CN103929164A - Device with controllable switch end voltage - Google Patents

Abstract

The invention discloses a device with the controllable switch end voltage. The device comprises a switching signal unit and a bias unit, wherein the switching signal unit is used for outputting corresponding switching signals according to the state of a switch, and the switch is coupled between the switching signal unit and the output end of a power supply; the bias unit is coupled to the switching signal unit and used for outputting bias voltage to the switching signal unit. When the switch is turned off and conducting liquid and/or steam of the conducting liquid exists in the switch, the bias unit is matched with the switching signal unit to control the end voltage of the switch and the current flowing through the switch. Through the technical scheme, the switch end voltage can be lower than 1V when the switch is turned off, and the electrochemical reaction of the switch is greatly restrained; consequently, the service life of the switch is prolonged, and meanwhile the possibility of oxy-hydrogen explosion is eliminated.

Description

The device that switch terminals voltage is controlled

Technical field

The present invention generally relates to domestic circuit field, more specifically, relates to one under wet environment, can effectively reduce the device of switch terminals voltage.

Background technology

Switch is commonly used to start or cut out electrical appliance, and switch also can be used for selecting the different working modes of electrical appliance, and switch is the device contacting between people and electrical appliance for realizing.Current have a lot of electrical appliances to comprise the power supply such as rechargeable battery or dry cell, so electrical appliance contains the power supply that output voltage is greater than 1V, and on market, the terminal voltage of the switch of general electrical appliance approximates electric power output voltage or higher than electric power output voltage.

As everyone knows, as the electrical appliance of electric toothbrush, razors or hair removal Device and so on, be often positioned over and in moist toilet and use procedure thereof or cleaning process, have an opportunity to touch the various aqueous solution.The aqueous solution normally conducts electricity, this aqueous solution is in the time that the water-stop of electrical appliance goes wrong, can make to have conductivity water solution or conductivity water solution vapor between the contact that has potential difference of switch inside, or conductivity water solution and aqueous solution vapour mixture, and the liquid of this conduction or gas or liquids and gases mixture are under the effect of above-mentioned switch terminals voltage, can produce electrochemical reaction, this type of electrochemical reaction will be corroded switch, make switch failure.

Therefore, need one badly and can make switch be applicable under wet environment, and there is higher stability and the circuit of fail safe.

Summary of the invention

For above problem, the invention provides a kind of can steady operation and the safe controlled device of switch terminals voltage under wet environment.

One aspect of the present invention has proposed a kind of controlled device of terminal voltage of switch, comprising: switching signal unit, for according to the state of switch, export corresponding switching signal, and described switch is coupled between described switching signal unit and the output of power supply; Bias unit, is coupled to described switching signal unit, for to described switching signal unit output offset voltage; Wherein, when described switch disconnects and when its inside has the steam of conducting liquid and/or conducting liquid, described bias unit matches with described switching signal unit, to control the electric current of the terminal voltage of described switch and the described switch of flowing through.

Preferably, described switching signal unit comprises the first transistor, and described switch is coupled between described the first transistor and power supply, for controlling the break-make of the current path between described the first transistor and described power supply.

Preferably, described the first transistor is bipolar transistor, one end of described switch is coupled to the emitter of described the first transistor, wherein, PN junction between emitter and the base stage of described switch and described the first transistor is connected and is formed the first series circuit, the upper offset part parallel connection of described the first series circuit and described bias unit; Or NP knot between emitter and the base stage of described switch and described the first transistor formation the second series circuit of connect, the below-center offset part parallel connection of described the second series circuit and described bias unit.

Preferably, described first and second series circuit also comprises at least one resistance.

Preferably, in the time that described switch disconnects, if there is the steam of conducting liquid and/or conducting liquid in described switch inside, the state of described the first transistor in conducting; If described switch is inner dry, the state of described the first transistor in cut-off.

Preferably, described device also comprises: motor, described motor is coupled to the output of described switching signal unit.

Preferably, described device also comprises: output module, the motor that comprises transistor seconds and be in series with described transistor seconds; Wherein, described output module is coupled to the output of described switching signal unit, and output signal based on described switching signal unit configures the operating state of described motor.

Preferably, at least one pull-up resistor of connecting between the output of described switching signal unit and low level.

Preferably, described circuit also comprises signal analyse block, described signal analyse block is coupling between described output module and the output of described switching signal unit, to be used for controlling the control signal of described output module according to the output signal output of described switching signal unit.

Preferably, described transistor seconds is field-effect transistor, and wherein, described motor in series is to the drain electrode of described transistor seconds.

Preferably, described transistor seconds is bipolar transistor, and wherein, described motor in series is to the collector electrode of described transistor seconds.

Preferably, described the first transistor is field effect transistor, one end of described switch is coupled to the source electrode of described the first transistor, wherein, NP knot connection between grid and the source electrode of described switch and described the first transistor forms the first series circuit, the upper offset part parallel connection of described the first series circuit and described bias unit; PN junction between grid and the source electrode of described switch and described the first transistor is connected and is formed the second series circuit, the below-center offset part parallel connection of described the second series circuit and described bias unit.

The present invention has proposed a kind of electric toothbrush on the other hand, comprises the brush that is coupled to motor, and described motor determines whether driving brush work according to the control of described switch.

By adopting technical scheme of the present invention, the switch terminals voltage can make switch disconnect time is less than 1V, has suppressed widely the electrochemical reaction of switch, thereby has extended the life-span of switch, has stopped the possibility of hydrogen detonation simultaneously.

