JP6613951B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device, and more particularly, to a power conversion device including a flying capacitor.

  Conventionally, a power converter provided with a flying capacitor is known (for example, refer to patent documents 1).

  Patent Document 1 discloses a DC-DC converter including a flying capacitor. The DC-DC converter includes a reactor, a current detection circuit that detects a current value of a current flowing through the reactor, a switch circuit connected to the reactor, and a control circuit that controls driving of the switch circuit. . The control circuit is configured to feedback control the drive of the switch circuit so that the current value of the current flowing through the reactor becomes the command current value based on the current value detected by the current detection circuit.

JP 2013-192383 A

  However, in the DC-DC converter described in Patent Document 1, the control circuit controls the driving of the switch circuit based on the current value detected by the current detection circuit that detects the current value of the current flowing through the reactor. It is configured as follows. Here, the main component of the current flowing through the reactor is a DC component, while a ripple component (high-frequency component) resulting from switching of the switch circuit is superimposed on the current flowing through the reactor. In order to accurately detect the current value flowing through the reactor, it is necessary to detect not only the DC component but also the ripple component, so the current detection circuit is configured to detect both the DC component and the ripple component. There is a need to. The ripple component has a frequency twice as high as the switching frequency of the switch circuit, and the waveform of the ripple component is a triangular wave. Therefore, in order to accurately observe the ripple component waveform, it is necessary to detect the current at a frequency that is five times or more the frequency of the ripple component (a frequency that is ten times or more the switching frequency). Therefore, in the DC-DC converter described in Patent Document 1, the current detection circuit is required to have a wide detection frequency band whose lower limit is direct current (0 Hz) and whose upper limit is 10 times or more the switching frequency. Therefore, there is a problem that the configuration of the current detection circuit (current detection unit) is complicated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power conversion device capable of suppressing the configuration of the current detection unit from becoming complicated. It is to be.

  In order to achieve the above object, a power converter according to one aspect of the present invention includes a reactor having one end connected to one end of a DC output circuit, and a first end connected to the other end of the reactor. A switching circuit including a first switching element and a second switching element having one end connected to the other end of the first switching element and the other end connected to the other end of the DC output circuit; A flying capacitor connected to a connection point between the switching element and the second switching element, a capacitor current detection unit for detecting a current value of an alternating current flowing through the flying capacitor, and a current value of the alternating current detected by the capacitor current detection unit The first switching element is acquired based on the acquired current value flowing through the reactor based on the acquired current value flowing through the reactor. And a control section for controlling the on-off period of the second switching element.

  Here, an alternating current corresponding to charge / discharge flows in the flying capacitor. In addition, the alternating current flowing through the flying capacitor does not substantially include a direct current component and a low frequency component, but includes only a substantially high frequency component, while the magnitude of the current value (amplitude magnitude) is the value of the current flowing through the reactor. (DC component, low frequency component and ripple component). Accordingly, the inventors of the present application have come up with the present invention by paying attention to the above phenomenon of the flying capacitor. That is, in the power conversion device according to one aspect of the present invention, as described above, the control unit acquires the current value flowing through the reactor based on the current value of the alternating current of the flying capacitor detected by the capacitor current detection unit. Thus, the ON / OFF period of the first switching element and the second switching element is controlled based on the acquired value of the current flowing through the reactor. Thereby, based on the high frequency component of the current value of the alternating current of the flying capacitor detected by the capacitor current detector, the direct current component, low frequency component, and ripple component of the current value flowing through the reactor can be acquired. As a result, a reactor current detector configured to detect a high frequency component from a direct current component when controlling the on / off period of the first switching element and the second switching element based on the value of the current flowing through the reactor. It is possible to use a capacitor current detector that can detect only high-frequency components without using them. Therefore, since the capacitor current detection unit capable of detecting only the high frequency component can be used, it is possible to prevent the configuration of the current detection unit from becoming complicated. In the present specification, “high frequency” means, for example, a frequency of 10 kHz or more, and “low frequency” means, for example, a frequency from 400 Hz or less to direct current (frequency is 0). It is described.

  The power conversion device according to the above aspect preferably further includes an amplitude detection unit that detects the amplitude of the current value of the alternating current detected by the capacitor current detection unit, and the control unit detects the magnitude of the amplitude detected by the amplitude detection unit. Based on this, control is performed to acquire the value of the current flowing through the reactor. If comprised in this way, since the amplitude of the electric current value of the alternating current which flows into a flying capacitor respond | corresponds to the direct current | flow component (or low frequency component) of the electric current value which flows into a reactor, the amplitude detection part of the electric current value of alternating current By detecting the amplitude, the direct current component (or low frequency component) of the current value flowing through the reactor can be easily obtained.

  In the power conversion device according to the above aspect, the capacitor current detection unit is preferably configured such that the lower limit of the detection frequency band for detecting the current value of the alternating current is equal to or more than 1/10 of the switching frequency of the switching circuit. ing. With this configuration, it is not necessary to configure the capacitor current detection unit to have a wide detection frequency band in which the lower limit of the detection frequency band is less than 1/10. A current detection unit (for example, a general-purpose high-frequency current transformer) that does not have a function of detecting a frequency component can be used. As a result, the capacitor current detector can be easily configured, so that the power converter can be easily configured.

  In the power conversion device according to the above aspect, the control unit preferably includes a first period in which the first switching element is turned off and the second switching element is turned on in one cycle of the switching operation of the switching circuit, The second period during which the first switching element is turned on and the second switching element is turned off is controlled alternately, and the minimum length of the first period and the minimum length of the second period are set to a predetermined length. It is comprised so that it may set above. If comprised in this way, while setting predetermined length to the length which can be sampled, and performing sampling in at least one period of the 1st period and the 2nd period, the alternating current which flows into a flying capacitor The current value of the current can be acquired more reliably.

