JP2011147229A - Dc power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC power supply unit having improved responsiveness to changes in an input voltage or a load. <P>SOLUTION: The DC power supply unit includes a chopper circuit 10 having switching elements 12, 14 each operating based on a PWM signal, a filter circuit 20 for smoothing the output of the chopper circuit 10, a reference current calculating section 39 for obtaining a first reference current I<SB>ref1</SB>on the basis of the difference between an output voltage V<SB>out</SB>of the filter circuit 20 and a target voltage V<SB>ref</SB>, an adder 41 for obtaining a second reference current I<SB>ref2</SB>obtained by adding the first reference current I<SB>ref1</SB>to the output current I<SB>2</SB>of the filter circuit 20, and a PWM control section 36 for generating the PWM signal on the basis of the output current I<SB>1</SB>of the chopper circuit 10. The PWM control section 36 executes feedback control based on the output current I<SB>1</SB>by using the second reference current I<SB>ref2</SB>as a target current. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a DC power supply device, and more particularly to improvement of a DC power supply device that converts a DC voltage by a switching operation based on a PWM signal.

  As a DC-DC converter that steps down or boosts a DC voltage supplied from a DC power source and outputs it to a load, a DC-DC converter including a chopper circuit, a filter circuit, and a PWM (Pulse Width Modulation) controller is known. . The chopper circuit includes a switching element such as a transistor and a drive circuit that turns on or off the switching element, and converts the DC voltage by switching the switching element based on the PWM signal. The filter circuit is a low-pass filter for smoothing the output of the chopper circuit, and includes a coil and a capacitor.

The PWM controller adjusts the duty ratio of the PWM signal, that is, the ratio between the repetition interval of the rectangular wave (pulse) and the ON time (pulse width), and controls the switching timing of the chopper circuit to thereby obtain a desired voltage output. Switching control means for obtaining Duty ratio of the PWM signal is determined based on a ratio between the input voltage _{V in} and the target voltage _{V ref} for the chopper circuit. Usually, in the PWM control unit, in order to stabilize the output, an output voltage and an output current are detected, and feedback control is performed so that these detected values coincide with a target value. For example, in the case of constant voltage control, a PWM signal having a duty ratio corresponding to the difference between the output voltage _Vout of the filter circuit and the target voltage _Vref is generated (for example, Patent Documents 1 to 3).

JP 2005-218157 A JP-A-10-225105 JP 2006-136146 A

  In general, the voltage output of the filter circuit is delayed in response to input and load fluctuations from the current output because the capacitor in the filter circuit acts as an integrating circuit. For this reason, in the conventional DC power supply device as described above, the response to input voltage and load fluctuations is not good.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a DC power supply device with improved responsiveness to changes in input voltage and load. In particular, it is an object to improve the responsiveness of a DC power supply device that performs feedback control based on the output current of a chopper circuit, and to reduce the fluctuation range of the output voltage.

  A DC power supply device according to a first aspect of the present invention includes a chopper circuit having a switching element that operates based on a PWM signal, a filter circuit that smoothes an output of the chopper circuit, an output voltage of the filter circuit, and a target voltage. First reference current calculation means for obtaining a first reference current based on the difference; second reference current calculation means for obtaining a second reference current obtained by adding the first reference current and the output current of the filter circuit; and PWM control means for generating the PWM signal based on the output current of the chopper circuit, and the PWM control means performs feedback control based on the output current of the chopper circuit with the second reference current as a target current. Configured.

  With such a configuration, the output voltage of the filter circuit and the output current of the filter circuit can be reflected on the target current of feedback control based on the output current of the chopper circuit. Therefore, it is possible to realize feedback control of the chopper circuit with good response characteristics while controlling the output voltage of the filter circuit to approach the target voltage. Further, the first reference current is obtained from the error in the output voltage of the filter circuit, and the second reference current is obtained by adding the output current of the filter circuit, and the second reference current is set as the target current. Adjustment can be facilitated.

  The DC power supply according to the second aspect of the present invention further includes a limiter for comparing the second reference current with the upper limit current in addition to the above configuration, and the PWM control means is configured so that the second reference current exceeds the upper limit current. The feedback control is performed using the upper limit current as a target current.

