JP3629958B2 - Solenoid drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, the solenoid applied voltage is PWM-controlled, and in the initial stage of driving, a voltage higher than the rated voltage of the solenoid is applied to drive the solenoid at a high speed. It relates to solenoid burnout protection.
[0002]
[Prior art]
Conventionally, in equipment that needs to drive the solenoid at high speed, in order to minimize the response operation time of the solenoid as much as possible, a voltage higher than the rated voltage of the solenoid is applied at the beginning of driving, and then the rated voltage that can maintain the operation of the solenoid is exceeded. The temperature rise was suppressed by switching to a lower voltage. Further, since the response operation time itself is required to be stable, the voltage applied to the solenoid is stabilized.
[0003]
FIG. 4 is a circuit diagram of a conventional solenoid high-speed drive device, which is an example rewritten with a configuration necessary for easy understanding of the present invention (for example, Japanese Patent Laid-Open No. 7-14458).
In FIG. 4, reference numeral 1 denotes an unstabilized power source, which includes an AC power source 11, a transformer 12, a rectifier 13, and a smoothing capacitor 14, and outputs an unstabilized power source voltage E. 2 is a solenoid to be driven, 3 is an FET which is a switch means for driving the solenoid 2, 4 is a diode for a flywheel, 5 is an A / D converter which is an analog-digital conversion means, 6 is a PWM arithmetic circuit, 7 is This is a PWM control circuit.
[0004]
The operation of the solenoid driving apparatus configured as described above will be described below.
The output voltage E of the non-stabilized power supply 1 is converted into digital data by the A / D converter 5 and input to the PWM arithmetic circuit 6. The PWM calculation circuit 6 calculates the PWM duty so that the average voltage applied to the solenoid 2 becomes a predetermined voltage from the input data, and outputs a PWM signal.
[0005]
For example, in order to make the response operation time of the solenoid 2 as short as possible, a voltage EH higher than the rated voltage of the solenoid 2 is applied in the initial stage of driving, and then the driving is performed by switching to a voltage EL lower than the rated voltage that can maintain the operation of the solenoid 2. In this case, the PWM calculation circuit 6 calculates and outputs a PWM signal PWM-EH in which the average voltage applied to the solenoid 2 becomes EH and a PWM signal PWM-EL in which the average voltage applied to the solenoid 2 becomes EL. . IN is an ON / OFF control signal for the solenoid 2, and is a signal that is input from outside the device (not shown) or is generated by signal processing inside the device (not shown). The PWM control circuit 7 selects the PWM signal for driving the solenoid 2 from the signal IN and the input signals of the PWM signals PWM-EH and PWM-EL, and drives the FET 3 by PWM.
[0006]
Further, the operation when the solenoid 2 is driven will be described with reference to FIG. 5. The horizontal axis T is time, the vertical axis IN is the solenoid ON / OFF control signal, EP is the applied voltage of the solenoid 2, and IP is the energization current of the solenoid 2. , EA is an average applied voltage to the solenoid 2. The solenoid ON / OFF control signal IN is in the interval T1 + T2 and instructs to drive the solenoid 2. A section T1 is an overdrive section in which a constant voltage having an average applied voltage EH higher than the rated voltage is applied to the solenoid 2, T2 is a holding section in which a constant voltage having an average applied voltage EL lower than the rated voltage is applied, and T1 is The predetermined time is determined by the PWM control circuit.
[0007]
Further, since the average voltage EH is PWM-controlled, the output voltage E of the non-stabilized power supply 1 is set to be larger than the average applied voltage EH even if the AC power supply 11 fluctuates.
[0008]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, since the average applied voltage EH higher than the rated voltage of the solenoid is applied to the solenoid, the output voltage E of the unstabilized power supply is higher than the rated voltage of the solenoid. Therefore, when the solenoid-driven FET is short-circuited for some reason, a voltage higher than the rated voltage is continuously applied to the solenoid, and the solenoid burns out, requiring a thermal fuse in the solenoid, increasing the cost and size of the solenoid. There was a problem that caused a decrease in versatility.
[0009]
SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and can provide a solenoid driving device that can protect the solenoid from burning even if the solenoid driving switch means is short-circuited, eliminates the need for a solenoid temperature fuse, and is inexpensive and easy to use. The purpose is to provide.
[0010]
[Means for Solving the Problems]
In order to solve this problem, in the present invention, two or more sets of switch means for driving a solenoid and a solenoid connected in series to the solenoid are connected to an unstabilized power source, and the voltage of the unstabilized power source is detected. The analog-to-digital conversion means for converting to digital data and the average voltage for driving the solenoid by this digital data become a predetermined plurality of constant voltage values.
