WO2025027944A1 - Power conversion device and control method - Google Patents

Abstract

A power conversion device (1) comprises: a resonator (30); a primary-side full-bridge circuit (10) having a first switch (Q1), a second switch (Q2), a third switch (Q3) and a fourth switch (Q4); a secondary-side full-bridge circuit (20) having a fifth switch (Q5), a sixth switch (Q6), a seventh switch (Q7) and an eighth switch (Q8); and a controller (40). The controller (40) operates the fifth switch (Q5), the sixth switch (Q6), the seventh switch (Q7) and the eighth switch (Q8) in synchronisation with control signals for the first switch (Q1), the second switch (Q2), the third switch (Q3) and the fourth switch (Q4) by means of drive signals for durations that are the result of subtracting a resonance period of the resonator (30) from the switching periods of the first switch (Q1), the second switch (Q2), the third switch (Q3) and the fourth switch (Q4), and controls the on times of the drive signals using the lengths of the durations as an upper limit.

Description

Power conversion device and control method

This disclosure relates to a power conversion device capable of unidirectional or bidirectional power conversion and a method for controlling the power conversion device.

Toward the realization of a carbon-neutral society, there is a demand for charging circuits that can charge home storage batteries or automotive batteries with high efficiency. Such charging circuits require isolated DC-DC converters, and resonant converters are commonly used to reduce size and improve efficiency. Among resonant converters, LLC converters, which can achieve high efficiency with a simple circuit configuration, are attracting particular attention.

LLC converters generally use frequency control to control the output power. The loads to which power is supplied from LLC converters range from light loads to heavy loads, and to accommodate these the frequency control range is wide, making it necessary to take measures appropriate for all operating conditions (for example, EMC (ElectroMagnetic Compatibility) measures).

In response to this, Patent Document 1 describes an LLC type DCDC converter that controls output power by making the transformer current have an asymmetric positive and negative waveform through duty control.

JP 2022-17179 A

However, in the DC-DC converter disclosed in Patent Document 1, the transformer current has an asymmetric waveform between positive and negative, which can cause problems such as worsening common-mode noise.

The present disclosure provides a power conversion device that can effectively control output power while suppressing the frequency control range width.

The power conversion device according to the present disclosure is a power conversion device capable of unidirectional or bidirectional power conversion, and includes a resonator having a transformer and a resonant capacitor, a primary-side full bridge circuit connected to the primary side of the resonator, a secondary-side full bridge circuit connected to the secondary side of the resonator, and a controller for controlling the primary-side full bridge circuit and the secondary-side full bridge circuit, the primary-side full bridge circuit having a first switch element provided on the high side of a first leg, a second switch element provided on the low side of the first leg, a third switch element provided on the high side of the second leg, and a fourth switch element provided on the low side of the second leg, and the secondary-side full bridge circuit having a fifth switch element provided on the high side of the third leg. The controller calculates a period obtained by subtracting the resonance period of the resonator from the switching periods of the first switch element, the second switch element, the third switch element, and the fourth switch element, and operates the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element in synchronization with the control signals for the first switch element, the second switch element, the third switch element, and the fourth switch element by a drive signal during the period, and controls the on-time of the drive signal with the length of the period as an upper limit.

The control method according to the present disclosure is a control method for a power conversion device capable of unidirectional or bidirectional power conversion, the power conversion device including a resonator having a transformer and a resonant capacitor, a primary-side full bridge circuit connected to the primary side of the resonator, and a secondary-side full bridge circuit connected to the secondary side of the resonator, the primary-side full bridge circuit having a first switch element provided on the high side of a first leg, a second switch element provided on the low side of the first leg, a third switch element provided on the high side of the second leg, and a fourth switch element provided on the low side of the second leg, the secondary-side full bridge circuit having a fifth switch element provided on the high side of a third leg, and a fifth switch element provided on the low side of the third leg. The control method includes a sixth switch element provided on the low side of the fourth leg, a seventh switch element provided on the high side of the fourth leg, and an eighth switch element provided on the low side of the fourth leg, and the control method calculates a period obtained by subtracting the resonance period of the resonator from the switching periods of the first switch element, the second switch element, the third switch element, and the fourth switch element, and operates the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element in synchronization with the control signal for the first switch element, the second switch element, the third switch element, and the fourth switch element by a drive signal during the period, and controls the on-time of the drive signal with the length of the period as an upper limit.

These comprehensive or specific aspects may be realized as a system, method, integrated circuit, computer program, or computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, method, integrated circuit, computer program, and recording medium.

The power conversion device according to one embodiment of the present disclosure can effectively control the output power while suppressing the frequency control range width.

1 is a circuit configuration diagram illustrating an example of a power conversion device according to an embodiment. FIG. 4 is a diagram for explaining the operation of a controller according to the embodiment. FIG. 4 is a diagram for explaining an example of operation in a first mode of the controller according to the embodiment. 11A and 11B are diagrams for explaining the effect of the operation of the controller in the first mode according to the embodiment. FIG. 11 is a diagram for explaining an example of operation in a second mode of the controller according to the embodiment. 11A and 11B are diagrams for explaining an example of an operation in a phase shift control mode of a controller according to an embodiment. 11 is a diagram for explaining an example of operation in an intermittent operation mode of a controller according to an embodiment. FIG. 13 is a flowchart illustrating an example of a control method according to another embodiment.

