JP2011135444A - Driving driver, driving amplifier, and information apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving driver, along with a driving amplifier and information apparatus, capable of driving a capacitive load such as a piezoelectric element with low power consumption without wastefully consuming energy charged in the capacitive load. <P>SOLUTION: Energy transferred to a piezoelectric speaker 15 as a capacitive load is not consumed by a resistance or the like as much as possible, but recharged to a capacitor 41 through a coil 42 so that the energy can be reused for the driving of the capacitive load. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a driving driver, a driving amplifier, and an information device, and more particularly to a driving driver, a driving amplifier, and an information device that can drive a capacitive load such as a piezoelectric element with low power consumption.

  In recent years, small electronic devices such as portable music players and mobile phones have been rapidly reduced in size and power consumption. From such a background, there are an increasing number of piezoelectric speakers that can be manufactured in a thin shape with a much higher efficiency than conventional dynamic speakers and the like in speakers mounted on electronic devices. In these small electronic devices, a driving amplifier for driving a piezoelectric element such as a piezoelectric speaker is mounted.

  For example, in the digital amplifier of Patent Document 1, a PWM signal obtained by PWM-modulating an audio signal as an input signal and a power supply voltage are first input to a waveform conversion circuit, and the PWM signal is converted into an analog high voltage waveform by the waveform conversion circuit. The The analog high voltage waveform is input to a piezoelectric speaker as a load, that is, energy is charged into the piezoelectric speaker, and the piezoelectric speaker is driven. The energy charged in the piezoelectric speaker is consumed by a resistor connected in parallel with the piezoelectric speaker.

  As described above, in a general driving amplifier, energy is charged to the piezoelectric element from a DC-DC converter or the like that boosts the power supply or the power supply voltage, and the energy charged in the capacitive load is consumed by a resistor, or is connected to the ground. A capacitive load such as a piezoelectric speaker is driven by repeatedly discharging.

JP 2006-60549 A

However, since the drive amplifier described above consumes all of the energy charged in the piezoelectric speaker by a resistor connected in parallel with the load, it is necessary to recharge the consumed energy in the piezoelectric speaker. . Further, even when the energy charged in the piezoelectric speaker is discharged to the ground, it is necessary to charge the piezoelectric speaker again with the energy discharged to the ground.
Therefore, in view of the above-described problems, the present invention provides a driver for driving that can drive a capacitive load with low power consumption without wasting energy charged to the capacitive load such as a piezoelectric element. The purpose is to provide an amplifier and information equipment.

In order to achieve the above object, a driver for driving, a driver for driving, and an information device according to the present invention are configured as follows.
A first driver for driving according to the present invention is a driver for driving a capacitive load, and includes a first charge / discharge element that holds energy, and the first charge / discharge element or the capacitive load. The second charge / discharge element that temporarily holds the held energy, between the first charge / discharge element and the second charge / discharge element, and between the second charge / discharge element and the capacitor. A switching element connected to each other, and a control means for controlling the electrical connection state of the switching element to be switched between an on state and an off state, the control means comprising: The energy charged in the first charge / discharge element is charged into the capacitive load via the second charge / discharge element, and the energy charged in the capacitive load is passed through the second charge / discharge element. Again before And controlling the switching of the electrical connection state of the switching element to be charged to the first charge and discharge device.

  According to the above driver for driving, the first charging / discharging element such as a capacitor and the second charging / discharging element such as a coil are provided, and the energy charged in the capacitive load such as a piezoelectric speaker is transmitted by an element such as a resistor. The first charge / discharge element is charged again via the second charge / discharge element again without being wasted. By using the energy charged in the first charge / discharge element again to drive the capacitive load, the capacitive load can be driven with low power consumption.

The second driver for driving according to the present invention comprises replenishing means for replenishing energy from the power source to the first charging / discharging element, and the control means supplies energy from the power source to the first charging / discharging element. The operation state of the replenishing means is controlled so that is replenished.
According to the above driver for driving, it is possible to replenish the first charge / discharge element from the power source with the energy consumed mainly by the wiring and the resistance of each element or the kinetic energy of the capacitive load.

  In the third driver for driving according to the present invention, the control means charges energy from the power source to the first charge / discharge element in the first phase, and the first charge / discharge element in the second phase. The second charge / discharge element is charged with energy, transferred from the second charge / discharge element to the capacitive load in a third phase, and transferred from the capacitive load to the second load in a fourth phase. The charging / discharging element is charged with energy, and the energy is transferred from the second charging / discharging element to the first charging / discharging element in the fifth phase. The switching of the electrical connection state is controlled.

  According to the above driver for driving, the control means controls the operation of the replenishing means and the switching of the electrical connection state of the switching element, thereby charging energy from the power source to the first charge / discharge element in the first phase. Subsequently, in the second phase and the third phase, the capacitive load is charged from the first charge / discharge element through the second charge / discharge element, and in the fourth phase and the fifth phase. It becomes possible to recharge the energy from the capacitive load to the first charge / discharge element via the second charge / discharge element.

  In the fourth driving driver according to the present invention, when the control unit charges the first charging / discharging element with energy from the power source, the first phase is executed, and the first charging / discharging element performs the operation. When charging energy to the capacitive load, the second phase and the third phase are executed. When discharging energy from the capacitive load to the first charge / discharge element, the fourth phase and the fifth phase are performed. It is characterized by controlling the operation of the replenishing means and switching of the electrical connection state of the switching element so as to be executed.

  According to the driver for driving described above, the first phase is executed first, the first charge / discharge element is charged with energy from the power source, and the phases from the second phase to the fifth phase are executed. . Then, after each phase is executed, the first phase is executed again, and the first charge / discharge element can be charged with the energy consumed by the wiring, the resistance of each element, or the like.

