JP2017041997A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device which can obtain an output current with high accuracy even in a small current region.SOLUTION: A power conversion device 1, which includes a switching circuit 11, a transformer T, a rectifier circuit 13 and a smoothing circuit 15, further includes: a calculation unit 172 which obtains an output current Iout on the basis of the number of turns Np of the primary winding T1 of the transformer T, the number of turns Ns of the secondary winding T2 of the transformer T, a load current Ip which flows from the switching circuit 11 to the primary winding T1 of the transformer T, and an excitation current Im generated at the primary winding T1 of the transformer T; and a drive unit 18 which controls to drive the switching circuit 11 on the basis of the duty ratio D of a voltage Vp, which is obtained from the output current Iout by the calculation unit 172 and an output voltage Vout output from the smoothing circuit 15, and applied to the primary winding T1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device.

  Conventionally, various sensors that provide an input voltage on the input side of the power supply without providing a current detection unit on the output side of the power supply and obtain the output voltage based on the detected input voltage have been proposed (for example, (See Patent Documents 1 and 2).

  Further, for example, in order to obtain the output current based on the detection result of the current sensor installed on the input side of the power source, the input voltage sensor and the detection result of the output voltage sensor are used, or calculated by a DSP or the like Some use duty values.

Japanese Patent No. 555571 JP 2012-90406 A JP-A-2015-89192

  However, the prior art described above does not take into account the excitation current flowing through the transformer in any case. Therefore, no consideration is given to the fact that the current flowing on the secondary side of the transformer is reduced by the excitation current. Therefore, in the conventional technique, in the case of the large current region, even if the output current is obtained from the load current, a large error does not occur, but in the case of the small current region, the accuracy of the output current is deteriorated. It was.

  This invention is made | formed in view of this situation, The objective is to provide the power converter device which can obtain | require an output current accurately even if it is a small electric current area | region.

  A power converter according to the present invention includes a switching circuit that converts direct current to alternating current, a transformer connected to the switching circuit, and an output current that is provided on the secondary side of the transformer and is generated in the secondary winding of the transformer. And a smoothing circuit for smoothing the current rectified by the rectifier circuit, the number of turns of the primary winding of the transformer, and the secondary winding of the transformer Based on the number of turns, the load current flowing from the switching circuit to the primary winding of the transformer, and the excitation current generated in the primary winding of the transformer, the calculation unit for obtaining the output current, and the calculation unit Control of the driving of the switching circuit based on the duty ratio of the voltage applied to the primary winding obtained from the current and the output voltage output from the smoothing circuit It is characterized in further comprising a that driver.

  According to the power conversion device of the present invention, the output current can be accurately obtained even in a small current region.

  Further, in the power conversion device according to the present invention, when the calculation unit obtains the output current from the number of turns of the primary winding, the number of turns of the secondary winding, the load current, and the excitation current, the switching circuit Preferably, the exciting current is obtained based on an input voltage input to the first inductor, an exciting inductor generated in parallel with the inductor of the primary winding, and the duty ratio.

  According to this power conversion device, the output current Iout can be obtained particularly remarkably accurately in all current regions from the small current region to the large current region.

  Further, in the power conversion device according to the present invention, a current transformer provided on the primary winding side of the transformer for detecting the load current and an input voltage provided on the input side of the switching circuit for detecting the input voltage. When the excitation current is obtained based on the input voltage, the excitation inductor, and the duty ratio by the detection unit and the calculation unit, the characteristic value of the current transformer and the input voltage detection unit are detected. It is preferable that the apparatus further includes a current correction unit that linearly corrects a correlation between the input voltage and the load current based on the input voltage that has been detected and the load current detected by the current transformer.

  According to this power converter, the current value detected by the current transformer can be corrected by an inexpensive and easy method.

  According to the present invention, when the output current is obtained from the load current, the fluctuation due to the excitation current is reflected in the output current flowing on the secondary side of the transformer by considering the excitation current. Thus, it is possible to provide a power conversion device that can obtain the output current with high accuracy.

