JP7487883B2 - DCDC conversion circuit, and control device and control method thereof - Google Patents

Description

This disclosure relates to a DCDC conversion circuit, as well as a control device and control method thereof.

Patent Document 1 discloses a power conversion device that converts three-phase AC power to DC power. As shown in Patent Document 1, a power conversion device (AC-DC converter) equipped with a rectifier circuit and a DCDC conversion circuit is usually used to extract DC power from a three-phase AC power source. A DAB (Dual Active Bridge) circuit is known as a configuration of a DCDC conversion circuit. A DAB circuit is configured by connecting a bridge circuit to each of the two windings that make up a transformer.

JP 2012-222999 A

To increase efficiency and reduce noise in DAB circuits, it is important to prevent the occurrence of hard switching. Hard switching is the switching of switching elements during the period when voltage and current overlap. Hard switching causes surges in the voltage and current, which in turn generates high-frequency noise.

It is known that soft switching (zero current switching or zero voltage switching), which switches when the current or voltage is zero, can be expected to improve efficiency and reduce noise. A known method of controlling a DAB circuit is to set the duty ratio of the voltage applied to the transformer from the bridge on the primary side (input side) to 50% positive and negative, and the duty ratio of the voltage applied to the transformer from the bridge on the secondary side (output side) to 50% positive and negative, and to shift the timing of switching between positive and negative voltages applied from each bridge to the transformer (to create a phase difference). However, this switching method has a problem in that the difference between the secondary side voltage converted to the primary side by the transformer turns ratio and the primary side voltage is large, and zero voltage switching cannot be performed if the output current is small.

The objective of this disclosure is to provide a DCDC conversion circuit that can achieve zero voltage switching even when the difference between the secondary side voltage converted to the primary side and the primary side voltage is large and the output current is small, as well as a control device and control method thereof.

According to one aspect of the present invention, a control device for a DC-DC conversion circuit includes a first bridge circuit having a first leg in which two arm elements are connected in series, a second leg in which two arm elements are connected in series, a second bridge circuit having a third leg in which two arm elements are connected in series, and a fourth leg in which two arm elements are connected in series, a first winding connected to the first bridge circuit, and a second winding magnetically coupled to the first winding and connected to the second bridge circuit. The control device for a DC-DC conversion circuit includes an acquisition unit that acquires voltage values of the terminal voltage of the first bridge circuit and the terminal voltage of the second bridge circuit based on the voltage values, a determination unit that determines the phase shift amounts of the first leg, the second leg, the third leg, and the fourth leg based on the zero cross timing of the current flowing through the first winding, and a switching control unit that switches the first leg, the second leg, the third leg, and the fourth leg based on the determined phase shift amount.

According to the above aspect, the control device of the DCDC conversion circuit can control the control device with four degrees of freedom corresponding to each leg by determining the amount of phase shift based on the zero crossing timing. This allows the control device of the DCDC conversion circuit to determine switching timing that can achieve zero voltage switching even when the difference between the secondary side voltage converted to the primary side and the primary side voltage is large and the output current is small.

1 illustrates a DCDC conversion circuit according to a first embodiment. FIG. 2 is a schematic block diagram showing a software configuration of a control device. 4 is a time chart showing the switching timing of each arm and the changes in instantaneous voltage of the bridge circuit and instantaneous current of the transformer circuit. FIG. 4 is a diagram showing an operating range in which zero voltage switching is possible in the first mode according to the first embodiment. FIG. 11 is a diagram showing an operating range in which zero voltage switching is possible in the second mode according to the first embodiment. 4 is a flowchart showing an operation of the control device according to the first embodiment. FIG. 1 is a schematic block diagram illustrating a configuration of a computer according to at least one embodiment.

First Embodiment
<<Configuration of DCDC conversion circuit>>
Hereinafter, the embodiments will be described in detail with reference to the drawings.
FIG. 1 shows a DCDC conversion circuit according to the first embodiment.
The DCDC conversion circuit 1 according to the first embodiment is a dual active bridge (DAB) circuit having an input terminal pair and an output terminal pair. The DCDC conversion circuit 1 controls switching of each leg constituting a bridge circuit under the control of a control device 20.

