DC / DC Converter

Abstract

To provide a DC / DC converter capable of suppressing reduction of power conversion efficiency and increase of switching noise caused by variations of resonance times.SOLUTION: A DC / DC converter comprises: a DC / DC converter circuit; an ARCP circuit 2; a control unit 11A which controls main switches S1 and S2 and switches S3 and S4 for resonance; and a storage unit 12A storing a first formula relating to operation timing in which the main switches S1 and S2 are turned on. The control unit 11A executes: switching processing for calculating a first time from turning on the switches S3 and S4 for resonance to turning on the main switches S1 and S2 based on the first formula and for turning on the main switches S1 and S2 in the end of the first time; and update processing for correcting and updating the first formula so as to decrease a deviation amount between intersection timing, in which a fall of a resonance current IL2 intersects with a reactor current IL1, and the operation timing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a DC / DC converter including an ARCP (Auxiliary Resonant Commutated Pole) circuit.

Background Art

[0002] As a DC / DC converter including an ARCP circuit, for example, a bidirectional DC / DC converter described in Patent Document 1 is known. The bidirectional DC / DC converter described in Patent Document 1 has the same circuit configuration as the bidirectional DC / DC converter 1C shown in FIG. 7.

[0003] The bidirectional DC / DC converter 1C includes a DC / DC converter circuit, an ARCP circuit 2, a control circuit 10C for controlling the DC / DC converter circuit and the ARCP circuit 2, and input / output terminals Ta to Td.

[0004] A bidirectional inverter is connected to the input / output terminals Ta and Tb. A storage battery (for example, a battery of an electric vehicle) is connected to the input / output terminals Tc and Td.

[0005] The DC / DC converter circuit includes main switches S1, S2, a DC reactor L1, and capacitors C1, C2. The main switch S1 includes a switching element Q1 made of a MOSFET and a diode D1 connected in parallel between the drain and source of the switching element Q1. Similarly, the main switch S2 includes a switching element Q2 made of a MOSFET and a diode D2 connected in parallel between the drain and source of the switching element Q2.

[0006] The ARCP circuit 2 includes resonance switches S3 and S4, a regeneration transformer TR1 including a main winding N1 and an auxiliary winding N2, a resonance reactor L2, resonance capacitors C3 and C4, and regeneration diodes D5 and D6. The resonance switch S3 includes a switching element Q3 made of a MOSFET and a diode D3 connected in parallel between the drain and source of the switching element Q3. Similarly, the resonance switch S4 includes a switching element Q4 made of a MOSFET and a diode D4 connected in parallel between the drain and source of the switching element Q4.

[0007] The bidirectional DC / DC converter 1C performs a power conversion operation (boost operation) from the capacitor C2 side to the capacitor C1 side and a power conversion operation (buck operation) from the capacitor C1 side to the capacitor C2 side.

[0008] FIG. 8 shows various waveform diagrams when turning off the switching element Q2 in the boost operation. FIG. 8(A) is a waveform diagram of the gate voltages Vgs of the switching elements Q2 and Q4, FIG. 8(B) is a waveform diagram of the reactor current flowing through the DC reactor L1 and the resonance current flowing through the resonance reactor L2, and FIG. 8(C) is a waveform diagram of the drain current Id and the drain-source voltage Vds of the switching element Q2.

[0009] Time t 11 When the control circuit 10C turns off the switching element Q2 at time t, the current flowing through the switching element Q2 is commutated to the resonance capacitor C4, and the resonance capacitor C4 is charged. While the drain current Id of the switching element Q2 decreases relatively quickly, the drain-source voltage Vds of the switching element Q2 increases gradually, so the overlapping region between the fall of the drain current Id and the rise of the drain-source voltage Vds decreases. As a result, zero voltage switching is achieved at time t 11 ~t 12 and the switching loss at the turn-off of the switching element Q2 is reduced.

[0010] Fig. 9 shows various waveform diagrams when turning on the switching element Q2 in the boosting operation. Fig. 9(A) is a waveform diagram of the gate voltages Vgs of the switching elements Q2 and Q4, Fig. 9(B) is a waveform diagram of the reactor current and the resonance current, and Fig. 9(C) is a waveform diagram of the drain current Id and the drain-source voltage Vds of the switching element Q2.

