JP2012085462A - Load control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load control device that suppresses variations in potential of a cathode of a diode due to variations in forward voltage of the diode.SOLUTION: An output circuit 11 applies a first potential to an anode of a diode D10 according to a function having a variable that is an input command value. A command output section 10 subtracts a first correction value from a reference command value and then adds a second correction value to compute a command value. The reference command value is set according to a reference end-to-end voltage that is a difference between a first potential at the anode and a second potential at a cathode of the diode D10 at a predetermined temperature and in a situation in which a predetermined current flows, and to load control. The first correction value is a command value difference computed according to an inverse function of the function from the reference end-to-end voltage. The second correction value is a difference between a command value computed according to the inverse function from the first potential detected by a voltage detection section 101 and a command value computed according to the inverse function from the second potential detected by the voltage detection section 101.

Description

  The present invention relates to a load control device, and more particularly to a load control device that outputs a voltage via a diode.

  The motor device includes a motor, a drive unit (for example, an inverter) that drives the motor, and a control unit that controls the drive unit. The control unit receives a command value from the outside, and controls the drive unit according to the command value.

  The control device that outputs the command value includes a diode. The control device outputs a command value to the control device via the diode. Such a diode prevents, for example, a motor device from being broken and a relatively large voltage, specifically, an operating voltage of the motor device, from being applied to the control device.

  Patent documents 1 to 6 are disclosed as techniques related to the present invention.

Japanese Patent Laid-Open No. 10-34938 JP-A-9-243672 JP 2002-280520 A Utility Model Registration No. 3152324 JP 2001-168687 A JP 2005-65439 A

  In such a control device, the forward voltage of the diode fluctuates according to the ambient temperature and the current flowing through the diode, and takes a different value for each product due to manufacturing variations.

  Therefore, the control device outputs a command value that varies according to the forward voltage of the diode, and the desired command value is not output.

  Therefore, an object of the present invention is to provide a load control device that suppresses fluctuations in the potential of the cathode of the diode due to fluctuations in the forward voltage of the diode.

The load control device according to the present invention includes a diode (D10) having an output terminal (22), an anode, and a cathode connected to the output terminal, and a first potential (Vsp1) of the anode of the diode (D10). ) And a second potential (Vsp2) of the cathode of the diode (D10), a command output unit (10) for outputting a command value (V_f), and the command value And an output circuit (11) for applying the first potential to the anode according to a function (f (x) ⁻¹ ) using the command value as a variable, and at the command output unit at a predetermined temperature and a predetermined temperature. Based on a reference both-end voltage (Vf (typ)) that is a difference between the first potential and the second potential under a current flow condition, and a control set for an operation of a load connected to the output end. The command value set in this way is set as a reference command value (V_fduty0), and is obtained from the reference both-end voltage according to the inverse function of the function. The command value difference (f (Vf (typ))) to be obtained is set as a first correction value, and the command value (f (f (V)) obtained from the first potential detected by the voltage detector according to the inverse function of the function is used. Vsp1)) and the command value (f (Vsp2)) obtained according to the inverse function of the function from the second potential detected by the voltage detector is set as a second correction value, and the command value is It is obtained by subtracting the first correction value from the reference command value and adding the second correction value.

  Preferably, the rate of change of the inverse function (f (x)) increases as the first potential increases. Preferably, the cathode of the diode (D10) is directly connected to the output terminal (22). Desirably, the command value (V_f) is a pulse signal.

  Further, the load is a motor device, the command value (V_f) is a command value for the rotational speed of the motor (210) included in the motor device, and the load control device (100) is a rotational speed of the motor. The command output unit (10) further detects the first correction value (f) from the reference command value (V_fduty0) at startup when the motor starts to rotate. (Vftyp)) is subtracted and the second correction value is added to obtain the command value. After the rotational speed of the motor reaches a predetermined value, the rotational speed detected by the rotational speed detector The command value is output based on the reference voltage command value and the deviation.

