Charging circuit of shared communication bus

Abstract

The invention relates to a charging circuit of a shared communication bus, and aims to solve the problem that a traditional charging mode needs to occupy extra cable space and is limited in charging power. A charging function is realized by multiplexing a communication bus, and the device comprises a solid-state relay isolation module, a circuit voltage division module and a power supply access module. Wherein the solid-state relay isolation module detects bus voltage in real time, and when the voltage exceeds a threshold value (greater than or equal to 20V), the solid-state relay isolation module is automatically switched to a charging mode and isolates the communication chip; the circuit voltage division module accurately detects voltage through voltage division resistors R3, R4 and R5, and the resistance value of the circuit voltage division module meets the relational expressions # imgabs0 # and # imgabs1 # to ensure reliable switching between a communication mode and a charging mode; the power supply access module adopts back-to-back NMOS switches (VT1-VT4) and a photoelectric coupling driver, and bus high voltage is safely led into a power supply network. The communication chip is protected from transient high-voltage impact through the clamping diode and the resettable fuse, meanwhile, a special charging cable is omitted, the proportion of a charging circuit is remarkably reduced, and the charging power is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of charging circuits, and in particular to a charging circuit that shares a communication bus. The charging function is achieved by multiplexing the physical lines of the communication bus, significantly reducing the volume and weight of the charging circuit in the device while increasing the charging power. Background Art

[0002] Battery-powered mobile devices require a dedicated charging port or wireless charging, but both methods take up additional space and weight, creating significant inconvenience in product designs that prioritize miniaturization and compactness. When fast charging is required, traditional methods can only increase the wire diameter of the charging cable and the size of the charging connector, further increasing the proportion of the charging circuit in the device, reducing the proportion of the device's normal operating area and increasing the overall size and weight of the product. The communication bus in traditional charging circuits still performs only a single communication function, making it impossible to further increase charging power without changing the cable configuration. Summary of the Invention

[0003] The present invention aims at devices using a communication bus and proposes a charging method for a cable network that can share the communication bus, especially for devices where the diameters of the communication cables and power supply cables are similar, which can multiply the charging power.

[0004] The technical solution adopted by the present invention is a charging circuit for sharing a communication bus, comprising: A solid-state relay isolation module detects the voltage on the communication bus and switches to charging mode when the voltage exceeds a set threshold, isolating the communication bus from the communication chip. The circuit voltage divider module is electrically connected to the solid-state relay isolation module and includes voltage divider resistors R3, R4, and R5 connected in series, which are used to perform voltage division detection on the communication bus voltage; R6, R7, and R8 are used to control the switch of the photoelectric coupling driver; The power path module includes an optocoupler driver and back-to-back NMOS switches VT1 to VT4, which are used to direct the power of the communication bus into the power grid in charging mode; The voltage-dividing resistance value of the circuit voltage-dividing module satisfies the following relationship: , ; Among them, U is the communication bus charging voltage, u is the solid-state relay turn-on voltage, is the turn-on current of the solid-state relay; when the communication bus voltage is lower than the threshold, the solid-state relay isolation module enters the communication mode and the power path module is disconnected; when the voltage exceeds the threshold, the solid-state relay isolation module shuts off the communication path and activates the power path module to achieve charging mode switching.

[0005] Preferably, the resistance of the voltage-dividing resistor R3 is 940Ω, the resistance of R4 is 240Ω, and the resistance of R5 is the same as that of R3.

[0006] Preferably, the solid-state relay isolation module includes: a solid-state relay U5, whose control end is connected to both ends of the voltage-dividing resistor R4, and is used to control the switching of the communication bus according to the voltage division; solid-state relays U3 and U4, whose control ends are connected to point A, and are used to conduct the connection between the communication chip and the bus in the communication mode, and disconnect the connection in the charging mode.

[0007] Preferably, the charging circuit also includes a clamping diode VD1, which is connected in parallel between the positive and negative ends of the communication bus to limit the transient voltage at the moment of charging mode switching; a self-recovery fuse FUSE is connected in series between the negative end of the communication bus and the external circuit to limit the transient current at the moment of charging mode switching, thereby jointly protecting the communication chip.

[0008] Preferably, the withstand voltage value of the clamping diode VD1 matches the maximum withstand voltage of the communication chip, and the holding current of the resettable fuse is 10mA and the withstand voltage is 80V.