Brief description of the drawings

After the description below with reference to the given the specific embodiment of the present invention of following accompanying drawing, will understand better the present invention, and other objects of the present invention, details, feature and advantage will become more apparent.In the accompanying drawings:

Fig. 1 is the application circuit schematic diagram of trigger switch of the prior art;

Fig. 2 is the equivalent circuit diagram of the switch inside of Fig. 1 while having the aqueous solution;

Fig. 3 is typical power switch circuit schematic diagram in prior art;

Fig. 4 is equivalent circuit diagram when there is the aqueous solution switch inside in Fig. 3;

Fig. 5 is the circuit diagram according to the reduction switch terminals voltage of the embodiment of the present invention;

Fig. 6 is the equivalent circuit diagram of the switch inside of Fig. 5 while having the aqueous solution;

Fig. 7 is according to the another kind of circuit diagram that reduces switch terminals voltage of the embodiment of the present invention;

Fig. 8 is the equivalent circuit diagram of the switch inside of Fig. 7 while having the aqueous solution;

Fig. 9 is according to the another kind of circuit diagram that reduces switch terminals voltage of the embodiment of the present invention;

Figure 10 is according to the another kind of circuit diagram that reduces switch terminals voltage of the embodiment of the present invention;

Figure 11 is the equivalent circuit diagram of the switch inside of Fig. 9 while having the aqueous solution;

Figure 12 is the equivalent circuit diagram of the switch inside of Figure 10 while having the aqueous solution.

Embodiment

Preferred implementation of the present disclosure is described below with reference to accompanying drawings in more detail.Although shown preferred implementation of the present disclosure in accompanying drawing, but should be appreciated that, can realize the disclosure and the execution mode that should do not set forth limits here with various forms.On the contrary, it is in order to make the disclosure more thorough and complete that these execution modes are provided, and can be by the those skilled in the art that conveys to complete the scope of the present disclosure.

What those skilled in the art can understand is, because electrochemical reaction and equivalent electric circuit that switch inside has conductivity water solution, aqueous solution steam or both mixtures to occur are similar, therefore the present embodiment is split inside, pass has conductivity water solution to analyze, and the result of analysis is equally applicable to switch inside the situation of aqueous solution steam or conductivity water solution and the aqueous solution vapour mixture of conduction.In the present embodiment, the object definitions that equivalent resistance is less than to 1M Ω is conductive object.

Fig. 1 is the application circuit schematic diagram of trigger switch of the prior art.It will be appreciated by persons skilled in the art that and work as K switch ₁₁when disconnection, K switch ₁₁on voltage equal VDD ₁₁, and then equal the output voltage U of power supply ₁₁, and in most of electrical appliance, U is pressed in the output village of power supply ₁₁conventionally be greater than 1V, in the present embodiment, U ₁₁equal 3V.

Operation principle to circuit in Fig. 1 is analyzed:

(1) switch is in dry air

Work as K switch ₁₁when disconnection, the port I/O of signal processing module IC1 ¹¹with low level () be not connected, so port I/O ¹¹in high level, and port I/O ¹²output low level, motor M ₁₁cannot work.When user presses K switch ₁₁and the time of pressing is while being greater than 100ms, K switch ₁₁port I/0 ¹¹directly be shorted to low level, i.e. port I/O ¹¹from high level bust to low level, IC1 detects I/O ¹¹level produce sudden change, regard as switch and be triggered, thus at port I/O ¹²output high level, drives field effect transistor Q ₁₁work, and then drive motors M ₁₁work.

When after machine operation, when user's release-push, port I/O ¹¹level return to high level from low level, this process is regarded as the d/d process of switch by IC1, therefore do not change existing electric machine operation state, maintains the work of motor.Work as K switch ₁₁again be pressed while exceeding 100ms, i.e. I/O ¹¹level suddenlys change when low from height again, and IC1 assert that switch is triggered again, thereby at port I/O ¹²output low level, and then close field effect transistor Q ₁₁, make motor M ₁₁close.So circulation, with repeated work.

If V _dDfor the supply power voltage of IC1, in the present embodiment, high level is defined as to the V that is more than or equal to 0.7 times _dD, low level is defined as the V that is less than or equal to 0.3 times _dD.Obviously, when the level of port is in 0.3V _dDto 0.7V _dDbetween time, IC1 cannot judge that this level is for high or low.Conventionally, the inside of IC1 is at I/O ¹¹and V _dDbetween seal in the pull-up resistor R of an about 100K Ω left and right ₁₂(as shown in Figure 1), i.e. I/O ¹¹and V _dDbe communicated with by pull-up resistor.

In the time there is because electrical appliance sealing is bad the aqueous solution conducting electricity in electrical appliance switch inside, K switch ₁₁be equivalent to perfect switch K ₂₁with equivalent resistance R _{water 2}in parallel.Fig. 2 is the equivalent circuit diagram of the switch inside of Fig. 1 while having the aqueous solution.

Conductivity water solution is equivalent to electrolyte, and the switch both positive and negative polarity with terminal voltage and electrolyte have formed an electrolysis system.According to electrochemical theory, the theoretical decomposition voltage of water is 1.23V, and when switch terminals voltage is greater than 1.23V, water just likely disengages hydrogen at negative pole, and disengages oxygen at positive pole.Hydrogen and oxygen are dangerous in the mixing in the space of a relative closure, when to sneak into the volume of hydrogen in air be cumulative volume 4% to 74.2% time, the spark producing when machine operation can be ignited hydrogen, thereby damages electrical appliance or cause more serious security incident.

In addition, even if switch terminals voltage is less than 1.23V, but because the aqueous solution has conductivity, Electrolysis still exists.Electrolytic process, by making the oxidized and passivation of anodal metal, makes anodal conductivity variation, by cause switch both positive and negative polarity contact time produce loose contact, and then make switch failure, shortened the life-span of switch.Obviously, along with the increase of switch terminals voltage, Electrolysis aggravation, the speed of switch failure will be more and more faster.

Conventionally the supply voltage of electrical appliance is greater than 1.0V, and in typical case's application of battery supply, supply voltage is 1.2V, 1.5V, 2.4V and 3V.Therefore, typical circuit in the market possesses the risk of above-mentioned analysis.

Known according to electrochemical theory, equivalent resistance R _{water 2}relevant to the electrolysis degree of the aqueous solution,, in the time that the aqueous solution just starts electrolysis, because the ion in the aqueous solution is less, electric conductivity is poor, therefore equivalent resistance R _{water 2}relatively large, in the present embodiment, record now R through experiment _{water 2}approximate 100K Ω.Carry out after certain hour when electrolysis, the ion in the aqueous solution increases, and electric conductivity strengthens, equivalent resistance R _{water 2}relatively diminish, record now R through experiment _{water 2}approximate 40K Ω.

