TW201530956A - Over-current protection circuit for expansion card - Google Patents

Abstract

A over-current protection circuit for expansion card includes a voltage terminal, a voltage output terminal, a control chip, first and second resistors, and a first electronic switch. A detecting pin of the control chip is connected to a first end of the first resistor. A second end of the first resistor is connected to the voltage terminal. An input pin of the control chip is connected to the second end of the first resistor. A gate pin of the control chip is grounded through the second resistor. The gate pin of the control chip is also connected to a first terminal of the first electronic switch. A second terminal of the first electronic switch is connected to the voltage output terminal. A third terminal of the first electronic switch is connected to the first end of the first resistor. A preset current value is stored in the control chip and regulated through selecting different resistances of the second resistor.

Description

擴展卡過流保護電路Expansion card overcurrent protection circuit

本發明係關於一種擴展卡過流保護電路。The present invention relates to an expansion card overcurrent protection circuit.

擴展卡，如PCIe卡被廣泛的使用在電腦系統中來擴展電腦系統的功能。目前的PCIe卡在工作時使用P12V、P3V3及P3V3_AUX三種電壓，其中P12V及P3V3兩種電壓採用從主機板獲得或者直接從電源供應器獲得的雙供電方式。然而，當該PCIe卡產生過流或者短路時，可能造成其損壞甚至引起主機板損壞。Expansion cards, such as PCIe cards, are widely used in computer systems to extend the functionality of computer systems. The current PCIe card uses three voltages: P12V, P3V3, and P3V3_AUX. The P12V and P3V3 voltages are dual-powered from the motherboard or directly from the power supply. However, when the PCIe card is overcurrent or short-circuited, it may cause damage or even cause damage to the motherboard.

鑒於上述內容，有必要提供一種擴展卡過流保護電路，以防止擴展卡產生過流時毀壞甚至引起主機板毀壞。In view of the above, it is necessary to provide an expansion card overcurrent protection circuit to prevent the expansion card from being damaged when the overcurrent occurs, or even causing the motherboard to be destroyed.

一種擴展卡過流保護電路，包括一電流偵測電路，該電流偵測電路包括一電壓端、一電壓輸出端、一控制晶片、第一及第二電阻及一第一電子開關，該控制晶片的偵測引腳連接該第一電阻的第一端，該第一電阻的第二端連接該電壓端，該控制晶片的輸入引腳連接該第一電阻的第二端，該控制晶片的門控引腳經該第二電阻接地，該控制晶片的門控引腳還連接該第一電子開關的第一端，該第一電子開關的第二端連接該電壓輸出端，該第一電子開關的第三端連接該第一電阻的第一端，該控制晶片內存儲一預設電流值，透過設置該第二電阻的電阻值來設置該控制晶片內存儲的預設電流值；該控制晶片透過偵測引腳及輸入引腳偵測透過該第一電阻的電流，並將偵測到的電流與存儲的預設電流值進行比較，若偵測到的電流小於該預設電流值，該控制晶片透過門控引腳輸出第一控制訊號控制該第一電子開關的第二端與第三端連通，該電壓端透過該第一電阻及該第一電子開關提供電壓給該電壓輸出端；若該控制晶片偵測到的電流大於或等於該預設電流值，該控制晶片透過門控引腳輸出一第二控制訊號控制該第一電子開關的第二端與第三端斷開，該電壓端不提供電壓給該電壓輸出端。An expansion card overcurrent protection circuit includes a current detection circuit including a voltage terminal, a voltage output terminal, a control chip, first and second resistors, and a first electronic switch, the control chip The detecting pin is connected to the first end of the first resistor, the second end of the first resistor is connected to the voltage end, and the input pin of the control chip is connected to the second end of the first resistor, the gate of the control chip The control pin is grounded via the second resistor, the gate pin of the control chip is further connected to the first end of the first electronic switch, and the second end of the first electronic switch is connected to the voltage output end, the first electronic switch The third end is connected to the first end of the first resistor, the control chip stores a preset current value, and the preset current value stored in the control chip is set by setting the resistance value of the second resistor; the control chip Detecting a current through the first resistor through the detection pin and the input pin, and comparing the detected current with the stored preset current value, if the detected current is less than the preset current value, Control wafer through the gate The pin output first control signal controls the second end of the first electronic switch to communicate with the third end, and the voltage terminal supplies a voltage to the voltage output terminal through the first resistor and the first electronic switch; if the control chip detects The measured current is greater than or equal to the preset current value, and the control chip outputs a second control signal through the gate pin to control the second end of the first electronic switch to be disconnected from the third end, and the voltage terminal does not provide a voltage. Give this voltage output.