It is a figure which shows the structural example of the power converter device 1 which concerns on 1st Embodiment. It is a figure explaining the exciting current Im which arises in the trans | transformer T which concerns on 1st Embodiment. It is a flowchart explaining the control example of the power converter device 1 which concerns on 1st Embodiment. It is a figure explaining an example of the various waveforms which arise on the primary side and the secondary side of transformer T concerning a 1st embodiment. It is a figure explaining the detail of the waveform of the exciting current Im which concerns on 1st Embodiment. It is a figure which shows the structural example of the power converter device 1 which concerns on 2nd Embodiment. It is a flowchart explaining the example of control of the power converter device 1 which concerns on 2nd Embodiment. It is a figure which shows an example of the measured value and calculated value of the electric current and voltage from the micro electric current area | region A which concern on 2nd Embodiment to the steady current area | region B. FIG. It is a figure which shows an example of the specific measurement point of the electric current from the micro electric current area | region A which concerns on 2nd Embodiment, and the steady current area | region B, and a voltage. It is a figure which shows the structural example of the power converter device 1 which concerns on 3rd Embodiment. It is a figure which shows the structural example of the power converter device 1 which concerns on 4th Embodiment.

<First Embodiment>
FIG. 1 is a diagram illustrating a configuration example of a power conversion device 1 according to the first embodiment. As shown in FIG. 1, the power conversion device 1 includes a switching circuit 11, a transformer T connected to the switching circuit 11, a rectifier circuit 13 provided on the secondary side of the transformer T, and a smoothing circuit 15. In addition, the power conversion device 1 includes a control unit 17 and a drive unit 18. Further, the power conversion device 1 includes a current transformer CT, an input voltage detection unit 21, and an output voltage detection unit 25.

  A capacitor C1 is connected in parallel to the input side of the switching circuit 11. The capacitor C1 is provided with a DC power supply 2 via a fuse 3. A load 4 is connected to the output side of the smoothing circuit 15.

  The DC power source 2 is a high-voltage power source, and is composed of, for example, an assembled battery to which a plurality of cells are connected, and is mounted on a vehicle. Note that the DC power source 2 may be any device that supplies a stable DC voltage such as a primary battery or a secondary battery.

  The switching circuit 11 converts direct current into alternating current, and specifically includes a plurality of switching elements Q1 to Q4. Each of the plurality of switching elements Q1 to Q4 functions as, for example, a full-bridge inverter composed of an optical MOSFET. The switching circuit 11 converts the DC voltage supplied from the DC power supply 2 into an AC voltage and supplies it to the transformer T by alternately turning on the switching elements Q1 and Q4 and the switching elements Q2 and Q3.

  The switching element Q1 and the switching element Q2 are connected in series, and the switching element Q3 and the switching element Q4 are connected in series. However, the elements connected in series do not turn on at the same time. In addition, the turn-on timing has been adjusted.

  Each of the plurality of switching elements Q1 to Q4 includes a parasitic diode and a parasitic capacitance.

  In the transformer T, the primary winding T1 is wound on the primary side, and the secondary winding T2 is wound on the secondary side. The rectifier circuit 13 rectifies the current generated in the secondary winding T2 of the transformer T. The rectifier circuit 13 includes, for example, a switching element Q5 and a switching element Q6. Each of the switching elements Q5 and Q6 is made of, for example, an optical MOSFET. Each of switching elements Q5 and Q6 includes a parasitic diode and a parasitic capacitance.

  The smoothing circuit 15 smoothes the current rectified by the rectifier circuit 13, and includes a smoothing inductor L1 and an output capacitor C2. The smoothing inductor L1 is connected to the center tap side of the transformer T. The output capacitor C <b> 2 is connected between the smoothing inductor L <b> 1 and the rectifier circuit 13, and supplies the output voltage Vout of the smoothing circuit 15 to the load 4.

  The input voltage detection unit 21 is provided on the input side of the switching circuit 11 and detects the input voltage Vin. The output voltage detector 25 is provided on the output side of the output capacitor C2, and detects the output voltage Vout. The current transformer CT is provided on the primary winding T1 side of the transformer T and detects the load current Ip.

