JPH06105550A - Ac voltage controller - Google Patents

Abstract

PURPOSE:To detect the presence or absence of a trouble of a main switching element and a load connection exceeding a rating by supplying a maximum voltage to a load at the time of applying a power source and supplying a set voltage after a predetermined time until becoming a steady state is elapsed. CONSTITUTION:A power source of a controller is formed of a power source circuit 14, and a switching pulse signal is input to a gate driver 16 of a MOSFET 7 of a main switching element by a microcomputer 15. An inverted pulse signal of a signal to be input to the driver 16 of the MOSFET 7 is generated from a pulse inverter 17, and input to a gate driver 18 of a MOSFET 13 of a switching element for a flywheel. A current flowing to a motor 2 is detected by a resistor 8 provided in a switch circuit to detect a load current. When a current value is detected by the microcomputer 15 and a current larger than a rating flows, an overload state is judged, the output of the pulse signal is stopped, and the supply of a voltage to the motor 2 of the load is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention switches an AC power supply voltage at a frequency higher than that frequency and supplies it to an inductive load, and when a switching element is turned off for a flywheel element connected in parallel to the load. The present invention relates to an AC voltage control device that uses a microcomputer as a control circuit by flowing a flowing induced current to make a load current uniform.

[0002]

2. Description of the Related Art A conventional AC voltage control device is disclosed, for example, in Japanese Examined Patent Publication No. Sho 56-33724 and is shown in the circuit diagram of FIG. That is, in FIG. 5, 31 is an AC power supply, and 32 is a switching transistor connected in series with the AC power supply 31. 33,
34, 35 and 36 are diodes for switching in both positive and negative directions, 37 is a flywheel transistor, 38, 39, 40 and 41 are diodes for performing both positive and negative flywheels, and 42 Is an inductive load such as a motor.

In the AC voltage control device having the above structure, when the AC power supply 31 is positive, current flows through the load 42 such as a motor through the diode 33, the transistor 32, and the diode 36, and when the AC power supply 31 is negative, the diode 35,
A voltage is supplied to the load 42 by passing a current through the load 42 such as a motor through the transistor 32 and the diode 34. Here, the main switching element transistor 3
2 is switched at a frequency higher than the power supply frequency,
Moreover, the voltage supplied to the load 42 is controlled by controlling the on-time of the main switching element. When the load 42 is an inductive load such as a motor, an induced current flows when the main switching element is off, and the voltage across the terminals of the load 42 fluctuates greatly. Therefore, a flywheel circuit that performs flywheeling in both positive and negative directions is connected in parallel to the inductive load 42, and the flywheel element of the flywheel circuit is turned on when the switching element for AC voltage switching is turned off. The voltage across the terminals of the load 42 is averaged by causing the induced current flowing when the element is off to flow through the flywheel element.

[0004]

In the conventional AC voltage control device as described above, since a signal for turning on / off the main switching element and the switching element for the flywheel is constituted by an analog circuit, complicated control is required. Is difficult to realize, and if various protection functions are added, the circuit becomes complicated and the control device becomes large.

The present invention has been made in order to solve such a conventional problem. A first object thereof is to supply a maximum voltage when the power is turned on, particularly in an AC voltage control device using a microcomputer as a control device. Then, it is to obtain an AC voltage control device capable of detecting a failure of the main switching element and detecting whether or not a load exceeding the rating is connected. Secondly, a current flowing in the inductive load and , Constantly monitoring the temperature of the main switching element, if there is an abnormality, stop the supply of voltage to the load, to obtain an AC voltage control device that can protect the main switching element,
The third is to obtain an AC voltage control device in which the cause of the abnormality is clarified when the supply of the voltage to the load is stopped due to the abnormality, and the fourth is the external control by the local remote controller or the temperature controller. Is to obtain an AC voltage control device capable of

[0006]

An AC voltage control apparatus according to a first aspect of the present invention supplies a maximum voltage to a load regardless of a set voltage when the power is turned on so that a maximum starting current flows through a load such as a motor. The voltage corresponding to the set voltage is supplied to the load after a certain period of time until it becomes steady.