該擴展卡過流保護電路透過該控制晶片對該擴展卡上的電流進行偵測，以在偵測到的電流大於或等於預設電流值時切斷該擴展卡上的電源，從而防止電流過大造成該擴展卡毀壞或甚至引起該主機板毀壞。The expansion card overcurrent protection circuit detects the current on the expansion card through the control chip to cut off the power on the expansion card when the detected current is greater than or equal to the preset current value, thereby preventing the current from being excessive. Causes the expansion card to be destroyed or even caused the motherboard to be destroyed.

圖1是本發明擴展卡過流保護電路的較佳實施方式的電路圖。1 is a circuit diagram of a preferred embodiment of an expansion card overcurrent protection circuit of the present invention.

請參考圖1，本發明擴展卡過流保護電路設置在一擴展卡，如PCIe卡上，該擴展卡過流保護電路的較佳實施方式包括一供電電路10及一電流偵測電路20。Referring to FIG. 1 , the expansion card overcurrent protection circuit of the present invention is disposed on an expansion card, such as a PCIe card. The preferred embodiment of the expansion card overcurrent protection circuit includes a power supply circuit 10 and a current detection circuit 20.

該供電電路10包括電子開關（在本實施方式中為兩N溝道場效應電晶體Q1及Q2）、電阻R1及R2及反相器U1。該場效應電晶體Q1的閘極經該電阻R1連接一電壓輸入端VIN_MB，該場效應電晶體Q1的源極連接該電壓輸入端VIN_MB，該場效應電晶體Q1的汲極連接一電壓端V1。該場效應電晶體Q2的閘極經該電阻R2連接一電壓輸入端VIN_PSU，該場效應電晶體Q2的源極連接該電壓輸入端VIN_PSU，該場效應電晶體Q2的汲極連接該電壓端V1。該場效應電晶體Q2的閘極連接該反相器U1的輸入端，該反相器U1的輸出端連接該場效應電晶體Q1的閘極。其中，該電壓輸入端VIN_MB從一主機板接收電壓，該電壓輸入端VIN_PSU從一電源供應器接收電壓。The power supply circuit 10 includes electronic switches (two N-channel field effect transistors Q1 and Q2 in this embodiment), resistors R1 and R2, and an inverter U1. The gate of the field effect transistor Q1 is connected to a voltage input terminal VIN_MB via the resistor R1. The source of the field effect transistor Q1 is connected to the voltage input terminal VIN_MB, and the drain of the field effect transistor Q1 is connected to a voltage terminal V1. . The gate of the field effect transistor Q2 is connected to a voltage input terminal VIN_PSU via the resistor R2. The source of the field effect transistor Q2 is connected to the voltage input terminal VIN_PSU, and the drain of the field effect transistor Q2 is connected to the voltage terminal V1. . The gate of the field effect transistor Q2 is connected to the input terminal of the inverter U1, and the output terminal of the inverter U1 is connected to the gate of the field effect transistor Q1. The voltage input terminal VIN_MB receives a voltage from a motherboard, and the voltage input terminal VIN_PSU receives a voltage from a power supply.

