Switch circuit, charging circuit, electronic device, and charging apparatus

Abstract

Provided in the present application are a switch circuit, a charging circuit, an electronic device, and a charging apparatus. The switch circuit comprises: a series circuit, which comprises a first transistor and N second transistors that are connected in series, wherein a second end of the first transistor is a second end of the series circuit, a control electrode of the first transistor receives a control signal, and a first end of an Nth second transistor is a first end of the series circuit; a first clamping circuit, which comprises diodes that are connected in series, wherein end points and common connection points of the first clamping circuit are connected to control electrodes of the transistors in the series circuit, and when the series circuit is conducted, the first clamping circuit performs, on the basis of the control signal, potential clamping on the control electrodes of the transistors in the series circuit; and a second clamping circuit, which comprises a plurality of resistors that are connected in series, wherein a first end of the second clamping circuit is connected to the first end of the series circuit, and when the series circuit is disconnected, the second clamping circuit is used for performing clamping on the control electrodes of the N second transistors. By means of the technical solution provided in the embodiments of the present application, a voltage withstand requirement for a single transistor can be reduced.

Description

Switching circuit, charging circuit, electronic device and charging device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 30, 2024, with application number 202410131758.2 and application name “Switching circuit, charging circuit, electronic device and charging device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of circuits, and more specifically, to a switching circuit, a charging circuit, an electronic device, and a charging device. Background Art

[0003] With the development of consumer electronic products such as mobile phones, tablets, and laptops, people's requirements for wired / wireless charging power of electronic products have gradually increased, and the charging voltage has increased from 5V to 20V, 40V, 70V and even higher.

[0004] The charging link usually includes a switching circuit, which controls the disconnection and connection of the link through transistors. As the charging voltage in various charging scenarios increases, the switching circuit needs to withstand higher and higher voltages.

[0005] In order to meet higher voltage requirements, it is necessary to select transistors with higher voltage capabilities. However, transistors with high voltage capabilities are taller and the device thickness may not meet the requirements. Summary of the Invention

[0006] The present application provides a switching circuit, a charging circuit, an electronic device, and a charging device, which can improve the voltage resistance of the circuit while reducing the height of the device.

[0007] In a first aspect, a switching circuit is provided, comprising: a series circuit, a first clamping circuit, and a second clamping circuit; wherein the series circuit comprises a first transistor and N second transistors connected in series in sequence, N ≥ 1, the second end of the first transistor is the second end of the series circuit, the first end of the first transistor is connected in sequence to the N second transistors, the control electrode of the first transistor is used to receive a control signal, and the first end of the Nth second transistor is the first end of the series circuit; the first clamping circuit comprises at least one diode connected in series in sequence, the endpoints and the common connection point of the first clamping circuit are connected to the control electrodes of the N second transistors and the first transistor, and the first diode The second end of the transistor is the second end of the first clamping circuit and is connected to the control electrode of the first transistor. The first end of the last diode is the first end of the first clamping circuit and is connected to the control electrode of the Nth second transistor. When the control signal causes the series circuit to be turned on, the first clamping circuit is used to clamp the control electrode potentials of the first transistor and the N second transistors according to the control signal. The second clamping circuit includes a plurality of resistors connected in series. The first end of the second clamping circuit is connected to the first end of the series circuit. When the control signal causes the series circuit to be turned off, the second clamping circuit is used to clamp the control electrodes of the N second transistors.

[0008] The transistor may be a field-effect transistor (FET) or a bipolar junction transistor (BJT). For a FET, the control electrode is the gate of the transistor, and the first and second ends may be the source and drain of the transistor, or the first and second ends may be the drain and source of the transistor. For a BJT, the control electrode may be the base of the transistor, and the first and second ends may be the emitter and collector of the transistor, respectively, or the first and second ends may be the collector and emitter of the transistor, respectively.

[0009] In this embodiment, the power supply voltage of the switching circuit is distributed across multiple transistors, resulting in a lower voltage for each transistor, reducing the possibility of transistor burnout due to overvoltage. Furthermore, the lower voltage requirements for each transistor can reduce the height of the transistor, facilitating the slimming and miniaturization of electronic devices or other charging devices when the switching circuit is used.

[0010] In combination with the first aspect, in some implementations of the first aspect, the transistor in the series circuit is a metal oxide semiconductor field effect transistor (MOSFET).

[0011] In combination with the first aspect, in some implementations of the first aspect, the transistor in the series circuit is an N-channel MOSFET.

[0012] For an N-channel MOSFET, a high-level control signal can be input to turn on or connect the switch circuit, while a low-level control signal can be input to turn off or disconnect the switch circuit.

[0013] In some embodiments, the transistors in the series circuit may also be P-channel MOSFETs.