The DCDC conversion circuit 1 includes a primary bridge circuit 11, a transformer circuit 12, a secondary bridge circuit 13, and a control device 20. The transformer circuit 12 has a primary winding W1 and a secondary winding W2 that are electromagnetically coupled.

The primary bridge circuit 11 is a bridge circuit that is composed of two legs, i.e., a first leg L1 and a second leg L2. The first leg L1 is composed of arm elements A11 and A12 that are connected in series. The second leg L2 is composed of arm elements A21 and A22 that are connected in series.
Arm element A is an element in which a diode and a switch are connected in parallel. When the switch is off (OFF, open), arm element A passes current only in the direction of the diode. On the other hand, when the switch is on (ON, closed), arm element A passes current in both directions. Hereinafter, of the pair of terminals of arm element A, the terminal on the anode side of the diode will be referred to as the anode, and the terminal on the cathode side of the diode will be referred to as the cathode.

The anode of the arm element A11 is connected to a first terminal (a terminal shown on the upper side of the paper in FIG. 1) of the primary winding W1 and to a cathode of the arm element A12.
The cathode of the arm element A11 is connected to the positive terminal on the input side of the DCDC conversion circuit 1 and the cathode of the arm element A21.
The anode of the arm element A12 is connected to the negative terminal on the input side of the DCDC conversion circuit 1 and the anode of the arm element A22.
The cathode of the arm element A12 is connected to a first terminal of the primary winding W1 and to the anode of the arm element A11.

The anode of the arm element A21 is connected to a second terminal (a terminal shown on the lower side of the paper in FIG. 1) of the primary winding W1 and to a cathode of the arm element A22.
The cathode of the arm element A21 is connected to the positive terminal on the input side of the DCDC conversion circuit 1 and the cathode of the arm element A11.
The anode of the arm element A22 is connected to the negative terminal on the input side of the DCDC conversion circuit 1 and the anode of the arm element A12.
The cathode of the arm element A22 is connected to the second terminal of the primary winding W1 and the anode of the arm element A21.

The secondary bridge circuit 13 is a bridge circuit consisting of two legs, namely the third leg L3 and the fourth leg L4. The third leg L3 consists of arm elements A31 and A32 connected in series. The fourth leg L4 consists of arm elements A41 and A42 connected in series.

The anode of the arm element A31 is connected to a first terminal (a terminal shown on the upper side of the paper in FIG. 1) of the secondary winding W2 and to a cathode of the arm element A32.
The cathode of the arm element A31 is connected to the positive terminal on the output side of the DCDC conversion circuit 1 and the cathode of the arm element A41.
The anode of the arm element A32 is connected to the negative terminal on the output side of the DCDC conversion circuit 1 and the anode of the arm element A42.
The cathode of the arm element A32 is connected to a first terminal of the secondary winding W2 and to the anode of the arm element A31.

The anode of the arm element A41 is connected to a second terminal (a terminal shown on the lower side of the paper in FIG. 1) of the secondary winding W2 and to a cathode of the arm element A42.
The cathode of the arm element A41 is connected to the positive terminal on the output side of the DCDC conversion circuit 1 and the cathode of the arm element A31.
The anode of the arm element A42 is connected to the negative terminal on the output side of the DCDC conversion circuit 1 and the anode of the arm element A32.
The cathode of the arm element A42 is connected to the second terminal of the secondary winding W2 and the anode of the arm element A41.

Configuration of the control device
The control device 20 according to the first embodiment controls the switching of each arm element A of the DCDC conversion circuit 1 so that the DCDC conversion circuit 1 performs soft switching. The control device 20 is realized by, for example, a microcomputer. The control device 20 includes a first voltmeter 21 that measures the terminal voltage of the primary bridge circuit 11 and a second voltmeter 22 that measures the terminal voltage of the secondary bridge circuit 13.

