KR100799832B1 - A method for setting driving frequency of piezo-actuator - Google Patents

Abstract

A method for setting a driving frequency of a piezo-actuator is provided to optimally drive the piezo-actuator without depending on characteristic changes due to the dispersion or the temperature between actuators and without an assembly state. A method for setting a driving frequency of a piezo-actuator includes the steps of: controlling generation of a lowest oscillation frequency within a previously set variable frequency(S100); driving the piezo-actuator by the use of a driving signal having a current oscillation frequency(S200); storing a variance by each oscillation frequency(S330) by detecting a variance of the piezo-actuator(S200); determining whether or not the oscillation frequency of the current driving signal is a highest oscillation frequency within the driving frequency range(S400); controlling generation of an oscillation frequency higher than the current oscillation frequency by a previously set one step if the oscillation frequency of the current driving signal is the highest oscillation frequency(S500); and setting a driving frequency by selecting a frequency corresponding to a highest variance among the variances for each frequency as an optimum driving frequency(S600).

Description

A METHOD FOR SETTING DRIVING FREQUENCY OF PIEZO-ACTUATOR}

1 is a block diagram of a camera device for performing the present invention.

2 is a waveform diagram of a drive signal of the piezoelectric actuator of FIG. 1;

Figure 3 is a flow chart showing a piezoelectric actuator drive frequency setting method according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: battery 200: crystal oscillator

300: actuator driving IC 400: piezoelectric actuator element

410: first piezoelectric actuator 420: second piezoelectric actuator

500: image sensor 600: image signal processor

The present invention relates to a method for setting a driving frequency of a piezoelectric actuator of a digital camera device applicable to a mobile communication terminal. Particularly, in a digital camera device, an optimum of an actuator used for focus or zoom control is provided. A piezoelectric actuator drive frequency setting method for searching and setting a drive frequency.

In general, in the camera-mounted mobile phone, there is an increasing demand for high resolution and high definition of still images and moving images, and accordingly, the need for an auto focusing device, a macro device, and an optical zoom device is increasing.

In a camera module for a mobile phone, various methods have been tried to date to implement macro and auto focus functions.

In the case of using a DC motor as a driving source among various conventional methods, there are disadvantages in that it is difficult to precisely control the position due to increase in volume and noise, deterioration of response speed, and rotational speed deviation because several reduction gears must be connected.

In addition, when adopting the conventional solenoid method of the conventional method, the resolution is degraded due to the deviation of the magnet and the winding has a weak disadvantage in the structural shock.

In order to solve these disadvantages, a method using a piezoelectric actuator has been adopted.

In the conventional camera module using a piezo actuator (Piezo Actuator), a high voltage alternating current signal is applied to increase the displacement during driving, and a constant displacement occurs even under the same conditions depending on the assembly state of the piezo actuator and the piezo actuator. Since there is a lot of difficulties in mass production.

In addition, since only a certain driving signal is applied by the driving IC of the actuator, since the actual displacement of the piezoelectric actuator is not known, it is difficult to ensure safe driving of the piezoelectric actuator, thereby making it difficult to obtain a stable screen.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems, and an object thereof is to provide an actuator product by searching for and setting an optimum driving frequency of an actuator used for focus or zoom adjustment in a digital camera device. A piezoelectric actuator drive frequency setting method is provided that enables optimum driving of an actuator regardless of the dispersion of the liver or the change of characteristics due to temperature.

In order to achieve the above object of the present invention, the piezoelectric actuator drive frequency setting method according to an embodiment of the present invention, the initial oscillation step of controlling the generation of the lowest oscillation frequency in a predetermined variable frequency range; A driving step of driving the piezoelectric actuator using a driving signal having a current oscillation frequency; Detecting the displacement of the piezoelectric actuator to store the displacement for each oscillation frequency; A determination step of determining whether an oscillation frequency of a current driving signal is the highest oscillation frequency in the driving frequency range; If the oscillation frequency of the current drive signal is not the highest frequency, an iterative oscillation step of controlling the generation of the oscillation frequency by one step higher than the current oscillation frequency and then proceeding to the driving step; And setting the driving frequency by selecting a frequency corresponding to the highest displacement among the displacements of each frequency as an optimum driving frequency when the oscillation frequency of the current driving signal is the highest frequency.

The detecting step may include detecting a displacement corresponding to the movement of the piezoelectric actuator; Converting the displacement into a voltage; And storing the voltage corresponding to the displacement for each frequency.