  In the power conversion device according to the above aspect, preferably, the current value flowing through the reactor is detected, and the upper limit of the detection frequency band for detecting the current value flowing through the reactor is set to be less than 10 times the switching frequency of the switching circuit. The reactor current detector further includes a first switching element and a second switching element when the current value of the alternating current detected by the capacitor current detector exceeds a predetermined first threshold value. Both the elements are turned off, the first switching element and the second switching element are both turned off, and the value of the current flowing through the reactor detected by the reactor current detector is less than a predetermined second threshold value. In such a case, the control for restarting the driving of the first switching element and the second switching element is performed. It has been made. Here, for example, when a surge is applied to the DC output circuit, an overcurrent may be generated in the reactor. In this case, if the driving of the switching circuit is continued, the overcurrent may be further amplified. Therefore, the driving of the switching circuit is stopped (the first switching element is turned off and the second switching element is turned off). It is conceivable to perform control to turn off. In this case, since no current flows through the flying capacitor, it becomes difficult to obtain the current value flowing through the reactor based on the current value of the alternating current flowing through the flying capacitor, and it is determined whether or not the overcurrent has disappeared. It will be difficult to judge. In contrast, in the present invention, when the value of the current flowing through the reactor detected by the reactor current detection unit is less than a predetermined second threshold value, the first switching element and the second switching element By performing the control to resume the drive, even when the first switching element and the second switching element are both off and no current flows through the flying capacitor, it is less than the second threshold value. When this occurs (when the overcurrent disappears), driving of the first switching element and the second switching element can be resumed. Further, in the present invention, since it is not necessary to detect the ripple component by the reactor current detection unit, as described above, the upper limit of the detection frequency band for detecting the current value flowing through the reactor of the reactor current detection unit is set to the switching frequency of the switching circuit. By setting it to less than 10 times, the reactor current detection unit can be easily configured.

  In the power conversion device according to the above aspect, the switching circuit preferably further includes a first diode and a second diode, and the first diode, the second diode, the first switching element, and the second diode The switching elements are connected in series in this order, and the flying capacitor has one end connected to the connection point between the first switching element and the second switching element, and the third diode and the fourth diode. The other end is connected to a connection point with the other diode. If comprised in this way, compared with the case where it is provided with four switching elements in a switching circuit and it is comprised so that each of four switching elements may be controlled, the structure and control of a power converter device can be simplified. .

  In the power conversion device according to the above aspect, the switching circuit preferably further includes a third switching element and a fourth switching element, and the third switching element, the fourth switching element, and the first switching element. And the second switching element are connected in series in this order, and the flying capacitor has one end connected to the connection point between the first switching element and the second switching element, The other end is connected to a connection point between the switching element and the fourth switching element. According to this configuration, when the current is passed from the reactor to the DC output circuit, the third switching element and the fourth switching element are used. When the current is passed from the DC output circuit to the reactor, the second switching element and the second switching element are used. Control can be performed in the same manner as the switching element 1. As a result, the power converter can be configured to have a function of regenerating power (a function of generating power) in the DC output circuit.

  In the power conversion device according to the above aspect, preferably, the first switching element and the second switching element are made of a wide band gap semiconductor, and the capacitor current detection unit detects a current value of the alternating current. Is lower than 1/10 of the switching frequency of the wide band gap semiconductor. With this configuration, since the wide band gap semiconductor can set a relatively high switching frequency (for example, compared with a silicon semiconductor), the first switching element and the second switching element can be set as the wide band gap semiconductor. By configuring from the above, the switching frequency can be increased (for example, 100 kHz or more), and the reactor can be downsized. Here, when a wide band gap semiconductor is provided in a conventional power conversion device, the lower limit of the detection frequency band of the current detection unit for detecting the current value flowing through the reactor is DC (0 Hz) and the upper limit is 100 kHz or more. There is a need. However, when a general Hall element is used as a current detection unit for detecting the current value flowing through the reactor, the lower limit of the detection frequency band is direct current (0 Hz) and the upper limit is about 50 kHz. In addition, when a wide band gap semiconductor is provided, it is necessary to specially configure the current detection unit to have a detection frequency band corresponding to the wide band gap semiconductor. As a result, the configuration of the current detection unit is considered to be particularly complicated (expensive). Therefore, in the present invention, the capacitor current detection unit is configured such that the lower limit of the detection frequency band for detecting the current value of the alternating current is one tenth or more of the switching frequency of the wide band gap semiconductor. A current detection unit (for example, a general-purpose high-frequency current transformer) that does not have a function of detecting a low-frequency component can be used without providing the current detection circuit configured as described above, and the current detection unit can be easily configured. Can do. Therefore, the present invention is particularly effective when a wide band gap semiconductor is provided in the power conversion device.

  In the power conversion device according to the above aspect, the DC output circuit preferably includes an AC power source and a rectifier circuit that rectifies an AC current from the AC power source into a DC current, and one end of the reactor is one of the rectifier circuits. The other end of the second switching element is connected to the other end of the rectifier circuit. If comprised in this way, even when it comprises a power converter device which is a case where an alternating current power supply is used as a power supply as an AC-DC converter, a current detection part (power converter device) can be comprised easily.

  According to the present invention, it is possible to prevent the configuration of the current detection unit from becoming complicated as described above.

1 is an electric circuit diagram showing an overall configuration of a power conversion device according to a first embodiment of the present invention. It is a figure for demonstrating the voltage waveform and current waveform in the power converter device by 1st Embodiment of this invention. It is an electric circuit diagram for demonstrating the state of the switching circuit of the power converter device by 1st Embodiment of this invention, and how to flow an electric current. It is an electric circuit diagram which shows the whole structure of the power converter device by 2nd Embodiment of this invention. It is an electric circuit diagram which shows the whole structure of the power converter device by 3rd Embodiment of this invention. It is a figure for demonstrating the voltage waveform and current waveform in the power converter device by 3rd Embodiment of this invention. It is an electric circuit diagram which shows the whole structure of the power converter device by the modification of 1st Embodiment of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Embodiments of the invention will be described below with reference to the drawings.

[First Embodiment]
With reference to FIGS. 1-3, the structure of the power converter device 100 by 1st Embodiment is demonstrated. In FIG. 1, the electric circuit diagram of the power converter device 100 is shown.

