JP2005109665A - Load driver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load driver applicable even to a battery driven portable apparatus by suppressing increase in the load current of a capacitive load even if many high frequency components are included in a driving signal. <P>SOLUTION: After a high-pass attenuating section 110 attenuated the high region of a driving signal from a driving signal source 1 according to a control signal, a driving section 120 drives a load 2 with that driving signal. A load current detecting section 130 detects a load current and provides the results to a control signal adjusting section 140. The control signal adjusting section 140 increases attenuation of high-pass components at the high-pass attenuating section 110 when the load current value increases over the detection results from the load current detecting section 130 and decreases attenuation of high-pass components at the high-pass attenuating section 110 when the load current value increases thus suppressing increase in load current and increase in power supply current interlocked therewith. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a load driving device for driving a capacitive load such as a piezoelectric actuator such as a piezoelectric speaker.

  A piezoelectric actuator such as a piezoelectric speaker does not require a magnetic circuit and a voice coil unlike an electrodynamic actuator. For example, a cellular phone, a PDA (Personal Digital Assistant), a pager (so-called pager), a notebook PC (Personal Computer) and other small and lightweight battery-operated portable devices. Such a piezoelectric actuator is also driven by a linear type (AB class) driving device or a switching type (D class) driving device, similarly to the conventional electrodynamic type.

  A conventional load driving device used for driving a capacitive load is composed of a general linear type amplifier and a switching type amplifier as well as driving other loads (for example, non-patent). Reference 1 and Non-Patent Document 2). Note that Non-Patent Document 1 describes a linear type load driving device and a switching type method with large output power. Non-Patent Document 2 describes points to be noted about the driving power source of the piezoelectric actuator, and particularly describes a large output current.

  FIG. 9 is a circuit diagram showing a configuration of a load driving device based on a conventional technique. The conventional load driving device shown in this figure has a BTL (Bridged Tide Load) connection configuration using a class AB linear amplifier. In FIG. 9, the drive signal from the drive signal source 1 is amplified by the drive unit 220 and then supplied to a load 2 such as a piezoelectric actuator. The power source 3 supplies power to the drive unit 220. The driving unit 220 includes a non-inverting voltage amplifier 21, an inverting voltage amplifier 26, and driving output units 22 and 27. The drive unit 220 is driven by applying a signal whose polarity is inverted to both ends of the load 2, and can supply a positive or negative peak voltage close to the voltage value of the power source 3 to the load 2. . Therefore, it is suitable for a piezoelectric actuator having a higher drive voltage than an electrodynamic type.

  Next, the operation of the conventional load driving apparatus having the above configuration will be described. The drive signal output from the drive signal source 1 is amplified by the non-inverted voltage amplifier 21 and the inverted voltage amplifier 26 having different output polarities, and then is amplified by the drive output units 22 and 27, and is the output terminal. Drive power is supplied from P and point N to the load 2. That is, when the signal from the drive signal source 1 is positive, the voltage at the point P is larger than that at the point N and supplies a positive voltage to the load 2, but on the contrary, the signal from the drive signal source 1 is negative. In this case, the voltage at the point P is smaller than that at the point N, and a negative voltage is supplied to the load 2.

  In this case, when the signal from the drive signal source 1 is positive, the current is the power source 3 → the collector / emitter of the output transistor 23 → (point P) the load 2 (point N) → the emitter / collector of the output transistor 29 → ground. It flows in the route. On the other hand, when the signal from the drive signal source 1 is negative, in contrast to the positive signal, the current is supplied from the power source 3 → the collector / emitter of the output transistor 28 → (point N) load 2 (point P) → output. It flows in the path of the emitter / collector of transistor 24 → ground. Both load currents in the positive direction and the negative direction are supplied from the power source 3. Thus, the capacitive load 2 that is a piezoelectric actuator can be driven, and a current corresponding to the load current is supplied from the power source 3.

Kenji Uchino, “Piezoelectric / Electrostrictive Actuator Basic to Application” 1st edition, published by Morikita Publishing Co., Ltd. (ISBN4-627-77120-7), September 30, 1994, pp.213-215 (linear type) , Pp.104-106 (Pulse width modulation type which is a kind of switching type)

Kenji Uchino, “Practices: From Piezoelectric Actuator Basics to Ultrasonic Motors” 1st Edition, published by Morikita Publishing Co., Ltd. (ISBN4-627-77160-6), July 06, 1991, pp.48 (Piezoelectric Actuator Power Supply) )

  However, the conventional load driving apparatus described above has the following problems. That is, when the load 2 is capacitive and the drive signal contains many high frequency components, the impedance at that frequency is lowered and the load current is increased. For this reason, particularly in portable devices such as mobile phones that are operated by batteries, the power supply current to the load drive device increases, leading to a decrease in battery life, or the heat generated in the transistors in the load drive device due to the output current. It was difficult to use for battery-operated portable devices, such as the need to deal with it.

  The present invention has been made in view of the above points, and it is a capacitive load, and even if a high frequency component is included in a drive signal, an increase in load current can be suppressed to a low level, and a portable device that operates on a battery. It is another object of the present invention to provide a load drive device that can be used for the above.

  In order to solve the above problem, a load driving device according to a first aspect of the present invention includes a high-frequency attenuation unit that attenuates a high-frequency component of a drive signal input from a drive signal source with an attenuation amount according to a control signal; A drive unit that drives a capacitive load with a drive signal that has passed through the high-frequency attenuation unit, a load current detection unit that detects a load current flowing through the capacitive load, and the high current according to the output of the load current detection unit Control signal adjusting means for generating and supplying the control signal for adjusting the attenuation amount of the high frequency component of the high frequency attenuation means to the high frequency attenuation means.

  According to this configuration, the load current during load driving is detected, and when the load current value increases, the amount of attenuation that attenuates the high frequency component of the drive signal is increased, and when the load current value decreases, the high frequency range of the drive signal is increased. Decreases the amount of attenuation that attenuates the component. This suppresses the increase in load current even when the load is capacitive and the drive signal contains a lot of high frequency components. It is possible to provide a load driving device for a piezoelectric actuator that can be suppressed to a low level and is suitable for battery-operated portable equipment such as a cellular phone.

  According to a second aspect of the present invention, there is provided a load driving apparatus comprising: a high-frequency attenuation unit that attenuates a high-frequency component of a drive signal input from a drive signal source with an attenuation amount according to a control signal; and the high-frequency attenuation unit. Drive means for driving the capacitive load with the passed drive signal, temperature detection means for detecting the temperature at which the drive means generates heat by driving the capacitive load, and the high level according to the output of the temperature detection means Control signal adjusting means for generating and supplying the control signal for adjusting the attenuation amount of the high frequency component of the high frequency attenuation means to the high frequency attenuation means.

  According to this configuration, when the current flows through the load, that is, the load current flows, the driving means generates heat, detects the temperature value due to the heat generation, and when the temperature value increases, the attenuation amount that attenuates the high frequency component of the drive signal is reduced. When the temperature value is decreased, the amount of attenuation that attenuates the high frequency component of the drive signal is decreased. This suppresses the increase in load current even when the load is capacitive and the drive signal contains a lot of high frequency components. It is possible to provide a load driving device for a piezoelectric actuator that can be suppressed to a low level and is suitable for battery-operated portable equipment such as a cellular phone.

  According to a third aspect of the present invention, there is provided a load driving device comprising: a high-frequency attenuation unit that attenuates a high-frequency component of a drive signal input from a drive signal source with an attenuation amount according to a control signal; and the high-frequency attenuation unit. Drive means for driving a capacitive load with the passed drive signal; load current estimation means for causing a drive signal input from the drive signal source to flow through a pseudo load and estimating a load current flowing through the capacitive load; and Control signal adjusting means for generating the control signal for adjusting the amount of attenuation of the high frequency component of the high frequency attenuating means in accordance with the load current estimated by the current estimating means and giving the control signal to the high frequency attenuating means.

  According to this configuration, a pseudo load having the same electrical characteristics as a capacitive load is used, a driving current is passed through the pseudo load, and the load current that flows when the actual load is driven is estimated. When the load current value increases, the amount of attenuation that attenuates the high frequency component of the drive signal is increased, and when the load current value decreases, the amount of attenuation that attenuates the high frequency component of the drive signal is decreased. This suppresses the increase in load current even when the load is capacitive and the drive signal contains a lot of high frequency components. It is possible to provide a load driving device for a piezoelectric actuator that can be suppressed to a low level and is suitable for battery-operated portable equipment such as a cellular phone.

  According to a fourth aspect of the present invention, there is provided a load driving apparatus comprising: a high-frequency attenuation unit that attenuates a high-frequency component of a drive signal input from a drive signal source with an attenuation amount according to a control signal; and the high-frequency attenuation unit. Drive means for driving the capacitive load with the passed drive signal, load current estimation means for estimating the load current based on the voltage-current characteristic equivalent value of the capacitive load, and the load estimated by the load current estimation means Control signal adjusting means for generating the control signal for adjusting the amount of attenuation of the high-frequency component of the high-frequency attenuating means according to the current and giving the control signal to the high-frequency attenuating means.

