Power supply switching circuit and electric equipment
By designing a power supply switching circuit to automatically switch power supply modes, the problem of current backflow when an external power source is connected is solved, thus achieving battery protection and efficient and reliable operation of the equipment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2026-04-03
AI Technical Summary
When an external power source is connected, current may flow back into the battery of the portable medical device, causing the battery to overcharge, overheat, or even be damaged, affecting the normal operation of the device and the safety of the patient.
Design a power supply switching circuit, including a first input terminal, a second input terminal, an output terminal, an enable unit, and first to fourth switching units. By controlling the conduction and shutdown of the switching units, the power supply mode is automatically switched to ensure that the external power supply is given priority. When the external power supply is connected, the second switching unit is automatically shut off to reduce current backflow.
It effectively reduces reverse current flow, protects the battery from damage, reduces conduction and heat loss, and improves the safety and reliability of the equipment.
Smart Images
Figure CN224083253U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power supply technology, specifically to a power supply switching circuit and an electrical device. Background Technology
[0002] With the rapid development of medical devices, especially the widespread use of portable medical devices (such as portable monitors, defibrillators, and infusion pumps), the reliability and safety of power supply systems have become critical issues. These devices typically use built-in batteries as their primary power source to ensure continuous operation during power outages or when the device is in motion. Simultaneously, medical devices also support external power sources (such as AC adapters or DC power supplies) to power the device and charge the battery when used in a fixed location.
[0003] However, after an external power source is connected, due to the voltage difference between the external power source and the battery, the current from the external power source may flow back into the battery, causing the battery to overcharge, overheat, or even be damaged, thereby affecting the normal operation of the equipment and the safety of the patient.
[0004] Therefore, there is an urgent need for a power supply switching circuit that can reduce current backflow in order to solve the above-mentioned problems and improve the safety and reliability of the equipment. Utility Model Content
[0005] This application provides a power supply switching circuit and an electrical device that reduces the phenomenon of current flowing back into the battery when an external power source is connected.
[0006] In a first aspect, embodiments of this application provide a power supply switching circuit, comprising: a first input terminal, a second input terminal, an output terminal, an enable unit, a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit. The first switch unit is connected to the first input terminal and the first terminal of the second switch unit, respectively. The third switch unit is connected to the second input terminal, the enable unit, and the first terminal of the fourth switch unit, respectively. The second terminals of both the second and fourth switch units are connected to the output terminal. The third terminal of the fourth switch unit is connected to the enable unit. The first input terminal is used to connect a battery, and the second input terminal is used to connect an external power source. The first switch unit is configured to turn on in response to receiving a drive signal after the battery is connected to the first input terminal, thereby connecting the battery to the first terminal of the second switch unit. The second switch unit is configured to turn on when the voltage at the first terminal of the second switch unit is greater than the voltage at the second terminal of the second switch unit, and to turn off when the voltage at the first terminal of the second switch unit is less than the voltage at the second terminal of the second switch unit. The third switching unit is configured to turn on when the external power supply is connected to the second input terminal, thereby connecting the external power supply to the first terminal of the fourth switching unit and the enabling unit. The enabling unit is configured to output a first enabling signal to the fourth switching unit when the external power supply is connected. The fourth switching unit is configured to turn on in response to receiving the first enabling signal.
[0007] In one or more embodiments, the first switching unit includes a first switching transistor, a first resistor, a second resistor, and a first Zener diode; a first terminal of the first switching transistor is connected to the first input terminal, a second terminal of the first switching transistor is connected to the first terminal of the second switching unit, the anode of the first Zener diode, and the first terminal of the first resistor, respectively, a third terminal of the first switching transistor is connected to the cathode of the first Zener diode, the second terminal of the first resistor, and the first terminal of the second resistor, and the second terminal of the second resistor is used to receive the drive signal.
[0008] In one or more embodiments, the second switching unit includes a second switching transistor, a first control chip, a third resistor, a fourth resistor, and a second Zener diode; the first terminal of the second switching transistor is connected to the first switching unit, the first terminal of the first control chip, the first terminal of the third resistor, and the anode of the second Zener diode, respectively; the second terminal of the second switching transistor is connected to the second terminal of the fourth switching unit, the second terminal of the first control chip, and the output terminal, respectively; the third terminal of the second switching transistor is connected to the second terminal of the third resistor, the cathode of the second Zener diode, and the first terminal of the fourth resistor, respectively; and the second terminal of the fourth resistor is connected to the third terminal of the first control chip.
[0009] In one or more embodiments, the second switching unit further includes a first diode, a fifth resistor, and a first capacitor; the anode of the first diode is connected to the first terminal of the first switching unit and the second switching transistor, the cathode of the first diode is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the power supply terminal of the first control chip and the first terminal of the first capacitor, and the second terminal of the first capacitor is grounded.
[0010] In one or more embodiments, the third switching unit includes a third switching transistor, a second control chip, a sixth resistor, a seventh resistor, and a third Zener diode; the first terminal of the third switching transistor is connected to the second input terminal, the first terminal of the second control chip, the first terminal of the sixth resistor, and the anode of the third Zener diode, respectively; the second terminal of the third switching transistor is connected to the first terminal of the fourth switching unit, the second terminal of the second control chip, and the enable unit, respectively; the third terminal of the third switching transistor is connected to the second terminal of the sixth resistor, the cathode of the third Zener diode, and the first terminal of the seventh resistor, respectively; and the second terminal of the seventh resistor is connected to the third terminal of the second control chip.
