This application claims the benefit of Korean Patent Application Nos. 10-2005-0014228, filed on Feb. 21, 2005, and 10-2005-0051982, filed on Jun. 16, 2005 and 10-2005-0111882 filed on 22 Nov. 2005 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a circuit for protecting an electrical and/or electronic system, and more particularly, to a circuit for protecting electronic components included in an electrical and/or electronic system from an external high-voltage high-frequency noise signal or static electricity.
2. Description of the Related Art
Noise that affects electronic components flows in through a power line that supplies power to an electric and electronic system and a signal line that receives and outputs an electrical signal from and to the electric and electronic system. Accordingly, an electrical and/or electronic system protecting circuit is installed between the power line and an internal electronic component or between the signal line and the internal electronic component. The electrical and/or electronic system protecting circuit is so important as to say that the electrical and/or electronic system protecting circuit is required by almost all electronic products.
Low-voltage noise signals coming via a power line or a signal line are generally blocked by a noise signal removing filter included in an electrical and/or electronic system protecting circuit. On the other hand, it is known that high-voltage power noise is removed by a varistor which is a semiconductor resisting element formed of ZnO. When a high voltage or large current is applied to the varistor, the electrical characteristics of the varistor change. In other words, when a voltage dropping from, the varistor is high or much current flow in the varistor, high heat is generated. The electrical characteristics of the varistor are changed by the heat so that the varistor turns into a low resistor. The varistor having the characteristics of a resistor in that its resistance value changes according to a voltage value of a received signal can reduce a received surge noise signal.
When the electrical and/or electronic system is installed in a place where a motor exists or in a place where static electricity or a high-voltage electromagnetic wave exists, the possibility that high-frequency noise with a high voltage larger than a rated standard voltage is received via the power line and/or signal line of the electrical and/or electronic system cannot be excluded. The varistor is remarkably good at blocking the low-frequency noise signal with a high voltage but is poor at blocking a high-voltage, high-frequency noise signal. This fact is due to the physical characteristics of the varistor.
However, the thing that destroys most of electrical and/or electronic systems or their internal electronic components is high-voltage high-frequency noise having several mega hertz (MHz) or greater or an instantaneous high voltage, such as, static electricity.
To protect electronic components from unwanted signals, such as, such high-voltage, high-frequency noise signals and static electricity, a constant voltage protecting apparatus, such as, an inverter surge filter, has been proposed. The inverter surge filter can be manufactured by adequately combining a low pass filter with a high pass filter. Each of the low pass filter and the high pass filter may be made up of a resistor, an inductor, and a capacitor. However, it is not simple to form such an inverter surge filter having predetermined electrical characteristics, and the formation requires a high cost. In addition, although the inverter surge filter is installed in an electrical and/or electronic system, if an incoming noise signal has a high frequency and a high voltage, the security of the electrical and/or electronic system cannot be 100% guaranteed:
A noise signal having a high voltage and a high-frequency component may stop an operation of a microprocessor installed within an electrical and/or electronic system. The interruption of the operation of the microprocessor can may not occur by using a watch dog that always monitors an operational state of the microprocessor. However, the use of such a watch dog requires high costs regardless of whether the monitoring is achieved using software or hardware.
As described above, a conventional protecting circuit cannot protect internal electronic components from a received high-voltage, high-frequency noise signal and requires high costs to achieve protection.
The present invention provides a circuit and method of protecting an electrical and/or electronic system, by which when high-frequency noise with a high voltage, that is, a voltage greater than a rated standard voltage, flows into the electrical and/or electronic system via a power line or a signal line, the noise can be effectively removed. Here, the noise denotes any noise that can cause the electrical and/or electronic system to disorder while having a voltage greater than the rated standard voltage. Examples of the noise include lightning, high-voltage discharge, etc.
According to an aspect of the present invention, there is provided an electrical and/or electronic system protecting circuit comprising an abrupt metal-insulator transition (MIT) device connected in parallel to an electrical and/or electronic system to be protected from noise.