  According to this configuration, the load current is estimated from the function corresponding to the voltage-current characteristic of the capacitive load, and when the estimated load current value increases, the amount of attenuation that attenuates the high frequency component of the drive signal is increased, and the load current value When is decreased, the attenuation amount for attenuating the high frequency component of the drive signal is decreased. This suppresses the increase in load current even when the load is capacitive and the drive signal contains a lot of high frequency components. It is possible to provide a load driving device for a piezoelectric actuator that can be suppressed to a low level and is suitable for battery-operated portable equipment such as a cellular phone.

  A load driving device according to a fifth aspect of the present invention is the load driving device according to the third or fourth aspect, further comprising frequency analysis means for performing frequency analysis of the input drive signal. The high-frequency attenuation means includes frequency-specific gain operation means that divides the frequency into a plurality of bands and operates the gain for each frequency, and the control signal adjustment means uses the frequency analysis means when the load current increases. A control signal for attenuating a main high frequency component that causes an increase in load current is output from the frequency analysis result of the drive signal, and the high frequency attenuating means outputs the control signal of the drive signal according to the control signal from the control signal adjusting means. Selectively attenuates high frequency components.

  According to this configuration, only the main high-frequency component that causes an increase in load current can be attenuated, so that a low-level high-frequency component that does not contribute to an increase in load current is not attenuated. As a result, when the load is, for example, a piezoelectric speaker and the drive signal source is a sound source, the high frequency component of the audio signal is not attenuated over a wide range, but is attenuated over a narrow range, thereby minimizing deterioration in sound quality. Can be suppressed.

  According to a sixth aspect of the present invention, there is provided a load driving device according to any one of the first to fifth aspects, wherein the control signal generated by the control signal adjusting means is used as a recording medium. Recording means for recording is provided.

  According to this configuration, since the control signal indicating the amount of attenuation for attenuating the high frequency component of the drive signal is recorded on the recording medium, it is only necessary to read out the control signal corresponding to the load current from the recording medium. A process for generating a control signal is not necessary. It is also possible to give a recording medium control signal to a load driving device having the same function.

  The load driving measure of the invention according to claim 7 is generated by the control signal adjusting means using a telecommunication line in the load driving device of the invention according to any one of claims 1 to 6. Distribution means for distributing the control signal is provided.

  According to this configuration, since the control signal corresponding to the load current can be distributed via the telecommunication line, the control signal can be given to an unspecified number of portable devices including the load driving device having the same function. .

  According to an eighth aspect of the present invention, there is provided a load driving device according to any one of the first to fifth aspects, wherein the drive signal that has passed through the high-frequency attenuation means is recorded on a recording medium. Means.

  According to this configuration, since the drive signal that has passed through the high-frequency attenuation means that attenuates the high-frequency component of the drive signal is recorded on the recording medium, it is only necessary to read the drive signal from the recording medium thereafter. The process for generating the control signal is not necessary. It is also possible to give a recording medium control signal to a load driving device having the same function.

  According to a ninth aspect of the present invention, there is provided the load driving device according to any one of the first to sixth aspects, wherein the driving signal passes through the high frequency attenuating means using a telecommunication line. The distribution means for performing the distribution is provided.

  According to this configuration, the drive signal that has passed through the high-frequency attenuating means can be distributed over a telecommunication line, so that a control signal is given to a large number of unspecified portable devices having a load drive device having the same function. be able to.

  According to a tenth aspect of the present invention, there is provided a load driving method comprising: a high-frequency attenuation step for attenuating a high-frequency component of a drive signal input from a drive signal source with an attenuation amount according to a control signal; A load current acquisition step for acquiring a load current value flowing through the load, and a control for generating the control signal for adjusting the attenuation amount of the high frequency component of the drive signal supplied to the capacitive load according to the acquired load current value A signal adjustment step.

  According to this method, the load current value at the time of driving the load is obtained. When the load current value increases, the attenuation amount for attenuating the high frequency component of the drive signal is increased, and when the load current value decreases, the drive signal value is increased. Decreases the amount of attenuation that attenuates the band components. This suppresses the increase in load current even when the load is capacitive and the drive signal contains a lot of high frequency components. It becomes possible to keep the load low, and a load driving device for a piezoelectric actuator can be realized that matches battery-operated portable equipment applications such as cellular phones.

  According to the present invention, when the load current value flowing through the load increases, the attenuation amount for attenuating the high frequency component of the drive signal for driving the load is increased, and when the load current value decreases, the drive signal high value is increased. Since the amount of attenuation that attenuates the frequency component is reduced, even when the drive signal contains a lot of high frequency components, the load current can be kept low, even with capacitive loads. It is possible to provide a possible load driving device.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a load driving device according to Embodiment 1 of the present invention, and FIG. 2 is a circuit diagram showing a configuration of the device. As shown in these drawings, the load driving apparatus according to the present embodiment has the high-frequency attenuating unit 110, the load current detecting unit 130, and the control signal adjusting unit 140 described above with reference to FIG. This is different from the conventional load driving device shown in FIG.

  In FIG. 1, the load driving device according to the present embodiment has a variable high-frequency attenuating unit 110 that attenuates a high-frequency component from a signal input from the drive signal source 1, and a high-frequency attenuating unit 110 that has a high frequency range. The drive unit 120 that drives the load 2 with the attenuated drive signal, the load current detection unit 130 that detects the load current that flows through the load 2 when the drive unit 120 drives the load, and the load that is detected by the load current detection unit 130 And a control signal adjustment unit 140 that adjusts the high-frequency attenuation in the high-frequency attenuation unit 110 based on the current.

  The high frequency attenuating unit 110 selectively attenuates high frequency band components such as LPF (low frequency attenuating filter), for example, and the attenuation amount and cut-off frequency are determined by a control signal to an attached control input terminal. It is moderated. The output of the high-frequency attenuating unit 110 is input to the driving unit 120 and drives a capacitive load 2 such as a piezoelectric actuator. The load current detection unit 130 detects the current flowing through the load 2 directly or indirectly as described below, and generates a signal corresponding to the detected load current. The output signal of the load current detection unit 130 is subjected to processing according to the behavior of the load 2 such as rectification, dead band setting, attack time and recovery time by the control signal adjustment unit 140 in the subsequent stage, and then the high-frequency attenuation unit 110 Is applied as a control signal to adjust the amount of the high frequency component of the signal output from the drive unit 120.

  In FIG. 2, the high-frequency attenuating unit 110 includes an LPF (low-pass filter) 11 having a fixed cutoff frequency, a resistor 12, a variable capacitor (for example, a variable capacitor) 13 that can change capacitance, and a buffer amplifier 14. It consists of. The resistor 12 and the variable capacitor 13 constitute a primary LPF, and the cutoff frequency is adjusted by changing the capacitance of the variable capacitor 13. The LPF 11 is a filter that sets the upper frequency limit of the high-frequency attenuating unit 110, and prevents an increase in load current due to unnecessary high-frequency noise such as clock leakage from a digital circuit, for example. Therefore, the upper limit of the cutoff frequency of the high frequency attenuating unit 110 is the cutoff frequency of the LPF 11, and works as an LPF whose cutoff frequency can be controlled by the control signal adjustment unit 140.

  The driving unit 120 has a BTL configuration including a non-inverting voltage amplifier 21, an inverting voltage amplifier 26, a driving output unit 22, and a driving output unit 27, and the polarities are inverted at both ends of the load 2. Since the signal is applied, a peak voltage close to a positive value or a negative value close to the voltage value of the power source 3 can be supplied to the load 2. Therefore, it is suitable for a piezoelectric actuator having a higher drive voltage than an electrodynamic type.

  The load current detection unit 130 includes a transistor 24 and a transistor 29 that constitute the drive output unit 22 and the drive output unit 27, and a resistor 31, and flows to the load 2 by causing each collector current to flow through the resistor 31. The absolute value of the current is indirectly detected. When such a drive unit 120 is configured as a BTL, the load currents in the positive and negative directions flow as collector currents to the transistors in the drive output unit 22 and the drive output unit 27, respectively. By combining, the rectifier circuit for obtaining the absolute value of the load current to be provided in the control signal adjustment unit as in the above configuration is not necessary. The terminal voltage of the resistor 31 proportional to the absolute value of the load current is adjusted by the control signal adjusting unit 140 such as amplification by the amplifier 41, smoothing by the diode 42, the capacitor 43 and the resistor 44, and attack time and release time. As a smooth control signal, the high-frequency attenuation unit 110 is used for control.

  Next, regarding the operation of the load driving device according to the present embodiment, in addition to FIGS. 1 and 2, a plot of the load driving voltage and load current with respect to the signal frequency of FIG. 3 and the load driving device of FIG. A specific description will be given together with a spectrum distribution at the time of sweeping a sine wave of a signal generated by signal processing.

