Electronic flash device of a separate excitation oscillating type

• US 6,219,493 B1
• Filed: 08/18/1999
• Issued: 04/17/2001
• Est. Priority Date: 08/19/1998
• Status: Expired due to Term

• Current Assignee: Konica Corporation (Konica Minolta Inc.)
• Original Assignee: Konica Corporation (Konica Minolta Inc.)
• Inventors: Aoki, Toshiyuki, Yasui, Teruhiko
• Primary Examiner(s): PERKEY, WILLIAM B
• Application Number:
  US09/376,371
• Time in Patent Office: 608 Days
• Field of Search: 396/205, 396/206, 315/241.P
• US Class Current: 396/206
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/05 Combinations of cameras with electronic flash units

Abstract

An electronic flash charger having an electronic flash charging circuit of a separate excitation oscillating. The charger includes: a flyback transformer, having at least a primary coil and a secondly coil; a switching element for turning on or off electric power, to be supplied to the primary coil, based on control signals supplied to a control input terminal; a rectifying diode for rectifying a flyback pulse generated on the secondly coil when the switching element is changed from ON state, that the electric power is turned on, to OFF state, that the electric power is turned off; a main capacitor for charging a current rectified by the rectifying diode; and an oscillation controller for generating control signals for changing at least one of time spans of ON state and OFF state of the switching element in accordance with a period from generation to extinction of the flyback pulse generated on the secondly coil, and for supplying the control signals to the control input terminal of the switching element.

Claims

1. An electronic flash charging apparatus having an electronic flash charging circuit of a separate excitation oscillating, comprising:

a flyback transformer, having at least a primary coil and a secondly coil;

a switching element for turning on or off electric power, to be supplied to said primary coil, based on control signals supplied to a control input terminal;

a rectifying diode for rectifying a flyback pulse generated on said secondly coil when said switching element is changed from ON state, that said electric power is turned on, to OFF state, that said electric power is turned off;

a main capacitor for charging a current rectified by said rectifying diode; and

an oscillation controller for generating control signals for changing at least one of time spans of ON state and OFF state of said switching element in accordance with a period from generation to extinction of said flyback pulse generated on said secondly coil, and for supplying said control signals to said control input terminal of said switching element.

2. The electronic flash charging apparatus of claim 1, wherein said oscillation controller generates said control signals which change time span of said OFF state of said switching element in accordance with a period from generation to extinction of said flyback pulse generated on said secondly coil.

3. The electronic flash charging apparatus of claim 1, wherein said oscillation controller generates said control signals which control time span of said OFF state of said switching element to be made substantially the same as a period from generation to extinction of said flyback pulse generated on said secondly coil.

4. The electronic flash charging apparatus of claim 1, comprising:

a charging voltage detector for detecting charging voltage of said main capacitor;

wherein said oscillation controller generates said control signals in accordance with said charging voltage of said main capacitor detected by said charging voltage detector.

5. The electronic flash charging apparatus of claim 1, comprising:

a timer means for starting measurement of time when said main capacitor is started to be charged;

wherein said oscillation controller generates said control signals in accordance with a result of said measurement of time by the timer.

6. The electronic flash charging apparatus of claim 5, comprising:

a battery voltage detector for detecting voltage of a power supply battery;

wherein said oscillation controller changes relationship between said result of measurement of time by said timer means and said control signals in accordance with said battery voltage detected by said battery voltage detector.

7. The electronic flash charging apparatus of claim 1, wherein said switching element is capable of being driven by a voltage lower than that by which said oscillation controller is driven, and said switching element is a voltage control element having ON resistance lower than a sum total of internal resistance of said power supply battery and line resistance of power supply from said power supply battery.

8. The electronic flash charging apparatus of claim 1, comprising:

a power supply capacitor connected with a power supply battery in parallel;

wherein said power supply capacitor has an impedance lower than a sum total of internal resistance of said power supply battery and line resistance of power supply from said power supply battery.

9. The electronic flash charging apparatus of claim 1, wherein said rectifying diode is an element having a small capacity between terminals.

10. The electronic flash charging apparatus of claim 1, comprising:

a flyback detector for detecting a flyback pulse generated on said secondary coil;

wherein said oscillation controller generates said control signals in accordance with a result of detection conducted by said flyback detector.

11. The electronic flash charging apparatus of claim 10, wherein said oscillation controller generates said control signals for changing at least one of time spans of said ON state and said OFF state of said switching element in accordance with a period from generation to extinction of said flyback pulse generated on said secondary coil detected by said flyback detector.

12. The electronic flash charging apparatus of claim 10, wherein said oscillation control device generates said control signals which control, in accordance with said period during said flyback pulse is being generated, a time span of said OFF state of the switching element to be made substantially the same as a period from generation to extinction of said flyback pulse.

13. The electronic flash charging apparatus of claim 10, wherein said flyback detector detects generation of a flyback pulse by voltage of said primary coil.

14. The electronic flash charging apparatus of claim 1, wherein said oscillation controller maintains time spans of on/off signals which said control signals have, to be supplied to said control input terminal, when a duty ratio of said on/off signals arrives at a predetermined value wherein said on/off signals are for making the switching element switched between said ON state and said OFF state.

15. The electronic flash charging apparatus of claim 1, comprising:

a battery voltage detector for detecting voltage of a power supply battery;

wherein said oscillation controller maintains a time span of on/off signals, supplied to said control input terminal, when a duty ratio of said on/off signals, which said control signals have, arrives at a predetermined value established in accordance with battery voltage detected by said battery voltage detector, wherein said on/off signals are for making the switching element switched between said ON state and said OFF state.

16. The electronic flash charging apparatus of claim 1, comprising:

a battery voltage detector for detecting voltage of a power supply battery;

wherein said oscillation controller generates said control signals in accordance with results of detection conducted by said battery voltage detector.