By the U in Fig. 2 ₁₁-R ₁₂-K ₂₁the voltage distribution of branch road, can obtain suc as formula the voltage relationship shown in (1):

Wherein, R ₁₂for default 100K Ω, U ₁₁for supply voltage, this voltage is resistance R ₁₂and K switch ₂₁on voltage sum, U _k21for K switch ₂₁the voltage at two ends, U _r12for IC internal pull-up resistor R ₁₂on voltage, i ₂₁for the resistance R of flowing through ₁₂and R _{water 2}on electric current.

From formula (1), work as R ₁₂=R _{water 2}time, the voltage U of switch ends _k21=0.5U ₁₁≈ 0.5V _dD11.Therefore, IC1 is difficult to judge I/O ¹¹on level be high or low.As user's push switch, I/O ¹¹upper level is from 0.5V _dD11while suddenling change to low level, because IC1 can assert I/O ¹¹original levels be low, so IC1 thinks that this switch press is invalid pressing, IC1 can not starter motor work.Now, user can assert switch failure.

Work as R ₁₂=100K Ω, R _{water 2}when=40K Ω, substitution formula (1) is known, U _k21=0.286U ₁₁≈ 0.286V _dD11.Now I/O ¹¹upper level is 0.286V _dD11, IC1 determines I/O ¹¹on level be low.In like manner, though user's push switch now, can not starter motor work.

In sum, because switch terminals voltage is higher than 1.0V,, the aqueous solution equivalent resistance of switch ends directly affects the function of switch, also can cause switch failure.In addition, in long electrolytic process, switch inside will produce a large amount of free electric conductors.Because the gap of the both positive and negative polarity of switch is conventionally very little, some time, the both positive and negative polarity that these free electric conductors can shorting switchs causes switch short circuit, thereby makes switch failure.

As from the foregoing, when switch is under off-state, directly bear the supply voltage that is greater than 1V, once the inner aqueous solution and/or the aqueous solution steam that has conduction of switch will have the risk of hydrogen-oxygen mixed explosion, and various switch failure problem.

Fig. 3 is typical power switch circuit in prior art, and Fig. 4 is equivalent circuit diagram when there is the aqueous solution switch inside in Fig. 3.

Obviously, in K switch ₃₁when disconnection, K switch ₃₁on voltage equal supply voltage U ₃₁, and U ₃₁often be greater than 1V, in the present embodiment, U ₃₁equal 3V.

Operation principle to circuit in Fig. 3 is analyzed briefly:

(1) K switch ₃₁in dry air time, K switch ₃₁place's equivalent resistance is infinitely great, and therefore, the operating state of circuit depends on K switch ₃₁state.

(2) K switch ₃₁in moist lower time of environment, K switch ₃₁be equivalent to a perfect switch K ₄₁with equivalent resistance R _{water 4}in parallel.

In like manner, work as K switch ₃₁when the voltage at two ends is larger, once the inner aqueous solution and/or the aqueous solution steam that has conduction of switch will have the risk of hydrogen-oxygen mixed explosion, and various switch failure problem.

The present invention seals in transistorized at least one PN or NP knot at switch to the current path of power supply, particularly as shown in Fig. 5,7,9, switch one end is coupled to the emitter of the first transistor, NP knot between base stage and the emitter of switch and the first transistor is connected, form the first series circuit, and the upper offset part parallel connection of this first series circuit and the first transistor biasing circuit.Be understandable that, the first series circuit can also comprise suitable resistance, that is to say that NP knot and the suitable resistance between base stage and the emitter of switch and the first transistor forms the first series circuit.The upper offset part of above-mentioned biasing circuit is the biasing circuit part of electrical connection the first transistor base stage and positive source.

Correspondingly, when after the type change of the first transistor, for example, as shown in figure 10, switch one end is coupled to the emitter of the first transistor, PN junction the second series circuit in series between base stage and the emitter of switch and the first transistor, and the below-center offset part parallel connection of this second series circuit and the first transistor biasing circuit.In like manner, the second series circuit also can comprise suitable resistance, that is to say that PN junction and the suitable resistance between base stage and the emitter of switch and the first transistor forms the second series circuit.The below-center offset part of above-mentioned biasing circuit is the biasing circuit part of electrical connection the first transistor base stage and power cathode.

The voltage of upper (or under) biasing circuit of above-mentioned first (or second) series circuit parallel connection must be less than supply voltage.Obviously, switch terminals voltage adds that the voltage of voltage between the first transistor emitter and base stage and corresponding upper (or under) biasing circuit equates.Therefore, the terminal voltage of switch is the poor of voltage between the voltage of corresponding upper (or under) biasing circuit and the first transistor emitter and base stage, thereby by the biasing circuit of reasonable disposition the first transistor and the model of the first transistor, can be set in switch disconnection time, switch terminals voltage while having conductivity water solution in switch, and make it be less than 1V and be greater than 0V.

Be analyzed as follows in more detail:

In the time that switch disconnects, owing to there being switch one end of conductivity water solution to be coupled to the emitter of the first transistor, if the first transistor does not have conducting, there is no electric current by the emitter of the first transistor, there is no electric current by perfect switch and switch equivalent resistance, so the terminal voltage of switch is zero.Obviously, the voltage of now going up accordingly (or under) biasing circuit is less than or equal to the threshold voltage of PN between the first transistor emitter and base stage (or NP) knot, that is to say, even switch closure, the first transistor is effectively conducting also, and motor can not be worked, so the biasing of this biasing circuit is inadvisable.