  In the fifth driver for driving according to the present invention, the first charging / discharging element is connected between the power source and the ground, and the second charging / discharging element is connected to the first charging / discharging element. The positive terminal is connected between the positive terminal of the capacitive load, the replenishing means is connected between the power source and the positive terminal of the first charge / discharge element, and the capacitive load is The negative terminal is connected to the terminal on the power supply side of the second charge / discharge element, and the switching element includes a terminal on the capacitive load side of the second charge / discharge element and a negative terminal of the first charge / discharge element. A first switching element connected between the terminals, a capacitive load side terminal of the second charge / discharge element, and a second switching element connected between the positive terminal of the capacitive load And the control means has an operating state of the replenishing means in the first phase. Control is performed so that energy is charged to the first charge / discharge element from the source, and control is performed so that the electrical connection state of the first switching element is turned on in the second and fifth phases. In the third and fourth phases, control is performed such that the electrical connection state of the second switching element is turned on.

  According to the driving driver described above, the control means charges the energy from the power source to the first charge / discharge element by the replenishment means in the first phase, and only the first switching element is supplied in the second and fifth phases. Energy is transferred between the first charge / discharge element and the second charge / discharge element by turning on, and only the second switching element is turned on in the third and fourth phases. Energy can be transferred between the two charge / discharge elements and the capacitive load. That is, energy can be transferred between the power supply and the capacitive load via the second charge / discharge element with a simple circuit configuration that only controls the electrical connection state of the three switching elements. .

  In the sixth driving driver according to the present invention, the capacitive load has a negative terminal connected to the ground or a voltage source, the switching element includes a power supply side terminal of the second charge / discharge element, Connected between the third switching element connected between the positive terminal of the first charge / discharge element, the terminal on the power source side of the second charge / discharge element, and the negative terminal of the capacitive load And the control means controls so that the electrical connection state of the third switching element is turned on in the second and fifth phases, and the third and Control is performed so that the electrical connection state of the fourth switching element is turned on in the fourth phase.

  According to the driving driver, the third switching element that switches the electrical connection state at the same timing as the first switching element, and the fourth switching that switches the electrical connection state at the same timing as the second switching element. And the control means turns on only the first and third switching elements in the second and fifth phases, and the second and fourth switching elements in the third and fourth phases. Only turn on. By this, it becomes possible to obtain the same operation as the fifth driving driver. Further, it is possible to share the circuit ground formed by the third switching element and the circuit ground formed by the fourth switching element.

In the seventh driver for driving according to the present invention, the control means does not charge the second charging / discharging element with energy or discharge energy from the second charging / discharging element, and Control is performed so as to enter a standby phase in which the connection state is turned off.
According to the driver for driving described above, the control unit controls the switching element so that the electrical connection state is turned off, so that no energy is transferred from the second charge / discharge element. As a result, the phase can be executed next after the current flowing through the second charge / discharge element is completely zero, that is, when there is no energy transfer.

In an eighth drive driver according to the present invention, the control means may be configured so that the switching element is in an electrically connected state so as to enter the standby phase immediately after the first, third and fifth phases are executed. It is characterized by controlling switching.
According to the driver for driving described above, immediately after the first, third, and fifth phases are executed, the phase is executed after the energy is not transferred from the second charge / discharge element. It becomes possible.

The drive amplifier according to the present invention generates an output signal for driving a capacitive load based on an input signal modulating means for modulating an input signal and a signal modulated by the input signal modulating means. The drive driver according to any one of 8 is provided.
According to the above driving amplifier, since the first to seventh driving drivers are configured, it is possible to drive the capacitive load with low power consumption.

An information device according to the present invention outputs a capacitive load, input signal generating means for generating an input signal, and an output signal for driving the capacitive load from the input signal generated by the input signal generating means. The drive amplifier according to claim 9, and a drive power supply that supplies a voltage to the input signal generation unit and the drive amplifier.
According to the information device described above, since the drive amplifier is provided, the capacitive load can be driven with low power consumption, and the overall power consumption of the information device can be suppressed.

  According to the present invention, the first charging / discharging element and the second charging / discharging element are provided, and energy charged in a capacitive load such as a piezoelectric speaker is consumed as much as possible by an element such as a resistor without waste. The energy is again charged to the first charge / discharge element via the second charge / discharge element. The energy charged in the first charge / discharge element is used in the phase for driving the capacitive load. For this reason, the energy passed from the power source to the first charge / discharge element is mainly the energy consumed by the wiring and the resistance of each element or the kinetic energy of the capacitive load such as the piezoelectric speaker. It can be driven with low power consumption.

1 is a circuit diagram showing a configuration of a portable music player 10 according to the present invention. It is a circuit diagram which shows the structure of the amplifier 14 for piezoelectric speaker drive which concerns on this invention. It is a circuit diagram which shows the structure of the switching drive circuit 24 which concerns on this invention. 3 is a circuit diagram showing an equivalent circuit in each circuit of the switching drive circuit 24. FIG. 4 is a graph showing changes in energy in a capacitor 41, a coil 42, and a piezoelectric speaker 15 of a switching drive circuit 24. 4 is a graph showing changes in energy in a capacitor 41, a coil 42, and a piezoelectric speaker 15 of a switching drive circuit 24. 4 is a graph showing changes in energy in a capacitor 41, a coil 42, and a piezoelectric speaker 15 of a switching drive circuit 24. It is a circuit diagram which shows the structure of the gate driver 23 which concerns on this invention. 6 is a circuit diagram showing a configuration of a switching drive circuit 100 according to a first modification of the switching drive circuit 24. FIG. FIG. 10 is a circuit diagram showing a configuration of a switching drive circuit 200 according to a second modification of the switching drive circuit 24.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing referred to in the following description, components equivalent to those in the other drawings are denoted by the same reference numerals.
(Configuration of portable music player 10)
First, with reference to FIG. 1, a configuration of a portable music player 10 will be described as an example of an information device incorporating a driving amplifier according to the present invention. FIG. 1 is a circuit diagram showing a configuration of a portable music player 10 according to the present invention.

