JP3950817B2 - Square wave generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a square wave generation circuit, and more particularly to a square wave generation circuit having a long cycle, a relatively large output power, and an overcurrent protection for a load side.
[0002]
[Prior art]
This type of square wave generation circuit is generally used for an intermittent operation switch signal source, a power source such as an intermittently lit signal lamp, or a switching power source such as a chopper. In particular, an overcurrent protection function against such a short circuit failure on the load side is built in without being externally attached.
[0003]
FIG. 4 shows a conventional example of a square wave generating circuit incorporating this type of overcurrent protection function. FIG. 4 is a circuit diagram showing a conventional circuit.
[0004]
In FIG. 4, SW1 is a switch made of a ferromagnetic material that is normally in an ON (connected) state, and the state changes due to this ferromagnetic material. The switch SW1 performs ON / OFF control of the current I flowing from the power source (not shown) through the input terminal Tin. SW2 is a switch made of a ferromagnetic material that is normally in an OFF (disconnected) state. The state is changed by the ferromagnetic material, and ON / OFF control of the flowing current I is performed.
[0005]
L1 is an electromagnet, which is inserted between the switch SW1 and the anode of the diode D1, and changes the state of the ferromagnetic body of the switch SW2 when energized, thereby controlling the ON / OFF state of the switch SW2. That is, when current flows through the electromagnet L1, the electromagnet L1 functions as a magnet, turns on the switch SW2, and turns on the switch SW2. In addition, the electromagnet L1 is disposed at a position that affects the switch without contacting the switch SW2.
[0006]
Similarly, L2 is an electromagnet, which is inserted between the switch SW2 and the anode of the diode D2, and changes the state of the ferromagnetic body of the switch SW1 when energized to control the ON / OFF state of the switch SW1. To do. That is, when an electric current flows through the electromagnet L2, the electromagnet L2 functions as a magnet, the switch SW1 is turned off, and the switch SW1 is opened and non-conductive. Further, the electromagnet L2 is disposed at a position that affects the switch without touching the switch SW1.
In addition, when a load (not shown) is connected to the output terminal Tout, the current I is input to the input terminal Tin, so that the current I flows through the switch SW1 in the ON state and the electromagnet L1 and the diode D1. The capacitor C1 is charged. At this time, when the current I flows through the electromagnet L1, the switch SW2 is turned on.
Further, the current I flows through the switch SW2, flows through the electromagnet L2 and the diode D2, and the current I charges the capacitor D2. As a result, the current I is transmitted to a load (not shown) connected to the output terminal Tout. At this time, when the current I flows through the electromagnet L2, the electromagnet L2 functions as an electromagnet, and the switch SW1 is turned off.
For this reason, the current I does not flow to the electromagnet L1, the electromagnet L1 loses the magnet function, and the switch SW2 that has been changed to the ON state returns to the OFF state again. As a result, since the current I does not flow to the electromagnet L2 via the switch SW2, the current I does not flow to the output terminal Tout.
And since switch SW2 will be in an OFF state, electric current I will not flow into electromagnet L2, and switch SW1 which was changed into the OFF state by electromagnet L2 will return to an ON state. As a result, the square wave transmission circuit returns to the initial state, so that the same condition as the state in which the current I is input from the input terminal Tin is obtained. By repeating the above-described processing, the voltage of the current I is output from the output terminal Tout, for example. A square wave signal of Vout is output to a load (not shown).
In addition, since either one of the switch SW1 or the switch SW2 in the oscillation circuit is designed to be opened, it serves to prevent excessive current from continuing to flow in the square wave oscillation circuit. . (For example, refer to Patent Document 1.)
[Patent Document 1]
JP 20000183699 A (page 1-2)
[0007]
[Problems to be solved by the invention]
In the above-described conventional example, since an electromagnet is used, there is a problem that the magnetic field is influenced by the surroundings and at the same time the magnetic field from the surroundings is easily affected. In addition, since two electromagnets are used, there is a problem that the outer shape cannot be reduced.
[0008]
An object of the present invention is to provide a square wave generating circuit which can eliminate the influence of a magnetic field and can be reduced in size.
[0009]
[Means for Solving the Problems]
The square wave generating circuit of the present invention is a square wave generating circuit that is inserted in series between a power source and a load and includes switching means for intermittently connecting a power supply path between the power supply and the load. A temperature switch for intermittently connecting the power supply path, and a heating element that is thermally coupled to the temperature switch and connected in series in a circuit and driven by the current of the power supply path when the temperature switch is turned on , A cooling element that is thermally coupled to a temperature switch and that is current-driven by a drive circuit provided outside when the temperature switch is turned off .
