The commutation circuit of external and built-in power
Technical field
The utility model relates to the electric equipment field, relates more specifically to a kind of commutation circuit of external and built-in power.
Background technology
Along with improving constantly of the progress people's living standard of society, make people pursue comfortable all the more and life style easily.In order to satisfy the requirement of people to facility life, various electrical equipment production firm brings in constant renewal in always and improves its electric equipment products, makes each electric equipment products more simple and convenient for use, and reduces electric equipment products in use to the degree of dependence of external environment condition.
For achieving the above object, one of way of using always in the electric equipment products is now: for each electric equipment products is provided with two kinds of power supply supply modes, built-in power and external power supply are set promptly; When having external power source to can be its power supply around this electrical equipment, then by using external power supply to be this electric power supply operate as normal, this moment, built-in power was not worked, and promptly was not this electric power supply yet; Not being provided with external power source around this electrical equipment or power-off condition taking place and this electrical equipment is carried when going out, can be this electric power supply by built-in power then; And use more convenient for this electrical equipment, common described built-in power is a rechargeable battery, when using external power supply, can be built-in rechargeable battery charging simultaneously, thereby do not need just can normally use described rechargeable battery for the rechargeable battery charging in addition, make that the use of this electrical equipment is more convenient.
But built-in power and external power supply in present electric equipment products, in use can not fast and effeciently switch, thereby make described electrical equipment quit work switching momentary power failure, after built-in power and external power supply finishing switching, need restart this electrical work, for use brings inconvenience.
Therefore, be necessary to provide a kind of commutation circuit of the external and built-in power that between built-in power and external power supply, switches fast to overcome above-mentioned defective.
The utility model content
The purpose of this utility model provides a kind of commutation circuit of external and built-in power, and this commutation circuit can be switched between built-in power and external power supply fast, makes the sustainable and stable work of employed electrical equipment.
For achieving the above object, the utility model provides a kind of commutation circuit of external and built-in power, this external and commutation circuit built-in power comprises external power supply and built-in power, wherein also comprise a metal-oxide-semiconductor, the output of described built-in power is connected with the drain electrode of described metal-oxide-semiconductor, the grounded-grid of described metal-oxide-semiconductor, the source electrode of described metal-oxide-semiconductor is connected with the lead-out terminal of the commutation circuit of described external and built-in power, when described built-in power work output voltage, described metal-oxide-semiconductor conducting and by described lead-out terminal output voltage; The output of described external power supply is connected with the grid of described metal-oxide-semiconductor, and when inserting described external power supply, described metal-oxide-semiconductor ends so that described built-in power stops output voltage, and described external power supply is by described lead-out terminal output voltage.
Preferably, the output of described external power supply is connected with the positive pole of one first diode, and the negative pole of described first diode is connected with described lead-out terminal.
Preferably, the output voltage values of described external power supply is greater than the output voltage values of described built-in power, and the difference of two output voltages is more than or equal to the tube voltage drop of described first diode.
Preferably, described external and commutation circuit built-in power also comprises second diode, and the positive pole of described second diode is connected with the drain electrode of described metal-oxide-semiconductor, and described second diode cathode is connected with described lead-out terminal.
Preferably, described external and commutation circuit built-in power also comprises at least one filter capacitor, and at least one described filter capacitor is connected between the described external power supply and first diode.
Compared with prior art, the commutation circuit of external and built-in power of the present utility model because: the grounded-grid of described metal-oxide-semiconductor, the source electrode of described metal-oxide-semiconductor is connected with the lead-out terminal of the commutation circuit of described external and built-in power, and the output of described external power supply is connected with the grid and the lead-out terminal of described metal-oxide-semiconductor respectively; When inserting described external power supply and using described external power supply to be used electric power supply, the voltage of external power supply output is added on the grid of described metal-oxide-semiconductor at once, make that described metal-oxide-semiconductor grid is that high level ends metal-oxide-semiconductor, to block being connected between described built-in power and the described lead-out terminal, only external power supply is outwards powered by described lead-out terminal; When using built-in power as electric power supply when removing external power supply, the grid of described metal-oxide-semiconductor is a low level because of connecing electricity, thereby makes described metal-oxide-semiconductor conducting, and described built-in power then passes through described metal-oxide-semiconductor output voltage to described lead-out terminal.Thereby, commutation circuit external and built-in power of the present utility model can be switched between built-in power and external power supply fast and effectively, handoff procedure can not closed the electrical equipment in the work, makes the sustainable and stable work of employed electrical equipment, and makes that the use of this electrical equipment is more convenient.
By following description also in conjunction with the accompanying drawings, it is more clear that the utility model will become, and these accompanying drawings are used to explain embodiment of the present utility model.
Description of drawings
Fig. 1 is the structure principle chart of the commutation circuit of the external and built-in power of the utility model.
