JP2011160309A - Capacitive load driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To configure a capacitive load driving circuit which suppresses an energy loss caused by charging/discharging of a capacitive load accompanying moving of a voltage application position to the capacitive load, without degrading rising/falling sharpness of a pulsed voltage. <P>SOLUTION: A capacitive load driving circuit 101 includes: a DC power source 10 which generates a positive voltage Vc; four output terminals V1-V4; eight voltage selection switch elements S<SB>1H</SB>, S<SB>1L</SB>, S<SB>2H</SB>, S<SB>2L</SB>, S<SB>3H</SB>, S<SB>3L</SB>, S<SB>4H</SB>, S<SB>4L</SB>; and a switch control section 12. Furthermore, a charge transfer serial circuit including inductors L1-L4 and charge transfer switch elements S<SB>1&Gamma;</SB>-S<SB>4&Gamma;</SB>is provided for each between two output terminals among the four output terminals V1-V4. Switching of the voltage selection switch elements is then performed by the switch control section 12, and a charge transfer switch element provided between two output terminals wherein a voltage is switched, among the plurality of output terminals, is turned on during shifting in which the output voltage is switched. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a capacitive load driving circuit that sequentially charges and discharges a plurality of capacitive loads such as linear electrodes of a gas transport device and piezoelectric elements of a wire dot printer.

  For example, a linear electrode of a gas transfer device, a piezoelectric element of a wire dot printer, and the like include a plurality of capacitive loads, and these capacitive loads are sequentially charged and discharged by a capacitive load driving circuit.

  In the gas transfer device of Patent Document 1, linear electrodes parallel to each other are formed on the surface of the substrate, and the linear electrodes are arranged in parallel in a predetermined number n in the order of arrangement of the linear electrodes, and are constant with respect to each other. The n-phase drive voltage is applied so that the voltage of the same pattern periodically changes.

  FIG. 1 is a plan view of an array electrode substrate portion 50 provided in the gas conveyance device of Patent Document 1. FIG. On the upper surface of the dielectric substrate 51, a plurality of linear electrodes 52 are arranged in parallel and at regular intervals. Four-phase drive voltages are input from the output terminals V1 to V4 of the periodic pulse power supply. The linear electrodes 52 are connected in parallel at the connection portions 53 every four in the arrangement order, and are connected to the output terminals V1 to V4 of the periodic pulse power supply. When the number of phases is n = 4 and the period is T, the time of (T / 4) × (i−1) <t <(T / 4) × i (i = 1, 2, 3 or 4) is a linear electrode (capacitance). A positive voltage is applied to the electrode of the capacitive load, and a ground potential is applied at other times of the period T. Due to this potential difference, a dielectric barrier discharge is generated between the linear electrodes, the gas molecules are ionized, the generated charged particles are accelerated by the electric field, and the charged particles and nearby gas molecules move in the direction of movement of the electric field.

  Patent Document 2 discloses a capacitive load drive circuit that can suppress the generation of Joule heat due to an excessive current accompanying charging and discharging of a piezo element used in a wire dot printer. That is, a transformer including a charging side coil and a discharging side coil is provided so that a voltage generated in the charged capacitive load is used for charging the capacitive load to be charged next.

  In Patent Document 3, in a capacitive load driving circuit that charges and discharges a plurality of capacitive loads via a circuit element including an inductance component, the circuit element including the inductance component is charged and discharged for each capacitive load. It is provided on a common path of the circuit.

International Publication No. 2008/099569 Pamphlet Japanese Patent Laid-Open No. 2-67006 JP 2005-41076 A

  In the capacitive load driving circuit of Patent Document 2, a capacitive load (piezo element) is charged via a transistor and a diode. At this time, the current supplied to the piezoelectric element has a gentle slope due to the inductance component of the transformer. Increases linearly from 0. Therefore, the rise time of the pulse voltage becomes long. Therefore, it is not used as a drive circuit for the gas transfer device.

