JP5074993B2 - DC voltage buck-boost circuit - Google Patents

Description

  The present invention relates to a DC voltage step-up / step-down circuit for stepping up / down an input voltage to obtain a predetermined output voltage.

  As a DC voltage step-up / down circuit for obtaining a predetermined DC output voltage from a fluctuating DC input voltage (for example, when a DC power source combining a power source such as an engine, a generator, and a rectifier is used as an input) There exists a thing of patent document 1. FIG. 9 is a diagram illustrating a schematic configuration of a DC voltage step-up / down circuit described in Patent Document 1. In FIG.

  As shown in FIG. 9, the configuration of the DC voltage step-up / down circuit described in Patent Document 1 is such that when the input voltage Vin is stepped down, the first switch S1 is switched (ON / OFF) with a predetermined duty ratio. While the switch S2 is fixed to OFF, when the input voltage Vin is boosted, the first switch S1 is fixed to ON and the second switch S2 is switched (ON / OFF) with a predetermined duty ratio. The step-up / step-down operation classification for stepping down or stepping up the input voltage Vin is determined by a comparison between the input voltage Vin and the output voltage Vout by the comparator CP.

  Specifically, when the input voltage Vin> the output voltage Vout, the comparator CP outputs an OFF signal (Low level), and the comparison controller CCP outputs a switching (ON / OFF) signal determined based on the duty ratio. These output signals are input to an OR gate G1 connected to the switch S1 and an AND gate G2 connected to the switch S2. Thereby, the switch S1 is subjected to switching control based on the duty ratio of the comparison controller CCP, while the switch S2 is turned off (step-down operation).

  When the input voltage Vin <the output voltage Vout, the comparator CP outputs an ON signal (High level), and the comparison controller CCP outputs a switching (ON / OFF) signal determined based on the duty ratio. Are output to an OR gate G1 connected to the switch S1 and an AND gate G2 connected to the switch S2. Thereby, the switch S2 is subjected to switching control based on the duty ratio of the comparison controller CCP, while the switch S1 is turned on (step-up operation).

Here, the duty ratio of the comparison controller CCP is a value determined by a comparison between the target output voltage Vr and an output voltage (hereinafter referred to as an actual output voltage) Vout.
JP-A-56-101222

  However, in the configuration of the conventional DC voltage step-up / step-down circuit shown in FIG. 9, the input voltage Vin is only used as a signal of the step-up / step-down operation section, and the duty ratio is the target output voltage Vr and the actual output voltage Vout. Since it is determined only by comparison, the response to the fluctuation of the input voltage Vin is poor. That is, when the input voltage Vin becomes smaller than the actual output voltage Vout, the input voltage Vin is boosted (hereinafter simply referred to as a boosting operation). On the other hand, when the input voltage Vin becomes larger than the actual output voltage Vout, the input voltage Vin is lowered. However, whether the input voltage Vin is stepped up or stepped down is determined by whether the input voltage Vin is smaller or larger than the actual output voltage Vout, and the comparison controller CCP It is not reflected as a signal for obtaining the duty ratio. That is, instead of determining a signal for obtaining the duty ratio of the comparison controller CCP when the input voltage Vin changes, the actual output voltage Vout changes due to the change in the input voltage Vin. Since the signal for obtaining the duty ratio is determined, the response to the fluctuation of the input voltage Vin is poor accordingly.

  In addition, although the switching target of the first switch S1 and the second switch S2 is switched between the step-up operation and the step-down operation, when the input voltage Vin is in the vicinity of the actual output voltage Vout (Vin≈Vout) The duty ratio for the first switch S1 is close to 1, whereas the duty ratio for the second switch S2 during boosting when the input voltage Vin is close to the actual output voltage Vout (Vin≈Vout) is 0. The duty ratio changes discontinuously due to switching of the step-up / step-down. That is, since the calculation of the duty ratio at the time of step-up and step-down of the first switch S1 and the second switch S2 is performed inside the comparison controller CCP, the comparison controller CCP is switched when the step-up / step-down is switched. The operation of determining the duty ratio to the first switch S1 near 1 and the operation of determining the duty ratio to the second switch S2 near 0 are performed. As a result, the comparison controller CCP cannot cope with a sudden change in the duty ratio, and the duty ratio should be a value close to 1 with respect to the first switch S1, or a value close to 0, or the second switch S2. On the other hand, when the step-up / step-down switching is performed such that the duty ratio should be a value close to 0, the switching control cannot be stably performed with the correct duty ratio. Inconvenience that the output voltage cannot be obtained.

  In this regard, in the DC voltage step-up / step-down circuit described in Patent Document 1, when the input voltage Vin is in the vicinity of the actual output voltage Vout, a period in which the input voltage Vin is simultaneously turned on is provided to turn on / off the first and second switches S1, S2. Control off. However, such a configuration complicates the circuit configuration.

  Therefore, the present invention can directly reflect the fluctuation of the input voltage in the determination of the duty ratio without complicating the circuit configuration, thereby improving the responsiveness to the fluctuation of the input voltage. In addition, the DC voltage that can change the duty ratio continuously at the time of switching of the step-up / step-down, thereby enabling stable switching control with the correct duty ratio and thus obtaining a stable output voltage An object is to provide a step-up / down circuit.

  In order to solve the above-described problems, the present invention provides the following DC voltage step-up / step-down circuit according to the first and second aspects.

(1) DC voltage step-up / down circuit of the first aspect A first switch and an inductor are connected in series in this order from the input side to the output side, and the direction from the first switch to the inductor toward these connection lines The first diode is connected in parallel to both the input and output terminals as the conduction direction, and the second diode is connected in series to the output side of the inductor with the direction toward the output side as the conduction direction. In a DC voltage step-up / down circuit configured such that the second switch is connected in parallel to both input and output terminals between two diodes, it is unambiguous based on the input voltage and the target output voltage that is the target of the actual output voltage. A duty ratio calculating means for calculating a duty ratio that is determined continuously and continuously, the duty ratio as a command signal for the second switch, A shift duty ratio obtained by adding a duty ratio for the step-up / step-down control of the input voltage when at least the input voltage is equal to the target output voltage as a command signal of the first switch, and the duty ratio is equal to or less than zero ( The second switch is fixed to OFF at the time of step-down, while the first switch is fixed to OFF when the shift duty ratio is less than zero, and the first switch is turned off when the shift duty ratio is 1 or more (during step-up). DC voltage step-up / down circuit characterized by being fixed to ON.

