JP2008060461A - Electromagnetic drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-loss magnetic drive unit that makes a prescribed electric current flow through an operation coil, without detecting the electric current running through the operation coil, regardless of the changes in power supply voltage and kinds of power sources. <P>SOLUTION: The magnetic drive unit has an operation coil 1 and switching element 7, mutually connected to P-N DC power source terminals. For power supply voltage detected from the DC power source terminal P that is higher than a prescribed value, there are provided a voltage detecting circuit 4 for outputting an injection pulse for a certain period of time, a one-shot pulse generating circuit 5, a triangular wave generating circuit 43, and a comparison circuit 44. The circuits 43, 44 respectively set each on-duty for a first and a second oscillation pulses, such that the higher the power supply voltage is, the smaller it becomes, the first oscillation pulse outputted over a period of time during which an injection pulse is outputted, and the second one outputted for a period of time after the first oscillation pulse has been outputted, so as to output the first and second oscillation pulses, by using the first and second pulses to drive the switching element 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnet driving device for passing a predetermined current through an operation coil by an on / off operation of a semiconductor switching element in an apparatus using an electromagnet such as an electromagnetic contactor.

The electromagnet of the magnetic contactor is designed to withstand fluctuations in the power supply voltage that drives the electromagnet to some extent. Specifically, it is determined by the standard so that it can be used within the range of 85 to 110% of the rated voltage. .
For this reason, if the electromagnet is designed to generate a predetermined attraction force even when the power supply voltage is low, the current flowing through the coil of the electromagnet increases in proportion to the power supply voltage when the power supply voltage is high, and the attraction force is excessive. It becomes.

Since the attractive force of an electromagnet is proportional to the square of the current flowing through the coil, a difference of 1.5 times or more is generated in the attractive force when the power supply voltage is the lowest and the highest, resulting in the electromagnet Damage of parts due to mechanical shock during suction, chattering of contacts of the magnetic contactor, etc. occur.
As countermeasures, various methods for controlling the coil current to be constant even when the power supply voltage fluctuates have been proposed. For example, a DC electromagnet device described in Patent Document 1 is known.

Hereinafter, the prior art described in Patent Document 1 will be outlined.
FIG. 4 is a circuit configuration diagram of a DC electromagnet drive device according to this prior art, in which a switching element 7 and a current detection resistor 8 are connected in series with an operation coil (electromagnet coil) 1 and between DC power supply terminals P-N. It is connected to the. Reference numeral 14 denotes a freewheeling diode.

Reference numeral 2 denotes a constant voltage circuit that generates a constant voltage V _S for a control power supply from the DC power supply voltage V and supplies it to an internal circuit. Reference numeral 4 denotes a voltage detection circuit that outputs a signal when the power supply voltage V exceeds a predetermined value. Reference numeral 5 denotes a one-shot pulse generation circuit for generating a one-shot pulse using the output signal of the voltage detection circuit 4 as an input, and 29 denotes a mirror circuit (trapezoidal wave generation circuit) to which the output pulse of the one-shot pulse generation circuit 5 is input. Is a comparator that compares the voltages at the input terminals a and b and outputs a drive pulse for the switching element 7.

Here, the comparator 3 has a higher one of the voltage obtained by dividing the output of the voltage detection circuit 4 by the resistors 15 and 16 and the voltage obtained by dividing the output voltage by the resistors 26 and 27 in the mirror circuit 29. The voltage obtained by integrating the voltage of the current detection resistor 8 by the integrating circuit 13 is input to the other terminal b, and the voltages of both terminals a and b are compared. It is configured.
In FIG. 4, 9, 12, 19, 21, and 23 are resistors, 10, 18, 20, 30, and 31 are diodes, 11, 17 are capacitors, 22 is an operational amplifier, and 28 is a constant voltage diode.

Next, this operation will be described with reference to FIG.
When the power supply voltage V is equal to or higher than a predetermined value at time t _1, "High" level signal from the voltage detection circuit 4 is output (FIG. 5 (1), (2)). In response to this signal, the one-shot pulse generating circuit 5 outputs a one-shot pulse that becomes “Low” level over a predetermined period T _C (time t _{1 to} t ₃ ) (FIG. 5 (3)).