  According to such a configuration, when the second reference current exceeds the upper limit current, feedback control is performed using the upper limit current as the target current. Therefore, by setting the upper limit current smaller than the rating, the chopper circuit It is possible to suppress the current output from exceeding the rating.

  In the DC power supply according to the third aspect of the present invention, in addition to the above configuration, the first reference current calculation means calculates the first reference current based on the difference and the history information, and exceeds the upper limit current. 2 When the reference current becomes equal to or lower than the upper limit current, the history information is reset.

  According to such a configuration, it is possible to prevent the error history information accumulated when the second reference current exceeds the upper limit current from being reflected in the feedback control. It is possible to stabilize the feedback control at the time of transition from the state exceeding the current to the state below the upper limit current.

  In addition to the above configuration, the DC power supply according to the fourth aspect of the present invention is configured such that the PWM control means updates the duty ratio of the PWM signal at a cycle shorter than the update interval of the second reference current. According to such a configuration, the duty ratio of the PWM signal is updated at a shorter time interval than when the output voltage or output current of the filter circuit is sampled and the second reference current is updated. In addition, the response characteristics can be improved without increasing both the update of the duty ratio and the duty ratio. Therefore, compared to speeding up both the updating of the second reference current and the updating of the duty ratio, a direct current power supply device with improved response characteristics against fluctuations in input voltage and load while suppressing an increase in manufacturing cost is realized. can do.

  According to the DC power supply device of the present invention, changes in the output voltage and output current of the filter circuit are reflected in the target current, and fluctuations in the input voltage and load are quickly reflected in feedback control. Responsiveness can be improved. Therefore, it is possible to improve the responsiveness of the DC power supply device that performs feedback control based on the output current of the chopper circuit, and to reduce the fluctuation range of the output voltage.

1 is a diagram showing a configuration example of a DC power supply device according to Embodiment 1 of the present invention, in which a DC-DC converter 2 that steps down or boosts a DC voltage from a DC power supply 1 is shown. FIG. 2 is a diagram illustrating a configuration example of a chopper circuit 10 in the DC-DC converter 2 of FIG. 1. It is the figure which showed the structural example of the filter circuit 20 in the DC-DC converter 2 of FIG. 2 is a flowchart illustrating an example of an operation during constant voltage control in the DC-DC converter 2 of FIG. 1. It is the figure which showed an example of schematic structure of the DC power supply device by Embodiment 2 of this invention, and the other structural example of the DC-DC converter 2 is shown. FIG. 6 is a block diagram illustrating a configuration example of a main part of the DC-DC converter 2 of FIG. 5, in which an example of a functional configuration in the reference current calculation unit 30 is illustrated. It is the block diagram which showed the structural example of the DC power supply device by Embodiment 3 of this invention, and the other structural example of the reference current calculating part 30 is shown. It is the block diagram which showed the structural example of the DC power supply device by Embodiment 4 of this invention, and the other structural example of the reference current calculating part 30 is shown. It is the figure which showed the structural example of the direct-current power supply device by Embodiment 5 of this invention, and the DC-DC converter 2 to which the arithmetic circuit which determines a target duty was added is shown.

Embodiment 1 FIG.
<DC-DC converter>
FIG. 1 is a diagram illustrating a configuration example of a DC power supply device according to Embodiment 1 of the present invention, and a DC-DC converter that steps down or boosts a DC voltage supplied from the DC power supply 1 and outputs the voltage to a load 3. 2 is shown.

  The DC-DC converter 2 is a DC power supply device that converts DC voltage, and includes a chopper circuit 10, a filter circuit 20, voltage sensors 31, 32, current sensors 33, 34, subtractors 35, 38, a PWM control unit 36, The target voltage generation unit 37, the reference current calculation unit 39, the history information storage unit 40, an adder 41, and a limiter 42 are included. As the load 3, a secondary battery, an inverter for an AC motor, or the like is assumed.

  The chopper circuit 10 is a DC voltage conversion unit that converts a DC voltage supplied from the DC power supply 1 and outputs the DC voltage to the filter circuit 20 by a switching operation based on the PWM signal input from the PWM control unit 36. The filter circuit 20 is a low-pass filter for smoothing the output of the chopper circuit 10.

Voltage sensor 31 detects the input voltage V _in for the chopper circuit 10, an input voltage detection means for outputting the detected value to the PWM control unit 36. The voltage sensor 32 is output voltage detection means for detecting the output voltage V _out of the filter circuit 20 and outputting the detected value to the subtracter 38.