[0011] In one or more embodiments, the third switching unit further includes a second diode, an eighth resistor, and a second capacitor; the anode of the second diode is connected to the second input terminal and the first terminal of the third switching transistor, the cathode of the second diode is connected to the first terminal of the eighth resistor, the second terminal of the eighth resistor is connected to the power supply terminal of the second control chip and the first terminal of the second capacitor, and the second terminal of the second capacitor is grounded.
[0012] In one or more embodiments, the fourth switching unit includes a fourth switching transistor, a third control chip, a ninth resistor, a tenth resistor, and a fourth Zener diode; the first terminal of the fourth switching transistor is connected to the third switching unit and the enable unit, the second terminal of the fourth switching transistor is connected to the anode of the fourth Zener diode, the first terminal of the ninth resistor, and the output terminal, the third terminal of the fourth switching transistor is connected to the cathode of the fourth Zener diode, the second terminal of the ninth resistor, and the first terminal of the tenth resistor, the second terminal of the tenth resistor is connected to the first terminal of the third control chip, and the second terminal of the third control chip is connected to the enable unit.
[0013] In one or more embodiments, the fourth switching unit further includes a third capacitor and an eleventh resistor; the first terminal of the third capacitor is connected to the third terminal of the third control chip, the second terminal of the third capacitor is grounded, the first terminal of the eleventh resistor is connected to the first terminals of the enable unit, the third switching unit and the fourth switching transistor respectively, and the second terminal of the eleventh resistor is connected to the fourth terminal of the third control chip.
[0014] In one or more embodiments, the enabling unit includes a first voltage divider resistor, a second voltage divider resistor, a fourth capacitor, a fifth switch transistor, and a twelfth resistor. The first terminal of the first voltage divider resistor is connected to the first terminal of the third switch unit and the first terminal of the fourth switch transistor. The second terminal of the first voltage divider resistor is connected to the first terminal of the second voltage divider resistor, the first terminal of the fourth capacitor, the first terminal of the fifth switch transistor, and the enable terminal of the third control chip. The second terminal of the fifth switch transistor is connected to the first terminal of the twelfth resistor. The second terminal of the twelfth resistor is used to receive control signals. The second terminal of the second voltage divider resistor, the second terminal of the fourth capacitor, and the third terminal of the fifth switch transistor are grounded.
[0015] Secondly, embodiments of this application also provide an electrical device, which includes a power supply switching circuit as described in any embodiment of the first aspect.
[0016] The beneficial effects of this application embodiment are as follows: This application embodiment provides a power supply switching circuit and an electrical device, including: a first input terminal, a second input terminal, an output terminal, an enable unit, a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit; the first switch unit is connected to the first input terminal and the first terminal of the second switch unit respectively; the third switch unit is connected to the second input terminal, the enable unit, and the first terminal of the fourth switch unit respectively; the second terminals of the second and fourth switch units are both connected to the output terminal; the third terminal of the fourth switch unit is connected to the enable unit; the first input terminal is used to connect to a battery; the second input terminal is used to connect to an external power source; this power supply switching circuit automatically switches the power supply mode according to the connection status of the external power source. When the external power source is connected, the circuit prioritizes using the external power source; when the external power source is not connected, the circuit automatically switches to battery power. Moreover, through the second switch unit, when the external power source is connected, the second switch unit automatically turns off, reducing the phenomenon of current flowing back from the external power source to the battery, thereby protecting the battery from damage. Attached Figure Description
[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.
[0018] Figure 1 A structural block diagram of a power supply switching circuit provided in an embodiment of this application;
[0019] Figure 2 This is a partial structural diagram of a power supply switching circuit provided in an embodiment of this application;
[0020] Figure 3 This is a partial structural diagram of another power supply switching circuit provided in an embodiment of this application. Detailed Implementation
[0021] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "electrically connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "upper," "lower," "inner," "outer," "bottom," etc., used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0022] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items. Furthermore, technical features involved in the different embodiments of this application described below may be combined with each other as long as they do not conflict with each other.
[0023] In traditional power supply switching control circuits, the battery power supply circuit between the battery and the load typically lacks effective reverse current protection. To prevent current and voltage reverse current flow, a common solution is to add a diode as a protective element to the battery power supply circuit. Due to its unidirectional conductivity, the diode can effectively block reverse current, thereby ensuring stable circuit operation and preventing potential damage.
[0024] However, despite their excellent performance in preventing reverse current flow, diodes also present a series of challenges in practical applications. First, diodes have a relatively high forward voltage drop, typically between 0.6V and 0.7V. This voltage drop leads to significant conduction losses, especially in high-current applications. As the current increases, the diode's power loss increases significantly, reducing the overall system's energy conversion efficiency. For high-power devices, this efficiency loss not only increases energy consumption but may also affect the long-term operational stability of the equipment. Second, diodes generate heat during conduction, particularly in high-power applications. Addressing this issue typically requires additional heat dissipation measures, such as installing heat sinks or adding ventilation designs. This not only increases the system's manufacturing cost but also occupies more space, posing a significant challenge to the miniaturization and integration of the device. In conclusion, although diodes play a crucial role in preventing reverse current flow, their high forward voltage drop and heat generation issues limit their application in efficient, compact power switching circuits.
[0025] To address the aforementioned issues, this application provides a power switching circuit and an electrical device. This power switching circuit effectively reduces the phenomenon of current flowing back into the battery when an external power source is connected. Furthermore, it eliminates the need for diodes, thereby reducing conduction losses and heat losses, and meeting the demands of electronic devices for high efficiency, high integration, and high reliability.
