JP2020072605A - Power conversion device - Google Patents

Abstract

To obtain a power converter capable of suppressing a variation in an output limit start current corresponding to an output current when an output limit is started.SOLUTION: The power conversion device includes: a power converter; a control unit for controlling the power converter; and an offset circuit for obtaining an offset voltage based on an input voltage detected by an input voltage detection unit and an output voltage detected by an output voltage detection unit. The control unit is configured to limit an output based on an offset voltage, a detection voltage corresponding to an input current detected by an input current detection unit, and a threshold voltage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device.

  In recent years, electric vehicles and hybrid vehicles such as HEVs (Hybrid Electric Vehicles) and PHEVs (Plug-in Hybrid Electric Vehicles) have been developed as eco-friendly vehicles. Such an automobile is equipped with a drive battery that drives an electric motor for traveling with the charged electric power, in addition to a battery for an auxiliary machine that operates a control circuit. In the field of such automobiles, with the progress of power electronics technology, there is an urgent need to improve the reliability of power conversion devices.

  As an example of the above-described power conversion device, there is a power conversion device that is equipped with an output limiting function that lowers the output voltage when the output current needs to be equal to or higher than the rated current due to load fluctuation (for example, Patent Document 1). reference). This output limiting function reduces the output voltage output from the power converter to prevent overcurrent from flowing into the power converter itself or from flowing into an external device connected to the power converter. This is a function for suppressing.

  The power conversion device described in Patent Document 1 obtains an offset voltage based on a detected value of an input voltage that is input, and adds the obtained offset voltage to a detected voltage that corresponds to a detected value of an input current that is input. Is calculated. In addition, the power conversion device is configured to compare the obtained correction detection voltage and the threshold voltage, and perform output limitation when the correction detection voltage is equal to or higher than the threshold voltage as a result of the comparison. Specifically, this power converter reduces the output voltage by reducing the reactor current flowing in the smoothing reactor by turning off all the switching elements of the inverter circuit as an output limit.

JP, 2016-226225, A

  However, the related art has the following problems. That is, in the conventional technique described in Patent Document 1, since the offset voltage is obtained based only on the input voltage, the output current at the time when the above-mentioned output limitation is started is caused by the fluctuation of parameters other than the input voltage. The corresponding output limit start current fluctuates.

  The present invention has been made to solve the above problems, and obtains a power conversion device capable of suppressing a variation in the output limit start current corresponding to the output current when the output limit is started. The purpose is to

  The power converter in the present invention includes an inverter circuit that converts an input DC voltage into an AC voltage, a transformer that transforms the AC voltage converted by the inverter circuit, a rectifier circuit that rectifies the AC voltage transformed by the transformer, and a smoothing reactor. From a smoothing circuit that smoothes the output of the rectifier circuit, an input current detection unit that detects the input current input to the inverter circuit, an input voltage detection unit that detects the input voltage input to the inverter circuit, and a smoothing circuit. A power converter having an output voltage detector that detects the output voltage that is output, a controller that controls the power converter, an input voltage detected by the input voltage detector, and an output detected by the output voltage detector. An offset circuit that obtains an offset voltage based on the voltage and Based on the offset voltage generated, the detection voltage corresponding to the input current detected by the input current detection unit, and the threshold voltage, the inverter circuit is controlled to reduce the reactor current flowing in the smoothing reactor to reduce the output voltage. This is to limit the output to be lowered.

  The power converter in the present invention includes an inverter circuit that converts an input DC voltage into an AC voltage, a transformer that transforms the AC voltage converted by the inverter circuit, a rectifier circuit that rectifies the AC voltage transformed by the transformer, and a smoothing reactor. And a power converter having a smoothing circuit for smoothing the output of the rectifier circuit, and an input current detector for detecting an input current input to the inverter circuit, a controller for controlling the power converter, and a power converter. The temperature detection unit that detects the temperature as a target temperature, and an offset circuit that determines an offset voltage based on the target temperature detected by the temperature detection unit, and the control unit includes an offset voltage that is determined by the offset circuit. , Based on the detection voltage corresponding to the input current detected by the input current detection unit and the threshold voltage And performs output restriction to decrease the output voltage outputted from the smoothing circuit by reducing the reactor current flowing through the smoothing reactor by controlling the inverter circuit.

  According to the present invention, it is possible to obtain the power conversion device capable of suppressing the variation in the output limit start current corresponding to the output current when the output limit is started.

It is a block diagram which shows the power converter device in Embodiment 1 of this invention. It is explanatory drawing which shows the electric current path in case the operation mode of the power converter device in Embodiment 1 of this invention is mode 1. It is explanatory drawing which shows the current path in case the operation mode of the power converter device in Embodiment 1 of this invention is mode 2. It is explanatory drawing which shows the electric current path in case the operation mode of the power converter device in Embodiment 1 of this invention is mode 3. It is explanatory drawing which shows the current path in case the operation mode of the power converter device in Embodiment 1 of this invention is mode 4. 5 is a timing chart showing how the operation modes of the power conversion device according to Embodiment 1 of the present invention are switched. It is explanatory drawing which shows the output limitation performed by the control part of the power converter device in Embodiment 1 of this invention. It is a block diagram which shows each of the control part and offset circuit of the power converter device in Embodiment 1 of this invention. It is explanatory drawing which shows the output current each output when input / output voltage conditions differ with the power converter device in a comparative example. It is explanatory drawing which shows the output current each output when input / output voltage conditions differ with the power converter device in Embodiment 1 of this invention. It is a block diagram which shows the power converter device in Embodiment 2 of this invention. It is explanatory drawing which shows the output current each output when temperature conditions differ with the power converter device in a comparative example. It is explanatory drawing which shows the output current each output when temperature conditions differ by the power converter device in Embodiment 2 of this invention. 9 is a timing chart showing how the operation modes of the modified examples of the power conversion devices according to the first and second embodiments of the present invention are switched.

  Hereinafter, a power converter according to the present invention will be described with reference to the drawings according to a preferred embodiment. In the description of the drawings, the same portions or corresponding portions will be denoted by the same reference symbols, without redundant description.

Embodiment 1.
1 is a configuration diagram showing a power conversion device according to a first embodiment of the present invention. In FIG. 1, the high voltage battery 2 connected to the input side of the power converter 1, the load 3 and the low voltage battery 4 connected to the output side of the power converter 1 are also shown. The power converter shown in FIG. 1 includes a power converter 1 that functions as a DC-DC converter, a control unit 13 that controls the power converter 1, and an offset circuit 14.

  The power converter 1 includes an inverter circuit 5 including a plurality of semiconductor switching elements 5a to 5d, a transformer 6 including a primary winding 6a and a secondary winding 6b, and a rectifier including diodes 7a and 7b. The circuit 7 includes a smoothing circuit 8 including a smoothing reactor 8a and a smoothing capacitor 8b, an input voltage detector 10, an input current detector 11, and an output voltage detector 12.

