Integrated step-down private protocol vehicle-mounted USB charging module

Abstract

The utility model relates to the technical field of vehicle-mounted USB charging, and mainly relates to an integrated step-down private protocol vehicle-mounted USB charging module, which comprises an input port, an input protection filter circuit module, a charging circuit module and an output port. A mobile phone charging private protocol and a standard charging protocol are implanted into an internal ROM (Read Only Memory) of a chip after being compiled by utilizing an integrated structure of a fast charging protocol controller, a voltage reduction controller and two groups of power MOS (Metal Oxide Semiconductor) tubes, PDO power gear configuration is synchronously burnt, and then a chip MCU (Microprogrammed Control Unit) changes an output voltage value by adjusting a feedback circuit and a duty ratio; according to the vehicle-mounted high-power USB charging module, the BOM cost and the design difficulty of the vehicle-mounted high-power USB charging module are reduced, the structure of the vehicle-mounted high-power USB charging module is simplified, and the production and manufacturing cost is reduced.

Description

Technical Field

[0001] This utility model relates to the field of vehicle USB charging technology, and mainly to an integrated step-down proprietary protocol vehicle USB charging module. Background Technology

[0002] Currently, the charging protocols used in cars are limited, with most using the BC1.2 protocol and a few high-end cars equipped with a PD3.0 protocol 60W boost / buck solution. As a result, the actual user experience of existing PD chargers is the same as that of ordinary chargers due to the proprietary protocols of mobile phone suppliers.

[0003] Chinese invention patent application number 202310701800.5 discloses a vehicle-mounted high-power USB charging module. Through the configuration of a first charging circuit, a second charging circuit, a first USB interface, and a second USB interface, and in conjunction with CPSQ5206_A chip, CPSQ8841_A chip, CPSQ5206_B chip, and CPSQ8841_B chip, it can support not only standard charging protocols but also proprietary charging protocols. This allows it to meet the high-power charging requirements of most mobile phones on the market and greatly alleviate people's anxiety about low battery and slow charging speed.

[0004] However, the above-mentioned technical solutions involve a complex structure for the vehicle-mounted high-power USB charging module, which requires two sets of chips for each USB interface, resulting in high production costs. Utility Model Content

[0005] To address the above issues, this utility model provides an integrated step-down proprietary protocol vehicle USB charging module. By using the CPSQ8831 step-down chip as the main chip and leveraging its integrated fast charging protocol controller, step-down controller, and two sets of power MOSFETs, the BOM cost and design complexity of the vehicle high-power USB charging module are reduced, the structure of the vehicle high-power USB charging module is simplified, and the manufacturing cost is lowered.

[0006] The technical solution adopted in this application for an integrated step-down proprietary protocol vehicle USB charging module is as follows:

[0007] An integrated step-down proprietary protocol vehicle USB charging module includes:

[0008] Input port, input protection filter circuit module, charging circuit module, and output port;

[0009] The input port is connected to the vehicle power supply and receives the DC current input from the vehicle power supply.

[0010] The input protection and filtering circuit module is connected to the input port and the charging circuit module. The input protection and filtering circuit module provides reverse connection protection, surge protection and filtering for the vehicle power supply.

[0011] The charging circuit module connects the input protection filter circuit module and the output port. The charging circuit module includes a chip, a charging circuit, and a control circuit. The chip is connected to the input protection filter circuit module, the charging circuit, and the control circuit. The charging circuit is connected to the chip and the output port. The chip uses the charging circuit to convert the current received from the vehicle power supply at the input port into DC power and supply it to the output port. The control circuit is connected to the chip and the output port. The chip uses the control circuit to control the charging circuit to supply power to the output port based on a standard charging protocol or a proprietary charging protocol.

[0012] The output port is connected to an external device to be charged, and the device is charged.

[0013] As an improvement, an input anti-reverse diode D4 is also connected to the input port. The positive terminal of the input anti-reverse diode D4 is connected to the input port, and the negative terminal of the input anti-reverse diode D4 is grounded.