  According to the first aspect of the load control device of the present invention, the voltage across the diode fluctuates depending on the current flowing through the diode and its temperature. The command value can be corrected by the deviation amount of the two correction amounts with respect to the first correction amount.

  Further, if the cathode of the diode is directly connected to the output end, the potential applied to the output end and the second potential applied to the cathode of the diode match each other, so that correction can be made with higher accuracy. .

  Further, the motor can be started more appropriately by obtaining the command value based on the first correction value and the second correction value at the time of start-up where it is difficult to control based on the deviation between the rotation speed and the reference voltage command value. it can. On the other hand, since the command value is output based on the deviation between the rotation speed and the reference voltage command value after the motor rotation speed reaches the predetermined value, the influence of the forward voltage of the diode is eliminated and the motor rotation speed is Can be made closer to the command value.

It is a figure which shows an example of a notional structure of a load control apparatus. It is a figure which shows an example of the dispersion | variation in a diode. It is a figure which shows an example of the simple structure of a load control apparatus. It is a figure which shows the relationship between a voltage and a duty. It is a figure which shows the relationship between a voltage and a duty. It is a figure which shows an example of a notional structure of load and a load control apparatus.

First embodiment.
As illustrated in FIG. 1, the load control device 100 includes an output end 22, a diode D <b> 10, a command generation unit 1, and a voltage detection unit 101. In the example of FIG. 1, the voltage detection unit 101 is included in the command generation unit 1, but the configuration is not limited thereto, and may be realized as another configuration.

  A load is connected to the output terminal 22. The load is, for example, a motor device. As a more detailed example, the load is a control unit that controls a drive unit (for example, an inverter) that drives the motor. Then, for example, the load control device 100 gives a command value about the rotation speed of the motor to the control unit via the output terminal 22. The control unit controls the drive unit based on the command value.

  The diode D <b> 10 is connected to the output terminal 22, and its cathode is connected to the output terminal 22. In the example of FIG. 1, the cathode of the diode D <b> 10 is directly connected to the output terminal 22.

  The voltage detection unit 101 detects the first potential Vsp1 applied to the anode of the diode D10 and the second potential Vsp2 applied to the cathode thereof.

  The command generator 1 is connected to the output terminal 22 via the diode D10. The command generator 1 applies the first potential Vsp1 to the anode of the diode D10. As a result, the second potential Vsp2 is applied to the cathode of the diode D10. Therefore, the second potential Vsp2 is applied to the output terminal 22. This is output to the load as a command value. The second potential Vsp2 is smaller than the first potential Vsp1 by the forward voltage Vf of the diode D10.

  The command generator 1 has a command output unit 10 and an output circuit 11. The command output unit 10 outputs a command signal V_f to the output circuit 11. The command signal V_f is a pulse signal that is repeatedly output, for example.

  The output circuit 11 applies the first potential Vsp1 to the anode of the diode D10 based on the command signal V_f. In the illustration of FIG. 1, the output circuit 11 includes switching elements S1 and S2, resistors R1 to R5, capacitors C1 and C2, and a diode D1. The switching element S1 has, for example, an NPN transistor and two resistors. One resistor is provided between the emitter electrode and the base electrode of the NPN transistor. The other is provided between the base electrode of the NPN transistor and the command output unit 10. The command signal V_f is input to the base electrode of the NPN type NPN transistor through another one resistor. The collector electrode is connected to the DC power source E1 through the resistors R1 and R2, and the emitter electrode of the NPN transistor is connected to the output terminal 24.

  The output terminal 24 is also connected to the load described above, for example, the control unit. Note that the potential applied to the output terminal 24 is adopted as the reference potential of the first potential Vsp1 and the second potential Vsp2. Therefore, the second potential Vsp2 viewed from the reference potential is a voltage between the output terminals 22 and 24, and this voltage is a command value given to the control unit.

  The capacitor C1 is connected in parallel with the switching element S1.

  The switching element S2 is a PNP transistor, for example, and its base electrode is connected to a point between the resistors R1 and R2, and its emitter electrode is connected to the DC power source E1.

