Apparatus and method for controlling electric currents with pulse width modulation signal

1. An apparatus for controlling electric currents, comprising:

a pulse width modulation (PWM) signal generating unit configured to generate a PWM signal based on a difference between a voltage of a battery and a voltage of a rectifier;

a first switch unit connected with the PWM signal generating unit, and configured to receive the PWM signal and generate a switch control signal corresponding to the PWM signal;

a second switch unit connected with the first switch unit, and configured to receive the switch control signal and connect or block a flow of a current from the rectifier to the battery according to the switch control signal; and

a current decreasing unit connected with the second switch unit, and configured to decrease a current value of a current passing through the second switch unit and provide the battery with a current having the decreased current value.

2. The apparatus of claim 1 , further comprising:

a battery voltage measuring unit configured to measure the voltage of the battery; and

a rectifier voltage measuring unit configured to measure the voltage of the rectifier,

wherein the PWM signal generating unit transmits the PWM signal when the voltage of the rectifier is higher than the voltage of the battery.

3. The apparatus of claim 1 , further comprising:

a current measuring unit configured to measure a current value, which passes through the current decreasing unit and flows into the battery,

wherein the PWM signal generating unit decreases a pulse width of the PWM signal when the measured current value is equal to or larger than a predetermined current value, and increases the pulse width of the PWM signal when the measured current value is smaller than the predetermined current value.

4. The apparatus of claim 1 , further comprising:

a temperature measuring unit configured to measure a temperature of the second switch unit,

wherein the PWM signal generating unit decreases the pulse width of the PWM signal when the measured temperature is higher than a predetermined temperature.

5. The apparatus of claim 1 , wherein the first switch unit includes an NPN-type transistor.

6. The apparatus of claim 1 , wherein the second switch unit includes a P-channel field effect transistor (FET).

7. The apparatus of claim 1 , wherein the current decreasing unit is a buck converter, which removes a high frequency component of a waveform of a current passing through the second switch unit, and outputs an average of a current value of the current, in which the high frequency component is removed, as a current value.

8. The apparatus of claim 1 , wherein a high PWM signal puts the first switch unit in an on-state and a low PWM signal puts the first switch in an off-state.

9. The apparatus of claim 1 , wherein a base of the first switch unit is connected to the PWM signal generating unit and a collector of the first switch unit is connected to the second switch unit.

10. The apparatus of claim 1 , wherein a gate of the second switch unit is connected to the first switch unit, a source of the second switch unit is connected to a rectifier and a drain of the second switch unit is connected to the current decreasing unit.

11. A method of controlling electric currents, comprising:

measuring, by a battery voltage measuring unit, a voltage of a battery;

measuring, by a rectifier voltage measuring unit, a voltage of a rectifier;

generating, by a pulse width modulation (PWM) signal generating unit, a PWM signal based on a difference between the voltage of the battery and the voltage of the rectifier;

receiving, by a first switch unit connected with the PWM signal generating unit, the PWM signal and generating a switch control signal corresponding to the PWM signal;

receiving, by a second switch unit connected with the first switch unit, the switch control signal and connecting or blocking a flow of a current from the rectifier to the battery according to the switch control signal; and

decreasing, by a current decreasing unit connected with the second switch unit, a current value of a current passing through the second switch unit and providing the battery with a current having the decreased current value.

12. The method of claim 11 , further comprising:

transmitting, by the PWM signal generating unit, the PWM signal when the voltage of the rectifier is higher than the voltage of the battery.

13. The method of claim 11 , further comprising:

measuring, by a current measuring unit, a current value, which passes through the current decreasing unit and flows into the battery; and

when the measured current value is equal to or larger than a predetermined current value, decreasing, by the PWM signal generating unit, a pulse width of the PWM signal, and when the measured current value is smaller than the predetermined current value, increasing, by the PWM signal generating unit, the pulse width of the PWM signal.

14. The method of claim 11 , further comprising:

measuring, by a temperature measuring unit, a temperature of the second switch unit; and

decreasing, by the PWM signal generating unit, the pulse width of the PWM signal when the measured temperature is higher than a predetermined temperature.

15. The method of claim 11 , wherein the first switch unit includes an NPN-type transistor.

16. The method of claim 11 , wherein the second switch unit includes a P-channel field effect transistor (FET).

17. The method of claim 11 , wherein the current decreasing unit is a buck converter, which removes a high frequency component of a waveform of a current passing through the second switch unit, and outputs an average of a current value of the current, in which the high frequency component is removed, as a current value.

18. The method of claim 11 , further comprising placing the first switch unit in an on-state when the PWM signal is high and placing the first switch unit in an off-state when the PWM signal is low.