JPH0320984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device that performs digital phase control of an exposure lamp, etc. of a copying machine using a microcomputer.

[Prior art]

Conventionally, for example, when the exposure amount of a copying machine is phase-controlled by a microcomputer, especially when performing feedback control, as shown in FIG.
A circuit 1 for detecting the V zero-crossing point of the power supply voltage is provided, and the output of this circuit 1, that is, the zero-crossing signal A, is input to the microcomputer 2 as an interrupt signal, and the internal of the microcomputer 2 is synchronized with the power supply voltage V. A timer is started to operate the tri-attack trigger circuit 3 and the like at predetermined time intervals.

[Problem to be solved by the invention]

However, as shown in FIG. 2, even if the microcomputer 2 starts interrupt processing in response to the zero-crossing signal A of the power supply voltage V, the time until the interrupt processing starts depends on the processing status of the CPU. Since the processing time varies due to variations in time or due to differences in processing conditions before starting the internal timer, the starting point of the internal timer that counts the set time T inevitably changes.

At this time, due to the variation ΔT in the starting point of the internal timer, a voltage variation ΔV appears in the voltage finally supplied to the load, which poses a technical problem in that it impedes accurate phase control.

This invention was made in order to solve the above technical problems, and it is possible to reliably absorb the difference in software processing time and realize accurate phase control by a microcomputer. A digital phase control device is provided.

[Means to solve the problem]

That is, the present invention is based on a digital phase control device in which a microcomputer performs feedback control of a semiconductor control element in synchronization with a predetermined phase of a commercial power supply voltage, and generates an interrupt signal in synchronization with a synchronization signal of the commercial power supply voltage. an interrupt signal generating means for counting a preset predetermined time; and a timer means for starting the timer means when the interrupt signal from the interrupt signal means is input, and when the timer means finishes counting. a control means for outputting a predetermined control signal to the semiconductor control element; and when the above-mentioned interrupt signal is input, a certain period of time longer than the maximum processing time from the time when the interrupt signal is input to the control means until the start time of the timer means. , and timer activation prohibition means for prohibiting activation of the timer means.

[Effect]

According to the above-mentioned technical means, when an interrupt signal is generated from the interrupt signal generating means, this interrupt signal is inputted to the control means and also inputted to the timer activation inhibiting means.

Then, the control means starts a series of interrupt processing, starts a timer, and outputs a predetermined control signal to the semiconductor control element when the timer means finishes counting.

At this time, the timer activation prohibition means prohibits the activation of the timer means for a certain period of time that is longer than the maximum processing time from the time when the interrupt signal is input to the control means until the time when the timer means starts activation. Activation always starts at a specific point in time when a predetermined period of time has elapsed from the point in time when the interrupt signal was input.

〔Example〕

Hereinafter, the configuration of the present invention will be explained based on embodiments shown in the accompanying drawings.

3 and 4, a specific configuration of a digital phase control device according to an embodiment of the present invention is shown. This device includes a zero-cross detection circuit 1 that outputs a pulse signal A at the zero-cross point of a power supply voltage V as a means for generating an interrupt signal synchronized with the power supply (commercial power supply) voltage, and an output from the zero-cross detection circuit 1. a microcomputer 2 that starts an internal timer set to count a predetermined time T upon receiving the pulse signal A, and outputs a predetermined control signal when the internal timer finishes counting; A timer start prohibition signal generation circuit 4 receives the pulse signal A output from the circuit 1 and generates a timer start prohibition signal B for delaying the start of the internal timer of the microcomputer 2 by a predetermined time t.
It is equipped with.

In this embodiment, the control signal that the microcomputer 2 outputs when its internal timer finishes counting is a trigger signal for a triact used to control the exposure lamp of a copying machine, and as shown in FIG. A triac trigger circuit 3 is connected to the computer 2 and is controlled by a control signal output from the computer 2. In the control device of the above embodiment, the timer activation prohibition signal B is a signal with a time width t, as shown in FIG. It is set to a certain period of time that is longer than the maximum processing time until the start of startup.