The detecting step is characterized in that the displacement corresponding to the movement of the piezoelectric actuator is detected based on the width and frequency of the pulse output according to the movement of the piezoelectric actuator.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is not limited to the embodiments described, and the embodiments of the present invention are used to assist in understanding the technical spirit of the present invention. In the drawings referred to in the present invention, components having substantially the same configuration and function will use the same reference numerals.

1 is a block diagram of a camera apparatus for carrying out the present invention.

Referring to FIG. 1, a camera device for implementing the present invention includes a battery 100 for supplying an operating power of approximately 3.0 V to 4.5 V, a crystal oscillator 200 for oscillating a reference frequency of approximately 19.2 MHz, An actuator driving IC 300 receiving operating power from the battery 100, converting a reference oscillation frequency from the crystal oscillator 200 into a preset driving frequency, and outputting a driving signal having the driving frequency; A piezoelectric actuator element unit 400 for adjusting focus or / and zoom according to a drive signal of the actuator driving IC 300, an image sensor 500 for acquiring an image, and an image signal from the image sensor 500. And an image signal processor 600 for processing.

The piezoelectric actuator element 400 may zoom in accordance with a first piezoelectric actuator 410 for adjusting focus according to a driving signal of the actuator driving IC 300 and a driving signal of the actuator driving IC 300. A second piezoelectric actuator 420 for adjustment.

The use of the first and second piezoelectric actuators 410 and 420 is advantageous in miniaturization as compared with the conventional motor or solenoid methods.

FIG. 2 is a waveform diagram of a drive signal of the piezoelectric actuator of FIG. 1.

As illustrated in FIG. 2, the driving signal may have a peak-peak voltage (Vp-p) of about 30V ± 3V and a frequency of about 37.5K ± 500Hz.

3 is a flowchart illustrating a piezoelectric actuator driving frequency setting method according to an embodiment of the present invention.

3, the piezoelectric actuator driving frequency setting method according to an embodiment of the present invention, the initial oscillation step (S100) for controlling the generation of the lowest oscillation frequency in the predetermined variable frequency range, and the drive having the current oscillation frequency A driving step of driving a piezoelectric actuator using a signal (S200), a detecting step of detecting displacement of the piezoelectric actuator and storing displacement for each oscillation frequency (S300), and an oscillation frequency of a current driving signal within the driving frequency range Determination step (S400) for determining whether the highest oscillation frequency, and if the oscillation frequency of the current drive signal is not the highest frequency after controlling the generation of the oscillation frequency by a predetermined step higher than the current oscillation frequency proceeds to the driving step Repeated oscillation step (S500) and, if the oscillation frequency of the current drive signal is the highest frequency, each frequency And a setting step (S600) of selecting a frequency corresponding to the highest displacement among the respective displacements as an optimum driving frequency and setting the driving frequency.

The detecting step (S300), detecting a displacement corresponding to the movement of the piezoelectric actuator (S310), converting the displacement into a voltage (S320), and storing the voltage corresponding to the displacement for each frequency It includes a step (S330).

The detecting step S300 detects a displacement corresponding to the movement of the piezoelectric actuator based on the width and the frequency of the pulse output according to the movement of the piezoelectric actuator.

Hereinafter, the operation and effects of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a process of searching for and setting an optimal driving frequency in a camera apparatus for carrying out the present invention is performed, which will be described with reference to FIGS. 1 to 3.

Referring to the piezoelectric actuator driving frequency setting method according to an embodiment of the present invention, first referring to FIG. 3, in the initial oscillation step, the lowest oscillation frequency is generated in a preset variable frequency range (S100).

That is, referring to FIG. 1, the actuator driving IC 300 is supplied with operating power from the battery 100 included in the range of 3.0V to 4.5V, and the oscillation frequency from the crystal oscillator 200 (approximately 19.2). MHz to generate the lowest oscillation frequency in a preset variable frequency range.

Next, in the driving step, the piezoelectric actuator is driven using a driving signal having a current oscillation frequency (S200).

That is, referring to FIG. 1, the actuator driving IC 300 generates a driving signal having the lowest oscillation frequency and outputs the driving signal to the piezoelectric actuator element unit 400, specifically, the driving having the lowest oscillation frequency. The signal is generated and output to the first piezoelectric actuator 410 or the second piezoelectric actuator 420 of the piezoelectric actuator element unit 400, respectively. Here, the first piezoelectric actuator 410 is for focus, and the second piezoelectric actuator 420 is for zoom.

Next, in the detecting step, the displacement of the piezoelectric actuator is detected and stored for each oscillation frequency (S300).

Specifically, in the detecting step S300, the actuator driving IC 300 detects a displacement corresponding to the movement of the piezoelectric actuator through a displacement sensor (not shown) (S310), and the detected displacement. After converting to a voltage (S320), and matching the voltage corresponding to the displacement for each frequency and stored in the internal memory (not shown) (S330).