  Further, in the capacitive load driving circuit of Patent Document 3, the inductor connected between the capacitive load and the energy storage capacitor prevents a sudden change in current, so that the rise of the pulse voltage is delayed. Therefore, it is not used as a drive circuit for the gas transfer device.

  An object of the present invention is to provide a capacitive load driving circuit that suppresses energy loss associated with charging and discharging of a capacitive load accompanying movement of a voltage application position to the capacitive load without impairing the steepness of rising and falling of the pulse voltage. Is to provide.

At least three output terminals to which the input terminals of the capacitive load circuit are connected;
Provided for each output terminal, selectively connected to one of a plurality of voltage sources having different potentials, and outputs the voltage of the voltage source to the output terminal to charge / discharge the capacitive load. In capacitive load drive circuit with switch element,
A charge transfer series circuit including an inductor and a charge transfer switch element provided between two output terminals of the at least three output terminals;
The voltage selection switch element is switched, and the charge transfer switch element provided between two output terminals of which the voltage is switched among the plurality of output terminals is turned on at the time of transition in which the voltage of the output terminal is switched. Switch control means.

  For example, the capacitance of the capacitive load circuit is substantially unchanged with respect to the cyclic replacement of the input terminal Pi (n: an integer equal to or greater than 3; i = 1, 2,... N).

  For example, in the charge transfer series circuit, a diode in a direction in which a discharge current from a capacitive load flows in a forward direction is connected in series to the inductor and the charge transfer switch element.

  For example, the switch control unit turns on the charge transfer switch element and turns off the charge transfer switch element in a state where all the voltage selection switches provided in the output terminals are opened. Later, a predetermined voltage selection switch element is turned on among the voltage selection switch elements provided in the output terminals.

  According to the present invention, the charge stored in a certain capacitive load moves to the other capacitive load by the resonance current, and most of the charge is transferred without waste. Further, it is not consumed as Joule heat due to resistance loss at the time of charge transfer, power required for the voltage source is reduced, and temperature rise is also suppressed.

  In addition, since a diode is connected to the charge transfer series circuit in a direction in which the discharge current from the capacitive load flows in the forward direction, only a half cycle of the current flowing due to resonance between the capacitive load and the inductor is automatically performed. Current flows. Therefore, it is not necessary to strictly control the on-time of the charge transfer switch element, and the switching control is simplified.

  In addition, the charge transfer switch element is turned on in a state where all of the voltage selection switches provided in each output terminal are in an open state, and the charge transfer switch element is turned off. By turning on a predetermined voltage selection switch element among the voltage selection switch elements, it is possible to transfer charges between capacitive loads without affecting the voltage source that outputs a voltage to each output terminal.

FIG. 11 is a plan view of an array electrode substrate unit 50 provided in the gas transfer device of Patent Document 1. 1 is a circuit diagram of a capacitive load drive circuit 100 as a comparative example of the capacitive load drive circuit according to the first embodiment. FIG. It is a wave form diagram of each part of FIG. 1 is a circuit diagram of a capacitive load driving circuit 101 according to a first embodiment. FIG. FIG. 5 is a diagram in which each switch element in FIG. 4 is replaced with a switch symbol. Switching elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , and S _{4L as} the time elapses, switch elements S _{1T to} S _4T for charge transfer It is a figure which shows the change of an ON / OFF state, and the voltage change of output terminal V1-V4. It is an equivalent circuit diagram of a capacitive load. It is the figure which expanded and showed the time axis of the time area | region 1 enclosed with the dashed-dotted line in FIG. FIG. 6 is an equivalent circuit diagram of the circuit shown in FIG. 5 at time t2 to time t3. FIG. 10 is an equivalent circuit diagram when the capacitive load shown in FIG. 7 is connected to the equivalent circuit of FIG. 9. The voltage selection switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , S _4L are turned on by the control of the switch control unit of the capacitive load driving circuit according to the second embodiment. FIG. 4 is a diagram showing a change in / off state, a change in on / off state of the charge transfer switch elements S _{1T to} S _4T , and a voltage change in output terminals V1 to V4.