  The resistors R4 and R5 are connected in series between the DC power supply E1 and the output terminal 24. A diode D1 is connected in parallel to the resistor R4, and the cathode of the diode D1 is directed to the DC power supply E1 side. The diode D1 protects the switching element S2. A capacitor C2 is connected in parallel to the resistor R5. One end on the high potential side of both ends of the capacitor C2 is connected to the anode of the diode D10. Therefore, the higher potential among the potentials applied to both ends of the capacitor C2 is the first potential Vsp1.

  The resistor R3 is provided between a point between the resistors R4 and R5 and the collector electrode of the switching element S2.

  When the inactive command signal V_f is input to such an output circuit 11, the switching element S1 is turned off. At this time, since the switching element S2 is also non-conductive, the resistors R4 and R5 divide the voltage V1 of the DC power supply E1. For example, assuming that the voltage V1 is 15V and the resistance values of the resistors R4 and R5 are 20 kΩ and 1 kΩ, respectively, the voltages applied to the resistors R4 and R5 are about 14.3 V and 0.7 V, respectively. It is. Therefore, at this time, the voltage across the capacitor C2 connected in parallel to the resistor R5 (that is, the first potential Vsp1) is also 0.7V.

  On the other hand, when the activated command signal V_f is input to the output circuit 11, the switching element S1 becomes conductive. Along with this conduction, current flows from the DC power source E1 to the resistors R1 and R2, and the voltage V1 is divided by the resistors R1 and R2. This divided voltage is applied as a bias voltage to the base electrode of the switching element S2. As a result, the switching element S2 becomes conductive. Here, the resistance value of the resistor R3 is sufficiently smaller than the resistance value of the resistor R4, for example, 750Ω. At this time, it can be considered that the voltage V1 of the DC power supply E1 is divided by the resistors R3 and R5. Therefore, the voltages applied to the resistors R3 and R5 are normally about 6.4V and 8.6V, respectively. Accordingly, the voltage across the capacitor C2 (that is, the first potential Vsp1) is approximately 8.6V. Actually, since the voltage between the emitter electrode and the collector electrode of the switching element S2 and the influence of the resistor R4 are present, the first potential Vsp is lower than 8.6V.

  The command output unit 10 gives a command signal V_f repeatedly activated / deactivated to the output circuit 11. Therefore, the voltage across the capacitor C2 takes a value in the range from about 0.7V to about 8.6V depending on the ratio between the active period and the inactive period. Therefore, the first potential Vsp1 takes a value in a range from about 0.7V to about 8.6V.

  As described above, since the capacitor C2 functions as an integrator for obtaining the first potential Vsp1, for example, a capacitance of about 100 μF is employed. On the other hand, since the capacitor C1 is provided for noise removal, for example, a capacitance of about 1000 pF is employed.

  Hereinafter, the ratio of the active period to the sum of the active period and the inactive period of the command signal V_f is referred to as duty V_fduty. When the command output unit 10 outputs the command signal V_f with a desired duty V_fduty, the command generation unit 1 applies a desired first potential Vsp1 to the anode of the diode D10. Then, a second potential Vsp2 obtained by subtracting the forward voltage Vf of the diode D10 from the first potential Vsp1 is given to the load as a rotational speed command value, for example.

  In the illustration of FIG. 1, the DC power source E1 is connected to the output terminal 23 through a parallel body composed of a resistor and a diode in series. The voltage applied to the output terminal 23 is used as, for example, a switching power source of a drive unit (inverter) that drives a motor. Moreover, in the illustration of FIG. 1, DC power supply E2 is connected with the input terminal 21 via resistance and a diode in series. For example, a rotational speed sensor for detecting the rotational speed of the motor is connected to the input terminal 21. A detection signal from the rotation speed sensor is input to the command output unit 10, for example. The detection signal from the rotation speed sensor will be described in detail later. In the example of FIG. 1, a DC power source E <b> 3 is connected to the output terminal 25. The voltage applied to the output terminal 25 is used as, for example, an operating power supply for the motor. Such an operating voltage is sufficiently larger than the voltage V1, for example, 300V.

