JP2011142706A - Inverter control device, drive device, air conditioner, capacitor discharge control program, and method of controlling capacitor discharge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a large current from flowing in an inverter circuit at capacitor discharge, and to terminate the capacitor discharge, in a short period. <P>SOLUTION: An inverter controller 2 includes a rectifier circuit RC, a main relay 10, a smoothing capacitor C, the inverter circuit 30 having switching elements Tr1-6, a capacitor discharge control section 110, a voltage detection section 120, and a memory 130, which stores a reference voltage value Vs and a reference duty ratio D, corresponding to the reference voltage Vs. When the main relay 10 is opened (at discharging of capacitor), the voltage detecting section 120 detects the discharge voltage value of the smoothing capacitor C, while the capacitor discharge control section 110 corrects the reference duty ratio D and calculates a revised duty ratio D', based on the discharge voltage value and the reference voltage value Vs, and opens and closes the switching elements Tr1-6 at the revised duty ratio D'. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a capacitor discharge technique for discharging a residual charge of a smoothing capacitor.

  The inverter circuit is provided with a smoothing capacitor for smoothing DC power after rectification, and a main relay for opening and closing a connection with a power supply that supplies power to the inverter circuit. The main relay is connected to stop the power supply to the load when the inverter circuit or a load connected to the inverter circuit, for example, maintenance, inspection, repair or the like of a motor, or when the load is stopped. Open. Even if the main relay is opened, since the residual charge is charged in the smoothing capacitor, it is necessary to discharge the residual charge (capacitor discharge).

  For example, in Patent Document 1, a voltage is converted between a smoothing capacitor connected to the input side of an inverter that drives a motor, a secondary battery that outputs a DC voltage, and the secondary battery and the capacitor. And a step-up converter that supplies the converted voltage to the smoothing capacitor or the secondary battery. A voltage difference between the output voltage value of the secondary battery and the voltage value of the residual charge of the smoothing capacitor is predetermined. A technique is disclosed in which the residual charge is charged back to the secondary battery when the value α is greater than or equal to the value α, and the residual charge is discharged to the motor when the value is less than a predetermined value α.

JP 2004-48983 A

When an overcurrent flows through the switching mechanism constituting the inverter circuit, excessive stress is applied to the switching mechanism. Therefore, the overcurrent is prevented from flowing through the switching mechanism by opening and closing the switching mechanism with a predetermined duty ratio during capacitor discharge. The duty ratio is a ratio of the opening time Ton to the closing time Toff in the carrier cycle T ₀ of the opening / closing operation of the switching mechanism (see FIG. 5).

  In the motor drive device disclosed in Patent Document 1, by controlling the duty ratio variably instead of a fixed value, it is possible to more surely prevent an overcurrent from flowing to the transistors constituting the boost converter during the chargeback. ing. That is, when the voltage difference is less than or equal to the reference value V1, the duty ratio is constant, and when the voltage difference exceeds the reference value V1, the duty ratio is decreased in proportion to the voltage difference.

  By the way, the power source in the motor drive device is a secondary battery. However, when the power source is a commercial AC power source, the effective voltage value of the power from the commercial power source supplied to the inverter circuit is a standard voltage value (for example, 200V). Since the voltage fluctuates up and down across 200 V) in the case of a power supply, the voltage value of the residual charge also fluctuates. Therefore, when a commercial AC power supply is used as the power supply, it is necessary to set the duty ratio in accordance with the upper limit value of the residual charge voltage value. In this case, compared with the case where the duty ratio is set according to the voltage value of the residual charge when power is supplied at the standard voltage value, the duty ratio is set to be small, and the capacitor discharge time is set. Will become longer. When the duty ratio is reduced in proportion to the voltage difference (the same applies to the voltage value of the residual charge) as in the technique disclosed in Patent Document 1, the capacitor discharge is further reduced. The time will be longer.

  However, in order to improve safety and workability during work such as maintenance, inspection, and repair, it is preferable that the capacitor discharge time is short. For this reason, conventionally, in order to shorten the capacitor discharge time, it is necessary to use the switching mechanism for large current, resulting in an increase in cost.