[0014] In combination with the first aspect, in certain implementations of the first aspect, N≥2, the directions of the body diodes of the first transistor and the N second transistors are opposite; the first clamping circuit includes N-1 diodes, the first end of the first clamping circuit and the common connection point of the diodes in the first clamping circuit are respectively connected to the control electrodes of the Nth second transistor to the second second transistor, and the second end of the first clamping circuit is connected to the control electrodes of the first transistor and the first second transistor; the second clamping circuit includes N resistors, the common connection point of the N resistors is sequentially connected to the control electrodes of the Nth second transistor to the second second transistor, and the second end of the second clamping circuit is connected to the second end of the series circuit.

[0015] In this embodiment, the directions of the body diodes of the first transistor and the second transistor are opposite, so when the power supply is an AC power supply, current backflow will not be caused to damage components in the switching circuit.

[0016] When the switch circuit is in the off state, the body diode of the first transistor acts to ensure that the voltage difference across the first transistor is equal to the conduction voltage drop of the body diode. The power supply voltage can be distributed to the multiple second transistors, and the distribution ratio can be positively correlated with the resistance value of each resistor in the second clamping circuit.

[0017] In some embodiments, the first clamping circuit may include N diodes, so that N-1 common connection points and two endpoints of the N transistors may be connected to the control electrodes of the first transistor and the N second transistors, respectively.

[0018] In some embodiments, the second end of the second clamping circuit may also be connected to a common connection point between the first second transistor and the first transistor, or may be connected to a control electrode of the first second transistor, which is not limited in this application.

[0019] In combination with the first aspect, in some implementations of the first aspect, a ratio of the resistance values ​​of the N resistors is the same as a ratio of the withstand voltage values ​​of the N second transistors.

[0020] In some embodiments, if the parasitic capacitance of the transistor is large, the parasitic capacitance of the Nth second transistor connected in parallel with the Nth resistor may cause the voltage across the Nth second transistor to be too low. The resistance of the resistor connected to the last second transistor can be appropriately increased to make the power supply voltage distribution more reasonable.

[0021] In combination with the first aspect, in certain implementations of the first aspect, the second end of the first resistor is the second end of the second clamping circuit, the first end of the Nth resistor is the first end of the second clamping circuit, the N second transistors have the same withstand voltage, and the resistance of the first resistor is greater than the resistance of other resistors in the second clamping circuit.

[0022] Since the first resistor has a greater impact on the voltage division after being connected in parallel with the parasitic capacitance, the resistance value of the first resistor can be increased to reduce the impact of the voltage division.

[0023] When the withstand voltages of the N transistors are different, the resistance of the Nth resistor may be greater than a first value, which is the resistance of the Nth resistor calculated according to the ratio of the withstand voltages of the Nth second transistor to the first second transistor.

[0024] In combination with the first aspect, in certain implementations of the first aspect, the body diodes of the first transistor and the N second transistors have the same direction; the first clamping circuit includes N diodes, and the endpoints and common connection points of the first clamping circuit are connected to the control electrodes of the first transistor and the N second transistors in sequence; the second clamping circuit includes N+1 resistors, and the common connection point of the N+1 resistors is connected to the control electrodes of the N second transistors in sequence, and the second end of the second clamping circuit is connected to the second end of the series circuit.

[0025] In this embodiment, when the switch circuit is in the off state, the power supply voltage can be distributed to the N second transistors and the first transistor. The second end of the second clamping circuit can also be connected to the control electrode of the first transistor.

[0026] In combination with the first aspect, in some implementations of the first aspect, the transistors in the series circuit are bipolar junction transistors (BJTs).

[0027] In combination with the first aspect, in some implementations of the first aspect, the transistor in the series circuit is an NPN-type BJT.

[0028] Optionally, the transistor may also be a PNP transistor.

[0029] In combination with the first aspect, in some implementations of the first aspect, the ratio of the resistance values ​​of the N+1 resistors is the same as the ratio of the withstand voltage values ​​of the N second transistors and the first transistor.

[0030] That is, the ratio of the resistance values ​​of the N+1 resistors is equal to the ratio of the withstand voltage values ​​of the N+1 transistors.

[0031] In a second aspect, a charging circuit is provided, comprising the switching circuit as described in the first aspect or any implementation manner of the first aspect.

[0032] In a third aspect, an electronic device is provided, comprising the switching circuit as described in the first aspect or any implementation manner of the first aspect or the charging circuit as described in the second aspect.

[0033] In a fourth aspect, a charging device is provided, comprising the switching circuit as described in the first aspect or any one implementation of the first aspect or the charging circuit as described in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic structural diagram of a switching circuit.

