SMALL HIGH-VOLTAGE POWER DRIVING CIRCUIT FOR PIEZOELECTRIC

ELEMENT

Technical Field

The present invention relates to a piezoelectric element driving circuit, and, in particular, to a small high-voltage power driving circuit for a piezoelectric element, which is small and can generate high voltage from a low voltage power source .

Background Art

Currently, with the rapid development of household electronic appliances and industrial electronic appliances, the size thereof is also required to be minimized, through quality based on performance takes top priority.

Although existing electric motors have excellent performance, they have disadvantages in that they are heavy, reduction in size is difficult, and the efficiency thereof is deteriorated as they are minimized. However, since a piezoelectric element functions as an actuator in itself, such a piezoelectric element has advantages in that the size thereof can be considerably reduced, an actuator can be directly included in a structure, and the weight thereof is low. However, high voltage is required to drive a piezoelectric element, so that the dimensions of a power driving circuit are increased,- and thus the overall dimensions of ^" a piezoelectric

element ^' driving, system, including the power driving circuit, are increased. As the dimensions thereof increase, the cost thereof tends to increase .

Meanwhile, when, according to the trend towards reduction in size, emphasis is put on the reduction in the dimension of an electronic appliance, the electronic appliance cannot be smoothly driven, so that an effect desired by a user cannot be obtained.

That is, since an electronic appliance is driven by consuming power, power consumption is directly related to the energy efficiency of the electronic appliance. The energy efficiency is a factor that indicates the excellence of the quality of an electronic appliance.

Therefore, a problem of realizing reduction in size, which is a recent trend, while enabling power to be supplied to smoothly drive an electronic appliance, has arisen.

A piezoelectric element, occasionally called a "piezo element" , has advantages in that it is not only small and lightweight but also effectively generates a large amount of power. However, the size and price of a driving circuit limit a range of various applications of such a piezoelectric element .

Disclosure of the Invention

The present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a small high-voltage power driving circuit for a piezoelectric element, which is small ^'" arid

can generate high voltage from a low voltage power source.

Another object of the present invention is to provide power using a battery.

Still another object of the present invention is to provide a circuit that is constructed by connecting resistors in series, so that it can be prevented from being unstable when a large amount of current is momentarily applied to a piezoelectric element .

In order to accomplish the above objects, the present invention provides a small high-voltage power driving circuit for a piezoelectric element, including a radio wave control unit for generating radio waves; a piezoelectric drive unit including a reception module unit for receiving a radά o wave signal from the radio wave control unit using a Radio Frequency (RF) transmitting/receiving unit, a power module unit for providing a drive voltage using a separately provided battery, a microprocessor module unit for generating a Pulse Width Modulation (PVJM) control signal using the radio frequency signal, a buffer module unit for buffering an electrical problem that may occur when the PWM control signal is transmitted to the full bridge drive module unit from the microprocessor module unit, a full bridge drive module unit for converting the PWM control signal into a PWM signal so as to drive the piezoelectric element, and a high voltage conversion drive module unit for outputting a high voltage PWM signal using the PWM signal and a Direct Current (DC) voltage,- _. and a piezoelectric element actuator for generating displacement in response to a high voltage Pulse Width ^" Modulation ^" (PWM-)- signal .

Preferably, the power module unit includes, a DC/DC conversion module unit for receiving DC voltage from the battery, and converting it into another DC voltage or power having another polarity; a voltage adjustment module unit for receiving and adjusting the DC voltage; and a high voltage conversion module unit for receiving the DC voltage and converting it into high voltage.

Preferably, the buffer module unit- buffers the an electrical problem so as to prevent the piezoelectric drive unit from being affected when external noise is attenuated, impedance matching is performed, and a capacitive load is driven.

Preferably, the piezoelectric drive unit connects resistors in series, so that a circuit can be prevented from being unstable when a large amount of current is momentarily applied to a piezoelectric element .

