This application is based upon and claims the benefit of priority from the prior Japanese Patent Application Nos. 2006-218630, filed on Aug. 10, 2006, and 2007-167553, filed on Jun. 26, 2007, the entire contents of which are incorporated herein by reference.
The present invention relates to an inverter device that outputs an AC voltage of a rectangular wave and a method for designing a duty cycle setting section of an inverter device.
Some recent models of vehicles include an inverter device that converts voltage of a battery mounted in the vehicle into voltage used in home appliances, which is, for example, AC voltage of single-phase 100V or 120V. Such an inverter device, or a DC/AC inverter device, includes a DC/AC inverting circuit. However, since a conventional inverter device changes output voltage in proportion with fluctuation of input voltage, the effective value of the output voltage cannot be maintained constant. To solve this problem, Japanese Laid-Open Patent Publication No. 2000-209867 discloses an inverter device that maintains a constant effective value of output voltage regardless of fluctuation of input voltage. The inverter device outputs an AC rectangular wave and includes a D/A inverting section, an output voltage detecting section, and a duty cycle control section. The duty cycle control section controls the duty cycle of the output voltage, which is an output period or output suspending period, at an output of the D/A inverting section, in accordance with the voltage detected by the output voltage detecting section. This maintains the effective value of the output voltage at a constant level. Although the aforementioned document does not mention a specific method for determining the duty cycle, it is assumed that the duty cycle is determined by means of a microcomputer based on the description of the embodiment.
Alternatively, a method for determining the duty cycle without using a microcomputer but solely with hardware is known. In this case, as in typical pulse width modulation control (PWM control), the width of the rectangular wave is determined through comparison between a voltage of a signal based on an output waveform and a voltage of a signal based on a triangular or sawtooth wave.
As has been described, it is assumed that the inverter device of Japanese Laid-Open Patent Publication No. 2000-209867 determines the duty cycle using a microcomputer. However, in this case, prolonged time and increased cost are necessary for developing a software program, in accordance with which the duty cycle is determined.
To avoid the use of a microcomputer in determination of a duty cycle, the width of the rectangular wave may be determined through comparison between the voltage of the signal based on the rectangular wave and the voltage of the signal based on the triangular or sawtooth wave. However, in this case, the accuracy of the effective value of the output voltage of the inverter device becomes low. That is, there is a large error between a target value and the design value of the effective value of the output voltage.
Accordingly, it is an objective of the present invention to provide an inverter device that allows the effective value of output voltage to approximate to a theoretical value regardless of changes in input voltage, compared to the conventional art. It is another objective of the present invention to provide a method for designing a duty cycle setting section of an inverter device.
According to one aspect of the invention, an inverter device including a DC/AC inverter section is provided. The DC/AC inverter section converts an input DC voltage into an AC voltage of a rectangular wave and outputs the AC voltage. The DC/AC inverter section has a switching element. A controller controls turning on and off of the switching element. A duty cycle setting section sets a duty cycle for control of the switching element by the controller. The duty cycle setting section has a CR circuit. The duty cycle setting section determines the duty cycle using a signal based on the value of the DC voltage and a charging curve determined by the CR circuit.
According to another aspect of the invention, a method for designing a duty cycle setting section of an inverter device is provided. The inverter device includes a DC/DC converter section and a DC/AC inverter section. The DC/DC converter section generates a DC voltage by converting a power supplied from a DC voltage source. The DC/AC inverter section converts the DC voltage into an AC voltage with a rectangular wave and outputs the AC voltage. The duty cycle setting section sets a duty cycle for controlling turning on and off of a switching element of the DC/AC inverter section. The method includes calculating a theoretical value of the duty cycle in such a manner that an effective value of an output voltage becomes a target value when the DC voltage is changed in a predetermined range. The method further includes calculating a duty cycle determined in correspondence with a designing parameter for setting the duty cycle for each one of the values in the predetermined range; determining a proportion of an error between the theoretical value and the duty cycle obtained using the designing parameter with respect to the theoretical value; and setting the designing parameter in such a manner that the proportion falls in a target range for each one of the values in the predetermined range.
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
FIGS. 1 to 8 illustrate a first embodiment of the present invention.
The DC/DC converter section 12 includes a pair of switching elements 12a, 12b, a step-up transformer 12c, and a rectifier circuit 12d. The controller 14 controls switching of the switching elements 12a, 12b in such a manner that the DC voltage of the battery 15 is stepped up to the DC voltage VH. In the first embodiment, the DC voltage VH corresponds to any value from 100 V to 155 V in correspondence with the voltage of the battery 15. An electrolytic capacitor 16 is connected in parallel with the DC/DC converter section 12.