FIG. 2 is a schematic block diagram showing the software configuration of the control device 20. As shown in FIG.
The control device 20 includes an acquisition unit 201 , a mode determination unit 202 , a first calculation unit 203 , a second calculation unit 204 , a timer 205 , and a switching control unit 206 .

The acquisition unit 201 acquires the measurement signals of the first voltmeter 21 and the second voltmeter 22.

The mode determination unit 202 determines the switching mode based on the input current value of the primary bridge circuit 11. The switching mode has a first mode that is executed when the input current value of the primary bridge circuit 11 is equal to or greater than a threshold, and a second mode that is executed when the input current value of the primary bridge circuit 11 is less than the threshold. The input current value of the primary bridge circuit is obtained by dividing the product of the measured output voltage and the set value of the output current by the measured input voltage.

The first calculation unit 203 calculates the switching timing for the first mode based on the measurement signal of the first voltmeter 21 and the measurement signal of the second voltmeter 22 acquired by the acquisition unit 201. The first mode is a switching mode in which the pulse of the voltage applied to the primary winding W1 is maximized in order to increase the transmission power. Therefore, when the first leg L1 switches from ON to OFF, the second leg L2 switches from OFF to ON. Also, when the first leg L1 switches from OFF to ON, the second leg L2 switches from ON to OFF. That is, in the first mode, the switching timings of the first leg L1 and the second leg L2 match. In the first mode, it can be said that the switching timing of the first leg L1 and the switching timing of the second leg L2 are shifted by 180 degrees. A method of calculating the switching timing for the first mode will be described later.

The second calculation unit 204 calculates the switching timing for the second mode based on the measurement signal of the first voltmeter 21 and the measurement signal of the second voltmeter 22 acquired by the acquisition unit 201. The second mode is a switching mode that minimizes the time from the switching timing of the second leg L2 to the zero crossing timing and the time from the zero crossing timing to the switching timing of the third leg L3 while maintaining soft switching in order to reduce reactive power. The method of calculating the switching timing for the second mode will be described later.

The timer 205 measures the elapsed time from a timing related to a predetermined switching period _Tsw . The switching control unit 206 performs switching at a switching timing described below based on the elapsed time measured by the timer 205, so that the time measured by the timer 205 coincides with the elapsed time from the zero crossing timing at which the current value of the primary winding W1 switches from negative to positive.

The switching control unit 206 controls the switching of the first leg L1, the second leg L2, the third leg L3, and the fourth leg L4 according to the switching timing determined by the first calculation unit 203 or the second calculation unit 204 based on the elapsed time from the zero cross timing measured by the timer 205. The two arm elements A constituting each leg are controlled to be driven with a duty ratio of 50%.

<<Behavior of DCDC conversion circuit 1>>
3 is a time chart showing the switching timing of each arm A, and changes in the instantaneous voltage of the bridge circuit and the instantaneous current of the transformer circuit. Hereinafter, the state of the DCDC conversion circuit 1 at each timing will be described with reference to FIG.
The control device 20 according to the first embodiment controls the switching timing of each leg L based on the zero cross timing of the primary winding W1. Hereinafter, as shown in FIG. 3, the time from the switching timing of the first leg L1 to the zero cross timing of the primary winding W1 is referred to as a phase shift amount _T1 . Also, the time from the switching timing of the second leg L2 to the zero cross timing of the primary winding W1 is referred to as a phase shift amount _T2 . The time from the zero cross timing of the primary winding W1 to the switching timing of the third leg L3 is referred to as a phase shift amount _T3 . The time from the zero cross timing of the primary winding W1 to the switching timing of the fourth leg L4 is referred to as a phase shift amount _T4 . The control device 20 switches ON/OFF of each leg L every time half of a predetermined switching period _Tsw has elapsed. Therefore, the time between the zero cross timings of the current flowing through the primary winding W1 is also half of the switching period _Tsw .

