JPS596476B2 - flash discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flash discharge device, and more specifically, when discharging the residual charge of a charging capacitor after completing a flash discharge,
The idea is to reduce the electric charge in advance and discharge it reliably and quickly using parts with small ratings.

Generally, some electronic devices are equipped with a flash discharge device and operate the flash discharge device continuously.

For example, a copying machine is configured to utilize flash discharge heat for exposure or toner fixing, and the exposure or toner fixing process using flash discharge is performed on sheets that are continuously fed. By the way, as is well known, the main elements of a flash discharge device include a flash discharge tube, a discharge capacitor for storing discharge charge, and a flash trigger section, and it is necessary to always store charge in the discharge capacitor in advance. On the other hand, in order to ensure safety, it is desirable to eliminate the charge in the discharge capacitor when flash discharge is not performed. Furthermore, if inspection work is to be carried out frequently, the charge in the discharge capacitor must be able to be discharged quickly. Fig. 1 shows a conventional flash discharge device equipped with a residual charge discharging circuit of a discharging capacitor.
In the figure, 1 is an AC power supply, 2 is a power switch, 3 is a power supply circuit equipped with a rectifier, etc., 4 is a discharge coil capacitor connected to the power supply circuit 3, 5 is a flash discharge tube that receives charge from the discharge capacitor 4, 6 is a light emission trigger pulse generation circuit connected to the trigger electrode 7 of the flash discharge tube 5; 8 is a light emission command signal generation circuit for driving the light emission trigger pulse generation circuit T; 9 is a residual charge discharge circuit connected in parallel to the discharge capacitor 4 and is composed of a resistor 10 and a relay switch 11; 12 is a voltage detector for detecting the voltage of the discharge capacitor 4; 13 is a reference voltage generator 14; A voltage ratio comparator 15 which compares the voltage of the capacitor voltage detector 12 with the voltage of the capacitor voltage detector 12 and outputs a control signal is controlled by the respective signals of the voltage comparator 13 and the charging start operation switch 16. This is a charging control circuit and controls opening and closing of the power switch 2.

The charging start operation switch 16 is adapted to open and close a main power supply relay switch 17 and a relay switch 11 of the discharge circuit 9. In the above conventional flash discharge device, when the charge start operation switch 16 is closed, the main power relay switch 17 is closed, the relay switch 11 of the residual charge discharge circuit 9 is opened, and a charge start command signal is given to the power switch 2. Discharge capacitor 4
When the voltage of and charging control circuit 15
This opens the power switch 2 and stops charging. When the light emission command signal generator 8 is operated and a light emission command signal is issued, a light emission trigger pulse is given from the light emission trigger pulse generator 6 to the trigger electrode 7 of the flash discharge tube 5, and the flash discharge tube 5 generates a flash discharge. Let's do it. Due to this flash discharge, the voltage of the discharge capacitor 5 decreases, and the output voltage of the capacitor voltage detector 12 decreases. Therefore, the voltage comparator 13 gives a signal to the photoelectric control circuit 15 to close the power switch 2, and closes the power switch 2. Close 2. At this time, if the charging start operation switch 16 is closed, the discharge capacitor 4 is charged again and flash discharge is performed repeatedly. When the photoelectric start operation switch 16 is opened, the signal sent to the charging control circuit 15 is stopped, so the power switch 2 is opened and charging is stopped, the main power relay switch 17 is opened, and the residual charge discharge circuit is opened. 9, close the relay switch 11.

Therefore, the residual charge stored in the discharge capacitor 4 is discharged through the resistor 10. By the way, when such residual charge is discharged, the voltage of the discharge capacitor 4 is not constant and may be close to the charging completion voltage.

When the voltage of the discharge capacitor 4 is high, the rush current and energy flowing into the residual charge discharge circuit 9 are large. Therefore, there is a problem in that a resistor with a large maximum rating and a relay switch are required. The present invention solves the above-mentioned conventional problems, and examples thereof will be described below. FIG. 2 shows an embodiment of the flash discharge device of the present invention, which is equipped with a charge start operation switch 16 and a charge command signal generation circuit 18 controlled by a light emission command signal generation circuit 8 in addition to the conventional flash discharge device. The charging control circuit 15 is controlled by the signal from the charging command signal generating circuit 18, and the gate circuit 19 to the discharging circuit 9 is also controlled.