  In such a configuration, the diode D <b> 10 can prevent the operating voltage from being applied to the command generator 1 even if a relatively large operating voltage is applied to the output terminal 22 due to a failure of the motor device. Therefore, the command generator 1 can be protected.

  The forward voltage Vf of the diode D10 varies depending on temperature and current as illustrated in FIG. 2, and also varies due to manufacturing variations. In the illustration of FIG. 2, for example, the relationship between the forward voltage Vf when the temperature is 25 degrees and the current If flowing through the diode D10 is shown by a solid line. In the example of FIG. 2, three solid lines are shown as this relationship, and the difference between these three solid lines is caused by the manufacturing variation of the diode D10. In the example of FIG. 2, even if the temperature is 25 degrees and the current If is constant, the forward voltage Vf has a variation of, for example, about 0.15 V due to manufacturing variations. In the illustration of FIG. 2, the relationship between the forward voltage Vf and the current If when the temperature is 80 degrees and −30 degrees is indicated by a broken line and a two-dot broken line, respectively. In the example of FIG. 2, even if the current If is constant, if the temperature increases from −30 degrees to 80 degrees, the forward voltage Vf decreases by about 0.4V. Even if the temperature is constant, the forward voltage Vf increases as the current If increases.

  As described above, since the forward voltage Vf of the diode D10 varies, even if the command generation unit 1 outputs the desired first potential Vsp1 and applies the desired second potential Vsp2 to the output terminal 22, The potential Vsp2 varies according to the variation of the forward voltage Vf. In the present application, such fluctuations are suppressed.

  The command output unit 10 receives the first potential Vsp1 and the second potential Vsp2 of the diode D10. The command output unit 10 outputs a command signal V_f based on, for example, control on the rotational speed of the motor and the first potential Vsp1 and the second potential Vsp2. Hereinafter, generation of the command signal V_f based on the first potential Vsp1 and the second potential Vsp2 will be described. FIG. 3 simply shows a configuration when the command signal V_f is output.

  FIG. 4 schematically illustrates the relationship between the voltage applied to the anode of the diode D10 and the duty of the command signal V_f. In the illustration of FIG. 4, the horizontal axis indicates voltage, and the vertical axis indicates duty. In the following, the curve in FIG. 4 is represented by a function f (x).

  The function f (x) is a function caused by the output circuit 11. Such a function f (x) can be obtained by calculation from the circuit constants of the output circuit 11 or can be obtained by experiments. In the example of FIG. 4, the function f (x) is non-linear, and more specifically, the derivative (rate of change) of the function f (x) with respect to the voltage increases monotonously with the increase in voltage.

  Now, the forward voltage Vf of the diode D10 under the condition where a predetermined temperature (for example, 25 degrees) and a predetermined current If (typ) flows is set to the reference both-ends voltage Vf (typ). The reference both-end voltage Vf (typ) varies depending on the manufacturing variation of the diode D10, and the reference both-end voltage Vf (typ) is a value (for example, a median value or an average value) considering the manufacturing variation.

  Then, under a condition where a predetermined temperature (for example, 25 degrees) and a predetermined current If (typ) flow, the duty V_fduty at the predetermined first potential Vsp1 (typ) is obtained based on Expression (1). The first potential Vsp1 (typ) is the first potential Vsp1 under a condition where a predetermined temperature and a predetermined current If (typ) flow. In other words, the first potential Vsp (typ) is the first potential Vsp1 adjusted so that the current flowing through the diode D10 at the predetermined temperature becomes the predetermined current If (typ). Further, a duty at a value Vsp1 (typ) −Vf (typ) that is smaller than the first potential Vsp1 (typ) by the reference both-ends voltage Vf (typ) is obtained based on the function f (x). That is, this duty is expressed by f (Vsp1 (typ) −Vf (typ)). Then, these differences, that is, f (Vsp1 (typ)) − f (Vsp1 (typ) −Vf (typ)) are obtained, and the result is set as the first correction value f (typ) as illustrated in FIG. .

