JP2013150424A - Switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply device capable of enhancing especially an accuracy of an output voltage in a steady state while improving responsibility of control to an output voltage in a transient state.SOLUTION: A switching power supply device comprises: a DC-DC converter having switching elements 2 and 3, a reactor 4, and a capacitor 5; reactor current detection means 6; output current detection means 7; average reactor current value calculation means 81; target output current value compensation means 83 compensating a target output current value and outputting the compensated target output current value as a target reactor current value Idclref; and PWM control means 84 determining a duty ratio of PWM control on the basis of a reactor current deviation between the target reactor current value Idclref compensated and outputted by the target output current value compensation means 83 and an average reactor current value calculated by the average reactor current value calculation means 81, and driving and controlling the switching elements 2 and 3 on the basis of the duty ratio.

Description

  The present invention relates to a switching power supply apparatus including a DC-DC converter that includes a switching element, a reactor, and a capacitor and converts an input voltage from a DC power supply into an output voltage having a different magnitude and outputs the output voltage to a load.

  The switching power supply device performs ON / OFF control of the switching element, thereby repeatedly storing and releasing energy in the reactor, thereby increasing or decreasing the DC input voltage to obtain DC output voltages of different sizes. It is configured to be able to.

  The switching power supply device having the above configuration is configured to convert an input voltage from a DC power source into an output voltage so that the DC output voltage becomes a command voltage. Specifically, the switching power supply apparatus includes two reactors arranged one above the other, a reactor having one end connected to a connection line connecting the emitter of the upper switching element and the collector of the lower switching element. A load is connected to the other end of the reactor via a connection line, and a capacitor is branched from the connection line and connected in parallel to the load. The two switching elements, the reactor, and the capacitor constitute a step-down DC-DC converter. Moreover, the current detector which detects the reactor current which flows into a reactor from a DC-DC converter, and the voltage detector which detects the voltage of the both ends of a capacitor | condenser are provided. And a controller for setting a DC voltage set value to be a target output voltage value, a first subtractor for subtracting a voltage value at both ends of the capacitor detected by the voltage detector from the DC voltage set value from the controller, An automatic voltage regulator (AVR) for outputting a current command value for setting the voltage error value obtained as a result to 0, and a reactor current detected by the current detector are subtracted from the output current command value. A second subtractor, an automatic current regulator (ACR) that generates a voltage command value based on a subtraction result from the second subtractor, and a reactor current time obtained by averaging the reactor current detected by the current detector A low-pass filter that outputs an average value, a compensation signal generator that outputs a compensation signal based on the time average value of the reactor current from the low-pass filter, and an automatic current regulator An adder for adding the compensation signal from the compensation signal generator to the voltage command value from the ACR), and PWM pulse generation means for modulating the pulse width in accordance with the voltage command value added by the adder (for example, , See Patent Document 1).

  In the switching power supply device configured as described above, the voltage value at both ends of the capacitor detected by the voltage detector is subtracted by the first subtracter from the DC voltage setting value set by the controller, and the voltage error value obtained as a result is obtained. A current command value for setting 0 to 0 is output from the automatic voltage regulator (AVR). Subsequently, the reactor current detected by the current detector is subtracted from the output current command value by the second subtracter, and the voltage command value is output from the automatic current regulator (ACR) to the adder based on the subtraction result. To do.

  The adder adds the compensation signal from the compensation signal generator to the output voltage command value, and outputs the added voltage command value to the PWM pulse generating means. This PWM pulse generating means generates a pulse whose pulse width is modulated in accordance with the voltage command value, and performs feedback control for turning on and off the switching element based on the generated pulse.

JP 2000-295869 A (see FIG. 1)

  As described above, the reactor current used for feedback control for turning on and off the switching element is a current before flowing through the capacitor, and therefore there is no time delay with respect to the response. Therefore, by performing ON / OFF control of the switching element based on the reactor current, the control responsiveness to the command voltage can be improved, but there are the following disadvantages.

  Such a switching power supply device detects a reactor current with a current detector, calculates an average value of the detected plurality of reactor currents, and controls ON / OFF of the switching element based on the calculated average reactor current value. However, when the current detector is configured to detect the reactor current at predetermined intervals (digital sampling), the following inconvenience occurs. That is, since the reactor current includes a large ripple (AC current depending on the switching frequency), the average reactor current value calculated by detecting the reactor current at a predetermined period depends on the magnitude of the output voltage. Current is continuously detected (analog), and an error is included in the average actual reactor current value obtained by averaging the detected actual reactor currents.

  Next, it will be described that the error is included. When the reactor current flowing through the reactor is detected by the current detector when the upper transistor constituting the switching power supply device is in the ON state, the detected reactor current includes a ripple. Here, the reactor current is detected every predetermined period, the average reactor current value obtained by calculating the average value of the detected currents, and the current flowing through the reactor is detected continuously (analog), and the detected actual reactor is detected. A graph obtained by plotting an average actual reactor current value obtained by averaging currents is shown in FIGS.