(Overall configuration of power converter)
As shown in FIG. 1, the power conversion device 100 converts power having a voltage Vr1 (voltage value e) of the DC output circuit 1 into power having a voltage value E that is equal to or higher than the voltage value e of the voltage Vr1, It is configured to supply the load 101. For example, the power conversion apparatus 100 is configured as a so-called boost chopper. The power converter 100 is provided with a flying capacitor 2 and a switching circuit 3. The power converter 100 is driven by the switching circuit 3 at a high frequency, whereby the flying capacitor 2 is repeatedly charged and discharged. A voltage having a desired voltage value E (a boosted voltage) is supplied to the load 101 side. In other words, the power conversion device 100 is configured as a so-called switched capacitor type (flying capacitor type) power conversion circuit. The power conversion circuit 100 is configured as a PFC (Power Factor Correction) circuit, that is, a circuit having a high input power factor. In this specification, “high frequency” means, for example, a frequency of 10 kHz or more, and “low frequency” means a frequency from 400 Hz or less to direct current (frequency is 0). ing.

  Further, in the first embodiment, the power conversion device 100 is configured as a DC-DC converter that converts (boosts) the DC current from the DC output circuit 1 and supplies it to the load 101. In the present specification, the “direct current” is not limited to a current having a waveform with a constant current value, but has a waveform (rectification waveform) in which the alternating current of the alternating current source 11 is rectified and the current value fluctuates. It is described as meaning a broad concept including current.

(Configuration of each part of the power converter)
Here, in the first embodiment, as shown in FIG. 1, the DC output circuit 1 includes an AC power supply 11 and a rectifier circuit 12 that rectifies an AC current from the AC power supply 11 into a DC current.

  The AC power supply 11 has, for example, a sinusoidal waveform having a commercial frequency (50 Hz or 60 Hz), and is configured to supply an AC current of voltage Vin and current Iin to the rectifier circuit 12 (load 101 side). .

  The rectifier circuit 12 includes rectifier diodes 12a to 12d and a capacitor 12e, and is configured to rectify an alternating current having a voltage Vin from the alternating current power supply 11 into a direct current having a voltage Vr1 (for example, a voltage value e). Yes. Thereby, for example, the voltage value e is at node N1, and the voltage value is 0 at node N2. Since the direct current having the voltage Vr1 has a rectified waveform, the voltage value e is not limited to a constant value but may be a fluctuating value.

  Moreover, the power converter 100 is provided with a reactor 4 (chopper reactor). Reactor 4 has one end connected to DC output circuit 1 and is connected in series to DC output circuit 1. That is, as shown in FIG. 1, the reactor 4 and the DC output circuit 1 (rectifier circuit 12) are connected via the node N1. The reactor 4 is configured to supply a direct current from the direct current output circuit 1 to the switching circuit 3. Then, when the driving of the switching circuit 3 is controlled by the control unit 5 described later, the current value IL flowing through the reactor 4 is changed to a rectified waveform similar to the voltage Vr1, so that the current Iin is equal to the voltage Vin. A sine wave of phase can be obtained.

  Here, in the first embodiment, the switching circuit 3 includes a first switching element 31 having one end connected to the other end (load 101 side) of the reactor 4, and one end at the other end of the first switching element 31. And a second switching element 32 connected to the other end of the DC output circuit 1 (rectifier circuit 12).

  That is, the reactor 4 and the first switching element 31 are connected via the node N3. The DC output circuit 1 (rectifier circuit 12) and the second switching element 32 are connected via a node N4.

  The switching circuit 3 further includes a first diode 33 and a second diode 34. The first diode 33, the second diode 34, the first switching element 31, and the second switching element 32 are They are connected in series. That is, in the first embodiment, the first diode 33, the second diode 34, the first switching element 31, and the second switching element 32 constitute a diode bridge circuit and a bridge circuit of the switching element.

  Specifically, the anode of the first diode 33 and the cathode of the second diode 34 are connected in series via the node N5. The first switching element 31 and the second switching element 32 are connected in series via the node N6. The anode of the second diode 34 and the first switching element 31 are connected in series via the node N3. The node N5 is an example of the “connection point between the first diode and the second diode” in the claims. The node N6 is an example of the “connection point between the first switching element and the second switching element” in the claims.

  Here, in the first embodiment, the first switching element 31 and the second switching element 32 are made of a wide band gap semiconductor. Specifically, the first switching element 31 and the second switching element 32 are semiconductors including any one of SiC, GaN, diamond, AlN, or ZnO, and have a wider (wide) band gap than a silicon semiconductor. It is comprised by. For example, the first switching element 31 and the second switching element 32 are configured as reverse blocking IGBTs, MOSFETs, or bipolar transistors made of the above wide band gap semiconductor.

  Further, the first diode 33 and the second diode 34 are arranged so as to function as a backflow prevention diode. The first diode 33 and the second diode 34 are made of a wide band gap semiconductor (for example, a wide gap semiconductor of the same type as the first switching element 31 and the second switching element 32) or a silicon semiconductor.

  Accordingly, the switching circuit 3 is configured to be able to be driven by a high-frequency switching frequency f having a frequency of 100 kHz or more and several MHz or less, for example. The first switching element 31 and the second switching element 32 are connected to a control unit 5 described later, and are configured to be turned on / off (driven) based on a control signal from the control unit 5.

  Here, in the first embodiment, as shown in FIG. 1, the flying capacitor 2 has one end connected to a node N6 that is a connection point between the first switching element 31 and the second switching element 32, and The other end is connected to a node N5 that is a connection point between the first diode 33 and the second diode. Thus, the flying capacitor 2 repeats charging and discharging by driving the first switching element 31 and the second switching element 32 so that the voltage value on the load 101 side (potential difference between both ends of the capacitor 6) becomes E. It is configured.

  Further, the power converter 100 is provided with a control unit 5. In the first embodiment, the current value IL flowing through the reactor 4 is acquired based on the current value Ic of the alternating current detected by the current detection unit 7 described later, and based on the acquired current value IL flowing through the reactor 4, The on / off period of the first switching element 31 and the second switching element 32 is controlled. This will be specifically described below.

  Here, FIG. 2 shows a half cycle of the voltage waveform and the current waveform in the power conversion apparatus 100 with the vertical axis representing the voltage value or current value and the horizontal axis representing time. Specifically, FIG. 2 shows the waveform of the potential difference (voltage Vs1) across the first switching element 31, the waveform of the potential difference (voltage Vs2) across the second switching element 32, and the nodes N3 and N4. 5 shows a waveform of the potential difference (voltage Vr2), a waveform of the current value IL of the reactor 4, and a waveform of the current value Ic of the flying capacitor 2. The current value Ic represents the magnitude of the current value flowing in the direction of discharging from the flying capacitor 2 as positive, and represents the magnitude direction of the current value flowing in the direction of charging as negative.