At time _t0 , arm A11 is ON, arm A12 is OFF, arm A21 is OFF, arm A22 is ON, arm A31 is OFF, arm A32 is ON, arm A41 is ON, and arm A42 is OFF. Also, the instantaneous _I0 of the primary winding W1 at time _t0 is zero. That is, time _t0 is the zero-cross timing.
At this time, the primary side of the DCDC conversion circuit 1 forms a circuit that passes through the arm A11, the primary winding W1, and the arm A22. The secondary side of the DCDC conversion circuit 1 forms a circuit that passes through the arm A41, the secondary winding W2, and the arm A32. As a result, a current flows from the first terminal to the second terminal of the primary winding W1, and the instantaneous voltage of the primary winding W1 becomes _E1 . The secondary side of the DCDC conversion circuit 1 forms a circuit that passes through the arm element A32, the secondary winding W2, and the arm element A41. Therefore, the voltage _E2 of the external power storage device connected to the DCDC output terminal is applied to the secondary winding W2, and the instantaneous voltage of the secondary winding W2 becomes _-E2 .

At time _t1 , arm A31 switches from OFF to ON, and arm A32 switches from ON to OFF. That is, time _t1 is the switching timing of the third leg L3. In other words, the time from time _t0 , which is the zero crossing timing, to the switching timing _t1 of the third leg L3 is equal to the phase shift amount _T3 of the third leg L3.
By switching the third leg L3, the secondary side of the DCDC conversion circuit 1 is short-circuited, and the instantaneous voltage of the secondary winding W2 becomes zero.
Since the voltage applied to the leakage inductance converted to the primary side during the period from time _t0 to time _t1 is _E1 + _E2 ', the current _I1 flowing through the primary winding W1 at time _t1 is expressed by the following formula (1). Note that _E2 ' represents the instantaneous voltage of the secondary winding W2 converted to the primary side by the transformer turns ratio. Note that in formula (1), L represents inductance.

At time _t2 , arm A41 switches from ON to OFF, and arm A42 switches from OFF to ON. That is, time _t2 is the switching timing of the fourth leg L4. That is, the time from time _t0 , which is the zero-cross timing, to the switching timing _t2 of the fourth leg L4 is equal to the phase shift amount _T4 of the fourth leg L4.
By switching the fourth leg L4, the secondary side of the DCDC conversion circuit 1 forms a circuit passing through the arm A31, the secondary winding W2, and the arm A42. As a result, the output voltage of the secondary bridge circuit 13 becomes _E2 .
Since the voltage applied to the leakage inductance converted to the primary side during the period from time _t1 to time _t2 is _E1 , the current _I2 flowing through the primary winding W1 at time _t2 is expressed by the following equation (2).

At time _t3 , arm A11 switches from ON to OFF, and arm A12 switches from OFF to ON. That is, time _t3 is the switching timing of the first leg L1. Since the next zero crossing timing is the time when _Tsw /2 has elapsed since time _t0 , the time from time _t0 to the switching timing _t3 of the first leg L1 is equal to the time obtained by subtracting the phase shift amount _T1 of the first leg L1 from half the switching period _Tsw .
By switching the first leg L1, the primary side of the DCDC conversion circuit 1 is short-circuited, and the instantaneous voltage of the primary winding W1 becomes zero.
Since the voltage applied to the leakage inductance converted to the primary side during the period from time _t2 to time _t3 is _E1 - _E2 ', the current _I3 flowing through the primary winding W1 at time _t3 is expressed by the following equation (3).

At time _t4 , arm A21 switches from OFF to ON, and arm A22 switches from ON to OFF. That is, time _t4 is the switching timing of the second leg L2. Therefore, the time from time _t0 to the switching timing _t4 of the second leg L2 is equal to the time obtained by subtracting the phase shift amount _T2 of the second leg L2 from half the switching period _Tsw .
By switching the second leg L2, a circuit passing through the arm A21, the secondary winding W2, and the arm A12 is formed on the primary side of the DCDC conversion circuit 1. As a result, the input voltage of the primary bridge circuit 11 becomes _−E1 .
Since the voltage applied to the leakage inductance converted to the primary side during the period from time _t3 to time _t4 is _-E2 ', the current _I4 flowing through the primary winding W1 at time _t3 is expressed by the following equation (4).