該電流偵測電路20包括電容C1-C5、電阻R3-R10、控制晶片U2及電子開關（在本實施方式中為N溝道場效應電晶體Q3）。該控制晶片U2的偵測引腳SENSE連接該電阻R3的第一端，該電阻R3的第二端連接該供電電路10的電壓端V1及依次經該電阻R4-R6接地，該電容C1及C2分別連接在該電阻R3的第二端與地之間。該控制晶片U2的輸入引腳VIN連接該電阻R3的第二端，該控制晶片U2的輸入輸出引腳UVLO連接於該電阻R4與R5之間的節點，該控制晶片U2的輸入輸出引腳OVLO連接於該電阻R5與R6之間的節點，該控制晶片U2的接地引腳GND接地，該控制晶片U2的門控引腳GATE依次經該電容C5及電阻R10接地。該控制晶片U2的門控引腳GATE還經該電阻R8連接該場效應電晶體Q3的閘極，該場效應電晶體Q3的源極經該電容C4接地，該場效應電晶體Q3的源極還連接一電壓輸出端Vout，該場效應電晶體Q3的汲極連接該電阻R3的第一端，該控制晶片U2的輸出引腳OUT連接該電壓輸出端Vout及經該電阻R9連接該控制晶片U2的輸入輸出引腳PGD，該控制晶片U2的輸入輸出引腳PWR經該電阻R7接地，該控制晶片U2的時鐘引腳TIMER經該電容C3接地。其中，該電壓輸出端Vout用於輸出電壓給該擴展卡上的電子元件。其中，該控制晶片U2內存儲一預設電流值，透過設置該電阻R10的電阻值來設置該控制晶片U2內存儲的預設電流值。The current detecting circuit 20 includes capacitors C1-C5, resistors R3-R10, a control wafer U2, and an electronic switch (in the present embodiment, an N-channel field effect transistor Q3). The detection pin SENSE of the control chip U2 is connected to the first end of the resistor R3. The second end of the resistor R3 is connected to the voltage terminal V1 of the power supply circuit 10 and is grounded via the resistor R4-R6. The capacitors C1 and C2 are connected. Connected between the second end of the resistor R3 and the ground. The input pin VIN of the control chip U2 is connected to the second end of the resistor R3. The input and output pin UVLO of the control chip U2 is connected to the node between the resistors R4 and R5. The input and output pins of the control chip U2 are OVLO. Connected to the node between the resistors R5 and R6, the ground pin GND of the control chip U2 is grounded, and the gate pin GATE of the control chip U2 is grounded through the capacitor C5 and the resistor R10 in sequence. The gate pin GATE of the control chip U2 is further connected to the gate of the field effect transistor Q3 via the resistor R8. The source of the field effect transistor Q3 is grounded via the capacitor C4, and the source of the field effect transistor Q3 A voltage output terminal Vout is also connected. The drain of the field effect transistor Q3 is connected to the first end of the resistor R3. The output pin OUT of the control chip U2 is connected to the voltage output terminal Vout and the control chip is connected via the resistor R9. The input and output pin PGD of the U2, the input and output pin PWR of the control chip U2 is grounded via the resistor R7, and the clock pin TIMER of the control chip U2 is grounded via the capacitor C3. The voltage output terminal Vout is used to output a voltage to the electronic components on the expansion card. The control chip U2 stores a preset current value, and the preset current value stored in the control chip U2 is set by setting the resistance value of the resistor R10.

