JPS59137964A - Load control device - Google Patents

Abstract

PURPOSE:To eliminate the influence on the 2nd load member arising from a fluctuation in a power source voltage by compensating the quantity of the electricity to be conducted to the 2nd load member for a prescribed time since the conduction of electricity to the 1st load member is started. CONSTITUTION:A heater driving signal 6 is supplied to a one-shot timer 8 as well and the signal of a high level is supplied as a compensation signal 9 to a driving circuit 1 for a lighting voltage for the prescribed period since said signal is inputted. The circuit 1 expedites the ignition timing at which the phase of the AC power source to be supplied to a halogen lamp A is controlled for said input period. The decrease in the source voltage during the driving of a heater B is thus compensated and the fluctuation in the quantity of the light from the lamp is prevented. The rate of advancing the ignition timing is obtd. by measuring preliminarily the fluctuation in the voltage value upon turning on a heater and obtaining the fluctuating voltage value as compensable quantity. The output period of a compensation signal 9 by the timer 8 is determined according to the measured value obtd. by measuring preliminarily the period when the influence of an abrupt fluctuation 7 in the power source by the heater on is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load control device for an image forming apparatus, and more particularly to a load control device that controls energization of a plurality of load members driven by one energization.

An image forming apparatus such as a copying machine is generally provided with at least two or more load members, such as a light source for exposing an original, a heat source for heat fixing, a heat source for removing humidity, and a cooling fan, as necessary. These load members come in a wide variety of types, such as those that are driven all the time and those that are driven only for a necessary period. For example, the light source for exposing the original remains on at least during the exposure period of the original, and the heat source for fixing is controlled on and off so that the fuser is always kept at the required temperature by temperature detection using a thermistor, etc., regardless of the exposure period. ing. The amount of light from the exposure light source must be constant during the exposure period, and is controlled in this way. However, if power is started to the fixing heat source during this exposure period, the input power supply voltage to the light source may suddenly change. This may cause fluctuations such as a decrease in the amount of electricity supplied to the light source. However, with conventional control methods, even if fluctuations are detected, they cannot be dealt with instantly. When such a situation occurs, the amount of light from the light source also fluctuates, which eventually causes the image quality of the copied image to deteriorate. Although such a relationship can be similarly applied to other load members, the amount of light from the light source in particular directly affects the copied image and is therefore an important issue.

The present invention has been made in consideration of the point L, and provides a load control device that eliminates the influence on the second load member at the time of starting energization to the first load member.

The present invention will be further explained below using the drawings.

FIG. 1 shows an example of a control circuit in which the present invention is used to control energization of a document exposure light source (lamp) and a fixing heat source (heater) of a copying machine.

In FIG. 1, A is a halogen lamp, B is a fixing heater, and AC is an alternating current 100V power source.

The halogen lamp A is supplied with an AC voltage whose phase is controlled to compensate for fluctuations in the power supply voltage by a lighting voltage control circuit 1. Reference numeral 2 denotes a main control section consisting of a well-known microcomputer, which outputs a lighting timing signal 5 for the halogen lamp A and inputs/outputs signals for sequence control of various parts of the copying machine. Lighting timing signal 5 from main control unit 2
The lighting voltage control circuit 1 operates while the voltage is supplied, and the halogen lamp A lights up with a predetermined amount of light.

The heater B is energized and turned on and off by turning on and off the zero cross switching relay 5SR3.

A temperature detecting thermistor 4 of the heater B is provided near or in contact with the fixing device, and the terminal voltage due to the change in resistance value of the thermistor 4 depending on the temperature is compared with a predetermined voltage by a comparator 7. As a result, when the heater temperature is lower than a predetermined value, the heater drive signal 6 is output from the comparator 7, and 5SR3 is turned on via the driver to energize the heater.

The heater drive signal 6 is also supplied to a one-shot timer 8. The one-shot timer 8 supplies a high-level signal output for a predetermined period from the input of this signal to the lighting voltage drive circuit 1 as a compensation signal 9. The lighting voltage drive circuit 1 inputting the compensation signal 9 accelerates the ignition timing of the phase control of the AC power supply supplied to the halogen lamp A during the manual power period.

FIG. 2 is a circuit diagram showing an example of a detailed circuit configuration of the lighting voltage drive circuit l. A in the frame is an N-gate thyristor (PU
This is a phase control circuit that controls the point and tilt angle of the bidirectional control element 12 using T) to maintain the effective value of the AC voltage applied to the lamp A at a predetermined value. Here, the firing angle is determined by the output of a differential amplifier B, which compares the terminal voltage of the lamp A with a constant value to detect an error, and the line voltage applied to the 7-node terminal of the PUT via the resistor 14.

To explain this differential amplifier B, transistors 30, .
31 connects the emitters in common and is grounded from this contact through a resistor 32. Also transistor 3
The collector of 0 is connected to the input terminal INI of the lighting timing signal 5 from the main control section 2 via the resistor 29. On the other hand, the collector of the transistor 31 is directly connected to the input terminal INI.
connected to. Further, the base of the transistor 31 is connected to a constant potential point created by resistors 33, 34, 36 and a variable resistor 35, and this potential can be changed arbitrarily by the variable resistor 35.