  1 and 2, the signal output from the driving signal source 1 is amplified by the non-inverting voltage amplifier 21 and the inverting voltage amplifier 26 having different output polarities in the driving unit 120 via the high frequency attenuating unit 110. Thereafter, power is amplified by each of the drive output unit 22 and the drive output unit 27, and appears at points P and N, which are output terminals, to supply power to the load 2. That is, when the signal from the drive signal source 1 is positive, the voltage at the point P is larger than that at the point N and supplies a positive voltage to the load 2. When it is negative, the voltage at the point P is smaller than that at the point N and supplies a negative voltage to the load 2.

  Therefore, when the signal from the drive signal source 1 is positive, the current is the power source 3 → the collector / emitter of the output transistor 23 → (point P) the load 2 (point N) → the emitter / collector of the output transistor 29 → resistor. It flows in the path of 31 → ground. On the other hand, when the signal from the drive signal source 1 is negative, the current is symmetrical to the power source 3 → the collector / emitter of the output transistor 28 → (point N) load 2 (point P) → output transistor 24. It flows in the path of emitter-collector → resistor 31 → ground.

  Since the current passing through the load 2 flows through the resistor 31 in any polarity, the voltage generated between the terminals is proportional to the absolute value obtained by rectifying the load current. Here, the value of the resistor 31 needs to be reduced. This is because when the voltage drop of the resistor 31 is increased, the lower limit values of the output voltages of the drive output unit 22 and the drive output unit 27 are increased due to the circuit configuration, and the maximum value of the drive voltage is decreased. The voltage proportional to the rectified load current is once amplified by the amplifier 41, and then smoothed by the diode 42, the capacitor 43, and the resistor 44, and becomes a smooth control signal to set the cutoff frequency of the high frequency attenuating unit 110. Control. Here, the diode 42 uses the forward voltage value to generate a dead zone that stops control when the load current is small, and the diode 42 and the capacitor 43 determine an attack time that responds to a sudden increase in load current, The capacitor 43 and the resistor 44 determine a recovery time for slowly returning to a steady state with respect to a decrease in load current.

  The control in FIG. 2 proceeds as follows according to the signal. That is, the increase of the high frequency component of the input signal → the current of the load 2 temporarily increases due to the response delay of the high frequency attenuation unit 110 → the voltage across the terminals of the resistor 31 → the output voltage of the control signal adjustment unit 140 increases → Increase in high-frequency attenuation of high-frequency attenuating section 110 → Decrease in high-frequency component of this output signal → Decrease in current of load 2 Further, the voltage across the resistor 31 decreases → the output voltage of the control signal adjustment unit 140 decreases → the high-frequency attenuation of the high-frequency attenuation unit 110 decreases → the output signal The negative feedback operation is performed such that the high-frequency component is increased and the current of the load 2 is increased to exhibit a reverse reaction.

  Here, the gain and time constant of the control signal adjustment unit 140 are set so as to stabilize this negative feedback. Finally, the system of FIG. 1 automatically selects a stable cut-off frequency according to the frequency spectrum distribution and amplitude of the input signal, and suppresses the load current, that is, the power supply current when the high frequency component of the input signal is large. Thus, the heat generation of the drive output units 22 and 27 can also be suppressed. Here, when the high frequency component of the input signal further decreases or the signal level itself decreases, the cutoff frequency of the high frequency attenuating unit 110 increases, and approaches the cutoff frequency of the LPF 11 that is the upper limit of the cutoff frequency. When the dead band of the diode 42 of the control signal adjustment unit 140 is not exceeded, the cutoff frequency of the high-frequency attenuation unit 110 remains at the upper limit, so that the frequency spectrum of the drive voltage supplied to the load 2 by the drive unit 120 No change occurs, and the characteristics are the same as those of the conventional drive unit 220 (FIG. 9).

  Next, the frequency characteristics of the load driving device according to the present embodiment and the increasing tendency of the load current will be described with reference to FIG. FIG. 3 is a plot of the drive voltage of the load 2 and the load current passing through the load 2 when the cutoff frequency of the high-frequency attenuating unit 110 is set separately and a sine wave of a certain level is swept in frequency. Since the absolute value of the load current of the load 2 has the same magnitude as the current flowing out from the power source 3 toward the drive output units 22 and 27 in the circuit configuration, the current axis of the Y axis in FIG. You can think.

  In FIG. 3, plots (i1) and (e1) are for the case where there is no attenuation in the high-frequency attenuation unit 110, and the drive voltage (e1) is constant regardless of the frequency, but the load current (i1) Increases at +6 dB / Oct in proportion to the increase in frequency from the impedance characteristic of the load 2. Plots (i2) and (e2) are obtained by setting the cutoff frequency of the high-frequency attenuation unit 110 to the upper limit of 16 KHz and setting the attenuation shoulder characteristic to −6 dB / Oct, and the drive voltage (e2). Decreases at −6 dB / Oct from the vicinity of the cutoff frequency, and the load current (i2) stops increasing from the vicinity of the cutoff frequency. The disappearance of the increasing tendency of the load current above the cut-off frequency is a result of offsetting the +6 dB / Oct increasing tendency of the load current due to the decrease of the load impedance and the -6 dB / Oct decreasing tendency of the driving voltage. The next plots (i3) and (e3), (i4) and (e4), (i5) and (e5) are, in order, the load current when the cutoff frequency of the high-frequency attenuation unit 110 is set low. It is a plot of a drive voltage. In either case, the attenuation shoulder characteristic is −6 dB / Oct.

  Since these only differ in the cut-off frequency as compared with the high-frequency attenuator 110 in plots (i2) and (e2), the drive voltage plot is directed toward the frequency axis (X axis) according to the cut-off frequency. It will be a low frequency shift. On the other hand, with respect to the load current plot, the current increase stops at the cut-off frequency of the drive voltage or higher. Therefore, the lower the cut-off frequency, the smaller the passing current and the less the power supply current flowing out from the power source 3. Go. The cut-off frequency characteristics in these plots change continuously depending on the magnitude of the high frequency component included in the input signal. For example, the plots (i2) and (e2) are the high frequency components of the input signal in the above operation. The input signal is amplified almost as it is and supplied to the load 2, but the plots (i3), (e3), (i4), (e4), (i5) increase as the high frequency component increases. ) And (e5) in this order, so that the high range is attenuated, and works to suppress an increase in load current.

  In the description of the plots in FIG. 3 so far, all the attenuation shoulder characteristics above the cutoff frequency are set to −6 dB / Oct. However, if this attenuation shoulder characteristic is reinforced to −18 dB / Oct, The current plot tends to increase up to the vicinity of the cutoff frequency, but starts to decrease at higher frequencies and decreases at −12 dB / Oct. Thus, by making the attenuation shoulder characteristic of the high-frequency attenuating unit 110 a second-order or higher-order type, an increase in current due to a high-frequency component of the input signal can be effectively suppressed.

  In the operation of FIG. 3 described above, the drive signal of the drive signal source 1 is a sine wave having a single spectrum and is a sweep signal with a constant magnitude, but the actual drive signal has many spectra, The size of fluctuates. In the case of such a drive signal, the power supply current flowing from the power source 3 to the drive unit 120 is an average value obtained by integrating the current value in the equal minute bandwidth for each frequency in the signal waveform of the drive signal source 1 over the entire band. become. This current value is the area surrounded by this plot and the frequency axis when the spectrum of the signal is plotted on the coordinates where the X axis is the frequency and the Y axis is the current value in the equal minute bandwidth.

  If a white noise input signal having a uniform spectrum is applied, the current increases in proportion to the frequency. This plot is a logarithmic scale with the frequency axis and current axis of FIG. 3 linearly redrawn, and as the current increases rapidly at a high frequency, the frequency width increases in the same way. Obviously, the increase in area becomes significant. That is, the contribution rate of the high frequency component in the power supply current is extremely high. Therefore, the current reduction effect by the amplitude attenuation operation of the high frequency component in the load 2 becomes very large.

  On the other hand, side effects due to the operation of the high frequency component of the signal must be taken into account.For example, in the case of an acoustic signal such as a piezoelectric speaker, considering the influence of human auditory characteristics, The effect of attenuation is not so great. In other words, the frequency characteristic of human auditory sensitivity when the sound pressure is low is a thick mountain shape with low sensitivity at high and low frequencies, but it approaches flatness as the sound pressure increases. This is because, in the sound source made, when the sound pressure becomes high, the sensitivity increase in the high frequency range and the low frequency range tends to be annoying. In addition to this, since the high frequency component in the actual voice or musical tone signal is often a harmonic component of the fundamental tone, the adverse effect of some high frequency attenuation is less than that of the current reduction effect.

  Next, with reference to FIG. 4, a spectrum distribution at the time of sweeping a sine wave of a signal generated by the load driving device according to the present embodiment will be described. Although FIG. 3 shows the response when the cutoff frequency of the high-frequency attenuation unit 110 is fixedly set, FIG. 4 shows the response based on the control signal obtained by the load current detection unit 130 and the control signal adjustment unit 140. The cut-off frequency of the band attenuating unit 110 changes, and as a result, the response of the signal that drives the resulting load (the load applied to the driving unit 120) is shown. This characteristic is the same as the spectrum of the signal that drives the load when the white noise-like signal having the broadband spectrum described above is applied (here, since the frequency axis is logarithmic, strictly speaking, The drive signal source is pink noise with the same energy per octave).

