JP2008261763A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device allowing reduction of response time with a simple constitution, in order to eliminate the factor in elongating the period for detecting an analog quantity in detecting an analog input value using voltage frequency conversion and in degrading the response in a control system of the latter stage using the detected value. <P>SOLUTION: This power conversion device comprises a power conversion circuit having a regular conversion section, a smoothing section, and an inverse conversion section, a control section for controlling the inverse conversion section, and a voltage frequency conversion section 4 for converting the voltage variation of the input analog signal into frequency variation, and controls the output frequency with the output from the voltage frequency conversion section 4. The power conversion device also comprises a signal processing circuit 3 for converting the first analog signal Vin from the outside and outputting the second analog signal V1 to the voltage frequency conversion section 4. The signal processing circuit 3 outputs the lower limit voltage as the second analog signal V1 when the upper limit voltage of the first analog signal Vin is input, and outputs the upper limit voltage as the second analog signal V1 when the lower limit voltage of the first analog signal Vin is input. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power converter, and more particularly to a technique related to an analog input value detection circuit system.

  A power converter that variably controls the output frequency of the power converter is known and disclosed in Patent Document 1.

JP 61-293175 A

  Conventionally, a variable voltage signal Vin input to an analog input terminal IN having a reference potential GND1 as shown in FIG. 3 is an arbitrarily set voltage frequency conversion function F (V) using the variable voltage signal Vin as an input voltage. Through the voltage frequency conversion unit 4 that outputs a pulse signal F1 having a frequency determined by the above, and then the electrical insulation unit 5 converts the reference potential to GND2 and converts it to a pulse signal F2 having the same frequency as the pulse signal F1, thereby measuring the pulse at the next stage. The pulse measurement unit 6 measures the pulse 1 cycle time T1 of the input pulse signal F2 and outputs it to the analog amount calculation unit 7. There is known an analog input value detection method in which the analog amount calculation unit 7 calculates a pulse frequency from the pulse 1 cycle time T1, and calculates the analog amount AN by using the inverse function of F (V) for the calculated pulse frequency. . At this time, the electrical insulating portion 5 may be omitted.

  The relationship between the variable voltage signal Vin and the analog amount AN is such that when the variable voltage signal Vin as shown in FIG. 4 is determined to be the voltage Vinref, the analog amount AN is uniquely ANref.

  Further, when calculating the analog quantity AN, the inverse function of F (V) can be multiplied by an arbitrary characteristic function to give an arbitrary characteristic.

  In the pulse measuring unit 6 and the analog amount calculating unit 7 described above, a means for obtaining the pulse frequency by measuring the number of pulses within a predetermined time in addition to measuring the pulse one cycle time T1 and obtaining the pulse frequency, When the on / off ratio of the pulse signal is known, there are means for measuring the ratio and obtaining the pulse frequency. Further, the pulse measurement unit 6 and the analog amount calculation unit 7 can be realized together by a timer function and a calculation function built in the microcomputer as shown by a broken line portion 8.

  Here, when performing voltage frequency conversion in the voltage frequency conversion unit 4, an IC that can construct a circuit that provides the conversion characteristic F (V) as shown in FIG. 5 is generally known.

  At this time, the characteristic F (V) is generally determined by (Equation 2), and Fref and Vref can be arbitrarily set. From the IC manufacturer, how to use the IC, application circuit examples, etc. There are disclosure materials.

この様にして得られたアナログ量ＡＮは、可変電圧信号Ｖｉｎに応じて変化するので、このアナログ量ＡＮを用いれば、可変電圧信号Ｖｉｎによる電力変換装置の出力を可変制御できる。

Since the analog quantity AN obtained in this way changes in accordance with the variable voltage signal Vin, the output of the power conversion device using the variable voltage signal Vin can be variably controlled by using the analog quantity AN.

  Here, the power supply range supplied to the IC capable of constructing a circuit that provides the characteristic F (V) is a positive voltage. For this reason, the input voltage range of V, which is the input of the characteristic F (V), is also limited to a positive voltage, and the upper limit value is limited to a value determined from the power supply voltage range of the IC.

  Therefore, the voltage range of the variable voltage signal Vin input to the voltage frequency conversion unit 4 is similarly limited, and there is a problem that a negative voltage cannot be used for the variable voltage signal Vin.