  The inverter circuit 5 converts the input DC voltage into AC voltage. That is, in the inverter circuit 5, each of the semiconductor switching elements 5a to 5d is controlled to be turned on and off by the control unit 13, so that the input DC voltage is converted into an AC voltage.

  The semiconductor switching elements 5a and 5c are provided on the upper arm on the high voltage side, and the semiconductor switching elements 5b and 5d are provided on the lower arm on the low voltage side. The connection point between the source of the semiconductor switching element 5a and the drain of the semiconductor switching element 5b is connected to one end of the primary winding 6a. The connection point between the source of the semiconductor switching element 5c and the drain of the semiconductor switching element 5d is connected to the other end of the primary winding 6a.

  As the semiconductor switching elements 5a to 5d, for example, MOSFET (Metal Oxide Semiconductor Field Effect Transistor) can be used.

  The transformer 6 transforms the AC voltage converted by the inverter circuit 5. The secondary winding 6b of the transformer 6 is configured by connecting two windings of a first secondary winding and a second secondary winding in series.

  The rectifier circuit 7 is a diode rectifier circuit, and rectifies the AC voltage transformed by the transformer 6. The diode 7a of the rectifier circuit 7 is provided on the upper arm on the high voltage side, and the diode 7b is provided on the lower arm on the low voltage side. The anode of the diode 7a is connected to one end of the secondary winding 6b of the transformer 6, and the cathode thereof is connected to the smoothing reactor 8a. The anode of the diode 7b is connected to the other end of the secondary winding 6b of the transformer 6, and the cathode thereof is connected to the smoothing reactor 8a.

  The smoothing circuit 8 smoothes the output of the rectifier circuit 7. One end of smoothing reactor 8a is connected to each cathode of diodes 7a and 7b, and the other end of smoothing reactor 8a is connected to one end of smoothing capacitor 8b. The other end of the smoothing capacitor 8b is connected to the connection point of the two windings that form the secondary winding 6b of the transformer 6.

  Hereinafter, the voltage input to the inverter circuit 5 will be referred to as an input voltage Vin, and the current input to the inverter circuit 5 will be referred to as an input current Iin. Further, the voltage output from the smoothing circuit 8 is referred to as an output voltage Vout, and the current output from the smoothing circuit 8 is referred to as an output current Iout. Further, the current flowing through the smoothing reactor 8a of the smoothing circuit 8 will be referred to as the reactor current ILf.

  The input voltage detection unit 10 is connected in parallel with the high voltage battery 2 and detects the input voltage Vin input from the high voltage battery 2 to the inverter circuit 5. The input current detection unit 11 is connected in series with the high voltage battery 2 and detects the input current Iin input from the high voltage battery 2 to the inverter circuit 5. The output voltage detection unit 12 is connected in parallel with the load 3 and the low voltage battery 4, and detects the output voltage Vout output from the smoothing circuit 8 to the load 3 and the low voltage battery 4. A voltage sensor is used as the input voltage detection unit 10 and the output voltage detection unit 12, for example. As the input current detection unit 11, for example, a current sensor is used.

  The control unit 13 acquires the input voltage Vin from the input voltage detection unit 10 and acquires the output voltage Vout from the output voltage detection unit 12. The control unit 13 also controls switching of each of the semiconductor switching elements 5a to 5d of the inverter circuit 5.

  The offset circuit 14 acquires the input voltage Vin from the input voltage detection unit 10, acquires the input current Iin from the input current detection unit 11, and acquires the output voltage Vout from the output voltage detection unit 12. The offset circuit 14 determines the offset voltage Voffset based on the input voltage Vin detected by the input voltage detection unit 10 and the output voltage Vout detected by the output voltage detection unit 12.

  The control unit 13 limits the output based on the offset voltage Voffset obtained by the offset circuit 14, the detection voltage Vd corresponding to the input current Iin detected by the input current detection unit 11, and the threshold voltage Vth. The output limitation mentioned here is a process of controlling the inverter circuit 5 to reduce the reactor current ILf flowing through the smoothing reactor 8a to lower the output voltage Vout. The detection voltage Vd corresponding to the input current Iin is obtained by converting the input current Iin into a voltage as described below, for example. That is, using the current transformer, the input current Iin is converted into a current I proportional to the turns ratio of the current transformer, and the current I flows through the resistor R to be converted into a voltage V. That is, the relationship represented by V = I × R is established. This voltage V corresponds to the detection voltage Vd.

  Specifically, the offset circuit 14 outputs the correction detection voltage Vd ′, which is a value obtained by adding the obtained offset voltage Voffset to the detection voltage Vd, to the control unit 13. The control unit 13 compares the correction detection voltage Vd ′ output by the offset circuit 14 with the threshold voltage Vth, and when the correction detection voltage Vd ′ is equal to or higher than the threshold voltage Vth, limits the output.

  Next, the basic operation of the power conversion device will be described with reference to FIGS. FIG. 2 is an explanatory diagram showing a current path when the operation mode of the power conversion device according to Embodiment 1 of the present invention is mode 1. FIG. 3 is an explanatory diagram showing current paths when the operation mode of the power conversion device according to Embodiment 1 of the present invention is mode 2.

  FIG. 4 is an explanatory diagram showing current paths when the operation mode of the power conversion device according to Embodiment 1 of the present invention is mode 3. FIG. 5 is an explanatory diagram showing current paths when the operation mode of the power conversion device according to Embodiment 1 of the present invention is mode 4.

  FIG. 6 is a timing chart showing how the operation modes of the power conversion device according to Embodiment 1 of the present invention are switched. Note that FIG. 6 illustrates the on / off states of the semiconductor switching elements 5 a to 5 d, the primary side voltage of the transformer 6, the input current Iin, and the reactor current ILf with time.

  The operation mode of the power conversion device is switched among four operation modes of mode 1, mode 2, mode 3 and mode 4 according to the switching states of the semiconductor switching elements 5a to 5d. Further, a series of operations consisting of these four operation modes is performed every switching cycle Tsw.

  In mode 1 shown in FIG. 2, the semiconductor switching elements 5a and 5d are on, and the semiconductor switching elements 5b and 5c are off. In this case, the current flowing through the primary side of the transformer 6 flows through the path of the high voltage battery 2, the semiconductor switching element 5a, the primary winding 6a and the semiconductor switching element 5d. The transformer 6 transfers electric power from the primary side to the secondary side. The current flowing on the secondary side of the transformer 6 flows through the path of the secondary winding 6b, the diode 7a, the smoothing reactor 8a and the load 3.

  In mode 2 shown in FIG. 3, the semiconductor switching elements 5a to 5d are all in the off state. In this case, no current flows in the primary side of the transformer 6, and no power is transmitted from the primary side of the transformer 6 to the secondary side. However, on the secondary side, current flows through the path of the load 3, the secondary winding 6b, the diode 7a, the diode 7b, and the smoothing reactor 8a due to the self-induction of the smoothing reactor 8a. In this case, since no voltage is generated on the secondary side of the transformer 6, the reactor current ILf decreases.