(2) DC voltage step-up / step-down circuit of the second mode A first switch and an inductor are connected in series in this order from the input side to the output side, and the direction from the first switch to the inductor toward these connection lines The first diode is connected in parallel to both the input and output terminals as the conduction direction, and the second diode is connected in series to the output side of the inductor with the direction toward the output side as the conduction direction. In a DC voltage step-up / down circuit configured such that the second switch is connected in parallel to both input and output terminals between two diodes, it is unambiguous based on the input voltage and the target output voltage that is the target of the actual output voltage. A duty ratio calculating means for calculating a duty ratio that is determined continuously and continuously, the duty ratio as a command signal of the first switch, The shift duty ratio obtained by subtracting the duty ratio for the step-up / step-down control of the input voltage when the input voltage and the target output voltage are equal to each other as a command signal of the second switch, and the shift duty ratio is less than zero The second switch is fixed to OFF at the time of step-down, while the first switch is fixed to OFF when the duty ratio is less than zero, and the first switch is turned on when the duty ratio is 1 or more (when boosting). A DC voltage step-up / down circuit characterized by being fixed to

  In the DC voltage step-up / step-down circuit according to the first and second aspects of the present invention, the duty ratio is calculated based on the input voltage and the target output voltage by the duty ratio calculation means. That is, since the duty ratio is calculated using the input voltage, fluctuations in the input voltage can be directly reflected in the duty ratio. Thereby, the responsiveness with respect to the fluctuation | variation of the said input voltage can be improved.

  Furthermore, in the DC voltage step-up / step-down circuit according to the first aspect of the present invention, the duty ratio that is uniquely and continuously determined is used as a command signal for the second switch, and the shift duty ratio is used as a command signal for the first switch. Therefore, while the command signal to the second switch is used as the command signal at the time of boosting as the duty ratio calculated inside the duty ratio calculation means, the command signal to the first switch is used as the duty ratio calculation means. As the shift duty ratio calculated externally, it can be used as a command signal at the time of step-down, and therefore the duty ratio calculation means is not forced to change the duty ratio calculation as in the prior art. When switching, the duty ratio can be changed continuously (gentle), which ensures stable switching at the correct duty ratio. It can be quenching control.

  In the DC voltage step-up / step-down circuit according to the second aspect of the present invention, the unambiguous and continuously determined duty ratio is used as the first switch command signal, and the shift duty ratio is used as the second switch command signal. Therefore, the command signal to the first switch is used as the command signal at the time of step-down as the duty ratio calculated inside the duty ratio calculation means, while the command signal to the second switch is used as the duty ratio calculation means. As the shift duty ratio calculated outside, the command signal at the time of boosting can be used. Therefore, the duty ratio calculating means is not forced to change the duty ratio calculation as in the prior art. When switching, the duty ratio can be changed continuously (gently), which ensures stable switching at the correct duty ratio. It is possible to ring control.

  In addition, in the DC voltage step-up / step-down circuit according to the first and second aspects of the present invention, since the control configuration devised the duty ratio to the first and second switches, it is stable without complicating the circuit configuration. An output voltage can be obtained.

  In the DC voltage step-up / step-down circuit according to the first and second aspects of the present invention, the duty ratio calculation means is configured to calculate the duty ratio using a target voltage ratio between the input voltage and the target output voltage as a variable, The target voltage ratio may be corrected by a PI calculation value obtained by performing PI calculation on the difference between the actual voltage ratio calculated from the input voltage and the actual output voltage and the target voltage ratio. Here, the PI calculated value is a calculated value for PI (Proportinal Integral) control in which an integral operation for integrating a residual error is added to a proportional operation for converging the actual output voltage to the target output voltage. .

  By this specific matter, the duty ratio can be corrected based on the actual output voltage, and accordingly, the error of the actual output voltage due to the response delay of the actual output voltage and the loss of each element constituting the circuit is corrected. Therefore, the actual output voltage can be accurately converged to the target output voltage, and thereby the accuracy of convergence of the actual output voltage to the target output voltage can be improved.

  As a specific aspect of such a configuration, PI calculation is performed on the deviation between the target voltage ratio and the actual voltage ratio, the obtained PI calculation value is added to the target voltage ratio, and the added value is a variable. As an example, the duty ratio calculating means calculates the duty ratio.

  In the DC voltage step-up / step-down circuits according to the first and second aspects of the present invention, the shift amount may be a value larger by a predetermined amount or a value smaller by a predetermined amount than the duty ratio for the step-up / step-down control.

  Due to this specific matter, in the DC voltage step-up / step-down circuit according to the first aspect of the present invention, the shift amount to be added to the duty ratio is larger by a predetermined amount or a predetermined amount than the duty ratio for the step-up / down control. Since the value is small, the first switch can be stopped in an on state in a first range between the step-up / down control duty ratio of the target voltage ratio and the shift position corresponding to the predetermined amount. Thus, since the first switch can be stopped in the first range while being on, the switching loss of the first switch can be reduced accordingly. In the DC voltage step-up / step-down circuit according to the second aspect of the present invention, the shift amount to be subtracted from the duty ratio is set to a value larger by a predetermined amount or a value smaller by a predetermined amount than the step-up / down control duty ratio. Therefore, the second switch can be stopped in an OFF state in a second range between the step-up / down control duty ratio of the target voltage ratio and the shift position corresponding to the predetermined amount. Thus, since the second switch can be stopped in the second range while being in the OFF state, the switching loss of the second switch can be reduced accordingly. In this case, the actual output voltage finally obtained with respect to the target output voltage is shifted by an amount corresponding to the predetermined amount. When it is not necessary to match the output voltage, it is useful in that the switching loss of the first switch and the second switch can be reduced.