<< First Embodiment >>
Before describing the capacitive load driving circuit according to the first embodiment, a configuration of a capacitive load driving circuit 100 as a comparative example is shown in FIG. In addition, FIG. 3 shows waveforms of each part of the circuit.
This capacitive load driving circuit 100 includes a DC power supply 10 that generates a positive voltage Vc, four output terminals V1 to V4, and eight switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , S _4L , and a switch control unit 11 are provided.

FIG. 3 shows changes in the on / off states of the switching elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , and S _4L and the voltage changes in the output terminals V1 to V4 with time. Show.

Thus, each of the output terminals V1 to V4 includes the high-side switch elements _S1H , _S2H , _S3H , _S4H and the low-side switch elements _S1L , _S2L , _S3L , _S4L . By providing a circuit having a half bridge configuration, a high level voltage Vc and a low level voltage 0 can be selectively output. In this example, if the number of phases is n = 4 and the period is T, (T / 4) × (i−1) <t <(T / 4) × i (i = 1, 2, 3 or 4) is high. The level (Vc) is output, and a low level (ground potential) is applied at other times of the period T.

However, in the capacitive load driving circuit 100 shown in FIG. 2, a loss occurs every time the voltage of the output terminal is switched as described below. Taking the timing shown in time domain 1 in FIG. 3 as an example, at this timing, the output terminal V1 changes from high level to low level, and the output terminal V2 changes from low level to high level. At that time, the electric charge charged in the capacitive load connected to the output terminal V1 is discharged through the low-side switch element _S1L . On the other hand, a charging current for the capacitive load connected to the output terminal V2 flows through the high-side switch element _S2H of the output terminal V2. That is, the charge path and the discharge path are different, and each time discharge is performed from the capacitive load, almost all of the charge energy is consumed as Joule heat in the switch element.

  FIG. 4 is a circuit diagram of the capacitive load driving circuit 101 according to the first embodiment. FIG. 5 is a diagram in which each switch element in FIG. 4 is replaced with a switch symbol. In order to facilitate comparison with FIG. 2, the configuration and operation of the capacitive load driving circuit 101 according to the first embodiment will be described first with reference to FIG.

The capacitive load driving circuit 101 includes a DC power supply 10 that generates a positive voltage Vc, four output terminals V1 to V4, and eight voltage selection switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , _S4H , _S4L, and the switch control part 12 are provided. Unlike the circuit shown in FIG. 2, among the four output terminals V1-V4, each between two output terminals, the diode D1 to D4, a charge comprising an inductor L1~L4 and charge transfer switch S _1T to S _4T Each series circuit for transfer is provided. The switch control unit 12 corresponds to “switch control means” according to the present invention.

FIG. 6 shows switching elements for voltage selection switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , and S _{4L over time,} a switch for charge transfer change the on / off state of the element S _1T to S _4T, and shows the voltage change of the output terminal V1-V4.

As described above, the voltage selection switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , S _4L are switched to turn on the voltages of the output terminals V 1, V 2, V 3, V 4 in order. Switch to When the voltage at one output terminal is on, the voltage at the remaining output terminals is off. There is provided a time region (transition time) in which both are turned off when switching from the previous output terminal to the next output terminal, and the charge transfer switch element S _1T provided between the two output terminals at the transition time. ~ S _4T turns on.

In FIG. 6, for example, focusing on the time domain 1, the output terminal V1 changes from high level to low level and the output terminal V2 changes from low level to high level. At this transition, the charge transfer switch element S _1T Turn on.