  In mode 3 shown in FIG. 4, the semiconductor switching elements 5b and 5c are on, and the semiconductor switching elements 5a and 5d are off. In this case, the current flowing through the primary side of the transformer 6 flows through the path of the high voltage battery 2, the semiconductor switching element 5c, the primary winding 6a and the semiconductor switching element 5b. The transformer 6 transfers electric power from the primary side to the secondary side. The current flowing on the secondary side of the transformer 6 flows through the path of the secondary winding 6b, the diode 7b, the smoothing reactor 8a and the load 3.

  In mode 4 shown in FIG. 5, all the semiconductor switching elements 5a to 5d are in the off state. In this case, no current flows in the primary side of the transformer 6, and no power is transmitted from the primary side of the transformer 6 to the secondary side. However, on the secondary side, current flows through the path of the load 3, the secondary winding 6b, the diode 7a, the diode 7b, and the smoothing reactor 8a due to the self-induction of the smoothing reactor 8a. In this case, since no voltage is generated on the secondary side of the transformer 6, the reactor current ILf decreases.

  As shown in FIG. 6, the control unit 13 adjusts the on-duty D of each of the semiconductor switching elements 5a to 5d while controlling the switching of each of the semiconductor switching elements 5a to 5d, so that the output voltage Vout is equal to the target value Vt. Control to become.

  Here, in mode 1 and mode 3, the relationship expressed by the following equation (1) is established. However, V1 is a voltage applied to the primary winding 6a of the transformer 6, N1 is the number of turns of the primary winding 6a, and I1 is a current flowing through the primary winding 6a. V2 is a voltage applied to the secondary winding 6b, N2 is the number of turns of the secondary winding 6b, and I2 is a current flowing through the secondary winding 6b. N1 / N2 is the winding ratio of the transformer 6.

    N1 / N2 = V1 / V2 = I2 / I1 (1)

  Since the input voltage Vin is applied to the primary side of the transformer 6, the relationship represented by V1 = Vin is established. Therefore, the following equation (2) is obtained from the equation (1).

    N1 / N2 = Vin / V2 (2)

  As shown in the equation (2), a voltage V2, which is a value obtained by dividing the input voltage Vin applied to the primary side of the transformer 6 by the turn ratio (N1 / N2), is generated on the secondary side of the transformer 6. To do. That is, the relationship expressed by V2 = (1 / (N1 / N2)) × Vin = (N2 / N1) × Vin holds.

  A magnitude of a difference between the voltage V2 and the output voltage Vout, that is, a voltage represented by | V2-Vout | is applied to both ends of the smoothing reactor 8a. Therefore, as can be seen from FIG. 6, in mode 1 and mode 3, the reactor current ILf increases. An input current Iin, which is a value obtained by dividing the reactor current ILf by the turn ratio (N1 / N2), flows through the primary side of the transformer 6. That is, the relationship expressed by Iin = (1 / (N1 / N2)) × ILf = (N2 / N1) × ILf is established.

  In modes 2 and 4, the semiconductor switching elements 5a to 5d are controlled to be off by the control unit 13. Therefore, no voltage is generated on the primary side of the transformer 6. That is, the relationship represented by V1 = Vin = 0 holds. Further, no current flows on the primary side of the transformer 6. That is, the relationship represented by Iin = 0 holds.

  In mode 2 and mode 4, the output voltage Vout is applied to the smoothing reactor 8a, and as can be seen from FIG. 6, the reactor current ILf decreases. Further, a current having the same value as the reactor current ILf flows into the secondary side of the transformer 6 by the center tap. That is, the relationship expressed by I2 = ILf is established. Further, no voltage is generated on the secondary side of the transformer 6. That is, the relationship represented by V2 = 0 holds.

  Next, the output limiting function of the control unit 13 will be described with reference to FIG. FIG. 7: is explanatory drawing which shows the output limitation performed by the control part 13 of the power converter device in Embodiment 1 of this invention. Note that FIG. 7 shows the relationship between the output current Iout on the horizontal axis and the output voltage Vout on the vertical axis.

  Here, in the output limiting function of the control unit 13, when the output current Iout needs to be equal to or higher than the rated current due to the load change, the output limiting is started. Here, the output current Iout when the output limitation is started will be referred to as an output limitation start current.

  As shown in FIG. 7, when the output current Iout is less than the rated current, the control unit 13 controls each of the semiconductor switching elements 5a to 5a so that the output voltage Vout detected by the output voltage detection unit 12 becomes the target value Vt. 5d is switching-controlled. The target value Vt is, for example, a preset fixed value.

  As described above, in the region where the output current Iout is less than the rated current, the control unit 13 performs the output voltage stabilization control for controlling the output voltage Vout to be the constant voltage.

  Next, a case where the control unit 13 limits the output will be described. As shown in FIG. 7, when the output current Iout is equal to or higher than the rated current, the control unit 13 limits the output.

  When limiting the output, the control unit 13 controls all of the semiconductor switching elements 5a to 5d to be turned off. As a result, as can be seen from FIG. 6, the reactor current ILf decreases. In this way, the control unit 13 limits the peak of the reactor current ILf by controlling all of the semiconductor switching elements 5a to 5d to be off. As a result, the output voltage Vout drops, and the output limiting function is realized.

  The change in the output voltage Vout when the control unit 13 limits the output is as shown in FIG. 7. That is, as can be seen from FIG. 7, the output limitation is started when the output current Iout exceeds the rated current as a trigger. It can be seen that the output voltage Vout is reduced due to this output limitation.

  Although FIG. 7 exemplifies the case where the hysteresis is provided so that the output limitation is not performed immediately at the timing when the output current Iout becomes the rated current or more, the hysteresis is not provided. Good.

  Next, the respective configurations of the control unit 13 and the offset circuit 14 will be described with reference to FIG. FIG. 8 is a configuration diagram showing each of control unit 13 and offset circuit 14 of the power conversion device according to Embodiment 1 of the present invention.

  In FIG. 8, the control unit 13 has a threshold value generator 131 and a comparator 132. The threshold generator 131 generates a threshold voltage Vth.

  The threshold voltage Vth generated by the threshold generator 131 and the correction detection voltage Vd ′ described later output from the offset circuit 14 are input to the comparator 132. The corrected detection voltage Vd ′ is a value obtained by adding the offset voltage Voffset to the detection voltage Vd corresponding to the input current Iin detected by the input current detection unit 11. The offset voltage Voffset will be described later.

  The comparator 132 compares the correction detection voltage Vd ′ output by the offset circuit 14 with the threshold voltage Vth. The comparison by the comparator 132 is repeatedly performed at a constant cycle. As a result of the comparison by the comparator 132, when the corrected detection voltage Vd 'is less than the threshold voltage Vth, the control unit 13 performs the above-described output voltage stabilization control. On the other hand, when the correction detection voltage Vd 'becomes equal to or higher than the threshold voltage Vth, the control unit 13 limits the output.