[0035] FIG2 is a schematic structural diagram of a switching circuit provided in an embodiment of the present application.

[0036] FIG3 is an equivalent circuit diagram of a switch circuit provided in an embodiment of the present application when it is turned on.

[0037] FIG4 is a schematic structural diagram of a switching circuit provided in an embodiment of the present application.

[0038] FIG5 is a schematic structural diagram of a switching circuit provided in an embodiment of the present application.

[0039] FIG6 is a schematic structural diagram of a switching circuit provided in an embodiment of the present application.

[0040] FIG7 is a schematic structural diagram of a switching circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0042] The terms "first", "second", etc. in the specification, embodiments, claims, and drawings of this application are only used for the purpose of distinguishing descriptions and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. "Connected", "connected", and similar words are used to express the intercommunication or interaction between different components, which may include connection, direct connection, indirect connection through other components, etc. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, including a series of steps or units. Methods, systems, products, or devices are not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products, or devices.

[0043] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0044] Figure 1 is a schematic diagram of a switch circuit. As shown in Figure 1, the switch circuit includes capacitor C1, transistors Q1, and transistor Q2. The body diodes of transistors Q1 and Q2 are in opposite directions. The switch circuit can control the connection and disconnection of the link between port X and port Y.

[0045] When the control terminal outputs a high level, Q1 and Q2 are turned on. The on-resistance of transistors Q1 and Q2 is small, typically in the milliohm level, resulting in a small on-voltage drop.

[0046] When the control terminal outputs a low level, Q1 and Q2 are cut off, and due to the action of the body diode of Q2, the level of point A is pulled to the ground level 0V.

[0047] Assuming the power supply voltage is 70V, when the control input is low, the 70V power supply voltage will be handled by transistor Q1, for example, increasing Q1's voltage tolerance to 90V. However, transistors with voltages above 50V are rarely used in end products, and the height of high-voltage transistors cannot meet the requirements of lightweight and thin consumer electronics.

[0048] An embodiment of the present application provides a switching circuit that can reduce the height of the device while improving the voltage resistance of the switching circuit.

[0049] FIG2 is a schematic structural diagram of a switch circuit provided in an embodiment of the present application. As shown in FIG2 , the switch circuit includes: a series circuit 20 , a first clamping circuit 30 , and a second clamping circuit 40 .

[0050] The series circuit 20 includes a first transistor Q0 and two second transistors Q1 and Q2 connected in series. The drain of transistor Q2 is the first end of the series circuit, and the source of transistor Q2 is connected to the drain of transistor Q1. The source of transistor Q1 is connected to the source of transistor Q0, and the drain of transistor Q0 is the second end of the series circuit.

[0051] The first clamping circuit 30 includes a diode D1. The cathode of the diode D1 is the first end of the first clamping circuit 30 and is connected to the gate of the transistor Q2. The anode of the diode D1 is the second end of the first clamping circuit 30 and is used to input a control signal and is connected to the gates of the transistors Q1 and Q0.

[0052] The second clamping circuit 40 includes two voltage-dividing resistors R1 and R2. The first end of resistor R2 forms the first end of the second clamping circuit 40 and is connected to the first end of the series circuit 20. The second end of resistor R2 is connected to the first end of resistor R1 and the gate of transistor Q2. The second end of resistor R1 is connected to the second end of the series circuit 20. The resistance of the voltage-dividing resistors R1 and R2 can be in the order of kilohms (KΩ) to hundreds of kilohms, or higher or lower, such as hundreds of ohms, but this application does not limit this.

[0053] The control signal can be high level V H or low level V L , thereby controlling the on or off state of the entire switch circuit. Taking the transistors in FIG2 as N-type transistors as an example, when the control signal is high, the two ends of the series circuit 20 are connected, and the entire switch circuit is in the on state; when the control signal input is low, the two ends of the series circuit 20 are disconnected, and the entire switch circuit is in the off state. Schematically, when the transistor is an N-channel transistor, the high level of the control signal V H Can be 5V, low level V L It can be 0V, and the high and low levels of the control signal can also be other values, such as 3V, 8V or higher or lower levels, as long as the high level value can turn on the first transistor Q0 and the second transistors Q1 and Q2, and the low level value can turn off the above transistors, this application does not limit this.