Embodiment
With reference now to accompanying drawing, describe embodiment of the present utility model, the similar elements label is represented similar elements in the accompanying drawing.As mentioned above, the utility model provides a kind of commutation circuit of external and built-in power, and this commutation circuit can be switched between built-in power and external power supply fast, makes the sustainable and stable work of employed electrical equipment.
Please refer to Fig. 1, Fig. 1 is the structure principle chart of the commutation circuit of the external and built-in power of the utility model.As shown in the figure, described external and commutation circuit built-in power comprises external power supply V1, built-in power V2, metal-oxide-semiconductor Q1 and lead-out terminal OUT1; The output of described built-in power V2 is connected with the drain D of described metal-oxide-semiconductor Q1, and the grid G of described metal-oxide-semiconductor Q1 is by two resistance R 1, R2 ground connection, the source S of described metal-oxide-semiconductor Q1 is connected with described lead-out terminal OUT1, when described built-in power V2 works, the grid G of described metal-oxide-semiconductor Q1 is a low level because of ground connection, thereby make described metal-oxide-semiconductor Q1 conducting, described built-in power V2 then by described metal-oxide-semiconductor Q1 and output voltage to described lead-out terminal OUT1, give the electric equipment of electricity consumption with power supply.Described external power supply V1 is connected with described lead-out terminal OUT1 by connecting one first diode D1, and the output of described external power supply V1 is connected with the positive pole of the described first diode D1, and the negative pole of the described first diode D1 is connected with described lead-out terminal OUT1; In addition, also be provided with at least one filter capacitor between described external power supply V1 and the described first diode D1, in embodiment of the present utility model, described filter capacitor is set to two C1, C2, thereby when using described external power supply V1, the voltage of described external power supply V1 output is just exported stably voltage to described lead-out terminal OUT1 through the described first diode D1 behind two described filter capacitor C1, C2 filtering clutter; And the magnitude of voltage of exporting to described lead-out terminal OUT1 is the output voltage of described external power supply V1 and the difference of the described first diode D1 tube voltage drop.Wherein, magnitude of voltage during for described external power supply V1 of use or built-in power V2 on the described lead-out terminal OUT1 is a stable numerical value, in embodiment of the present utility model, the output voltage values of described external power supply V1 is more than or equal to the output voltage values of described built-in power V2, and the difference of the output voltage of two described power supplys is more than or equal to the tube voltage drop of the described first diode D1.
The output of described external power supply V1 also is connected with the grid G of described metal-oxide-semiconductor Q1 by resistance R 2, thereby when using described external power supply V1, the voltage of described external power supply V1 output is added on the grid G of described metal-oxide-semiconductor Q1 through described resistance R 2, the grid G that makes described metal-oxide-semiconductor Q1 is a high level, and described metal-oxide-semiconductor Q1 is ended, cut off being connected of described built-in power V2 and described lead-out terminal OUT1, therefore only can use described external power supply V1 power supply.Between the drain D of described metal-oxide-semiconductor Q1 and source S (being connected lead-out terminal), the second diode D2 is arranged; The positive pole of the described second diode D2 connects with the drain D (being connected built-in power V2) of described metal-oxide-semiconductor Q1, and its negative pole is connected with the source S of described metal-oxide-semiconductor Q1; Only just conducting work when switching to described built-in power V2 work by described external power supply V1 of the described second diode D2, particularly: when removing described external power supply V1, but described metal-oxide-semiconductor Q1 conducting at once, reason is, though two described filter capacitor C1, C2 appearance value is little but have the discharge of small size amount, make that the grid G of described metal-oxide-semiconductor Q1 can be because of ground connection at once become low level, and described metal-oxide-semiconductor Q1 itself needs also the regular hour just to understand conducting; This moment, the voltage of described built-in power V2 output then outputed to described lead-out terminal OUT1 apace by the described second diode D2; Then along with the conducting of described metal-oxide-semiconductor Q1 because of the voltage of the described second diode D2 positive and negative polarities near identical ending, thereby the switching between described external power supply V1 and the described built-in power V2 can not delayed time because of the time-delay conducting of described metal-oxide-semiconductor, make employed electrical equipment when described external power supply V1 and built-in power V2, need not quit work and restart again, the therefore sustainable and stable work of employed electrical equipment; When described external power supply V1 works, because the output voltage values of described external power supply V1 is more than or equal to the output voltage values of described built-in power V2, the difference of the output voltage of two described power supplys is more than or equal to the tube voltage drop of the described first diode D1, thereby make the magnitude of voltage of the described second diode D2 positive pole be less than or equal to the magnitude of voltage of its negative pole, and cause the described second diode D2 can not conducting work.In addition, at described lead-out terminal OUT1 and the described second diode D2(or the first diode D1) between also be provided with filter capacitor C3, presumable clutter in the described filter capacitor C3 filtering circuit is so that described lead-out terminal OUT1 can export voltage stably at last.
Abovely the utility model is described, but the utility model is not limited to the embodiment of above announcement, and should contains various modification, equivalent combinations of carrying out according to essence of the present utility model in conjunction with most preferred embodiment.