The following describes the embodiment in detail with reference to the drawings.

The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

(Embodiment)
Hereinafter, a power conversion device according to an embodiment will be described.

FIG. 1 is a circuit diagram showing an example of a power conversion device 1 according to an embodiment.

The power conversion device 1 is a power conversion device capable of unidirectional or bidirectional power conversion, and is, for example, an isolated DC-DC converter that steps up or steps down an input voltage to a predetermined voltage and outputs it. For example, the power conversion device 1 is an LLC converter. An LLC converter is a circuit that utilizes LLC resonance caused by a transformer's leakage inductance, excitation inductance, and a resonance capacitor. In an LLC converter, the input/output voltage ratio (Gain) changes by changing the switching frequency, making it possible to output the desired power. However, the following describes a power conversion device 1 that can control the output power without frequency control.

The power conversion device 1 has terminals t1, t2, t3, and t4. Terminal t1 is an input terminal. Terminal t2 is a ground terminal. Terminal t3 is an output terminal. Terminal t4 is a ground terminal. Note that, since the power conversion device 1 is an isolated DCDC converter, terminals t2 and t4 are electrically isolated.

The power conversion device 1 includes a primary side full bridge circuit 10, a secondary side full bridge circuit 20, a resonator 30, capacitors Cin and Cout, and a controller 40. Note that the capacitors Cin and Cout do not have to be components of the power conversion device 1.

Capacitor Cin is an input capacitor connected between terminals t1 and t2, and capacitor Cout is an output capacitor (smoothing capacitor) connected between terminals t3 and t4.

The primary side full bridge circuit 10 is connected to the primary side of the resonator 30. The primary side full bridge circuit 10 has a first switch element provided on the high side of the first leg, a second switch element provided on the low side of the first leg, a third switch element provided on the high side of the second leg, and a fourth switch element provided on the low side of the second leg.

The primary side full bridge circuit 10 has switches Q1, Q2, Q3, and Q4, where switch Q1 is an example of a first switch element, switch Q2 is an example of a second switch element, switch Q3 is an example of a third switch element, and switch Q4 is an example of a fourth switch element.

The switch Q1 is, for example, an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The drain of the switch Q1 is connected to the terminal t1, and the source of the switch Q1 is connected to the drain of the switch Q2.

Switch Q2 is, for example, an N-channel MOSFET. The drain of switch Q2 is connected to the source of switch Q1, and the source of switch Q2 is connected to terminal t2.

Switch Q3 is, for example, an N-channel MOSFET. The drain of switch Q3 is connected to terminal t1, and the source of switch Q3 is connected to the drain of switch Q4.

Switch Q4 is, for example, an N-channel MOSFET. The drain of switch Q4 is connected to the source of switch Q3, and the source of switch Q4 is connected to terminal t2.

The secondary full bridge circuit 20 is connected to the secondary side of the resonator 30. The secondary full bridge circuit 20 has a fifth switch element provided on the high side of the third leg, a sixth switch element provided on the low side of the third leg, a seventh switch element provided on the high side of the fourth leg, and an eighth switch element provided on the low side of the fourth leg. The secondary full bridge circuit 20 also functions as a rectifier circuit capable of full-wave rectification.

The secondary side full bridge circuit 20 has switches Q5, Q6, Q7 and Q8, where switch Q5 is an example of a fifth switch element, switch Q6 is an example of a sixth switch element, switch Q7 is an example of a seventh switch element, and switch Q8 is an example of an eighth switch element.

Switch Q5 is, for example, an N-channel MOSFET. The drain of switch Q5 is connected to terminal t3, and the source of switch Q5 is connected to the drain of switch Q6.

Switch Q6 is, for example, an N-channel MOSFET. The drain of switch Q6 is connected to the source of switch Q5, and the source of switch Q6 is connected to terminal t4.

Switch Q7 is, for example, an N-channel MOSFET. The drain of switch Q7 is connected to terminal t3, and the source of switch Q7 is connected to the drain of switch Q8.

Switch Q8 is, for example, an N-channel MOSFET. The drain of switch Q8 is connected to the source of switch Q7, and the source of switch Q8 is connected to terminal t4.

The resonator 30 has a transformer T and a capacitor Cr.

Capacitor Cr is an example of a resonant capacitor. Capacitor Cr is connected to the node between switch Q1 and switch Q2 in the first leg.

The transformer T is an isolated transformer and has a primary winding and a secondary winding that are insulated from each other. One end of the primary winding of the transformer T is connected to a node between the switches Q1 and Q2 in the first leg via a capacitor Cr, and the other end of the primary winding of the transformer T is connected to a node between the switches Q3 and Q4 in the second leg. One end of the secondary winding of the transformer T is connected to a node between the switches Q5 and Q6 in the third leg, and the other end of the secondary winding of the transformer T is connected to a node between the switches Q7 and Q8 in the fourth leg.

