Voltage switching circuit and power supply system using the same

Abstract

The application discloses a voltage switching circuit and a power supply system using the same. The voltage switching circuit is used for selectively transmitting voltages applied to first and second input terminals to an output terminal, and comprises a first transistor connected between the first input terminal and the output terminal, a second transistor connected between the second input terminal and the output terminal, and a switching module connected with the gates of the first and second transistors and used for controlling one of the first and second transistors to be turned on according to a voltage difference between a first input voltage of the first input terminal and a second input voltage of the second input terminal. The voltage loss of a diode is saved through the channel conduction of the transistor, so that the working voltage of a chip and the overall power of a system are reduced.

Description

Technical Field

[0001] This invention relates to the field of power management system technology, and more specifically, to a voltage switching circuit and a power system using it. Background Technology

[0002] With the widespread adoption of wireless charging technology, wireless charging receiver chips are widely used in various portable electronic devices such as mobile phones and wireless Bluetooth headsets. These devices typically offer two charging methods: wireless charging via a wireless charger and wired charging via a power adapter. However, wireless charging may generate high voltage at the receiving end during communication. If both charging methods are used simultaneously, this high voltage may travel through the power path to the power adapter, potentially damaging it or even causing safety issues. Therefore, these products need to incorporate a power switching mechanism to safely switch between the two charging methods.

[0003] Figure 1 A schematic diagram of a conventional voltage switching circuit 100 is shown, including transistors M1 and M2. Diodes D1 and D2 are the substrate diodes of transistors M1 and M2, respectively. The first terminals of transistors M1 and M2 receive input voltages Vin1 and Vin2, respectively. The control terminals of transistors M1 and M2 are electrically connected to each other, and their second terminals are electrically connected to each other, outputting a voltage Vin_h. The conventional approach utilizes the substrate diodes D1 and D2 of transistors M1 and M2 to achieve unidirectional conduction for voltage switching, selecting a higher input voltage to power other modules within the chip. However, this method generates a diode voltage drop within the chip, which is detrimental to reducing the chip's operating voltage and consumes overall system power. Furthermore, forward bias of the diodes is prone to latch-up effects, resulting in poor system stability. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a voltage switching circuit and a power supply system using it, which can automatically turn on the corresponding transistor when the voltage difference between the input terminals is greater than the transistor's conduction threshold. By turning on the transistor's channel, the voltage loss of the diode is eliminated, which facilitates the reduction of the chip's operating voltage and the overall power of the system.

[0005] According to one aspect of the present invention, a voltage switching circuit is provided for selectively transmitting voltages applied to a first input terminal and a second input terminal to an output terminal, comprising: a first transistor connected between the first input terminal and the output terminal; a second transistor connected between the second input terminal and the output terminal; and a switching module connected to the gates of the first transistor and the second transistor, for controlling one of the first transistor and the second transistor to conduct based on a voltage difference between a first input voltage of the first input terminal and a second input voltage of the second input terminal.

[0006] Optionally, the first transistor is turned on when the first input voltage is greater than the second input voltage and the voltage difference between them is greater than the turn-on threshold of the first transistor; the second transistor is turned on when the second input voltage is greater than the first input voltage and the voltage difference between them is greater than the turn-on threshold of the second transistor.

[0007] Optionally, the switching module includes: a Zener diode and a resistor, wherein the cathode of the Zener diode is connected to the output terminal, the anode is connected to a first end of the resistor, and the second end of the resistor is grounded; a third transistor, wherein the gate is connected to the intermediate node of the Zener diode and the resistor, the drain is connected to the second input voltage, and the source is connected to the gate of the first transistor; and a fourth transistor, wherein the gate is connected to the intermediate node of the Zener diode and the resistor, the drain is connected to the first input voltage, and the source is connected to the gate of the second transistor.

[0008] Optionally, the third transistor and the fourth transistor are clamping transistors, which can clamp the gate-source voltages of the first transistor and the second transistor within a safe voltage range, respectively.

[0009] Optionally, the third transistor and the fourth transistor are always in the on state.

[0010] Optionally, the first to fourth transistors are each implemented using P-type transistors.