[0054] When the control signal is high level V HWhen Q0 turns on, the potential at point C is pulled down, and the voltage difference between the gate and source of Q1 increases. When the voltage difference reaches the threshold voltage of Q1, Q1 also turns on. The potential at point E is pulled up by diode D1 to a value that is Uon different from point F, where Uon is the forward voltage drop of diode D1, which is generally about 0.6-0.7V for silicon transistors and about 0.2-0.3V for germanium transistors. The potential at point B is pulled down due to the conduction of Q1, and the voltage difference between the gate and source of Q2 increases, and Q2 also turns on. In this way, the voltage applied to the switching circuit by the power supply voltage is borne by capacitor C1 and series circuit 20, as shown in Figure 3. At this time, the three transistors can be equivalent to a resistor Rdson, which is the on-resistance of the three transistors. Because the on-resistance of transistors Q0, Q1, and Q2 is relatively small, typically in the milliohm range, and the capacitive reactance of capacitor C1 is generally much larger than the on-resistance Rdson of the three transistors, the voltage applied to the switching circuit by the AC power source AC is mostly borne by capacitor C1. The voltage borne by the three transistors when the switching circuit is in the on state is generally relatively small.

[0055] When the control signal is low level V L When the voltage is 0, transistor Q0 is turned off. However, because the current through Q0's body diode (also known as a parasitic diode) flows from point C to point D, the potential at point C is still pulled down, slightly above ground (by the forward voltage drop of transistor Q0's body diode). At this point, diode D1 is turned off, and both transistors Q1 and Q2 are turned off, with the power supply voltage now borne by transistors Q1 and Q2.

[0056] When the voltage resistance of transistors Q1 and Q2 is the same, resistors R1 and R2 can be made completely equal. Without considering the forward conduction voltage drop of the body diode of transistor Q0, the power supply voltage can be evenly distributed to transistors Q1 and Q2.

[0057] Specifically, taking the instantaneous power supply voltage as 70V as an example, the voltage at point A is 70V. Since the resistors R1 and R2 are equal, the voltage at point E is 35V, and the transistor Q2 is in the off state. When the voltage at point B decreases due to power supply fluctuations or individual differences in transistors, the gate-source voltage difference V EB If the value is greater than 0, transistor Q2 will slowly turn on and current will flow from point A to point B. At this time, the voltage at point B will increase, forming negative feedback, thus V EB When the voltage drops to 0V, transistor Q2 turns off again. As the voltage at point B increases, transistor Q2 is slowly turned off, and the voltage at point B decreases due to negative feedback. Therefore, for transistor Q2, the voltage at point B always follows the voltage at point E, resulting in a source-drain voltage difference of 35V. When the forward-phase voltage drop of transistor Q0's body diode is ignored, the potential at point C is 0V, and the source-drain voltage difference of transistor Q2 is also 35V.

[0058] Through the technical solution introduced in the embodiment of the present application, the power supply voltage will be evenly distributed to the second transistor, and the power supply voltage will not be unevenly divided due to differences in the manufacturing process of the second transistor or fluctuations in the power supply voltage. Under certain power supply voltage requirements, the voltage resistance requirements of a single transistor can be reduced. When the voltage resistance of the transistor is reduced, the height of the device can also be appropriately reduced, so that the switching circuit meets the requirements of lightweight electronic equipment or other equipment.

[0059] In the embodiment of the present application, the first transistor Q0 and the second transistors Q1 and Q2 can be N-channel transistors, for example, bipolar junction transistors (BJTs) or field effect transistors (FETs). When they are BJTs, they can be PNP or NPN transistors. When they are FETs, they can be metal oxide semiconductor field effect transistors (MOSFETs), for example, enhancement mode MOSFETs or depletion mode MOSFETs, or junction field FETs (JFETs).

[0060] FIG2 illustrates the technical solution of an embodiment of the present application using an example in which the first transistor Q0 and the second transistors Q1 and Q2 are N-channel MOS transistors. As previously described, when the transistors in the switch circuit are N-channel transistors or NPN transistors, a high-level control signal input can turn the switch circuit on or conduct, while a low-level control signal input can turn the switch circuit off or cut off.

[0061] In some embodiments, the first transistor Q0 and the second transistors Q1 and Q2 may also be P-channel MOS transistors. In this case, a low-level control signal input can turn the switch circuit on or conduct, while a high-level control signal input can turn the switch circuit off or cut off.

[0062] FIG4 takes a P-channel MOS transistor as an example to show a schematic structural diagram of a switch circuit provided in an embodiment of the present application.

[0063] The series circuit 20 includes a first transistor Q0 and second transistors Q1 and Q2; wherein the drain of transistor Q2 (point A) is the first end of the series circuit 20, and the source of transistor Q2 is connected to the drain of transistor Q1; the source of transistor Q1 is connected to the source of transistor Q0, and the drain of transistor Q0 is the second end of the series circuit 20 (point D).

[0064] The first clamping circuit 30 includes a diode D1. The anode (point E) of the diode D1 is the first end of the first clamping circuit 30 and is connected to the gate of the transistor Q2. The cathode (point F) of the diode D1 is the second end of the first clamping circuit 30 and is used to input a control signal and is connected to the gates of the transistors Q1 and Q0.