  As shown in FIG. 3, the first switching element 31 and the second switching element 32 are configured such that the pulse width (on / off period) and the pulse period are controlled by the control unit 5 (see FIG. 1). Specifically, the controller 5 repeatedly charges and discharges the flying capacitor 2 by repeatedly forming the states of FIGS. 3A to 3D in one cycle of the switching operation of the switching circuit 3. The voltage difference E between both ends of the capacitor 6 (potential difference between both ends of the load 101) is controlled to be maintained at the voltage value E. Note that the potential difference between both ends of the load 101 corresponds to the potential difference between the node N7 and the node N8. In FIG. 3, the current flow is indicated by thick arrows. The capacitor 6 has a function of charging and discharging so as to generate a voltage having a voltage value E and smoothing a current flowing from the switching circuit 3 to the load 101.

  Specifically, as shown in FIG. 3A, the control unit 5 turns on both the first switching element 31 and the second switching element 32 so that the voltage value of the voltage Vr2 is substantially zero and The flying capacitor 2 is in a state where no current flows (current value Ic is 0). This period is referred to as period T1 (see FIG. 2). In FIG. 2, a part of the period T <b> 1 is labeled, but the state in which both the first switching element 31 and the second switching element 32 are on (Vs1 = 0 and Vs2 = 0) is as follows: Both are assumed to be in the period T1. Also in the following periods T2 to T4, only a part of the reference numerals are given in FIG.

  Further, as shown in FIG. 3B, the control unit 5 turns the first switching element 31 off (Vs1 = Vc) and the second switching element 32 on (Vs2 = 0). The voltage value of the voltage Vr2 is approximately E / 2 (approximately Vc), and a current flows through the flying capacitor 2 (current value Ic is negative). During this period, the flying capacitor 2 is charged. This period is referred to as period T2 (see FIG. 2). The period T2 is an example of the “first period” in the claims.

  Further, as shown in FIG. 3C, the control unit 5 sets the first switching element 31 on (Vs1 = 0) and the second switching element 32 off (Vs2 = E−Vc). As a result, the voltage value of the voltage Vr2 is approximately E / 2 (approximately E-Vc) and a current flows from the flying capacitor 2 (the current value Ic is positive). During this period, the flying capacitor 2 is discharged. A period in this state is a period T3 (see FIG. 2). The period T3 is an example of the “second period” in the claims.

  Further, as shown in FIG. 3D, the control unit 5 sets the first switching element 31 to the off state (Vs1 = Vc) and the second switching element 32 to the off state (Vs2 = E−Vc). As a result, the voltage value of the voltage Vr2 is E and no current flows in the flying capacitor 2 (current value Ic is 0). A period in this state is a period T4 (see FIG. 2).

  Here, in the first embodiment, as shown in FIG. 2, the control unit 5 performs control so that the periods T2 and T3 are alternately provided, and the minimum length T2m of the period T2 and the minimum length of the period T3. The length T3m is set to a predetermined lower limit length Tp1 or more. More preferably, the control unit 5 sets the minimum length T2m of the period T2 and the minimum length T3m of the period T3 to be not less than a predetermined lower limit length Tp1 and not more than a predetermined upper limit length Tp2 (not shown). It is configured.

  Here, when the current value Ic is sampled by the control unit 5 (amplitude detection unit 8), the current value Ic is a stable value regardless of the ON or OFF edge of the current waveform of the current value Ic. (Level). For example, when the minimum length T2m of the period T2 and the minimum length T3m of the period T3 are smaller than 5% of the pulse period TM (upper limit values of the periods T2 and T3) from the control unit 5 to the switching circuit 3, sampling is performed. May fail. Therefore, in the first embodiment, the predetermined lower limit length Tp1 is set to be about 5% (1/20) of the pulse period TM from the control unit 5 to the switching circuit 3. Accordingly, the minimum length T2m of the period T2 and the minimum length T3m of the period T3 are configured to be 5% or more (Tp1 or more) of the pulse period TM.

  Further, if the minimum length T2m of the period T2 and the minimum length T3m of the period T3 are too long, for example, if they exceed 10% of the pulse period TM, the variable range of the period T2 and the period T3 (from the lower limit value to the upper limit) Therefore, there is a problem that the control performance as a boost chopper is lowered. Therefore, in the first embodiment, the predetermined upper limit length Tp2 is set to be about 10% (1/10) of the pulse period TM, and the minimum length T2m of the period T2 and the minimum of the period T3 are set. The length T3m is configured to be 10% or less of the pulse period TM.

  As shown in FIG. 1, in the first embodiment, the power conversion device 100 is provided with a current detection unit 7. The current detection unit 7 is provided in the vicinity of the flying capacitor 2 and is configured to detect the current value Ic of the alternating current flowing through the flying capacitor 2. For example, the current detection unit 7 is configured as a high-frequency current transformer. In principle, the current transformer can be reduced in size as the frequency increases. The current detector 7 is an example of the “capacitor current detector” in the claims.

  As shown in FIG. 2, the absolute value of the instantaneous value of the current value Ic and the absolute value of the instantaneous value of the current value IL are substantially equal during the charge / discharge periods (periods T2 and T3). Therefore, the value during charging (negative value) of the current value Ic is inverted to supplement the values of the current value Ic during periods (periods T1 and T4) (determining the envelope of the current waveform). Thus, the current value IL can be acquired based on the current value Ic.

  Here, as shown in FIG. 2, a ripple component is superimposed on the current value IL. In order to maintain the stability of the control of the current value IL, it is necessary to change the operation of the switching circuit 3 so as to follow the change of the current value IL including the ripple component. Here, since ripple occurs every time the flying capacitor 2 is charged and discharged, the ripple frequency is twice the switching frequency f (2 × f). In addition, as shown in FIG. 2, the ripple waveform is a triangular wave, so in order to accurately observe (capture) the waveform, it is necessary to detect at least the harmonic component (fifth harmonic component) of the ripple frequency. There is. That is, in order to detect ripple, it is necessary to detect at a frequency 10 times the switching frequency f. In addition, the magnitude | size (impedance) of the reactor 4 is comprised so that a ripple component may be 10%-20% of a direct current component or a commercial frequency component.

