Three-power-supply switching circuit of medical portable equipment
By using a combination of PMOS transistors and current-limiting resistors in the three-power switching circuit of a portable medical device, the problems of power conflict and reverse current backflow when three power sources are input simultaneously are solved, achieving efficient automatic power switching and stable power supply.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-04-07
AI Technical Summary
The existing three-power switching circuit of portable medical devices is prone to power conflicts when three power sources are input simultaneously and the voltages are different. The forward voltage drop of the diode increases with the increase of current, which leads to increased power consumption and affects power efficiency.
The system employs a combination of 5 PMOS transistors and 5 current-limiting resistors. The gate-source voltage threshold judgment logic of the PMOS transistors is formed by the voltage difference of the three power supplies. The power supply priority is clearly set, and the cutoff characteristics of the PMOS transistors are used to realize the mutual blocking of each power supply path to prevent power supply conflicts and reverse current backflow.
It effectively solves the problems of power conflict and reverse current backflow, reduces power consumption, improves power efficiency, and ensures continuous and stable operation of the equipment.
Smart Images
Figure CN121813653A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of switching circuit technology, specifically a three-power switching circuit for a portable medical device. Background Technology
[0002] The three-power switching circuit for portable medical devices is an electronic circuit that automatically / manually switches between power sources. Its core function is to allow the device to seamlessly switch between three power sources (such as a built-in lithium battery, an external adapter, and a backup emergency power supply), ensuring continuous and stable operation of the device. This is like installing "triple power protection" for medical devices, preventing equipment downtime due to a single power failure, which could lead to serious consequences such as disruption of diagnosis and treatment, damage to medical equipment, increased medical costs, or even endangering the patient's life.
[0003] The three-power automatic switching circuit disclosed in publication (announcement) number CN216356087U is described as including: "a first input terminal, a second input terminal, a third input terminal, an output terminal, a first field-effect transistor, a second field-effect transistor, a third field-effect transistor, a fourth field-effect transistor, a first resistor, a second resistor, a third resistor, and a diode." However, it does not explicitly define the power input priority logic, relying solely on a combination of field-effect transistors and diodes for conduction control. When three power supplies are input simultaneously with voltage differences, the lack of a mutual interlocking mechanism among the power supply paths leads to multiple power supplies attempting to supply power to the output terminal simultaneously, resulting in current competition and power conflict. Furthermore, the forward voltage drop of the diode increases with increasing current, leading to increased power consumption and impacting power efficiency. Summary of the Invention
[0004] (a) Technical problems to be solved:
[0005] To address the shortcomings of existing technologies, this invention provides a three-power switching circuit for portable medical devices, which solves the problems mentioned in the background art, such as power conflicts caused by simultaneous input of three power sources with voltage differences, and the increase in diode forward voltage drop as current increases, leading to increased power consumption and affecting power efficiency.
[0006] (II) Technical Solution:
[0007] To achieve the above objectives, the present invention provides the following technical solution: a three-power switching circuit for a portable medical device, comprising:
[0008] Three power sources, including adapter, wireless charger, and lithium battery;
[0009] Five PMOS transistors, including Q1, Q2, Q3, Q4 and Q5 for controlling the priority of the adapter with the wireless charger;
[0010] 5 current-limiting resistors;
[0011] The five PMOS transistors correspond to the power supply paths and priority control of the three power supplies, respectively. The five current-limiting resistors are connected in series with the gates of the corresponding PMOS transistors. The gate-source voltage of the PMOS transistor is formed by the voltage difference of the three power supplies. When the gate-source voltage is less than the turn-on threshold voltage, the PMOS transistor is turned on. When it is greater than the turn-on threshold voltage, the PMOS transistor is turned off, thereby completing the automatic switching of the three power supplies and the reverse current blocking.
[0012] Preferably, the adapter includes an access port power terminal V_BUS;
[0013] The wireless charger includes an access port power terminal V_Wireless;
[0014] The lithium battery includes an access port power terminal V_BAT.
[0015] Preferably, the five current-limiting resistors are resistors R1, R2, R3, R4, and R5, and all five current-limiting resistors are gate pull-down resistors, used to cooperate with the corresponding PMOS transistor to stabilize the gate voltage and assist in the threshold judgment of the gate-source voltage.