The current sensor 33 is a first current detection unit that detects the output current I ₁ of the chopper circuit 10 and outputs the detected value to the subtractor 35. The current sensor 34 is a second current detection unit that detects the output current I ₂ of the filter circuit 20 and outputs the detected value to the reference current calculation unit 39 and the adder 41. In this example, the output current I ₁ is an input current to the filter circuit 20.

The subtractor 35 is an arithmetic circuit that calculates a difference between the output current I ₁ and the output of the limiter 42 and outputs the difference as a current error ΔIa to the PWM control unit 36. The PWM control unit 36 is a switching control unit that controls the switching timing of the chopper circuit 10 by adjusting the duty ratio of the PWM signal, and includes a command value generation unit 36a and a PWM generation circuit 36b.

Command value generation unit 36a, based on the input voltage _{V in} and the target voltage _{V ref,} generates a command value for determining the duty ratio of the PWM signal, and outputs to the PWM generating circuit 36b. The command value generation unit 36a performs feedback control to update the duty ratio of the PWM signal at a constant cycle by sampling the current error ΔIa at a predetermined cycle T1 and updating the command value based on the current error ΔIa. Is called.

  The command value is obtained from the current current error ΔIa and the past current error ΔIa using, for example, a PI control or PID control method. Specifically, in the case of PI control, the command value is determined based on the sum of a proportional term proportional to the current current error ΔIa and an integral term obtained by integrating the past current error ΔIa. In the case of PID control, the command value is determined based on the sum of a proportional term proportional to the current current error ΔIa, an integral term obtained by integrating the past current error ΔIa, and a differential term obtained by differentiating the current error ΔIa. Is done.

The PWM generation circuit 36 b generates a PWM signal based on the command value from the command value generation unit 36 a and outputs the PWM signal to the chopper circuit 10. The PWM control unit 36 performs an operation of sampling the current error ΔIa at a constant cycle and updating the duty ratio of the PWM signal so that the output current I ₁ matches the output of the limiter 42.

The target voltage generation unit 37 generates a predetermined target voltage V _ref for comparison with the output voltage V _out and outputs it to the subtracter 38. The subtractor 38 is an arithmetic circuit that calculates a difference between the output voltage V _out and the target voltage V _ref and outputs the difference as a voltage error ΔV to the reference current calculation unit 39. The voltage error ΔV is expressed by, for example, ΔV = V _out −V _ref . In the constant voltage control, the duty ratio of the PWM signal is adjusted so that the voltage error ΔV approaches 0 by sampling and feeding back the voltage error ΔV at a predetermined period T2.

The reference current calculation unit 39 is a first reference current generation unit that calculates the first reference current I _ref1 based on the voltage error ΔV from the subtractor 38 and outputs the first reference current I _ref1 to the adder 41. For example, the first reference current I _ref1 is obtained from the voltage error ΔV and the history information held in the history information storage unit 40 by using a method of PI control or PID control. The history information is history information of the voltage error ΔV, and the voltage error ΔV extracted in the past and the first reference current I _ref-1 obtained in the past are held as history information for a certain period. Specifically, a proportional term proportional to the voltage error ΔV is obtained from the voltage error ΔV, and the current first reference current I _ref1 is obtained from the proportional term and the first reference current I _ref1 obtained in the past.

The adder 41 is a second reference current calculation unit that calculates the sum of the first reference current I _ref1 and the output current I ₂ from the reference current calculation unit 39 and outputs the sum to the limiter 42 as the second reference current I _ref2 . The second reference current I _ref2 is represented by I _ref2 = I _ref1 + I ₂ .

The limiter 42 compares the second reference current I _ref2 from the adder 41 with a predetermined upper limit current I _max, and based on the comparison result, either the second reference current I _ref2 or the upper limit current I _max is set as the target current. As a target current limiting means for outputting to the subtractor 35.

If the second reference current I _ref2 is equal to or lower than the upper limit current I _max , the limiter 42 outputs the second reference current I _ref2 . Therefore, when the second reference current I _ref2 is equal to or lower than the upper limit current I _max , the PWM control unit 36 performs feedback control based on the output current I ₁ of the chopper circuit 10 with the second reference current I _ref2 as the target current. .

