JPH0990522A - Lamp light intensity control device - Google Patents

Abstract

(57) Abstract: In the past, it was necessary to shape the waveform of an AC input by using expensive parts for controlling the light quantity of an exposure lamp of a copying machine. SOLUTION: The light intensity of an exposure lamp of a copying machine is detected at a zero cross point of an AC input supplied to the exposure lamp, and the phase angle of the AC input supplied to the exposure lamp is controlled with reference to the zero cross point. The zero-cross signal is sampled for the time corresponding to the measurement section and stored in the shift register 11. Further, ON and OFF of 1 to n are checked in a constant transfer cycle. Within one transfer clock, the data of Q _{1 to} Qn are sequentially selected by the multiplexer 12, and this is input to the enable terminal of the counter 13. Of the signals sampled n times in the past, the number of times of ON is output from the counter 13, and when the number of times of ON is larger than the value of the comparison value register 14, it is latched by the latch circuit 16 as zero-cross ON.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lamp light quantity control device, and more particularly, to controlling the light quantity of an exposure lamp of a copying machine and other lamps by controlling the phase angle of an AC signal supplied to the lamp. The present invention relates to a lamp light amount control device for controlling.

[0002]

2. Description of the Related Art Generally, the light quantity of an exposure lamp in a copying machine or the like is controlled by controlling the phase angle of an AC input supplied to the exposure lamp.

FIG. 9 is a view for explaining an example of a conventional lamp light amount control device by phase angle control for controlling the light emission amount of an exposure lamp by controlling the phase angle of an AC input supplied to the exposure lamp. In the figure, 1 is an AC power supply, 2 is a trigger pulse generation circuit, 3 is a triac, 4
Is a feedback voltage generation circuit, 5 is an exposure lamp, and 6 is a controller. As shown in FIG. 10, the trigger pulse generation circuit 2 detects the zero-cross point of the AC voltage (FIG. 10A) from the AC power supply 1, At the same time, the trigger pulse generating circuit 2 outputs a trigger point for turning on the triac 3.

The feedback voltage generation circuit 4 detects the voltage across the exposure lamp 5 and feeds it back to the controller 6, which resets the trigger point. Zero-cross signal (Fig. 10
When the trigger pulse (FIG. 10C) is input to the triac 3 after the off section Toff from (b)), the AC input voltage (FIG. 10A) is supplied to the exposure lamp 5 only in the shaded portion. The light amount of the lamp 5 can be controlled by the amount of the shaded portion.

[0005]

[Problems to be Solved by the Invention]
If an AC signal containing noise (No) as shown in (a) is input, after the zero-cross signal (FIG. 11 (b)) is detected at the regular position (T), as described above. , The noise portion is detected again (No), and the lamp 5 is off during the period Toff from this noise portion (No) (see FIG. 11).
(B)). Therefore, the timing of turning on the exposure lamp 5 is delayed by the width T _w shown by the dotted line in FIG. 11C, and the light amount of the lamp is insufficient. Therefore, conventionally, it has been necessary to shape the waveform of the AC input by using expensive parts.

[0006]

According to a first aspect of the present invention, in a lamp light amount control device for controlling the light amount of an exposure lamp of a copying machine, a zero cross detecting means for detecting a zero cross point of an AC input supplied to the exposure lamp. A lamp light quantity control means for controlling the phase of an AC input supplied to the exposure lamp to control the light quantity of the exposure lamp by performing a phase angle control based on the zero cross point, and the AC input from the zero cross signal. And a zero-cross point determining means for determining the zero-cross point when the number of active times is detected a predetermined number of times or more out of the number of times of sampling in the certain period. It is characterized by.

According to a second aspect of the invention, in the first aspect of the invention, after the zero cross point is determined,
It is characterized in that it has a zero-cross point detection prohibiting means for prohibiting the detection of the zero-cross point.