[0065] The second clamping circuit includes two voltage-dividing resistors, R1 and R2. The first end of resistor R2 (point A) forms the first end of second clamping circuit 40, and the second end of resistor R2 connects to the first end of resistor R1 and the gate of transistor Q2. The second end of resistor R1 (point D) forms the second end of second clamping circuit 30 and is connected to the second end of series circuit 20.

[0066] When the control signal input is low, transistor Q0 turns on, raising the potential at point C. Q1 turns on, raising the potential at point B, and diode D1 turns on, lowering the potential at point E. This increases the absolute value of the gate-source voltage difference at transistor Q2, turning it on as well. The three transistors can be considered equivalent to an on-resistance. Because the on-resistance is relatively small, capacitor C1 bears most of the supply voltage.

[0067] When the control signal input is high, transistors Q0 and Q1 are turned off, D1 is turned off, and the potential at point E is determined by the resistance values ​​of R2 and R1. Assuming the instantaneous value of the power supply voltage is 70V and the resistance values ​​of R1 and R2 are equal, the potential at point E is 35V. Similar to an N-channel transistor, the potential at point C follows the potential at point F, and the potential at point B follows the potential at point E. This allows the second transistors Q1 and Q2 to evenly share the power supply voltage, reducing the source-drain withstand voltage requirements of a single transistor.

[0068] It should be understood that the second transistors in Figure 2 include Q1 and Q2. In some embodiments, the number of second transistors can be further increased, so that more transistors can share the power supply voltage and reduce the withstand voltage requirements of individual transistors. Figure 5 shows a schematic structural diagram of a switch circuit provided in an embodiment of the present application, taking the number of second transistors as 3 as an example.

[0069] As shown in FIG5 , series circuit 20 includes a first transistor Q0 and second transistors Q1, Q2, and Q3. The drain of transistor Q2 is connected to the source of transistor Q3, and the drain of transistor Q3 is the first end of series circuit 20. First clamp circuit 30 includes diodes D1 and D2. The cathode of diode D2 is the first end of first clamp circuit 30 and is connected to the gate of transistor Q3. The anode of diode D2 is connected to the cathode of diode D1 and the gate of transistor Q2. The anode of diode D1 is the second end of first clamp circuit 30 and is connected to the gates of transistors Q1 and Q0. Second clamp circuit 40 includes resistors R1, R2, and R3. The first end of R3 is the first end of second clamp circuit 40, and the second end of R1 is the second end of second clamp circuit 40.

[0070] When the control signal input is low, similar to the case when there are two second transistors, the potential at point B follows the potential at point E, the potential at point C follows the potential at point F, and the potential at point D follows the potential at point G. When R1, R2, and R3 are equal, the power supply voltage can be evenly distributed to the second transistors Q1, Q2, and Q3. This can appropriately reduce the source-drain withstand voltage requirement for each second transistor.

[0071] From the foregoing description, it can be seen that when the number of second transistors is greater, more voltage-dividing resistors and diodes can be set in the switching circuit, so that the power supply voltage can be borne by more transistors, which can reduce the voltage resistance requirement for a single transistor.

[0072] Specifically, taking the N-channel transistor shown in Figures 2 and 5 as an example, the series circuit may include a first transistor Q0 and N second transistors Q1, Q2...QN, then Q0 can be connected in series with Q1, Q2 to QN in sequence, the drain of QN is the first end of the series circuit, and the drain of Q0 is the second end of the series circuit.

[0073] The first clamping circuit may include N-1 diodes connected in series, the cathode of the N-1th diode may be the first end of the first clamping circuit, the anode of the first diode may be the second end of the first clamping circuit, the first end and N-2 common connection points (nodes between any two diodes) may sequentially connect the gate of the Nth second transistor to the gate of the second second transistor, and the second end may be connected to the gate of the first second transistor and the gate of the first transistor and may receive a control signal. When the control signal outputs an active level (active high for an N-channel transistor or an NPN transistor, active low for a P-channel transistor or a PNP transistor), the first clamping circuit may sequentially transmit the control signal to the control electrode (gate or base) of the second transistor through the first clamping circuit.

[0074] The second clamping circuit may include N resistors connected in series, wherein the first end of the Nth resistor is the first end of the second clamping circuit, connected to the first end of the series circuit. The second end of the first resistor is the second end of the second clamping circuit, connected to the second end of the series circuit. The N-1 common connection point formed by the N resistors (the node between any two resistors) can be connected in sequence to the gate of the Nth second transistor to the gate of the second second transistor. When the control signal outputs an invalid level, the second clamping circuit can disperse the voltage difference between the two ends of the second clamping circuit to each second transistor.