  Therefore, in the first embodiment, the current detection unit 7 is configured such that the upper limit of the detection frequency band is 10 times or more the switching frequency f of the switching circuit 3. Preferably, in order to further improve detection accuracy, the current detection unit 7 is configured such that the upper limit of the detection frequency band is 50 times or more the switching frequency f.

  Moreover, since the capacitance of the flying capacitor 2 is relatively small, a low frequency component is not superimposed on the current value Ic. The low frequency component of the current value IL appears as a magnitude (change) in amplitude with respect to the current value Ic. Therefore, it is not necessary to detect the low frequency component (DC component and commercial frequency component) of the current value Ic. Therefore, in the first embodiment, the current detection unit 7 is configured such that the lower limit of the detection frequency band for detecting the current value Ic is 1/10 or more of the switching frequency f of the switching circuit 3. In the first embodiment, the switching frequency f corresponds to the switching frequency f of the first switching element 31 and the second switching element 32 made of a wide band gap semiconductor.

  Here, in the first embodiment, the power converter 100 is provided with an amplitude detector 8. The amplitude detector 8 is configured to detect the amplitude of the current value Ic of the alternating current detected by the current detector 7. Specifically, the amplitude detection unit 8 includes an absolute value acquisition unit 81 and a sample hold unit 82.

  The absolute value acquisition unit 81 is configured to acquire (detect) the absolute value of the current value Ic of the alternating current detected by the current detection unit 7. As a result, the current value Ic detected by the current detection unit 7 during the charging period (period T2) is inverted, and the magnitude of the amplitude of the current value IL can be acquired.

  The sample hold unit 82 is configured to acquire (sample) the magnitude of the amplitude of the current value IL acquired by the absolute value acquisition unit 81 for each sampling period TS.

  The sampling period TS may be set so as to perform sampling in each of the charging period T2 and the discharging period T3, or either the charging period T2 or the discharging period T3. It may be set to perform sampling. For example, the sampling period TS may be set to a value equal to the pulse period TM, or may be set to be 1/2 of the pulse period TM.

  And the control part 5 is comprised so that the value sampled from the sample hold part 82 (magnitude of amplitude of electric current value IL) may be acquired. Thereby, in 1st Embodiment, the control part 5 is comprised so that the electric current value IL which flows into the reactor 4 can be acquired based on the magnitude | size of the amplitude detected by the amplitude detection part 8. FIG.

  And in 1st Embodiment, the control part 5 is comprised so that the time ratio control of the on-off period (period T1-T4) of the switching circuit 3 may be performed based on the acquired electric current value IL which flows into the reactor 4. FIG. Yes. For example, the control unit 5 compares the current value IL with the command current value Io so that when the current value IL is smaller than the command current value Io, the switching circuit 3 increases the voltage value of the voltage Vr2. When the current value IL is larger than the command current value Io, the switching circuit 3 is controlled so that the voltage value of the voltage Vr2 becomes smaller. Thereby, the control unit 5 is configured to be able to perform feedback control so that the current value IL substantially matches the command current value Io while maintaining the voltage value E applied to the load 101.

[Effect of the first embodiment]
In the first embodiment, the following effects can be obtained.

  In the first embodiment, as described above, the control unit 5 acquires and acquires the current value IL flowing through the reactor 4 based on the current value Ic of the alternating current of the flying capacitor 2 detected by the current detection unit 7. Based on the current value IL flowing through the reactor 4, the ON / OFF period (time ratio of the periods T1 to T4) of the first switching element 31 and the second switching element 32 is controlled. As a result, the control unit 5 determines the DC component, low frequency component, and ripple component of the current value IL flowing through the reactor 4 based on the high frequency component of the current value Ic of the alternating current of the flying capacitor 2 detected by the current detection unit 7. Can be acquired. As a result, a reactor current detector configured to detect a high frequency component from a direct current component when controlling the on / off period of the first switching element 31 and the second switching element 32 based on the current value IL is used. The current detector 7 (current transformer) can be used. Therefore, by using the current detection unit 7 (current transformer), it is possible to prevent the configuration of the current detection unit 7 from becoming complicated.

  In the first embodiment, as described above, the power conversion device 100 is provided with the amplitude detection unit 8 that detects the amplitude of the current value Ic of the alternating current detected by the current detection unit 7. Then, the control unit 5 is configured to perform control for acquiring the current value IL flowing through the reactor 4 based on the magnitude of the amplitude detected by the amplitude detection unit 8. As a result, the amplitude of the current value Ic of the alternating current flowing through the flying capacitor 2 corresponds to the direct current component and the low frequency component of the current value IL flowing through the reactor 4. By detecting the amplitude, the direct current component and the low frequency component of the current value IL flowing through the reactor 4 can be easily obtained.

  In the first embodiment, as described above, the current detection unit 7 is configured such that the lower limit of the detection frequency band for detecting the current value Ic of the alternating current is 1/10 or more of the switching frequency f of the switching circuit 3. Configure. As a result, it is not necessary to configure the current detection unit 7 to have a wide detection frequency band in which the lower limit of the detection frequency band is less than 1/10. Therefore, the current detection unit 7 detects a low frequency component. It is possible to use a current detection unit (for example, a general-purpose high-frequency current transformer) that does not have a function to perform. As a result, since the current detection unit 7 can be easily configured, the power conversion device 100 can be easily configured.

  In the first embodiment, as described above, the control unit 5 performs the period T2 in which the first switching element 31 is turned off and the second switching element 32 is turned on in one cycle of the switching operation of the switching circuit 3; The period T3 during which the first switching element 31 is turned on and the second switching element 32 is turned off is controlled alternately, and the minimum length T2m of the period T2 and the minimum length T3m of the period T3 are set to a predetermined length. It is configured to be set to Tp1 or more. As a result, the predetermined length Tp1 is set to a length that allows sampling, and sampling is performed during at least one of the period T2 and the period T3, whereby the current value of the alternating current flowing in the flying capacitor 2 is obtained. The current value Ic can be acquired more reliably with Ic.