  The offset circuit 14 has an adder 141. The adder 141 is provided between the input current detection unit 11 and the ground that serves as the reference potential Vref. The adder 141 outputs a value obtained by adding the reference potential Vref, the detection voltage Vd corresponding to the input current Iin, and the offset voltage Voffset as a corrected detection voltage Vd '.

  With such a configuration of the adder 141, the detection voltage Vd rises above the reference potential Vref by the offset voltage Voffset.

  As described above, the control unit 13 compares the correction detection voltage Vd ′ output by the offset circuit 14 with the threshold voltage Vth, and when the correction detection voltage Vd ′ is equal to or higher than the threshold voltage Vth, limits the output. .. As a result, the reactor current ILf is reduced, and as a result, the output voltage Vout is reduced as shown in FIG. 7.

  In this way, the control unit 13 limits the output, so that it is possible to prevent an overcurrent from flowing through the power conversion device itself or an overcurrent through an external device connected to the power conversion device. Become. In addition, as will be described later, when the output current Iout changes depending on the duty ratio, the value of the output limit start current at which the output limit is started varies.

  On the other hand, in the first embodiment, the control unit 13 limits the output based on the comparison between the corrected detection voltage Vd ′, which is a value obtained by adding the offset voltage Voffset to the detection voltage Vd, and the threshold voltage Vth. Is configured. Therefore, the offset voltage Voffset can compensate for changes in the input voltage Vin and the output voltage Vout. As a result, it is possible to suppress the fluctuation of the output limit start current due to the fluctuations of the input voltage Vin and the output voltage Vout.

  Next, based on the comparison between the correction detection voltage Vd 'and the threshold voltage Vth, the effect obtained by the configuration for limiting the output will be described with reference to FIGS. 9 and 10.

  FIG. 9: is explanatory drawing which shows the output current Iout each output when input / output voltage conditions differ with the power converter device in a comparative example. FIG. 10 is an explanatory diagram showing the output current Iout output when the input / output voltage conditions are different depending on the power conversion device according to the first embodiment of the present invention.

  It is assumed that the power converter in the comparative example is not provided with the offset circuit 14 and is configured to limit the output based on the comparison between the detection voltage Vd and the threshold voltage Vth.

  On the left side of FIG. 9, when the input / output voltage condition is the condition (I), temporal changes of the reactor current ILf, the threshold voltage Vth, and the detection voltage Vd obtained by the power conversion device in the comparative example are illustrated. On the right side of FIG. 9, when the input / output voltage condition is the condition (II), temporal changes of the reactor current ILf, the threshold voltage Vth, and the detection voltage Vd obtained by the power conversion device in the comparative example are illustrated.

  On the left side of FIG. 10, when the input / output voltage condition is the condition (I), each of the reactor current ILf, the threshold voltage Vth, the detection voltage Vd, and the correction detection voltage Vd ′ obtained by the power conversion device according to the first embodiment. The time variation is shown. On the right side of FIG. 10, each of the reactor current ILf, the threshold voltage Vth, the detection voltage Vd, and the correction detection voltage Vd ′ obtained by the power conversion device in the first embodiment when the input / output voltage condition is the condition (II). The time variation is shown.

  The above condition (I) is a condition that the input voltage Vin is low or the output voltage Vout is high. Under such a condition (I), the duty ratio becomes large. The condition (II) described above is a condition that the input voltage Vin is higher or the output voltage Vout is lower than the condition (I). Under such a condition (II), the duty ratio becomes smaller than that under the condition (I).

  The threshold voltage Vth used in the comparator 132 is set in consideration of slope compensation in order to suppress subharmonic oscillation. The waveform of the threshold voltage Vth has a sawtooth-like shape as shown in FIGS. 9 and 10.

  As shown in FIG. 9, the detection voltage Vd changes depending on the duty ratio, and as a result, the output current Iout obtained by converting the reactor current ILf into the direct current by the smoothing capacitor 8b changes depending on the duty ratio.

  Therefore, in the comparative example, as can be seen from FIG. 9, when the condition (I) and the condition (II) are compared, there is a variation between the DC-converted output currents Iout.

  Here, assuming that the output voltage Vout is constant, the duty ratio is smaller as the input voltage Vin is higher, and is larger as the input voltage Vin is lower. Further, as shown in FIG. 10, the slope compensation is largely compensated as the duty ratio increases.

  Similarly, assuming that the input voltage Vin is constant, the duty ratio becomes smaller as the output voltage Vout becomes lower and becomes larger as the output voltage Vout becomes higher. Further, as shown in FIG. 10, the slope compensation is largely compensated as the duty ratio increases.

  As can be seen from the above, the slope compensation amount increases as the input voltage Vin decreases or the output voltage Vout increases. The slope compensation amount decreases as the input voltage Vin increases or the output voltage Vout decreases.

  In this way, the slope compensation amount changes depending on the input voltage Vin and the output voltage Vout. Therefore, in the first embodiment, the offset circuit 14 obtains the offset voltage Voffset such that the higher the input voltage Vin, the larger the offset voltage Voffset, and the lower the output voltage Vout, the larger the offset voltage Voffset. This offset voltage Voffset is added to the detection voltage Vd. With such a configuration, it is possible to suppress the fluctuation of the output limit start current due to the fluctuations of the input voltage Vin and the output voltage Vout. As a result, the output can be restricted with high accuracy.

  Next, an example of a method of obtaining the offset voltage Voffset will be described. The offset circuit 14 calculates the offset voltage Voffset according to a function having the input voltage Vin and the output voltage Vout as parameters. Specifically, the offset circuit 14 calculates the offset voltage from the input voltage Vin detected by the input voltage detection unit 10 and the output voltage Vout detected by the output voltage detection unit 12 according to the following equation (3), for example. Calculate Voffset. However, α, β and γ are coefficients.

Voffset = α × Vin−β × Vout + γ (3)
α and β are predetermined such that the higher the input voltage Vin, the higher the offset voltage Voffset, and the higher the output voltage Vout, the lower the offset voltage Voffset. Further, γ is predetermined as a correction term.

  In this way, the offset circuit 14 obtains the offset voltage Voffset based on the input voltage Vin and the output voltage Vout. Further, the offset circuit 14 outputs a corrected detection voltage Vd ′, which is a value obtained by adding the obtained offset voltage Voffset to the detection voltage Vd, to the comparator 132 of the control unit 13.

  As a result, the difference due to the slope compensation can be absorbed according to the input voltage Vin and the output voltage Vout, and thus the fluctuation of the output limit start current due to the fluctuation of the input voltage Vin and the output voltage Vout can be suppressed. it can.

  In addition, although the case where the linear equation is used as shown in the above-described equation (3) is exemplified as the function having the input voltage Vin and the output voltage Vout as parameters, the present invention is not limited to this. That is, as a function having the input voltage Vin and the output voltage Vout as parameters, a quadratic expression or a higher-order mathematical expression of a third order or higher may be used.

