200937841 九、發明說明： 【發明所屬之技術領域】 本發明係有關於一種電壓至電流轉換電路，尤指一種 使用低電壓製程放大器推動低電壓製程N型金氧半場效電 晶體，使電壓至電流轉換電路可直接於高電壓製程之電路 下應用者。 【先前技術】 習知電壓至電流轉換電路主要係利用電壓隨耦器的架 構，然後利用外掛電阻來決定電流值，在低電壓電路中此 種方式是可行的。因為在低電壓製程中N型金氧半場效電 晶體的臨界電壓大約是在0. 5〜0. 8V左右，所以放大器的輸 出級的擺幅（swing)還可以推動下一級的N型金氧半場效 電晶體，並且使放大器内部的金氧半場效電晶體保持在飽 和區。 圖一為習知電壓至電流轉換電路1。給定一輸入電壓 VI至放大器2的正輸入端，然後經由負迴授使輸出電壓VO 等於輸入電壓VI，透過電阻R調整電流I，但是這一切都 必須要所有的金氧羊場效電晶體3都在飽和區才會成立， 因為只有在飽和區，放大器2才會是一個線性放大器，並 滿足負迴授的條件。 但是在高電壓電路中想要使用電壓至電流轉換電路的 話，就會面臨到是要用高電壓製程放大器還是用低電壓製 200937841 程放大器，假如使用高電壓製程放大器的話就會使面積及 功率增加許多，而要是使用低電壓製程放大器的話就會面 , 臨到擺幅（swing)受限的問題，因為在高電壓製程放大器的 臨界電壓變化很大，大約是在卜2V之間，所以一般低電壓 製程放大器可能無法推動高電壓製程N型金氧半場效電晶 體。 另外在製程方面，因高電壓製程並不及低電壓製程穩 定，所以臨界電壓也就很不穩定，一般而言在卜2V之間， 〇 所以放大器的擺幅（swing)必須要大於臨界電壓Vt (高電 壓製程N型金氧半場效電晶體）加輸入電壓VI才可以推動 高電壓製程N型金氧半場效電晶體，要是低電壓電路的供 應電壓VDD=3V的話，放大器就不一定可以推動高電壓製程 N型金氧半場效電晶體，因為此時放大器的擺幅（swing) — 定比3V小，除非輸入電壓VI很小，但是在實際使用上輸 入電壓VI的值都不可能太小 •因此，如何研發出一種電壓至電流轉換電路，其使用 • 〇 低電壓製程放大器推動低電壓製程N型金氧半場效電晶 體，使電壓至電流轉換電路可直接於高電壓製程之電路下 應用，進而降低製造成本，將是本發明所欲積極探討之處。 【發明内容】 本發明提出一種電壓至電流轉換電路，其主要目的為 解決習知電壓至電流轉換電路，其需要高電壓製程放大器 來推動高電壓製程N型金氧半場效電晶體的問題。 本發明之一樣態係為一種電壓至電流轉換電路，包 6 200937841 括：一高電壓製程N型金氧半場效電晶體；一低電壓製程 N型金氧半場效電晶體，其汲極與該高電壓製程N型金氧 . 半場效電晶體之源極相接；一低電壓製程放大器，其具有 一正輸入端、一負輸入端以及一輸出端，其中該輸出端係 與該低電壓製程N型金氧半場效電晶體之閘極相接，一輸 入電壓輸入該正輸入端以及該負輸入端與該低電壓製程N 型金氧半場效電晶體之源極相接以產生一輸出電壓；以及 一電阻，其一端係與該低電壓製程N型金氧半場效電晶體 〇 之源極相接，另一端係接地。 藉此，使用低電壓製程放大器推動低電壓製程N型金 氧半場效電晶體，使電壓至電流轉換電路可直接於高電壓 製程之電路下應用，進而達到降低製造成本的目的。 【實施方式】 為充分瞭解本發明之目的、特徵及功效，茲藉由下述 '具體之實施例，並配合所附之圖式，對本發明做一詳細說 ••日月，說明如後： 圖二為本發明一種電壓至電流轉換電路之電路圖。請 參考圖二，本發明之電壓至電流轉換電路4包括：一高電 壓製程N型金氧半場效電晶體（HV NM0S)5 ; —低電壓製程 N型金氧半場效電晶體（LV NM0S)6，其汲極7與該高電壓 製程N型金氧半場效電晶體5之源極8相接；一低電壓製 程放大器9,其具有一正輸入端10、一負輸入端11以及一 輸出端12，其中該輸出端12係與該低電壓製程N型金氧 半場效電晶體6之閘極13相接，一輸入電壓VII輸入該正 7 200937841 . 輸入端10以及該負輸入端11與該低電壓製程N型金氧半 場效電晶體6之源極14相接以產生一輸出電壓V01，其中， . 該輸入電壓VII係與該輸出電壓V01相等；以及一電阻R1， 其一端係與該低電壓製程N型金氧半場效電晶體6之源極 14相接，另一端係接地，其中，輸入該高電壓製程N型金 氧半場效電晶體5之〉及極15的輸入電流11係等於該輸出 電壓V01之值除以該電阻R1之值。因為低電壓製程N型金 氧半場效電晶體6是在高電壓的路徑下，所以必須限制低 ❹ 電壓製程N型金氧半場效電晶體6的汲級7電壓以防元件 燒毀，因此較佳係在高電壓製程N型金氧半場效電晶體5 之閘極16給予一鉗位電壓17，藉此使低電壓製程N型金 氧半場效電晶體6的没級7電壓在元件可忍党的範圍内。 圖三為本發明應用於一種LED顯示單元較佳具體實施 例之電路圖。請參考圖三並配合圖二，因LED顯示單元18 在定電流時，其亮度係為最穩定的，在此使用本發明之電 -壓至電流轉換電路4的輸入電流II做為一個參考電流，然 -_ 後藉由電流映射（Current Mirror)的架構經由高電壓製程 P型金氧半場效電晶體（HV PM0S)以及高電壓製程N型金氧 半場效電晶體（HV NM0S)映射給LED元件19端，如此就可 產生一個定電流源，在此電路架構下必須先產生一固定之 電壓源，所以較佳係使用能隙（BandGap)電路來產生一固定 電壓源20，在實際應用上因為低電壓製程N型金氧半場效 電晶體5和高電壓製程N型金氧半場效電晶體6係為串 聯，故可能有雜訊從高電壓製程元件過來，若怕參考電流 受到雜訊干擾的話，可以在電阻R1並聯一電容C1來濾掉 200937841 雜訊，但需考慮到LED顯示單元18穩定度的問題，若電容 C1太大的話，則相位餘裕度（Phase Margin)太小，LED顯 . 示單元18在負迴授下就可能會振盪，而若電容Cl太小的 話，則又達不到濾波的效果，此時則需先決定一適當的電 容值，然後再決定放大器的架構，使LED顯示單元18的相 位餘裕度（Phase Margin)在適當的範圍内。 由以上所述可以清楚地明瞭，本發明係提供一種電壓 至電流轉換電路，其使用低電壓製程放大器推動低電壓製 © 程N型金氧半場效電晶體，使電壓至電流轉換電路可直接 於高電壓製程之電路下應用，進而達到降低製造成本的目 的。因此，本發明在專利的角度上具備了新穎性與進步性， 市場上更具備了產業上的利用性，足適貴審查委員給予 專利。 以上已將本發明專利申請案做一詳細說明，惟以上所 述者，僅為本發明專利申請案之較佳實施例而已，當不能 限定本發明專利申請案實施之範圍。即凡依本發明專利申 •β 請案申請範圍所作之均等變化與修飾等，皆應仍屬本發明 專利申請案之專利涵蓋範圍内。 【圖式簡單說明】 圖一為習知電壓至電流轉換電路。 圖二為本發明一種電壓至電流轉換電路之電路圖。 圖三為本發明應用於一種LED顯示單元較佳具體實施例之 電路圖。 9 200937841 【主要元件符號說明】 • 1電壓至電流轉換電路 . 2放大器 3金氧半場效電晶體 4電壓至電流轉換電路 5高電壓製程N型金氧半場效電晶體 A 6低電壓製程N型金氧半場效電晶體 7汲極 8源極 9低電壓製程放大器 10正輸入端 11負輸入端 12輸出端 13閘極 ® 14源極 15沒極 16閘極 17鉗位電壓 18 LED顯示單元 19 LED元件 20固定電壓源 C1電容 200937841 I電流 11輸入電流 _ R電阻 . R1電阻 VI輸入電壓 VII輸入電壓 V0輸出電壓 • V01輸出電壓200937841 IX. Description of the Invention: [Technical Field] The present invention relates to a voltage to current conversion circuit, and more particularly to a low voltage process N-type MOS half-field effect transistor using a low voltage process amplifier to make a voltage to current The conversion circuit can be used directly under the circuit of the high voltage process. [Prior Art] Conventional voltage-to-current conversion circuits mainly utilize a voltage follower structure, and then use an external resistor to determine a current value, which is feasible in a low voltage circuit. Because the threshold voltage of the N-type MOSFET in the low-voltage process is about 0. 