  The present invention has been made to solve such a conventional problem, and protects the switching mechanism constituting the inverter circuit from overcurrent at the time of discharging the capacitor, and shortens the time for discharging the capacitor. The purpose of this is to make it possible to achieve both of these without incurring cost increases.

  An inverter control device according to claim 1 of the present invention is connected to a rectifier circuit connected to a power supply side, a first switching mechanism provided between the rectifier circuit and the power supply, and the rectifier circuit. When the smoothing capacitor, the inverter circuit connected between the smoothing capacitor and the load, the second switching mechanism provided in the inverter circuit, and the first switching mechanism are opened, the second A capacitor discharge control unit that opens and closes the switching mechanism to discharge the electric charge charged in the smoothing capacitor to the inverter circuit, a voltage detection unit that detects a discharge voltage value discharged to the inverter circuit during the discharge, A storage unit that stores a predetermined reference voltage value and a predetermined reference duty ratio corresponding to the reference voltage value; The dense discharge control unit calculates a corrected duty ratio by correcting the reference duty ratio based on the discharge voltage value and the reference voltage value, and changes the open / close time of the second switching mechanism to change the corrected duty ratio. The electric charge charged in the smoothing capacitor by the ratio is discharged to the inverter circuit.

  A capacitor discharge control program according to claim 6 of the present invention is connected to a rectifier circuit connected to a power supply side, a first switching mechanism provided between the rectifier circuit and the power supply, and the rectifier circuit. In order to cause a computer to control a circuit having a smoothing capacitor, an inverter circuit connected between the smoothing capacitor and a load, and a second switching mechanism provided in the inverter circuit, the first switching A first step of opening the mechanism; a second step of discharging the electric charge charged in the smoothing capacitor to the inverter circuit at a predetermined reference duty ratio corresponding to a predetermined reference voltage value; A third step of detecting a discharge voltage value discharged to the inverter circuit in a second step, the discharge voltage value and the reference A fourth step of calculating a corrected duty ratio by correcting the reference duty ratio based on a pressure value; and changing the opening / closing time of the second switching mechanism to charge the smoothing capacitor at the corrected duty ratio. And causing the computer to execute a fifth step of discharging electric charges to the inverter circuit.

  The capacitor discharge control method according to claim 7 of the present invention is connected to the rectifier circuit connected to the power supply side, the first switching mechanism provided between the rectifier circuit and the power supply, and the rectifier circuit. Discharge electric charges charged in the smoothing capacitor to a circuit having a smoothing capacitor, an inverter circuit connected between the smoothing capacitor and a load, and a second switching mechanism provided in the inverter circuit. A first step of opening the first switching mechanism, and a predetermined reference duty ratio corresponding to a predetermined reference voltage value, the charge charged to the smoothing capacitor. And detecting the discharge voltage value discharged to the inverter circuit in the second step. A third step of calculating a corrected duty ratio obtained by correcting the reference duty ratio based on the discharge voltage value and the reference voltage value; and an opening / closing time of the second switching mechanism. And a fifth step of causing the inverter circuit to discharge the electric charge charged in the smoothing capacitor with the modified duty ratio.

  According to the invention according to any one of claims 1, 6, and 7, the electric charge charged in the smoothing capacitor is discharged to the inverter circuit at the corrected duty ratio, so that the inverter circuit is configured when the capacitor is discharged. The value of the current flowing through the second switching mechanism may be a value close to the value of the current flowing through the second switching mechanism when the voltage value of the charge charged in the smoothing capacitor is the reference voltage value. It becomes possible. Therefore, even when the supply voltage value from the power supply fluctuates and increases, it is possible to prevent an overcurrent from flowing through the second switching mechanism without reducing the duty ratio too much. Accordingly, since it is not necessary to use the second switching mechanism corresponding to the upper limit voltage value in the fluctuation of the supply voltage value, the protection and capacitor of the second switching mechanism constituting the inverter circuit without causing an increase in cost. It is possible to simultaneously reduce the time required for discharge.

  The inverter control device according to claim 2 of the present invention is the inverter control device according to claim 1, wherein the capacitor discharge control unit multiplies the reference duty ratio by a value obtained by dividing the reference voltage value by the discharge voltage value. The corrected duty ratio is calculated.

