JP2000113993A - Light source control device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably control a light quantity. SOLUTION: When a light source 1-8 is controlled by the voltage obtained at the prescribed phase timing of an AC power supply, a microcomputer 1-9 holds the detected voltage value in a RAM 1-10 and compares it with the next detected voltage value. When the difference between the detected voltage value and the held voltage value exceeds an allowable range, the microcomputer 1-9 judges that noise occurs, and it uses the held voltage value and determines the value of the voltage for driving the light source 1-8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source control device and method used in an image forming apparatus or the like.

[0002]

2. Description of the Related Art Conventionally, as a light source control method for controlling the light quantity of a light source by a voltage applied to the light source in a light source lighting device, for example, a method of controlling an AC input voltage by phase control has been widely used. As a method of performing the phase control, control by a hardware circuit and software control by a microcomputer can be performed.

[0003] Among these methods, phase control using a microcomputer is widely used because it is easy to cope with the change of control by changing software.

The phase control by the microcomputer is configured, for example, as shown in FIG. In FIG.
2-1 is an AC power supply. Reference numeral 2-2 denotes a transformer connected to both poles of the AC power supply 2-1. A transformer having a winding ratio such that the output on the secondary side has a peak value of about 0 V to 10 V according to the AC input voltage is used. 2-3 is a circuit for rectifying the AC voltage from the transformer, which is adjusted and output by a volume or the like in the circuit of 2-3 so that the output according to the input voltage becomes DC 0V to 5V. In this circuit,
A circuit for outputting a zero-cross signal based on the rectified signal is provided. This signal is supplied to a control circuit 2-5 described later.
Connected to the interrupt input of the microcomputer 2-8. On the other hand, the output according to the input voltage from 2-3 has a form in which the minus side of the AC waveform is brought to the plus side (see the voltage monitor waveform in FIG. 2), and the microcomputer (CPU) A / D of 2-8 (described later)
Input to the port.

Reference numeral 2-7 denotes a light source lamp. 2-5 is a control circuit, a microcomputer 2-8 in the control circuit,
It is composed of a RAM 2-9 and a ROM 2-10.

Reference numeral 2-6 denotes a driving element for driving the light source 2-7, which uses a triac.
5 is fired at a phase corresponding to the control voltage of the light source by a trigger signal from the microcomputer 2-8 in the light source 2;
Supply power to -7. Reference numeral 2-11 denotes a control operation unit for the user to set the control circuit 2-5, and performs various settings such as setting of a lighting voltage of the light source 2-7.

[0007]

However, in the above-described conventional example, the A / D of the microcomputer 2-8 is used.
Since the input voltage read at the port is an instantaneous value, the voltage read at the A / D port despite the fact that the effective value has not changed to the actual input voltage due to AC line noise or the like. However, if the input voltage is calculated based on this voltage value and the light source is controlled, there is a problem that control cannot be performed with a stable light amount. I was

Further, in the above conventional example, as shown in FIG. 3, since the peak value and the waveform are different between the negative side and the positive side of the AC input voltage waveform, when the AC input voltage fluctuates, an accurate value is obtained. There has been a problem that the AC input voltage cannot be detected, and stable control of the light source cannot be performed.

[0009]

In order to achieve such an object, the invention according to claim 1 provides an A for turning on a light source.
Zero cross detection means for detecting a zero cross point of the C power supply, voltage detection means for detecting the voltage of the AC power supply at a predetermined phase timing from the detected zero cross point, and driving the light source based on the detection result First control means for determining a voltage value; holding means for holding the detection result of the voltage detection means for each zero cross; values of the detection result held by the holding means; It is determined whether the difference value of the detection result detected by the voltage means is larger than a predetermined value, and when it is determined to be larger, the detection result used in the control means is held in the holding means. And a second control means for changing to a detection result.

According to a second aspect of the present invention, in the light source control device according to the first aspect, there are a plurality of types of voltage levels of the AC power supply, and a maximum voltage to be controlled among the plurality of types is selectively selected. Switching means for switching the predetermined phase timing in accordance with the selected voltage.

