JPH01321427A - Power source circuit for stroboscope - Google Patents

Abstract

PURPOSE:To simplify circuit constitution by controlling the charging action of a main capacitor by means of one control signal outputted from a control circuit side, and providing an input stage with a coupling capacitor. CONSTITUTION:A clock pulse is inputted from a control circuit made of a microcomputer, etc., through the coupling capacitor CC. The main capacitor CM is charged which impresses a specified high voltage on a discharge tube DT constituting a stroboscope device by the output signal of an oscillator circuit which is operated in synchronism with the clock pulse. When the terminal voltage of the main capacitor CM reaches a specified level, a charge completion signal is outputted from a voltage detecting circuit to the control circuit. The control circuit receives the charge completion signal and stops the output of the clock pulse. Therefore, charging the main capacitor CM is controlled only by the clock pulse. Thus, the circuit constitution can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a strobe power supply circuit used in a strobe device built into a camera that is controlled by a control circuit composed of a microcomputer or the like.

[Conventional technology]

The configuration of a conventional strobe power supply circuit is shown in FIG. 3, and its operating state is shown in FIG. 4. In FIG. 3, charging of the main capacitor Cal for applying a predetermined high voltage to the discharge tube DT constituting the strobe device is performed as follows. First, a charging start signal is sent from the microcomputer at time 1. When input to the transistor Q2 from the terminal TM2 via the resistor R5, as shown in FIG. 4(a), the resistor R3
, an oscillation circuit consisting of capacitors C1 and C2, transistors Q, and transformer T starts oscillation, and its oscillation output is transmitted via diode D1 to main capacitor Cx.
is applied to Terminal voltage VCX of main capacitor CM
At the time t when the voltage reaches a predetermined high voltage v1, the Zener diode ZD and the resistor R? , Re and transistor Q
, this state is detected by a voltage detection circuit consisting of transistor Q and terminal T closer to the microcomputer.
A charging completion signal is output via M s (Fig. 4 (
b), (C)).

On the other hand, the microcombination unit receives the charging completion signal and outputs a charging stop signal from the terminal TM to the transistor Q via the resistor R2 (FIG. 4(d)). As a result, transistor Q1 becomes conductive, and the pace and emitter of transistor Q, which constitutes the oscillation circuit, are short-circuited, so transistor Q becomes non-conductive, stopping the oscillation operation, and the main capacitor C is connected. Charging operation is stopped.

In addition, in order to prevent overcharging of the main capacitor C8 in the event that control by the microcomputer becomes impossible, the terminal voltage VCM of the main capacitor C1l is charged until it becomes higher than the voltage V, and the voltage VP at point P is the reference voltage. When the voltage reaches V2 (>Vl), the transistor Q
The constants of the resistors Ri and Rs are selected such that , are in a conductive state. When transistor Q becomes conductive, the base and emitter of transistor Q are shorted,
Charging to the main capacitor CH is stopped.

[Problem that the invention seeks to solve]

As mentioned above, in conventional strobe power supply circuits, the microcomputer that controls the charging operation of the main capacitor uses two types of signals: a charging start signal to start the charging operation and a charging stop signal to stop the charging operation. Since the circuit was constructed on the premise that it would output vl, there was a problem that the circuit configuration became sloppy.

The present invention was made in view of these circumstances, and
It is an object of the present invention to provide a strobe power supply circuit with a simplified circuit configuration.

[Means for solving problems]

To achieve the above object, the present invention provides a strobe power supply circuit used in a strobe device built into a camera controlled by a control circuit composed of a microcomputer, etc., in which both ends of a discharge tube constituting the strobe device are provided. a main capacitor connected to the discharge tube for applying a predetermined high voltage to the discharge tube; an oscillation circuit that generates a voltage signal for charging the main capacitor in synchronization with a clock pulse output from the control circuit; a voltage detection circuit that outputs a charge completion signal to the control circuit when the terminal voltage of the main capacitor reaches a predetermined level; and a coupling capacitor provided at the input stage of the oscillation circuit to which the clock pulse from the control circuit is input. It is characterized by having the following.

[Effect]

In the strobe power supply circuit according to the present invention, a clock pulse is input from a control circuit composed of a microcomputer or the like through a coupling capacitor, and a strobe device is configured by an output signal of an oscillation circuit that operates in synchronization with the clock pulse. A main capacitor for applying a predetermined high voltage to the discharge tube is charged.

