JPS6026277B2 - Flash lamp light emission control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of light emitted from a flash lamp.

As shown in FIG. 1, a flash lamp 24 is connected to an AC power supply 21 via a step-up leakage transformer 22, a rectifier 23, and a capacitor C, and the terminal voltage of the capacitor C is connected to a voltage dividing resistor R, R'. When the capacitor C is charged and its terminal voltage matches the reference voltage, the output of the comparator 26 causes the switching element 27 provided on the primary side of the leakage transformer 22 to be activated. The flash lamp 2 turns off and stops charging the capacitor C, thereby emitting light in response to a trigger signal.
4 was controlling the amount of light emitted.

However, in this conventional method, since the light emission amount control circuit 30 operates by detecting the voltage of the high voltage section for the flash lamp 24, the detection resistor R' etc. must be made with high withstand voltage. The ground of the power supply for the circuit 30 must be made common to the ground of the power supply for the flash lamp 24. Furthermore, since the control circuit 301 is connected to the high voltage section for the flash lamp 24, if the ground of the control circuit 30 is floating or the detection resistor R' is disconnected, high voltage will be applied to the control circuit 30'. Therefore, not only is there a danger, but there is also a risk that the control circuit 30 may break down or that other circuits that share a power source with the control circuit 30 may be damaged. Furthermore, if the ground of the control circuit 30 is shared with the ground of a circuit in which a large current flows in pulses, such as a flash lamp, there are various drawbacks such as being susceptible to noise interference. It is an object of the present invention to eliminate the drawbacks of the conventional methods described above and to provide a method for controlling the amount of light emitted from a flash lamp, which controls the amount of light emitted from the flash lamp without directly detecting the voltage of the high voltage section for the flash lamp. be.

The present invention will be described with reference to embodiments shown in the drawings.

As shown in Fig. 2, the secondary winding of the step-up leakage transformer 2 to which the AC power supply 1 is input is divided into two parts, N, and N2, and the secondary winding is connected to N through a rectifier 3 and a capacitor C. Flash lamp 4 is connected.

The resistor R is used to discharge the charge in the capacitor C when there is a power outage while charging the flash lamp 4 or when the flash lamp 4 is defective, and the trigger circuit 5
The flash lamp 4 uses a part of the charge in the capacitor C as trigger energy and receives a trigger signal from the outside to cause the flash lamp 4 to emit light. A capacitor C2 is connected to the secondary winding N2 of the leakage transformer 2 via a rectifier 3', and a resistor R is connected to this capacitor C2.
2 and a comparator 6 are connected, and the output of the comparator 6 controls the switching element 7 provided on the primary side of the leakage transformer 2 so that the charging voltage of the capacitor C2 is maintained at a predetermined level. The control system is configured. The power supply 8 is for the control circuit including the comparator 6, and the transistor TR discharges the charge of the capacitor C2 in response to an external command signal synchronized with the trigger signal. Here, the characteristics of capacitors C, , C2 are selected in relation to each other as follows.

That is, the short terminal voltages of the secondary windings N, N2 wound around the common iron core of the leakage transformer 2 are respectively EN・
, EN2 then EN, :EN2=N, :N2
""""""...Since the relationship [1} holds true, the charging voltage Vc of the capacitor C is expressed as a function of time t.

,=f(t) ............ When expressed as f21, the charging voltage Vc2 of the capacitor C2 is V ground = A
f(t) (where A=band)......C so that it becomes '3,
Select 2 characteristics. In this way, capacitor C
, and C2, their charging voltages Vc, , Vc2 show charging progresses that are similar to each other as shown in FIG. Moreover, the winding N. and N2, the load is N. is much larger, so if we set the number of turns accordingly to N,》N2, the internal impedance of N2 becomes extremely small by 4. Therefore, the terminal voltage EN of N is determined by the charging current of capacitor C. From '1} formula, the terminal voltage E of N2 is
Since N2 is determined and capacitor C2 can be considered to be charged by a constant voltage source having an instantaneous value of EN2, the capacitance of capacitor C2 can be selected from a wide range. The above circuit works as follows.