On the other hand, when the second reference current I _ref2 exceeds the upper limit current I _max , the upper limit current I _max is output from the limiter 42. Therefore, when the second reference current I _ref2 exceeds the upper limit current I _max , the PWM control unit 36 performs feedback control based on the output current I ₁ of the chopper circuit 10 with the upper limit current I _max as the target current. become. This feedback control corresponds to constant current control using the output of the limiter 42 as a target value. By feeding back the current error ΔIa, the duty ratio of the PWM signal is adjusted so that the current error ΔIa approaches zero. .

Seek current error ΔIa is fed back to the detection value of the output current I ₁ from the current sensor 33, the control loop A1 for updating the duty ratio of the PWM signal based on the current error ΔIa the update interval of the second reference current I _ref2 This is a high-speed feedback loop that updates the duty ratio in a shorter cycle T1 (T1 <T2). By speeding only feedback output current I ₁ in this manner, while suppressing the cost increase, it is possible to improve the response characteristics.

In order to stabilize the output voltage V _out , the reference current calculation unit 39 stores history information when the second reference current I _ref2 transitions from a state in which the second reference current I _ref2 exceeds the upper limit current I _max to a state in which the second reference current I _ref2 is lower than the upper limit current I _max. The history information held in the unit 40 is reset, and the difference between the upper limit current I _max and the output current I ₂ of the filter circuit 20 is output as the current first reference current I _ref1 .

This time, the upper limit current _{I max} is output from the adder 41 as a second reference current _{I ref2.} That is, the history information of the voltage error ΔV accumulated when the second reference current I _ref2 exceeds the upper limit current I _max is reset at the time of transition to a state below the upper limit current I _max. It can suppress that information is reflected in feedback control. Further, by setting the difference between the upper limit current I _max and the output current I ₂ as the first reference current I _ref1 , the target of the feedback control before and after the second reference current I _ref2 transitions to a state equal to or lower than the upper limit current I _max. It can suppress that an electric current changes a lot.

<Chopper circuit>
FIG. 2 is a diagram showing a configuration example of the chopper circuit 10 in the DC-DC converter 2 of FIG. The chopper circuit 10 is a step-down type switch circuit comprising a drive circuit 11, switching elements 12, 14 and diodes 13 and 15, and by alternately turning on or off the two switching elements 12, 14, the input voltage V _in is converted into a predetermined output voltage.

  The switching elements 12 and 14 are semiconductor elements capable of transitioning between a conductive state and a cut-off state based on a control signal from the drive circuit 11, and are an IGBT (Insulated Gate Bipolar Transistor) or an FET (electric field). A transistor such as an effect transistor) or a thyristor is used.

The diodes 13 and 15 are free-wheeling diodes (free wheel diodes) for discharging an electromotive force generated in the coil 21 of the filter circuit 20 to which the output current I ₁ is supplied, and are connected in parallel with the switching elements 12 and 14, respectively. ing.

  For example, when the switching element 12 is an IGBT, the collector terminal of the IGBT and the cathode terminal of the diode 13 are connected to the positive input terminal, and the emitter terminal and the anode terminal are connected to the positive output terminal. The collector terminal of the switching element 14 and the cathode terminal of the diode 15 are connected to the positive output terminal, and the emitter terminal and the anode terminal are connected to the negative input terminal and output terminal.

  The drive circuit 11 is a drive circuit that turns on or off the switching elements 12 and 14 based on the PWM signal from the PWM control unit 36, and is connected to the gate terminals of the switching elements 12 and 14.

<Filter circuit>
FIG. 3 is a diagram showing a configuration example of the filter circuit 20 in the DC-DC converter 2 of FIG. The filter circuit 20 is a low-pass filter including a coil 21 having an inductance L and a circuit element 22 having an impedance Z. The circuit element 22 includes a capacitor having a capacitance C and a resistance element having an electric resistance R.

Output current I ₁ of the chopper circuit 10 is passed through the coil 21 is output to the current and I ₁ the sum of the output current I ₂ as a load 3 through the circuit element 22. The circuit element 22 may be composed of only a capacitor, or may be composed of a capacitor and a resistance element connected in series. Alternatively, a first capacitor and a resistance element connected in series and a second capacitor may be connected in parallel.