In the AC voltage control device according to the second aspect of the present invention, a resistor for current detection is inserted in a current path portion between a diode for performing switching in both positive and negative directions and a main switching element, and the main switching element is also provided. A thermosensitive element such as a thermistor is attached to a heat radiation plate or the like to which is attached, the temperature of the switching element is constantly detected, and these states are monitored by a microcomputer.

In the AC voltage control apparatus according to the third invention, the magnitude of the load current and the temperature of the main switching element are read by the microcomputer, and when the abnormality occurs, the voltage supply to the load is stopped, and It is designed to display whether any abnormalities have occurred.

In the AC voltage control device according to the fourth aspect of the present invention, the output voltage is set by the variable resistor, and the DC voltage for the control circuit divided by the variable resistor is converted into the voltage frequency conversion circuit (V
/ F circuit), the number of pulses is proportional to the magnitude of the voltage, the number of pulses is input to the microcomputer, and the output voltage is controlled.

[0010]

In the first aspect of the present invention, the maximum voltage is supplied to the load when the power is turned on, regardless of the set value of the voltage. Therefore, the maximum starting current of the load such as the motor can be passed.
In addition, even when the starting current gradually decreases and enters the steady state, the maximum current in the steady state flows, and if a large amount of current flows even in the steady state after a certain time has elapsed from the start, It can be seen that it is under load. Also, if a rated current or less is reached after a lapse of a certain time, it is understood that a load within the rating is connected, so the set voltage is output. Furthermore, since this type of AC voltage control device switches at an audible frequency or higher and controls the magnitude of the output voltage by varying the duty width, the main switching element and the transistor for the flywheel have failed. When the short-circuit current flows and the set voltage is low, the duty width may be narrow and the pulse detection by the overcurrent detection circuit may not be possible.Therefore, if the maximum voltage is supplied so that the overcurrent can be detected reliably, the main switching element Is always on, the overcurrent can be reliably detected.

In the second aspect of the present invention, a resistor for current detection is inserted in a portion of the current path between the diode for performing switching in both positive and negative directions and the main switching element, and a load current flows through this resistor. Since a potential difference is generated across the resistor, the magnitude of the load current can be detected by constantly monitoring this potential. Also,
A thermosensitive element such as a thermistor is attached to the heat sink to which the main switching element is attached, and the temperature of the switching element is constantly detected.The microcomputer monitors these states and supplies a voltage to the load when an abnormality occurs. You can stop.

In the third aspect of the invention, since the current flowing through the load and the temperature of the main switching element are monitored by the microcomputer, if there is an abnormality, the type of abnormality can be discriminated and the type of abnormality can be identified by LSD or the like. Can be displayed.

The AC voltage control device according to the fourth invention is
The output voltage is set by a variable resistor, and the DC voltage for the control circuit, which is divided by this variable resistor, is replaced by the number of pulses proportional to the magnitude of the voltage in the voltage frequency conversion circuit (V / F circuit), Since it is input to the computer, the set value of the output voltage can be known by counting the number of pulses, and by supplying a DC voltage from the other circuit to the input of the voltage frequency conversion circuit (V / F circuit) The control from the circuit becomes possible.

[0014]

1 is a block diagram of an AC voltage control apparatus showing an embodiment of the present invention, FIG. 2 is a flow chart showing a control flow of the AC voltage control apparatus of the same embodiment, and FIG. 3 is an AC voltage control of the same embodiment. FIG. 4 is a configuration diagram of the error display circuit of the control device, and FIG. 4 is an explanatory diagram showing the relationship between the temperature and the rotation speed of the load when external control is performed by the AC voltage control device of the embodiment.

