Class-d power amplifier

Abstract

To provide a class-D power amplifier using a half-bridge system or a full-bridge system capable of reducing a switching loss occurring at power amplification.SOLUTION: A class-D power amplifier for outputting a modulation signal which is power-amplified in a half-bridge system or a full-bridge system by using modulation wave generation means for generating a modulation wave signal, carrier wave generation means for generating a carrier wave signal, the modulation wave signal, and the carrier wave signal, has a low-pass filter for transmitting low frequency components within the power-amplified modulation signal, and the modulation wave generation means generates the modulation wave signal at a plurality of different frequencies fs, and fc (cut-off frequency of the low pass filter), fb (frequency of the carrier wave signal), and the fs (frequency of the modulation wave signal) satisfy a predetermined relation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a class-D power amplifier device.

Background Art

[0002] In recent years, with the increasing demands for energy conservation and miniaturization, high power efficiency is required for power amplifier devices used in electrical equipment. Among them, the so-called class-D power amplifier device is known to have very high power efficiency compared with conventional power amplifier devices such as class-A, class-B, and class-AB. Therefore, in recent years, it has been used for driving electric motors such as induction motors and for driving medical equipment that uses high frequencies.

[0003] Patent Document 1 discloses a technique for making the ratio of the frequencies of the modulation wave signal and the carrier wave signal of a class-D power amplifier constant when driving an induction motor. Patent Document 2 also discloses a technique for making the ratio of the frequencies of the modulation wave signal and the carrier wave signal an integer multiple when driving an induction motor with a class-D power amplifier. By these techniques, it is possible to suppress the loss of the switching elements constituting the inverter in the harmonic region.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, the class-D power amplifier amplifies the modulated wave signal as follows. First, the modulated wave signal to be amplified and the carrier signal are input to a comparator (element) to obtain a PWM (Pulse Width Modulation) modulated wave signal. Further, by inputting the PWM modulated wave signal to a driver IC (Integrated Circuit) such as a half-bridge circuit or a full-bridge circuit, the switching of the input DC voltage is performed, and a PWM modulated wave signal amplified in power is output. By passing the PWM modulated wave signal through a low-pass filter, a modulated wave signal amplified to the desired power can be obtained. Although the power efficiency of the class-D power amplifier is high, the problem is that losses occur during the switching in the above driver IC. The larger the number of switchings, the greater the switching loss, and furthermore, the number of switchings is proportional to the frequency of the carrier signal. Therefore, it is an issue to amplify the modulated wave signal after power amplification with a carrier signal whose frequency is reduced.

Means for Solving the Problems

[0006] The class-D power amplifier according to the present invention includes a modulated wave generation means for generating a modulated wave signal, a carrier wave generation means for generating a carrier wave signal, a class-D power amplifier that outputs a modulated signal power-amplified in a half-bridge manner using the modulated wave signal and the carrier wave signal, having a low-pass filter that transmits the low-frequency components of the power-amplified modulated signal, the modulated wave generation means generates modulated wave signals of a plurality of different frequencies f s and satisfies the relationships of the following formulas (1) and (2). Satisfies the following relationships of formulas (1) and (2).

[0007]

Number

[0008] However, in the above formulas (1) and (2), f c is the cut-off frequency of the low-pass filter, f b is the frequency of the carrier signal, fs represents the frequency of the modulation wave signal.

[0009] Another class-D power amplifier according to the present invention includes a modulation wave generation means for generating a modulation wave signal and a carrier wave generation means for generating a carrier wave signal, is a class-D power amplifier that outputs a modulated signal power-amplified in a full-bridge manner using the modulation wave signal and the carrier wave signal, has a low-pass filter that transmits the low-frequency components of the power-amplified modulated signal, the modulation wave generation means generates modulation wave signals of a plurality of different frequencies f s and satisfies the relationship of the following formulas (4) and (5). A class-D power amplifier that satisfies the relationship of the following formulas (4) and (5).

[0010]

Equation

[0011] However, in the above formulas (4) and (5), f c represents the cut-off frequency of the low-pass filter, f b represents the frequency of the carrier wave signal, f s represents the frequency of the modulation wave signal.

Advantages of the Invention

[0012] According to the present invention, for a desired modulation wave signal, it is possible to perform modulation with a carrier wave signal having a minimum frequency for power amplification in a state with less noise, so that the switching loss in the bridge circuit can be reduced compared to the conventional case. Therefore, the possibility that the bridge circuit stops due to heat loss can be reduced.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the power amplifier in the embodiment and the comparative form of the present invention will be described in detail with reference to the drawings. Note that the configurations described in the following embodiments are merely examples, and the scope of the present invention is not limited by the configurations described in the embodiments.

[0015] [Embodiment 1] There are mainly two methods for class-D power amplifiers, one is the half-bridge method and the other is the full-bridge method. In Embodiment 1, a power amplifier using the half-bridge method is shown. FIG. 1 is a circuit block diagram for explaining the class-D power amplifier according to Embodiment 1 of the present invention.

[0016] The class-D power amplifier according to the present embodiment includes a modulation wave generation means for generating a modulation wave signal and a carrier wave generation means for generating a carrier wave signal, and outputs a modulation signal power-amplified by the half-bridge method using the modulation wave signal and the carrier wave signal. The class-D power amplifier according to the present embodiment further includes a low-pass filter that transmits the low-frequency component of the power-amplified modulation signal.