[0016] Preferably, the drain of Q1 is connected to the power supply terminal V_BUS;
[0017] Node V1 is connected to the source of the PMOS transistor Q1;
[0018] The resistor R1 is connected to the gate of the PMOS transistor Q1 at one end and grounded at the other end.
[0019] Resistor R6 has one end connected to the gate of PMOS transistor Q1, and the other end connected to ground in parallel with resistor R1.
[0020] Preferably, the drain of Q2 is connected to the power supply terminal V_BAT;
[0021] The output terminal V_OUT is connected to the source of Q2;
[0022] The resistor R2 is connected at one end to the gate of Q2 and at the other end to the node V1;
[0023] Resistor R7 is connected at one end to the gate of PMOS transistor Q2, and at the other end is connected in parallel with resistor R2 to node V1.
[0024] Preferably, the drain of Q3 is connected to the output terminal V_OUT, and the source is connected to the node V1;
[0025] The resistor R3 is connected at one end to the gate of Q3 and at the other end to the power supply terminal V_BAT.
[0026] Resistor R8 is connected at one end to the gate of PMOS transistor Q3, and at the other end is connected in parallel with resistor R3 to the power supply terminal V_BAT.
[0027] Preferably, in the case of Q4, the drain is connected to node V1 and the source is connected to node V2;
[0028] The resistor R4 is connected at one end to the gate of Q4 and at the other end to node V2;
[0029] Resistor R9 is connected at one end to the gate of PMOS transistor Q4, and at the other end is connected in parallel with resistor R4 to node V2.
[0030] Preferably, in the case of Q5, the drain is connected to the node V2, and the source is connected to the power supply terminal V_Wireless;
[0031] The resistor R5 is connected to the gate of Q5 at one end and to the power supply terminal V_BUS at the other end.
[0032] Resistor R10 is connected at one end to the gate of PMOS transistor Q5, and at the other end is connected in parallel with resistor R5 to the power supply terminal V_BUS.
[0033] Preferably, the power supply priorities of the three power sources are, in order, power supply terminal V_BUS, power supply terminal V_Wireless, and power supply terminal V_BAT. The circuit automatically selects the highest priority power supply based on the status of the three power sources connected.
[0034] (III) Beneficial Effects:
[0035] The three-power switching circuit for a portable medical device provided by this invention has the following beneficial effects:
[0036] 1. The three-power switching circuit for a portable medical device employs a combination structure of five PMOS transistors and five current-limiting resistors. It relies on the voltage difference of the three power supplies to form the gate-source voltage threshold judgment logic of the PMOS transistors, clearly setting the power supply priority of the adapter > wireless charging > lithium battery. At the same time, it utilizes the cutoff characteristics of the PMOS transistors to achieve mutual interlocking of each power path, thereby solving the defects of the prior art in which there is no interlocking mechanism when three power supplies are input at the same time and the voltages are different, which easily leads to power conflicts.
[0037] 2. The three-power switching circuit of this portable medical device uses a PMOS transistor instead of a traditional diode as the core component for backflow prevention and power supply path. By utilizing the characteristic that the internal resistance of the PMOS transistor can be as low as tens of milliohms, the input voltage drop is determined by the internal resistance of the MOS transistor and the input current. Compared with the diode, whose on-state voltage drop increases with the current, this circuit significantly reduces the power supply voltage drop under high current input, reduces power consumption, and solves the defects of low power efficiency and severe heat generation caused by diodes in the prior art.
[0038] 3. This three-power switching circuit for a portable medical device utilizes the reverse current blocking function of a PMOS transistor, along with a current-limiting resistor to stabilize the gate voltage and ensure precise conduction and cutoff of the PMOS transistor. This achieves reverse current blocking between the three power supplies, effectively preventing backflow of current from the high-priority power supply to the low-priority power supply, avoiding power supply damage and energy waste. This also solves the shortcomings of existing switching circuits that rely on diodes for limited backflow prevention and cannot completely avoid the risk of power backflow. Attached Figure Description
[0039] Figure 1 This is the circuit diagram of the present invention. Detailed Implementation
[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0041] Example 1
[0042] refer to Figure 1 A preferred embodiment of the present invention provides a three-power switching circuit for a portable medical device, which will be described in detail below, including:
[0043] Three power sources, including an adapter, a wireless charger, and a lithium battery, provide different power options for portable medical devices. The adapter meets the stable power supply needs of fixed locations, the wireless charger enables convenient power supply without cables, and the lithium battery ensures mobile use when the device is disconnected from an external power source. The three complement each other to ensure the continuous operation of the device.