  6 to 11 are graphs of data obtained when an experiment was performed using the switching power supply device disclosed in Patent Document 1. FIG. In the figure, fc is a PWM carrier wave. samp is a timing signal for detecting the reactor current Idcl. VGP is an ON signal of the upper switching element (11 in FIG. 1 of Patent Document 1). VGN is an ON signal of the lower switching element (13 in Patent Document 1). Idcl is a value of a continuous reactor current in which a current flowing through the reactor (16 in FIG. 1 of Patent Document 1) is detected continuously (analog). IdclAve is an average actual reactor current value obtained by continuously detecting and averaging the reactor current flowing through the reactor (16 in FIG. 1 of Patent Document 1), that is, the average value of the continuous reactor current. is there. IdclSamp is a detection value (reactor current value) obtained by detecting the reactor current at predetermined intervals. IdclSampAve is an average reactor current value obtained by averaging the plurality of reactor current values.

  First, FIGS. 6A, 6B, and 7C, and FIGS. 7A, 7B, and 7C are all output voltage Vout = 0.5 × input voltage Vi, that is, output voltage. In this example, no error occurs when is half the input voltage. FIG. 6 shows the case of powering, and FIG. 7 shows the case of regeneration. 6 (c) and 7 (c), in each case, the current values obtained by continuously detecting the reactor current flowing through the reactor (16 in FIG. 1 of Patent Document 1) are averaged. The average actual reactor current value IdclAve and the average reactor current value IdclSampAve obtained by detecting the reactor current every predetermined period and averaging the detected reactor current values are on the same line. This is because the difference between the current values of the two is zero, and thus the average reactor current value IdclSampAve does not include an error.

  On the other hand, FIGS. 8 to 11 show examples in which an error occurs. FIGS. 8A, 8B and 8C show the case of power running when the output voltage Vout> 0.5 × the input voltage Vi, that is, when the output voltage is larger than half of the input voltage. FIGS. 9A, 9B, and 9C show the case where the output voltage Vout> 0.5 × the input voltage Vi, but the regeneration time, as in FIG. FIGS. 10A, 10B, and 10C show the case where the output voltage Vout <0.5 × the input voltage Vi, that is, the case where the output voltage is smaller than half of the input voltage and during power running. 11 (a), 11 (b), and 11 (c) show the case where the output voltage Vout <0.5 × the input voltage Vi at the time of regeneration, as in FIG. 8 (c), 9 (c), 10 (c), and 11 (c), there is a difference between the average actual reactor current value IdclAve and the average reactor current value IdclSampAve. It can be seen that the average reactor current value IdclSampAve includes an error S corresponding to the difference. In this example, in order to make the error S easy to understand, the dead time (the switching free time of the two switching elements 11 and 13) is extremely increased.

  Thus, when the target output voltage value is set to a value larger or smaller than half the input voltage value, there is an error between the average reactor current value IdclSampAve and the average actual reactor current value IdclAve. Will occur.

  The error S occurs because the slope of the increase or decrease of the reactor current changes according to the magnitude of the output voltage value. Specifically, in FIGS. 6 and 7 where the error S does not occur, the absolute value of the rising slope K1 and the falling slope K2 of the reactor current value Idcl is the same, whereas FIG. The absolute values of the rising slope K11 and the falling slope K21 of the reactor current value Idcl in FIG. 9 are different. Also, the absolute values of the rising slope K12 and the falling slope K22 of the reactor current value Idcl in FIGS. 10 and 11 are different. For this reason, the error S occurs. In order to eliminate this error S, it is conceivable to increase the number of detections of the reactor current. However, the number of detections cannot be increased because there is a limit to the calculation capability of the CPU that calculates the average reactor current value. For this reason, the output voltage (output current) is deviated from the command value during feedback control in a steady state that particularly requires accuracy, and there is a disadvantage that the accuracy of the output voltage cannot be increased.

  Incidentally, it is conceivable to perform ON / OFF control of the switching element based on an average output current value obtained by detecting an output current to the load and averaging a plurality of detected output current values. However, the feedback control using the output current value has poor response in a transient state and is difficult to use.

  Therefore, an object of the present invention is to provide a switching power supply device that can improve the accuracy of output voltage in a steady state, while improving the control response to an output voltage in a transient state.