<Constant voltage control>
Steps S101 to S112 in FIG. 4 are flowcharts showing an example of an operation at the time of constant voltage control in the DC-DC converter 2 in FIG. First, the subtractor 38 calculates a voltage error ΔV from the detected value of the output voltage _Vout and the target voltage _Vref (steps S101 and S102). The reference current calculation unit 39 calculates the first reference current I _ref1 based on this voltage error ΔV (step S103).

The adder 41 adds the output current _{I 2} in the first reference current _{I ref1,} and outputs a second reference current _{I ref2} (step S104). If the second reference current I _ref2 does not exceed the upper limit current I _max , the limiter 42 outputs the second reference current I _ref2 as it is, and the second reference current I _ref2 is a target for feedback control based on the output current I _1. A value is set (steps S105 and S109). Then, feedback control is performed based on a difference (current error .DELTA.Ia) between the output current _{I 1} and the target value (step S110).

On the other hand, when the second reference current I _ref2 exceeds the upper limit current I _max , the upper limit current I _max is output from the limiter 42, and the upper limit current I _max is set to a target value (steps S105 and S112). feedback control is performed based on the difference between the output current I ₁ and the target value (step S110).

When calculating the first reference current I _ref1 in the reference current calculation unit 39, if the second reference current I _ref2 does not exceed the upper limit current I _max , the previous second reference current I _{ref2 sets the} upper limit current I _max . if exceeded, reset the history information held in the history information storage unit 40, the difference between the upper limit current _{I max} and the output current _{I 2} is outputted as the first reference current _{I ref1} current (step S106~ S108). At this time, the upper limit current I _max is output as the second reference current I _ref2 and set to the target value (step S109).

When the previous second reference current I _ref2 does not exceed the upper limit current I _max , the current first reference current I _ref1 is obtained from the voltage error ΔV and the first reference current I _ref1 obtained in the past. The added value of the first reference current I _ref1 and the output current I ₂ is output as the second reference current I _ref2 and set to the target value (steps S106 and S109). Feedback control based on the output current _{I 1} is repeated until the second reference current _{I ref2} is updated (step S111).

According to this embodiment, with respect to the target current of the feedback control based on the output current I ₁ of the chopper circuit 10, since the output voltage V _out of _the filter circuit 20 and the output current I ₂ can be reflected, the output voltage The feedback control of the chopper circuit 10 with good response characteristics can be realized while controlling the V _out so as to approach the target voltage V _ref . Further, the first reference current I _ref1 is obtained from the voltage error ΔV with respect to the output voltage V _out of the filter circuit 20, and the second reference current I _ref2 is obtained by adding the output current I ₂ of the filter circuit 20 to obtain the second reference current. Adjustment of the control parameter can be facilitated by setting I _ref2 as the target current. Furthermore, since the amount of fluctuation in the output voltage _Vout is reduced, the compensation amount of the feedback control may be small, so that the resolution of the constant voltage control based on the target voltage _Vref can be improved.

The interval for updating the second reference current I _ref2 samples the output voltage V _out and output current I _2, be longer than the interval for updating the duty ratio of the PWM signal by sampling the output current I _1, the load Since the responsiveness to the fluctuation is improved, an increase in manufacturing cost can be suppressed as compared with a case where both the update interval of the second reference current I _{ref2 and} the update interval of the duty ratio are shortened.

Embodiment 2. FIG.
In the first embodiment, the feedback control is performed by using the second reference current I _ref2 obtained by adding the output current I ₂ to the first reference current I _ref1 obtained from the voltage error ΔV as a target current, so that the output voltage during the constant voltage control is achieved. An example of reducing the fluctuation range of V _out has been described. In contrast, in the present embodiment, a case will be described in which constant voltage control based on the target voltage V _ref , constant current control based on the target current I _ref , and constant power control based on the target power P _ref can be switched. .

FIG. 5 is a diagram showing an example of a schematic configuration of the DC power supply device according to Embodiment 2 of the present invention, and shows another configuration example of the DC-DC converter 2. The DC-DC converter 2 includes a reference current calculation unit 30 that calculates a reference current I _ref0 based on the output voltage V _out and the output currents I ₁ and I ₂ as compared with the DC-DC converter 2 of FIG. Is different.

