JPS622655Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a load power control circuit using switching elements controlled via a control circuit.

For convenience of explanation, a case where the present invention is applied to an air conditioner whose operation is controlled by an electronic thermo control circuit will be described as an example.

Generally, an air conditioner is selectively operated by a single-pole double-throw switch in either an automatic operation mode using an electronic thermo control circuit or a continuous operation mode not using an electronic thermo control circuit.

The conventional method will be explained below with reference to FIG.

In Fig. 1, 1 and 2 are terminals connected to an AC power source (not shown), 3 is a load such as a fan motor or a heater, one end of which is connected to terminal 1 and the other end to a first fixed terminal 4b of a single-pole double-throw switch 4 (described later). 4 is a single-pole double-throw changeover switch (hereinafter simply referred to as switch) having a movable terminal 4a electrically connected to terminal 2, a first fixed terminal 4b electrically connected to the load 3 at connection point A, and a second fixed terminal 4c for energizing an electronic thermo control circuit (described later). 5 is a bidirectional thyristor (hereinafter referred to as BCR) which is a switching element having one end connected to the load 3 via connection point A and the other end connected to the second fixed terminal 4c of the switch 4 via connection point B. 6 and 7 are resistors and capacitors connected in series with each other, and the resistor 6 and capacitor 7 are provided in parallel with the BCR 5 and have the function of protecting the BCR 5 from surge voltages. A transformer 8 has one end of its primary winding electrically connected to the terminal 1 via a connection point C, and the other end electrically connected to the fixed terminal 4c of the switch 4 via a connection point B. A well-known diode bridge 9 is connected to the secondary winding of the transformer 8.
A smoothing capacitor 0 is connected between a connection point D on the positive side of the DC terminal of the diode bridge and a connection point E on the negative side. One end of the smoothing capacitor 11 is connected to the connection point D.
A resistor 13 has one end connected to a connection point F between the resistor 11 and the Zener diode 12, and the other end connected to a connection point E via the Zener diode 12.
The other end of the resistor 16 is connected to the connection point E via a series circuit consisting of an NTC thermistor 14 and a temperature setting variable resistor (hereinafter simply referred to as a variable resistor) 15.
A resistor connected to the connection point E via
is a known comparator, the two power supply terminals of which are connected to the connection points F and E, respectively, the non-inverting input terminal is connected to the connection point G between the resistor 13 and the NTC thermistor 14, and the inverting input terminal is connected to the connection point G between the resistor 16 and the resistor 17.
The comparator 18 has a non-inverting input terminal connected to a connection point H between the resistors 19 and 20, and an output terminal connected to a connection point I between the resistors 19 and 20. If the potential of the non-inverting input terminal of the comparator 18 is V _G and the potential of the inverting input terminal is V _H , then the output potential is H _i when V _G >V _H , and V _G
<V _H to become L _p potential.
The potential V _G of the non-inverting input terminal can be adjusted by changing the value of the variable resistor 15.
This adjustment is also performed by the second fixed terminal 4c of the switch 4.
The switch 4 and the variable resistor 15 are configured to work together so that this is possible only when the movable terminal 4a is in a closed state. 21 is a diode whose anode is connected to the connection point G and whose cathode is connected to the connection point I via a resistor 22. The series combination of this diode 21 and resistor 22 constitutes a feedback circuit for providing a hysteresis characteristic to the comparator 18. 23 is a resistor 20 connected to the connection point J at one end.
a resistor 24, the other end of which is connected to the connection point E;
The base is connected to node J, the emitter is connected to node E,
The collectors of these transistors are connected to the gate of the BCR 5. Reference numeral 25 denotes a resistor having one end connected to the connection point D and the other end connected to the cathode of the BCR 5. The transformer 8 to the resistor 25 constitute an electronic thermo control circuit 26.

With this configuration, when the second fixed terminal 4c and movable terminal 4a of the switch 4 are closed, the electronic thermo control circuit 26 enters the automatic operation mode,
On the other hand, when the connection between the first fixed terminal 4b and the movable terminal 4a is closed, the continuous operation mode is entered.

