The commutation circuit of a kind of handheld device and battery thereof and external power source
Technical field
The utility model relates to a kind of commutation circuit, relates in particular to the commutation circuit of a kind of handheld device and battery thereof and external power source.
Background technology
As everyone knows, there are a lot of handheld devices to use powered battery, the interface of external power source input are provided simultaneously, the problem that will exist powered battery and external power source to switch like this.Battery is most important service time in the handheld device, when carrying out circuit design, need use up the energy that utilizes to greatest extent in the battery.In the prior art, generally use two Schottky diodes to isolate, have reliable, the with low cost characteristics of circuit simple and stable.But because there is certain voltage loss in Schottky diode itself, so the battery power utilance is lower.
The utility model content
The technical problem that the utility model will solve is; The low defective of battery power utilance when using two Schottky diodes to isolate to above-mentioned prior art provides the high battery of a kind of battery power utilance and the commutation circuit of external power source.
The utility model solves the technical scheme that its technical problem adopted: the commutation circuit of constructing a kind of battery and external power source; Said commutation circuit comprises Schottky diode D1, resistance R 1, resistance R 2, switching tube; Wherein, the input interface of external power source is successively through resistance R 1, resistance R 2 ground connection, and the tie point of resistance R 1 and resistance R 2 connects first end of switching tube; The input of the second termination battery of switching tube; The 3rd termination power output of switching tube, the positive pole of Schottky diode D1 connects the input interface of external power source, and the negative pole of Schottky diode D1 connects power output end.
In the commutation circuit of described battery of the utility model and external power source; Said switching tube is P channel MOS tube Q1; First end of switching tube is the grid of P channel MOS tube Q1; Second end of switching tube is the drain electrode of P channel MOS tube Q1, and the 3rd end of switching tube is the source electrode of P channel MOS tube Q1.
The utility model is also constructed a kind of handheld device, comprises the input interface of battery and external power source, and said handheld device also comprises commutation circuit; Said commutation circuit comprises Schottky diode D1, resistance R 1, resistance R 2, switching tube; Wherein, the input interface of external power source is successively through resistance R 1, resistance R 2 ground connection, and the tie point of resistance R 1 and resistance R 2 connects first end of switching tube; The input of the second termination battery of switching tube; The 3rd termination power output of switching tube, the positive pole of Schottky diode D1 connects the input interface of external power source, and the negative pole of Schottky diode D1 connects power output end.
In the described handheld device of the utility model, said switching tube is the P channel MOS tube, and first end of switching tube is the grid of P channel MOS tube Q1, and second end of switching tube is the drain electrode of P channel MOS tube Q1, and the 3rd end of switching tube is the source electrode of P channel MOS tube Q1.
Implement the technical scheme of the utility model, when having only powered battery, the switching tube conducting; Conduction voltage drop is little, can reduce the wastage greatly, has improved the battery power utilance; And because the existence of Schottky diode D1, the power supply of battery can't be poured in down a chimney to external power source.When external power supply begins to supply power, switching tube by, battery powered path cuts off, and is only supplied power by external power source.
Description of drawings
To combine accompanying drawing and embodiment that the utility model is described further below, in the accompanying drawing:
Fig. 1 is the circuit diagram of the commutation circuit embodiment one of the utility model battery and external power source.
Embodiment
As shown in Figure 1, in the circuit diagram of the commutation circuit embodiment one of the utility model battery and external power source, this commutation circuit comprises Schottky diode D1, resistance R 1, resistance R 2, switching tube.Should be noted that in this embodiment switching tube is selected P channel MOS tube Q1 for use; Wherein, the input interface of external power source is successively through resistance R 1, resistance R 2 ground connection, and the tie point of resistance R 1 and resistance R 2 connects the grid of metal-oxide-semiconductor Q1; The drain electrode of metal-oxide-semiconductor Q1 connects the input of battery; The source electrode of metal-oxide-semiconductor connects power output end, and the positive pole of Schottky diode D1 connects the input interface of external power source, and the negative pole of Schottky diode D1 connects power output end.
The operation principle of this commutation circuit is described below: as shown in Figure 2, be example with the 4.2V lithium battery, when having only this lithium battery power supply; The grid of metal-oxide-semiconductor Q1 (G) utmost point is low level through resistance R 2 ground connection, and metal-oxide-semiconductor Q1 raceway groove is opened; And channel resistance is less than 50 milliohms, and under the situation of 1A electric current, conduction voltage drop is merely 0.05 volt; The pressure drop of Schottky diode 0.4-0.6V can reduce the wastage more than 87% relatively.Because the existence of Schottky diode D1, the power supply of battery can't be poured in down a chimney to external power source.When external power supply began to supply power, it was high level that the grid of metal-oxide-semiconductor Q1 (G) utmost point connects external power source through resistance R 1, R2, and metal-oxide-semiconductor Q1 raceway groove is closed, and battery powered path cuts off, and is only supplied power by external power source.When using external power source, the utilance of electric energy is not to be concerned about very much, uses the Schottky diode simplicity of design reliable.In addition, the components and parts that this circuit relates to are device commonly used, and it is the metal-oxide-semiconductor of AO3401 that metal-oxide-semiconductor Q1 adopts model, and it is the diode of SS24 that Schottky diode D1 adopts model, reasonable in design with low cost, help producing in enormous quantities.
The utility model is also constructed a kind of handheld device, and this handheld device comprises the input interface and the commutation circuit of battery, external power source, and wherein, commutation circuit is the commutation circuit in the foregoing description, please with reference to the description of preceding text.
Be an embodiment of the utility model more than, only be used to explain the utility model, and be not used in the scope that limits the utility model, in another embodiment, switching tube can select for use relay to substitute.
The preferred embodiment that the above is merely the utility model is not limited to the utility model, and for a person skilled in the art, the utility model can have various changes and variation.All within the spirit and principle of the utility model, any modification of being done, be equal to replacement, improvement etc., all should be included within the claim scope of the utility model.