The reference current calculation unit 30 is a reference current generation unit that samples the output voltage V _out and the output currents I ₁ and I ₂ in a predetermined cycle, obtains the reference current I _ref0 from these detection values, and outputs the reference current I _ref0 to the limiter 42. . In the PWM control unit 36, feedback control is performed using the reference current _Iref0 as a target current.

<Reference current calculation unit>
FIG. 6 is a block diagram illustrating a configuration example of a main part of the DC-DC converter 2 of FIG. 5, and illustrates an example of a functional configuration in the reference current calculation unit 30. The reference current calculation unit 30 can switch the control mode to any one of the constant voltage mode, the constant current mode, and the constant power mode, and the reference current I _ref0 is output to the limiter 42 according to the selected control mode.

  Specifically, the constant voltage control block includes a target voltage generation unit 37, a subtractor 38, a reference current calculation unit 39, a history information storage unit 40, and an adder 41, and the target current generation unit 51 as a constant current control block. , A subtractor 52, a reference current calculation unit 53, and a history information storage unit 54.

  The constant power control block includes a multiplier 61, a target power generation unit 62, a subtractor 63, a reference current calculation unit 64, and a history information storage unit 65, and is in any one of a constant voltage mode, a constant current mode, and a constant power mode. And a control mode switching unit 70 for selecting. The constant voltage control block is the same as that in FIG.

The target current generator 51 generates a target current I _ref for comparison with the output current I ₁ and outputs it to the subtractor 52. The subtractor 52 is an arithmetic circuit that calculates a difference between the output current I ₁ and the target current I _ref and outputs the difference as a current error ΔIb to the reference current calculation unit 53. The current error ΔIb is expressed by, for example, ΔIb = I ₁ −I _ref .

The reference current calculation unit 53 is a third reference current generation unit that _obtains the third reference current I _ref3 based on the current error ΔIb and outputs the third reference current I _ref3 to the control mode switching unit 70. The third reference current I _ref3 is _obtained from the current error ΔIb and the history information held in the history information storage unit 54 by using a PI control or PID control method.

The multiplier 61 is an arithmetic circuit that multiplies the output voltage V _out and the output current I ₂ to obtain an output power P and outputs the output power P to the subtracter 63. The target power generation unit 62 generates a target power P _ref for comparison with the output power P and outputs the target power P _ref to the subtracter 63. The subtracter 63 is an arithmetic circuit that calculates a difference between the output power P and the target power P _ref and outputs the difference as a power error ΔP to the reference current calculation unit 64. The power error ΔP is expressed by, for example, ΔP = P−P _ref = V _out × I ₂ −P _ref .

The reference current calculation unit 64 is a fourth reference current generation unit that _obtains the fourth reference current I _ref4 based on the power error ΔP and _outputs the fourth reference current I _ref4 to the control mode switching unit 70. The fourth reference current I _ref4 is _obtained from the power error ΔP and the history information held in the history information storage unit 65 using a PI control or PID control method.

The control mode switching unit 70 selects any one of the constant voltage mode, the constant current mode, and the constant power mode, and the second reference current I _ref2 , the third reference current I _ref3, and the fourth reference according to the selected control mode. One of the currents I _ref4 is output as the reference current I _ref0 . Switching of the control mode is performed based on, for example, a mode switching request from another device.

According to the present embodiment, the reference current I _ref0 is set as a common parameter to the target value for feedback control regardless of the control mode of constant voltage, constant current, or constant power mode. And the configuration of the DC power supply device can be simplified.

Embodiment 3 FIG.
In the first embodiment, the feedback control is performed by using the second reference current I _ref2 obtained by adding the output current I ₂ to the first reference current I _ref1 obtained from the voltage error ΔV as a target current, so that the output voltage during the constant voltage control is achieved. An example of reducing the fluctuation range of V _out has been described. In contrast, in the present embodiment, by defining the reference current in consideration of the influence of the current flowing into the filter circuit 20, it will be described for reducing the variation range of the output current I ₂ during the constant current control.

  FIG. 7 is a block diagram illustrating a configuration example of the DC power supply device according to the third embodiment of the present invention, and illustrates another configuration example of the reference current calculation unit 30. Compared with the reference current calculation unit 30 of FIG. 6, the reference current calculation unit 30 functions as a constant current control block as a target current generation unit 51, a subtractor 52, a history information storage unit 54, and a first reference current calculation unit 81. And the second reference current calculation unit 82 is provided.

