JP2011160565A - Switching power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply device that can improve stability and responsiveness of output voltage due to dynamic fluctuation of load current. <P>SOLUTION: A feedback current value I<SB>fb</SB>being a difference value of respective currents I<SB>L</SB>and I<SB>out</SB>obtained by a first transformer 51 and a second transformer 52 is calculated, and it is fed back to a control unit 6. The respective currents I<SB>L</SB>and I<SB>out</SB>fluctuate in accordance with fluctuation of current of a load 9, so that the difference value of the currents is calculated. Thus, a current value I<SB>c</SB>(difference value) of a capacitor 4 which is not affected by fluctuation can be obtained. The feedback current value I<SB>fb</SB>which is not affected by the fluctuation of the load current is fed back and control by the control unit 6 is stabilized, and also overshoot is also suppressed by less fluctuation of the feedback current value I<SB>fb</SB>, thereby responsiveness of control can also be improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a switching power supply device that performs power conversion by a chopper circuit.

  There is a switching power supply device using a chopper circuit to variably control and output a DC voltage value. In Patent Document 1, for example, a switching power supply device including a step-down chopper circuit is disclosed as a power supply device for a battery simulator that simulates a battery of an electric vehicle or the like.

  In this power supply device, a current detector that detects a current flowing through the reactor is connected in order to monitor a current change corresponding to a dynamic change in the load current. A voltage detector is connected across the capacitor to monitor the output voltage. This power supply device feeds back an output voltage value to an automatic voltage regulator (AVR) and controls a current value detected by a current detector in order to control the input voltage so as to keep the output voltage constant. Feedback to the automatic current regulator (ACR). The current detector detects a current fluctuation corresponding to the load current fluctuation described above. Therefore, this power supply device passes the current corresponding to the variation of the load current to the capacitor through the reactor so as to compensate for the variation, and makes the voltage across the capacitor constant so that the output voltage is constant. Is kept constant.

  The two switching elements are used in order to realize both a power running operation and a regenerative operation.

JP 2000-295869 A

  However, since the detected current value flowing through the reactor to be fed back corresponds to the fluctuation amount of the load current, when the fluctuation of the load current is large, the stability and responsiveness of the control, that is, the stability and responsiveness of the output voltage are reduced. There is a problem of getting worse.

  Although it is conceivable to directly detect the current flowing through the capacitor, there is a problem because the inductance increases and the circuit constant changes.

  In view of the circumstances as described above, an object of the present invention is to provide a switching power supply device that can improve the stability and responsiveness of an output voltage due to dynamic fluctuations in load current.

In order to achieve the above object, a switching power supply device according to an embodiment of the present invention includes a chopper unit, a reactor, a connection line, a capacitor, a current detection unit, and a control unit.
The reactor portion is connected to the output side of the chopper portion.
The connection line can connect the reactor to a load.
The capacitor is branched from the connection line and connected in parallel to the load.
The current detection means detects a difference value between a current flowing through the connection line before branching to the capacitor and a current flowing through the connection line after branching to the capacitor.
The control unit controls the chopper unit so that an output voltage to the load is constant based on at least the difference value detected by the current detection unit.

  The current flowing through the connection line before branching to the capacitor is, for example, a current output from the reactor, and the current flowing through the connection line after branching is, for example, the output current to the load. Since the currents flowing before and after the branching fluctuate in response to fluctuations in the load current, the current detection means obtains the current value (difference value) of the capacitor that is not affected by the fluctuations by taking the difference between them. Can do. This difference value is fed back to the control means, and the control means controls the chopper unit so that the output voltage becomes constant based on at least this difference value. As described above, the difference value that is not influenced by the fluctuation of the load current is fed back, so that the control by the control means is stabilized, and since the fluctuation of the difference value is small, the overshoot is also suppressed, so the control responsiveness is also improved. Can be improved.

  In the present invention, the current flowing through the capacitor is not directly detected, but the difference value of the current before and after branching to the capacitor is detected in the connection line to the load, thereby avoiding the problem of increased circuit inductance. can do.

  You may further comprise the voltage detection means which detects the voltage value of the both ends of the said capacitor | condenser. In this case, the control means is configured so that the output voltage to the load is constant based on the difference value detected by the current detection means and the voltage value detected by the voltage detection means. To control.

  The voltage across the capacitor detected by the voltage detection means is fed back to the control means. Since the chopper unit is controlled based on both the difference value and the voltage value across the capacitor detected by the voltage detection means, more accurate control can be realized.

