A kind of USB charging circuitTechnical field
The utility model relates to charger field, relates in particular to a kind of USB charging circuit.
Background technology
At present a lot of compact electric apparatus for example MP3 player, camera, phone all can be by the charger charging of self band, also can be inserted on the equipment that computer etc. has USB interface by data wire and charge.If but situation about having a power failure or do not have the next charging that can't finish electrical equipment of situation of external power supply causes great inconvenience to the user.
The utility model content
The purpose of this utility model provides a kind of USB charging circuit, charges for the electrical equipment with USB interface.
The utility model adopts following technical proposals: a kind of USB charging circuit, comprise voltage conversion circuit and USB interface, and the input of voltage conversion circuit is used to connect battery, and the output of voltage conversion circuit is connected with USB interface.
Described voltage conversion circuit comprises the boost conversion chip, and the mode of operation selecting side of boost conversion chip is used to connect anode, and output voltage selecting side ground connection, a reference source voltage output end are by shunt capacitance ground connection; Be connected with inductance between drain electrode end and the anode, and also be connected by the output of voltage stabilizing didoe with the boost conversion chip; The output of boost conversion chip is connected with the power end of USB interface, and the transfer of data negative terminal of USB interface is used to connect anode by the 4th resistance, and the transfer of data anode is by the 5th grounding through resistance, earth terminal ground connection; The electric capacity of wherein powering is used to be connected between battery cathode and the anode.
The negative pole end of described voltage stabilizing didoe also is connected with two ground capacities.
The battery low-voltage of described boost conversion chip detects output and is connected with the positive pole of battery by luminous indicating circuit, and the battery voltage detection input is connected with anode by first resistance, also by second grounding through resistance.
The utility model utilizes the electric energy of battery self by voltage conversion circuit voltage transitions to be the required voltage of USB interface, when power failure occurring or not having the situation of external power supply, the equipment of needs charging can be inserted into USB interface can charge for it, make its continuous firing in case of emergency, greatly facilitate the user.
Description of drawings
Fig. 1 is circuit theory diagrams of the present utility model.
Embodiment
As shown in Figure 1, a kind of USB charging circuit of the utility model, comprise voltage conversion circuit and USB interface IC2, wherein voltage conversion circuit comprises boost conversion chip IC 1(MAX756), the mode of operation selecting side of IC1 (pin 1) is connected with anode, and wherein battery cathode is connected with anode by power supply capacitor C 3; Output voltage selecting side (pin 2) ground connection, a reference source voltage output end (pin 3) are by shunt capacitance C1 ground connection; Be connected with inductance L between drain electrode end (pin 8) and the anode, and also be connected with the output of IC1 by voltage stabilizing didoe D1, the negative pole end of voltage stabilizing didoe D1 also is connected with two ground capacity C2, C4.The output of IC1 is connected with the power end (1 pin) of USB interface IC2, the transfer of data negative terminal of USB interface (pin 2) is connected with anode by the 5th resistance R 4, transfer of data anode (pin 3) is by the 5th resistance R 5 ground connection, earth terminal (pin 4) ground connection; The battery low-voltage of IC1 detects output (pin 4) and is connected with the positive pole of battery by the luminous indicating circuit that is made of resistance R 3 and LED 1, battery voltage detection input (pin 5) is connected with anode by first resistance R 1, also by second resistance R, 2 ground connection; Power supply ground end (pin 7) ground connection of IC1.The utility model with the electric energy of battery by boost conversion chip IC 1 with voltage raise for 5V from its output output, charge for equipment such as the MP3 player that needs charging, camera, phones by USB interface IC2, easy to use.