electrostatic motor drive circuit

Abstract

To achieve high output without increasing a size of a circuit configuration.SOLUTION: A voltage application circuit 3 includes: a half-bridge circuit 12 including switching elements Q1 and Q2; an inductor L1 having one terminal connected to the half-bridge circuit 12 and the other terminal connected to a stator electrode 5; a half-bridge circuit 13 including switching elements Q3 and Q4; and an inductor L2 having one terminal connected to the half-bridge circuit 13 and the other terminal connected to the stator electrode 5. The voltage application circuit 3 utilizes resonance between each of the inductors L1 and L2, which is generated by complementarily turning on and off the switching elements Q1, Q2 and Q3, Q4, and an electrode capacitance 6 formed with the stator electrode 5 as one electrode, to output an output voltage, which is a voltage having an amplitude higher than that of a power supply voltage VDD, from the other terminal of each of the inductors L1 and L2, and uses the output voltage to generate a positive fixed voltage, a negative fixed voltage, an A-phase voltage, and a B-phase voltage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrostatic motor drive circuit for driving an electrostatic motor.

Background Art

[0002] An electrostatic motor is configured to obtain a rotational force by an electrostatic force generated between a rotor electrode which is an electrode provided on a rotor and a stator electrode which is an electrode provided on a stator. An electrostatic motor drive circuit for driving such an electrostatic motor applies a fixed voltage to one of each electrode, and applies a voltage of phase A whose level is switched according to the rotational position and a voltage of phase B which is opposite in phase to the voltage of phase A to the other of each electrode. Patent Document 1 discloses an electrostatic motor drive circuit employing a circuit configuration of an isolated flyback converter. In the following description, the configuration disclosed in Patent Document 1 will be referred to as the prior art.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, since the output voltage of the drive circuit, that is, the motor applied voltage which is the voltage applied to the electrostatic motor is only the positive electrode, a high voltage corresponding thereto is required to achieve high output. Further, in the prior art, since the voltage between the ground and the ground becomes high when applying such a high voltage, insulation design becomes difficult, and there is a risk of causing a large size of the circuit configuration.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrostatic motor drive circuit capable of achieving high output without causing a large size of the circuit configuration. [Means for solving the problem]

[0006] The electrostatic motor drive circuit described in claim 1 drives an electrostatic motor (2) configured to obtain rotational force by the electrostatic force generated between an electrode (4) provided on the rotor and an electrode (5) provided on the stator, and includes a voltage application circuit (3, 41). In this case, one of the electrodes provided on the rotor and the electrode provided on the stator is designated as the first electrode and the other as the second electrode, and the voltage on the higher potential side is designated as the positive voltage and the voltage on the lower potential side is designated as the negative voltage, with the ground (10), which is the reference potential of the circuit, as the boundary. The voltage application circuit applies a positive fixed voltage and a negative fixed voltage to the first electrode, and applies a first phase voltage, which is switched between positive and negative according to the rotation position of the electrostatic motor, and a second phase voltage that is in opposite phase to the first phase voltage, to the second electrode.

[0007] The voltage application circuit includes a first half-bridge circuit (12, 21, 31) including two switching elements (Q1, Q2, Q21, Q22, Q31, Q32) connected in series between a power line (9) to which a power supply voltage is applied and the ground; a first inductor (L1) with one terminal connected to the first half-bridge circuit and the other terminal connected to the second electrode; a second half-bridge circuit (13) including two switching elements (Q3, Q4) connected in series between the power line and the ground; and a second inductor (L2) with one terminal connected to the second half-bridge circuit and the other terminal connected to the second electrode.

[0008] The voltage application circuit utilizes the resonance between the first inductor and the second inductor, which occurs when the two switching elements are switched on and off complementaryly, and the electrode capacitance (6) formed with the second electrode as one of the electrodes, to output an output voltage having a higher amplitude than the power supply voltage from the other terminal of the first inductor and the second inductor. The voltage application circuit uses the output voltage to generate the positive fixed voltage, the negative fixed voltage, the first phase voltage, and the second phase voltage.