Electrical characteristics of the abrupt metal-insulator transition device abruptly change according to a voltage level of the noise. That is, the abrupt metal-insulator transition device has a characteristic of an insulator below a predetermined limit voltage and has a characteristic of a metal at or over the limit voltage.
The abrupt metal-insulator transition device is connected in parallel to a power voltage source which supplies the power voltage to the electrical and/or electronic system or to a signal source which supplies the signal to the electrical and/or electronic system. The abrupt metal-insulator transition device is connected to the power voltage source or the signal source via a protecting resistor which protects the abrupt metal-insulator transition device. The electrical and/or electronic system protecting circuit further includes a power voltage reinforcing capacitor connected in parallel to the power voltage source or the signal source.
According to another aspect of the present invention, there is provided an electrical and/or electronic system protecting circuit comprising an abrupt metal-insulator transition device that is connected in parallel to an electrical and/or electronic system to be protected from noise and includes an abrupt metal-insulator transition thin film containing low-concentration holes and a first electrode thin film and a second electrode thin film that contact the abrupt metal-insulator transition thin film.
The abrupt MIT device may have either a stacked structure or a planar-type structure according to the locations of a transition thin film, a first electrode thin film, and a second electrode thin film. The abrupt metal-insulator transition thin film may be formed of at least one material selected from the group consisting of an inorganic semiconductor to which low-concentration holes are added, an inorganic insulator to which low-concentration holes are added, an organic semiconductor to which low-concentration holes are added, an organic insulator to which low-concentration holes are added, a semiconductor to which low-concentration holes are added, an oxide semiconductor to which low-concentration holes are added, and an oxide insulator to which low-concentration holes are added, wherein the above-described materials each include at least one of oxygen, carbon, a semiconductor element (i.e., groups III-V and groups II-IV), a transition metal element, a rare-earth element, and a lanthanum-based element.
Each of the first and second electrode thin films is formed of at least one material selected from the group consisting of W, Mo, W/Au, Mo/Au, Cr/Au, Ti/W, Ti/Al/N, Ni/Cr, Al/Au, Pt, Cr/Mo/Au, YB2Cu3O7-d, Ni/Au, Ni/Mo, Ni/Mo/Au, Ni/Mo/Ag, Ni/Mo/Al, Ni/W, Ni/W/Au, Ni/W/Ag, and Ni/W/Al.
According to another aspect of the present invention, there is provided an electrical and/or electronic system, the system including a load electric and electronic system to be protected from noise and an electrical and/or electronic system protecting circuit including an abrupt metal-insulator transition (MIT) device connected in parallel to the load electrical and/or electronic system.
The electrical and/or electronic system may include a power voltage source which supplies the power voltage to the load electrical and/or electronic system or a signal source which supplies the signal to the load electrical and/or electronic system. The electrical and/or electronic system protecting circuit may further include at least one abrupt MIT device connected in parallel to the previous abrupt MIT device.
The attached drawings for illustrating preferred embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by the implementation of the present invention.
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
The present invention proposes an electrical and/or electronic system protecting circuit which removes static electricity or high-voltage high frequency noise from an electrical and/or electronic system by using a new medium whose electrical characteristics abruptly vary according to a voltage level of a received signal. The new medium is referred as a metal-insulator transition (MIT) device.
Referring to
The transition of the electrical characteristic of the abrupt MIT device to the metallic material resulting in the discontinuous jump of current is described in some papers, namely, New J. Physics 6 (2004) 52; http//xxx.lanl.gov/abs/con-mat/041328; and Appl. Phys. Lett. 86 (2005) 242101, and U.S. Pat. No. 6,624,463 to the inventors of the present invention.
A voltage at which the electrical characteristic of an abrupt MIT device transits from an insulator to a metallic material is defined as a limit voltage. According to this definition, the limit voltage of the abrupt MIT device of
An abrupt MIT device used in the present invention may have either a stacked (or vertical) structure or a planar-type structure according to the locations of a transition thin film, a first electrode thin film, and a second electrode thin film.
The buffer layer 920 buffers a lattice mismatch between the substrate 910 and the first electrode thin film 930. When the lattice mismatch between the substrate 910 and the first electrode thin film 930 is very small, the first electrode thin film 930 may be formed directly on the substrate 910 without the buffer layer 920. The buffer layer 920 may include a SiO2 or Si3N4 film.
Each of the first and second electrode thin films 930 and 950 is formed of at least one material of W, Mo, W/Au, Mo/Au, Cr/Au, Ti/W, Ti/Al/N, Ni/Cr, Al/Au, Pt, Cr/Mo/Au, YB2Cu3O7-d, Ni/Au, Ni/Mo, Ni/Mo/Au, Ni/Mo/Ag, Ni/Mo/Al, Ni/W, Ni/W/Au, Ni/W/Ag, and Ni/W/Al. The substrate 910 is formed of at least one material of Si, SiO2, GaAs, Al2O3, plastic, glass, V2O5, PrBa2Cu3O7, YBa2Cu3O7, MgO, SrTiO3, Nb-doped SrTiO3, and silicon-on-insulator (SOI).
The buffer layer 1200 buffers a lattice mismatch between the transition thin film 1300 and the substrate 1100. When the lattice mismatch between the substrate 1100 and the transition thin film 1300 is very small, the transition thin film 1300 may be formed directly on the substrate 1100 without the buffer layer 1220.
Of course, the buffer layer 1200, the first and second electrode thin films 1400 and 1500, and the substrate 1100 may be formed of the materials of the buffer layer 920, the first and second electrode thin films 930 and 950, and the substrate 910.
Although the electrical conductivities of the abrupt MIT devices change abruptly, the structures of the transition thin films 940 and 1300 do not change.
The electricity-voltage characteristics of the planar-type abrupt MIT device depending on the material of the transition thin film 1300 will now be described.
The diffraction patterns of
Such an abrupt MIT, that is, a fast switching operation, is achieved by the transition film of the abrupt MIT device. The transition film may be obtained by suitably adding low-concentration holes to an insulator. A mechanism for an abrupt MIT caused due to an addition of low-concentration holes to an insulator is disclosed in some papers, namely, New J. Phys. 6 (2004) 52 and http//xxx.lanl.gov/abs/cond-mat/0411328 and Appl. Phys. Lett. 86 (2005) 242101, and U.S. Pat. No. 6,624,463.
Each of the transition thin films 940 and 1300, which cause an abrupt MIT to occur in the abrupt MIT devices of
As described above, electrical and/or electronic system protecting circuits according to embodiments of the present invention to be described below use an abrupt MIT device whose electrical characteristics abruptly change according to the level of a dropping voltage. The abrupt MIT device is connected in parallel to a power voltage source or a signal source.
A load impedance ZL is an equivalent impedance that corresponds to an electrical and/or electronic system and is used to verify the characteristics of the electrical and/or electronic system protecting circuit 200. Static electricity or high-voltage high-frequency noise may be applied via a power line L1 that applies a power voltage to the electrical and/or electronic system ZL. The electrical and/or electronic system ZL may be any electrical and/or electronic system as long as it needs to be protected from high-voltage high-frequency noise, such as, all sorts of electronic devices, electrical components, electronic systems, or high-voltage electrical systems.
The protecting resistor Rp is serially connected to the abrupt MIT device MIT and restricts a voltage or current applied to the abrupt MIT device MIT to protect the abrupt MIT device MIT. The protecting resistor Rp and the abrupt MIT device MIT as a whole are connected to a power voltage source Vp or the electrical and/or electronic system ZL in parallel.
The power voltage reinforcing capacitor Cp prevents the voltage level of the power voltage source Vp from dropping to a rated standard voltage or less when an abrupt MIT occurs in the abrupt MIT device MIT. Hence, the power voltage reinforcing capacitor Cp and the power voltage source Vp should be connected to each other in parallel. Consequently, the power voltage reinforcing capacitor Cp should be connected to a line of the protecting resistor Rp and the abrupt MIT device MIT in parallel.