[0014] As an improvement, the input protection filter circuit module includes a voltage stabilizing filter unit, an input reverse protection unit, and a filter unit. The voltage stabilizing filter unit stabilizes the voltage in the input protection filter circuit module and removes noise signals. The input reverse protection unit prevents the current in the input protection filter circuit module from flowing in reverse. The filter unit removes noise signals from the input protection filter circuit module.

[0015] As an improvement, the voltage regulation and filtering unit includes a bidirectional diode D2, a capacitor C7, and a capacitor C8. The bidirectional diode D2 is connected between the input port and ground, and both the capacitor C7 and the capacitor C8 are connected between the input port and ground.

[0016] As an improvement, the input anti-reverse unit includes a PMOS transistor Q1, a Zener diode D3, and a resistor R13. The source of the PMOS transistor Q1 is connected to the input port, the gate of the PMOS transistor Q1 is connected to the Zener diode D3 and the resistor R13, and the drain of the PMOS transistor Q1 is connected to the filter unit. The anode of the Zener diode D3 is connected to both the PMOS transistor Q1 and the resistor R13, and the cathode of the Zener diode D3 is connected to the filter unit. One end of the resistor R13 is connected to both the PMOS transistor Q1 and the Zener diode D3, and the other end of the resistor R13 is grounded.

[0017] As an improvement, the filtering unit includes capacitor C9, inductor L2, capacitor C6, capacitor C17, capacitor C10, and capacitor C18. Capacitor C9 is connected between the input anti-reverse unit and ground. Inductor L2 is connected between capacitor C9 and capacitor C6. Capacitors C17, C10, and C18 are all connected between inductor L2 and ground.

[0018] As an improvement, the chip includes an integrated MCU, a buck controller, a charging protocol controller, and two sets of power MOSFETs;

[0019] The charging protocol programmed into the MCU communicates with the external mobile device to obtain information on the required output power.

[0020] The buck controller is connected to the MCU and the power MOSFET, and the buck controller converts the voltage output by the chip;

[0021] The charging protocol controller is connected to the MCU, and the charging protocol controller is responsible for identifying and processing standard charging protocols or proprietary charging protocols.

[0022] The power MOSFET controls the on / off state and magnitude of the current within the chip.

[0023] As an improvement, the charging circuit includes a charging filter unit and a capacitor C19;

[0024] The charging filter unit is connected to the OUT pin on the chip and the USB. - Between the IN pins, the charging filter unit includes a resistor R1, an inductor L1, capacitors C13, C14, C15, and C16. The resistor R1 is connected to the OUT pin and the USB port. - Between the IN pins, the inductor L1 is connected to the USB. - Between the IN pin and the SW pin on the chip, capacitors C13, C14, C15 and C16 are all connected between the inductor L1 and ground.

[0025] The capacitor C19 is connected to the USB port on the chip. - The OUT pin is connected to ground, and the USB... - The OUT pin is connected to the VBUS on the output port.

[0026] As an improvement, the control circuit is connected between the CC1 pin on the chip and the CC1 pin of the output port, and between the CC2 pin on the chip and the CC2 pin of the output port. The control circuit is provided with transient voltage suppression diodes TVS1 and TVS2, capacitors C1, C2, C3, and C4, and resistors R2 and R3.

[0027] The beneficial effects of this utility model are as follows:

[0028] This invention uses the CPSQ8831 step-down chip as the main chip, utilizing its integrated fast charging protocol controller, step-down controller, and two sets of power MOSFETs. After the mobile phone charging private protocol and standard charging protocol are written, they are embedded into the chip's internal ROM. The PDO power level configuration is also programmed simultaneously. Then, the chip's MCU changes the output voltage value by adjusting the feedback circuit and duty cycle to achieve fast charging. This reduces the BOM cost and design difficulty of the in-vehicle high-power USB charging module, simplifies the structure of the in-vehicle high-power USB charging module, and reduces manufacturing costs.