  The control means takes in a voltage reference value and differentiates the voltage reference value; and a proportional integration that executes a proportional integration process to bring the voltage value detected by the voltage detection means closer to the voltage reference value And a processing unit. In this case, the control means adds the output value output from the differentiation processing unit and the output value output from the proportional integration processing unit, and uses the value obtained by the addition as a current command for the capacitor. As a value, the chopper unit is controlled so that the difference value detected by the current detection means approaches the current command value.

  In the present invention, the control means includes a differentiation processing unit for differentiating the voltage reference value in addition to the proportional integration processing unit. In the present invention, the voltage reference value is differentiated by the differentiation processing unit, and the value is added to the output value output from the proportional performance controller. As a result, it is possible to obtain a current command value with high responsiveness to the voltage reference value.

  As described above, according to the present invention, it is possible to improve the stability and responsiveness of the output voltage due to the dynamic fluctuation of the load current.

It is a figure which shows the switching power supply device which concerns on the 1st Embodiment of this invention. It is an operation of the switching power supply device during power running and is a diagram showing a current loop when a capacitor is charged. It is operation | movement of the switching power supply device at the time of power running, Comprising: It is a figure which shows a current loop when a capacitor | condenser is discharged. It is a waveform which shows the output current value to a load, the electric current value of a capacitor | condenser, and a voltage command value. It is a wave form diagram of simulation of current and voltage of each part of a switching power supply concerning a 1st embodiment. It is a wave form diagram of simulation of the current and voltage of each part when a reactor current value is fed back. It is a figure which shows the switching power supply device which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 is a diagram showing a switching power supply device according to the first embodiment of the present invention.

  The switching power supply apparatus 100 is a battery simulator (battery emulator) that simulates a battery unit mounted on an electric vehicle, for example. Alternatively, switching power supply device 100 may be switching power supply device 100 as a product that is actually mounted on an electric vehicle.

  The switching power supply device 100 includes an input capacitor 2, a chopper unit 1, a reactor 3, a capacitor 4, a voltage detector 8, a current detection unit 5, and a control unit 6.

  The chopper unit 1 includes two switching elements 11 and 12 by transistors. Diodes 13 and 14 are connected in parallel to these two switching elements 11 and 12 in opposite directions, respectively. The switching elements 11 and 12 are typically IGBT (Insulated Gate Bipolar Transistor) elements, but are not limited thereto, and FETs (Field Effect Transistors) may be used.

  The reason why the switching power supply device 100 includes the two switching elements 11 and 12 is to execute both power running and regenerative operations.

  A primary power source such as a commercial power source (not shown) is connected to both ends of the input capacitor 2. One end of the reactor 3 is connected to the output side of the chopper unit 1, and a load 9 can be connected to the other end of the reactor 3 via a connection line 7. The capacitor 4 simulates a battery (secondary battery), branches from the connection line 7 and is connected in parallel to the load 9. As the load 9, an inverter as a specimen is typically used.

  The reactor 3 and the capacitor 4 have a function of a smoothing filter that smoothes the output of the chopper unit 1. The chopper unit 1, the reactor 3 and the capacitor 4 constitute a step-down chopper circuit.

The current detection unit 5 includes a first current transformer 51 that detects a current before branching from the connection line 7 to the capacitor 4 (that is, a current I _{L of the} reactor 3), and an output to the load that is the current after branching. And a second current transformer 52 for detecting the current _Iout . The current detector 5 calculates a difference value (feedback current value I _fb ) between the current values I _L and I _out detected by the first current transformer 51 and the second current transformer 52. The current detection unit 5 outputs the calculated difference value to the control unit 6.

Note that the current value detected by the second current transformer 52 is the output current I _out from the switching power supply device 100 to the load 9 during powering, but from the load 9 to the switching power supply device during regeneration. Input current to 100.

The voltage detector 8 includes a voltage detector 8 that detects a voltage value (feedback voltage value V _fb ) across the capacitor 4.

Based on the feedback current value I _fb detected by the current detector 5 and the voltage value V _fb at both ends of the capacitor 4 detected by the voltage detector 8, the controller 6 determines the output voltage V _out to the load 9. The chopper unit 1 is controlled to be constant.

Specifically, the control unit 6 includes an AVR (Automatic Voltage Regulator) 61, an ACR (Automatic Current Regulator) 62, and a PWM (Pulse Width Modulation) control unit 63, and takes in the feedback voltage value V _fb . Further, the control unit 6 takes in the voltage reference value V _ref generated by, for example, a block (not shown).

The AVR 61 generates a current command value I _ref for bringing the feedback voltage value V _fb close to the voltage reference value V _ref , and outputs this. ACR62 generates a voltage command value V _Dref to approximate the feedback current I _fb outputted from the current detector 5 to the current command value I _ref, and outputs this.

The voltage control value V _Dref output from the ACR 62 is input to the PWM control unit 63, and the PWM control unit 63 outputs a gate signal applied to the two switching elements 11 and 12 based on the voltage command value V _Dref. Control each one.

