# US 4,396,870 A · Electronic flash device

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- Number: US 4,396,870 A
- Document ID: US4396870A
- Status: Granted
- Kind: A
- Application number: 06/276,882
- Filed: 1981-06-24
- Granted: 1983-08-02
- Earliest claimed: 1980-07-01
- Assignees: West Electric Company, Ltd.
- Inventors: Takahiro Ikeda
- Web page: https://patentgrep.com/patent/US4396870A

## CPC

- H05B 41/32: for single flash operation
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

An electronic flash device provided with an auxiliary winding electromagnetically coupled to a winding in a DC-DC converter which is connected to a main power supply and generates a voltage for charging a main flash capacitor, an auxiliary capacitor adapted to be charged with at least the voltage induced across the auxiliary winding, and a control circuit for maintaining the voltage charged across the auxiliary capacitor at a predetermined level, whereby the voltage charged across the auxiliary capacitor can be delivered to integrated circuits for the flash device.

## Claims

### Claim 1

An electronic flash device of the type in which an auxiliary winding is electromagnetically coupled to a winding in a DC-DC converter for charging a main flash capacitor and an auxiliary capacitor is charged with the voltage induced across said auxiliary winding through a diode so that the voltage across said auxiliary capacitor can be used as an auxiliary power supply,
characterized by the provision of
a voltage control circuit comprising
a voltage detector for detecting the voltage across said auxiliary capacitor, and
a control circuit which is connected in series to said auxiliary winding and which is adapted to decouple of said auxiliary winding from said winding in said DC-DC converter in response to the output signal from said voltage detector,
whereby the voltage across said auxiliary capacitor can be controlled as desired.

### Claim 2 (depends on 1)

An electronic flash device as set forth in claim 1 further characterized in that
said auxiliary capacitor is connected through a second diode to said DC-DC converter so that said auxiliary capacitor can be also charged with a voltage generated in said DC-DC converter.

### Claim 3 (depends on 1, 2)

An electronic flash device as set forth in claim 1 or 2 further characterized in that
said auxiliary capacitor is connected through a third diode to a main power supply for said DC-DC converter so that said auxiliary capacitor can be also charged with a voltage of said main power supply.

### Claim 4 (depends on 1)

An electronic flash device as set forth in claim 1 further characterized in that
said voltage detector comprises
a first transistor adapted to detect the voltage being charged across said auxiliary capacitor in terms of a voltage across a resistor connected in parallel with said auxiliary capacitor, and
a second transistor which is controlled by said first transistor so as to control said control circuit.

### Claim 5 (depends on 1)

An electronic flash device as set forth in claim 1 further characterized in that
said voltage detector includes a constant-voltage regulator.

### Claim 6 (depends on 1)

An electronic flash device as set forth in claim 1 further characterized in that
said control circuit includes a transistor.

### Claim 7 (depends on 1)

An electronic flash device as set forth in claim 1 further characterized in that
said auxiliary power supply is used for supplying power to one more ICs.