In the detection step (S300), the displacement corresponding to the movement of the piezoelectric actuator is detected based on the width and frequency of the pulse output according to the movement of the piezoelectric actuator.

For example, the displacement sensor for measuring the displacement of the actuator may be used as a sensor for detecting a pulse according to the movement speed of the actuator. At this time, the displacement sensor outputs a pulse signal having a narrow pulse width and a high pulse frequency when the movement speed is high, and on the contrary, outputs a pulse signal having a wide pulse width and a high pulse frequency when the movement speed is low.

Next, in the determining step, it is determined whether the oscillation frequency of the current driving signal is the highest oscillation frequency in the driving frequency range (S400).

Referring to FIG. 1, the actuator driving IC 300 determines whether the oscillation frequency of the current driving signal is the highest oscillation frequency within a preset driving frequency range. This will be described later.

Next, in the repetitive oscillation step, when the oscillation frequency of the current driving signal is not the highest frequency, the generation of the oscillation frequency by one step higher than the current oscillation frequency is controlled and then proceeds to the driving step (S500).

Referring to FIG. 1, when the oscillation frequency of the current driving signal is not the highest frequency in the driving frequency range, the actuator driving IC 300 includes an oscillation frequency of one step higher than the current oscillation frequency. After controlling the generation, proceed to the drive step.

Here, the one step may be determined according to the environment of the system to be applied, for example, when the driving frequency range is 1MHz ~ 10MHz, the one step is 1MHz, the lowest oscillation frequency is 1MHz, the highest oscillation The frequency is 10 MHz.

In the setting step, when the oscillation frequency of the current driving signal is the highest frequency, the frequency corresponding to the highest displacement among the displacements for each frequency is selected as the optimum driving frequency and set as the driving frequency (S600).

Referring to FIG. 1, the actuator driving IC 300 compares a plurality of voltages matched with each frequency to find the largest voltage, and converts the frequency matched with the largest voltage into an optimal driving frequency of the actuator. Select to set.

For example, the driving signal may have a peak-peak voltage (Vp-p) of about 30V ± 3V and a frequency of about 37.5K ± 500Hz as shown in FIG. 2.

As described above, after the optimal driving frequency is set, the camera shown in FIG. 1 can drive the actuator by using the driving signal having the optimal driving frequency, and also the digital camera macro and auto focus adjustment functions. In the device that adjusts the relative distance between the image sensor and the lens to perform the operation, as a driving source, it can be mounted on a mobile phone while using a piezo actuator that can be driven by a simple control circuit of low voltage. Control was made possible.

According to the present invention as described above, in the method of setting the drive frequency of the piezoelectric actuator of the digital camera device applicable to the mobile communication terminal, in the digital camera device of the actuator used for the focus (focus) or zoom (zoom) adjustment By searching for and setting the optimum drive frequency, the actuator can be optimally driven regardless of the dispersion between actuator products or the characteristic change due to temperature, and it can be driven at the optimum drive frequency regardless of the assembly state, thereby improving productivity. It has an effect.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, but is defined by the claims, and the apparatus of the present invention may be substituted, modified, and modified in various ways without departing from the spirit of the present invention. It is apparent to those skilled in the art that modifications are possible.

Claims (3)

An initial oscillation step of controlling generation of a lowest oscillation frequency in a predetermined variable frequency range; A driving step of driving the piezoelectric actuator using a driving signal having a current oscillation frequency; Detecting the displacement of the piezoelectric actuator to store the displacement for each oscillation frequency; A determination step of determining whether an oscillation frequency of a current driving signal is the highest oscillation frequency in the driving frequency range; If the oscillation frequency of the current drive signal is not the highest frequency, an iterative oscillation step of controlling the generation of the oscillation frequency by one step higher than the current oscillation frequency and then proceeding to the driving step; And If the oscillation frequency of the current drive signal is the highest frequency, a setting step of selecting a frequency corresponding to the highest displacement among the displacements of each frequency as the optimum drive frequency, and setting the drive frequency Piezoelectric actuator drive frequency setting method comprising a. The method of claim 1, wherein the detecting step, Detecting a displacement corresponding to the movement of the piezoelectric actuator; Converting the displacement into a voltage; And Storing the voltage corresponding to the displacement for each frequency Piezoelectric actuator drive frequency setting method comprising a. The method of claim 2, wherein the detecting step, And detecting the displacement corresponding to the movement of the piezoelectric actuator based on the width and the frequency of the pulse output according to the movement of the piezoelectric actuator.

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