  The operation of the switching power supply device 100 configured as described above will be described. 2 and 3 are diagrams for explaining the operation. A thick arrow indicates a current loop.

  First, in order to obtain the chopper output of the chopper unit 1, the switching element 11 is turned on and the switching element 12 is turned off. As a result, voltage and current are applied to the load 9 and power is consumed by the load 9.

  Next, as shown in FIG. 3, the switching element 11 is turned off and the switching element 12 is turned on. As a result, the charge charged in the capacitor 4 during the operation shown in FIG. 2 is discharged.

  Note that the switching element 12 is turned ON during power running. This is because the control to turn ON the switching elements 11 and 12 alternately is executed. According to the principle of the chopper circuit, the charge charged in the capacitor 4 is not necessarily discharged. It does not have to be ON.

  Even during regeneration, the switching elements 11 and 12 are switched so as to be alternately turned on, as in powering. Even when the switching element 11 is ON and the switching element 12 is ON, power is supplied from the load 9 to the switching power supply device 100 side.

  Next, the operation of the control unit 6 of the switching power supply apparatus 100 will be described.

The control unit 6 uses the AVR 61 to generate a current command value I _ref for bringing the feedback voltage value V _fb close to the voltage reference value V _ref . Control unit 6, the ACR62, as close a feedback current I _fb to the current command value I _ref, and generates a voltage command value V _Dref to the PWM control unit 63. The PWM control unit 63 controls the two switching elements 11 and 12 based on the voltage command value V _Dref .

That is, the control unit 6 controls the chopper unit 1 based on the difference value detected by the current detection unit 5 and the feedback voltage value V _{fb so} that the output voltage V _out to the load 9 becomes constant.

FIG. 4A shows the output current I _out to the load 9 detected by the second current transformer 52 and the current value I _c of the capacitor 4. For example, during the power running operation, as indicated by the output current _Iout in FIG. 4A, the current consumed by the load 9 increases. At this time, I _c decreases as shown in FIG. 4A by the increase in the output current I _out , that is, the capacitor 4 is discharged. The control unit 6 controls the voltage command value as shown in FIG. 4B so that the voltage of the capacitor 4 (output voltage V _out to the load 9) becomes constant, that is, so as to compensate for the discharge of the capacitor 4. V _Dref is generated.

At the time of regeneration, a current is supplied from the load 9 to the switching power supply device 100, contrary to the powering operation, and a part of the current at that time is accumulated in the capacitor 4. Therefore, the control unit 6 generates the voltage command value V _Dref so that the voltage of the capacitor 4 becomes constant, that is, the voltage increase of the capacitor 4 due to charging of the capacitor 4 is suppressed.

As described above, in the present embodiment, the feedback current I _fb is a difference value between the current I _L and I _out is obtained by the first current transformer 51 and the second current transformer 52 is calculated, which is Feedback is provided to the control unit 6. Since each of the currents I _L and I _out fluctuates corresponding to the fluctuation of the load current, the difference value is calculated to obtain the current value I _c (difference value) of the capacitor 4 that is not affected by the fluctuation. be able to. As described above, the feedback current value _Ifb that is not affected by the fluctuation of the load current is fed back, so that the control by the control unit 6 is stabilized, and the overshoot is suppressed by the small fluctuation of the feedback current value _Ifb. Therefore, control responsiveness can also be improved.

  Further, in the present embodiment, the current flowing through the capacitor 4 is not directly detected, and the difference value between the currents before and after branching to the capacitor 4 is detected in the connection line 7 to the load 9, so that the circuit inductance is large. The problem of becoming can be avoided.

FIG. 5 is a waveform diagram of a simulation of current and voltage at each part of the switching power supply apparatus 100. FIG. In particular, as shown in FIG. 5D, the currents I _L and I _out obtained by the first current transformer 51 and the second current transformer 52 fluctuate in response to load fluctuations. The difference between them is less fluctuating.

FIG. 6 shows, for example, a simulation waveform when the reactor current value I _L is fed back and a voltage command value is generated by the voltage ACR based on the reactor current value I _L (= Ifb). 6A to 6E correspond to FIGS. 5A to 5E, respectively. As shown in FIG. 6 (D), the reactor current value I _L (= Ifb) affected by the load fluctuation is fed back, so that the output voltage V _out is unstable as shown in FIG. 6 (B). Become.

[Second Embodiment]
FIG. 7 is a diagram showing a switching power supply device according to the second embodiment of the present invention. In the following description, the same elements, functions, and the like included in the switching power supply device 100 according to the first embodiment will be simplified or omitted, and different points will be mainly described.

