CN103929164B - 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 controllable device of switch terminal voltage

Technical field

The present invention is generally related to domestic circuit field, more specifically, is related to one kind in wet condition, Neng Gouyou Effect reduces the device of switch terminal voltage.

Background technology

Switch is commonly used to start or cut out electrical appliance, and switch may also be used for the different working modes for selecting electrical appliance, Switch is for realizing the device contacted between people and electrical appliance.Currently there are many electrical appliances to include rechargeable battery or aneroid battery etc. Power supply, so electrical appliance contains power supply of the output voltage more than 1V, and the terminal voltage of the switch of electrical appliance universal on market is about Equal to electric power output voltage or higher than electric power output voltage.

It is well known that such as the electrical appliance of electric toothbrush, razors or hair removal Device etc, being often positioned over humidity Toilet and its touch various aqueous solutions using having an opportunity in process or cleaning process.Aqueous solution is typically conductive, this Aqueous solution is planted when the water-stop of electrical appliance goes wrong, can make switch internal has presence between the contact of potential difference conductive water-soluble Liquid or conductivity water solution vapor, or conductive aqueous solution and aqueous solution vapour mixture, and this conductive liquid or gas or liquid Body and admixture of gas can produce electrochemical reaction in the presence of above-mentioned switch terminal voltage, and such electrochemical reaction will be corroded Switch, makes switch failure.

Therefore, need one kind badly and enable to switch and be applied under wet environment, and with higher stability and safety Circuit.

The content of the invention

For problem above, the invention provides a kind of steady operation and safe can open in wet condition Close the controllable device of terminal voltage.

One aspect of the present invention proposes a kind of controllable device of terminal voltage of switch, including：Switching signal unit, for root According to the state of switch, corresponding switching signal is exported, the switch is coupled in the outfan of the switching signal unit and power supply Between；Bias unit, is coupled to the switching signal unit, for exporting bias voltage to the switching signal unit；Wherein, During the steam for switching off and there is conducting liquid and/or conducting liquid inside which when described, the bias unit is opened with described OFF signal unit is engaged, to control the terminal voltage of the switch and flow through the electric current of the switch.

Preferably, the switching signal unit includes the first transistor, the switch be coupled in the first transistor with Between power supply, for controlling the break-make of the current path between the first transistor and the power supply.

Preferably, the first transistor is bipolar transistor, and one end of the switch is coupled to the first crystal The emitter stage of pipe, wherein, the switch and the PN junction between the emitter stage and base stage of the first transistor are connected and to form first The upper offset part in parallel of series circuit, first series circuit and the bias unit；Or the switch and described first NP knot series connection between the emitter stage and base stage of transistor forms the second series circuit, second series circuit and the biasing The below-center offset part in parallel of unit.

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

Preferably, when described switching off, if there is the steaming of conducting liquid and/or conducting liquid in the switch internal Vapour, the then state that the first transistor is on；If the switch internal is dried, the first transistor is in cut-off State.

Preferably, described device also includes：Motor, the motor are coupled to the output of the switching signal unit End.

Preferably, described device also includes：Output module, including transistor seconds and be in series with the transistor seconds Motor；Wherein, the output module is coupled to the outfan of the switching signal unit, and is based on the switching signal list The output signal of unit configures the working condition of the motor.

Preferably, connect between the outfan and low level of the switching signal unit at least one pull-up resistor.

Preferably, the circuit also includes signal analysis module, and the signal analysis module is coupling in the output module And the outfan of the switching signal unit between, to be exported for controlling according to the output signal of the switching signal unit State the control signal of output module.

Preferably, the transistor seconds is field-effect transistor, wherein, the motor in series is to second crystal The drain electrode of pipe.

Preferably, the transistor seconds is bipolar transistor, wherein, the motor in series is to second crystal The colelctor electrode of pipe.

Preferably, the first transistor is field-effect transistor, and one end of the switch is coupled to the first crystal The source electrode of pipe, wherein, the switch and the knots of the NP between the grid and source electrode of the first transistor are connected and form the first series connection The upper offset part in parallel of circuit, first series circuit and the bias unit；The switch and the first transistor Grid and source electrode between PN junction connect to form the second series circuit, under second series circuit and the bias unit Offset portion is in parallel.

Another aspect of the present invention proposes a kind of electric toothbrush, comprising the brush for being coupled to motor, the motor root Decide whether that according to the control of the switch driving brush works.

By adopting technical scheme, switch terminal voltage when switching off can be caused to be less than 1V, greatly The electrochemical reaction of switch is inhibited, so as to extend the life-span of switch, while having prevented the probability of hydrogen detonation.

Description of the drawings

After description by the specific embodiment below with reference to the present invention given by drawings below, will be more preferably geographical Solution is of the invention, and other objects of the present invention, details, feature and advantage will become apparent from.In the accompanying drawings：

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

Equivalent circuit diagram when Fig. 2 has an aqueous solution for the switch internal of Fig. 1；

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

Fig. 4 is equivalent circuit diagram when having aqueous solution inside Fig. 3 breaker in middle；

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

Equivalent circuit diagram when Fig. 6 has an aqueous solution for the switch internal of Fig. 5；

Fig. 7 is according to another kind of circuit diagram for reducing switch terminal voltage of the embodiment of the present invention；

Equivalent circuit diagram when Fig. 8 has an aqueous solution for the switch internal of Fig. 7；

Fig. 9 is according to another kind of circuit diagram for reducing switch terminal voltage of the embodiment of the present invention；

Figure 10 is according to another kind of circuit diagram for reducing switch terminal voltage of the embodiment of the present invention：

Equivalent circuit diagram when Figure 11 has an aqueous solution for the switch internal of Fig. 9；

Equivalent circuit diagram when Figure 12 has an aqueous solution for the switch internal of Figure 10.