In addition, the capacitor Cr may be connected to a node between the switches Q3 and Q4 in the second leg. In this case, one end of the primary winding of the transformer T is connected to a node between the switches Q1 and Q2 in the first leg, and the other end of the primary winding of the transformer T is connected to a node between the switches Q3 and Q4 in the second leg via the capacitor Cr.

The controller 40 controls the primary side full bridge circuit 10 and the secondary side full bridge circuit 20. Specifically, the controller 40 is a circuit for controlling the switching (on and off) of the switches (e.g., switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8) included in the power conversion device 1. For example, the controller 40 controls the switching of the switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 by controlling a gate drive circuit (not shown) connected to the gates of the switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 via a PWM generator (not shown) or the like.

The controller 40 is, for example, a computer including a processor (microprocessor) and a memory. The memory may be a ROM (Read Only Memory) or a RAM (Random Access Memory), and can store programs executed by the processor. For example, the controller 40 is a microcontroller.

The controller 40 calculates a period obtained by subtracting the resonance period of the resonator 30 (the period of resonance due to the capacitance of the capacitor Cr and the leakage inductance of the transformer T, etc.) from the switching period of the switches Q1, Q2, Q3, and Q4, and operates the switches Q5, Q6, Q7, and Q8 in synchronization with the control signals for the switches Q1, Q2, Q3, and Q4 using the drive signal during that period. The controller 40 also controls the on-time of the drive signal with the length of the above-mentioned period as the upper limit.

The operation of the controller 40 will now be described in detail with reference to FIG. 2.

FIG. 2 is a diagram for explaining the operation of the controller 40 according to the embodiment.

As shown in FIG. 2, for example, the controller 40 controls the switching of the switches Q1 and Q4 in the same phase, and controls the switching of the switches Q2 and Q3 in the same phase. The controller 40 controls the switches Q1, Q2, Q3, and Q4 so that the phase difference between the switching of the switches Q1 and Q4 and the switching of the switches Q2 and Q3 is 180 degrees. As a result, the control signals for the switches Q1, Q2, Q3, and Q4 become, for example, those shown in FIG. 2. Specifically, the switches Q1 and Q4 are repeatedly turned on and off with a duty ratio of 50%, the switches Q2 and Q3 are repeatedly turned on and off with a duty ratio of 50%, and when the switches Q1 and Q4 are in the on state, the switches Q2 and Q3 are in the off state, and when the switches Q2 and Q3 are in the on state, the switches Q1 and Q4 are in the off state.

When the controller 40 turns on the switches Q1 and Q4 and turns off the switches Q2 and Q3, or turns on the switches Q2 and Q3 and turns off the switches Q1 and Q4, a current (primary side current) flows through the primary winding of the transformer T. The primary side current resonates with the resonance period of the resonator 30. Furthermore, when a current flows through the primary winding of the transformer T, a current (secondary side current) flows through the secondary winding of the transformer T. The secondary side current also resonates with the resonance period of the resonator 30. As a result, the primary side current and secondary side current become as shown in FIG. 2.

The controller 40 calculates the period obtained by subtracting the resonance period of the resonator 30 (for example, the resonance half period shown in FIG. 2) from the switching period of the switches Q1, Q2, Q3, and Q4 (for example, the switching half period shown in FIG. 2, which is the period during which the switches are on at a duty ratio of 50%). This period is the period during which no current is passed through the load connected to the terminals t3 and t4, and is also called the no-current period.

The controller 40 operates the switches Q5, Q6, Q7, and Q8 in synchronization with the control signals for the switches Q1, Q2, Q3, and Q4 by the drive signals during the non-energized period. At this time, the controller 40 performs pulse width control for the ON period of the switches Q5, Q6, Q7, and Q8, as shown in FIG. 2. As shown in FIG. 2, it can be seen that the control signals for the switches Q1, Q2, Q3, and Q4 and the drive signals for the switches Q5, Q6, Q7, and Q8 are synchronized. Note that the control signal and drive signal being synchronized means that there is a certain relationship between the ON timing of the control signal and the ON timing of the drive signal, and in this specification, the control signal and drive signal being synchronized means that the drive signal is turned on a certain period after the control signal is turned on.

The controller 40 has a first mode and a second mode as control modes for switching the switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8. First, the first mode will be described.

FIG. 3 is a diagram for explaining an example of operation of the controller 40 in the first mode according to the embodiment. From the top, FIG. 3 shows a timing chart of the gate signals of the switches Q1, Q4, Q5, and Q8, the gate signals of the switches Q2, Q3, Q6, and Q7, the voltage generated in the secondary winding of the transformer T (transformer secondary voltage), the current flowing in the primary winding of the transformer T (transformer primary current), the excitation current of the transformer T (transformer excitation current) and the voltage input to the primary winding of the transformer T (transformer input voltage), and the excitation voltage of the transformer T (transformer excitation voltage). The same applies to FIG. 5, which will be described later.