[0029] In summary, the in-vehicle USB charging module of this utility model is based on the CPSQ8831 step-down chip and includes BC1.2 protocol, APPLE2.4A, QC3.0, QC2.0, PD3.0, Huawei FCP / SCP and standard charging protocols, which makes the manufacturing cost of the in-vehicle USB charging module low and the structure simple, making it particularly suitable for the field of in-vehicle USB charging technology. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the connection structure of the vehicle-mounted USB charging module of this utility model;

[0031] Figure 2 This is a circuit diagram of the CPSQ8831 chip and its peripheral circuits according to this utility model;

[0032] Figure 3 This is a schematic diagram of the internal structure of the CPSQ8831 chip of this utility model. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0034] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or component 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 utility model.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] Example:

[0037] like Figure 1 As shown, an integrated step-down proprietary protocol vehicle USB charging module includes:

[0038] Input port 100, input protection filter circuit module 200, charging circuit module 300 and output port 400;

[0039] The input port 100 is connected to the vehicle power supply and receives the DC current input from the vehicle power supply. The input port 100 is a connector such as a plug, socket, or pin header and female header.

[0040] The input protection and filtering circuit module 200 is connected to the input port 100 and the charging circuit module 300. The input protection and filtering circuit module 200 provides reverse connection protection, surge protection and filtering for the vehicle power supply.

[0041] The charging circuit module 300 connects the input protection filter circuit module 200 to the output port 400. The charging circuit module 300 includes a chip 301, a charging circuit 302, and a control circuit 303. The chip 301 is connected to the input protection filter circuit module 200, the charging circuit 302, and the control circuit 303. The charging circuit 302 connects the chip 301 to the output port 400. The chip 301 uses the charging circuit 302 to convert the current received from the vehicle power supply at the input port 100 into DC-DC power and supply it to the output port 400. The control circuit 303 connects the chip 301 to the output port 400. The chip 301 uses the control circuit 303 to control the charging circuit 302 to supply power to the output port 400 based on a standard charging protocol or a proprietary charging protocol.

[0042] The output port 400 is connected to an external device to be charged, and is a USB Type-C interface.

[0043] It should be noted that this utility model is based on the CPSQ8831 chip, which uses the dual MOS transistors built into the CPSQ8831 chip for power conversion. The chip's internal MCU (microcontroller unit) communicates with the external mobile device through a charging protocol "handshake" to obtain the charging power information required by the device. Then, the MCU changes the output voltage by adjusting the feedback circuit and duty cycle, thereby achieving fast charging.

[0044] Specifically, when an external mobile device is connected to the in-vehicle USB fast charging module, the MCU inside the CPSQ8831 chip begins to operate. It communicates with the mobile device (such as a mobile phone or tablet) through built-in charging protocols (such as PD3.1 / PPS, QC2.0 / 3.0, etc.). This process is similar to both parties confirming each other's identity and needs; the chip asks the device, "How much charging power do you need?", and the device replies with its required charging power and other relevant information.

[0045] After receiving the charging power information from the mobile device, the MCU knows how much power to provide to meet its fast charging needs. This is the basis for subsequent adjustments to the output voltage.

[0046] The MCU adjusts the output voltage by modifying the feedback circuit based on the acquired power information. The feedback circuit monitors the output voltage status and feeds this information back to the MCU. The MCU controls the on and off times of the built-in dual MOSFETs by changing the duty cycle. The duty cycle refers to the ratio of the on-time to the total time within a pulse cycle.

[0047] For example, when it is necessary to increase the output voltage, the MCU will increase the on-time of the MOSFET (i.e., increase the duty cycle) so that more electrical energy can be transferred to the output terminal, thereby increasing the output voltage; conversely, when it is necessary to decrease the output voltage, the duty cycle will be reduced, the on-time of the MOSFET will be reduced, and the output voltage will decrease.

[0048] Through the voltage adjustment process described above, the output voltage reaches the value required by the mobile device, and fast charging begins. During charging, the MCU continuously monitors the feedback circuit and dynamically adjusts the duty cycle to ensure stable output voltage, thereby maintaining the fast charging state.