A transistor 37 is connected in parallel to the resistor 34. The transistor 37 performs a switching operation, and is turned on by the compensation signal 9 from the one-shot timer 8, which is turned on by the heater drive signal 6 input to the input terminal IN2, thereby forming a path that bypasses the resistor 34.

The base of the transistor 30 is connected to the base of the transistor 30, in order to detect the terminal voltage of the lamp A, the output of the error detection transformer 21 connected to the lamp A is rectified by a diode bridge 22, divided by resistors 23 and 24, and then pulsed by a capacitor 25. An error signal with some of the flow removed is applied through resistor 26. Furthermore, a feedback path in which a capacitor 27 and a resistor 28 are connected in series is provided between the base and collector of the transistor 30.

The firing phase angle of the bidirectional control element 12 is determined by the pulse obtained from the PUT, and this pulse and the AC power supply A
The phase relationship of C with the power supply frequency changes depending on the current charging the capacitor 16, that is, the sum of the current amplified by β times in the transistor 13 and the current flowing through the resistor -14.

In such a configuration, when the lighting timing signal 5 is input as a DC power supply voltage from the main control section 2 via the driver, the following control operation is performed.

Now, if we look at the case where the voltage across the lamp A becomes lower than the reference voltage for some reason, the voltage at the output end of the diode bridge 22 decreases, the base current in the transistor 30 decreases, and this transistor 30 keeps the base potential constant. Since the differential amplifier is formed together with the transistor 31 suppressed to , the collector current decreases, and therefore the collector potential rises to approach the DC power supply voltage applied to the input terminal INI. For this reason, the current flowing through the resistor 15 and the emitter current of the I transistor 13 increase, and the capacitor 16
It takes less time per AC half cycle for the PUT to charge to the potential required to turn the PUT on.

That is, the phase of the ignition pulse advances, and the bidirectional control element 12 conducts one pulse per half cycle more than in the original case, so that the voltage at the terminals of lamp A increases and approaches the reference voltage. When the lamp voltage increases, the opposite operation occurs.

- On the other hand, a case will be described in which the heater drive signal 6 for driving the heater B is output while the lamp A is lit, that is, while the lighting timing signal 5 is being output.

As described above, the circuit shown in FIG. 2 cannot respond instantaneously to sudden changes in voltage because of the stabilization control based on feedback looseness. Therefore, as described above, the heater drive signal 6 is supplied to the one-shot timer 8, and a high-level signal from the one-shot timer 8 for a predetermined period of time is supplied as the compensation signal 9 to the input terminal IN2 of the lighting control circuit 1. When the transistor 37 is turned on by the compensation signal 9, the resistor 3
4 is bypassed, the base potential of the transistor 31 increases by a predetermined value. As a result, the collector current of the transistor 30 of the differential amplifier B decreases, and therefore its collector potential increases by a predetermined value. For this reason, the current flowing through the resistor 15 and the emitter current of the transistor 13 increase for a period determined by the one-shot timer 8, and the time until the capacitor 16 is charged to the potential required to turn on the PUT is shortened. Become. This allows the phase of the ignition timing of lamp drive to be advanced by a predetermined amount.

In this way, by advancing the ignition timing of lamp A by a predetermined amount for a predetermined period of time from the start of driving heater B, the drop in power supply voltage when heater B is driven is compensated for, and fluctuations in the amount of lamp light are prevented. be. The amount by which the ignition timing is advanced is determined by measuring the fluctuation in voltage value caused by turning on the heater in advance, and is obtained as an amount that can compensate for this fluctuation in voltage value. Then, in order to achieve the obtained advance amount, the upper H portion of the base voltage of the transistor 31 is determined.

Further, the output period of the compensation signal 9 by the one-shot timer 8 is determined in accordance with the measured value by measuring in advance the period during which the influence of the sudden power fluctuation 7 caused by turning on the heater is eliminated.

In this embodiment, a case has been described in which power fluctuations to a lamp are compensated for when a heater is turned on, but the present invention can also be applied to control of load members other than heaters and lamps, such as motors and fans. Alternatively, the base voltage may be directly changed without forming the /hay2f circuit.

As described above, according to the present invention, it is possible to eliminate and compensate for the influence on other load members due to fluctuations in the power supply voltage accompanying the start of energization to the load member without delay.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example of the lighting voltage control circuit shown in FIG. 1, where A is a halogen lamp, B is a heater, and l is a In the lighting voltage control circuit, 2 is a main control section, 3 is a 5SR14 thermistor, 7 is a comparator, and 8 is a one-shot timer. Applicant Canon Co., Ltd.

Claims (1)

[Claims] A load control device that controls energization of a plurality of load members driven by energization, and is characterized in that the amount of energization to a second load member is compensated for a predetermined time from the start of energization to the first load member. Load control device.