  The first correction value f (typ) and the function f (x) are both recorded in advance on a recording medium (not shown) included in the command output unit 10, for example.

  Next, the command signal V_f generated by the command output unit 10 when controlling the load will be described. Here, the duty V_fduty when assuming that the forward voltage Vf of the diode D10 is the reference both-ends voltage Vf (typ) is assumed to be the duty V_fduty0. The duty V_fduty0 is determined based not only on the control set for the load operation but also on the reference both-end voltage. In other words, V_fduty0 gives the second voltage Vsp2 to be applied based on the control set for the operation of the load when the forward voltage Vf of the diode D10 is assumed to be the reference both-ends voltage Vf (typ). Value. For example, V_fduty0 is expressed as f (Vsp2 + Vf (typ)) when expressed using the function f (x).

  Then, the command output unit 10 calculates the duty V_fduty by correcting the duty V_fduty0 based on the following equation (2).

  V_fduty = V_fduty0 + f (Vsp1) -f (Vsp2) -f (typ) (2)

  Consider equation (2). The first correction value f (typ) is a duty difference when the forward voltage Vf of the diode D10 is the reference both-ends voltage Vf (typ), and the second correction value f (Vsp1) −f (Vsp2) is It is a duty difference in the forward voltage Vf of the diode D10. Therefore, the difference between the first correction value and the second correction value represents the influence of the difference between the forward voltage Vf of the diode D10 and the reference both-end voltage Vf (typ) on the duty. According to equation (2), the difference between the first correction value and the second correction value is added to the duty V_fduty0 to obtain the duty V_fduty. Therefore, if the forward voltage Vf of the diode D10 is larger than the reference both-ends voltage Vf (typ), the duty V_fduty is obtained by increasing the duty V_fduty. If the forward voltage Vf of the diode D10 is smaller than the reference both-ends voltage Vf (typ), the duty V_fduty is obtained by reducing the duty V_fduty.

  Then, the command output unit 10 outputs a command signal V_f having the duty V_fduty obtained by the equation (2) to the output circuit 11. As a result, fluctuations in the second potential Vsp2 due to fluctuations in the forward voltage Vf can be suppressed. Further, if the cathode of the diode D10 is directly applied to the output terminal 22, the potential applied to the output terminal 22 and the second potential Vsp1 applied to the cathode of the diode D10 coincide with each other, thereby improving accuracy. Can be corrected.

  Next, the maximum value V_fdutymax of the duty V_fduty will be considered with respect to the effect of the command generator 1. The maximum value V_fdutymax is limited, for example, in order to achieve a motor rated upper limit (for example, an upper limit for torque) or less and to achieve a capability lower than or equal to the lower limit. Here, the lower limit of the capability is the lower limit of the capability that the motor should exhibit when controlling the motor at the maximum rotational speed. Conventionally, it is necessary to consider the variation in the forward voltage Vf. That is, the maximum value V_fdutymax is determined so that the motor rated upper limit is not reached even with the smallest forward voltage Vf and the lower limit of the capability is exceeded even with the largest forward voltage Vf. Therefore, if the motor is controlled with the maximum value V_fdutymax when the forward voltage Vf is small, the motor exhibits a capability that greatly exceeds the lower limit of the capability. This is an unnecessary capability and has led to an increase in power consumption.

  On the other hand, if the duty V_fduty is obtained based on the equation (2), the influence of the variation in the forward voltage Vf is reduced and the second potential Vsp2 is applied to the load. Therefore, the smaller maximum value V_fdutymax can be determined. As a result, when the motor is controlled at the maximum value V_fdutymax, it is possible to reduce power consumption while achieving the lower limit of the capacity.

  As described above, the function f (x) is determined by the circuit constant of the output circuit 11. Therefore, even if the load (for example, the motor) is changed, the function f (x) can be employed as it is.

