Universal serial bus adaptor and universal serial bus cable
A universal serial bus (USB) adaptor supplies a large charging current to charge a device. The USB adaptor includes a voltage conversion circuit, a USB interface, a current detection circuit, a first switch, a second switch, and a third switch. The USB interface includes a power pin, a first data pin, a second data pin, and a ground pin. The current detection circuit detects a charging current of the device, and converts the charging current into a voltage to compare the charging current with a reference voltage to output a comparison signal. The first switch, the second switch, and the third switch control connection relationships between the power pin and the first data pin, the first data pin and the second data pin, and the second data pin and the ground pin according to the comparison signal, respectively. A USB cable is also provided.
1. A universal serial bus (USB) adaptor comprising:
a voltage conversion circuit converting voltage signals output by an external power;
a USB interface comprising a power pin connected to the voltage conversion circuit, a first data pin, a second data pin, and a ground pin;
a current detection circuit connected to the voltage conversion circuit and the ground pin, the current detection circuit detecting a charging current of a device, and converting the charging current into a voltage to compare the charging current with a reference voltage to output a comparison signal;
a first switch connected to the current detection circuit, the power pin, and the first data pin, the first switch controlling a connection relationship between the power pin and the first data pin according to the comparison signal output by the current detection circuit;
a second switch connected to the current detection circuit, the first data pin, and the second data pin, the second switch controlling a connection relationship between the first data pin and the second data pin according to the comparison signal output by the current detection circuit; and
a third switch connected to the current detection circuit, the second data pin, and the ground pin, the third switch controlling a connection relationship between the second data pin and the ground pin according to the comparison signal output by the current detection circuit.
2. The USB adaptor of claim 1 , wherein in response to the charging current of the device being greater than the reference voltage, the current detection circuit outputs a first comparison signal, the first switch controls the power pin connected to the first data pin according to the first comparison signal so that the power pin and the first data pin can transmit the charging current in parallel, the second switch controls the first data pin not connected to the second data pin according to the first comparison signal, and the third switch controls the second data pin connected to the ground pin according to the first comparison signal so that the second data pin and the ground pin can transmit the charging current in parallel.
3. The USB adaptor of claim 1 , wherein in response to the charging current of the device not greater than the reference voltage, the current detection circuit outputs a second comparison signal, the first switch controls the power pin not connected to the first data pin according to the second comparison signal, the second switch controls the first data pin connected to the second data pin according to the second comparison signal, and the third switch controls the second data pin not connected to the ground pin according to the second comparison signal.
4. The USB adaptor of claim 1 , further comprising a voltage detection circuit connected to the first data pin or the second data pin, the voltage detection circuit detects and determines whether a direct current (DC) voltage exists at the first data pin or the second data pin or not.
5. The USB adaptor of claim 4 , wherein in response to the DC voltage existing at neither the first data pin nor the second data pin, the voltage detection circuit outputs a first control signal, the first switch controls the power pin not connected to the first data pin according to the first control signal, the second switch controls the first data pin connected to the second data pin according to the first control signal, and the third switch controls the second data pin not connected to the ground pin according to the first control signal.
6. The USB adaptor of claim 4 , further comprising a control circuit connected to the current detection circuit, the voltage detection circuit, the first switch, and the third switch, wherein the voltage detection circuit outputs a second control signal in response to the DC voltage existing at either the first data pin or the second data pin, the current detection circuit outputs a first comparison signal in response to the charging current of the device being greater than the reference voltage, the control circuit outputs a third control signal according to the first comparison signal and the second control signal, the first switch controls the power pin connected to the first data pin according to the third control signal so that the power pin and the first data pin can transmit the charging current in parallel, the second switch controls the first data pin not connected to the second data pin according to the second control signal, and the third switch controls the second data pin connected to the ground pin according to the third control signal so that the second data pin and the ground pin can transmit the charging current in parallel.
7. The USB adaptor of claim 6 , wherein the second switch is connected to the voltage detection circuit, the control circuit comprises:
an AND gate comprising a first input terminal connected to the voltage detection circuit, a second input terminal connected to the current detection circuit, and an output terminal; and
a trigger with an input terminal connected to the output terminal of the AND gate, a first output terminal connected to the first switch, and a second output terminal connected to the third switch.
8. The USB adaptor of claim 4 , further comprising a control circuit connected to the current detection circuit, the voltage detection circuit, the first switch, and the third switch, wherein the voltage detection circuit outputs a second control signal in response to the DC voltage existing at either the first data pin or the second data pin, the current detection circuit outputs a second comparison signal in response to the charging current of the device not greater than the reference voltage, the control circuit outputs a fourth control signal according to the second comparison signal and the second control signal, the first switch controls the power pin not connected to the first data pin according to the fourth control signal, the second switch controls the first data pin not connected to the second data pin according to the second control signal, and the third switch controls the second data pin not connected to the ground pin according to the fourth control signal.
9. The USB adaptor of claim 8 , wherein the second switch is connected to the voltage detection circuit, the control circuit comprises:
an AND gate comprising a first input terminal connected to the voltage detection circuit, a second input terminal connected to the current detection circuit, and an output terminal; and
a trigger with an input terminal connected to the output terminal of the AND gate, a first output terminal connected to the first switch, and a second output terminal connected to the third switch.
10. The USB adaptor of claim 1 , wherein the current detection circuit comprises:
a sampling resistor with a first end connected to the voltage conversion circuit, and a second end connected to the ground pin; and
a comparator with a positive input terminal connected to a node between the sampling resistor and the ground pin, a negative input terminal receiving the reference voltage, and an output terminal connected to the first switch, the second switch, and the third switch.