[0044] Five PMOS transistors, including Q1, Q2, Q3, Q4 and Q5 for controlling the priority of the adapter and wireless charging, are used to meet the requirements of medical devices for power switching efficiency and power consumption control by utilizing the low conduction loss and fast switching response of PMOS transistors.
[0045] Five current-limiting resistors can limit the gate current to prevent excessive current from damaging the PMOS transistor, while also stabilizing the gate position and ensuring accurate gate voltage determination.
[0046] Five PMOS transistors correspond to the power supply paths and priority control of the three power sources. Five current-limiting resistors are connected in series with the gates of the corresponding PMOS transistors. The gate-source voltage of the PMOS transistors is formed by the voltage difference between the three power sources. When the gate-source voltage is less than the turn-on threshold voltage, the PMOS transistor turns on; when it is greater than the turn-on threshold voltage, the PMOS transistor turns off, thus completing the automatic switching of the three power sources and reverse current blocking. This eliminates the need for an additional control chip, implementing control logic through voltage differences. This simplifies the circuit structure, reduces hardware costs, and prevents high-priority power sources from flowing back into low-priority power sources through reverse current blocking, avoiding power supply damage and energy waste, and ensuring safe and stable circuit operation.
[0047] The adapter includes the power supply terminal V_BUS at the access port, which is a high-priority power supply access point and provides a reference voltage signal for subsequent priority determination and circuit conduction control.
[0048] The wireless charger includes the power supply terminal V_Wireless at the access port. Its voltage characteristics differ from those of the adapter, and this difference provides a voltage signal basis for priority identification, ensuring that the wireless charger can promptly provide power when the adapter is not connected.
[0049] The lithium battery includes the power terminal V_BAT at the access port, which has a voltage lower than that of the adapter and wireless charger, and is adapted to the conduction threshold characteristics of the PMOS transistor to ensure rapid power supply when the external power is disconnected, thus avoiding device shutdown.
[0050] The five current-limiting resistors are R1, R2, R3, R4, and R5. All five are gate pull-down resistors, used to stabilize the gate voltage of the corresponding PMOS transistors and assist in determining the threshold voltage of the gate-source voltage. The gate pull-down resistors pull the PMOS transistor's gate potential to a stable state, preventing false turn-on or cut-off due to a floating gate. This ensures that the gate-source voltage accurately reflects the power supply voltage difference, thereby achieving precise switching between the three power supplies. Simultaneously, the pull-down characteristic enhances the circuit's anti-interference capability, preventing external signals from interfering with the gate voltage.
[0051] Q1 has its drain connected to the power supply terminal V_BUS, ensuring that the adapter's power can be directly transmitted to Q1. Furthermore, the direct interception between the drain and the power supply terminal V_BUS also reduces transmission loss and ensures power supply efficiency.
[0052] Node V1 is connected to the source of PMOS transistor Q1. Node V1 is the connection node between the adapter power supply path and other power supply paths. Its function is to receive the power output from the source of Q1, and at the same time provide a connection point for components such as Q2 and Q3, so as to realize the signal interaction and power convergence of multiple power supply paths, and assist in the determination of the gate-source voltage of each PMOS transistor.
[0053] Resistor R1 is connected to the gate of PMOS transistor Q1 at one end and grounded at the other end. R1 stabilizes the gate of Q1 by pulling it down through grounding. When the power supply V_BUS is connected, the voltage difference between the gate and the source can accurately trigger Q1 to conduct. The grounding design ensures that the gate potential of Q1 is stable at a low level when the power supply V_BUS is disconnected, avoiding false turn-on and limiting the gate current to protect the gate of Q1 from damage.
[0054] Resistor R6 is connected to the gate of PMOS transistor Q1 at one end and to ground in parallel with resistor R1 at the other end. Together with resistor R1, it forms a double pull-down resistor structure for the gate of Q1, which further enhances the stability of the gate voltage.