  In particular, in the configuration as shown in FIG. 3, it is necessary to insulate the power supply system in which the analog input terminal IN, which is the first stage of the circuit, has the reference potential GND1, and the power supply system in which the finally used analog amount AN has the reference potential GND2. When a small and inexpensive system is to be configured in a certain system, there is a means for making it possible to use a negative voltage with the variable voltage signal Vin by providing a negative power supply in a power supply system having a reference potential GND1. This is an obstacle to the purpose of miniaturization and low cost.

  For example, when the variable voltage signal Vin is such that the frequency of the pulse signal F1 that is the output of the voltage frequency converter 4 is 0.1 Hz, the pulse signal F2 that is electrically insulated from the pulse signal F1 is also 0.1 Hz. It becomes.

  When the pulse signal F2 is input to the pulse measuring unit 6, the pulse measuring unit 6 measures the pulse 1 cycle time T1 of the pulse signal F2, but since the frequency of the pulse signal F2 is 0.1 Hz, T1 is 10 seconds because it is determined by the reciprocal thereof. This means that it takes 10 seconds to obtain T1, and similarly, it takes 10 seconds until the analog quantity AN, which is the output of the analog quantity calculation unit having T1 as an input, is calculated. become.

  Now, although the case where the frequency of the pulse signal F2 is 0.1 Hz is taken up here, in principle, it takes time to detect only one period (T1) regardless of the frequency of the pulse signal F2.

  Therefore, in the system in which T1 is measured using the pulse measuring unit 6 in FIG. 3 and the variable voltage signal Vin is obtained as the analog amount AN by the analog amount calculating unit 7, the lower the variable voltage signal Vin is input to the pulse measuring unit 6. The frequency of the pulse signal F2 generated is low, and it takes time to obtain the input voltage of the variable voltage signal Vin, and there is a problem that the control response for changing the output of the power converter becomes slow.

  In addition, since the characteristic F (V) is determined as in (Equation 2), the frequency of the pulse signal F2 may take 0 Hz, and at this time, T1 determined by the reciprocal of the frequency of the pulse signal F2 becomes impossible to measure. Therefore, if the pulse 1 cycle time T1 of the pulse signal F2 cannot be measured even after waiting for an arbitrary time, it is necessary to stop the measurement and take a means for forcibly determining that the variable voltage signal Vin is 0V. This waiting time for an arbitrary time also causes a delay in control response.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a power conversion device that improves the response time with a simple configuration.

In order to achieve the above object, a first specific aspect of the present invention includes a forward conversion unit that converts AC power into DC power, a smoothing unit that smoothes the output of the forward conversion unit, and an output of the smoothing unit. An inverse conversion unit for converting to AC power, a control unit for controlling the inverse conversion unit, and a voltage frequency conversion unit for converting a voltage change of the input analog signal into a frequency change, from the voltage frequency conversion unit In the power converter in which the output is input to the control unit, and the output frequency is controlled by the output from the voltage frequency conversion unit,
A signal processing circuit that converts the first analog signal from the outside and outputs the second analog signal to the voltage frequency conversion unit in the previous stage of the voltage frequency conversion unit,
When the upper limit voltage of the first analog signal is input, the signal processing circuit outputs a lower limit voltage as the second analog signal, and when the lower limit voltage of the first analog signal is input, the signal processing circuit An upper limit voltage is output as a second analog signal.

  In addition, the apparatus having the above aspect is characterized in that the output frequency is set to zero when the upper limit voltage of the first analog signal is input.

Moreover, the 2nd specific aspect of this invention is the forward conversion part which converts alternating current power into direct-current power, the smoothing part which smoothes the output of this forward conversion part, and the output of this smoothing part is converted into alternating current power. An inverse conversion unit; a control unit that controls the inverse conversion unit; and a voltage frequency conversion unit that converts a voltage change of the input analog signal into a frequency change, and an output from the voltage frequency conversion unit is the control unit In the power conversion device in which the output frequency is controlled by the output from the voltage frequency conversion unit,
A signal processing circuit is provided in the previous stage of the voltage frequency converter,
In this signal processing circuit, an input portion of an analog signal input to the signal processing circuit is connected to the negative input terminal of the operational amplifier and the second resistor through the first resistor. The end is connected to the output of the operational amplifier,
The DC voltage source and the reference potential are divided by the third resistor and the fourth resistor, and the divided potential is inputted from the positive input terminal of the operational amplifier.
The output signal after the output from the signal processing circuit is processed by the voltage frequency converter has the following characteristics.