[0009] According to the above configuration, the electrode capacitance unique to electrostatic motors is utilized, and an output voltage with a higher amplitude than the power supply voltage is generated by LC resonance between the electrode capacitance and the first and second inductors. This output voltage is then used to generate a positive fixed voltage, a negative fixed voltage, a first phase voltage, and a second phase voltage. In this way, positive and negative voltages can be applied to each electrode of the electrostatic motor, making it possible to increase the motor applied voltage. As a result, the torque, which increases in proportion to the square of the voltage, can be improved, or in other words, the output power can be increased. Furthermore, this makes it easier to ensure withstand voltage to ground, allowing for miniaturization of the circuit configuration. Therefore, the above configuration provides the excellent effect of achieving high output power without increasing the size of the circuit configuration. [Brief explanation of the drawing]

[0010] [Figure 1] This figure schematically shows the configuration of the electrostatic motor drive circuit according to the first embodiment. [Figure 2] This figure schematically shows the configuration of each electrode of the electrostatic motor according to the first embodiment. [Figure 3] Figure 1 shows an example of a specific electrode configuration of an electrostatic motor according to the first embodiment. [Figure 4] Figure 2 shows an example of a specific electrode configuration of the electrostatic motor according to the first embodiment. [Figure 5] This diagram schematically shows the waveforms of the voltages applied to each electrode of the electrostatic motor by the voltage application circuit according to the first embodiment. [Figure 6] This diagram shows only the configuration for one phase of the voltage application circuit according to the first embodiment. [Figure 7] A diagram illustrating the operation of a single-phase configuration of the voltage application circuit according to the first embodiment. [Figure 8] This diagram schematically shows the waveforms of each part of one phase of the voltage application circuit during startup and boosting according to the first embodiment. [Figure 9]This diagram schematically shows the waveforms of each part of one phase of the voltage application circuit during actual operation according to the first embodiment. [Figure 10] This diagram schematically shows the waveforms of each part of the voltage application circuit during actual operation according to the first embodiment. [Figure 11] This diagram shows only the configuration for one phase of the voltage application circuit according to the second embodiment. [Figure 12] This diagram shows only the configuration for one phase of the voltage application circuit according to the third embodiment. [Figure 13] Figure 1 shows only the configuration for one phase of the voltage application circuit according to the fourth embodiment. [Figure 14] Figure 2 shows only the configuration for one phase of the voltage application circuit according to the fourth embodiment. [Modes for carrying out the invention]

[0011] Several embodiments will be described below with reference to the drawings. In each embodiment, substantially identical components are denoted by the same reference numerals and their descriptions are omitted. (First Embodiment) The first embodiment will be described below with reference to Figures 1 to 10.

[0012] <Overall Structure> As shown in Figure 1, the electrostatic motor drive circuit 1 of this embodiment drives the electrostatic motor 2 and includes a voltage application circuit 3. In the following description, the electrostatic motor drive circuit 1 may be abbreviated as drive circuit 1. As shown in Figure 2, the electrostatic motor 2 is configured to obtain rotational force by the electrostatic force generated between the rotor electrode 4, which is an electrode provided on the rotor, and the stator electrode 5, which is an electrode provided on the stator. In this configuration, the stator electrode 5 is used as one electrode and the rotor electrode 4 is used as the other electrode to form an electrode capacitance 6. In the following description, the rotor electrode 4 and the stator electrode 5 may be abbreviated as electrode 4 and electrode 5, respectively.

[0013] As a specific electrode configuration of the electrostatic motor 2, for example, a configuration as shown in FIGS. 3 and 4 can be adopted. FIG. 3 shows a configuration in which a large number of electrodes 4 and 5 are arranged circumferentially, that is, in a direction parallel to the axis 7. FIG. 4 shows a configuration in which a large number of electrodes 4 and 5 are arranged radially, that is, in a direction perpendicular to the axis 7. In this case, the rotor electrode 4, which is one of the rotor electrode 4 and the stator electrode 5, corresponds to the first electrode, and the other stator electrode 5 corresponds to the second electrode. Also, in this case, with the ground serving as the reference potential of the circuit, the voltage on the high-potential side is set as a positive voltage and the voltage on the low-potential side is set as a negative voltage.