  The switching power supply apparatus of the present invention includes a switching element, a reactor, and a capacitor, converts a DC power supply input voltage into an output voltage of a different magnitude and outputs the output voltage to a load, and is output to the load. Input means for inputting a target output current value of the current to be output; reactor current detection means for detecting the current flowing through the reactor every predetermined period; output current detection means for detecting a current output from the reactor to a load; An average reactor current value indexing means for determining an average value of a plurality of current values detected by the reactor current detection means, and an output current deviation of the output current value detected by the output current detection means with respect to the target output current value The target output current value is compensated based on the output, and the compensated target output current value is output as the target reactor current value. Based on the output current value compensation means, and the reactor current deviation of the average reactor current value calculated by the average reactor current value indexing means relative to the target reactor current value compensated and output by the target output current value compensation means PWM control means for determining a duty ratio of PWM control and drivingly controlling the switching element based on the duty ratio is provided.

  According to the present invention, the PWM control means determines the duty ratio of the PWM control based on the reactor current deviation of the average reactor current value with respect to the target reactor current value, and drives and controls the switching element. Since the average reactor current value is an average value of the current before flowing into the capacitor, there is no time delay with respect to the response. Therefore, the control response to the output voltage in the transient state can be improved by controlling the driving of the switching element using the average reactor current value. The target reactor current value output from the target output current value compensation means is a value obtained by compensating the target output current value based on the output current deviation of the output current value with respect to the target output current value. That is, the target reactor current value is a value obtained by compensating the target output current value based on the output current value in which the ripple is smoothed. Here, the output current deviation corresponds to an error between the average reactor current value and the average actual reactor current value obtained by continuously (analogically) detecting and averaging the reactor current flowing through the reactor. Therefore, by compensating the target output current value based on the output current deviation, it is possible to obtain a target reactor current value that allows for an error occurring between the average reactor current value and the average actual reactor current value. . Therefore, it is possible to improve the accuracy of the output voltage (output current) particularly in the steady state. Also, the accuracy of the output voltage (output current) can be increased even in a transient state.

  The switching power supply apparatus according to the present invention further includes an average output current value indexing unit that calculates an average value of a plurality of current values detected at predetermined intervals by the output current detecting unit, and the target output current value compensating unit Is obtained by subtracting the average output current value calculated by the average output current value indexing means from the target output current value, if the output current deviation is positive, A means for compensating the target output current value by adding the output current deviation to the target output current value and subtracting the output current deviation from the target output current value when the output current deviation is negative. There may be.

  According to the above configuration, the output current deviation is obtained by subtracting the average output current value from the target output current value, and when the obtained output current deviation is positive, the output current deviation is added to the target output current value, When the output current deviation is negative, the target reactor current value is obtained by subtracting the output current deviation from the target output current value, so that the target output current value is appropriately compensated according to the output current deviation state. It can be carried out.

  In addition, the switching power supply device of the present invention includes a switching element, a reactor, and a capacitor, converts a DC power supply input voltage into an output voltage having a different magnitude and outputs the output voltage to a load, and the load Input means for inputting the target output current value of the current output to the load based on the output voltage command value, reactor current detection means for detecting the current flowing through the reactor at predetermined intervals, and from the reactor to the load An output current detecting means for detecting the output current, an average reactor current value calculating means for calculating an average value of a plurality of current values detected by the reactor current detecting means, and an average reactor current value calculating means. The reactor current flowing through the reactor is continuously detected (analog) and averaged from the average reactor current value The target output current value is compensated by estimating the error with respect to the average actual reactor current value obtained by the target output current value, and outputting the compensated target output current value as the target reactor current value. And a duty ratio of the PWM control based on the reactor current deviation of the average reactor current value calculated by the average reactor current value indexing unit with respect to the target reactor current value output from the target output current value compensating unit And PWM control means for drivingly controlling the switching element based on the duty ratio.

  According to the above configuration, the PWM control means determines the duty ratio of the PWM control based on the reactor current deviation that is the deviation of the average reactor current value from the target reactor current value, and drives and controls the switching element. Since the average reactor current value is an average value of the current before flowing into the capacitor, there is no time delay with respect to the response. Therefore, the control response to the output voltage in the transient state can be improved by controlling the driving of the switching element using the average reactor current value. Further, the target reactor current value output from the target output current value compensating means is a value obtained by performing compensation that allows an error of the average reactor current value with respect to the average actual reactor current value to the target output current value. Therefore, it is possible to improve the accuracy of the output voltage (output current) particularly in the steady state. Also, the accuracy of the output voltage (output current) can be increased even in a transient state.

  According to the present invention, the switching state of the switching element is controlled by using the average reactor current value calculated by the average reactor current value indexing means, that is, the current value flowing through the reactor with no time delay with respect to the response. The control responsiveness can be improved. In addition, the target output current value is compensated by the target output current value compensation means to obtain the target reactor current value, thereby obtaining a target reactor current value that allows for an error between the average reactor current value and the average actual reactor current value. be able to. By determining the duty ratio of the PWM control based on the reactor current deviation between the target reactor current value and the average reactor current value, and driving the switching element based on the determined duty ratio, in particular, the output in the steady state Voltage accuracy can be increased.