[0055] Q5, with its drain connected to node V2 and its source connected to the power supply V_Wireless, is used to control the priority of the wireless charger and the adapter. By connecting the source to the wireless charging power and the drain to node V2, the wireless charging power is transmitted to the subsequent path, ensuring the independence of the wireless charging power supply path. At the same time, it is linked with the V_BUS signal to achieve priority control.
[0056] Resistor R5 is connected to the gate of Q5 at one end and the power supply terminal V_BUS at the other end. Resistor R5 directly connects the gate of Q5 to the power supply terminal V_BUS, so that the gate voltage of Q5 can follow the change of the power supply terminal V_BUS voltage in real time. The gate-source voltage is formed by the voltage difference between the power supply terminal V_BUS and the power supply terminal V_Wireless, thereby controlling the conduction and cutoff of Q5 and realizing the logic of the adapter taking priority over wireless charging power supply.
[0057] Resistor R10 is connected to the gate of PMOS transistor Q5 at one end and to the power supply terminal V_BUS in parallel with resistor R5 at the other end. Together with resistor R5, it forms a dual resistor to further stabilize the gate voltage of Q5 and ensure the reliability of the priority judgment logic between the adapter and the wireless charger.
[0058] The following is the complete working process and working principle of the above embodiments:
[0059] During operation, each current-limiting resistor stabilizes the corresponding PMOS transistor gate voltage. Resistors R1 and R6 are connected in parallel to form a double pull-down resistor structure for the gate of Q1, further enhancing gate voltage stability and preventing gate potential fluctuations caused by a single resistor failure. Resistors R5 and R10 are connected in parallel to further stabilize the gate voltage of Q5, ensuring the reliability of the priority judgment logic between the adapter and the wireless charger. The PMOS transistor conducts when the gate-source voltage is less than the turn-on threshold and is turned off when it is greater. When the adapter is connected, the power supply voltage V_BUS creates an effective voltage difference between the gate and source of Q1, causing it to conduct. Power is transferred through the source node V1 of Q1. Simultaneously, the power supply voltage V_BUS controls Q5 to turn off through resistor R5, blocking the wireless charging path. The voltage at node V1 then controls Q2 to turn off and Q3 to turn on through resistors R2 and R3 respectively, achieving priority power supply to the adapter. If the adapter is disconnected, the power supply V_BUS loses power, causing Q1 to turn off. The power supply V_Wireless voltage at the wireless charger's power supply terminal creates an effective voltage difference between the gate and source of Q5 and Q4, enabling them to conduct sequentially. Power is transferred through nodes V2 and Q4 to node V1, and then delivered to the output terminal V_OUT via Q3. At this time, Q2 remains off, achieving priority power supply for wireless charging. When all external power supplies are disconnected, the power supply V_BAT voltage creates an effective voltage difference between the gate and source of Q2, enabling it to conduct directly to the output terminal V_OUT. Simultaneously, Q3, Q4, and Q5 are all off, preventing reverse current flow. No additional control chip is required throughout the process; priority power supply switching is automatically completed through hardware voltage logic, ensuring the continuous and stable operation of the portable medical device.
[0060] Example 2
[0061] refer to Figure 1 Q2, the drain of which is connected to the power supply terminal V_BAT, ensures that the lithium battery power can be efficiently input into Q2.
[0062] The output terminal V_OUT is connected to the source of Q2. The source of Q2 is directly connected to the output terminal V_OUT, which can shorten the power supply path and reduce power loss. Its switching state is controlled by the gate voltage, thereby ensuring that the lithium battery is accurately powered in the appropriate scenario.
[0063] Resistor R2 is connected to the gate of Q2 at one end and to node V1 at the other end, so that the gate of resistor R2 is linked to the signal of node V1. The gate voltage of Q2 can reflect the voltage change of node V1 in real time, and the conduction and cutoff of Q2 are controlled by the voltage difference between node V1 and power supply terminal V_BAT.
[0064] Resistor R7 is connected at one end to the gate of PMOS transistor Q2, and at the other end in parallel with resistor R2 to node V1. It is used to help stabilize the gate potential of Q2 and improve the anti-interference capability of gate-source voltage judgment.