[0075] When the control signal is input at a high level, the first transistor and the second transistor are turned on in sequence through the diodes D1 to D(N-1), and the gate potentials are clamped by the first clamping circuit.

[0076] When the control signal input is at a low level, each transistor is cut off, and through the second clamping circuit, the gate potentials of the second to N-th second transistors are directly clamped by voltage division, and the control electrode potential of the first second transistor is clamped through the first resistor. The power supply voltage can be distributed to the N second transistors according to the resistance values ​​of the N resistors.

[0077] It should be understood that in the embodiments of Figure 2, Figure 4 or Figure 5 or in which the number of second transistors is greater, the first transistor and the first second transistor may not be directly connected, but a diode may be provided. The direction of the diode may be consistent with the direction of other diodes in the first clamping circuit. In this way, when the control signal outputs a high level, the gate potentials of the first transistor and the first second transistor differ by a diode conduction transistor voltage drop, rather than being equal.

[0078] In addition, the above description only describes the case where the second transistors have the same voltage withstand capability, in which case the resistance values ​​of the voltage divider resistors in the second clamping circuit 40 can be made equal. Those skilled in the art will readily appreciate that when the second transistors have different voltage withstand capabilities, the resistance values ​​of the voltage divider resistors can be appropriately adjusted based on the ratio of their voltage withstand capabilities, thereby distributing the power supply voltage to each second transistor according to their voltage withstand capability, thereby reducing the possibility of burning out a single transistor. Taking Figure 5 as an example, if the maximum voltage withstand capability ratio of the second transistors Q3, Q2, and Q1 is x:y:z, then R3:R2:R1 can be set to x:y:z, thereby distributing the power supply voltage to transistors Q3, Q2, and Q1 according to the x:y:z ratio. When there are more second transistors, the resistance values ​​of the resistors can also be set based on the voltage withstand capability ratio. When there are more second transistors, for example, if the maximum source-to-drain voltage withstand capability ratio of QN...Q2 and Q1 is VN:...V2:V1, then RN:...R2:R1 can be set to VN:...V2:V1.

[0079] In the previous embodiments, the parasitic capacitance of the transistors was not considered. If the parasitic capacitance of the selected transistors is large and cannot be ignored, and the power supply frequency is high, the parasitic capacitance may cause a certain deviation between the voltage division of different second transistors and the voltage resistance of these second transistors. In this case, the values ​​of the different resistors in the second clamping circuit can be appropriately adjusted to ensure that the voltage division of the transistors is positively correlated with the voltage resistance.

[0080] Still taking the example of the second transistor including three transistors Q1, Q2 and Q3, the parasitic capacitance of the transistor includes: gate-source capacitance C gs , gate-drain capacitance C gd and drain-source capacitance C ds In the switching circuit of the embodiment of the present application, the parasitic capacitance that affects the voltage division of the second clamping circuit includes the gate-source capacitance C gs , gate-drain capacitance C gd .

[0081] FIG6 shows a schematic structural diagram of a switch circuit when parasitic capacitance is considered. The gate-drain capacitance C of the third second transistor Q3 is gd3 Affects the voltage division of the third resistor R3, the gate-source capacitance C of the third second transistor Q3 gs3 and the gate-drain capacitance C of the second transistor Q2 gd2 Affects the voltage division of the second resistor R2...due to C gd3 The voltage is divided after being directly connected in parallel with R3, while other parasitic capacitors are connected in series with the corresponding resistors. In general, the gate-source voltage of the transistor is small, so except for the voltage division of R3, the voltage division of other resistors has little effect. Therefore, in order to reduce the parasitic capacitance causing the power supply voltage to make the voltage division of the second transistor inappropriate, the resistance of the third resistor R3 can be appropriately increased or the resistance of other resistors can be reduced, so that the voltage division ratio of each second transistor is close to its withstand voltage value, reducing the possibility of transistor burning and increasing its life. In principle, (R3||C gs3 ):R2:R1=V Q3 :V Q2 :V Q1 , where V Q3 、V Q2 and V Q1 are the maximum source-drain withstand voltages of transistors Q3, Q2, and Q1, respectively. R3||C gs3 is the total impedance Z after parallel connection, which can satisfy the following formula:

[0082] Where ω is the frequency of the power supply voltage and j is the sign of the imaginary part.

[0083] In order to facilitate the adjustment of the resistor, for example, in one embodiment, the resistor R3 can be a variable resistor, thereby facilitating the adjustment of the divided voltage of each second transistor.

[0084] Of course, it is also possible to consider not only the influence of the parasitic capacitance of the last second transistor on the last resistor voltage divider, but also the influence of other parasitic capacitances on other resistor voltage dividers. In this way, the resistor can be set as an adjustable resistor, thereby facilitating precise control of the voltage divider of each second transistor.