It is a block diagram which shows one Embodiment of the switching power supply device of this invention. It is a block diagram which shows the structure of a control part. It is a graph which shows a target output current and the actual output current without output current correction. 4 is a graph showing a target output current and an actual output current with output current correction according to the present invention. It is a graph which shows the actual output current when the target output current and the ACR constant are set stably and feedback control is performed only by the output current. (A) is a graph showing the timing of pwm carrier wave and sampling, (b) is a graph showing ON signals of two switching elements, (c) Is an actual reactor current flowing through the reactor, an average value of the reactor current, a current value obtained by sampling the reactor current, and an average value of the reactor current. Output voltage = 0.5 × input voltage and regenerative case, (a) graph showing pwm carrier wave and sampling timing, (b) graph showing ON signals of two switching elements, (c) Is an actual current flowing through the reactor, an average value of the reactor current, a current value obtained by sampling the reactor current, and an average value of the reactor current. (A) is a graph showing pwm carrier wave and sampling timing, (b) is a graph showing ON signals of two switching elements, (c). Is an actual reactor current flowing through the reactor, an average value of the reactor current, a current value obtained by sampling the reactor current, and an average value of the reactor current. When output voltage> 0.5 × input voltage and regenerative, (a) is a graph showing pwm carrier wave and sampling timing, (b) is a graph showing ON signals of two switching elements, (c) Is an actual reactor current flowing through the reactor, an average value of the reactor current, a current value obtained by sampling the reactor current, and an average value of the reactor current. (A) is a graph showing the pwm carrier wave and sampling timing, (b) is a graph showing the ON signals of the two switching elements, and (c). These are the graphs which show the actual reactor current value which flows into a reactor, the average value of the reactor current, the current value which sampled the reactor current, and the average value of the reactor current. When the output voltage is less than 0.5 × input voltage, the case of regeneration is shown, (a) is a graph showing the PWM carrier wave and sampling timing, (b) is the graph showing the ON signals of the two switching elements, (c) These are the graphs which show the actual reactor current value which flows into a reactor, the average value of the reactor current, the current value which sampled the reactor current, and the average value of the reactor current.

  Next, the present invention will be described by taking up embodiments.

  A switching power supply device D according to the present invention shown in FIG. 1 is used as a variable voltage power supply in a battery simulator (battery emulator) simulating a battery unit mounted on an electric vehicle, for example. Alternatively, the switching power supply device D may be a switching power supply device as a product that is actually mounted on an electric vehicle. In particular, the switching power supply D according to the present invention is effective for a battery simulator (battery emulator) that requires high responsiveness and high accuracy.

  The switching power supply device D includes a DC power supply 1, two switching elements 2 and 3, a reactor 4, a capacitor 5, two current detectors 6 and 7, and a control unit 8. The two switching elements 2 and 3, the reactor 4 and the capacitor 5 constitute a DC-DC converter, and the DC-DC converter of FIG. 1 is configured as a step-down type that lowers the input voltage of the DC power source 1 and outputs it. Yes.

  As the switching elements 2 and 3, IGBT (Insulated Gate Bipolar Transistor) elements are used. However, the present invention is not limited to this, and FETs (Field Effect Transistors) and bipolar transistors may be used. Further, diodes 9 and 10 are connected in parallel to the two switching elements 2 and 3 in opposite directions, respectively.

  The reason why the two switching elements 2 and 3 are used in the switching power supply device D is to execute both power running and regenerative operations.

  One end (input side end) of the reactor 4 is connected to a connection line 11 that connects the emitter of one switching element 2 (upper side in the figure) and the collector of the other switching element 3 (lower side in the figure). Further, a load 13 is connected to the other end (output side end) of the reactor 4 via a connection line 12. The capacitor 5 branches from the connection line 12 and is connected to the load 13 in parallel. As the load 13, an inverter as a specimen is used.

  The reactor 4 and the capacitor 5 function as a smoothing filter that smoothes the output including ripples (AC current depending on the switching frequency) from the switching elements 2 and 3.

  One current detector 6 constitutes a reactor current detecting means for detecting a current before branching from the connection line 12 to the capacitor 5 (that is, a reactor current Idcl flowing through the reactor 4). The other current detector 7 constitutes output current detection means for detecting the output current Io output to the load 13 on the side opposite to the capacitor 5 side.

  Note that the current value detected by the output current detecting means 7 is the output current Io from the switching power supply D to the load 13 during power running, but the input from the load 13 to the switching power supply D during regeneration. The current Iin.

  Based on the current values Idcl and Io detected by the current detectors 6 and 7, the control unit 8 switches the switching elements 2 and 3 so that the output voltage Vout to the load 13 becomes the target output voltage (output voltage command value). Is to control.