[0011] At time t 21 when the control circuit 10C turns on the switching element Q4, the current flowing through the diode D1 commutates to the resonance reactor L2, and further the resonance reactor L2 acts to extract charge from the resonance capacitor C4. As a result, the resonance reactor L2, the leakage inductance of the transformer TR1, and the resonance capacitor C4 resonate. Thereby, a resonance current flows through the resonance reactor L2, and the drain-source voltage Vds of the switching element Q2 decreases.

[0012] At time t 22 when the control circuit 10C turns on the switching element Q2 at the intersection timing where the current waveform at the falling edge of the resonance current intersects with the current waveform of the reactor current, since the switching element Q4 is in the on state, the drain-source voltage Vds of the switching element Q2 becomes approximately 0 [V], and the drain current Id of the switching element Q2 rises from 0 [A]. As a result, zero voltage switching and zero current switching are realized, and the switching loss at the turn-on of the switching element Q2 is reduced.

[0013] When the charge extracted from the resonance capacitor C4 flows as a resonance current into the primary winding N1 of the transformer TR1, a voltage is induced in the auxiliary winding N2 of the transformer TR1. The voltage induced in the auxiliary winding N2 is regenerated to the capacitor C1 via the diodes D5 and D6.

[0014] Incidentally, the control circuit 10C stores in advance the operation timing for turning on the switching element Q2. The above operation timing is such that the switching element Q2 turns on at the crossing timing when the falling resonance current and the reactor current cross each other. Using the design values (average values) of the inductance of the resonance reactor L2, the leakage inductance of the transformer TR1, and the capacitance of the resonance capacitor C4, it is calculated by an experiment in which the input voltage and the load conditions are varied.

[0015] However, the inductance of the resonance reactor L2, the leakage inductance of the transformer TR1, and the capacitance of the resonance capacitor C4 vary from the design values. When variations occur from the design values, variations also occur in the time during which the resonance current flows (resonance time), and a deviation occurs between the crossing timing and the operation timing.

[0016] Fig. 10 shows various waveform diagrams when variations occur in the inductance. Fig. 10(A) is common to Fig. 9(A). Fig. 10(B) is obtained by adding the waveforms of the resonance current when the inductance is smaller and larger than the design value to Fig. 9(B). Fig. 10(C) is obtained by adding the waveforms of the drain-source voltage Vds of the switching element Q2 when the inductance is smaller and larger than the design value to Fig. 9(C).

[0017] As shown in Fig. 10, when the inductance is smaller than the design value, the operation timing (time t 22 ) at which the switching element Q2 turns on is later than the crossing timing (time t 221 ) when the falling resonance current and the reactor current cross each other. As a result, after a predetermined time has elapsed since the drain-source voltage Vds of the switching element Q2 has become approximately 0 [V], the drain current Id of the switching element Q2 rises from 0 [A].

[0018] On the other hand, when the inductance is larger than the design value, the operation timing (time t 22) is earlier than the intersection timing (time t 222 ) at which the fall of the resonance current and the reactor current intersect. As a result, before the drain-source voltage Vds of the switching element Q2 becomes almost 0 [V], the drain current Id of the switching element Q2 rises from 0 [A].

[0019] Thus, when a deviation occurs between the intersection timing and the operation timing due to the variation in the resonance time, a deviation also occurs in the timing of the fall of the drain-source voltage Vds of the switching element Q2. As a result, the switching of the switching element Q2 deviates from zero-voltage switching and zero-current switching, leading to a decrease in power conversion efficiency and an increase in switching noise. Further, in the bidirectional DC / DC converter 1C, since the boost operation and the buck operation have the same operating principle, the same problem occurs during the buck operation.

[0020] In order to suppress the variation in the resonance time, it is conceivable to fabricate or select components with reduced variations in the inductance of the resonance reactor L2, the leakage inductance of the transformer TR1, and the capacitances of the resonance capacitors C3 and C4. However, in that case, other problems such as cost increase and reduced yield occur.

Prior Art Documents

Patent Documents

[0021]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0022] The present invention has been made in view of the above circumstances, and an object thereof is to provide a DC / DC converter capable of suppressing a decrease in power conversion efficiency and an increase in switching noise caused by variations in resonance time.