  In the first embodiment, as described above, the switching circuit 3 is provided with the first diode 33 and the second diode 34, and the first diode 33, the second diode 34, the first switching element 31, and the second diode 34 are provided. The switching element 32 is configured to be connected in series in this order. The flying capacitor 2 has one end connected to a connection point (node N6) between the first switching element 31 and the second switching element 32, and a connection point (node N5) between the first diode 33 and the second diode 34. ) Is connected to the other end. Thereby, compared with the case where the switching circuit 3 is provided with four switching elements and each of the four switching elements is controlled, the configuration of the power conversion device 100 can be simplified.

  In the first embodiment, as described above, the first switching element 31 and the second switching element 32 are made of wide band gap semiconductors, and the current detection unit 7 detects the current value Ic of the alternating current. The lower limit of the frequency band is configured to be 1/10 or more of the switching frequency f of the wide band gap semiconductor. Accordingly, since the wide band gap semiconductor can set a relatively large switching frequency (compared to, for example, a silicon semiconductor), the first switching element 31 and the second switching element 32 are configured from the wide band gap semiconductor. Thus, the switching frequency f can be increased (for example, 100 kHz or more), and the reactor 4 can be reduced in size.

  In the first embodiment, as described above, the DC output circuit 1 is provided with the AC power supply 11 and the rectifier circuit 12 that rectifies an AC current from the AC power supply 11 into a DC current. Further, one end of the reactor 4 is connected to one end (node N1) of the rectifier circuit 12, and the other end of the second switching element 32 is connected to the other end (node N2) of the rectifier circuit 12. Thereby, even when the power converter 100 which is the case where the alternating current power supply 11 is used as a power supply is comprised as an AC-DC converter, the electric current detection part 7 (power converter 100) can be comprised easily.

[Second Embodiment]
Next, with reference to FIG. 4, the structure of the power converter device 200 by 2nd Embodiment is demonstrated. In the second embodiment, unlike the power conversion device 100 according to the first embodiment, a reactor current detection unit 204a is provided. In addition, about the structure same as the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

(Configuration of Power Conversion Device according to Second Embodiment)
As illustrated in FIG. 4, the power conversion device 200 according to the second embodiment includes a reactor current detection unit 204 a, a control unit 205, and a capacitor current detection unit 207.

  Reactor current detection unit 204a detects current value IL flowing through reactor 4 and sets the upper limit of the detection frequency band for detecting current value IL flowing through reactor 4 to less than 10 times the switching frequency f of switching circuit 3. Has been. That is, the reactor current detection unit 204a can acquire the magnitude of the current value IL, but does not have a function of detecting a ripple component (a component having a frequency that is 10 times the switching frequency f). It is configured.

  For example, the reactor current detection unit 204 a is configured by a shunt resistor (general-purpose shunt resistor) whose upper limit of the detection frequency band is less than 10 times the switching frequency f of the switching circuit 3.

  The capacitor current detection unit 207 is configured by a high-frequency current transformer, like the current detection unit 7 according to the first embodiment.

  In addition, the control unit 205 switches the first switching element 31 and the second switching element 32 when the current value Ic of the alternating current detected by the capacitor current detection unit 207 exceeds a predetermined first threshold value It1. The current value IL flowing through the reactor 4 detected by the reactor current detection unit 204a when both the first switching element 31 and the second switching element 32 are turned off and both are turned off (see FIG. 3D) is When it becomes less than a predetermined second threshold value It2, control is performed to resume driving of the first switching element 31 and the second switching element 32.

  Specifically, control unit 205 determines that an overcurrent has occurred in power conversion device 200 when current value Ic of the alternating current detected by capacitor current detection unit 207 exceeds first threshold value It1. The control for protecting the power conversion device 200 is configured to start. That is, the first threshold value It1 is set to a value larger than the current value Ic flowing through the flying capacitor 2 when the switching circuit 3 is normally driven (not overcurrent).

  And the control part 205 performs control which stops the drive of the switching circuit 3 by making both the 1st switching element 31 and the 2nd switching element 32 into an OFF state as control for protecting the power converter device 200. It is configured as follows.

  And the control part 205 is comprised so that the electric current value IL which flows into the reactor 4 detected by the reactor current detection part 204a may be acquired, in order to detect extinction of overcurrent. Then, when the current value IL becomes less than the second threshold value It2, the control unit 205 determines that the overcurrent has disappeared, and the first switching element 31, the second switching element 32 (switching circuit 3) ) Is restarted. For example, the second threshold value It2 is set to the upper limit value of the current value IL flowing through the reactor 4 in a normal state (when it is not an overcurrent).

  Note that also in the power conversion device 200 according to the second embodiment, the control unit 205 acquires and acquires the current value IL flowing through the reactor 4 based on the current value Ic of the alternating current detected by the capacitor current detection unit 207. The on / off period of the first switching element 31 and the second switching element 32 is controlled based on the current value IL flowing through the reactor 4.

  Moreover, the other structure of the power converter device 200 by 2nd Embodiment is the same as that of the power converter device 100 in 1st Embodiment.

[Effects of Second Embodiment]
In the second embodiment, the following effects can be obtained.

  In 2nd Embodiment, the reactor current detection part 204a which detects the electric current value IL which flows into the reactor 4 is provided in the power converter device 200 as mentioned above. Further, the control unit 205 turns off both the first switching element 31 and the second switching element 32 when the current value Ic of the alternating current detected by the capacitor current detection unit 207 exceeds the first threshold value It1. Thus, both the first switching element 31 and the second switching element 32 are in the off state, and the current value IL flowing through the reactor 4 detected by the reactor current detection unit 204a becomes less than the second threshold value It2. In such a case, the control for resuming the driving of the first switching element 31 and the second switching element 32 is performed. Here, an overcurrent may occur in the reactor 4 (power converter 200) due to a surge applied to the DC output circuit 1 or the like. Therefore, in the second embodiment, when the driving of the switching circuit 3 is continued, the control unit 205 may further amplify the overcurrent, so that the driving of the switching circuit 3 is stopped (first switching) The control (turning off the element 31 and turning off the second switching element 32) (control for protecting the power converter 200) is performed. In this case, since no current flows through the flying capacitor 2, it is difficult to obtain the current value IL flowing through the reactor 4 based on the current value Ic of the alternating current flowing through the flying capacitor 2. On the other hand, in the second embodiment, the configuration as described above allows the first switching element 31 and the second switching element 32 to be both off and no current flows through the flying capacitor 2. When the current value IL flowing through the reactor 4 is acquired and becomes less than the second threshold value It2 (when the overcurrent disappears), the driving of the first switching element 31 and the second switching element 32 is resumed. can do.