  An input means 14 for calculating a target output current value (Iref) of a current output to the load 13 based on a command value for setting the output voltage to the load 13 to a predetermined voltage and inputting the target output current value (Iref) to the controller 8 (FIG. 2). See).

  As shown in FIGS. 1 and 2, the control unit 8 includes an average reactor current value indexing unit 81 that calculates an average value of a plurality of reactor current values detected every predetermined period by the reactor current detection unit 6, and an output current. An average output current value indexing means 82 for calculating an average value of a plurality of output current values detected at predetermined intervals by the detecting means 7, and an average output current value index for the target output current value Iref input from the input means 14 The output current deviation of the average output current value determined by the means 82 is obtained, the target output current value Iref is compensated based on the output current deviation, and the compensated target output current value is output as the target reactor current value Idclref. The target output current value compensating means 83 and the target reactor current value Idclref output after being compensated by the target output current value compensating means 83 are received and the target reactor is received. The duty ratio of the PWM control is determined based on the reactor current deviation of the average reactor current value calculated by the average reactor current value indexing means 81 with respect to the flow value Idclref, and the switching elements 2 and 3 are driven based on the duty ratio. PWM control means 84 for controlling.

  The timing at which the reactor current is detected by the reactor current detection means 6 is, for example, when the timing signal samp shown in FIG. 6A rises, and within one cycle of switching of the switching elements 2 and 3 shown in FIG. Are detected at a ratio of plural (here, two times, but any number of times). The timing for detecting the output current by the output current detecting means 7 is set to be the same as the timing for detecting the reactor current.

  The various means included in the control unit 8 will be described more specifically. The average reactor current value indexing means 81 performs an operation of averaging a plurality of current values detected at the timing (predetermined period) by the reactor current detection means 6 by the CPU, and the calculated average reactor current value is stored in a RAM (memory). ) In order. The average output current value indexing means 82 performs an arithmetic operation for averaging a plurality of current values detected by the output current detecting means 7 at the timing (predetermined period) by the CPU, and the calculated average output current value is stored in the RAM. It is means for sequentially storing in (memory).

  The target output current value compensating means 83 detects the average actual current value obtained by the average reactor current value calculated by the average reactor current value calculating means 81 by continuously detecting and averaging the current flowing through the reactor 4. This is a means for compensating for the error with respect to the reactor current value by incorporating it into the target output current value Iref. Specifically, the target output current value compensating means 83 has a function of compensating (correcting) the target output current value Iref by an error of the average reactor current value with respect to the average actual reactor current value. Specifically, the target output current value compensation unit 83 calculates the average output current value calculated (calculated here) by the average output current value indexing unit 82 from the target output current value Iref input from the input unit 14. A subtracter 831 for subtracting and calculating the output current deviation, an ACR (Automatic Current Regulator) 832 for outputting the output current deviation calculated by the subtractor 831, and the output current deviation output from the ACR 832 as the target output current value Iref And an adder 833 to be added. In the adder 833 of this embodiment, when the output current deviation is positive, the output current deviation is added to the target output current value, and when the output current deviation is negative, the output current deviation is output to the target output current value. Current deviation is subtracted. The target output current value compensation means 83 sends the compensated target output current value to the PWM control means 84 as the target reactor current value Idclref (in other words, the target reactor current value).

  The PWM control unit 84 subtracts the average reactor current value calculated (calculated here) by the average reactor current value indexing unit 81 from the target reactor current value Idclref, and calculates a reactor current deviation. The ACR (Automatic Current Regulator) 842 that outputs the reactor current deviation calculated by the subtractor 841 and the duty ratio of the PWM control are determined based on the reactor current deviation from the ACR 842, and the switching elements 2 and 3 are determined based on the duty ratio. And a PWM control unit (Pulse Width Modulation) 843 for controlling the driving of the. The PWM control unit 843 controls the gate signals applied to the gates of the two switching elements 2 and 3 based on the determined duty ratio. That is, when the reactor current deviation from ACR 842 is positive, the duty ratio is increased, and when the reactor current deviation from ACR 842 is negative, the duty ratio is decreased.

  A current monitoring unit that monitors whether the target reactor current value Idclref output from the adder 833 is positioned between the upper limit current threshold and the lower limit current threshold between the adder 833 and the subtractor 841. 85 is provided.

  Based on the reactor current deviation of the average reactor current value with respect to the target reactor current value Idclref compensated as described above, ON / OFF of the switching elements 2 and 3 is controlled. At this time, when the target output voltage value is set to a value that is larger or smaller than half the input voltage value, an error occurs between the average reactor current value and the average actual reactor current value. This error is included in the output current deviation when the average output current value is subtracted from the target output current value Iref. In the present embodiment, the average reactor current value including an error is obtained by setting the target reactor current value Idclref in which the output current deviation (error) is estimated as the target output current value Iref, which is the output target value, as a reference value for PWM control. Can be made to coincide with the target reactor current value Idclref that anticipates an error (compensation amount) with respect to the target output current value Iref, and as a result, the average actual reactor current value (and hence the average output current value) that does not include an error. Can be made to coincide with the target output current value Iref which is the target value of the output not including an error (compensation amount).