As shown in FIG. 3, in the first mode, the controller 40 turns on the switches Q5 and Q8 before the switches Q1 and Q4 are turned off from their on state in response to the drive signal. Also, in the first mode, the controller 40 turns on the switches Q6 and Q7 before the switches Q2 and Q3 are turned off from their on state in response to the drive signal. The non-energized period is the period before the switches Q1 and Q4 are turned off from their on state (the period that exists in the latter half of the period that the switches Q1 and Q4 are on) and the period before the switches Q2 and Q3 are turned off from their on state (the period that exists in the latter half of the period that the switches Q2 and Q3 are on).

The upper limit of the length of the period before switches Q1 and Q4 change from an on state to an off state, and the period before switches Q2 and Q3 change from an on state to an off state, is the length of the no-current period. In other words, the end of the period before switches Q1 and Q4 change from an on state to an off state is the timing when switches Q1 and Q4 turn off, and the start of this period is a period up to the length of the no-current period before switches Q1 and Q4 turn off. Also, the end of the period before switches Q2 and Q3 change from an on state to an off state is the timing when switches Q2 and Q3 turn off, and the start of this period is a period up to the length of the no-current period before switches Q2 and Q3 turn off. For this reason, the controller 40 controls the on time of the drive signal with the length of the no-current period as the upper limit.

The power conversion device 1, which is an LLC converter, is a circuit that can obtain a gain of 1 or more (i.e., increase the output power) by setting the switching frequency to a frequency lower than the resonant frequency of the resonator 30 (the resonant frequency due to the capacitance of the capacitor Cr and the leakage inductance of the transformer T, etc.). Here, setting the switching frequency to a frequency lower than the resonant frequency of the resonator 30 is equivalent to the phase of the resonant current leading the phase of the input voltage (transformer input voltage) of the resonator 30. In other words, the output power can be increased by leading the phase of the resonant current with respect to the phase of the transformer input voltage. In the first mode, the controller 40 controls the switching of the switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 with the switching frequency fixed so that the phase of the resonant current leads the phase of the input voltage of the resonant circuit. Here, the operation of the controller 40 in the first mode will be described in detail.

As shown in part A of FIG. 3, the controller 40 turns on the switches Q6 and Q7 during the non-energized period, which is the period before the switches Q2 and Q3 are turned off from their on state.

As a result, the polarity of the transformer secondary voltage is reversed, as shown in part B of Figure 3. It can be seen that the timing of polarity reversal is earlier than the conventional transformer secondary voltage shown by the dashed line (specifically, the transformer secondary voltage when switches Q6 and Q7 are not controlled during the non-energized period).

As shown in part C of Figure 3, when the polarity of the transformer secondary voltage is reversed, the polarity of the transformer excitation voltage is also reversed in response to the reversal of the polarity of the transformer secondary voltage.

As shown in part D of Figure 3, because the polarity of the transformer excitation voltage is reversed at an earlier timing than before, the transformer excitation current reaches an extreme value at an earlier timing than before. Specifically, because the phase of the polarity reversal of the transformer excitation voltage advances, the phase of the transformer excitation current advances. Because the resonant current is superimposed on the transformer excitation current, if the phase of the transformer excitation current advances, the phase of the resonant current also advances. Therefore, the phase of the resonant current advances relative to the phase of the transformer input voltage, and the output power can be increased. Note that by further extending the on-time of switches Q6 and Q7 during the non-energized period, the phase of the resonant current advances further, and the output power can be further increased.

FIG. 4 is a diagram for explaining the effect of operation of the controller 40 in the first mode according to the embodiment. The horizontal axis of the graph shown in FIG. 4 is the on time of the switches Q5, Q6, Q7, and Q8 during the non-energized period, and the vertical axis is the output current. There is a correlation between the output current and the output power, and as the output current increases, the output power also increases.

As shown in FIG. 4, the longer the on time of switches Q5, Q6, Q7, and Q8 during the non-energized period, the larger the output current, i.e., the output power. Specifically, it can be seen that the power conversion device 1 has a power adjustment function capable of handling a light load of about 1 A to a heavy load of about 15 A. For example, when the output voltage is 250 V, the output power can be adjusted from 250 W to 3.7 kW.

In this way, in the first mode, the output power can be increased while keeping the switching frequency fixed.

Next, the second mode of the controller 40 will be explained.

FIG. 5 is a diagram illustrating an example of the operation of the controller 40 in the second mode according to the embodiment.

As shown in FIG. 5, in the second mode, the controller 40, in response to the drive signal, turns on the switches Q6 and Q7 before the switches Q1 and Q4 are changed from an on state to an off state. Also, in the second mode, the controller 40, in response to the drive signal, turns on the switches Q5 and Q8 before the switches Q2 and Q3 are changed from an on state to an off state.

The power conversion device 1, which is an LLC converter, is a circuit that can obtain a gain smaller than 1 (i.e., reduce the output power) by setting the switching frequency higher than the resonant frequency of the resonator 30. Here, setting the switching frequency to a frequency higher than the resonant frequency of the resonator 30 is equivalent to delaying the phase of the resonant current relative to the phase of the input voltage (transformer input voltage) of the resonator 30. In other words, the output power can be reduced by delaying the phase of the resonant current relative to the phase of the transformer input voltage. In the second mode, the controller 40 controls the switching of the switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 with the switching frequency fixed so that the phase of the resonant current lags the phase of the input voltage of the resonant circuit. Here, the operation of the controller 40 in the second mode will be described in detail.