  On the other hand, when the shift amount is set to a value that is smaller by a predetermined amount than the step-up / down control duty ratio, it avoids the problem that a short ON period or OFF period disappears due to a response delay of a switch element or the like. Can do.

  The duty ratio calculation means is configured to calculate the duty ratio using a target voltage ratio between the input voltage and the target output voltage as a variable, and an actual voltage ratio calculated from the input voltage and the actual output voltage and the target In the case where the target voltage ratio is corrected by the PI calculation value obtained by PI calculation of the difference from the voltage ratio, the shift amount may be a value larger by a predetermined amount than the step-up / down control duty ratio. Good. In this case, in the DC voltage step-up / step-down circuit according to the first aspect of the present invention, the target voltage ratio is shifted from the predetermined amount by 1 at the time of step-down when the second switch is stopped in the OFF state. When it is in the first range on the step-down side, the first switch is stopped in the ON state. For this reason, it is not necessary to perform the PI calculation in the first range. In the DC voltage step-up / step-down circuit according to the second aspect of the present invention, the target voltage ratio is increased by an amount corresponding to a shift of the predetermined amount from 1 when the first switch is stopped while being on. When it is in the second range on the side, the second switch is stopped in the OFF state. For this reason, the PI calculation does not have to be performed in the second range.

  Therefore, the duty ratio calculation means is configured to calculate the duty ratio using a target voltage ratio between the input voltage and the target output voltage as a variable, and an actual voltage ratio calculated from the input voltage and the actual output voltage; When the target voltage ratio is corrected by a PI calculation value obtained by PI calculation of the difference from the target voltage ratio, the shift amount is a value larger by a predetermined amount than the step-up / down control duty ratio In this case, it is preferable that the PI calculation of the actual voltage ratio is stopped when the target voltage ratio is in a predetermined approximate range near 1.

  In this case, a width may be provided between the stop boundary value of the approximate range for stopping the PI calculation and the restart boundary value for restarting the PI calculation.

  Due to this specific matter, by providing a width between the stop boundary value and the restart boundary value of the approximate range, the target voltage ratio arrives at the stop boundary value of the approximate range and stops the PI calculation. Even if the target voltage ratio again exceeds the stop boundary value and moves to the restart side, the PI calculation does not restart for a while, and the restart boundary value having a width from the stop boundary value is used. The PI calculation can be resumed (hysteris), whereby the stability of the PI control can be improved.

  In the DC voltage step-up / step-down circuit according to the first and second aspects of the present invention, when the actual output voltage exceeds a predetermined value (overvoltage), the first switch is fixed off and the second switch is It is preferable to fix on.

  According to this specific matter, when the actual output voltage is equal to or higher than a predetermined value (overvoltage), the first switch is fixed to be off to stop the voltage input and the second switch is to be fixed to be on. Thus, surplus current in the DC voltage step-up / down circuit can be consumed by recirculation in the circuit. Thereby, the raise of the said actual output voltage resulting from the said DC voltage buck-boost circuit can be suppressed.

  In the DC voltage step-up / step-down circuit according to the first and second aspects of the present invention, the input voltage is supplied from a generator, the number of revolutions of the generator or the number of revolutions of a drive source that drives the generator, The input voltage may be estimated based on the output side demand load.

  With this specific matter, voltage measuring means (for example, a voltage sensor) that should be provided on the input side in order to measure the input voltage can be omitted.

  As described above, according to the DC voltage step-up / down circuit according to the present invention, it is possible to directly reflect the fluctuation of the input voltage in the determination of the duty ratio without complicating the circuit configuration. In addition, the duty ratio can be continuously changed when switching the buck-boost, thereby enabling stable switching control with the correct duty ratio and thus stable. An output voltage can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

  FIG. 1 is a diagram showing a schematic configuration of a DC voltage step-up / down circuit 1a according to a first embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a DC voltage step-up / down circuit 1b according to the second embodiment of the present invention. In FIGS. 1 and 2, members having substantially the same configuration and action are denoted by the same reference numerals. The same applies to FIGS. 5 and 6 described later.

[Common elements of the first and second embodiments]
1 and 2 includes a first switch S1, a second switch S2, a first diode D1, a second diode D2, an inductor L, and a capacitor C. The DC voltage buck-boost circuits 1a and 1b shown in FIGS. Is a DC power source (for example, engine) E, a generator DC and a rectifier D) PS, and a load (for example, electrical equipment in a heat pump air conditioner) Pe is connected to the output side.

  The first switch S1 and the inductor L are connected in series in this order from the input side to the output side. The first diode D1 is connected in parallel to both input and output terminals between the first switch S1 and the inductor L connected in series with the direction toward the connection line as a conduction direction. The second diode D2 is connected in series to the output side of the inductor L with the direction toward the output side as the conduction direction. The second switch S2 is connected in parallel to both the input and output terminals between the inductor L and the second diode D2. The capacitor C is connected in parallel to both input and output terminals on the output side of the second diode D2.

  The DC voltage step-up / step-down circuits 1a and 1b include control units 10a and 10b that perform switching (on / off) control between the first switch S1 and the second switch S2.

  The control units 10a and 10b include duty ratio calculation means (for example, duty ratio calculator, hereinafter referred to as duty ratio calculator) 11a, 11b and first switching control means (for example, first comparator, hereinafter referred to as first comparator). ) 13 and second switching control means (for example, a second comparator, hereinafter referred to as a second comparator) 14.