  ADVANTAGE OF THE INVENTION According to this invention, the power converter device which aimed at the improvement of response time with a simple structure can be provided.

  The present embodiment relates to a device that takes in a control signal by analog voltage input from the outside of the device, such as a power conversion device, and is a technology that provides function expansion and improved response.

  In the following embodiments, a method for detecting an analog voltage input value is described. However, the present invention can be applied even when an analog input from an external device is an analog current input value. In that case, for example, a conversion circuit such as a resistor or an operational amplifier for converting a current into a voltage is inserted between the analog input terminal IN and the conversion circuit 3 in FIG. 1 and is equivalent to the variable voltage signal Vin in FIG. It is possible to apply the control shown in the embodiment of the present invention after performing the conversion.

  Hereinafter, embodiments of the present invention for solving the above-described problems will be described with reference to the drawings.

  FIG. 1 shows a variable voltage signal Vin (first analog signal) as a voltage signal V1 (second analog signal) as a signal processing circuit between the analog input terminal IN and the voltage frequency converter 4 with respect to FIG. There is provided a conversion circuit unit 3 for converting into

  The conversion circuit unit 3 includes an operational amplifier OP1 and resistors R1, R2, R3, and R4. The conversion characteristic of the conversion circuit unit 3 is (Equation 3).

変換回路部３を導入することによって得られる可変電圧信号Ｖｉｎとパルス信号Ｆ１の周波数Ｆ（Ｖｉｎ）の関係を、（式２）、（式３）から導出すると（式４）となる。

When the relationship between the variable voltage signal Vin obtained by introducing the conversion circuit unit 3 and the frequency F (Vin) of the pulse signal F1 is derived from (Expression 2) and (Expression 3), (Expression 4) is obtained.

この周波数Ｆ（Ｖｉｎ）は、パルス信号Ｆ１の周波数となり、電気的絶縁部５を介しパルス信号Ｆ２の周波数となる。

This frequency F (Vin) becomes the frequency of the pulse signal F1 and becomes the frequency of the pulse signal F2 through the electrical insulating portion 5.

  When the pulse signal F2 is measured by the pulse measuring unit 6 in the same manner as in the prior art, a pulse one cycle time T1 of the frequency F (Vin) of the pulse signal F2 is obtained. The analog quantity calculation unit 7 calculates the F (Vin) by taking the reciprocal of this T1, and uses the inverse function of the characteristic function (Equation 4) from the point of the analog input terminal IN to the input point of the pulse measurement unit 6. The relationship between the variable voltage signal Vin and the analog quantity AN is uniquely determined.

  At this time, the relationship between the variable voltage signal Vin and the frequency F (Vin) of the pulse signal F1 is as shown in FIG.

  F (Vin) takes a value of 0 or more from the characteristics provided by the IC of FIG. From this, when the variable voltage signal Vin in FIG. 2 is Va {a point where F (Va) = 0}, the upper limit voltage of the variable voltage signal Vin is obtained, as shown in (Equation 5).

可変電圧信号Ｖｉｎが０の点でパルス信号の周波数Ｆ（０）は（式６）となる。

When the variable voltage signal Vin is 0, the frequency F (0) of the pulse signal becomes (Expression 6).

可変電圧信号Ｖｉｎの下限電圧をＶｂとすると、Ｖｂの点でのパルス信号の周波数Ｆ（Ｖｂ）は（式７）となる。

Assuming that the lower limit voltage of the variable voltage signal Vin is Vb, the frequency F (Vb) of the pulse signal at the point of Vb is (Equation 7).

この時、可変電圧信号Ｖｉｎの下限電圧Ｖｂは、図１中の変換回路部３の出力電圧信号Ｖ１の出力上限によって制限される。前述した様に、電圧信号Ｖ１は電圧周波数変換部４の入力電圧の為、図５の特性Ｆ（Ｖ）を提供可能とするＩＣによって電圧信号Ｖ１の上限値が決まる。該ＩＣはＩＣメーカや回路電源電圧Ｖｃｃ１等の設定によって変わってくるので、ここでは電圧信号Ｖ１の上限値をＶｃｃ１−Ｖｌｉｍと置く。ただし、一般に、Ｖｃｃ１−Ｖｌｉｍは該ＩＣの電源電圧Ｖｃｃ１未満に指定されるので、Ｖｌｉｍ＞０を満足するものとする。

