CN203520090U - Hand-held terminal hard switching circuit - Google Patents
Hand-held terminal hard switching circuit Download PDFInfo
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- CN203520090U CN203520090U CN201320684567.6U CN201320684567U CN203520090U CN 203520090 U CN203520090 U CN 203520090U CN 201320684567 U CN201320684567 U CN 201320684567U CN 203520090 U CN203520090 U CN 203520090U
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Abstract
The utility model provides a hand-held terminal hard switching circuit. After jitter elimination is performed on a key pulse signal produced by an on/off key through a charge-discharge loop, filtering shaping is further performed on the key pulse signal through three phase inverters with schmitt triggers, and thus a complete-waveform monopulse trigger signal is produced, the flipping of a pulse trigger is triggered, an output voltage control terminal of a DC/DC converter is a high level and outputs a 3.3 V voltage for supplying a working voltage for a main circuit, and a hand-held terminal device is in a normal power-on working state. Compared with the prior art, the hand-held terminal hard switching circuit can enable a cell voltage, under the condition of being triggered by the on/off key, to output a working voltage enabling the hand-held terminal to start without a boost circuit, so that even though the electric quantity of a cell is reduced to 2V and below, the whole device can also be guaranteed to work normally.
Description
Technical field
The utility model relates to handheld terminal, and what be specifically related to is a kind of handheld terminal hard switching circuit.
Background technology
Handheld terminal refer to there is SOS, internal memory, CPU, video card, screen and keyboard, and portable data processing terminal, himself has battery, can move use.Generally speaking handheld terminal is divided into technical grade handheld terminal and consumption handheld terminal.Because handheld terminal has carrying convenience, and can carry out the independently function such as data acquisition and data processing, therefore be widely used in the fields such as logistics, mobile government, insurance and move transaction.
The switching on and shutting down of handheld terminal at present adopt hard switching conventionally, by being arranged on the switch key on handheld terminal, realize its start or shutdown.And the length of handheld terminal service time has much relations with battery, conventionally can not use for a long time, once in dead battery and situation about cannot charge, can only be by means of dry cell (No. 7 batteries of two joints) continuation of the journey, when but current handheld terminal passes through No. 7 powered battery after dead battery, the voltage producing due to No. 7 battery-end is more than 3V, there is decline process from high to low in it, if directly handheld terminal is powered without booster circuit, along with battery electric quantity drops to 2V when following, whole equipment cannot be worked.
Utility model content
For this reason, the purpose of this utility model is to provide a kind of handheld terminal hard switching circuit, while saving No. 7 powered battery to solve current handheld terminal by two, because of the problem that exists battery electric quantity to decline and cause whole equipment to use.
The purpose of this utility model is achieved through the following technical solutions.
A handheld terminal hard switching circuit, comprising:
Switching on and shutting down button JM2, for generation of key pulse signal;
Charging and discharging circuit, for carrying out debounce processing to described key pulse signal; Described charging and discharging circuit comprises resistance R 20, capacitor C 13, resistance R 21, resistance R 22, resistance R 23 and triode V9, one end of described switching on and shutting down button JM2 is connected with resistance R 20, the other end is divided into two-way, the capacitor C 13 of leading up to is connected with the emitter of triode V9, and the resistance R 21 of separately leading up to is connected with the base stage of triode V9;
Filtering shaping circuit, carries out filter shape for the key pulse signal to after debounce processing, and exports monopulse trigger pip; Described filtering shaping circuit comprises phase inverter U25A, phase inverter U25B and phase inverter U25C, and the collector of described triode V9 is connected with phase inverter U25A, and described phase inverter U25A is connected with phase inverter U25C by phase inverter U25B;
Pulse trigger U24A, No. 3 pin of described pulse trigger U24A are connected with the output terminal of described phase inverter U25C, described phase inverter U25C output monopulse trigger pip is to pulse trigger U24A, described pulse trigger U24A triggers upset, No. 5 pin output low levels of described pulse trigger U24A, No. 6 pin output high level;
DC/DC converter, No. 1 pin of described DC/DC converter is connected with No. 6 pin of pulse trigger U24A, and No. 2 pin of voltage controling end of described DC/DC converter are high level, No. 6 pin output 3.3V voltages of described DC/DC converter.
Preferably, described pulse trigger U24A is 74HC74 chip, after being connected with resistance R 26, its No. 5 pin are divided into two-way, one tunnel is connected with transistor V11 base stage, separately lead up to resistance R 27 respectively with the emitter of transistor V11, No. 2 pin of the voltage controling end of DC/DC converter be connected, described pulse trigger U24A5 pin output low level, described transistor V11 conducting.
Preferably, in described charging and discharging circuit, resistance R 20 is that 10K Ω, capacitor C 13 are that 4.7 μ F, resistance R 21 are 5.1K Ω.