  As shown in FIG. 10, by adding the offset voltage Voffset to the detection voltage Vd, the difference due to the slope compensation can be absorbed. That is, as can be seen from FIG. 10, the detection voltage Vd is offset by the offset voltage Voffset. Therefore, as can be seen from FIG. 10, when the condition (I) and the condition (II) are compared, there is no variation between the DC-converted output currents Iout.

  Further, comparing the condition (I) with the condition (II) in FIG. 10, the value of the offset voltage Voffset is smaller as the input voltage Vin is lower, and the value of the offset voltage Voffset is larger as the input voltage Vin is higher. There is.

  In this way, by adding the offset voltage Voffset to the detection voltage Vd, the difference due to the slope compensation can be absorbed. Therefore, it is possible to suppress the fluctuation of the output limit start current due to the fluctuations of the input voltage Vin and the output voltage Vout. As a result, it is possible to suppress variations in the output current Iout due to variations in the input voltage Vin and the output voltage Vout, and it is possible to achieve high reliability of the power conversion device.

  In the first embodiment, the control unit 13 is configured to control all of the semiconductor switching elements 5a to 5d to be turned off when the output is limited, but the semiconductor switching elements 5a to 5d are controlled. Not all have to be turned off. That is, if one or more semiconductor switching elements of the semiconductor switching elements 5a to 5d are turned off according to the combination of the semiconductor switching elements 5a to 5d such that the value of the input current Iin becomes 0, the reactor current ILf decreases. As a result, the output voltage Vout can be reduced.

  As described above, according to the power conversion device of the first embodiment, the offset circuit 14 is based on the input voltage Vin detected by the input voltage detection unit 10 and the output voltage Vout detected by the output voltage detection unit 12. , The offset voltage Voffset is obtained. Further, the control unit 13 limits the output based on the offset voltage Voffset obtained by the offset circuit 14, the detection voltage Vd corresponding to the input current Iin detected by the input current detection unit 11, and the threshold voltage Vth. Is configured.

  More specifically, the offset circuit 14 and the control unit 13 are configured as follows, respectively. That is, the offset circuit 14 is configured to output the corrected detection voltage Vd ′ that is a value obtained by adding the obtained offset voltage Voffset to the detection voltage Vd. Further, the control unit 13 compares the correction detection voltage Vd ′ output by the offset circuit 14 with the threshold voltage Vth, and when the correction detection voltage Vd ′ is equal to or higher than the threshold voltage Vth, the output is limited. Has been done.

  Accordingly, it is possible to suppress the fluctuation of the output limit start current due to the fluctuations of the input voltage Vin and the output voltage Vout. That is, since the offset voltage Voffset can compensate the change in the input voltage Vin and the change in the output voltage Vout, the output limit start current is caused by the change in the input voltage Vin and the change in the output voltage Vout. Can be suppressed. As a result, high reliability of the power conversion device can be realized.

Embodiment 2.
In the second embodiment of the present invention, unlike the first embodiment, the offset voltage Voffset is obtained in consideration of the detection value of the temperature detection unit 15 that detects the temperature of the power converter 1 as the target temperature. The configured power converter will be described. In the second embodiment, description of the same points as those in the first embodiment will be omitted, and points different from the first embodiment will be mainly described.

  FIG. 11: is a block diagram which shows the power converter device in Embodiment 2 of this invention. The power conversion device shown in FIG. 11 further includes a temperature detection unit 15 in addition to the power converter 1, the control unit 13, and the offset circuit 14.

  The temperature detection unit 15 is provided inside the power converter 1 and detects the temperature of the power converter 1 as the temperature TL that is the target temperature. More specifically, the temperature of the power converter is, for example, the temperature of the rectifier circuit 7 or the temperature of the smoothing reactor 8a of the smoothing circuit 8. A temperature sensor, for example, is used as the temperature detector 15.

  The offset circuit 14 calculates the offset voltage Voffset based on the temperature TL detected by the temperature detection unit 15. As another example, the offset circuit 14 includes an input voltage Vin detected by the input voltage detection unit 10, an output voltage Vout detected by the output voltage detection unit 12, and a temperature TL detected by the temperature detection unit 15. The offset voltage Voffset may be obtained based on the above.

  Next, the temperature TL will be described. Here, for example, when the power conversion device is applied to an electric vehicle or a hybrid vehicle, a lithium ion battery is used as the high voltage battery 2 and a lead battery is used as the low voltage battery 4. The voltage range of the lithium-ion battery is larger than that of the lead battery. Therefore, even under the same load condition, that is, the same output current, the input current Iin input to the power converter 1 differs depending on the voltage of the high voltage battery 2, and the loss of the power converter 1 also varies.

  That is, when the temperature on the primary side of the transformer 6, for example, the temperature of any of the semiconductor switching elements 5a to 5d is set to the temperature TL, the temperature detection unit 15 detects the input voltage Vin even under the same load condition. The temperature TL changes. Therefore, in order to accurately detect the temperature proportional to the magnitude of the load without depending on the input voltage Vin, the temperature of the secondary side of the transformer 6, that is, the temperature of the rectifier circuit 7 or the smoothing circuit 8 is set. It is desirable that the temperature of is the temperature TL.

  Here, since the diodes 7a and 7b that form the rectifier circuit 7 are generally formed of a Si-based semiconductor, the forward voltage Vf decreases in a high temperature environment. Therefore, even with the same input voltage Vin and the same output voltage Vout, the forward voltage Vf is reduced in a high temperature environment, so that the voltage drop is small. As a result, under a high temperature environment, the duty ratio becomes smaller than in a normal environment, for example, a room temperature environment. That is, in a high temperature environment, the smaller the duty ratio, the smaller the slope compensation amount.

  As described above, in the power converter 1, the slope compensation amount changes depending on the temperature TL even with the same input voltage Vin and the same output voltage Vout. Therefore, in the second embodiment, the offset circuit 14 obtains the offset voltage Voffset so that the offset voltage Voffset increases as the temperature TL detected by the temperature detection unit 15 increases. As a result, it becomes possible to perform the output restriction with high accuracy in consideration of the temperature condition.

  Next, based on the comparison between the correction detection voltage Vd 'and the threshold voltage Vth, the effect obtained by the configuration for limiting the output will be described with reference to FIGS. 12 and 13.

  FIG. 12 is an explanatory diagram showing the output current Iout that is output when the temperature conditions differ depending on the power conversion device in the comparative example. FIG. 13 is an explanatory diagram showing the output current Iout that is output when the temperature conditions differ depending on the power conversion device according to the second embodiment of the present invention.

  It is assumed that the power converter in the comparative example is not provided with the offset circuit 14 and is configured to limit the output based on the comparison between the detection voltage Vd and the threshold voltage Vth.

  On the left side of FIG. 12, the temporal changes of the reactor current ILf, the threshold voltage Vth, and the detection voltage Vd obtained by the power conversion device in the comparative example are illustrated when the temperature condition is the condition (i). On the right side of FIG. 12, the temporal changes of the reactor current ILf, the threshold voltage Vth, and the detection voltage Vd obtained by the power conversion device in the comparative example are illustrated when the temperature condition is the condition (ii).