As illustrated in
With reference to
Referring to
The curve generating circuit 21 is a charging curve generating circuit that generates a charging curve G. In other words, the curve generating circuit 21 is a circuit that determines the charging curve G. Referring to
The comparator 22 compares the output signal (Vc) of the signal generating circuit 20 with the output signal (Vs) of the curve generating circuit 21. If the output signal (Vc) of the signal generating circuit 20, or the output signal of the operational amplifier 24, exceeds the output signal (Vs) of the curve generating circuit 21, the comparator 22 outputs a high-level signal. The comparator 22 otherwise outputs a low-level signal.
Operation of the AC inverter 11 will hereafter be explained.
When the start switch of the AC inverter 11 is turned on, control of switching of the switching elements 12a, 12b of the DC/DC converter section 12 is started. As a result, an AC voltage exceeding the voltage of the battery 15 is generated in a secondary coil of the transformer 12c. The AC voltage is inverted to the DC voltage VH higher than the voltage of the battery 15 by the rectifier circuit 12d. The DC voltage VH is then supplied to the DC/AC inverter section 13. In the first embodiment, the DC/DC converter section 12 is configured in such a manner that the value of the DC voltage VH changes in correspondence with the voltage of the battery 15. In other words, the DC voltage VH is substantially equal to the value obtained by multiplying the voltage of the battery 15 by the turns ratio of the transformer 12c.
The set of the first and fourth switching elements Q1, Q4 and the set of the second and third switching elements Q2, Q3 are turned on and off alternately at the frequency of commercial alternating current, which is, for example, 60 Hz. Specifically, referring to
The first and second durations t1ON, t2ON are adjusted in such a manner that the effective value of the output voltage of the DC/AC inverter section 13 becomes a target value, which is 100 V in the first embodiment, in correspondence with the output voltage of the DC/DC converter section 12, or the DC voltage VH. This causes the AC inverter 11 to output DC voltage with an effective value of 100 V, regardless of fluctuation of the input voltage (VH) input to the DC/AC inverter section 13.
The duty cycle of the first to fourth switching elements Q1 to Q4 is set by the duty cycle setting section 19. The “duty cycle” can be understood as a period in which any of the first to fourth switching elements Q1 to Q4 is turned on. When the start switch of the AC inverter 11 is turned on, the signal generating circuit 20 inputs the reference voltage Vc corresponding to the DC voltage VH to the non-inverting input terminal of the comparator 22. The voltage Vs generated in correspondence with the charging time of the capacitor 27 and the integrating circuit 29 is input to the inverting input terminal of the comparator 22. If the condition: Vc>Vs is satisfied, the high-level signal is provided from the comparator 22. If the condition: Vc≦Vs is satisfied, the low-level signal is provided from the comparator 22.
The period setting switching element 28 receives an ON signal each time the period T, which is a half of the switching period 2T of the first to fourth switching elements Q1 to Q4, elapses. As a result, substantially at the same time as the ON signal is input, or after the capacitor 27 is discharged instantly, the second constant voltage source 26 starts charging of the capacitor 27. The voltage Vs supplied to each of the two ends of the capacitor 27 reaches the reference voltage Vc after the duration tON has elapsed since the start of charging of the capacitor 27. In other words, the condition: Vc>Vs is satisfied in the period from when charging of the capacitor 27 has started to when the duration tON ends. Thus, the comparator 22 outputs the high-level signal. The condition: Vc≦Vs is satisfied in the period from when the duration tON has ended to when the capacitor 27 is discharged. Thus, the comparator 22 generates the low-level signal. In other words, with reference to
In correspondence with the signal output by the comparator 22, the control section 18 controls switching of the first to fourth switching elements Q1 to Q4 in accordance with the duty cycle corresponding to the DC voltage VH at the aforementioned timings. Specifically, as long as the comparator 22 outputs the high-level signal, the first and fourth switching elements Q1, Q4 or the second and third switching elements Q2, Q3 are maintained in an ON state. Otherwise, the first to fourth switching elements Q1 to Q4 are all turned off. As a result, the DC voltage (VH) supplied from the DC/DC converter section 12 is inverted into the AC voltage (VAC) of 60 Hz with the effective value of 100 V. The AC voltage (VAC) is then output from the AC inverter 11.
