A wireless charging device, comprising: a wireless transmitting circuit; a transmitting coil, comprising multiple pairs of joints, a joint being formed by a wire drawn from a certain position of the transmitting coil, wherein each of the multiple pairs of joints of the transmitting coil defines the transmitting coil of certain turns and the transmitting-coil turns defined by each pair of joints is different; and a control circuit, configured to select one of the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit; wherein the wireless charging device is operable in a first wireless charging mode or in a second wireless charging mode, and a charging speed at which the wireless charging device charges a device to-be-charged in the first wireless charging mode is higher than in the second wireless charging mode, wherein the control circuit is configured to: control a first pair of joints among the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit to make the wireless transmitting circuit transmit a wireless charging signal through the transmitting coil defined by the first pair of joints, when the wireless charging device charges the device to-be-charged in the first wireless charging mode; and control a second pair of joints among the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit to make the wireless transmitting circuit transmit a wireless charging signal through the transmitting coil defined by the second pair of joints, when the wireless charging device charges the device to-be-charged in the second wireless charging mode; wherein transmitting-coil turns defined by the first pair of joints is smaller than transmitting-coil turns defined by the second pair of joints, wherein transmitting-coil turns defined by the first pair of joints can produce less heat than transmitting-coil turns defined by the second pair of joints. a wireless transmitting circuit; a transmitting coil, comprising multiple pairs of joints, a joint being formed by a wire drawn from a certain position of the transmitting coil, wherein each of the multiple pairs of joints of the transmitting coil defines the transmitting coil of certain turns and the transmitting-coil turns defined by each pair of joints is different; and wherein the wireless charging device is operable in a first wireless charging mode or in a second wireless charging mode, and a charging speed at which the wireless charging device charges a device to-be-charged in the first wireless charging mode is higher than in the second wireless charging mode, wherein the control circuit is configured to: control a first pair of joints among the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit to make the wireless transmitting circuit transmit a wireless charging signal through the transmitting coil defined by the first pair of joints, when the wireless charging device charges the device to-be-charged in the first wireless charging mode; and control a second pair of joints among the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit to make the wireless transmitting circuit transmit a wireless charging signal through the transmitting coil defined by the second pair of joints, when the wireless charging device charges the device to-be-charged in the second wireless charging mode; wherein transmitting-coil turns defined by the first pair of joints is smaller than transmitting-coil turns defined by the second pair of joints, wherein transmitting-coil turns defined by the first pair of joints can produce less heat than transmitting-coil turns defined by the second pair of joints. control a first pair of joints among the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit to make the wireless transmitting circuit transmit a wireless charging signal through the transmitting coil defined by the first pair of joints, when the wireless charging device charges the device to-be-charged in the first wireless charging mode; and control a second pair of joints among the multiple pairs of joints to be electrically coupled with the wireless transmitting circuit to make the wireless transmitting circuit transmit a wireless charging signal through the transmitting coil defined by the second pair of joints, when the wireless charging device charges the device to-be-charged in the second wireless charging mode; wherein transmitting-coil turns defined by the first pair of joints is smaller than transmitting-coil turns defined by the second pair of joints, wherein transmitting-coil turns defined by the first pair of joints can produce less heat than transmitting-coil turns defined by the second pair of joints.