[0014] The voltage application circuit 3 applies a positive fixed voltage and a negative fixed voltage to the rotor electrode 4, and applies a phase-A voltage and a phase-B voltage whose positive and negative are switched according to the rotational position of the electrostatic motor 2 to the stator electrode 5. In this case, the phase-A voltage corresponds to the first-phase voltage, and the phase-B voltage corresponds to the second-phase voltage. The positive fixed voltage, the negative fixed voltage, the phase-A voltage, and the phase-B voltage are voltages having waveforms as shown in FIG. 5. In FIGS. 1 and 5, etc., the positive fixed voltage is abbreviated as "positive", the negative fixed voltage as "negative", the phase-A voltage as "A", and the phase-B voltage as "B".

[0015] The positive fixed voltage is a voltage that is constant with a voltage value higher than 0V, which is the potential of the ground 10. The negative fixed voltage is a voltage that is constant with a voltage value lower than 0V. The phase-A voltage and the phase-B voltage are voltages in which a voltage value higher than 0V and a voltage value lower than 0V are alternately switched. However, the phase-B voltage is a voltage having a phase opposite to that of the phase-A voltage. That is, the phase-A voltage and the phase-B voltage are shifted from each other by a half cycle in phase.

[0016] The voltage application circuit 3 operates by receiving a power supply voltage VDD supplied from a DC power supply 8. The high-potential terminal of the DC power supply 8 is connected to the power line 9 via resistor R1, and its low-potential terminal is connected to ground 10. Between the power line 9 and ground 10, a capacitor C1 is connected, which together with resistor R1 forms a filter circuit 11 for smoothing the power supply voltage VDD.

[0017] The voltage application circuit 3 includes half-bridge circuits 12 and 13, inductors L1 and L2, diodes D1 to D4, etc. Half-bridge circuit 12 corresponds to the first half-bridge circuit and includes two switching elements Q1 and Q2 connected in series between the power line 9 to which the power supply voltage VDD is supplied and ground 10. Half-bridge circuit 12 includes diodes D5 and D6 which function as reverse current prevention units to prevent reverse current flow in the two switching elements Q1 and Q2.

[0018] The switching elements Q1 and Q2 can be composed of transistors such as MOSFETs or IGBTs. In this case, both switching elements Q1 and Q2 are N-channel MOSFETs. The drain of switching element Q1 is connected to the power line 9, and its source is connected to node N1 via diode D5 in the forward direction. The drain of switching element Q2 is connected to node N1 via diode D6 in the reverse direction, and its source is connected to ground 10.

[0019] A binary drive signal Sa output from the control circuit 14 is supplied to the gate of switching element Q1 via buffer 15. A binary drive signal Sb output from the control circuit 14 is supplied to the gate of switching element Q2 via buffer 16. With this configuration, the on / off state of switching elements Q1 and Q2 is controlled by the control circuit 14. The control circuit 14 is supplied with a rotation signal Sc representing the rotation position of the electrostatic motor 2. Based on the rotation signal Sc, the control circuit 14 controls the operation of the drive circuit 1 so that the rotation position of the electrostatic motor 2 is at the desired position.

[0020] Inductor L1 corresponds to the first inductor, with one terminal connected to node N1 of the half-bridge circuit 12 and the other terminal connected to the stator electrode 5. Diode D1 corresponds to the first diode, with its anode connected to the other terminal of inductor L1. The cathode of diode D1 is connected to the rotor electrode 4. Diode D2 corresponds to the second diode, with its cathode connected to the other terminal of inductor L1. The anode of diode D2 is connected to the rotor electrode 4.

[0021] The half-bridge circuit 13 corresponds to the second half-bridge circuit and includes two switching elements Q3 and Q4 connected in series between the power line 9 to which the power supply voltage VDD is supplied and ground 10. The half-bridge circuit 13 is equipped with diodes D7 and D8 which function as reverse current prevention units to prevent reverse current flow to the two switching elements Q3 and Q4. The switching elements Q3 and Q4 can be composed of transistors such as MOSFETs or IGBTs. In this case, both switching elements Q3 and Q4 are N-channel type MOSFETs. The drain of switching element Q3 is connected to the power line 9, and its source is connected to node N2 via diode D7 in the forward direction.