For in the time that switch is closed, effectively conducting of transistor, the voltage that corresponding upper (or under) biasing circuit can be set is greater than the threshold voltage that PN between emitter and base stage (or NP) ties.In the time that the voltage of corresponding upper (or under) biasing circuit is greater than the threshold voltage of PN between emitter and base stage (or NP) knot, the terminal voltage of switch is the poor of voltage between the voltage of corresponding upper (or under) biasing circuit and the first transistor emitter and base stage, and the terminal voltage of switch is greater than 0V.In the time that switch disconnects, while having the aqueous solution of conduction in switch, the first transistor that its emitter and switch one end couple is in conducting state, and because the terminal voltage of switch is the poor of voltage between the voltage of corresponding upper (or under) biasing circuit and the first transistor emitter and base stage, go up accordingly voltage between the voltage of (or under) biasing circuit and the first transistor emitter and base stage and determined the size of the terminal voltage of switch.Conventionally between emitter and base stage, change in voltage is little, thus the voltage control of corresponding upper (or under) biasing circuit the size of terminal voltage of switch.Therefore, in the present embodiment, by the model of reasonable disposition biasing circuit and the first transistor, can be set in switch disconnection time, the switch terminals voltage while having conductivity water solution in switch, and make it be less than 1V and be greater than 0V.In the present embodiment, adopt two resistance to form transistorized biasing circuit, obviously, the electronic component combination of any biasing circuit that can realize dividing potential drop all can be applied in the present embodiment.For example, multiple resistance combinations, resistance and diode combinations, resistance and voltage stabilizing didoe combination etc.

Above analytical proof can utilize transistorized on state characteristic to reduce the terminal voltage at two ends when switch disconnects, especially, when switch disconnect and inside have conductivity water solution or aqueous solution steam, or when conductivity water solution and aqueous solution vapour mixture, utilize transistorized on state characteristic effectively to reduce switch terminals voltage and inner electric current.Known by electrochemical theory, enough low voltage and enough low electric current can suppress the electrochemical reaction of electrolyte and switch.

Fig. 5 is the circuit diagram according to the reduction switch terminals voltage of the embodiment of the present invention.This circuit comprises:

(1) power supply U ₅₁, for providing operating voltage to circuit;

(2) switching signal unit, comprises the first transistor Q ₅₁, for according to K switch ₅₁state, output switching signal, wherein, K switch ₅₁be coupling in the first transistor Q ₅₁with power supply U ₅₁output between, for controlling the first transistor Q ₅₁with power supply U ₅₁the break-make of the current path between output;

(3) bias unit, by the resistance R of connecting ₅₁and R ₅₂composition, is coupled to respectively power supply U ₅₁output and switching signal unit, for to switching signal unit output offset voltage, namely resistance R ₅₁and R ₅₂node be coupled to transistor Q ₅₁base stage;

(4) signal analyse block IC5, is coupled to the first transistor Q ₅₁collector electrode, for according to the first transistor Q ₅₁the switching signal of the output of collector electrode and export corresponding control signal;

(5) output module, comprises transistor seconds Q ₅₂, motor M ₅₁, whether output module determines actuating motor M according to the control signal of signal analyse block IC5 output ₅₁.

As shown in Figure 5, K switch ₅₁the voltage at two ends is by transistor Q ₅₁the type of (being the first transistor) and bias unit determine, shown in (2):

$U_{K51}=\frac{R_{51}}{R_{51}+R_{52}}\·U_{51}-V_{\mathrm{EB}}---\left(2\right)$

Wherein, U _k51for K switch ₅₁both end voltage, V _eBfor transistor Q ₅₁the absolute value of voltage of the PN junction between emitter and base stage.

Therefore, by bias unit and transistor Q ₅₁carry out reasonable disposition, can make K switch ₅₁when disconnection and inside exist conducting solution and/or steam, the voltage at its two ends is less than 1V and is greater than 0V.

In order to allow K switch ₅₁transistor Q when closed ₅₁can conducting, the output voltage of bias unit is configured to be greater than V _eBthereby, make voltage U _k51can be greater than 0V.It will be appreciated by persons skilled in the art that the transistor for same type, V _eBvalue change very little, therefore, the output voltage of bias unit has determined voltage U _k51value.

Compared to Fig. 1, the K switch in Fig. 5 ₅₁to power supply U ₅₁current path on sealed in transistor Q ₅₁.Work as K switch ₅₁when closed, the K switch of flowing through ₅₁emitter current I _e=I _eB+ I _eC, wherein, I _eC=I _r53+ I _iC, collector current will pass through respectively resistance R ₅₃flow into power supply U with IC5 inside ₅₁.

Operation principle to Fig. 5 circuit is set forth:

(1) work as K ₅₁when disconnection, Q ₅₁there is no conducting, I/O ⁵¹on level be R ₅₃voltage, now, I/O ⁵¹on level be low level.

(2) work as K ₅₁when closure exceedes 100ms, Q ₅₁effectively conducting, resistance R ₅₃by on draw collector potential, until be greater than 0.7U ₅₁, i.e. I/O ⁵¹on level can be identified as height, IC5 detects I/O ⁵¹on sudden change from low to high of level, IC5 assert that switch is effectively triggered by user, will be at I/O ⁵²output high level, to drive field effect transistor Q ₅₂thereby, starter motor M ₅₁.As user's cut-off switch K ₅₁time, Q ₅₁be cut off I/O ⁵¹revert to low level from high level, I/O ⁵¹level is from high to low time, and IC5 assert K switch ₅₁be released, IC5 maintains the work of motor.Work as K switch ₅₁again be closed while exceeding 100ms I/O ⁵¹level again from low sudden change to height, IC5 assert switch again triggered by user, IC5 is by I/O ⁵²output change low level into from high level, thereby close field effect transistor Q ₅₂and motor M ₅₁.So circulation, with repeated work.

Below to how configuring biasing circuit and load resistance R ₅₃be described in detail:

Work as K ₅₁in the time that dry air breaks, due to Q ₅₁not conducting, resistance R ₅₃on voltage be 0V, work as K ₅₁when closed in dry air, K ₅₁by short circuit, K switch ₅₁two ends resistance is 0 Ω.Can draw suc as formula the voltage relationship shown in (3) according to bias unit, transistorized on state characteristic:

$\left\{\begin{array}{c}{U}_{51}=i_{51}{R}_{51}+(i_{b51}+i_{51})R_{52}\\ i_{b51}=I_s\left(e^{\frac{(U_{\mathrm{eb}}-{=U}_d)}{0.026}-1}\right)\\ U_{\mathrm{eb}}=i_{51}{R}_{51}\\ U_{\mathrm{eb}}>U_d\end{array}\right.---\left(3\right)$

Wherein, I _sfor the reverse saturation current of the NP knot between transistor base and emitter, U _dfor the conducting threshold voltage of this NP knot.Conventionally i, _b5lbe far smaller than i ₅₁therefore, in calculating process, ignore i _b51impact, silicone tube transistor U _dconventionally be about 0.5V.