  The control part 17 controls the drive part 18, for example, is comprised mainly by a microcomputer. The control unit 17 includes an absolute value circuit 171 and a calculation unit 172. The absolute value circuit 171 takes the absolute value of the detection result of the current transformer CT and supplies the result to the calculation unit 172.

  The calculation unit 172 includes the number of turns Np of the primary winding T1 of the transformer T, the number of turns Ns of the secondary winding T2 of the transformer T, the load current Ip flowing from the switching circuit 11 to the primary winding T1 of the transformer T, and the transformer T The output current Iout is obtained based on the excitation current Im generated in the primary winding T1.

  When calculating the output current Iout from the number of turns Np of the primary winding T1, the number of turns Ns of the secondary winding T2, the load current Ip, and the excitation current Im, the calculation unit 172 includes the input voltage Vin input to the switching circuit 11; The exciting current Im is obtained based on the exciting inductor Lm generated in parallel with the inductor of the primary winding T1 and the duty ratio D of the voltage Vp applied to the primary winding T1.

  When calculating the excitation current Im, the calculation unit 172 calculates the duty ratio D based on the output current Iout and the output voltage Vout, and the output current setting value and the output voltage setting value.

  The drive unit 18 includes a pulse generation unit 181 and a drive circuit 182, and the voltage Vp applied to the primary winding T1 obtained from the output current Iout and the output voltage Vout output from the smoothing circuit 15 by the calculation unit 172. The driving of the switching circuit 11 is controlled based on the duty ratio D. The pulse generation unit 181 generates a pulse signal based on the duty ratio D, and supplies the generated pulse signal to the drive circuit 182. The drive circuit 182 controls the driving of the gates of the switching elements Q1 to Q4 based on the pulse signal supplied from the pulse generator 181.

  Next, the load current Ip and the excitation current Im will be specifically described with reference to FIG. FIG. 2 is a diagram for explaining the excitation current Im generated in the transformer T according to the first embodiment. The load current Ip ′ flowing through the primary winding T1 of the transformer T and the load current Is generated in the secondary winding T2 of the transformer T are the number of turns Np of the primary winding T1 and the number of turns Ns of the secondary winding T2. And is represented by the following formula (1).

  In the equation (1), the load current Ip ′ flowing through the primary winding T1 of the transformer T is expressed by the following equation (2) using the load current Ip flowing through the primary winding T1 of the transformer T and the excitation current Im. Is done.

  Therefore, from the expressions (1) and (2), the load current Is generated in the secondary winding T2 of the transformer T is expressed by the following expression (3).

  The magnitude of the output current Iout flowing through the load 4 is the same as the average value of the load current Is flowing through the smoothing circuit 15. Therefore, if the excitation current Im can be accurately obtained, the accurate magnitude of the output current Iout can be obtained from the load current Ip flowing through the primary winding T1 of the transformer T.

  Next, details of the calculation process of the excitation current Im and the output current Iout will be described with reference to FIGS. 4 and 5 while describing a control example of the power conversion apparatus 1 with reference to FIG. FIG. 3 is a flowchart for explaining a control example of the power conversion apparatus 1 according to the first embodiment. FIG. 4 is a diagram illustrating examples of various waveforms generated on the primary side and the secondary side of the transformer T according to the first embodiment. FIG. 5 is a diagram for explaining the details of the waveform of the excitation current Im according to the first embodiment.

(Step S11)
The calculation unit 172 calculates the excitation current Im based on the input voltage Vin, the excitation inductor Lm, and the duty ratio D.

(Step S12)
The calculation unit 172 obtains the output current Iout based on the number of turns Np of the primary winding T1, the number of turns Ns of the secondary winding T2, the load current Ip, and the excitation current Im.

  The output current Iout is a current on the secondary side of the transformer T, that is, a current obtained by smoothing the load current Is generated in the secondary winding T2 of the transformer T by the smoothing circuit 15, and is equal to the average value of the load current Is. Is represented by the following equation (4).