  In the second embodiment, as described above, the reactor current detection unit 204a sets the upper limit of the detection frequency band for detecting the current value flowing through the reactor IL to less than 10 times the switching frequency f of the switching circuit 3. Thereby, since it is not necessary to detect a ripple component by the reactor current detection unit 204a, even when a wide band gap semiconductor is provided in the switching circuit 3, the upper limit of the detection frequency band of the reactor current detection unit 204a is set to the wide band gap semiconductor. The reactor current detector 204a can be easily configured without having to increase the size. For example, as described above, the reactor current detection unit 204a can be configured by a general-purpose shunt resistor.

  Moreover, the other effect of the power converter device 200 by 2nd Embodiment is the same as that of the power converter device 100 in 1st Embodiment.

[Third embodiment]
Next, with reference to FIG. 5, the structure of the power converter device 300 by 3rd Embodiment is demonstrated. In the third embodiment, unlike the power conversion device 100 configured by a combination of a diode bridge circuit and a switching element bridge circuit, a switching element bridge circuit is provided. In addition, about the structure same as the said 1st Embodiment and the said 2nd Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

(Configuration of the power conversion device according to the third embodiment)
As shown in FIG. 5, the power conversion device 300 according to the third embodiment includes a switching circuit 303, a control unit 305, and an amplitude detection unit 308.

  Here, in the third embodiment, the switching circuit 303 includes a third switching element 333 and a fourth switching element 334, and the third switching element 333, the fourth switching element 334, the first switching element 31, and the second switching element. The element 32 is connected in series in this order. Moreover, the 3rd switching element 333 and the 4th switching element 334 are comprised by the wide band gap semiconductor.

  Then, the control unit 305 acquires the current value IL of the reactor 4 based on the current value Ic acquired from the current detection unit 7, and based on the acquired current value IL, the third switching element 333 and the fourth switching element. The on / off period of each of the element 334, the first switching element 31, and the second switching element 32 is controlled.

  Here, as shown in FIG. 6, when power regeneration (for example, power generation) is performed from the load 101 to the DC output circuit 1, the voltage Vr <b> 2 is the waveform (FIG. 2) of the power converter 100 according to the first embodiment. On the other hand, the polarity of the current (current values Ic and IL) is reversed. Therefore, in the second embodiment, the amplitude detection unit 308 is provided with a polarity reversing unit 381 without providing the absolute value acquisition unit 81.

  The polarity inversion unit 381 is configured to invert the polarity of the detection signal only when the first switching element 31 is off and the second switching element 32 is on by the control signal from the control unit 305. . That is, the polarity reversing unit 381 sets Ic = IL when the first switching element 31 is on and the second switching element 32 is off, and the first switching element 31 is off and the second switching element 32 is on. In this state, Ic = −IL is detected. Thereby, in the power converter device 300 by 3rd Embodiment, the bipolar current detection is possible.

  The flying capacitor 2 has one end connected to a connection point (node N302) between the first switching element 31 and the second switching element 32, and between the third switching element 333 and the fourth switching element 334. The other end is connected to the connection point (node N302).

  Then, the control unit 305 acquires the current value IL flowing through the reactor 4 by the amplitude detection unit 308 based on the current value Ic of the alternating current detected by the current detection unit 7, and acquires the current value IL flowing through the reactor 4. Is configured to control the on / off periods of the first switching element 31, the second switching element 32, the third switching element 333, and the fourth switching element 334.

  When power is regenerated from the load 101 to the DC output circuit 1, the control unit 305 causes the third switching element 333 and the fourth switching element 334 to flow from the DC output circuit 1 to the reactor 4. The second switching element 32 and the first switching element 31 are configured to be controlled similarly.

  Moreover, the other structure of the power converter device 300 by 3rd Embodiment is the same as that of the power converter device 100 in 1st Embodiment.

[Effect of the third embodiment]
In the third embodiment, the following effects can be obtained.

  In the third embodiment, as described above, the switching circuit 303 is provided with the third switching element 333 and the fourth switching element 334, and the third switching element 333, the fourth switching element 334, and the first switching element 31 are provided. The second switching element 32 is connected in series in this order. Then, one end of the flying capacitor 2 is connected to a connection point (node N302) between the first switching element 31 and the second switching element 32, and a connection point (node) between the third switching element 333 and the fourth switching element 334. N301) is connected to the other end of the flying capacitor 2. As a result, when current flows from the reactor 4 to the DC output circuit 1, the third switching element 333 and the fourth switching element 334, and when the current flows from the DC output circuit 1 to the reactor 4, Control can be performed in the same manner as the one switching element 31. As a result, the power conversion device 300 can be configured to have a function of regenerating power (a function of generating power) in the DC output circuit 1.

  Moreover, the other effect of the power converter device 300 by 3rd Embodiment is the same as that of the power converter device 100 in 1st Embodiment.

[Modification]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to third embodiments, the example in which the AC power supply 11 is provided in the DC output circuit 1 has been described, but the present invention is not limited to this. For example, as in the modification shown in FIG. 7, the DC output circuit 401 may be configured as a DC power source. FIG. 7 shows an example in which the DC output circuit 1 (see FIG. 1) of the power conversion device 100 according to the first embodiment is replaced with a DC output circuit 401 composed of a DC power supply, but the power conversion according to the second embodiment. The DC output circuit 1 (see FIGS. 4 and 5) of the device 200 or the power conversion device 300 according to the third embodiment may be replaced with a DC output circuit 401 composed of a DC power supply.

  Moreover, in the said 1st Embodiment and the said 2nd Embodiment, although the amplitude detection part 8 showed the example comprised so that the absolute value acquired by the absolute value acquisition part 81 might be sampled by the sample hold part 82, The present invention is not limited to this. For example, the amplitude detection unit 8 may be configured to acquire the absolute value by the absolute value acquisition unit 81 after sampling the current value Ic detected by the current detection unit 7 by the sample hold unit 82.