As shown in part A of FIG. 5, the controller 40 turns on the switches Q6 and Q7 during the non-energized period, which is the period before the switches Q1 and Q4 are turned off from their on state.

As a result, the polarity of the transformer secondary voltage is reversed, as shown in part B of Figure 5. It can be seen that the timing of polarity reversal is delayed compared to the conventional transformer secondary voltage shown by the dashed line (specifically, the transformer secondary voltage when switches Q6 and Q7 are not controlled during the non-energized period).

As shown in part C of Figure 5, when the polarity of the transformer secondary voltage is reversed, the polarity of the transformer excitation voltage is also reversed in response to the reversal of the polarity of the transformer secondary voltage.

As shown in part D of Figure 5, the polarity of the transformer excitation voltage is reversed at a later timing than before, so the transformer excitation current takes an extreme value at a later timing than before. Specifically, the phase of the polarity reversal of the transformer excitation voltage is delayed, so the phase of the transformer excitation current is delayed. Since the resonant current is superimposed on the transformer excitation current, when the phase of the transformer excitation current is delayed, the phase of the resonant current is also delayed. Therefore, the phase of the resonant current is delayed relative to the phase of the transformer input voltage, so the output power can be reduced. Note that by further extending the on-time of switches Q6 and Q7 during the non-energized period, the phase of the resonant current is further delayed, and the output power can be further reduced.

Although illustrations for explaining the effect of the operation of the controller 40 in the second mode according to the embodiment are omitted, the longer the on time of the switches Q5, Q6, Q7, and Q8 during the non-energized period, the smaller the output current, i.e., the output power.

In this way, in the second mode, the output power can be reduced while keeping the switching frequency fixed.

Note that there are cases where the output power of the power conversion device 1 cannot be reduced to the target power simply by delaying the phase of polarity reversal of the transformer excitation voltage through operation of the controller 40 in the second mode. Therefore, the controller 40 may further have at least one of a phase shift control mode that controls the phase between the switching of the switches Q1 and Q2 and the switching of the switches Q3 and Q4, and an intermittent operation mode that intermittently controls the switching of the switches Q1, Q2, Q3 and Q4. First, the phase shift control mode will be described.

FIG. 6 is a diagram for explaining an example of operation of the controller 40 according to the embodiment in the phase shift control mode. From the top, FIG. 6 shows a timing chart of the gate signals of the switches Q1 and Q4, the gate signals of the switches Q2 and Q3, the voltage generated in the secondary winding of the transformer T (transformer secondary voltage), the current flowing in the primary winding of the transformer T (transformer primary current), the excitation current of the transformer T (transformer excitation current) and the voltage input to the primary winding of the transformer T (transformer input voltage), and the excitation voltage of the transformer T (transformer excitation voltage).

As shown in FIG. 6, in the phase shift control mode, the controller 40 controls the switching of the switches Q1, Q2, Q3, and Q4 so as to delay the switching phase of the switches Q3 and Q4 relative to the switching phase of the switches Q1 and Q2. Note that in the phase shift control mode, the controller 40 does not input signals to the gates of the switches Q5, Q6, Q7, and Q8, the switches Q5, Q6, Q7, and Q8 are in the off state, and the secondary full bridge circuit 20 functions as a full wave rectifier circuit using the body diodes of the switches Q5, Q6, Q7, and Q8.

As a result, the waveform of the transformer input voltage (in other words, the output voltage of the primary side full bridge circuit 10) is not a square wave, but rather includes a period in which the phase shift causes switch Q1 to be on and switch Q4 to be off, resulting in 0 V, and a period in which the phase shift causes switch Q2 to be on and switch Q3 to be off, resulting in 0 V. Therefore, the period in which the transformer excitation voltage is applied is shortened, making it possible to reduce the gain (output power).

Next, we will explain the intermittent operation mode.

FIG. 7 is a diagram for explaining an example of operation of the controller 40 in the intermittent operation mode according to the embodiment. From the top, FIG. 7 shows a timing chart of the gate signals of the switches Q1 and Q4, the gate signals of the switches Q2 and Q3, and the output current of the power conversion device 1.

As shown in FIG. 7, in the intermittent operation mode, the controller 40 intermittently controls the switching of the switches Q1, Q2, Q3, and Q4. Specifically, the controller 40 controls the switches Q1, Q2, Q3, and Q4 to repeatedly turn on and off in a first period, and then controls the switches Q1, Q2, Q3, and Q4 to the off state in the following second period, repeating the control in the first period and the control in the second period. As a result, the output current waveform becomes an intermittent waveform that is output in the first period and not output in the second period. In the intermittent operation mode, the average current (average power) can be reduced in the long term.