當該擴展卡（如PCIe卡）上的電壓（如P12V及P3V3）採用雙供電方式時，若該主機板為該擴展卡供電，則該電壓輸入端VIN_MB接收一高電平訊號，該場效應電晶體Q1導通，該電壓輸入端VIN_PSU接收一低電平訊號，該場效應電晶體Q2截止，此時，該主機板提供的電壓透過該電壓輸入端VIN_MB、該場效應電晶體Q1及該電壓端V1輸出給該電流偵測電路20。若該電源供應器為該擴展卡供電，則該電壓輸入端VIN_PSU接收一高電平訊號訊號，該場效應電晶體Q2導通，該反相器U1的輸入端接收該高電平訊號，該反相器U1的輸出端輸出一低電平訊號給該場效應電晶體Q1的閘極，該場效應電晶體Q1截止，此時，該電源供應器提供的電壓透過該電壓輸入端VIN_PSU、該場效應電晶體Q2及該電壓端V1輸出給該電流偵測電路20。When the voltage on the expansion card (such as the PCIe card) (such as P12V and P3V3) adopts the dual power supply mode, if the motherboard supplies power to the expansion card, the voltage input terminal VIN_MB receives a high level signal, and the field effect The transistor Q1 is turned on, the voltage input terminal VIN_PSU receives a low level signal, and the field effect transistor Q2 is turned off. At this time, the voltage provided by the motherboard passes through the voltage input terminal VIN_MB, the field effect transistor Q1 and the voltage. The terminal V1 is output to the current detecting circuit 20. If the power supply supplies power to the expansion card, the voltage input terminal VIN_PSU receives a high level signal, the field effect transistor Q2 is turned on, and the input terminal of the inverter U1 receives the high level signal, the The output terminal of the phase device U1 outputs a low level signal to the gate of the field effect transistor Q1, and the field effect transistor Q1 is turned off. At this time, the voltage supplied by the power supply device passes through the voltage input terminal VIN_PSU, the field. The effect transistor Q2 and the voltage terminal V1 are output to the current detecting circuit 20.

該電流偵測電路20的控制晶片U2透過偵測引腳SENSE及輸入引腳VIN偵測透過該電阻R3的電流，並將偵測到的電流與存儲的預設電流值進行比較，若偵測到的電流小於該預設電流值，該控制晶片U2透過其門控引腳GATE輸出一高電平訊號給該場效應電晶體Q3的閘極，該場效應電晶體Q3導通，該供電電路10的電壓端V1輸出的電壓透過該電阻R3、該場效應電晶體Q3及該電壓輸出端VOUT輸出給該擴展卡上的電子元件，該擴展卡工作。若該控制晶片U2偵測到的電流大於或等於該預設電流值，該控制晶片U2透過其門控引腳GATE輸出一低電平訊號給該場效應電晶體Q3的閘極，該場效應電晶體Q3截止，該供電電路10的電壓端V1輸出的電壓不能輸出給該擴展卡上的電子元件，該擴展卡停止工作。The control chip U2 of the current detecting circuit 20 detects the current passing through the resistor R3 through the detecting pin SENSE and the input pin VIN, and compares the detected current with the stored preset current value. The current is less than the preset current value, and the control chip U2 outputs a high level signal to the gate of the field effect transistor Q3 through its gate pin GATE, and the field effect transistor Q3 is turned on, and the power supply circuit 10 is turned on. The voltage outputted from the voltage terminal V1 is output to the electronic component on the expansion card through the resistor R3, the field effect transistor Q3 and the voltage output terminal VOUT, and the expansion card operates. If the current detected by the control chip U2 is greater than or equal to the preset current value, the control chip U2 outputs a low level signal to the gate of the field effect transistor Q3 through its gate pin GATE. When the transistor Q3 is turned off, the voltage output from the voltage terminal V1 of the power supply circuit 10 cannot be output to the electronic component on the expansion card, and the expansion card stops operating.

當該擴展卡上的電壓（如P3V3_AUX）採用主機板或者電源供應器的單一供電方式時，則該供電電路10可以省略，而直接將該電壓端V1連接至該主機板或者該電源供應器即可，其工作原理與上述相同，在此不再贅述。When the voltage on the expansion card (such as P3V3_AUX) adopts a single power supply mode of the motherboard or the power supply, the power supply circuit 10 can be omitted, and the voltage terminal V1 is directly connected to the motherboard or the power supply. However, the working principle is the same as the above, and details are not described herein again.