At this time, the lower limit voltage Vb of the variable voltage signal Vin is limited by the output upper limit of the output voltage signal V1 of the conversion circuit unit 3 in FIG. As described above, since the voltage signal V1 is the input voltage of the voltage frequency converter 4, the upper limit value of the voltage signal V1 is determined by an IC that can provide the characteristic F (V) of FIG. Since the IC varies depending on the IC manufacturer, the circuit power supply voltage Vcc1, and the like, the upper limit value of the voltage signal V1 is set to Vcc1-Vlim here. However, in general, Vcc1−Vlim is specified to be less than the power supply voltage Vcc1 of the IC, so that Vlim> 0 is satisfied.

  This Vcc1-Vlim is substituted into (Expression 3), and Vin at that time, that is, Vb is expressed as (Expression 8).

ここで、Ｖｂ＜０となる様に抵抗器Ｒ１、Ｒ２、Ｒ３、Ｒ４の抵抗値、正の電源電圧Ｖｃｃ１、Ｖｌｉｍの値を選定すれば、可変電圧信号Ｖｉｎの下限電圧Ｖｂが負の電圧を取ることが可能となる。

Here, if the resistance values of the resistors R1, R2, R3, and R4 and the values of the positive power supply voltages Vcc1 and Vlim are selected so that Vb <0, the lower limit voltage Vb of the variable voltage signal Vin becomes a negative voltage. It becomes possible to take.

  The frequency F (Vb) of the pulse signal when the variable voltage signal Vin takes the lower limit voltage Vb is obtained from (Equation 7) and (Equation 8) (Equation 9).

図１の構成の様に、基準電位をＧＮＤ１とする回路部に供給する電源を単一の正電圧電源で構成しても、可変電圧信号Ｖｉｎを正負の電圧範囲で扱える様になり、図２の特性Ｆ（Ｖｉｎ）を得ることができるようになる。

As shown in FIG. 1, even if the power supplied to the circuit unit having the reference potential GND1 is constituted by a single positive voltage power supply, the variable voltage signal Vin can be handled in a positive and negative voltage range. Characteristic F (Vin) can be obtained.

  Further, the lower the voltage of the variable voltage signal Vin, the longer the time for detecting the analog amount AN, and the problems such as the slower control response for changing the output of the power converter can be solved.

  However, in the case of this embodiment, the higher the voltage of the variable voltage signal Vin, the longer the time for detecting the analog amount AN and the slower the control response, but the actual response of the variable voltage signal Vin. The upper limit of the use range may be set to be sufficiently lower than the value obtained from (Equation 5), and the control of this embodiment may be used within a range in which no control response delay or the like occurs.

  Further, as can be seen by comparing FIG. 1 and FIG. 3, compared to the conventional method, the operational amplifier OP1 can be configured by adding one circuit, resistors R1, R2, R3, R4 and a total of four elements. A small and inexpensive system can be provided.

  Specifically, the form of FIG. 1 or the form of FIG. 6 in which the electrical insulating portion 5 is omitted from FIG. 1 is suitable. The form of FIG. 1 and the form of FIG. 6 are implemented by selecting an appropriate form depending on the insulation form of the entire power converter.

  A more specific circuit diagram of the embodiment of FIG. 1 is shown in FIG.

  A variable voltage signal Vin having a reference potential GND1 is input to the conversion circuit unit 3, the conversion circuit unit 3 outputs a voltage signal V1 corresponding to the variable voltage signal Vin, and the voltage signal V1 is input to the voltage frequency conversion unit 4. The voltage frequency conversion unit 4 outputs a pulse signal F1 having a frequency corresponding to the voltage signal V1, the pulse signal F1 is input to the electrical insulation unit 5, and the electrical insulation unit 5 is the same as the pulse signal F1 whose reference potential is GND2. A frequency pulse signal F2 is output, and the pulse signal F2 is input to the microcomputer built-in function unit 8.

  In the pulse measuring unit 6 and the analog amount calculating unit 8 which are functions built in the microcomputer, first, the pulse measuring unit 6 measures the pulse 1 cycle time T1 of the pulse signal F2, and calculates the analog amount AN from the measured T1. It is an example.