According to a third aspect of the present invention, there is provided a zero-crossing detecting means for detecting a zero-crossing point of an AC power supply for lighting a light source, and reducing the voltage of the AC power supply at a predetermined phase timing from the detected zero-crossing point. Voltage detection means for detecting each wave and control means for determining a voltage value for driving the light source based on a result of the detection are provided.

According to a fourth aspect of the present invention, a zero cross point of an AC power supply for lighting a light source is detected, and a voltage of the AC power supply at a predetermined phase timing from the detected zero cross point is detected. A voltage value for driving the light source is determined based on the result, and the detection result of the voltage of the AC power supply at the predetermined timing is held by a holding unit for each zero cross, and the value of the detection result held by the holding unit is held. It is determined whether the difference value of the detection result of the voltage of the AC power supply at the detected predetermined timing next to the held detection result is larger than a predetermined value. The detection result used for determining the voltage for driving the light source is changed to the detection result held in the holding unit.

According to a fifth aspect of the present invention, in the light source control method according to the fourth aspect, there are a plurality of types of voltage levels of the AC power supply, and a maximum voltage to be controlled among the plurality of types is selectively selected. And the predetermined phase timing is variably set according to the selected voltage.

According to a sixth aspect of the present invention, a zero cross point of an AC power supply for lighting a light source is detected, and a voltage of the AC power supply at a predetermined phase timing from the detected zero cross point is detected for each half wave. Then, a voltage value for driving the light source is determined based on the detected result.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 3 shows a circuit configuration of an embodiment of the present invention. Explanation will be made based on FIG. In FIG. 4, 1-1 is an AC power supply, and here, a commercial 100V
Power supply. 1-2 is a transformer connected to both poles of the AC power supply 1-1. A transformer having a winding ratio such that the output on the secondary side has a peak value of about 0V to 10V according to the AC input voltage is used. I have.

1-3 is a circuit for rectifying the AC voltage from the transformer, and the input voltage (100 V or 200 V)
Is adjusted by a volume or the like in the circuit 1-3 so that the output corresponding to DC0V to 5V is output. In this circuit, a circuit for outputting a zero-cross signal based on the rectified signal is provided. This signal is connected to an interrupt input of a microcomputer 1-9 in a control circuit 1-6 described later. I have.

Reference numeral 1-8 denotes a light source lamp.
A 0 W halogen lamp is used. 1-6 is a control circuit, a microcomputer 1-9 in the control circuit, a RAM
1-10 and a ROM 1-11. The output from the AC voltage detection circuit 1-3 is supplied to the control circuit 1-6.
Connected to the A / D port of the microcomputer 1-9.

Reference numeral 1-7 denotes a driving element for driving the light source 1-8, which uses a triac.
6 is fired by a trigger signal from a microcomputer 1-9 in a phase corresponding to the control voltage (drive) of the light source, and supplies power to the light source 1-8. Reference numeral 1-12 denotes a control operation unit for the user to set the control circuit 1-6, and performs various settings such as setting of the lighting voltage of the light source 1-8.

Reference numeral 1-13 denotes input voltage switching means such as a dip switch (not shown) for instructing input voltage switching. The switching signal output from the switching means 1-13 is supplied to a microcomputer 1-9. And the input voltage is switched between the 100 V system and the 200 V system.

Referring to FIG. 5, a method of controlling the exposure lamp 1 will be described. With the input of the zero-cross signal and the input voltage signal described in FIG. 4, the microcomputer 1-9 causes the input voltage and the period T of the input voltage (see FIG. 5).
Is detected. According to the preset output voltage, the microcomputer 1-9 calculates the phase t,
A trigger pulse is output to turn on the light source. By controlling the phase t, the voltage applied to the heater is controlled.