Specific embodiment

The preferred implementation of the disclosure is more fully described below with reference to accompanying drawings.Although the disclosure is shown in accompanying drawing Preferred implementation, however, it is to be appreciated that may be realized in various forms the disclosure and the embodiment party that should not be illustrated here Formula is limited.Conversely, these embodiments are provided so that the disclosure is more thorough and complete, and can be by the disclosure What scope was complete conveys to those skilled in the art.

It will be appreciated to those of skill in the art that as switch internal has conductive aqueous solution, aqueous solution steam or both The electrochemical reaction that occurs of mixture and equivalent circuit it is similar, therefore the present embodiment has conductive aqueous solution to enter to switch internal Row analysis, the result of analysis is equally applicable to switch internal the aqueous solution steam or conductive aqueous solution and aqueous solution steam of conduction The situation of mixture.In the present embodiment, object of the equivalent resistance less than 1M Ω is defined as into 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 As switch K₁₁During disconnection, K is switched₁₁On voltage be equal to VDD₁₁, and then equal to the output voltage U of power supply₁₁, and in most of use In electrical equipment, the output voltage U of power supply₁₁Typically larger than 1V, in the present embodiment, U₁₁Equal to 3V.

The operation principle of circuit in Fig. 1 is analyzed：

(1) switch is in dry air

As switch K₁₁During disconnection, the port I/O of signal processing module IC1¹¹With low level () without connect, so end Mouth I/O¹¹In high level, and port I/O¹²Output low level, motor M₁₁Cannot work.When user presses switch K₁₁And press Time be more than 100ms when, switch K₁₁Port I/O¹¹Low level, i.e. port I/O are shorted to directly¹¹From high level bust to Low level, IC1 detect I/O¹¹Level produce mutation, then regard as switch be triggered, so as in port I/O¹²Output is high Level, driving FET Q₁₁Work, and then motor M₁₁Work.

After motor works, during user's release-push, port I/O¹¹Level recover to high level from low level, IC1 will The process regards as switching the process being released, therefore does not change existing electric machine operation state, maintains the work of motor.Work as switch K₁₁When be pressed more than 100ms again, i.e. I/O¹¹When level is mutated low from height again, IC1 assert that switch is triggered again, So as in port I/O¹²Output low level, and then close field effect transistor Q₁₁So that motor M₁₁Close.So circulate, to repeat work Make.

If V_DDFor the supply voltage of IC1, in the present embodiment, high level is defined as greater than into the V equal to 0.7 times_DD, it is low Level is defined as less than the V equal to 0.3 times_DD.Obviously, when the level of port is in 0.3V_DDTo 0.7V_DDBetween when, IC1 will This level cannot be judged for high or low.Generally, the inside of IC1 is in I/O¹¹And V_DDBetween seal in an about 100K Ω's or so Pull-up resistor R₁₂(as shown in Figure 1), i.e. I/O¹¹And V_DDConnected by pull-up resistor.

When electrical appliance switch internal has conductive aqueous solution as electrical appliance sealing is bad, K is switched₁₁It is equivalent to reason Look on the bright side of things pass K₂₁With equivalent resistance R_{Water 2}It is in parallel.Equivalent circuit diagram when Fig. 2 has an aqueous solution for the switch internal of Fig. 1.

Conductivity water solution constitutes an electrolysis system equivalent to electrolyte, the switch both positive and negative polarity with terminal voltage and electrolyte System.According to electrochemical theory, the theoretical decomposition voltage of water is 1.23V, that is, when switching terminal voltage more than 1.23V, water is possible to Negative pole disengages hydrogen, and disengages oxygen in positive pole.The mixing of hydrogen and oxygen in the space of a relative closure is dangerous, works as sky When the volume that hydrogen is mixed in gas is the 4% to 74.2% of cumulative volume, the spark that motor is produced when working can ignite hydrogen, from And damage electrical appliance or cause more serious security incident.

Even if in addition, switch terminal voltage is less than 1.23V, but as aqueous solution has electric conductivity, Electrolysis are still present. The metal for making positive pole is oxidized and is passivated by electrolytic process, makes the electric conductivity of positive pole be deteriorated, the both positive and negative polarity for causing switch is contacted When produce loose contact, and then cause switch failure, shortened the life-span of switch.Obviously, with the increase of switch terminal voltage, electricity Solution phenomenon aggravation, the speed of switch failure will be more and more faster.

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

Understand according to electrochemical theory, equivalent resistance R_{Water 2}It is related to the electrolysis degree of aqueous solution, i.e., when aqueous solution just starts During electrolysis, as the ion in aqueous solution is less, electric conductivity is poor, therefore equivalent resistance R_{Water 2}It is relatively large, in the present embodiment In, Jing experiments measure now R_{Water 2}It is approximately equal to 100K Ω.After electrolysis carries out certain hour, the ion in aqueous solution increases, conductive Performance enhancement, equivalent resistance R_{Water 2}Relative to diminish, Jing experiments measure now R_{Water 2}It is approximately equal to 40K Ω.