As explained above, the period obtained by subtracting the resonance period of resonator 30 from the switching period of switches Q1, Q2, Q3, and Q4 is a non-energized period during which no current is passed through the load. During the non-energized period, by turning on switches Q5, Q6, Q7, and Q8 for a certain period, the timing at which the polarity of the voltage generated in the secondary winding of transformer T (transformer secondary voltage) is reversed can be adjusted. When the polarity of the transformer secondary voltage is reversed, the polarity of the excitation voltage of transformer T is also reversed in accordance with the reversal of the polarity of the transformer secondary voltage. In other words, the timing at which the polarity of the excitation voltage of transformer T is reversed (in other words, the phase of polarity reversal of the excitation voltage of transformer T) can be adjusted.

For example, when the phase of polarity inversion of the excitation voltage of the transformer T is advanced, the phase of the excitation current of the transformer T is advanced. Since the resonant current is superimposed on the excitation current, if the phase of the excitation current is advanced, the phase of the resonance current is also advanced, and the output power of the power conversion device 1 can be increased. For example, when the phase of polarity inversion of the excitation voltage of the transformer T is delayed, the phase of the excitation current of the transformer T is delayed. Since the resonant current is superimposed on the excitation current, if the phase of the excitation current is delayed, the phase of the resonance current is also delayed, and the output power of the power conversion device 1 can be reduced. Therefore, by controlling the on-time of the drive signal for the switches Q5, Q6, Q7, and Q8 during the non-energized period, the output power can be controlled without frequency control, and the output power can be effectively controlled while suppressing the frequency control range width. In addition, in the DC-DC converter described in Patent Document 1, the transformer current has an asymmetric waveform in the positive and negative directions, which causes effects such as deterioration of common mode noise, but in the power conversion device 1, the transformer current has a symmetric waveform in the positive and negative directions, so noise performance is less likely to deteriorate.

For example, by being able to suppress the frequency control range width, it becomes possible to miniaturize the transformer T, improve efficiency, and miniaturize the EMC filter. Specifically, since it is not necessary to operate the power conversion device 1 at a low switching frequency, it becomes possible to miniaturize the transformer T. Also, since it is not necessary to operate the power conversion device 1 at a high switching frequency, AC resistance loss is reduced and efficiency can be improved. Also, since the frequency control range width is narrow or a fixed value, EMC measures can be taken with a narrow-band EMC filter, and the EMC filter can be miniaturized.

The power conversion device 1 is capable of bidirectional power conversion, and terminal t3 can be the input terminal and terminal t1 can be the output terminal. In this case, the control performed on switches Q1, Q2, Q3, and Q4 in the above explanation is performed on switches Q5, Q6, Q7, and Q8, and the control performed on switches Q5, Q6, Q7, and Q8 in the above explanation is performed on switches Q1, Q2, Q3, and Q4. In this case, capacitor Cout becomes the input capacitor, and capacitor Cin becomes the output capacitor.

Other Embodiments
As described above, the embodiment has been described as an example of the technology according to the present disclosure. However, the technology according to the present disclosure is not limited to this, and can be applied to an embodiment in which appropriate changes, substitutions, additions, omissions, etc. are made. For example, the following modified examples are also included in one embodiment of the present disclosure.

For example, in the above embodiment, an example was described in which the power conversion device was an LLC converter, but this is not limiting. For example, the power conversion device may be a resonant converter including a resonator configured with LC in series and parallel, such as an LCC converter or a CLLC converter.

For example, in the above embodiment, an example of an LLC converter consisting of a transformer's excitation inductance, leakage inductance, and a resonant capacitor was described, but instead of the leakage inductance, a separate inductor equivalent to the leakage inductance may be provided.

For example, the controller 40 may further have a frequency control mode that controls the switching frequency, and may adjust the output power by controlling the switching frequency.

For example, the present disclosure can be realized not only as a power conversion device, but also as a control method for controlling the power conversion device (specifically, a control method including steps (processing) performed by components constituting the power conversion device (specifically, controller 40)).

FIG. 8 is a flowchart showing an example of a control method according to another embodiment.

For example, the control method is a control method for a power conversion device capable of unidirectional or bidirectional power conversion, the power conversion device including a resonator having a transformer and a resonance capacitor, a primary-side full bridge circuit connected to the primary side of the resonator, and a secondary-side full bridge circuit connected to the secondary side of the resonator, the primary-side full bridge circuit having a first switch element provided on the high side of the first leg, a second switch element provided on the low side of the first leg, a third switch element provided on the high side of the second leg, and a fourth switch element provided on the low side of the second leg, the secondary-side full bridge circuit having a fifth switch element provided on the high side of the third leg, and a sixth switch element provided on the low side of the third leg. The control method includes, as shown in FIG. 8, calculating a period obtained by subtracting the resonance period of the resonator from the switching periods of the first, second, third and fourth switch elements (step S11), operating the fifth, sixth, seventh and eighth switch elements in synchronization with the control signals for the first, second, third and fourth switch elements by the drive signal during the period (step S12), and controlling the on-time of the drive signal with the length of the period as an upper limit (step S13).