  The occurrence of the error is shown in FIGS. 6 (a), (b), and (c) to FIGS. 11 (a), (b), and (c) as described above.

  A case where an error occurs and a case where no error occurs will be described. First, when no error occurs, the target output voltage is set to a voltage value that is half the input voltage. 6 (a), (b), and (c) show the case of power running, and FIGS. 7 (a), (b), and (c) show the case of regeneration. The case where it does not occur is shown. FIGS. 6A and 7A are graphs showing the relationship between the PWM carrier fc and the timing signal samp for detecting the reactor current Idcl. FIGS. 6B and 7B are graphs. FIG. 6 is a graph showing the relationship between the ON signal VGP of the upper switching element 2 shown in FIG. 1 and the ON signal VGN of the lower switching element 3 shown in FIG. ) Indicates the current value Idcl obtained by continuously detecting the reactor current flowing through the reactor 4 (analog) and the average actual reactor current obtained by continuously detecting and averaging the reactor current flowing through the reactor 4 (analog). The value IdclAve, the reactor current value IdclSamp when the reactor current is detected every predetermined cycle (digitally), and a plurality of reactor currents where the reactor current is detected every predetermined cycle (digitally) Is a graph showing the relationship between the average reactor current value IdclSampAve obtained by averaging the.

  6C and 7C, the absolute value of the rising slope K1 and the falling slope K2 of the triangular wave of the reactor current value Idcl is the same. For this reason, the rising period of the triangular wave and the falling period of the triangular wave are the same, and an intermediate value between the lowest value and the highest value of the triangular wave is the average actual reactor current value IdclAve. On the other hand, since the detection of the reactor current at every predetermined cycle (digital) is performed at a timing synchronized with the PWM carrier wave fc, the reactor current value IdclSamp detected at every predetermined cycle (digital) is continuously (analog). Similarly to the detected reactor current value Idcl, the highest value and the lowest value are switched in the same cycle. Therefore, it can be seen that the average reactor current value IdclSampAve coincides with the average actual reactor current value IdclAve, and the average reactor current value IdclSampAve does not include an error.

  On the other hand, the occurrence of the error is shown in FIGS. 8A, 8B, and 8C to 11A, 11B, and 11C. 8 (a), (b), and (c) show the case of powering when the output voltage is larger than half of the input voltage, and FIGS. 9 (a), (b), and (c). Indicates a case where the output voltage is larger than half of the input voltage and is in regeneration. FIGS. 10A, 10B, and 10C show a case where the output voltage is smaller than half of the input voltage and during powering. FIGS. 11A, 11B, and 11C are used. Indicates a case where the output voltage is smaller than half of the input voltage and during regeneration. The graphs of FIG. 8 to FIG. 11 are graphs showing the same relationship only with different waveforms from those of FIG. 6 and FIG.

  8C and 9C, the absolute values of the rising slope K11 and the falling slope K21 of the triangular wave of the reactor current value Idcl are different. For this reason, the rising period of the triangular wave is different from the falling period of the triangular wave, and there is a gap between the detection timing, and the intermediate value between the lowest value and the highest value of the triangular wave is the average actual reactor current value IdclAve. On the other hand, the average reactor current value IdclSampAve is located at a position shifted downward from the average actual reactor current value IdclAve. For this reason, there is a difference between the average actual reactor current value IdclAve and the average reactor current value IdclSampAve. Therefore, it can be seen that the average reactor current value IdclSampAve includes an error S corresponding to the difference.

  10C and 11C, the absolute values of the rising slope K12 and the falling slope K22 of the triangular wave of the reactor current value Idcl are different. For this reason, the rising period of the triangular wave is different from the falling period of the triangular wave, and there is a gap between the detection timing, and the intermediate value between the lowest value and the highest value of the triangular wave is the average actual reactor current value IdclAve. On the other hand, the average reactor current value IdclSampAve is located at a position shifted upward from the average actual reactor current value IdclAve. For this reason, there is a difference between the average actual reactor current value IdclAve and the average reactor current value IdclSampAve. Therefore, it can be seen that the average reactor current value IdclSampAve includes an error S corresponding to the difference.

  In the switching power supply device D according to the present embodiment, even when the error S occurs as described above, the target output current value compensated by considering the error S to the target output current value Iref that is the target value of the output. Is output as the target reactor current value Idclref, and the switching elements 2 and 3 are subjected to PWM control so that the average reactor current value IdclSampAve matches the target reactor current value Idclref using the target reactor current value Idclref as a reference value for PWM control. As a result, the average actual reactor current value IdclAve (corresponding to the output current value Io) obtained by removing the error from the average reactor current value IdclSampAve matches the target output current value Iref obtained by removing the compensation from the target reactor current value Idclref. In particular, the accuracy of the output voltage Vout in the steady state can be increased.