[0022] The drain of switching element Q4 is connected to node N2 via diode D8 in reverse, and its source is connected to ground 10. The gate of switching element Q3 is supplied with a binary drive signal Sd output from control circuit 14 via buffer 17. The gate of switching element Q4 is supplied with a binary drive signal Se output from control circuit 14 via buffer 18. With this configuration, the on / off state of switching elements Q3 and Q4 is controlled by control circuit 14.

[0023] Inductor L2 corresponds to the second inductor, with one terminal connected to node N2 of the half-bridge circuit 13 and the other terminal connected to the stator electrode 5. Diode D3 corresponds to the first diode, with its anode connected to the other terminal of inductor L2. The cathode of diode D3 is connected to the rotor electrode 4. Diode D4 corresponds to the second diode, with its cathode connected to the other terminal of inductor L2. The anode of diode D4 is connected to the rotor electrode 4.

[0024] The voltage application circuit 3 utilizes the LC resonance between the inductor L1 and the electrode capacitance 6, which is generated by complementary switching on and off of the two switching elements Q1 and Q2 of the half-bridge circuit 12, to output an output voltage from the other terminal of inductor L1, which has an amplitude higher than the power supply voltage VDD. The voltage application circuit 3 then uses this output voltage to generate a positive fixed voltage, a negative fixed voltage, and an A-phase voltage. Specifically, the voltage application circuit 3 outputs the cathode voltage of diode D1 as a positive fixed voltage and the anode voltage of diode D2 as a negative fixed voltage. In addition, the voltage application circuit 3 outputs the output voltage output from the other terminal of inductor L1 as the A-phase voltage.

[0025] The voltage application circuit 3 utilizes the LC resonance between the inductor L2 and the electrode capacitance 6, which is generated by complementary switching on and off of the two switching elements Q3 and Q4 of the half-bridge circuit 13, to output an output voltage with an amplitude higher than the power supply voltage VDD from the other terminal of the inductor L2. The voltage application circuit 3 then uses this output voltage to generate a positive fixed voltage, a negative fixed voltage, and a B-phase voltage. Specifically, the voltage application circuit 3 outputs the cathode voltage of diode D3 as a positive fixed voltage and the anode voltage of diode D4 as a negative fixed voltage. In addition, the voltage application circuit 3 outputs the output voltage output from the other terminal of the inductor L2 as the B-phase voltage.

[0026] Next, the operation of the voltage application circuit 3 with the above configuration will be explained with reference to Figures 6 to 10. In [1] to [3] below, the operation will be explained using the half-bridge circuit 12 and the configuration corresponding to the half-bridge circuit 12, that is, the configuration for one phase, as examples, but the operation of the half-bridge circuit 13 and the configuration corresponding to the half-bridge circuit 13 will be explained similarly. Also, in Figure 6, the illustration of configurations that are not relevant to the explanation of operation has been omitted.

[0027] [1] Overview of operation As mentioned above, the voltage application circuit 3 utilizes the resonance between the inductor L1 and the electrode capacitance 6. During the period Ta when the switching element Q1 is turned on, current flows through the inductor L1 and electrode capacitance 6 via path A1, indicated by the dotted arrow in Figure 6, thus performing a voltage boost operation. During the period Tb when the switching element Q2 is turned on, half a cycle after the voltage boost operation, current flows through the inductor L1 and electrode capacitance 6 via path A2, indicated by the dotted arrow in Figure 6, thus performing a regenerative operation, or voltage inversion operation.

[0028] As a result of these operations, the output voltage output from the other terminal of inductor L1 is as shown in Figure 7. In Figure 7 and other figures, the output voltage is denoted as Vo and the inductor current as IL. In Figure 7 and other figures, the drive signals Sa and Sb are such that a high level turns on the switching element, and a low level turns off the switching element. As shown in Figure 7, the output voltage Vo has a higher amplitude than the power supply voltage VDD. Specifically, in the initial operation in Figure 7, the drive signal Sa becomes high, causing a boost operation due to resonance, and the output voltage Vo is boosted to approximately twice the power supply voltage VDD. Then, after half a cycle, the drive signal Sb becomes high, causing an inversion operation, and the output voltage Vo becomes a negative voltage, that is, a negative voltage is generated.