Means for Solving the Problems

[0023] In order to solve the above problems, the DC / DC converter according to the present invention includes: a DC / DC converter circuit including a main switch and a DC reactor; an ARCP circuit including a resonance switch, a resonance reactor, and a resonance capacitor connected in parallel with the current path of the main switch; a control circuit that turns on the resonance switch and turns on the main switch during the on-period of the resonance switch; A DC / DC converter comprising: The control circuit includes: a control unit that controls the switching of the main switch and the resonance switch; a storage unit that stores a first calculation formula regarding the operation timing for turning on the main switch, The control unit: Based on the first calculation formula, calculates a first time from when the resonance switch is turned on until the main switch is turned on, and performs a switching process of turning on the main switch with the end of the first time as the operation timing; An update process of correcting and updating the first calculation formula so that the deviation amount between the intersection timing at which the falling resonance current flowing through the resonance reactor intersects the reactor current flowing through the DC reactor and the operation timing decreases.

[0024] According to this configuration, even when a deviation occurs between the intersection timing and the operation timing due to variations in the resonance time, the deviation amount between the intersection timing and the operation timing can be reduced by executing the update process and correcting the first calculation formula. Therefore, according to this configuration, it is possible to suppress a decrease in power conversion efficiency and an increase in switching noise caused by variations in the resonance time.

[0025] The DC / DC converter further includes: first current measurement means for measuring the reactor current; second current measuring means for measuring the resonance current; and is provided with the control unit can be configured to detect the crossover timing based on the measurement results of the first current measuring means and the second current measuring means.

[0026] the DC / DC converter is provided with voltage measuring means for measuring the voltage across both ends of the current path of the main switch, the control unit can be configured to detect the crossover timing by detecting that the voltage across both ends reaches the minimum value during the on-period of the resonance switch based on the measurement result of the voltage measuring means.

[0027] in the DC / DC converter the first time in the first calculation formula is the first first half time from when the resonance switch is turned on until the first point in time when the rise of the resonance current and the reactor current cross, is the first second half time from the first point in time until the second point in time when the fall of the resonance current and the reactor current cross, and can be configured to include a correction time corrected by the update process according to the deviation amount.

[0028] in the DC / DC converter the storage unit stores a second calculation formula related to a second time from when the main switch is turned on until the resonance switch is turned off, the control unit can be configured to turn off the resonance switch at the end of the second time with reference to the second calculation formula.

Advantages of the Invention

[0029] According to the present invention, it is possible to provide a DC / DC converter capable of suppressing a decrease in power conversion efficiency and an increase in switching noise caused by variations in resonance time.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0031] Hereinafter, with reference to the accompanying drawings, an embodiment of a DC / DC converter according to the present invention will be described by taking a bidirectional DC / DC converter as an example.

[0032] [First Embodiment] Fig. 1 shows a bidirectional DC / DC converter 1A according to the first embodiment. The bidirectional DC / DC converter 1A includes a DC / DC converter circuit, an ARCP circuit 2, a first voltage measuring means 3, a second voltage measuring means 4, a first current measuring means 5, a second current measuring means 6, a control circuit 10A for controlling the DC / DC converter circuit and the ARCP circuit 2, and input / output terminals Ta to Td.

[0033] The bidirectional DC / DC converter 1A performs a power conversion operation (boost operation) from the input / output terminals Tc and Td sides to the input / output terminals Ta and Tb sides, and a power conversion operation (buck operation) from the input / output terminals Ta and Tb sides to the input / output terminals Tc and Td sides. For example, a bidirectional inverter is connected to the input / output terminals Ta and Tb, and for example, a battery of an electric vehicle is connected to the input / output terminals Tc and Td.

[0034] The DC / DC converter circuit includes main switches S1 and S2, a DC reactor L1, and capacitors C1 and C2.

[0035] The main switches S1 and S2 are connected in series with each other. One end of the serially connected current path is connected to the input / output terminal Ta, and the other end is connected to the input / output terminals Tb and Td. The connection point X1 between the main switch S1 and the main switch S2 is connected to the input / output terminal Tc via the DC reactor L1. The capacitor C1 is connected between the input / output terminals Ta and Tb on the input / output terminals Ta and Tb sides with respect to the main switches S1 and S2. The capacitor C2 is connected between the input / output terminals Tc and Td on the input / output terminals Tc and Td sides with respect to the DC reactor L1.

[0036] The main switch S1 includes a switching element Q1 composed of a MOSFET and a diode D1 connected in parallel between the drain and source of the switching element Q1. Similarly, the main switch S2 includes a switching element Q2 composed of a MOSFET and a diode D2 connected in parallel between the drain and source of the switching element Q2. The diode D1 may be a parasitic diode of the switching element Q1 or an individual diode independent of the switching element Q1. The same applies to the diode D2.