  According to the second aspect of the invention, the capacitor discharge control unit calculates the corrected duty ratio by multiplying the reference duty ratio by a value obtained by dividing the reference voltage value by the discharge voltage value. The value of the current flowing through the second switching mechanism constituting the inverter circuit is the value of the current flowing through the second switching mechanism when the voltage value of the charge charged in the smoothing capacitor is the reference voltage value. Will be equal. Therefore, it is more preferable to achieve both the protection of the second switching mechanism constituting the inverter circuit and the reduction of the time required for capacitor discharge.

  An inverter control device according to a third aspect of the present invention is the inverter control device according to the first or second aspect, wherein the voltage detection unit detects the discharge voltage value at predetermined intervals, and the capacitor discharge The control unit calculates the corrected duty ratio for each predetermined period.

  According to the third aspect of the present invention, in the capacitor discharge in which the discharge voltage decreases with time, the voltage detection unit detects the discharge voltage value at predetermined intervals, and the capacitor discharge control unit Since the correction duty ratio is calculated every fixed period, an optimal correction duty ratio is calculated every fixed period. Therefore, the time required for capacitor discharge can be further shortened.

  A drive device according to a fourth aspect of the present invention includes the inverter control device according to any one of the first to third aspects, and a motor.

  According to the invention concerning Claim 4, in the drive device provided with a motor, the effect of the invention concerning any one of Claims 1-3 can be acquired.

  An air conditioner according to a fifth aspect of the present invention includes the inverter control device according to any one of the first to third aspects and a motor.

  According to the invention which concerns on Claim 5, in the air conditioner provided with a motor, the effect of the invention which concerns on any one of Claims 1-3 can be acquired.

  According to the present invention, even when the supply voltage value from the power supply fluctuates, the current value close to the current value discharged from the smoothing capacitor at the standard voltage value is rated, not the upper limit value of the supply voltage value. The second switching mechanism having a current value can be used. Therefore, it is possible to achieve both the protection of the second switching mechanism constituting the inverter circuit and the reduction of the time required for capacitor discharge without incurring an increase in cost due to the second switching mechanism corresponding to a large current. .

It is a block diagram which shows schematic structure of the drive device with which the air conditioner which concerns on one Embodiment of this invention is provided. It is a time chart for demonstrating calculation of the correction duty ratio at the time of capacitor discharge. (A) is a figure which shows the time-dependent change of the discharge voltage value of the smoothing capacitor in capacitor | condenser discharge, (B) is a figure which shows the time-dependent change of the electric current value which flows into the switching element of an inverter circuit at the time of capacitor | condenser discharge. (A) is a figure which illustrates the voltage fluctuation of AC power supply, (B) is a figure which shows the effective value of DC power obtained by rectifying the output of AC power supply shown to (A). It is a figure for demonstrating a duty ratio.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a drive device 1 provided in an air conditioner according to an embodiment of the present invention. The drive device 1 includes an inverter control device 2 and a motor M (load), and drives the compressor included in the air conditioner by the motor M controlled by the inverter control device 2.

  The motor M is, for example, a three-phase brushless DC motor, and is rotated by switching the direction of winding currents of U, V, and W phases (currents iu, iv, and iw respectively flow) by the inverter control device 2. To drive.

  The inverter control device 2 includes a main relay 10 (first switching mechanism), a coil L, a rectifier circuit RC, a smoothing capacitor C, voltage dividing resistors R1 and R2, an inverter circuit 30, and a controller 100. Configured.

  The main relay 10 is provided on a current path between an external power source E that is, for example, a commercial AC 200V power source and the rectifier circuit RC, and opens and closes the current path. That is, the main relay 10 is energized and opened when the air conditioner is in operation, and is de-energized and closed when stopped.

  The rectifier circuit RC is composed of, for example, a diode bridge circuit, is connected to the external power supply E via the main relay 10 and the coil L, and rectifies AC power output from the external power supply E. The coil L is a reactor provided for improving the power factor of the inverter circuit 30, and the main relay 10 and the coil L are connected in series upstream of the rectifier circuit RC.

  The smoothing capacitor C is an electrolytic capacitor, for example. The smoothing capacitor C is connected downstream of the rectifier circuit RC, and smoothes the power output from the rectifier circuit RC by temporarily storing the power output from the rectifier circuit RC and then releasing it. .