  Therefore, the following equation (5) is derived from the equations (3) and (4).

  Therefore, the output current Iout is expressed by the following equation (6) derived from the following equation (5), the current on the primary side of the transformer T, that is, the load current Ip flowing through the primary winding T1 of the transformer T. Is obtained from the average value of the values passed through the absolute value circuit 171 and the average value of the absolute values of the excitation current Im.

  The average absolute value of the load current Ip is detectable by the circuit configuration of the power conversion device 1. On the other hand, the average value of the absolute values of the excitation current Im is expressed by the following equation (7).

  The absolute value waveform of the exciting current Im is a trapezoidal wave as shown in FIG. The amplitude of the excitation current Im is expressed by the following equation (8).

  The duty ratio D shown in the equation (8) is a ratio of the power transmission period as shown in the following equation (9), and is as shown in FIG. From the above formulas (7) to (9), the average value of the absolute values of the excitation current Im is obtained as represented by the following formula (10).

  As a result, the output current Iout is obtained by subtracting the average value of the excitation current Im from the average value of the absolute value of the load current Ip, as shown in the equations (4) to (6). Is obtained by weighting the turn ratio.

  The duty ratio D is obtained by the calculation unit 172. As shown in the following equation (11), the duty ratio D of the input voltage Vin, the output voltage Vout, the number of turns Np, and the number of turns Ns Can also be obtained.

(Step S13)
The drive unit 18 controls the drive of the switching circuit 11 based on the duty ratio D obtained from the output current Iout and the output voltage Vout.

  In addition, the process which calculates the output electric current Iout is performed by the process of step S11 and step S12. Further, the drive control process is executed by the process of step S13.

  From the above description, in the first embodiment, the power conversion device 1 is based on the number of turns Np of the primary winding T1, the number of turns Ns of the secondary winding T2, the load current Ip, and the excitation current Im. The output current Iout is obtained. Thereby, since the exciting current Im is taken into consideration, the output current Iout is obtained with high accuracy.

  In other words, when the power conversion device 1 obtains the output current Iout from the load current Ip, the fluctuation due to the excitation current Im is reflected in the output current Iout flowing on the secondary side of the transformer T by considering the excitation current Im. Therefore, the output current Iout can be accurately obtained even in a small current region.

  Specifically, when determining the output current Iout, the power converter 1 determines the excitation current Im based on the input voltage Vin, the excitation inductor Lm, and the duty ratio D of the voltage Vp applied to the primary winding T1. Ask for. Thereby, the excitation current Im is obtained by calculation. On the other hand, the load current Ip can be detected via the current transformer 23. Therefore, the output current Iout obtained based on the load current Ip as the detection result and the excitation current Im as the calculation result is calculated particularly remarkably with high accuracy. Therefore, the power conversion device 1 can obtain the output current Iout particularly remarkably accurately in all current regions from the small current region to the large current region.

  As described above, the power conversion device 1 according to the first embodiment includes the switching circuit 11 that converts direct current into alternating current, the transformer T connected to the switching circuit 11, and the secondary side of the transformer T. The power converter device 1 includes a rectifier circuit 13 that rectifies an output current Iout generated in a secondary winding T2, and a smoothing circuit 15 that smoothes a current rectified by the rectifier circuit 13, and includes a primary winding of a transformer T. The number of turns Np of the line T1, the number of turns Ns of the secondary winding T2 of the transformer T, the load current Ip flowing from the switching circuit 11 to the primary winding T1 of the transformer T, and the exciting current Im generated in the primary winding T1 of the transformer T Is calculated from the output current Iout and the output voltage Vout output from the smoothing circuit 15 by the calculation unit 172 that calculates the output current Iout. Based on the duty ratio D of the voltage Vp applied to the primary winding T1, in which and a driving unit 18 for controlling the driving of the switching circuit 11.

  With such a configuration, the power conversion device 1 can obtain the output current Iout with high accuracy even in a small current region.