  Here, the IC used for the voltage frequency converter 4 in FIG. 7 outputs the voltage input to the Vinput terminal as a pulse signal to the Fo terminal. Since the voltage frequency conversion characteristic coefficient when the voltage input to the Vinput terminal of this IC is converted to a pulse signal of an arbitrary frequency and output to the Fo terminal is defined by (Equation 10), the voltage frequency conversion unit The characteristic F (V) of 4 is expressed by (Equation 11).

また、同ＩＣのＶｉｎｐｕｔ端子の入力上限電圧は（Ｖｃｃ１−２）と定義されている為、電圧信号Ｖ１の上限電圧は（式１２）となる。

Further, since the input upper limit voltage of the Vinput terminal of the IC is defined as (Vcc1-2), the upper limit voltage of the voltage signal V1 is (Expression 12).

図７中の基準電位がＧＮＤ１の電源Ｖｃｃ１を１２Ｖ、基準電位がＧＮＤ２の電源Ｖｃｃ２を５Ｖ、抵抗器Ｒ１を２２ｋΩ、抵抗器Ｒ２を１０ｋΩ、抵抗器Ｒ３を２２ｋΩ、抵抗器Ｒ４を１０ｋΩとし、これら定数と（式１１）の関係を（式４）に代入すると、可変電圧信号Ｖｉｎとパルス信号Ｆ１の周波数Ｆ（Ｖｉｎ）の関係は（式１３）となる。

In FIG. 7, the power supply Vcc1 of the reference potential GND1 is 12V, the power supply Vcc2 of the reference potential GND2 is 5V, the resistor R1 is 22 kΩ, the resistor R2 is 10 kΩ, the resistor R3 is 22 kΩ, and the resistor R4 is 10 kΩ. If the relationship between the constant and (Equation 11) is substituted into (Equation 4), the relationship between the variable voltage signal Vin and the frequency F (Vin) of the pulse signal F1 becomes (Equation 13).

ここで、抵抗器ＲＳを１０ｋΩ、抵抗器ＲＢを１００ｋΩ、抵抗器Ｒｏを１０ｋΩ、コンデンサＣｏを０．００１μＦとし、（式１３）に代入すると、パルス信号Ｆ１の周波数Ｆ（Ｖｉｎ）は（式１４）となる。

Here, when the resistor RS is 10 kΩ, the resistor RB is 100 kΩ, the resistor Ro is 10 kΩ, the capacitor Co is 0.001 μF, and is substituted into (Equation 13), the frequency F (Vin) of the pulse signal F1 is expressed by (Equation 14). )

（式１４）からＦ（Ｖｉｎ）が０となる点の可変電圧信号Ｖｉｎの上限電圧Ｖａは、１２Ｖになり、可変電圧信号Ｖｉｎが０の点でパルス信号Ｆ１の周波数Ｆ（０）は約２７．３ｋＨｚとなり、可変電圧信号Ｖｉｎの下限電圧Ｖｂは（式８）に各定数と（式１２）を代入して求まり−１０Ｖ、この時のパルス信号Ｆ１の周波数Ｆ（Ｖｂ）は５０ｋＨｚとなる図２の特性が得られる。

The upper limit voltage Va of the variable voltage signal Vin at which F (Vin) is 0 from (Equation 14) is 12V, and the frequency F (0) of the pulse signal F1 is about 27 when the variable voltage signal Vin is 0. .3 kHz, the lower limit voltage Vb of the variable voltage signal Vin is obtained by substituting each constant and (Equation 12) into (Equation 8), and is -10 V, and the frequency F (Vb) of the pulse signal F1 at this time is 50 kHz. Two characteristics are obtained.

  Here, the frequency F (10) of the pulse signal F1 when the variable voltage signal Vin takes 10V is about 4.6 kHz. The pulse 1 cycle time T1 obtained by measuring the pulse signal F2 transmitted with the frequency of the pulse signal F1 by the pulse measuring unit 6 is obtained by the reciprocal of F (10), and is 0.22 milliseconds. Therefore, the time required to obtain the analog quantity AN is 0.22 milliseconds, and the time is sufficiently short to variably control the output of a general power converter, so that problems such as delay in control response do not occur. It can be said.

  Therefore, in the present embodiment, by utilizing the characteristics obtained here and defining the actual use range of the variable voltage signal Vin as a range from -10V to + 10V, it is applied to the circuit portion having the reference potential GND1. Even if the power source to be supplied is a single power source with a positive voltage, the variable voltage signal Vin can be handled even with a negative voltage, and a sufficient control response can be obtained.

