JP2008022510A - Power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power amplifier which achieves high sound quality or high power efficiency by supplying electric power according to a desired utilization status of a user and an output signal or an input signal. <P>SOLUTION: This power amplifier includes a control means which controls a voltage rise and the fall operation of the voltage rise and a fall means based on a control mode, so that electric power suited for the utilization status of the user is supplied to an amplifying means. Then, when a result of comparison between the voltage supplied to the amplifying means and the input or output signal of the amplifying means is inputted from a comparing means, the control means controls the voltage rise and the fall means based on the result of the comparison and the control mode which is selected by a mode selecting means. Thus, the power amplifier can supply electric power according to the desired utilization status of the user with high sound quality or high power efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power amplifier, and more particularly to a power amplifier capable of providing high sound quality or high power efficiency by supplying power according to a usage situation desired by a user in an acoustic amplifier, for example.

  In conventional acoustic amplifiers, it is necessary to supply a high power supply voltage according to the maximum output of the output signal. In this case, when the dynamic range of the output signal is small, such as when listening to music at night, the power supply voltage and output The difference from the voltage is a loss, leading to a reduction in power efficiency. Therefore, a circuit configuration for adjusting the supply voltage so as to follow the input signal has been devised. There are roughly two types, one using a step-down switching power supply that supplies a power supply voltage corresponding to the maximum output, and the other supplying a voltage lower than the power supply voltage corresponding to the maximum output. A step-up switching power supply device is used.

FIG. 5a is a circuit diagram of a step-down switching power supply device connected to the amplifying means. The step-down switching power supply device controls the switching of the transistor Q5a by a control circuit, converts the input voltage Vi into a high frequency voltage, and smoothes it by the choke coil L5a and the capacitor C5a, thereby stepping down the input voltage Vi. Then, the supply voltage Vo to the amplification means is output. The supply voltage Vo by the step-down switching power supply device is determined by the duty A1 at which the transistor Q5a is turned on / off, as shown in the following equation (1). In Expression 1, t _on is a period in which the transistor Q5a is turned on, and t _off is a period in which the transistor Q5a is turned off.

  In the step-down switching power supply, the transistor Q5a performs a switching operation by the control circuit when the output of the amplifying unit is a small output, and the power supplied to the amplifying unit is lowered to improve the power efficiency. However, the noise generated from the transistor Q5a causes the performance and sound quality to deteriorate. In particular, when the output of the amplifying means is a small output, the noise ratio is relatively increased, and the performance and sound quality are significantly deteriorated. Therefore, when the step-down switching power supply device is used, it is suitable for the case where the user desires high power efficiency (power saving reproduction, etc.), but the user desires low output and high sound quality (such as night music appreciation). Not suitable for).

FIG. 5b is a circuit diagram of the step-up switching power supply device connected to the amplification means. In the step-up switching power supply, energy is stored in the coil L5b while the transistor Q5b is on, and the capacitor C5b is charged by the back electromotive force generated from the moment the transistor Q5b is turned off. The transistor Q5b is on / off controlled by a control circuit. The greater the energy stored in the coil L5b, the greater the energy stored in the capacitor C5b, and the supply voltage Vo to the amplification means increases. The supply voltage Vo by the step-up switching power supply device is determined by the duty A2 at which the transistor Q5b is turned on / off, as shown in the following equation (1). In Expression 1, t _on is a period in which the transistor Q5b is turned on, and t _off is a period in which the transistor Q5b is turned off.

  In the step-up switching power supply device, the transistor Q5b operates when the output of the amplifying means is large, and the power efficiency is improved by increasing the voltage supplied to the amplifying means. Since the switching operation is performed at the time of high output, the above-described problem due to noise is reduced. Therefore, when a step-up switching power supply is used, it is suitable when the user desires high output, high performance and high sound quality (such as general music appreciation), but the user desires high power efficiency. (For movie viewing with a wide dynamic range, etc.), it is necessary to perform a switching operation from a small output, so the noise ratio due to the switching operation is increased, and high performance and high sound quality cannot be maintained.

  As described above, the above-described conventional technique has a problem in that it cannot perform power supply according to a situation desired by the user.

Japanese Utility Model Publication No. 6-41385 Japanese Utility Model Publication No. 5-9186

  The present invention has been made in order to solve the above-described problems of the prior art, and its purpose is to supply power according to the usage situation desired by the user and the output signal or input signal. An object of the present invention is to provide a power amplifier that realizes high sound quality or high power efficiency.