A portable music player 10 shown in FIG. 1 includes a control unit 11, a touch panel 12, a memory 13, a piezoelectric speaker drive amplifier 14, a piezoelectric speaker 15, and a lithium ion battery 16.
The control unit 11 transmits / receives control signals and the like to / from each unit constituting the portable music player 10 and controls the portable music player 10 as a whole. The control unit 11 is supplied with the power supply voltage VDD from the lithium ion battery 16. The control unit 11 generates an audio signal Vin that is an input signal, and outputs the generated audio signal Vin to the piezoelectric speaker driving amplifier 14.

The touch panel 12 is used by the user to select a song to be played and a volume, and to display the song being played and the current device status.
The memory 13 is for storing programs executed by the control unit 11, music files, and the like.
The piezoelectric speaker driving amplifier 14 is a switching amplifier circuit amplifier that inputs the power supply voltage VDD from the lithium ion battery 16 and the audio signal Vin output from the control unit 11 and drives the piezoelectric speaker 15.

The piezoelectric speaker 15 is a piezoelectric element that outputs a sound by vibrating a piezoelectric body by applying a voltage to electrodes sandwiching the piezoelectric body.
The lithium ion battery 16 is a secondary battery that can be charged from a commercial power source or the like, and is a power source that supplies an operating voltage to the control unit 11 and the piezoelectric speaker driving amplifier 14. When the operating voltage of the piezoelectric speaker driving amplifier 14 is higher than the power supply voltage VDD output from the lithium ion battery 16, the power supply voltage VDD may be boosted using a booster circuit such as a DC-DC converter. good.

  In the present embodiment, the information device incorporating the piezoelectric speaker driving amplifier 14 according to the present invention will be described as the portable music player 10, but a mobile phone, a portable DVD player, or the like may be used. Further, the load driven by the piezoelectric speaker driving amplifier 14 may be a capacitive load, and is not limited to the piezoelectric speaker 15. For example, the load may be a capacitive load such as various piezoelectric elements or modulators other than the piezoelectric speaker 15.

(Configuration of the amplifier 14 for driving the piezoelectric speaker)
Next, the configuration of the piezoelectric speaker driving amplifier 14 incorporating the driving driver according to the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram showing a configuration of the piezoelectric speaker driving amplifier 14 according to the present invention.
The piezoelectric speaker drive amplifier 14 shown in FIG. 2 includes an error suppression circuit 21, a PWM (Pulse Width Modulation) circuit 22, a gate driver 23, a switching drive circuit 24, and an LPF 25.
The error suppression circuit 21 detects an error between the amplitude of the audio signal Vin input as a differential signal from the input terminals 26 and 27 and the amplitude of the output signal Vout fed back from the output side as a differential signal, and detects the detected amplitude. This circuit outputs a signal in which the amplitude of the audio signal Vin is corrected based on the error.

The PWM circuit 22 is a circuit that PWM-modulates the signal output from the error suppression circuit 21 and outputs it as a PWM signal. Although the modulation method in this embodiment is PWM modulation, the modulation method is not limited to PWM modulation, and may be PDM (Pulse Density Modulation) including delta-sigma modulation.
The gate driver 23 is a circuit that generates and outputs drive control signals φ0 to φ2 for driving the switching elements constituting the switching drive circuit 24.

The switching drive circuit 24 is driven by drive control signals φ0 to φ2 output from the switching drive circuit 24, and outputs an output signal Vout to the piezoelectric speaker 15 connected via the output terminals 28 and 29.
The LPF 25 is a filtering circuit that removes a high frequency component of the output signal Vout and extracts a low frequency component of the signal when the output signal Vout output from the switching drive circuit 24 is fed back to the input side.

(Configuration of the switching drive circuit 24)
Next, the configuration of the switching drive circuit 24 according to the present invention will be described with reference to FIG. FIG. 3 is a circuit diagram showing a configuration of the switching drive circuit 24 according to the present invention.
The switching drive circuit 24 illustrated in FIG. 3 includes a capacitor 41, a coil 42, and switching elements 43 to 47.
The capacitor 41 is connected between the power supply voltage VDD and the ground. The capacitor 41 is a charge / discharge element that charges energy corresponding to the power supply voltage VDD of the lithium ion battery 16 and discharges the charged energy. In the present embodiment, the capacitance of the piezoelectric speaker 15 is about 1 μF, whereas the capacitance of the capacitor 41 is about 50 μF, which is larger than the capacitance of the piezoelectric speaker 15.

The coil 42 is connected between the power supply voltage VDD and the positive terminal of the piezoelectric speaker 15. The coil 42 is a charging / discharging element that is temporarily charged with energy corresponding to the amount of current flowing and that discharges the charged energy.
The switching element 43 is connected between the power supply voltage VDD and the positive terminal of the capacitor 41. The switching element 43 is an element for replenishing the capacitor 41 with energy corresponding to the power supply voltage VDD by switching the electrical connection state between the on state and the off state by the drive control signal φ0. When the drive control signal φ0 becomes H level, the switching element 43 is turned on and the capacitor 41 is charged with energy. When the drive control signal φ0 becomes L level, the electrical connection is turned off and the capacitor 41 is turned on. Stop charging.

  The switching element 44 is connected between the power supply side terminal of the coil 42 and the positive terminal of the capacitor 41. The switching element 45 is connected between the terminal on the capacitive load side of the coil 42 and the negative terminal of the capacitor 41. These switching elements 44 and 45 are elements for switching the electrical connection state between the on state and the off state in accordance with the drive control signal φ1. The switching elements 44 and 45 are turned on when the drive control signal φ1 is at the H level, and turned off when the drive control signal φ1 is at the L level.