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram showing the configuration of a small high-voltage power driving circuit for a piezoelectric element according to an embodiment of the present invention; FIG. 2 is a block diagram showing the detailed configuration of ^~ a power module unit according to the

embodiment of the present invention;

FIG. 3 is a view showing the cycle of a signal received from a Radio Frequency (RF) transmitting/receiving unit according to the embodiment of the present invention; FIG. 4 is a detailed circuit diagram showing a voltage adjustment module unit according to the embodiment of the present invention; and

FIG. 5 is a detailed circuit diagram showing a full bridge only having N-channels according to the embodiment of the present invention.

Best Mode for Carrying Out the Invention

Features and advantages of the present invention will be described in detail with reference to the attached drawings below. It should be noted that, in the following description, when it is determined that a detailed description of well-known functions related to the present invention and the construction thereof would make the gist of the present invention obscure, they will be omitted. The present invention will be described in detail with reference to the accompanying drawings below.

A small high-voltage power driving circuit for a piezoelectric element according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5 as follows .

FIG. 1 is a block diagram showing the configuration of a small high-voltage power driving circuit for a piezoelectric ^■

element according to an embodiment of the present invention. FIG. 2 is a block diagram showing the detailed configuration of a power module unit according to the embodiment of the present invention. FIG. 3 is a view showing the cycle of a signal received from an RF transmitting/receiving unit according to the embodiment of the present invention. FIG. 4 is a detailed circuit diagram showing a voltage adjustment module unit according to the embodiment of the present invention. FIG. 5 is a detailed circuit diagram showing a full bridge only having N-channels according to the embodiment of the present invention.

First, as shown in FIG. 1, the small high-voltage power driving circuit for a piezoelectric element includes a radio wave control unit 100 for generating radio waves, a piezoelectric drive unit 200 for providing power so as to drive a small piezoelectric element, and a piezoelectric element actuator 300.

In particular, the piezoelectric drive unit 200 will be described in detail with reference to FIG. 2. The piezoelectric drive unit 200 includes a reception module unit 210, a power module unit 220, a microprocessor module unit 230, a buffer module unit 240, a full bridge drive module unit 250, and a high voltage conversion drive module unit 260.

First, the reception module unit 210 receives a radio wave signal from the radio wave control unit 100, that is, receives a radio frequency signal in which a minimum turned-on time is 1.1 ms and a maximum turned-on time is 1.9 ms, through an RF transmitting/receiving unit, as shown in ^" FIG. 3.

Although a 72 MHz radio frequency signal is received in the present embodiment, the present invention is not limited thereto .

Meanwhile, the power module unit 220 provides drive voltage using a separately equipped battery ^λ B' , and includes a

Direct Current/Direct Current (DC/DC) conversion module unit

221, a voltage adjustment module unit 222, and a high voltage conversion module unit 223.

The DC/DC conversion module unit 221 receives DC voltage from the separately equipped battery "B' and converts it into another DC voltage. In particular, the DC/DC conversion module unit 221 includes a first DC/DC conversion module 2211 for converting a received 7.4 V DC voltage into another voltage, that is, a 12 V voltage, or into the power having another polarity, and a second DC/DC conversion module 2212 for converting the received 7.4 V DC voltage into another voltage, that is, a 3.3 V voltage, or into the power having another polarity.

Here, the 12 V DC voltage, obtained through the conversion of the first DC/DC conversion module 2211, is transmitted to the voltage adjustment module unit 222 and the full bridge drive module unit 250 which will be described later.

Although, in the present embodiment, the battery ^X B' is described as a 7.4 V /1200 mA sky-holic lithium poly battery, that is, a high capacity battery, which has an energy capacity to weight ratio as high as three to five times that of Remote

Control (RC) -dedicated Nickel-Cadmium (Ni-Cd) and Nick ^' el~Meta-l ^r

Hydride (Ni-MH) , and which can be discharged at 10 C (> 92 %) or more, contrary to an existing lithium poly battery, the present invention is not limited thereto.

The voltage adjustment module unit 222 receives DC voltage from the first DC/DC conversion module 2211, and adjusts the voltage, that is, adjusts a 12 V DC voltage to a 5 V DC voltage.