  The voltage dividing resistors R1 and R2 are connected in series between both electrodes of the smoothing capacitor C. The voltage detector 120 detects the voltage value at the connection point between the voltage dividing resistor R1 and the voltage dividing resistor R2 as the discharge voltage value of the smoothing capacitor C.

  The inverter circuit 30 is connected between the smoothing capacitor C and the motor M, and includes, for example, switching elements Tr1 to Tr6 that are insulated gate bipolar transistors (Insulated Gate Bipolar Transistor (IGBT), second switching mechanism), diodes, and the like. Has been. The inverter circuit 30 converts the DC power output from the smoothing capacitor C into AC power having a predetermined frequency, and turns on and off the switching elements Tr1 to 6 in a predetermined order to wind the windings of each phase of the motor M. The motor M is driven by changing the direction of the current.

  The controller 100 controls the operation of the air conditioner by controlling the motor M and the fan motor that drive the compressor and the opening degrees of the plurality of electric valves included in the air conditioner. The controller 100 includes a capacitor discharge control unit 110, a voltage detection unit 120, and a storage unit 130.

  The capacitor discharge control unit 110 is configured by a CPU (Central Processing Unit) or the like, and executes a capacitor discharge control program stored in advance in the storage unit 130, so that when the main relay 10 is opened, the switching element Tr1 -6 are opened and closed, and the residual charge charged in the smoothing capacitor C is discharged to the inverter circuit 30 (capacitor discharge). The residual charge discharged to the inverter circuit 30 flows to the motor M connected to the inverter circuit 30, and is converted into heat energy by the winding of the motor M and consumed.

  The voltage detection unit 120 detects the voltage value between both electrodes of the smoothing capacitor C, that is, the discharge voltage value of the electric charge discharged from the smoothing capacitor C to the inverter circuit 30. That is, the voltage detection unit 120 detects the voltage value at the connection point between the voltage dividing resistor R1 and the voltage dividing resistor R2 as the discharge voltage value.

  The storage unit 130 includes, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and includes a control program for operating the air conditioner, the capacitor discharge control program, a reference voltage value and a reference duty described later. Memorize the ratio etc.

  At the time of work such as maintenance, inspection, and repair of the air conditioner, capacitor discharge for discharging the residual charge of the smoothing capacitor C is essential in order to prevent electric shock and ensure the safety of the work. When the capacitor is discharged, a large current flows through the switching elements Tr1 to Tr6. If a current (overcurrent) exceeding the rated current value flows through the switching elements Tr1 to 6, excessive stress is applied to the switching elements Tr1 to 6, and in the worst case, the switching elements Tr1 to 6 may be damaged. . Therefore, during capacitor discharge, the capacitor discharge control unit 110 opens and closes the switching elements Tr1 to Tr6 with a predetermined duty ratio.

FIG. 5 is a diagram for explaining the duty ratio. At the time of capacitor discharge, the capacitor discharge control unit 110 causes the switching elements Tr1 to 6 to repeatedly turn on and off, that is, open and close at regular intervals. Thereby, it can prevent that overcurrent flows into switching element Tr1-6. Called the fixed cycle carrier cycle (indicated by _{T 0} in FIG. 5) shows the carrier period _{T 0,} the open hours against between closing of the switching element Tr1～6 (indicated by Toff in FIG. 5) (in Figure 5 in Ton ) Is called the duty ratio.

  FIG. 4A is a diagram exemplifying voltage variation with time of the AC power output from the external power source E, and FIG. 4B is a diagram rectifying the output of the external power source E shown in FIG. It is a figure which shows the effective value of the direct-current power obtained. When the AC power output from the external power source E, which is a commercial AC power source, is rectified into DC power, the voltage value of the DC power after rectification is substantially equal to the maximum value Vm of the voltage value of the AC power before rectification. Become. For example, when the external power source E is a 200V power source (the standard voltage value of the supplied power is an effective value of 200V), Vm is about 280V. Accordingly, when the drive device 1 is connected to the external power source E and used, if there is no fluctuation in the power supplied to the external power source E, the DC power of the voltage value Vm (about 280V if the external power source E is a 200V power source). Is applied to the smoothing capacitor C.