[0065] Q3, with its drain connected to the output terminal V_OUT and its source connected to node V1, serves as the path for external power (adapter or wireless charger) to supply power to the output terminal. It also serves to block reverse current. Connecting the drain to the output terminal V_OUT ensures that external power can be directly transmitted to the output terminal V_OUT. Connecting the source to node V1 enables connection to the external power supply path and allows it to adapt to the current flow requirements of different power supply scenarios by utilizing its bidirectional switching characteristics.
[0066] Resistor R3 is connected at one end to the gate of Q3 and at the other end to the power supply terminal V_BAT. Connecting the gate of Q3 to the power supply terminal V_BAT via resistor R3 causes the gate voltage of Q3 to follow the voltage changes at the power supply terminal V_BAT. The voltage difference between the power supply terminal V_BAT and node V1 controls the conduction and cutoff of Q3. When an external power supply is connected, the voltage at node V1 rises, and Q3 conducts to supply power. When the external power supply is disconnected, Q3 is cut off to prevent current from the output terminal V_OUT from flowing back into node V1, ensuring circuit safety.
[0067] Resistor R8 is connected at one end to the gate of PMOS transistor Q3, and at the other end in parallel with resistor R3 to the power supply terminal V_BAT, thereby enhancing the stability of the gate voltage of Q3 and ensuring that the turn-on and turn-off logic accurately responds to changes in the power supply voltage.
[0068] Q4 is an intermediate switching element in the wireless charging power supply path. Its drain is connected to node V1 and its source is connected to node V2, realizing the power transfer between node V2 and node V1. The drain being connected to node V1 ensures that the wireless charging power can flow into the main power supply path, and the source being connected to node V2 receives the power transferred by Q5. Its switching state is controlled by the gate voltage to ensure the orderly access of the wireless charging power supply.
[0069] Resistor R4 is connected at one end to the gate of Q4 and at the other end to node V2. R4 acts as a pull-down resistor for the gate of Q4, relating its gate potential to the voltage at node V2. This allows the gate-source voltage of Q4 to automatically adjust according to changes in the voltage at node V2. When wireless charging is connected, the voltage at node V2 increases. Since the gate-source voltage of Q4 is below the turn-on threshold voltage, Q4 turns on, enabling wireless charging energy transfer to node V1. Simultaneously, it limits the gate current, protecting the Q4 component.
[0070] Resistor R9 is connected at one end to the gate of PMOS transistor Q4, and at the other end in parallel with resistor R4 to node V2. It is used to help limit the gate current of Q4 and improve the gate potential resistance of Q4.
[0071] The power supply priorities for the three power sources are, in descending order: V_BUS, V_Wireless, and V_BAT. The circuit automatically selects the highest priority power source based on the availability of the three power sources: the adapter has the highest priority to ensure stable power supply in fixed scenarios; the wireless charger is next to it to meet the need for convenient wireless power supply; and the lithium battery serves as a backup power source to ensure emergency use when no external power is available. By prioritizing power sources, conflicts caused by simultaneous power supply from multiple sources are avoided, while ensuring the stability and continuity of power supply, thus improving the reliability of the device.
[0072] The following is the complete working process and working principle of the above embodiments:
[0073] During operation, Q2's drain is connected to the power supply terminal V_BAT, and its source is directly connected to the output terminal V_OUT. Its gate is linked to node V1 via resistor R2, and resistors R7 and R2 are connected in parallel to node V1 to help stabilize Q2's gate potential and improve the anti-interference capability of the gate-source voltage judgment. The voltage difference between node V1 and the power supply terminal V_BAT controls the on / off state, ensuring that the lithium battery only starts supplying power when the external power supply is disconnected. Q3's drain is connected to the output terminal V_OUT, and its source is connected to node V1. Its gate is connected to the power supply terminal V_BAT via resistor R3, and resistors R8 and R3 are connected in parallel to the power supply terminal V_BAT to enhance the stability of Q3's gate voltage, ensuring that the on / off logic responds to changes in the power supply voltage. When an external power supply is connected, causing the voltage at node V1 to rise, Q3 forms an effective voltage difference between its gate and source, enabling the external power supply to the output terminal. When the external power supply is disconnected, it is cut off to prevent current from flowing back into node V1. Q4 serves as the intermediate switch in the wireless charging power supply path, with its drain connected to node V1 and its source connected to node V2. Its gate is connected to node V2 via resistor R4, and resistor R9 is connected in parallel with R4 to node V2 to help limit the gate current of Q4 and improve its gate potential's resistance to fluctuations. When the wireless charger is connected and the adapter is disconnected, the voltage at node V2 increases, causing Q4 to conduct, transferring wireless charging energy to node V1 and then to the output terminal V_OUT via Q3. Throughout this process, each current-limiting resistor stably corresponds to the gate voltage of the PMOS transistor. Threshold judgment of the gate-source voltage is achieved based on the voltage difference between the three power supplies, enabling automatic priority switching without the need for an additional control chip, ensuring circuit safety and power supply continuity.