[0037] The ARCP circuit 2 includes resonance switches S3, S4, a regeneration transformer TR1 including a main winding N1 and an auxiliary winding N2, a resonance reactor L2, resonance capacitors C3, C4, and regeneration diodes D5, D6.

[0038] The resonance switches S3, S4 are provided between the main switches S1, S2 and the capacitor C1, are connected in series with each other, and are connected in parallel to the main switches S1, S2. The connection point X2 between the resonance switch S3 and the resonance switch S4 is connected to the connection point X1 via the main winding N1 of the transformer TR1 and the resonance reactor L2. The resonance capacitor C3 is connected in parallel between the drain and source of the switching element Q1, and the resonance capacitor C4 is connected in parallel between the drain and source of the switching element Q2. One end and the other end of the auxiliary winding N2 of the transformer TR1 are connected to the input / output terminal Ta via the diodes D5, D6, respectively. The auxiliary winding N2 has a center tap, and the center tap is connected to the input / output terminal Tb. Note that the turn ratio of the main winding N1 to the auxiliary winding N2 is N1:N2 = 1:2 in this embodiment.

[0039] The resonance switch S3 includes a switching element Q3 composed of a MOSFET and a diode D3 connected in parallel between the drain and source of the switching element Q3. Similarly, the resonance switch S4 includes a switching element Q4 composed of a MOSFET and a diode D4 connected in parallel between the drain and source of the switching element Q4. The diode D3 may be a parasitic diode of the switching element Q3 or an individual diode independent of the switching element Q3. The same applies to the diode D4.

[0040] The first voltage measuring means 3 measures the voltage across the capacitor C1, that is, the link voltage V between the input / output terminals Ta and Tb. The second voltage measuring means 4 measures the voltage across the capacitor C2. The first current measuring means 5 is provided between the DC reactor L1 and the input / output terminal Tc and measures the reactor current I L1 flowing through the DC reactor L1. The second current measuring means 6 is provided between the resonance reactor L2 and the connection point X1 and measures the resonance current I L2 flowing through the resonance reactor L2. The first voltage measuring means 3, the second voltage measuring means 4, the first current measuring means 5, and the second current measuring means 6 output the measurement results (sensor signals corresponding to the measured voltage values or current values) to the control circuit 10A.

[0041] The control circuit 10A includes a control unit 11A and a storage unit 12A. The control circuit 10A is constituted by, for example, a microcomputer.

[0042] The storage unit 12A stores a first calculation formula regarding the first timing (corresponding to the "operation timing" of the present invention) at which the control unit 11A turns on the switching elements Q1 and Q2 of the main switches S1 and S2, and a second calculation formula regarding the second timing at which the control unit 11A turns off the switching elements Q3 and Q4 of the resonance switches S3 and S4.

[0043] During the boosting operation, the control unit 11A executes a switching process of turning on the switching element Q2 at a first timing calculated based on a first calculation formula and turning off the switching element Q4 at a second timing calculated based on a second calculation formula. During the bucking operation, the control unit 11A executes a switching process of turning on the switching element Q1 at a first timing calculated based on a first calculation formula and turning off the switching element Q3 at a second timing calculated based on a second calculation formula. Further, the control unit 11A executes an update process of correcting and updating the first calculation formula.

[0044] The storage unit 12A stores a plurality of condition tables regarding the operating conditions for the operation stop of the ARCP circuit 2. The operating conditions include, for example, the operating conditions consisting of the input voltage value, output voltage value, and output current value of the DC / DC converter circuit when stopping the operation of the ARCP circuit 2 during the boosting operation, and the operating conditions consisting of the input voltage value, output voltage value, and output current value of the DC / DC converter circuit when stopping the operation of the ARCP circuit 2 during the bucking operation.

[0045] During the boosting operation, the control unit 11A L2 performs PWM control of the switching element Q2 during a period when the resonance current I L2 is not flowing (for example, the PWM controllable period in FIG. 2: time t4 to t8), and turns on the switching element Q2 at a first timing calculated based on the first calculation formula during a period when the resonance current I

[0046] is flowing (for example, time t3). Similarly, during the bucking operation, the control unit 11A performs PWM control of the switching element Q1 during the PWM controllable period and turns on the switching element Q1 at a first timing calculated based on the first calculation formula during the PWM uncontrollable period. During the boosting operation, the control unit 11A performs PWM control by varying the duty of the switching element Q2 within the PWM controllable period, but it is necessary to increase the off period of the switching element Q2 as the load becomes lighter. When the light load further progresses, the resonance current I L2There is a need to perform PWM control (turn off the switching element Q2) even during the PWM control inoperable period when the current is flowing. In that case, the control unit 11A stops the operation of the ARCP circuit 2 so that the resonance current I L2 does not flow, and makes the PWM control inoperable period into a PWM control operable period.