Can obtain R by formula (3) ₅₁, R ₅₂resistance meet following relation:

$R_{51}\≥\frac{0.5}{U_{51}-0.5}{R}_{52}---\left(4\right)$

In the present embodiment, get R ₅₂=120K Ω, U ₅₁=3V, R ₅₁>24K Ω.

Fig. 6 is the equivalent circuit diagram of the switch inside of Fig. 5 while having the aqueous solution.

Work as K switch ₅₁when the inner aqueous solution that has conduction, it is equivalent to perfect switch K ₆₂with equivalent resistance R _{water 6}in parallel.In order to ensure effective work of switch, the switch of avoiding containing conductivity water solution is to the switching signal of IC5 mistake, require: in the time that switch disconnects, level on the I/O port that IC5 is connected with switching signal is low level, in the time that switch is effectively closed, the level on the I/O port that IC is connected with switching signal is high level.

Work as K switch ₅₁inside there are the aqueous solution and K switch ₅₁when disconnection, according to resistance R _{water 6}, transistor Q ₅₁and resistance R ₅₃the branch road forming can obtain following voltage relationship:

Be understandable that, be set to be less than equivalent resistance R by load resistance R53 _{water 6}, as (i _b51+i _c51) R _{water 6}< 0.3U ₅₁time, I _c51r ₅₃must be less than 0.3U ₅₁.

Therefore, can draw the scope of resistance R 53:

In order to make this circuit in the time that supply voltage is 2-3V, U _k61can be less than 1V, get U _k61maximum U _k61maxfor 1V, get U ₅₁minimum value U _51minfor 2V, get R _{water 6}minimum value R _{water 6min}for 40K Ω, resistance R ₅₃scope be:

Work as K switch ₆₁when closed, R _{water 6}by short circuit, there is following voltage relationship:

$\left\{\begin{array}{c}{U}_{R53}=R_{53}\&CenterDot;i_{c51}\\ U_{51}=U_{\mathrm{ec}51}+U_{R53}\end{array}\right.---\left(8\right)$

Obviously, resistance R 5 now ₃q will pull up transistor ₅₁the current potential of collector electrode, according to transistor turns characteristic, works as U conventionally _ec51when < 0.7V, ib ₅₁and I _c51close to linear relationship, shown in (9):

$\left\{\begin{array}{c}{i}_{c51}={\mathrm{\&beta;}}_{51}{i}_{b51}\\ \frac{U_{\mathrm{ec}51}}{0.7}=\frac{{\mathrm{\&beta;}}_{51}}{{\mathrm{\&beta;}}_{510}}\end{array}\right.---\left(9\right)$

At U _ec51after > 0.7V, I _c51=β ₅₁₀i _b51, wherein, β ₅₁₀for transistorized direct current multiplication factor, β ₅₁for U _ecwhen < 0.7V, transistorized instantaneous direct current multiplication factor.

According to the aforementioned definition to high level, need U _r53> 0.7U ₅₁so, U _ec51< 0.3U ₅₁; In order to ensure the sensitivity of switching signal, conventionally require U _ec51< 0.6V.

In general, be greater than its output termination voltage U at the output voltage of power supply ₅₁₉time, need to keep motor still can normally work, now the U of the first transistor _ec51< 0.3U ₅₁₉.

Preferably, in order to make circuit safer, can get U _ec51≤ 0.24U ₅₁₉.Therefore can draw following relation:

${\mathrm{\&beta;}}_{51}\&le;\frac{12{\mathrm{\&beta;}}_{510}{U}_{519}\mathrm{}}{35}---\left(10\right)$

$R_{53}>\frac{133}{60{\mathrm{\&beta;}}_{510}{i}_{b51}}---\left(11\right)$

Obviously, power supply output termination voltage U ₅₁₉time, transistor base current is minimum value (, i _b519), R ₅₃span can be adjusted into:

$R_{53}>\frac{133}{60{\mathrm{\&beta;}}_{510}{i}_{b519}}---\left(12\right)$

In sum, resistance R ₅₃span be:

In the present embodiment, transistor Q ₅₁get 9014 models, corresponding R ₅₃span be: 11.07K Ω < R ₅₃< 24K Ω

Further, for the steady operation of circuit, also need circuit working at power supply final voltage U ₅₁₉time base current i _b519do further restriction.A presets with this understanding, flows through resistance R ₅₁on current i ₅₁₉than base current i _b519multiple, conventionally getting A is 100.From bipolar transistor characteristic, work as i _b519≈ 10i _stime, approx, can obtain following relation:

$\left\{\begin{array}{c}{U}_{519}=i_{519}(R_{51}+R_{52})+i_{b519}{R}_{52}>(i_{519}+i_{b519})\&CenterDot;(R_{51}+R_{52})\\ i_{b519}\&ap;i_s(e^{\frac{(U_{\mathrm{cb}519}-U_d)}{0.026}}-1)\end{array}\right.---\left(14\right)$

For the voltage that makes switch terminals is less than 1V, need to meet the relation shown in formula (15):

i ₅₁R ₅₁-U _eb＜1V (15)

Can determine R by formula (14) and (15) ₅₁scope:

$R_{51}\&GreaterEqual;\frac{R_{52}(U_d+0.026\ln 11)}{(U_{519}-{10i}_s{R}_{52}-U_d-0.026\ln 11)}---\left(16\right)$

And the scope of the all-in resistance of biasing circuit is:

