Power converter and power conversion method

Abstract

Provide a power converter that can perform soft switching control with higher accuracy in the ARCP method. 【Solution means】Leg 1 includes main switches S1 and S2, resonance capacitors C connected in parallel to each main switch r , an auxiliary switch A1 and A2 and a resonance inductor L whose one end is connected to the common connection point of the main switches r . The detection unit 13 detects the voltage V of the DC power supply 4 supplied to leg 1 H . The current sensor 7 detects the inductor current I flowing through the resonance inductor L r , and the capacitance of the resonance capacitor C is stored in the storage unit 15 r . The calculation unit 14 controls to perform soft switching for leg 1, and estimates the inductance of the resonance inductor L based on the power supply voltage V r and the inductor current I H , and determines the timing for switching each main switch based on the inductance and the capacitance of the resonance capacitor C r . r r ​

Description

Technical Field

[0001] The present invention relates to a power converter and a power conversion method for performing switching control in an ARCP (Auxiliary Resonant Commutated Pole) manner.

Background Art

[0002] In recent years, in order to miniaturize power converters and reduce losses in electric motors, efforts have been made to increase the switching frequency of switching control of power converters. When the switching control frequency is increased, the switching loss increases. Therefore, as a countermeasure, it is necessary to apply soft switching technology to reduce losses.

[0003] In the ARCP method, which is one of the soft switching technologies, a partial resonance operation by a resonance inductor Lr and a snubber capacitor Cr is utilized, but there is variation in the resonance time. Therefore, it is important to accurately adjust the relative switching timing between the on-timing of the auxiliary switching that constitutes the auxiliary resonance circuit and the on-timing of the main switch that is the target of soft switching.

[0004] For example, in Patent Documents 1 and 2, in a DC / DC converter circuit provided with an ARCP circuit, a control unit 11A that controls main switches S1, S2 and resonance switches S3, S4, and a storage unit 12A that stores a first calculation formula regarding the operation timing for turning on the main switches S1, S2 are provided. The control unit 11A calculates a first time from when the resonance switches S3, S4 are turned on until the main switches S1, S2 are turned on based on the first calculation formula, and performs switching processing for turning on the main switches S1, S2 at the end of the first time, and controls to correct and update the first calculation formula so that the deviation amount between the crossing timing when the falling of the resonance current IL2 and the reactor current IL1 cross and the operation timing decreases.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-96959 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 discloses a combination of feedforward control and feedback control. However, if the accuracy of the circuit element constants used in the first calculation formula for pre-determining the switching timing of the main switch is poor, the effect of reducing switching losses becomes limited.

[0007] The present invention has been made in view of the above circumstances, and its object is to provide a power converter and a power conversion method that can perform soft switching control with higher precision in the ARCP system. [Means for solving the problem]

[0008] According to the power converter described in claim 1, the power conversion unit comprises a series circuit of a high-potential side main switch (S1) and a low-potential side main switch (S2), and a resonant capacitor (C) connected in parallel to each of the main switches. r ), two auxiliary switches (A1, A2) which constitute a bidirectional switch with one end connected to the common connection point of the two main switches and the other end connected to the common connection point, and a resonant inductor (L r It comprises one or more legs (1) having a series circuit of ).

[0009] The terminal voltage detection unit (23) detects the voltage between the conductive terminals of the main switch, and the control unit (24) controls the legs of the power conversion unit to perform soft switching. Based on the terminal voltage, it detects the period of resonant operation in the legs, calculates the product of the inductance of the resonant inductor and the capacitance of the resonant capacitor from that period, and determines the timing for switching each main switch based on that product. In other words, by obtaining the so-called LC product of the resonant inductor and resonant capacitor, it becomes possible to determine the timing for switching the main switches based on other factors such as the power supply voltage and load current, enabling soft switching control with higher precision.

[0010] The power converter according to claim 3 includes a power conversion unit having the same configuration as in claim 1, and a power supply voltage detection unit (13) detects the DC power supply voltage supplied to the power conversion unit. A current detection unit (7) detects the inductor current flowing through the resonant inductor, and a storage unit (15) stores the capacitance of the resonant capacitor. A control unit (14) controls the legs constituting the power conversion unit to perform soft switching, estimates the inductance of the resonant inductor based on the power supply voltage and the inductor current, and determines the timing for switching each main switch based on the inductance and capacitance.