  However, in the case of a commercial AC power supply, the voltage value of the supplied power varies by about ± 10% with respect to the standard voltage value. At this time, the maximum value is a value having Vml as a lower limit and Vmh as an upper limit. Therefore, in controlling the capacitor discharge, it is necessary to prevent an overcurrent from flowing through the switching elements Tr1 to 6 even if the capacitor discharge is performed when the DC power having the voltage value Vmh is applied to the smoothing capacitor C. .

  Details of the control performed by the inverter control device 2 at the time of discharging the capacitor will be described based on FIG. 2, FIG. 3 (A), and FIG. 3 (B). FIG. 2 is a time chart for explaining the calculation of the corrected duty ratio D ′ during capacitor discharge. FIG. 3A is a diagram showing a change with time in the discharge voltage value of the smoothing capacitor C in the capacitor discharge, and FIG. 3B is a diagram showing the change in the current value flowing through the switching elements Tr1 to Tr6 of the inverter circuit during the capacitor discharge. It is a figure which shows a change.

  The storage unit 130 stores a reference voltage value Vs and a reference duty ratio D in advance. The reference voltage value Vs is the residual charge discharged from the smoothing capacitor C when the capacitor is discharged when the power supplied from the external power source E is a standard voltage value and DC power having the voltage value Vm is applied to the smoothing capacitor C. It is a voltage value. The reference duty ratio D is a duty ratio corresponding to the reference voltage value Vs. That is, the reference duty ratio D is set so that the current value flowing through the switching elements Tr1 to 6 does not exceed the rated current value of the switching elements Tr1 to 6 when the residual charge discharged from the smoothing capacitor C is the reference voltage value Vs. It is a predetermined value.

The capacitor discharge controller 110 corrects the reference duty ratio D for each carrier cycle T ₀ and calculates the corrected duty ratio D ′ based on the discharge voltage value V of the smoothing capacitor C and the reference voltage value Vs during capacitor discharge. Then, the switching elements Tr1 to 6 are opened and closed with the corrected duty ratio D ′. The voltage detection unit 120 detects the discharge voltage value V every carrier cycle T ₀ . The corrected duty ratio D ′ is calculated by the following equation.
D ′ = D × Vs / V

Based on FIG. 2, changes with time of the opening time Ton and the closing time Toff of the switching elements Tr <b> 1 to 6 during capacitor discharge will be described. FIG. 2 illustrates a case where the duration of capacitor discharge corresponds to N times of the carrier cycle T ₀ . In the i (i is a natural number greater than or equal to 1 and less than or equal to N), the opening time in the first carrier cycle T _{0 is} represented by Toni, and the closing time is represented by Toffi.

When the capacitor is discharged, the residual charge of the smoothing capacitor C decreases with time, so the discharge voltage value V also decreases with time. Therefore, the corrected duty ratio D ′ increases every time the carrier cycle T ₀ is repeated. That is, the opening time Ton of the switching elements Tr1 to 6 during capacitor discharge increases with time (Ton1 <Ton2 <... <TonK-1, K is a natural number of 2 or more and less than N), and the closing time Toff decreases with time. (Toff1>Toff2>...> ToffK-1). In FIG. 2, when the entire carrier period T ₀ is an open time at the K-th carrier period T ₀ that starts at the elapsed time Tk from the start of capacitor discharge, that is, the discharge voltage value V is sufficient at Tk. In this case, the current value of the electric charge discharged from the smoothing capacitor C is less than the rated current value of the switching elements Tr1 to Tr6.

Here, unlike the present embodiment, it is assumed that the duty ratio is fixed. In this case, if the discharge voltage value V of the smoothing capacitor C at the start of capacitor discharge is the reference voltage value Vs, it flows to the switching elements Tr1 to Tr6 of the inverter circuit at the time of capacitor discharge, as indicated by a broken line in FIG. current value over time decreased from C _R to 0, duration of capacitor discharge becomes Tc2. In addition, the discharge capacity in the capacitor discharge in this case is indicated by S2 in FIG. 3B, and the change with time in the discharge voltage value V of the smoothing capacitor C is indicated by a broken line in FIG.