A method for designing the duty cycle setting section 19 will hereafter be explained.
As illustrated in
The effective value Vrms of the output voltage of the AC inverter 11, the period T, the ON duration tON, and the DC voltage VH are mutually related as represented by the following equation. In the following explanation, the duty cycle represents the proportion of the ON duration tON with respect to the period T. That is, the reference period of the duty cycle tON/T is different from the reference periods of the duty cycle t1ON/2T of the set of the first and fourth switching elements Q1, Q4 and the duty cycle t2ON/2T of the set of the second and third switching elements Q2, Q3.
The equation (1) indicates the relationship represented by the equation: tON/T=Vrms2/VH2. Thus, if the duty cycle tON/T is changed in inverse proportion to VH2, the effective value Vrms of the output voltage of the AC inverter 11 is maintained constant.
In the first embodiment, the duty cycle tON/T is set using the charging curve G generated by the CR circuit (the integrating circuit 29). If the voltage supplied to the two ends of the capacitor 27 when the period setting switching element 28 is turned on in accordance with the period T is Vs, the voltage of the second constant voltage source 26 is Vamp, the resistance value of the fifth resistor R5 is R, and the capacity of the capacitor 27 is C, the voltage Vs is represented by the following equation. The voltage Vs is then input to the inverting input terminal of the comparator 22. The value CR is the time constant of the integrating circuit 29, which forms the CR circuit.
The reference voltage Vc determined by the DC voltage VH is represented by the equation: Vc=b−a×VH in which the values a and b are constants. The values a, b are determined by the first to fourth resistors R1 to R4 of the signal generating circuit 20 and the first constant voltage source 25.
If the condition: Vc>Vs is satisfied for the time corresponding to tON, the following equation holds true.
The equation (3) is modified to obtain the following equation.
tON/T=−(CR/T)×log [(a×VH+Vamp−b)/Vamp] (4)
The values a, b, Vamp, C, and R of the equation (4) are referred to as designing parameters. If the designing parameters are selected appropriately, the difference (the error) between the theoretical value and the design value of the duty cycle will be small.
Specifically, the theoretical value of the duty cycle that causes the effective value of the output voltage (VAC) of the AC inverter 11 to become 100 V is calculated for every 0.1 V of VH from 106 V to 155 V. In the first embodiment, the acceptable range of fluctuation of the DC voltage VH is 106 V to 155 V. Such range is determined in accordance with, for example, a range of the DC voltage VH that can be inverted to an acceptable range of AC voltage VAC designated by specifications of a product.
Then, the designing parameters (a, b, Vamp, C, R) are set to initial values. The design values of the duty cycle determined by given designing parameters are calculated for every 0.1 V of VH from 106 V to 155 V.
Subsequently, the difference between the theoretical value of the duty cycle and the design value of the duty cycle determined in correspondence with the designing parameters is calculated for every 0.1 V of VH from 106 V to 155 V. The proportion of the difference (the error) between the theoretical value and the design value of the duty cycle with respect to the theoretical value (the ratio of the aforementioned difference to the theoretical value) is raised to the second power for every case and the obtained values are added together. While varying the designing parameters by small amounts, the square sum of the proportion of the difference with respect to the theoretical value is calculated for every case. In this manner, the values of the designing parameters that result in a minimum value of such square sum are determined. That is, the square integral of the proportion of the error with respect to the theoretical value is employed as an evaluation function. The values of the designing parameters that result in a minimum value of such evaluation function are optimal values of the designing parameters.
As a result, if the value a is 0.0179, the value b is 4.9900, Vamp is 3.4850, and CR/T is 0.410, the equation (4) represents the actual curve X, which is represented by the broken lines in
A first comparative example will now be explained. In the first comparative example, an equation for setting the duty cycle is determined using a triangular wave, more specifically, a sawtooth wave, in accordance with a conventional design method. Referring to
Similarly to the above-described case, the reference voltage Vc determined by the DC voltage VH is represented by the equation: Vc=b−a×VH. In this case, the following equation holds true instead of the equation (3).
b−a×VH=(tON/T)Vamp (5)
The equation (5) is modified to obtain the following equation.
tON/T=(b−a×VH)/Vamp (6)
If the values a, b, and Vamp are selected appropriately, the equation (6) is set in such a manner that the error between the theoretical value and the design value of the duty cycle is reduced.