[0011] When comparing the inductance of a resonant inductor and the capacitance of a resonant capacitor in catalog values, the error in the former tends to be larger in general. Therefore, even if the inductance is estimated and the capacitance is a value pre-stored in the memory unit, the timing for switching the main switch in soft switching control can be determined with high accuracy. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram showing the configuration of the power converter, representing the first embodiment. [Figure 2] Flowcharts primarily showing the processing performed by the control unit. [Figure 3] Timing chart showing the ideal turn-on timing for main switch S1. [Figure 4] Timing chart showing the case where the turn-on timing of main switch S1 is delayed. [Figure 5] Timing chart showing the case where the main switch S1 turns on early. [Figure 6] This is a second embodiment, and is a flowchart mainly showing the processing content by the control unit. [Figure 7] This is a third embodiment, and the diagram shows the configuration of the power converter. [Figure 8] This figure shows a specific configuration example of the part of the detection unit that detects the drain-source voltage Vds of the main switch S1. [Figure 9] Timing chart explaining the measurement of the resonant period T [Figure 10] Flowcharts primarily showing the processing performed by the control unit. [Figure 11] This is the fourth embodiment, and is a flowchart mainly showing the processing content by the control unit. [Figure 12] Diagram showing mathematical formulas [Modes for carrying out the invention]

[0013] (First Embodiment) As shown in Figure 1, the power converter 11 of this embodiment includes a leg 1 which is an ARCP-type power circuit section. The series circuits of the high-potential side main switch S1 and the low-potential side main switch S2 that constitute leg 1 are connected in parallel to the DC power supply 4 together with the series circuits of the smoothing capacitor 2, capacitors 3a and 3b. Leg 1 also includes auxiliary switches A1 and A2 and a resonant inductor L, which are connected between the midpoint of capacitors 3a and 3b, i.e., the neutral point, and the common connection point of main switches S1 and S2. r It is equipped with a series circuit.

[0014] The main switches S1 and S2, and the auxiliary switches A1 and A2 are all, for example, N-channel MOSFETs in this embodiment. The series circuit of the auxiliary switches A1 and A2 forms a bidirectional switch, and for example, their sources or drains are connected in common. Resonance capacitors C r composed of parasitic capacitance or additional capacitance are connected in parallel to the main switches S1 and S2, respectively.

[0015] A load 5 is connected between the common connection point of the main switches S1 and S2, which is the output terminal of leg 1, and the negative electrode of the DC power supply 4. A current sensor 6 is arranged between the output terminal of leg 1 and the load 5. The current sensor 6 detects the load current I load flowing through the load 5. A current sensor 7 is arranged between the auxiliary switch A2 and the resonance inductor L r . The current sensor 7 detects the resonance current I r flowing through the resonance inductor L r .

[0016] The control device 12 is composed of, for example, a microcomputer or the like, and includes a detection unit 13, a calculation unit 14, a storage unit 15, and a drive unit 16. The detection unit 13, which is a power supply voltage detection unit, includes a voltage sensor (not shown) that detects the voltage V H of the DC power supply 4, and the sensor signals of the current sensors 6 and 7 are input thereto. The current sensor 7 is a current detection unit.

[0017] The calculation unit 14 corresponding to the control unit generates, by calculation, a signal for controlling the switching of the main switches S1 and S2, and the auxiliary switches A1 and A2 based on the voltage and current input via the detection unit 13 and the data stored in the storage unit 15. The capacitance of the resonance capacitor C r is stored in the storage unit 15 in advance. The drive unit 16 outputs a signal for driving each gate of the main switches S1 and S2, and the auxiliary switches A1 and A2 based on the signal generated by the calculation unit 14.

[0018] Next, the operation of this embodiment will be described. As shown in Figure 2, the calculation unit 14 detects the voltage V of the DC power supply 4 via the detection unit 13. H and load current I load The following is measured (S1). Figure 3 shows, for example, the case where the main switch S1 is turned on after the auxiliary switch A1, and the above measurement is performed during this period. The values ​​measured here are written to the storage unit 15 for storage. These values ​​are then stored in the storage unit 15, which contains the power supply voltage V from the previous control cycle. H , load current I load Determine whether the value is different from the previous value (S2). If the current value is the same as the previous value (NO), proceed to step S8.