The duty ratio calculators 11a and 11b are uniquely and continuously determined duty ratios using a value λ ^* obtained based on the input voltage Vs and the target output voltage Vo ^{* as} the target of the actual output voltage Vo as a variable λ. Dy1 and Dy2 are calculated. Here, the duty ratios Dy1 and Dy2 that are uniquely and continuously determined are duty ratios that gently change before and after switching between step-up and step-down described later. The input voltage Vs can be measured by, for example, a voltage measuring unit (for example, a voltage sensor) (not shown) provided on the input side of the DC voltage step-up / step-down circuits 1a and 1b.

[About the first embodiment]
The control unit 10a of the DC voltage step-up / down circuit 1a shown in FIG. 1 further includes an adding means (for example, an adder, hereinafter referred to as an adder) 12a.

  As shown in FIG. 1, the duty ratio calculator 11a has an output side connected to one terminal on the input side of the second comparator 14 and also connected to one terminal on the input side of the adder 12a. Thus, the duty ratio calculator 11a can transmit the duty ratio Dy1 to both the second comparator 14 and the adder 12a.

The adder 12a adds (by the plus side) the duty ratio Dy1 calculated by the duty ratio calculator 11a by the duty ratio (see δ1 in FIG. 3 described later) of the input voltage Vs from the other terminal on the input side. The output side is connected to one terminal of the input side of the first comparator 13. The step-up / step-down control duty ratio δ1 is not limited to this, but here is a value (ie, 1) when the input voltage Vs is equal to the target output voltage Vo ^* .

  The first comparator 13 generates the first command signal P1 of the first switch S1 based on the shift duty ratio Ds1 from the adder 12a, and the output side is connected to the first switch S1.

  The second comparator 14 generates the second command signal P2 of the second switch S2 based on the duty ratio Dy1 from the duty ratio calculator 11a, and the output side is connected to the second switch S2.

  The first and second comparators 13 and 14 fix the second switch S2 off when the duty ratio Dy1 is less than zero, while fixing the first switch S1 off when the shift duty ratio Ds1 is less than zero. When the shift duty ratio Ds1 is 1 or more, the first switch S1 is fixed to be on.

In the present embodiment, the DC voltage step-up / step-down circuit 1 a further includes first computing means (for example, a first computing unit, hereinafter referred to as a first computing unit) 15. Although not limited to this, the first calculator 15 calculates the target voltage ratio λ ^* of the target output voltage Vo ^{* with} respect to the input voltage Vs, and the output side is the input of the duty ratio calculator 11a. Connected to the side. Thus, the first calculator 15 can transmit the target voltage ratio λ ^* to the duty ratio calculator 11a.

The duty ratio calculator 11a is configured to calculate the duty ratio Dy1 using the target voltage ratio λ ^* as a variable λ.

  Specifically, the duty ratio calculator 11a calculates the duty ratio Dy1 so that the relationship of the following expressions (1) and (2) is established, although not limited thereto.

そうすると、シフトデューティ比Ｄｓ１は、次の式（３）及び式（４）の関係が成り立つように加算器１２ａから出力できる。

Then, the shift duty ratio Ds1 can be output from the adder 12a so that the relationship of the following expressions (3) and (4) is established.

図３は、式（１）〜式（４）の関係をグラフに示した図である。なお、図３において、式（１）と式（３）の一部と式（４）とは破線で示している。

FIG. 3 is a graph showing the relationship between the equations (1) to (4). In FIG. 3, the formula (1), a part of the formula (3), and the formula (4) are indicated by broken lines.

  In the present embodiment, the first and second comparators 13 and 14 are supplied with a predetermined signal Sp for switching control of the first and second switches S1 and S2 from the other terminals on the input side, respectively. ing. The predetermined signal Sp is a comparison signal having peaks at 0 and 1, and examples thereof include a pulse signal (triangular wave signal in the illustrated example) such as a sawtooth wave signal and a triangular wave signal.

  As a result, when the duty ratio Dy1 for the second switch S2 is greater than zero, the duty ratio Dy1 (formula (2)) is set as the switching target of the second switch S2, and the second command of the second switch S2 by the comparison signal Sp. When the signal P2 is generated and the duty ratio Dy1 for the second switch S2 is equal to or less than zero, the second switch S2 is in the position of the broken line in the formula (1) (the position on the off side with respect to the comparison signal Sp). Can be fixed off. On the other hand, when the shift duty ratio Ds1 for the first switch S1 is larger than 0 and smaller than 1, the shift duty ratio Ds1 (the solid line portion of the expression (3)) is set as the switching target of the first switch S1 by the comparison signal Sp. When the first command signal P1 of the first switch S1 is generated and the shift duty ratio Ds1 for the first switch S1 is less than or equal to zero, the position of the broken line in the equation (3) (the off-side position with reference to the comparison signal Sp) Therefore, when the shift duty ratio Ds1 is equal to or greater than 1, the first switch S1 is fixed to the OFF position, and is in the position of the broken line (the ON side position with respect to the comparison signal Sp) when the shift duty ratio Ds1 is 1 or more. Therefore, the first switch S1 can be fixed on.

  In the DC voltage step-up / step-down circuit 1a having such a configuration, as shown in FIG. 3, the second switch S2 is fixed to be off (see the broken line in Expression (1)) at the time of step-down (see α in the figure). ), Switching control of the first switch S1 is performed on the basis of the shift duty ratio Ds1 of the solid line portion of the equation (3), and the first switch S1 is fixed to ON at the time of boosting (see β in the figure) (equation) The switching control of the second switch S2 is performed based on the duty ratio Dy1 of the equation (2).

[About the second embodiment]
The control unit 10b of the DC voltage step-up / step-down circuit 1b shown in FIG. 2 further includes subtracting means (for example, a subtractor, hereinafter referred to as a subtractor) 12b.

  As shown in FIG. 2, the duty ratio calculator 11b has an output side connected to one terminal on the input side of the first comparator 13, and also connected to one terminal on the input side of the subtractor 12b.