On the other hand, in the case of this embodiment, if the discharge voltage value V of the smoothing capacitor C at the start of capacitor discharge is the reference voltage value Vs, as shown by the solid line in FIG. current flowing through the Tr1~6 is up to Tk constant at _{C R,} it decreases over time from subsequent _{C R} 0. The discharge capacity S1 in the capacitor discharge at this time is equal to the discharge capacity S2 when the duty ratio is fixed. Therefore, compared with the case where the duty ratio is fixed, the time required for capacitor discharge is shortened from Tc2 to Tc1. In addition, the change with time of the discharge voltage value V of the smoothing capacitor C in the capacitor discharge in this case is shown by a solid line in FIG.

  Next, it is assumed that the voltage value of the power supplied from the external power source E at the start of capacitor discharge is higher than the standard voltage value, and the discharge voltage value of the smoothing capacitor C at the start of capacitor discharge is Vd (Vd> Vs). To do. The time-dependent change at this time is shown with a dashed-dotted line and a dashed-two dotted line in FIG. 3 (A) and (B). A one-dot chain line indicates a change with time in the case of the present embodiment in which the duty ratio is corrected, and a two-dot chain line indicates a change with time when the duty ratio is fixed.

When the duty ratio is fixed, as indicated by a two-dot chain line in FIG. 3B, the current value flowing through the switching elements Tr1 to Tr6 of the inverter circuit at the start of capacitor discharge is the value of the smoothing capacitor C at the start of capacitor discharge. discharge voltage value V increases from C _R in the case where the reference voltage value Vs to C2. Therefore, the rated current value of the switching elements Tr1 to Tr6 needs to be C2 or more. At this time, the time required for capacitor discharge increases from Tc2 to Tc2 ′.

On the other hand, in the case of the present embodiment, as indicated by a one-dot chain line in FIG. 3B, the value of the current flowing through the switching elements Tr1 to Tr6 of the inverter circuit at the start of capacitor discharge is the discharge of the smoothing capacitor C at the start of capacitor discharge. a similarly C _R and if the voltage value V is a reference voltage value Vs, for a period of time C _R is constant extends Tk 'from Tk. At this time, the time required for capacitor discharge increases from Tc1 to Tc1 ′. However, there is no change in the time required for capacitor discharge as compared with the case where the duty ratio is fixed. Thus, in the present embodiment, the rated current of the switching element Tr1~6 is sufficient in C _R corresponding to the standard voltage value rather than the upper limit of the electric power supplied from external power supply E.

  According to the driving device 1 according to the above-described embodiment described above, even if the supply voltage value from the external power supply E fluctuates and increases, an overcurrent exceeding the rated current value is present in the switching elements Tr1 to Tr6. In addition, the corrected duty ratio D ′ can be a value corresponding to the rated current value. Accordingly, since it is not necessary to use a switching element for large current corresponding to the upper limit voltage value Vmh in the fluctuation of the supply voltage value, the protection of the switching element constituting the inverter circuit and the capacitor discharge can be prevented without increasing the cost. It is possible to achieve both reduction in required time.

Furthermore, according to the driving device 1 according to the above-described embodiment, in the capacitor discharge in which the discharge voltage value V decreases with time, the voltage detection unit 120 detects the discharge voltage value V every carrier cycle T ₀ , and the capacitor discharge control unit 110 'so it calculates the optimum corrected duty ratio D in each carrier period T _0' corrected duty ratio D in each carrier period T ₀ is calculated. Therefore, the time required for capacitor discharge can be shortened compared to the case where the corrected duty ratio D ′ is calculated only at the start of capacitor discharge.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention. For example, the main relay 10 may be provided on a current path between the rectifier circuit RC and the smoothing capacitor C, and the current path may be opened and closed.