  According to FIG. 4, according to the configuration of the present invention, the processing of the present invention is simply shown as to how the drive signal source 1 is operated in accordance with the level of the pass signal spectrum. That is, as described in the above operation, while the signal level is small, the spectrum does not change particularly, but as the level increases, the attenuation in the high band increases. And even if the signals have different levels, the attenuation shoulder characteristics at which high-frequency attenuation starts approaching one sloping line that goes down to the right. In the case of driving with a sine wave, due to the circuit configuration, this inclined line has a driving voltage value corresponding to the upper limit of the current flowing through the load 2.

  As described above, according to the load driving apparatus according to the present embodiment, after the high frequency attenuating unit 110 attenuates the high frequency of the driving signal from the driving signal source 1 according to the control signal, the driving unit is driven by the driving signal. 120 drives the load 2. Then, the load current detection unit 130 detects the load current after driving the load, and gives the result to the control signal adjustment unit 140. The control signal adjustment unit 140 determines the load current value from the load current detection result of the load current detection unit 130. Increases the attenuation of the high-frequency component of the high-frequency attenuation unit 110, and decreases the attenuation of the high-frequency component of the high-frequency attenuation unit 110 when the load current value decreases. And the increase of the power supply current (current flowing out from the power source 3) linked with this is suppressed. As a result, it is possible to reduce the battery life and the amount of heat generated by the output transistor of the driving unit 120, and a load driving device for a piezoelectric actuator that is suitable for battery-operated portable equipment such as a cellular phone. realizable.

  In the present embodiment, the resistor 31 for detecting the load current is provided between the drive output units 22 and 27 and the ground, but the positive side of the drive output units 22 and 27 and the power source 3, that is, the power source side. Functions and effects are the same even if they are provided between the two.

  In this embodiment, a linear class AB amplifier is used for the drive unit 120. However, a switching class D amplifier may be used, and the same effect can be obtained by using it.

  In the present embodiment, the high frequency component of the drive signal is manipulated by the high frequency attenuating unit 110, but other bands may be manipulated according to the size of the drive signal source and its spectrum. When a function such as AGC (automatic gain adjustment) or ALC (automatic level adjustment) is provided, it is possible to have an effect of suppressing generation of distortion due to saturation of the drive unit 120 in an excessive signal.

  In the present embodiment, the high-frequency attenuating unit 110 is configured with an LPF. However, the high-frequency component to be operated may be a main high-frequency component that causes an increase in load current. A method of giving a stepped frequency characteristic that selectively attenuates the band components or uniformly attenuates the entire high frequency band may be used.

  Further, in the present embodiment, the drive signal input from the drive signal source is obtained by operating the high-frequency attenuator sequentially by the generated control signal to obtain a drive signal that has passed through this. The drive signal processed in step 1 may be recorded on a recording medium. As described above, once recording is performed, it is only necessary to read the processed drive signal from the recording medium and drive the load by the drive unit. Therefore, in a portable device having such a configuration, a processing circuit that generates a control signal is not necessary, and power consumption can be reduced. In this way, the processed drive signal is not only recorded on the recording medium, but also by distribution via a telecommunication line, the same effect can be obtained by receiving and driving it. In this configuration, the boundary between the production side and the use side of the drive signal in the present embodiment may be considered to be set on the output side of the high-frequency attenuation unit. Here, the drive signal production side is recording on a recording medium or sending to a telecommunication line, and the drive signal utilization side is a device including an actuator to be driven.

  Further, in the configuration provided with the recording medium and the distribution path in the present embodiment as described above, a configuration in which the boundary between the production side and the usage side of the drive signal is set to the input side of the high-frequency attenuation unit, that is, not yet. Both the drive signal of the processing drive signal source and the control signal for operating the high-frequency attenuation unit may be paired and sent to the recording medium or transmitted to the transmission path. In this case, since the drive signal of the unprocessed drive signal source reaches the use-side device, this information can be used even in a device using an electrodynamic actuator that does not require a high-frequency attenuation unit. Become. That is, the piezoelectric actuator mounting side device includes a high-frequency attenuation unit and a drive unit, the drive signal is applied to the signal input end of the high-frequency attenuation unit, and the control signal is applied to the control input end. On the other hand, on the electrodynamic actuator-equipped device side, it is not necessary to attenuate the high range, and it can be configured only by a drive unit that drives an unprocessed drive signal. Therefore, on the production side, the same signal can be recorded or distributed for electrodynamic equipment and piezoelectric equipment.

(Embodiment 2)
FIG. 5 is a block diagram showing the configuration of the load driving apparatus according to Embodiment 2 of the present invention. In FIG. 5, the load drive device according to the present embodiment is obtained by replacing the load current detection unit 130 in the load drive device according to the first embodiment described above with a temperature detection unit 250. The high frequency attenuating unit 110 attenuates the high frequency component from the high frequency component of the drive signal input from the drive signal source 1. The high frequency attenuating unit 110 selectively attenuates high frequency band components such as LPF (low frequency attenuating filter), for example, and the attenuation amount and cut-off frequency are control signals to an attached control input terminal. It is adjusted by. The drive signal that has passed through the high frequency attenuating unit 110 is input to the drive unit 220 to drive the load 2 such as a piezoelectric actuator. The temperature detection unit 250 mainly detects the temperature of the output stage transistor of the drive unit 220.

  The output signal of the temperature detection unit 250 is input to the control signal adjustment unit 240 in the subsequent stage, and after being subjected to processing according to the behavior of the load 2 such as rectification, dead band setting, attack time and recovery time, the high frequency attenuation unit 110 is applied as a control signal, and the amount of the high frequency component of the signal output from the drive unit 220 is adjusted. Here, as a specific circuit, the temperature detector 250 is a current source that generates a current that is proportional to the absolute temperature and inversely proportional to the resistance value (for example, Japanese Patent Application Laid-Open No. 60-191508 “Current Current”). The temperature detecting function can be provided by disposing this in the vicinity of the driving unit 220. The circuit of the drive unit 220 is the same as that of the conventional drive unit 220 (see FIG. 9), and the other circuits are the same as those of the load drive device according to the first embodiment shown in FIG. .

  As described above, the point that the load current detection unit 130 is replaced with the temperature detection unit 250 is different from the first embodiment, but the basic operation is similar to the operation of the first embodiment described above. . The replacement here is made by paying attention to the following points, so the basic idea and effect are almost the same. That is, in the first embodiment described above, the load current is directly measured, and the high frequency component of the signal is controlled based on this, and the heat generation is subordinately suppressed. Then, the heat generation of the output transistor of the drive unit 220 is directly measured, and the high frequency component of the signal is controlled based on this, and the load current is subordinately suppressed.

  In the load driving device configured as described above, when detecting the accurate temperature of the output transistor that constitutes the drive output unit of the drive unit 220 (same as the drive output units 22 and 27 in FIG. 2), the temperature detection unit 250 The output transistors (same as the transistors 23, 24, 28, and 29 in FIG. 2) constituting the drive output unit must be arranged so that close thermal coupling can be obtained. It is best to form it on the same semiconductor integrated circuit.

  When these transistors are integrated on a semiconductor integrated circuit, the speed of heat transfer between adjacent transistors on the same semiconductor substrate is high, but it is affected by the LPF effect due to the thermal resistance and specific heat of the semiconductor material and package. Since the signal is converted into heat, the output signal of the temperature detection unit 250 has already been subjected to the root mean square process, and thus there is an advantage that the process in the control signal adjustment unit 240 can be simplified. The operation of the other blocks is the same as that of the first embodiment described above, and the cut-off frequency of the high frequency attenuating unit 110 is controlled by the control signal adjusting unit 240, and the control signal adjusting unit 240 performs smoothing. In addition, the attack time, the release time, and the like are adjusted, and the control is performed for the control of the high frequency attenuating unit 110 as a smooth control signal.

  Next, the main part of the operation of the load driving device according to the present embodiment is the same as that of the load driving device according to the first embodiment, and the operation of the load current detection unit 130 (see FIG. 1) is the temperature. The part replaced with the detection unit 250 is different. That is, in the load drive device (see FIG. 5) according to the second embodiment, the drive output unit (similar to the drive output units 22 and 27) of the drive unit 220 generates heat as the load current increases, and this is detected by temperature detection. Therefore, the output voltage of the control signal adjustment unit 240 is increased, and the high frequency attenuation unit 110 finally attenuates the high frequency component. Therefore, the high frequency component dominant to the passing current of the capacitive load 2 is reduced, the amount of heat generated in the drive output unit of the drive unit 220 is reduced, the output voltage of the control signal adjusting unit 240 is reduced, and the high frequency attenuation unit 110 is reduced. The amount of attenuation of the high-frequency component decreases at, and normal operation resumes.