A PWM operation circuit for calculating a PWM duty and outputting a plurality of PWM signals corresponding to the desired constant voltage value, and selecting the plurality of PWM signals, and individually controlling the switch means. In addition, there is no PWM control circuit corresponding to each switch means to be driven, current detection means for detecting the DC output current of the unstabilized power supply, and a section in which the current becomes zero within the PWM carrier cycle time. An abnormal current determination circuit that determines an abnormality when there is no section in which the current becomes zero, and a power cutoff unit that shuts off the power by the output signal, and the plurality of PWM signals have the same carrier frequency Thus, the solenoid driving device is characterized by being synchronized.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve this problem, in the present invention , two or more sets of switch means for driving a solenoid and a solenoid connected in series to the solenoid are connected to an unstabilized power source, and the voltage of the unstabilized power source is detected. Then, the analog-to-digital conversion means for converting to digital data, and the PWM duty is calculated so that the average voltage for driving the solenoid becomes a predetermined plurality of constant voltage values by this digital data, and the desired constant voltage value is obtained. A PWM arithmetic circuit for outputting a plurality of corresponding PWM signals, a PWM control circuit for selecting each of the plurality of PWM signals, individually controlling each of the switch means, and driving each switch means; and Current detection means for detecting the DC output current of the unregulated power supply and whether there is a section where the current is zero within the PWM carrier cycle time And an abnormal current determination circuit that determines an abnormality when there is no section in which the current becomes zero, and a power cutoff unit that shuts off the power by the output signal. The plurality of PWM signals have the same carrier frequency. The solenoid driving device is characterized by being synchronized.
[0012]
Thus, even when the solenoid broken drive switch means short when plural drive the solenoid, since the plurality of PWM signals carrier frequency is synchronized identical, the carrier period of the PWM to the detected current time When there is no section in which the current becomes zero, the power is turned off by determining that there is an abnormality, so that the solenoid can be protected from burning.
[0013]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same part as the prior art example of FIG. 4, and the description is abbreviate | omitted.
( Reference Example )
In FIG. 1, reference numeral 21 denotes an unstabilized power source, which has a configuration in which a contactor 15 as a power shut-off means is added between an AC power source 11 and a transformer 12. 22 is a direct current detector for detecting a direct current such as DC-CT, 23 is an abnormal current determination circuit, and it is determined that the current when the FET3 which is the solenoid drive switch means is short-circuit broken is abnormal. A contactor driving circuit 24 opens and closes the contactor 15.
[0014]
The operation of the solenoid driving apparatus configured as described above will be described.
When the device power supply (not shown) is turned on, the contactor drive circuit 24 turns on the contactor 15 (closed), and the unstabilized power supply 21 outputs the voltage E. Similarly to the conventional example, when the solenoid 2 is driven by applying a voltage EH higher than the rated voltage of the solenoid in the initial stage of driving and then switching to a voltage EL lower than the rated voltage that can hold the solenoid, the operation of PWM driving of the solenoid is as follows: This is the same as the conventional example.
[0015]
The abnormal current judgment circuit 23 distinguishes whether or not there is a section where the current is zero within the PWM carrier cycle time based on the current IDC detected by the DC current detector 22, and when there is no section where the current becomes zero, It is determined that there is an abnormality, and an abnormality signal is output to the contactor drive circuit 24. When the abnormal current determination circuit 23 outputs an abnormal signal, the contactor driving circuit 24 turns off the contactor 15 and shuts off the output of the unstable power supply 21.
[0016]
When the solenoid is PWM-driven, the output current IDC of the non-stabilized power supply 21 is flowing through the solenoid energizing current IP when the FET 3 is on, but when the FET 3 is off, the solenoid energizing current IP is flowing. Is flowing as a circulating current through the diode 4 and no current is supplied from the non-stable power source 21, so the output current IDC is zero. That is, in a state where the FET 3 is normal and PWM-driven, the current IDC always has a zero interval within the PWM carrier cycle, so the abnormal current determination circuit 23 determines that it is normal and does not output a signal.
[0017]
Here, the operation when the FET is short-circuit broken will be described. Since the unstable power supply voltage E is constantly applied to the solenoid 2 when the FET 3 is short-circuited, the output current IDC of the unstabilized power supply 21 always flows a direct current limited by the resistance value of the solenoid. In the PWM carrier cycle, there is no section in which the current becomes zero. Therefore, the abnormal current determination circuit 23 determines that there is an abnormality, and shuts off the unstabilized power supply by the above-described operation.
[0018]
Thereby, since the power supply voltage applied to the solenoid is eliminated, the burnout of the solenoid can be protected.
( Example 1 )
For Example 1 of the present invention will be described with reference to FIG. The same parts as those in the reference embodiment are denoted by the same reference numerals, and the description thereof is omitted.
[0019]
FIG. 2 shows an example in which a plurality of solenoids are driven in two, and a second solenoid 2a, a switching means FET3a, a flywheel diode 4a, and a PWM control circuit 7a for driving the solenoid 2a are added to the first embodiment. Has been.