In order for the current in the primary winding W1 to reach a periodic steady state in which positive and negative currents repeat symmetrically in a switching period _Tsw , the instantaneous current in the primary winding W1 must become zero at time _t5 , which is half the switching period after time _t0 .
Since the voltage applied to the leakage inductance converted to the primary side during the period from time _t4 to time _t5 is -( _E1 + _E2 '), the current _I5 flowing through the primary winding W1 at time _t5 is expressed by the following equation (5).

When the phase shift amounts _{T1 -T4} are all positive numbers, the inductor current becomes negative when the voltage of the primary bridge circuit 11 rises, and the inductor current becomes positive when the voltage of the secondary bridge circuit 13 rises, enabling zero voltage switching. Calculating backwards from the fact that the current _I5 is zero, the currents _I4 and _I3 can be expressed as the following equations (6) and (7).

Here, the charge taken in from the power supply connected to the primary side of the DCDC conversion circuit 1 will be calculated.
The charge _Q1 taken from the power supply during the period from time _t0 to time _t1 is expressed by equation (8). The charge _Q2 taken from the power supply during the period from time _t1 to time _t2 is expressed by equation (9). The charge _Q3 taken from the power supply during the period from time _t2 to time _t3 is expressed by equation (10). The charge _Q4 taken from the power supply during the period from time _t3 to time _t4 is expressed by equation (11). The charge _Q5 taken from the power supply during the period from time _t4 to time _t5 is expressed by equation (12).

Here, the energy _W1 taken in from the power source connected to the primary side of the DCDC conversion circuit 1 during a half cycle is expressed by equation (13), and the energy _W2 supplied to the load connected to the secondary side of the DCDC conversion circuit 1 is expressed by equation (14). From these relationships, equation (15) can be obtained.

Calculation of the first mode
Based on the above relational expressions, the switching timing of the DCDC conversion circuit 1 in the first mode by the first calculation unit 203 of the control device 20 will be described.
In the first mode, the duty ratio of the voltage applied from the primary side to the transformer circuit 12 is maintained at 50% for both positive and negative, while the zero-cross timing of the current passing through the primary winding W1 is adjusted by the duty ratio on the secondary side so as to enable zero voltage switching. That is, in the first mode, the phase shift amount _T1 of the first leg L1 and the phase shift amount _T2 of the second leg L2 are equal. In the first mode, the phase shift amount _T1 of the first leg L1 and the phase shift amount _T2 of the second leg L2 are determined by the following equation (16).

In addition, T _δ1 in the formula (16) is shown in the formula (17).

Moreover, the phase shift amount _T3 of the third leg L3 and the phase shift amount _T4 of the fourth leg L4 are determined by the following equations (18) and (19), respectively.

The transmission power _P1 in the first mode is given by equation (20).

In addition, T _δ0 in the formula (20) is shown in the formula (21).

From equation (20), the average value of the input current of the DCDC conversion circuit 1 in the first mode is expressed by equation (22).

FIG. 4 is a diagram showing an operating range in which zero voltage switching is possible in the first mode according to the first embodiment.
From equation (22), the maximum value I1 _(max) and minimum value I1 _(min) of the input current in the operating range in which zero voltage switching is possible in the first mode are expressed by equations (23) and (24), respectively.

That is, the minimum value _I1(min) of the input current in the operating range where zero voltage switching in the first mode is possible is maximum when the primary side voltage _E1 is half the value _E2 ' obtained by converting the secondary side voltage into the primary side. The minimum value I1 _(min) of the input current at this time is equal to half the maximum value I1 _(max) of the input current.

