Charging device for camera flash

1. A charging device for a camera flash, comprising:

a digital signal processor for providing a pulse width modulation signal and receiving a feedback signal;

a voltage boosting circuit electrically connected with the digital signal processor for outputting an induced current under the control of the pulse width modulation signal;

a flash capacitor; and

a charging circuit electrically connected with the voltage boosting circuit and the flash capacitor, the charging circuit charging the flash capacitor by means of the induced current, and comprising a protection circuit parallelly connected with the flash capacitor, and a feedback circuit outputting the feedback signal to the digital signal processor.

2. The charging device for a camera flash as claimed in claim 1 , wherein, once the feedback signal reaches a predetermined critical voltage, the digital signal processor stops to provide the pulse width modulation signal.

3. The charging device for a camera flash as claimed in claim 2 , wherein the digital signal processor comprises an analog-to-digital converter for receiving the feedback signal and converting the feedback signal from an analog signal to a digital signal.

4. The charging device for a camera flash as claimed in claim 3 , wherein the digital signal processor comprises a pulse control unit for outputting the pulse width modulation signal in terms of the feedback signal.

5. The charging device for a camera flash as claimed in claim 4 , wherein the feedback circuit comprises a pair of serially connected first and second resistors, and the feedback signal is output from between the first and second resistors.

6. The charging device for a camera flash as claimed in claim 5 , wherein the critical voltage is predetermined in the digital signal processor in accordance with an inherent maximum value of the flash capacitor and a ratio of the value of the first resistor to that of the second resistor.

7. The charging device for a camera flash as claimed in claim 4 , wherein the charging circuit comprises a current rectifying diode electrically connected with the flash capacitor for converting the induced current from an alternating current into a direct current.

8. The charging device for a camera flash as claimed in claim 4 , wherein the protection circuit at least comprises a Zener diode.

9. The charging device for a camera flash as claimed in claim 1 , wherein the voltage boosting circuit comprises a field effect transistor electrically connected with the digital signal processor and a transformer electrically connected with the field effect transistor and the charging circuit.

10. The charging device for a camera flash as claimed in claim 9 , wherein the field effect transistor is a metal oxide semiconductor field effect transistor with a channel of N-type, and the transformer is a boosting transformer.

11. The charging device for a camera flash as claimed in claim 9 , further comprising a filtering circuit with one end thereof electrically connected with the voltage boosting circuit and the other end thereof electrically connected with a battery, the filtering circuit being adapted for preventing an oscillation current in the transformer from influencing the battery.

12. A charging device for a camera flash comprising:

a flash capacitor;

a pulse control unit for outputting a pulse width modulation signal;

an analog-to-digital converter for receiving a feedback signal and converting the feedback signal from an analog signal into a digital signal;

a micro processing unit electrically connected with the pulse control unit and the analog-to-digital converter, the micro processing unit controlling the output of the pulse width modulation signal in accordance with the feedback signal;

a voltage boosting circuit electrically connected with the pulse control unit and outputting an induced current under the control of the pulse control unit; and

a charging circuit with one port electrically connected with the voltage boosting circuit for receiving the induced current and another port electrically connected with the flash capacitor, the charging circuit comprising a protection circuit parallelly connected with the flash capacitor, and outputting said feedback signal to the analog-to-digital converter.

13. The charging device for a camera flash as claimed in claim 12 , wherein, once the feedback signal reaches a predetermined critical voltage, the digital signal processor stops to outputting the pulse width modulation signal.

14. The charging device for a camera flash as claimed in claim 13 , wherein the charging circuit comprises a feedback circuit for providing the feedback signal from between a pair of serially connected first and second resistors, and the critical voltage is predetermined in the micro processing unit according to a maximum value of the flash capacitor and a ratio of the value of the first resistor to that of the second resistor.

15. The charging device for a camera flash as claimed in claim 13 , wherein the protection circuit comprises at least a Zener diode.

16. The charging device for a camera flash as claimed in claim 13 , wherein the voltage boosting circuit comprises a metal oxide semiconductor field effect transistor electrically connected with the pulse control unit and a boosting transformer electrically connected with the metal oxide semiconductor field effect transistor and the charging circuit.