The subtractor 12b subtracts the duty ratio Dy2 calculated by the duty ratio calculator 11b by a duty ratio (see δ2 in FIG. 4 described later) of the input voltage Vs from the other terminal on the input side (minus side). The output side is connected to one terminal of the input side of the second comparator 14. The step-up / step-down control duty ratio δ2 is not limited to this, but here is a value when the input voltage Vs and the target output voltage Vo ^* are equal (that is, 1).

  The first comparator 13 generates the first command signal P1 of the first switch S1 based on the duty ratio Dy2 from the duty ratio calculator 11b, and the output side is connected to the first switch S1.

  The second comparator 14 generates the second command signal P2 of the second switch S2 based on the shift duty ratio Ds2 from the subtractor 12b, and the output side is connected to the second switch S2.

  The first and second comparators 13 and 14 fix the second switch S2 off when the shift duty ratio Ds2 is less than zero, while fixing the first switch S1 off when the duty ratio Dy2 is less than zero. When the duty ratio Dy2 is 1 or more, the first switch S1 is fixed to be on.

In the present embodiment, the DC voltage step-up / step-down circuit 1b further includes first computing means (for example, a first computing unit, hereinafter referred to as a first computing unit) 15. Although not limited to this, the first calculator 15 is configured to calculate the target voltage ratio λ ^* of the target output voltage Vo ^{* with} respect to the input voltage Vs, and the output side is the input of the duty ratio calculator 11b. Connected to the side. Thereby, the first calculator 15 can transmit the target voltage ratio λ ^* to the duty ratio calculator 11b.

The duty ratio calculator 11b is configured to calculate the duty ratio Dy2 using the target voltage ratio λ ^* as a variable λ.

  Specifically, the duty ratio calculator 11b is configured to calculate the duty ratio Dy2 so that the following expressions (5) and (6) are satisfied, although not limited thereto.

そうすると、シフトデューティ比Ｄｓ２は、次の式（７）及び式（８）の関係が成り立つように減算器１２ｂから出力できる。

Then, the shift duty ratio Ds2 can be output from the subtractor 12b so that the relationship of the following expressions (7) and (8) is satisfied.

図４は、式（５）〜式（８）の関係をグラフに示した図である。なお、図４において、式（５）の一部と式（６）と式（７）とは破線で示している。

FIG. 4 is a graph showing the relationship between the equations (5) to (8). In FIG. 4, a part of formula (5), formula (6), and formula (7) are indicated by broken lines.

  In the present embodiment, the first and second comparators 13 and 14 are supplied with a predetermined signal Sp for switching control of the first and second switches S1 and S2 from the other terminals on the input side, respectively. ing. The predetermined signal Sp is a comparison signal having peaks at 0 and 1, and examples thereof include a pulse signal (triangular wave signal in the illustrated example) such as a sawtooth wave signal and a triangular wave signal.

  Thus, when the shift duty ratio Ds2 for the second switch S2 is greater than zero, the shift duty ratio Ds2 (formula (8)) is set as the switching target of the second switch S2, and the second switch S2 of the second switch S2 is detected by the comparison signal Sp. 2 command signal P2 is generated, and when the shift duty ratio Ds2 for the second switch S2 is less than or equal to zero, since it is in the position of the broken line in the equation (7) (the position on the OFF side with respect to the comparison signal Sp), 2 The switch S2 can be fixed off. On the other hand, when the duty ratio Dy2 for the first switch S1 is larger than 0 and smaller than 1, the duty ratio Dy2 (solid line part of the equation (5)) is set as the switching target of the first switch S1 by the comparison signal Sp. When the first command signal P1 of the switch S1 is generated and the duty ratio Dy2 for the first switch S1 is less than or equal to zero, the position of the broken line in the equation (5) (the position on the off side with respect to the comparison signal Sp) Therefore, when the first switch S1 is fixed to OFF and the duty ratio Dy2 is 1 or more, the first switch S1 is at the position of the broken line (the position on the side with respect to the comparison signal Sp) in the equation (6). The switch S1 can be fixed on.

  In the DC voltage step-up / step-down circuit 1b having such a configuration, as shown in FIG. 4, the second switch S2 is fixed to be off (see the broken line in Expression (7)) at the time of step-down (see α in the figure). ), The switching control of the first switch S1 is performed based on the duty ratio Dy2 of the solid line part of the equation (5), and the first switch S1 is fixed to ON at the time of boosting (see β in the figure) (equation ( 6), the switching control of the second switch S2 is performed based on the shift duty ratio Ds2 of the equation (8).

  According to the DC voltage step-up / step-down circuits 1a and 1b of the first and second embodiments described above, the variable λ obtained from the parameter including the input voltage Vs is used for the duty ratios Dy1 and Dy2 calculations. The fluctuation can be directly reflected in the command values to the first and second switches S1, S2. Thereby, the responsiveness with respect to the fluctuation | variation of the input voltage Vs can be improved.

  Furthermore, in the DC voltage step-up / step-down circuit 1a of the first embodiment, the duty ratio Dy1 that is uniquely and continuously determined is set as the command signal P2 of the second switch S2, and the shift duty ratio Ds1 is set as the command signal P1 of the first switch S1. Therefore, the command signal P2 to the second switch S2 is used as a duty ratio command signal Dy1 calculated inside the duty ratio calculator 11a, and the command signal P1 to the first switch S1 is set to the duty ratio. The shift duty ratio Ds1 calculated outside the calculator 11a can be used as a command signal for the step-down time α, and therefore the duty ratio calculator 11a is not forced to change the duty ratio calculation as in the prior art. , The duty ratio Dy1 can be changed continuously (slowly) at the time of switching of the step-up / down pressure. Switching (ON / OFF) can be stably performed with the new duty ratios Dy1 and Ds1.

