Semiconductor light source driving apparatus

1. A semiconductor light source driving apparatus comprising:

a switching power supply that supplies a DC voltage;

a first switching device that switches on/off an output of a positive terminal of the switching power supply in accordance with an input PWM signal;

an inductor having a first end connected to an output of the first switching device;

a second switching device connected between a second end of the inductor and a negative terminal of the switching power supply, the second switching device being switched on/off in accordance with an inversion of the input PWM signal;

a semiconductor light source device connected between the second end of the inductor and the negative terminal of the switching power supply; and

a free-wheeling diode to which the first end of the inductor and the negative terminal of the switching power supply are connected.

2. The semiconductor light source driving apparatus according to claim 1 , wherein each of the first switching device and the second switching device is a field effect transistor.

3. The semiconductor light source driving apparatus according to claim 2 , further comprising:

a surge protection diode connected between the second end of the inductor and the second switching device; and

a snubber circuit provided between a first end of the second switching device and a second end of the second switching device, the snubber circuit including a resistor and a capacitor connected in series.

4. A semiconductor light source driving apparatus that drives a semiconductor light source device, the semiconductor light source device being connected to a first output terminal of the semiconductor light source driving apparatus and to a second output terminal of the semiconductor light source driving apparatus, the semiconductor light source driving apparatus comprising:

a power supply section that outputs a DC voltage;

a first switching device connected to an output of the power supply section;

a current flowback section connected to an output of the first switching device;

a bypass section connected to an output of the current flowback section; and

a controller that controls the first switching device and the bypass section,

the current flowback section including:

an inductor provided in a path connecting a first end of the power supply section to a corresponding output terminal of the first and second output terminals; and

a free-wheeling diode having a first end connected to an input end of the inductor,

the bypass section including:

a first node being a first end of the bypass section, the first node being connected to a positive terminal of the first and second output terminals;

a second node being a second end of the bypass section, the second node being connected to a negative terminal of the first and second output terminals; and

a second switching device controlled by the controller, and

the second switching device being provided in a path connecting the first node to the second node in the bypass section, and

wherein the controller controls the first switching device so that the first switching device is in an ON state when the second switching device is in an OFF state.

5. The semiconductor light source driving apparatus according to claim 4 , wherein the bypass section includes a surge protection diode that rectifies a current flowing between the first node and the second node so that the current flows in a direction from the first node and the second node.

6. The semiconductor light source driving apparatus according to claim 5 , wherein the bypass section includes a surge suppression circuit that is provided in parallel to the second switching device.

7. The semiconductor light source driving apparatus according to claim 6 , wherein the surge suppression circuit is a snubber circuit including a resistor and a capacitor connected in series.

8. The semiconductor light source driving apparatus according to claim 5 , wherein the bypass section includes a surge suppression circuit that is provided in a path connecting the first node to the second node in parallel to the second switching device and in series with the surge protection diode.

9. The semiconductor light source driving apparatus according to claim 5 , wherein the second switching device is a field effect transistor.

10. The semiconductor light source driving apparatus according to claim 4 , wherein the bypass section includes a surge suppression circuit that is provided in parallel to the second switching device.

11. The semiconductor light source driving apparatus according to claim 10 , wherein the surge suppression circuit is a snubber circuit including a resistor and a capacitor connected in series.

12. The semiconductor light source driving apparatus according to claim 4 , wherein the second switching device is a field effect transistor.

13. The semiconductor light source driving apparatus according to claim 4 , further comprising a current sensor,

wherein the current sensor is provided between a first end of the free-wheeling diode and one of the first and second output terminals, and the current sensor measures a current flowing through the current sensor, and

the controller controls the power supply section, based on the amount of the current detected by the current sensor.