The operation of the automatic operation mode using the electronic thermo control circuit is as follows. That is, since the switch 4 is closed between the second fixed terminal 4c and the movable terminal 4a, an AC power supply voltage is applied to the primary side of the transformer 8, and a pulsating DC voltage is applied between the connection point D and E. Furthermore, a stabilized DC voltage is generated between the connection points E and F. Here, when the potential of the input terminal of the comparator 18 is V _G >V _H , the potential of the connection point I is H _i
potential, turns on transistor 24, and BCR
5 becomes conductive, so that the load 3 is energized. On the other hand, when V _H > V _G , the potential at the connection point I is L _p
potential, transistor 24, and therefore BCR
5 is off, so the load 3 is not energized. That is, if the resistance value of the NTC thermistor 14, whose resistance value changes in response to the temperature of the room heated by the air conditioner, is larger than a predetermined value with respect to the preset value of the variable resistor 15, then V _G > The voltage becomes _VH and the air conditioner is energized. Further, if the resistance value of the NTC thermistor 14 is smaller than a predetermined value, V _G <V _H and no current is applied to the air conditioner. Therefore, when the room temperature is below the set value, the air conditioner is operated, and when the room temperature exceeds the set value, the operation of the air conditioner is stopped, so that automatic operation by the so-called electronic thermo control circuit 26 is achieved.

On the other hand, when the connection between the first fixed terminal 4b and the movable terminal 4a of the switch 4 is closed, a continuous operation mode that is not controlled by the electronic thermo control circuit is entered. In this continuous operation mode, the series body of the transformer 8 and the BCR 5 is in a parallel relationship with the load 3. Therefore, the voltage across the load 3 is the same as the voltage across the primary winding of the transformer 8.
Applied to both ends of the series BCR5. Therefore,
When the BCR 5 is in the on state in the automatic operation mode by the electronic thermo control circuit 26 and is switched to the continuous operation mode, the BCR 5 remains on and the electronic thermo control circuit 26 is also continuously energized, and in particular, the smoothing capacitor 10 This tendency is exacerbated when the capacity is large.

This idea was made in view of the conventional situation, and by connecting a control circuit in parallel to a series body of a load and a switching element via a changeover switch, in continuous operation mode, It is an object of the present invention to provide a load power control circuit in which the control circuit is completely disconnected from the power source.

An embodiment of this invention will be described below with reference to FIG. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

In Fig. 2, reference numeral 4 denotes a single-pole, double-throw changeover switch.
6 is connected in parallel to the series body of load 3 and BCR5. The movable terminal 4a of this switch 4 is connected to the terminal 2, and the first fixed contact 4b is connected to the load 3 at the connection point A.
The second fixed contact 4c is electrically connected to the connection point C, that is, to the terminal 1 via the primary winding of the transformer 8. 5
BCR is a switching element provided between the connection point A and the terminal 2, and is always connected to the power source via the load 3 regardless of the switching position of the switch 4.

In the device configured in this way, when the second fixed terminal 4c and the movable terminal 4a of the switch 4 are closed, the electronic thermo control circuit 2
6 automatic driving will be realized.

On the other hand, when the first fixed terminal 4b and movable terminal 4a of the switch 4 are closed, the second fixed terminal 4c-
The movable terminals 4a are opened, and the transformer 8, that is, the electronic thermo control circuit 26 is not energized. Therefore, wasteful power consumption is prevented, and at the same time, the mean time between failures of each component is lengthened. At this time, BCR5
Since both ends of the resistor 6 and the capacitor 7 are short-circuited by the switch 4, the connection point A-terminal 2
Even if a surge is applied during this period, there is no risk of damage, and since the electronic thermo-control circuit 26 is completely disconnected from the power supply, there is no risk of damage due to the surge.

In the example, BCR5 is used as a switching element.
Although an example using a relay is shown, a relay in which the de-excitation of the coil is controlled by a transistor may also be used.

Further, in the embodiment, an example was shown in which the BCR 5 is turned on and off regardless of the phase of the AC power supply voltage, but the BCR 5 may be turned on and off in synchronization with the phase of the AC power supply voltage.

In this way, in this invention, a control circuit that controls the operation of the switching element is connected in parallel to the load and the switching element that are connected in series, and the switch energizes the load. Since the continuous energization mode and the automatic energization mode by the control circuit are selected as the mode, there is an effect that a load power control circuit can be obtained in which the control circuit is in a non-energized state in the continuous energization mode.

[Brief explanation of the drawing]

FIG. 1 is a conventional circuit diagram, and FIG. 2 is a circuit diagram showing an embodiment of this invention. In the figure, 3 is a load, 4 is a single-pole double-throw switch, 4a is a movable terminal, 4b is a first fixed terminal, 4
c is a second fixed terminal, 5 is a bidirectional thyristor,
26 is an electronic thermo control circuit. Note that the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] A series body of a load and a switching element is connected in parallel to a pair of AC power supply terminals, and a first fixed contact of a switch for automatic operation mode and continuous operation mode is connected to a connection point between the load and the switching element, and a second a fixed contact to one of the pair of power supply terminals via a control circuit that controls the switching element,
A load power control circuit characterized in that each movable contact is connected to the other power supply terminal.