Calculation of the second mode
Next, the switching timing of the DCDC conversion circuit 1 in the second mode by the second calculation unit 204 of the control device 20 will be described.
In the second mode, in order to realize zero current switching in a small current region, the duty ratios of the primary and secondary sides are controlled so that the circulation period of the current flowing through the primary winding W1 is extended. In the second mode, the phase shift amount T1 of the first leg L1 _, the phase shift amount _T2 of the second leg L2, the phase shift amount _T3 of the third leg L3, and the phase shift amount _T4 of the fourth leg L4 are determined by the following equations (25) to (28), respectively.

Here, the sum of the phase shift amount _T2 and the phase shift amount _T4 is equal to half the switching period _Tsw , so that in the second mode, the second leg L2 and the fourth leg L4 are switched simultaneously.
In addition, T _δ2 in the formulas (25) to (28) is shown in the formula (29).

In addition, T _min in equation (29) is a parameter that determines the minimum pulse width under no load, and has the relationship shown in equation (30).

Note that T3 _(min) in formula (30) is the minimum value of _T3 . _T3 has the relationship shown in formula (31) and is set in consideration of the variations in the turn-off delay time of the gate circuit and MOSFET.

The transmission power _P2 in the second mode is given by equation (32).

From equation (32), the average value _I2 of the input current of the DCDC conversion circuit 1 in the second mode is expressed by equation (33).

FIG. 5 is a diagram showing an operating range in which zero voltage switching is possible in the second mode according to the first embodiment.
From equation (33), the maximum value I2 _(max) of the input current in the operating range in which zero voltage switching is possible in the second mode is expressed by equation (34).

4, the maximum value I1 _(min) of the lower limit of the input current in the operating range where zero voltage switching is possible in the first mode is equal to the upper limit I2 _(max) of the input current in the operating range where zero voltage switching is possible in the second mode shown in equation (34). That is, the control device 20 can realize zero voltage switching without omission in the operating range shown in the following equation (35) by switching between the first mode and the second mode using, for example, the current value _I2(max) shown in equation (34) as a threshold value.

<<Control method of the control device 20>>
FIG. 6 is a flowchart showing the operation of the control device 20 according to the first embodiment.
When the control device 20 starts controlling the DCDC conversion circuit 1, the control device 20 starts the process shown in Fig. 6 for each predetermined switching period _Tsw . The control device 20 specifies the processing timing based on a clock signal that is driven with a switching period _Tsw , for example. Note that the processing timing and the zero cross timing are matched by executing the process shown in Fig. 6 for each processing timing.

The acquisition unit 201 acquires measurement signals from the first voltmeter 21 and the second voltmeter 22 (step S1). The timer 205 starts measuring the elapsed time from the timing related to the switching period _Tsw (step S2). The mode determination unit 202 determines whether the current value of the current flowing through the primary winding W1 is equal to or greater than the threshold value _I2(max) shown in equation (33) based on the primary input current value calculated from the measurement signals of the first voltmeter 21 and the second voltmeter 22 acquired in step S1 (step S3).

If the input current value on the primary side is equal to or greater than the threshold value I2 _(max) (step S3: YES), the first calculation unit 203 calculates the phase shift amounts T1-T4 of each leg related to the first mode using the above-mentioned equations (16) to (19) based on the measurement signals of the first voltmeter 21 and the second voltmeter ₂₂ acquired by the acquisition unit ₂₀₁ (step S4).
On the other hand, if the input current value on the primary side is less than the threshold value _I2(max) (step S3: NO), the second calculation unit 204 calculates the phase shift amounts T1-T4 of each leg related to the second mode based on the measurement signals of the first voltmeter 21 and the second voltmeter 22 acquired by the acquisition unit 201 using the above-mentioned equations ( ₂₅ ) to ( ₂₈ ) (step S5).
It is assumed that the setting values of the switching period _Tsw and the output current are set in advance in the control device 20.

The switching control section 206 switches the third leg L3 when the elapsed time measured by the timer 205 reaches the phase shift amount _T3 calculated in step S4 or S5 (step S6).
Next, when the elapsed time measured by the timer 205 reaches the phase shift amount _T4 calculated in step S4 or S5, the switching control unit 206 switches the fourth leg L4 (step S7).