  On the left side of FIG. 13, when the temperature condition is the condition (i), the reactor current ILf, the threshold voltage Vth, the detection voltage Vd, and the correction detection voltage Vd ′ obtained with the power conversion device according to the second embodiment change with time. Are shown. On the right side of FIG. 13, when the temperature condition is the condition (ii), the reactor current ILf, the threshold voltage Vth, the detection voltage Vd, and the correction detection voltage Vd ′ obtained with the power converter according to the second embodiment change with time. Are shown.

  The above-mentioned condition (i) is a condition that the power converter 1 is in a low temperature environment, that is, the temperature TL is low. Under such a condition (i), the duty ratio becomes large. The condition (ii) described above is a condition that the power converter 1 is in a high temperature environment, that is, the temperature TL is higher than the condition (i). Under such a condition (ii), the duty ratio is smaller than that under the condition (i). Further, between the condition (i) and the condition (ii), the input voltage Vin and the output voltage Vout are assumed to be the same condition.

  As shown in FIG. 12, the detection voltage Vd changes due to the change of the duty ratio due to the temperature condition, and as a result, the output current Iout obtained by converting the reactor current ILf into the direct current by the smoothing capacitor 8b changes according to the duty ratio. ..

  Therefore, in the comparative example, as can be seen from FIG. 12, when the condition (i) and the condition (ii) are compared, there is a variation between the DC-converted output currents Iout. Under the condition (i), since the forward voltage Vf of the diodes 7a and 7b is large and the voltage drop is large, the on-duty D is large. Under the condition (ii), the forward voltage Vf of the diodes 7a and 7b is small and the voltage drop is small, so the on-duty D is small.

  Here, assuming that each of the input voltage Vin and the output voltage Vout is constant, the duty ratio becomes smaller as the temperature TL is higher and becomes larger as the temperature TL is lower. Further, as in the first embodiment, as shown in FIG. 13, the slope compensation is larger as the duty ratio is larger.

  As can be seen from the above, the lower the temperature TL, the larger the slope compensation amount, and the higher the temperature TL, the smaller the slope compensation amount.

  Thus, the slope compensation amount changes depending on the temperature TL. Therefore, in the second embodiment, the offset circuit 14 obtains the offset voltage Voffset so that the offset voltage Voffset increases as the temperature TL increases. This offset voltage Voffset is added to the detection voltage Vd. With such a configuration, it is possible to suppress the fluctuation of the output limit start current due to the temperature TL. As a result, the output can be restricted with high accuracy. Further, it is possible to prevent a situation in which the output limit start current fluctuates when the power converter 1 is in a high temperature environment, for example, and the output current Iout becomes an overcurrent, which causes a component failure. You can

  Next, an example of a method of obtaining the offset voltage Voffset will be described. The offset circuit 14 calculates the offset voltage Voffset according to a function having the temperature TL as a parameter. Specifically, the offset circuit 14 calculates the offset voltage Voffset from the temperature TL detected by the temperature detection unit 15, for example, according to the following equation (4). However, T0 is a reference temperature, for example, 25 degreeC. Further, δ and γ are coefficients.

Voffset = δ × (TL-T0) + γ (4)
δ is set in advance so that the offset voltage Voffset increases as the temperature TL increases. Further, γ is predetermined as a correction term.

  In this way, the offset circuit 14 obtains the offset voltage Voffset based on the temperature TL. Further, the offset circuit 14 outputs a corrected detection voltage Vd ′, which is a value obtained by adding the obtained offset voltage Voffset to the detection voltage Vd, to the comparator 132 of the control unit 13.

  As a result, the difference due to the slope compensation can be absorbed according to the temperature TL, so that the fluctuation of the output limit start current due to the temperature characteristic can be suppressed.

  In addition, although the case where the linear equation is used as shown in the above equation (4) is illustrated as the function having the temperature TL as a parameter, the function is not limited to this. That is, a quadratic expression or a higher-order mathematical expression of a third order or higher may be used as the function having the temperature TL as a parameter.

  As shown in FIG. 13, by adding the offset voltage Voffset to the detection voltage Vd, the difference due to the slope compensation can be absorbed. Therefore, as can be seen from FIG. 13, when the condition (i) and the condition (ii) are compared, there is no variation between the DC-converted output currents Iout.

  Further, comparing the condition (i) with the condition (ii) in FIG. 13, the value of the offset voltage Voffset is smaller as the temperature TL is lower, and the value of the offset voltage Voffset is larger as the temperature TL is higher.

  In addition, as described above, the offset circuit 14 may be configured to obtain the offset voltage Voffset based on the input voltage Vin, the output voltage Vout, and the temperature TL. Specifically, in the offset circuit 14, the higher the input voltage Vin, the larger the offset voltage Voffset, the lower the output voltage Vout, the larger the offset voltage Voffset, and the higher the temperature TL, the larger the offset voltage Voffset. The offset voltage Voffset is calculated.

  In the above case, the offset circuit 14 calculates the offset voltage Voffset according to a function having the input voltage Vin, the output voltage Vout, and the temperature TL as parameters. Specifically, the offset circuit 14 includes an input voltage Vin detected by the input voltage detection unit 10, an output voltage Vout detected by the output voltage detection unit 12, and a temperature detection unit, for example, according to the following equation (5). The offset voltage Voffset is calculated from the temperature TL detected by 15. However, T0 is a reference temperature, for example, 25 degreeC. Further, α, β, γ and δ are coefficients.

Voffset = α × Vin−β × Vout + δ × (TL-T0) + γ (5)
α, β, and δ are predetermined such that the higher the input voltage Vin, the higher the offset voltage Voffset, the higher the output voltage Vout, the lower the offset voltage Voffset, and the higher the temperature TL, the higher the offset voltage Voffset. Further, γ is predetermined as a correction term.

  In addition, although the case where a linear expression is used as shown in Expression (5) above is illustrated as a function having the input voltage Vin, the output voltage Vout, and the temperature TL as parameters, the present invention is not limited to this. That is, as a function having the input voltage Vin, the output voltage Vout, and the temperature TL as parameters, a quadratic expression or a higher-order mathematical expression of a third order or higher may be used.

  As a result, the difference due to the slope compensation can be absorbed according to the input voltage Vin, the output voltage Vout, and the temperature TL, so that the fluctuation of the output limit start current due to the input / output voltage and the temperature characteristic can be suppressed. it can. That is, in addition to the fluctuations in the input voltage Vin and the output voltage Vout, fluctuations in the output limit start current due to fluctuations in the temperature TL can be suppressed. As a result, the output can be restricted with high accuracy.

  Although the case where the rectifier circuit 7 is a diode rectifier circuit is illustrated, the present invention is not limited to this, and the rectifier circuit 7 may be a synchronous rectifier circuit. When the rectifier circuit 7 is a synchronous rectifier circuit using a MOSFET, the higher the temperature TL, the higher the on-resistance of the MOSFET. Therefore, the loss of the voltage drop is large contrary to the diode, and in order to output the same output voltage Vout, the duty ratio needs to be increased and the offset voltage Voffset needs to be decreased.