The same reference numerals as in FIG. 1 indicate the same components, and 20 in the figure is a voltage comparator that compares the detected voltage of the capacitor voltage detector 12 with the voltage of the reference voltage emitter 21 and sends a signal to the gate circuit 19. It is. In the flash discharge device of the present invention, after a predetermined number of flash discharges are performed by the charge start operation switch 16 and the light emission command signal generation circuit 8, the photoelectric command signal generation circuit 18 generates a charge command signal before the last light emission command. A signal is issued to turn down the charge control circuit 15, which opens the power switch 2 and prohibits charging. Thereafter, when the last light emission command signal is output from the light emission command signal generation circuit 8, a flash discharge occurs and the voltage of the discharge capacitor 4 decreases. Therefore, the output voltage of capacitor voltage detector 12 will be lower than the reference voltage, and voltage comparator 20 will issue a signal. Then, the gate circuit 19 outputs a command signal based on the low level of the charge command signal and the output signal of the voltage comparator 20, and operates the residual charge discharge circuit 9, causing the discharge capacitor 4 to discharge the residual charge. do. Since charging of this discharge capacitor 4 has already been prohibited before the last flash discharge described above, most of the charge has been discharged by the last flash discharge, and therefore the residual charge discharge circuit 9 is activated. The amount of residual charge to be discharged is extremely small, and the resistors, switches, etc. of this residual charge discharge circuit 9 may have low ratings. 3A, b, c, and d show an embodiment of the residual charge discharge circuit, which mainly consists of a resistor 10 and a relay switch 11 or semiconductor switches 22, 22', and 2, all of which have low ratings. It consists of

FIG. 4 shows the configuration of the light emission command signal generating circuit 8 and the charging command signal generating circuit 18 in the device of the present invention, and will be explained below along with their operation.

When the charging start operation switch 16 is turned on, the mono-multivibrator 23 issues a trigger pulse to set the flip-flop circuit 24. When the flip-flop circuit 24 is set, it outputs a charging command signal to the charging control circuit 15, thereby starting charging of the discharge capacitor 4. In the light emission command signal generation circuit 8, when the light emission timing pulse is output from the light emission timing signal generation circuit 25, the mono-multi-vibrator 26, which operates at the trailing edge of this light emission timing pulse, emits light with a delay of the width of the light emission timing pulse. A command signal is issued and applied to the light emission trigger pulse generator 6. At the same time, the light emission timing pulse is applied to the counter 2T of the charge command signal generation circuit 18, and the count number is increased by one. Note that this counter 27 is cleared to O by the trigger pulse output of the mono multivibrator 23. The reference number setting circuit 28 is preset to a number smaller than the required number of flashes. Comparator 29 compares counter 27 and reference number setting circuit 28. If the flash discharge is repeated here, the output of the counter 27 and the output of the reference number setting circuit 28 will match at the time of the flash discharge one time before the last flash discharge set in advance, and the comparator 29 will output the output signal. put out. Subsequent light emission timing signal generation circuit 25
A reset pulse is output from the AND gate circuit 30 based on the light emission timing pulse output from the AND gate circuit 30 and the output signal of the comparator 29. This reset pulse resets the flip-flop circuit 24, causing the charging command signal to fall.
On the other hand, the light emission command signal is output by the mono-multivibrator 26 with a delay equal to the width of the light emission timing pulse, so that it is output after the charge command signal. As described above, according to the light emitting command signal generation circuit and the charging command signal generating circuit of the device of the present invention, the charging command signal is lowered before the final light emitting command signal to prohibit charging, and when the desired residual charge is discharged. Residual charge can be reduced.
The counter 27 in the embodiment shown in FIG. 4 is used as means for detecting the light emission command signal immediately before the final light emission command signal.
It is also possible to use a subtraction counter and preset a number smaller than the required number of times, so that the time when the count number of the counter 27 reaches O is one time before the final flash discharge.

In addition, when the flash discharge device is used for exposure or fixing in an electronic copying machine, the charging signal can be lowered before the final light emission command signal using the operation signal of the copying machine main body. Furthermore, when used in a fixing device of a facsimile receiving device, the charging signal can be made to fall before the final light emission command signal by signal processing the transmission end signal or the like. As described above, the flash discharge device of the present invention performs the final flash discharge in a state where recharging is prohibited, lowers the voltage of the discharge capacitor, and then discharges the residual charge. It is possible to reduce the ratings of resistors, switches, etc., and has great industrial effects.

[Brief explanation of drawings]

Figure 1 is a program diagram of a conventional flash discharge device.
Fig. 2 is a block diaphragm of a flash discharge device according to an embodiment of the present invention, Fig. 3 A, b, c, and d are wiring diagrams of the residual charge discharge circuit of the same device, and Fig. 4 is a light emission command of the same device. This is a block diaphragm of a signal generating circuit and a charging command signal generating circuit. 1...AC power supply, 2...Power switch, 3...Power circuit, 4...Discharge capacitor, 5...Flash discharge tube , 6... Light emission trigger pulse generation circuit, 8... Light emission command signal generation circuit, 9... Residual charge discharge circuit, 12...
... Voltage detector, 13 ... Voltage comparator, 14
...Reference voltage generator, 15...Charging control circuit, 16...Charging start operation switch, 18
...Charging command signal generation circuit, 19...
Gate circuit, 20... Voltage comparator, 21...
...Reference voltage generator.

Claims (1)

[Claims] 1. A discharge capacitor that is charged by a current boosted and rectified by a power supply circuit, a flash discharge tube that emits light by the charged charge of the discharge capacitor, a charging command signal generation circuit, a light emission command signal generation circuit, and residual charge discharge of the discharge capacitor. What is claimed is: 1. A flash discharge device comprising a circuit, having means for prohibiting charging of a discharge capacitor before a preset final flash discharge, and configured to activate a residual charge discharge circuit after the final flash discharge.