Next, the switching control unit 206 switches the first leg L1 when the elapsed time measured by the timer 205 becomes the difference between half the switching period _Tsw and the phase shift amount _T1 calculated in step S4 or S5 (step S8).
Next, the switching control unit 206 switches the second leg L2 when the elapsed time measured by the timer 205 becomes the difference between half the switching period _Tsw and the phase shift amount _T2 calculated in step S4 or S5 (step S9).

The control device 20 then ends the process and waits for the next processing timing.

<Action and Effects>
In this way, the control device 20 according to the first embodiment determines the phase shift amounts T1-T4 of the first leg L1, the second leg L2, the third leg L3, and the fourth leg L4 _, respectively, based on the zero-cross timing of the current flowing through the primary winding _W1 , and switches each leg based on the switching period _Tsw and the determined phase shift amounts. In this way, by setting the four phase shift amounts as variables based on the zero-cross timing, it is possible to satisfy the periodicity of the waveform and the adjustment of the output current, while leaving two degrees of freedom. As a result, the control device 20 can easily identify the switching timing at which zero voltage switching can be realized by using the remaining two degrees of freedom.

The control device 20 according to the first embodiment determines the amount of phase shift so that the first leg L1 and the second leg L2 switch simultaneously in the first mode. This allows the control device 20 to maximize the effective value of the primary side voltage and expand the operating range in which zero voltage switching is possible for the low input voltage and high input current regions.

The control device 20 according to the first embodiment determines the amount of phase shift so that the second leg L2 and the fourth leg L4 switch simultaneously in the second mode. This allows the control device 20 to lengthen the circulating period of the current flowing through the primary winding W1, and to expand the operating range in which zero voltage switching is possible in the region where the input current is small.

Moreover, the control device 20 according to the first embodiment calculates the phase shift amount in the first mode when the current value of the current flowing through the primary winding W1 is equal to or greater than the threshold value I2 _(max) , and calculates the phase shift amount in the second mode when the current value is less than the threshold value _I2(max) . This allows the control device 20 to realize zero voltage switching in the entire range covered by the first mode and the second mode.

Other Embodiments
Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes are possible. That is, in other embodiments, the order of the above-mentioned processes may be changed as appropriate. Also, some of the processes may be executed in parallel.

Furthermore, the control device 20 according to another embodiment may calculate the phase shift amounts _T1 to _T4 by a calculation method other than the above-described first and second modes. In this case as well, by calculating the phase shift amounts of the first leg L1, the second leg L2, the third leg L3, and the fourth leg L4 based on the zero-cross timing of the current flowing through the primary winding W1, it is possible to ensure a sufficient degree of freedom for determining the switching timing at which zero voltage switching can be realized.

In addition, in the above-described embodiment, the control device 20 switches the calculation method of the phase shift amount based on the current value of the current flowing through the primary winding W1, but this is not limited to this. For example, when the DCDC conversion circuit 1 according to another embodiment is not used beyond the operating range in which zero voltage switching in the first mode is possible, the control device 20 may always calculate the phase shift amount in the first mode regardless of the current value of the current flowing through the primary winding W1. Similarly, for example, when the DCDC conversion circuit 1 according to another embodiment is not used beyond the operating range in which zero voltage switching in the second mode is possible, the control device 20 may always calculate the phase shift amount in the second mode regardless of the current value of the current flowing through the primary winding W1.

Computer Configuration
FIG. 7 is a schematic block diagram illustrating a computer configuration according to at least one embodiment.
The computer 90 comprises a processor 91 , a main memory 92 , a storage 93 , and an interface 94 .
The above-mentioned control device 20 is implemented in a computer 90. The operations of each of the above-mentioned processing units are stored in the form of a program in a storage 93. The processor 91 reads the program from the storage 93, loads it in the main memory 92, and executes the above-mentioned processing in accordance with the program. The processor 91 also secures storage areas in the main memory 92 corresponding to each of the above-mentioned storage units in accordance with the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor.

