JPH0246952B2 - HODENKANNOTORIGAKAIRO - Google Patents

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 toner fixing in a laser printer.

One method of fixing toner in laser printers is to instantly dissolve the toner using the light energy emitted during the discharge of a xenon discharge tube.
There is a way to fix it on 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 a 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 toner fixing in a laser printer. In the figure, 1 is a trigger timing generation circuit, 2 is a high voltage source, and 3 is a trigger timing generation circuit.
is a resistor, 4 is a capacitor, 5 is a constant voltage diode, 6 is a switch element, 7 is a pulse transformer,
Reference numeral 8 indicates a xenon discharge tube, 9 indicates a photodetection element, and 10 indicates a trigger electrode of the xenon discharge tube.

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

A switch element 5 such as a thyristor is made conductive by the trigger signal generated by the trigger timing generating circuit 1, and the energy stored in the capacitor 4 is supplied to the pulse transformer 7.

As a result, the pulse transformer 7 induces a high voltage of several kilovolts to several tens of kilovolts on its secondary side, 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 drops, 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 and the capacitor 4
is charged again and waits for the next trigger signal. In this way, the discharge tube 8 is discharged at regular intervals.

The discharge tube 8 changes over time, and as it ages, it becomes difficult to discharge due to deterioration of the electrode surface, decrease in gas pressure, etc., and a sustained discharge state cannot be reached unless the duration of excitation is lengthened. Therefore, the photodetector element 9 is used, and if no discharge occurs, a trigger signal is sent out again to encourage discharge again.

The discharge cycle of the discharge tube 8 is determined by the paper feeding speed in the printer and the area that can be fixed with one discharge.
For high speed printers this is typically 2-4 times per second.

The charging time of the capacitor 4 is determined by the capacitance of the capacitor 4 and the time constant depending on the resistance value of the resistor 3, and is usually several hundred milliseconds, but in the case of retriggering, it is necessary to keep the paper feeding speed constant. , the capacitor 4 must be charged within several milliseconds. If the battery cannot be charged in such a short time, paper feeding must be temporarily stopped.

If the resistance value of the resistor 3 is lowered, the charging time will be shortened, but a significant reduction will be accompanied by a very large amount of power consumption.

As a solution to the above problem, a method has been proposed in which a plurality of pulse circuits are provided and the pulse circuits are sequentially operated, and an application has been filed by the present applicant. (Japanese Patent Application No. 59-138603 [Japanese Unexamined Patent Publication No. 61-22378]).

FIG. 3 shows the above-mentioned plurality of pulse circuits provided,
FIG. 2 is a circuit diagram of a method in which pulse circuits are sequentially operated by a frequency dividing circuit. In the figure, the same symbols as in FIG. 2 indicate the same objects, 11 and 11' indicate a pulse circuit, 12 a trigger frequency divider circuit, 17 and 18 a drive amplifier, and 19 and 20 a pulse transformer, respectively. .

[Problems to be Solved by the Invention] The circuit of FIG. 3 usually works well and can repeatedly retrigger the discharge tube in a short period of time. However, if the trigger signal pulse is broken by noise or the like and operates like two pulse signals, the pulse circuits 11 and 11' will operate continuously.

At this time, the pulse transformer 7 is excited by the first pulse circuit that operates first, and the current flowing through the switch element 6 and the terminal voltage Vc of the capacitor 4 are as shown in FIG. ing.

When current is flowing through the switch element 6, the second
When the pulse circuit of is ignited, the result is as shown in Fig. 5. This is because the terminal voltage Vc ₁ of the capacitor 4 of the first pulse circuit has decreased, and the terminal voltage Vc ₂ of the capacitor 4 of the second pulse circuit has been higher.
The switch element 6 of the pulse circuit of is cut off.
This is because ₁ becomes zero.

The rise of the current ₂ in the second pulse circuit is extremely steep, and if a thyristor or the like is used as the switch element, di/dt breakdown will occur.

[Means for solving the problem] The above problem is caused by the trigger timing generation circuit that generates a signal with a fixed time relationship with respect to the printer's printing operation and paper feeding operation, resistors, capacitors, and constant voltage. It includes a plurality of pulse circuits made up of diodes and switch elements, a waveform modification circuit, a frequency dividing circuit, and a pulse transformer, and the trigger signal generated by the trigger timing generation circuit is adjusted to a certain value or more in the waveform modification circuit. After correcting the pulse width to the pulse width, applying the frequency divided output to each of the plurality of pulse circuits in addition to the frequency dividing circuit,
The problem is solved by the discharge tube trigger circuit of the present invention, in which the power supply terminal and the output terminal of the pulse circuit are connected in common.