[0010]
Moreover, you may make it equip the said load side with the load fluctuation adjustment means for suppressing a load fluctuation .
[0011]
The switching means may include a cooling element that is thermally coupled to the temperature switch and is current-driven by a drive circuit provided outside when the temperature switch is turned off.
[0012]
In addition, the drive circuit detects an off state of the temperature switch and is turned on to supply a current from the power supply side to the cooling element, and a current adjustment unit connected to the cooling element in series (for off time adjustment) ) Variable resistor.
[0013]
For example, the cooling element is a Peltier element.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a second embodiment of the present invention, and FIG. 3 is a schematic diagram of the structure of the temperature switch module in FIG. FIG.
[0017]
First, a first embodiment of the present invention will be described with reference to FIG. The square wave generating circuit 1 of the present invention is inserted in series between a power source 2 and a load 4 and supplies a square wave current to the load 4 side by interrupting a power feeding path therebetween.
[0018]
The square wave generating circuit 1 is a switching means for intermittently connecting a power feeding path, that is, a temperature switch module 11, capacitors 12 and 13 for absorbing surge noise generated at the time of switching, and a resistance value fluctuation of the load 4 is suppressed. It is composed of a buffer, that is, a variable resistor 14.
[0019]
The temperature switch module 11 is turned on at room temperature and turned off at high temperature, and the power switch is intermittently connected. The temperature switch module 11 is thermally coupled to the temperature switch 111 and connected in series in a circuit so that the temperature switch 111 is turned on. It is composed of a heating element, that is, a heating element 112 that is sometimes driven by a current in the power feeding path.
[0020]
Next, the operation of this square wave generating circuit 1 will be described. When the power switch 3 is turned on, a voltage from the power source 2 is input, and a current flows through the load 4 via the temperature switch module 11. The heating element 112 of the temperature switch module 11 generates heat by this load current and warms the temperature switch 111. When the temperature switch 111 reaches a predetermined temperature, the contact is opened and the load current is stopped.
When the temperature of the temperature switch 111 decreases and reaches a predetermined temperature, the contact is closed and turned on. Then, the first operation is repeated for the first time when the load current again flows, and a square wave current is supplied to the load 4.
[0021]
The period of this square wave current is determined by the characteristics of the temperature switch module 11 set in advance in the design stage. However, since the ON period is the time from when the temperature switch 111 is turned off to when it is turned off, The amount of heat generated per time and the characteristics of the temperature switch are determined, and the off period is the time from when the temperature switch 111 is turned off to when it is turned on, and thus is determined by the amount of hysteresis of the temperature switch 111.
[0022]
However, since this cycle varies depending on the change in ambient temperature or the resistance value of the load, the following is considered in order to reduce this variation. That is, for the change in ambient temperature, the temperature region of the on / off operation of the temperature switch 111 is set to a high temperature region in order to reduce this influence. Further, although a fixed load is targeted for load fluctuation, a buffer is provided on the output side in the case of variable load. In this embodiment, the initial fluctuation of the load is adjusted by the variable resistor 14.
[0023]
Next, a second embodiment of the present invention will be described with reference to FIG.
The difference from FIG. 1 is that the period of the square wave can be adjusted. That is, the square wave generating circuit 5 according to the present invention includes switching means for interrupting the power supply path, that is, a temperature switch module 51, capacitors 52 and 53 for absorbing surge noise generated during switching, and fluctuations in the resistance value of the load 4. And a drive circuit for current-driving a cooling element of the temperature switch module 51, that is, a transistor 54, a variable resistor 57, a resistor 55, and heat generation of the temperature switch module 51. It is comprised with the variable resistor 56 which shunts the electric current of a body.
The temperature switch module 51 is obtained by adding a cooling element to the temperature switch module 11 of FIG. That is, a temperature switch 511 that performs an off operation at normal temperature and an on-off operation at high temperatures, and is thermally coupled to the temperature switch 511 and connected in series in a circuit, and when the temperature switch 511 is turned on, A heating element that is driven by current, that is, a heating element 512, and a cooling element that is thermally coupled to a temperature switch and is driven by a drive circuit provided outside when the temperature switch is turned off, that is, a Peltier element 513 ing.
The drive circuit detects the off state of the temperature switch 511 and turns it on to supply a transistor 54 that supplies current to the Peltier element 513 from the power supply 2 side, and a current adjustment circuit connected in series with the Peltier element 513 (off period) And a variable resistor 57 for adjustment).
[0024]
The variable resistor 56 shunts the current of the heating element 512, and is for current adjustment (on period adjustment) for adjusting the current of the heating element 512 by varying this value.