  Next, the conditions for calculating the duty V_fduty using Expression (2) will be devised. In describing the conditions, first, the load controlled by the load control device 100 will be described, and then a problem that triggers the device will be described. As illustrated in FIG. 6, the load is, for example, a motor device. The motor device is mounted on, for example, an air conditioner. The motor device includes a motor 210, a drive unit 220 that drives the motor 210, and a control unit 230 that controls the drive unit 220. These are connected to the load control device 100 as described above. In the illustration of FIG. 6, components other than the input end 21 and the output ends 22 to 25 in the load control device 100 are omitted. A rotation speed sensor 240 is connected to the input terminal 21. The rotation speed sensor 240 detects the rotation speed of the motor 210.

  The motor device is provided in the outdoor unit and drives, for example, a compressor or a fan. In such an air conditioner, if the outdoor temperature is low, the forward voltage Vf of the diode D10 is high, and the motor device may not be started due to this. That is, when the motor device is started, a relatively small rotational speed command value is given to the motor device. Since the forward voltage Vf of the diode D10 is large, this rotational speed command value (that is, the second potential Vsp2) becomes the diode D10. In some cases, the motor does not start rotating.

  Therefore, it is desirable that the command output unit 10 performs the correction based on the formula (2) at the time of starting when the motor 210 starts rotating. As a result, the second potential Vsp2 in which the increase in the forward voltage Vf is suppressed is given to the motor device as the rotational speed command value, so that the motor device can be started up appropriately. On the other hand, after the motor 210 reaches a stable rotational speed, the command output unit 10 obtains the rotational speed from the rotational speed sensor 240 via the input terminal 21, and the rotational speed and the rotational speed command value are obtained. Feedback control (for example, PI control) may be performed based on the deviation. As a result, the rotational speed of the motor can be appropriately controlled regardless of the fluctuation of the forward voltage Vf of the diode D10.

Claims (5)

Output terminal (22),
A diode (D10) having an anode and a cathode connected to the output end;
A voltage detector (101) for detecting a first potential (Vsp1) of the anode of the diode (D10) and a second potential (Vsp2) of the cathode of the diode (D10);
Command output unit (10) that outputs the command value (V_f),
An output circuit (11) for inputting the command value and applying the first potential to the anode according to a function (f (x) ⁻¹ ) having the command value as a variable;
In the command output unit,
The reference terminal voltage (Vf (typ)), which is the difference between the first potential and the second potential under a condition where a predetermined temperature and a predetermined current flow, is set to the operation of the load connected to the output terminal. The command value set based on the control to be the reference command value (V_fduty0),
A difference (f (Vf (typ))) of the command value obtained from the reference both-end voltage according to an inverse function of the function is set as a first correction value,
The command value (f (Vsp1)) obtained from the first potential detected by the voltage detection unit according to the inverse function of the function, and the inverse function of the function from the second potential detected by the voltage detection unit. The difference from the command value (f (Vsp2)) obtained according to
A load control device that obtains the command value by subtracting a first correction value from the reference command value and adding the second correction value.   The load control device according to claim 1, wherein the rate of change of the inverse function (f (x)) increases as the first potential increases.   The load control device according to claim 1 or 2, wherein a cathode of the diode (D10) is directly connected to the output terminal (22).   The load control device according to any one of claims 1 to 3, wherein the command value (V_f) is a pulse signal. The load is a motor device, and the command value (V_f) is a command value for the rotational speed of the motor (210) of the motor device,
The load control device (100) further includes a rotation speed detector (240) for detecting the rotation speed of the motor,
The command output unit (10) subtracts the first correction value (f (Vftyp)) from the reference command value (V_fduty0) during startup when the motor starts to rotate, and obtains the second correction value. The command value is obtained by addition, and after the rotation speed of the motor reaches a predetermined value, the command value is calculated based on the rotation speed, the reference voltage command value, and the deviation detected by the rotation speed detector. The load control device according to claim 1, wherein the load control device outputs the load control device.

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