Low voltage buffer circuit for mobile phone buttons

Abstract

The low-voltage buffer circuit and mode adapted for the keys of a mobile phone with compartment diving belong to the field of mechanical structure. The components of the buffer circuit include: NPN or PNP or field effect switching transistors, diodes, resistors, and voltage-stabilizing diodes; the location and connection method of the voltage buffer circuit: a voltage buffer circuit is added to the main board PCB or the peripheral PCB board: the characteristics are: the base or emitter voltage of the transistor is constant by using the voltage-stabilizing diode, and at the same time, a voltage-stabilizing diode or diode is connected in series in the emitter or base loop, and the diode is used as a voltage-stabilizing diode for its forward conduction constant voltage drop characteristics; the diode is directly connected to the mobile phone key switch; the NPN or PNP or field effect switching transistor in the peripheral power-off mode is connected in series to the power supply path, which is widely used in handheld electronic devices.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology; specifically, it uses a buffer circuit to reduce the voltage of a key electrode and cut off the 1.8 volt power supply mode of a SIM card and the 5 volt power supply mode of a USB. Background Art

[0002] With the continuous development of the communications industry, smartphones already have open source operating systems, coupled with hardware and software scalability, fully supporting secondary development by third parties.

[0003] The overall structure of a smartphone: A smartphone can be considered a pocket computer. It has a processor, memory, input and output devices (keyboard, display, USB interface, headphone interface, camera, etc.) and I / O channels. The mobile phone communicates with the base station through an air interface protocol (such as GSM, CDMA, PHS, etc.), and can transmit both voice and data.

[0004] The main circuit board of a smartphone is the most important component in the phone: it is located inside the smartphone and is connected to various components through data cables or contacts. The main circuit board can be said to be the core component of the mobile phone. It is responsible for the input, output, processing, and transmission of mobile phone signals, as well as the power supply and control of the entire machine. The design of the circuit boards of smartphones of different brands may be different. Some smartphones have only one circuit board, while some smartphones have a sub-circuit board in addition to the main circuit. The sub-circuit board generally connects to accessories such as interfaces and cameras. The main circuit board of a smartphone is installed with surface-mount components, which are arranged very closely, and the main chips on the circuit board are soldered on the circuit board in the form of BGA.

[0005] Smartphone circuit structure: The circuit of a smartphone is the core of the smartphone, responsible for the power supply, control and realization of various functions of the smartphone. The circuit of a smartphone mainly includes: RF circuit, voice circuit, processor and memory circuit, power and charging circuit, operation and display circuit, interface circuit, and other functional circuits (such as Bluetooth, antenna, radio, sensor, vibrator, camera circuit, etc.).

[0006] The specific design process includes:

[0007] Determination of the motherboard solution, determination of the mobile phone appearance, structural modeling, production and adjustment of the appearance prototype, structural design, structural design optimization, structural review, verification of large structural prototypes, etc.

[0008] In addition, it also has to go through the process of mold review, project follow-up during mold investment, mold trial and mold modification, trial production, and mass production.

[0009] For most current mobile phone motherboard circuits: except for the common end of the button electrode being grounded, the other ends are connected to the ground only when the button is pressed; when the button is not pressed, the other non-common ends are in an open floating connection state, and the voltage value is mostly between 1.5 and 4.0 volts.

[0010] Currently, there is a mobile phone designed with the Dayu method of flood control, which combines dredging and blocking in the "separate compartment waterproof mobile phone solution". The basic principle is to place "peripheral devices: such as SIM cards, speakers, microphones, headphones and USB sockets" that must interact with the outside world in the outer compartment, allowing water to penetrate, while the main board, battery, display screen, etc. are placed in a sealed compartment. There is no need to set up a waterproof door or specially designed sealing devices. This not only greatly reduces the difficulty of waterproofing, but also has excellent waterproofing effects.