In the illustrated AC voltage control device, an AC power supply 1 is connected in series with a motor 2 which is an inductive load and a switch circuit for switching in both positive and negative directions at a frequency higher than the power supply frequency. The switch circuit is composed of diodes 3, 4, 5 and 6 and the main switching element MO.
It is composed of an SFET 7 and a load current detecting resistor 8. Diodes 9 and 1 are provided at both ends of the motor 2, which is a load.
A flywheel circuit including 0, 11, 12 and MOSFET 13 is provided. A power supply for the control circuit is generated by the power supply circuit 14, and a microcomputer (hereinafter referred to as a microcomputer) 15 mainly controls the power supply.

The microcomputer 15 inputs a switching pulse signal to the gate drive circuit 16 of the MOSFET 7 of the main switching element. Further, the flywheel switching element MOSFET 13 turns on when the main switching element MOSFET 7 turns off, and
Since the ET7 must be turned off when it is turned on, the pulse inversion circuit 17 generates a pulse signal that is an inversion of the signal input to the gate drive circuit 16 of the MOSFET7 of the main switching element, and the MOSFET13 which is a switching element for the flywheel. Gate drive circuit 1
8 is input.

The load current detection resistor 8 provided in the switch circuit detects the current flowing through the motor 2, and the microcomputer 15 monitors the current value. When a current larger than the rated value is flowing, the microcomputer 15 determines that it is in the overload state, stops the output of the pulse signal, and stops the supply of the voltage to the motor 2, which is the load. When an excessive short-circuit current flows due to a failure of the switching element or the like, the overcurrent detection circuit 19 instantly stops the gate drive circuit 16.
The overheat detection circuit 20 has a structure in which a heat-sensitive element such as a thermistor is attached to a radiator plate to which the main switching element is attached, and the temperature of the main switching element is monitored by the microcomputer 15. The microcomputer 15 stops the supply of voltage to the motor 2 when the temperature detected by the overheat detection circuit 20 rises abnormally.

The microcomputer 15 stops the supply of the voltage to the motor 2 due to such an abnormality, and the error display circuit 21
The display means such as the LEDs 21a, 21b, 21c are operated to display what kind of abnormality causes the motor 2 to stop. In addition, external control by the external control circuit 22 can also be performed by inputting a signal from the external control circuit 22 such as a local remote controller or a temperature controller to the microcomputer 15 via the V / F conversion circuit 23.

FIG. 3 is a block diagram of the error display circuit 21. As shown in FIG. 3, the microcomputer 15 performs overcurrent detection, overheat detection, and overload detection. LEDs 21a, 21b corresponding to the abnormality,
21c is turned on.

Next, the control flow of this AC voltage control apparatus will be described with reference to the flow chart of FIG. When the AC power supply 1 is turned on and started, the maximum voltage, that is, the AC power supply voltage is directly supplied to the load motor 2 in step S1 regardless of the set value of the output voltage. Next, in step S2, it is determined whether or not the overcurrent is detected. If the overcurrent is detected, the output is stopped in step S4 and an error is displayed in step S5. If no overcurrent is detected, the process proceeds to step S3, and the overheat detection is determined in step S3. When overheat is detected in step S3,
The output is stopped in step S4 and an error is displayed in step S5. If the overheat is not detected in step S3, it is determined in step S6 whether or not the activation is completed. If the start is completed, the process proceeds to step S7. If the start is not completed, the process returns to step S1. In step S6, the completion of the startup is determined by counting the time when the startup state is settled to the steady state, and the maximum voltage is supplied to the motor 2 during that period.

In step S7, it is judged whether or not a current larger than the maximum rating is flowing. If a current larger than the maximum rating is flowing, the output is stopped in step S4 and an error is displayed in step S5. If a current larger than the maximum rating is not flowing, step S8
Then, the set value of the output voltage is read here, and the voltage corresponding to the set value is output in step S9. After that, step S10, step S11, step S12
The voltage corresponding to the set value is output until the power is turned off while detecting overcurrent, overheat state, and overload respectively.
If there is any abnormality during this period, the output is stopped in step S4 and an error is displayed in step S5.

