Contactless charging method for charging battery
View Patent ↗A system, method and apparatus for contact-less charging of battery operated devices is presented. There is a host charger with a power converter and resonant tank circuit and a portable device where the battery is located, with a battery charging control IC. The method obviates the need for a voltage controller in each of both the host and the portable stages, thus decreasing complexity and increasing efficiency. The charging of the battery in the portable device is controlled by a charging controller therein, which is in continual electric communication with the host, whose output power the control IC dynamically monitors and controls. Two embodiments for the charging circuitry in the portable device are presented. In one embodiment component count is minimized but battery charging is not optimized when the battery voltage is very low. In the other embodiment charging efficiency is maximized regardless of the output voltage of the battery, but additional components are utilized.
1. A contactless charging method for charging a battery in a contact charger system that includes a primary charging unit having a primary coil and a wireless receiving module, a secondary charging unit having a wireless transmitting module and a secondary coil magnetically coupled with the primary coil, and a battery for receiving a charging voltage from the secondary charging unit, the method comprising:
(A) applying a power pulse train having a pulse width (W 1 ) to the primary coil to emit out a corresponding magnetic field;
(B) generating a train of an induced charging power pulse corresponding to the power pulse train with the pulse width (W 1 ) as the primary coil and the secondary coil are magnetically coupled, wherein the train of the induced charging power pulse is a standby mode pulse;
(C) waking up an internal circuit of the secondary charging unit by using the standby mode pulse, checking a falling edge of the standby mode pulse, and reading previously stored charging status information of the battery when said failing edge is detected;
(D) when the charging status information does not exist, generating a charging start signal for an initial charging, and transmitting the charging start signal through the wireless transmitting module of the secondary charging unit to the wireless receiving module of the primary charging unit;
(E) generating a charging power pulse train having a pulse width (W 2 ) at least greater than the pulse width (W 1 ) according to the charging start signal, and applying the charging power pulse train to the primary coil to generate a train of the corresponding induced charging power pulse to the secondary coil, wherein the charging power pulse train is a charging mode pulse;
(F) charging the battery using the charging mode pulse;
(G) feeding back the charging status information of the battery from the secondary charging unit; and
(H) checking falling edge of the charging mode pulse, and, when a falling edge of the charging mode pulse is detected, reading charging status information of the battery, then transmitting the charging status information to the primary charging unit, and controlling a pulse width of the charging mode pulse based on the transmitted charging status information of the battery,
wherein:
when the battery is fully charged as a result of analysis of the charging status information of the battery in the step (H), a full-charged mode power pulse train having a pulse width (W 3 ) is applied to the primary coil; and the pulse width (W 3 ) is controlled to be smaller than the pulse width (W 2 ) and equal to or greater than the pulse width (W 1 ).
2. The contactless charging method of claim 1 , wherein the pulse width (W 3 ) is equal to W 1 .
3. The contactless charging method of claim 1 , wherein the full-charged mode power pulse train is generated by means for modulating a pulse width of an AC voltage having a higher frequency than a commercial frequency.
4. The contactless charging method of claim 1 , wherein the charging status information includes a charging voltage value or a charging current value of the battery.
5. The contactless charging method of claim 1 , wherein the step (A) includes:
rectifying a common AC voltage into a DC voltage;
generating an AC voltage having a higher frequency than a commercial frequency using the rectified DC;
modulating a pulse width of the AC voltage to generate the power pulse train having the pulse width (W 1 ); and
applying the power pulse train having the pulse width (W 1 ) to the primary coil.
6. The contactless charging method of claim 1 , wherein the step (F) includes:
rectifying the charging mode pulse representing AC voltage into a DC voltage;
generating a constant voltage and a constant current of a predetermined level, which is to be charged to the battery, using the rectified DC voltage; and
charging the battery in mode of the constant current until a battery voltage reaches a predetermined level, and then charging the battery in mode of the constant voltage by controlling an amount of a charging current.