When the terminal voltage of the main capacitor reaches a predetermined level, the voltage detection circuit outputs a charging completion signal to the control circuit.

Upon receiving this charge completion signal, the control circuit stops outputting clock pulses.

Therefore, charging control for the main capacitor is performed only by clock pulses, which simplifies the circuit configuration. Furthermore, even if the clock pulse is fixed at a high level due to a malfunction of a microcomputer or the like, the DC component is cut off by the coupling capacitor, so there is no problem with the power supply circuit.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure shows the configuration of an embodiment of a strobe power supply circuit according to the present invention. In this figure, the same members as those in the conventional example shown in FIG. 3 are given the same reference numerals. The strobe power supply circuit shown in Fig. 1 differs from the conventional example shown in Fig. 3 in terms of configuration by resistors R, , R, , R, , ) transistors Q
A coupling capacitor C6 is newly installed in the input circuit consisting of a resistor R3 that performs an oscillation operation in synchronization with the clock pulse inputted via this coupling capacitor Cc, a transistor Q3, and a transformer T. The oscillation circuit was provided in place of the conventional free-running oscillation circuit, and the resistor R was provided in the control circuit in order to stop the oscillation operation by a signal input from the control circuit side.
,,R2) The transistor Q1 is removed, and the other configurations are exactly the same.

In the above configuration, a control circuit composed of a microcomputer or the like starts inputting a tarock pulse, which is a charging signal, from terminal TM2 (Fig. 2(a)), and resistor R3 and transistor Q oscillate in synchronization with this clock pulse. , and a transformer T, the main capacitor CM is charged by the oscillation output of the oscillation circuit. Time t2 when the terminal voltage VCX of the main capacitor C8 reaches a predetermined high voltage V1
This state is detected by a voltage detection circuit consisting of a Zener diode ZD, resistors Rt and Re, and a transistor Q, and a charging completion signal is output from the transistor Q to the control circuit side via the terminal TM3 (see Fig. 2). b),
(C)).

On the other hand, upon receiving the charge completion signal, the control circuit stops outputting the clock pulse, and the charging operation to the main capacitor C8 is stopped.

Further, if the control circuit becomes unable to control charging due to a runaway of the microcomputer on the control circuit side and the tarock pulse continues to be output, charging to the main capacitor C8 is stopped by the same operation as in the conventional example. That is, the main capacitor Cx is charged until the terminal voltage V (X becomes higher than the voltage Vl, and the voltage V at point P becomes the reference voltage V2.
(>Vl), the transistor Q becomes conductive, and the oscillation operation of the oscillation circuit is stopped.

Furthermore, even if the clock pulse is maintained at a high level due to a ruff-down phenomenon in the control circuit, a coupling capacitor is provided at the input stage of the clock pulse to provide capacitive coupling, so that the power supply circuit is protected.

〔Effect of the invention〕

As explained above, in the present invention, one control signal output from the control circuit side controls the charging operation of the main capacitor that maintains the supply voltage of the discharge tube of the strobe device, and the control signal is inputted. Since a coupling capacitor is provided in the input stage, the circuit configuration is simplified, and therefore the number of parts can be reduced and reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the strobe power supply circuit according to the present invention, FIG. 2 is a timing chart showing the operation of the strobe power supply circuit shown in FIG. 1, and FIG. 3 is a conventional strobe power supply circuit. FIG. 4 is a timing chart showing the operation of the strobe power supply circuit shown in FIG. 3. Cc...Coupling capacitor, co...Main capacitor, DT...Discharge tube, Ql ~Q,...Transistor, TM, ~TM,...Terminal, T...
Trance.

Claims (1)

[Claims] In a strobe power supply circuit used in a strobe device built into a camera controlled by a control circuit composed of a microcomputer or the like, the strobe power supply circuit is connected to both end tubes of a discharge tube constituting the strobe device, a main capacitor for applying a predetermined high voltage to the discharge tube; an oscillation circuit that generates a voltage signal for charging the main capacitor in synchronization with a clock pulse output from the control circuit; and a terminal voltage of the main capacitor. a voltage detection circuit that outputs a charge completion signal to a control circuit when the voltage reaches a predetermined level; and a coupling capacitor provided at an input stage of an oscillation circuit to which clock pulses from the control circuit are input. Strobe power supply circuit.