By the U in Fig. 2₁₁-R₁₂-K₂₁The voltage distribution of branch road, can obtain the voltage relationship as shown in formula (1)：

Wherein, R₁₂For default 100K Ω, U₁₁For supply voltage, the voltage is resistance R₁₂With switch K₂₁On voltage it With U_K21To switch K₂₁The voltage at two ends, U_R12For IC internal pull-up resistors R₁₂On voltage, i₂₁To flow through resistance R₁₂And R_{Water 2}On Electric current.

From formula (1), work as R₁₂=R_{Water 2}When, the voltage U of switch ends_K21=0.5U₁₁≈0.5V_DD11.Therefore, IC1 is difficult To judge I/O¹¹On level for high or low.When user is by compressing switch, I/O¹¹Upper level is from 0.5V_DD11When being mutated to low level, Due to IC1 it can be assumed that I/O¹¹Original levels for low, so IC1 thinks this switch press for invalid pressing, IC1 can not be opened Galvanic electricity machine works.Now, user can assert switch failure.

Work as R₁₂=100K Ω, R_{Water 2}During=40K Ω, substitute into formula (1) and understand, U_K21=0.286U₁₁≈0.286V_DD11.Now I/O¹¹Upper level is 0.286V_DD11, IC1 determines I/O¹¹On level for low.In the same manner, even if now user is by compressing switch, also not Motor work can be started.

In sum, due to switching terminal voltage higher than 1.0V, the aqueous solution equivalent resistance of switch ends directly affects switch Function, it is also possible to cause switch failure.In addition, in prolonged electrolytic process, switch internal will produce what is dissociated in a large number Electric conductor.Due to the usual very little in gap of the both positive and negative polarity of switch, sometimes, these free electric conductors meeting shorting switch Both positive and negative polarity causes switch short, so that switch failure.

From the foregoing, it will be observed that when switching in the off state, the supply voltage more than 1V is directly born, once switch internal is present Conductive aqueous solution and/or aqueous solution steam, by the risk with hydrogen-oxygen mixed explosion, and various switch failure problems.

Fig. 3 is typical power switch circuit in prior art, and Fig. 4 is equivalent when having aqueous solution inside Fig. 3 breaker in middle Circuit diagram.

Obviously, in switch K₃₁During disconnection, K is switched₃₁On voltage be equal to supply voltage U₃₁, and U₃₁Commonly greater than 1V, at this In embodiment, U₃₁Equal to 3V.

The operation principle of circuit in Fig. 3 is briefly analyzed：

(1) switch K₃₁When in dry air, K is switched₃₁Place's equivalent resistance is infinity, therefore, the work of circuit State depends on switch K₃₁State.

(2) switch K₃₁When under moist environment, K is switched₃₁It is equivalent to a perfect switch K₄₁With equivalent resistance R_{Water 4} It is in parallel.

In the same manner, as switch K₃₁When the voltage at two ends is larger, once there is conductive aqueous solution and/or aqueous solution in switch internal Steam, by the risk with hydrogen-oxygen mixed explosion, and various switch failure problems.

The present invention seals at least one PN or NP knot of transistor on the current path of power supply in switch, specifically as schemed 5th, shown in 7,9, the emitter stage that one end is coupled to the first transistor is switched, between switch and the base stage and emitter stage of the first transistor NP knot series connection, constitute the first series circuit, and the upper offset part of first series circuit and the first transistor biasing circuit It is in parallel.It is understood that the first series circuit can also include appropriate resistance, that is to say, that switch and the first transistor NP knots and appropriate resistance between base stage and emitter stage constitutes the first series circuit.The upper offset part of above-mentioned biasing circuit To electrically connect the bias circuit portion of the first transistor base stage and positive source.

Correspondingly, after the type change of the first transistor, for example, as shown in Figure 10, switching one end, to be coupled to first brilliant The emitter stage of body pipe, switch and the second series circuit in series of the PN junction between the base stage and emitter stage of the first transistor, and The below-center offset part in parallel of second series circuit and the first transistor biasing circuit.In the same manner, the second series circuit can also be wrapped Containing appropriate resistance, that is to say, that switch and the PN junction between the base stage and emitter stage of the first transistor and appropriate resistance are constituted Second series circuit.The below-center offset part of above-mentioned biasing circuit is the biasing for electrically connecting the first transistor base stage and power cathode Circuit part.

The voltage of above-mentioned first (or second) series circuit upper (or under) biasing circuit in parallel is certainly less than power supply electricity Pressure.Obviously, switch terminal voltage and add between the first transistor emitter stage and base stage voltage and corresponding upper (or under) biasing circuit Voltage it is equal.Therefore, voltage and the first transistor emitter stage of the terminal voltage of switch for corresponding upper (or under) biasing circuit The difference in voltage and base stage between, so as to pass through the model of the biasing circuit and the first transistor of reasonable disposition the first transistor, can Be set in switch off when, switch terminal voltage when having a conductive aqueous solution in switch, and make it less than 1V and be more than 0V.

It is analyzed as follows in more detail：

When switching off, as the switch one end for having conductive aqueous solution is coupled to the emitter stage of the first transistor, if the One transistor is not turned on, then do not have emitter stage of the electric current by the first transistor, i.e., no electric current is by perfect switch and opens Equivalent resistance is closed, so the terminal voltage of switch is zero.Obviously, the voltage of now corresponding upper (or under) biasing circuit is less than or waits The threshold voltage that PN (or NP) is tied between the first transistor emitter stage and base stage, that is to say, that even if switch closure, first is brilliant Body pipe also effectively cannot be turned on, and motor can not work, so, the biasing of this biasing circuit is inadvisable.