  In the power conversion device 1 according to the first embodiment, the calculation unit 172 calculates the output current Iout based on the number of turns Np of the primary winding T1, the number of turns Ns of the secondary winding T2, the load current Ip, and the excitation current Im. When obtaining, the exciting current Im is obtained based on the input voltage Vin input to the switching circuit 11, the exciting inductor Lm generated in parallel with the inductor of the primary winding T1, and the duty ratio D.

  With such a configuration, the power conversion device 1 can obtain the output current Iout particularly remarkably accurately in all current regions from the small current region to the large current region.

<Second Embodiment>
FIG. 6 is a diagram illustrating a configuration example of the power conversion device 1 according to the second embodiment. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The circuit configuration different from that of the first embodiment is provided with a current detection unit 27 to which the detection result of the current transformer CT is transmitted, and a current correction unit 174 is provided between the current detection unit 27 and the absolute value circuit 171. It is a point.

Although the current transformer CT is provided as a circuit configuration for detecting current, in the minute current region A, the ratio of the core exciting current Im _{CT to} the output current Iout on the secondary side of the current transformer CT becomes large. As a result, the output linearity when detecting the current may be reduced.

  Therefore, in the power conversion device 1 according to the second embodiment, the detected current value is easily and inexpensively corrected. Specifically, the current correction unit 174 of FIG. 6 is based on the characteristic value of the current transformer CT, the input voltage Vin detected by the input voltage detection unit 21, and the load current Ip detected by the current transformer CT. The correlation between the input voltage Vin and the load current Ip is linearly corrected.

  Next, a control example including a correction process for the detected current value will be described with reference to FIG. 7, and details of the correction process will be described with reference to FIGS. 8 and 9. FIG. 7 is a flowchart illustrating a control example of the power conversion device 1 according to the second embodiment. FIG. 8 is a diagram illustrating an example of measured values and calculated values of current and voltage from the minute current region A to the steady current region B according to the second embodiment. FIG. 9 is a diagram illustrating an example of specific measurement points of current and voltage from the minute current region A to the steady current region B according to the second embodiment.

(Step S31)
The current correction unit 174 determines whether or not the correlation between the load current Ip and the input voltage Vin is linearly corrected. If the correlation between the load current Ip and the input voltage Vin is linearly corrected, the process proceeds to step S33. On the other hand, when the correlation between the load current Ip and the input voltage Vin is not linearly corrected, the process proceeds to step S32.

(Step S32)
The current correction unit 174 linearly corrects the correlation between the load current Ip and the input voltage Vin. Specifically, the correlation between the voltage value detected by the input voltage detection unit 21 and the current value detected by the current detection unit 27 is obtained as shown in FIG. The detected voltage value and the detected current value can be approximated to a linear function characteristic having two slopes. Here, as shown in FIG. 8, the characteristics of the detected voltage value and current value are divided into the minute current region A and the steady current region B, and the correction coefficient k1 described later is divided into the minute current region A and the steady current region B. , K2, a1, and a2 are prepared, and correction processing is executed.

  More specifically, the calculated value is represented by a linear function as in the following equation (12), and the measured value is represented by a linear function as in the following equations (13) and (14). Of these, the following equation (13) corresponds to the minute current region A, and the following equation (14) corresponds to the steady current region B.

  Here, x represents current, y represents voltage value obtained by calculation, and y1 and y2 represent measured voltage values. The correction coefficient k is obtained from the characteristics of the current transformer CT, and the values of the correction coefficients k1, k2, a1, and a2 are obtained from the measured values.

  As shown in FIG. 8, when correction is performed separately for the minute current region A and the steady current region B, they are expressed as shown in the following equations (15) and (16).

  Next, the derivation of the correction coefficients k1, k2, a1, and a2 will be described with reference to FIG. As shown in FIG. 9, it is assumed that three measurement points are obtained. Measurement points (X1, Y1), (X2, Y2) satisfy equation (13), and measurement points (X2, Y2), (X3, Y3) satisfy equation (14). Thereby, the thing corresponding to the minute electric current area | region A is represented by following Formula (17). Therefore, the correction coefficients k1 and a1 are obtained by deriving the following expressions (18) and (19) from the following expression (17). On the other hand, the thing corresponding to the steady current area | region B is represented by following Formula (20). Therefore, the correction coefficients k2 and a2 are obtained by deriving the following expressions (21) and (22) from the following expression (20).