Due to the one-shot pulse, a trapezoidal wave is output from the mirror circuit 29 (FIG. 5 (4-2)). Divided by the voltage _{V a1} by a resistor 26 and 27 in FIG. 4 this trapezoidal wave, the voltage _{V a2} (Fig. 5 (4 divided by the resistors 15 and 16 in FIG. 4, "High" level signal of the voltage detection circuit 4 The higher voltage of -1)) is the reference voltage input to one terminal a of the comparator 3.
Then, a voltage (FIG. 5 (6)) obtained by integrating the voltage drop of the current detecting resistor 8 by the integrating circuit 13 is input to the other terminal b of the comparator 3 and compared with the reference voltage, thereby obtaining a voltage. The switching element 7 is controlled so that the current i determined by the voltage drop of V _a1 , V _a2 and the current detection resistor 8 flows to the operation coil 1.

Incidentally, a trapezoidal wave output from the mirror circuit 29 increases the voltage V _a1 by increasing the voltage value, while a value that can flow a large current required when turned, the voltage detection circuit 4 The voltage V _{a2 obtained} by dividing the “High” level signal is set to such a value that the voltage value is lowered to decrease the current after being supplied, and a small current is supplied to hold the electromagnet. That is, there is a relationship of V _a1 > V _a2 .
Thus, the current i flowing through the operation coil 1 has a waveform as shown in FIG.

As described above, in the prior art, since the current i corresponding to the trapezoidal waveform output from the mirror circuit 29 can be passed through the operation coil 1, the current i flowing through the operation coil 1 even when the power supply voltage V fluctuates. This keeps the attraction force of the electromagnet constant.
Although not shown, a power supply circuit (hereinafter referred to as a rectified power supply) formed by connecting a single-phase full-wave rectifier circuit to an AC power supply can also be used by connecting it between DC power supply terminals PN. .

Japanese Laid-Open Patent Publication No. 6-236813 ([0014] to [0019], FIG. 1, FIG. 4 etc.)

In the above-described prior art, the current i flowing through the operation coil 1 is detected by the current detection resistor 8, and the current i of the operation coil 1 is obtained via the switching element 7 as a result of comparing the integrated value of the voltage drop with the reference voltage. Since it is controlled, it is possible to perform reliable current control.
However, the voltage drop due to the current detection resistor 8 does not affect so much when the power supply voltage V is high. However, when the power supply voltage V is low (for example, DC 12 V or 24 V), the voltage drop causes the current i of the operation coil (ie, This will affect the suction force.

For example, when the power supply voltage V is constant, assuming that the value of the voltage drop by the current detection resistor 8 is 1 V, the voltage applied to the operation coil 1 is reduced accordingly, and the voltage drop rate When the voltage is 12V, it becomes a little over 8%. Further, when the power supply voltage V is high, the current i of the operation coil 1 also increases, so that the loss in the current detection resistor 8 also increases.
As a countermeasure for this, it is conceivable to reduce the voltage drop (detection voltage) caused by the current detection resistor 8, but a new problem of weakening against noise occurs.

  Therefore, the problem to be solved by the present invention is that the current flowing through the operation coil is not detected, and a predetermined current is passed through the operation coil regardless of the change in power supply voltage or the type of power supply (DC power supply or rectified power supply). An object of the present invention is to provide a low-loss electromagnet drive device that is made possible.

In order to solve the above problem, the present invention does not detect the current of the operating coil and control the on / off of the switching element. The current of the operation coil is controlled to be constant by changing the signal accordingly to obtain the drive pulse for the switching element.
When using a rectified power supply obtained by single-phase full-wave rectification of an AC power supply voltage having the same effective value as the DC power supply voltage, the average value of the DC voltage output from the rectified power supply is 90% of the effective value. Compared with the time of use, the current of the operating coil is also 90%, and the attractive force is also reduced. In order to correct this, it is determined whether the power source is a rectified power source or a DC power source. The current of the operation coil determined by the average value is made equal to that when the DC power source is used.

That is, the invention described in claim 1 includes an operation coil and a semiconductor switching element connected in series with each other between DC power supply terminals, and an electromagnet drive that controls on / off of the switching element to pass a current through the operation coil. In the device
When a power supply voltage detected from the DC power supply terminal is equal to or higher than a predetermined value, a supply pulse generating means for outputting a supply pulse over a predetermined period;
Means for outputting a first oscillation pulse that is output over a predetermined period during which the input pulse is output and a second oscillation pulse that is output in a period including a period after the end of the output of the first oscillation pulse. Oscillation pulse output means for setting each on-duty of the first and second oscillation pulses to be smaller as the power supply voltage is higher,
The switching element is driven using first and second oscillation pulses output from the oscillation pulse output means.

