a series circuit of resistors R <b> 1 and R <b> 2, and is supplied via a multiplier circuit 6. The output voltage Vout supplied to the output load 20 can be controlled in proportion to the control voltage Pc. The slope of the output voltage with respect to the power supply voltage + Vcc (input voltage) can be changed by the amplification factor of the feedback circuit 4. The multiplier circuit 6 is realized by an operational amplifier or the like.

  In FIG. 2, the saturation prevention circuit 5 includes a comparison circuit 7 and a division circuit 8. The comparison circuit 7 compares the power supply voltage + Vcc with the reference voltage. The reference voltage arbitrarily gives a voltage from the outside that saturates when the transistor 3 in the control unit 1 becomes equal to or lower than the power supply voltage.

  The comparison circuit 7 gives the H level voltage to the division circuit 8 when saturation is detected in the comparison result, and gives the L level voltage to the division circuit 8 when saturation is not detected. The comparison circuit 7 is realized by an operational amplifier or the like as shown in FIG.

  The division circuit 8 outputs a value corresponding to the saturation detection result from the comparison circuit 7 to the multiplication circuit 6. Specifically, the division circuit 8 when saturation is detected outputs a value obtained by dividing the power supply voltage + Vcc by the reference voltage to the multiplication circuit 6. This value is 1 volt or less because the power supply voltage is below the reference voltage. When the saturation is not detected, the division circuit 8 outputs 1 volt to the multiplication circuit 6. The multiplication circuit 6 multiplies the output voltage from the division circuit 8 and outputs the multiplied voltage to the control unit 1.

  In a state where saturation of the control unit 1 is not detected, the comparison circuit 7 outputs the L level voltage to the division circuit 8 because the power supply voltage is higher than the reference voltage in the comparison circuit 7. In the division circuit 8, since the L level voltage is input from the comparison circuit 7, a voltage of 1 volt is output to the multiplication circuit 6. In the multiplier circuit 6, since a voltage of 1 volt is input from the divider circuit 8, the same voltage as the control voltage from the outside is output to the control unit 1.

  In a state where saturation of the control unit 1 is detected, the comparison circuit 7 outputs the H level voltage to the division circuit 8 because the power supply voltage + Vcc is lower than the reference voltage in the comparison circuit 7. In the division circuit 8, since the H level voltage is input from the comparison circuit 7, the power supply voltage + Vcc is divided by the reference voltage Vs 1, and the divided voltage is output to the multiplication circuit 6. The divided voltage is 1 volt or less because the power supply voltage + Vcc is lower than the reference voltage. The multiplication circuit 6 multiplies the control voltage by the output voltage of the division circuit 8 and outputs the multiplied voltage to the control unit 1. Accordingly, since the control voltage is multiplied by the output voltage of 1 volt or less of the dividing circuit 8, saturation can be prevented by reducing the voltage input to the control unit 1.

(Embodiment 2)
FIG. 3 shows (Embodiment 2) of the present invention.
In FIG. 2, the saturation prevention circuit 5 is composed of the comparison circuit 7 and the division circuit 8. However, the saturation prevention circuit 5 of the power supply circuit shown in FIG. 3 includes a multiplication circuit 9, a feedback circuit 10, and a comparison circuit 11. ing. The division circuit 8 is not controlled only by the output of the comparison circuit 7 but is controlled based on the output of the comparison circuit 7 and the output of the comparison circuit 11. Others are the same as (Embodiment 1) shown in FIG. 1 and will be described with the same reference numerals.

The saturation prevention circuit 5 of FIG. 3 will be described in detail.
The comparison circuit 7 realized by an operational amplifier or the like compares the power supply voltage + Vcc with the reference voltage Vs1. The reference voltage Vs1 arbitrarily gives from the outside a voltage that saturates when the transistor 3 in the control unit 1 falls below this power supply voltage. The comparison circuit 7 applies the H level voltage to the division circuit 8 when saturation is detected in the comparison result, and applies the L level voltage to the division circuit 8 when saturation is not detected. The control voltage Pc is applied to one input terminal (+) of the multiplication circuit 9, and the same amplification as that of the feedback circuit 4 is provided between the output of the multiplication circuit 9 and the other input terminal (−) of the multiplication circuit 9. A rate feedback circuit 10 is connected. The multiplication circuit 9 multiplies the control voltage Pc by the same amplification factor as that of the control unit 1 and outputs the multiplication result to the comparison circuit 11 realized by an operational amplifier or the like.

  The output voltage of the multiplication circuit 9 is applied to one input terminal (+) of the comparison circuit 11, and the output voltage of the control unit 1 is input to the other input terminal (−) of the comparison circuit 11 for comparison. When the control unit 1 is not saturated, the output voltage of the control unit 1 and the output voltage of the multiplication circuit 9 are the same, and the comparison circuit 11 outputs the L level voltage to the division circuit 8. When the control unit 1 is saturated, the output voltage of the control unit 1 becomes smaller than the output voltage of the multiplication circuit 9, and the comparison circuit 11 outputs the H level voltage to the division circuit 8.