  A power amplifier according to a preferred embodiment of the present invention includes an amplifying unit that amplifies an input signal and outputs an output signal, a first power source unit that supplies a first voltage to the positive power source side of the amplifying unit, and a second power unit. Second power supply means for supplying the first voltage to the negative power supply side of the amplifying means, first step-up / step-down means for boosting or stepping down the first voltage and supplying the first voltage to the amplifying means, and the second voltage A first step-up / step-down unit that boosts or lowers the voltage and supplies the first voltage to the amplifying unit, compares the first voltage with the input signal or the output signal, and outputs a first comparison result. A comparison unit; a second comparison unit that compares the second voltage with the input signal or the output signal and outputs a second comparison result; and has a plurality of control modes; The first step-up / step-down means is controlled based on the first comparison result, and the control mode and the second ratio are controlled. Based on the results and a control means for controlling the buck-boost means the second, and a mode switching means for switching the control mode.

  In the power amplifier of the present invention configured as described above, the control unit controls the step-up / step-down operation of the step-up / step-down unit based on the control mode, so that the power suitable for the use situation of the user is supplied to the amplifier unit . The control means further receives a comparison result between the voltage supplied to the amplification means and the input signal or output signal of the amplification means from the comparison means, and controls the step-up / step-down means based on the comparison result and the control mode. . The control mode is switched by mode switching means. As a result, it is possible to provide a power amplifier that performs high power quality or high power efficiency by supplying power according to the usage situation desired by the user.

  In a further preferred embodiment, the first comparing means has a first level when the voltage difference between the first voltage and the output signal or the input signal is greater than or equal to a first predetermined voltage difference. A second level signal is output when a voltage difference between the first voltage and the output signal or the input signal is less than a second predetermined voltage difference; When the voltage difference between the second voltage and the output signal or the input signal is greater than or equal to a predetermined voltage difference, the comparing means outputs a third level signal, and the second voltage, When the voltage difference from the output signal or the input signal is less than a predetermined voltage difference, a fourth level signal is output.

  By the above comparison means, it is possible to easily detect the excess or deficiency of power supplied from the power supply means to the amplification means without requiring a complicated circuit.

  In a further preferred embodiment, the control means controls the step-down operation of the first step-up / step-down means based on the control mode and the first comparison result, and the control mode and the second comparison result. Step-down control means for controlling the step-down operation of the second step-up / step-down means based on the control method; controlling the step-up operation of the first step-up / step-down means based on the control mode and the first comparison result; Boosting control means for controlling a boosting operation with the second step-up / step-down means based on the control mode and the second comparison result.

  The step-down control unit controls the step-down operation of the step-up / step-down unit based on the control mode and the comparison result, and the step-up unit controls the step-up operation of the step-up / step-down unit based on the control mode and the comparison result. As a result, the operation of the step-up / step-down means can be controlled efficiently.

  In a further preferred embodiment, in the first control mode, the step-down control means and the step-up control means are configured to provide the first step-up / step-down pressure regardless of the first comparison result and the second comparison result. The step-up / step-down operation is not performed on the means and the second step-up / step-down means.

  When the control unit is in the first control mode, no noise is generated because the step-up / step-down unit does not operate regardless of the comparison result. Therefore, high sound quality can be realized in the case of a small output such as night music appreciation.

  In a further preferred embodiment, in the second control mode, when the first comparison result is a first level, the step-down control unit causes the first step-up / step-down unit to perform a step-down operation, and When the comparison result of 2 is the third level, the second step-up / step-down means is caused to perform a step-down operation; when the first comparison result is the second level, the step-up control means When the second comparison result is the fourth level, the second step-up / step-down means is not operated.

  When the control means is in the second control mode, when the output signal is a small output or the input signal is a small input, the power loss can be reduced by reducing the supply voltage. Therefore, high power efficiency at the time of small output, that is, power saving regeneration can be realized.

  In a further preferred embodiment, in the third control mode, when the first comparison result is the first level, the step-down control unit does not cause the first step-up / step-down unit to perform a step-up / step-down operation, When the second comparison result is the third level, the second step-up / step-down means is not caused to perform the step-up / step-down operation; when the first comparison result is the second level, the boost control means When the second comparison result is the fourth level, the first step-up / step-down means is caused to perform a step-up operation.

  When the control means is in the third control mode, the switching operation is performed only when the output signal is a large output or the input signal is a large input, thereby reducing the influence of noise generated from the step-up / step-down means. Accordingly, it is possible to achieve high output and high sound quality when listening to general music.

  In a further preferred embodiment, in the fourth control mode, when the first comparison result is a first level, the step-down control means causes the first step-up / step-down means to perform a step-down operation, and When the comparison result of 2 is the third level, the second step-up / step-down means is caused to perform a step-down operation; when the first comparison result is the second level, the step-up control means When the second comparison result is the fourth level, the second step-up / step-down means is caused to perform a boost operation.