[0029] In the above configuration, since resonance is utilized, it is desirable to set the on-time Ton, which is the time for turning on the switching elements Q1 and Q2, to a time that is equal to or greater than half a period of resonance. Therefore, in this embodiment, the control circuit 14 controls the operation of the drive circuit 1 so that the on-time Ton satisfies the following equation (1). However, the inductance value of the inductor L1 is L, and the capacitance value of the electrode capacitance 6 is C.

[0030]

number

[0031] In this embodiment, for example, if the capacitance value C of electrode capacitance 6 is 100 pF and the inductance value L of inductor L1 is 1 H, the on-time Ton will be set to 31.4 μs.

[0032] [2] Waveforms of each part during startup boost (1 phase) During startup voltage boosting, that is, immediately after the drive circuit 1 starts up and there is no load, the waveforms of each part of one phase are as shown in Figure 8. In this case, each operation is repeated every half cycle in the order of "voltage boosting due to resonance" → "generation of negative voltage due to inversion" → "voltage boosting due to resonance"..., so the output voltage Vo gradually increases as the resonant amplitude with respect to the power supply voltage VDD increases. As a result, a voltage sufficiently larger than the power supply voltage VDD is obtained as the output voltage. With the above configuration, after the amplitude of the output voltage reaches the desired value, the output voltage can be set to any voltage by controlling the pulse width of the drive signals Sa and Sb, that is, the on time of the switching elements Q1 and Q2.

[0033] [3] Waveforms of each part during actual operation (one phase) During actual operation, that is, when the drive circuit 1 is driving the electrostatic motor 2, the waveforms of each part of one phase are as shown in Figure 9. In this case, the output voltage increases with each repetition of the operation, while the output voltage decreases due to power consumption by the electrostatic motor 2 and changes in capacitance due to electrode movement. As a result, the output voltage balances out at a predetermined level higher than the power supply voltage VDD.

[0034] As shown in Figure 9, the output voltage decreases at a predetermined slope from the boost operation to the inversion operation. This is due to power consumption by the electrostatic motor 2 and changes in capacitance associated with electrode movement, as mentioned above. In the inversion operation, the remaining voltage that has decreased in this way is reversed, so the absolute value of the negative voltage is smaller than that of the positive voltage in the output voltage.

[0035] [4] Waveforms of each part during actual operation (overall) The waveforms of each part of the overall system during actual operation, that is, when the output voltage is in equilibrium, are as shown in Figure 10. The A-phase voltage applied to the stator electrode 5 is the output voltage output from the other terminal of inductor L1, and therefore has a waveform similar to the output voltage shown in Figure 9. The B-phase voltage applied to the stator electrode 5 is the output voltage output from the other terminal of inductor L2, and therefore has a waveform similar to the output voltage shown in Figure 9. However, the A-phase voltage and B-phase voltage have waveforms that are in opposite phases to each other. In Figure 10, the inductor current flowing through inductor L1 is denoted as ILA, and the inductor current flowing through inductor L2 is denoted as ILB.

[0036] The positive fixed voltage applied to rotor electrode 4 is a DC voltage with a voltage value approximately equal to the peak values ​​on the positive side of the A-phase and B-phase voltages, since it is obtained by rectifying the cathode voltages of diodes D1 and D3, i.e., the A-phase voltage and B-phase voltage by diodes D1 and D3 and smoothing them by the electrode capacitance between the positive and negative sides of the rotor. The negative fixed voltage applied to rotor electrode 4 is a DC voltage with a voltage value approximately equal to the peak values ​​on the negative side of the A-phase and B-phase voltages, since it is obtained by rectifying the anode voltages of diodes D2 and D4, i.e., the A-phase voltage and B-phase voltage by diodes D2 and D4 and smoothing them by the electrode capacitance between the positive and negative sides of the rotor.

[0037] According to the embodiment described above, the following effects can be obtained. The drive circuit 1 of this embodiment utilizes the electrode capacitance 6 specific to the electrostatic motor 2, and generates an output voltage with an amplitude higher than the power supply voltage VDD through LC resonance between the electrode capacitance 6 and inductors L1 and L2. This output voltage is then used to generate a positive fixed voltage, a negative fixed voltage, an A-phase voltage, and a B-phase voltage.