  Next, description will be made based on the operation description of the switching power supply device D. First, in order to obtain the output voltage Vout, the switching element 2 is turned on and the switching element 3 is turned off. As a result, voltage and current are applied to the load 13, and power is consumed by the load 13.

  Subsequently, the switching element 2 is turned off and the switching element 3 is turned on. Thereby, the electric charge charged in the capacitor 5 is discharged.

  Note that the switching element 3 is turned on during powering. This is because the control for alternately turning on the switching elements 2 and 3 is executed. According to the principle of the switching circuit, the switching element 3 is not necessarily turned on in order for the charge charged in the capacitor 5 to be discharged. Need not be.

  Also at the time of regeneration, the switching elements 2 and 3 are switched so that they are alternately turned on, as in the case of powering. Even when the switching element 2 is ON and the switching element 3 is ON, power is supplied from the load 13 to the switching power supply D side.

  Next, the operation of the control unit 8 of the switching power supply device D will be described.

  The control unit 8 calculates the average value of the plurality of output currents detected by the output current detection unit 7 using the average output current value indexing unit 82 and outputs the result to the subtracter 831. The subtractor 831 calculates the output current deviation by subtracting the average output current value from the target output current value Iref input from the input means 14. Subsequently, the calculated output current deviation is output from the ACR 832 to the adder 833. Even when the output current deviation is zero, zero is output from the ACR 832 to the adder 833, and the adder 833 outputs the compensated target output current value to the PWM control unit 84 as the target reactor current value Idclref. The adder 833 adds the output current deviation to the target output current value Iref when the output current deviation is positive, and outputs the output current to the target output current value Iref when the output current deviation is negative. The target output current value Iref is compensated by subtracting the deviation, and the compensated target output current value is output to the subtracter 841 of the PWM control means 84 under the name of the target reactor current value Idclref. The output target reactor current value Idclref is checked by the current monitoring unit 85 to determine whether it is located between the upper limit current threshold and the lower limit current threshold. 841 is output. Further, the control unit 8 calculates an average value of a plurality of reactor currents detected by the real-toler current detection means 6 using an average reactor current value indexing means 81, and outputs the calculated average reactor current value to a subtracter 841. Output. The subtractor 841 obtains a reactor current deviation by subtracting the average reactor current value from the target reactor current value Idclref. The reactor current deviation is amplified by the ACR 842 and output to the PWM controller 843. The PWM control unit 843 determines (calculates) the duty ratio of the PWM control based on the reactor current deviation, and drives and controls the switching elements 2 and 3 based on the duty ratio.

  Therefore, the control response in the transient state can be improved by driving and controlling the switching elements 2 and 3 using the current value (average reactor current value) flowing through the reactor with no time delay with respect to the response. In addition, by outputting the target output current value compensated by the target output current value compensating means 83 as the target reactor current value Idclref, the target reactor current that allows for an error between the average reactor current value and the average actual reactor current value. The value Idclref can be obtained. By determining the duty ratio of the PWM control based on the reactor current deviation between the target reactor current value Idclref and the average reactor current value, and driving the switching elements 2 and 3 based on the determined duty ratio, in particular, The accuracy of the output voltage Vout (output current Io) in the steady state can be increased.

  As described above, it is possible to confirm by experiments that the control response to the output voltage Vout in the transient state can be improved and the accuracy of the output voltage Vout in the steady state can be improved. FIG. 3 shows the waveform of the output current of the conventional switching power supply device (when the target output current value is not compensated), and FIG. 4 shows the output current of the switching power supply device (when the target output current value is compensated) of the present invention. The waveform is shown. In the figure, the broken line is the target output current value Iref, and the solid line is the measured output current value. 3 and FIG. 4, it can be seen that the slope angle of the rising portion W1, which is a transient state, is larger in FIG. 4 than in FIG. 3, and the responsiveness is good. Further, in the steady state W2 where the current value is constant from the transient state, the actual output current value is lower than the target output current value Iref in FIG. 3, whereas in FIG. It can be seen that the current value Iref and the actual output current value are the same value, and the accuracy of the output voltage Vout can be increased. Further, even in the transient state W3 in the falling portion, the followability to the target output current value Iref is better in FIG. 4 than in FIG.

  Moreover, the graph of FIG. 5 is shown as a comparative example. FIG. 5 shows an output current waveform in the case where the ACR constant is set stably, the output current is detected, and the switching elements 2 and 3 are controlled by the detected output current value. In this case, since the response of the output current value in the transient state W1 is very bad, the response of the output voltage is also very bad and cannot be used.