  Thus, the control in FIG. 5 proceeds as follows according to the signal. That is, the increase of the high frequency component of the input signal → the current of the load 2 temporarily increases due to the response delay of the high frequency attenuation unit 110 → the temperature of the drive output unit → the output of the temperature detection unit 250 → the control signal adjustment unit The operation is as follows: the output voltage of 240 increases, the increase of the high-frequency attenuation of the high-frequency attenuation section 110 increases, the high-frequency component of this output signal decreases, and the current of the load 2 decreases. Then, further (decrease in the current of the load 2 →) temperature decrease of the drive output unit → output of the temperature detection unit 250 decreases → output voltage of the control signal adjustment unit 240 decreases → high frequency attenuation amount of the high frequency attenuation unit 110 Decrease → High frequency component of this output signal is increased → Current of load 2 is increased. Negative feedback operation is performed so as to exhibit a reverse reaction.

  Here, the gain and time constant of the control signal adjustment unit 240 are set in consideration of the response characteristics of the temperature detection unit 250 so as to stabilize the negative feedback. Finally, the system of FIG. 5 automatically selects a stable cut-off frequency according to the frequency spectrum distribution and amplitude of the input signal, and suppresses the load current, that is, the power supply current when the high frequency component of the input signal is large. Thus, the heat generation of the drive output unit can also be suppressed.

  Here, when the high frequency component of the input signal further decreases or the signal level itself decreases, the cutoff frequency of the high frequency attenuating unit 110 increases, and approaches the cutoff frequency of the LPF 11 that is the upper limit of the cutoff frequency. When the level does not exceed the dead band of the control signal adjustment unit 240, the cutoff frequency of the high-frequency attenuation unit 110 remains at the upper limit, so that the frequency spectrum of the drive voltage supplied to the load 2 by the drive unit 220 is changed. It does not occur and becomes the same as the characteristics of the conventional drive unit 220 (see FIG. 9).

  As described above, according to the load driving device according to the present embodiment, the load driving device according to the first embodiment described above detects the load current and knows the increase in the load current. The increase in the load current is detected by the heat generated in the drive output unit, and the basic operation and effect and the plot shown in FIG. 3 of the first embodiment have the same characteristics in this embodiment. Is.

Therefore, in the load drive device according to the present embodiment, after the high frequency attenuating unit 110 attenuates the high frequency of the drive signal from the drive signal source 1 according to the control signal, the drive unit 220 uses the drive signal to load the load 2. To drive. Then, the temperature detection unit 250 detects the temperature based on the power consumption by the load current, and gives the result to the control signal adjustment unit 240. The control signal adjustment unit 240 increases the temperature value from the temperature detection result of the temperature detection unit 250. In this case, the attenuation amount of the high-frequency component of the high-frequency attenuation unit 110 is increased, and when the temperature value decreases, the attenuation amount of the high-frequency component of the high-frequency attenuation unit 110 is decreased, thereby suppressing an increase in load current. The increase of the power supply current (current flowing out from the power source 3) linked with this is suppressed. As a result, the battery life is reduced and the drive output unit (
The heat generation amount of the output transistor) can be kept low, and a load driving device for a piezoelectric actuator that matches the battery-operated portable device application such as a cellular phone can be realized.

  In this embodiment, a linear class AB amplifier is used for the drive unit 120. However, a switching class D amplifier may be used, and the same effect can be obtained by using it.

  In the present embodiment, the high frequency component of the drive signal is manipulated by the high frequency attenuating unit 110, but other bands may be manipulated according to the size of the drive signal source and its spectrum. When a function such as AGC (automatic gain adjustment) or ALC (automatic level adjustment) is provided, it is possible to have an effect of suppressing the occurrence of distortion due to saturation of the drive unit 220 in an excessive signal.

  In the present embodiment, the high-frequency attenuating unit 110 is configured with an LPF. However, the high-frequency component to be operated may be a main high-frequency component that causes an increase in load current. A method of giving a stepped frequency characteristic that selectively attenuates the band components or uniformly attenuates the entire high frequency band may be used.

  Further, in the present embodiment, the drive signal input from the drive signal source is obtained by operating the high-frequency attenuator sequentially by the generated control signal to obtain a drive signal that has passed through this. The drive signal processed in step 1 may be recorded on a recording medium. As described above, once recording is performed, it is only necessary to read the processed drive signal from the recording medium and drive the load by the drive unit. Therefore, in a portable device having such a configuration, a processing circuit that generates a control signal is not necessary, and power consumption can be reduced. In this way, the processed drive signal is not only recorded on the recording medium, but also by distribution via a telecommunication line, the same effect can be obtained by receiving and driving it. In this configuration, the boundary between the production side and the use side of the drive signal in the present embodiment may be considered to be set on the output side of the high-frequency attenuation unit. Here, the drive signal production side is recording on a recording medium or sending to a telecommunication line, and the drive signal utilization side is a device including an actuator to be driven.

  Further, in the configuration provided with the recording medium and the distribution path in the present embodiment as described above, a configuration in which the boundary between the production side and the usage side of the drive signal is set to the input side of the high-frequency attenuation unit, that is, not yet. Both the drive signal of the processing drive signal source and the control signal for operating the high-frequency attenuation unit may be paired and sent to the recording medium or transmitted to the transmission path. In this case, since the drive signal of the unprocessed drive signal source reaches the use-side device, this information can be used even in a device using an electrodynamic actuator that does not require a high-frequency attenuation unit. Become. That is, the piezoelectric actuator mounting side device includes a high-frequency attenuation unit and a drive unit, the drive signal is applied to the signal input end of the high-frequency attenuation unit, and the control signal is applied to the control input end. On the other hand, on the electrodynamic actuator-equipped device side, it is not necessary to attenuate the high range, and it can be configured only by a drive unit that drives an unprocessed drive signal. Therefore, on the production side, the same signal can be recorded or distributed for electrodynamic equipment and piezoelectric equipment.

(Embodiment 3)
FIG. 6 is a block diagram showing the configuration of the load driving device according to Embodiment 3 of the present invention, and FIG. 7 is a circuit diagram showing the configuration of the device. The main difference from the load driving apparatus according to the first embodiment described above (see FIG. 1) is that the load current detecting unit 130 in FIG. 1 is replaced with the load current estimating unit 360. This configuration is a feed-forward type control that obtains an original signal for control of the high-frequency attenuating unit 110 from the input side of the high-frequency attenuating unit 110, and the load driving device according to the first embodiment described above and As in the load driving device according to the second embodiment (see FIG. 5), this is different from feedback-type control in which an original signal used for control is obtained from the output side of the high-frequency attenuation unit 110. However, such a difference does not affect the effect, and also in this embodiment, it can be easily replaced with feedback type control depending on how the original signal used for control is extracted, and the same effect can be obtained.

  In FIG. 6, a high frequency attenuating unit 110 is a variable attenuator that attenuates a high frequency component from the drive signal input from the drive signal source 1. For example, a high frequency attenuator such as an LPF (low frequency attenuating filter) is used. The frequency band component is selectively attenuated, and the attenuation amount and cut-off frequency are adjusted by a control signal to an attached control input terminal. The drive signal output from the high-frequency attenuation unit 110 is input to the drive unit 220, and drives a capacitive load 2 such as a piezoelectric actuator. The configuration up to this point is the same as that of the load driving device according to the first embodiment.

  The load current estimation unit 360 includes a pseudo load unit 361 having impedance characteristics similar to those of the load 2 and a pseudo load current detection unit 362 that detects a current flowing through the pseudo load unit 361. The output signal of the load current estimation detection unit 360 is subjected to processing according to the behavior of the load 2 such as rectification, dead band setting, attack time and recovery time by the control signal adjustment unit 340 in the subsequent stage, and then the high frequency attenuation unit 110 Is applied as a control signal to adjust the amount of the high frequency component of the signal output from the drive unit 220.

  In FIG. 7, the high-frequency attenuating unit 110 includes an LPF 11 having a fixed cutoff frequency, a resistor 12, a variable capacitor 13 that can vary the capacitance, and a buffer amplifier 14. The resistor 12 and the variable capacitor 13 constitute a primary LPF, and the cutoff frequency can be adjusted by changing the capacitance of the variable capacitor 13. The LPF 11 is a filter that sets the upper frequency limit of the high frequency attenuating unit 110, and prevents an increase in load current due to unnecessary high frequency noise such as clock leakage from a digital circuit, for example. Therefore, the upper limit of the cutoff frequency of the high-frequency attenuating unit 110 is the cutoff frequency of the LPF 11, and functions as an LPF that can control the cutoff frequency by the control signal adjustment unit 340.

  Next, the driving unit 220 has a BTL configuration including a non-inverting voltage amplifier 21, an inverting voltage amplifier 26, and driving output units 22 and 27, and signals having opposite polarities at both ends of the load 2. Therefore, a peak voltage close to a positive value or a negative value close to the voltage value of the power source 3 can be supplied to the load. Therefore, it is suitable for a piezoelectric actuator having a higher drive voltage than an electrodynamic type. Up to this point, the configuration is the same as that of the first embodiment.