  In the DC voltage step-up / step-down circuit 1b of the second embodiment, the duty ratio Dy2 that is uniquely and continuously determined is the command signal P1 of the first switch S1, and the shift duty ratio Ds2 is the command signal P2 of the second switch S2. Therefore, the command signal P1 to the first switch S1 is set as a duty ratio Dy2 calculated inside the duty ratio calculator 11b, and the command signal P2 to the second switch S2 is set to the duty ratio Dy2. The shift duty ratio Ds2 calculated outside the ratio calculator 11b can be used as a command signal for boosting β. Therefore, the duty ratio calculator 11b is not forced to change the duty ratio calculation as in the prior art. Therefore, the duty ratio Dy2 can be continuously (gradually) changed when the step-up / step-down is switched. Switching (ON / OFF) can be stably performed with the correct duty ratios Dy2 and Ds2.

  Moreover, in the DC voltage step-up / step-down circuits 1a and 1b according to the first and second embodiments, the duty ratios Dy2 and Dy1 to the first and second switches S1 and S2 are devised, so that the circuit configuration is complicated. A stable output voltage can be obtained without this.

[Modification 1]
In the DC voltage step-up / step-down circuits 1a and 1b of the first and second embodiments shown in FIGS. 1 and 2, the difference λd between the actual voltage ratio λn of the actual output voltage Vo and the target voltage ratio λ ^* with respect to the input voltage Vs is defined as PI. The target voltage ratio λ ^* may be corrected by the PI calculation value λp obtained by calculation.

FIG. 5 is a diagram showing an example in which the target voltage ratio λ ^* is corrected by the PI calculation value λp in the DC voltage step-up / down circuit 1a of the first embodiment shown in FIG. FIG. 6 is a diagram showing an example in which the target voltage ratio λ ^* is corrected by the PI calculation value λp in the DC voltage step-up / down circuit 1b of the second embodiment shown in FIG.

  The control units 10a ′ and 10b ′ in the DC voltage step-up / down circuits 1a ′ and 1b ′ of the third and fourth embodiments shown in FIGS. 5 and 6 have the same configuration as the control units 10a and 10b shown in FIGS. In addition, second calculation means (for example, second calculation unit, hereinafter referred to as second calculation unit) 16, deviation calculation means (for example, deviation calculation unit, hereinafter referred to as deviation calculation unit) 17, and PI calculation unit (for example, PI). An arithmetic unit (hereinafter referred to as a PI arithmetic unit) 18 and a correction value adding means (for example, a correction value adder, hereinafter referred to as a correction value adder) 19 are provided.

  The first computing unit 15 has an output side connected to one terminal on the input side of the deviation computing unit 17 and is connected to one terminal on the input side of the correction value adder 19.

  Here, the second calculator 16 calculates the actual voltage ratio λn of the actual output voltage Vo with respect to the input voltage Vs, and is connected to the other terminal on the input side of the deviation calculator 17. The actual output voltage Vo can be measured by, for example, a voltage measuring means (for example, a voltage sensor) (not shown) provided on the output side of the DC voltage step-up / step-down circuits 1a 'and 1b'.

The deviation calculator 17 calculates a deviation λd between the target voltage ratio λ ^* from the first calculator 15 and the actual voltage ratio λn from the second calculator 16, and the output side is the PI calculator 18. Connected to the input side.

  The PI calculator 18 calculates the PI calculation value λp from the deviation λd from the deviation calculator 17, and the output side is connected to the other terminal on the input side of the correction value adder 19.

The correction value adder 19 calculates an addition value λa obtained by adding the target voltage ratio λ ^* from the first calculator 15 and the PI calculation value λp from the PI calculator 18, and the duty ratio calculator 11a and 11b are connected to the input side.

According to such a configuration, since the duty ratios Dy1 and Dy2 can be corrected based on the actual output voltage Vo, the convergence accuracy to the target output voltage Vo ^* can be improved.

[Modification 2]
In the DC voltage step-up / step-down circuits 1a, 1b, 1a ', 1b' of the first to fourth embodiments shown in FIGS. 1, 2, 5, and 6, the shift amount (offset amount) is set as the step-up / down control duty. The value may be larger by a predetermined amount than the ratios δ1 and δ2, or may be a value smaller by a predetermined amount than the step-up / down control duty ratios δ1 and δ2. In the example of FIGS. 3 and 4, the shift amount is set to a value that is larger by a predetermined amount (see δ1 ′ in FIG. 3 and δ2 ′ in FIG. 4) than the duty ratio δ1, δ2 (here, 1) for the buck-boost control. (Refer to the one-dot chain line in FIGS. 3 and 4).

In the DC voltage step-up / step-down circuits 1a, 1a ′ of the first and third embodiments, as indicated by the one-dot chain line in FIG. 3, the amount of shift added to the duty ratio Dy1 is set to the step-up / down control duty ratio δ1 (here Then, by setting the value to be larger by a predetermined amount δ1 ′ than 1), at the time of step-down α in which the second switch S2 is fixed to OFF, an extra (that is, the target voltage ratio λ ^* is changed from 1 to the predetermined amount δ1 ′). The first switch S1 can be fixed to be on (even when the voltage is in the first range R1 on the step-down side by the amount shifted). Thus, since the first switch S can be fixed on even in the first range R1, the switching loss of the first switch S1 can be reduced accordingly.

Further, in the DC voltage step-up / step-down circuits 1b and 1b ′ according to the second and fourth embodiments, as shown by the one-dot chain line in FIG. 4, the amount of shift to be subtracted from the duty ratio Dy2 is set as the step-up / step-down control duty ratio δ2. By setting the value to be larger by a predetermined amount δ2 ′ than (here, 1), an extra (that is, the target voltage ratio λ ^* is changed from 1 to a predetermined amount at the time of boost β in which the first switch S1 is fixed to ON. The second switch S2 can be fixed to OFF (even when it is within the second range R2 on the boosting side by an amount corresponding to the shift of δ2 ′). Thus, since the second switch S2 can be fixed off even in the second range R2, the switching loss of the second switch S2 can be reduced accordingly.

