JPS6122378A - Trigger circuit of discharge tube - Google Patents

Abstract

PURPOSE:To execute repeatedly retrigger in a short time even if a charging time of a capacitor of a pulse circuit is long, and to operate a printer at a high speed, by frequency circuit, and triggering the pulse circuit. CONSTITUTION:With respect to each on of the trigger signals TRG from a timing generting circuit 1, a switching element 6 of pulse circuits 11, 11' is conducted alternately, and it is applied to a pulse transformer 7. Also, when the element 6 of the circuit 11 conducts, and a capacitor 4 is discharged, the capacitor 4 of the circuit 11' becomes a charged state, it is detected that a discharge tube 8 is not discharged, and even if the signal TRG for reignitionis outputted immediately by the circuit 1, the element 6 of the circuit 11' conducts by an output A of a frequency dividing circuit 12, and the reingnition is executed. Accordingly, the retrigger can be executed in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a trigger circuit for a xenon discharge tube used for fixing toner in a laser printer.

One method for fixing the toner in a laser printer is to use light energy emitted during discharge from a xenon discharge tube to instantly dissolve the toner and fix it on the paper. In order to discharge this xenon discharge tube, it is necessary to apply a high voltage to its anode and to apply a voltage even higher than the anode voltage to the trigger electrode. A circuit for applying high voltage to this trigger electrode is a trigger circuit, and the present invention relates to an improvement thereof.

[Prior Art] FIG. 2 is a diagram showing a typical circuit configuration for discharging a xenon discharge tube used for constant toner loading of a laser printer. In the figure, 1 is a trigger timing generation circuit, 2 is a high voltage source, 3 is a resistor, 4 is a capacitor, and 5
is a constant voltage diode, 6 is a switch element, 7 is a pulse
transformer, 8 a xenon discharge tube, 9 a photodetector element, 10
1 and 2 show the trigger electrodes of the xenon discharge tube, respectively.

The trigger timing generation circuit 1 is a circuit that generates a xenon discharge tube discharge trigger signal with a constant time relationship between the printing operation and the paper feeding operation in a laser printer. The capacitor 4 is connected to the voltage of the high voltage source 2 (approximately 2
KV) through a resistor 3 and clamped to a constant voltage by a constant voltage diode 5.

A trigger signal generated by the trigger timing generating circuit 1 turns on a switching element 5 such as a cyrisk, and the energy stored in the capacitor 4 is supplied to the pulse transformer 7.

As a result, the pulse transformer 7 has, on its secondary side,
A high voltage of several kilovolts to several tens of kilovolts is induced, which is applied to the trigger electrode 10 of the xenon discharge tube 8 to ignite the discharge tube.

The ignited discharge tube 8 receives energy from the power source 2 and discharges, and the anode potential of the discharge tube 8 rapidly decreases. When the voltage decreases, the power supply 2 stops supplying energy, and thereby the discharge tube 8 also stops discharging.

When the discharge of the discharge tube 8 stops, the output voltage of the power supply 2 is restored, the capacitor 4 is also charged again, and the next trigger signal is waited for. In this way, the discharge tube 8 is discharged at regular intervals.

[Problems to be Solved by the Invention] The discharge tube 8 described above changes over time, and as it ages, it becomes difficult to discharge. This is a change caused by deterioration of the electrode surface or a drop in gas pressure, and a sustained discharge state cannot be reached unless the duration of excitation is lengthened. Therefore, using the photodetection element 9, if no discharge occurs, a trigger signal is sent out again to encourage discharge again.

The discharge cycle of the discharge tube is determined by the paper feeding speed in the printer and the area that can be fixed with one discharge, and is usually 2 to 4 times per second in the case of a high-speed printer. The charging time of the capacitor 4 is determined by the time constant determined by the capacitance of the capacitor 4 and the resistance value of the resistor 3, and is usually several hundred m5ec.
However, in the case of re-triggering, if the paper feeding speed is kept constant, the capacitor 4 must be charged within several m5ec. If the battery cannot be charged in such a short time, paper feeding must be temporarily stopped. If the resistance value of resistor 3 is lowered, the charging time will be shortened, but
Significant reductions will be accompanied by very large power losses.

Means for Solving Problem E] The present invention provides a trigger circuit for a discharge tube that solves the above problems. This is achieved by connecting the terminal and the output terminal in parallel, and applying the frequency-divided trigger signal generated by the trigger timing generation circuit to the trigger input terminal of the pulse circuit.

[Function] By preparing multiple pulse circuits consisting of resistors, capacitors, constant voltage diodes, and switching elements, and connecting their power terminals in parallel, they are constantly charged, and the trigger input terminal is used to generate trigger timing. By dividing the frequency of the trigger signal generated by the circuit and supplying it, the pulse circuit operates sequentially, and even if the charging time of the capacitor in the pulse circuit is long, re-triggering can be repeated in a short time. be.