[0017] (Carrier wave generation means) The carrier wave generation means 120 in the present embodiment includes a rectangular wave generation circuit 101 and an integration circuit 102, and transmits a carrier wave signal. First, the rectangular wave generation circuit 101 transmits a rectangular wave signal. In the present embodiment, a pulse circuit, a microcomputer, an FPGA, etc. are used as the rectangular wave generation circuit. Then, in the integration circuit 102, the rectangular wave signal transmitted from the rectangular wave generation circuit 101 is converted into a triangular wave or sawtooth wave signal having the same frequency as the rectangular wave. The signal output from the integration circuit 102 is called a carrier wave signal.

[0018] (Modulation wave generation means) On the other hand, a modulation wave signal to be power-amplified is transmitted from the modulation wave generation means 107. Examples of the modulation wave signal include a sine wave signal having a single frequency component, but a signal obtained by synthesizing sine waves of a plurality of different frequencies may also be used. The signal output from the modulation wave generation means 107 is called a modulation wave signal.

[0019] (Comparator, half - bridge circuit, low - pass filter) As described above, the carrier wave signal and the modulation wave signal are input to the comparator 103 to generate a PWM modulation wave signal. In the half - bridge circuit 104, the positive and negative DC power supplies 108 with two polarities are switched by the PWM modulation wave signal, so that a power - amplified PWM modulation wave signal can be output. The amplitude of this PWM modulation wave signal is equal to that of the DC power supply 108. The power - amplified PWM modulation wave signal has its harmonic components removed by the low - pass filter 105, and a power - amplified sine wave signal 106 having the same frequency as the modulation wave signal is output. The cut - off frequency f c of the low - pass filter is a value inherent to the circuit constituting the power amplifier device.

[0020] Figure 2 is a graph showing the output signals of each circuit block according to Embodiment 1 of the present invention. 201 is an example of the waveform of the modulation wave signal output from the modulation wave generation means 107. In this example, a sine wave with an amplitude ν s is output as the modulation wave signal. 202 is an example of the waveform of the carrier wave signal output from the integrating circuit 102. In this example, a sawtooth wave with an amplitude ν b is output as the carrier wave signal. Here, the frequency of the modulation wave signal of 201 is 1 / 20 of the frequency of the carrier wave signal of 202.

[0021] 203 is the PWM modulation wave signal output from the comparator 103. This signal compares the modulation wave signal 201 and the carrier wave signal 202 with a comparator. If the modulation wave signal 201 is larger than the carrier wave signal 202, the voltage ν d is output, and conversely, if the carrier wave signal 202 is larger than the modulation wave signal 201, the voltage - ν d is output. 204 is the sine wave signal output as the sine wave signal 106 after the PWM modulation wave signal 203 is input to the low - pass filter 105. The amplitude of this voltage signal is

[0022]

Number

[0023] It is.

[0024] Here, E u represents the voltage value of the positive polarity of the DC power supply 108, and M represents the modulation degree

[0025]

Number

[0026] is represented.

[0027] Figure 3 is a graph showing an example of the spectrum diagram of the PWM modulation wave signal after power amplification in Embodiment 1 of the present invention. That is, it is the spectrum of the signal output from the half-bridge circuit 104 in FIG. 1. When this signal waveform is expressed by a mathematical formula, it is as follows.

[0028]

Number

[0029] Here, ω s is the angular frequency of the modulation wave signal, and J 0 represents the Bessel function of the first kind of order 0. According to this mathematical formula, 301 corresponds to the frequency f s of the modulation wave signal, 302 corresponds to the frequency f b -2f s of the modulation wave signal, 303 corresponds to the frequency f b of the carrier wave signal, 304 corresponds to the frequency f b +2f s of the modulation wave signal, 305 corresponds to the frequency f b -4f s of the modulation wave signal, 306 corresponds to the frequency f b +4f s of the modulation wave signal. Actually, there are spectra at frequency positions corresponding to f b -6f s 、f b +6f s 、f b -8f s 、f b +8f s 、···, but the intensity is small and the spectral intensity can be substantially ignored.

[0030] The low-pass filter 105 is provided to allow only components approximately equal to the frequency of the modulated wave signal to pass through and cut off the others. Therefore, considering the above spectral distribution, the cut-off frequency f of the low-pass filter c is set to satisfy the relationship with the frequency f of the modulated wave signal s , the frequency f of the carrier wave signal b and the following formula. f s ≦f c ≦f b -2f s ···(a4) According to the above formula, especially f c +2f s ≦f b ···(a5) That is, it can be seen that the condition of the lower limit value of the frequency f of the carrier wave signal b is determined by the cut-off frequency f c and the modulated wave frequency f s .

[0031] Also, f c ≦f c +4f s ≦f b ···(a6) If the condition such that b -4f s is applied, the sideband wave of the frequency f of 305 b can also be cut off. However, accordingly, the frequency f of the carrier wave signal

[0032] Therefore, f c +2f s ≦f b ≦f c +4f s ···(a7) When the range of the frequency f of the carrier wave signal b is limited to the range where c +2f s the sideband wave of the frequency f bThe frequency components can be reduced.