[0026] In a first aspect, embodiments of this application provide a power supply switching circuit, see below. Figure 1 The power supply switching circuit includes: a first input terminal I NPUT1, a second input terminal I NPUT2, an output terminal OUT1, an enable unit 50, a first switch unit 10, a second switch unit 20, a third switch unit 30, and a fourth switch unit 40.
[0027] The first switch unit 10 is connected to the first input terminal I NPUT1 and the first terminal of the second switch unit 20 respectively. The third switch unit 30 is connected to the second input terminal I NPUT2, the enable unit 50 and the first terminal of the fourth switch unit 40 respectively. The second terminals of the second switch unit 20 and the fourth switch unit 40 are both connected to the output terminal OUT1. The third terminal of the fourth switch unit 40 is connected to the enable unit 50. The first input terminal I NPUT1 is used to connect to the battery, and the second input terminal I NPUT2 is used to connect to the external power supply.
[0028] The first switching unit 10 is configured to turn on in response to receiving a drive signal after the battery is connected to the first input terminal I NPUT1, thereby connecting the battery to the first terminal of the second switching unit 20. The second switching unit 20 is configured to turn on when the voltage at the first terminal of the second switching unit 20 is greater than the voltage at the second terminal of the second switching unit 20, and to turn off when the voltage at the first terminal of the second switching unit 20 is less than the voltage at the second terminal of the second switching unit 20. The third switching unit 30 is configured to turn on when the second input terminal I NPUT2 is connected to an external power supply, thereby connecting the external power supply to the first terminal of the fourth switching unit 40 and the enable unit 50. The enable unit 50 is configured to output a first enable signal to the fourth switching unit 40 when the external power supply is connected. The fourth switching unit 40 is configured to turn on in response to receiving the first enable signal.
[0029] A battery is used to store electrical energy and provide power to a load. A battery may consist of one cell, or multiple cells connected in series and / or parallel to meet different voltage or capacity requirements. The first input terminal I NPUT1 refers to the interface between the power supply switching circuit and the battery; the first input terminal I NPUT1 is connected to the positive terminal of the battery.
[0030] The external power supply is a DC power supply. The second input terminal I NPUT2 is the interface connecting the power supply switching circuit to the external power supply. The second input terminal I NPUT2 is connected to the positive terminal of the external power supply, and the voltage of the external power supply is greater than the battery voltage. In this application, the connection between the external power supply and the second input terminal I NPUT2 means that the second input terminal I NPUT2 receives electrical energy transmitted from the external power supply; that is, when the external power supply is connected to the second input terminal I NPUT2, the second input terminal I NPUT2 is energized.
[0031] Output terminal OUT1 refers to the interface connecting the power supply switching circuit to the load. Output terminal OUT1 is connected to the positive terminal of the load. A load is a device, component, or system that consumes or receives electrical energy; a load can be any electronic device that requires electricity to operate.
[0032] The first switching unit 10 refers to a switching device that is turned on or off based on the reception state of a drive signal. It is turned on when a drive signal is received and turned off when no drive signal is received. The drive signal can be output by an analog front-end chip (AFE). The analog front-end chip collects at least one parameter from the battery cells, such as voltage, temperature, and current. The analog front-end chip is powered by the battery.
[0033] The second switching unit 20 refers to a switching device that turns on or off based on the magnitude relationship between the voltage at the first terminal of the second switching unit 20 and the voltage at the second terminal of the second switching unit 20.
[0034] The third switching unit 30 refers to a switching device that is turned on or off based on the connection state of the second input terminal INPUT2 with an external power supply. When the second input terminal INPUT2 is connected to an external power supply, the third switching unit 30 is turned on; when the second input terminal INPUT2 is not connected to an external power supply, the third switching unit 30 is turned off.
[0035] The enabling unit 50 generates a first enabling signal to the fourth switching unit 40 based on the access status of the external power supply, so as to turn on the fourth switching unit 40.
[0036] In this power supply switching circuit, when the battery is connected to the first input terminal I NPUT1 and the external power supply is not connected to the second input terminal I NPUT2, the third switch unit 30 and the fourth switch unit 40 are turned off. The first switch unit 10 turns on after receiving the drive signal, so that the battery is connected to the first terminal of the second switch unit 20. At this time, the voltage of the first terminal of the second switch unit 20 is greater than the voltage of the second terminal (output terminal OUT1) of the second switch unit 20, and the second switch unit 20 turns on. That is, the battery power supply circuit between the battery, the first switch unit 10, the second switch unit 20 and the output terminal OUT1 is connected, and the battery supplies power to the load through the output terminal OUT1. Next, if an external power supply is connected to the second input terminal I NPUT2, the third switching unit 30 is turned on, and the external power supply is connected to the enable unit 50. The enable unit 50 outputs the first enable signal to the fourth switching unit 40, and the fourth switching unit 40 is turned on. At this time, the voltage at the first terminal of the second switching unit 20 is less than the voltage at the second terminal (output terminal OUT1) of the second switching unit 20, and the second switching unit 20 is turned off. That is, the battery power supply circuit between the battery, the first switching unit 10, the second switching unit 20 and the output terminal OUT1 is turned on, and the external power supply circuit between the external power supply, the third switching unit 30, the fourth switching unit 40 and the output terminal OUT1 is turned on. The external power supply supplies power to the load through the output terminal OUT1.
[0037] As can be seen, in this application, the power supply switching circuit automatically switches the power supply mode according to the external power supply connection status. When the external power supply is connected, the circuit prioritizes using the external power supply; when the external power supply is not connected, the circuit automatically switches to battery power. Moreover, through the second switching unit 20, when the external power supply is connected, the second switching unit 20 automatically turns off, reducing the phenomenon of current flowing back from the external power supply to the battery, thereby protecting the battery from damage.