Typical configuration diagram of this embodiment Voltage frequency conversion characteristic diagram obtained by this embodiment Typical configuration diagram using conventional technology Input / output characteristics obtained by conventional technology Conversion characteristics diagram of general IC for voltage frequency conversion Modification of this embodiment Typical circuit example of this embodiment

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vin input part, 2 ... Reference potential part of Vin, 3 ... Conversion circuit part which converts Vin into V1, 4 ... Voltage frequency conversion part, 5 ... Electrical insulation part, 6 ... Pulse measurement part, 7 ... Analog quantity Calculation unit, 8 ... Part of microcomputer built-in function having functions of pulse measurement unit 6 and analog quantity calculation unit 7, 9 ... (synonymous with IC) General IC (VF converter) having voltage frequency conversion function, 10 ... Photo Coupler, AN ... analog amount, ANref ... arbitrary and known analog amount AN, CB ... capacitor, Ci ... capacitor, Co ... capacitor and capacitance value determining IC (VF converter) characteristics, F1 ... pulse signal, F2 ... Pulse signal, Fo ... IC (VF converter) pulse signal output terminal, F (V) ... Voltage frequency function, Fref ... Arbitrary reference frequency value of voltage frequency converter, GND1 ... Reference 1, GND 2... Reference potential 2, IC... (Synonymous with 9) general IC (VF converter) having voltage frequency conversion function, IN... Analog input terminal, OP 1... Operational amplifier, R 1. R2 ... second resistor and resistance value, R3 ... third resistor and resistance value, R4 ... fourth resistor and resistance value, R5 ... resistor, R6 ... resistor, RB ... IC (VF converter) ) Resistors and resistance values for determining the characteristics of Ri, resistors, resistors for determining the characteristics of Ro (IC converter) and resistors for determining the characteristics of RS (IC converter), T1... One cycle time of pulse, V... F (V) argument, analog voltage value input to voltage frequency conversion unit 4, V1... Output of conversion circuit unit 3, analog voltage input to voltage frequency conversion unit 4. Value, Va ... Vin Effective range upper limit value, Vb ... Vin effective range lower limit value, Vcc1 ... DC voltage source and voltage value with reference potential GND1, Vcc2 ... DC voltage source and voltage value with reference potential GND2, Vin ... Variable voltage signal, Vinput: voltage input terminal of IC (VF converter), Vinref: value of arbitrary and known variable voltage signal Vin, Vlim: allowable input upper limit value of Vin determined by IC (VF converter), Vref: arbitrary voltage frequency conversion unit 4 Reference voltage value for.

Claims (3)

A forward converter that converts AC power into DC power, a smoother that smoothes the output of the forward converter, an inverse converter that converts the output of the smoother to AC power, and a control that controls the inverse converter And a voltage frequency conversion unit that converts a voltage change of the input analog signal into a frequency change, and an output from the voltage frequency conversion unit is input to the control unit, and an output from the voltage frequency conversion unit In the power conversion device in which the output frequency is controlled,
A signal processing circuit that converts the first analog signal from the outside and outputs the second analog signal to the voltage frequency conversion unit in the previous stage of the voltage frequency conversion unit,
When the upper limit voltage of the first analog signal is input, the signal processing circuit outputs a lower limit voltage as the second analog signal, and when the lower limit voltage of the first analog signal is input, the signal processing circuit A power converter that outputs an upper limit voltage as a second analog signal.   The power converter according to claim 1, wherein the output frequency is set to zero when an upper limit voltage of the first analog signal is input. A forward converter that converts AC power into DC power, a smoother that smoothes the output of the forward converter, an inverse converter that converts the output of the smoother to AC power, and a control that controls the inverse converter And a voltage frequency conversion unit that converts a voltage change of the input analog signal into a frequency change, and an output from the voltage frequency conversion unit is input to the control unit, and an output from the voltage frequency conversion unit In the power conversion device in which the output frequency is controlled,
A signal processing circuit is provided in the previous stage of the voltage frequency converter,
In this signal processing circuit, an input portion of an analog signal input to the signal processing circuit is connected to the negative input terminal of the operational amplifier and the second resistor through the first resistor. The end is connected to the output of the operational amplifier,
The DC voltage source and the reference potential are divided by the third resistor and the fourth resistor, and the divided potential is inputted from the positive input terminal of the operational amplifier.
The output signal after the output from the signal processing circuit is processed by the voltage frequency converter has the following characteristics.

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