[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A three-power switching circuit for a portable medical device, characterized in that, include: Three power sources, including adapter, wireless charger, and lithium battery; Five PMOS transistors, including Q1, Q2, Q3, Q4 and Q5 for controlling the priority of the adapter with the wireless charger; 5 current-limiting resistors; The five PMOS transistors correspond to the power supply paths and priority control of the three power supplies, respectively. The five current-limiting resistors are connected in series with the gates of the corresponding PMOS transistors. The gate-source voltage of the PMOS transistor is formed by the voltage difference of the three power supplies. When the gate-source voltage is less than the turn-on threshold voltage, the PMOS transistor is turned on. When it is greater than the turn-on threshold voltage, the PMOS transistor is turned off, thereby completing the automatic switching of the three power supplies and the reverse current blocking.
2. The three-power switching circuit for a portable medical device according to claim 1, characterized in that: The adapter includes an access port power supply terminal V_BUS; The wireless charger includes an access port power terminal V_Wireless; The lithium battery includes an access port power terminal V_BAT.
3. The three-power switching circuit for a portable medical device according to claim 1, characterized in that: The five current-limiting resistors are resistors R1, R2, R3, R4, and R5. All five current-limiting resistors are gate pull-down resistors, used to work with the corresponding PMOS transistors to stabilize the gate voltage and assist in the threshold determination of the gate-source voltage.
4. The three-power switching circuit for a portable medical device according to claim 1, characterized in that: The drain of Q1 is connected to the power supply terminal V_BUS; Node V1 is connected to the source of the PMOS transistor Q1; The resistor R1 is connected to the gate of the PMOS transistor Q1 at one end and grounded at the other end. Resistor R6 has one end connected to the gate of PMOS transistor Q1, and the other end connected to ground in parallel with resistor R1.
5. The three-power switching circuit for a portable medical device according to claim 4, characterized in that: The drain of Q2 is connected to the power supply terminal V_BAT; The output terminal V_OUT is connected to the source of Q2; The resistor R2 is connected at one end to the gate of Q2 and at the other end to the node V1; Resistor R7 is connected at one end to the gate of PMOS transistor Q2, and at the other end is connected in parallel with resistor R2 to node V1.
6. The three-power switching circuit for a portable medical device according to claim 5, characterized in that: The drain of Q3 is connected to the output terminal V_OUT, and the source is connected to node V1; The resistor R3 is connected at one end to the gate of Q3 and at the other end to the power supply terminal V_BAT. Resistor R8 is connected at one end to the gate of PMOS transistor Q3, and at the other end is connected in parallel with resistor R3 to the power supply terminal V_BAT.
7. The three-power switching circuit for a portable medical device according to claim 4, characterized in that: Q4 has its drain connected to node V1 and its source connected to node V2; The resistor R4 is connected at one end to the gate of Q4 and at the other end to node V2; Resistor R9 is connected at one end to the gate of PMOS transistor Q4, and at the other end is connected in parallel with resistor R4 to node V2.
8. The three-power switching circuit for a portable medical device according to claim 7, characterized in that: Q5 has its drain connected to node V2 and its source connected to the power supply terminal V_Wireless; The resistor R5 is connected to the gate of Q5 at one end and to the power supply terminal V_BUS at the other end. Resistor R10 is connected at one end to the gate of PMOS transistor Q5, and at the other end is connected in parallel with resistor R5 to the power supply terminal V_BUS.
9. The three-power switching circuit for a portable medical device according to claim 1, characterized in that: The power supply priorities of the three power sources are, in order, power supply terminal V_BUS, power supply terminal V_Wireless, and power supply terminal V_BAT. The circuit automatically selects the highest priority power source based on the status of the three power sources connected.