[0038] In some of these embodiments, see Figure 2The first switching unit 10 includes a first switching transistor Q1, a first resistor R1, a second resistor R2, and a first Zener diode ZD1. The first terminal of the first switching transistor Q1 is connected to the first input terminal I NPUT1. The second terminal of the first switching transistor Q1 is connected to the first terminal of the second switching unit 20, the anode of the first Zener diode ZD1, and the first terminal of the first resistor R1. The third terminal of the first switching transistor Q1 is connected to the cathode of the first Zener diode ZD1, the second terminal of the first resistor R1, and the first terminal of the second resistor R2. The second terminal of the second resistor R2 is used to receive a drive signal.
[0039] Specifically, the first switch Q1 is an NMOS transistor. The first terminal of Q1 is the drain, the second terminal is the source, and the third terminal is the gate. The first resistor R1 discharges the parasitic capacitance of Q1 when Q1 is turned off, helping to reduce voltage spikes during turn-off. The second resistor R2 limits the current input from the analog front-end chip to Q1, protecting it. The first Zener diode ZD1 limits the voltage input from the analog front-end chip to Q1, also protecting it.
[0040] In some of these embodiments, see Figure 2 The second switching unit 20 includes a second switching transistor Q2, a first control chip U1, a third resistor R3, a fourth resistor R4, and a second Zener diode ZD2. The first terminal of the second switching transistor Q2 is connected to the first switching unit 10, the first terminal of the first control chip U1, the first terminal of the third resistor R3, and the anode of the second Zener diode ZD2. The second terminal of the second switching transistor Q2 is connected to the second terminal of the fourth switching unit 40, the second terminal of the first control chip U1, and the output terminal OUT1. The third terminal of the second switching transistor Q2 is connected to the second terminal of the third resistor R3, the cathode of the second Zener diode ZD2, and the first terminal of the fourth resistor R4. The second terminal of the fourth resistor R4 is connected to the third terminal of the first control chip U1.
[0041] The first control chip U1 uses an LTC4357 chip. The first terminal of the first control chip U1 is the IN pin of the LTC4357 chip, the second terminal is the OUT pin, and the third terminal is the GATE pin. Specifically, the second switch Q2 is an NMOS transistor. The first terminal of the second switch Q2 is the source of the NMOS transistor, the second terminal of the first switch Q1 is the drain of the NMOS transistor, and the third terminal of the second switch Q2 is the gate of the NMOS transistor. The LTC4357 chip is a positive high-voltage ideal diode controller. By driving the second switch Q2 to replace a Schottky diode, compared to embodiments that directly use a Schottky diode, the on-resistance of the second switch Q2 is lower, reducing conduction losses and improving overall efficiency. Furthermore, the LTC4357 chip can quickly detect changes in input and output voltage and rapidly control the switching state of the second switch Q2, which helps reduce reverse current and voltage spikes.
[0042] In addition, in this embodiment, the third resistor R3 discharges the parasitic capacitance of the second switch Q2 when it is turned off, which helps reduce the voltage spike when the second switch Q2 is turned off and helps reduce potential circuit interference or damage. The fourth resistor R4 limits the current input from the first control chip U1 to the second switch Q2, protecting the second switch Q2. The second Zener diode ZD2 can limit the voltage input to the second switch Q2, reducing the possibility of damage to the second switch Q2 due to overvoltage.
[0043] In some of these embodiments, see Figure 2 The second switching unit 20 also includes a first diode D1, a fifth resistor R5, and a first capacitor C1; the anode of the first diode D1 is connected to the first terminal of the first switching unit 10 and the second switching transistor Q2, the cathode of the first diode D1 is connected to the first terminal of the fifth resistor R5, the second terminal of the fifth resistor R5 is connected to the power supply terminal of the first control chip U1 and the first terminal of the first capacitor C1, and the second terminal of the first capacitor C1 is grounded to PGND.
[0044] In this embodiment, the power supply terminal of the first control chip U1 is the VDD pin of the LTC4357 chip. By configuring the above circuit, when the first switching unit 10 is turned on, the battery can supply power to the first control chip U1 through the circuit. Additionally, when the battery is connected to the first input terminal I NPUT1, the fifth resistor R5 limits the current input from the battery to the first control chip U1 to protect the chip. The first capacitor C1 filters the signal input from the battery to the first control chip U1, reducing electrostatic interference. The first diode D1 restricts the direction of current flow, reducing the phenomenon of current flowing back into the battery.
[0045] In some of these embodiments, see Figure 3 The third switching unit 30 includes a third switching transistor Q3, a second control chip U2, a sixth resistor R6, a seventh resistor R7, and a third Zener diode ZD3. The first terminal of the third switching transistor Q3 is connected to the second input terminal INPUT2, the first terminal of the second control chip U2, the first terminal of the sixth resistor R6, and the anode of the third Zener diode ZD3. The second terminal of the third switching transistor Q3 is connected to the first terminal of the fourth switching unit 40, the second terminal of the second control chip U2, and the enable unit 50. The third terminal of the third switching transistor Q3 is connected to the second terminal of the sixth resistor R6, the cathode of the third Zener diode ZD3, and the first terminal of the seventh resistor R7. The second terminal of the seventh resistor R7 is connected to the third terminal of the second control chip U2.