該擴展卡過流保護電路透過該控制晶片U2對該擴展卡上的電流進行偵測，以在偵測到的電流大於或等於預設電流值時控制該場效應電晶體Q3截止，以此切斷該擴展卡上的電源，從而防止電流過大造成該擴展卡毀壞或甚至引起該主機板毀壞。The expansion card overcurrent protection circuit detects the current on the expansion card through the control chip U2, and controls the field effect transistor Q3 to cut off when the detected current is greater than or equal to the preset current value. The power supply on the expansion card is broken, thereby preventing the current card from being damaged due to excessive current or even causing the motherboard to be destroyed.

綜上所述，本發明符合發明專利要件，爰依法提出專利申請。惟，以上所述者僅為本發明之較佳實施例，舉凡熟悉本案技藝之人士，在爰依本發明精神所作之等效修飾或變化，皆應涵蓋於以下之申請專利範圍內。In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

10‧‧‧供電電路10‧‧‧Power supply circuit

20‧‧‧電流偵測電路20‧‧‧ Current detection circuit

VIN_MB、VIN_PSU‧‧‧電壓輸入端VIN_MB, VIN_PSU‧‧‧ voltage input

V1‧‧‧電壓端V1‧‧‧ voltage end

Q1-Q3‧‧‧場效應電晶體Q1-Q3‧‧‧ Field Effect Transistor

U1‧‧‧反相器U1‧‧‧Inverter

VOUT‧‧‧電壓輸出端VOUT‧‧‧ voltage output

U2‧‧‧控制晶片U2‧‧‧Control chip

R1-R10‧‧‧電阻R1-R10‧‧‧ resistance

C1-C5‧‧‧電容C1-C5‧‧‧ capacitor

無no

10‧‧‧供電電路 10‧‧‧Power supply circuit

20‧‧‧電流偵測電路 20‧‧‧ Current detection circuit

VIN_MB、VIN_PSU‧‧‧電壓輸入端 VIN_MB, VIN_PSU‧‧‧ voltage input

V1‧‧‧電壓端 V1‧‧‧ voltage end

Q1-Q3‧‧‧場效應電晶體 Q1-Q3‧‧‧ Field Effect Transistor

U1‧‧‧反相器 U1‧‧‧Inverter

VOUT‧‧‧電壓輸出端 VOUT‧‧‧ voltage output

U2‧‧‧控制晶片 U2‧‧‧Control chip

R1-R10‧‧‧電阻 R1-R10‧‧‧ resistance

C1-C5‧‧‧電容 C1-C5‧‧‧ capacitor

Claims (7)