  On the other hand, the pseudo load unit 361 is a circuit network having impedance characteristics similar to those of the load 2, and when the load 2 is a piezoelectric actuator, the circuit network may be considered as a capacitor. A voltage of the drive signal source 1 that is a signal on the input side of the high frequency attenuating unit 110 is applied to one end of the pseudo load unit 361, and a virtual voltage configured by an operational amplifier 364 and a current-voltage conversion resistor 363 is applied to the other end. It is connected to a pseudo load current detector 362 that receives the ground point as an input. For this reason, the voltage of the drive signal source 1 is applied between both terminals of the pseudo load unit 361, and the current passing therethrough is substantially proportional to the relationship between the drive voltage applied to the actual load 2 and its impedance. It becomes the size.

  Then, the current flowing through the pseudo load unit 361 is converted into a voltage proportional to the current value flowing through the pseudo load unit 361 by the current-voltage conversion resistor 363, and is supplied to the high frequency attenuating unit 110 via the control signal adjusting unit 340. Supplied as a control signal. The control signal adjustment unit 340 includes a polarity inverter composed of a resistor 45, a resistor 46, and an operational amplifier 48 and diodes 42 and 43 for both-wave rectification of a voltage proportional to the pseudo load current. A capacitor 43 and a resistor 44 are provided to adjust the attack time, release time, and the like to obtain a smooth control signal.

  Next, the operation of the load driving device according to the present embodiment will be described. 6 and 7, the driving signal output from the driving signal source 1 is amplified by the non-inverting voltage amplifier 21 and the inverting voltage amplifier 26 having different output polarities in the driving unit 220 via the high frequency attenuating unit 110. After that, power is amplified by each of the drive output units 22 and 27 and appears at points P and N which are the output terminals, and power is supplied to the load 2.

  On the other hand, due to the circuit configuration, the voltage of the drive signal source 1 is applied between the terminals of the pseudo load unit 361, and the current passing therethrough is converted into a voltage by the pseudo load current detection unit 362. The magnification of current-voltage conversion in the pseudo load current detection unit 362 can be freely set by the value of the resistor 363. Therefore, in order to reduce the power consumption of the circuit and reduce the value of the capacitor serving as the pseudo load unit 361, it is preferable to set the current passing through the pseudo load current detection unit 362 to be low.

  Here, since the impedance characteristic of the pseudo load unit 361 is similar to the impedance of the load 2, the voltage value obtained by the pseudo load current detection unit 362 should be high if the high frequency attenuation of the high frequency attenuation unit 110 is small. The amount is almost proportional to the current flowing through the load 2. Next, the control signal adjustment unit 340 rectifies a signal that changes positively or negatively depending on the direction of the current flowing through the pseudo load unit 361 to a positive polarity, and then smoothes the signal by the capacitor 43 and the resistor 44 to obtain a smooth control signal. Thus, the cutoff frequency of the high-frequency attenuation unit 110 is controlled. Here, the diodes 42 and 47 use the forward voltage value to generate a dead zone that stops control when the load current is small, and the diodes 42 and 47 and the capacitor 43 attack quickly responding to a sudden increase in load current. The capacitor 43 and the resistor 44 determine the recovery time for slowly returning to the steady state with respect to the decrease in the load current.

  The control in FIG. 7 proceeds as follows according to the signal. That is, the increase of the high frequency component of the input signal → the load current temporarily increases due to the response delay of the high frequency attenuation unit 110 → the current of the pseudo load unit 361 also increases → the output voltage of the pseudo load current detection unit 362 increases → control The output voltage of the signal adjustment unit 340 increases → the high frequency attenuation amount of the high frequency attenuation unit 110 increases → the high frequency component of this output signal decreases → the current of the load 2 decreases → the current of the pseudo load unit 361 also decreases It works like this. Further, (the decrease in the current of the load 2 → the current in the pseudo load unit 361 also decreases) → the output voltage of the pseudo load current detection unit 362 decreases → the output voltage of the control signal adjustment unit 340 decreases → the high frequency attenuating unit 110 The high frequency component of the output signal increases, the current of the load 2 increases, and the current of the pseudo load unit 361 also increases.

  Finally, the system shown in FIG. 7 is stable according to the frequency spectrum distribution and amplitude of the input signal by appropriately setting the gain of the control signal adjustment unit 340 and the sensitivity of the control input terminal of the high-frequency attenuation unit 110. The cut-off frequency is automatically selected, and the load current when the high frequency component of the input signal is large, that is, the power supply current is operated to be kept low, thereby suppressing the heat generation of the drive output units 22 and 27. . Here, when the high frequency component of the input signal further decreases or the signal level itself decreases, the cutoff frequency of the high frequency attenuating unit 110 increases, and approaches the cutoff frequency of the LPF 11 that is the upper limit of the cutoff frequency. When the dead band of the diodes 42 and 47 of the control signal adjustment unit 340 is not exceeded, the cutoff frequency of the high-frequency attenuation unit 110 remains at the upper limit, so that the drive voltage of the drive voltage supplied to the load 2 by the drive unit 220 is maintained. The frequency spectrum does not change and is similar to the characteristics of the conventional drive unit 220 (see FIG. 9).

  As described above, in the load drive device according to the present embodiment, after the high frequency attenuating unit 110 attenuates the high frequency of the drive signal from the drive signal source 1 according to the control signal, the drive unit 220 is driven by the drive signal. The load 2 is driven. The drive signal from the drive signal source 1 is applied to the pseudo load unit 361 having impedance characteristics similar to those of the load 2, the pseudo load current detection unit 362 detects a pseudo load current similar to the load 2, and the control signal adjustment unit 340 According to the detection result of the pseudo load current detection unit 362, when the pseudo load current value increases, the attenuation amount of the high frequency component of the high frequency attenuation unit 110 is increased, and when the pseudo load current value decreases, the high frequency attenuation unit 110 increases. By reducing the attenuation of the band component, an increase in the load current is suppressed, and an increase in the power source current (current flowing out from the power source 3) associated therewith is suppressed. As a result, it is possible to reduce the battery life and the amount of heat generated by the output transistor of the drive unit 220 to be low, and a load driving device for a piezoelectric actuator that matches battery-operated portable equipment applications such as a cellular phone. realizable.

  In this embodiment, as described at the beginning, feed-forward control is performed in which a signal on the input side of the high-frequency attenuation unit 110 is applied to the load current estimation unit 360 in order to estimate the load current. The load current estimation unit 360 may be configured to apply a signal on the output side of the high frequency attenuating unit 110, and in this case, feedback type control is performed. Even with such a configuration, the same effect as the configuration of FIG. 6 as described above can be obtained.

  In this embodiment, a linear class AB amplifier is used for the drive unit 220. However, a switching class D amplifier may be used, and the same effect can be obtained by using it.

  In the present embodiment, the high frequency component of the drive signal is manipulated by the high frequency attenuating unit 110, but other bands may be manipulated according to the size of the drive signal source and its spectrum. When a function such as AGC (automatic gain adjustment) or ALC (automatic level adjustment) is provided, it is possible to have an effect of suppressing the occurrence of distortion due to saturation of the drive unit 220 in an excessive signal.

  In the present embodiment, the high-frequency attenuating unit 110 is configured with an LPF. However, the high-frequency component to be operated may be a main high-frequency component that causes an increase in load current. A method of giving a stepped frequency characteristic that selectively attenuates the band components or uniformly attenuates the entire high frequency band may be used.

  In particular, when a high level component at a specific level is selectively attenuated, the load current estimation unit 360 is provided with frequency analysis means (not shown) for frequency analysis of the drive signal, and the high frequency attenuation unit 110 has a frequency. May be divided into a plurality of bands, and frequency-specific gain operation means (not shown) for operating the gain for each frequency may be provided. In this case, when the load current increases, the control signal adjustment unit 340 outputs a control signal for attenuating a main high frequency component that causes an increase in the load current from the frequency analysis result of the drive signal by the frequency analysis means. The high frequency attenuating unit 110 selectively attenuates the high frequency part of the drive signal according to the control signal from the control signal adjusting unit 340.

  With this configuration, it is possible to attenuate only the main high-frequency component that causes an increase in load current, and it is not possible to attenuate a low-level high-frequency component that does not contribute to an increase in load current. As a result, when the load is, for example, a piezoelectric speaker and the drive signal source is a sound source, the high frequency component of the audio signal is not attenuated over a wide range, but is attenuated over a narrow range, thereby minimizing deterioration in sound quality. It becomes possible to suppress to.

  Further, in the present embodiment, the drive signal input from the drive signal source is obtained by operating the high-frequency attenuator sequentially by the generated control signal to obtain a drive signal that has passed through this. The drive signal processed in step 1 may be recorded on a recording medium. As described above, once recording is performed, it is only necessary to read the processed drive signal from the recording medium and drive the load by the drive unit. Therefore, in a portable device having such a configuration, a processing circuit that generates a control signal is not necessary, and power consumption can be reduced. In this way, the processed drive signal is not only recorded on the recording medium, but also by distribution via a telecommunication line, the same effect can be obtained by receiving and driving it. In this configuration, the boundary between the production side and the use side of the drive signal in the present embodiment may be considered to be set on the output side of the high-frequency attenuation unit. Here, the drive signal production side is recording on a recording medium or sending to a telecommunication line, and the drive signal utilization side is a device including an actuator to be driven.