The switching element 46 is connected between the terminal on the capacitive load side of the coil 42 and the positive terminal of the piezoelectric speaker 15. The switching element 47 is connected between the terminal on the power supply voltage VDD side of the coil 42 and the negative terminal of the capacitor 41. These switching elements 46 and 47 are elements for switching the electrical connection state between the on state and the off state by the drive control signal φ2. The switching elements 46 and 47 are turned on when the drive control signal φ2 is at the H level, and are turned off when the drive control signal φ2 is at the L level.
In this switching drive circuit 24, the ground of the circuit that can be turned on in the electrical connection state of the switching elements 44 and 45 and the ground of the circuit that can be turned in the electrical connection state of the switching elements 46 and 47. And are common.

(Operation of the switching drive circuit 24)
Next, an operation method of the switching drive circuit 24 will be described with reference to FIG. In the switching drive circuit 24, the state of the circuit changes into a plurality of types of phases by switching the switching elements 43 to 47 by the drive control signals φ0 to φ2. FIG. 4 is a circuit diagram showing an equivalent circuit of the switching drive circuit 24 in each phase.
4A shows an equivalent circuit of the switching drive circuit 24 in phase 1 in which energy corresponding to the power supply voltage VDD is charged in the capacitor 41, and FIG. 4B shows phase 2 in which energy is charged from the capacitor 41 to the coil 42. 4C shows an equivalent circuit of the switching drive circuit 24 in FIG. 4, FIG. 4C shows an equivalent circuit of the switching drive circuit 24 in the phase 3 in which energy is transferred from the coil 42 to the piezoelectric speaker 15, and FIG. FIG. 4E shows an equivalent circuit of the switching drive circuit 24 in phase 5 in which energy is transferred from the coil 42 to the capacitor 41. FIG.

  First, as shown in FIG. 4A, in phase 1 in which the energy corresponding to the power supply voltage VDD is charged to the capacitor 41, the electrical connection state of the switching element 43 is turned on, and the + terminal of the capacitor 41 is connected to the power source. Connected to the voltage VDD, the negative terminal of the capacitor 41 is connected to the ground. As a result, the energy corresponding to the power supply voltage VDD is charged in the capacitor 41.

Next, as shown in FIG. 4B, in phase 2 in which energy is charged from the capacitor 41 to the coil 42, the electrical connection state of the switching elements 44 and 45 is turned on, and the capacitor 41 and the coil 42 are connected. Connected. As a result, the energy charged in the capacitor 41 is moved and charged in the coil 42.
Here, assuming that the voltage between both terminals of the capacitor 41 before the energy of the capacitor 41 moves is V _1, and the voltage between both terminals of the capacitor 41 after the energy of the capacitor 41 is moved is V ₂ , the capacitor 41 The voltage between the two terminals decreases from V ₁ to V ₂ before and after energy transfer. Therefore, the energy ΔE _C1 transferred from the capacitor 41 is
ΔE _C1 = (1/2) C ₁ (V ₁ ² −V ₂ ² ) Equation (1)
It becomes.

Further, the current flowing through the coil 42 before the energy is transferred to the coil 42 is 0, and the current flowing through the coil 42 after the energy is transferred to the coil 42 is I _1. , Increases from 0 to I ₁ before and after energy is transferred. Therefore, the energy ΔE _L transferred to the coil 42 is
ΔE _L = (1/2) L (I ₁ ² −0)
= (1/2) LI ₁ ² ...... Formula (2)
It becomes.

Assuming that the inductance of the coil is L, the capacitance of the capacitor is C, the voltage is V, and the current is I, impedance Z = √ (L / C) and V = IZ.
V = I × √ (L / C) (3)
It becomes. Substituting capacitance (C) of the capacitor to C ₁ and substituting equation (3) into equation (1),
ΔE _C1 = (1/2) C ₁ (V ₁ ² −V ₂ ² )
= (1/2) C ₁ (I ₁ ² (L / C ₁ ) −0 ² (L / C ₁ ))
= (1/2) LI ₁ ² -0
= (1/2) LI ₁ ² ...... Formula (4)
It becomes. Therefore, the energy ΔE _C1 transferred from the capacitor 41 is equal to the energy ΔE _L charged in the coil 42. That is, when energy is transferred from the capacitor 41 to the coil 42, it can be said that energy is not wasted if the wiring and resistance values of the respective elements are ignored. However, since energy is actually consumed by the resistance of the wiring and each element, etc., if the loss energy consumed by the resistance of the wiring and each element is E _LOSS , the capacitor is The energy ΔE _C1 transferred from 41 is
ΔE _C1 = ΔE _L + E _LOSS ...... Formula (5)
It becomes.

As shown in FIG. 4C, in phase 3 in which energy is transferred from the coil 42 to the piezoelectric speaker 15, the electrical connection state of the switching elements 46 and 47 is turned on, and the coil 42 and the piezoelectric speaker 15 are connected. Connected.
As in the phase 2, the current flowing through the coil 42 before the energy is transferred to the piezoelectric speaker 15 is I ₁ , and the current flowing through the coil 42 after the energy is transferred to the piezoelectric speaker 15 is 0. The current flowing through the coil 42 decreases from I ₁ to 0 before and after energy is transferred. Therefore, the energy ΔE _L transferred to the coil 42 is
ΔE _L = (1/2) LI ₁ ² ...... Formula (6)
It becomes.

Further, if the voltage between both terminals of the piezoelectric speaker 15 before the energy is transferred to the piezoelectric speaker 15 is V _3, and the voltage between both terminals of the piezoelectric speaker 15 after the energy is transferred to the piezoelectric speaker 15 is V _4. The voltage between both terminals of the piezoelectric speaker 15 increases from V ₃ to V ₄ before and after the energy moves. Therefore, the energy ΔE _C2 moved from the piezoelectric speaker 15 is
ΔE _C2 = (1/2) C ₂ (V ₄ ² −V ₃ ² ) (7)
It becomes.