一種擴展卡過流保護電路，包括一電流偵測電路，該電流偵測電路包括一電壓端、一電壓輸出端、一控制晶片、第一及第二電阻及一第一電子開關，該控制晶片的偵測引腳連接該第一電阻的第一端，該第一電阻的第二端連接該電壓端，該控制晶片的輸入引腳連接該第一電阻的第二端，該控制晶片的門控引腳經該第二電阻接地，該控制晶片的門控引腳還連接該第一電子開關的第一端，該第一電子開關的第二端連接該電壓輸出端，該第一電子開關的第三端連接該第一電阻的第一端，該控制晶片內存儲一預設電流值，透過設置該第二電阻的電阻值來設置該控制晶片內存儲的預設電流值；該控制晶片透過偵測引腳及輸入引腳偵測透過該第一電阻的電流，並將偵測到的電流與存儲的預設電流值進行比較，若偵測到的電流小於該預設電流值，該控制晶片透過門控引腳輸出第一控制訊號控制該第一電子開關的第二端與第三端連通，該電壓端透過該第一電阻及該第一電子開關提供電壓給該電壓輸出端；若該控制晶片偵測到的電流大於或等於該預設電流值，該控制晶片透過門控引腳輸出一第二控制訊號控制該第一電子開關的第二端與第三端斷開，該電壓端不提供電壓給該電壓輸出端。An expansion card overcurrent protection circuit includes a current detection circuit including a voltage terminal, a voltage output terminal, a control chip, first and second resistors, and a first electronic switch, the control chip The detecting pin is connected to the first end of the first resistor, the second end of the first resistor is connected to the voltage end, and the input pin of the control chip is connected to the second end of the first resistor, the gate of the control chip The control pin is grounded via the second resistor, the gate pin of the control chip is further connected to the first end of the first electronic switch, and the second end of the first electronic switch is connected to the voltage output end, the first electronic switch The third end is connected to the first end of the first resistor, the control chip stores a preset current value, and the preset current value stored in the control chip is set by setting the resistance value of the second resistor; the control chip Detecting a current through the first resistor through the detection pin and the input pin, and comparing the detected current with the stored preset current value, if the detected current is less than the preset current value, Control wafer through the gate The pin output first control signal controls the second end of the first electronic switch to communicate with the third end, and the voltage terminal supplies a voltage to the voltage output terminal through the first resistor and the first electronic switch; if the control chip detects The measured current is greater than or equal to the preset current value, and the control chip outputs a second control signal through the gate pin to control the second end of the first electronic switch to be disconnected from the third end, and the voltage terminal does not provide a voltage. Give this voltage output. 如申請專利範圍第1項所述之擴展卡過流保護電路，其中第一電子開關為一N溝道場效應電晶體，該第一電子開關的第一至第三端分別對應該場效應電晶體的閘極、源極及汲極。The expansion card overcurrent protection circuit according to claim 1, wherein the first electronic switch is an N-channel field effect transistor, and the first to third ends of the first electronic switch respectively correspond to the field effect transistor The gate, source and bungee. 如申請專利範圍第2項所述之擴展卡過流保護電路，其中該第一控制訊號為一高電平訊號，該第二控制訊號為一低電平訊號。The expansion card overcurrent protection circuit of claim 2, wherein the first control signal is a high level signal, and the second control signal is a low level signal. 如申請專利範圍第1項所述之擴展卡過流保護電路，其中該電流偵測電路還包括第三至第八電阻，該第三至第五電阻依次連接在該第一電阻的第一端與地之間，該控制晶片的第一輸入輸出引腳連接於該第三及第四電阻之間的節點，該控制晶片的第二輸入輸出引腳連接於該第四及第五電阻之間的節點，該第六電阻連接在該控制晶片的第三輸入輸出引腳與地之間，該第七電阻連接在該控制晶片的門控引腳與該第一電子開關的第一端之間，該第八電阻連接在該控制晶片的第四輸入輸出引腳與該電壓輸出端之間，該控制晶片的輸出引腳連接該電壓輸出端。The expansion card overcurrent protection circuit of claim 1, wherein the current detection circuit further includes third to eighth resistors, wherein the third to fifth resistors are sequentially connected to the first end of the first resistor a first input/output pin of the control chip is connected to a node between the third and fourth resistors, and a second input/output pin of the control chip is connected between the fourth and fifth resistors a node, the sixth resistor is connected between the third input and output pin of the control chip and the ground, and the seventh resistor is connected between the gate pin of the control chip and the first end of the first electronic switch The eighth resistor is connected between the fourth input and output pins of the control chip and the voltage output terminal, and an output pin of the control chip is connected to the voltage output terminal. 