[0019] If the current value is different from the previous value (S2; Yes), the load current I load However, the resonant current I r Determine whether the load current I is large enough to be measured (S3). load If the resonant current I is sufficiently large (Yes), the calculation unit 14 detects the resonant current I via the detection unit 13. r (S4) The resonant current I is measured. In the following step S5, the resonant current I is measured. r The difference between the measured value I2 and the previous measured value I1, and the current resonant current I r Using the difference between the measurement time t2 and the previous measurement time t1, (dI r Calculate ( / dt).

[0020] In step S6, the resonant inductor L is set based on equation (1) shown in Figure 12. r The inductance is estimated. In step S7, the target value Tt of the switching timing is calculated based on equation (2). For the capacitance of the resonant capacitor Cr, the value pre-stored in the memory unit 15 is used. In the example shown in Figure 3, the turn-on timing of the main switch S1 is set to the target value Tt. t This is the result.

[0021] In step S8, when the auxiliary switch A1 or A2 and the main switch S1 or S2 are driven by soft switching control, a correct or incorrect determination is made regarding the switching timing of the main switch S1 or S2 (S9). As shown in Figure 3, when the main switch S1 is turned on at the target value Tt, the timing is determined to be correct for the resonant current I r The value of the load current I load The result is "positive" if it coincides with the timing when the value becomes equal to [the specified value]. Note that t=0, which is the reference time for the target value Tt, corresponds to the time when the execution of step S1 in the flowchart shown in Figure 2 begins.

[0022] Figures 4 and 5 show cases where the result is "incorrect". Resonant current I r The value of the load current I load The time to which the value equals T rl Therefore, in the former case, if the timing of turning on the main switch S1 is late (T rl <T t ), the latter is earlier (T rl >T t ) In the following step S10, for example, time T t , T rl If the difference is less than the threshold (No), it is determined that no correction is necessary and the process returns to step S1. On the other hand, if the difference is greater than or equal to the threshold (Yes), it is determined that correction is necessary, and the timing for switching the main switch S1 is corrected (S11) before returning to step S1.

[0023] In the case shown in Figure 4, the timing of turning on the auxiliary switch A1 should be delayed by the difference mentioned above, or the timing of turning on the main switch S1 should be advanced. In the case shown in Figure 5, the timing of turning on the auxiliary switch A1 should be advanced by the difference mentioned above, or the timing of turning on the main switch S1 should be delayed.

[0024] As described above, according to this embodiment, in the power converter 11, the power conversion section Leg 1 consists of a series circuit of main switches S1 and S2, and a resonant capacitor C connected in parallel to each of the main switches S1 and S2. r Auxiliary switches A1 and A2, and a resonant inductor L, are connected at one end to the common connection point of main switches S1 and S2, and the other end is connected to the common point. r It is equipped with a series circuit.

[0025] The detection unit 13 detects the voltage V of the DC power supply 4 supplied to leg 1. H The current sensor 7 detects the resonant inductor L. r Inductor current I flowing through r The memory unit 15 detects this and stores a resonant capacitor C r The capacitance is stored. The calculation unit 14 controls the leg 1 to perform soft switching, and the power supply voltage V H and inductor current I r Based on this, the resonant inductor L r The inductance is estimated, and the inductance and the resonant capacitor C are used. r The timing for switching each main switch S1 and S2 is determined based on their capacitances.

[0026] Resonant inductor L in catalog value r The inductance and resonant capacitor C r When comparing the capacitance with that of the main switches, the error in the former tends to be larger in general. Therefore, even if the inductance is estimated and the capacitance is a value that has been stored in the memory unit 15 in advance, the timing for switching the main switches S1 and S2 in soft switching control can be determined with high accuracy.

[0027] (Second Embodiment) In the following description, parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted, while the differences are described. The configuration of the second embodiment is the same as that of the first embodiment, with only slight differences in the control content. In the first embodiment, during the period when normal switching control is performed, the resonant inductor L r The inductance is being estimated.

[0028] In the second embodiment, as shown in Figure 6, a sequence for estimating the inductance is executed only once before starting normal switching control, and then the system proceeds to normal switching control. Therefore, the auxiliary switch A1 is first turned on (S12), steps S4 to S6 are executed, and the auxiliary switch A1 is turned off (S13). Then, following step S1, steps S8 to S11 are executed. As described above, the calculation process for estimating the inductance can be reduced according to the second embodiment.

[0029] (Third embodiment) As shown in Figure 7, the power converter 21 of the third embodiment includes a control device 22 instead of the control device 12. In the control device 22, the current sensor 7 is omitted, and a detection unit 23 and a calculation unit 24 are included instead of the detection unit 13 and calculation unit 14. The detection unit 23 is a terminal voltage detection unit, and the drain-source voltage V is the voltage between the conductive terminals of the main switches S1 and S2. ds It detects.

[0030] The component that detects the drain-source voltage Vds consists of an operational amplifier 25 and a comparator 26, as shown in Figure 8, for example. The voltage Vds detected by the operational amplifier 25 ds In the comparator 26, a reference voltage V is set near zero V. ref It is compared to the voltage V on the main switch S1 side. ds In a configuration that detects the reference voltage V ref The negative terminal is connected to the source of the main switch S1. As shown in Figure 9, the comparator 26 checks when the input voltage from the operational amplifier 25 is equal to the reference voltage V ref When it falls below this level, the comparator 26 outputs V oTo transform it to a high level.

[0031] Next, the operation of the third embodiment will be described. As shown in Figure 10, in the third embodiment, steps S14 and S15 are provided in place of steps S3 to S6 in the first embodiment. In step S14, the drain-source voltage V ds The system is made to resonate multiple times, and the resonance period T is measured. In the example shown in Figure 9, the drain-source voltage V ds Power supply voltage V H The first resonance occurs when the voltage changes from zero to zero, followed by a change from zero to the power supply voltage V. H When the change reaches a certain point, the resonance period T is measured as the second resonance occurs.

[0032] In the following step S15, from equation (3) which shows the resonant period T, L r C r Calculate the product. Then proceed to step S7. L r C r By calculating the product, similar to the first embodiment, the turn-on timing target value T of the main switch S1 can be expressed in equation (2). t It is possible to find this.

[0033] As described above, according to the third embodiment, the detection unit 23 detects the drain-source voltage V of the main switches S1 and S2. ds Upon detecting this, the calculation unit 24 controls the leg 1 to perform soft switching, and the drain-source voltage V ds Based on this, the period T of the resonant operation in Leg 1 is detected, and from that period T, L r C r The product is calculated, and the timing for switching each main switch S1 and S2 is determined based on that product. That is, L r C r By obtaining the product, other power supply voltages V H or load current I load Based on this, it becomes possible to determine the timing for switching the main switches S1 and S2, enabling more precise soft switching control.

[0034] (Fourth Embodiment) The configuration of the fourth embodiment is the same as that of the third embodiment, but the control content is slightly different. As shown in Figure 11, in the fourth embodiment, when processing starts, steps S14 and S15 are executed first, and then steps S1, S7 to S11 are executed. In other words, the measurement of the resonance period T and L r C r The calculation of the product is performed only once at the beginning.

[0035] (Other embodiments) By combining the first embodiment with the third or fourth embodiment, the estimated inductance L r and L r C r From the product, the capacitance C of the resonant capacitor is obtained. r You may ask for it. The number of legs can be two or more, and the same control can be applied to each leg.

[0036] Each switch is not limited to an N-channel MOSFET. This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure. [Explanation of Symbols]

[0037] In the drawing, 1 is a leg, 4 is a DC power supply, 5 is a load, 6 and 7 are current sensors, 11 is a power converter, 12 is a control device, 13 is a detection unit, 14 is a calculation unit, 15 is a memory unit, S1 is a high-potential side main switch, S2 is a low-potential side main switch, A1 and A2 are auxiliary switches, L r This is a resonant inductor, C r This indicates a resonant capacitor.

Claims

1. High-potential side main switch (S １ ) and low-potential side main switch (S ２ ) in series, A resonant capacitor (C) is connected in parallel to the high-potential main switch and the low-potential main switch, respectively. ｒ )and, Two auxiliary switches (A) are two transistors that have a common drain or emitter or source or collector, and one end of each transistor is connected to the common connection point of the high-potential side main switch and the low-potential side main switch, and the other end of each transistor is connected to the common point, thereby constituting a bidirectional switch. １ A ２ ) and resonant inductor (L ｒ A power conversion unit comprising one or more legs (1) having a series circuit of ) A terminal voltage detection unit (23) for detecting the voltage between the conductive terminals of the main switch, The power conversion unit comprises a control unit (24) that controls the switching of each switch constituting the power conversion unit, The control unit controls the leg to perform soft switching, A power converter that detects the period of resonant operation in the leg based on the terminal voltage, calculates the product of the inductance of the resonant inductor and the capacitance of the resonant capacitor from the period, and determines the timing for switching each of the main switches based on the product.

2. The power converter according to claim 1, wherein the control unit performs the calculation of the product only once when the operating power is turned on.

3. High-potential side main switch (S １ ) and low-potential side main switch (S ２ ) in series, A resonance capacitor (C ｒ ) is connected in parallel to each of the high-potential-side main switch and the low-potential-side main switch, Two auxiliary switches (A) are two transistors that have a common drain or emitter or source or collector, and one end of each transistor is connected to the common connection point of the high-potential side main switch and the low-potential side main switch, and the other end of each transistor is connected to the common point, thereby constituting a bidirectional switch. １ A ２ ) and resonant inductor (L ｒ A power conversion unit comprising one or more legs (1) having a series circuit of ) A power supply voltage detection unit (13) detects the DC power supply voltage supplied to this power conversion unit, A current detection unit (7) for detecting the inductor current flowing through the resonant inductor, A memory unit (15) in which the capacitance of the resonant capacitor is stored, The power conversion unit comprises a control unit (14) that controls the switching of each switch constituting the power conversion unit, The control unit controls the leg to perform soft switching, A power converter that estimates the inductance of the resonant inductor based on the power supply voltage and the inductor current, and determines the timing for switching each of the main switches based on the inductance and the capacitance.

4. The power converter according to claim 3, wherein the control unit performs the estimation of the inductance only once when the operating power is turned on.

5. A series circuit of a high-potential side main switch and a low-potential side main switch, A resonant capacitor is connected in parallel to the high-potential main switch and the low-potential main switch, respectively. A power conversion unit having one or more legs comprising two auxiliary switches and a resonant inductor in series, each having one end connected to the common connection point of the high-potential side main switch and the low-potential side main switch, and the other end connected to a common connection point, and the drain or emitter or source or collector common to two transistors that constitute a bidirectional switch, and a resonant inductor, The voltage between the conductive terminals of the main switch is detected, The aforementioned leg is controlled to perform soft switching, A power conversion method that detects the period of resonant operation in the leg based on the terminal voltage, calculates the product of the inductance of the resonant inductor and the capacitance of the resonant capacitor from the period, and determines the timing for switching each of the main switches based on the product.

6. The power conversion method according to claim 5, wherein the calculation of the product is performed only once when the operating power is turned on.

7. A series circuit of a high-potential side main switch and a low-potential side main switch, A resonant capacitor is connected in parallel to the high-potential main switch and the low-potential main switch, respectively. A power conversion unit having one or more legs comprising two auxiliary switches and a resonant inductor in series, each having one end connected to the common connection point of the high-potential side main switch and the low-potential side main switch, and the other end connected to a common connection point, and the drain or emitter or source or collector common to two transistors that constitute a bidirectional switch, and a resonant inductor, The capacitance of the aforementioned resonant capacitor is stored in advance, The DC power supply voltage supplied to the power conversion unit is detected, The inductor current flowing through the aforementioned resonant inductor is detected, The aforementioned leg is controlled to perform soft switching, A power conversion method that estimates the inductance of the resonant inductor based on the power supply voltage and the inductor current, and determines the timing for switching each of the main switches based on the inductance and the capacitance.

8. The power conversion method according to claim 7, wherein the control unit performs the estimation of the inductance only once when the operating power is turned on.

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