Referring to FIG. 4, the voltage adjustment module unit

222 includes an input pin 1, a ground pin 2, and an output pin 3. The voltage adjustment module unit 222 receives a 12 V DC voltage through the input pin 1, and outputs a 5 V DC voltage through the output pin 3. Here, in the case in which power supply is unstable, the voltage adjustment module unit 222 includes a bypass capacitor C35 configured to prevent internal oscillation, and an output bypass capacitor C36 connected to the output pin 3 and configured to improve the transient response of stable output voltage.

The high voltage conversion module unit 223 receives DC voltage from the second DC/DC conversion module 2212, and converts it into high voltage.

In other words, output voltage is varied by input voltage, so that a 200 V DC voltage can be output when a 3.3 V DC voltage is input.

For the reference, approximately a + 200 V DC voltage is required to drive a piezoelectric element.

Although smart materials require a large amount of current when a large amount of motion is momently performed, the smart materials have an advantage of ^■"■ •requiring little

current when the smart materials reach a normal state. Therefore, a voltage source, required to drive smart materials, can be constructed using a charge accumulation unit and a capacitor. Meanwhile, the microprocessor module unit 230 generates Pulse Width Modulation (PWM) control signals using radio frequency signals received through the reception module unit 210.

In the present invention, it has been described as ATMEGA 128 from ATMEL Corporation generates dual 8-bit PWM channels, that is, PWM control" signals. However, the present invention is not limited thereto.

In order to generate the PWM control signals, timer 3, included in the microprocessor module unit 230, is used. In particular, 2 MHz clocks obtained by dividing the clock of Central Processing Unit (CPU) are used as the reference clock of the timer 3. While the timer 3 continuously counts up, the timer 3 measures a time point value at which an input signal changes from a low level to a high level and a time point value at which the input signal changes from a high level to a low level, and obtains the difference therebetween, thereby obtaining a time period value during the high level of the pulse .

For example, the pulse clocks based on a minimum value 'min' , that is, 1.1 ms, can be obtained by calculating as follows:, pulse clocks = (2E6) x (1.1 E - 3) = (2.2E3).. Further, the pulse clocks based on a maximum value 'max' , that is, 1.9 ^" ms, can be obtained by calculating as ^' follows : ^: pulse

clocks = (2E6) x ( 1 . 9E - 3 ) = (3 . 8E3 ) .

For reference, the microprocessor module unit 230 has values ranging from 0 to 255 based on 8-bit resolution, that is, the microprocessor module unit 230 can output a minimum duty ratio when the value is 0, and output a maximum duty ratio when the value is 255.

That is, in the case in which the pulse clock of a counter is 2.2E3, the microprocessor module unit 230 outputs 0, that is, the minimum duty ratio, and in the case in which the pulse clock of a counter is 3.8E3, the microprocessor module unit 230 outputs 255, that is, the maximum duty ratio.

Therefore, in the case of linear PWM = pulse_clocks/6.3 - 349, if the pulse clock ranges from 2.2E3 to 3.8E3, the value of the PWM ranges from 0 to 255. Here, in the case of a duty ratio of 0%, if 0.2 is input, the value of the PWM is changed to 0, and in the case of a duty ratio of 100%, if 254.17 is input, the value of the PWM is changed to 254.

That is, if a time point value is read and interrupt is generated when a signal is at a rising edge, the read time point value is read during the interrupt. Further, a time point value is measured when the signal is at the falling edge, and interrupt is generated. Therefore, interrupt is generated again when the signal is at the falling edge. Further, a time period value occupied by pulse width can be obtained by subtracting the previously measured time point value from the currently measured time point value. Since the counter continuously counts up, overflow may occur. In this case, a time period value- at a rising edge is subtracted from the

maximum value, in which the counter can have, and then a time point value measured at the rising edge is added to the resulting value. The overflow occurs when the time period value of a falling edge is smaller than the time period value of a rising edge.

The buffer module unit 240 buffers an electrical problem that may occur when the PWM control signal, received from the microprocessor module unit 230, is transmitted to the full bridge drive module unit 250. That is, when the operation of attenuating external noise, matching impedance, or driving a condenser, is performed, the buffer module unit 240 buffers an electrical problem so as to prevent the piezoelectric drive unit 200 from being affected. Here, the buffer module unit 240 receives a 5 V DC voltage form the first DC/DC conversion module 2211 and uses it as driving power.