[0046] Similarly, the second control chip U2 uses an LTC4357 chip. The first terminal of the second control chip U2 is the IN pin of the LTC4357 chip, the second terminal is the OUT pin, and the third terminal is the GATE pin. Specifically, the third switch Q3 is an NMOS transistor. The first terminal of the third switch Q3 is the source of the NMOS transistor, the second terminal of the first switch Q1 is the drain of the NMOS transistor, and the third terminal of the third switch Q3 is the gate of the NMOS transistor. By using the LTC4357 chip and the third switch Q3 instead of a Schottky diode, compared to the embodiment that directly uses a Schottky diode, the on-resistance of the third switch Q3 is lower, which can reduce conduction losses and improve overall efficiency.
[0047] In addition, in this embodiment, the sixth resistor R6 discharges the parasitic capacitance of the third switch Q3 when the third switch Q3 is turned off, which helps reduce the voltage spike when the third switch Q3 is turned off, and helps reduce potential circuit interference or damage. The seventh resistor R7 limits the current input from the second control chip U2 to the third switch Q3, reducing the possibility of excessive current damaging the third switch Q3. The third Zener diode ZD3 can limit the voltage input to the third switch Q3, reducing the possibility of damage to the third switch Q3 due to overvoltage, thus protecting the third switch Q3.
[0048] In some of these embodiments, see Figure 3The third switching unit 30 also includes a second diode D2, an eighth resistor R8, and a second capacitor C2; the anode of the second diode D2 is connected to the second input terminal I NPUT2 and the first terminal of the third switching transistor Q3, respectively; the cathode of the second diode D2 is connected to the first terminal of the eighth resistor R8; the second terminal of the eighth resistor R8 is connected to the power supply terminal of the second control chip U2 and the first terminal of the second capacitor C2, respectively; and the second terminal of the second capacitor C2 is grounded PGND.
[0049] In this embodiment, the power supply terminal of the second control chip U2 is the VDD pin of the LTC4357 chip. By configuring the above circuit, when an external power supply is connected to the second input terminal I NPUT2, the external power supply can power the second control chip U2 through the above circuit. Additionally, the eighth resistor R8 limits the current input to the second control chip U2 when the second input terminal I NPUT2 is connected to the external power supply, thus protecting the second control chip U2. The second capacitor C2 filters the signal input from the external power supply to the second control chip U2, reducing electrostatic interference. The second diode D2 restricts the direction of current flow, reducing current backflow.
[0050] In some of these embodiments, see Figure 3 The fourth switching unit 40 includes a fourth switching transistor Q4, a third control chip U3, a ninth resistor R9, a tenth resistor R10, and a fourth Zener diode ZD4. The first terminal of the fourth switching transistor Q4 is connected to the third switching unit 30 and the enable unit 50. The second terminal of the fourth switching transistor Q4 is connected to the anode of the fourth Zener diode ZD4, the first terminal of the ninth resistor R9, and the output terminal OUT1. The third terminal of the fourth switching transistor Q4 is connected to the cathode of the fourth Zener diode ZD4, the second terminal of the ninth resistor R9, and the first terminal of the tenth resistor R10. The second terminal of the tenth resistor R10 is connected to the first terminal of the third control chip U3. The second terminal of the third control chip U3 is connected to the enable unit 50.
[0051] Specifically, the third control chip U3 is a MIC2587 chip. The first terminal of the third control chip U3 is the GATE pin of the MIC2587 chip, and the second terminal is the ON pin of the MIC2587 chip. The third control chip U3 can be powered by an external power supply. (See [link / reference]). Figure 3 The power supply terminal of the third control chip U3 (VCC pin of the MIC2587 chip) is connected to the first terminal of the fourth switch Q4, the third switch unit 30 and the enable unit 50 respectively. In this way, when the third switch unit 30 is turned on, the external power supply can supply power to the third control chip U3 through the third switch unit 30.
[0052] The fourth switch, Q4, is an NMOS transistor. The first terminal of Q4 is the drain, the second terminal is the source, and the third terminal is the gate. The MIC2587 chip controls the switching on and off of Q4 via its GATE pin, thereby managing power switching and output. It receives a first enable signal via its ON pin to determine whether to activate Q4. When the first enable signal is received, the MIC2587 chip turns on Q4 via the GATE pin; when the first enable signal is not received, the MIC2587 chip turns off Q4 via the GATE pin.
[0053] In addition, in this embodiment, the ninth resistor R9 discharges the parasitic capacitance of the fourth switch Q4 when the fourth switch Q4 is turned off, which helps to reduce the voltage spike when the fourth switch Q4 is turned off, and helps to reduce potential circuit interference or damage. The tenth resistor R10 limits the current input from the third control chip U3 to the fourth switch Q4 to protect the fourth switch Q4. The fourth Zener diode ZD4 reduces the possibility of damage to the fourth switch Q4 due to excessive voltage input from the third control chip U3, thus protecting the fourth switch Q4.
[0054] In some of these embodiments, see Figure 3 The fourth switching unit 40 also includes a third capacitor C3; the first end of the third capacitor C3 is connected to the third end of the third control chip U3, and the second end of the third capacitor C3 is grounded to PGND.
[0055] Specifically, the third terminal of the third control chip U3 is the TI MER pin of the MIC2587 chip, and the third capacitor C3 is the overcurrent detection delay configuration capacitor for the MIC2587 chip. By changing the capacitance value of the third capacitor C3, the overcurrent detection delay time is adjusted, causing the MIC2587 chip to delay for a certain period of time after detecting an overcurrent condition before triggering the protection action. This reduces false triggering of overcurrent protection actions caused by instantaneous current fluctuations, improving the stability and reliability of the system. A larger capacitance value of the third capacitor C3 results in a longer overcurrent detection delay time, while a smaller capacitance value results in a shorter overcurrent detection delay time.
