1313841 九、發明說明： 【發明所屬之技術領域】 本發月"及種無源射頻識別（Radio Frequency • *臟—η’腳）¾片，特別是涉及-種具有磁場過 強保護功能的無源RFID芯片。 【先前技術】 近年來，無源射頻識別芯片越來越多的被使用，例如 > 用作電子標籤，此外，1C卡也是一種RFID芯片。 參閱圖1，所示為現有技術的無源RFID芯片。所述無 源RFID芯片1包括一天線單元100、一電源產生單元200、 一輪入/輪出電路單元300及一邏輯電路單元4⑻。天線單 元100與電源產生單元200連接’電源產生單元20〇分別 與輸入/輸出電路單元300及一邏輯電路單元連接。 天線電路100包括天線線路1〇1和天線電容1〇2。無 源RFID芯片自身沒有電源，其通過接收由讀卡器產生的 > 電磁波8所供給的電磁波而工作。無源RFID芯片邏輯電 路單元4〇0中的耗電由電源產生單元2〇〇供給，其可以產 生直流電源VDD。VDD是在電源產生單元2〇〇中通過對天 線單元100所接收到的電磁波8進行檢波和平滑而產生 的。電源產生單元200包括〆第一二極體203、—第一電 容器201、第二二極體202及〆第二電容器204。第二電容 器204有足夠大的電容量值以向邏輯電路單元400供電。 天線單元100輸出給電源產生單元200的信號的負分量由 第一二極體203和第二二極體遽除，只有其正分量通 6 1313841 過第二二極體202供給各電路。第二電容器2〇4存儲已經 通過第二二極體202的正分量並在天線單元伸麥為^ -時供電。因此，VDD基本上為恒定值，因而電源^生U單i • 200起直流電壓源的作用，其輸出直流電源VDD端為電= 產生單元200的電源輸出端。 ,、 無源RFID芯片的優點是可以無觸點的方式讀出所記 錄的資料，可以不用電池工作，其耐用性好。但是人們還 是期望得到更高的性能，例如’人們希望能使無源RFm 芯片讀取識別範圍增大，因而讀取器需要發出很強的功 率。而在無源RHD芯片内天線受強電磁波作用時會產生 出高交流電信號’通過對該交流電信號整流後所得到的直 流電壓也隨之變高。因此，會出現該rFID芯片内部的邏 輯電路和時鐘發生器發熱甚至損壞。 【發明内容】 有繁於此，本發明提供具有磁場過強保護功能的無源 • RFID芯片’當所述無源RFID芯片接收到的磁場強度過高 時降低其天線感應出的電信號電壓強度。 本發明提供一種無源RFID芯片，包括一天線單元， 用於接收讀取器發出的電磁信號；一電源產生單元，為所 述無源RFID芯片系統提供直流電源，一輸入/輸出電路單 元3〇〇，一邏輯電路單元400 ;—變容二極體，該變容二極 體陽極連接於所述天線單元與電源產生單元之間，其陰極 接Ί士 · — 一極體’該—極體陽極與所述電源產生單元電源 輸出端連接，陰極與天線單元連接。 1313841 本發明提供的無源RFID晶圓具有磁場過強保護功 能’當所述無源RHD晶圓接受到的磁場強度過高時降低 • 其天線感應出的電信號。 .【實施方式】 參閱圖2，本發明具有磁場過強保護功能的無源 晶圓一實施方式的示意圖。本發明的實施方案與圖丄所示 現有技術不同在於：在天線單元100與電源產生電源2〇〇 之間接一變容二極體802，所述變容二極體802 —側連於 天線單元100與電源產生單元200之間，另一侧接地.在 回饋通路上接一二極體801，該二極體801 —側與所述電 源產生單元200連接，一侧與天綠單元1〇〇連接。 根據無源RFID晶圓各電路的安全電壓值選擇變容二 極體802’設所述變容二極體802的閥值電壓為v。當直流 電源VDD輸出的電壓小於V時，無源RFID晶圓各電路輸 入的為安全電壓。由於VDD輸出的電壓小於V，變容二極 體802截止。當直流電源VDD輪出的電壓大於v的時， 變容二極體802導通。此時天線單元100與變容二極體802 並聯，天線單元100的品質因數（Q值）降低，感應電磁 波8的能力減弱，使電源產生單元200整流後產生的直流 電壓VDD降低。這樣避免當直流電源VDD輸出的電壓過 高而引起無源RFID晶圓各電路故障甚至燒壞。 【圖式簡單說明】 圖1是現有無源RFID晶圓的示意圖。 圖2是本發明無源RFID晶圓一實施方式的示意圖。 8 1313841 【主要元件符號說明】 無源RFID晶圓 1 天線線路 101 天線電容 102 第一電容器 201 第二二極體 202 第一二極體 203 第二電容器 204 輸入/輸出電路單元 300 邏輯電路單元 400 變容二極體 802 二極體 8011313841 IX. Description of the invention: [Technical field of invention] This month's "and passive radio frequency identification (Radio Frequency • *dirty-η' foot) 3⁄4 piece, especially related to the type of magnetic field protection Passive RFID chip. [Prior Art] In recent years, passive radio frequency identification chips have been used more and more, for example, as an electronic tag, and in addition, a 1C card is also an RFID chip. Referring to Figure 1, a prior art passive RFID chip is shown. The passive RFID chip 1 includes an antenna unit 100, a power generating unit 200, a wheel in/out circuit unit 300, and a logic circuit unit 4 (8). The antenna unit 100 is connected to the power generating unit 200. The power generating unit 20 is connected to the input/output circuit unit 300 and a logic circuit unit, respectively. The antenna circuit 100 includes an antenna line 1〇1 and an antenna capacitor 1〇2. The passive RFID chip itself has no power supply, and it operates by receiving electromagnetic waves supplied by the > electromagnetic wave 8 generated by the card reader. The power consumption in the passive RFID chip logic circuit unit 〇0 is supplied by the power generating unit 2, which can generate the DC power supply VDD. VDD is generated by detecting and smoothing the electromagnetic wave 8 received by the antenna unit 100 in the power generating unit 2A. The power generating unit 200 includes a first diode 203, a first capacitor 201, a second diode 202, and a second capacitor 204. The second capacitor 204 has a sufficiently large capacitance value to supply power to the logic circuit unit 400. The negative component of the signal output from the antenna unit 100 to the power generating unit 200 is removed by the first diode 203 and the second diode, and only its positive component is passed through the second diode 202 to the respective circuits. The second capacitor 2〇4 stores the positive component that has passed through the second diode 202 and supplies power when the antenna unit is extended. Therefore, VDD is basically a constant value, so that the power supply generates a DC voltage source, and