Preferably, described DC/DC converter is MAX756 chip, and the battery low pressure of described DC/DC converter detects pin and is divided into two-way after by resistance R 3, and the inductance L 1 of leading up to is connected with No. 8 pin of DC/DC converter; The electric battery of another Lu Zeyu 3V connects.
The handheld terminal hard switching circuit that the utility model provides, the key pulse signal that switching on and shutting down button produces is by after charging and discharging circuit debounce, through three further filter shapes of the phase inverter with Schmidt trigger, produce the monopulse trigger pip of complete waveform, pulse trigger upset is triggered, thereby making the output voltage control end of DC/DC converter is high level, and export 3.3V voltage for main circuit provides operating voltage, make hand-held terminal device in normal boot-strap duty.Compared with prior art, the utility model does not need booster circuit can make cell voltage under switching on and shutting down button triggering situation, output makes the operating voltage of handheld terminal start, even if battery electric quantity drops to 2V when following, also can guarantee the normal work of whole equipment.
Accompanying drawing explanation
Fig. 1 is the circuit theory diagrams of the utility model handheld terminal hard switching circuit.
Embodiment
In order to make the purpose of this utility model, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the utility model is further elaborated.Should be appreciated that specific embodiment described herein is only in order to explain the utility model, and be not used in restriction the utility model.
Refer to shown in Fig. 1, Fig. 1 is the circuit theory diagrams of the utility model handheld terminal hard switching circuit.The utility model provides a kind of handheld terminal hard switching circuit, and the key pulse signal that it mainly produces by switching on and shutting down button triggers pulse trigger upset, thereby makes the work of DC/DC converter, and corresponding output can be for the 3.3V voltage of main circuit work.
The present embodiment hard switching circuit is by DC/DC converter MAX756, to convert the series voltage of No. 7 batteries of two joints the operating voltage of 3.3V to.It mainly includes switching on and shutting down button JM2, charging and discharging circuit, filtering shaping circuit, pulse trigger U24A and DC/DC converter.
Wherein JM2 button is switching on and shutting down button, when pressing JM2, due to the shake of button, can produce misoperation.Therefore need to pass through a charging and discharging circuit, described key pulse signal is carried out to debounce processing; Described charging and discharging circuit is by R20, C13, R21, R22, R23, V9 forms, and resistance R 20 for 10K Ω, capacitor C 13 be that 4.7 μ F, resistance R 21 are 5.1K Ω, one end of described switching on and shutting down button JM2 is connected with resistance R 20, the other end is divided into two-way, the capacitor C 13 of leading up to is connected with the emitter of triode V9, and the resistance R 21 of separately leading up to is connected with the base stage of triode V9, in described capacitor C 13, is parallel with resistance R 22.The present embodiment is by selecting R20, C13, and the value of R21, can make the duration of charging of charging and discharging circuit with the key that is all greater than JM2 discharge time and shake the time, thus the shake of cancel key effectively.
Filtering shaping circuit, comprise phase inverter U25A, phase inverter U25B and phase inverter U25C, the collector of described triode V9 is connected with phase inverter U25A, described phase inverter U25A is connected with phase inverter U25C by phase inverter U25B, it is mainly used in the key pulse signal after debounce processing to carry out filter shape, and exports monopulse trigger pip; The key pulse of the collector output of triode V9 is after debounce, again by three further filter shapes of the phase inverter with Schmidt trigger of U25 (74HC14), produce the complete monopulse of waveform, then by the upset of this pulse trigger U24A (74HC74D trigger).If the 5 pin output high level of U24A, 6 pin output low levels, this low level is input to 1 pin of DC/DC converter MAX756 and forbids end (Low level effective).Now MAX756 is in off state, but due to the existence of the impulse commutation pipe V5 in DC/DC change-over circuit, cell voltage still arrives output terminal 6 pin of DC/DC converter MAX756 through pulse commutator tube V5.Therefore, in circuit, also must add a transistor V11 as on-off element.When the 6 pin output low levels of U24A make MAX756 in illegal state, the 5 pin output high level of U24A make transistor V11 in cut-off state, thereby make battery to the path of the power supply VCC of main circuit in thorough off state, machine is in off-mode, and complete machine electric current is minimum during shutdown, through measuring, be no more than 5uA.When key pulse triggers U24A (74HC74D trigger) upset, the 5 pin output low levels of U24A, during 6 pin output high level, MAX756 is in running order, because output voltage control end 2 pin are high level, so the voltage of output+3.3V.Meanwhile, the 5 pin output low levels of U24A impel transistor V11 in conducting state, and MAX756 output can be main circuit like this provides working power, and machine is in open state.The 5 pin LBI of MAX756 are detection pins of battery low-voltage, if the voltage drop on this pin is to below internal reference reference voltage 1.25V, the 4 pin LBO of MAX756 (output of open-drain type) just can output low level, can be used as battery low pressure alarming signal.