[0033] Here, the frequency f of the carrier signal b is set as a linear function of the frequency f of the modulation wave signal s with constants a and b as f b (f s ) = af s + b ··· (a8) When changing as such, the following relational expressions are satisfied.

[0034]

Equation

[0035] However, in the above formulas (1) and (2), f c is the cut-off frequency of the low-pass filter, f b is the frequency of the carrier signal, f s is the frequency of the modulation wave signal.

[0036] In order to make f b not included in the signal as noise as in the prior art, the condition of the above formula (1) is necessary. Also, since the lower limit is 2 as in formula (2), the cut-off frequency of the low-pass filter is set to 302 in FIG. 3, and noise can be reduced. Further, since the upper limit is 6, switching loss can be reduced.

[0037] Also, from the viewpoint of further reducing noise, it is more preferable to satisfy the relationship of the following formula (3).

[0038]

Equation

[0039] Let the numerical constraint condition for this carrier signal frequency f b be condition A.

[0040] On the other hand, the frequency f of the carrier signal b and the frequency f of the modulation wave signals It is known that in order for the modulated wave signal to be output as a smooth sine wave, it is necessary to satisfy the relationship of the following formula (7). 10f s ≦f b ··· Formula (7)

[0041] Regarding the numerical constraint conditions for the frequency f of this carrier wave signal as Condition B b

[0042] In this embodiment, for the frequency f of the modulated wave signal s among the frequencies f of the carrier wave signals that satisfy the above Condition A and Condition B b the lowest frequency f of the carrier wave signal b is used for modulation. By doing so, all sidebands can be cut off, and the switching loss can be minimized.

[0043] Figure 4 is a graph showing the relationship between the frequencies of the carrier wave signal and the modulated wave signal in Embodiment 1 of the present invention. The X-axis of the graph is the frequency f of the modulated wave signal s and the dotted line 402 is a straight line represented by f c +2f s and the dashed-dotted line 403 is a straight line represented by 10f s . Here, the cut-off frequency f of the low-pass filter c is set to 100 [kHz]. In order to satisfy the above Condition A and B, the frequency f of the carrier wave signal b must be the same as or greater than the values of the straight lines 402 and 403. Therefore, the lower limit value of the possible values of the frequency f of the carrier wave signal b is represented by the solid line 401. The solid line 401 has the same frequency f of the carrier wave signal as the straight line 402 when the frequency f of the modulated wave signal s ranges from 0 [kHz] to 14.29 [kHz], which is the intersection of the straight lines 402 and 403 b . And when the frequency f of the modulated wave signal s is 14.29 [kHz] or more, it takes the value of the frequency f of the carrier wave signal that is the same as the straight line 403 b . In this embodiment, the lower limit value of the frequency of the carrier wave signal represented by this solid line 401 is the frequency f of the carrier wave signal​b is defined as follows.

[0044] In Embodiment 1, the frequency f of the carrier signal is determined as described above. b However, if the frequency f of the carrier signal b is not an integer multiple of the frequency f of the modulation wave signal s , noise may occur in the output signal. Therefore, a value that is an integer multiple of the frequency f of the modulation wave signal s may be determined as the frequency f of the carrier signal b using the value closest to the upper side of the solid line 401.

[0045] Note that f b may be represented by a linear function with f s as a variable and a non - negative y - intercept. Also, f b may be greater than or equal to the value of a linear function with f s as a variable and a non - negative y - intercept, and may be an integer multiple of f s .

[0046] [Embodiment 2] FIG. 5 is a circuit block diagram according to Embodiment 2 of the present invention. Embodiment 2 shows a power amplification device using a full-bridge method. The full-bridge method has two carrier generation means (circuits for generating carrier signals) used in the half-bridge method described in Embodiment 1. That is, a carrier signal A generated by the first carrier generation means including the rectangular wave generation circuit A501 and the integration circuit A502, and a carrier signal B generated by the second carrier generation means including the rectangular wave generation circuit B504 and the integration circuit B505. The rectangular wave signals output from the rectangular wave generation circuit A501 and the rectangular wave generation circuit B504 have a phase difference of 180 degrees, and correspondingly, the carrier signals output from the integration circuit A502 and the integration circuit B505 have a phase difference of 180 degrees. Each of the carrier signals A and B and the modulation wave signals A and B are input to the comparator A503 and the comparator B506, and PWM modulation wave signals A and B are output respectively. The PWM modulation wave signals A and B and the output voltage from the DC power supply 508 are input to the full-bridge circuit 509. Different from the above-described Embodiment 1, the DC power supply 508 is a single DC voltage power supply having a positive or negative polarity. The PWM modulation wave signal output from the full-bridge circuit 509 and power-amplified has its harmonic components removed by the low-pass filter 510, and a power-amplified sine wave signal 511 having the same frequency as the modulation wave signal is output. The cut-off frequency f c of the low-pass filter is a value specific to the circuit constituting the power amplification device.