Next, the full bridge drive module unit 250 converts the received PWM control signal into a PWM signal so as to drive a piezoelectric element.

In particular, the full bridge drive module unit 250 drives Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) . External operation functions and an oscillator (not shown) for performing internal adjustment using low voltage level shift may be restrained so as to drive the full bridge drive module unit 250.

For reference, as shown in FIG. 5, four Switching Mode Power Supply ( ^" SMPS) MOSFETs are diagonally grouped ¹ into uwp

pairs, and the MOSFETs, included in the same group, equally perform turned-on/off operations . If the turned-on/off operations are equally performed, the output thereof is maintained as average ±0 voltage. In other words, when a plurality of turned-on operations is performed, positive (+) voltage is supplied on average. When a plurality of turned-off operations is performed, negative (-) voltage is supplied on average.

That is, the PWM driving circuit can change a direction using a signal power source, thereby leading the effect of using two positive and negative power sources.

Meanwhile, resistors are connected in series, so that a circuit can be prevented from being unstable when a large amount of current is momentarily applied to a piezoelectric element .

Here, the MOSFETs are switching output circuits and are only four N-channels .

In particular, the full bridge circuit is a circuit in which a load is connected between the output terminals of half bridge circuits. When N-channels Tr2 and Tr3 are turned on and

N-channels Tr4 and TrI are turned off, current flows through the load in an IL+ direction.

In contrast, when the N-channels Tr4 and TrI are turned on and the N-channels Tr2 and Tr3 are turned off, current flows through the load in an IL- direction.

As described above, the pair of N-channels Tr2 and Tr3 or Tr4 and TrI is operated while repeatedly alternating between conduction ^~ and cut-off. ^"

Therefore, voltage, as high as two times the case in which a half bridge circuit drives the load, is applied to both terminals of the load, so that the maximum power applied to the load becomes as high as four times that of the half bridge circuit. That is, the voltage power can be effectively used through the full bridge circuit .

The high voltage conversion drive module unit 260 receives a PWM signal capable of driving a piezoelectric element from the full bridge drive module unit 250, and outputs a high voltage PWM signal using the DC voltage received from the second DC/DC conversion module 2212.

Here, the high voltage conversion drive module unit 260 can output a maximum of +250 V DC voltage using 3.3 V DC voltage . For reference, the high voltage conversion drive module unit 260 is used in the same way as a general operational amplifier, thereby amplifying an analog input signal to have high voltage. Such an operational amplifier is stabilized when gain is 10 or more, and should be connected to a compensation capacitor of 10 pF or more. In the case in which output voltage is too high, a piezoelectric element may be damaged. Therefore, a zener diode is connected so as to prevent momentary overvoltage, and a free-wheeling diode is also connected so as to prevent the piezoelectric element from being damaged by inductive load.

Finally, the piezoelectric element actuator 300 generates displacement in response to a high voltage PWM signal.

Although the present invention has been described such that the piezoelectric element can be driven using high voltage, that is, approximately PWM ± 200 V DC voltage, the present invention is not limited thereto.

Industrial Applicability

According to the present invention, a small high-voltage power driving circuit for a piezoelectric element, which is small and can generate high voltage using low voltage, can be manufactured in a small and lightweight form. For example, the small high-voltage power driving circuit for a piezoelectric element can be manufactured in a considerably small and light form, for example, a weight of 3Og and a dimension of 5 x 10 cm, thereby being applied to various fields .

Therefore, the small high-voltage power driving circuit for a piezoelectric element can directly receive PWM-type digital input, wireless RC controller input, or analog input, so that a user can issue a desired high voltage generation command using a microprocessor, an RC controller, an analog signal generator, or commands, thereby realizing convenience of use.

Further, a small low-voltage external power source, such as an external battery, can be used as a power source, thereby easily incorporating with a system which uses high voltage.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those ^~ skilled in the art will appreciate that various modifications ^'

additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims .