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Patent Issued for Current Sensor, Inverter Circuit, and Semiconductor Device Having the Same

August 13, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- DENSO CORPORATION (Kariya, JP) has been issued patent number 8791690, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Shiraki, Satoshi (Toyohashi, JP); Tokura, Norihito (Okazaki, JP); Takahashi, Shigeki (Okazaki, JP); Yamamoto, Masahiro (Kasugai, JP); Yamada, Akira (Nukata-gun, JP); Kudo, Hiroyasu (Ichinomiya, JP); Ashida, Youichi (Nukata-gun, JP); Nakagawa, Akio (Chigasaki, JP).

This patent was filed on June 1, 2011 and was published online on July 29, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "U.S. Pat. No. 5,253,156 corresponding to JP-A-8-34709 discloses a semiconductor integrated circuit including a main cell having a lateral insulated gate bipolar transistor (IGBT) and a current detector (hereafter referred to as 'sense cell') for detecting an electric current flowing through an emitter of the IGBT. The sense cell has a lateral IGBT with the same structure as the lateral IGBT of the main cell except the length of the emitter. The IGBTs are coupled in a current mirror configuration so that an electric current flowing through the emitter of the IGBT of the sense cell becomes smaller than the electric current flowing through the emitter of the IGBT of the main cell by a predetermined ratio that depends on the ratio between the lengths of the emitters. Thus, the current flowing through the main cell can be detected based on the current flowing through the sense cell.

"However, when the semiconductor integrated circuit disclosed in U.S. Pat. No. 5,253,156 is used to form a circuit shown in FIG. 14, the following disadvantages may occur.

"In the circuit shown in FIG. 14, an electric current flowing through a main cell 1000 is detected based on an electric current flowing through a sense cell 1001, and the electric current flowing through the sense cell 1001 is detected based on a voltage across a resistor Rs. When a resistance of the resistor Rs is increased to increase the voltage, an emitter potential of the sense cell 1001 is increased. Accordingly, a potential of a p-type body layer, which is electrically connected to an emitter electrode, is increased. As a result, a PN junction between the p-type body layer and an n.sup.--type drift layer is forward biased, an output (i.e., the voltage across the resistor Rs) becomes unstable. In order to stabilize the output voltage, it is preferable that the output voltage should be limited up to 0.3 volts (V). Further, when a high voltage (e.g., from 200V to 600V) is applied to a collector, the output voltage can have an error due to a coupling with the high voltage.

"Such a problem can occur in a semiconductor element other than an IGBT.

"By the way, such a circuit shown in FIG. 14 is used to form an inverter circuit. For example, US 2009/0057832 corresponding to JP-A-2009-268054 discloses a method for detecting a current in the inverter circuit by using a shunt resistor. The method disclosed in US 2008/0246426 is directed to detect a value of the current, not a direction of the current. It is preferable to detect not only the value of the current, but also the direction of the current in order to perform sensorless sinusoidal control of the current as disclosed in US 2008/0246426 corresponding to JP 4396762."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In view of the above, it is an object of the present invention to provide a semiconductor device having an inverter circuit and a current sensor for detecting value and direction of an electric current.

"According to a first aspect of the present invention, a semiconductor device with a lateral semiconductor element includes a semiconductor substrate, a first electrode on a surface of the substrate, a second electrode on the surface of the substrate, and an isolation structure located in the substrate to divide the substrate into a first island and a second island. The first and second islands are electrically insulated from the each other by the isolation structure. The lateral semiconductor element includes a main cell located in the first island and a sense cell located in the second island. The main cell causes a first current to flow between the first electrode and the second electrode so that the first current flows in a lateral direction along the surface of the substrate. The first current is detected by detecting a second current flowing though the sense cell.

"According to a second aspect of the present invention, a semiconductor device with a lateral IGBT for controlling supply of an electric current to a load includes a semiconductor substrate having a first conductivity-type drift layer, a second conductivity-type collector region located in a surface portion of the drift layer and having a longitudinal direction, a second conductivity-type channel layer located in the surface portion of the drift layer and having a straight portion extending parallel to the collector region, and an emitter region located in a surface portion of the channel layer and terminated inside the collector region. The emitter region has a straight portion extending in the longitudinal direction. The semiconductor device further includes a gate insulating layer located on a channel region of the channel layer. The channel region is located between the emitter region and the drift layer. The semiconductor device further includes a gate electrode located on the gate insulating layer, a first electrode electrically connected to the collector region, and a second electrode electrically connected to the emitter region and the channel layer. The emitter region is divided to form a main cell and a sense cell, each of which has the lateral IGBT. The lateral IGBT of the main cell is configured to control the supply of the electric current to the load. The lateral IGBT of the sense cell is identical in structure to the lateral IGBT of the main cell and configured as a current detector. The main cell is located on each side of the sense cell so that the sense cell is located in the main cell in the longitudinal direction.

"According to a third aspect of the present invention, a current sensor for detecting an electric current in a current path connected to a load includes a power element located in the current path and turned ON and OFF to control the electric current. The electric current flows through the power element in a forward direction, when the power element is turned ON. The current sensor further includes a freewheeling diode located in the current path and connected in antiparallel with the power element. The electric current flows through the freewheeling diode in a backward direction, when the power element is turned OFF from ON. The current sensor further includes a first sense cell connected to the power element in such a manner that the electric current flowing through the first sense cell is in proportional to the electric current flowing through the power element. The current sensor further includes a first sense resistor connected in series with the first sense cell. The current sensor further includes a second sense cell connected to the freewheeling diode in such a manner that the electric current flowing through the second sense cell is in proportional to the electric current flowing through the freewheeling diode. The current sensor further includes a second sense resistor connected in series with the second sense cell."

For the URL and additional information on this patent, see: Shiraki, Satoshi; Tokura, Norihito; Takahashi, Shigeki; Yamamoto, Masahiro; Yamada, Akira; Kudo, Hiroyasu; Ashida, Youichi; Nakagawa, Akio. Current Sensor, Inverter Circuit, and Semiconductor Device Having the Same. U.S. Patent Number 8791690, filed June 1, 2011, and published online on July 29, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8791690.PN.&OS=PN/8791690RS=PN/8791690

Keywords for this news article include: Electronics, High Voltage, Semiconductor, DENSO CORPORATION.

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Source: Electronics Newsweekly


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