  The temperature detection unit 15 may be configured to detect the temperature of the cooler that cools the power converter 1 as the temperature TL instead of the temperature of the power converter 1.

  In this case, the cooler is, for example, a water-cooled cooler and includes a water pump for circulating cooling water. The temperature of the cooler is the temperature of the cooling water. More specifically, the temperature detection unit 15 acquires the temperature of the cooling water from an ECU (Electronic Control Unit) that monitors the cooler via a communication line such as a CAN (Controller Area Network). The temperature detection unit 15 detects the acquired temperature of the cooling water as the temperature TL.

  As described above, according to the power converter of Embodiment 2, the offset circuit 14 is configured to obtain the offset voltage Voffset based on the temperature TL detected by the temperature detection unit 15. As a result, it is possible to prevent the output limit start current from changing due to the change in the temperature TL. As a result, high reliability of the power conversion device can be realized.

  Further, according to another example of the power conversion device of the second embodiment, the offset circuit 14 includes the input voltage Vin detected by the input voltage detection unit 10 and the output voltage Vout detected by the output voltage detection unit 12. In addition to the above, the offset voltage Voffset is obtained based on the temperature TL detected by the temperature detection unit 15. As a result, it is possible to prevent the output limit start current from varying due to variations in the input voltage Vin, the output voltage Vout, and the temperature TL. As a result, high reliability of the power conversion device can be realized.

  In each of the first and second embodiments, the transformer 6 of the power converter 1 has a center tap type configuration, but the present invention is not limited to this. For example, the transformer 6 may have a configuration in which both ends of the secondary winding are connected to the middle point of a diode having a full bridge configuration.

  In each of the first and second embodiments, the middle point of the secondary winding 6b of the transformer 6 is connected to the negative electrode side of the low voltage battery 4, and both ends of the secondary winding 6b are connected to the anode sides of the diodes 7a and 7b, respectively. Connected, but not limited to. For example, the middle point of the secondary winding 6b is connected to the smoothing reactor 8a, both ends of the secondary winding 6b are connected to the cathode sides of the diodes 7a and 7b, respectively, and the anodes of the diodes 7a and 7b are the negative electrodes of the low voltage battery 4. It may be connected to the side.

  In each of the first and second embodiments, power converter 1 is in the form of a step-down converter in which the voltage on the output side is lower than the voltage on the input side, but the present invention is not limited to this. For example, the power converter 1 may be in the form of a boost converter in which the voltage on the output side is higher than the voltage on the input side.

  In each of the first and second embodiments, the switching method of power converter 1 is the hard switching method, but the invention is not limited to this. For example, the switching method of the power converter 1 may be a phase shift control method. In this case, the control unit 13 controls the semiconductor switching element 5a and the semiconductor switching element 5d as one switching element pair and shifts the phases of the respective semiconductor switching elements 5b and 5c by a half cycle for control.

  FIG. 14 is a timing chart showing how the operation modes of the modified examples of the power conversion devices according to Embodiments 1 and 2 of the present invention are switched. As shown in FIG. 14, the semiconductor switching elements 5a and 5b and the semiconductor switching elements 5c and 5d are switching-controlled by providing a dead time Td so that the upper and lower arms are not short-circuited. In this case, as shown in FIG. 14, in mode 2 and mode 4, the input current Iin becomes 0 and the reactor current ILf decreases although all the semiconductor switching elements 5a to 5d are not turned off. This indicates that the above-described effects can be obtained even if the switching method of the power converter 1 is the method shown in FIG.

  In each of the first and second embodiments, the control unit 13 is configured to compare the corrected detection voltage Vd ′, which is a value obtained by adding the offset voltage Voffset to the detection voltage Vd, with the threshold voltage Vth. , But is not limited to this. For example, the control unit 13 may be configured to compare the detected voltage Vd with the corrected threshold voltage Vth ′, which is a value obtained by subtracting the offset voltage Voffset from the threshold voltage Vth.

  In this case, the offset circuit 14 outputs the corrected threshold voltage Vth 'which is a value obtained by subtracting the obtained offset voltage Voffset from the threshold voltage Vth. The control unit 13 compares the detection voltage Vd corresponding to the input current Iin detected by the input current detection unit 11 with the correction threshold voltage Vth ′ output by the offset circuit 14. As a result of the comparison, the control unit 13 limits the output when the detected voltage Vd is equal to or higher than the correction threshold voltage Vth '.

  Each function of the control unit 13 and the offset circuit 14 in each of the first and second embodiments described above is realized by a processing circuit. The processing circuit may be dedicated hardware or a processor that executes a program stored in the memory.

  When the processing circuit is dedicated hardware, the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array). , Or a combination of these.

  On the other hand, when the processing circuit is a processor, each function of the control unit 13 and the offset circuit 14 is realized by software, firmware, or a combination of software and firmware. Software and firmware are described as programs and stored in memory. The processor realizes each function described above by reading and executing the program stored in the memory.

  Note that each of the above-described functions may be partially implemented by dedicated hardware and partially implemented by software or firmware.

  As described above, the processing circuit can realize each function described above by hardware, software, firmware, or a combination thereof.

  Although the first and second embodiments have been described as examples of the present invention, the present invention is not limited to the respective configurations of the first and second embodiments, and may be carried out within a range not departing from the spirit of the present invention. It is possible to appropriately combine the respective configurations of the first and second embodiments, to partially modify the respective configurations, and to partially omit the respective configurations.

  1 power converter, 2 high voltage battery, 3 load, 4 low voltage battery, 5 inverter circuit, 5a-5d semiconductor switching element, 6 transformer, 6a primary winding, 6b secondary winding, 7 rectifier circuit, 7a, 7b diode, 8 smoothing circuit, 8a smoothing reactor, 8b smoothing capacitor, 10 input voltage detecting section, 11 input current detecting section, 12 output voltage detecting section, 13 control section, 131 threshold value generator, 132 comparator, 14 offset circuit, 141 adder , 15 Temperature detector.

The power converter according to the present invention includes an inverter circuit that converts an input DC voltage into an AC voltage, a transformer that transforms the AC voltage converted by the inverter circuit, a rectifier circuit that rectifies the AC voltage transformed by the transformer, and a smoothing reactor. From a smoothing circuit that smoothes the output of the rectifier circuit, an input current detection unit that detects the input current input to the inverter circuit, an input voltage detection unit that detects the input voltage input to the inverter circuit, and a smoothing circuit. A power converter having an output voltage detector that detects the output voltage that is output, a controller that controls the power converter, an input voltage detected by the input voltage detector, and an output detected by the output voltage detector. An offset circuit that obtains an offset voltage based on the voltage and An offset voltage is because, a detection voltage corresponding to the input current detected by the input current detecting unit, based on the threshold voltage, the offset voltage, calculates a correction detection voltage is a value obtained by adding the detected voltage correction When the detected voltage is equal to or higher than the threshold voltage, or the offset voltage is subtracted from the threshold voltage to calculate a corrected threshold voltage, and when the detected voltage is equal to or higher than the corrected threshold voltage, the inverter circuit is controlled. The output current is limited by reducing the reactor current flowing in the smoothing reactor and lowering the output voltage.