$R_{51}+R_{52}\&le;\frac{U_{519}}{{\mathrm{Ai}}_s}---\left(17\right)$

As the maximum U of electric power output voltage ₅₁₈time, the terminal voltage while requiring switch inside to have the aqueous solution and its disconnection is less than nV, can draw following relation:

$\left\{\begin{array}{c}{U}_{518}=i_{518}(R_{51}+R_{52})+i_{b518}{R}_{52}\\ i_{b518}=i_s(e^{\frac{(U_{\mathrm{eb}518}-U_d)}{0.026}}-1)\\ i_{b518}{R}_{51}\&le;U_{\mathrm{eb}518}+n\\ i_{b518}\&GreaterEqual;{10i}_s\end{array}\right.---\left(18\right)$

From formula (18), R ₅₁at the maximum U of the exportable voltage of power supply ₅₁₈at present span, convolution (16), resistance R ₅₁span can be defined as:

$\frac{R_{52}(U_d+0.026\ln 11)}{(U_{519}-10i_s{R}_{52}-U_d-0.026\ln 11)}\&le;R_{51}\&le;\frac{R_{52}(U_d+0.026\ln 11+n)}{(U_{518}-{10i}_s{R}_{52}-U_d-0.026\ln 11-n)}---\left(19\right)$

Further, can determine resistance R ₅₃scope:

In the present embodiment, get U ₅₁₉=2V, U _d=0.5V, U ₅₁₈=3V, β ₅₁₀=200, i _s=0.0001mA, R ₅₂=120K Ω, n=1V, A=100, R ₅₁scope as follows:

51.21KΩ≤R ₅₁≤142.28KΩ (21)

$R_{51}>\frac{{0.5R}_{52}}{U_{51}-0.5}=24\mathrm{K\&Omega;}---\left(22\right)$

Therefore,, according to formula (20), (21) and (22), can get R ₅₁=56K Ω, R ₅₂=120K Ω, R ₅₃=18K Ω.

Above-mentioned computational process proves that the circuit in Fig. 5 can match suitable transistor Q ₅₁, resistance R ₅₁-R ₅₃.Based on above-mentioned configuration, level on the I/O mouth that IC5 is connected with switching signal changes disconnection or the closed action that can correctly reflect switch, meanwhile, makes the switch terminals voltage of switch in the time of off-state be less than 1V, thereby suppress widely the electrochemical reaction in switch, extended the life-span of switch.

Fig. 7 is the circuit diagram that reduces switch terminals voltage according to the another kind of the embodiment of the present invention.Compared to Fig. 3, K switch ₇₁to the current path of power supply, seal in transistor Q ₇₁(being the first transistor).Resistance R ₇₁and R ₇₂composition biasing circuit, for giving transistor Q ₇₁base stage bias voltage is provided.

Fig. 7 is the circuit diagram of improveing in conjunction with the present invention for the circuit of Fig. 3, and the switch in Fig. 7 is in dry air.Compared to Fig. 3, K switch ₇₁to the current path of power supply, seal in transistor Q ₇₁.K switch ₇₁when closed, a part for the electric current that power supply flows out the K that flows through ₇₁the PN junction of a part by between transistorized emitter and base stage through resistance R ₇₂flow into power supply, K flows through ₇₁another part of electric current cross motor M by the PN junction between transistorized emitter and collector electrode and NP tying-in ₇₁flow into power supply.Obviously the electric current that power supply flows out in Fig. 3 is through K switch ₃₁and motor M ₃₁directly flow back to power supply, in K switch ₃₁to the current path of power supply, do not seal in transistorized PN junction or NP knot.R in Fig. 7 ₇₁and R ₇₂composition transistor Q ₇₁biasing circuit, be divided into upper offset circuit near the offset part of positive source, be divided into below-center offset part, i.e. R near the offset part of power cathode ₇₁for upper offset part, R ₇₂for below-center offset part.In Fig. 7, K switch ₇₁one end be electrically connected to transistor Q ₇₁emitter, K switch ₇₁with transistor Q ₇₁emitter and base stage between PN junction series connection, form the first series circuit, and this series circuit and transistor Q ₇₁upper offset part (the R of biasing circuit ₇₁) parallel connection.

In Fig. 7, the operation principle of circuit is as follows:

K switch ₇₁be in dry air, work as K switch ₇₁when disconnection, Q ₇₁not conducting, motor M ₇₁cannot work.Work as K switch ₇₁when closed, Q ₇₁conducting, motor M ₇₁work, electrical appliance work.Work as K switch ₇₁while again disconnection, transistor Q ₇₁cut-off again, motor M ₇₁quit work.

Fig. 8 is the equivalent circuit diagram of the switch inside of Fig. 7 while having the aqueous solution.Now, K switch ₇₁be equivalent to perfect switch K ₈₁with equivalent resistance R _{water 8}in parallel.Work as K switch ₈₁when disconnection, can obtain following voltage relationship:

U _r71=U _k81+ U _eb71=U _{r water 8}+ U _eb71(23)

U ₇₁=U _r71+ U _r72=U _m71+ U _ec71+ (i _b71+ i _c71) R _{water 8}(24)

Conventionally R, _{water 8}for several ten thousand ohm, and motor M ₇₁equivalent resistance be several ohm to tens ohm, so, work as K switch ₈₁when disconnection, U _k81be far longer than U _m71.By preceding method reasonable disposition R ₇₁and R ₇₂, can make K switch ₈₁the voltage at two ends is less than 1V and is greater than 0V, correspondingly U _m71at least be less than 0.1V, motor M ₇₁can not work.Work as K switch ₈₁inside have conductivity water solution, and switch is when closed, transistor Q ₇₁conducting work, U _ec71very little, therefore motor M ₇₁on obtain high voltage, motor is started working.In the time that switch is cut off again, is greater than 0V and is greater than out and away U because switch terminals voltage is less than 1V _m71so, U _m71at least be less than 0.1V, motor can not start.

Fig. 9 is according to the another kind of circuit diagram that reduces switch terminals voltage of the embodiment of the present invention.