According to a third aspect of the invention, in the second aspect of the invention, when the zero-cross point detection cycle differs from the previous detection cycle (or a plurality of previous cycles) by a predetermined time or more, the detected zero-cross point is detected. It is characterized in that the output of the signal is stopped and the zero-cross signal is output in the cycle of the previous time (a plurality of times up to the previous time).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1A shows a correct zero-cross signal, and FIG. 1B shows a signal when noise (No) is added thereto. The noise is removed by sampling in a rather short interval.

FIG. 2 is a block diagram for explaining the invention of the first embodiment, and FIG. 3 is a timing chart for explaining the operation of FIG. 2. In the figure, 11 is a shift register, 12 is a multiplexer, and 13 is. Is a counter, 14 is a comparison value register, 15
Is a comparator, and 16 is a latch circuit. In the first embodiment, the zero-cross signal is sampled for a time corresponding to the measurement section shown in FIG.
Stored in 1.

In the timing chart shown in FIG.
In a constant transfer cycle, 1 to n ON and O
The FF is checked (Fig. 3 (a)). That is, if sampling is performed n times, ON / OFF check is performed in the n ² measurement section. In one transfer clock, Q ₁ select ~Qn data (FIG. 3 (b)) sequentially at multiple grasses 12, and inputs it to the enable terminal of the counter 13.

By doing the above, how many times the signal has been ON among the signals sampled n times in the past,
When it is output from the counter 13 and the number of times of ON is larger than the value of the comparison value register 14, it is latched by the latch circuit 16 as a zero cross ON (FIG. 3 (e)). By doing so, the noise component can be easily removed, and there is no fear of outputting an erroneous zero-cross signal.

(Embodiment 2) Since the cycle of the zero-cross signal is almost completely constant, the zero-cross signal is not output in a place unrelated to the original cycle. For this reason,
In the circuit shown in FIG. 2, if the re-detection is prohibited for a certain period after the zero-cross signal is detected once, it can be considered that there is almost no possibility of false detection of noise.

FIG. 4 is a block diagram for explaining an embodiment (embodiment 2) of the invention based on the above logic, and FIG. 5 is a timing chart thereof, in which 21 is, for example, FIG. The zero-cross detection circuit 22 and the re-detection prohibition section setting circuit 22 shown in FIG. 1 always have an edge of the zero-cross signal once in one cycle (because re-detection is prohibited once detected). If the edge detection circuit is connected after the re-detection prohibited section setting circuit 22, no malfunction occurs.

(Embodiment 3) As described above, the cycle of the zero-cross signal is almost constant. Therefore, when noise is generated, the conventional signal is forcibly output continuously. It is 3.

FIG. 6 is a block diagram for explaining the third embodiment, and FIG. 7 is a timing diagram for explaining the operation of FIG. 6, in which 31 is a counter, 32 and 33 are latch circuits, 34 is a subtractor, 35 is a comparator, 36 is a shift register, 37 is an AND circuit, 38 is a latch circuit, 39
Is a multiplexer, and 40 is a down counter. First, the cycle of the detection signals of the first and second embodiments (FIG. 7A) is measured with the combination of the counter 31 and the latch 32, and as a result, the deviation of the cycle from the previous time The subtracter (absolute value output) 34 and the comparator 35 calculate whether or not the value is equal to or less than a certain value, and the result is input to the shift register 36. As a result, when the deviation is, for example, three times or more consecutively below a certain value,
The output of the AND circuit 37 becomes 1 (FIG. 7B), and the period at that time is latched by the latch circuit 38 (FIG. 7).
(C)). In this state (periodic stable state), the detection signal (waveform-shaped zero-cross signal) (FIG. 7 (d))
Is output as is as the zero-cross signal 2.

When the cycle of the zero-cross signal deviates from the stable state due to noise (FIG. 8 (a)), the output of the AND circuit 37 of FIG. 6 falls to low (FIG. 8 (b)). When this happens, the multiplexer 39 selects the borrow output of the down counter 40 (FIG. 8 (c)). The down counter 40 is loaded with the cycle when the cycle is stable, so even when noise occurs, the zero cross signal 2
Can be output (FIG. 8C).