[0049] Furthermore, it should be noted that the PSQ8831 chip is an ultra-simplified automotive-grade USB-PD fast charging chip launched by EasyCharge Semiconductor. It integrates the fast charging protocol controller, buck controller and two power MOSFETs into one chip, reducing BOM cost and design complexity.

[0050] Supports multiple fast charging protocols including PD3.1 / PPS, QC2.0 / 3.0, BC1.2CDP / DCP, Apple 5V2.4A, AFC, and SCPA / B, offering broad protocol support. It boasts excellent performance, with a recommended input voltage range of 5.5V to 36V and a maximum withstand voltage of 40V; an output voltage range of 3.3V to 21V, a 3A output current, and a power output of up to 35W. It features comprehensive protection functions, including CC, DP / DM to VBUS short-circuit protection, as well as OTP, OVP, UVP, OCP, and SCP protection. Optimized EMC performance, it supports configurable 250kHz and 420kHz switching frequencies and spread spectrum functionality. AEC-Q100 certified, it is suitable for automotive USB QC3.0, USB-C, and PD charging interfaces, meeting the charging needs of new energy vehicles. It supports single C or A ports and can also cascade two chips for power reduction applications, suitable for charging smartphones, tablets, and other smart devices.

[0051] like Figure 2 As shown, in addition, the vehicle-mounted USB charging module of this utility model also has an input reverse protection diode D4 connected to the input port 100. The positive terminal of the input reverse protection diode D4 is connected to the input port 100, and the negative terminal of the input reverse protection diode D4 is grounded. By setting the input reverse protection diode D4, the reverse current flow in the input port 100 is prevented.

[0052] Furthermore, the input protection filter circuit module 200 includes a voltage stabilizing filter unit 201, an input reverse protection unit 202, and a filter unit 203. The voltage stabilizing filter unit 201 stabilizes the voltage in the input protection filter circuit module 200 and removes noise signals. The input reverse protection unit 202 prevents the current in the input protection filter circuit module 200 from flowing in the reverse direction. The filter unit 203 removes noise signals from the input protection filter circuit module 200.

[0053] Specifically, the voltage stabilizing filter unit 201 includes a bidirectional diode D2, a capacitor C7, and a capacitor C8. The bidirectional diode D2 is connected between the input port 100 and ground, and the capacitors C7 and C8 are both connected between the input port 100 and ground.

[0054] More specifically, the input anti-reverse unit 202 includes a PMOS transistor Q1, a Zener diode D3, and a resistor R13. The source of the PMOS transistor Q1 is connected to the input port 100, the gate of the PMOS transistor Q1 is connected to the Zener diode D3 and the resistor R13, and the drain of the PMOS transistor Q1 is connected to the filter unit 203. The anode of the Zener diode D3 is connected to both the PMOS transistor Q1 and the resistor R13, and the cathode of the Zener diode D3 is connected to the filter unit 203. One end of the resistor R13 is connected to both the PMOS transistor Q1 and the Zener diode D3, and the other end of the resistor R13 is grounded.

[0055] More specifically, the filter unit 203 includes capacitor C9, inductor L2, capacitor C6, capacitor C17, capacitor C10, and capacitor C18. Capacitor C9 is connected between the input anti-reverse unit 202 and ground. Inductor L2 is connected between capacitor C9 and capacitor C6. Capacitors C17, C10, and C18 are all connected between inductor L2 and ground.

[0056] like Figure 3 As shown, the chip 301 includes an integrated MCU 3011, a buck controller 3012, a charging protocol controller 3013, and two sets of power MOSFETs 3014;

[0057] The charging protocol programmed into the MCU3011 communicates with the external mobile device to obtain information on the required output power.

[0058] The buck controller 3012 is connected to the MCU 3011 and the power MOSFET 3014, and the buck controller 3012 converts the voltage output by the chip 301;

[0059] The charging protocol controller 3013 is connected to the MCU 3011, and the charging protocol controller 3013 is responsible for identifying and processing standard charging protocols or proprietary charging protocols.

[0060] The power MOSFET 3014 controls the on / off state and magnitude of the current within the chip 301.