17. The electronic flash charging apparatus of claim 1, comprising:

a temperature measuring means for measuring temperature inside a camera;

wherein said oscillation controller maintains a time span of on/off signals, which said control signals have, supplied to said control input terminal when said temperature measuring means detects that a temperature in said camera arrives at a predetermined temperature and a duty ratio of said on/off signals arrives at a predetermined value, wherein said on/off signals are for making the switching element switched between said ON state and said OFF state.

18. The electronic flash charging apparatus of claim 1, comprising:

a timer for starting measurement of time when said main capacitor is started to be charged;

wherein said oscillation controller generates, in accordance with results of measurement by said timer, said control signals for changing at least one of time spans of said ON state and said OFF state of said switching element in accordance with a period from generation to extinction of said flyback pulse generated on said secondary coil.

19. The electronic flash charging apparatus of claim 18, wherein said oscillation controller sets an elapsed time, corresponding to a remaining voltage of said main capacitor, as an initial value of said timer in accordance with an emission time of an electronic flash for a preceding emission of said electronic flash.

20. The electronic flash charging apparatus of claim 18, wherein said oscillation controller conducts an interruption of charging of said main capacitor when a predetermined operation is performed in a camera;

said oscillation controller maintains said results of measurement conducted by said timer when said interruption is made; and

said oscillation controller resumes charging of said main capacitor after completion of said predetermined operation in a camera from a state that said results of measurement are maintained.

21. The electronic flash charging apparatus of claim 18, wherein said oscillation controller supplies said control signals, having said time spans of said ON sate and said OFF state for reducing a current, to said control input terminal when said result of measurement by said timer arrives at a predetermined time.

22. The electronic flash charging apparatus of claim 18, wherein said oscillation controller generates said control signals, having said time spans of said ON state and said OFF state for reducing a current, to said control input terminal when said result of measurement by said timer exceeds a first predetermined time;

and said oscillation controller generates said control signals for cutting off said current when said result of measurement by said timer exceeds a second predetermined time which is longer than said first predetermined time.

23. An electronic flash apparatus of a separate excitation oscillating type, comprising:

a flyback transformer, having at least a primary coil and a secondary coil;

a switching element for turning on and off electric power, to be supplied to said primary coil, based on control signals on a control input terminal;

a rectifying diode for rectifying a flyback pulse generated in said secondly coil when said switching element is changed from ON state, that said electric power is turned on, to OFF state, that said electric power is turned off;

a main capacitor for charging a current rectified by said rectifying diode;

an oscillation controller for generating control signals for changing from said ON state to said OFF state or said OFF state to said ON state of said switching element and for supplying said control signals to said control input terminal of said switching element;

a charging voltage detector for detecting a charging voltage of said main capacitor; and

a storing means for storing data of said control signals, determined for respective charging voltage, in each accessible address based on results of detection by said charging voltage detector;

wherein said oscillation controller reads said data from an address selected in accordance with results of detection by said charging voltage detector when said main capacitor is being charged; and

said oscillation controller outputs said data as said control signals.

24. The electronic flash apparatus of claim 23, comprising:

a battery voltage detector for detecting voltage of a power supply battery;

wherein said oscillation controller changes said address, selected in accordance with results of detection by said charging voltage detector when said main capacitor is being charged, to other address in accordance with battery voltage detected by said battery voltage detector; and

said oscillation controller reads data from said other address and outputs said data as control signals.

25. An electronic flash device of a separate excitation oscillating type, comprising:

a flyback transformer, having at least a primary coil and a secondary coil;

a switching element for turning on and off electric power, to be supplied to said primary coil, based on control signals on a control input terminal;

a rectifying diode for rectifying a flyback pulse generated in said secondly coil when said switching element is changed from ON state, that said electric power is turned on, to OFF state, that said electric power is turned off;

a main capacitor for charging a current rectified by said rectifying diode;

a timer means for starting measurement of time when said main capacitor is started to be charged;

a storing means for storing data of said control signals, determined for respective time, in each accessible address based on results of measurement of time by said timer means; and

an oscillation controller for supplying control signals for changing from said ON state to said OFF state or said OFF state to said ON state of said switching element;

wherein said oscillation controller reads data from an address selected in accordance with results of measurement of time by said timer; and

said oscillation controller outputs said data as control signals.

26. The electronic flash apparatus of claim 25, comprising:

a battery voltage detector for detecting voltage of a power supply battery;

wherein said oscillation controller changes said address, selected in accordance with result of measurement of time by said timer means, to other address in accordance with said battery voltage detected by said battery voltage detector; and

said oscillation controller reads data from said other address and outputs said data as control signals.

27. A camera, comprising:

an electronic flash charging apparatus having an electronic flash charging circuit of a separate excitation oscillating, including;

1) a flyback transformer, having at least a primary coil and a secondly coil;

2) a switching element for turning on or off electric power, to be supplied to said primary coil, based on control signals supplied to a control input terminal;

3) a rectifying diode for rectifying a flyback pulse generated on said secondly coil when said switching element is changed from ON state, that said electric power is turned on, to OFF state, that said electric power is turned off;

4) a main capacitor for charging a current rectified by said rectifying diode; and

5) an oscillation controller for generating control signals for changing at least one of time spans of ON state and OFF state of said switching element in accordance with a period from generation to extinction of said flyback pulse generated on said secondly coil, and for supplying said control signals to said control input terminal of said switching element.

28. The camera of claim 27, wherein said oscillation controller maintains time spans of on/off signals which said control signals have, to be supplied to said control input terminal, when a duty ratio of said on/off signals arrives at a predetermined value wherein said on/off signals are for making the switching element switched between said ON state and said OFF state.