[Example] Hereinafter, the gist of the present invention will be specifically explained using examples shown in FIGS. 1(A) to 1(C). Although this embodiment describes an example in which two pulse circuits are provided, the present invention is not limited to two pulse circuits.

FIG. 1(A) is a circuit diagram of an embodiment of the present invention. In the figure, 1 to 10 indicate the same objects as in Figure 2,
11, 11° is a pulse circuit consisting of a resistor 3, a capacitor 4, a constant voltage diode 5, and a switching element 6;
1 and 2 respectively show trigger frequency divider circuits which will be explained in detail later.

FIG. 1(B) is a circuit diagram showing the contents of the trigger frequency dividing circuit 12 shown in FIG. 1(A), and FIG.
1 is a timing diagram showing the operation of the trigger frequency divider circuit 12. FIG.

In FIG. 1(B), 13 is a flip-flop;
4.15 is an AND gate, 16 is an OR gate, 17°1
Reference numeral 8 indicates a driving amplifier. The Q side output of the flip-flop 13 and the output TRG of the trigger timing generation circuit 1 are ANDed by the AND gate 14.
Its output is applied to the drive amplifier 17, and its output becomes A.

Similarly, the ◇ side output of the flip-flop 13 and the output TRG of the trigger timing generation circuit 1 are ANDed by the AND gate 15, and the output is sent to the drive amplifier 1.
8 and its output becomes B.

The outputs of AND gates 14 and 15 are applied to an OR gate 16 whose output is applied to input terminal T of flip-flop 13. Therefore, the flip-flop 13 is inverted for each output pulse TRG of the trigger timing generation circuit 1, and A and B are outputted alternately.

FIG. 1(C) is a timing diagram showing the timing relationship between voltage waveforms of each part of the trigger frequency divider circuit 12.

From the top of the diagram, outputs Q and ◇ of flip-flop 13, trigger output human power TRG, output trigger signals A and B
The waveforms of the human power T of the flip-flop 1 and the flip-flop 13 are shown respectively.

Next, returning to FIG. 1(A) again, the pulse circuits 11 and 11', each consisting of a resistor 3, a capacitor 4, a constant voltage diode 5, and a switching element 6, have their power terminals and output terminals connected in parallel. , whose trigger input terminals are connected to outputs A and B of the trigger frequency divider circuit 12, respectively.

Therefore, the 11 and 11'' switch elements 6 are alternately turned on and applied to the pulse transformer 7 for each trigger signal TRG generated by the trigger timing generating circuit 1.

The switch element 6 on the 11 side is now conductive, and the capacitor 4
Even if the discharge tube 8 is discharged, the capacitor 4 on the 11' side remains in a charged state, and if the photodetection element 9 detects that the discharge tube 8 is not discharged, the trigger timing generation circuit 1 immediately triggers the restart. Even if the trigger signal TRG is output, the A output of the trigger frequency dividing circuit 12 makes the switch element 7 on the pulse circuit 11'' conductive, and re-ignition is performed.

In this way, even if the charging time of the capacitor 4 of the pulse circuit 11, 11' is long, retriggering can be performed in a short time by operating the pulse circuits in sequence.

[Effects of the Invention] As explained above, according to the present invention, it becomes possible to repeatedly retrigger the discharge tube in a short period of time, and the laser
This is highly effective in increasing the speed of printers.

[Brief explanation of drawings]

Fig. 1(A) is a circuit diagram of a discharge tube trigger circuit which is an embodiment of the present invention, Fig. 1(B) is a circuit diagram of a trigger frequency dividing circuit, and Fig. 1(C)
2 is a timing chart of a trigger frequency divider circuit, and FIG. 2 is a circuit diagram of a typical conventional discharge tube trigger circuit. In the drawing, 1 is a trigger timing generation circuit, 2 is a high voltage source, 3 is a resistor, 4 is a capacitor, 5 is a constant voltage diode, 6 is a switch element, 7 is a pulse transformer, 8 is a discharge tube,
9 is a photodetection element, 10 is a discharge tube trigger electrode, 11.11' is a pulse circuit, 12 is a trigger frequency dividing circuit,
13 is a flip-flop, 14.15 is an AND gate,
16 is an OR gate, and 17 and 18 are drive amplifiers, respectively.

Claims (1)

[Claims] A discharge tube equipped with a trigger timing generation circuit that generates signals with a fixed time relationship with respect to the printing operation and paper feeding operation of the printer, and a pulse circuit consisting of a resistor, a capacitor, a constant voltage diode, and a switching element. The trigger circuit includes a plurality of the pulse circuits, the power supply terminals and output terminals of the pulse circuits are connected in parallel, and the trigger input terminal of the pulse circuit receives the trigger signal generated by the trigger timing generation circuit. A trigger circuit for a discharge tube, characterized in that the trigger circuit is configured to divide the frequency and apply the voltage.