The electricity of corresponding upper (or under) biasing circuit, in order in switch closure, transistor effectively can be turned on, can be set Pressure is more than the threshold voltage that PN (or NP) is tied between emitter and base stage.When the electricity of corresponding upper (or under) biasing circuit When pressure is more than PN (or NP) is tied between emitter and base stage threshold voltage, the terminal voltage of switch for it is corresponding it is upper (or Under) difference in voltage between the voltage of biasing circuit and the first transistor emitter stage and base stage, and the terminal voltage for switching is more than 0V.When When switching off, when having the aqueous solution of conduction in switch, the first transistor of its emitter stage and the coupling of switch one end is on State, and as the terminal voltage that switchs is the voltage and the first transistor emitter stage and base of corresponding upper (or under) biasing circuit Difference in voltage between pole, i.e., voltage between the voltage and the first transistor emitter stage and base stage of corresponding upper (or under) biasing circuit Determine the size of the terminal voltage of switch.Generally between emitter stage and base stage, change in voltage is little, so upper accordingly (or under) The voltage of biasing circuit controls the size of the terminal voltage of switch.Therefore, in the present embodiment, by reasonable disposition biasing circuit With the model of the first transistor, may be set in when switching off, the switch terminal voltage having in switch during conductive aqueous solution, and make It is less than 1V and is more than 0V.In the present embodiment, the biasing circuit of transistor is constituted using two resistance, it is clear that any to realize The electronic component combination of the biasing circuit of partial pressure is can apply in the present embodiment.For example, multiple resistance combinations, resistance and two Pole pipe is combined, resistance and Zener diode combination etc..

Above analytical proof can utilize the on state characteristic of transistor to reduce the terminal voltage at two ends when switching off, especially It is, when switching off and there are conductive aqueous solution or aqueous solution steam in inside, or when conductive aqueous solution and aqueous solution vapour mixture, Effectively reduce switching the electric current of terminal voltage and inside using the on state characteristic of transistor.Known by electrochemical theory, sufficiently low electricity Pressure and sufficiently low electric current can suppress the electrochemical reaction of electrolyte and switch.

Fig. 5 is the circuit diagram of the reduction switch terminal voltage according to the embodiment of the present invention.The electricity. road includes：

(1) power supply U₅₁, for providing running voltage to circuit；

(2) switching signal unit, comprising the first transistor Q₅₁, for according to switch K₅₁State, output switching signal, Wherein, switch K₅₁It is coupling in the first transistor Q₅₁With power supply U₅₁Outfan between, for controlling the first transistor Q₅₁With power supply U₅₁The break-make of the current path between outfan；

(3) bias unit, by the resistance R for connecting₅₁And R₅₂Composition, is respectively coupled to power supply U₅₁Outfan with switch letter Number unit, for exporting bias voltage, that is, resistance R to switching signal unit₅₁And R₅₂Node be coupled to transistor Q₅₁'s Base stage；

(4) signal analysis module I C5, is coupled to the first transistor Q₅₁Colelctor electrode, for according to the first transistor Q₅₁Collection The switching signal of the output of electrode and export corresponding control signal；

(5) output module, including transistor seconds Q₅₂, motor M₅₁, output module is defeated according to signal analysis module I C5 The control signal for going out decides whether actuating motor M₅₁。

As shown in Figure 5, switch K₅₁The voltage at two ends is by transistor Q₅₁The type of (i.e. the first transistor) is determined with bias unit It is fixed, as shown in formula (2)：

Wherein, U_K51To switch K₅₁Both end voltage, V_EBFor transistor Q₅₁The voltage of the PN junction between emitter stage and base stage Absolute value.

Therefore, by bias unit and transistor Q₅₁Reasonable disposition is carried out, switch K can be caused₅₁Disconnect and inside is deposited In conducting solution and/or steam, the voltage at its two ends is less than 1V and is more than 0V.

K is switched in order to allow₅₁Transistor Q during closure₅₁Can turn on, the output voltage of bias unit is configured to more than V_EB, So that voltage U_K510V can be more than.It will be appreciated by persons skilled in the art that for the transistor of same type, V_EB Value changes very little, therefore, the output voltage of bias unit determines voltage U_K51Value.

Compared to Fig. 1, the switch K in Fig. 5₅₁To power supply U₅₁Current path on sealed in transistor Q₅₁.As switch K₅₁Close During conjunction, switch K is flowed through₅₁Emitter current I_E=I_EB+I_EC, wherein, I_EC=I_R53+I_IC, i.e. collector current passed through respectively Resistance R₅₃With inflow power supply U inside IC5₅₁。

The operation principle of Fig. 5 circuits is illustrated：

(1) work as K₅₁During disconnection, Q₅₁It is not turned on, I/O⁵¹On level be R₅₃Voltage, now, I/O⁵¹On level be Low level.

(2) work as K₅₁During closure of more than 100ms, Q₅₁Effectively turn on, resistance R₅₃Collector potential will be pulled up, until being more than 0.7U₅₁, i.e. I/O⁵¹On level can be identified as height, IC5 detects I/O⁵¹On level mutation from low to high, IC5 recognizes Fixed switch is effectively triggered by user, then will be in I/O^S2Output high level, with driving FET Q₅₂, so as to start motor M₅₁.When User disconnects switch K₅₁When, Q₅₁It is cut off, I/O⁵¹Low level, I/O are reverted to from high level⁵¹Level from high to low when, IC5 recognizes Surely switch K₅₁It is released, IC5 maintains the work of motor.As switch K₅₁When be closed more than 100ms again, I/O⁵¹Level again From low mutation to height, IC5 assert that switch is triggered by user again, and IC5 is by I/O⁵²Output be changed to low level from high level, so as to Close field effect transistor Q₅₂With motor M₅₁.So circulate, with repeated work.