[0038] In this way, positive and negative voltages can be applied to each electrode 4 and 5 of the electrostatic motor 2, making it possible to increase the motor applied voltage. As a result, the torque, which increases in proportion to the square of the voltage, can be improved, or in other words, the output can be increased. Furthermore, this method makes it easier to ensure the withstand voltage to ground, allowing for a smaller circuit configuration. Therefore, according to this embodiment, the excellent effect of achieving high output without increasing the size of the circuit configuration can be obtained.

[0039] In the drive circuit 1 of this embodiment, as described above, the electrode capacitance 6 that originally exists in the electrostatic motor 2 is used as the configuration for resonance, so the circuit configuration can be made smaller compared to when a separate capacitor is provided for resonance. In addition, in this embodiment, the voltage application circuit 3 is configured with inductors L1 and L2, and the switching operation for generating the output voltage is soft switching, so switching losses and electromagnetic interference noise are reduced, and the load on each element including the switching elements Q1 to Q4 is reduced, resulting in the effect of suppressing surges, heat generation, etc.

[0040] Conventional technology simply boosts the voltage using a transformer, and since it does not take load characteristics into consideration, there is a risk of high losses and reduced efficiency. In contrast, the drive circuit 1 of this embodiment enables high output by boosting the voltage through resonance, and further reduces losses and achieves high efficiency by performing regenerative operation. In this embodiment, transistors such as MOSFETs and IGBTs can be used as switching elements Q1 to Q4. By doing so, a configuration for resonance can be formed using general-purpose elements, which offers advantages such as reduced manufacturing costs and easier parts procurement.

[0041] Half-bridge circuit 12 is equipped with diodes D5 and D6, which function as a reverse current prevention unit to prevent reverse current flow to switching elements Q1 and Q2. Half-bridge circuit 13 is equipped with diodes D7 and D8, which function as a reverse current prevention unit to prevent reverse current flow to switching elements Q3 and Q4. In this way, the resonance effect can be made to function as a boosting operation.

[0042] In the voltage application circuit 3, the on-time Ton, which is the time it takes to turn on each of the switching elements Q1 to Q4, can be set to a time that is greater than or equal to half a period of resonance. In this way, it becomes possible to reliably obtain the voltage boosting effect due to resonance, and to more reliably achieve higher output power.

[0043] (Second Embodiment) Below, a second embodiment in which the configuration of the half-bridge circuit is modified compared to the first embodiment will be described with reference to Figure 11. In Figure 11, the explanation uses a configuration corresponding to the first half-bridge circuit as an example, but the configuration corresponding to the second half-bridge circuit can be similarly implemented.

[0044] As shown in Figure 11, the half-bridge circuit 21 of this embodiment corresponds to the first half-bridge circuit and includes two switching elements Q21 and Q22 connected in series between the power line 9 and the ground 10. The switching elements Q21 and Q22 are reverse-blocking IGBTs, or RB-IGBTs. The collector of switching element Q21 is connected to the power line 9 and its emitter is connected to node N1. The collector of switching element Q22 is connected to node N1 and its emitter is connected to the ground 10.

[0045] A drive signal Sa is supplied to the gate of switching element Q21 via a buffer 15 (not shown). A drive signal Sb is supplied to the gate of switching element Q22 via a buffer 16 (not shown). In this case, the switching elements Q21 and Q22 themselves, which are composed of reverse-blocking IGBTs, function as a reverse current prevention unit that prevents reverse current flow in the two switching elements Q21 and Q22.

[0046] This embodiment also provides the same effects as the first embodiment. Furthermore, this embodiment allows for the omission of four diodes D5 to D7 compared to the first embodiment, thereby reducing the number of elements and, as a result, further miniaturizing the circuit configuration.

[0047] (Third embodiment) A third embodiment, in which the configuration of the half-bridge circuit is modified compared to the first embodiment, will be described below with reference to Figure 12. In Figure 12, the explanation uses a configuration corresponding to the first half-bridge circuit as an example, but the configuration corresponding to the second half-bridge circuit can be similarly implemented.