[0009] Preferably, the gates of the back-to-back NMOS switches VT1-VT4 are controlled by optocoupler drivers U1 and U2, the turn-on voltage of the optocoupler drivers is 2.4V, the turn-on current is 5~20mA, and the corresponding voltage divider resistors R6, R7, and R8 have resistances of: r6=r8=880Ω, r7=480Ω.

[0010] Preferably, the voltage range of the communication bus in the charging mode is 20V to 60V, and the absolute value of the voltage in the communication mode is less than 2V.

[0011] The beneficial effects of this invention are: it utilizes the communication bus that is unavailable during normal charging, thereby increasing total charging power, reducing charging time, reducing the weight of the charging cable, and reducing the proportion of the charging circuit in the device. Compared with increasing the diameter of the charging cable, this invention only changes the circuit design without changing the structural design, shortening design time and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the electrical schematic diagram of the solid-state relay isolation module and circuit voltage divider module of the present invention.

[0013] Figure 2 This is the electrical schematic diagram of the power path module of the present invention. DETAILED DESCRIPTION

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0015] In an embodiment of the present invention, Figure 1 As shown, three voltage-dividing resistors R3, R4, and R5 are connected in series to the external output port of the communication bus.

[0016] 1) When the bus is in communication mode, the absolute value of the communication bus voltage is typically less than 2V. Therefore, the voltage across R4 is insufficient to activate the U5 solid-state relay, causing the voltage at point A to equal 5V_ISO. This in turn activates the U3 and U4 solid-state relays, ultimately outputting U6's communication signal to the bus's external interface. Simultaneously, the voltage across R7 is insufficient to activate the U1 and U2 optocouplers, disconnecting the four NMOS transistors (VT1, VT2, VT3, and VT4). Because the NMOS transistors are designed back-to-back, they achieve electrical isolation between the battery and the communication bus.

[0017] 2) When charging via the bus, the charger's + and - pins are connected to the bus's external + and - pins, respectively. At this point, the voltage between the BC pins can reach 20-60V. The R4 voltage divider resistor reaches the U5 solid-state relay's on-state threshold, bringing the voltage at point A to GND_ISO. At this point, regardless of whether there's voltage to the left of R1 (i.e., whether U6 is operating), the U3 and U4 solid-state relays cannot meet their on-state thresholds. Therefore, the voltage between the BC pins cannot reach the pins of the communication chip U6. Simultaneously, due to the charger's connection, the voltage across R7 meets the U1 and U2 on-state thresholds, turning on the four NMOS transistors mentioned above, allowing the voltage between the BC pins to charge the battery smoothly.

[0018] 3) When entering charging mode, to prevent the solid-state relay from shutting down late, which could cause voltage between the bus and bus terminals to enter U6, a clamping diode (VD1) and a resettable fuse (FUSE1) are added. When the voltage between the bus and bus terminals surges across VD1, the clamping diode conducts instantaneously, keeping the voltage between Bus+ and Bus- on U6 within a safe range. If the instantaneous current is too high, the resettable fuse's resistance increases, reducing the current flowing through the clamping diode. Together, the clamping diode and resettable fuse protect U6 from damage caused by the charging voltage.

[0019] Assume that the turn-on current of the solid-state relay is , the turn-on voltage is , the voltage between BC is , the resistances of R3, R4, and R5 are 、 、 , the current flowing through R4 is , we can conclude , , Without loss of generality, we can let , , substituting into the above two formulas, we have , Available Under normal circumstances, the turn-on current of the solid-state relay is , turn-on voltage .

[0020] When the communication bus is in the charging state, the minimum voltage between BC is , substituting into formula (4), we can get , Thus we can get The value range of is: , Substituting actual values, we can get , When the communication bus is in charging state, the maximum voltage between BC is , similarly we can get In order to meet the charging voltage of 20~60V and minimize the power consumption of the voltage divider resistor, . According to formula (1)(2) and , Available , From the solid-state relay's turn-on current range, we can get Move item to get Will and Substituting into the above formula respectively, we can get and , so take .