5~0. 8V or so, so the swing of the output stage of the amplifier can also promote the next-stage N-type gold oxide. The half field effect transistor, and the gold oxide half field effect transistor inside the amplifier is kept in the saturation region. FIG. 1 is a conventional voltage to current conversion circuit 1. Given an input voltage VI to the positive input of amplifier 2, then the output voltage VO is equal to the input voltage VI via negative feedback, and the current I is adjusted through the resistor R, but all of this requires all the MOS field-effect transistors. 3 is only true in the saturation region, because only in the saturation region, amplifier 2 will be a linear amplifier and meet the conditions of negative feedback. However, if you want to use a voltage-to-current conversion circuit in a high-voltage circuit, you will need to use a high-voltage process amplifier or a low-voltage 200937841 amplifier. If you use a high-voltage process amplifier, the area and power will increase. A lot, if you use a low-voltage process amplifier, it will face the problem of limited swing, because the threshold voltage of the high-voltage process amplifier varies greatly, about between 2V, so the general low-voltage process The amplifier may not be able to drive a high-voltage process N-type gold-oxygen half-field effect transistor. In addition, in terms of process, because the high-voltage process is not stable with the low-voltage process, the threshold voltage is very unstable. Generally speaking, between 2V, the swing of the amplifier must be greater than the threshold voltage Vt ( High-voltage process N-type gold-oxygen half-field effect transistor) can increase the high-voltage process N-type gold-oxygen half-field effect transistor by adding input voltage VI. If the supply voltage of low-voltage circuit is VDD=3V, the amplifier may not be able to push high. The voltage process N-type MOS half-field effect transistor, because the swing of the amplifier is smaller than 3V, unless the input voltage VI is small, but the value of the input voltage VI cannot be too small in actual use. Therefore, how to develop a voltage-to-current conversion circuit that uses a low-voltage process amplifier to drive a low-voltage process N-type gold-oxygen half-field effect transistor, so that the voltage-to-current conversion circuit can be directly applied to a high-voltage process circuit. Further reducing the manufacturing cost will be a positive discussion of the present invention. SUMMARY OF THE INVENTION The present invention provides a voltage to current conversion circuit whose main purpose is to solve a conventional voltage to current conversion circuit that requires a high voltage process amplifier to drive a high voltage process N-type gold-oxygen half field effect transistor. The same state of the present invention is a voltage-to-current conversion circuit, and package 6 200937841 includes: a high-voltage process N-type gold-oxygen half-field effect transistor; a low-voltage process N-type gold-oxygen half-field effect transistor, the