[0061] Among them, the charging protocol controller 3013 is divided into a USB Power Delivery protocol controller, a BC1.2 (Battery Charging Specification 1.2) Dedicated Charging Port (DCP) / Charging Downlink Port (CDP) protocol controller and a 2.4A (Ampere) Shunt Mode protocol controller.

[0062] like Figure 2 As shown, the charging circuit 302 includes a charging filter unit 3020 and a capacitor C19;

[0063] The charging filter unit 3020 is connected to the OUT pin on the chip 301 and the USB. - Between the IN pins, the charging filter unit 3020 includes a resistor R1, an inductor L1, capacitors C13, C14, C15, and C16. The resistor R1 is connected to the OUT pin and the USB pin. - Between the IN pins, the inductor L1 is connected to the USB. - Between the IN pin and the SW pin on the chip 301, capacitors C13, C14, C15 and C16 are all connected between the inductor L1 and ground.

[0064] The capacitor C19 is connected to the USB port on chip 301. - The OUT pin is connected to ground, and the USB... - The OUT pin is connected to the VBUS on the output port 400.

[0065] The control circuit 303 is connected between the CC1 pin on the chip 301 and the CC1 pin on the output port 400, and between the CC2 pin on the chip 301 and the CC2 pin on the output port 400. The control circuit 303 is provided with transient voltage suppression diodes TVS1 and TVS2, capacitors C1, C2, C3, and C4, and resistors R2 and R3.

[0066] When the reverse voltage across a TVS diode is lower than its breakdown voltage, it is in a high-resistance state and essentially does not conduct. When the reverse voltage exceeds the breakdown voltage, its impedance drops rapidly, absorbing most of the energy quickly and clamping the voltage to a relatively low level, thus protecting downstream circuit components. For example, in circuits requiring lightning protection or electrostatic discharge protection, TVS diodes can respond quickly and suppress instantaneous high voltages.

[0067] Work process:

[0068] After a device (such as a mobile phone) is connected to the output port 400, the fast charging protocol controller on the PSQ8831 chip detects the fast charging protocol supported by the connected device, such as PD 3.1 / PPS, QC 2.0 / 3.0, BC 1.2 CDP / DCP, etc., through the control circuit 303 on the detection terminal (pin CC1 and pin CC2). Based on the detection results, it negotiates charging voltage, current and other parameters with the device to determine the optimal charging mode.

[0069] The step-down controller changes the output voltage value by adjusting the feedback circuit and duty cycle, converting the input 12V-36V DC power into 3.3V-21V DC power to meet the charging needs of different devices. Then, the DC power is delivered to the VBUS at the output port through the charging circuit to charge the device to be charged.

[0070] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An integrated step-down proprietary protocol vehicle USB charging module, characterized in that, include: Input port (100), input protection filter circuit module (200), charging circuit module (300) and output port (400); The input port (100) is connected to the vehicle power supply and receives the DC current input by the vehicle power supply; The input protection filter circuit module (200) is connected to the input port (100) and the charging circuit module (300). The input protection filter circuit module (200) provides reverse connection protection, surge protection and filtering for the vehicle power supply. The charging circuit module (300) is connected to the input protection filter circuit module (200) and the output port (400). The charging circuit module (300) includes a chip (301), a charging circuit (302), and a control circuit (303). The chip (301) is connected to the input protection filter circuit module (200), the charging circuit (302), and the control circuit (303). The charging circuit (302) is connected to the chip (301) and the output port (400). The chip (301) supplies power to the output port (400) through the charging circuit (302) by converting the current received by the vehicle power supply at the input port (100) into DC-DC power. The control circuit (303) is connected to the chip (301) and the output port (400). The chip (301) controls the charging circuit (302) to supply power to the output port (400) based on a standard charging protocol or a proprietary charging protocol through the control circuit (303). The output port (400) is connected to an external device to be charged, and the device to be charged is charged.

2. The integrated step-down proprietary protocol vehicle USB charging module according to claim 1, characterized in that: An input anti-reverse diode D4 is also connected to the input port (100). The positive terminal of the input anti-reverse diode D4 is connected to the input port (100), and the negative terminal of the input anti-reverse diode D4 is grounded.