In the first comparative example, the theoretical value of the duty cycle is calculated in such a manner that the effective value of the output voltage (VAC) of the AC inverter 11 becomes 100 V, while VH is changed by 0.1 V from 106 V to 155 V, in the same manner as the first embodiment.
Next, the designing parameters (a, b, Vamp) are set to initial values. The duty cycle determined by given designing parameters is calculated for every 0.1 V of VH from 106 V to 155 V.
Subsequently, the difference between the theoretical value and the design value of the duty cycle is calculated for every 0.1 V of VH from 106 V to 155 V. The obtained differences are each raised to the second power and the results are added together. Then, while varying the values of the designing parameters by small amounts, the values of the designing parameters that result in the minimum value of the square sum of the difference between the theoretical value and the design value of the duty cycle are determined. In other words, the square integral of the error between the theoretical value and the design value of the duty cycle is employed as evaluation function. The values of the designing parameters that result in the minimum value of the evaluation function are defined as the optimal values of the designing parameters.
Thus, if a/Vamp is 0.00100 and b/Vamp is 1.9100, the equation (6) represents the first comparative line Y1, which is indicated by the double-dotted chain lines in
Next, a second comparative example will be explained. Also in the second comparative example, a triangular wave, more specifically, a sawtooth wave, is used. In the second comparative example, instead of the square integral of the error between the theoretical value and the design value of the duty cycle, the square integral of the proportion of the error with respect to the theoretical value is used as the evaluation function for determining the equation for setting the duty cycle. Specifically, when the equation (6) is set in such a manner that the error is reduced through appropriate selection of the values a, b, and Vamp, the square integral of the proportion of the error with respect to the theoretical value is used as the evaluation function. The values of the designing parameters that result in the minimum value of the evaluation function are the optimal values of the designing parameters.
As a result, when a/Vamp is 0.0080 and b/Vamp is 1.6500, the equation (6) is represented by the second comparative line Y2 indicated by the corresponding solid line in
The first embodiment has the following advantages:
(1) The AC inverter 11 has the DC/AC inverter section 13, which converts the output voltage (VH) of the DC/DC converter section 12 to the AC voltage VAC with the rectangular wave and outputs the AC voltage VAC. The AC inverter 11 has the control section 18, which controls switching of the first to fourth switching elements Q1 to Q4 of the DC/AC inverter section 13, and the duty cycle setting section 19. The duty cycle setting section 19 determines the duty cycle for control of the first to fourth switching elements Q1 to Q4 by the control section 18 in correspondence with the signal (Vc) based on the value of the DC voltage VH input to the DC/AC inverter section 13 and the charging curve G generated by the CR circuit (the integrating circuit 29). If the duty cycle of the first to fourth switching elements Q1 to Q4 is changed in inverse proportion to the square of the DC voltage VH input to the DC/AC inverter section 13, the effective value of the output voltage of the AC inverter 11, which outputs the rectangular wave, becomes constant.
If the duty cycle is determined using, for example, a triangular or sawtooth wave, the duty cycle changes in a linear-function-like manner with respect to the DC voltage VH. The first comparative line Y1 and the second comparative line Y2 in
Accordingly, in the first embodiment, the width of the rectangular wave output by the DC/AC inverter section 13 is controlled simply by hardware in such a manner that effective value of the output voltage (VAC) approximates to the theoretical value compared to the prior art, regardless of changes in the input voltage (the DC voltage VH) input to the DC/AC inverter section 13.
(2) The duty cycle setting section 19 has the curve generating circuit 21, which determines the charging curve G. The curve generating circuit 21 is formed by the second constant voltage source 26, the capacitor 27, and the period setting switching element 28. The capacitor 27 is connected in series with the second constant voltage source 26 through the fifth resistor R5. The period setting switching element 28 is connected to the connection point 27a of the capacitor 27 with respect to the fifth resistor R5. The ON signal is input to the period setting switching element 28 each time the period T elapses. The period T corresponds to a half of the switching period 2T of the first to fourth switching elements Q1 to Q4 of the DC/AC inverter section 13. Thus, approximation for achieving inverse proportion of the duty cycle of the first to fourth switching elements Q1 to Q4 to the square of the DC voltage VH input to the DC/AC inverter section 13 is brought about through simple configuration.
In other words, the ON signal is input to the period setting switching element 28 in a pulse-like manner each time the period T elapses. In response to the reception of the ON signal by the period setting switching element 28, the charge in the capacitor 27 of the CR circuit is instantly discharged and charging of the capacitor 27 is resumed. The duration tON, or a period from when charging of the capacitor 27 is resumed to when the charged voltage of the capacitor 27 reaches the voltage of the signal (Vc) based on the value of the DC voltage VH, corresponds to the ON duration of the first to fourth switching elements Q1 to Q4.