Compared to Fig. 3, K switch ₉₁to the current path of power supply, seal in transistor Q ₉₁(being the first transistor), resistance R ₉₁and R ₉₂composition transistor Q ₉₁biasing circuit.Transistor Q ₉₁collector electrode be coupled to field effect transistor Q ₉₂the grid of (being transistor seconds), to provide metal-oxide-semiconductor Q ₉₂switching signal, thereby control the operating state of motor M91.

Work as K switch ₉₁be in dry air K switch ₉₁when disconnection, transistor Q ₉₁not conducting, field effect transistor Q ₉₂grid be 0V, field effect transistor Q ₉₂cut-off, motor cannot be worked.Work as K switch ₉₁when closed, transistor Q ₉₁conducting, resistance R ₉₃will be transistor Q ₉₁collector potential on the supply voltage that furthers, thereby field effect transistor Q ₉₂conducting, motor M ₉₁work.Work as K switch ₉₁while again disconnection, transistor Q ₉₁cut-off again, motor M ₉₁quit work.

In the time of the inner aqueous solution that has conduction of switch, K switch ₉₁be equivalent to perfect switch K ₁₁₁with equivalent resistance R _{water 11}in parallel.Figure 11 is the K switch of Fig. 9 ₉₁equivalent circuit diagram when there is the aqueous solution inside.

Work as K switch ₉₁while inside having the aqueous solution, K switch ₉₁voltage relationship when disconnection is suc as formula shown in (25) and (26):

U _r91=U _k111+ U _eb91=U _{r water 11}+ U _eb91(25)

U ₉₁=U _r91+ U _r92=U _r93+ U _ec91+ (i _b91+ i _c91) R _{water 11}(26)

Equally, according to aforesaid method, to resistance R ₉₁-R ₉₃be configured, can make switch disconnect time, switch terminals voltage is less than 1V and is greater than 0V, correspondingly, and resistance R ₉₃on voltage be less than 1V.In general, field effect transistor Q ₉₂conducting threshold voltage V _gs> 1.5V, therefore, field effect transistor Q ₉₂can not conducting, motor M ₉₁do not work.Meanwhile, because switch terminals voltage is less than 1V, the electric current that flows through switch reduces widely, thereby lower switch terminals voltage and little electric current have suppressed the electrochemical reaction of switch greatly, thereby improves the life-span of switch.

In the time having conductivity water solution and closure in switch, Q ₉₁effectively conducting, now supply voltage equals transistor Q ₉₁and resistance R ₉₃on voltage sum.By to resistance R ₉₁-R ₉₃be configured, can make U _r93approach supply voltage, thereby make field effect transistor conducting, with drive motors M ₉₁.

In sum, in Fig. 9,11, by suitable configuration R ₉₁-R ₉₃, can make inside have the switch of conductivity water solution in the time disconnecting, its terminal voltage is less than 1V and is greater than 0V, and keeps motor not work.In the time that switch is closed, can normal starter motor.Switch terminals voltage while disconnection due to switch is less than 1V, has suppressed widely the electrochemical reaction of switch, thereby has greatly extended the life-span of switch, has stopped the possibility of hydrogen detonation simultaneously.

Figure 10 is according to the another kind of circuit diagram that reduces switch terminals voltage of the embodiment of the present invention, equivalent circuit diagram when there is the aqueous solution switch inside that Figure 12 is Figure 10.

As shown in figure 10, K switch ₁₀₁in dry air.Compared to Fig. 3, K switch ₁₀₁to the current path of power supply, seal in transistor Q ₁₀₁(being the first transistor).Work as K switch ₁₀₁when closed, a part for the electric current that power supply flows out is through R ₁₀₁, flowing through by the PN junction between transistorized base stage and emitter, K flows through ₁₀₁flow into power supply; K flows through ₁₀₁another part of electric current from the resistance R of flowing through ₁₀₃and NP between transistorized emitter and collector electrode knot and PN junction flow back to the electric current of power supply.Therefore, in K switch ₁₀₁to the current path of power supply, seal in transistor Q ₁₀₁base stage and emitter between PN junction and NP between collector electrode and emitter knot and PN junction.R in Figure 10 ₁₀₁and R ₁₀₂composition transistor Q ₁₀₁biasing circuit, be divided into upper offset circuit near the offset part of positive source, be divided into below-center offset part, i.e. R near the offset part of power cathode ₁₀₁for upper offset part, R ₁₀₂for below-center offset part.K switch ₁₀₁with transistor Q ₁₀₁the emitter e of (being the first transistor) ₁₀₁with base stage b ₁₀₁between NP knot series connection, form the second series circuit, and this series circuit and transistor Q ₁₀₁below-center offset part (the R of biasing circuit ₁₀₂) parallel connection.

According to aforesaid method, configuration resistance R ₁₂₁-R ₁₂₃, work as K switch ₁₀₁be in dry air and while disconnection transistor Q ₁₀₁not conducting, its collector potential U _c101equal supply voltage U ₁₀₁, therefore, transistor Q ₁₀₂(being transistor seconds) not conducting, motor cannot be worked.Work as K switch ₁₀₁when closed, transistor Q101 conducting, UC ₁₀₁diminish, thereby make transistor Q ₁₀₂conducting, motor M ₁₀₁work.In the time of the inner aqueous solution that has conduction of electrical appliance switch, K switch ₁₀₁be equivalent to perfect switch K ₁₂₁with equivalent resistance R _{water 12}in parallel.

Work as K switch ₁₀₁while inside having the aqueous solution, K switch ₁₀₁when disconnection,

U _r102=U _k121+ U _bz121=U _{r water 12}+ U _be121(27)

U ₁₀₁=U _r103+ U _ce101+ (i _b101+ i _c101) R _{water 12}(28)

By aforesaid method configuration resistance R ₁₀₁-R ₁₀₃, for example, establish U _101max=3V, gets R ₁₀₁=120K Ω, R ₁₀₂=56K2, R ₁₀₃=18K Ω, thus can make the voltage of switch ends be less than 1V, correspondingly U _r103at least be less than 0.5V, so, transistor Q ₁₀₂can not conducting, motor M ₁₀₁cannot work.Due to U _k121be less than 1V, the electric current that flows through switch reduces widely, thereby low switch terminals voltage and little electric current have suppressed the electrochemical reaction of switch, the life-span of having improved switch greatly.