  On the other hand, when the shift amount is set to a value that is smaller by a predetermined amount than the step-up / down control duty ratio, it avoids the problem that a short ON period or OFF period disappears due to a response delay of a switch element or the like. Can do. When it is desired to control the output voltage with high accuracy, a value of 1 or less is selected as the shift amount. When it is not necessary to control the output voltage with high accuracy, it is preferable to select a value of 1 or more as the shift amount.

[Modification 3]
In the DC voltage step-up / down circuits 1a ′ and 1b ′ of the third and fourth embodiments, the actual voltage ratio when the target voltage ratio λ ^* is within a predetermined approximate range (here, the first and second ranges R1 and R2). The PI calculation of λn may be stopped.

That is, in the DC voltage step-up / down circuit 1a ′ of the third embodiment, the target voltage ratio λ ^* is in the approximate range R1 and the first switch S1 is turned on at the time of step-down α while the second switch S2 is fixed to be off. It is useless to perform the PI calculation of the actual voltage ratio λn. In the DC voltage step-up / step-down circuit 1b ′ of the fourth embodiment, the target voltage ratio λ ^* is in the approximate range R2 and the second switch S2 is turned off at the time of boosting β while the first switch S1 is fixed on. It is useless to perform the PI calculation of the actual voltage ratio λn.

Therefore, in the DC voltage step-up / step-down circuits 1a ′ and 1b ′ of the third and fourth embodiments, when the target voltage ratio λ ^* is within the approximate ranges R1 and R2, the PI calculation of the actual voltage ratio λn is stopped. The useless PI calculation of the actual voltage ratio λn in the approximate ranges R1 and R2 can be avoided, and the PI control can be performed more efficiently.

[Modification 4]
In the DC voltage step-up / step-down circuits 1a ′ and 1b ′ according to the third modification, a width may be provided between the stop boundary value of the approximate ranges R1 and R2 where the PI calculation is stopped and the restart boundary value where the PI calculation is restarted.

  FIG. 7 is a diagram for explaining a configuration in which a width γ is provided between the stop boundary value E1 of the approximate ranges R1 and R2 for stopping the PI calculation and the restart boundary value E2 for restarting the PI calculation.

As shown in FIG. 7, when the target voltage ratio λ ^* moves to the PI calculation stop side and reaches the stop boundary value E1 of the approximate ranges R1 and R2, the PI calculation stops. Thereafter, even if the target voltage ratio λ ^* moves to the PI calculation restart side and exceeds the stop boundary value E1 of the approximate ranges R1 and R2, the PI calculation is stopped (see γ in the figure), and the target voltage ratio λ ^* is Furthermore, when it moves to the PI calculation restart side and reaches the restart boundary value E2, the PI calculation is stopped and the PI calculation is restarted.

According to such a configuration, the target voltage ratio λ ^* reaches the stop boundary value E1 of the approximate ranges R1 and R2 by providing the width γ between the stop boundary value E1 and the restart boundary value E2 of the approximate ranges R1 and R2. Then, even if the PI calculation is stopped and the target voltage ratio λ ^* again exceeds the stop boundary value E1 and moves to the restart side, the PI calculation is not restarted for a while and the width γ is set from the stop boundary value E1. It is possible to restart at the restart boundary value E2 (hysteris), thereby improving the stability of PI control.

[Modification 5]
In the DC voltage step-up / step-down circuits 1a, 1b, 1a ′, 1b ′ of the first to fourth embodiments shown in FIGS. 1, 2, 5 and 6, the actual output voltage Vo becomes a predetermined value or more (overvoltage). In this case, the first switch S1 may be fixed off and the second switch S2 may be fixed on.

  According to such a configuration, when the actual output voltage Vo becomes equal to or higher than a predetermined value (overvoltage), the voltage input is stopped by fixing the first switch S1 to OFF and the second switch S2 is fixed to ON. Thus, surplus current in the DC voltage step-up / step-down circuits 1a, 1b, 1a ′, 1b ′ can be consumed by recirculation in the circuit. Thereby, it is possible to suppress an increase in the actual output voltage Vo caused by the DC voltage step-up / step-down circuits 1a 'and 1b'.

[Modification 6]
By the way, when it is set as the structure which supplies the input voltage Vs from the generator Ge, the output side demand load Pe is the rotation speed N of the generator Ge or the rotation speed N of the drive source (for example, engine) E which drives the generator Ge. The relationship with the input voltage Vs corresponds to the slope of the input voltage Vs with respect to the rotation speed N. For example, the change amount (slope) of the input voltage Vs per unit rotation speed of the generator Ge or the drive source E tends to increase as the output-side demand load Pe decreases, and decreases as the output-side demand load Pe increases. It is in.

  From this viewpoint, the input voltage Vs may be estimated based on the rotational speed N of the generator Ge or the drive source E and the output-side demand load Pe.

  FIG. 8 is a graph showing characteristics in which the change amount (slope) of the input voltage Vs per unit rotation speed of the generator Ge or the drive source E changes in accordance with the magnitude of the output demand load Pe.

  For example, as shown in FIG. 8, in the relationship between the rotational speed N of the generator Ge or the drive source E and the input voltage Vs, the slope of the input voltage Vs with respect to the rotational speed N corresponds to the magnitude of the output demand load Pe. The conversion table and the arithmetic expression corresponding to the characteristic that changes can be stored in advance in a storage unit such as a nonvolatile memory. In this way, the slope of the input voltage Vs with respect to the rotational speed N can be obtained by using the magnitude of the output demand load Pe as a parameter. And the input voltage Vs can be calculated | required by making rotation speed N into a parameter with respect to this inclination. That is, the input voltage Vs can be estimated by determining the magnitude of the output side demand load Pe and the rotational speed N.

  According to such a configuration, voltage measuring means (for example, a voltage sensor) that should be provided on the input side in order to measure the input voltage Vs can be omitted, and the cost can be reduced accordingly.

  In the above description, the analog-based various arithmetic units and comparators have been described. However, a digital-based configuration using a DSP, a CPU, or the like may be used.

1 is a diagram illustrating a schematic configuration of a DC voltage step-up / down circuit according to a first embodiment of the present invention. It is a figure which shows schematic structure of the DC voltage buck-boost circuit of 2nd Embodiment which concerns on this invention. It is the figure which showed the relationship of Formula (1)-Formula (4) on the graph. It is the figure which showed the relationship of Formula (5)-Formula (8) on the graph. FIG. 2 is a diagram illustrating an example of a configuration in which a target voltage ratio is corrected by a PI calculation value in the DC voltage step-up / down circuit of the first embodiment shown in FIG. 1. FIG. 3 is a diagram illustrating an example of a configuration in which a target voltage ratio is corrected by a PI calculation value in the DC voltage step-up / step-down circuit according to the second embodiment illustrated in FIG. 2. It is a figure for demonstrating the structure which gave the width | variety between the stop boundary value of the approximate range which stops PI calculation, and the restart boundary value which restarts PI calculation. It is a graph which shows the characteristic in which the variation | change_quantity (slope) of the input voltage per unit rotation speed of a generator or a drive source changes according to the magnitude | size of an output side demand load. It is a figure which shows schematic structure of the DC voltage step-up / step-down circuit described in Patent Document 1.

Explanation of symbols

1a, 1a ′ DC voltage step-up / down circuit 1b, 1b ′ DC voltage step-up / down circuit 11a, 11b Duty ratio calculator (an example of duty ratio calculation means)
D1 1st diode D2 2nd diode Ds1, Ds2 Shift duty ratio Dy1, Dy2 Duty ratio E Drive source E1 Stop boundary value E2 Restart boundary value Ge Generator L Inductor N Speed Pe Output side demand load R1, R2 Approximate range S1 First 1 switch S2 2nd switch Vo actual output voltage Vo ^* target output voltage Vs input voltage γ width between stop boundary value and restart boundary value δ1, δ2 shift amount δ1 ', δ2' predetermined amount λ variable λ ^* target voltage ratio λn Actual voltage ratio λp PI calculation value

Claims (9)

The first switch and the inductor are connected in series in this order from the input side to the output side, and the first diode is connected to both the input and output terminals with the direction toward the connection line between the first switch and the inductor as the conduction direction. And a second diode connected in series to the output side of the inductor with a direction toward the output side as a conduction direction, and a second switch is input / output between the inductor and the second diode. In a DC voltage step-up / down circuit configured to be connected in parallel to both terminals of
A duty ratio calculating means for calculating a duty ratio that is uniquely and continuously determined based on the input voltage and the target output voltage that is the target of the actual output voltage is provided,
The duty ratio is a command signal for the second switch,
A shift duty ratio obtained by adding a duty ratio for the step-up / step-down control of the input voltage when at least the input voltage is equal to the target output voltage is used as the command signal for the first switch,
When the duty ratio is less than or equal to zero, the second switch is fixed to OFF, while when the shift duty ratio is less than or equal to zero, the first switch is fixed to OFF, and when the duty ratio is greater than or equal to 1, the first switch is turned on. A DC voltage step-up / down circuit characterized by being fixed to The first switch and the inductor are connected in series in this order from the input side to the output side, and the first diode is connected to both the input and output terminals with the direction toward the connection line between the first switch and the inductor as the conduction direction. And a second diode connected in series to the output side of the inductor with a direction toward the output side as a conduction direction, and a second switch is input / output between the inductor and the second diode. In a DC voltage step-up / down circuit configured to be connected in parallel to both terminals of
A duty ratio calculating means for calculating a duty ratio that is uniquely and continuously determined based on the input voltage and the target output voltage that is the target of the actual output voltage is provided,
The duty ratio is a command signal for the first switch,
A shift duty ratio obtained by subtracting the duty ratio for the step-up / step-down control of the input voltage when at least the input voltage is equal to the target output voltage as the command signal of the second switch,
When the shift duty ratio is less than zero, the second switch is fixed off. When the duty ratio is less than zero, the first switch is fixed off, and when the duty ratio is greater than 1, the first switch is turned on. A DC voltage step-up / down circuit characterized by being fixed. In the DC voltage step-up / step-down circuit according to claim 1 or 2,
The duty ratio calculating means is configured to calculate the duty ratio using a target voltage ratio between the input voltage and the target output voltage as a variable,
The target voltage ratio is corrected by a PI calculation value obtained by PI calculation of a difference between the actual voltage ratio calculated from the input voltage and the actual output voltage and the target voltage ratio. DC voltage buck-boost circuit. In the DC voltage step-up / step-down circuit according to claim 1 or 2,
The DC voltage step-up / step-down circuit, wherein the shift amount is set to a value larger by a predetermined amount than the step-up / step-down control duty ratio. In the DC voltage step-up / step-down circuit according to claim 1 or 2,
The DC voltage step-up / step-down circuit is characterized in that the shift amount is set to a value smaller than the step-up / step-down control duty ratio by a predetermined amount. In the DC voltage step-up / step-down circuit according to claim 3,
The shift amount is set to a value larger by a predetermined amount than the step-up / down control duty ratio,
A DC voltage step-up / step-down circuit that stops PI calculation of the actual voltage ratio when the target voltage ratio is in a predetermined approximate range near 1. In the DC voltage step-up / step-down circuit according to claim 6,
A DC voltage step-up / down circuit having a width between a stop boundary value of the approximate range for stopping the PI operation and a restart boundary value for restarting the PI operation. In the DC voltage step-up / step-down circuit according to any one of claims 1 to 7,
A DC voltage step-up / down circuit that fixes the first switch to OFF and the second switch to ON when the actual output voltage exceeds a predetermined value. In the DC voltage step-up / step-down circuit according to any one of claims 1 to 8,
The input voltage is supplied from a generator.
A DC voltage step-up / down circuit configured to estimate the input voltage based on the number of revolutions of the generator or the number of revolutions of a drive source that drives the generator and an output side demand load.

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