Below to how to configure biasing circuit and load resistance R₅₃It is described in detail：

Work as K₅₁When dry air breaks, due to Q₅₁Do not turn on, resistance R₅₃On voltage be 0V, work as K₅₁It is empty being dried When closing in gas, K₅₁It is shorted, switchs K₅₁Two ends resistance is 0 Ω.Can be obtained according to the on state characteristic of bias unit, transistor Go out the voltage relationship as shown in formula (3)：

Wherein, I_SFor the reverse saturation current of the NP knots between transistor base and emitter stage, U_dFor the conducting door of the NP knots Sill voltage.Generally, i_b51Far smaller than i₅₁, therefore ignore i in calculating process_b51Impact, silicone tube transistor U_dOrdinarily be about 0.5V。

R can be obtained by formula (3)₅₁、R₅₂Resistance meet following relation：

In the present embodiment, take R₅₂=120K Ω, U₅₁=3V, then R₅₁≥24KΩ。

Equivalent circuit diagram when Fig. 6 has an aqueous solution for the switch internal of Fig. 5.

As switch K₅₁During the aqueous solution of internal presence conduction, which is equivalent to perfect switch K₆₁With equivalent resistance R_{Water 6}It is in parallel.For Ensure effective work of switch, it is to avoid the switch containing conductive aqueous solution then required to the switching signal of IC5 mistakes：Opening When opening, the level on the I/O ports of IC5 and switching signal connection is low level for shut-off, when switching effectively closed, IC and switch Level on the I/O ports of signal connection is high level.

As switch K₅₁Inside there is aqueous solution and switch K₅₁During disconnection, according to resistance R_{Water 6}, transistor Q₅₁And resistance R₅₃Constitute Branch road can obtain following voltage relationship：

It is understood that by by load resistance R₅₃It is set smaller than equivalent resistance R_{Water 6}, as (i_b51+I_C51)R_{Water 6}＜ 0.3U₅₁When, I_C51R₅₃0.3U must be less than₅₁。

Therefore, it can draw resistance R₅₃Scope：

In order that the circuit is when supply voltage is 2-3V, U_k611V can be less than, then takes U_k61Maximum U_k61maxFor 1V, takes U₅₁Minima U_51minFor 2V, R is taken_{Water 6}Minima R_{Water 6min}For 40K Ω, then resistance R₅₃Scope be：

As switch K₆₁During closure, R_{Water 6}It is shorted, has following voltage relationship：

Obviously, now resistance R₅₃To be pulled up transistor Q₅₁The current potential of colelctor electrode, according to transistor turns characteristic, generally works as U_ec51 During ＜ 0.7V, i_b51And I_C51Close to linear relationship, as shown in formula (9)：

In U_ec51After ＞ 0.7V, I_C51=β₅₁₀i_b51, wherein, β₅₁₀For the direct current amplification of transistor, β₅₁For U_ec＜ During 0.7V, the instantaneous direct current amplification of transistor.

According to the aforementioned definition to high level, U is needed_R53＞ 0.7U₅₁, so U_ec51＜ 0.3U₅₁；In order to ensure switch letter Number susceptiveness, usually require that U_ec51＜ 0.6V.

In general, the output voltage in power supply is more than its output termination voltage U₅₁₉When, need to keep motor just to remain to Often work, now the U of the first transistor_ec51＜ 0.3U₅₁₉。

Preferably, in order that circuit is safer, U can be taken_ec51≤0.24U₅₁₉.Therefore following relation can be drawn：

Obviously, power supply output termination voltage U₅₁₉When, transistor base current is minima (that is, i_b519), then R₅₃Value Scope can be adjusted to：

In sum, resistance R₅₃Span be：

In the present embodiment, transistor Q₅₁9014 models are taken, then corresponding R₅₃Span be：11.07K Ω ＜ R₅₃ ＜ 24K Ω

Further, for the steady operation of circuit, in addition it is also necessary to power termination voltage U is operated in circuit₅₁₉When base stage electricity Stream i_b519Do and further limit.A for it is default with this understanding, flow through resistance R₅₁On electric current i₅₁₉Than base current i_b519's Multiple, generally takes A for 100.From bipolar transistor characteristic, work as i_b51910i_sWhen, approx, following relation can be obtained：

In order that the voltage of switch terminals is less than 1V, then need to meet the relation shown in formula (15)：

i₅₁R₅₁-U_eb＜ 1V (15)

R can determine that by formula (14) and (15)₅₁Scope：

Also, the scope of the all-in resistance of biasing circuit is：

As the maximum U of electric power output voltage₅₁₈When, it is desirable to switch internal has terminal voltage when aqueous solution and its disconnection little In nV, then following relation can be drawn：

From formula (18), R₅₁In the maximum U of the exportable voltage of power supply₅₁₈At present span, convolution (16), Resistance R₅₁Span can determine for：

Further, it is possible to determine resistance R₅₃Scope：

In the present embodiment, take U₅₁₉=2V, U_d=0.5V, U₅₁₈=3V, β₅₁₀=200, i_s=0.0001mA, R₅₂= 120K Ω, n=1V, A=100, then R₅₁Scope it is as follows：

51.21KΩ≤R₅₁≤142.28KΩ (21)

Therefore, according to formula (20), (21) and (22), R can be taken₅₁=56K Ω, R₅₂=120K Ω, R₅₃=18K Ω.