  3 outputs a value obtained by dividing the power supply voltage by the reference voltage to the multiplication circuit 6 only when the output voltage of the comparison circuit 7 is at the H level and the output voltage from the comparison circuit 11 is at the H level. . Therefore, the saturation prevention circuit 5 operates according to the power supply voltage and the control voltage, so that a more accurate saturation prevention function can be provided.

(Embodiment 3)
4 and 5 show (Embodiment 3) of the present invention.
4 shows an amplifying apparatus with a saturation prevention function in which the power supply circuit of the amplifier 12 is connected as the output load 20 shown in FIG. 2 and power is supplied to the amplifier 12. FIG. 5 shows the time when the amplifier 12 operates in a time division manner. This is a standard for output.

  When the input signal level of the amplifier 12 is constant, the output level of the amplifier 12 changes in proportion to the control voltage input to the control unit 1 via the multiplication circuit 6. Further, by inputting a pulse voltage as the control voltage Pc input to the control unit 1 via the multiplication circuit 6, the amplifier 12 operates in a time-sharing manner, and there is a time-to-output standard as shown in FIG. In this case, the time-to-output waveform when the control unit 1 is not saturated satisfies the standard as shown in the non-saturated waveform in FIG.

  When the control unit 1 does not have a saturation prevention function and is saturated, the output rises in the time-to-output characteristics of the amplifier 12 as in the case of non-saturation. However, since the control unit 1 is saturated, the maximum value of the output is lower than when it is not saturated. Even if the control voltage is started to decrease from the maximum output value, the control unit 1 is saturated. Therefore, when the control voltage starts decreasing, the output voltage of the control unit 1 decreases in proportion to the control voltage. In addition, since the output of the amplifier 12 does not decrease, as shown by a dotted line in FIG.

Therefore, by having the function of detecting saturation in the control unit 1, it is possible to prevent the amplifier 12 from deviating from the time-to-output standard.
2 to 4, a MOS transistor is used as the transistor 3, but a bipolar transistor may be used.

  Further, in (Embodiment 3), the case of FIG. 2 has been described as an example, but the same can be applied to the case of FIG.

  The present invention is useful as a power supply circuit that can prevent saturation of the power supply circuit without affecting the path between the amplifier and the transistor.

Block diagram of a power supply circuit in (Embodiment 1) of the present invention Circuit diagram of the power supply circuit of the same embodiment Circuit diagram of power supply circuit according to (Embodiment 2) of the present invention The circuit diagram of the amplifier in (Embodiment 3) of the present invention and the standard diagram of time versus output when this amplifier operates in time division Standard diagram of time vs. output when the amplification device of the same embodiment operates in a time-sharing manner Circuit diagram of conventional power supply circuit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control part 2 Operational amplifier 3 Transistor 4 Feedback circuit 5 Saturation prevention circuit 6 Multiplication circuit 7 Comparison circuit 8 Division circuit 9 Multiplication circuit 10 Feedback circuit 11 Comparison circuit 12 Amplifier 20 Output load Pc Control voltage Vs1 Reference voltage Vout Output voltage + Vcc Power supply voltage

Claims (5)

A control unit for controlling the power supply voltage and applying the output voltage to the output load;
A saturation prevention circuit that detects that the power supply voltage has fallen below the reference voltage;
A multiplication circuit that multiplies a control voltage for controlling the control unit and an output of the saturation prevention circuit and inputs the multiplication result to the control unit, and prevents saturation of the control unit when a power supply voltage becomes a reference voltage or lower. A power supply circuit configured such that the saturation prevention circuit controls the output voltage of the multiplication circuit. A control unit that changes an output voltage in proportion to the control voltage supplied via the multiplication circuit;
A transistor in which an output circuit is connected in series between a power supply output and an output load;
A feedback circuit that attenuates and outputs the output of the transistor;
2. The operational amplifier according to claim 1, wherein an output voltage of the multiplication circuit is applied to one input terminal, an output voltage of the feedback circuit is applied to the other input terminal, and an output terminal is connected to a control input of the transistor. Power supply circuit. The saturation prevention circuit;
A comparison circuit that compares the power supply voltage with an external reference voltage;
The power supply circuit according to claim 1, further comprising: a division circuit that divides a power supply voltage and an external reference voltage in accordance with an output of the comparison circuit, and using the output of the division circuit as an output signal to the multiplication circuit. The saturation prevention circuit;
A comparison circuit that compares the power supply voltage with an external reference voltage;
A multiplication circuit for multiplying a control voltage for controlling the control unit;
A comparison circuit that compares the output voltage of the multiplication circuit with the output voltage of the control unit; and a division circuit that divides a power supply voltage and an external reference voltage in accordance with the output of the comparison circuit and the output of the comparison circuit. 2. The power supply circuit according to claim 1, wherein an output of the divider circuit is an output signal to the multiplier circuit. An amplifying apparatus with a saturation prevention function, wherein power is supplied from a power supply circuit according to any one of claims 1 to 4 to a power supply line of an amplifier that amplifies and outputs an input signal.

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