[0047] Next, the operation mode of the bidirectional DC / DC converter 1A during the boost operation will be described. The operation mode is a repetition of cycles from mode 0 to mode 5. During the buck operation, only the switching elements Q1 and Q3 are switched instead of the switching elements Q2 and Q4, and the cycles from mode 0 to mode 5 are repeated in the same manner as during the boost operation.

[0048] In mode 0, the switching element Q2 is on, and current flows through the path of capacitor C2 → DC reactor L1 → switching element Q2, and energy is stored in the DC reactor L1 (see Fig. 3(A)). When the switching element Q2 turns off, it shifts to mode 1.

[0049] In mode 1, the current flowing through the switching element Q2 transfers to the resonance capacitors C3 and C4, and current paths of capacitor C2 → DC reactor L1 → resonance capacitor C3 and capacitor C2 → DC reactor L1 → resonance capacitor C4 are formed (see Fig. 3(B)). The resonance capacitor C4 is charged and the resonance capacitor C3 is discharged. Due to the charging of the resonance capacitor C4, the drain-source voltage Vds of the switching element Q2 gradually increases, so zero voltage switching is realized.

[0050] In mode 2, since the energy of the DC reactor L1 is released through the path of capacitor C2 → DC reactor L1 → diode D1, current flows through the same path (see Fig. 3(C)). When the switching element Q4 turns on, it shifts to mode 3.

[0051] In Mode 3, the current flowing through diode D1 gradually transfers to resonance reactor L2, forming a current path of capacitor C2 → DC reactor L1 → resonance reactor L2 → primary winding N1 of transformer TR1 → switching element Q4 (see Fig. 4(A)). When all the current flowing through diode D1 transfers to resonance reactor L2, it shifts to Mode 4.

[0052] In Mode 4, since resonance reactor L2 acts to continuously draw charge from resonance capacitors C3 and C4 as it tries to conduct current, resonance reactor L2, the leakage inductance of transformer TR1, and resonance capacitors C3 and C4 resonate (see Fig. 4(B)). As a result, the drain-source voltage Vds of switching element Q2 decreases. When switching element Q2 turns on, it shifts to Mode 5.

[0053] In Mode 5, since switching element Q2 is on, the voltage across resonance reactor L2 is fixed by the voltage at the connection point X3 between resonance reactor L2 and the primary winding N1 of transformer TR1 and ground (GND), and the resonance current I L2 decreases (see Fig. 4(C)). As a result, the current flowing through the path of capacitor C2 → DC reactor L1 → resonance reactor L2 → primary winding N1 of transformer TR1 → switching element Q4 changes to flow through the path of capacitor C2 → DC reactor L1 → switching element Q2, and it shifts to Mode 0.

[0054] Next, the first calculation formula and the second calculation formula stored in the storage unit 12A will be described. The first calculation formula and the second calculation formula include the calculation formulas during boost operation and step-down operation. Since the calculation methods for both are common, the boost operation will be described below.

[0055] The first calculation formula during the boosting operation relates to the first timing for turning on the switching element Q2. Specifically, it relates to the first time T1 (for example, the time t1 to t3 in FIG. 2) from turning on the switching element Q4 to turning on the switching element Q2. The end of the first time T1 is the first timing.

[0056] The second calculation formula during the boosting operation relates to the second timing for turning off the switching element Q4. Specifically, it relates to the second time T2 (for example, the time t3 to t5 in FIG. 2) from turning on the switching element Q2 to turning off the switching element Q4. The end of the second time T2 is the second timing.

[0057] The first time T1 and the second time T2 can be calculated from the operating principle (modes 3 to 5) and theoretical values of the resonance waveform when the switching element Q2 is turned on.

[0058] The equivalent circuit of the bidirectional DC / DC converter 1A in mode 3 is shown in FIG. 5(A). In FIG. 5(A), V X3 is the voltage at the connection point X3 between the resonance reactor L2 and the primary winding N1 of the transformer TR1, and I0 is the current flowing through the diode D1. In the initial state of mode 3, the resonance current I L2 = 0 [A], and I0 = I L1 .

