Charging circuit
Technical field
The utility model relates to a kind of charging circuit, especially a kind of charging circuit that secondary cell is charged.
Background technology
Traditional charging circuit charges to secondary cell as isolating device by Schottky diode, and the tube voltage drop of Schottky diode is generally 0.3-0.5V, and this just requires the high 0.3-0.5V of voltage ratio cell voltage of charge power supply to charge to battery.For the low-tension supply as the solar panel, the such pressure drop meeting of charging circuit causes under the low light level and can't charge, and can consume many power on diode, greatly reduces the efficient of charging circuit.
Summary of the invention
The technical problems to be solved in the utility model provides a kind of low pressure drop, high efficiency charging circuit.It is little that the technical problem that the utility model further will solve provides a kind of volume, charging circuit with low cost.
In order to solve the problems of the technologies described above, the technical solution adopted in the utility model is, a kind of charging circuit comprises a metal-oxide-semiconductor, and its drain electrode and source electrode are connected in the charging circuit main circuit, in order to the open and close charging circuit; One voltage comparator in order to the same cell voltage of charge power supply voltage relatively, and is controlled the break-make of described metal-oxide-semiconductor, two inputs of described voltage comparator, one termination charge power supply, another termination battery, the grid of the described metal-oxide-semiconductor of output termination of voltage comparator.
Above-described charging circuit preferably also comprises divider resistance R2, R3, R4, R5; Divider resistance R2 connects with R3, be connected between the both positive and negative polarity of charge power supply, the contact of divider resistance R2 and R3 connects the inverting input of voltage comparator, and divider resistance R4 connects with R5, be connected between the both positive and negative polarity of battery, the contact of divider resistance R4 and R5 connects the in-phase input end of voltage comparator.
Above-described charging circuit, described metal-oxide-semiconductor can be the N-MOS pipes, and the drain electrode of described N-MOS pipe connects the charge power supply negative pole, and source electrode connects battery cathode.
Above-described charging circuit, described metal-oxide-semiconductor can also be the P-MOS pipes, and the source electrode of described P-MOS pipe connects anode, and drain electrode connects the charge power supply positive pole.
The circuit that above-described charging circuit, described charging circuit both can have been made discrete device separately also can be made independent integrated circuit or be integrated in the integrated circuit as functional module.
The utility model is because adopt metal-oxide-semiconductor to battery charge, and when detecting charge power supply voltage and be higher than cell voltage, the metal-oxide-semiconductor conducting is to battery charge, when detecting supply voltage and be lower than cell voltage, then turns off metal-oxide-semiconductor.The voltage drop of metal-oxide-semiconductor is understood usually less than 0.1V during conducting, and traditional Schottky diode charging circuit has 0.3-0.5V, so under the battery situation identical with power supply, this circuit charging current can be bigger than traditional circuit, and the charge efficiency height.
If the utility model adopts integrated circuit, then can dwindle the volume of charging circuit greatly, reduce the cost of charging circuit.
Description of drawings
Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.
Fig. 1 is the circuit theory diagrams of the utility model charging circuit embodiment 1.
Fig. 2 is the circuit theory diagrams of the utility model charging circuit embodiment 2.
Embodiment
The embodiment 1 of the utility model charging circuit shown in Figure 1 is the N-MOS charging circuit.Wherein, divider resistance R2=R4, R3=R5, A1 are voltage comparator, T1 is the N-MOS pipe.S+, S-are respectively the charge power supply both positive and negative polarity, and B+, B-are respectively the both positive and negative polarity of battery.
N-MOS charging circuit principle: when voltage comparator detected charge power supply voltage and is lower than battery, low level of voltage comparator output was ended metal-oxide-semiconductor, and electric current can not constitute the loop.When detecting charge power supply voltage and be higher than cell voltage, high level of voltage comparator output makes the metal-oxide-semiconductor conducting, charging current, is got back to charge power supply negative pole S-through metal-oxide-semiconductor T1 again and is constituted charge circuit through anode B+, battery cathode B-by the anodal S+ of charge power supply.
The embodiment 2 of the utility model charging circuit shown in Figure 2 is the P-MOS charging circuit.P-MOS charging circuit principle is consistent with N-MOS charging road, has just replaced the N-MOS pipe with the P-MOS pipe, slightly change on the circuit connecting.When voltage comparator A1 detected charge power supply voltage and is lower than battery, high level of voltage comparator A1 output ended metal-oxide-semiconductor T2, and electric current does not constitute the loop.When detecting charge power supply voltage and be higher than cell voltage, low level of voltage comparator A1 output makes the metal-oxide-semiconductor conducting, electric current by the anodal S+ of charge power supply through metal-oxide-semiconductor T2, anode B+, again through battery cathode () get back to the charge power supply negative pole () constitute charge circuit.
Charging circuit of the present utility model is the same with traditional charging circuit, all be when charge power supply voltage is higher than cell voltage to battery charge, charge power supply voltage is lower than when keeping conducting inadequately and ends, not to battery charge.
The utility model adopts metal-oxide-semiconductor as charge member; voltage drop during conducting usually can be less than 0.1V; and traditional Schottky diode charging circuit is wanted 0.3-0.5V; under the charge power supply situation identical with rechargeable battery; this circuit is bigger than traditional circuit charging current, thereby has reduced waste of electric energy.
The circuit that described charging circuit both can have been made discrete device separately also can be made independent integrated circuit or be integrated in the integrated circuit as functional module.