In addition, under open state, the output SWPW of single-chip microcomputer remains low level.When single-chip microcomputer changes SWPW output into high level, the negative circuit output low level consisting of V10, makes U24A put 1 end effective, the 5 pin output high level of U24A, and 6 pin output low levels, machine will be shut down, so SWPW can be used as " automatic shutdown " signal.Because 1/O mouth when the single-chip microcomputer electrification reset is output as high level, SWPW high level during reset can cause " reset error cut-off machine " phenomenon.For preventing the generation of this phenomenon, in SWPW output circuit, added by R25, the charge circuit that C14 forms, suitably select R25, the value of C14, after reset, at R25, the threshold level 0.7V that C14 charge circuit is not charged to V10 conducting is set to low level by SWPW before, just can avoid " reset error cut-off machine " phenomenon.
The foregoing is only preferred embodiment of the present utility model; not in order to limit the utility model; all any modifications of doing within spirit of the present utility model and principle, be equal to and replace and improvement etc., within all should being included in protection domain of the present utility model.
Claims (4)
1. a handheld terminal hard switching circuit, is characterized in that, comprising:
Switching on and shutting down button JM2, for generation of key pulse signal;
Charging and discharging circuit, for carrying out debounce processing to described key pulse signal; Described charging and discharging circuit comprises resistance R 20, capacitor C 13, resistance R 21, resistance R 22, resistance R 23 and triode V9, one end of described switching on and shutting down button JM2 is connected with resistance R 20, the other end is divided into two-way, the capacitor C 13 of leading up to is connected with the emitter of triode V9, and the resistance R 21 of separately leading up to is connected with the base stage of triode V9;
Filtering shaping circuit, carries out filter shape for the key pulse signal to after debounce processing, and exports monopulse trigger pip; Described filtering shaping circuit comprises phase inverter U25A, phase inverter U25B and phase inverter U25C, and the collector of described triode V9 is connected with phase inverter U25A, and described phase inverter U25A is connected with phase inverter U25C by phase inverter U25B;
Pulse trigger U24A, No. 3 pin of described pulse trigger U24A are connected with the output terminal of described phase inverter U25C, described phase inverter U25C output monopulse trigger pip is to pulse trigger U24A, described pulse trigger U24A triggers upset, No. 5 pin output low levels of described pulse trigger U24A, No. 6 pin output high level;
DC/DC converter, No. 1 pin of described DC/DC converter is connected with No. 6 pin of pulse trigger U24A, and No. 2 pin of voltage controling end of described DC/DC converter are high level, No. 6 pin output 3.3V voltages of described DC/DC converter.
2. handheld terminal hard switching circuit according to claim 1, it is characterized in that, described pulse trigger U24A is 74HC74 chip, after being connected with resistance R 26, its No. 5 pin are divided into two-way, one tunnel is connected with transistor V11 base stage, separately lead up to resistance R 27 respectively with the emitter of transistor V11, No. 2 pin of the voltage controling end of DC/DC converter be connected, described pulse trigger U24A5 pin output low level, described transistor V11 conducting.
3. handheld terminal hard switching circuit according to claim 1, is characterized in that, in described charging and discharging circuit, resistance R 20 is that 10K Ω, capacitor C 13 are that 4.7 μ F, resistance R 21 are 5.1K Ω.
4. handheld terminal hard switching circuit according to claim 1, it is characterized in that, described DC/DC converter is MAX756 chip, and the battery low pressure of described DC/DC converter detects pin and is divided into two-way after by resistance R 3, and the inductance L 1 of leading up to is connected with No. 8 pin of DC/DC converter; The electric battery of another Lu Zeyu 3V connects.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320684567.6U CN203520090U (en) | 2013-10-30 | 2013-10-30 | Hand-held terminal hard switching circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320684567.6U CN203520090U (en) | 2013-10-30 | 2013-10-30 | Hand-held terminal hard switching circuit |
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| Publication Number | Publication Date |
|---|---|
| CN203520090U true CN203520090U (en) | 2014-04-02 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201320684567.6U Expired - Fee Related CN203520090U (en) | 2013-10-30 | 2013-10-30 | Hand-held terminal hard switching circuit |
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| CN (1) | CN203520090U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103973287B (en) * | 2014-05-21 | 2017-01-04 | 华为技术有限公司 | On/off circuit |
| CN107577535A (en) * | 2017-09-01 | 2018-01-12 | 深圳市智微智能科技开发有限公司 | The method and Related product of one key control video card video memory |
-
2013
- 2013-10-30 CN CN201320684567.6U patent/CN203520090U/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103973287B (en) * | 2014-05-21 | 2017-01-04 | 华为技术有限公司 | On/off circuit |
| CN107577535A (en) * | 2017-09-01 | 2018-01-12 | 深圳市智微智能科技开发有限公司 | The method and Related product of one key control video card video memory |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20140402 Termination date: 20181030 |