Above-mentioned calculating process proves that the circuit in Fig. 5 can match suitable transistor Q₅₁, resistance R₅₁-R₅₃.It is based on Above-mentioned configuration, the level change on the I/O mouths that IC5 is connected with switching signal can correctly reflect that being opened or closed for switch is dynamic Make, while so that switch terminal voltage of the switch in off-state is less than 1V, so as to greatly inhibit the electrochemistry in switch Reaction, extends the life-span of switch.

Fig. 7 is another kind of circuit diagram for reducing switch terminal voltage according to the embodiment of the present invention.Compared to Fig. 3, open Close K₇₁Transistor Q is sealed in on the current path of power supply₇₁(i.e. the first transistor).Resistance R₇₁And R7₂Composition biasing circuit, uses In to transistor Q₇₁Base stage provide bias voltage.

Fig. 7 is the circuit diagram of the circuit combination present invention improvement for Fig. 3, and the switch in Fig. 7 is in dry air.Phase Compared with Fig. 3, K is switched₇₁Transistor Q is sealed in on the current path of power supply₇₁.Switch K₇₁During closure, the one of the electric current that power supply flows out Part flows through K₇₁A part by the PN junction between the emitter stage of transistor and base stage through resistance R₇₂Power supply is flowed into, is flowed through K₇₁Electric current emitter stage and colelctor electrode of the another part by transistor between PN junction and NP tying-ins cross motor M₇₁Flow into electricity Source.Obviously the electric current that power supply flows out in figure 3 is through switch K₃₁With motor M₃₁Power supply is flowed back to directly, in switch K₃₁Arrive power supply The PN junction or NP knot of transistor is not sealed on current path.R7 in Fig. 7₁And R7₂Composition transistor Q₇₁Biasing circuit, lean on The offset portion of nearly positive source is upper offset circuit, is below-center offset part, i.e. R near the offset portion of power cathode₇₁For upper Offset portion, R₇₂For below-center offset part.In the figure 7, switch K₇₁One end be electrically connected to transistor Q₇₁Emitter stage, switch K₇₁ With transistor Q₇₁Emitter stage and base stage between PN junction series connection, constitute the first series circuit, and the series circuit and transistor Q₇₁Upper offset part (the R of biasing circuit₇₁) in parallel.

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

Switch K₇₁It is in dry air, as switch K₇₁During disconnection, Q₇₁Do not turn on, motor M₇₁Cannot work.Work as switch K₇₁During closure, Q₇₁Conducting, motor M₇₁Work, electrical appliance work.As switch K₇₁When being again off, transistor Q₇₁End again, Motor M₇₁Quit work.

Equivalent circuit diagram when Fig. 8 has an aqueous solution for the switch internal of Fig. 7.Now, switch K₇₁It is equivalent to perfect switch K₈₁ With equivalent resistance R_{Water 8}It is in parallel.As switch K₈₁During disconnection, following voltage relationship can be obtained：

U_R71=U_K81+U_eb71=U_{R water 8}+U_eb71 (23)

U₇₁=U_R71+U_R72=U_M71+U_ec71+(i_b71+i_c71)R_{Water 8} (24)

Generally, R_{Water 8}For tens of thousands of ohms, and motor M₇₁Equivalent resistance be several ohm to more than ten ohm, so, when switch K₈₁ During disconnection, U_K81It is far longer than U_M71.By preceding method reasonable disposition R₇₁And R₇₂, switch K can be caused₈₁The voltage at two ends is little In 1V and it is more than 0V, correspondingly U_M71At least below 0.1V, motor M₇₁Will not work.As switch K₈₁Inside there is conductive aqueous solution, and During switch closure, transistor Q₇₁ON operation, U_ec71Very little, therefore motor M₇₁On obtain high voltage, motor is started working.When opening When closing cut-off again, it is more than 0V less than 1V and is more than U far away due to switching terminal voltage_M71, so U_M71At least below 0.1V, motor can not start.

Fig. 9 is according to another kind of circuit diagram for reducing switch terminal voltage of the embodiment of the present invention.

Compared to Fig. 3, K is switched₉₁Transistor Q is sealed in on the current path of power supply₉₁(i.e. the first transistor), resistance R₉₁ And R₉₂Composition transistor Q₉₁Biasing circuit.Transistor Q₉₁Colelctor electrode be coupled to field effect transistor Q₉₂(i.e. transistor seconds) Grid, to provide metal-oxide-semiconductor Q₉₂Switching signal, so as to control the working condition of motor M91.

As switch K₉₁It is in dry air, switchs K₉₁During disconnection, transistor Q₉₁Do not turn on, field effect transistor Q₉₂Grid Extremely 0V, field effect transistor Q₉₂Cut-off, motor cannot work.As switch K₉₁During closure, transistor Q₉₁Conducting, resistance R₉₃Will be crystalline substance Body pipe Q₉₁Collector potential on further supply voltage, so as to field effect transistor Q₉₂Conducting, motor M₉₁Work.As switch K₉₁Again During secondary disconnection, transistor Q₉₁End again, motor M₉₁Quit work.

When switch internal has conductive aqueous solution, K is switched₉₁It is equivalent to perfect switch K₁₁₁With equivalent resistance R_{Water 11}And Connection.Switch Ks of the Figure 11 for Fig. 9₉₁There is the equivalent circuit diagram during aqueous solution inside.