The program may be for implementing some of the functions to be performed by the computer 90. For example, the program may be implemented by combining it with other programs already stored in the storage or with other programs implemented in other devices. In other embodiments, the computer 90 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor 91 may be implemented by the integrated circuit. Such an integrated circuit is also included as an example of a processor.

Examples of storage 93 include optical disks, magnetic disks, magneto-optical disks, and semiconductor memories. Storage 93 may be internal media directly connected to the bus of computer 90, or external media connected to computer 90 via interface 94 or a communication line. In addition, when this program is distributed to computer 90 via a communication line, computer 90 that receives the program may expand the program into main memory 92 and execute the above-mentioned processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium.

The program may be for realizing part of the above-mentioned functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-mentioned functions in combination with another program already stored in storage 93.

1...DC-DC conversion circuit 11...Primary bridge circuit L1...First leg L2...Second leg 12...Transformer circuit W1...Primary winding W2...Secondary winding 13...Secondary bridge circuit L3...Third leg L4...Fourth leg 20...Control device 21...Voltmeter 22...Voltmeter 201...Acquisition unit 202...Mode determination unit 203...First calculation unit 204...Second calculation unit 205...Timer 206...Switching control unit

Claims (6)

a first bridge circuit having a first leg in which two arm elements are connected in series and a second leg in which two arm elements are connected in series;
a second bridge circuit having a third leg in which two arm elements are connected in series and a fourth leg in which two arm elements are connected in series;
a first winding connected to the first bridge circuit;
a second winding magnetically coupled to the first winding and connected to the second bridge circuit;
A control device for a DC-DC conversion circuit comprising:
a voltage measurement unit that measures a voltage value of a terminal voltage of a first bridge circuit and a terminal voltage of the second bridge circuit;
a determination unit that determines phase shift amounts of the first leg, the second leg, the third leg, and the fourth leg based on a zero cross timing of a current flowing through the first winding, based on the measured voltage value; and
and a switching control unit that switches the first leg, the second leg, the third leg, and the fourth leg based on the determined phase shift amount. The determination unit is
determining the phase shift amount such that the first leg and the second leg are switched simultaneously;
A control device for a DCDC conversion circuit according to claim 1. The determination unit is
The control device for a DCDC conversion circuit according to claim 1 or 2, wherein the amount of phase shift is determined so that the second leg and the fourth leg are switched simultaneously. The determination unit is
determining the phase shift amount such that the first leg and the second leg are switched simultaneously when a current value of an input current to the first bridge circuit is equal to or greater than a threshold;
The control device for a DCDC conversion circuit according to claim 1 , further comprising: determining the amount of phase shift such that the second leg and the fourth leg are switched simultaneously when the current value is less than the threshold value. a first bridge circuit having a first leg in which two arm elements are connected in series and a second leg in which two arm elements are connected in series;
a second bridge circuit having a third leg in which two arm elements are connected in series and a fourth leg in which two arm elements are connected in series;
a first winding connected to the first bridge circuit;
a second winding magnetically coupled to the first winding and connected to the second bridge circuit;
A control device for a DCDC conversion circuit according to any one of claims 1 to 4;
A DCDC conversion circuit comprising: a first bridge circuit having a first leg in which two arm elements are connected in series and a second leg in which two arm elements are connected in series;
a second bridge circuit having a third leg in which two arm elements are connected in series and a fourth leg in which two arm elements are connected in series;
a first winding connected to the first bridge circuit;
a second winding magnetically coupled to the first winding and connected to the second bridge circuit;
A control method for a DC-DC conversion circuit comprising:
acquiring a voltage value of a terminal voltage of a first bridge circuit and a terminal voltage of the second bridge circuit;
determining, based on the measured voltage value, phase shift amounts of the first leg, the second leg, the third leg, and the fourth leg relative to a zero cross timing of a current flowing through the first winding;
switching the first leg, the second leg, the third leg, and the fourth leg based on the determined phase shift amount.

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