Further, when the output voltage is switched, the output terminals V1 to V4 are temporarily opened, and the charge transfer switch elements S _{1T to} S _4T are turned on at that time.
In FIG. 6, for example, focusing on the time domain 1, the voltage selection switch element S _1T is turned on after the voltage selection switch element S _1H is turned off, and the voltage selection is performed after the charge transfer switch element S _1T is turned off. Switch element S _1L is turned on.

When the charge transfer switch element S _1T is turned on, the charge charged in the capacitive load connected to the output terminal V1 is connected to the diode D1 → the inductor L1 → the charge transfer switch element S _1T → the output terminal V2. Current flows through the capacitive load path. At this time, resonance occurs between the capacitance of the capacitive load connected to the output terminal V1 and the inductance of the inductor L1. That is, the current flowing through the path is a resonance current. However, since the diode D1 is inserted in the path, current does not flow in the reverse direction and energy is not alternately converted between the capacitance and the inductance, but discharge from the capacitive load connected to the output terminal V1. When the above is completed, the energization of the resonance current ends.

  In this way, the electric charge stored in a certain capacitive load (first capacitive load) is transferred to another capacitive load (second capacitive load) using an inductor (inductive reactor). Therefore, most of the electric charge of the first capacitive load moves to the second capacitive load due to the resonance current. Further, it is not consumed as Joule heat due to resistance loss at the time of charge transfer, power required for the voltage source is reduced, and temperature rise is also suppressed.

Next, the charge transfer principle will be described more theoretically.
First, FIG. 7 shows an example of an equivalent circuit of a capacitive load. In FIG. 7, the four capacitors have the same capacitance Co. Here, the capacitance between the input terminals Pi of the capacitive load circuit shown in FIG. 7 is almost unchanged with respect to the cyclic replacement of the input terminals Pi (i = 1, 2, 3, 4). Here, “invariant to cyclic permutation” means that the permutation {1, 2, 3, 4} of the subscript of the input terminal Pi (i = 1, 2, 3, 4) is {2, 3, 4, 1} indicates that the circuit cannot be distinguished.

The capacitive load input terminal Pi (i = 1, 2, 3, 4) shown in FIG. 7 is connected to the output terminal Vi (i = 1, 2, 3, 4) shown in FIG.
FIG. 8 is an enlarged view of the time axis of the time region 1 surrounded by the one-dot chain line in FIG. In FIG. 8, before time t1, each switch (voltage selection switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , S _4L and the charge transfer switch shown in FIG. From the setting of the elements S _{1T to} S _4T ), the voltage at the output terminal V1 is Vc, and the voltages at the output terminals V2, V3, and V4 are all zero.

From time t1 to time t2, the voltages V1 to V4 are all held from the setting of each switch element shown in FIG.
From time t2 to time t3, the circuit shown in FIG. 5 is equivalent to the circuit shown in FIG. 9 because of the setting of each switch element shown in FIG. FIG. 10 shows an equivalent circuit when the capacitive load shown in FIG. 7 is connected to the equivalent circuit shown in FIG.

  In FIG. 8, from time t2 to time t3, since the relationship of the voltage of the output terminal V1> the voltage of the output terminal V2 is satisfied, the analysis may be performed without the diode D1 in FIG. As shown in FIG. 10, the electric charges of the two electrodes of each capacitor are set as q1, q2, and q4, and the currents i1 and i2 are determined as shown in the figure. At this time, from the relationship of the potential with respect to the closed circuit around the three capacitors,

Is obtained. Also, from the relationship between the potentials at both ends of the inductor,

Is obtained. Also, from the relationship between charge and current in each capacitor,

Is obtained. Moreover, each voltage of V1-V4 is

It is expressed as In addition, for the charge at t = t2,

Holds. Moreover, since the current flowing through the inductor is zero at t = t2,

Holds. When equations (1) to (6) are solved for each voltage of V1 to V4,

Is obtained. here,

It is. The current flowing through the inductor is

It is. The time for the forward current to flow through the diode D1 in FIG.

It is. After this time, the current stops.