[0011] According to another aspect of the present invention, a power supply system is provided for charging a battery, comprising: the voltage switching circuit described above, configured to receive a first input voltage provided by a power adapter; a wireless charging receiving circuit, configured to provide a second input voltage to the voltage switching circuit by receiving energy emitted by a wireless charger, wherein the voltage switching circuit selectively transmits either the first input voltage or the second input voltage to an output terminal; and a battery charging management circuit, configured to manage the charging of the battery according to the voltage at the output terminal of the voltage switching circuit.

[0012] In summary, the voltage switching circuit of the present invention can automatically turn on the corresponding transistor when the voltage difference between the input terminals is greater than the transistor's conduction threshold by controlling the gates of the two transistors. By turning on the transistor's channel, the voltage loss of the diode is eliminated, which facilitates the reduction of the chip's operating voltage and the overall power of the system. Therefore, the latch-up effect caused by the forward bias of the diode will not occur.

[0013] In addition, the voltage switching circuit of the present invention also includes a clamping transistor, which can clamp the gate-source voltage of the transistor within a safe voltage range when the voltage difference between the input terminals is too large, thereby avoiding damage to the transistor. Attached Figure Description

[0014] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0015] Figure 1 A circuit diagram of a conventional voltage switching circuit is shown;

[0016] Figure 2 A circuit diagram of a voltage switching circuit according to an embodiment of the present invention is shown;

[0017] Figure 3 A schematic diagram of a power supply system for wired and wireless charging according to an embodiment of the present invention is shown. Detailed Implementation

[0018] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale. Furthermore, some well-known parts may not be shown.

[0019] It should be understood that, in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0020] This invention can be presented in various forms, some of which will be described below.

[0021] Figure 2 A circuit diagram of a voltage switching circuit 200 according to an embodiment of the present invention is shown. Figure 3 The installation is shown Figure 2 The diagram shows the structure of a power system 300 for wired and wireless charging, including a voltage switching circuit 200. The power system 300 includes a wireless charging receiver circuit 320, a battery charging management circuit 330, and a voltage switching circuit 200.

[0022] The output terminal of the power adapter 301 is connected to the input terminal of the voltage switching circuit 200, providing an input voltage Vin1 to the voltage switching circuit 200. The output terminal of the wireless charging receiver circuit 320 is connected to the input terminal of the voltage switching circuit 200, receiving energy emitted by the wireless charger 302 to provide an input voltage Vin2 to the voltage switching circuit 200. The voltage switching circuit 200 compares the input voltages Vin1 and Vin2, and outputs the voltage Vin_h based on the higher of the two. The input terminal of the battery charging management circuit 330 is connected to the output terminal of the voltage switching circuit 200, and the output terminal of the battery charging management circuit 330 is connected to the battery 303, used to manage the charging of the battery 303 according to the voltage Vin_h. The following is based on... Figure 2 The structure of the voltage switching circuit 200 is described in detail.

[0023] like Figure 2 As shown, the voltage switching circuit 200 includes input terminals 201 and 202, an output terminal 203, transistors M1 and M2, and a switching module 210. Input terminals 201 and 202 are used to receive input voltages Vin1 and Vin2, respectively. The voltage switching circuit 200 selectively transmits the voltages applied to input terminals 201 and 202 to the output terminal 203. Transistors M1 and M2 are implemented, for example, as P-type transistors. Transistor M1 is connected between input terminal 201 and output terminal 203, and transistor M2 is connected between input terminal 202 and output terminal 203. The switching module 210 is connected to the gates of transistors M1 and M2 and controls one of transistors M1 and M2 to conduct based on the voltage difference between the input voltage Vin1 at input terminal 201 and the input voltage Vin2 at input terminal 202.

[0024] Specifically, the switching module 210 includes a Zener diode Dz, a resistor R1, and transistors M3 and M4. The cathode of the Zener diode Dz is connected to the output terminal 203, the anode is connected to the first end of the resistor R1, and the second end of the resistor R1 is grounded. Transistors M3 and M4 are implemented, for example, as P-type transistors. The gate of transistor M3 is connected to the intermediate node between the Zener diode Dz and the resistor R1, the source of transistor M3 is connected to the gate of transistor M1, and the drain of transistor M3 is connected to the input voltage Vin2. The gate of transistor M4 is connected to the intermediate node between the Zener diode Dz and the resistor R1, the source of transistor M4 is connected to the gate of transistor M2, and the drain of transistor M4 is connected to the input voltage Vin1.