[Function] That is, by inserting a waveform correction circuit such as a monostable multivibrator into the input of the trigger frequency divider circuit,
By correcting the input pulse to a width greater than a certain value and then applying it to the trigger frequency divider circuit, two pulses can be input at the same time.
A plurality of pulse circuits can be sequentially operated without firing a single pulse circuit, and retriggering can be repeated in a short period of time.

[Example] Hereinafter, the gist of the present invention will be explained as a specific example using the example shown in FIGS. 1a to 1c.

FIG. 1a is a main circuit diagram of an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 3 indicate the same objects, and 21 indicates a monostable multivibrator which is a typical waveform correction circuit.

The output TRG of trigger timing generation circuit 1 is
By AND gate 14, flip-flop 1
The output is ANDed with the Q side output of No. 3, and the output thereof is added to the drive amplifier 17, and the output becomes A.
Similarly, the output of trigger timing generation circuit 1
TRG is ANDed with the side output of flip-flop 13 by AND gate 15, and its output is applied to drive amplifier 18, and its output is B
becomes.

Moreover, the outputs of AND gates 14 and 15 are:
It is applied to an OR gate 16 and its output is applied to a monostable multivibrator 21.

The monostable multivibrator 21 is adjusted to a time that is sufficiently long compared to the trigger timing signal and shorter than the restriking period, and an output pulse having that width is applied to the input terminal T of the flip-flop circuit 13. It will be done. Therefore, for each output pulse TRG of the trigger timing generation circuit 1, the flip-flop circuit 13 is inverted, and A
and B are output alternately.

FIG. 1b is a diagram showing the timing relationship between the voltage waveforms of the trigger frequency divider circuit 12 and various parts around it. From the top of the figure, the output Q of the flip-flop circuit 13, the output TRG of the trigger timing generation circuit 1, the output trigger signals A and B, the input C of the monostable multivibrator 19,
Also, the waveform and timing of the input T of the flip-flop circuit 13 are shown.

As shown in the figure, even if the trigger signal TRG is broken by noise, the input T of the flip-flop circuit 13 becomes a single pulse with a constant pulse width, and the input T of the flip-flop circuit 13 becomes is inverted for each trigger signal TRG.

FIG. 1c shows another embodiment of the present invention, and although the insertion position of the monostable multivibrator 19 is different from FIG. 1a, the operation and effect are exactly the same.

[Effects of the Invention] As explained above, according to the present invention, it is possible to repeatedly retrigger the discharge tube in a short period of time without any trouble, which is highly effective for speeding up laser printers. It is.

[Brief explanation of drawings]

FIG. 1a is a circuit diagram of a main part of an embodiment of the present invention, FIG. 1b is a timing diagram of an embodiment of the invention, and FIG. 1c is a circuit diagram of a main part of another embodiment of the invention. Figure 2 is a circuit diagram of a typical conventional discharge tube trigger circuit, and Figure 3 is a circuit diagram of a typical conventional discharge tube trigger circuit.
The figure is a circuit diagram of a conventional discharge tube trigger circuit with multiple pulse circuits, Figure 4 is a current and voltage waveform diagram in the pulse circuit, and Figure 5 is a current and voltage waveform during double ignition in the pulse circuit. It is a diagram. 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,
19, 20 are pulse transformers, 8 is a discharge tube, 9
1 is a photodetecting element, 10 is a trigger electrode of a discharge tube, 1
1 and 11' are pulse circuits, 12 is a trigger frequency divider circuit,
13 is a flip-flop circuit, 14 and 15 are
AND gate, 16 is OR gate, 17 and 18 are drive amplifiers, 19 is monostable multivibrator,
Each is shown below.

Claims (1)

[Claims] 1. A trigger timing generation circuit that generates signals with a fixed time relationship with respect to the printer's printing operation and paper feeding operation, multiple pulse circuits consisting of resistors, capacitors, voltage regulator diodes, and switch elements, and waveform A correction circuit, a frequency division circuit, and a pulse transformer are provided, and after the trigger signal generated by the trigger timing generation circuit is modified to a pulse width of a certain value or more in the waveform modification circuit, the trigger signal is transmitted to the frequency division circuit. In addition, the trigger circuit for a discharge tube is characterized in that the divided output is applied to each of the plurality of pulse circuits, and the power supply terminal and output terminal of the pulse circuits are connected in common.