[0059] In mode 3, since the switching element Q4 is on, the voltage across the resonance reactor L2 is V - V X3 . Therefore, the following equations (1) to (3) hold. In equations (1) to (3), L is the inductance of the resonance reactor L2.

Equation

Equation

Equation

[0060] When the period of Mode 3 is T1’ (corresponding to the “first half time” of the present invention), T1’ is the period from the rise of the resonance current I L2 to I L2 =I L1 Thus, T1’ can be expressed by the following formula (4).

Number

Number

Number

[0061] The equivalent circuit of the bidirectional DC / DC converter 1A in Mode 4 is shown in Fig. 5(B). In Mode 4, the following formula (7) holds.

Number

Number

Number

Equation

Equation

Equation

Equation

[0062] V C Since the mode switches when V = 0 [V], if the period of mode 4 is T1’’ (corresponding to the "second half of the first time" in the present invention), T1’’ is the time of half the resonance period. Therefore, the following equations (14) and (15) hold.

Equation

Equation

[0063] Therefore, the first time T1 can be expressed by the following equation (16).

Equation

[0064] In the bidirectional DC / DC converter 1A, the following equation (17), which is equation (16) plus the correction value α (corresponding to the "correction time" in the present invention), is stored in the storage unit 12A as the first calculation formula.

Equation

[0065] The second time T2 may be a period exceeding the period of Mode 5 as shown in FIG. 2. Since the period of Mode 5 is the same as the period of Mode 3, i.e., the first half time T1', the calculation formula for the period of Mode 5 can be calculated in the same manner as formula (6).

[0066] However, the second timing for turning off the switching element Q4 is not particularly limited as long as resonance is completed. Therefore, in the bidirectional DC / DC converter 1A, the second time T2 = β (where β is a constant greater than T1'. For example, β = 2 [μs].), and the constant β is stored in the storage unit 12A as the second calculation formula.

[0067] Next, the control of the control unit 11A during the boost operation will be described.

[0068] The control unit 11A first performs a stop determination process. During the stop determination process, the control unit 11A compares the operating conditions acquired by the first voltage measuring means 3, the second voltage measuring means 4, and the first current measuring means 5 with the operating conditions in the condition table stored in the storage unit 12A, and makes a stop determination as to whether to stop the operation of the ARCP circuit 2.

[0069] If it is determined in the stop determination to stop the operation of the ARCP circuit 2, the control unit 11A stops the operation of the ARCP circuit 2 (by keeping the switching element Q4 in a continuous off state) so that no resonance current flows, and sets the PWM non-control period (the period from time t1 to t4 in FIG. 2) as the PWM control period. The control unit 11A makes a stop determination again after a predetermined time has elapsed.

[0070] If it is determined in the stop determination not to stop the operation of the ARCP circuit 2, the control unit 11A performs a switching process. During the switching process, the control unit 11A calculates the first time T1 based on the first calculation formula (formula (17) in this embodiment) stored in the storage unit 12A, and then turns on the switching element Q4 at a predetermined timing (time t1).

[0071] The control unit 11A turns on the switching element Q2 at the first timing when the first time T1 has elapsed since turning on the switching element Q4 (time t3). The control unit 11A stores the measured values (at least the measured values of the first current measuring means 5 and the second current measuring means 6) when the switching element Q2 is turned on.

[0072] The control unit 11A refers to the second calculation formula (= the second time T2 = constant β) stored in the storage unit 12A, and turns off the switching element Q4 at the second timing when the second time T2 has elapsed since turning on the switching element Q2 (time t5). Thereafter, the control unit 11A turns off the switching element Q2 according to the duty of the PWM control (time t6).

[0073] The control unit 11A performs an update process in parallel with the switching process. During the update process, the control unit 11A calculates the first timing calculated from the first calculation formula stored in the storage unit 12A and the actual resonance current I calculated from the measured values of the first current measuring means 5 and the second current measuring means 6 L2 of the falling edge and the reactor current I L1 and compares it with the intersection timing at which they cross.

[0074] For example, the control unit 11A compares the current value of the reactor current I L1 at the turn-on of the switching element Q2 (time t3) with the current value of the resonance current I L2 . As a result of the comparison, if the two match, the control unit 11A ends the update process without updating the first calculation formula stored in the storage unit 12A. If the two do not match, the control unit 11A corrects the correction value α of the first time T1 to increase or decrease so that the deviation amount between the first timing and the intersection timing decreases, updates the first calculation formula, and ends the update process.