When the capacitor C in Expression (3) is C ₂ and Expression (7) is expanded by substituting Expression (3) into Expression (7), the energy ΔE _L transferred to the coil 42 shown in Expression (6) The energy ΔE _C2 moved to the piezoelectric speaker 15 represented by the equation (7) becomes equal. For this reason, when energy is transferred from the coil 42 to the piezoelectric speaker 15 in the phase 3, it can be said that the energy is not wasted if the wiring and the resistance value of each element are ignored as in the phase 2. However, since energy is actually consumed by the resistance of the wiring and each element, etc., if the loss energy consumed by the resistance of the wiring and each element is E _LOSS , the piezoelectricity is determined by the law of energy conservation. The energy ΔE _C2 moved from the speaker 15 is
ΔE _C2 = ΔE _L + E _LOSS ...... Formula (8)
It becomes.

Next, as shown in FIG. 4D, in phase 4 in which energy is charged from the piezoelectric speaker 15 to the coil 42, the electrical connection state of the switching elements 46 and 47 remains unchanged and the coil 42 and the piezoelectric element are not changed. A speaker 15 is connected. Then, the energy charged in the piezoelectric speaker 15 is charged in the coil 42.
Assuming that the voltage between both terminals of the piezoelectric speaker 15 before the energy of the piezoelectric speaker 15 moves is V _5, and the voltage between both terminals of the capacitor 41 after the energy of the piezoelectric speaker 15 is moved is V ₆ , the piezoelectric speaker. The voltage between both terminals of 15 decreases from V ₅ to V ₆ before and after energy transfer. Therefore, the energy ΔE _C3 moved from the piezoelectric speaker 15 is
ΔE _C3 = (1/2) C ₂ (V ₅ ² −V ₆ ² ) (9)
It becomes.

Further, the current flowing through the coil 42 to the coil 42 before the energy can be transferred is 0, if the current flowing through the coil 42 after the energy has been transferred to the coil 42 and I _2, the current flowing through the coil 42 , Increases from 0 to I ₂ before and after energy is transferred. Therefore, the energy ΔE _L transferred to the coil 42 is
ΔE _L = (1/2) LI ₂ ² ...... Equation (10)
It becomes.

When the capacitance C in Expression (3) is C ₂ and Expression (9) is substituted by substituting Expression (3) into Expression (9), the energy ΔE _C3 moved from the piezoelectric speaker 15 and the energy transferred to the coil 42 are transferred. It becomes equal to ΔE _L. For this reason, when charging energy from the piezoelectric speaker 15 to the coil 42 in the phase 4, it can be said that the energy is not wasted similarly to the phase 2 and the phase 3. However, since energy is actually consumed by the resistance of the wiring and each element, etc., if the loss energy consumed by the resistance of the wiring and each element is E _LOSS , the piezoelectricity is determined by the law of energy conservation. The energy ΔE _C3 moved from the speaker 15 is
ΔE _C3 = ΔE _L + E _LOSS ...... Formula (11)
It becomes.

Next, as shown in FIG. 4E, in phase 5 in which energy is transferred from the coil 42 to the capacitor 41, only the electrical connection state of the switching elements 44 and 45 is switched on, and the capacitor 41 is connected to the coil 42. Connected. Then, the energy charged in the coil 42 is transferred to the capacitor 41.
If the voltage between both terminals of the coil 42 before the energy of the coil 42 moves is V _7, and the voltage between both terminals of the coil 42 after the energy of the coil 42 moves is V ₈ , both terminals of the coil 42 The voltage between them increases from V ₇ to V ₈ before and after energy transfer. Therefore, the energy ΔE _C4 transferred from the capacitor 41 is
ΔE _C4 = (1/2) C ₁ (V ₈ ² −V ₇ ² ) (12)
It becomes.

Further, if the current flowing through the coil 42 before the energy is transferred to the coil 42 is I ₂ and the current flowing through the coil 42 before the energy is transferred to the coil 42 is 0, the current flowing through the coil 42 is It decreases from I ₂ to 0 before and after energy is transferred. Therefore, the energy ΔE _L transferred to the coil 42 is
ΔE _L = (1/2) LI ₂ ² ...... Formula (13)
It becomes.

When the capacitance C of the capacitor in the equation (3) is C ₁ and the equation (12) is expanded by substituting the equation (3) into the equation (12), the energy ΔE _L transferred from the coil 42 and the capacitor 41 are transferred. The energy ΔE _C4 is equal. From this, it can be said that energy is not wasted even when energy is transferred from the coil 42 to the capacitor 41 in the phase 5. However, since energy is actually consumed by the resistance of the wiring and each element, etc., if the loss energy consumed by the resistance of the wiring and each element is E _LOSS , the capacitor is The energy ΔE _C4 transferred to 41 is
ΔE _C4 = ΔE _L + E _LOSS ...... Formula (14)
It becomes.

First, after the above-described phase 1 is executed, for example, “phase 2”, “phase 3”,..., “Phase 2”, “phase 3”, “phase 4”, “phase 5”,. , “Phase 4” and “Phase 5” are executed. During this time, energy is gradually lost as heat or the like due to the resistance of the wiring or each element.
For this reason, when predetermined energy is lost, or when each phase from phase 2 to phase 5 is performed a predetermined number of times, the process returns to phase 1 again, and the amount of energy lost due to wiring, resistance of each element, etc. Only the energy is charged in the capacitor 41. Then, the operation | movement which performs each phase similarly is repeated.