  When the control means is in the fourth control mode, when the output signal is a small output or the input signal is a small input, the supply voltage is lowered, and when the output signal is a large output or the input signal is a small output The voltage can be boosted. Therefore, when watching a movie with a wide dynamic range, it is possible to achieve high output and high power efficiency.

  In a more preferred embodiment, the step-up / step-down means is a step-up / step-down chopper type DC-DC converter.

  By using the step-up / step-down chopper type DC-DC converter, a complicated circuit configuration is not required, and the power supplied from the power supply means to the amplification means can be boosted or lowered.

  A power amplifier according to another preferred embodiment of the present invention has a first power supply side grounded, amplifying means for amplifying an input signal and outputting an output signal, and supplying a voltage to a second power supply side of the amplifying means. A power supply means, a step-up / step-down means for stepping up or down the voltage and supplying the voltage to the amplifying means, a comparison means for comparing the voltage with the input signal or the output signal, and outputting a comparison result; A mode switching unit that has a control mode, controls the step-up / step-down unit based on the control mode and the comparison result, and switches the control mode;

  The power amplifier of the present invention configured as described above controls the step-up / step-down means based on the control mode and the comparison result even in a single-end push-pull type amplification means and supplies a suitable voltage to the amplification means. can do. As a result, it is possible to provide a power amplifier that performs high power quality or high power efficiency by supplying power according to the usage situation desired by the user.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the power amplifier which implement | achieves high sound quality or high power efficiency by supplying the electric power according to the utilization condition which a user desires, and an output signal or an input signal.

  Hereinafter, although the power amplifier in the audio equipment by preferable embodiment of this invention is demonstrated, this invention is not limited to these embodiment. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is incorporated.

  First, a schematic configuration of the power amplifier 10 will be described with reference to FIG. 1 and FIG. FIG. 1 is a block diagram illustrating a schematic configuration of the power amplifier 10. FIG. 2 is a circuit diagram of the power amplifier 10. In FIG. 2, the output end 5 is not shown. The power amplifier 10 includes amplification means 1, comparison means 211 and 212, control means 22, step-up / step-down means 231 and 232, mode switching means 24, power supply means E, input end 4, and output end 5.

  The amplifying unit 1 amplifies an audio signal input from a tuner, a disc player, or the like based on power supplied from a power supply unit 2 described later, and drives the speaker with high power. The power supply unit 2 supplies power to the electronic elements in the power amplifier 10 such as the amplification unit 1.

  The power source means E includes a positive power source E1 and a negative power source E2, each including a power transformer, a rectifying and smoothing circuit, etc., transforming power supplied from a commercial power source, and rectifying and smoothing to output a DC voltage. . The plus side power supply E1 supplies a voltage to the amplification means 1 as a plus side supply voltage Vcc + via the step-up / step-down means 231, and the minus side power supply E2 serves as a minus side supply voltage Vcc− via the step-up / down means 232. To do.

  The step-up / step-down means 231 steps up or down the voltage supplied from the plus side power supply E1, and supplies the boosted or stepped down voltage to the amplifying means 1 as the plus side supply voltage Vcc +. Similarly, the step-up / step-down means 232 boosts or steps down the voltage supplied from the minus side power supply E2, and supplies the boosted or stepped down voltage to the amplifying means 1 as the minus side supply voltage Vcc−. The voltage boosting / lowering means 231 and 232 supply the voltage supplied from the plus-side power sources E1 and E2 to the amplifying means 1 as the plus-side supply voltage Vcc + and the minus-side supply voltage Vcc− when neither boosting nor lowering is performed. The step-up / step-down means 231 and 232 in this embodiment are step-up / step-down chopper type DC-DC converters.

  The step-up / step-down means 231 includes switches (for example, bipolar transistors) S1, S2, a coil L1, a capacitor C1, and diodes D1, D3. As shown in FIG. 2, the switch S1, the coil L1, and the diode D3 are connected in series to the positive power source E1. The switch S1 has one end connected to the positive power source E1 and the other end connected to one end of the coil L1. The other end of the coil L1 is connected to the anode side of the diode D3. The cathode side of the diode D3 is connected to the positive power supply side of the amplification means 1. The diode D1 has a cathode side connected between the switch S1 and the coil L1, and is connected in parallel to the switch S1. The anode side of the diode D1 is grounded. One end of the switch S2 is connected between the coil L1 and the diode D3, and the other end is grounded. One end of the capacitor C1 is connected between the cathode side of the diode D3 and the positive power supply side of the amplifier 1, and the other end is grounded.