[0047] FIG. 6 is a graph showing the output signals of the respective circuit blocks according to Embodiment 2 of the present invention. 601 is the output signal waveform from the modulation wave generation means 507. A sine wave with an amplitude ν s is output as the modulation wave signal. 602 is the output signal waveform from the integration circuit A502. 603 is the output signal waveform from the integration circuit B505. These outputs are both triangular waves with an amplitude ν b output as carrier signals, but their phases are shifted by 180 degrees. Here, the frequency of the modulation wave signal of 601 is 1 / 20 of the frequencies of the carrier signals of 602 and 603. 604 is the power-amplified PWM modulation wave signal output from the full-bridge circuit 509.

[0048] This signal compares the modulated wave signal 201 and the carrier wave signal 202 using a comparator. If the modulated wave signal 201 is greater than the carrier wave signal 202, the voltage ν d is output, and conversely, if the carrier wave signal 202 is greater than the modulated wave signal 201, the voltage -ν d is output. 605 is a sine wave signal that is output as a sine wave signal 511 after inputting the PWM modulated wave signal into the low-pass filter 510. The amplitude of this voltage signal is ν u =ME u ···(a9) Here, E u represents the absolute value of the voltage value of the DC power supply 508, and M represents the modulation degree.

[0049]

Number

[0050] Figure 7 is a graph showing the spectrum diagram of the PWM modulated wave signal after power amplification in Embodiment 2 of the present invention. That is, it is the spectrum of the signal output from the full-bridge circuit 509 in Figure 5. When this signal waveform is expressed by a mathematical formula, it is as follows.

[0051]

Number

[0052] According to this mathematical formula, 701 corresponds to the frequency f s of the modulated wave signal, 702 corresponds to the frequency 2f b - 3f s of the modulated wave signal, 703 corresponds to the frequency 2f b - f s of the modulated wave signal, 704 corresponds to the frequency 2f b + f s of the modulated wave signal, 705 corresponds to the frequency 2f b + 3f s of the modulated wave signal, 706 corresponds to the frequency 2f b - 5f s of the modulated wave signal, 707 corresponds to the frequency 2f b + 5f s of the modulated wave signal. Actually, there are further frequencies corresponding to 2f b-7f s 、2f b +7f s 、2f b -9f s 、2f b +9f s Although spectra stand at the frequency positions corresponding to ···, their intensities are small and of a magnitude that can be substantially ignored. The low-pass filter 510 is provided to pass only the components equal to the frequency of the modulated wave signal and cut off the others. Therefore, considering the above spectral distribution, the cut-off frequency f c of the low-pass filter has the following relationship with the frequency f s of the modulated wave signal and the frequency f b of the carrier wave signal. f s ≦f c ≦2f b -3f s ···(a12)

[0053] From this, especially

[0054]

Number

[0055] It can be seen that the condition for the lower limit value of the frequency f b of the carrier wave signal is determined by the cut-off frequency f c and the frequency f s of the modulated wave signal. f c ≦f s ≦2f b -5f s ···(a14) That is, the condition

[0056]

Number

[0057] If applied, the frequency 2f b -5f sThe sideband can also be cut off. However, since the frequency f of the carrier signal will increase accordingly, in this embodiment b the range of the frequency f of the carrier signal is limited to the range where

[0058] [Number]

[0059] it becomes. b .

[0060] Here, when the frequency f of the carrier signal is changed as a function of the first-order expression of the frequency f of the modulation wave signal with a and b as constants b f s f(f f b (f s ) = af s + b ··· (a17) , the following equations (4) and (5) are satisfied.

[0061] [Number]

[0062] However, in the above equations (4) and (5), f c is the cut-off frequency of the low-pass filter, f b is the frequency of the carrier signal, and f s is the frequency of the modulation wave signal.

[0063] As in the prior art, in order for f b not to be included in the signal as noise, the condition of the above equation (4) is necessary. Also, since the lower limit is 3 as in equation (5), the cut-off frequency of the low-pass filter is set to 702 in FIG. 7, and noise can be reduced. Also, since the upper limit is 7, switching loss can be reduced.

[0064] Also, from the viewpoint of further reducing noise, it is more preferable to satisfy the relationship of the following equation (6).

[0065]

Number

[0066] The frequency f of this carrier wave signal b is set as the numerical constraint condition for it to be condition C.

[0067] Even when using the full-bridge method as in this embodiment, for the frequency f of the carrier wave signal b and the frequency f of the modulation wave signal s to output the modulation wave signal as a smooth sine wave, it is necessary to satisfy the above-mentioned condition B as in Embodiment 1. In this example, for the frequency f of the modulation wave signal s the frequency f of the carrier wave signal that satisfies the above condition B and condition C with respect to b Among them, modulation is performed with the lowest frequency f of the carrier wave signal b . By doing this, all sidebands can be cut off and the switching loss can be minimized.

[0068] Figure 8 is a graph showing the relationship between the frequencies of the carrier wave signal and the modulation wave signal in Embodiment 2 of the present invention. The X-axis of the graph is the frequency f of the modulation wave signal s and the dotted line 802 is the straight line represented by (a18), and the dashed-dotted line 803 is the straight line represented by 10f s .