[0011] The waterproof design of Apple and Samsung uses special waterproof rings and waterproof devices, rather than a simple "water-to-earth" four-wheel design; this not only greatly increases the cost and process difficulty; the cost is extremely high, and the final waterproof effect is still unsatisfactory. Summary of the invention

[0012] The defects of current mobile phone button electrodes:

[0013] Since the voltage value of the open floating electrode of the button is mostly between 1.5-4.0 volts, the exposed electrodes include 1.8 volts of the SIM card and 5 volts of the USB; when using a split-compartment waterproof mobile phone structure, these electrodes are exposed to the water medium of the outer compartment. Under relatively high voltage, long-term immersion in water will produce certain adverse electrolytic reactions.

[0014] Purpose of the present invention:

[0015] The addition of a voltage buffer circuit reduces the voltage of the open suspended electrode to below 0.3 volts by making the 1.8 volts of the key electrode and SIM card and the 5 volts of the USB power switch mode, so that no adverse electrolytic reaction will occur even if it is immersed in water for a long time.

[0016] Features of the present invention:

[0017] Simple in concept, low in cost and reliable in operation.

[0018] The location and connection method of the voltage buffer circuit: add a voltage buffer circuit on the mainboard PCB or peripheral PCB board: the so-called peripheral PCB board refers to the PCB board on which the SIM card, speaker, microphone, earphone and USB socket are soldered and used in the split-compartment diving mobile phone; the voltage buffer circuit is inserted into the path of the button electrode in a relay manner, and the original button electrode of the mainboard is directly connected to the voltage buffer circuit, and the voltage buffer circuit is then connected to the button electrode.

[0019] Devices and features of voltage buffer circuit: Zener diode is used to keep the base or emitter voltage of the triode constant. At the same time, a Zener diode or diode is connected in series in the emitter or base loop. The diode is used as a Zener diode due to its forward conduction constant voltage drop characteristic. The diode is directly connected to the mobile phone key switch.

[0020] The circuit characteristics are divided into NPN type and PNP type switching transistor circuits:

[0021] Circuit using NPN transistor:

[0022] A voltage buffer circuit is inserted between the mainboard and the electrode of key K. 1 Connected to the button electrode of the motherboard, resistor R 1 , is a voltage divider device, which makes the voltage of the connection end consistent with the voltage of the key electrode, or increases the voltage of the transistor Q 1 The current sourcing and sinking capabilities can generally be ignored. 1 , R 2 Directly connected.

[0023] Diode D 1 Here, as a voltage regulator, the germanium semiconductor can obtain a voltage drop of 0.2-0.3 volts; the resistor R 2 The resistance value should be selected to ensure that there is enough current to protect the voltage regulator diode D 1 The clamping effect of the voltage regulator diode D 1 The voltage value should be less than the transistor Q 1 The be junction voltage drop when the diode D is turned on 1 The sum of the conduction voltage drops; and the transistor Q 1 The be junction voltage drop when it is turned on.

[0024] When the mobile phone button K is pressed, it is equivalent to short-circuiting diode D 1 , Zener diode D 1 The voltage is directly applied to the transistor Q 1 be junction, transistor Q 1 When it is turned on, the voltage of the collector C drops to 0.2-0.3 volts. If a field effect tube is used, it will drop even lower, achieving the purpose of reducing the key electrode voltage of the motherboard.

[0025] Circuit using PNP transistor:

[0026] Resistor R 4 , resistor R 5 The function is to ensure that there is enough current to make the Zener diode D 4 , D 5 To ensure the normal operation of the voltage regulator tube; voltage regulator diode D 4 The voltage value should be less than the transistor Q 2The voltage drop of the eb junction when it is turned on is related to the diode D 3 The conduction voltage drop and voltage regulator diode D 4 The sum of the voltage regulation values; and the transistor Q 1 The voltage drop of the eb junction during conduction is related to the voltage regulator diode D 4 The sum of the regulated voltage values.