3. The integrated step-down proprietary protocol vehicle USB charging module according to claim 1, characterized in that: The input protection filter circuit module (200) includes a voltage stabilizing filter unit (201), an input anti-reverse unit (202), and a filter unit (203). The voltage stabilizing filter unit (201) stabilizes the voltage in the input protection filter circuit module (200) and removes noise signals. The input anti-reverse unit (202) prevents the current on the input protection filter circuit module (200) from flowing in reverse. The filter unit (203) removes noise signals on the input protection filter circuit module (200).

4. The integrated step-down proprietary protocol vehicle USB charging module according to claim 3, characterized in that: The voltage stabilizing filter unit (201) includes a bidirectional diode D2, a capacitor C7 and a capacitor C8. The bidirectional diode D2 is connected between the input port (100) and ground, and the capacitors C7 and C8 are both connected between the input port (100) and ground.

5. The integrated step-down proprietary protocol vehicle USB charging module according to claim 3, characterized in that: The input anti-reverse unit (202) includes a PMOS transistor Q1, a Zener diode D3, and a resistor R13. The source of the PMOS transistor Q1 is connected to the input port (100), the gate of the PMOS transistor Q1 is connected to the Zener diode D3 and the resistor R13, and the drain of the PMOS transistor Q1 is connected to the filter unit (203). The anode of the Zener diode D3 is connected to the PMOS transistor Q1 and the resistor R13, and the cathode of the Zener diode D3 is connected to the filter unit (203). One end of the resistor R13 is connected to the PMOS transistor Q1 and the Zener diode D3, and the other end of the resistor R13 is grounded.

6. The integrated step-down proprietary protocol vehicle USB charging module according to claim 3, characterized in that: The filtering unit (203) includes capacitor C9, inductor L2, capacitor C6, capacitor C17, capacitor C10 and capacitor C18. Capacitor C9 is connected between the input anti-reverse unit (202) and ground. Inductor L2 is connected between capacitor C9 and capacitor C6. Capacitors C17, C10 and C18 are all connected between inductor L2 and ground.

7. The integrated step-down proprietary protocol vehicle USB charging module according to claim 1, characterized in that: The chip (301) includes an integrated MCU (3011), a buck controller (3012), a charging protocol controller (3013), and two sets of power MOSFETs (3014). The charging protocol programmed into the MCU (3011) communicates with the external mobile device to obtain information on the required output power. The buck controller (3012) is connected to the MCU (3011) and the power MOSFET (3014), and the buck controller (3012) converts the voltage output by the chip (301); The charging protocol controller (3013) is connected to the MCU (3011), and the charging protocol controller (3013) is responsible for identifying and processing standard charging protocols or proprietary charging protocols. The power MOSFET (3014) controls the on / off state and magnitude of the current within the chip (301).

8. The integrated step-down proprietary protocol vehicle USB charging module according to claim 1, characterized in that: The charging circuit (302) includes a charging filter unit (3020) and a capacitor C19; The charging filter unit (3020) is connected between the OUT pin and the USB-IN pin on the chip (301). The charging filter unit (3020) includes a resistor R1, an inductor L1, and capacitors C13, C14, C15, and C16. The resistor R1 is connected between the OUT pin and the USB-IN pin. The inductor L1 is connected between the USB-IN pin and the SW pin on the chip (301). The capacitors C13, C14, C15, and C16 are all connected between the inductor L1 and ground. The capacitor C19 is connected between the USB-OUT pin on the chip (301) and ground, and the USB-OUT pin is connected to the VBUS on the output port (400).

9. The integrated step-down proprietary protocol vehicle USB charging module according to claim 1, characterized in that: The control circuit (303) is connected between the CC1 pin on the chip (301) and the CC1 pin on the output port (400), and between the CC2 pin on the chip (301) and the CC2 pin on the output port (400). The control circuit (303) is provided with transient voltage suppression diodes TVS1 and TVS2, capacitors C1, C2, C3, and C4, and resistors R2 and R3.

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