The invention described in claim 2 is the electromagnet drive device described in claim 1,
The oscillation pulse output means includes
The first oscillation pulse is generated by comparing the first reference voltage proportional to the power supply voltage and the triangular wave, and the second oscillation pulse is generated by comparing the second reference voltage proportional to the power supply voltage and the triangular wave. It is generated by comparison.

The invention described in claim 3 is the electromagnet drive device described in claim 1 or 2,
Comprising a power source discriminating means for discriminating whether the power source connected to the DC power source terminal is a DC power source or a rectified power source comprising an AC power source and a rectifier circuit;
The on-duty of the first and second oscillation pulses is changed according to the discrimination result of the power source discrimination means.

The invention described in claim 4 is the electromagnet drive device according to claim 3,
When the power source discriminating means discriminates that the power source connected to the DC power source terminal is a rectified power source, the on-duty of the first and second oscillation pulses is made larger than when the DC power source is connected. .

According to the present invention, it is possible to cause a predetermined current to flow through the operation coil regardless of fluctuations in the power supply voltage and the type of the power supply without providing a detection circuit for the current flowing through the operation coil, and also the impact when the electromagnet is turned on. Can be small.
Further, since a current detection circuit for the operation coil is not required, a voltage drop of the current detection resistor does not occur, and it is possible to reduce the loss and efficiently supply current to the operation coil.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing an embodiment of the present invention. The same components as those in FIG. 4 are denoted by the same reference numerals.
In FIG. 1, a series circuit of an operation coil 1 and a semiconductor switching element (transistor) 7 is connected between the DC power supply terminals PN on the output side of the single-phase full-wave rectifier circuit 41. A freewheeling diode 14 is connected to the operation coil 1 in parallel.
Here, a DC power supply can be connected between the DC power supply terminals P-N, and an AC power supply can be connected to the AC input side of the single-phase full-wave rectifier circuit 41. Hereinafter, a power supply circuit including the AC power supply and the single-phase full-wave rectifier circuit 41 is referred to as a rectified power supply.

Connected to the DC power supply terminal P are a constant voltage circuit 2 that generates a constant voltage V _S for a control power supply and a voltage detection circuit 4 that outputs a signal when the power supply voltage exceeds a predetermined value. The output of the voltage detection circuit 4 is inputted to the one-shot pulse generating circuit 5, a one-shot pulse output from one-shot pulse generating circuit 5 is applied to the base of transistor T _2.
Here, the voltage detection circuit 4 and the one-shot pulse generation circuit 5 constitute the input pulse generation means in the claims, and the one-shot pulse will be referred to as an input pulse for convenience.

On the other hand, between the DC power supply terminals P-N, a power supply determination circuit 42 including resistors R ₂ and R ₃ connected in series for dividing the power supply voltage, a resistor R ₄ , a transistor T ₁ and a latch circuit 421 is connected. ing. A series circuit of the resistor R ₄ and the transistor T ₁ is connected between the constant voltage circuit 2 and the power supply terminal N, and an interconnection point between the resistors R ₂ and R ₃ is connected to the base of the transistor T ₁ . At the same time, an interconnection point between the resistor R ₄ and the transistor T ₁ is connected to the input side of the latch circuit 421, and its output side is connected to the base of the transistor T ₃ .

Reference numeral 43 denotes a known triangular wave generating circuit, which includes an operational amplifier OP ₁ constituting an integrating circuit, OP ₂ constituting a Schmitt circuit, resistors R _{5 to} R ₇ and a capacitor C ₁ . V _S is the output voltage of the constant voltage circuit.
The output voltage (triangular wave) V ₃ of the triangular wave generation circuit 43 is applied to the non-inverting input terminal of the operational amplifier OP ₄ in the comparison circuit 44 and also to the non-inverting input terminal of the operational amplifier OP ₃ via the transistor T _2. It has been added.
Here, the triangular wave generation circuit 43 and the comparison circuit 44 constitute oscillation pulse output means in the claims.