[0085] In the embodiments of Figures 2, 4, and 5, the direction of the body diode of the first transistor in the series circuit is opposite to that of the body diode of the second transistor, thereby preventing current backflow when the power supply is AC. Furthermore, when the switch circuit is in the off state, the voltage drop across the first transistor is the voltage drop across its body diode, and the power supply voltage is primarily borne by the second transistor.

[0086] When the power supply is an AC power supply, the maximum value of the power supply voltage can be 70V, 50V, 20V, 100V, etc., and this application does not limit this.

[0087] When the influence of current backflow is not considered or the current backflow problem does not exist, for example, when the transistor is a BJT or the power supply of the switching circuit is a DC power supply and there is no current backflow problem, the structure of the switching circuit may be different from that described above.

[0088] Taking the case where the transistors in the series circuit are still N-channel MOS tubes and the power supply of the switching circuit is a DC power supply as an example, Figure 7 shows a schematic structural diagram of a switching circuit provided in an embodiment of the present application. As shown in Figure 7, the series circuit 20 includes a first transistor Q0 and a second transistor Q1, and the body diodes of the two transistors are in the same direction. The first clamping circuit 30 includes a diode D1, and the two ends of the diode D1 are respectively connected to the gates of the first transistor Q0 and the second transistor Q1. The second clamping circuit 40 includes resistors R1 and R2, and the common connection point of the two resistors is connected to the gate of the second transistor Q1.

[0089] When the control signal provides a high level, the first transistor Q0 is turned on, the potential at point B is pulled low, the diode D1 is turned on, the potential at point E is pulled high, the gate-source voltage difference of the second transistor Q1 increases, Q1 is turned on, and the power supply voltage of the entire switching circuit is borne by the resistor R0 and the two transistors. The resistor R0 can be a protection resistor of the switching circuit, and its resistance value can be much larger than the on-resistance of the two transistors, so that most of the power supply voltage is borne by the resistor R0.

[0090] When the control signal is low, the first transistor Q0 turns off, D1 turns off, and the second transistor Q1 turns off, shutting down the series circuit. The power supply voltage of the switching circuit is then borne by the first and second transistors Q0 and Q1. Continuing with the example of a 70V power supply voltage and two equal resistors, due to the voltage divider effect of the two resistors in the second clamping circuit, the potential at point E is 35V. The potential at point B follows the potential at point E, evenly distributing the power supply voltage across the first and second transistors Q0 and Q1.

[0091] Figure 7 shows only one second transistor. When there are N second transistors, the first clamping circuit can include N diodes connected in series, and the two endpoints and N-1 common connection points of the first clamping circuit can be connected in sequence to the gates of the N second transistors and the first transistor. The second clamping circuit can include N+1 resistors, and the N-1 common connection points formed by the resistors can be connected in sequence to the Nth second transistor through the second second transistor, with the two ends of the second clamping circuit respectively connected to the two ends of the series circuit. The specific structure can be referred to the previous description and will not be repeated here.

[0092] In the switch circuit of Figure 7 , since the power supply voltage is borne not only by the second transistor but also by the first transistor, the resistance values ​​of the various resistors in the second clamp circuit can be set based on the highest source-drain withstand voltage of the second and first transistors. Specifically, assuming that the source-drain withstand voltage ratio of the N second transistors and the first transistor is: VN: ... V2: V1: V0, then R(N+1): ... R2: R1 = VN: ... V2: V1: V0 can be set.

[0093] It should be understood that the above description uses MOS transistors as an example to describe the technical solutions of the embodiments of the present application. When the transistors are BJTs, the gate can correspond to the base (which can be called the control electrode), the emitter corresponds to the source, and the collector corresponds to the drain. When the first and second transistors are BJTs, there is no current backflow problem, and the structure of the switch circuit can be as shown in Figure 7.

[0094] When considering the parasitic capacitance of a BJT transistor, the parasitic capacitances that may affect the transistor's voltage division include the parasitic capacitance between the base and emitter, and the capacitance between the base and collector. For details, please refer to the previous article and will not be repeated here.

[0095] It should also be understood that when the transistor is a BJT, the first resistor and the last resistor are only connected in parallel with one parasitic capacitor, so it will have a greater impact on the voltage division of the first transistor and the Nth second transistor. The resistance values ​​of the first resistor and the last resistor can be appropriately increased or the resistance values ​​of other resistors can be reduced. For details, please refer to the previous introduction and will not be repeated here.