  Further, in the configuration provided with the recording medium and the distribution path in the present embodiment as described above, a configuration in which the boundary between the production side and the usage side of the drive signal is set to the input side of the high-frequency attenuation unit, that is, not yet. Both the drive signal of the processing drive signal source and the control signal for operating the high-frequency attenuation unit may be paired and sent to the recording medium or transmitted to the transmission path. In this case, since the drive signal of the unprocessed drive signal source reaches the use-side device, this information can be used even in a device using an electrodynamic actuator that does not require a high-frequency attenuation unit. Become. That is, the piezoelectric actuator mounting side device includes a high-frequency attenuation unit and a drive unit, the drive signal is applied to the signal input end of the high-frequency attenuation unit, and the control signal is applied to the control input end. On the other hand, on the electrodynamic actuator-equipped device side, it is not necessary to attenuate the high range, and it can be configured only by a drive unit that drives an unprocessed drive signal. Therefore, on the production side, the same signal can be recorded or distributed for both electrodynamic devices and piezoelectric devices.

(Embodiment 4)
FIG. 8 is a block diagram showing a configuration of a load driving device according to Embodiment 4 of the present invention. The load driving device according to the present embodiment is an embodiment in the case where the place and time for executing the processing of the driving signal and the driving of the actual load are separated, and temporarily stores the processed driving signal. Then, the load 2 is driven by, for example, transferring to the drive unit 220 using a transmission line (electric communication line). Furthermore, in the load driving device according to the present embodiment, the load current is estimated by performing a numerical calculation in the load current estimating unit 460. Note that the present invention also includes a drive signal source and a method thereof subjected to the signal processing of the present plan on the assumption of driving of the capacitive load 2 disclosed herein.

  The main difference from the load driving device according to the third embodiment described above is that the signal flowing through the drive signal source and each part is data, and the value of the load current is also estimated by numerical calculation from the function of the load impedance. Further, the remote load 2 is driven by recording processed data on a recording means such as a semiconductor recording medium, a magnetic recording medium, or a magneto-optical recording medium, or by distributing the processed data using an electric communication line.

  As in the case of FIG. 6, the configuration of the load driving device according to the present embodiment is a feed-forward type control that obtains an original signal for control of the high-frequency attenuation unit 410 from the input side of the high-frequency attenuation unit 410. Although it is a system, the same effect can be obtained as feedback-type control in which the original signal used for this control is obtained from the output side of the high-frequency attenuating unit 410.

  In FIG. 8, a high-frequency attenuating unit 410 is a variable attenuator that attenuates a high-frequency component from the drive signal input from the drive signal source 1, and is a high-frequency attenuator such as an LPF (low-frequency attenuation filter). The frequency band component is selectively attenuated, and the attenuation amount and cut-off frequency are adjusted by a control signal to an attached control input terminal. The output of the high-frequency attenuation unit 410 is converted into a signal that can be transmitted to the transmission system or recorded in a storage medium via the modulation unit 5 as processed data, and is transmitted or stored. This processed data is read from the transmission or storage medium, restored as processed data by the demodulator 7, converted to an analog signal by a DA (Digital / Analog) converter 4, and the load 2 is applied by the driver 220. Driven.

  The load current estimation unit 460 performs calculation by dividing the signal data obtained from the input side of the high-frequency attenuation unit 410 by the load equivalent function unit 461. In the load equivalent function unit 461, a function of impedance characteristics similar to that of the capacitive load 2 is described. By dividing the signal data approximate to the drive signal applied to the load 2, the actual load can be obtained. 2 is estimated. Here, since the impedance characteristic of the load equivalent function unit 461 is similar to the impedance of the load 2, the voltage value calculated by the load current calculation unit 462 has a small amount of high-frequency attenuation of the high-frequency attenuation unit 410. For example, the amount is substantially proportional to the current flowing through the load 2.

  The control signal adjustment unit 440 performs processing according to the behavior of the capacitive load such as rectification, dead band setting, attack time and recovery time on the output signal of the load current estimation detection unit 460, and then the high frequency attenuation unit 410 is applied as a control signal, and the amount of the high frequency component of the signal output from the drive unit 220 is adjusted.

  Next, the operation of the load driving device according to the present embodiment will be described. The signal output from the drive signal source 1 is given high frequency attenuation according to the control signal to the attached control input terminal by the high frequency attenuation unit 410, and appears as processed data from the output terminal. The processed data is modulated by the modulation unit 5 and placed on the transmission path or the storage medium 6. Thereafter, the data is restored as processed data by the demodulator 7 as necessary, converted to an analog signal by the DA converter 4, and the load 2 is driven by the driver 220.

  On the other hand, the load current estimation unit 460 estimates the current flowing through the load 2 based on the drive signal, and gives the result to the control signal adjustment unit 440 in the subsequent stage. The control signal adjustment unit 440 performs processing according to the behavior of the capacitive load such as rectification, dead zone setting, attack time and recovery time, and then applies the control signal to the high-frequency attenuation unit 110 as a control signal. Modifies the amount of high frequency components in the output signal.

  In the control signal adjusting unit 440, a signal that changes positively or negatively depending on the direction of the current flowing through the load equivalent function unit 461 is subjected to absolute value processing to be positive, and then smooth calculation processing using a time constant is performed to obtain a smooth control signal. Controls the cutoff frequency of the high-frequency attenuation unit 410. In addition, a dead zone for stopping the control when the load current is small, an attack time that responds to an abrupt increase in load current, and a recovery time to a steady state for a decrease in load current are set.

  The control in FIG. 8 proceeds as follows according to the signal. That is, the increase in the high frequency component of the input signal → the load current temporarily increases due to the response delay of the high frequency attenuation unit 410 → the output of the load current estimation unit 460 increases → the output of the control signal adjustment unit 440 increases → the high frequency The high frequency attenuation of the attenuating unit 410 increases, the high frequency component of the output signal decreases, the current of the load 2 decreases, and the output of the load current estimating unit 460 also decreases. Further, the output of the load current estimating unit 460 is also reduced, the output voltage of the control signal adjusting unit 440 is reduced, the high frequency attenuation amount of the high frequency attenuating unit 410 is reduced, the high frequency component of the output signal is increased, and the load 2 The operation is such that the current increases → the output of the load current estimation unit 460 increases.

  Finally, in the system of FIG. 8, the gain of the control signal adjustment unit 340 and the sensitivity of the control input terminal of the high frequency attenuating unit 110 are appropriately set, so that the frequency spectrum distribution and amplitude of the input signal are adjusted. A stable cut-off frequency is automatically selected, and the load current when the high frequency component of the input signal is large, that is, the power supply current is operated to be kept low, thereby generating heat in the drive output units 22 and 27 of the drive unit 220. Can be kept low. Further, when the high frequency component of the input signal decreases or the signal level itself decreases, the cutoff frequency of the high frequency attenuation unit 410 increases, approaches the upper limit of the cutoff frequency, and the control signal adjustment unit 440 When the level does not exceed the dead band, the cutoff frequency of the high-frequency attenuation unit 410 remains at the upper limit, so that the frequency spectrum of the driving voltage supplied to the load 2 by the driving unit 220 does not change, and the conventional driving unit The characteristic is the same as that of 220 (see FIG. 9).

  As described above, according to the load driving device according to the present embodiment, after the high frequency attenuation unit 410 attenuates the high frequency of the driving signal from the driving signal source 1, the driving unit 220 uses the driving signal to attenuate the high frequency. The load 2 is driven. In addition, the load current estimating unit 460 having impedance characteristics similar to that of the capacitive load 2 calculates the current flowing through the load 2 based on the drive signal, and gives the result to the control signal adjusting unit 440. When the load current value tends to increase, the control signal adjustment unit 440 increases the attenuation amount of the high frequency component of the high frequency attenuation unit 410 and tends to decrease the load current value. Therefore, the amount of attenuation of the high frequency component of the high frequency attenuating unit 410 is decreased to suppress an increase in the load current and to suppress an increase in the power supply current (current flowing out from the power source 3) associated therewith. As a result, the battery life can be reduced and the amount of heat generated by the output transistor can be kept low, and a load driving device for a piezoelectric actuator can be realized that matches battery-operated portable equipment applications such as mobile phones. For example, even if the above-mentioned processing is performed on the data of notification sound, voice, musical sound, and mechanical vibration pattern, and this is stored in a memory such as a small and light battery-powered portable device, the battery life And the amount of heat generated by the output transistor can be kept low. In this case, since signal processing inside the portable device can be omitted, a processor with lower power consumption and lower processing capability can be used, and the power consumption of the portable device itself can be further reduced. A signal for driving such a capacitive load is not only stored in the portable device itself, but also can be obtained by receiving it through a transmission line such as a communication circuit.