its output DC power supply VDD terminal is the power supply terminal of the generating unit 200. The advantage of the passive RFID chip is that the recorded data can be read out in a contactless manner, and the battery can be operated without a battery, and the durability is good. But people also expect higher performance, such as 'people want to make the passive RFm chip read recognition range, so the reader needs to send a strong power. In the passive RHD chip, the antenna generates a high AC signal when it is subjected to strong electromagnetic waves. The DC voltage obtained by rectifying the AC signal also becomes high. Therefore, the logic circuit and the clock generator inside the rFID chip may be heated or damaged. SUMMARY OF THE INVENTION In view of the above, the present invention provides a passive RFID chip with a magnetic field over-protection function. When the magnetic field strength received by the passive RFID chip is too high, the voltage strength of the electrical signal induced by the antenna is lowered. . The invention provides a passive RFID chip, comprising an antenna unit for receiving electromagnetic signals emitted by a reader; a power generating unit for supplying DC power to the passive RFID chip system, and an input/output circuit unit逻辑, a logic circuit unit 400; a varactor diode, the varactor diode is connected between the antenna unit and the power generating unit, and the cathode thereof is connected to a gentleman's body. The anode is connected to the power supply output end of the power generating unit, and the cathode is connected to the antenna unit. 1313841 The passive RFID wafer provided by the present invention has a magnetic field over-strength protection function. When the magnetic field strength received by the passive RHD wafer is too high, the electrical signal induced by the antenna is reduced. [Embodiment] Referring to Figure 2, there is shown a schematic diagram of an embodiment of a passive wafer having a magnetic field over-strength protection function. The embodiment of the present invention is different from the prior art shown in FIG. 2 in that a varactor diode 802 is connected between the antenna unit 100 and the power generating power source 2, and the varactor diode 802 is connected to the antenna unit. 100 is connected to the power generating unit 200, and the other side is grounded. A diode 801 is connected to the feedback path, and the side of the diode 801 is connected to the power generating unit 200, and the side is connected to the green unit. connection. The variable capacitance diode 802' is selected to have a threshold voltage of the varactor diode 802 of v according to a safe voltage value of each circuit of the passive RFID wafer. When the voltage output from the DC power supply VDD is less than V, each circuit of the passive RFID wafer is input with a safe voltage. Since the voltage of the VDD output is less than V, the varactor diode 802 is turned off. When the voltage of the DC power supply VDD is greater than v, the varactor diode 802 is turned on. At this time, the antenna unit 100 is connected in parallel with the varactor diode 802, the quality factor (Q value) of the antenna unit 100 is lowered, the capability of the induced electromagnetic wave 8 is weakened, and the DC voltage VDD generated by the rectification of the power generating unit 200 is lowered. This avoids the failure of the circuits of the passive RFID wafer to be destroyed or even burned out when the voltage output from the DC power supply VDD is too high. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a conventional passive RFID wafer. 2 is a schematic diagram of an embodiment of a passive RFID wafer of the present invention. 8 1313841 [Description of main component symbols] Passive RFID wafer 1 Antenna line 101 Antenna capacitor 102 First capacitor 201 Second diode 202 First diode 203 Second capacitor 204 Input/output circuit unit 300 Logic circuit unit 400 Variable capacitance diode 802 diode 801
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