Next, the operation of this square wave generating circuit 5 will be described. Since the basic operation is the same as that described with reference to FIG. 1, only the adjustment function of the different periods will be described below. The transistor 54 is turned on when the temperature switch 511 is turned off, and supplies a current to the Peltier element 513. The Peltier element 51 thereby cools the temperature switch 511 and accelerates the temperature drop. The speed of this temperature drop can be adjusted by the variable resistor 57. That is, the OFF period of the square wave is adjusted with this.
Further, since the current of the heating element 512 can be adjusted by the variable resistor 56, the temperature switch 511 is thereby adjusted to be on. That is, the on-period of the square wave is adjusted with this.
Next, an outline of the structure of the temperature switch module 51 will be described with reference to FIG. The temperature switch 511 is made of a bimetal material, and its contact is closed as shown in the drawing at room temperature, but is warped outward at a high temperature. The heating element 512 is made of a nichrome wire or the like, and is provided by winding the outer periphery of the temperature switch 511. The Peltier element 513 is provided in close contact with the temperature switch 511 through a heat transfer material.
The temperature when the temperature switch 511 is turned on and off is determined by the specific conditions of the switch itself, but the on and off time of the module is the temperature when the temperature switch 511 is turned on and off and the heating element 512 and the Peltier element 513 are heated. And cooling characteristics. These are first designed from the period, duty, output voltage, and current of a square wave set as design conditions.
The temperature switch module 11 shown in FIG. 1 is the same as that shown in FIG. 3, except that the Peltier element is deleted from that shown in FIG.
Finally, the overcurrent protection function of the square wave generating circuits 1 and 5 shown in FIG. 1.2 will be described. In FIG. 1, when the load 4 causes a short-circuit failure, the heating element 112 rapidly generates heat due to the short-circuit current and warms the temperature switch 111. When the temperature switch 111 reaches a predetermined temperature, the contact is opened and turned off, and the short-circuit current is stopped. When the temperature of the temperature switch 111 decreases and reaches a predetermined temperature, the contact is closed, and the first operation is repeated for the first time when a short-circuit current flows again.
In this way, the short-circuit current flows repeatedly, but the flowing time is limited to an instantaneous time. That is, since a short circuit current larger than usual flows through the heating element 112, the temperature rapidly rises and the temperature switch 111 is turned off in a short time. That is, the short-circuit current is limited to normal power in terms of power, and the peak can be suppressed by the induction of the heating element 112, so that it does not cause a failure or danger, and sufficiently fulfills the protection function. Furthermore, if the short circuit fault on the load side is restored, the waveform generating circuit side is also automatically restored.
[0025]
【The invention's effect】
As described above, since the square wave generating circuit of the present invention uses the temperature switch, there is an effect that it is not affected by the surrounding magnetic field and is not affected. In addition, since it has a simple configuration using only one temperature switch, there is an effect that it can contribute to miniaturization and cost reduction.
Furthermore, it is possible to adjust the period of the square wave, and there is an effect that versatility is high.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention.
FIG. 2 is a circuit diagram showing a second embodiment of the present invention.
3 is a schematic diagram showing a schematic structure of a temperature switch module in FIG. 2;
FIG. 4 is a circuit diagram showing a circuit showing a conventional example.
[Explanation of symbols]
1, 5 Square wave generating circuit 2 Power source 3 Power switch 4 Load 11, 51 Temperature switch module 12, 13, 52, 53 Capacitor 14, 56, 57, 58 Variable resistor 111, 511 Temperature switch 112, 512 Heating element 513 Peltier element

Claims (4)

In a square wave generating circuit that is inserted in series between a power source and a load and includes switching means for interrupting a power supply path therebetween, the switching means is turned on at normal temperature and turned off at high temperature to interrupt the power supply path. A temperature switch, a heat generating element that is thermally coupled to the temperature switch and connected in series in a circuit and is driven by the current of the power supply path when the temperature switch is on, and is thermally coupled to the temperature switch; A square wave generating circuit comprising: a cooling element that is current-driven by a driving circuit provided outside when the temperature switch is turned off . 2. The square wave generating circuit according to claim 1, further comprising load fluctuation adjusting means for suppressing load fluctuation on the load side. The drive circuit detects a turn-off state of the temperature switch and is turned on to supply a current from the power supply side to the cooling element, and for current adjustment (off time adjustment) connected in series with the cooling element. 3. The square wave generating circuit according to claim 1, further comprising a variable resistor. The cooling element is a square wave generating circuit according to claim 1, characterized by using a Peltier element.

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