[0021] According to the above calculation results 、 , the voltage between BC can be When the voltage divider on R4 This is much smaller than the minimum turn-on voltage of the solid-state relay (1V). That is, during normal communication, the solid-state relay U5 will definitely not turn on, thus ensuring that the solid-state relays U3 and U4 remain in the on state, allowing the communication chip U6 to communicate normally with the outside world.

[0022] When the voltage between BC is When , we can use formula (5) to get , which is obviously greater than the turn-on threshold of the solid-state relay U5, thereby ensuring that the solid-state relays U3 and U4 remain in the off state, so that in the charging state, the BC voltage will not reach the pin of the communication chip U6.

[0023] In the power path module, the turn-on current of each photo MOS driver , turn-on voltage , so after U1 and U2 are connected in series, the turn-on voltage between DE is 2.4V, and the turn-on current is still According to the above analysis method, we can get 、 .

[0024] For other components, parameters can be selected according to actual conditions. For example, R1=R2=R7=200Ω, the clamping diode VD1 should have a suitable withstand voltage according to the voltage indicator of the communication chip U6, the resettable fuse FUSE1 should have a withstand voltage of 80V and a holding current of 10mA, and the four NMOS (VT1~4) should have a withstand voltage of 80V. The current should be based on the charging current.

[0025] This invention proposes a charging circuit design for a shared isolated communication bus. Using only solid-state relays and voltage-divider resistors, it automatically switches between communication and charging functions, while protecting the bus chip from damage caused by charging voltage. This charging circuit design is crucial for reducing the proportion of charging circuits within a device.

[0026] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A charging circuit sharing a communication bus, characterized in that: include: A solid-state relay isolation module detects the voltage on the communication bus and switches to charging mode when the voltage exceeds a set threshold, isolating the communication bus from the communication chip. The circuit voltage divider module is electrically connected to the solid-state relay isolation module and includes voltage divider resistors R3, R4, and R5 connected in series, which are used to perform voltage division detection on the communication bus voltage; R6, R7, and R8 are used to control the switch of the photoelectric coupling driver; The power path module includes an optocoupler driver and back-to-back NMOS switches VT1 to VT4, which are used to guide the power of the communication bus into the power grid in charging mode. The voltage divider resistance value of the circuit voltage divider module satisfies the following relationship: ， ， Among them, U is the communication bus charging voltage, u is the solid-state relay turn-on voltage, is the turn-on current of the solid-state relay; when the communication bus voltage is lower than the threshold, the solid-state relay isolation module enters the communication mode and the power path module is disconnected; when the voltage exceeds the threshold, the solid-state relay isolation module shuts off the communication path and activates the power path module to achieve charging mode switching.

2. The charging circuit according to claim 1, wherein: The resistance of the voltage divider resistor R3 is 940Ω, the resistance of R4 is 240Ω, and the resistance of R5 is the same as that of R3.

3. The charging circuit according to claim 1, wherein: The solid-state relay isolation module includes: a solid-state relay U5, whose control end is connected to the two ends of the voltage-dividing resistor R4, and is used to control the switching of the communication bus according to the voltage division; solid-state relays U3 and U4, whose control ends are connected to point A, and are used to conduct the connection between the communication chip and the bus in the communication mode, and disconnect the connection in the charging mode.

4. The charging circuit according to claim 1, wherein: It also includes a clamping diode VD1, which is connected in parallel between the positive and negative ends of the communication bus to limit the transient voltage at the moment of charging mode switching; a self-recovery fuse FUSE is connected in series between the negative end of the communication bus and the external circuit to limit the transient current at the moment of charging mode switching, thereby jointly protecting the communication chip.

5. The charging circuit according to claim 4, characterized in that: The withstand voltage of the clamping diode VD1 matches the maximum withstand voltage of the communication chip, and the holding current of the resettable fuse is 10mA and the withstand voltage is 80V.

6. The charging circuit according to claim 1, wherein: The gates of the back-to-back NMOS switches VT1 to VT4 are controlled by optocoupler drivers U1 and U2. The turn-on voltage of the optocoupler drivers is 2.4V, the turn-on current is 5 to 20mA, and the corresponding voltage divider resistors R6, R7, and R8 have resistances of: r6 = r8 = 880Ω, r7 = 480Ω.

7. The charging circuit according to claim 1, wherein: The voltage range of the communication bus in the charging mode is 20V to 60V, and the absolute value of the voltage in the communication mode is less than 2V.

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