C Smoothing capacitor E External power supply M Motor (load)
RC rectifier circuit Tr1-6 Switching element (second switching mechanism)
DESCRIPTION OF SYMBOLS 1 Drive apparatus 2 Inverter control apparatus 10 Main relay (1st switching mechanism)
30 Inverter circuit 100 Controller 110 Capacitor discharge controller 120 Voltage detector 130 Storage unit

Claims (7)

A rectifier circuit (RC) connected to the power supply (E) side;
A first switching mechanism (10) provided between the rectifier circuit (RC) and the power source (E);
A smoothing capacitor (C) connected to the rectifier circuit (RC);
An inverter circuit (30) connected between the smoothing capacitor (C) and a load (M);
A second switching mechanism (Tr1-6) provided in the inverter circuit (30);
When the first switching mechanism (10) is opened, the second switching mechanism (Tr1-6) is opened and closed to discharge the electric charge charged in the smoothing capacitor (C) to the inverter circuit (30). A capacitor discharge control unit (110) for causing
A voltage detector (120) for detecting a discharge voltage value discharged to the inverter circuit (30) during the discharge;
A storage unit (130) for storing a predetermined reference voltage value (Vs) and a predetermined reference duty ratio (D) corresponding to the reference voltage value (Vs);
The capacitor discharge controller (110)
Based on the discharge voltage value and the reference voltage value (Vs), a corrected duty ratio (D ′) obtained by correcting the reference duty ratio (D) is calculated,
An inverter control device for changing the opening / closing time of the second switching mechanism (Tr1-6) to discharge the electric charge charged in the smoothing capacitor (C) to the inverter circuit (30) with the corrected duty ratio (D ′). .   The capacitor discharge controller (110) calculates the corrected duty ratio (D ') by multiplying the reference duty ratio (D) by a value obtained by dividing the reference voltage value (Vs) by the discharge voltage value. The inverter control device according to 1. The voltage detection unit (120) detects the discharge voltage value at predetermined intervals (T ₀ ),
3. The inverter control device according to claim 1, wherein the capacitor discharge control unit (110) calculates the corrected duty ratio (D ′) for each of the fixed periods (T ₀ ). The inverter control device (2) according to any one of claims 1 to 3,
A drive device comprising a motor (M). The inverter control device (2) according to any one of claims 1 to 3,
An air conditioner comprising a motor (M). A rectifier circuit (RC) connected to the power source (E) side, a first switching mechanism (10) provided between the rectifier circuit (RC) and the power source (E), and a rectifier circuit (RC) A smoothing capacitor (C) connected to the inverter, an inverter circuit (30) connected between the smoothing capacitor (C) and the load (M), and a second switching provided in the inverter circuit (30). In order to make the computer control the circuit having the mechanism (Tr1-6),
A first step of opening the first switching mechanism (10);
A second step of discharging the electric charge charged in the smoothing capacitor (C) to the inverter circuit (30) at a predetermined reference duty ratio (D) corresponding to a predetermined reference voltage value (Vs); ,
A third step of detecting a discharge voltage value discharged to the inverter circuit (30) in the second step;
A fourth step of calculating a corrected duty ratio (D ′) obtained by correcting the reference duty ratio (D) based on the discharge voltage value and the reference voltage value (Vs);
A fifth switching mechanism (Tr1-6) that changes the open / close time of the second switching mechanism (Tr1-6) and causes the inverter circuit (30) to discharge the electric charge charged in the smoothing capacitor (C) with the corrected duty ratio (D ′) And a step of causing the computer to execute a step. A rectifier circuit (RC) connected to the power source (E) side, a first switching mechanism (10) provided between the rectifier circuit (RC) and the power source (E), and a rectifier circuit (RC) A smoothing capacitor (C) connected to the inverter, an inverter circuit (30) connected between the smoothing capacitor (C) and the load (M), and a second switching provided in the inverter circuit (30) A capacitor discharge control method for discharging a charge charged in the smoothing capacitor (C) to a circuit having a mechanism (Tr1-6),
A first step of opening the first switching mechanism (10);
A second step of discharging the electric charge charged in the smoothing capacitor (C) to the inverter circuit (30) at a predetermined reference duty ratio (D) corresponding to a predetermined reference voltage value (Vs); ,
A third step of detecting a discharge voltage value discharged to the inverter circuit (30) in the second step;
A fourth step of calculating a corrected duty ratio (D ′) obtained by correcting the reference duty ratio (D) based on the discharge voltage value and the reference voltage value (Vs);
A fifth switching mechanism (Tr1-6) is used to change the opening / closing time of the second switching mechanism (Tr1-6) to cause the inverter circuit (30) to discharge the electric charge charged in the smoothing capacitor (C) with the corrected duty ratio (D ′). And a capacitor discharge control method.

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