如申請專利範圍第4項所述之擴展卡過流保護電路，其中該電流偵測電路還包括第一至第五電容，該第一及第二電容分別連接在該電壓端與地之間，該第三電容連接在該控制晶片的時鐘引腳與地之間，該第四電容連接在該第一電子開關的第二端與地之間，該第五電容連接在該控制晶片的門控端與該第二電阻之間。The expansion card overcurrent protection circuit of claim 4, wherein the current detection circuit further includes first to fifth capacitors, wherein the first and second capacitors are respectively connected between the voltage terminal and the ground. The third capacitor is connected between the clock pin of the control chip and the ground, the fourth capacitor is connected between the second end of the first electronic switch and the ground, and the fifth capacitor is connected to the gate of the control chip. Between the end and the second resistor. 如申請專利範圍第5項所述之擴展卡過流保護電路，其中該擴展卡過流保護電路還包括一供電電路，該供電電路包括一用於連接一主機板的第一電壓輸入端、一用於連接一電源供應器的第二電壓輸入端、第九及第十電阻、第二及第三電子開關及一反相器，該第二電子開關的第一端經該第九電阻連接該第一電壓輸入端，該第二電子開關的第二端連接該第一電壓輸入端，該第二電子開關的第三端連接該電壓端，該第三電子開關的第一端經該第十電阻連接該第二電壓輸入端，該第三電子開關的第二端連接該第二電壓輸入端，該第三電子開關的第三端連接該電壓端，該第三電子開關的第一端還連接該反相器的輸入端，該反相器的輸出端連接該第二電子開關的第一端；當該主機板為該擴展卡供電時，該第一電壓輸入端接收一高電平訊號，該第二電子開關的第二端與第三端連通，該第二電壓輸入端接收一低電平訊號，該第三電子開關的第二端與第三端斷開，該主機板提供的電壓透過該第一電壓輸入端及該第二電子開關輸出給該電壓端；當該電源供應器為該擴展卡供電時，該第二電壓輸入端接收一高電平訊號，該第三電子開關的第二端與第三端連通，該反相器的輸入端接收該高電平訊號，該反相器的輸出端輸出一低電平訊號給該第二電子開關的第一端，該第二電子開關的第二端與第三端斷開，該電源供應器提供的電壓透過該第二電壓輸入端及該第三電子開關輸出給該電壓端。The expansion card overcurrent protection circuit of claim 5, wherein the expansion card overcurrent protection circuit further comprises a power supply circuit, the power supply circuit comprising a first voltage input terminal for connecting a motherboard, a second voltage input terminal for connecting a power supply, a ninth and tenth resistor, second and third electronic switches, and an inverter, wherein the first end of the second electronic switch is connected to the ninth resistor a first voltage input end, a second end of the second electronic switch is connected to the first voltage input end, a third end of the second electronic switch is connected to the voltage end, and the first end of the third electronic switch is connected to the tenth The second end of the third electronic switch is connected to the second voltage input end, the third end of the third electronic switch is connected to the voltage end, and the first end of the third electronic switch is further Connecting the input end of the inverter, the output end of the inverter is connected to the first end of the second electronic switch; when the motherboard supplies power to the expansion card, the first voltage input receives a high level signal Second of the second electronic switch The second voltage input end is connected to the third end, the second voltage input end receives a low level signal, the second end of the third electronic switch is disconnected from the third end, and the voltage provided by the motherboard passes through the first voltage input end and The second electronic switch outputs the voltage terminal; when the power supply supplies power to the expansion card, the second voltage input terminal receives a high level signal, and the second electronic switch has a second end connected to the third end The input end of the inverter receives the high level signal, and the output end of the inverter outputs a low level signal to the first end of the second electronic switch, and the second end of the second electronic switch The three terminals are disconnected, and the voltage provided by the power supply is output to the voltage terminal through the second voltage input terminal and the third electronic switch. 如申請專利範圍第6項所述之擴展卡過流保護電路，其中該第二及第三電子開關均為N溝道場效應電晶體，該第二及第三電子開關的第一至第三端分別對應該場效應電晶體的閘極、源極及汲極。The expansion card overcurrent protection circuit of claim 6, wherein the second and third electronic switches are N-channel field effect transistors, and the first to third ends of the second and third electronic switches are Corresponding to the gate, source and drain of the field effect transistor.