Therefore, Expression (7) is effective during the time of Expression (10), and it can be seen that the voltages V1 to V4 change as illustrated in FIG. This curve is part of a sine wave. Here, Trf1 in FIG. 8 is obtained by using ω ₀ in Equation (8).

It can be expressed.

  In the above description, the discussion was focused on the time domain 1 in FIG. 6, but the charge movement occurs similarly in other time domains, and the output terminals V1 to V4 as shown in FIG. Time change of each voltage can be realized.

  According to the present invention, in addition to the above-described effects, a diode is connected to the charge transfer series circuit in a direction in which a discharge current from the capacitive load flows in the forward direction. A current automatically flows only in a half cycle of the current flowing due to resonance. Therefore, it is not necessary to strictly control the on-time of the charge transfer switch element, and the switching control is simplified.

  In addition, the charge transfer switch element is turned on in a state where all of the voltage selection switches provided in each output terminal are in an open state, and the charge transfer switch element is turned off. By turning on a predetermined voltage selection switch element among the voltage selection switch elements, it is possible to transfer charges between capacitive loads without affecting the voltage source that outputs a voltage to each output terminal.

  Of course, there are actually Joule loss due to the resistance of each element and conductor, dielectric loss due to the dielectric loss tangent of the substrate material, and radiation loss due to the generation of electromagnetic waves due to changes in current over time. small.

FIG. 4 is a circuit diagram in the case where each switch element of the circuit shown in FIG. 5 is composed of an enhancement type n-channel MOSFET. MOSFETs Q _1H , Q _1L , Q _2H , Q _2L , Q _3H , Q _3L , Q _4H , Q _4L in FIG. ₄ are voltage selection switch elements S _1H , S _1L , S _2H , S _2L , The MOSFETs Q _1T , Q _2T , Q _3T , Q _4T in FIG. 4 correspond to the charge transfer switch elements S _1T , S _2T , S _3T , S _4T respectively corresponding to S _3H , S _3L , S _4H , S _4L . Each corresponds.

The switch control unit 12 shown in FIG. 4 outputs a control signal between the gate and source of each MOSFET, thereby turning on each MOSFET. Since each MOSFET is an enhancement type n-channel MOSFET, the gate voltages V _G1H , V _G1L , V _G1T , V _G2H , V _G2L , V _G2T , V _G3H , V _G3L , V _G3T , V _G4H , V _G4T , V _G4T , V _G4T It remains off when it is at low level (0V) and turns on when the gate voltage is high.

  The diodes D1 to D4 are, for example, fast recovery diodes having a withstand voltage higher than the voltage Vc. By using the fast recovery diode, only the current corresponding to a half cycle of the resonance current is reliably energized, and the energy is transferred from the capacitive load to the inductors L1 to L4 with high efficiency.

<< Second Embodiment >>
In the first embodiment, switching (selective connection) of the voltage selection switch element is performed, and among the plurality of output terminals, only the charge transfer switch element provided between the two output terminals where the voltage is switched is Although it is turned on at the time of transition when the output voltage is switched, the on-control of the charge transfer switch element is not limited to this. For example, in the example shown in FIGS. 9 and 10, the output voltage of the output terminals V3 and V4 is 0, and this is equivalent to the state where no capacitive load is connected to any of the output terminals V3 and V4. At this timing, the charge transfer switch element _S3T provided between the output terminals V3 and V4 may be controlled to be turned on. That is, both of the charge transfer switch elements S _1T and S _3T are turned on at this timing.

FIG. 11 shows ON / OFF states of voltage selection switch elements S _1H , S _1L , S _2H , S _2L , S _3H , S _3L , S _4H , and S _4L as time elapses when the above control is performed. , Changes in the on / off states of the charge transfer switch elements S _{1T to} S _4T , and voltage changes in the output terminals V 1 to V 4. The circuit itself is the same as that shown in FIGS.