[0069]

Number

[0070] Here, the cut-off frequency f of the low-pass filter c is set to 100 [kHz]. To satisfy the above conditions B and C, the frequency f of the carrier wave signal b must be the same as or greater than the straight lines 802 and 803. Therefore, the lower limit value of the possible values that the frequency f of the carrier wave signal b can take is represented by the solid line 801. That is, the frequency f of the modulation wave signal stakes on a value of the carrier signal frequency greater than the frequency represented by the straight line 802 from 0 [kHz] to 5.88 [kHz], which is the intersection of the straight lines 802 and 803. And for the modulation wave signal with a frequency f s if it is 5.88 [kHz] or more, it takes on a value of the carrier signal frequency greater than the frequency represented by the straight line 803. In this embodiment, the lower limit value of the carrier signal frequency represented by this solid line 801 is defined as the carrier signal frequency f b .

[0071] Note that in Embodiment 2, the carrier signal frequency f b is determined as described above. However, when the carrier signal frequency f b is not an integer multiple of the modulation wave signal frequency f s , noise will occur in the output signal. Therefore, a value that is an integer multiple of the modulation wave signal frequency f s and is the closest value above the solid line 801 may be defined as the carrier signal frequency f b .

[0072] [Embodiment 3] Embodiment 3 is a class D power amplifier device using the half-bridge method, similar to Embodiment 1, with the same circuit configuration, and only the range of possible values of the carrier signal frequency f s with respect to the modulation wave signal frequency f b is different. The carrier signal frequency f b in Embodiment 3 is determined so that it can be removed by a low-pass filter with a cut-off frequency f b -4f s for the sideband wave of the PWM modulation wave signal described in Embodiment 1 up to the sideband wave of the frequency f c shown in FIG. 3 at 305. As already described, although the spectral intensity of the sideband wave of the frequency f b -4f s is small, by removing it with a low-pass filter, the noise of the output signal after power amplification can be made smaller than in Embodiment 1. On the other hand, if the carrier signal frequency f b is increased too much, the switching loss will increase.

[0073] Therefore, fs ≤ f b -6f s ≤ f c ≤ f b -4f s ···(a20) in the range of, that is f c +4f s ≤ f b ≤ f c +6f s ···(a21) the frequency f of the carrier wave signal is set within the range of b Although the switching loss increases compared to Embodiment 1, power amplification with low noise can be achieved

[0074] FIG. 9 is a graph showing the relationship between the frequencies of the carrier wave signal and the modulation wave signal in Embodiment 3 of the present invention. The X-axis of the graph is the frequency f s of the modulation wave signal. The dotted line at 902 is the straight line represented by f c +4f s and the one-dot chain line at 903 is the straight line represented by 10f s . Here, the cut-off frequency f c of the low-pass filter is set to 100 [kHz]. The solid line 901 represents the frequency f b of the carrier wave signal in this embodiment. It takes the same value as 902 up to the intersection of 902 and 903, and takes the same value as 903 for frequencies f s of the modulation wave signal above that

[0075] [Embodiment 4] Embodiment 4 is a class-D power amplifier device using the full-bridge method, similar to Embodiment 2, with the same circuit configuration, and only the range of the frequency f s of the carrier wave signal with respect to the frequency f b of the modulation wave signal is different. The frequency f b of the carrier wave signal in Embodiment 4 is up to the sideband wave of frequency 2f b -5f s among the sideband waves existing in the PWM modulation wave signal described in Embodiment 4, with a cut-off frequency f cis determined to be removable by the low-pass filter. As already described, the sideband spectral intensity of the frequency 2f b -5f s is small, but by removing it with a low-pass filter, the noise of the output signal after power amplification can be made smaller than in Embodiment 1. On the other hand, if the frequency f of the carrier signal b is increased too much, the switching loss increases. Therefore, f c ≦2f b -7f s ≦f s <2f b -5f s ···(a22) that is, in the range of

[0076]

Number

[0077] By setting the frequency f of the carrier signal in the range of b Although the switching loss increases compared to Embodiment 2, power amplification with low noise can be realized.

[0078] Figure 10 is a graph showing the relationship between the frequencies of the carrier signal and the modulation wave signal in Embodiment 3 of the present invention. The X-axis of the graph is the frequency f of the modulation wave signal s is.

[0079] The dotted line at 1002 is

[0080]

Number

[0081] is the straight line represented by, and the dashed-dotted line at 1003 is 10f b is the straight line represented by. Here, the cut-off frequency f of the low-pass filter c is set to 100 [kHz]. The solid line 1001 is the frequency f of the carrier signal in this embodiment brepresents. Up to the intersection of 1002 and 1003, it takes the same value as 1002, and for higher frequencies of the modulation wave signal f s it takes the same value as 1003.

[0082] [Embodiment 5] Embodiment 5 is a class-D power amplifier device using the half-bridge method, similar to Embodiment 1 in circuit configuration. Only the range of the frequency f s of the carrier wave signal with respect to the frequency f b of the modulation wave signal is different. In the case of Condition A

[0083] [Number]

[0084] when f c = f b ···(a26) becomes such that the frequency f b - 2f s of the sideband wave, the frequency f b of the carrier wave signal, and the cut-off frequency f c of the low-pass filter are the same value. Therefore, in this embodiment, to further reduce the noise of the sideband wave after passing through the low-pass filter, with C being a positive constant, the frequency f b of the carrier wave signal is

[0085] [Number]

[0086] is determined as. Further, Condition B is also imposed. In this embodiment, C = 50 [kHz], and

[0087] [Number]

[0088] is set as f b = f c + 50 [kHz] + 2fs ···(a29) By doing so, compared with Embodiment 1, the components of the sideband waves can be more completely removed, and a signal with less noise can be output.