[0056] In some of these embodiments, see Figure 3 The fourth switching unit 40 also includes an eleventh resistor R11. The first end of the eleventh resistor R11 is connected to the first end of the enable unit 50, the third switching unit 30 and the fourth switching transistor Q4, respectively. The second end of the eleventh resistor R11 is connected to the fourth end of the third control chip U3.
[0057] Specifically, the fourth terminal of the third control chip U3 is the SENSE pin of the MIC2587 chip, and the eleventh resistor R11 is the configuration resistor for the current limiting protection and circuit breaker function of the MIC2587 chip. The parameters of the current limiting protection and circuit breaker function are adjusted by changing the resistance value of the eleventh resistor R11. Specifically, by adjusting the resistance value of the eleventh resistor R11, the maximum allowable current of the circuit can be set. When the current exceeds the set value, the chip will quickly cut off the power output to achieve overcurrent protection. In addition, when the current continuously exceeds the set threshold, the chip will trigger the circuit breaker function, permanently shutting off the power output until the system restarts or the fault is cleared, improving the reliability of the circuit operation.
[0058] In some of these embodiments, see Figure 3 The enabling unit 50 includes a first voltage divider resistor Rf1, a second voltage divider resistor Rf2, a fourth capacitor C4, a fifth switch Q5, and a twelfth resistor R12. The first end of the first voltage divider resistor Rf1 is connected to the first end of the third switching unit 30 and the first end of the fourth switch Q4. The second end of the first voltage divider resistor Rf1 is connected to the first end of the second voltage divider resistor Rf2, the first end of the fourth capacitor C4, the first end of the fifth switch Q5, and the enable terminal of the third control chip U3. The second end of the fifth switch Q5 is connected to the first end of the twelfth resistor R12. The second end of the twelfth resistor R12 is used to receive control signals. The second end of the second voltage divider resistor Rf2, the second end of the fourth capacitor C4, and the third end of the fifth switch Q5 are grounded to PGND.
[0059] Specifically, the fifth switch Q5 is an NMOS transistor. The first terminal of the fifth switch Q5 is the drain of the NMOS transistor, the second terminal of the fifth switch Q5 is the gate of the NMOS transistor, and the third terminal of the fifth switch Q5 is the source of the NMOS transistor. The enable terminal of the third control chip U3 is the ON pin of the MIC2587 chip.
[0060] The control signal can be output by the Battery Management System (BMS). The control signal includes a high-level signal and a low-level signal. The control signal is transmitted to the fifth switch Q5 via the twelfth resistor R12. The fifth switch Q5 turns on when it receives a high-level signal and turns off when it receives a low-level signal. The twelfth resistor R12 limits the current transmitted from the control signal to the fifth switch Q5 to protect it.
[0061] When the external power supply is not connected to the second input terminal INPUT2 and the fifth switching transistor Q5 is turned off, the enable terminal of the third control chip U3 is grounded to PGND through the second voltage-dividing resistor Rf2, and the third control chip U3 controls the fourth switching transistor Q4 to turn off. When the external power supply is connected to the second input terminal INPUT2, the third switching unit 30 is turned on, and the fifth switching transistor Q5 is turned off, the first voltage-dividing resistor Rf1 and the second voltage-dividing resistor Rf2 divide the voltage of the external power supply, and a voltage-dividing signal (first enable signal) is output to the enable terminal of the third control chip U3 through the first end of the second voltage-dividing resistor Rf2, and the third control chip U3 controls the fourth switching transistor Q4 to turn on. When the fifth switching transistor Q5 is turned on, the enable terminal of the third control chip U3 is grounded to PGND through the fifth switching transistor Q5, and the third control signal controls the fourth switching transistor Q4 to turn off.
[0062] In some embodiments, the fourth switching unit 40 further includes a fifth capacitor. The first end of the fifth capacitor is respectively connected to the second end of the fourth switching transistor Q4, the output terminal OUT1, the anode of the fourth voltage-regulating diode ZD4, and the first end of the ninth resistor R9. The second end of the fifth capacitor is respectively connected to the third end of the fourth switching transistor Q4, the cathode of the fourth voltage-regulating diode ZD4, the second end of the ninth resistor R9, and the first end of the tenth resistor R10.
[0063] The fifth capacitor can absorb the voltage spikes generated by the fourth switching transistor Q4 during the switching process, reduce the influence of switching noise on the fourth switching transistor Q4, extend the service life of the fourth switching transistor Q4, and improve the reliability of the circuit.
[0064] In some embodiments, refer to Figure 3 , the fourth switching unit 40 further includes a thirteenth resistor R13 and a fourteenth resistor R14. The first end of the thirteenth resistor R13 is respectively connected to the second end of the fourth switching transistor Q4, the output terminal OUT1, the anode of the fourth voltage-regulating diode ZD4, and the first end of the ninth resistor R9. The second end of the thirteenth resistor R13 is respectively connected to the fifth terminal of the third control chip U3 and the first end of the fourteenth resistor R_{14}. The second end of the fourteenth resistor R14 is grounded to PGND.
[0065] Specifically, the fifth terminal of the third control chip U3 is the FB pin of the MIC2587 chip. The voltage at the output terminal OUT1 is divided by resistors R13 (13th) and R14 (14th), allowing the third control chip U3 to monitor changes in the output voltage in real time. Subsequently, the third control chip U3 can stabilize the output voltage at the target value by adjusting the drive signal of the GATE pin. Alternatively, when the output voltage rises abnormally, the voltage signal detected by the FB pin will exceed the set threshold of the third control chip U3. In this case, the third control chip U3 will immediately shut down the output of the GATE pin, cutting off the power supply circuit to the external power source, reducing the possibility of overvoltage damage to the load equipment, and improving the reliability of the circuit operation.