For example, the present disclosure can be realized as a program for causing a computer (processor) to execute the steps included in the control method. Furthermore, the present disclosure can be realized as a non-transitory computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

For example, when the present disclosure is realized as a program (software), each step is performed by running the program using hardware resources such as a computer's CPU, memory, and input/output circuits. In other words, each step is performed by the CPU obtaining data from memory or input/output circuits, etc., performing calculations, and outputting the results of the calculations to memory or input/output circuits, etc.

In the above embodiment, each component included in the power conversion device may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

Some or all of the functions of the power conversion device according to the above embodiment are typically realized as an LSI, which is an integrated circuit. These may be individually integrated into one chip, or may be integrated into one chip that includes some or all of the functions. Furthermore, the integrated circuit is not limited to an LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacture, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may also be used.

Furthermore, if an integrated circuit technology that can replace LSIs emerges due to advances in semiconductor technology or other derived technologies, it is natural that each component included in the power conversion device may be integrated using that technology.

In addition, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art may conceive, and forms realized by arbitrarily combining the components and functions of each embodiment within the scope that does not deviate from the spirit of this disclosure.

(Additional Note)
The above description of the embodiments discloses the following techniques.

(Technology 1) A power conversion device capable of unidirectional or bidirectional power conversion, comprising: a resonator having a transformer and a resonance capacitor; a primary-side full bridge circuit connected to the primary side of the resonator; a secondary-side full bridge circuit connected to the secondary side of the resonator; and a controller for controlling the primary-side full bridge circuit and the secondary-side full bridge circuit, wherein the primary-side full bridge circuit has a first switch element provided on the high side of a first leg, a second switch element provided on the low side of the first leg, a third switch element provided on the high side of the second leg, and a fourth switch element provided on the low side of the second leg, and the secondary-side full bridge circuit has a fifth switch element provided on the high side of the third leg, and A power conversion device having a sixth switch element provided on the low side of the third leg, a seventh switch element provided on the high side of the fourth leg, and an eighth switch element provided on the low side of the fourth leg, and the controller calculates a period obtained by subtracting the resonance period of the resonator from the switching periods of the first switch element, the second switch element, the third switch element, and the fourth switch element, and operates the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element in synchronization with the control signals for the first switch element, the second switch element, the third switch element, and the fourth switch element by a drive signal during the period, and controls the on-time of the drive signal with the length of the period as an upper limit.

Accordingly, the period obtained by subtracting the resonance period of the resonator from the switching periods of the first element, second element, third element, and fourth element becomes a non-current-carrying period in which no current is passed through the load. By turning on the fifth switch element, sixth switch element, seventh switch element, and eighth switch element for a certain period during the non-current-carrying period, it is possible to adjust the timing at which the polarity of the voltage generated in the secondary winding of the transformer (transformer secondary voltage) is reversed. When the polarity of the transformer secondary voltage is reversed, the polarity of the transformer excitation voltage is also reversed in accordance with the reversal of the polarity of the transformer secondary voltage. In other words, it is possible to adjust the timing at which the polarity of the transformer excitation voltage is reversed (in other words, the phase of polarity reversal of the transformer excitation voltage).

For example, when the phase of polarity reversal of the excitation voltage of the transformer is advanced, the phase of the excitation current of the transformer is advanced. Since the resonant current is superimposed on the excitation current, if the phase of the excitation current is advanced, the phase of the resonance current is also advanced, and the output power of the power conversion device can be increased. For example, when the phase of polarity reversal of the excitation voltage of the transformer is delayed, the phase of the excitation current of the transformer is delayed. Since the resonant current is superimposed on the excitation current, if the phase of the excitation current is delayed, the phase of the resonance current is also delayed, and the output power of the power conversion device can be reduced. Therefore, by controlling the on-time of the drive signal for the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element during the non-energized period, the output power can be controlled without frequency control, and the output power can be effectively controlled while suppressing the frequency control range width.

(Technology 2) The power conversion device described in Technology 1, in which the controller turns on the fifth switch element and the eighth switch element by the drive signal before the first switch element and the fourth switch element are turned off from an on state, and turns on the sixth switch element and the seventh switch element by the drive signal before the second switch element and the third switch element are turned off from an on state.

This allows the phase of polarity reversal of the transformer excitation voltage to be advanced, thereby increasing the output power of the power conversion device.

(Technology 3) The power conversion device described in Technology 1, in which the controller turns on the sixth switch element and the seventh switch element by the drive signal before the first switch element and the fourth switch element are turned off from an on state, and turns on the fifth switch element and the eighth switch element by the drive signal before the second switch element and the third switch element are turned off from an on state.

This allows the phase of polarity reversal of the transformer excitation voltage to be delayed, thereby reducing the output power of the power conversion device.

(Technology 4) The power conversion device described in any one of Technologies 1 to 3, wherein the controller further controls the phase between the switching of the first switch element and the second switch element and the switching of the third switch element and the fourth switch element.

This allows the output power of the power conversion device to be reduced. For example, if the output power of the power conversion device cannot be reduced to the target power by simply delaying the phase of polarity reversal of the transformer excitation voltage, the output power of the power conversion device can be reduced to the target power by controlling the phase.

(Technology 5) The power conversion device according to any one of techniques 1 to 4, wherein the controller further intermittently controls the switching of the first switch element, the second switch element, the third switch element, and the fourth switch element.