  The switching power supply device according to the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

  In the above embodiment, the output current detecting means 7 is constituted by means for detecting every predetermined period, but it may be constituted by means for constantly detecting (continuously detecting) the output current. Further, since the current detected by the output current detection means 7 contains almost no ripple, the difference from the actual output current value actually flowing is small. Therefore, the detected value as it is may be output to the target output current value compensation means 84 without calculating the average value so as to compensate the target output current Iref.

  In the above embodiment, the present invention is applied to the step-down DC-DC converter. However, the present invention may be applied to a step-up DC-DC converter. Further, the number of switching elements is not limited to two, and one or three or more switching elements may be provided.

  Moreover, in the said embodiment, the reactor current value indexing means 81 and the output current value indexing means 82 perform the calculation (calculation) that averages the plurality of current values detected by the detecting means 6 and 7, thereby obtaining the current value. However, the current value may be determined by reading a graph in which the average value with respect to the current value is plotted or by reading a table in which the average value with respect to the current value is tabulated.

  In the embodiment, the output current deviation of the average output current value calculated by the average output current value indexing means 82 with respect to the target output current value Iref input from the input means 14 is detected by the target output current value compensating means 84. Is calculated, the target output current value Iref is compensated based on the output current deviation, and the compensated target output current value is output as the target reactor current value Idclref. The error between the determined average reactor current value IdclSampAve and the average actual reactor current value IdclAve obtained by continuously detecting and averaging the current flowing through the reactor 4 is the target output current value Iref. In this case, the target output current value may be compensated for, and the compensated target output current value may be output as the target reactor current value Idclref.

  Moreover, in the said embodiment, although the reactor current detection means 6 was arrange | positioned so that it might detect on the load side of the reactor 4, you may arrange | position so that it may detect on the switching elements 2 and 3 side of the reactor 4. FIG.

  DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2, 3 ... Switching element, 4 ... Reactor, 5 ... Capacitor, 6 ... Reactor current detection means (current detector), 7 ... Output current detection means (current detector), 8 ... Control part, 9 , 10 ... Diode, 11, 12 ... Connection line, 13 ... Load, 81 ... Average reactor current value indexing means, 82 ... Average output current value indexing means, 83 ... Target output current value compensating means, 84 ... PWM control means 85 ... Current monitoring unit, 831 ... Subtractor, 833 ... Adder, 841 ... Subtractor, D ... Switching power supply

Claims (3)

A DC-DC converter having a switching element, a reactor, a capacitor, converting an input voltage from a DC power source into an output voltage of a different size and outputting the output voltage to a load;
Input means for inputting a target output current value of the current output to the load;
Reactor current detection means for detecting the current flowing through the reactor at predetermined intervals;
Output current detection means for detecting current output from the reactor to the load;
Average reactor current value indexing means for calculating an average value of a plurality of current values detected by the reactor current detection means;
A target that compensates the target output current value based on an output current deviation of the output current value detected by the output current detection unit with respect to the target output current value, and outputs the compensated target output current value as a target reactor current value Output current value compensation means;
The duty ratio of the PWM control is determined based on the reactor current deviation of the average reactor current value calculated by the average reactor current value indexing unit with respect to the target reactor current value compensated and output by the target output current value compensating unit. PWM control means for driving and controlling the switching element based on the duty ratio;
A switching power supply device comprising:   The output current detecting means further comprises an average output current value calculating means for calculating an average value of a plurality of current values detected at predetermined intervals, and the target output current value compensating means is configured to calculate the output current deviation as the target current value. When the average output current value calculated by the average output current value indexing unit is subtracted from the output current value, and the output current deviation is positive, the output current deviation is added to the target output current value. 2. The means according to claim 1, wherein when the output current deviation is negative, the target output current value is compensated by subtracting the output current deviation from the target output current value. The switching power supply device described. A DC-DC converter having a switching element, a reactor, a capacitor, converting an input voltage from a DC power source into an output voltage of a different size and outputting the output voltage to a load;
Input means for inputting a target output current value of the current output to the load;
Reactor current detection means for detecting the current flowing through the reactor at predetermined intervals;
Output current detection means for detecting current output from the reactor to the load;
Average reactor current value indexing means for calculating an average value of a plurality of current values detected by the reactor current detection means;
An error relative to the average actual reactor current value obtained by continuously detecting and averaging the reactor current flowing through the reactor of the average reactor current value calculated by the average reactor current value indexing means is calculated as a target output current value. A target output current value compensating means for compensating the target output current value by expecting and outputting the compensated target output current value as a target reactor current value;
The duty ratio of PWM control is determined based on the reactor current deviation of the average reactor current value calculated by the average reactor current value indexing unit with respect to the target reactor current value output from the target output current value compensating unit, PWM control means for driving and controlling the switching element based on a duty ratio;
A switching power supply device comprising:

Images