(3) The DC/AC inverter section 13, which outputs the rectangular wave, has the first to fourth switching elements Q1 to Q4. The duty cycle setting section 19 sets the duty cycle for controlling switching of the first to fourth switching elements Q1 to Q4. In the method for designing the duty cycle setting section 19, the designing parameters are set in such a manner as to minimize the proportion of the error between the theoretical value and the design value of the duty cycle with respect to the theoretical value. The design value of the duty cycle is obtained in correspondence with the designing parameters. Thus, in the first embodiment, the proportion of the error with respect to the theoretical value is minimized over the entire acceptable range of the DC voltage VH through optimization of the designing parameters, compared to the method in which the designing parameters are set in such a manner as to minimize, for example, the error between the theoretical value and the design value of the duty cycle. That is, in the first embodiment, the proportion of the error with respect to the theoretical value is minimized throughout the acceptable range of fluctuation of the DC voltage VH, or VH of 106 V to 155 V.
If the error in the duty cycle is reduced over the entire acceptable range through setting of the designing parameters in such a manner as to minimize, for example, the error, the proportion of the error with respect to the theoretical value cannot be optimized. Specifically, if the error of the duty cycle is, for example, 5%, the influence by such error differs depending on whether the value of the duty cycle is great or small. However, in the first embodiment, the proportion of the error with respect to the theoretical value is minimized over the entire acceptable range through setting of the designing parameters in such a manner as to minimize the proportion of the error with respect to the theoretical value.
(4) In the method for designing the duty cycle setting section 19, the square integral of the proportion of the error between the theoretical value and the design value of the duty cycle with respect to the theoretical value is employed as the evaluation function. The values of the designing parameters that results in the minimum value of the evaluation function are defined as the optimal values of the designing parameters. Thus, in the first embodiment, the proportion of the error with respect to the theoretical value is minimized over the entire acceptable range through optimization of the designing parameters, compared to the conventional method in which, for example, the square integral (the square sum) of the error is used as the evaluation function.
That is, in the first embodiment, the error is accepted to a greater extent for greater values of the duty cycle but reduced for smaller values of the duty cycle. As a result, the proportion of the error with respect to the theoretical value is minimized over the entire acceptable range.
(5) The duty cycle is set using the signal (Vc) based on the value of the DC voltage VH and the charging curve G determined by the CR circuit (the integrating circuit 29). The equation: (31 (CR/T)×log [(a×VH+Vamp−b}/Vamp]) is employed as the designing parameters for setting the duty cycle. The square integral of the proportion of the above-described error with respect to the theoretical value is used as the evaluation function. The value T is a half of the switching period 2T of the first to fourth switching elements Q1 to Q4. The values a and b are constants. VH is the DC voltage input to the DC/AC inverter section 13 and Vamp is the voltage applied to the CR circuit. In the case in which the effective value of the output voltage of the AC inverter 11 is controlled to become 100 V as the input voltage (VH) input to the DC/AC inverter section 13 changes from 106 V to 155 V, the maximum value of the error of the duty cycle of the first embodiment is reduced to approximately 1/16 of that of the case in which the triangular wave, for example, is used instead of the charging curve G.
(6) In the second comparative example, the duty cycle is set using the signal (Vc) based on the value of the DC voltage VH and the triangular wave. Further, the equation: (b−a×VH)/Vamp is used as the designing parameters. The square integral of the proportion of the error with respect to the theoretical value is used as the evaluation function. In the case in which the effective value of the output voltage of the AC inverter 11 is controlled to become 100 V as the DC voltage VH input to the DC/AC inverter section 13 changes from 106 V to 155 V, the second comparative line Y2 of the second comparative example decreases the maximum value of the error of the duty cycle by approximately 30% of, for example, the first comparative line Y1 using the square integral of the error as the evaluation function.
Specifically, in the second comparative example, the triangular wave generating circuit 30 is provided instead of the curve generating circuit 21, as in the case of the PWM control. Further, the designing parameters are optimized using the square integral of the proportion of the error with respect to the theoretical value, instead of the square integral of the error, as the evaluation function, which is greatly effective.