The configuration of the comparison circuit 44 will be further described. A series circuit of resistors R ₈ , R ₉ , and R _{10 and} a series circuit of resistors R ₁₁ , R ₁₂ , and R ₁₃ are connected between the DC power supply terminals PN. Yes. Among these, the first reference voltage V ₁ is formed by the interconnection point of the resistors R ₈ and R ₉ , and this reference voltage V ₁ is input to the inverting input terminal of the operational amplifier OP ₃ . Further, the second reference voltage V ₂ is formed by the interconnection point of the resistors R ₁₁ and R ₁₂ , and this reference voltage V ₂ is input to the inverting input terminal of the operational amplifier OP ₄ . The capacitors C ₂ and C ₃ are for smoothing the first and second reference voltages V ₁ and V ₂ when an AC power supply voltage is applied.

The interconnection point of the resistors R ₉ and R _{10 and} the interconnection point of the resistors R ₁₂ and R ₁₃ are connected to the collector of the transistor T ₃ via diodes D ₂ and D ₃ , respectively.
The outputs of the operational amplifiers OP ₃ and OP ₄ are connected to the base of the switching element 7 via an OR gate OR and a resistor R ₁ . Further, the connection point between the resistor R ₁ and the switching element 7 is connected to the anode of the diode D ₁ , and the cathode is connected to the output side of the voltage detection circuit 4.

Next, the operation of this embodiment will be described with reference to FIGS.
First, when the power supply voltage between the power on the DC power supply terminal P-N is equal to or greater than a predetermined value at time t ₀₁ in FIG. 2, the signal of "High" level is outputted from the voltage detection circuit 4 (FIG. 2 ( 1), (2)). Upon receipt of this signal, the one-shot pulse generation circuit 5 outputs a one-shot pulse that is at the “Low” level over a predetermined period T _C (time t _{01 to} t ₀₂ ) as an input pulse (FIG. 2 (3)). ).

At the same time that the constant voltage V _S is established by the constant voltage circuit 2, a triangular wave V ₃ as shown in FIG. 3A is output from the triangular wave generating circuit 43. Since one-shot pulse as described above is input to the base of the transistor T _2, during the period T _C is the transistor T ₂ is turned on, the triangular wave V ₃ is input to the non-inverting input terminal of the operational amplifier OP ₃ by this The

Since the first reference voltage V ₁ is input to the inverting input terminal of the operational amplifier OP ₃ , the first oscillation pulse (FIG. 3A) determined by the comparison between the triangular wave V ₃ and the first reference voltage V ₁ . dashed pulse _{P a1)} in) is outputted from the operational amplifier OP _3.
The first oscillation pulse P _a1 is applied to the switching element 7 via the OR gate OR, and the switching element 7 is turned on to pass a current through the operation coil 1. The oscillation pulse P _a1 is generated during the period T _C. transistor _{T 2} is completed at the same time is turned off after the lapse (FIG. 2 (4)). In other words, the first oscillation pulse P _a1 will be output by the period T _C of the input pulse output from the one-shot pulse generating circuit 5 (one-shot pulse).
Period T the first oscillation pulse P at _{C a1} is to have the objective of supplying a large current at put into operation the coil 1, the first reference voltages V ₁ is set low, the oscillation pulse P _a1 is "High "" Is a wide pulse with a long period (FIG. 3A).
The oscillation pulse P _a1 ′ in FIG. 3A will be described later.

On the other hand, the triangular wave V ₃ is also input to the non-inverting input terminal of the operational amplifier OP ₄ , and the second oscillation pulse determined by comparison with the second reference voltage V ₂ (the broken pulse P _b2 in FIG. 3B). ) is the time _{t 01} after, is output from the operational amplifier OP ₄ (FIG. 2 (5)).
The second oscillation pulses P _b2 is applied to the switching element 7 via the OR gate OR, but to flow through the current operation coil 1 by turning on the switching element 7, thereby holding the electromagnet after a said time period T _C Since the second reference voltage V ₂ is set to be high in order to have a current flow through the operation coil 1, the oscillation pulse P _{b 2} is a narrow pulse with a short “High” level period (FIG. 3). (B)).
The oscillation pulse P _b2 ′ in FIG. 3B will be described later.

As described above, the switching element 7 is turned on / off by the logical sum of the first and second oscillation pulses P _a1 and P _b2 output from the operational amplifiers OP ₃ and OP ₄ . A current as shown in FIG.
Since the first and second reference voltages V ₁ and V ₂ are obtained by resistance-dividing the voltage between the DC power supply terminals PN, these values are proportional to the power supply voltage. Accordingly, the first and second oscillation pulses P _a1 and P _b2 have a shorter “High” level period as the power supply voltage is higher, and a longer “High” level period as the power supply voltage is lower. The current flowing through 1 acts to be substantially constant regardless of the level of the power supply voltage.