  In the present embodiment, processed signal data is stored in a recording medium or sent to a transmission path. This is because the raw data of the drive signal before processing and the high-frequency attenuation unit are operated. The signal data to be set may be set. Here, the signal data for operating the high-frequency attenuation unit is a control signal from the control signal adjustment unit and an output signal from the load current calculation unit. By adopting such a configuration, it is possible to store or send common signal data even in a system where a portable device equipped with a piezoelectric actuator and a portable device equipped with an electrodynamic type are mixed. Can be driven by the method. That is, only the raw data of the drive signal needs to be used for the electrodynamic actuator. The handling of such two signals is complicated, but this can be easily solved by superimposing these signals using a digital encoding technique.

  In the above embodiment, the feedforward type control using the load current estimation unit 460 that applies the signal on the input side of the high-frequency attenuation unit 410 to the load equivalent function unit 461 is performed in order to estimate the load current. However, the load current estimating unit 460 configured to apply the signal on the output side of the high frequency attenuating unit 410 may be used, and in this case, feedback type control is performed. Even with such a configuration, the same effect as the configuration of FIG. 8 as described above can be obtained.

  Further, in the present embodiment, in the calculation of the signal data, a function similar to the impedance characteristic of the actual load is used. However, the admittance characteristic may be used, and the magnitude of the current flowing through the load 2 can be obtained. good.

  In the present embodiment, the calculation of the signal data may be a program written in a semiconductor integrated circuit such as a DSP (Digital Signal Processor) or a program that operates on a general-purpose PC (Personal Computer). good.

  In the present embodiment, the high frequency component of the drive signal is manipulated by the high frequency attenuating unit 410, but other bands may be manipulated according to the size of the drive signal source and its spectrum. When a function such as AGC (automatic gain adjustment) or ALC (automatic level adjustment) is provided, it is possible to have an effect of suppressing the occurrence of distortion due to saturation of the drive unit 220 in an excessive signal.

  In the present embodiment, the high-frequency attenuating unit 410 is configured with an LPF. However, the high-frequency component to be operated may be a main high-frequency component that causes an increase in load current. A method of giving a stepped frequency characteristic that selectively attenuates the band components or uniformly attenuates the entire high frequency band may be used.

  In particular, when a high level component of a specific high level is selectively attenuated, the load current estimation unit 460 is provided with frequency analysis means (not shown) for frequency analysis of the drive signal, and the high frequency attenuation unit 410 has a frequency. May be provided with frequency band-specific gain operating means (not shown) for operating the gain for each frequency band. In this case, when the load current increases, the control signal adjustment unit 440 outputs a control signal for attenuating a main high frequency component that causes an increase in the load current from the frequency analysis result of the drive signal by the frequency analysis means. The high frequency attenuating unit 410 selectively attenuates the high frequency part of the drive signal according to the control signal from the control signal adjusting unit 440.

  With this configuration, it is possible to attenuate only the main high-frequency component that causes an increase in load current, and it is not possible to attenuate a low-level high-frequency component that does not contribute to an increase in load current. As a result, when the load is, for example, a piezoelectric speaker and the drive signal source is a sound source, the high frequency component of the audio signal is not attenuated over a wide range, but is attenuated over a narrow range, thereby minimizing deterioration in sound quality. It becomes possible to suppress to.

  The above-mentioned Embodiments 1 to 4 may be combined in combination other than existing alone, and by adjusting the degree of each contribution, the effectiveness of the effect can be adjusted and the adaptability to the application can be increased. The advantage is that it can be increased.

  INDUSTRIAL APPLICABILITY The present invention has an effect that an increase in load current can be suppressed to a low level even when a high frequency component is included in a drive signal with a capacitive load, such as a mobile phone, a PDA, a pager, and a notebook PC. It can be applied to portable devices with small and lightweight battery operation.

The block diagram which shows the structure of the load drive device which concerns on Embodiment 1 of this invention. The circuit diagram which shows the structure of the load drive device which concerns on Embodiment 1 of this invention. The figure which shows the characteristic of the load drive voltage and load current at the time of the sine wave sweep of the load drive device which concerns on Embodiment 1 of this invention. The figure which shows the spectrum of the sine wave sweep signal processed with the load drive device which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the load drive device which concerns on Embodiment 2 of this invention. The block diagram which shows the structure of the load drive device which concerns on Embodiment 3 of this invention. The circuit diagram which shows the structure of the load drive device which concerns on Embodiment 3 of this invention. The block diagram which shows the structure of the load drive device which concerns on Embodiment 4 of this invention. Circuit diagram showing the configuration of a conventional load driving device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive signal source 2 Load 3 Electric power source 4 DA conversion part 5 Modulation part 6 Transmission path or storage medium 7 Demodulation part 11 LPF
DESCRIPTION OF SYMBOLS 12 Resistor 13 Variable capacity capacitor 14, 41 Buffer amplifier 21 Non-inverting voltage amplifier 22, 27 Drive output part 23, 24, 28, 29 Output transistor 26 Inverting voltage amplifier 31 Load current detection resistor 42, 47 Diode 43 Capacitor 44 Constant setting resistors 45, 46 Resistors 48 Operational amplifiers 110, 410 High-frequency attenuation units 120, 220 Drive units 130 Load current detection units 140, 240, 340, 440 Control signal adjustment units 250 Temperature detection units 360, 460 Load current estimation units 361 Pseudo load unit 362 Pseudo load current detection unit 363 Current-voltage conversion resistor 364 Operational amplifier 461 Load equivalent function unit 462 Load current calculation unit

Claims (10)

High-frequency attenuation means for attenuating the high-frequency component of the drive signal input from the drive signal source with an attenuation amount according to the control signal;
Drive means for driving a capacitive load with a drive signal that has passed through the high-frequency attenuation means;
Load current detection means for detecting a load current flowing through the capacitive load;
Control signal adjusting means for generating the control signal for adjusting the amount of attenuation of the high frequency component of the high frequency attenuating means in accordance with the output of the load current detecting means and giving the control signal to the high frequency attenuating means;
A load driving device comprising: High-frequency attenuation means for attenuating the high-frequency component of the drive signal input from the drive signal source with an attenuation amount according to the control signal;
Drive means for driving a capacitive load with a drive signal that has passed through the high-frequency attenuation means;
Temperature detecting means for detecting a temperature at which the driving means generates heat by driving the capacitive load;
Control signal adjusting means for generating the control signal for adjusting the amount of attenuation of the high frequency component of the high frequency attenuating means according to the output of the temperature detecting means and giving the control signal to the high frequency attenuating means;
A load driving device comprising: High-frequency attenuation means for attenuating the high-frequency component of the drive signal input from the drive signal source with an attenuation amount according to the control signal;
Drive means for driving a capacitive load with a drive signal that has passed through the high-frequency attenuation means;
Load current estimation means for estimating a load current flowing in the capacitive load by flowing either one of the drive signal input from the drive signal source and the drive signal that has passed through the high-frequency attenuation means to a pseudo load;
A control signal adjusting means for generating the control signal for adjusting the amount of attenuation of the high frequency component of the high frequency attenuating means according to the load current estimated by the load current estimating means and giving the control signal to the high frequency attenuating means;
A load driving device comprising: High-frequency attenuation means for attenuating the high-frequency component of the drive signal input from the drive signal source with an attenuation amount according to the control signal;
Drive means for driving a capacitive load with a drive signal that has passed through the high-frequency attenuation means;
Load current estimating means for estimating a load current based on a voltage-current characteristic equivalent value of the capacitive load; and attenuation of a high frequency component of the high frequency attenuating means according to the load current estimated by the load current estimating means Control signal adjusting means for generating and supplying the control signal for adjusting the amount to the high-frequency attenuation means;
A load driving device comprising:   Frequency analysis means for frequency analysis of the input drive signal, the high-frequency attenuation means includes frequency band-specific gain operation means for dividing the frequency into a plurality of bands and operating the gain for each frequency band, When the load current increases, the control signal adjustment means outputs a control signal for attenuating a main high frequency component that causes an increase in load current from the frequency analysis result of the drive signal by the frequency analysis means, and The load driving device according to claim 3 or 4, wherein the band attenuation means selectively attenuates a high frequency component of the drive signal in accordance with a control signal from the control signal adjustment means.   6. The load driving device according to claim 1, further comprising recording means for recording the drive signal that has passed through the high-frequency attenuation means on a recording medium.   The load driving device according to any one of claims 1 to 6, further comprising distribution means for distributing the control signal generated by the control signal adjustment means using an electric communication line.   The load drive according to any one of claims 1 to 5, further comprising recording means for recording the drive signal that has passed through the high-frequency attenuation means and the control signal generated by the control signal adjusting means on a recording medium. apparatus.   7. A distribution unit that distributes the drive signal that has passed through the high-frequency attenuation unit and the control signal generated by the control signal adjustment unit using a telecommunication line. A load driving device according to claim 1. A high-frequency attenuation step for attenuating the high-frequency component of the drive signal input from the drive signal source with an attenuation amount according to the control signal;
A load current acquisition step of acquiring a load current value flowing through the capacitive load to be driven;
A control signal adjusting step for generating the control signal for adjusting the attenuation amount of the high frequency component of the drive signal supplied to the capacitive load according to the acquired load current value;
A load driving method comprising:

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