[0018]

According to the invention of claim 1, in the lamp light quantity control device for controlling the light quantity of the exposure lamp of the copying machine,
Zero-cross detection means for detecting the zero-cross point of the AC input supplied to the exposure lamp, and performing phase angle control based on the zero-cross point, and controlling the phase of the AC input supplied to the exposure lamp to control the phase of the exposure lamp. Lamp light amount control means for controlling the light amount, monitoring the sampling period within the constant period of the AC input from the zero-cross signal, among the number of times sampled within the constant period, when detecting the number of active times more than a predetermined number of times, Since the zero-cross point determining means for determining the zero-cross point is provided, even if there is no tin on the zero-cross signal, it can be easily removed and the lamp light quantity is not affected.

According to the invention of claim 2, in the invention of claim 1, after the zero-cross point is determined, a zero-cross point detection inhibiting means for inhibiting the detection of the zero-cross point is provided for a certain period. By providing the zero-cross signal detection prohibited section, more stable noise removal can be performed, and even large noise can be dealt with.

According to the invention of claim 3, in the invention of claim 2, when the detection cycle of the zero-cross point is different from the previous detection cycle (or a plurality of previous cycles) by a predetermined time or more, it is detected. Since the output of the zero-cross signal is stopped and the zero-cross signal is output in the previous cycle (up to several times), the zero-cross signal will be output in the same cycle as before even when noise that changes the zero-cross cycle occurs. Can be generated.

[Brief description of drawings]

FIG. 1 is a diagram showing a comparison between a normal zero-cross signal and a zero-cross signal when noise occurs.

FIG. 2 is a block diagram for explaining an example (embodiment 1) of the invention of claim 1;

FIG. 3 is a timing chart for explaining the operation of FIG.

FIG. 4 is a block diagram for explaining an example (second embodiment) of the invention of claim 2;

FIG. 5 is a timing diagram for explaining the operation of FIG.

FIG. 6 is a block diagram for explaining an example (third embodiment) of the invention of claim 3;

7 is a timing chart for explaining the operation of FIG.

FIG. 8 is a timing chart for explaining another operation of FIG.

FIG. 9 is a block diagram for explaining an example of a lamp light amount control method by phase angle control.

10 is a timing chart for explaining the operation of FIG.

FIG. 11 is a diagram for explaining the operation of FIG. 9 when noise occurs.

[Explanation of symbols]

1 ... AC power supply, 2 ... Trigger pulse generating circuit, 3 ... Triac, 4 ... Feedback voltage generating circuit, 5 ... Exposure lamp, 6 ... Controller, 11 ... Shift register, 12
... multiplexer, 13 ... counter, 14 ... comparison value register, 15 ... comparator, 16 ... latch circuit, 21 ...
Zero-cross detection circuit, 22 ... Re-detection prohibited section setting circuit,
31 ... Counter, 32, 33 ... Latch circuit, 34 ... Subtractor, 35 ... Comparator, 36 ... Shift register, 37
... AND circuit, 38 ... Latch circuit, 39 ... Multiplexer, 40 ... Down counter.

Claims (3)

[Claims] 1. A lamp light quantity control device for controlling the light quantity of an exposure lamp of a copying machine, and a zero-cross detection means for detecting a zero-cross point of an AC input supplied to the exposure lamp, and a phase angle control based on the zero-cross point. The lamp light amount control means for controlling the phase of the AC input supplied to the exposure lamp to control the light amount of the exposure lamp, and the sampling period monitoring of the AC input from the zero-cross signal for the fixed period. A lamp light amount control device, comprising: zero-cross point determination means for determining the zero-cross point when the number of active times is detected a predetermined number of times or more out of the number of times of tumbling. 2. The lamp light amount control device according to claim 1, further comprising a zero-cross point detection prohibiting unit that prohibits detection of the zero-cross point for a certain period after the zero-cross point is determined. 3. When the detection cycle of the zero-cross point is different from the previous detection cycle (or a plurality of previous cycles) by a predetermined time or more, the output of the detected zero-cross signal is stopped and The lamp light amount control device according to claim 2, wherein the zero-cross signal is output in a cycle of (number of times).