The control unit 6 of the switching power supply apparatus 200 according to the present embodiment includes a differentiation (D) processing unit 162 and a proportional integration (PI) processing unit 161. The proportional integration processing unit 161 corresponds to, for example, the AVR 61 in the embodiment shown in FIG. The differentiation processing unit 162 takes in the voltage reference value V _ref , differentiates it, and outputs it. In order to make the feedback voltage value V _fb close to the voltage reference value V _ref , the proportional integration processing unit 161 executes a proportional integration calculation of the difference between these values and outputs the result. The output value I _refPI from the proportional integration processing unit 161 is added to the output value I _refD from the differentiation processing unit 162. A value obtained by this addition is input to the ACR 62 as the current command value I _ref .

As in the first embodiment, the control unit 6 detects the feedback current value I _fb that is the difference value between the currents from the first and second current transformers 52 detected by the current detection unit 5. _Is controlled to approach the current command value I _ref .

As described above, the control unit 6 includes the differentiation processing unit 162 that differentiates the voltage reference value V _ref in addition to the proportional integration processing unit 161. Since the response of only the proportional integration processing unit 161 is sacrificed, the voltage reference value V _ref is differentiated by the differentiation processing section 162, an output value I _RefPI whose output value I _REFD is output from the proportional績分processor 161 By adding, it is possible to obtain a current command value I _ref having high responsiveness to the voltage reference value V _ref .

Generally, in a power supply device that simulates a battery unit, the internal resistance is large due to the large-capacitance capacitor 4, so that tracking to a voltage command, that is, responsiveness tends to deteriorate. In control, stability and responsiveness are in a trade-off relationship. In the power supply device, stability is given priority over responsiveness, and a capacitor 4 having a larger capacity is used to enhance stability. Therefore, in the switching power supply device 200 according to the present embodiment, the voltage reference value V _ref is differentiated by the differentiation processing unit 162 as described above.

Further, in the differentiation processing unit 162 according to the present embodiment, the voltage reference value V _ref is differentiated, not the difference between the feedback voltage value V _fb and the voltage reference value V _ref . The difference between the feedback voltage value V _fb and the voltage reference value V _ref is inherently unstable due to a change in load current. Therefore, compared with the case where the difference between the feedback voltage value V _fb and the voltage reference value V _ref is PID-processed, the present embodiment can improve the stability.

  The embodiment according to the present invention is not limited to the above-described embodiment, and various other embodiments are conceivable.

  The switching power supply devices 100 and 200 according to the above embodiments include the two switching elements 11 and 12 in order to realize the power running operation and the regenerative operation. However, the switching power supply devices 100 and 200 may include a single switching element such as a general chopper circuit in order to realize control only during a power running operation, for example.

In the switching power supply devices 100 and 200 according to the above embodiment, the control unit 6 is based on the difference value detected by the current detection unit 5 and the voltage value V _fb across the capacitor 4 detected by the voltage detector 8. The chopper part 1 was controlled. However, the control unit 6 may generate the voltage command value V _Dref to the PWM control unit 63 based only on the difference value detected by the current detection unit 5 and control the chopper unit 1.

DESCRIPTION OF SYMBOLS 1 ... Chopper part 3 ... Reactor 4 ... Capacitor 5 ... Current detection part (equivalent to a current detection means)
6. Control unit (equivalent to control means)
7 ... Connection line 8 ... Voltage detector (corresponding to voltage detection means)
DESCRIPTION OF SYMBOLS 9 ... Load 11 ... Switching element 12 ... Switching element 100, 200 ... Switching power supply device 161 ... Proportional integral process part 162 ... Differentiation process part

Claims (3)

Chopper part,
A reactor connected to the output side of the chopper,
A connection line capable of connecting the reactor to a load;
A capacitor branched from the connection line and connected in parallel to the load;
Current detection means for detecting a difference value between a current flowing through the connection line before branching to the capacitor and a current flowing through the connection line after branching to the capacitor;
A switching power supply apparatus comprising: control means for controlling the chopper unit so that an output voltage to the load is constant based on at least the difference value detected by the current detection means. The switching power supply device according to claim 1,
Further comprising voltage detection means for detecting a voltage value across the capacitor;
The control unit controls the chopper unit so that an output voltage to the load is constant based on the difference value detected by the current detection unit and the voltage value detected by the voltage detection unit. Switching power supply. The switching power supply device according to claim 2,
The control means takes in a voltage reference value and differentiates the voltage reference value; A processing unit, adding an output value output from the differentiation processing unit and an output value output from the proportional integration processing unit, and obtaining a value obtained by the addition as a current command value for the capacitor And a switching power supply device that controls the chopper unit so that the difference value detected by the current detection means approaches the current command value.

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