FIG. 2 shows that the microcomputer 1-9 has an A
The timing at which the value of D (analog / digital conversion) is read is shown. The input voltage is rectified by the rectifier circuit and the zero-cross detection circuit 1-3, and is input to the AD converter of the microcomputer 1-9 as an input voltage monitor. In the microcomputer 1-9, an input timing management register is set, and when a zero-cross signal is input, the count-up starts every predetermined time (here, 1 μsec). The microcomputer 1-9 can further set an interrupt setting register. When this register value matches the input timing management register value, an interrupt occurs. In response to the interrupt, the A / D converter inside the microcomputer 1-9 is activated to start A / D conversion.

An AD value is read by an interrupt at the end of AD conversion. The interrupt setting register value is set around half of the zero-cross signal with the least error, and is read with high accuracy.

Next, a method of calculating the input voltage after reading the AD value will be described.

The AD value is calculated by a predetermined function.
Converted to instantaneous voltage. In addition, a table including the time from the zero cross signal is created (see FIG. 6). When the instantaneous voltage is read, the phase is

[0026]

(Phase) = (time from zero cross) / (zero cross period)

An effective voltage is obtained from the phase and the voltage. The effective voltage is

[0028]

(Effective voltage) = (instantaneous voltage) / (sin (π * phase) * √2) By these calculations, the table shown in FIG. 5 is completed.

For example, assuming that the zero-cross cycle is 10 ms, when the voltage measured at a time of 4.70 ms from the zero-cross is 135 V, the phase is 0.1 V.
47, the calculated effective voltage calculated by the above equation is 95.8
8V. A plurality of such calculation results are taken as shown in the table, and the average is the portion that intersects the "calculation result" at the bottom (98.27 V).

By taking these voltages for each waveform and averaging them, an effective input voltage value of one wave can be obtained.
In this way, the input voltage can be measured for each wave and reflected on the phase shown in FIG.

When the input instantaneous value of the AC monitor is extremely different from the previous instantaneous value due to the influence of noise, if the above-mentioned averaging for each wave is carried out with this value, the actual execution is performed. It is calculated as a value different from the voltage. For example, assuming that the voltage value at the above-described timing of 4.70 ms is 135 V in the previous detection and 180 V in the current detection, the execution voltage is calculated to be quite high.
Since such a change cannot occur in an actual power supply, a change in the instantaneous value of, for example, 30 V or more is determined to be noise, and the previous value of 135 V is used as it is in the calculation of the current execution voltage. By judging the detection result in this way, the input voltage can be detected without being affected by noise from the AC line.

Based on the configuration described above, the microcomputer 1-9 will be described with reference to the flowchart shown in FIG.
The control flow will be described. In # 1, initialization is performed. During the initial setting, a zero-crossing interrupt or an input detection interrupt is performed, and reflected in the setting after the initial setting. In the initial setting, the setting of the 100 V system or the 200 V system is also performed, and the predetermined value of the voltage change amount with respect to the change of the instantaneous voltage is also set here.

Here, in order to facilitate understanding of the main routine (# 2 to # 5), the zero-cross interrupt (from # 7) and the input detection interrupt (from # 13) will be described first. At step # 7, a zero-cross interrupt is generated, and a trigger and a timer serving as a base for detecting the input voltage are started. In step # 9, the number of zero crossings up to that time is compared with the number of times of a system counter (not shown) to detect a zero cross cycle. In step # 10, the timing of the trigger ON interrupt is set. In # 11, the input voltage detection interrupt (# 13) is set,
For example, when a plurality of detection timings are provided, a setting is made such that one of them is brought to the center of the zero-cross cycle.

# 13 is an input detection interrupt due to the setting of the input detection timing set in # 11.
Here, the AD value is read (# 14), and the actual timing is read (# 15).

Returning to the description of the main routine (# 2 and thereafter). In # 2, the instantaneous voltage is calculated from the AD values after # 13 (# 2). The calculated result is held at a predetermined address in a memory (RAM) 1-10. #
In step 3, the instantaneous voltage calculated from the AD value is compared with the instantaneous voltage in the memory calculated last time, and if the difference is equal to or smaller than a predetermined value, the process directly proceeds to the routine for calculating the execution voltage.