This allows the output power of the power conversion device to be reduced. For example, if the output power of the power conversion device cannot be reduced to the target power by simply delaying the phase of polarity reversal of the transformer excitation voltage, the output power of the power conversion device can be reduced to the target power by controlling the switching intermittently.

(Technology 6) A method for controlling a power conversion device capable of unidirectional or bidirectional power conversion, the power conversion device comprising a resonator having a transformer and a resonant capacitor, a primary-side full bridge circuit connected to the primary side of the resonator, and a secondary-side full bridge circuit connected to the secondary side of the resonator, the primary-side full bridge circuit having a first switch element provided on the high side of a first leg, a second switch element provided on the low side of the first leg, a third switch element provided on the high side of the second leg, and a fourth switch element provided on the low side of the second leg, the secondary-side full bridge circuit having a fifth switch element provided on the high side of a third leg, and a fifth switch element provided on the low side of the third leg. The control method includes a sixth switch element provided on the high side of the fourth leg, a seventh switch element provided on the high side of the fourth leg, and an eighth switch element provided on the low side of the fourth leg, and the control method calculates a period obtained by subtracting the resonance period of the resonator from the switching periods of the first switch element, the second switch element, the third switch element, and the fourth switch element, and operates the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element in synchronization with the control signal for the first switch element, the second switch element, the third switch element, and the fourth switch element by a drive signal during the period, and controls the on-time of the drive signal with the length of the period as an upper limit.

This provides a control method that can effectively control output power while suppressing the frequency control range width.

This disclosure can be applied to isolated DC-DC converters, etc.

REFERENCE SIGNS LIST 1 Power conversion device 10 Primary side full bridge circuit 20 Secondary side full bridge circuit 30 Resonator 40 Controller Cin, Cout, Cr Capacitor Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8 Switch T Transformer t1, t2, t3, t4 Terminal

Claims (6)

A power conversion device capable of unidirectional or bidirectional power conversion,
a resonator having a transformer and a resonance capacitor;
a primary-side full bridge circuit connected to a primary side of the resonator;
a secondary-side full bridge circuit connected to a secondary side of the resonator;
a controller for controlling the primary side full bridge circuit and the secondary side full bridge circuit,
the primary-side full-bridge circuit includes a first switch element provided on a high side of a first leg, a second switch element provided on a low side of the first leg, a third switch element provided on the high side of a second leg, and a fourth switch element provided on the low side of the second leg;
the secondary-side full bridge circuit includes a fifth switch element provided on a high side of a third leg, a sixth switch element provided on a low side of the third leg, a seventh switch element provided on the high side of a fourth leg, and an eighth switch element provided on the low side of the fourth leg,
The controller includes:
calculating a period obtained by subtracting a resonance period of the resonator from a switching period of the first switch element, the second switch element, the third switch element, and the fourth switch element;
by a drive signal during the period, the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element are operated in synchronization with a control signal for the first switch element, the second switch element, the third switch element, and the fourth switch element;
controlling an on-time of the drive signal with the length of the period as an upper limit;
Power conversion equipment. The controller includes:
the fifth switch element and the eighth switch element are turned on before the first switch element and the fourth switch element are turned off from an on state by the drive signal;
the sixth switch element and the seventh switch element are turned on before the second switch element and the third switch element are turned off from an on state by the drive signal;
The power conversion device according to claim 1 . The controller includes:
the sixth switch element and the seventh switch element are turned on before the first switch element and the fourth switch element are turned off from an on state by the drive signal;
the fifth switch element and the eighth switch element are turned on before the second switch element and the third switch element are turned off from an on state by the drive signal;
The power conversion device according to claim 1 . The controller further controls a phase between switching of the first switch element and the second switch element and switching of the third switch element and the fourth switch element.
The power conversion device according to any one of claims 1 to 3. The controller further intermittently controls switching of the first switch element, the second switch element, the third switch element, and the fourth switch element.
The power conversion device according to any one of claims 1 to 3. A method for controlling a power conversion device capable of unidirectional or bidirectional power conversion, comprising:
The power conversion device is
a resonator having a transformer and a resonance capacitor;
a primary-side full bridge circuit connected to a primary side of the resonator;
a secondary-side full bridge circuit connected to the secondary side of the resonator,
the primary-side full-bridge circuit includes a first switch element provided on a high side of a first leg, a second switch element provided on a low side of the first leg, a third switch element provided on the high side of a second leg, and a fourth switch element provided on the low side of the second leg;
the secondary-side full-bridge circuit includes a fifth switch element provided on a high side of a third leg, a sixth switch element provided on a low side of the third leg, a seventh switch element provided on the high side of a fourth leg, and an eighth switch element provided on the low side of the fourth leg,
In the control method,
calculating a period obtained by subtracting a resonance period of the resonator from a switching period of the first switch element, the second switch element, the third switch element, and the fourth switch element;
by a drive signal during the period, the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element are operated in synchronization with a control signal for the first switch element, the second switch element, the third switch element, and the fourth switch element;
controlling an on-time of the drive signal with the length of the period as an upper limit;
Control methods.

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