Here, the power source determination circuit 42 in FIG. 1 determines whether the power source connected to the DC power source terminal PN is a DC power source or a rectified power source composed of an AC power source and a rectifier circuit. Is.
As described above, when using a rectified power supply obtained by single-phase full-wave rectification of an AC power supply voltage having the same effective value as the DC power supply voltage, the average value of the DC voltage after single-phase full-wave rectification is 90% of the effective value Therefore, the current of the operation coil is 90% as compared with the case of using the DC power supply, and the attractive force is also reduced.

Therefore, a power source determination circuit 42 is provided to determine whether the connected power source is a DC power source or a rectified power source based on the voltage between the DC power source terminals PN.
Because when the power source is a rectified power supply is 0V to a full wave rectified voltage, the transistor T ₁ is turned off. At this time, the voltage of the collector of the transistor T ₁ is latched by the latch circuit 421, and a signal of “High” level is output from the latch circuit 421 to turn on the transistor T ₃ in the comparison circuit 44.

Since the resistors R ₁₀ and R ₁₃ in the comparison circuit 44 are short-circuited when the transistor T ₃ is turned on, the first and second reference voltages V ₁ and V ₂ are as shown in FIGS. 3 (a) and 3 (b). low value V _{1 ',} V 2', and the response to this, the first indicated by the solid line, the second oscillation pulses P _{a1 ',} P _b2' is the period of both "High" level to the long wide pulse Therefore, the current flowing through the operation coil 1 can be increased.
In this case, when the resistors R ₁₀ and R ₁₃ are short-circuited by turning on the transistor T ₃ , the period of the “High” level of the first and second oscillation pulses P _a1 ′ and P _b2 ′ is the first and second If the voltage division ratio of the first and second reference voltages is adjusted so as to be 10% longer than the period of “High” level of the oscillation pulses P _a1 and P _b2 , is a DC power source used? Regardless of whether the rectified power supply is used, it is possible to pass the same current through the operation coil 1.

It is a circuit diagram showing an embodiment of the present invention. It is a time chart which shows the operation | movement of FIG. 2 is a time chart showing the operation of the comparison circuit in FIG. 1. It is a circuit diagram which shows a prior art. It is a time chart which shows the operation | movement of FIG.

Explanation of symbols

1 Coil 2 constant voltage circuit 4 voltage detection circuit 5 one-shot pulse generating circuit 7 the semiconductor switching element 14 diode 41 single-phase full-wave rectifier circuit 42 power supply determination circuit 421 latch circuit 43 a triangular wave generating circuit 44 comparison circuit _R 1 _{to R 13} resistors C ₁ -C ₃ capacitor _T 1 through T ₃ transistor _OP 1 _{~OP 4} op OR gate _D 1 to D ₃ diode

Claims (4)

In an electromagnet drive device comprising an operation coil and a semiconductor switching element connected in series between DC power supply terminals, and controlling the on / off of the switching element to pass a current through the operation coil.
When a power supply voltage detected from the DC power supply terminal is equal to or higher than a predetermined value, a supply pulse generating means for outputting a supply pulse over a predetermined period;
Means for outputting a first oscillation pulse that is output over a predetermined period during which the input pulse is output and a second oscillation pulse that is output in a period including a period after the end of the output of the first oscillation pulse. Oscillation pulse output means for setting each on-duty of the first and second oscillation pulses to be smaller as the power supply voltage is higher,
An electromagnet drive device that drives the switching element using first and second oscillation pulses output from the oscillation pulse output means. In the electromagnet drive device according to claim 1,
The oscillation pulse output means includes
The first oscillation pulse is generated by comparing the first reference voltage proportional to the power supply voltage and the triangular wave, and the second oscillation pulse is generated by comparing the second reference voltage proportional to the power supply voltage and the triangular wave. An electromagnet drive device characterized by being generated by comparison. In the electromagnet drive device according to claim 1 or 2,
Comprising a power source discriminating means for discriminating whether the power source connected to the DC power source terminal is a DC power source or a rectified power source comprising an AC power source and a rectifier circuit;
An electromagnet driving device, wherein the on-duty of the first and second oscillation pulses is changed according to the discrimination result of the power source discrimination means. The electromagnet drive device according to claim 3.
When the power source discriminating means determines that the power source connected to the DC power source terminal is a rectified power source, the on-duty of the first and second oscillation pulses is made larger than when the DC power source is connected. Electromagnet drive device.

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