[0027] When the mobile phone button K is pressed, it is equivalent to short-circuiting diode D 3 , Zener diode D 4 The voltage is directly applied to the transistor Q 2 eb junction and voltage regulator diode D 4 On, transistor Q 2 When it is turned on, the voltage of the emitter e drops to 0.2-0.3 volts. If a field effect tube is used, it will drop even lower, achieving the purpose of reducing the key electrode voltage of the motherboard.

[0028] Peripheral power-off mode: By setting the phone to "diving mode" through the touch screen or key operation, you can turn off the 1.8 volt power supply of the SIM card and the 5 volt power supply of the USB, so that the exposed electrodes (the parts that cannot be waterproofed) are placed in a 0 volt state.

[0029] Further: triode also includes field effect tube. Like the crystal triode, the field effect tube is divided into: gate, drain, source, the gate is equivalent to the base, the drain and source are equivalent to the collector and emitter, and the current flows from the drain to the source.

[0030] Further: The technology of the present invention is not only applicable to mobile phones, but also to other handheld electronic devices: cameras, tablets.

[0031] The beneficial effect of the present invention is that when used in diving, the corrosion damage caused by electrolysis to the electrode contacts is reduced to a minimum. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of buffer circuit using NPN transistor

[0033] Figure 2 Schematic diagram of buffer circuit for circuit using PNP transistor

[0034] Description of the numbers: 20. Main board, 21. Button connecting wire. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings in terms of preferred embodiments:

[0036] like Figure 1 As shown:

[0037] The figure above shows that the key connection line (21) of the mainboard (20) is directly connected to the electrode of the mobile phone key K (volume, selection and other function keys), and the other end of the key K corresponds to the electrode which is often the common ground terminal. The mobile phone generally has 3-4 keys.

[0038] The figure below shows that a voltage buffer circuit is inserted between the mainboard and the electrode of key K. 1 Connected to the button electrode of the motherboard, resistor R 1 , is a voltage divider device, which makes the voltage of the connection end consistent with the voltage of the key electrode, or increases the voltage of the transistor Q 1 The current sourcing and sinking capabilities can generally be ignored. 1 , R 2 Directly connected.

[0039] Diode D 1 Here, as a voltage regulator, the germanium semiconductor can obtain a voltage drop of 0.2-0.3 volts; the resistor R 2 The resistance value should be selected to ensure that there is enough current to protect the voltage regulator diode D 1 The clamping effect of the voltage regulator diode D 1 The voltage value should be less than the transistor Q 1 The be junction voltage drop when the diode D is turned on 1 The sum of the conduction voltage drops; and the transistor Q 1 The be junction voltage drop when it is turned on.

[0040] When the mobile phone button K is pressed, it is equivalent to short-circuiting diode D 1 , Zener diode D 1 The voltage is directly applied to the transistor Q 1 be junction, transistor Q 1 When it is turned on, the voltage of the collector C drops to 0.2-0.3 volts. If a field effect tube is used, it will drop even lower, achieving the purpose of reducing the key electrode voltage of the motherboard.

[0041] like Figure 2 As shown:

[0042] Resistor R 4 , resistor R 5 The function is to ensure that there is enough current to make the Zener diode D 4 , D 5 To ensure the normal operation of the voltage regulator tube; voltage regulator diode D 4 The voltage value should be less than the transistor Q 2 The voltage drop of the eb junction when it is turned on is related to the diode D 3 The conduction voltage drop and voltage regulator diode D 4 The sum of the voltage regulation values; and the transistor Q 1The voltage drop of the eb junction during conduction is related to the voltage regulator diode D 4 The sum of the regulated voltage values.

[0043] When the mobile phone button K is pressed, it is equivalent to short-circuiting diode D 3 , Zener diode D 4 The voltage is directly applied to the transistor Q 2 eb junction and voltage regulator diode D 4 On, transistor Q 2 When it is turned on, the voltage of the emitter e drops to 0.2-0.3 volts. If a field effect tube is used, it will drop even lower, achieving the purpose of reducing the key electrode voltage of the motherboard.