[0075] After the update process ends, the control unit 11A performs a stop determination again after a predetermined time has elapsed. In this way, during the boosting operation, the control unit 11A repeatedly performs a series of controls including a stop determination process, a switching process, and an update process. Note that the control unit 11A during the bucking operation also performs similar controls.

[0076] The bidirectional DC / DC converter 1A according to the first embodiment does not adopt a real-time control method of turning on the switching element Q2 (switching element Q1 during the bucking operation) at the timing when the current value of the reactor current I L1 acquired by the first current measuring means 5 matches the current value of the resonance current I L2 acquired by the second current measuring means 6, but adopts a method of turning on the switching element Q2 (switching element Q1 during the bucking operation) at the first timing calculated from the first calculation formula. Therefore, the bidirectional DC / DC converter 1A can avoid the delay in control due to the real-time control method.

[0077] Also, in the bidirectional DC / DC converter 1A, even when a deviation occurs between the first timing calculated from the first calculation formula and the actual crossing timing due to variations in the resonance time, the control unit 11A executes an update process to correct the first calculation formula, thereby reducing the deviation amount between the first timing and the crossing timing. Therefore, according to the bidirectional DC / DC converter 1A, it is possible to suppress a decrease in power conversion efficiency and an increase in switching noise caused by variations in the resonance time.

[0078] [Second Embodiment] FIG. 6 shows a bidirectional DC / DC converter 1B according to the second embodiment. The bidirectional DC / DC converter 1B is different from the first embodiment in that it includes a third voltage measuring means 7 and a fourth voltage measuring means 8 instead of the second current measuring means 6, and includes a control circuit 10B instead of the control circuit 10A, and is common to the first embodiment in other points.

[0079] The third voltage measurement means 7 measures the voltage across the resonance capacitor C3, in other words, the drain-source voltage of the switching element Q1. The fourth voltage measurement means 8 measures the voltage across the resonance capacitor C4, in other words, the drain-source voltage of the switching element Q2. The third voltage measurement means 7 and the fourth voltage measurement means 8 output the measurement results (sensor signals corresponding to the measured voltage values) to the control circuit 10B.

[0080] The control circuit 10B includes a control unit 11B and a storage unit 12B. The control circuit 10B is configured by, for example, a microcomputer. The storage unit 12B has the same configuration as the storage unit 12A of the first embodiment.

[0081] The control unit 11B has the same configuration as the control unit 11A of the first embodiment, except that the measurement results of the third voltage measurement means 7 and the fourth voltage measurement means 8 are used instead of the measurement result of the second current measurement means 6.

[0082] The control unit 11B is the current waveform at the falling edge of the resonance current I L2 and the current waveform of the reactor current I L1 The intersection timing at which the two intersect is specified by detecting that the voltage value measured by the fourth voltage measurement means 8 has reached the minimum value (for example, 0 [V] or a value near 0 [V]) during the boost operation, and during the buck operation, by detecting that the voltage value measured by the third voltage measurement means 7 has reached the minimum value (for example, 0 [V] or a value near 0 [V]).

[0083] In the update process, the control unit 11B compares the first timing calculated from the first calculation formula stored in the storage unit 12B with the actual intersection timing at which the drain-source voltage of the switching element Q2 (switching element Q1 during the buck operation) becomes the minimum value calculated from the measurement value of the fourth voltage measurement means 8 (third voltage measurement means 7 during the buck operation).

[0084] For example, when the control unit 11B turns on the switching element Q2 (or switching element Q1 during step-down operation), it compares the voltage value measured by the fourth voltage measuring means 8 (or third voltage measuring means 7 during step-down operation) with the above minimum value. As a result of the comparison, if the voltage value is the above minimum value, the control unit 11B ends the update process without updating the first calculation formula stored in the storage unit 12B. If the voltage value is different from the above minimum value, the control unit 11B corrects the correction value α of the first time T1 so that the deviation amount between the first timing and the cross timing decreases, updates the first calculation formula, and ends the update process.

[0085] According to the bidirectional DC / DC converter 1B according to the second embodiment, the same effects as those of the first embodiment can be obtained.

[0086] [Modification Example] As described above, embodiments of the DC / DC converter according to the present invention have been described, but the present invention is not limited to the above embodiments.

[0087] The DC / DC converter according to the present invention includes a DC / DC converter circuit including a main switch and a DC reactor, an ARCP circuit including a resonant switch, a resonant reactor, and a resonant capacitor connected in parallel to the current path of the main switch, and a control circuit that turns on the resonant switch and turns on the main switch during the on period of the resonant switch. If the control circuit includes a control unit that controls the switching of the main switch and the resonant switch, and a storage unit that stores a first calculation formula regarding the operation timing for turning on the main switch, the configuration can be changed as appropriate.

[0088] Based on the first calculation formula, the control unit of the present invention calculates the first time from when the resonance switch is turned on until the main switch is turned on, and performs a switching process of turning on the main switch with the end of the first time as the operation timing. If an update process of correcting and updating the first calculation formula is performed so that the deviation amount between the intersection timing at which the falling resonance current flowing through the resonance reactor and the reactor current flowing through the DC reactor intersect and the operation timing decreases, the configuration can be changed as appropriate.

[0089] The first calculation formula can be appropriately changed as long as it includes the first first-half time from when the resonance switch is turned on until the first point in time at which the rising resonance current and the reactor current intersect, the first second-half time from the first point in time until the second point in time at which the falling resonance current and the reactor current intersect, and the correction time corrected in the update process. For example, an equation calculated by further transforming the equation (17) in the above embodiment may be stored as the first calculation formula. Note that the rising of the resonance current is a waveform in the direction in which the resonance current moves away from 0, and the falling of the resonance current is a waveform in the direction in which the resonance current approaches 0.

[0090] Similarly, the second calculation formula can be appropriately changed. For example, an equation including a variable such as the first first-half time T1' may be used without using the constant β.

[0091] In the above embodiment, the bidirectional DC / DC converters 1A and 1B that perform bidirectional power conversion operations (boost operation and buck operation) have been described. However, the present invention is also applicable to a DC / DC converter that performs unidirectional power conversion.

[0092] As the switching element of the main switch and / or the resonance switch, a switching element other than a MOSFET (for example, an IGBT) can be used.

Explanation of Reference Numerals

[0093] 1A, 1B Bidirectional DC / DC converter 2 ARCP circuit 3 First voltage measurement means 4 Second voltage measurement means 5 First current measurement means 6 Second current measurement means 7 Third voltage measurement means 8 Fourth voltage measurement means 10A, 10B Control circuit 11A, 11B Control unit 12A, 12B Memory unit

Claims

1. A DC / DC converter circuit including a main switch and a DC reactor, an ARCP circuit including a resonant switch, a resonant reactor, and a resonant capacitor connected in parallel to the current path of the main switch, a control circuit for turning on the resonant switch and turning on the main switch during the on-period of the resonant switch, first current measuring means for measuring the reactor current flowing through the DC reactor, second current measuring means for measuring the resonant current flowing through the resonant reactor, A DC / DC converter comprising: The control circuit includes: a control unit for controlling the switching of the main switch and the resonant switch; a storage unit storing a first calculation formula regarding the operation timing for turning on the main switch, The control unit: Based on the first calculation formula, calculates a first time from when the resonant switch is turned on until the main switch is turned on, and performs a switching process of turning on the main switch with the end of the first time as the operation timing; Performs an update process of correcting and updating the first calculation formula so that the deviation amount between the intersection timing at which the falling edge of the resonant current intersects the reactor current and the operation timing decreases; During the switching process, the control unit: Stores the first measured value of the first current measuring means and the second measured value of the second current measuring means when the main switch is turned on; During the update process, the control unit: Compares the first measured value and the second measured value, and if they do not match, corrects the first calculation formula so that the deviation amount between the intersection timing calculated from the measured values of the first current measuring means and the second current measuring means and the operation timing calculated from the first calculation formula decreases. A DC / DC converter characterized by the above.

2. The first time of the first calculation formula is: A first first-half time from when the resonant switch is turned on until a first point in time when the rising edge of the resonant current intersects the reactor current; A first second-half time from the first point in time until a second point in time when the falling edge of the resonant current intersects the reactor current; Including a correction time corrected by the update process according to the deviation amount. The DC / DC converter according to claim 1, characterized by the above.

3. The memory unit stores a second calculation formula regarding a second time period from when the main switch is turned on until the resonance switch is turned off. The control unit refers to the second calculation formula and turns off the resonance switch at the end of the second time period. The DC / DC converter according to claim 1 or 2, characterized in that.

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