[0066] The following is combined Figure 2 and Figure 3 The embodiments shown illustrate in detail the specific working process of the power supply switching circuit provided in this application.
[0067] When the battery is connected to the first input terminal I NPUT1 and the external power supply is not connected to the second input terminal I NPUT2, the third switch unit 30 and the fourth switch unit 40 are turned off. The high-level drive signal output by the analog front-end chip is current-limited by the second resistor R2 and output to the first switch Q1. The first switch Q1 is turned on, and the battery supplies power to the first control chip U1 through the first switch Q1, the first diode D1, and the fifth resistor R5. The first control chip U1 uses the voltage detected at the first terminal (IN pin) as a reference and outputs a drive voltage from the third terminal (GATE pin) to the second switch Q2. The value of the drive voltage is the voltage detected at the first terminal (IN pin) plus 12V. This drive voltage drives the second switch Q2 to turn on through the fourth resistor R4. At this time, the battery power supply circuit between the battery, the first switch unit 10, the second switch unit 20, and the output terminal OUT1 is connected, and the battery supplies power to the load through the output terminal OUT1. In addition, when the external power supply is not connected, the parasitic capacitance of the third switch Q3 can reduce the leakage voltage from the output terminal OUT1 to the second input terminal INPUT2.
[0068] When an external power supply is connected to the second input terminal I NPUT2, the external power supply powers the second control chip U2 through the second diode D2 and the eighth resistor R8. The second control chip U2 uses the voltage detected at the first terminal (IN pin) as a reference and outputs a drive voltage from the third terminal (GATE pin) to the third switch Q3. The value of the drive voltage is the voltage detected at the first terminal (IN pin) plus 12V. This voltage is output to the third switch Q3 through the seventh resistor R7, and the third switch Q3 is turned on. Next, the voltage EXT_P+ at the second terminal of the third switch Q3 supplies power to the third control chip U3, and the voltage EXT_P+ at the second terminal of the third switch Q3 outputs a voltage divider signal (first enable signal) to the third control chip U3 through the first voltage divider resistor Rf1 and the second voltage divider resistor Rf2. The third control chip U3 outputs a drive voltage to the fourth switch Q4 based on the voltage of the power supply terminal (VCC pin). The value of this drive voltage is the voltage of the power supply terminal (VCC pin) plus 7.5V. This drive voltage drives the fourth switch Q4 to conduct through the tenth resistor R10. At this time, the external power supply circuit between the external power supply, the third switch unit 30, the fourth switch unit 40 and the output terminal OUT1 is connected, and the external power supply supplies power to the load through the output terminal OUT1. Furthermore, the voltage of the external power supply is higher than the voltage of the battery. When the external power supply circuit is turned on, the voltage of the output terminal OUT1 will be pulled up by the external power supply, so that the voltage of the first terminal of the second switch Q2 is less than the voltage of the second switch Q2. At this time, the first control chip U1 detects that the voltage of the second terminal (OUT pin) is higher than the voltage of the first terminal (IN pin), and the third terminal (GATE pin) of the first control chip U1 stops outputting the drive voltage, causing the second switch Q2 to turn off, thereby disconnecting the battery power supply circuit.
[0069] In this power supply switching circuit, the circuit features hardware hot-swapping capability. The circuit automatically switches the power supply mode based on the external power supply's connection status. When an external power supply is connected, the circuit prioritizes using it; when no external power supply is connected, the circuit automatically switches to battery power. Furthermore, through the second switching transistor and the first control chip, the second switching transistor automatically turns off when an external power supply is connected, reducing the backflow of current from the external power supply to the battery, thus protecting the battery from damage. Moreover, the elimination of the need for diodes reduces conduction and heat losses, meeting the demands of electronic devices for high efficiency, high integration, and high reliability.
[0070] Furthermore, the first and second switching transistors Q1 and Q2 in the battery power supply circuit are source-connected, which is relatively unaffected by drain voltage fluctuations. This stabilizes the drive voltage, ensures consistent switching behavior, and reduces abnormal switching phenomena caused by unstable drive voltage, such as incomplete or excessive conduction. This ensures the reliability and safety of the battery power supply. The third and fourth switching transistors Q3 and Q4 in the external power supply circuit, on the other hand, are drain-connected. This drain-connection method facilitates the combination and switching of various driving modes and makes it easier to achieve isolation and protection between driving circuits in the driving circuit design.
[0071] Secondly, embodiments of this application also provide an electrical device, which includes a power supply switching circuit as described in any embodiment of the first aspect.
[0072] In this embodiment, the power supply switching circuit has the same structure and function as the power supply switching circuit described in any embodiment of the first aspect, and will not be repeated here.
[0073] Electrical equipment can be portable medical devices, power tools, or other devices that require electrical energy.
[0074] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.