[0048] As shown in Figure 12, the half-bridge circuit 31 of this embodiment corresponds to the first half-bridge circuit and includes two switching elements Q31 and Q32 connected in series between the power line 9 and the ground 10. The switching elements Q31 and Q32 are thyristors. The anode of switching element Q31 is connected to the power line 9 and its cathode is connected to node N1. The anode of switching element Q22 is connected to node N1 and its cathode is connected to the ground 10.

[0049] A drive signal Sa is supplied to the gate of switching element Q31 via a buffer 15 (not shown). A drive signal Sb is supplied to the gate of switching element Q32 via a buffer 16 (not shown). Generally, thyristors have the disadvantage of not being able to be turned off, but in this circuit, the switching elements Q31 and Q32, which are thyristors, can be turned off by stopping the current. In this case, the switching elements Q31 and Q32, which are composed of thyristors, themselves function as a reverse current prevention unit that prevents the current flowing back through the two switching elements Q31 and Q32.

[0050] This embodiment also provides the same effects as the first embodiment. Furthermore, this embodiment allows for the omission of four diodes D5 to D7 compared to the first embodiment, thereby reducing the number of elements and, as a result, further miniaturizing the circuit configuration. In addition, this embodiment uses thyristors as switching elements Q31 and Q32, which has the advantage of simplifying control compared to the first embodiment, which uses transistors such as MOSFETs as switching elements Q1 and Q2.

[0051] (Fourth Embodiment) A fourth embodiment, in which the configuration and arrangement of the inductors are changed from the first embodiment, will be described below with reference to Figures 13 and 14.

[0052] Figure 13 shows only the configuration corresponding to the first half-bridge circuit 12 of the voltage application circuit 41 in this embodiment, and Figure 14 shows only the configuration corresponding to the second half-bridge circuit 13 of the voltage application circuit 41 in this embodiment.

[0053] As shown in Figure 13, the voltage application circuit 41 of this embodiment includes an inductor L3. In this case, one terminal of inductor L1 is connected to the half-bridge circuit 12 and the other terminal is connected to node N41. Inductor L3 corresponds to a third inductor, and one terminal of it is connected to the half-bridge circuit 12 and the other terminal is connected to node N41. Node N41 is connected to the stator electrode 5 that forms the electrode capacitance 6.

[0054] Specifically, one terminal of inductor L1 is connected to the upstream switching element Q1 of the two switching elements Q1 and Q2 included in the half-bridge circuit 12 via diode D5 in the reverse direction. Also, one terminal of inductor L3 is connected to the downstream switching element Q2 of the two switching elements Q1 and Q2 included in the half-bridge circuit 12 via diode D6 in the forward direction.

[0055] As shown in Figure 14, the voltage application circuit 41 of this embodiment includes an inductor L4. In this case, one terminal of inductor L2 is connected to the half-bridge circuit 13 and the other terminal is connected to node N42. Inductor L4 corresponds to the fourth inductor, and one terminal of it is connected to the half-bridge circuit 13 and the other terminal is connected to node N42. Node N42 is connected to the stator electrode 5 that forms the electrode capacitance 6.

[0056] Specifically, one terminal of inductor L2 is connected to the upstream switching element Q3 of the two switching elements Q3 and Q4 included in the half-bridge circuit 13 via diode D7 in the reverse direction. Also, one terminal of inductor L4 is connected to the downstream switching element Q4 of the two switching elements Q3 and Q4 included in the half-bridge circuit 13 via diode D8 in the forward direction.

[0057] This embodiment also provides the same effects as the first embodiment. Furthermore, this embodiment and the first embodiment each have the following advantages. In the first embodiment, only one inductor is needed for each of the half-bridge circuits 12 and 13, thus simplifying the circuit configuration compared to this embodiment. In contrast, this embodiment requires two inductors for each of the half-bridge circuits 12 and 13. However, the inductors L1 and L2, located on the upstream side of the two inductors, make it difficult for a steep current to flow during recovery, thus reducing recovery losses compared to the first embodiment.

[0058] (Other embodiments) It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and can be arbitrarily modified, combined, or expanded without departing from its essence. The numerical values ​​and other figures shown in each of the above embodiments are illustrative examples and are not limiting.