[0089] FIG. 11 is a graph showing the relationship between the frequencies of the carrier signal and the modulation wave in Embodiment 5 of the present invention. The X-axis of the graph is the frequency f of the modulation wave signal s is. The dotted line 1102 is a straight line represented by f c +2f s and the dashed line 1103 is a straight line represented by 10f s . Here, the cut-off frequency f of the low-pass filter c is set to 100 [kHz]. The solid line 1101 represents the frequency f of the carrier signal in the present embodiment b .

[0090] [Embodiment 6] Embodiment 6 is a class D power amplifier device using the full-bridge method, similar to Embodiment 2, with the same circuit configuration, and only the range of the frequency f of the carrier signal relative to the frequency f of the modulation wave signal s is different. For condition C b

[0091]

Equation

[0092] when f s = 0,

[0093]

Equation

[0094] becomes and the sideband wave of frequency 2f b -3f s and the sideband wave of frequency 2f b and the cut-off frequency f of the low-pass filter cbecomes the same value. Therefore, in this embodiment, in order to further reduce the noise of the sideband wave after passing through the low-pass filter, C is set as a positive constant and the frequency f of the carrier signal b is

[0095]

Number

[0096] is defined as. Further, condition B is also imposed. In this embodiment, C = 50 [kHz],

[0097]

Number

[0098] is set as,

[0099]

Number

[0100] is set. By doing so, compared with Embodiment 2, the components of the sideband wave can be more completely removed and a signal with less noise can be output.

[0101] FIG. 12 is a graph showing the relationship between the frequencies of the carrier signal and the modulation wave signal in Embodiment 6 of the present invention. The X-axis of the graph is the frequency f of the modulation wave signal s is. The dotted line at 1202 is

[0102]

Number

[0103] is the straight line represented by, and the dashed-dotted line at 1203 is the straight line represented by 10f s is. Here, the cut-off frequency f of the low-pass filter c is set to 100 [kHz]. The solid line 1201 represents the frequency f of the carrier signal in this embodiment b is.

[0104] [Comparative form 1] The configuration of the power amplifier in Comparative form 1 and the output waveforms from each circuit block are the same as those in Embodiment 1. In Comparative form 1, the frequency f of the carrier signal b is a value C proportional to the frequency f of the modulation wave signal s and is set to it. In Comparative form 1, in order to cut off the sideband wave of frequency f 1 - 2f b the condition s f f c + 2f s ≤ f b ···(a35) is imposed. Here, when the proportionality coefficient C 1 is swept in the range of the frequency f of the modulation wave signal s as [f s min , f s max ,

[0105] [Number]

[0106] is taken. Further, when the condition B described in Embodiment 1 is also imposed and C 1 ≤ 10, a value such that 10 < C 1 is set as the slope with respect to the frequency f of the modulation wave signal of the frequency f b of the carrier signal s .

[0107] [Comparative form 2] The configuration of the power amplifier in Comparative form 2 and the output waveforms from each circuit block are the same as those in Embodiment 1. In Comparative form 2, the maximum value of the frequency f of the carrier signal in Embodiment 1 is set as a constant value for the frequency f b of the carrier signal b .

[0108] [Comparative form 3] The configuration of the power amplifier in Comparative Form 3 and the output waveforms from each circuit block are the same as those in Embodiment 2. In Comparative Form 3, the frequency f of the carrier signal b is set to a value C proportional to the frequency f of the modulation wave signal s . In Comparative Form 3, in order to cut off the sideband wave of the frequency f 2 -3f b , the condition similar to Condition A is imposed, s . Here, when the proportionality coefficient C

[0109]

Number

[0110] is swept within the range of [f 2 , f s , f s min , f s max ,

[0111]

Number

[0112] is set. Further, when the condition B described in Embodiment 1 is also imposed and C 2 ≤10 and 10 < C 2 , a value such that 10 < C b is set as the slope with respect to the frequency f of the modulation wave signal of the frequency f of the carrier signal s .

[0113] [Comparative Form 4] The configuration of the power amplifier in Comparative Form 4 and the output waveforms from each circuit block are the same as those in Embodiment 2. In Comparative Form 4, the maximum value of the frequency f of the carrier signal in Embodiment 2 is set as a constant value for the frequency f of the carrier signal b . b