When the step-up / step-down means 231 performs a step-down operation, the switch S1 is on / off controlled by the control means 22 described later with a duty B1 corresponding to the voltage level of the output signal, and the DC voltage VE1 supplied from the plus-side power supply E1 is supplied. Convert to high frequency voltage. Then, the smoothed voltage is smoothed by the coil L1 and the capacitor C1, so that the stepped down voltage is supplied as the positive supply voltage Vcc +. At this time, the positive supply voltage Vcc + is determined by the duty B1 at which the switch S1 is turned on and off as shown in Equation 3. In Equation 3, t _on is a period during which the switch S1 is on, and t _off is a period during which the switch S1 is off.

Further, when the step-up / step-down means 231 performs a boosting operation, energy is stored in the coil L1 during the period when the switch S1 is always on and the switch S2 is on, and the reverse generated in the coil L1 from the moment the switch S2 is turned off. The capacitor C1 is charged by the electromotive force. The greater the energy stored in the coil L1, the greater the energy stored in the capacitor C1, and the positive supply voltage Vcc + supplied to the amplification means 1 increases. The switch S2 is ON / OFF controlled by the control means 22 with a duty B2 corresponding to the voltage level of the output signal. At this time, the positive supply voltage Vcc + is determined by the duty B2 at which the switch S2 is turned on and off as shown in Equation 4. In Expression 4, t _on is a period during which the switch S2 is on, and t _off is a period during which the switch S2 is off.

  The step-up / step-down means 232 performs the step-up / step-down operation equivalent to the step-up / step-down means 231 connected to the positive power supply side of the amplification means 1 on the negative voltage side. The step-up / step-down means 232 includes switches S3 and S4, a coil L2, a capacitor C2, and diodes D2 and D4. A switch S3, a coil L2, and a diode D4 are connected in series to the negative power source E2. The switch S3 has one end connected to the negative power source E2 and the other end connected to one end of the coil L2. The other end of the coil L2 is connected to the cathode side of the diode D4. The anode side of the diode D4 is connected to the negative power supply side Vcc− of the amplification means 1. The diode D2 has an anode connected between the switch S3 and the coil L2, and is connected in parallel to the switch S3. The cathode side of the diode D2 is grounded. One end of the switch S4 is connected between the coil L2 and the diode D4, and the other end is grounded. One end of the capacitor C2 is connected between the anode side of the diode D4 and the negative power supply side of the amplifier 1, and the other end is grounded. In the step-up / step-down means 232, an operation for decreasing the absolute value of the voltage VE2 is a step-down operation, and an operation for increasing the absolute value of the voltage VE2 is a step-up operation.

  The comparison unit 211 compares the voltage of the plus-side power supply E1 with the output signal of the amplification unit, and outputs the comparison result to the control unit 22 described later. Specifically, when sufficient power is supplied to the amplification unit 1 with respect to the output signal output from the amplification unit 1, the comparison unit 211 outputs a high-level signal. On the other hand, when sufficient power is not supplied to the amplifying unit 1 with respect to the output signal output from the amplifying unit 1, the comparing unit 211 outputs a low level signal. Hereinafter, the high level and the low level are defined as a high level when the absolute value of the voltage from the ground potential is high and a low level when the absolute value is small. More specifically, for example, when the voltage difference between the voltage VE1 of the plus-side power supply E1 and the output voltage V1 of the amplification means 1 is equal to or greater than a predetermined voltage difference Va, a high level signal is output. Further, when the voltage difference between the voltage VE1 of the plus-side power supply E1 and the output voltage V1 of the amplification means 1 is less than a predetermined voltage difference Va, a low level signal is output.

  Comparison means 211 includes a transistor Q1 and a Zener diode D5. As shown in FIG. 2, the Zener diode D5 has an anode connected to the output terminal of the amplifying unit 1 and a cathode connected to the base of the transistor Q1. The transistor Q5 is a PNP type, and the emitter is connected to the positive side of the positive power source E1. The emitter and base of the transistor Q1 are connected. The collector of the transistor Q1 is grounded via a resistor R5. The comparison result Vp + is output from a point A between the collector of the transistor Q1 and the resistor R5.

  In the transistor Q1, when the voltage difference between the voltage VE1 of the plus-side power supply E1 and the output voltage V1 of the amplifying unit 1 is equal to or greater than the sum (predetermined voltage Va) of the Zener voltage VD5 and the base-emitter voltage Vbe, Turns on. As a result, a high level signal is output from the collector side (point A) to the control means 22 as a comparison result Vp + based on the voltage VE1 of the plus-side power supply E1. In the transistor Q1, the voltage difference between the voltage VE1 of the plus-side power supply E1 and the output voltage V1 of the amplification means 1 is less than the sum (predetermined voltage Va) of the Zener voltage VD5 and the base-emitter voltage. Is in the off state. As a result, since the collector of the transistor Q1 is grounded, a low level signal is output from the point A to the control means 22 as the comparison result Vp +.

  Similarly, the comparison unit 212 compares the voltage VE2 of the negative power source E2 with the output signal of the amplification unit, and outputs the comparison result to the control unit 22. Specifically, when the voltage difference between the voltage VE2 of the minus-side power supply E2 and the output voltage V1 of the amplifying unit 1 is equal to or greater than a predetermined voltage difference Vb, a high level signal is output. Further, when the voltage difference between the voltage VE2 of the minus side power supply E2 and the output voltage V1 of the amplification means 1 is less than the predetermined voltage difference Vb, a low level signal is output.

  Comparing means 212 includes a transistor Q2 and a Zener diode D6. As shown in FIG. 2, the Zener diode D6 is connected to the output terminal of the amplifying unit 1 on the cathode side and connected to the base of the transistor Q2 on the anode side. The transistor Q2 is an NPN type, and the emitter is connected to the negative electrode side of the negative power source E2. The emitter and base of the transistor Q2 are connected. The collector of the transistor Q2 is grounded via a resistor R6. The comparison result Vp− is output from a point B between the collector of the transistor Q2 and the resistor R6.

  The transistor Q2 is turned on when the voltage difference between the voltage VE2 of the plus-side power supply E1 and the output voltage V1 of the amplification means 1 is equal to or greater than the sum of the Zener voltage VD6 and the base-emitter voltage Vbe1 (predetermined voltage Vb). It becomes a state. As a result, a high level signal is output from the collector (point B) to the control means 22 as a detection result Vp− based on the voltage VE1 of the plus-side power supply E1. The transistor Q2 has a voltage difference between the voltage VE2 of the negative power source E2 and the output voltage V1 of the amplifying unit 1 less than the sum of the Zener voltage VD6 and the base-emitter voltage (predetermined voltage Vb). Off state. As a result, since the collector of the transistor Q2 is grounded, a low level signal is output from the point B to the control means 22 as the comparison result Vp−.

  The mode switching unit 24 switches a plurality of control modes of the control unit 22 described later. The mode switching unit 24 may be selected as appropriate from, for example, a rotary switch, an insertion / removal switch, a remote controller, or the like.

  The control means 22 has a plurality of control modes. Specifically, the control means 22 has four control modes. Based on these control modes and the comparison results Vp + and Vp− input from the comparison means 211 and 212, the step-up / step-down means 231 and 232 are controlled. The control means 22 in the first control mode is capable of realizing high sound quality even with a small output when listening to music at night or the like. Therefore, the control means 22 in the third control mode can control the fourth control so that a large output and high sound quality can be realized in general music appreciation. In the mode, the control means 22 controls the step-up / step-down means 231 and 232 based on the comparison results 211 and 212 so that high output and high power efficiency can be realized when watching a movie with a wide dynamic range. To do.

  The control unit 22 includes a step-down control unit 221 and a step-up control unit 222. The step-down control means 221 controls the step-down operation of the step-up / step-down means 231, 232, and the step-up control means 222 controls the step-up operation of the step-up / step-down means 231, 232. The control means 22 is, for example, a microcomputer.

  Hereinafter, the operations of the control unit 22 (the step-down control unit 221 and the step-up control unit 222) and the step-up / step-down units 231 and 232 in the four control modes will be described in detail with reference to FIG. FIG. 3 is a diagram illustrating four control modes. In FIG. 3, in each control mode, the use scene, the comparison results Vp + and Vp− output from the comparison means 211 and 212, the on / off operation of the switches S1, S2, S3, and S4, the power supply voltage VE1, The waveforms of VE2 and supply voltages Vcc + and Vcc− to the amplification means 1 and the output V1 are shown. The comparison result Vp + on the positive voltage side is shown above the waveform (the comparison result Vp− on the negative voltage side is not shown). In addition, when the waveforms of the power supply voltages VE1 and VE2 and the waveforms of the supply voltages Vcc + and Vcc− supplied to the amplifying means 1 coincide, the supply voltages Vcc + and Vcc− are preferentially drawn.

  When the first control mode is selected by the mode switching unit 24, the step-down control unit 221 turns on the switch S1 regardless of the level of the comparison result Vp + output from the comparison unit 211, and the step-up control unit 222 S2 is turned off. That is, the voltage VE1 supplied from the plus-side power supply E1 is supplied to the amplifying unit 1 as the plus-side supply voltage Vcc + without being stepped down and boosted. Similarly, the step-down control unit 221 turns on the switch S3 and the step-up control unit 222 turns off the switch S4 regardless of the level of the comparison result Vp− output from the comparison unit 212. That is, the voltage VE1 supplied from the minus side power supply E2 is supplied to the amplification means as the minus side supply voltage Vcc− without being stepped down and boosted. Since the switches S1, S2, S3, and S4 are not turned on / off, no noise is generated. Therefore, when the user selects the first control mode, the power amplifier of the present invention can achieve high sound quality in the case of a small output such as night music appreciation.

  When the second control mode is selected by the mode switching unit 24, when the comparison result Vp + output from the comparison unit 211 is at a high level, the boost control unit 222 turns off the switch S2, and the step-down control unit 221 S1 is turned on / off at the duty B1, and the step-up / step-down means 231 is stepped down. That is, the voltage VE1 supplied from the plus side power supply E1 is stepped down and supplied to the amplifying means as the plus side supply voltage Vcc +. When the comparison result Vp + output from the comparison unit 211 is at a low level, the step-down control unit 221 turns on the switch S1, the step-up control unit 222 turns off the switch S2, and the step-up / step-down unit 231 performs both step-down operation and step-up operation. Do not let it. That is, the voltage VE1 supplied from the positive power source E1 is supplied to the amplifying means as the positive supply voltage Vcc +.

  Similarly, when the comparison result Vp− output from the comparison unit 212 is at a high level, the step-up control unit 222 turns off the switch S4, and the step-down control unit 221 turns on / off the switch S3 with the duty B1 to increase / decrease the voltage boosting unit 232. To step down. That is, the voltage VE2 supplied from the negative side power source E2 is stepped down and supplied to the amplifying means as the negative side supply voltage Vcc−. When the comparison result Vp− output from the comparison unit 212 is at a low level, the step-down control unit 221 turns on the switch S3, the step-up control unit 222 turns off the switch S4, and the step-up / step-down unit 232 performs step-down operation. Also, the boost operation is not allowed. That is, the voltage VE2 supplied from the minus side power supply E2 is supplied to the amplifying means as the minus side supply voltage Vcc−. Therefore, when the output signal is a small output, the supply voltage can be lowered to reduce the power loss. Therefore, when the user desires the power saving regeneration, the second control mode is selected when the user desires the power saving regeneration. The power amplifier of the invention can realize small output and high power efficiency.

  When the third control mode is selected by the mode switching unit 24, when the comparison result Vp + output from the comparison unit 211 is high, the step-down control unit 221 turns on the switch S1, and the step-up control unit 222 S2 is turned off to prevent the step-up / step-down means 231 from performing a step-down operation or a step-up operation. As a result, the voltage VE1 supplied from the plus-side power supply E1 is supplied to the amplifying means as the plus-side supply voltage Vcc +. When the comparison result Vp + output from the comparison unit 211 is at a low level, the step-down control unit 221 turns on the switch S1, the step-up control unit 222 turns on / off the switch S2 with the duty B2, and Boost operation is performed. That is, the voltage VE1 supplied from the plus side power supply E1 is boosted and supplied to the amplifying means as the plus side supply voltage Vcc +.

  Similarly, when the comparison result Vp− output from the comparison unit 212 is at a high level, the step-down control unit 221 turns on the switch S3, the step-up control unit 222 turns off the switch S4, and steps down the voltage to the step-up / step-down unit 232. Do not perform any operation or step-up operation. That is, the voltage VE2 supplied from the minus side power supply E2 is supplied to the amplifying means as the minus side supply voltage Vcc−. When the comparison result Vp− output from the comparison unit 212 is at a low level, the step-down control unit 221 turns on the switch S3, the step-up control unit 222 turns on / off the switch S4 with the duty B2, and the step-up / step-down unit 232 To boost operation. That is, the voltage VE2 supplied from the minus side power supply E2 is boosted and supplied to the amplifying means as the minus side supply voltage Vcc−. Accordingly, the switching operation is performed only when the output is high, and the influence of noise generated from the switches S2 and S4 is reduced. Therefore, when the user selects the third control mode when listening to general music, The power amplifier of the present invention can achieve high output and high sound quality.

  When the fourth control mode is selected by the mode switching unit 24, when the comparison result Vp + output from the comparison unit 211 is at a high level, the boost control unit 222 turns off the switch S2, and the step-down control unit 221 S1 is turned on / off at duty B1, and the step-up / step-down means 231 is stepped down. As a result, the voltage VE1 supplied from the plus side power supply E1 is stepped down and supplied to the amplifying means as the minus side supply voltage Vcc−. When the comparison result Vp + output from the comparison unit 211 is at a low level, the step-down control unit 221 turns on the switch S1, the step-up control unit 222 turns on / off the switch S2 with the duty B2, and Boost operation is performed. That is, the voltage VE1 supplied from the plus side power supply E1 is boosted and supplied to the amplifying means as the plus side supply voltage Vcc +.