(Step S33)
The calculation unit 172 performs output current calculation processing. The output current calculation process is the process of steps S11 and S12 described above.

(Step S34)
The drive unit 18 executes a drive control process. The drive control process is the process of step S13 described above.

  The current correction process is executed by the processes in steps S31 and S32.

From the above description, in the second embodiment, the power conversion device 1 ensures linearity between the load current Ip and the input voltage Vin. Specifically, when the load current Ip is detected via the current transformer CT, the detection accuracy of the load current Ip depends on the characteristics of the current transformer CT. The current transformer CT is easily affected by the excitation current Im _{CT in} a small current region, particularly in the minute current region A. That is, if the load current Ip flowing on the primary side of the current transformer CT corresponds to the minute current region A, the current generated on the secondary side of the current transformer CT is the ratio of the excitation current Im _CT generated on the current transformer CT. Becomes larger.

  Therefore, the power conversion device 1 determines the characteristic value of the current transformer CT, the input voltage Vin detected by the input voltage detection unit 21, and the load detected by the current transformer CT when the calculation unit 172 calculates the excitation current Im. Based on the current Ip, the correlation between the input voltage Vin and the load current Ip is corrected linearly.

  Specifically, as described above, the power conversion device 1 uses the correction coefficients k1, k2, a1 obtained from the characteristics of the current transformer CT in the measured values of the minute current region A and the steady current region B, respectively. , A2 and a correction coefficient k obtained from the characteristics of the current transformer CT in the calculated values of the entire current region, the current value detected by the current transformer CT is corrected by an inexpensive and easy method. be able to.

  By doing in this way, the power converter device 1 can correct | amend with sufficient precision with respect to the shift | offset | difference from a calculated value in the micro electric current area | region A. Moreover, since the power converter device 1 corrects the current value by a process in the microcomputer and does not require an additional circuit, the cost can be reduced. Furthermore, since the correction coefficients k, k1, k2, a1, and a2 can be changed by software, it is possible to perform correction according to variations in the current transformer CT.

  As described above, the power conversion device 1 according to the second embodiment is provided on the primary winding T1 side of the transformer T, is provided on the input side of the switching circuit 11 and the current transformer CT that detects the load current Ip. When the excitation voltage Im is determined based on the input voltage Vin, the excitation inductor Lm, and the duty ratio D by the input voltage detection unit 21 that detects Vin and the calculation unit 172, the characteristic value of the current transformer CT, A current correction unit 174 that linearly corrects the correlation between the input voltage Vin and the load current Ip based on the input voltage Vin detected by the input voltage detection unit 21 and the load current Ip detected by the current transformer CT; Is further provided.

  With such a configuration, the current value detected by the current transformer CT can be corrected by an inexpensive and easy method.

<Third Embodiment>
FIG. 10 is a diagram illustrating a configuration example of the power conversion device 1 according to the third embodiment. In the third embodiment, the same components as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 10, the current transformer CT is provided on the input side of the switching circuit 11. When there is a difference between the calculated value and the measured value in the minute current region A due to the influence of the excitation current Im _CT on the secondary side of the current transformer CT, the measured current value and the measured voltage value are corrected by the correction coefficients k, k1, What is necessary is just to correct | amend using k2, a1, and a2. Therefore, the position where the current is detected is not particularly limited, and may be a position as shown in FIG.

  As described above, the power conversion device 1 according to the third embodiment is provided on the input side of the switching circuit 11 and is provided on the input side of the switching circuit 11 and the current transformer CT that detects current, and detects the input voltage Vin. When the excitation current Im is obtained based on the input voltage Vin, the excitation inductor Lm, and the duty ratio D by the input voltage detection unit 21 and the calculation unit 172, the characteristic value of the current transformer CT and the input voltage detection unit And a current correction unit 174 that linearly corrects the correlation between the input voltage Vin and the current based on the input voltage Vin detected by the current transformer 21 and the current detected by the current transformer CT.