The power converter according to the present invention includes an inverter circuit that converts an input DC voltage into an AC voltage, a transformer that transforms the AC voltage converted by the inverter circuit, a rectifier circuit that rectifies the AC voltage transformed by the transformer, and a smoothing reactor. From a smoothing circuit that smoothes the output of the rectifier circuit, an input current detection unit that detects the input current input to the inverter circuit, an input voltage detection unit that detects the input voltage input to the inverter circuit, and a smoothing circuit. A power converter having an output voltage detector that detects an output voltage that is output, a controller that controls the power converter, an input voltage detected by the input voltage detector , and an output detected by the output voltage detector. based only on the voltage, it includes an offset circuit for obtaining an offset voltage, a control unit, the offset circuit Based on the offset voltage obtained by the above, the detection voltage corresponding to the input current detected by the input current detection unit, and the threshold voltage, a corrected detection voltage that is a value obtained by adding the offset voltage to the detection voltage is calculated. If the corrected detection voltage is equal to or higher than the threshold voltage, or if the offset voltage is subtracted from the threshold voltage to calculate a corrected threshold voltage, and the detected voltage is equal to or higher than the correction threshold voltage, the inverter circuit is controlled. This reduces the reactor current flowing in the smoothing reactor and limits the output voltage to reduce the output voltage.
Further, the power conversion device according to the present invention includes an inverter circuit that converts an input DC voltage into an AC voltage, a transformer that transforms the AC voltage converted by the inverter circuit, a rectifier circuit that rectifies the AC voltage transformed by the transformer, A smoothing circuit that includes a smoothing reactor to smooth the output of the rectifier circuit, an input current detection unit that detects an input current input to the inverter circuit, an input voltage detection unit that detects an input voltage input to the inverter circuit, and a smoothing A power converter having an output voltage detector that detects the output voltage output from the circuit, a controller that controls the power converter, an input voltage detected by the input voltage detector, and an output voltage detector detected by the output voltage detector. And an offset circuit that obtains an offset voltage based on the output voltage Based on the offset voltage obtained by the above, the detection voltage corresponding to the input current detected by the input current detection unit, and the threshold voltage, a corrected detection voltage that is a value obtained by adding the offset voltage to the detection voltage is calculated. If the corrected detection voltage is equal to or higher than the threshold voltage, or if the offset voltage is subtracted from the threshold voltage to calculate a corrected threshold voltage, and the detected voltage is equal to or higher than the correction threshold voltage, the inverter circuit is controlled. A power converter that limits the reactor current flowing in the smoothing reactor to reduce the output voltage, and further includes a temperature detector that detects the temperature of the power converter as a target temperature, and the offset circuit In addition to the input voltage detected by the input voltage detection unit and the output voltage detected by the output voltage detection unit, Based on the target temperature detected Te, and requests the offset voltage.

Claims (12)

An inverter circuit that converts an input DC voltage into an AC voltage,
A transformer for transforming the AC voltage converted by the inverter circuit,
A rectifying circuit for rectifying the AC voltage transformed by the transformer,
A smoothing circuit that includes a smoothing reactor and that smoothes the output of the rectifier circuit;
An input current detection unit that detects an input current input to the inverter circuit,
An input voltage detection unit that detects an input voltage that is input to the inverter circuit; and a power converter that includes an output voltage detection unit that detects an output voltage output from the smoothing circuit,
A control unit for controlling the power converter,
An offset circuit that obtains an offset voltage based on the input voltage detected by the input voltage detection unit and the output voltage detected by the output voltage detection unit,
Equipped with
The control unit is
Based on the offset voltage obtained by the offset circuit, a detection voltage corresponding to the input current detected by the input current detection unit, and a threshold voltage, the inverter circuit is controlled to flow into the smoothing reactor. An electric power conversion device that limits an output by reducing a reactor current to reduce the output voltage. The offset circuit is
The power converter according to claim 1, wherein the offset voltage is calculated such that the higher the input voltage is, the larger the offset voltage is, and the lower the output voltage is, the larger the offset voltage is. The temperature of the power converter, further comprising a temperature detection unit for detecting as a target temperature,
The offset circuit is
In addition to the input voltage detected by the input voltage detection unit and the output voltage detected by the output voltage detection unit, the offset voltage is set based on the target temperature detected by the temperature detection unit. The power converter according to claim 1. The offset circuit is
The offset voltage is calculated such that the offset voltage increases as the input voltage increases, the offset voltage increases as the output voltage decreases, and the offset voltage increases as the target temperature increases. The power converter described. An inverter circuit that converts an input DC voltage into an AC voltage,
A transformer for transforming the AC voltage converted by the inverter circuit,
A rectifying circuit for rectifying the AC voltage transformed by the transformer,
A power converter including a smoothing reactor, a smoothing circuit that smoothes an output of the rectifier circuit, and an input current detection unit that detects an input current input to the inverter circuit;
A control unit for controlling the power converter,
A temperature detector that detects the temperature of the power converter as a target temperature;
An offset circuit that obtains an offset voltage based on the target temperature detected by the temperature detection unit,
Equipped with
The control unit is
Based on the offset voltage obtained by the offset circuit, a detection voltage corresponding to the input current detected by the input current detection unit, and a threshold voltage, the inverter circuit is controlled to flow into the smoothing reactor. An electric power conversion device that limits the reactor current to reduce the output voltage output from the smoothing circuit. The offset circuit is
The power conversion device according to claim 5, wherein the offset voltage is calculated such that the offset voltage increases as the target temperature increases. The power converter according to any one of claims 3 to 6, wherein the temperature of the power converter is the temperature of the rectifier circuit or the temperature of the smoothing circuit. The temperature detection unit,
The power conversion device according to claim 3, wherein instead of the temperature of the power converter, a temperature of a cooler that cools the power converter is detected as the target temperature. The cooler is a water-cooled cooler,
The power converter according to claim 8, wherein the temperature of the cooler is a temperature of cooling water. The offset circuit is
The offset voltage thus obtained is output as a corrected detection voltage that is a value obtained by adding the detection voltage,
The control unit is
The correction detection voltage output by the offset circuit is compared with the threshold voltage, and when the correction detection voltage is equal to or higher than the threshold voltage, the output limitation is performed. The power converter described. The offset circuit is
The corrected offset voltage, which is a value obtained by subtracting the offset voltage obtained from the threshold voltage,
The control unit is
The output limit is compared when the detected voltage is compared with the correction threshold voltage output by the offset circuit, and when the detected voltage is equal to or higher than the correction threshold voltage. The power converter described. The power conversion device according to any one of claims 1 to 11, wherein the rectifier circuit is a diode rectifier circuit.

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