Flash apparatus and camera having the flash apparatus

• US 20020047626A1
• Filed: 04/24/2001
• Published: 04/25/2002
• Est. Priority Date: 04/27/2000
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Odaka, Yukio, Ichimasa, Shoji
• Granted Patent: US 6,509,695 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 3/33515 with digital control
• CPC Class Codes: H02M 3/3378 in a push-pull configuration of the parallel type H02M3/3374 takes precedence
• CPC Class Codes: H05B 41/325 by measuring the incident light

Abstract

In a flash apparatus, when it is determined that the oscillation of a voltage boosting circuit is stopped before it is controlled so as to stop, it is possible to continuously charge a voltage to a main capacitor by causing the voltage boosting circuit to continue oscillation by providing a control circuit for oscillating the voltage boosting circuit again. Further, the flash apparatus includes a charged current detecting circuit for detecting the current charged in a main capacitor using an auxiliary power source as a power source. The charged current detecting circuit is simply arranged with a passive element for bypassing a part of the current charged in the main capacitor from a loop through the above-mentioned auxiliary power source.

Claims

1. A flash apparatus comprising:

a) a voltage boosting circuit having a transformer for boosting a battery voltage;

b) a main capacitor to be charged by said voltage boosting circuit; and

c) a control circuit for controlling starting and stopping of said voltage boosting circuit,

wherein, when an oscillation of said voltage boosting circuit is stopped before said control circuit stops said voltage boosting circuit, said control circuit starts said voltage boosting circuit.

9. A flash apparatus according to claim 1 or 2, wherein said voltage boosting circuit has an oscillation transformer which does not include a feedback winding.

10. A flash apparatus according to claim 1 or 2, wherein said voltage boosting circuit has a power source voltage compensating circuit for returning a power source voltage to an initial state thereof, when the power source voltage drops, by temporarily interrupting the oscillation of said voltage boosting circuit.

11. A flash apparatus according to claim 1 or 2, wherein said voltage boosting circuit is a single forward type voltage boosting circuit.

12. A flash apparatus according to claim 1 or 2, wherein said voltage boosting circuit is a push-pull type voltage boosting circuit.

13. A flash apparatus according to claim 1 or 2, wherein said control circuit charges said main capacitor by controlling the oscillation of said voltage boosting circuit by inputting an oscillation continuing signal thereto as well as momentarily inputting an oscillation start signal thereto, and stops charging said main capacitor by stopping inputting the oscillation continuing signal.

15. A flash apparatus according to claim 14, wherein said control circuit stops said voltage boosting circuit when the detected oscillation frequency of said voltage boosting circuit is not in approximate agreement with the reference frequency corresponding to the voltage charged in said main capacitor detected by said voltage detecting circuit.

17. A flash apparatus according to claim 16, wherein said switch element is an FET.

18. A flash apparatus according to claim 16, wherein said one-direction conduction element is a diode.

2. A flash apparatus comprising:

a) a voltage boosting circuit having a transformer for boosting a battery voltage;

b) a main capacitor to be charged by said voltage boosting circuit;

c) a voltage detecting circuit for detecting a voltage of said main capacitor;

d) a control circuit for controlling starting and stopping of said voltage boosting circuit; and

e) an oscillation detecting circuit for detecting an oscillating state of said voltage boosting circuit,

wherein, when said oscillation detecting circuit detects an oscillation stopping state of said voltage boosting circuit during a predetermined period of time before said control circuit stops said voltage boosting circuit, said control circuit starts said voltage boosting circuit.

3. A flash apparatus according to claim 2, wherein said oscillation detecting circuit detects a state of said voltage boosting circuit at timing of predetermined time intervals.

4. A flash apparatus according to claim 2, wherein said oscillation detecting circuit detects a state of said voltage boosting circuit at timing of time intervals of geometric progression.

5. A flash apparatus according to claim 2, wherein said oscillation detecting circuit detects a state of said voltage boosting circuit according to a voltage charged in said main capacitor.

6. A flash apparatus according to claim 2, wherein said oscillation detecting circuit includes a capacitor which is arranged to discharge electricity in response to detecting oscillation.

7. A flash apparatus according to claim 6, wherein an oscillation detection inputting position of said oscillation detecting circuit is a portion to which a driving signal for oscillation is inputted to an oscillation switch included in said voltage boosting circuit.

8. A flash apparatus according to claim 5, wherein said voltage detecting circuit detects the state of said voltage boosting circuit by measuring a voltage divided from the voltage charged in said main capacitor.

14. A flash apparatus comprising:

a) a voltage boosting circuit having a transformer for boosting a battery voltage;

b) a main capacitor to be charged by said voltage boosting circuit;

c) a voltage detecting circuit for detecting a voltage of said main capacitor;

d) a control circuit for controlling starting and stopping of said voltage boosting circuit; and

e) an oscillation frequency detecting circuit for detecting an oscillation frequency of said voltage boosting circuit,

wherein said control circuit compares the oscillation frequency of said voltage boosting circuit detected by said oscillation frequency detecting circuit with a reference frequency corresponding to a voltage charged in said main capacitor.

16. A flash apparatus comprising:

a) a transformer composed of a primary winding and a secondary winding;

b) a switch element connected to the primary winding of said transformer for causing a current to flow from a battery to the primary winding;

c) a main capacitor to be charged by being connected to the secondary winding of said transformer;

d) an auxiliary power source to be created by said battery;

e) a circuit member to be driven by said auxiliary power source for controlling conduction and non-conduction of said switch element; and

f) a one-direction conduction element having an input terminal and an output terminal disposed in a charge loop of said transformer and said main capacitor,

wherein an output end of said one-direction conduction element is connected to said auxiliary power source and said circuit member through a resistor, said switch element is made conductive through said circuit member in response to a voltage drop of the output end of said one-direction conduction element which is caused by a charged current flowing to a charge loop of a capacitor, and said switch element is made non-conductive through said circuit member by the charged current dropping and the output end of said one-direction conduction element being biased by said auxiliary power source.