When the AC power supply 1 is applied to the primary side of the leakage transformer 2, the capacitors C, , C2 are respectively curved Vc and C2 in FIG.
, Vc2, and when the charging voltage of the capacitor C2 reaches a predetermined level, the comparator 6 generates an output, and the switching element is configured to maintain this charging level of the capacitor C2. Control 7. And there is '2' between capacitors C and C2.
, derived from the glue formula. vC. = Harm = Mother vC2. ．．・
．． ．．・．． ．．・．． ．．・...Because of the relationship 4', if the charging voltage Vc2 of the capacitor C2 is maintained at a predetermined level, the charging voltage Vc of the capacitor C is also maintained at a predetermined level, and therefore, when the flash lamp 4 receives a trigger signal, The capacitor C2 emits light at a predetermined amount by discharging the capacitor C, or at this time, the capacitor C2 is simultaneously discharged by the command signal. Of course, by adjusting the comparator 6, the amount of light emitted from the flush lamp 4 can be set arbitrarily. FIG. 4 shows an embodiment in which an ordinary transformer 12 is used in place of the leakage transformer 2, and current limiting resistors R, , R2 are provided. In this case, capacitors C, , C2 are provided.
such that the charging time constants of are the same, that is, R, C, =
Except for selecting R2C2, the rest is the same as the embodiment shown in FIG. 2, so detailed explanation will be omitted.

In the above embodiment, the trigger signal and command signal are simply synchronized, but they may be the same signal, or the pulse width of the command signal synchronized with the trigger signal may be widened. By increasing the discharge time of the capacitor C2, it is possible to use a small capacity element as each element of the discharge circuit including the transistor TR, and in addition, the present invention allows various changes and modifications of the above embodiments. It goes without saying that there is.

As described above, the present invention divides the secondary winding of the transformer into two parts, provides a flash lamp charging circuit on one side, and provides a control charging circuit with a similar charging process to the charging circuit on the other side, The input of the transformer is controlled so that the voltage of the control charging circuit is maintained at a predetermined level, and the control charging circuit is discharged when a flash lamp trigger signal is generated, so that the voltage of the high voltage section for the flash lamp is reduced. It is possible to control the amount of light emitted by a flash lamp without direct detection, and therefore there is no need to use high-voltage parts or create any danger, making it suitable for use in various applications such as copying machines. It has excellent effects.

[Brief Description of the Drawings] Fig. 1 is a conventional circuit diagram, Fig. 2 is a circuit diagram showing one embodiment of the present invention, Fig. 3 is a graph of the main part of Fig. 2, and Fig. 4 is a circuit diagram showing an embodiment of the present invention. FIG. 3 is a circuit diagram of main parts showing another embodiment of the present invention. 1, 21... AC power supply, 2, 22...
IJ-keji transformer, 12...transformer, 3, 3', 1
3, 13', 23... Rectifier, 4, 24...
... Flash lamp, 6, 26 ... Comparator, 7, 27 ... Switching element, C,, C2
, C... Capacitor. Groove l figure 2 figure 3 figure 4 figure

Claims (1)

[Claims] 1. In a method for controlling the amount of light emitted by a flash lamp that is connected to an AC power source via a transformer, a rectifier circuit, and a charging circuit and that emits light in response to a trigger signal, the secondary winding of the transformer is divided into two parts, one is used for the charging circuit of the flash lamp, and the other is provided with a control charging circuit whose charging progress is similar to that of the charging circuit via a rectifier circuit, and this control charging circuit is used. 1 of said transformers
The transformer is connected to the next side, controls the input of the transformer so that the voltage of the control charging circuit is maintained at a predetermined level, and discharges the control charging circuit when the trigger signal is generated. A method for controlling the amount of light emitted by a flash lamp.