[0114] [Advantages of the Embodiment of the Present Invention over the Comparative Forms] Figure 13 is a graph showing the relationship between the frequencies of the carrier wave signal and the modulation wave signal in Embodiment 1, Comparative Form 1, and Comparative Form 2 of the present invention. 1301 is the frequency f of the carrier wave signal determined by the method of Embodiment 1, 1302 is that of Comparative Form 1, and 1303 is that of Comparative Form 2 b is shown. The horizontal axis represents the frequency f s of the modulation wave signal, and the frequency is swept from 5 [kHz] to 36 [kHz]. Also, in each embodiment and comparative form, the cut-off frequency f c of the low-pass filter is set to 100 [kHz]. In Comparative Form 1, after satisfying Conditions A and B, the frequency of the carrier wave signal is set to be proportional to the frequency of the modulation wave signal. Therefore, the chain line 1302 obtained by sweeping the straight line connecting the left end point of the solid line 1301 and the origin within the range of the frequency of the modulation wave signal is the frequency of the carrier wave signal in Comparative Form 1. Similarly, in Comparative Form 2, after satisfying Conditions A and B, the frequency of the carrier wave signal is set to maintain a constant value even when the frequency of the modulation wave signal changes. Therefore, the dotted line 1303 obtained by sweeping a graph that always takes the value of the frequency of the carrier wave signal at the right end point of the solid line 1301 as a constant value within the range of the frequency of the modulation wave signal is the frequency of the carrier wave signal in Comparative Form 1. Comparing 1301 with 1302 and 1303, it can be seen that the frequency of the carrier wave signal in Embodiment 1 is lower than those in Comparative Forms 1 and 2. The frequency of the carrier wave signal is proportional to the switching loss in the bridge IC. From the comparison in Figure 13, the ratio of the switching loss when the frequency is swept from 5 [kHz] to 36 [kHz] was estimated. As a result, when Embodiment 1 is set to 100, Comparative Form 1 is 198, and Comparative Form 2 is 250, indicating that the switching loss in Embodiment 1 is less. Embodiment 1, Comparative Forms 1 and 2 all have the same configuration of the power amplification circuit and use the half-bridge method, but there is a significant difference in power efficiency due to the difference in the way the frequency of the carrier wave signal is set with respect to the frequency of the modulation wave signal.

[0115] Figure 14 is a graph showing the relationship between the frequencies of the carrier wave signal and the modulation wave signal in Embodiment 2, Comparative Form 3, and Comparative Form 4 of the present invention. 1401 is the carrier wave signal frequency f determined by the method of Embodiment 2, 1402 is that of Comparative Form 3, and 1403 is that of Comparative Form 4 b which is shown in the same way as in FIG. 13. The horizontal axis represents the frequency f s of the modulation wave signal, and the frequency is swept from 0.25 [kHz] to 4.25 [kHz]. Also, in each embodiment and comparative form, the cut-off frequency f c of the low-pass filter is set to 100 [kHz]. Comparing 1401 with 1402 and 1403, it can be seen that the frequency of the carrier wave signal in Embodiment 2 is lower than those in Comparative Forms 3 and 4. The frequency of the carrier wave signal is proportional to the switching loss in the bridge IC. From the comparison in FIG. 10, the ratio of the switching loss when the frequency is swept from 0.25 [kHz] to 4.25 [kHz] was estimated. As a result, when Embodiment 2 is set to 100, Comparative Form 3 is 849, and Comparative Form 4 is 106, indicating that the switching loss in Embodiment 2 is less

[0116] Embodiments 2, Comparative Forms 3 and 4 have the same configuration of the power amplification circuit and use the full-bridge method, but there is a significant difference in power efficiency due to the difference in the way the frequency of the carrier wave signal is set with respect to the frequency of the modulation wave signal

[0117] (Other Embodiments) The cell detachment device according to the present embodiment includes the class-D power amplification device according to the present embodiment and vibration generating means. The vibration generating means generates vibration using the power-amplified modulation signal and applies the vibration to the cells adhered to the culture surface of the culture vessel, thereby detaching the cells from the culture surface. An ultrasonic vibrator can be mentioned as the vibration generating means

[0118] The motor device according to the present embodiment includes the class-D power amplification device according to the present embodiment and an ultrasonic motor, and the ultrasonic motor is driven using the power-amplified modulation signal

[0119] When a class-D power amplifier is used in such a device, the frequency of the modulation signal may be swept in the ultrasonic frequency band in the class-D power amplifier.

[0120] The disclosure of the embodiments according to the present invention includes the following configurations.

[0121] (Configuration 1) A modulation wave generation means for generating a modulation wave signal, a carrier wave generation means for generating a carrier wave signal, A class-D power amplifier that outputs a modulation signal power-amplified by a half-bridge method using the modulation wave signal and the carrier wave signal, Having a low-pass filter that transmits low-frequency components of the power-amplified modulation signal, The modulation wave generation means generates modulation wave signals of a plurality of different frequencies f s and is a class-D power amplifier that satisfies the relationships of the following formulas (1) and (2). A class-D power amplifier satisfying the relationships of the following formulas (1) and (2).

[0122]

Equation

[0123] However, in the above formulas (1) and (2), f c is the cut-off frequency of the low-pass filter, f b is the frequency of the carrier wave signal, and f s represents the frequency of the modulation wave signal.

[0124] (Configuration 2) The class-D power amplifier according to Configuration 1 that satisfies the relationship of the following formula (3).

[0125]

Equation

[0126] (Configuration 3) A modulation wave generation means for generating a modulation wave signal, a carrier wave generation means for generating a carrier wave signal, A class-D power amplifier device that outputs a modulated signal power-amplified in a full-bridge manner using the modulation wave signal and the carrier wave signal, having a low-pass filter that transmits low-frequency components of the power-amplified modulated signal, The modulation wave generation means generates modulation wave signals of a plurality of different frequencies f s and is a class-D power amplifier device that satisfies the relationships of the following formulas (4) and (5).