(Energy change in the capacitor 41 and the coil 42 of the switching drive circuit 24 and the piezoelectric speaker 15)
Next, changes in energy in the capacitor 41 and the coil 42 of the switching drive circuit 24 and the piezoelectric speaker 15 will be described with reference to FIGS. 5 to 7 are graphs showing energy changes in the capacitor 41, the coil 42, and the piezoelectric speaker 15 of the switching drive circuit 24. FIG.

As shown in FIG. 5, first, a standby phase is reached in which the current I _L42 flowing through the coil 42 is in a zero state. In this standby phase, for example, the drive control signals φ0 to φ2 are set to the L level, and the electrical connection state of the switching elements 44 to 47 is turned off. Thus, in the standby phase, no energy is transferred from the coil 42, and the current I _L42 flowing through the coil 42 is kept completely zero. For this reason, in the standby phase, the voltage V _C41 across the capacitor 41, the current I _L42 flowing through the coil 42, the voltage V _C15 across the piezoelectric speaker 15, the energy ΔE _{C41 of the} capacitor 41, the energy ΔE _{L42 of the} coil 42, and the piezoelectric The energy ΔE _{C15 of the} speaker 15 does not change.

Subsequently, in the phase 1, only the drive control signal φ0 of the drive control signals φ0 to φ2 is at the H level, and the electrical connection state of the switching element 43 is turned on. Then, the capacitor 41 is charged with energy corresponding to the power supply voltage VDD. For this reason, the voltage V _C41 across the capacitor 41 and the energy ΔE _{C41 of the} capacitor 41 gradually increase from zero.

Here, a standby phase is reached in which the current I _L42 flowing through the coil 42 is again in a zero state. For this reason, in the standby phase, the voltage V _C41 across the capacitor 41, the current I _L42 flowing through the coil 42, the voltage V _C15 across the piezoelectric speaker 15, the energy ΔE _{C41 of the} capacitor 41, the energy ΔE _{L42 of the} coil 42, and the piezoelectric The energy ΔE _{C15 of the} speaker 15 does not change.

Subsequently, in phase 2, the drive control signal φ0 becomes L level, only the drive control signal φ1 becomes H level, and the electrical connection state of the switching elements 44 and 45 is turned on. Then, the energy charged in the capacitor 41 is charged in the coil 42. Therefore, the voltage V _C41 across the capacitor 41 and the energy ΔE _{C41 of the} capacitor 41 decrease, the current I _L42 flowing through the coil 42 increases from 0 to I _1, and the energy ΔE _{L42 of the} coil 42 _changes from 0 to the capacitor 41. The energy of the decrease will increase. Note that the energy ΔE _{C41 of the} capacitor 41 changes as shown by a dotted line in the figure if the resistance value of the wiring and each element is ignored, but the energy is consumed little by little by the resistance of the wiring and each element. It changes as shown by the solid line.

Subsequently, in phase 3, the drive control signal φ1 becomes L level, only the drive control signal φ2 becomes H level, and the electrical connection state of the switching elements 46 and 47 is turned on. Then, the energy charged in the coil 42 is transferred to the piezoelectric speaker 15. Therefore, the current I _L flowing through the coil 42 decreases from I ₁ to 0, the energy ΔE _{L42 of the} coil 42 decreases, and the voltage V _C15 across the piezoelectric speaker 15 and the energy ΔE _C15 of the piezoelectric speaker 15 decrease from 0. The energy corresponding to the decrease of the coil 42 increases.

Here, a standby phase is reached in which the current I _L42 flowing through the coil 42 is again in a zero state. In this standby phase, for example, the drive control signals φ0 to φ2 are set to the L level, and the electrical connection state of the switching elements 44 to 47 is turned off. Thus, in the standby phase, no energy is transferred from the coil 42, and the current I _L42 flowing through the coil 42 is kept completely zero. For this reason, in the standby phase, the voltage V _C41 across the capacitor 41, the current I _L42 flowing through the coil 42, the voltage V _C15 across the piezoelectric speaker 15, the energy ΔE _{C41 of the} capacitor 41, the energy ΔE _{L42 of the} coil 42, and the piezoelectric The energy ΔE _{C15 of the} speaker 15 does not change.

Subsequently, in phase 4, only the drive control signal φ2 becomes H level, and the electrical connection state of the switching elements 46 and 47 is turned on. Then, the energy charged in the piezoelectric speaker 15 is charged in the coil 42. Therefore, the voltage V _C15 at both ends of the piezoelectric speaker 15 and the energy ΔE _C15 of the piezoelectric speaker 15 decrease, the current I _L42 flowing through the coil 42 increases from 0 to I _2, and the energy ΔE _{L of the} coil 42 is equal to the piezoelectric speaker. It increases by the energy of 15 reductions.

Subsequently, in phase 5, the drive control signal φ2 becomes L level, only the drive control signal φ1 becomes H level, and the electrical connection state of the switching elements 44 and 45 is turned on. Then, the energy charged in the coil 42 is transferred to the capacitor 41. Therefore, the voltage V _C41 across the capacitor 41 and the energy ΔE _{C41 of the} capacitor 41 increase, the current I _L42 flowing through the coil 42 decreases from I ₂ to 0, and the energy ΔE _{L42 of the} coil 42 increases as the capacitor 41 increases. Only the energy of the minute decreases. However, as described above, the energy ΔE _C41 of the capacitor 41 is indicated by a dotted line in the figure if the resistance of the wiring and each element is ignored, but the energy is consumed little by little due to the resistance of the wiring and each element. It will be done. For this reason, the difference between the theoretical energy indicated by the dotted line and the actual energy indicated by the solid line gradually increases.

The standby phase starts again. In this standby phase, the current I _L42 flowing through the coil 42 becomes zero. For this reason, in the standby phase, the voltage V _C41 across the capacitor 41, the current I _L42 flowing through the coil 42, the voltage V _C15 across the piezoelectric speaker 15, the energy ΔE _{C41 of the} capacitor 41, the energy ΔE _{L42 of the} coil 42, and the piezoelectric The energy ΔE _{C15 of the} speaker 15 does not change.
In addition, after the standby phase, when the above-described phases from phase 2 to phase 5 are executed with the standby phase included, the process returns to phase 1 again.

  In phase 1, among the drive control signals φ0 to φ2, only the drive control signal φ0 is at the H level, and the electrical connection state of the switching element 43 is turned on. Then, energy is charged from the power supply voltage VDD to the capacitor 41 as in the initial stage. However, the switching drive circuit 24 charges the capacitor 41 again via the coil 42 of the switching drive circuit 24 without wastefully consuming the energy transferred to the piezoelectric speaker 15 that is a capacitive load by a resistor or the like. Reused to drive sexual loads. Therefore, in the phase 1, not all the energy corresponding to the power supply voltage VDD is charged in the capacitor 41, but only the energy consumed by the wiring and the resistance of each element is charged.

  The energy corresponding to the power supply voltage VDD is charged in the capacitor 41 again, and the energy charged in the capacitor 41 increases to the same energy as when the first phase 1 is completed. Then, after the execution of the phase 1, the respective phases from the phase 2 to the phase 5 described above are similarly executed.

Here, it has been described that each phase from phase 2 to phase 5 is repeated twice, and then returns to phase 1 again. When phase 2 and phase 3 are repeated several times, or when energy is discharged from the piezoelectric speaker 15, phase 4 and phase 5 are repeated several times as shown in FIG. When charging energy to 41, phase 1 can be repeated a plurality of times. Even when the operation is performed in this way, the energy ΔE _{C41 of the} capacitor 41 changes as shown by a dotted line in the drawing if the resistance value of the wiring and each element is ignored, but the resistance of the wiring and each element, etc. As energy is consumed little by little, it changes as shown by the solid line. Then, only the energy consumed by the wiring and the resistance of each element is charged.

(Operation of the gate driver 23)
Next, the configuration of the gate driver 23 that executes each phase at the timing shown in FIG. 5 will be described with reference to FIG. FIG. 8 is a circuit diagram showing a configuration of the gate driver 23 according to the present invention.
The gate driver 23 to be described below is an example of a circuit that executes each phase as shown in FIG. 5, and the gate driver 23 can be variously configured in accordance with, for example, the timing at which the phase 1 is executed. .
The gate driver 23 shown in FIG. 8 includes flip-flop circuits 31a to 31e, AND circuits 32a to 32k, and OR circuits 33a to 33c.

The flip-flop circuits 31 a to 31 e and the AND circuit 32 a are counters that count counter values 0 to 23 based on the PWM signal output from the PWM circuit 22. When the counter value reaches 23, a reset signal RST for resetting the counter value to 0 is output again, and the count value returns to 0.
The AND circuit 32b is a drive control signal generation circuit for generating the drive control signal φ0. The AND circuit 32b outputs the drive control signal φ0 at the H level when all four input signals are input as “1”. In other cases, the AND circuit 32b outputs the drive control signal φ0 at the L level.

AND circuits 32c to 32f and OR circuit 33a are drive control signal generation circuits for generating drive control signal φ1. When “1” is output from any of the AND circuits 32c to 32f, the OR circuit 33a outputs the drive control signal φ1 at the H level. In other cases, the OR circuit 33a outputs the drive control signal 1 at the L level.
AND circuits 32g to 32j and OR circuit 33b are drive control signal generation circuits for generating drive control signal φ2. When “1” is output from any of the AND circuits 32g to 32j, the OR circuit 33b outputs the drive control signal φ2 at the H level. In other cases, the OR circuit 33b outputs the drive control signal φ2 at the L level.

(Modification of the switching drive circuit 24)
Next, the configuration of the switching drive circuits 100 and 200 according to a modification of the switching drive circuit 24 will be described with reference to FIGS. 9 is a circuit diagram showing a configuration of a switching drive circuit 100 according to a first modification of the switching drive circuit 24, and FIG. 10 is a circuit showing a configuration of a switching drive circuit 200 according to a second modification of the switching drive circuit 24. FIG.

  The switching drive circuit 100 shown in FIG. 9 includes the same elements as the switching drive circuit 24 shown in FIG. However, the difference is that the switching drive circuit 100 does not include the switching elements 44 and 47. In the switching drive circuit 100, only the circuit that can be turned on in the electrical connection state of the switching element 45 in phases 2 and 5 is connected to the ground, and the electrical connection state of the switching element 46 in phases 3 and 4. The circuit that can be turned on is not connected to ground.

  However, since the total number of switching elements in the switching drive circuit 24 described above is five, the total number of switching elements in the switching drive circuit 100 is three. The number of switching elements is two less than that of the switching drive circuit 24. For this reason, the entire resistance of the switching drive circuit 100 can be reduced by the resistance of the switching elements 44 and 47.

  In the switching drive circuit 100, each phase from the phase 1 to the phase 5 described above is performed in the same manner as the switching drive circuit 24, but the energy consumed in the switching drive circuit 100 is suppressed more than in the switching drive circuit 24. it can. Therefore, when the capacitor 41 is charged with energy in the phase 1, the charged energy is less than that of the switching drive circuit 24, and the piezoelectric speaker 15 can be driven with lower power consumption.

Further, the switching drive circuit 200 shown in FIG. 10 includes the same elements as the switching drive circuit 24 shown in FIG. However, the negative terminal of the piezoelectric speaker 15 and one terminal of the switching element 47 are connected to a voltage source different from the ground. That is, in the switching drive circuit 200, only a circuit that can be turned on in the electrical connection state of the switching elements 44 and 45 in the phases 2 and 5 is connected to the ground, and the switching elements 46 and 47 in the phases 3 and 4 are connected. A circuit that can be turned on is connected to a voltage source different from the ground. Also in the switching drive circuit 200, the piezoelectric speaker 15 can be driven with low power consumption by the control method described above.
Of course, a circuit in which the electrical connection state of the switching elements 44 and 45 can be turned on in phases 2 and 5 and a circuit in which the electrical connection state of the switching elements 46 and 47 can be turned on in phases 3 and 4. Can be connected to different grounds.

