JP6040799B2 - Boost converter and control method of boost converter - Google Patents

Description

The present invention complementarily turns on and off the high-potential side switching element and the low-potential side switching element while giving a dead time to a high-potential side switching element and a low-potential side switching element connected in series with each other. a basic operation unit for operating the current flowing through the reactor is about the control method of the boost converter and the boost converter includes an off operation portion for operating off the low-potential side switching element at a timing that exceeds the command value.

As this type of step-up converter, as described in Patent Document 1, series-connected high-potential side switching element及 beauty low potential side switching element to each other, one end connected to a connection point of the switching elements 2. Description of the Related Art A current mode control step-up converter including a reactor and a smoothing capacitor is known. Specifically, this step-up converter is not only used during powering in which the reactor current flows in the direction from the opposite side of the reactor to the connection point at both ends of the reactor when the low potential side switching element is turned on. A circuit is provided that can detect the reactor current even during regeneration when the reactor current flows in the direction from the connecting point toward the opposite side of the connecting point at both ends of the reactor.

  By adopting such a configuration, the response of the reactor current control is improved. Thus, even when the output voltage of the boost converter rises beyond the command voltage due to a sudden decrease in the load current, the raised output voltage is quickly lowered to the command voltage.

JP 2006-320042 A

  However, the boost converter described in Patent Document 1 has a concern that it is difficult to suppress a decrease in the response of the reactor current control during regeneration. This is for the reason explained below.

  During regeneration, even if the low potential side switching element is turned off, the low potential side switching element is low in the specified direction from the opposite side of the connection point to the reactor to the connection point. Current continues to flow through the body diode of the potential side switching element. For this reason, even if the low potential side switching element is turned off due to the reactor current exceeding the command value, it is a period from when the low potential side switching element is turned off until the high potential side switching element is turned on. In the dead time, current continues to flow through the body diode of the low potential side switching element. As a result, the reactor current exceeds the command value, and the responsiveness of the reactor current control is reduced.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a boost converter and a boost converter control method capable of suitably improving the responsiveness of the reactor current control. .

In order to solve the above-described problems, the present invention provides a connection between a high potential side switching element (10H) and a low potential side switching element (10L) connected in series to each other, and the high potential side switching element and the low potential side switching element. A reactor (12) having one end connected to the point, and allowing a current flow in a specified direction from the opposite side of the low-potential side switching element to the connection point from both ends of the low-potential side switching element, and Basic operation of complementarily turning on and off the high-potential side switching element and the low-potential side switching element while providing a dead time with a flow regulating element (15L) that regulates the flow of current in the direction opposite to the specified direction When the polarity of the current flowing in the direction from the side opposite to the connection point to the connection point among the ends of the part (38, 40) and the reactor is positive An off operation section (34, 44) for turning off the low potential side switching element at a timing when the current flowing through the reactor exceeds the command value under the situation where the low potential side switching element is turned on by the basic operation section. And). Based on such a configuration, the present invention provides a polarity predicting unit (28b, 28c) for predicting the polarity of the peak value of the current flowing through the reactor in one cycle of the next on / off operation of the low potential side switching element, and the polarity prediction. If the polarity of the peak value is predicted by the unit to be negative, an advance portion that advances the OFF operation timing of the low potential side switching element by the OFF operation unit by the dead time in the next ON / OFF operation cycle. 28d, 28e, 28f).

  The situation where the polarity of the peak value of the current flowing through the reactor is negative in one cycle of the on / off operation of the low potential side switching element is a dead time during which both the high potential side switching element and the low potential side switching element are off. Is a situation where current flows through the distribution regulation element. Such a situation is a situation in which the current flowing through the reactor exceeds the command value.

  Here, in the said invention, it can be estimated whether the electric current which flows into a reactor may exceed a command value in the next on-off operation 1 period of a low potential side switching element by providing a polarity estimation part. Then, when it is predicted that the current flowing through the reactor may exceed the command value, the advancement portion advances the off operation timing of the low potential side switching element in the next one cycle of the on / off operation by the dead time. Thereby, it can avoid that the electric current which flows into a reactor greatly exceeds command value, and can improve suitably the responsiveness of the electric current control which flows into a reactor by extension.

1 is a circuit diagram of a boost converter according to a first embodiment. The time chart which shows operation | movement of the boost converter at the time of power running. The time chart which shows the operation | movement of the boost converter at the time of regeneration. The figure which shows the detail of the off timing advance part concerning 1st Embodiment. The figure which shows the prediction method of the peak value of the reactor current signal concerning the embodiment. The figure which shows the calculation method of the offset voltage concerning the embodiment. 6 is a flowchart showing a procedure of off-timing advance processing according to the embodiment. The time chart which shows the operation | movement of the step-up converter at the time of regeneration concerning the embodiment. FIG. 5 is a circuit diagram of a boost converter according to a second embodiment. The figure which shows the detail of the off timing production | generation part concerning the embodiment. 6 is a flowchart showing a procedure of off-timing advance processing according to the embodiment. The time chart which shows an example of the superimposition aspect of the noise to the reactor current signal concerning 3rd Embodiment. 6 is a flowchart showing a procedure of off-timing advance processing according to the embodiment.

(First embodiment)
Hereinafter, a first embodiment embodying the boost converter that written to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the boost converter CV is a half comprising a high-side switch 10H (corresponding to “high potential side switching element”) and a low side switch 10L (corresponding to “low potential side switching element”) connected in series. A bridge circuit, a reactor 12, a smoothing capacitor 14, and a control circuit 16 for turning on and off the high side switch 10H and the low side switch 10L are provided. Here, in the present embodiment, N-channel MOSFETs are used as the high-side switch 10H and the low-side switch 10L. In the figure, the gate signal of the high-side switch 10H is indicated by “VgH”, and the gate signal of the low-side switch 10L is indicated by “VgL”.

  The source of the high side switch 10H and the drain of the low side switch 10L are connected, and the source of the low side switch 10L is grounded. A connection point between the high-side switch 10H and the low-side switch 10L is connected to one end of the reactor 12. One end of the smoothing capacitor 14 is connected to the opposite side of the high-side switch 10H from the connection point with the low-side switch 10L, and the other end of the smoothing capacitor 14 is grounded.

  A body diode (hereinafter, high-side body diode 15H) is formed in the high-side switch 10H, and a body diode (hereinafter, low-side body diode 15L) is also formed in the low-side switch 10L. Here, when the high-side switch 10H is turned off, the high-side body diode 15H moves in a direction from the connection point with the low-side switch 10L to the opposite side to the connection point, at both ends of the high-side switch 10H. Current flow is allowed and current flow in the direction opposite to this direction is restricted (more specifically, blocked). In addition, the low-side body diode 15L allows current flow in a specified direction from the grounded part to the connection point with the high-side switch 10H at both ends of the low-side switch 10L when the low-side switch 10L is turned off. Further, it corresponds to a “distribution restricting element” that restricts (more specifically, interrupts) the flow of current in the direction opposite to the prescribed direction.

  Boost converter CV includes a current detection circuit 18 that detects a current flowing through reactor 12 (hereinafter referred to as a reactor current). The current detection circuit 18 includes a current transformer 18a and a resistor 18b having one end connected to the current transformer 18a and the other end grounded. Here, when the reactor current is “IL”, the turn ratio of the current transformer 18a is “N”, and the resistance value of the resistor 18b is “Rc”, the current detection circuit 18 has a first voltage corresponding to the reactor current IL. A signal (hereinafter, reactor current signal Vc = Rc / N × IL) is output. In the present embodiment, the current detection circuit 18 constitutes a “first voltage output circuit”.

  Boost converter CV also includes output voltage detection circuit 20, input voltage detection circuit 22, and temperature sensor 24 that detects the temperature of reactor 12 (hereinafter, reactor temperature). Specifically, the output voltage detection circuit 20 includes a series connection body of a pair of resistors 20a and 20b, and a second voltage signal (hereinafter, referred to as an output voltage Vout (voltage between terminals of the smoothing capacitor 14) of the boost converter CV). , Output voltage signal Voutfb). More specifically, the output voltage detection circuit 20 outputs an output voltage signal Voutfb that is a value obtained by resistance-dividing the output voltage Vout of the boost converter CV by the pair of resistors 20a and 20b. The input voltage detection circuit 22 includes a series connection body of a pair of resistors 22a and 22b. The input voltage Vin of the boost converter CV (the connection point between the high-side switch 10H and the low-side switch 10L at both ends of the reactor 12) The input voltage signal Vinfb corresponding to the applied voltage on the opposite side is output. More specifically, the input voltage detection circuit 22 outputs an input voltage signal Vinfb which is a value obtained by resistance-dividing the input voltage Vin of the boost converter CV by the pair of resistors 22a and 22b. In the present embodiment, the output voltage detection circuit 20 constitutes a “second voltage output circuit”, and the temperature sensor 24 constitutes a “temperature detection unit”.

  The control circuit 16 includes an error amplifier 26 (error amplifier), an off timing advance unit 28, a first AD converter 30, a second AD converter 32, a comparator 34, a clock generation circuit 36 that generates a clock signal CK, and an RS flip-flop. 38 and a complementary drive unit 40. Specifically, the error amplifier 26 receives the output voltage signal Voutfb output from the output voltage detection circuit 20 at its inverting input terminal, and receives the reference voltage Vref at its non-inverting input terminal. The error amplifier 26 outputs an error voltage Ve obtained by amplifying the deviation between the output voltage signal Voutfb and the reference voltage Vref. The reference voltage is set based on a command value (hereinafter, command voltage) of the output voltage of boost converter CV. In the present embodiment, the calculation process of the error voltage Ve by the error amplifier 26 constitutes an “error amplification step”.

  The off-timing advance portion 28 receives the error voltage Ve output from the error amplifier 26, the reactor current signal Vc, the input voltage signal Vinfb, and the reactor temperature Td detected by the temperature sensor 24 as inputs, and turns off the low-side switch 10L. Has a function to advance (advance) the timing. The reactor current signal Vc is input to the off-timing advance portion 28 via the first AD converter 30, and the input voltage signal Vinfb is supplied to the off-timing advance portion 28 via the second AD converter 32. Entered. The off timing advance portion 28 will be described later in detail. Further, the output signal Ve * of the off-timing advance portion 28 (more specifically, the output signal Ve * subjected to slope compensation described later) corresponds to a “command value” of the reactor current.

  The comparator 34 receives the reactor current signal Vc output from the current detection circuit 18 at its inverting input terminal, and receives the output signal Ve * of the off-timing advance portion 28 at its non-inverting input terminal. Here, in the present embodiment, the comparator 34 further receives a compensation ramp wave from a slope compensation circuit (not shown) in order to avoid subharmonic oscillation of the reactor current. In this embodiment, when the reactor current signal Vc exceeds the output signal Ve * of the off-timing advance portion 28, the comparator 34 outputs a “comparator” that outputs a signal to turn off the low-side switch 10L. And an “off operation unit”. Further, the comparison process by the comparator 34 constitutes an “off operation step”.

  In the RS flip-flop 38, the output signal Sr (corresponding to “predetermined signal”) of the comparator 34 is input to the reset terminal, and the clock signal CK output from the clock generation circuit 36 is input to the set terminal. That is, the RS flip-flop 38 is a “latch circuit” that is reset by the output signal Sr of the comparator 34 and set by the clock signal CK. The RS flip-flop 38 receives the output signal Sr of the comparator 34 and the clock signal CK, and outputs a reference signal Sig for turning on and off the high-side switch 10H and the low-side switch 10L. In the present embodiment, the generation process of the reference signal Sig by the RS flip-flop 38 constitutes a “reference signal generation step”.

  As shown in FIG. 2, the complementary drive unit 40 is configured to turn on and off the high-side switch 10H and the low-side switch 10L based on the reference signal Sig output from the RS flip-flop 38, as shown in FIG. Gate signals VgH and VgL are generated and output to the gate of the switch 10L. Here, FIG. 2 shows that when the low-side switch 10L is turned on, the reactor current flows in the direction from the opposite side of the connection point of the high-side switch 10H and the low-side switch 10L to the connection point. The operation of boost converter CV during powering that flows is shown. 2A shows the transition of the error voltage Ve and the reactor current signal Vc, FIG. 2B shows the transition of the clock signal CK, and FIG. 2C shows the transition of the reference signal Sig. FIG. 2D shows the transition of the output signal Sr of the comparator 34. FIG. 2E shows the transition of the gate signal VgH for the high side switch 10H, and FIG. 2F shows the transition of the gate signal VgL for the low side switch 10L. Further, in the figure, the alternate long and short dash line indicates a compensation ramp wave generated based on the error voltage Ve.

  As shown in the figure, the complementary driver 40 starts from a timing (time t5) obtained by delaying the timing (time t4) at which the logic of the reference signal Sig is inverted to “H” by the input of the clock signal CK by the dead time. The period until the time when the logic of the output signal of the comparator 34 is inverted to “H” and the logic of the reference signal Sig is inverted to “L” (time t6) is the ON operation period of the low-side switch 10L. In addition, the complementary drive unit 40 receives the reference signal Sig from the timing (time t3) obtained by delaying the timing (time t2) at which the logic of the reference signal Sig is inverted to “L” by the dead time. The period until the logic is inverted to “H” (time t4) is defined as an ON operation period of the high side switch 10H. In the present embodiment, the RS flip-flop 38 and the complementary drive unit 40 constitute a “basic operation unit”. The driving process of the high-side switch 10H and the low-side switch 10L by the complementary driving unit 40 constitutes a “complementary driving step”. Furthermore, a series of processes executed by the RS flip-flop 38 and the complementary drive unit 40 constitute a “basic operation step”.

  Next, the operation of the boost converter CV during powering will be described with reference to FIG. In the illustrated example, when the low-side switch 10 </ b> L is turned on at time t <b> 1 to t <b> 2, a reactor current flows and magnetic energy is accumulated in the reactor 12. The reactor current flows to the smoothing capacitor 14 via the high-side body diode 15H from time t2 to time t3 when the low-side switch 10L is turned off and the dead time is reached. Then, when the high side switch 10H is turned on at time t3 to t4, the reactor current flows to the smoothing capacitor 14 via the high side switch 10H.

  According to the boost converter CV described above using the high-side switch 10H for synchronous rectification, the power conversion efficiency in the boost converter CV can be improved.

  Subsequently, when the low-side switch 10L is turned on, the regeneration in which the reactor current flows in the opposite direction from the connection point of the high-side switch 10H and the low-side switch 10L to the opposite side of the both ends of the reactor 12 is performed. The operation of boost converter CV at that time will be described. Here, the situation where the reactor current flows in the reverse direction is, for example, when the output voltage of the boost converter CV rises beyond the command voltage due to a sudden decrease in the current flowing through an electric load (not shown) connected to the output side of the boost converter CV. Can occur.

  FIG. 3 shows the operation of boost converter CV during regeneration. Specifically, FIGS. 3A to 3F correspond to FIGS. 2A to 2F described above.

  As shown in the figure, during regeneration, even if the low-side switch 10L is turned off because the reactor current signal Vc exceeds the compensation ramp wave, the high-side switch 10H is turned on after the low-side switch 10L is turned off. In the dead time (time t1 to t2, t3 to t4), the reactor current continues to flow in the specified direction through the low-side body diode 15L. For this reason, the reactor current signal Vc rises beyond the compensation ramp wave, and the reactor current signal Vc and the ideal reactor signal Vtgt are greatly deviated. Thereby, the responsiveness of reactor current control falls.

  In order to deal with such a problem, in the present embodiment, the control circuit 16 includes the off-timing advance portion 28. Hereinafter, the off-timing advance portion 28 will be described in detail with reference to FIG.

  FIG. 4 is a block diagram showing various processes in the off-timing advance portion 28.

  The inductance calculating unit 28a calculates the inductance L of the reactor 12 higher as the reactor temperature Td detected by the temperature sensor 24 is higher. Specifically, the inductance L of the reactor 12 is corrected based on the reactor temperature Td with reference to the inductance temperature special map of the reactor 12. Here, the temperature special map is a map in which the inductance L is related to the reactor temperature Td. In this embodiment, a memory (for example, a non-volatile memory) included in the control circuit 16 in which the temperature special map is stored constitutes a “storage unit”.

  The peak value prediction unit 28b predicts the peak value Vcpeak of the reactor current (more specifically, the peak value of the reactor current signal Vc) in the next cycle of the on / off operation of the low-side switch 10L. Here, in the present embodiment, the reactor current signal Vc (more specifically, the reactor current signal Vc at the timing when the low-side switch 10L is turned on), the input voltage signal Vinfb output from the input voltage detection circuit 22 is used. The peak value Vcpeak is predicted based on the error voltage Ve and the inductance L calculated by the inductance calculator 28a. Moreover, in this embodiment, the polarity of the reactor current which flows in the direction which goes to the said connection point from the opposite side to the connection point of the high side switch 10H and the low side switch 10L among the both ends of the reactor 12 is made into positive. Hereinafter, a prediction method of the peak value Vcpeak based on these parameters will be described with reference to FIG.

  FIG. 5 is a diagram illustrating transition of the reactor current signal Vc and the compensation ramp wave. Referring to FIG. 5, from the condition that the compensation ramp wave and the reactor current signal Vc have the same value at the timing when the predetermined time T1 elapses after the low-side switch 10L is switched on, the following equation (eq1) Is guided.

上式（ｅｑ１）において、「ｍ２」は補償ランプ波のスロープ係数（＜０）を示し、「Ｖα」は、ローサイドスイッチ１０Ｌがオン操作に切り替えられるタイミングのリアクトル電流信号Ｖｃを示す。以下、「Ｖα」を電流信号初期値と称すこととする。一方、ローサイドスイッチ１０Ｌがオン操作に切り替えられてから所定時間Ｔ１が経過するタイミングにおいて、リアクトル電流信号Ｖｃが電流信号初期値Ｖαからピーク値Ｖｃｐｅａｋまで上昇するとの条件から、下式（ｅｑ２）が導かれる。

In the above equation (eq1), “m2” represents the slope coefficient (<0) of the compensation ramp wave, and “Vα” represents the reactor current signal Vc at the timing when the low-side switch 10L is switched to the ON operation. Hereinafter, “Vα” is referred to as a current signal initial value. On the other hand, the following equation (eq2) is derived from the condition that the reactor current signal Vc rises from the current signal initial value Vα to the peak value Vcpeak at the timing when the predetermined time T1 elapses after the low-side switch 10L is turned on. It is burned.

上式（ｅｑ１），（ｅｑ２）から下式（ｅｑ３）が導かれる。

こうして導かれた上式（ｅｑ３）に基づき、ピーク値Ｖｃｐｅａｋを予測できる。なお、上式（ｅｑ３）で用いる昇圧コンバータＣＶの入力電圧Ｖｉｎは、抵抗体２２ａ，２２ｂの抵抗値に基づき入力電圧信号Ｖｉｎｆｂを換算することで算出すればよい。

The following equation (eq3) is derived from the above equations (eq1) and (eq2).

Based on the above equation (eq3) thus derived, the peak value Vcpeak can be predicted. The input voltage Vin of the boost converter CV used in the above equation (eq3) may be calculated by converting the input voltage signal Vinfb based on the resistance values of the resistors 22a and 22b.

  Returning to the description of FIG. 4, the comparator 28c receives the peak value Vcpeak predicted by the peak value prediction unit 28b as input, and whether the polarity of the peak value Vcpeak in the next cycle of the low-side switch 10L is negative. Predict whether or not. In the present embodiment, the peak value prediction unit 28b and the comparator 28c constitute a “polarity prediction unit”.

  The offset voltage calculation unit 28d calculates the offset voltage Voffset for advancing the OFF operation timing of the low-side switch 10L by the dead time DT using the input voltage signal Vinfb and the inductance L as inputs. Hereinafter, a method for calculating the offset voltage Voffset based on these parameters will be described with reference to FIG.

  FIG. 6 is a diagram showing transitions of the gate signals VgH and VgL, the reactor current signal Vc, and the compensation ramp wave. Referring to FIG. 6, the offset voltage Voffset is an addition value of the increase value V1 of the reactor current signal Vc and the absolute value of the decrease value V2 of the compensation ramp wave in the dead time DT. That is, the offset voltage Voffset is a voltage signal corresponding to the increase in the reactor current in the dead time DT. From this, the following formula (eq4) is derived.

ここで、リアクトル電流信号Ｖｃの増加分Ｖ１と、補償ランプ波の低下分Ｖ２とは、下式（ｅｑ５），（ｅｑ６）で表される。

Here, the increase V1 of the reactor current signal Vc and the decrease V2 of the compensation ramp wave are expressed by the following equations (eq5) and (eq6).

上式（ｅｑ４）〜（ｅｑ６）より、下式（ｅｑ７）が導かれる。

こうして導かれた上式（ｅｑ７）に基づき、オフセット電圧Ｖｏｆｆｓｅｔを算出することができる。なお、上式（ｅｑ７）で用いる入力電圧Ｖｉｎは、先ほどと同様に、抵抗体２２ａ，２２ｂの抵抗値に基づき入力電圧信号Ｖｉｎｆｂを換算することで算出すればよい。

From the above formulas (eq4) to (eq6), the following formula (eq7) is derived.

Based on the above equation (eq7) thus derived, the offset voltage Voffset can be calculated. Note that the input voltage Vin used in the above equation (eq7) may be calculated by converting the input voltage signal Vinfb based on the resistance values of the resistors 22a and 22b, as before.

  Returning to the description of FIG. 4, the deviation calculating unit 28e calculates a value obtained by subtracting the offset voltage Voffset from the error voltage Ve.

  The selection unit 28f switches the error voltage output to the non-inverting input terminal of the comparator 34 based on the output signal of the comparator 28c. Specifically, when the logic of the output signal of the comparator 28 c is “H” (the polarity of the peak value Vcpeak is positive), the error voltage Ve is output to the non-inverting input terminal of the comparator 34. On the other hand, when the logic of the output signal of the comparator 28c is “L” (the polarity of the peak value Vcpeak is negative), a value obtained by subtracting the offset voltage Voffset from the error voltage Ve with respect to the non-inverting input terminal of the comparator 34 is obtained. Output. Thereby, the OFF operation timing of the low-side switch 10L can be advanced by the dead time DT. In the present embodiment, the deviation calculation unit 28e and the selection unit 28f constitute an “advance angle unit”.

  FIG. 7 shows the procedure of the advance processing of the OFF operation timing of the low side switch 10L according to the present embodiment. This process is repeatedly executed by the control circuit 16 at a predetermined cycle, for example.

  In this series of processes, first, in step S10, it is determined whether or not it is time to switch the low-side switch 10L from the off operation to the on operation.

  When an affirmative determination is made in step S10, the process proceeds to step S12, and a current signal initial value Vα that is a reactor current signal Vc at a timing at which the low-side switch 10L is switched to the ON operation is acquired.

  In subsequent step S14, based on the reactor temperature Td detected by the temperature sensor 24, the inductance L of the reactor 12 is corrected with reference to the above-described inductance temperature special map of the reactor 12. In this embodiment, this step constitutes a “temperature detection step”.

  In the subsequent step S16, the offset voltage Voffset is calculated based on the input voltage Vin, the inductance L, the slope coefficient m2, and the dead time DT. In this embodiment, this step constitutes an “offset voltage calculation step”.

  In subsequent step S18, the peak value Vcpeak in the next cycle of the on / off operation of the low-side switch 10L is predicted based on the current signal initial value Vα, the input voltage Vin, the error voltage Ve, the inductance L, and the slope coefficient m2. In the present embodiment, the input voltage Vin used in the processing of steps S16 and S18 is acquired at the timing when the low-side switch 10L is switched to the on operation. In the present embodiment, the process of step S18 constitutes a “peak value prediction step”.

  In a succeeding step S20, it is determined whether or not the polarity of the peak value Vcpeak is negative. If a negative determination is made in step S20, the process proceeds to step S22, and the error voltage Ve output from the error amplifier 26 is used as it is as the error voltage Ve * output to the comparator 34. On the other hand, when an affirmative determination is made in step S20, the process proceeds to step S24, and a value obtained by subtracting the offset voltage Voffset from the error voltage Ve is used as the error voltage Ve * output to the comparator 34.

  Incidentally, in the present embodiment, the process of step S20 constitutes a “polarity prediction step”, and the process of step S24 constitutes an “advance step”.

  When a negative determination is made in step S10 or when the processes in steps S22 and S24 are completed, the series of processes is temporarily terminated.

  Next, the effect of the OFF operation timing advance processing of the low-side switch 10L will be described using FIG. Here, FIGS. 8A to 8F correspond to FIGS. 3A to 3F described above.

  According to the advance processing of the OFF operation timing, the compensation ramp wave can be reduced by the offset voltage Voffset as indicated by a two-dot chain line in the figure. For this reason, the OFF operation timing of the low-side switch 10L can be advanced by the dead time DT (time t1 to t2, t3 to t4), and consequently, the reactor current signal Vc can be prevented from deviating from the ideal reactor signal Vtgt. Therefore, the responsiveness of reactor current control can be improved suitably.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When the polarity of the peak value Vcpeak of the reactor current signal Vc in one cycle of the next on / off operation of the low-side switch 10L is predicted to be negative, the offset voltage calculation unit 28d from the error voltage Ve output from the error amplifier 26 The offset voltage Voffset calculated by the above is subtracted. Thereby, the OFF operation timing of the low-side switch 10L can be advanced by the dead time DT, and the reactor current signal Vc can be prevented from greatly exceeding the compensation ramp wave. Therefore, the responsiveness of the reactor current control can be preferably improved, and the output voltage of boost converter CV that has risen due to the sudden decrease in load current can be quickly reduced to the command voltage.

  (2) The inductance L of the reactor 12 calculated based on the reactor temperature Td was used for calculating the offset voltage Voffset. For this reason, the calculation accuracy of the offset voltage Voffset can be improved, and as a result, the setting accuracy of the OFF operation timing of the low-side switch 10L can be improved.

  (3) The inductance L of the reactor 12 calculated based on the reactor temperature Td was used to predict the peak value Vcpeak. For this reason, the prediction accuracy of the peak value Vcpeak can be improved, and as a result, the occurrence of a situation where the OFF operation timing of the low-side switch 10L is erroneously advanced can be avoided.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, the circuit configuration for turning off the low-side switch 10L in the control circuit 16 is changed.

  FIG. 9 shows a circuit diagram of the boost converter CV according to the present embodiment. In FIG. 9, the same members as those shown in FIG. 1 are given the same reference numerals for the sake of convenience.

  As shown in the figure, the control circuit 16 according to the present embodiment includes an off timing generation unit 44 instead of the comparator 34. In the present embodiment, the error voltage Ve * and the inductance L calculated by the off-timing advance unit 28 and the input voltage signal Vinfb are input to the off-timing generator 44.

  Further, the boost converter CV according to the present embodiment includes a current detection circuit 42. The current detection circuit 42 detects a voltage between the terminals of the low-side switch 10L when the low-side switch 10L is turned on as a first voltage signal (hereinafter, element current signal Vd) corresponding to the reactor current IL. The element current signal Vd output from 42 is input to the off-timing generation unit 44. In the present embodiment, the current detection circuit 42 constitutes a “first voltage output circuit”.

  FIG. 10 is a block diagram of the off timing generation unit 44.

  The operation time calculation unit 44a receives the peak value Vcpeak, the inductance L, the input voltage Vin of the boost converter CV calculated from the input voltage signal Vinfb, and the current signal initial value Vα calculated from the element current signal Vd as inputs. A 10 L on-operation time Tpeak (specifically, a time that is assumed until the element current signal Vd reaches the compensation ramp wave after the low-side switch 10 L is switched on) is calculated. Here, in this embodiment, since slope compensation is performed, the ON operation time Tpeak is calculated using the following equation (eq8). Here, the following equation (eq8) is obtained by solving the above equation (eq2) for “T1”.

上式（ｅｑ８）のピーク値Ｖｃｐｅａｋは、上式（ｅｑ３）において「Ｖｅ」を「Ｖｅ＊」に置き換えることで予測すればよい。つまり、ピーク値Ｖｃｐｅａｋは、誤差電圧Ｖｅ＊、入力電圧Ｖｉｎ、電流信号初期値Ｖα、インダクタンスＬ及びスロープ係数ｍ２に基づき予測すればよい。

The peak value Vcpeak of the above equation (eq8) may be predicted by replacing “Ve” with “Ve *” in the above equation (eq3). That is, the peak value Vcpeak may be predicted based on the error voltage Ve *, the input voltage Vin, the current signal initial value Vα, the inductance L, and the slope coefficient m2.

  The countdown timer 44b outputs a pulse signal of logic “H” at the timing when the ON operation time Tpeak calculated by the operation time calculation unit 44a has elapsed after the low side switch 10L is turned ON. The comparator 44c outputs a logic “H” pulse signal Sr (corresponding to a “predetermined signal”) instructing to turn off the low-side switch 10L in response to the input of the logic “H” pulse signal. In the present embodiment, the countdown timer 44b and the comparator 44c constitute a “determination unit”.

  FIG. 11 shows the procedure of the advance processing of the OFF operation timing of the low-side switch 10L according to this embodiment. This process is repeatedly executed by the control circuit 16 at a predetermined cycle, for example. In FIG. 11, the same steps as those shown in FIG. 7 are given the same step numbers for the sake of convenience.

  In this series of processes, after the process of step S16 is completed, in step S18a, the peak value Vcpeak is predicted based on the current signal initial value Vα, the input voltage Vin, the error voltage Ve *, the inductance L, and the slope coefficient m2. Thereafter, when the processes of steps S22 and S24 are completed via step S20, the process proceeds to step S26, and the on operation time Tpeak is calculated based on the peak value Vcpeak, the current signal initial value Vα, the input voltage Vin, and the inductance L. .

  In subsequent step S28, the countdown is started with reference to the timing at which the low-side switch 10L is turned on. In step S30, the process waits until the on-operation time Tpeak elapses after the countdown is started. In step S32, the pulse signal Sr is output.

  If a negative determination is made in step S10 or if the process in step S32 is completed, the series of processes is temporarily terminated.

  According to the present embodiment described above, the same effect as that obtained in the first embodiment can be obtained.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the second embodiment.

  In the present embodiment, in the step-up converter CV including the current detection circuit 42 that detects the reactor current IL as the element current signal Vd, the low side switch 10L is turned on and the low side switch 10L is switched on. Use of the device current signal Vd before the lapse of the specified time TBL (time t1 to t2) is prohibited. This is in consideration of the possibility that noise may be superimposed on the element current signal Vd immediately after the low-side switch 10L is switched to the ON operation, as shown in FIG. FIGS. 12A to 12C correspond to the previous FIGS. 8E, 8F, and 8A.

  FIG. 13 shows the procedure of the advance processing for the OFF operation timing of the low-side switch 10L according to this embodiment. This process is repeatedly executed by the control circuit 16 at a predetermined cycle, for example. In FIG. 13, the same steps as those shown in FIG. 11 are given the same step numbers for the sake of convenience.

  In this series of processes, if an affirmative determination is made in step S10, it is determined in step S34 whether or not a specified time TBL has elapsed since the low-side switch 10L was switched to the on operation. This process is a process for prohibiting the use of the element current signal Vd before the lapse of the specified time TBL after the low-side switch 10L is turned on in the off operation timing advance process. By this processing, the current signal initial value Vα according to the present embodiment becomes the element current signal Vd at a timing when the specified time TBL has elapsed after the low-side switch 10L is switched on. Incidentally, when it is determined in step S34 that the specified time TBL has elapsed, the process proceeds to step S12. In the present embodiment, the process of step S34 constitutes a “prohibiting means”.

  If a negative determination is made in step S10 or if the process in step S32 is completed, the series of processes is temporarily terminated.

  According to the present embodiment described above, the following effects are obtained in addition to the effects obtained in the second embodiment.

  (4) The use of the element current signal Vd before the lapse of the specified time TBL after the low-side switch 10L is switched on is prohibited. For this reason, the element current signal Vd on which no noise is superimposed can be used for the calculation of the offset voltage Voffset. Thereby, the calculation accuracy of the offset voltage Voffset and the prediction accuracy of the peak value Vcpeak can be further increased.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  In each of the above embodiments, a configuration in which slope compensation is not performed may be employed. In this case, the slope coefficient m2 may be set to “0” in the peak value prediction unit 28b and the offset voltage calculation unit 28d of the first embodiment. In this case, in the second embodiment, the on-operation time Tpeak may be calculated by replacing “Vcpeak” in the above equation (eq8) with “Ve *”.

  In the first embodiment, the current detection circuit 42 described in the second embodiment may be used. In this case, the method described in the third embodiment may be employed to avoid the use of the element current signal Vd on which noise is superimposed.

  The “advance angle portion” is not limited to that exemplified in the first embodiment. For example, instead of subtracting the offset voltage Voffset from the error voltage Ve, by adding the offset voltage Voffset to the reactor current signal Vc output from the current detection circuit 18, the OFF operation timing of the low-side switch 10L is set to the dead time DT. You can just get ahead.

  The “peak value prediction unit” is not limited to the one exemplified in the first embodiment. For example, the inductance L of the reactor 12 used for prediction of the peak value Vcpeak may be a fixed value. Even in this case, the peak value Vcpeak can be predicted. The fixed value of the inductance L may also be used in the calculation of the offset voltage Voffset by the “offset voltage calculation unit” and the calculation of the on-operation time Tpeak by the “operation time calculation unit” of the second embodiment.

  The “high potential side switching element” and the “low potential side switching element” are not limited to field effect transistors, and may be IGBTs, for example. In this case, the “distribution restricting element” may be, for example, a free wheel diode connected in reverse parallel to the IGBT.

  10H: High side switch, 10L: Low side switch, 12: Reactor, 15L: Low side body diode, 34 ... Comparator, 28b ... Peak value prediction unit, 28c ... Comparator, 28e ... Deviation calculation unit, 28f ... Selection unit, 38 ... RS Flip-flop, 40... Complementary drive unit.

Claims (10)

A high potential side switching element (10H) and a low potential side switching element (10L) connected in series with each other;
A reactor (12) having one end connected to a connection point of the high potential side switching element and the low potential side switching element;
Allow current flow in a specified direction from both sides of the low potential side switching element to the connection point from the opposite side to the connection point, and restrict current flow in the direction opposite to the specified direction. Distribution restriction element (15L),
In a step-up converter (CV) comprising a smoothing capacitor (14) having one end connected to the opposite side to the connection point of both ends of the high potential side switching element,
A first voltage output circuit (42) for outputting a voltage between terminals of the low potential side switching element when the low potential side switching element is turned on as a first voltage signal corresponding to the current flowing through the reactor. When,
A second voltage output circuit (20) for outputting a second voltage signal corresponding to the voltage across the terminals of the smoothing capacitor;
An error amplifier (26) for outputting an error voltage obtained by amplifying a deviation between the second voltage signal output from the second voltage output circuit and a reference voltage;
A latch circuit (38) for receiving a predetermined signal and a clock signal and outputting a reference signal for turning on and off the high potential side switching element and the low potential side switching element;
A complementary drive unit (40) that complementarily turns on and off the high-potential side switching element and the low-potential side switching element while giving a dead time by using the reference signal output from the latch circuit as an input ;
When the polarity of the current flowing in the direction from the opposite side of the reactor to the connection point is positive among both ends of the reactor, the low potential side switching element is turned on by the complementary drive unit. An off operation part ( 34) for turning off the low potential side switching element at a timing when the current flowing through the reactor exceeds the command value;
A polarity prediction unit (28b, 28c) for predicting the polarity of the peak value of the current flowing through the reactor in one cycle of the next on / off operation of the low potential side switching element;
When the polarity predicting unit predicts that the polarity of the peak value is negative, the turn-off operation timing of the low potential side switching element by the off operation unit is advanced by the dead time in the next cycle of the on / off operation. Corners (28e, 28f);
Equipped with a,
The off operation unit outputs a magnitude comparison result of the error voltage output from the error amplifier and the first voltage signal output from the first voltage output circuit as the predetermined signal to the latch circuit. Having a comparator (34);
When the first voltage signal exceeds the error voltage as the command value, the comparator outputs as the predetermined signal that the low potential side switching element is turned off,
The polarity predicting unit predicts the peak value based on the first voltage signal, an applied voltage on the opposite side of the both ends of the reactor, an inductance of the reactor, and the error voltage. part has (28b), the step-up converter, characterized by predicting the polarity of predicted the peak value by the peak value prediction unit. A high potential side switching element (10H) and a low potential side switching element (10L) connected in series with each other;
A reactor (12) having one end connected to a connection point of the high potential side switching element and the low potential side switching element;
Allow current flow in a specified direction from both sides of the low potential side switching element to the connection point from the opposite side to the connection point, and restrict current flow in the direction opposite to the specified direction. Distribution restriction element (15L),
The previous SL smoothing capacitor having one end on the opposite side is connected to the connection point of the two ends of the high-potential side switching element (14), step-up converter with a (CV),
A first voltage output circuit (18) for outputting a voltage between terminals of the low potential side switching element when the low potential side switching element is turned on as a first voltage signal corresponding to the current flowing through the reactor. When,
A second voltage output circuit (20) for outputting a second voltage signal corresponding to the voltage across the terminals of the smoothing capacitor;
An error amplifier (26) for outputting an error voltage obtained by amplifying a deviation between the second voltage signal output from the second voltage output circuit and a reference voltage;
As inputs Tokoro constant signal and the clock signal, the high-potential side switching elements and said latch circuit for outputting a reference signal for turning on and off the low-potential side switching element (38),
As inputs the reference signal outputted from the latch circuit, while applying de dead time, the high-potential side switching elements and said complementary driving part complementarily turning on and off the low-potential side switching element (40),
When the polarity of the current flowing in the direction from the opposite side of the reactor to the connection point is positive among both ends of the reactor, the low potential side switching element is turned on by the complementary drive unit. An off operation part (44) for turning off the low potential side switching element at a timing when the current flowing through the reactor exceeds the command value;
A polarity prediction unit (28b, 28c) for predicting the polarity of the peak value of the current flowing through the reactor in one cycle of the next on / off operation of the low potential side switching element;
When the polarity predicting unit predicts that the polarity of the peak value is negative, the turn-off operation timing of the low potential side switching element by the off operation unit is advanced by the dead time in the next cycle of the on / off operation. Corners (28e, 28f);
With
The off operation part is
Based on the error voltage output from the error amplifier and the first voltage signal output from the first voltage output circuit, an operation time calculation unit (44a) that calculates an ON operation time of the low potential side switching element. )When,
A determination unit (44c) that determines whether or not the on-operation time calculated by the operation time calculation unit has elapsed since the low-potential side switching element is turned on by the complementary drive unit;
Have
When the determination unit determines that the ON operation time has elapsed, the determination unit outputs , as the predetermined signal, an operation to turn OFF the low potential side switching element ,
The polarity predicting unit predicts the peak value based on the first voltage signal, an applied voltage on the opposite side of the both ends of the reactor, an inductance of the reactor, and the error voltage. And a step (28b) for predicting the polarity of the peak value predicted by the peak value prediction unit. The advance portion is
Wherein a offset voltage calculating unit that calculates an offset voltage which is a voltage signal corresponding to the increase in the current flowing through the reactor in the dead time of (28d),
By subtracting the offset voltage calculated by the offset voltage calculation unit from the error voltage output from the error amplifier, the OFF operation timing of the low potential side switching element is advanced by the dead time. The boost converter according to claim 1 or 2 . The boost voltage according to claim 3 , wherein the offset voltage calculation unit calculates the offset voltage based on an applied voltage opposite to the connection point at both ends of the reactor and the first voltage signal. Converter . A temperature detector (24) for detecting the temperature of the reactor;
A storage unit (28a) in which the inductance is stored in relation to the temperature of the reactor;
Further comprising
5. The boost converter according to claim 4, wherein the offset voltage calculation unit uses the inductance stored in the storage unit corresponding to the temperature detected by the temperature detection unit for calculation of the offset voltage. A temperature detector (24) for detecting the temperature of the reactor;
A storage unit (28a) in which the inductance is stored in relation to the temperature of the reactor;
Further comprising
The peak value prediction unit, any one of claims 1 to 5, characterized by using the inductance stored in the storage unit corresponding to the temperature detected by the temperature detection unit to the prediction of the peak value The step-up converter according to the item . Prohibiting means for prohibiting the use of the first voltage signal during a period in which the low-potential side switching element is turned on and before the lapse of a specified time after the low-potential side switching element is switched on. The boost converter according to any one of claims 1 to 6, further comprising: The low potential side switching element is a field effect transistor,
The boost converter according to any one of claims 1 to 7 , wherein the distribution restriction element is a body diode of the low potential side switching element. A high potential side switching element (10H) and a low potential side switching element (10L) connected in series with each other;
A reactor (12) having one end connected to a connection point of the high potential side switching element and the low potential side switching element;
Allow current flow in a specified direction from both sides of the low potential side switching element to the connection point from the opposite side to the connection point, and restrict current flow in the direction opposite to the specified direction. Distribution restriction element (15L),
A smoothing capacitor (14) having one end connected to the opposite side of the connection point of both ends of the high potential side switching element, and applied to a boost converter (CV) ,
A basic operation step of complementarily turning on and off the high-potential side switching element and the low-potential side switching element while giving a dead time;
When the polarity of the current flowing in the direction from the opposite side of the reactor to the connection point is positive among both ends of the reactor, the low potential side switching element is turned on by the basic operation step. An off operation step of turning off the low potential side switching element at a timing when the current flowing through the reactor exceeds the command value;
A polarity prediction step of predicting the polarity of the peak value of the current flowing through the reactor in one cycle of the next on / off operation of the low potential side switching element;
When the polarity prediction step predicts that the polarity of the peak value is negative, in the next cycle of the next on / off operation, the advance timing of turning off the low potential side switching element by the off operation step is advanced by the dead time. Corner step,
An error amplification step of calculating an error voltage obtained by amplifying a deviation of the second voltage signal and the reference voltage according to the voltage between the terminals of the smoothing capacitor;
An offset voltage calculating step for calculating an offset voltage that is a voltage signal corresponding to an increase in current flowing through the reactor in the dead time;
Equipped with a,
When the low-potential side switching element is turned on, the voltage between the terminals of the low-potential side switching element is a first voltage signal corresponding to the current flowing through the reactor,
In the off operation step, when it is determined that the first voltage signal exceeds the error voltage calculated in the error amplification step, a signal to turn off the low potential side switching element is generated,
The basic operation step includes
A reference signal generation step for generating a reference signal for turning on and off the high-potential side switching element and the low-potential side switching element, with the off-operation signal and the clock signal generated in the off-operation step as inputs. When,
Complementary driving step of complementarily turning on and off the high-potential side switching element and the low-potential side switching element while giving the dead time with the reference signal generated by the reference signal generation step as input,
Have
The advance step subtracts the offset voltage calculated by the offset voltage calculation step from the error voltage calculated by the error amplification step, thereby setting the OFF operation timing of the low potential side switching element to the dead time. Just early,
The polarity prediction step predicts the peak value based on the first voltage signal, an applied voltage opposite to the connection point among both ends of the reactor, an inductance of the reactor, and an error voltage. comprising the steps, the control method of the boost converter, characterized in that predicting the polarity of predicted the peak value by the peak value prediction step. A temperature detection step of detecting the temperature of the reactor;
10. The boost converter control method according to claim 9, wherein the peak value predicting step variably sets an inductance of the reactor used for predicting the peak value based on the temperature detected by the temperature detecting step.

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