[0096] In addition, it is understandable that for each transistor involved in the embodiments of the present application, it can be a single transistor or a plurality of transistors connected in series or in parallel. This application does not limit this. In practice, it can be designed according to the needs of each transistor during manufacture. In addition, the two poles (first end and second end) of the MOS tube other than the gate are one source and one drain, and the two are not clearly distinguished. For example, the first end is the source and the second end is the drain; or the first end is the drain and the second end is the source. For BJT, in addition to the base, the distinction between the emitter and the collector is not clearly defined.

[0097] An embodiment of the present application also provides a charging circuit, comprising any one of the switching circuits described above.

[0098] An embodiment of the present application further provides an electronic device, comprising any one of the switching circuits or charging circuits described above.

[0099] The electronic device may be a terminal device such as a mobile phone, computer, tablet, notebook, car computer, smart watch or smart bracelet.

[0100] An embodiment of the present application further provides a charging device, comprising any one of the switching circuits or charging circuits described above.

[0101] The charging device may be a charger, for example, a wired charger or a wireless charger.

[0102] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A switching circuit, characterized in that: include: a series circuit, a first clamping circuit, and a second clamping circuit; The series circuit includes a first transistor and N second transistors connected in series in sequence, where N is greater than or equal to 1. The second end of the first transistor is the second end of the series circuit. The first end of the first transistor is connected to the N second transistors in sequence. The control electrode of the first transistor is used to receive a control signal. The first end of the Nth second transistor is the first end of the series circuit. The first clamping circuit includes at least one diode connected in series, wherein endpoints and a common connection point of the first clamping circuit are connected to the control electrodes of the N second transistors and the first transistor, the second end of the first diode is the second end of the first clamping circuit and is connected to the control electrode of the first transistor, and the first end of the last diode is the first end of the first clamping circuit and is connected to the control electrode of the N second transistor. When the control signal causes the series circuit to be turned on, the first clamping circuit is used to clamp the control electrode potentials of the first transistor and the N second transistors according to the control signal; The second clamping circuit includes a plurality of resistors connected in series. The first end of the second clamping circuit is connected to the first end of the series circuit. When the control signal causes the series circuit to be closed, the second clamping circuit is used to clamp the control electrodes of the N second transistors.

2. The switching circuit according to claim 1, wherein: The transistors in the series circuit are metal oxide semiconductor field effect transistors (MOSFETs).

3. The switching circuit according to claim 1 or 2, wherein: The transistors in the series circuit are N-channel MOSFETs.

4. The switching circuit according to claim 3, wherein: N≥2, the directions of the body diodes of the first transistor and the N second transistors are opposite; The first clamping circuit includes N-1 diodes, a first end of the first clamping circuit and a common connection point of the diodes in the first clamping circuit are respectively connected to the control electrodes of the Nth second transistor to the second second transistor, and a second end of the first clamping circuit is connected to the control electrodes of the first transistor and the first second transistor; The second clamping circuit includes N resistors, a common connection point of the N resistors sequentially connects the control electrodes of the Nth second transistor and the second second transistor, and a second end of the second clamping circuit is connected to the second end of the series circuit.

5. The switching circuit according to claim 4, wherein: The ratio of the resistance values of the N resistors is the same as the ratio of the withstand voltage values of the N second transistors.

6. The switching circuit according to claim 4, wherein: The second end of the first resistor is the second end of the second clamping circuit, the first end of the Nth resistor is the first end of the second clamping circuit, the N second transistors have the same withstand voltage value, and the resistance of the first resistor is greater than the resistance of other resistors in the second clamping circuit.

7. The switching circuit according to claim 3, wherein: The body diodes of the first transistor and the N second transistors have the same direction; The first clamping circuit includes N diodes, and the endpoints and the common connection point of the first clamping circuit are sequentially connected to the control electrodes of the first transistor and the N second transistors; The second clamping circuit includes N+1 resistors, a common connection point of the N+1 resistors is sequentially connected to the control electrodes of the N second transistors, and a second end of the second clamping circuit is connected to the second end of the series circuit.

8. The switching circuit according to claim 1, wherein: The transistors in the series circuit are bipolar junction transistors (BJTs).

9. The switching circuit according to claim 8, wherein: The transistors in the series circuit are NPN-type BJTs.

10. The switching circuit according to claim 9, wherein: The ratio of the resistance values of the N+1 resistors is the same as the ratio of the withstand voltage values of the N second transistors and the first transistor.

11. A charging circuit, characterized in that: The device comprises the switching circuit according to any one of claims 1 to 10.

12. An electronic device, characterized in that: The method comprises the switching circuit according to any one of claims 1 to 10 or the charging circuit according to claim 11.

13. A charging device, characterized in that: The method comprises the switching circuit according to any one of claims 1 to 10 or the charging circuit according to claim 11.

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