If the difference is equal to or greater than the predetermined value, the process proceeds to a routine for calculating the execution voltage using the previous instantaneous voltage value without using the instantaneous voltage value. In # 4, the execution voltage input from the instantaneous voltage and the actual timing from the zero cross is calculated. The phase is calculated from the input execution voltage and the required output voltage (# 5). From the phase, the timing from the zero crossing to the trigger is set (# 6), which is reflected in the setting in # 8.

The output of the trigger pulse for actually driving the lamp is performed by an interrupt process in # 16. In # 16, a trigger ON interruption is performed, and in # 17, the trigger signal is turned ON. #
At 18, a trigger OFF interrupt is set. # 1
At 9, a trigger OFF interrupt is entered based on the trigger OFF interrupt set at # 18. Here, only the trigger signal is turned off.

(Embodiment 2) FIG. 8 shows a circuit configuration of Embodiment 2. 8, the same parts as those in the first embodiment in FIG. 4 are denoted by the same reference numerals. 1-1 is an AC power supply, here, a commercial 100V power supply, 1-2 is a transformer connected to both poles of the AC power supply 1-1, and the secondary output is 0V according to the AC input voltage. A transformer having a turns ratio such that the peak value is about 10 to 10 V is used. 1-
3 is a circuit for rectifying the AC voltage from the transformer,
1 so that the output corresponding to the input voltage is DC 0V to 5V.
The output is adjusted and adjusted by the volume in the circuit of -3.
In this circuit, a circuit for outputting a zero-cross signal based on the rectified signal is provided. This signal is connected to an interrupt input of a microcomputer 1-9 in a control circuit 1-6 described later. I have.

Reference numeral 1-8 denotes a lamp as a light source.
1-6 is a control circuit using a 0 W halogen lamp, a microcomputer 1-9 in the control circuit, and a RAM.
1-10 and a ROM 1-11. The output from the AC voltage detection circuit 1-3 is supplied to the control circuit 1-6.
Connected to the A / D port of the microcomputer 1-9. Reference numeral 1-7 denotes a driving element for driving the light source 1-8, which uses a triac.
The light source 1 is fired at a phase corresponding to the control voltage of the light source by a trigger signal from the microcomputer 1-6 in the light source 1.
Supply power to -8. Reference numeral 1-12 denotes a control operation unit for the user to set the control circuit 1-6, and performs various settings such as setting of the lighting voltage of the light source 1-8. 1-14 is AC
This is an AC power supply polarity detection circuit that detects the polarity of each half-wave of the power supply waveform.

The control method of the exposure lamp 1 is the same as in the first embodiment. The microcomputer 1-9 detects the input voltage and the period T of the input voltage based on the input of the zero cross signal and the input voltage signal. According to the preset output voltage, the microcomputer 1-9 sets the phase t
And outputs a trigger pulse. By controlling the phase t, the voltage applied to the heater is controlled.

FIG. 3 shows that the microcomputer 1-9 has A
This shows the timing of reading the value of D. The input voltage is rectified by a rectifier circuit and a zero-crossing detection circuit 1-3.
It is input to the D converter. In the microcomputer 1-9, an input timing management register is set, and when a zero-cross signal is input, a predetermined time (here, 1 μs
c) Start counting up every other time. The microcomputer 1-9 can further set an interrupt setting register. When this register value matches the input timing management register value, an interrupt occurs. In response to the interrupt, the A / D converter inside the microcomputer 1-9 is activated to start A / D conversion. The AD value is read by an interrupt at the end of AD conversion. The interrupt setting register value is set around half of the zero-cross signal with the least error, and is read with high accuracy.

Next, a method of calculating the input voltage after reading the AD value will be described.

The AD value is calculated by a predetermined function.
Converted to instantaneous voltage. In addition, a table including the time from the zero cross signal is created (see FIG. 6). When the instantaneous voltage is read, the phase is

[0044]

## EQU3 ## (Phase) = (time from zero cross) / (zero cross period).

An effective voltage is obtained from the phase and the voltage. The effective voltage is

[0046]

(Effective voltage) = (instantaneous voltage) / (sin (π * phase) * √2) By these calculations, the table shown in FIG. 6 is completed.

