JPS62120006A - Drive control system for inductive load - Google Patents

Abstract

PURPOSE:To always obtain a constant stable output by correcting a pulse width of a load driving pulse (MAG) in response to a variation in a power source voltage to eliminate the variation in a load output due to the variation in the power source voltage. CONSTITUTION:When a magnet-drive pulse MAG is turned ON, an AND gate 10, Trs 11, 12 are turned ON, and a current flows to a magnet 13. This current IM is detected across a resistor 15, compared by a comparator 16 with a refer ence voltage Vref, if it is larger than the voltage Vref, Tr 12 is turned OFF, while if smaller, Tr 12 is turned ON to control so that the current IM becomes constant. A power source voltage +V is compared by a comparator 17 through resistors R1, R2 with the voltage Vref. The output VF of the comparator 17 becomes H when the voltage +V exceeds the upper limit threshold value +VH, and becomes L when lower than the lower limit threshold value +VL. A micro computer 100 checks the output VF of the comparator 17 prior to the output of the pulse MAG and may control a time when the pulse MAG becomes OFF by H or L of the output VF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a drive control system for an inductive load such as a printing magnet.

[Prior art]

An example of the configuration of a conventional drive control system for printing magnets, etc. is shown in FIG. For convenience, the constant current type magnet drive current is shown here. In FIG. 5, when the magnet drive pulse MAG is turned on, the transistor 11 is turned on through the AND gate 10, and therefore the drive transistor 12 is also turned on, and a current IM flows through the magnet 13, driving the magnet. In order to keep the drive output of the magnet 13 constant, the magnet current is detected by the terminals of the resistor 15, and the comparator 16 converts this into the reference voltage V1. ．． Compared to this, the AND gate 10 is turned on and off, and the transistors 11 and 12 are controlled on and off accordingly, thereby generating a magnet current. Constant current control is performed so that the current is constant as shown in FIG. Note that the diode 14 is provided to prevent the magnet current IM from becoming completely zero by causing a current to flow due to the back electromotive force of the magnet 13 when the transistor 12 is turned off.

By the way, in the configuration of FIG. 5, the power supply 'tfLI+
When +V fluctuates, the rise of the magnet drive current IM changes, and as a result, the magnet drive output also fluctuates. For example, when the voltage +■ increases,
The magnet electrician is like the dotted line A, and on the other hand, the voltage is +■
When the voltage decreases, the magnet current becomes as shown by the dotted line B in FIG.

On the other hand, printing magnets used in daisy printers and the like require constant printing pressure and high stability in order to obtain high printing quality. However, when a conventional magnet drive circuit as shown in FIG. 5 is used, the magnet drive output fluctuates due to fluctuations in the power supply voltage, resulting in shading of characters and deterioration of print quality.

[Purpose of the invention]

An object of the present invention is to eliminate fluctuations in load output due to fluctuations in power supply voltage and always obtain a constant and stable output in a drive control system for an inductive load such as a printing magnet.

[Structure of the invention]

In order to achieve the above object, the present invention compensates the pulse width of the load driving pulse (MAG) according to fluctuations in the power supply voltage.
The inductive load output is kept constant, and will be explained in detail below using one embodiment.

FIG. 1 shows an embodiment of the present invention, which also shows a constant current type magnet drive circuit. In Figure 1, 100
is a microcomputer that controls the operation of a printer, etc., and when driving the magnet 13, outputs a magnet drive pulse MAG having a predetermined pulse width. When this magnet drive pulse MAG is turned on, the AND gate 10, the transistor 11 . J2
is turned on, and current flows through the magnet 13. This magnet current I, 4 is detected by the voltage across the resistor 15, and compared with the reference voltage v ref by the comparator 16. If it becomes larger than the reference voltage V r e I, the transistor 12 is turned off, and if it is smaller, the transistor 12 is turned off. is turned on to perform constant current control so that the magnet current IM remains constant.

On the other hand, the power supply voltage +V is passed through resistors Rs and R2.

Comparator 17 compares it with reference voltage V r o 4 .

Here, resistors R1 and R2 are the optimum value for the power supply voltage +V■TYP
, choose so that R, + R2. As shown in FIG. 2, the output of the comparator 17 becomes a high level (H) when the power supply voltage +V exceeds the upper threshold value +Vl+, and becomes a low level (L) when it falls below the lower threshold value 1.

The microcomputer 100 outputs the output VF of the comparator 17.
When is at a high level, the pulse width of the magnet drive pulse MAG is narrower than the predetermined reference value and output, and conversely, V
When F is at a low level, the pulse width of the magnet drive pulse MAG is increased and outputted. The increase/decrease in the magnet drive pulse width may be determined in advance so as to compensate for fluctuations in the magnet drive output due to increases or decreases in the power supply voltage +V so as to be constant. Specifically, the microcomputer 100 may check the output vF of the comparator 17 before outputting the magnet drive pulse MAG, and control the time when the drive pulse MAG is turned off depending on the high level and low level of the output vF.

This can be easily achieved by changing the setting value of the MAG's time monitoring timer.

FIG. 3 shows how the magnet current is controlled by changing the pulse width of the magnet drive pulse MAG.

In other words, the power supply voltage +V increases and the magnet current flow increases. is A
If it starts up like this, turn off the magnet drive pulse MAG early and use the magnet current. is lowered as shown in A'. Conversely, if the power supply voltage +V falls and the magnet current IM rises as shown in B, turn off the magnet drive pulse MAG late and adjust the magnet current. is lowered as shown in B'. Thereby, the drive output of the magnet 13 can always be kept constant.

FIG. 4 shows another embodiment of the present invention. In the embodiment shown in FIG.
Since the only thing to do is to shorten or lengthen the pulse width of the magnet drive pulse depending on whether it is higher or lower than ef, it is not possible to finely adjust the fall of the magnet current IM in response to fluctuations in the power supply voltage. It's impossible. On the other hand, in FIG. 4, the power supply voltage +V is converted into a digital value by an analog/digital converter 18 and inputted to the microcomputer 100. The pulse width of the magnet drive pulse can be varied in response to fluctuations in V, and the fall of the magnet current can be finely adjusted. The other operations are the same as in the case of FIG.

〔effect〕

As is clear from the above description, according to the present invention, when driving an inductive load such as a printing magnet, fluctuations in the load output due to fluctuations in the power supply voltage can be prevented, and a stable output can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the power supply voltage and comparator output in FIG. 1, and FIG. 3 is a diagram showing the relationship between the magnet drive pulse and the magnet drive current in FIG. 4 is a diagram showing the configuration of another embodiment of the present invention, FIG. 5 is a diagram showing a conventional configuration example, and FIG. 6 is a diagram showing the relationship between the magnet drive pulse and magnet drive current in FIG. 5. FIG. 10...AND gate, 11.12...Transistor, 13...Magnet, 14...Diode, 15...Resistance for magnet current detection, 1
6.17... Comparator, 100... Microcomputer, +V... Power supply voltage, MAG... Magnet drive pulse, vF... Comparator output. Figure 5 Figure 6

Claims (1)

[Claims] (1) In a control method in which an inductive load is connected to a power source via a switching means, and the switching means is turned on by an externally applied drive pulse to drive the inductive load, voltage fluctuations of the power source are detected, and the voltage A driving control method for an inductive load, characterized in that an on period of the switching means is adjusted by changing the pulse width of the driving pulse according to fluctuations.