As switch K₉₁When inside having aqueous solution, K is switched₉₁Shown in voltage relationship during disconnection such as formula (25) and (26)：

U_R91=UK₁₁₁+U_eb91=U_{R water 11}+U_eb91 (25)

U₉₁=U_R91+U_R92=U_R93+U_ec91+(i_b91+i_c91)R_{Water 11} (26)

Equally, according to aforesaid method, to resistance R₉₁-R₉₃Configured, when can cause to switch off, switch terminals electricity Pressure is less than 1V and is more than 0V, correspondingly, resistance R₉₃On voltage be less than 1V.In general, field effect transistor Q₉₂Conducting threshold electricity Pressure V_gs＞ 1.5V, therefore, field effect transistor Q₉₂Can not turn on, motor M₉₁Do not work.Simultaneously as switch terminal voltage is less than 1V, stream The electric current for crossing switch is greatly reduced, so as to the electrochemistry that relatively low switch terminal voltage and little electric current greatly suppress switch is anti- Should, so as to improve the life-span of switch.

When having conductive aqueous solution in switch and close, Q₉₁Effectively turn on, now supply voltage is equal to transistor Q₉₁And electricity Resistance R₉₃On voltage sum.By to resistance R₉₁-R₉₃Configured, U can be made_R93Supply voltage is close to, so that field effect Should pipe conducting, with motor M₉₁。

In sum, Fig. 9, in 11, by appropriately configured R₉₁-R₉₃, inside can be made to have the switch of conductive aqueous solution disconnected When opening, its terminal voltage is less than 1V and is more than 0V, and keeps motor not work.In switch closure, can normally start motor.Due to Switch terminal voltage when switching off is less than 1V, greatly inhibits the electrochemical reaction of switch, so as to substantially prolongs switch Life-span, while having prevented the probability of hydrogen detonation.

Figure 10 is that, according to another kind of circuit diagram for reducing switch terminal voltage of the embodiment of the present invention, Figure 12 is opened for Figure 10's Equivalent circuit diagram when there is an aqueous solution in portion inside the Pass.

As shown in Figure 10, switch K₁₀₁In dry air.Compared to Fig. 3, K is switched₁₀₁To on the current path of power supply Seal in transistor Q₁₀₁(i.e. the first transistor).As switch K₁₀₁During closure, a part for the electric current that power supply flows out is through R₁₀₁, stream PN junction between base stage and emitter stage of the Jing by transistor, flows through K₁₀₁Flow into power supply；Flow through K₁₀₁Electric current another part From flowing through resistance R₁₀₃And the NP knots and PN junction between the emitter stage and colelctor electrode of transistor flows back to the electric current of power supply.Therefore, exist Switch K₁₀₁Transistor Q has been sealed in on the current path of power supply₁₀₁Base stage and emitter stage between PN junction and colelctor electrode with send out NP knots and PN junction between emitter-base bandgap grading.R in Figure 10₁₀₁And R₁₀₂Composition transistor Q₁₀₁Biasing circuit, it is inclined near positive source Part is put for upper offset circuit, is below-center offset part, i.e. R near the offset portion of power cathode₁₀₁For upper offset part, R₁₀₂For Below-center offset part.Switch K₁₀₁With transistor Q₁₀₁The emitter e of (i.e. the first transistor)₁₀₁With base stage b₁₀₁Between NP knot string Connection, constitutes the second series circuit, and the series circuit and transistor Q₁₀₁Below-center offset part (the R of biasing circuit₁₀₂) in parallel.

According to aforesaid method, resistance R is configured₁₂₁.R₁₂₃, as switch K₁₀₁In being in dry air and when disconnecting, crystal Pipe Q₁₀₁Do not turn on, its collector potential U_C101Equal to supply voltage U₁₀₁, therefore, transistor Q₁₀₂(i.e. transistor seconds) does not lead Logical, motor cannot work.As switch K₁₀₁During closure, transistor Q101 conductings, U_C101Diminish, so that transistor Q₁₀₂Lead It is logical, motor M₁₀₁Work.When electrical appliance switch internal has conductive aqueous solution, K is switched₁₀₁It is equivalent to perfect switch K₁₂₁With Equivalent resistance R_{Water 12}It is in parallel.

As switch K₁₀₁When inside having aqueous solution, K is switched₁₀₁During disconnection,

U_R102=U_K121+U_be121=U_{R water 12}+U_be121 (27)

U₁₀₁=U_R103+U_ce101+(i_b101+i_c101)R_{Water 12} (28)

Resistance R is configured by aforesaid method₁₀₁-R₁₀₃, for example, if U_101max=3V, takes R₁₀₁=120K Ω, R₁₀₂=56K Ω、R₁₀₃=18K Ω, the voltage such that it is able to make switch ends are less than 1V, correspondingly U_R103At least below 0.5V, so, crystal Pipe Q₁₀₂Can not turn on, motor M₁₀₁Cannot work.Due to U_K121Less than 1V, the electric current for flowing through switch is greatly reduced, so as to low Switch terminal voltage and little electric current greatly suppress the electrochemical reaction of switch, improve the life-span of switch.

As switch K₁₂₁When inside having conductive aqueous solution, and when switching closure, U_K121=0V, according to above-mentioned to resistance R₁₀₁-R₁₀₃ Configuration, when the switch is closed, transistor Q₁₀₁Effectively turn on, and U can be made_R103＞ 0.7V, so as to transistor Q₁₀₂Effectively Conducting, motor M₁₀₁₀₁On obtain high voltage, motor is started working.