For example, assuming that the zero-cross cycle is 10 ms, when the voltage measured at a timing of 4.70 ms from the zero-cross is 135 V, the phase is 0.1 V.
47, the calculated effective voltage calculated by the above equation is 95.8
8V. A plurality of such calculation results are taken as shown in the table, and an average is obtained at the intersection with the bottom "calculation result" (98.27 V).

By taking these voltages for each waveform and averaging them, an effective input voltage value of one wave can be obtained. In this way, the input voltage can be measured for each wave and reflected on the phase shown in FIG.

By the way, as shown in FIG. 3, the input AC monitor waveform has a different peak value depending on the polarity of AC, and the same polarity is repeated for each half-wave, so that the peak value changes depending on the polarity. Become. This is the transformer 1-3
Due to the influence of the above, strict adjustment of this requires a cost including the adjustment mechanism.

Here, reference numeral 1-14 in FIG. 8 is a circuit for detecting whether the polarity of the AC is positive or negative, and a half-wave rectified waveform of the transformer 1-3 is transformed into a transistor (not shown). ) By inputting this signal to the port of the microcomputer 1-9, it is possible to determine whether the polarity of the AC power supply is positive or negative. That is, if this signal is "HIGH", it is determined to be a plus side, and if "LOW", it is determined to be a minus side (see FIG. 3). Therefore, when the execution value of the input voltage for each wave is calculated and averaged based on this signal, it is determined whether the input voltage is on the plus side or the minus side, and the averaging is performed separately (see FIG. 9). The input voltage can be detected without being affected by the difference between the positive and negative characteristics of the transformer.

Based on the configuration described above, the microcomputer 1-
9 will be described. In # 101,
Perform initial settings. During the initial setting, a zero-crossing interrupt or an input detection interrupt is performed, and reflected in the setting after the initial setting. Here, the main routine (# 102 to # 10)
In order to facilitate the understanding of 5), the zero cross interrupt (from # 106) and the input detection interrupt (from # 112) will be described first.

At # 106, a zero-cross interrupt occurs,
Start a trigger or a timer that is the basis for the time for input voltage detection. In # 108, the number of zero crossings so far and the system counter (not shown)
And the number of times is compared to detect the zero-cross period. # 1
At 09, the trigger ON interrupt timing is set. In # 110, the input voltage detection interrupt (# 11
The setting of 2) is performed. For example, when a plurality of detection timings are provided, a setting is made such that one of them is brought to the center of the zero-cross cycle.

# 112 is an input detection interrupt by setting the input detection timing set in # 110. Here, the AD value is read (# 113), and the actual timing is read (# 114).

Now, return to the description of the main routine (#
102 and later). In # 102, the instantaneous voltage is calculated from the AD values after # 112 (# 102). # 10
In No. 3, the effective input voltage is calculated from the instantaneous voltage and the actual timing from the zero cross, and the determination result of whether the polarity of the AC monitor is positive or negative (# 10).
3). The phase is calculated from the input effective voltage and the required output voltage (# 104). From the phase, set the timing from the zero crossing to the trigger (# 10
5), reflected in the setting in # 107.

The output of the trigger pulse for actually driving the lamp is performed in the interrupt processing in # 115. In # 115, a trigger ON interruption is performed, and in # 116, the trigger signal is turned ON. At step # 117, a trigger OFF interrupt is set. In # 118, the trigger set in # 117 is turned off
Based on the interrupt, a trigger OFF interrupt is entered. Here, only the trigger signal is turned off.

[0056]

As described above, according to the first and fourth aspects of the present invention, even if an abnormality occurs in the detected voltage value due to the influence of noise, the abnormality is detected, and the previous normal value drives the light source. Used to determine the voltage to apply. For this reason, the light amount of the light source is also stabilized.

According to the second and fifth aspects of the present invention, for example, a certain light source driving voltage can be sold from a separate power supply, so that the apparatus can be used in foreign countries having different commercial power supplies.