  Moreover, in the said 1st Embodiment and the said 2nd Embodiment, although the example which provides the sample hold part 82 in the amplitude detection part 8 was shown, this invention is not limited to this. For example, the amplitude detection unit 8 may be provided with a peak hold circuit instead of the sample hold unit 82. In this case, since the reset operation of the peak hold circuit is passively performed by discharging the capacitor inside the peak hold circuit, etc., the completion of the reset is relatively slow, and the control response is also relatively slow due to this. I think it may be. Therefore, in order to provide a peak hold circuit in the amplitude detector 8, it is preferable to use the power converter 100 with few problems (original stability is sufficiently high) even if the stability is somewhat reduced. Note that the power converter (control system) having sufficiently high stability is, for example, a case where the control unit performs only proportional control (not including an integral element) for current control, and gain of proportional control (proportional component). Is relatively small (to the extent that oscillation does not occur even with a detection delay of several pulses).

  Moreover, although the said 1st-3rd embodiment showed the example which comprises a current detection part so that the minimum of a detection frequency band may be 1/10 or more of the switching frequency f, and an upper limit may be 50 times or more. The present invention is not limited to this. That is, the current detection unit may be configured such that the lower limit of the detection frequency band is less than 1/10 of the switching frequency f and the upper limit is less than 50 times.

  In the first to third embodiments, an example in which the minimum length T2m of the period T2 and the minimum length T3m of the period T3 are set to be equal to or greater than the predetermined lower limit length Tp1 and equal to or less than the predetermined upper limit length Tp2. However, the present invention is not limited to this. That is, in the case of allowing some sampling failure, the minimum length T2m and the minimum length T3m may be set to be less than the predetermined lower limit length Tp1, and the variable range of T3 in the period T2 is relatively small. Otherwise, it may be set larger than the predetermined upper limit length Tp2.

  Moreover, although the said 1st-3rd embodiment showed the example which comprises the 1st switching element 31 and the 2nd switching element 32 from a wide band gap semiconductor, this invention is not limited to this. For example, the first switching element 31 and the second switching element 32 may be made of a silicon semiconductor.

DESCRIPTION OF SYMBOLS 1,401 DC output circuit 2 Flying capacitor 3, 303 Switching circuit 4 Reactor 5, 205, 305 Control part 7 Current detection part (capacitor current detection part)
8, 308 Amplitude detection unit 11 AC power supply 12 Rectifier circuit 31 First switching element (first switching element)
32 Second switching element (second switching element)
33 First diode (first diode)
34 Second diode (second diode)
100, 200, 300 Power converter 204a Reactor current detection unit 207 Capacitor current detection unit 333 Third switching element (third switching element)
334 Fourth switching element (fourth switching element)
N5 node (connection point of the first diode and the second diode)
N6 node (connection point between the first switching element and the second switching element)

Claims (9)

A reactor having one end connected to one end of the DC output circuit;
A first switching element having one end connected to the other end of the reactor, and one end connected to the other end of the first switching element and the other end connected to the other end of the DC output circuit. A switching circuit including a second switching element;
A flying capacitor connected to a connection point between the first switching element and the second switching element;
A capacitor current detector for detecting a current value of an alternating current flowing through the flying capacitor;
Based on the current value of the alternating current detected by the capacitor current detection unit, the current value flowing through the reactor is acquired, and the first switching element and the first current are acquired based on the acquired current value flowing through the reactor. And a control unit that controls an on / off period of the two switching elements. An amplitude detector for detecting the amplitude of the current value of the alternating current detected by the capacitor current detector;
The power conversion device according to claim 1, wherein the control unit is configured to perform control to acquire a value of a current flowing through the reactor based on the magnitude of the amplitude detected by the amplitude detection unit.   The said capacitor current detection part is comprised so that the minimum of the detection frequency band which detects the electric current value of the said alternating current may become 1/10 or more of the switching frequency of the said switching circuit. Power converter.   The control unit turns on the first switching element, a first period in which the first switching element is turned off and the second switching element is turned on in one cycle of the switching operation of the switching circuit, and Control is performed to alternately provide second periods for turning off the second switching elements, and the minimum length of the first period and the minimum length of the second period are set to be equal to or greater than a predetermined length. The power converter device according to any one of claims 1 to 3, wherein the power converter device is configured as follows. A reactor current detector that detects a current value flowing through the reactor and that has an upper limit of a detection frequency band for detecting a current value flowing through the reactor set to less than 10 times a switching frequency of the switching circuit;
When the current value of the alternating current detected by the capacitor current detection unit exceeds a predetermined first threshold value, the control unit sets both the first switching element and the second switching element. The first switching element and the second switching element are both turned off, and the value of the current flowing through the reactor detected by the reactor current detector is less than a predetermined second threshold value. The power conversion according to any one of claims 1 to 4, wherein the power conversion is configured to perform control to resume driving of the first switching element and the second switching element in the case of becoming apparatus. The switching circuit further includes a first diode and a second diode,
The first diode, the second diode, the first switching element, and the second switching element are connected in series in this order,
The flying capacitor has one end connected to a connection point between the first switching element and the second switching element, and the other end connected to a connection point between the first diode and the second diode. Is connected, The power converter device of any one of Claims 1-5. The switching circuit further includes a third switching element and a fourth switching element,
The third switching element, the fourth switching element, the first switching element, and the second switching element are connected in series in this order,
The flying capacitor has one end connected to a connection point between the first switching element and the second switching element, and a connection point between the third switching element and the fourth switching element. The power converter according to any one of claims 1 to 5, wherein the other end is connected. The first switching element and the second switching element are made of a wide band gap semiconductor,
The said capacitor current detection part is comprised so that the minimum of the detection frequency band which detects the electric current value of the said alternating current may become 1/10 or more of the switching frequency of the said wide band gap semiconductor. The power converter device according to any one of the above. The DC output circuit includes an AC power source and a rectifier circuit that rectifies an AC current from the AC power source into a DC current,
One end of the reactor is connected to one end of the rectifier circuit,
The power converter according to any one of claims 1 to 8, wherein the other end of the second switching element is connected to the other end of the rectifier circuit.

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