drain and the High voltage process N-type gold oxygen. The source of the half field effect transistor is connected; a low voltage process amplifier has a positive input terminal, a negative input terminal and an output terminal, wherein the output terminal is connected to the low voltage process The gate of the N-type gold-oxygen half-field effect transistor is connected, an input voltage is input to the positive input terminal, and the negative input terminal is connected to the source of the low-voltage process N-type gold-oxygen half-effect transistor to generate an output voltage. And a resistor, one end of which is connected to the source of the low-voltage process N-type gold-oxygen half-effect transistor, and the other end is grounded. In this way, the low-voltage process amplifier is used to drive the low-voltage process N-type gold-oxygen half-field effect transistor, so that the voltage-to-current conversion circuit can be directly applied to the circuit of the high-voltage process, thereby achieving the purpose of reducing the manufacturing cost. [Embodiment] In order to fully understand the object, features and effects of the present invention, the present invention will be described in detail by the following specific embodiments and the accompanying drawings. 2 is a circuit diagram of a voltage to current conversion circuit of the present invention. Referring to FIG. 2, the voltage to current conversion circuit 4 of the present invention comprises: a high voltage process N-type gold oxide half field effect transistor (HV NM0S) 5; - a low voltage process N type gold oxide half field effect transistor (LV NM0S) 6. The drain 7 is connected to the source 8 of the high voltage process N-type metal oxide half field effect transistor 5; a low voltage process amplifier 9 having a positive input terminal 10, a negative input terminal 11 and an output The terminal 12, wherein the output terminal 12 is connected to the gate 13 of the low-voltage process N-type MOS field-effect transistor 6, an input voltage VII is input to the positive 7 200937841. The input terminal 10 and the negative input terminal 11 are The source 14 of the low-voltage process N-type MOS field-effect transistor 6 is connected to generate an output voltage V01, wherein the input voltage VII is equal to the output voltage V01; and a resistor R1 is connected at one end thereof. The source 14 of the low-voltage process N-type MOS field-effect transistor 6 is connected, and the other end is grounded, wherein the high-voltage process N-type MOS field-effect transistor 5 and the input current of the pole 15 are input. It is equal to the value of the output voltage V01 divided by the value of the resistor R1. Since the low-voltage process N-type MOS field-effect transistor 6 is in a high-voltage path, it is necessary to limit the voltage of the 7-level 7 of the low-voltage process N-type MOS field-effect transistor 6 to prevent component burnout, so it is preferable. A clamping voltage 17 is applied to the gate 16 of the high-voltage process N-type MOS field-effect transistor 5, thereby making the voltage of the low-voltage process N-type MOS field-effect transistor 6 in the component 7 In the range. Figure 3 is a circuit diagram of a preferred embodiment of the present invention applied to an LED display unit. Referring to FIG. 3 and FIG. 2, since the brightness of the LED display unit 18 is the most stable when the current is constant, the input current II of