  As described above, the state of the charge transfer switch element may be arbitrarily determined at a timing not involved in charge transfer.

<< Other embodiments >>
In each of the embodiments described above, the case where the number of phases n is 4 is exemplified, but the present invention is generally applicable if the number of phases is 2 or more. Even if it is limited to the case where it is applied to a gas conveying device as shown in Patent Document 1, the number n of phases may be 3 or more.

The capacitance between the input terminals of the capacitive load circuit has been described as being almost unchanged with respect to the cyclic permutation of the input terminal Pi (n: integer of 3 or more, i = 1, 2,... N). In the operation of the capacitive load driving circuit, it is not always necessary that the plurality of capacitances C ₀ are exactly the same. Even if the capacitances C ₀ are slightly different from each other, the operation is performed without any problem. However, when the load capacity is not constant, the positive voltage Vc must be increased compared to the case where the load capacity is constant. Therefore, the fluctuation of the capacitance C ₀ is 10% or less from the viewpoint of ease of design of the periodic pulse power supply. It is preferable.

As the capacitive load circuit, a configuration is shown in which the equivalent capacitance C ₀ is connected in a ring shape between the input terminals P1 and P2, between P2 and P3, between P3 and P4, and between P4 and P1. It is not limited to. For example, it is substantially invariant to a cyclic permutation of the input terminal Pi be configured to further the capacitance C ₁ is connected between P1-P3 between the P2-P4.

D1 to D4 ... diodes L1 to L4 ... inductor P1 to P4 ... input terminal _{Q 1H, Q 1L, Q 2H} , Q 2L, Q 3H, Q 3L, Q 4H, Q 4L ... voltage selection MOSFET
Q _1T , Q _2T , Q _3T , Q _4T ... MOSFET for charge transfer
Vc: Positive voltage V _G1H , V _G1L , V _G1T , V _G2H , V _G2L , V _G2T , V _G3H , V _G3L , V _G3T , V _G4H , V _G4L , V _G4T ... Capacitive load Co ... Capacitive load _S1H , _S1L , _S2H , _S2L , _S3H , _S3L , _S4H , _S4L ... voltage selection switch elements _S1T , _S2T , _S3T , _S4T ... charge transfer switch elements V1 to V4 ... Output terminal 10 ... DC power supply 11, 12 ... Switch control unit 50 ... Array electrode substrate unit 51 ... Dielectric substrate 52 ... Linear electrode 53 ... Connection unit 100, 101 ... Capacitive load drive circuit

Claims (4)

At least three output terminals to which the input terminal of the capacitive load circuit is connected and each of the output terminals is selectively connected to one of a plurality of voltage sources having different potentials, and the voltage of the voltage source is In a capacitive load drive circuit including a voltage selection switch element that outputs to an output terminal and charges and discharges the capacitive load,
A charge transfer series circuit including an inductor and a charge transfer switch element provided between two output terminals of the at least three output terminals;
The voltage selection switch element is switched, and the charge transfer switch element provided between two output terminals of which the voltage is switched among the plurality of output terminals is turned on at the time of transition in which the voltage of the output terminal is switched. And a capacitive load drive circuit comprising switch control means.   The capacitance between the input terminals of the capacitive load circuit is substantially invariant with respect to the cyclic permutation of the input terminal Pi (n: an integer equal to or greater than 3; i = 1, 2,... N). Capacitive load driving device according to claim 1.   3. The charge transfer series circuit according to claim 1, wherein a diode in a direction in which a discharge current from a capacitive load flows in a forward direction is connected in series to the inductor and the charge transfer switch element. Capacitive load drive circuit.   The switch control means turns on the charge transfer switch element and turns off the charge transfer switch element in a state where all the voltage selection switch elements provided in each of the output terminals are opened. 4. The capacitive load drive circuit according to claim 1, wherein a predetermined voltage selection switch element is turned on later among the voltage selection switch elements provided in each of the output terminals.

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