  Similarly, when the comparison result Vp− output from the comparison unit 212 is at a high level, the step-up control unit 222 turns off the switch S4, and the step-down control unit 221 turns on / off the switch S3 with the duty B1, thereby increasing / decreasing the step-up / step-down unit. 231 is stepped down. As a result, the voltage VE2 supplied from the negative side power supply E2 is stepped down and supplied to the amplifying means as the negative side supply voltage Vcc−. When the comparison result Vp− output from the comparison unit 212 is at a low level, the step-down control unit 221 turns on the switch S3, the step-up control unit 222 turns on / off the switch S4 with the duty B2, and the step-up / step-down unit 232 To boost operation. That is, the voltage VE2 supplied from the minus side power supply E2 is boosted and supplied to the amplifying means as the plus side supply voltage Vcc−. Therefore, when the output signal is a small output, the supply voltage can be lowered, and when the output signal is a high output, the voltage can be raised. Therefore, when the user watches a movie with a wide dynamic range, the fourth control is performed. By selecting the mode, the power amplifier of the present invention can achieve high output and high power efficiency.

  Next, a power amplifier 100 according to another embodiment of the present invention will be described. Note that a description of the same parts as those of the power amplifier 10 is omitted.

  FIG. 4 is a block diagram (FIG. 4 (a)) and a circuit diagram (FIG. 4 (b)) of a power amplifier 100 including a power supply means 7 according to another embodiment of the present invention. As shown in FIG. 4A, the comparison means 711 and 712 may compare the input signal input to the amplification means 6 with the voltage VE3 of the plus-side power supply E3 and the voltage VE4 of the minus-side power supply E4. good. Specifically, as shown in FIG. 4B, the voltage difference between the input signal inputted to the amplifying means 6 and the voltage VE3 or VE4 is compared with predetermined potential differences Vc and Vd. It should be noted that each element (switch elements S5 to S8, coils L4 and L5, capacitors C3 and C4, diodes D7 to D10, Zener diodes D11 and D12, resistors R7 to R7) used for the comparing means 711 and 712 and the step-up / step-down means 721 and 722 are used. For R12), an element having a performance in accordance with an input signal input to the amplifying means, a power supply voltage to be used, or the like may be appropriately selected.

  As described above, the embodiment of the power amplifier according to the present invention has been described. In the power amplifier according to the present invention, the control unit controls the step-up / step-down operation of the step-up / step-down unit based on the control mode. The power suitable for the situation is supplied to the amplification means. The control means further receives a comparison result between the voltage supplied to the amplification means and the input signal or output signal of the amplification means from the comparison means, and controls the step-up / step-down means based on the comparison result and the control mode. . The control mode is switched by mode switching means. As a result, it is possible to provide a power amplifier that performs high power quality or high power efficiency by supplying power according to the usage situation desired by the user.

  Further, the amplification means in this embodiment is a differential type, and a power amplifier including a power supply, a step-up / step-down means, and a comparison means on the positive side and the negative side of the input power source of the amplification means has been described. An amplification means such as a mold may be used. In that case, it suffices if there is one set of power source, step-up / step-down means, and comparison means.

  Further, in this embodiment, the comparison means includes a voltage difference between the voltage VE1 (voltage VE2) of the plus side power supply E1 (minus side power supply E2) and the output voltage V1 of the amplification means 1, and a predetermined voltage difference Va (Vb). However, a comparison result of a plurality of levels to be output may be output by comparing with a plurality of predetermined voltage differences. As a result, it becomes possible to finely control the step-up / down pressure level.

  In the present embodiment, the user selects the control mode using the mode switching means. However, the night is automatically switched to the first control mode at night, or DVD is selected as the input source. If so, the control mode may be automatically switched according to the input source, such as switching to the fourth control mode.

  While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

  The power amplifier of the present invention can be used in electronic equipment for any application, but can be suitably used for audio equipment and the like.

It is a block diagram explaining the schematic structure of the power amplifier by preferable embodiment of this invention. 1 is a circuit diagram of a power amplifier according to a preferred embodiment of the present invention. It is a figure which shows four control modes in the control means by preferable embodiment of this invention. FIG. 2 is a block diagram (a) and a circuit diagram (b) of a power amplifier according to another preferred embodiment of the present invention. It is a circuit diagram which shows the conventional step-down switching power supply (a) and step-up switching power supply (b).