In addition, in this microcomputer 2, the off time of the phase control is determined during the interrupt processing before the start of the internal timer, and the internal timer is set to the time T.
After the internal timer is established, the internal timer starts counting, and when the internal timer finishes counting, the control operation for the try-out trigger circuit 3 is started.

Therefore, in the control device of the above embodiment, when the pulse signal A is output from the zero-cross detection circuit 1, the microcomputer 2 starts interrupt processing, and the internal timer of the microcomputer 2 is activated by the timer activation inhibiting means B. Activation is prohibited for a certain time t, after which this internal timer counts the designed time T, and when this internal timer finishes counting, the microcomputer 2 performs a certain control operation.

In this embodiment, the microcomputer mainly performs sequence control of the copying machine other than the phase control using the interrupt.

For example, as shown in FIG. 7, this sequence processing of the copying machine is performed in units of a predetermined time (for example, 10 ms) (step 1), and from the viewpoint of preventing chatter caused by the software, the input of each sensor is performed every 10 ms. Process (Step 2), 10
Execute the process reserved by the timer in ms units (step 3), and also check the current state (state:
For example, the input signal is judged and each functional component is controlled based on the copy state and warm-up state (step 4).

Here, regarding the sequence processing of copiers, 10
It is sufficient that the accuracy is carried out every ms,
With a CPU of about 1 μs/instruction, the sequence processing of a copying machine is completed in about 5 to 7 ms, while the above interrupt processing is completed in about 300 to 400 μs, so there is no problem in terms of CPU execution time. In addition to sequence control of the copying machine, the above-mentioned interrupt processing can be performed.

Next, FIGS. 5 and 6 show a control device according to another embodiment of the present invention, in which, unlike the above embodiment, an external timer 7 separate from the microcomputer 2 is counted. An oscillation circuit 5 is provided, and by inputting the output C of the oscillation circuit 5 and the above-mentioned timer activation prohibition signal B to an AND circuit 6, a certain period of time t after generation of the interrupt signal A is provided.
The external timer 7 is prohibited from counting until the time t has elapsed, and a count-up signal D to the external timer 7 is obtained after the elapse of the time t. The microcomputer 2 resets the external timer 7 and sets the time T while counting is prohibited. As a result, a trigger is automatically generated after time T has elapsed.

[Effect of generation] As explained above, according to the digital phase control device according to the present invention, the starting point of the timer means can be set regardless of the fluctuation in the processing time of the microcomputer software before starting the timer means. By keeping it constant, it is possible to effectively avoid phase control errors caused by fluctuations in the starting point of the timer means, thereby realizing accurate phase control that is not affected by differences in software processing time. can.

Therefore, according to the digital phase control device of the present invention, when it is used, for example, to control the exposure amount of a copying machine, the amount of light does not change due to input fluctuations, and stable image copies can be obtained. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional digital phase control device, FIG. 2 is a waveform diagram showing the timing of the phase control in FIG. 1, and FIG. 3 is a block diagram showing a digital phase control device according to an embodiment of the present invention. Figure 4 is a waveform diagram showing the timing of the phase control in Figure 3,
5 and 6 are block diagrams and waveform diagrams similar to FIGS. 3 and 4 showing another embodiment, and FIG. 7 is a flowchart showing an example of sequence processing of a copying machine. Symbol explanation, 1... Zero cross detection circuit, 2...
Microcomputer, 3 Triack trigger circuit, 4...Timer start inhibition signal generation circuit, 5
...Oscillation circuit, 6...AND circuit.

Claims (1)

[Claims] 1. In a digital phase control device that performs feedback control of a semiconductor control element in synchronization with a predetermined phase of a commercial power supply voltage using a microcomputer, an interrupt signal is generated in synchronization with a synchronization signal of the commercial power supply voltage. an interrupt signal generating means; a timer means for counting a predetermined time set in advance; and when the interrupt signal from the interrupt signal generating means is input, the timer means is activated and the count of the timer means is terminated. a control means for outputting a predetermined control signal to the semiconductor control element according to the above-described method; 1. A digital phase control device comprising timer activation prohibition means for prohibiting activation of the timer means.