FIG. 4 shows the number of rotations of the ventilation fan with respect to the temperature related to the operation control of the ventilation fan by the temperature controller as the external control circuit 22. The AC voltage control device determines the output voltage by the V / F conversion circuit. When the input voltage of 23 is, for example, 1 V, the minimum voltage is output, and when the input voltage of 5 is 5 V, the maximum voltage is output, and the temperature controller controls when the set temperature and the actual temperature match.
V is output, and when the actual temperature is higher than the set temperature, a voltage higher than 3V is output in proportion to the temperature difference, and when the actual temperature is lower than the set temperature, 3V is output in proportion to the temperature difference.
If you use a device that outputs a lower voltage, when the set temperature and the actual temperature are the same, set the ventilating fan's rotation speed to medium,
When the actual temperature is higher than the set temperature, the fan speed is increased according to the temperature difference, and when the actual temperature is lower than the set temperature, the fan speed is decreased according to the temperature difference. Fine control of the ventilation fan is possible.

[0023]

As is apparent from the above description of the embodiments, according to the first aspect of the present invention, a load larger than the rating is connected by supplying the maximum voltage to the load regardless of the set value when the power is turned on. You can easily determine whether or not
It is possible to reliably detect the overcurrent of the load.

According to the second invention, the current value can be monitored by the resistance for detecting the load current, and when an abnormality occurs by monitoring the temperature of the main switching element by the heat sensitive element or the like, the voltage to the load is immediately detected. The supply can be stopped to prevent damage to the main switching element.

According to the third aspect of the invention, since the type of abnormality can be discriminated when an abnormality occurs, the cause of the abnormality can be easily grasped and repairs and the like are facilitated.

According to the fourth aspect of the invention, external control is possible, the load can be controlled from a remote position by a remote controller at hand, and if external control is performed by a temperature controller, for example, the rotation speed of the ventilation fan with respect to temperature can be controlled. It is possible to control linearly and finely control the load.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an AC voltage control device showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control flow of the AC voltage control device according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of an error display circuit of the AC voltage control device of the embodiment.

FIG. 4 is an explanatory diagram showing a relationship between a temperature and a rotation speed of a load when external control is performed by the AC voltage control device of the embodiment.

FIG. 5 is a configuration diagram of a conventional AC voltage control device.

[Explanation of symbols]

 1 AC power supply 2 Motor 3 Diode 4 Diode 5 Diode 6 Diode 7 MOSFET 8 Resistance 9 Diode 10 Diode 11 Diode 12 Diode 13 MOSFET 15 Microcomputer 19 Overcurrent detection circuit 20 Overheat detection circuit 21 Error display circuit 22 External control circuit 23 V / F Conversion circuit

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[Procedure amendment]

[Submission date] November 11, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012] In the third invention, when an abnormality has occurred because it monitors the temperature of the current and the main switching element flowing through the load of a microcomputer, abnormality type can be determined and the type of abnormality by LED or the like Can be displayed.

Claims (4)

[Claims] 1. A switch circuit connected in series between a power supply and a load so as to perform positive / negative switching at a frequency higher than a power supply frequency, and flywheeling in both positive / negative directions. A flywheel element in a positive / negative direction connected in parallel between terminals of a load, and the fly is synchronized with ON / OFF of a main switching element for a switch circuit connected in series between the power source and the load. An AC voltage control device equipped with a microcomputer in the control circuit for turning the wheel element on and off is characterized in that the maximum voltage is always supplied for a fixed time regardless of the voltage setting state when the power is turned on. AC voltage control device. 2. The AC voltage control according to claim 1, wherein the control circuit constantly detects the current flowing in the load and the temperature of the main switching element, and immediately stops the supply of the voltage to the load if there is an abnormality. apparatus. 3. The AC voltage control device according to claim 1, wherein the control circuit displays the cause of the abnormality together with the stop of the voltage supply when the abnormality occurs. 4. The AC voltage control device according to claim 1, wherein the voltage supplied to the load can be controlled by an external control circuit such as a local remote controller or a temperature controller.