Work as K switch ₁₂₁while inside having conductivity water solution, and switch is when closed, U _k121=0V, according to above-mentioned to resistance R ₁₀₁-R ₁₀₃configuration, in the time that switch is closed, transistor Q ₁₀₁effectively conducting, and can make U _r103> 0.7V, thereby transistor Q ₁₀₂effectively conducting, motor M ₁₀₁on obtain high voltage, motor is started working.

In sum, by suitable configuration R ₁₀₁-R ₁₀₃, can make inside have the switch of conductivity water solution, in the time that switch disconnects, the terminal voltage of switch is less than 1V, and keeps motor not work.In the time that switch is closed, can normal actuating motor.In like manner, the switch terminals voltage while disconnection due to switch is less than 1V, has suppressed widely the electrochemical reaction of switch, thereby has greatly extended the life-span of switch, has stopped the possibility of hydrogen detonation simultaneously.

The present invention also discloses a kind of electrical appliance, such as electric toothbrush, and this electrical appliance comprises: (1) power supply, is generally rechargeable battery or dry cell, for providing operating voltage to this electrical appliance; (2) switch module, is coupled to power supply, for controlling the break-make of the current path between power supply and subsequent conditioning circuit; (3) motor, is coupled to switch module and power supply, for determining whether driving brush work according to the control of switch.

Based on above-mentioned configuration, this electrical appliance can ensure the validity of switch under moist environment, has extended the life-span of switch.

Those skilled in the art can understand, and above-described embodiment only, for setting forth design of the present invention and exemplary circuit, can not be used for limiting the scope of the invention.For example, switch can be connected to transistorized emitter by resistance, thereby reduces the voltage that switch can be assigned to; Bias unit can be made up of linear voltage regulator, Switching Power Supply or other circuit that can export appointment bias voltage.

Those skilled in the art can also understand, the first transistor in above-described embodiment, such as Q ₅₁also can be field-effect transistor.In the case, one end of switch is coupled to the source electrode of the first transistor, and the NP knot connection between grid and the source electrode of switch and the first transistor forms the first series circuit, the upper offset part parallel connection of the first series circuit and bias unit; Or PN junction between grid and the source electrode of switch and the first transistor is connected and is formed the second series circuit, the below-center offset part parallel connection of the second series circuit and bias unit.

Above description for making any those of ordinary skill of this area can realize or use the present invention of the present disclosure.To those skilled in the art, various amendments of the present disclosure are all apparent, and general principle defined herein also can be applied to other distortion in the situation that not departing from spirit of the present invention and protection range.Therefore, the present invention is not limited to example as herein described and design, but consistent with the widest scope of principle disclosed herein and novel features.

Claims (13)

1. the controlled device of switch terminals voltage, comprising:

Switching signal unit, for according to the state of switch, exports corresponding switching signal, and described switch is coupled between described switching signal unit and the output of power supply;

Bias unit, is coupled to described switching signal unit, for to described switching signal unit output offset voltage;

Wherein, when described switch disconnects and when its inside has the steam of conducting liquid and/or conducting liquid, described bias unit matches with described switching signal unit, to control the electric current of the terminal voltage of described switch and the described switch of flowing through.

2. device as claimed in claim 1, is characterized in that, described switching signal unit comprises the first transistor, and described switch is coupled between described the first transistor and power supply, for controlling the break-make of the current path between described the first transistor and described power supply.

3. device as claimed in claim 2, is characterized in that, described the first transistor is bipolar transistor, and one end of described switch is coupled to the emitter of described the first transistor,

Wherein, the PN junction between emitter and the base stage of described switch and described the first transistor is connected and is formed the first series circuit, the upper offset part parallel connection of described the first series circuit and described bias unit; Or

NP knot between emitter and the base stage of described switch and described the first transistor formation the second series circuit of connect, the below-center offset part parallel connection of described the second series circuit and described bias unit.

4. device as claimed in claim 3, is characterized in that, described first and second series circuit also comprises at least one resistance.

5. device as claimed in claim 2, is characterized in that, in the time that described switch disconnects,

If there is the steam of conducting liquid and/or conducting liquid in described switch inside, the state of described the first transistor in conducting;

If described switch is inner dry, the state of described the first transistor in cut-off.

6. device as claimed in claim 1, is characterized in that, described device also comprises motor, and described motor is coupled to the output of described switching signal unit.

7. device as claimed in claim 1, is characterized in that, described device also comprises:

Output module, the motor that comprises transistor seconds and be in series with described transistor seconds;

Wherein, described output module is coupled to the output of described switching signal unit, and output signal based on described switching signal unit configures the operating state of described motor.

8. device as claimed in claim 1, is characterized in that, at least one pull-up resistor of connecting between the output of described switching signal unit and low level.

9. device as claimed in claim 1, it is characterized in that, described device also comprises signal analyse block, described signal analyse block is coupling between described output module and the output of described switching signal unit, to be used for controlling the control signal of described output module according to the output signal output of described switching signal unit.

10. device as claimed in claim 7, is characterized in that, described transistor seconds is field-effect transistor, and wherein, described motor in series is to the drain electrode of described transistor seconds.

11. devices as claimed in claim 7, is characterized in that, described transistor seconds is bipolar transistor, and wherein, described motor in series is to the collector electrode of described transistor seconds.

12. devices as claimed in claim 2, is characterized in that, described the first transistor is field effect transistor, and one end of described switch is coupled to the source electrode of described the first transistor,

Wherein, the NP knot connection between grid and the source electrode of described switch and described the first transistor forms the first series circuit, the upper offset part parallel connection of described the first series circuit and described bias unit; Or

PN junction between grid and the source electrode of described switch and described the first transistor is connected and is formed the second series circuit, the below-center offset part parallel connection of described the second series circuit and described bias unit.

The electric toothbrush of 13. 1 kinds of employings device as described in claim 1 to 12 any one, comprises:

Be coupled to the brush of motor, described motor determines whether driving brush work according to the control of described switch.