[0025] The voltage switching circuit 200 in this embodiment works as follows: When the input voltage Vin1 is greater than the input voltage Vin2, the substrate diode D1 of transistor M1 is turned on, and the substrate diode D2 of transistor M2 is turned off. At this time, the voltage Vin_h at the output terminal 203 is Vin_h = Vin1 - VD1, where VD1 is the voltage drop across the substrate diode D1. Additionally, the gate voltages V_G3(G4) of transistors M3 and M4 are V_h - Vz, where Vz is the Zener voltage of the Zener diode Dz. Since the gate voltages of transistors M3 and M4 are lower than the voltage Vin_h by one Zener voltage, transistors M3 and M4 are always in the on state. Transistor M3 transmits the input voltage Vin2 to the gate of transistor M1, and transistor M4 transmits the input voltage Vin1 to the gate of transistor M2. That is, at this time, the gate voltage V_G1 of transistor M1 is V_h - V_D2. In step 2, the gate voltage of transistor M2 is V_G2 = Vin1. Since the source voltage of transistor M1 is V_S1 = Vin_h = Vin1 - VD, when Vin_h - Vin2 ≈ Vin1 - Vin2 > Vth_M1, where Vth_M1 is the turn-on threshold of transistor M1, the channel of transistor M1 is turned on, and the voltage at the output terminal 203 is Vin_h = Vin1. At this time, the gate-source voltage of transistor M2 is Vgs = 0, so transistor M2 is in the off state.

[0026] Similarly, when the input voltage Vin2 is greater than the input voltage Vin1, the substrate diode D2 of transistor M2 is turned on, and the substrate diode D1 of transistor M1 is turned off. At this time, the voltage Vin_h at the output terminal 203 is Vin_h = Vin2 - VD2, where VD2 is the voltage drop across the substrate diode D2. Likewise, the gate voltage V_G3(G4) of transistors M3 and M4 is Vin_h - Vz, where Vz is the Zener voltage of the Zener diode Dz. Since the gate voltages of transistors M3 and M4 are lower than the voltage Vin_h by one Zener voltage, transistors M3 and M4 are always in the on state. Transistor M3 transfers the input voltage Vin2 to the gate of transistor M1, and transistor M4 transfers the input voltage Vin1 to the gate of transistor M2. That is, at this time, the gate voltage V_G1 of transistor M1 is... Vin2, the gate voltage of transistor M2 is V_G2=Vin1, and since the source voltage of transistor M2 is V_S2=Vin_h=Vin2-VD, when Vin_h-Vin1≈Vin2-Vin1>Vth_M2, where Vth_M2 is the turn-on threshold of transistor M2, the channel of transistor M2 is turned on, and the voltage of the final output terminal 203 is Vin_h=Vin2. At this time, the gate-source voltage of transistor M1 is Vgs=0, so transistor M1 is in the off state.

[0027] As can be seen from the above, the voltage switching circuit 200 of the present invention can automatically turn on the corresponding transistor when the voltage difference between the input voltages Vin1 and Vin2 is greater than the transistor's turn-on threshold by means of mutual gate control. The voltage loss of the diode is eliminated by the conduction of the transistor channel, which makes it easier to reduce the chip's operating voltage and the overall power of the system. Therefore, the latch-up effect caused by the forward bias of the diode will not occur.

[0028] Furthermore, transistors M3 and M4 in the embodiments of the present invention can also be used as clamping transistors, which can clamp the gate-source voltage of transistors M1 and M2 within a safe voltage range (e.g., 5V, since the gate withstand voltage of most high-voltage transistors does not exceed 5V) when the voltage difference between the input voltages Vin1 and Vin2 is too large, thus avoiding damage to transistors M1 and M2. Taking the clamping of transistor M3 as an example, since transistor M3 is a P-type transistor and is always in the on state, the source voltage of transistor M3 cannot be lower than the gate voltage. The gate voltage of transistor M3 is V_G3 = Vin_h - Vz = Vin1 - VD1 - Vz. Therefore, when the input voltage Vin1 - Vin2 >> 5V, the source voltage of transistor M3 (i.e., the gate voltage of transistor M1) will become Vin1 - VD1 - Vz + Vth_M3, where Vth_M3 is the threshold voltage of transistor M3. This clamps the gate-source voltage of transistor M1 within the safe range of 5V, preventing damage to transistor M1.