According to the third and sixth aspects of the present invention, since the drive voltage of the light source is determined by the phase control for each odd part, the light amount control can be performed more stably than before.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional circuit configuration.

FIG. 2 is a timing chart showing processing timing in the first embodiment of the present invention.

FIG. 3 is a timing chart showing processing timing in Embodiment 2 of the present invention.

FIG. 4 is a block diagram illustrating a circuit configuration according to the first embodiment of the present invention.

FIG. 5 is a timing chart for explaining control contents of Embodiments 1 and 2 of the present invention.

FIG. 6 is an explanatory diagram showing contents of a table for storing a result of voltage determination.

FIG. 7 is a flowchart illustrating a processing procedure according to the first embodiment of the present invention.

FIG. 8 is a block diagram illustrating a circuit configuration according to a second embodiment of the present invention.

FIG. 9 is a waveform chart for explaining control contents according to the second embodiment of the present invention.

FIG. 10 is a flowchart illustrating a processing procedure according to the second embodiment of the present invention.

[Explanation of symbols]

 1-1, 2-1 AC (AC) power supply 2-2 Transformer 1-3, 2-3 Rectifier circuit (zero-cross detection circuit) 1-8, 2-7 Light source 1-9, 2-8 Microcomputer

Continued on front page F-term (reference) 2C362 AA01 AA59 DA45 2H027 DA03 DA32 DA38 DE09 EA18 EC08 EC10 EE02 EE06 EF09 EK13 ZA01 3K073 AA42 AA92 BA01 BA07 CF12 CF16 CG06 CG09 CG15 CH21 CJ15 CJ19 CB05 CC05 CC05 EB38 FF03 FF22 5H740 BA03 BB08 BC06 GG02 JA28

Claims (6)

[Claims] 1. A zero-crossing detecting means for detecting a zero-cross point of an AC power supply for lighting a light source, and a voltage detecting means for detecting a voltage of the AC power supply at a predetermined phase timing from the detected zero-crossing point. First control means for determining a voltage value for driving the light source based on the detection result; holding means for holding the detection result of the voltage detection means for each zero-cross; and detection of the detection result held by the holding means. It is determined whether or not a difference value between the value and the detection result detected by the voltage means next to the held detection result is larger than a predetermined value. A second control means for changing the detection result to be detected to the detection result held by the holding means. 2. A light source control device according to claim 1, wherein said AC power supply has a plurality of types of voltage levels, and said switching means selectively switches a maximum voltage to be controlled among said plurality of types. Having, depending on the selected voltage,
A light source control device, wherein the predetermined phase timing is variably set. 3. A zero-crossing detecting means for detecting a zero crossing point of an AC power supply for lighting a light source, and detecting a voltage of the AC power supply at a predetermined phase timing from the detected zero crossing point for each half wave. A light source control device comprising: voltage detection means; and control means for determining a voltage value for driving the light source based on a result of the detection. 4. A zero cross point of an AC power supply for lighting a light source is detected, a voltage of the AC power supply at a predetermined phase timing from the detected zero cross point is detected, and based on the detected result. A voltage value for driving the light source is determined, a detection result of the voltage of the AC power supply at the predetermined timing is held by a holding unit for each zero cross, a value of the detection result held by the holding unit, and the held value. After the detected result, it is determined whether or not a difference value of the detected result of the voltage of the AC power supply at the detected predetermined timing is larger than a predetermined value. If the difference value is determined to be larger, the light source is driven. A light source control method comprising: changing a detection result used for determining a voltage to be applied to a detection result held by the holding unit. 5. The light source control method according to claim 4, wherein there are a plurality of types of voltage levels of the AC power source, and the highest voltage to be controlled among the plurality of types is selectively switched, and the selection is performed. A light source control method, wherein the predetermined phase timing is variably set according to the applied voltage. 6. A zero-cross point of an AC power supply for lighting a light source is detected, a voltage of the AC power supply at a predetermined phase timing from the detected zero-cross point is detected for each half-wave, and the detected voltage is detected. Determining a voltage value for driving the light source based on the result.