[0044] Field effect transistor can also replace transistor Q because: gate, drain, source, the gate is equivalent to the base, the drain and source are equivalent to the collector and emitter, and the direction of current flow is from the drain to the source.

Claims

1. The low-voltage buffer circuit adapted for the keys of a mobile phone with compartment diving is characterized by: The components of the buffer circuit include: NPN or PNP or field effect switch transistors, diodes, resistors, and voltage regulator diodes; the location and connection method of the voltage buffer circuit: add a voltage buffer circuit on the main board PCB or peripheral PCB board: the peripheral PCB board refers to the PCB board used by the compartment diving mobile phone to weld the SIM card, speaker, microphone, earphone and USB socket; the voltage buffer circuit is inserted into the path of the key electrode in a relay manner, and the original key electrode of the main board is directly connected to the voltage buffer circuit, and the voltage buffer circuit is then connected to the key electrode; the electronic devices that need to be added to the main board in the peripheral power-off mode include: NPN or PNP or field effect switch transistors; voltage Devices and features of the buffer circuit: The base or emitter voltage of the transistor is constant by using a voltage-stabilizing diode. The diode is used as a voltage-stabilizing diode by using its constant voltage drop characteristic when it is forward-conducted. When the buffer circuit includes an NPN transistor, the collector of the transistor Q1 is connected to the original key electrode of the motherboard and one end of the resistor R1. The resistor R1 is a voltage-dividing device, which makes the voltage of the connection end consistent with the voltage of the original key electrode of the motherboard, or increases the ability to pull and sink current to the transistor Q1. The emitter of the transistor Q1 is connected to the anode of the diode D1, the cathode of the diode D1 is grounded, the diode D1 is connected to the key electrode, the base of the transistor Q1 is connected to the cathode of the voltage-stabilizing diode D2, and the transistor Q1 is stable. The anode of the voltage-stabilizing diode D2 is grounded; the diode D1 is used as a voltage-stabilizing diode here, and the voltage-stabilizing value of the diode D1 is smaller than the sum of the be junction voltage drop of the transistor Q1 when it is turned on and the conduction voltage drop of the diode D1, but larger than the be junction voltage drop of the transistor Q1 when it is turned on; when the buffer circuit includes a PNP transistor, the emitter of the transistor Q2 is connected to the original key electrode of the motherboard and one end of the resistor R4, the anode of the voltage-stabilizing diode D4 is connected to the collector of the transistor Q1 and grounded, the cathode of the voltage-stabilizing diode D4 is connected to the emitter of the transistor Q2, the base of the transistor Q2 is connected to the cathode of the voltage-stabilizing diode D5, the anode of the voltage-stabilizing diode D5 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the emitter of the transistor Q2. Grounded, diode D3 is connected to the button electrode; the voltage regulation value of the voltage regulator diode D4 is smaller than the sum of the eb junction voltage drop of the transistor Q2 being turned on, the conduction voltage drop of the diode D3 and the voltage regulation value of the voltage regulator diode D4, and is larger than the sum of the eb junction voltage drop of the transistor Q2 being turned on and the voltage regulation value of the voltage regulator diode D5; the NPN or PNP or field effect switch transistor in the peripheral power-off mode is connected in series to the power supply path, and the instructions of the motherboard CPU control the base or gate voltage to switch the NPN or PNP or field effect switch transistor switch; the mobile phone is set to switch the 1.8 volts of the SIM card and the 5 volts of the USB through the touch screen or button operation, so that the exposed electrodes are placed in a 0 volt state.

2. The low-voltage buffer circuit adapted for the keys of a compartmented diving mobile phone according to claim 1 is characterized in that: The diode is made of silicon material or germanium material.

3. The low-voltage buffer circuit adapted for the keys of a compartmented diving mobile phone according to claim 1 is characterized in that: The low voltage buffer circuit is also suitable for diving cameras and diving tablets.

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