[0029] Continue to refer to Figure 3 The wireless charging receiver circuit 320 includes an LC dual-resonant circuit composed of coils and capacitors, an ASK modulation circuit, an FSK demodulation circuit, and a synchronous rectification and filtering circuit. Energy transmitted by the wireless charger is received through the LC dual-resonant circuit and converted into DC power by the synchronous rectification and filtering circuit to power the wireless charging receiver module. The ASK modulation circuit is used for the wireless charging receiver to send data to the wireless charger. The FSK demodulation circuit is used to receive data sent from the wireless charger to the wireless charging receiver.

[0030] The battery charging management circuit 330 performs trickle, constant current and constant voltage charging on the battery, while monitoring the battery voltage, current and temperature in real time to prevent damage to the battery from excessive charging or discharging or overheating.

[0031] It should be noted that the wireless charging receiver circuit 320 and the battery charging management circuit 330 in this invention are common circuits in the art and will not be described in detail here.

[0032] In summary, the voltage switching circuit of the present invention can automatically turn on the corresponding transistor when the voltage difference between the input terminals is greater than the transistor's conduction threshold by controlling the gates of the two transistors. By turning on the transistor's channel, the voltage loss of the diode is eliminated, which facilitates the reduction of the chip's operating voltage and the overall power of the system. Therefore, the latch-up effect caused by the forward bias of the diode will not occur.

[0033] In addition, the voltage switching circuit of the present invention also includes a clamping transistor, which can clamp the gate-source voltage of the transistor within a safe voltage range when the voltage difference between the input terminals is too large, thereby avoiding damage to the transistor.

[0034] In the above description, well-known structural elements and steps have not been described in detail. However, those skilled in the art should understand that the corresponding structural elements and steps can be implemented through various technical means. Furthermore, in order to form the same structural elements, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0035] As described above, these embodiments of the present invention do not exhaustively describe all details, nor do they limit the invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The scope of protection of this invention should be determined by the scope defined in the claims of this invention.

Claims

1. A voltage switching circuit for selectively transmitting voltages applied to a first input terminal and a second input terminal to an output terminal, comprising: A first transistor is connected between the first input terminal and the output terminal; The second transistor is connected between the second input terminal and the output terminal; as well as A switching module, connected to the gates of the first transistor and the second transistor, is used to control one of the first transistor and the second transistor to turn on based on the voltage difference between the first input voltage at the first input terminal and the second input voltage at the second input terminal. The switching module includes: A Zener diode and a resistor, wherein the cathode of the Zener diode is connected to the output terminal, the anode is connected to the first end of the resistor, and the second end of the resistor is grounded; The third transistor has its gate connected to the midpoint between the Zener diode and the resistor, its drain connected to the second input voltage, and its source connected to the gate of the first transistor; and The fourth transistor has its gate connected to the midpoint between the Zener diode and the resistor, its drain connected to the first input voltage, and its source connected to the gate of the second transistor.

2. The voltage switching circuit according to claim 1, wherein, When the first input voltage is greater than the second input voltage, and the voltage difference between the two is greater than the conduction threshold of the first transistor, the first transistor is turned on. When the second input voltage is greater than the first input voltage, and the voltage difference between the two is greater than the conduction threshold of the second transistor, the second transistor is turned on.

3. The voltage switching circuit according to claim 2, wherein, The third transistor and the fourth transistor are clamping transistors, which can clamp the gate-source voltages of the first transistor and the second transistor within a safe voltage range, respectively.

4. The voltage switching circuit according to claim 3, wherein, The third transistor and the fourth transistor are always in the on state.

5. The voltage switching circuit according to claim 2, wherein, The first to fourth transistors are each implemented using P-type transistors.

6. A power system for charging a battery, comprising: The voltage switching circuit according to any one of claims 1-5 can be used to receive a first input voltage provided by a power adapter; The wireless charging receiving circuit receives energy emitted by the wireless charger and provides a second input voltage to the voltage switching circuit, which selectively transmits either the first input voltage or the second input voltage to the output terminal. as well as A battery charging management circuit is used to manage the charging of the battery according to the voltage at the output terminal of the voltage switching circuit.

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