In sum, by appropriately configured R₁₀₁-R₁₀₃, inside can be made to have the switch of conductive aqueous solution, switched off When, the terminal voltage of switch is less than 1V, and keeps motor not work.In switch closure, can normal actuating motor.In the same manner, by Switch terminal voltage when switching off is less than 1V, greatly inhibits the electrochemical reaction of switch, so as to substantially prolongs out The life-span of pass, while having prevented the probability of hydrogen detonation.

Invention additionally discloses a kind of electrical appliance, for example electric toothbrush, the electrical appliance include：(1) power supply, usually charge electricity Pond or aneroid battery, for providing running voltage to the electrical appliance；(2) switch module, is coupled to power supply, for control power supply with it is rear The break-make of the current path between continuous circuit；(3) motor, is coupled to switch module and power supply, for the control according to switch To decide whether that driving brush works.

Based on above-mentioned configuration, the electrical appliance can ensure the effectiveness for switching in a humidity environment, extend switch Life-span.

It will be appreciated to those of skill in the art that above-described embodiment is only intended to illustrate the design of the present invention and example electricity Road, can not be used for limiting the scope of the invention.For example, switch can be connected to the transmitting of transistor by resistant series Pole, so as to reduce switching the voltage that can be assigned to；Bias unit can by linear voltage regulator, Switching Power Supply or other can be defeated The circuit for going out specified bias voltage is constituted.

Those skilled in the art are also understood that, the first transistor in above-described embodiment, for example Q₅₁Can also be Field-effect transistor.In the case, one end of switch is coupled to the grid of the source electrode of the first transistor, switch and the first transistor NP knot series connection between pole and source electrode forms the upper offset part of the first series circuit, the first series circuit and bias unit simultaneously Connection；Or switch and the PN junction between the grid and source electrode of the first transistor connect to form the second series circuit, the second series circuit With the below-center offset part in parallel of bias unit.

The above description of the disclosure is used to enable any those of ordinary skill of this area to realize or using the present invention.It is right For those of ordinary skill in the art, the various modifications of the disclosure will be apparent from, and generality defined herein Principle can also be applied to other deformations in the case of without deviating from the spirit and scope of the disclosed invention.Therefore, the present invention simultaneously Example as herein described and design are not limited to, but it is consistent with the widest scope of principle disclosed herein and novel features.

Claims (13)

1. it is a kind of to switch the controllable device of terminal voltage, including：

Switching signal unit, for the state according to switch, exports corresponding switching signal, and the switch is coupled in the switch Between signal element and the outfan of power supply；

Bias unit, is coupled to the switching signal unit, for exporting bias voltage to the switching signal unit；

Wherein, during the steam for switching off and there is conducting liquid and/or conducting liquid inside which when described, the bias unit It is engaged with the switching signal unit, to control the terminal voltage of the switch and flow through the electric current of the switch.

2. device as claimed in claim 1, it is characterised in that the switching signal unit includes the first transistor, described to open Pass is coupled between the first transistor and power supply, is led to for controlling the electric current between the first transistor and the power supply The break-make on road.

3. device as claimed in claim 2, it is characterised in that the first transistor is bipolar transistor, the switch One end be coupled to the emitter stage of the first transistor,

Wherein, the switch and the PN junction between the emitter stage and base stage of the first transistor connect to form the first series electrical The upper offset part in parallel of road, first series circuit and the bias unit；Or

The switch and the knots of the NP between the emitter stage and base stage of the first transistor are connected and form the second series circuit, described The below-center offset part in parallel of the second series circuit and the bias unit.

4. device as claimed in claim 3, it is characterised in that first and second series circuit also includes at least one resistance.

5. device as claimed in claim 2, it is characterised in that when described switching off,

If there is the steam of conducting liquid and/or conducting liquid in the switch internal, what the first transistor was on State；

If the switch internal is dried, state of the first transistor in cut-off.

6. device as claimed in claim 1, it is characterised in that described device also includes motor, the motor is coupled to The outfan of the switching signal unit.

7. device as claimed in claim 1, it is characterised in that described device also includes：

Output module, including transistor seconds and the motor being in series with the transistor seconds；

Wherein, the output module is coupled to the outfan of the switching signal unit, and based on the switching signal unit Output signal configures the working condition of the motor.

8. device as claimed in claim 1, it is characterised in that go here and there between the outfan and low level of the switching signal unit Join at least one pull-up resistor.

9. device as claimed in claim 7, it is characterised in that described device also includes signal analysis module, the signal point Analysis module is coupling between the outfan of the output module and the switching signal unit, with according to the switching signal unit Output signal export for controlling the control signal of the output module.

10. device as claimed in claim 7, it is characterised in that the transistor seconds is field-effect transistor, wherein, institute State the drain electrode of motor in series to the transistor seconds.

11. devices as claimed in claim 7, it is characterised in that the transistor seconds is bipolar transistor, wherein, institute State the colelctor electrode of motor in series to the transistor seconds.

12. devices as claimed in claim 2, it is characterised in that the first transistor be field-effect transistor, the switch One end be coupled to the source electrode of the first transistor,

Wherein, the switch and the knots of the NP between the grid and source electrode of the first transistor are connected and form the first series circuit, The upper offset part in parallel of first series circuit and the bias unit；Or

The switch and the PN junction between the grid and source electrode of the first transistor connect to form the second series circuit, and described the The below-center offset part in parallel of two series circuits and the bias unit.

A kind of 13. electric toothbrushes of the device using as described in any one of claim 1 to 12, comprising：

It is coupled to the brush of motor, the motor decides whether driving brush according to the control of the switch and works.