The first reference current calculation unit 81 includes an arithmetic circuit that calculates the first reference current I _ref1 based on the current error ΔIb and outputs the first reference current I _ref1 to the second reference current calculation unit 82. The first reference current I _ref1 is obtained from the current error ΔIb and the history information held in the history information storage unit 54 using a PI control or PID control method.

The second reference current calculation unit 82 includes an arithmetic circuit that obtains the second reference current I _ref2 based on the first reference current I _ref1 and the output voltage V _out of the filter circuit 20 and outputs the second reference current I _ref2 to the control mode switching unit 70. Specifically, a divider for calculating a quotient _Vout / Z obtained by dividing the output voltage _Vout by the impedance Z of the filter circuit 20, and a difference between the quotient _Vout / Z and the first reference current _Iref1 is calculated. And a subtractor. The second reference current I _ref2 is represented by, for example, I _ref2 = I _ref1 −V _out / Z.

The control mode switching unit 70 selects any one of the constant voltage mode, the constant current mode, and the constant power mode, and outputs either the reference current I _ref2 or I _ref4 as the reference current I _ref0 according to the selected control mode. Is done.

According to the present embodiment, the second reference current I _ref2 obtained from the quotient V _out / Z obtained by dividing the output voltage V _out of the filter circuit 20 by the impedance Z of the filter circuit 20 and the first reference current I _ref1 is the target. By using the current, the influence of the filter current V _out / Z flowing into the filter circuit 20 is quickly reflected in the feedback control, so that the responsiveness to load fluctuation can be improved and the fluctuation range of the output current I ₂ is reduced. Can be made.

Embodiment 4 FIG.
In the first embodiment, the feedback control is performed by using the second reference current I _ref2 obtained by adding the output current I ₂ to the first reference current I _ref1 obtained from the voltage error ΔV as a target current, so that the output voltage during the constant voltage control is achieved. An example of reducing the fluctuation range of V _out has been described. In contrast, in the present embodiment, a case will be described in which the followability when the target voltage V _ref changes greatly before the output voltage V _out is next sampled during constant voltage control is described.

  FIG. 8 is a block diagram illustrating a configuration example of the DC power supply device according to the fourth embodiment of the present invention, and illustrates another configuration example of the reference current calculation unit 30. Compared with the reference current calculation unit 30 in FIG. 6, the reference current calculation unit 30 includes a target voltage generation unit 37, a subtractor 38, a reference current calculation unit 39, a history information storage unit 40, an addition as a constant voltage control block. The difference is that the device 41 includes a change amount extraction unit 91 and an adder 92.

The change amount extraction unit 91 obtains a change amount ΔV _ref per unit time of the target voltage V _ref based on the output of the target voltage generation unit 37, and the change amount ΔV _ref and the capacitance of the capacitor in the filter circuit 20. This is an arithmetic circuit that outputs the product C × ΔV _ref with C to the adder 92. The change amount ΔV _ref is, for example, a change amount ΔV of the target voltage V _ref with a unit time as a time interval in which the reference current calculation unit 39 repeatedly samples the voltage error ΔV and updates the first reference current I _ref1 at a constant period. _ref is extracted. Specifically, the target voltage _{V ref} at the previous sampling, the amount of change [Delta] V _ref from the difference between the current target voltage _{V ref} is determined.

The adder 92 calculates the sum of the reference current calculated by the adder 41 and the product C × ΔV _ref extracted by the change amount extraction unit 91 and outputs the sum to the control mode switching unit 70 as the second reference current I _ref2. Circuit. The second reference current I _ref2 is represented by I _ref2 = I _ref1 + I ₂ + C × ΔV _ref .

According to the present embodiment, the product of the capacitance C of the capacitor in the filter circuit 20 and the amount of change ΔV _ref per unit time of the target voltage V _ref is added to the first reference current I _ref1 . By setting the current I _ref2 as the target current, the influence of the current necessary for further charging the capacitor in the filter circuit 20 is quickly reflected in the feedback control, so that the fluctuation of the target voltage V _ref during the constant voltage control can be prevented. Responsiveness can be improved.