(7) The DC/DC converter section 12 outputs the DC voltage (VH) corresponding to the voltage of the battery 15. Thus, compared to, for example, the case in which the DC/DC converter section 12 outputs a constant value of a DC voltage regardless of fluctuation of the voltage of the battery 15, the first embodiment makes it unnecessary to perform feedback control and simplifies the configuration.
(8) When the square integral of the proportion of the error between the theoretical value and the design value of the duty cycle with respect to the theoretical value is used as the evaluation function, the maximum value of the proportion of the error caused by the second comparative line Y2 using the triangular wave as the voltage Vs is 9.89%. The maximum value of the proportion of the error with respect to the theoretical value caused by the actual curve X using the charging curve G of the CR circuit (the integrating circuit 29) as the voltage Vs is 0.61%. As a result, in the first embodiment using the actual curve X, the maximum value of the proportion of the error is reduced to 9% or less throughout the acceptable range of fluctuation of the DC voltage VH, which is 106 V to 155 V.
In other words, the duty cycle setting section 19 sets the duty cycle in such a manner that the error of the effective value of the output voltage of the DC/AC inverter section 13 with respect to the target value becomes 9% or less for any value that falls in the acceptable range of fluctuation of the DC voltage VH (VH=106 V to 155 V). Thus, the effective value of the output voltage of the DC/AC inverter section 13 is output with the error not greater than 9% with respect to the theoretical value.
Referring to
For example, in a circuit employing only a conventional power source control IC 31, the second capacitor Ct is charged with a constant current. In other words, conventionally, when the voltage at each of the two ends of the second capacitor Ct reaches a predetermined value, the discharging circuit (not shown) of the power source control IC 31 discharges the second capacitor Ct. Thus, the voltage at each end of the second capacitor Ct represents a cyclic triangular wave.
However, the second curve generating circuit 37 shown in
If the voltage of the constant voltage source 35 is V, the resistance value of the seventh resistor 36 is R, the capacity of the second capacitor Ct is Ct, and the current flowing in the second transistor 34 is I, the voltage Vct at each end of the second capacitor Ct, or the second charging curve, is represented by the following equation.
That is, the second curve generating circuit 37 having the CR circuit is formed through addition of the seventh resistor 36 to the conventional power source control IC 31. In other words, even if the conventional power source control IC 31 is employed, the second charging curve is generated and the duty cycle is set to a desirable value.
The illustrated embodiments may be modified as follows.
Contrastingly to the illustrated embodiments, the output (Vc) of the signal generating circuit 20 may be input to the inverting input terminal of the comparator 22 and the output (Vs) of the curve generating circuit 21 may be input to the non-inverting input terminal. In this case, the comparator 22 outputs a signal in accordance with the levels opposite to those of the illustrated embodiments. Specifically, if the condition: Vc≦Vs is satisfied, the comparator 22 outputs a high-level signal and if the condition: Vc>Vs is satisfied, the comparator 22 outputs a low-level signal. In other words, the control section 18 controls switching of the first to fourth switching elements Q1 to Q4 in such a manner that the period in which the low-level signal is output by the comparator 22 corresponds to the ON duration of each of the first to fourth switching elements Q1 to Q4.
The effective value of the output voltage of the AC inverter 11 is not restricted to 100 V but may be other voltages of commercial power sources, such as 120 V, 220 V, 230V, or 240 V.
Any type of evaluation function may be employed in optimization of the designing parameters, as long as the proportion of the error between the theoretical value and the design value of the duty cycle with respect to the theoretical value is evaluated through such evaluation function. In other words, the evaluation function does not necessarily have to be the square integral (the square sum) of the proportion of the error with respect to the theoretical value. Such evaluation function may be, for example, the sum of the absolute values of the proportion of the error or the 2nth power integral (n is an integer not smaller than 2) of the proportion of the error.
The frequency of the output voltage of the AC inverter 11 is not restricted to 60 Hz but may be, for example, 50 Hz.
The voltage of the battery 15 is not restricted to 12 V but may be, for example, 24 V or 48 V.
The first to fourth switching elements Q1 to Q4 are not restricted to the MOSFETs but may be other switching elements such as IGBTs.
The inverter device of the present invention is not restricted to use in a vehicle but may be employed for other purposes.
In setting of the designing parameters of the illustrated embodiments, the designing parameters are optimized through minimization of the evaluation function. However, the designing parameters may be calculated in such a manner that the evaluation function falls in a desirable range determined by specifications of a product.
Number | Date | Country | Kind |
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2006-218630 | Aug 2006 | JP | national |
2007-167553 | Jun 2007 | JP | national |