[0059] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure. [Explanation of Symbols]

[0060] 1...Electrostatic motor drive circuit, 2...Electrostatic motor, 3...Voltage application circuit, 4...Rotor electrode, 5...Stator electrode, 6...Electrode capacitance, 9...Power line, 10...Ground, 12...Half-bridge circuit, 13...Half-bridge circuit, 21...Half-bridge circuit, 31...Half-bridge circuit, 41...Voltage application circuit, D1, D3...Diodes, D2, D4...Diodes, D5, D6, D7, D8...Diodes, L1...Inductor, L2...Inductor, L3...Inductor, L4...Inductor, Q1, Q2...Switching element, Q3, Q4...Switching element, Q21, Q22...Switching element, Q31, Q32...Switching element.

Claims

1. An electrostatic motor drive circuit for driving an electrostatic motor (2) configured to obtain rotational force by the electrostatic force generated between an electrode (4) provided on the rotor and an electrode (5) provided on the stator, If one of the electrodes provided on the rotor and the electrode provided on the stator is designated as the first electrode and the other as the second electrode, and if the voltage on the higher potential side is defined as a positive voltage and the voltage on the lower potential side is defined as a negative voltage with respect to the ground (10) which is the reference potential of the circuit, The device includes a voltage application circuit (3, 41) that applies a positive fixed voltage and a negative fixed voltage to the first electrode, and applies a first phase voltage, which is switched between positive and negative according to the rotation position of the electrostatic motor, and a second phase voltage, which is in the opposite phase to the first phase voltage, to the second electrode. The voltage application circuit is A first half-bridge circuit (12, 21, 31) includes two switching elements (Q1, Q2, Q21, Q22, Q31, Q32) connected in series between a power line (9) to which a power supply voltage is supplied and the ground, A first inductor (L1) having one terminal connected to the first half-bridge circuit and the other terminal connected to the second electrode, A second half-bridge circuit (13) includes two switching elements (Q3, Q4) connected in series between the power line and the ground, A second inductor (L2) having one terminal connected to the second half-bridge circuit and the other terminal connected to the second electrode, Equipped with, By switching the two switching elements on and off in a complementary manner, the resonance between the first inductor and the second inductor and the electrode capacitance (6) formed with the second electrode as one of the electrodes is utilized to output an output voltage having an amplitude higher than the power supply voltage from the other terminal of the first inductor and the second inductor. An electrostatic motor drive circuit that generates the positive fixed voltage, the negative fixed voltage, the first phase voltage, and the second phase voltage using the output voltage.

2. The electrostatic motor drive circuit according to claim 1, wherein the first half-bridge circuit and the second half-bridge circuit are equipped with reverse current prevention units (D5, D6, D7, D8, Q21, Q22, Q31, Q32) that prevent reverse current flow to the two switching elements.

3. The electrostatic motor drive circuit according to claim 1 or 2, wherein the on-time, which is the time for turning on the two switching elements, is set to a time of half a cycle or more of the resonance.

4. The voltage application circuit is A first diode (D1, D3) whose anode is connected to the other terminal of one or both of the first and second inductors, A second diode (D2, D4) whose cathode is connected to the other terminal of one or both of the first and second inductors, Equipped with, The cathode voltage of the first diode is output as the positive fixed voltage. The voltage at the anode of the second diode is output as the negative fixed voltage. The output voltage output from the other terminal of the first inductor is output as the first phase voltage. The electrostatic motor drive circuit according to claim 1 or 2, wherein the output voltage output from the other terminal of the second inductor is output as the second phase voltage.

5. The voltage application circuit (41) is A third inductor (L3) having one terminal connected to the first half-bridge circuit and the other terminal connected to the second electrode, A fourth inductor (L4) having one terminal connected to the second half-bridge circuit and the other terminal connected to the second electrode, Equipped with, One terminal of the first inductor is connected to the upstream switching element of the two switching elements included in the first half-bridge circuit. One terminal of the third inductor is connected to the downstream switching element of the two switching elements included in the first half-bridge circuit. One terminal of the second inductor is connected to the upstream switching element of the two switching elements included in the second half-bridge circuit. The electrostatic motor drive circuit according to claim 1 or 2, wherein one terminal of the fourth inductor is connected to the downstream switching element of the two switching elements included in the second half-bridge circuit.

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