[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A power supply switching circuit, characterized in that, include: The system includes a first input terminal, a second input terminal, an output terminal, an enable unit, a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit. The first switch unit is connected to the first input terminal and the first terminal of the second switch unit respectively. The third switch unit is connected to the second input terminal, the enable unit and the first terminal of the fourth switch unit respectively. The second terminals of the second switch unit and the second terminals of the fourth switch unit are both connected to the output terminal. The third terminal of the fourth switch unit is connected to the enable unit. The first input terminal is used to connect to the battery and the second input terminal is used to connect to an external power source. The first switching unit is configured to turn on in response to receiving a drive signal after the battery is connected to the first input terminal, so as to connect the battery to the first terminal of the second switching unit; The second switching unit is configured to be turned on when the voltage at the first terminal of the second switching unit is greater than the voltage at the second terminal of the second switching unit, and to be turned off when the voltage at the first terminal of the second switching unit is less than the voltage at the second terminal of the second switching unit. The third switching unit is configured to be turned on when the external power supply is connected to the second input terminal, so as to connect the external power supply to the first terminal of the fourth switching unit and the enabling unit; The enabling unit is configured to output a first enabling signal to the fourth switching unit when the external power supply is connected; The fourth switching unit is configured to turn on in response to receiving a first enable signal.
2. The power supply switching circuit according to claim 1, characterized in that, The first switching unit includes a first switching transistor, a first resistor, a second resistor, and a first Zener diode; The first terminal of the first switching transistor is connected to the first input terminal. The second terminal of the first switching transistor is connected to the first terminal of the second switching unit, the anode of the first Zener diode, and the first terminal of the first resistor. The third terminal of the first switching transistor is connected to the cathode of the first Zener diode, the second terminal of the first resistor, and the first terminal of the second resistor. The second terminal of the second resistor is used to receive the drive signal.
3. The power supply switching circuit according to claim 1, characterized in that, The second switching unit includes a second switching transistor, a first control chip, a third resistor, a fourth resistor, and a second Zener diode; The first terminal of the second switching transistor is connected to the first switching unit, the first terminal of the first control chip, the first terminal of the third resistor, and the anode of the second Zener diode, respectively. The second terminal of the second switching transistor is connected to the second terminal of the fourth switching unit, the second terminal of the first control chip, and the output terminal, respectively. The third terminal of the second switching transistor is connected to the second terminal of the third resistor, the cathode of the second Zener diode, and the first terminal of the fourth resistor, respectively. The second terminal of the fourth resistor is connected to the third terminal of the first control chip.
4. The power supply switching circuit according to claim 3, characterized in that, The second switching unit further includes a first diode, a fifth resistor, and a first capacitor; The anode of the first diode is connected to the first terminal of the first switching unit and the second switching transistor, respectively. The cathode of the first diode is connected to the first terminal of the fifth resistor. The second terminal of the fifth resistor is connected to the power supply terminal of the first control chip and the first terminal of the first capacitor, respectively. The second terminal of the first capacitor is grounded.
5. The power supply switching circuit according to claim 1, characterized in that, The third switching unit includes a third switching transistor, a second control chip, a sixth resistor, a seventh resistor, and a third Zener diode; The first terminal of the third switch is connected to the second input terminal, the first terminal of the second control chip, the first terminal of the sixth resistor, and the anode of the third Zener diode, respectively. The second terminal of the third switch is connected to the first terminal of the fourth switch unit, the second terminal of the second control chip, and the enable unit, respectively. The third terminal of the third switch is connected to the second terminal of the sixth resistor, the cathode of the third Zener diode, and the first terminal of the seventh resistor, respectively. The second terminal of the seventh resistor is connected to the third terminal of the second control chip.
6. The power supply switching circuit according to claim 5, characterized in that, The third switching unit also includes a second diode, an eighth resistor, and a second capacitor; The anode of the second diode is connected to the second input terminal and the first terminal of the third switching transistor, the cathode of the second diode is connected to the first terminal of the eighth resistor, the second terminal of the eighth resistor is connected to the power supply terminal of the second control chip and the first terminal of the second capacitor, and the second terminal of the second capacitor is grounded.
7. The power supply switching circuit according to claim 1, characterized in that, The fourth switching unit includes a fourth switching transistor, a third control chip, a ninth resistor, a tenth resistor, and a fourth Zener diode; The first terminal of the fourth switching transistor is connected to the third switching unit and the enabling unit, the second terminal of the fourth switching transistor is connected to the anode of the fourth Zener diode, the first terminal of the ninth resistor and the output terminal, the third terminal of the fourth switching transistor is connected to the cathode of the fourth Zener diode, the second terminal of the ninth resistor and the first terminal of the tenth resistor, the second terminal of the tenth resistor is connected to the first terminal of the third control chip, and the second terminal of the third control chip is connected to the enabling unit.
8. The power supply switching circuit according to claim 7, characterized in that, The fourth switching unit also includes a third capacitor and an eleventh resistor; The first terminal of the third capacitor is connected to the third terminal of the third control chip, and the second terminal of the third capacitor is grounded. The first end of the eleventh resistor is connected to the first end of the enabling unit, the third switching unit, and the fourth switching transistor, respectively, and the second end of the eleventh resistor is connected to the fourth end of the third control chip.
9. The power supply switching circuit according to claim 7 or 8, characterized in that, The enabling unit includes a first voltage divider resistor, a second voltage divider resistor, a fourth capacitor, a fifth switching transistor, and a twelfth resistor; The first end of the first voltage divider resistor is connected to the first end of the third switching unit and the first end of the fourth switching transistor. The second end of the first voltage divider resistor is connected to the first end of the second voltage divider resistor, the first end of the fourth capacitor, the first end of the fifth switching transistor, and the enable terminal of the third control chip. The second end of the fifth switching transistor is connected to the first end of the twelfth resistor. The second end of the twelfth resistor is used to receive control signals. The second end of the second voltage divider resistor, the second end of the fourth capacitor, and the third end of the fifth switching transistor are grounded.
10. An electrical appliance, characterized in that, Includes the power supply switching circuit as described in any one of claims 1-9.