Embodiment 5 FIG.
In the first embodiment, the feedback control is performed by using the second reference current I _ref2 obtained by adding the output current I ₂ to the first reference current I _ref1 obtained from the voltage error ΔV as a target current, so that the output voltage during the constant voltage control is achieved. An example of reducing the fluctuation range of V _out has been described. In contrast, in this embodiment, it obtains the reference duty from the ratio of the input voltage V _in and the target voltage V _ref for the chopper circuit 10, a case of performing feedback control of the reference duty as the target duty.

  FIG. 9 is a diagram showing a configuration example of a DC power supply device according to Embodiment 5 of the present invention, and shows a DC-DC converter 2 to which an arithmetic circuit for determining a target duty is added. The DC-DC converter 2 is different from the DC-DC converter 2 of FIG. 5 in that dividers 101 and 102 and an adder 103 are provided.

The divider 101 is a first reference duty calculation unit that _obtains the first reference duty D _ref1 from the ratio of the input voltage V _in to the chopper circuit 10 and the target voltage V _ref and outputs the first reference duty D _ref1 to the adder 103. The first reference duty D _ref1 is represented by, for example, D _ref1 = V _ref / V _in .

Divider 102 obtains the duty D from the ratio of the output voltage _{V out} of _the input voltage _{V in} and the filter circuit 20 for the chopper circuit 10, an arithmetic circuit for outputting to the adder 103. The duty D is represented by, for example, D = V _out / V _in .

The adder 103 is a second reference duty calculating unit that calculates the sum of the duty D and the first reference duty D _ref1 and outputs the sum as the second reference duty D _ref2 to the command value generation unit 36a. The second reference duty D _ref2 is represented by D _ref2 = D + D _ref1 . The PWM control unit 36 performs an operation of updating the duty ratio of the PWM signal at a predetermined cycle T3 with the second reference duty D _ref2 as a target duty.

According to the present embodiment, the ratio of the input voltage V _in to the output voltage V _out of the filter circuit 20 is _added to the first reference duty D _ref1 obtained from the ratio of the input voltage V _in to the chopper circuit 10 and the target voltage V _ref. There since the feedback control is performed a second reference duty D _ref2 which is added as a target duty, the variation of the input voltage V _in is quickly reflected in the feedback control, it is possible to improve the responsiveness to the input variations.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 DC-DC converter 3 Load 10 Chopper circuit 11 Drive circuit 12, 14 Switching element 13, 15 Diode 20 Filter circuit 21 Coil 22 Circuit element 30 Reference current calculating part 31, 32 Voltage sensor 33, 34 Current sensor 35, 38 Subtractor 36 PWM Control Unit 36a Command Value Generation Unit 36b PWM Generation Circuit 37 Target Voltage Generation Unit 39 Reference Current Calculation Unit 40 History Information Storage Unit 41 Adder 42 Limiter 51 Target Current Generation Unit 52 Subtractor 53 Reference Current Calculation Unit 54 History information storage unit 61 Multiplier 62 Target power generation unit 63 Subtractor 64 Reference current calculation unit 65 History information storage unit 70 Control mode switching unit 81 First reference current calculation unit 82 Second reference current calculation unit 91 Change amount extraction unit 92 Adder 101, 102 Divider 103 Adder A1 Control loop

Claims (4)

A chopper circuit having a switching element that operates based on a PWM signal;
A filter circuit for smoothing the output of the chopper circuit;
First reference current calculation means for obtaining a first reference current based on a difference between an output voltage of the filter circuit and a target voltage;
Second reference current calculation means for obtaining a second reference current obtained by adding the first reference current and the output current of the filter circuit;
PWM control means for generating the PWM signal based on the output current of the chopper circuit,
The DC power supply apparatus characterized in that the PWM control means performs feedback control based on the output current of the chopper circuit using the second reference current as a target current. A limiter for comparing the second reference current with the upper limit current;
2. The DC power supply device according to claim 1, wherein when the second reference current exceeds the upper limit current, the PWM control unit performs the feedback control using the upper limit current as a target current.   The first reference current calculation means calculates the first reference current based on the difference and the history information, and when the second reference current that exceeds the upper limit current becomes equal to or lower than the upper limit current, the history information The DC power supply device according to claim 2, wherein: is reset.   2. The DC power supply device according to claim 1, wherein the PWM control unit updates the duty ratio of the PWM signal at a cycle shorter than the update interval of the second reference current.

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