[0127]

Number

[0128] However, in the above formulas (4) and (5), f c is the cut-off frequency of the low-pass filter, f b is the frequency of the carrier wave signal, and f s represents the frequency of the modulation wave signal.

[0129] (Configuration 4) The class-D power amplifier device according to Configuration 3, which satisfies the relationship of the following formula (6).

[0130]

Number

[0131] (Configuration 5) The class-D power amplifier device according to any one of Configurations 1 to 4, which satisfies the relationship of the following formula (7).

[0132]

Number

[0133] (Configuration 6) The f b is a class-D power amplifier device according to any one of Configurations 1 to 5, which is represented by a linear function having the f s as a variable and a non-negative y-intercept.

[0134] (Configuration 7) The aforesaid f b is a value equal to or greater than that of a linear function having the aforesaid f s as a variable and a non - negative y - intercept, and is an integer multiple of the aforesaid f s The class - D power amplifier device according to any one of Configurations 1 to 5.

[0135] (Configuration 8) The class - D power amplifier device is the class - D power amplifier device according to any one of Configurations 1 to 7, which sweeps the frequency of the modulation signal in an ultrasonic frequency band.

[0136] (Configuration 9) A cell detachment device having the class - D power amplifier device according to any one of Configurations 1 to 8 and vibration generating means, wherein the vibration generating means generates vibration using the power - amplified modulation signal, and imparts the vibration to cells adhered to a culture surface of a culture vessel to detach the cells from the culture surface.

[0137] (Configuration 10) A motor device having the class - D power amplifier device according to any one of Configurations 1 to 8 and an ultrasonic motor, wherein the ultrasonic motor is driven using the power - amplified modulation signal.

Explanation of Signs

[0138] 101 Square - wave generation circuit 102 Integrating circuit 103 Comparator 104 Half - bridge circuit 105 Low - pass filter 106 Sine - wave signal 107 Modulation - wave signal 108 DC power supply 501 Square - wave generation circuit A 502 Integrating circuit A 503 Comparator A 504 Square - wave generation circuit B 505 Integrating circuit B 506 Comparator B 507 Modulated wave signal 508 DC power supply 509 Full bridge circuit 510 Low-pass filter

Claims

1. A modulation wave generation means for generating a modulation wave signal, a carrier wave generation means for generating a carrier wave signal, A class-D power amplifier device that outputs a modulation signal power-amplified by a half-bridge method using the modulation wave signal and the carrier wave signal, Having a low-pass filter that transmits low-frequency components of the power-amplified modulation signal, The modulation wave generation means generates modulation wave signals of a plurality of different frequencies f ｓ and is configured to generate modulation wave signals of a plurality of different frequencies f A class-D power amplifier device that satisfies the relationships of the following formulas (1) and (2). 【Number 1】 However, in the above formulas (1) and (2), f ｃ represents the cut-off frequency of the low-pass filter, f ｂ represents the frequency of the carrier signal, f ｓ represents the frequency of the modulation wave signal.

2. The class-D power amplifier device according to claim 1, which satisfies the relationship of the following formula (3). 【Number 2】

3. A modulation wave generation means for generating a modulation wave signal, a carrier wave generation means for generating a carrier wave signal, A class-D power amplifier device that outputs a modulation signal power-amplified by a full-bridge method using the modulation wave signal and the carrier wave signal, Having a low-pass filter that transmits low-frequency components of the power-amplified modulation signal, The modulation wave generation means generates modulation wave signals having a plurality of different frequencies f ｓ and A class-D power amplifier device that satisfies the relationships of the following formulas (4) and (5). 【Number 3】 However, in the above formulas (4) and (5), f ｃ represents the cut-off frequency of the low-pass filter, f ｂ represents the frequency of the carrier signal, f ｓ represents the frequency of the modulation wave signal.

4. The class-D power amplifier device according to claim 3, which satisfies the relationship of the following formula (6). [Number 4]

5. The class-D power amplifier device according to claim 1 or 3, which satisfies the relationship of the following formula (7). 【Number 5】

6. The above-mentioned f ｂ is a D-class power amplifier device according to claim 1 or 3, which represents the above-mentioned f ｓ as a variable and has a y-intercept represented by a linear function that is non-negative.

7. The aforesaid f ｂ is a variable, and is not less than the value of a linear function having a non-negative y-intercept, and is an integral multiple of the aforesaid f ｓ in the class-D power amplifier according to claim 1 or 3. ｓ ​

8. The class-D power amplifier device according to claim 1 or 3, wherein the class-D power amplifier device sweeps the frequency of the modulation signal in an ultrasonic frequency band.

9. Having the class-D power amplifier device according to claim 1 or 3 and a vibration generation means, The vibration generation means generates vibration using the power-amplified modulation signal, A cell detachment device that detaches the cells from the culture surface by applying the vibration to the cells adhered to the culture surface of the culture vessel.

10. Having the class-D power amplifier device according to claim 1 or 3 and an ultrasonic motor, The ultrasonic motor is a motor device driven using the power-amplified modulation signal.

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