Explanation of symbols

10, 100 Power amplifier 1, 6 Amplification means 211, 212, 711, 712 Comparison means 22, 72 Control means 221, 721 Step-down control means 222, 722 Step-up control means 231, 232, 731, 732 Step-up / step-down means 24, 74 modes Switching means 4, 9 Input end 5, 11 Output end

Claims (9)

Amplifying means for amplifying the input signal and outputting the output signal;
First power supply means for supplying a first voltage to the positive power supply side of the amplification means;
Second power supply means for supplying a second voltage to the negative power supply side of the amplification means;
First step-up / step-down means for stepping up or stepping down the first voltage and supplying the first voltage to the amplification means;
Second step-up / step-down means for stepping up or stepping down the second voltage and supplying the second voltage to the amplification means;
A first comparing means for comparing the first voltage with the input signal or the output signal and outputting a first comparison result;
A second comparing means for comparing the second voltage with the input signal or the output signal and outputting a second comparison result;
A plurality of control modes, wherein the first step-up / step-down means is controlled based on the control mode and the first comparison result, and the second mode is controlled based on the control mode and the second comparison result. Control means for controlling the step-up / step-down means;
A power amplifier comprising: mode switching means for switching the control mode. The first comparing means comprises:
If the voltage difference between the first voltage and the output signal or the input signal is greater than or equal to a first predetermined voltage difference, a first level signal is output;
Outputting a second level signal if the voltage difference between the first voltage and the output signal or the input signal is less than a second predetermined voltage difference;
The second comparing means comprises:
If the voltage difference between the second voltage and the output signal or the input signal is greater than or equal to a predetermined voltage difference, a third level signal is output;
The power amplifier according to claim 1, wherein when the voltage difference between the second voltage and the output signal or the input signal is less than a predetermined voltage difference, a fourth level signal is output. The control means is
Controlling the step-down operation of the first step-up / step-down means based on the control mode and the first comparison result;
Step-down control means for controlling the step-down operation of the second step-up / step-down means based on the control mode and the second comparison result;
Controlling the boosting operation of the first step-up / step-down means based on the control mode and the first comparison result;
3. The power amplifier according to claim 1, further comprising: a boost control unit that controls a boost operation with the second step-up / step-down unit based on the control mode and the second comparison result. In the first control mode,
Regardless of the first comparison result and the second comparison result, the step-down control means and the step-up control means do not cause the first step-up / step-down means and the second step-up / step-down means to perform a step-up / step-down operation. Item 4. The power amplifier according to Items 1 to 3. In the second control mode,
The step-down control means is
When the first comparison result is a first level, the first step-up / step-down means is caused to perform a step-down operation,
When the second comparison result is a third level, the second step-up / step-down means is caused to perform a step-down operation;
The boost control means includes
When the first comparison result is the second level, the first step-up / step-down means is not allowed to perform step-up / step-down operation,
When the second comparison result is the fourth level, the second step-up / step-down means is not caused to perform the step-up / step-down operation.
The power amplifier according to claim 1. In the third control mode,
The step-down control means is
When the first comparison result is the first level, the first step-up / step-down means is not allowed to perform step-up / step-down operation,
When the second comparison result is the third level, the second step-up / step-down means is not operated to step up / down;
The boost control means includes
When the first comparison result is the second level, the first step-up / step-down means is caused to perform a boosting operation;
6. The power amplifier according to claim 1, wherein when the second comparison result is a fourth level, the second step-up / step-down means is caused to perform a boosting operation. In the fourth control mode,
The step-down control means is
When the first comparison result is a first level, the first step-up / step-down means is caused to perform a step-down operation,
When the second comparison result is a third level, the second step-up / step-down means is caused to perform a step-down operation;
The boost control means includes
When the first comparison result is the second level, the first step-up / step-down means is caused to perform a boost operation,
7. The power amplifier according to claim 1, wherein when the second comparison result is a fourth level, the second step-up / step-down unit is caused to perform a boosting operation.   The power amplifier according to claim 1, wherein the step-up / step-down means is a step-up / step-down chopper type DC-DC converter. Amplifying means for grounding the first power supply, amplifying the input signal and outputting the output signal;
Power supply means for supplying a voltage to the second power supply side of the amplification means;
Step-up / step-down means for stepping up or down the voltage and supplying the voltage to the amplification means;
A comparison means for comparing the voltage with the input signal or the output signal and outputting a comparison result;
Having a plurality of control modes, controlling the step-up / step-down means based on the control mode and the comparison result;
A power amplifier comprising: mode switching means for switching the control mode.

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