Similarly to the conventional example and the first embodiment, the solenoids 2 and 2a are driven by applying a voltage EH higher than the rated voltage of the solenoid at the initial stage of driving the solenoid and then switching to a voltage EL lower than the rated voltage capable of maintaining the operation of the solenoid. In this case, the PWM calculation circuit 6 calculates and outputs a PWM signal PWM-EH in which the average voltage applied to the solenoid is EH and a PWM signal PWM-EL in which the average voltage applied to the solenoid is EL. IN and INa are signals that are input from outside the device (not shown) as solenoid ON / OFF control signals, or generated by signal processing inside the device (not shown). The PWM control circuits 7 and 7a select the PWM for driving the solenoid from the signals IN and INa and the input signals of the PWM signals PWM-EH and PWM-EL, and drive the FETs 3 and 3a by PWM.
[0020]
Next, the operation when the solenoids 2 and 2a are driven will be described with reference to FIG. The horizontal axis T is time, the vertical axis IN, EA, EP, and IP are solenoid 2 ON / OFF control signals, average applied voltage, applied voltage, and energizing current, and INa, EAa, EPa, and IPa are solenoid 2a ON. / OFF control signal, average applied voltage, applied voltage, energization current, and each operation is the same as the conventional example, but the timing of the solenoid ON / OFF control signals IN and INa is different, so the two solenoids The operation timing is different.
[0021]
Further, IDC in FIG. 3 is an output current of the non-stable power source 21 and is a sum of currents supplied to the solenoid 2 and the solenoid 2a. When the solenoid is driven by PWM, the unstabilized power supply 21 supplies the solenoid energization current IP (IPa) when the FET 3 (3a) is ON, but the FET 3 (3a) is OFF. The energization current IP (IPa) of the solenoid flows as a circulating current to the diode 4 (4a), and no current is supplied from the unstable power supply 21.
[0022]
Here, PWM-EH and PWM-EL have the same carrier frequency and are synchronized signals, and FETs 3 and 3a are always turned OFF simultaneously even in the interval where EL of solenoid 2 and EH of solenoid 2a in FIG. 3 overlap. At this time, since the non-stabilized power supply does not supply current, a zero interval is generated in the IDC in the PWM carrier cycle.
[0023]
Next, the operation when the FET is short-circuit broken will be described.
Since the unstable power supply voltage E is always applied to the solenoid 2 (2a) when the FET3 (3a) is short-circuited, the output current IDC of the unstabilized power supply 21 is a direct current limited by the resistance value of the solenoid. Since there is no section in which the current becomes zero within the PWM carrier cycle, the abnormal current determination circuit 23 determines that there is an abnormality and shuts off the unstabilized power supply in the operation of the first embodiment described above. Thereby, since the power supply applied to the solenoid is eliminated, the burnout of the solenoid can be protected.
[0024]
In the first embodiment, an example in which two solenoids are driven has been described. However, two or more solenoids may be driven.
In the reference embodiment and the first embodiment , two types of constant voltages to be applied are EH and EL and two types of PWM signals are described. However, two or more types may be used.
[0025]
【The invention's effect】
As is apparent from the above embodiment, according to the first aspect of the present invention, a plurality of PWM signals, which are signals for PWM driving the solenoid, are the same carrier frequency and synchronized signals. Even when the switch means driven by the solenoid breaks short-circuiting, it is possible to protect the solenoid from burning, and even if there are multiple solenoids, the DC current detection circuit of the unstable power supply and abnormal current judgment Since only one circuit is required, an inexpensive and easy-to-use solenoid drive device can be obtained.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a solenoid driving device in a reference embodiment of the present invention. FIG. 2 is a circuit diagram of a solenoid driving device in a first embodiment of the present invention. Waveform diagram [Fig. 4] Circuit diagram of conventional solenoid drive device [Fig. 5] Operation waveform diagram of conventional solenoid drive device [Explanation of symbols]
2,2a Solenoid 3,3a FET
5 A / D converter 6 PWM arithmetic circuit 7, 7a PWM control circuit 15 Contactor 21 Unstabilized power supply 22 DC current detector 23 Abnormal current judgment circuit

Claims (1)

Two or more sets of switch means for driving a solenoid and a solenoid connected in series to the solenoid are connected to the non-stabilized power source, and the analog-digital conversion for detecting the voltage of the non-stabilized power source and converting it into digital data And PWM duty which calculates a PWM duty so that an average voltage for driving the solenoid becomes a predetermined plurality of constant voltage values based on the digital data, and outputs a plurality of PWM signals corresponding to the desired constant voltage values An arithmetic circuit, a plurality of PWM signals are selected, each switch unit is individually PWM controlled, a PWM control circuit corresponding to each switch unit to be driven, and a DC output current of the unstabilized power supply are detected There is a section in which the current detection means is distinguished from whether or not there is a section in which the current is zero within the PWM carrier cycle time, and the current is zero. A solenoid having an abnormal current determination circuit for determining an abnormal condition and a power shut-off means for shutting off the power by its output signal, wherein the plurality of PWM signals have the same carrier frequency and are synchronized Drive device.

Images