  With such a configuration, the current value detected by the current transformer CT can be corrected by an inexpensive and easy method.

<Fourth Embodiment>
FIG. 11 is a diagram illustrating a configuration example of the power conversion device 1 according to the fourth embodiment. In the fourth embodiment, the same components as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 11, the current transformer CT is provided on the output side of the smoothing circuit 15. When there is a difference between the calculated value and the measured value in the minute current region A due to the influence of the excitation current Im _CT on the secondary side of the current transformer CT, the measured current value and the measured voltage value are corrected by the correction coefficients k, k1, What is necessary is just to correct | amend using k2, a1, and a2. Therefore, the position where the current is detected is not particularly limited, and may be a position as shown in FIG.

  As described above, the power conversion device 1 according to the fourth embodiment is provided on the output side of the smoothing circuit 15 and is provided on the input side of the current transformer CT and the switching circuit 11 that detects current, and detects the input voltage Vin. When the excitation current Im is obtained based on the input voltage Vin, the excitation inductor Lm, and the duty ratio D by the input voltage detection unit 21 and the calculation unit 172, the characteristic value of the current transformer CT and the input voltage detection unit And a current correction unit 174 that linearly corrects the correlation between the input voltage Vin and the current based on the input voltage Vin detected by the current transformer 21 and the current detected by the current transformer CT.

  With such a configuration, the current value detected by the current transformer CT can be corrected by an inexpensive and easy method.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention.

  For example, in the first embodiment, the switching circuit 11 is a full-bridge inverter including four switching elements Q1 to Q4. However, the configuration is not limited to this, and any circuit configuration that realizes the function of the inverter may be used.

  In addition, in the second embodiment, an example has been described in which the linearity between the load current Ip and the input voltage Vin is ensured by the correction processing divided into the two regions of the minute current region A and the steady current region B. However, the present invention is not limited to this, and correction processing divided into three or more regions may be performed.

1: Power converter 2: DC power supply 3: Fuse 4: Load 11: Switching circuit 13: Rectifier circuit 15: Smoothing circuit 17: Control part 18: Drive part 21: Input voltage detection part 25: Output voltage detection part 27: Current Detection unit 171: Absolute value circuit 172: Calculation unit 174: Current correction unit 181: Pulse generation unit 182: Drive circuit

Claims (3)

A switching circuit that converts direct current to alternating current;
A transformer connected to the switching circuit;
A rectifier circuit provided on the secondary side of the transformer and rectifying an output current generated in the secondary winding of the transformer;
A power supply device comprising a smoothing circuit for smoothing the current rectified by the rectifier circuit,
Based on the number of turns of the primary winding of the transformer, the number of turns of the secondary winding of the transformer, the load current flowing from the switching circuit to the primary winding of the transformer, and the exciting current generated in the primary winding of the transformer A calculation unit for obtaining the output current;
A driving unit that controls driving of the switching circuit based on a duty ratio of a voltage applied to the primary winding obtained from the output current and an output voltage output from the smoothing circuit by the arithmetic unit; A power conversion device comprising: The computing unit is
When obtaining the output current from the number of turns of the primary winding, the number of turns of the secondary winding, the load current, and the excitation current,
2. The electric power according to claim 1, wherein the exciting current is obtained based on an input voltage inputted to the switching circuit, an exciting inductor generated in parallel with an inductor of the primary winding, and the duty ratio. Conversion device. A current transformer provided on the primary winding side of the transformer for detecting the load current;
An input voltage detector provided on the input side of the switching circuit for detecting the input voltage;
When the exciting current is obtained by the arithmetic unit based on the input voltage, the exciting inductor, and the duty ratio, a characteristic value of the current transformer and the input detected by the input voltage detecting unit The current correction unit according to claim 2, further comprising a current correction unit that linearly corrects a correlation between the input voltage and the load current based on a voltage and the load current detected by the current transformer. The power converter described.