The electrical and/or electronic system protecting circuit 200 removes static electricity or high-voltage high-frequency noise applied to the electrical and/or electronic system ZL, by using the abrupt MIT device MIT. In other words, when noise with a voltage equal to or greater than a predetermined voltage is applied to the electrical and/or electronic system, the abrupt MIT device MIT connected to the electrical and/or electronic system ZL via the protecting resistor Rp in parallel generates abrupt MIT so that most of current flows through the abrupt MIT device MIT, thereby protecting the electrical and/or electronic system ZL.
In the embodiment of
Since a power voltage source Vp is used in the embodiment of
Referring to
A relationship between the power voltage VI and the voltage VR of the circuit shown in
When the power voltage VI of 200 kHz and 4V was applied, an abrupt MIT did not occur in the abrupt MIT device MIT, because the 4V power voltage VI was lower than the 5.5V limit voltage of the abrupt MIT device MIT. In this case, the voltage VMIT dropping at the abrupt MIT device MIT was 3.66V, and the voltage VR dropping at the protecting resistor Rp was 0.34V. The resistance of the abrupt MIT device MIT was calculated to about 32 kΩ based on the above voltage values.
The resistance of the abrupt MIT device MIT after an abrupt MIT may be controlled by adequately changing the material and structure of the abrupt MIT device MIT. Due to the control of the resistance of the abrupt MIT device MIT, the ratio of a voltage dropped in the abrupt MIT device MIT to a voltage dropped in the protecting resistor Rp can be adequately controlled to answer the usage purpose.
To ascertain the characteristics of the circuit of
The currents flowing in the equivalent load resistor RL and the abrupt MIT device MIT was able to be calculated using the above-described dropping voltage values. The currents flowing in the equivalent load resistor RL was calculated to 0.8 mA, and the current flowing in the abrupt MIT device MIT was calculated to 1.4 mA. accordingly, the resistance of the abrupt MIT device MIT was 32 kΩ before an MIT, but it became about 2.7 kΩ after an MIT.
Considering the characteristics of general metals, the 2.7 kΩ resistance of the abrupt MIT device MIT obtained after an MIT is not small. However, the resistance of the abrupt MIT device MIT is not fixed but may be controlled by changing the structure and material of the abrupt MIT device MIT. In addition, a composite resistance can be significantly reduced by connecting several abrupt MIT devices MIT each having a high resistance to each other in parallel. In some cases, the composite resistance can bee reduced to 2Ω or less.
For example, when the abrupt MIT device MIT has a resistance less than or equal to 2Ω, a flow of overcurrent in an electrical and/or electronic system represented as the equivalent load resistor RL having a 10 kΩ resistance can be prevented by bypassing most of the current greatly increased due to external noise to go toward the abrupt MIT device MIT.
Referring to
A difference between current at the location D, where current rapidly increased when no equivalent load resistors RL exist in the circuit of
It can be seen from
In the above-described embodiments, the abrupt MIT device is manufactured such that it has a resistance of several hundreds to several thousands of Ω after its electrical characteristic changes from a characteristic of an insulator to a characteristic of a metal. However, the abrupt MIT device may be manufactured such that it has a resistance of several Ω. Hence, the electrical and/or electronic system can be protected from a received high-voltage, high-frequency noise signal by matching the current and voltage of the abrupt MIT device with a limit current and a limit voltage of the electrical and/or electronic system.
As described above, an electrical and/or electronic system protecting circuit according to the present invention uses an abrupt MIT device to bypass toward the abrupt MIT device most of the noise current generated when the voltage greater than the rated standard voltage is applied, thereby protecting an electrical and/or electronic system. The electrical and/or electronic system protecting circuit may be applied to all sorts of electronic devices, electrical components, electric and electronic systems, and noise filters for protecting high-voltage electrical systems.
In addition, the abrupt MIT device is very simple and low-priced and can be manufactured easily. Therefore, the electrical and/or electronic system protecting circuit using the abrupt MIT device can also be manufactured easily with a low cost.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
Number | Date | Country | Kind |
---|---|---|---|
10-2005-0014228 | Feb 2005 | KR | national |
10-2005-0051982 | Jun 2005 | KR | national |
10-2005-0111882 | Nov 2005 | KR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/KR2006/000542 | 2/17/2006 | WO | 00 | 8/21/2007 |