(Summary)
The energy transferred to the capacitive load such as the piezoelectric speaker 15 is not consumed as much as possible by the resistance, but is used via the coil 42 to charge the capacitor 41 again and reuse it for driving the capacitive load. For this reason, the energy passed from the power supply voltage VDD to the capacitor 41 is mainly the energy consumed by the wiring or the resistance of each element or the kinetic energy of the capacitive load such as the piezoelectric speaker 15 and is charged to the capacitive load. The capacitive load can be driven with low power consumption without wasting the consumed energy.

  In particular, a piezoelectric element driving amplifier and a piezoelectric element driving driver capable of driving a capacitive load such as a piezoelectric element with low power consumption are incorporated in information devices such as a portable music player, a cellular phone, and a portable DVD player.

DESCRIPTION OF SYMBOLS 10 Portable music player 11 Control part 12 Touch panel 13 Memory 14 Piezoelectric speaker drive amplifier 15 Piezoelectric speaker 16 Lithium ion battery 21 Error suppression circuit 22 PWM circuit 23 Gate driver 24 Switching drive circuit 25 LPF
41 Capacitor 42 Coil 43 to 47 Switching element

Claims (10)

A driver for driving a capacitive load,
A first charge / discharge element that retains energy;
A second charge / discharge element that temporarily holds the energy held by the first charge / discharge element or the capacitive load;
A switching element connected between the first charge / discharge element and the second charge / discharge element, and between the second charge / discharge element and the capacitive load;
Control means for controlling the electrical connection state of the switching element to switch between the on state and the off state;
With
The control unit is configured such that energy charged in the first charge / discharge element is charged into the capacitive load via a second charge / discharge element, and energy charged in the capacitive load is second charge / discharge. A drive driver for controlling switching of an electrical connection state of the switching element so that the first charge / discharge element is charged again through the element. Replenishment means for replenishing energy from the power source to the first charge / discharge element;
The control means includes
2. The driving driver according to claim 1, wherein an operation state of the replenishing means is controlled so that energy is replenished to the first charge / discharge element from the power source. The control means includes
In the first phase, energy is charged from the power source to the first charge / discharge element, in the second phase, energy is charged from the first charge / discharge element to the second charge / discharge element, and third Energy is transferred from the second charge / discharge element to the capacitive load in a phase, energy is charged from the capacitive load to the second charge / discharge element in a fourth phase, and the second charge / discharge element is charged in a fifth phase. 3. The switching of the operating state of the replenishing means and the electrical connection state of the switching element is controlled so that energy is transferred from the second charging / discharging element to the first charging / discharging element. The described driver for driving. The control means includes
When charging energy from the power source to the first charging / discharging element, the first phase is executed, and when charging energy from the first charging / discharging element to the capacitive load, the second phase and the third phase When the phase is executed and energy is discharged from the capacitive load to the first charge / discharge element, the operating state of the replenishing means and the switching element are set such that the fourth phase and the fifth phase are executed. 3. The driving driver according to claim 2, wherein switching of the electrical connection state is controlled. The first charge / discharge element is:
Connected between the power source and ground;
The second charge / discharge element is:
Connected between the positive terminal of the first charge / discharge element and the positive terminal of the capacitive load;
The replenishing means is
Connected between the power source and a positive terminal of the first charge / discharge element;
The capacitive load is
The negative terminal is connected to the power supply side terminal of the second charge / discharge element,
The switching element is
A first switching element connected between a capacitive load side terminal of the second charge / discharge element and a negative terminal of the first charge / discharge element;
A second switching element connected between a terminal on the capacitive load side of the second charge / discharge element and a positive terminal of the capacitive load;
With
The control means includes
In the first phase, the operation state of the replenishing means is controlled so as to charge energy from the power source to the first charge / discharge element, and the first switching is performed in the second and fifth phases. Control is performed so that the electrical connection state of the element is turned on, and control is performed so that the electrical connection state of the second switching element is turned on in the third and fourth phases. The driver for driving according to claim 3 or 4. The capacitive load is
Its negative terminal is connected to the ground or voltage source,
The switching element is
A third switching element connected between a terminal on the power source side of the second charge / discharge element and a positive terminal of the first charge / discharge element;
A fourth switching element connected between a power supply side terminal of the second charge / discharge element and a negative terminal of the capacitive load;
With
The control means includes
The electrical connection state of the third switching element is controlled to be turned on in the second and fifth phases, and the electrical connection state of the fourth switching element is turned on in the third and fourth phases. 6. The driving driver according to claim 5, wherein the driving driver is controlled so as to be in a state. The control means includes
Controlling the second charge / discharge element to enter a standby phase in which the electrical connection state of the switching element is turned off without charging energy from the second charge / discharge element or discharging energy from the second charge / discharge element. The driver for driving according to claim 2, wherein the driver is a driving driver. The control means includes
8. The driving driver according to claim 7, wherein switching of the electrical connection state of the switching element is controlled so as to be in the standby phase immediately after the execution of the first, third, and fifth phases. . Input signal modulating means for modulating the input signal;
The driver for driving according to any one of claims 1 to 8, wherein an output signal for driving a capacitive load is generated based on a signal modulated by the input signal modulating means;
A driving amplifier comprising: Capacitive load,
Input signal generating means for generating an input signal;
The drive amplifier according to claim 9, wherein an output signal for driving the capacitive load is output from the input signal generated by the input signal generation unit;
A driving power supply for supplying a voltage to the input signal generating means and the driving amplifier;
An information device comprising:

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