the electro-voltage to current conversion circuit 4 of the present invention is used as a reference current. , then -_ is mapped to the LED via a high-voltage process P-type MOS field oxide transistor (HV PM0S) and a high-voltage process N-type MOS field-effect transistor (HV NM0S) by a Current Mirror architecture. At the end of the component 19, a constant current source can be generated. In this circuit structure, a fixed voltage source must be generated first. Therefore, a bandgap circuit is preferably used to generate a fixed voltage source 20, which is practical. Because the low-voltage process N-type gold-oxygen half-field effect transistor 5 and the high-voltage process N-type gold-oxygen half-field effect transistor 6 are connected in series, there may be noise coming from the high-voltage process component, if the reference current is disturbed by noise. If you can connect the capacitor C1 in parallel with the resistor R1 to filter out the 200937841 noise, but you need to consider the stability of the LED display unit 18. If the capacitor C1 is too large, the phase margin (Phase Margin) is too small, LED The display unit 18 may oscillate under negative feedback, and if the capacitance Cl is too small, the filtering effect is not achieved. In this case, an appropriate capacitance value is determined first, and then the structure of the amplifier is determined. The phase margin of the LED display unit 18 is within an appropriate range. It will be apparent from the above that the present invention provides a voltage to current conversion circuit that uses a low voltage process amplifier to drive a low voltage process N-type gold-oxygen half-field effect transistor, so that the voltage-to-current conversion circuit can be directly Under the circuit of high-voltage process, the purpose of reducing manufacturing cost is achieved. Therefore, the present invention has novelty and progress in terms of patents, and the market is more industrially usable, and the appropriate examination committee gives patents. The above is a detailed description of the present patent application, but the above description is only a preferred embodiment of the present invention, and the scope of implementation of the patent application of the present invention is not limited. That is, the equivalent changes and modifications of the scope of application of the patent application file of the present invention should remain within the scope of the patent application of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a conventional voltage to current conversion circuit. 2 is a circuit diagram of a voltage to current conversion circuit of the present invention. Figure 3 is a circuit diagram of a preferred embodiment of the present invention applied to an LED display unit. 9 200937841 [Main component symbol description] • 1 voltage to current conversion circuit. 2 amplifier 3 gold oxygen half field effect transistor 4 voltage to current conversion circuit 5 high voltage process N type gold oxygen half field effect transistor A 6 low voltage process N type Gold Oxygen Half Field Effect Transistor 7 Dipper 8 Source 9 Low Voltage Process Amplifier 10 Positive Input 11 Negative Input 12 Output 13 Gate® 14 Source 15 Nopole 16 Gate 17 Clamp Voltage 18 LED Display Unit 19 LED component 20 fixed voltage source C1 capacitor 200937841 I current 11 input current _ R resistor. R1 resistor VI input voltage VII input voltage V0 output voltage • V01 output voltage