Power conversion device

Abstract

A power conversion device (1) comprises: a first switch (SW1); a second switch (SW2); a first inductor (L1); a first current-sensing circuit (11) that senses a current flowing through the first inductor (L1); and a first resonance period detection circuit (21) that detects the resonance period of a first resonance phenomenon generated by switching operations of the first switch (SW1) and the second switch (SW2). The first resonance phenomenon is generated by the energy of the first inductor (L1) accumulated during a first energy application period. The first resonance period detection circuit (21) detects the resonance period of the first resonance phenomenon on the basis of the results of a comparison between a reference voltage and the voltage generated from the resonant current flowing through the first inductor (L1) due to the first resonance phenomenon, the two voltages having been sensed by the first current-sensing circuit (11).

Description

Power Conversion Device

[0001] The present disclosure relates to a power conversion device.

[0002] Patent Document 1 describes a power conversion device that measures the resonance period required for so-called zero voltage switching (ZVS).

[0003] Patent No. 6711123

[0004] In the power conversion device described in Patent Document 1, the voltage at both ends of the inductor is detected when measuring the resonance period. In this case, a circuit for detecting the voltage at two locations is required, which increases the circuit size. In addition, the inductor voltage fluctuates greatly, making it easy for noise to be superimposed when detecting the resonance period.

[0005] Therefore, the present disclosure provides a power conversion device that can suppress noise and can be made smaller.

[0006] A power conversion device according to one aspect of the present disclosure includes: a first switch provided on a first path connecting a first input / output terminal and a second input / output terminal; a second switch provided on the first path and connected in series with the first switch; a first inductor provided on a second path connecting a connection node between the first switch and the second switch on the first path and a third input / output terminal; a first current detection circuit configured to detect a current flowing through the first inductor; and a parasitic capacitance of the first switch and the second switch generated by switching operations of the first switch and the second switch, as well as a parasitic capacitance of the first inductor. and a first resonance period detection circuit that detects a resonance period of a first resonance phenomenon caused by an inductance of the first inductor, wherein energy is accumulated in the first inductor during a first energy application period in which the second switch is turned off and the first switch is turned on, and the first resonance phenomenon occurs due to the energy of the first inductor accumulated during the first energy application period, and the first resonance period detection circuit detects the resonance period of the first resonance phenomenon based on a comparison result between a voltage generated from a resonance current flowing through the first inductor due to the first resonance phenomenon, which is detected by the first current detection circuit, and a reference voltage.

[0007] According to a power conversion device according to an aspect of the present disclosure, noise can be suppressed and the size can be reduced.

[0008] 1 is a configuration diagram showing an example of a power conversion device according to a first embodiment. FIG. 1 is a diagram for explaining zero voltage switching. FIG. 2 is a diagram showing an example of a resonance period detected for zero voltage switching. FIG. 3 is a diagram showing another example of a resonance period detected for zero voltage switching. FIG. 4 is a diagram showing an example of a correction timing of a set value for zero voltage switching. FIG. 5 is a diagram showing another example of the correction timing of a set value for zero voltage switching. FIG. 6 is a configuration diagram showing an example of a power conversion device according to a second embodiment. FIG. 7 is a diagram for explaining zero voltage switching when two inductors are coupled. FIG. 8 is a diagram showing an example of a first resonance period detection period. FIG. 9 is a diagram showing another example of the first resonance period detection period. FIG. 10 is a diagram showing an example of a first energy application period. FIG. 11 is a diagram showing another example of the first energy application period. FIG. 12 is a configuration diagram showing an example of a power conversion device according to a third embodiment. FIG. 13 is a diagram showing an example of a second resonance period detection period. FIG. 14 is a diagram showing another example of the second resonance period detection period. FIG. 15 is a diagram showing an example of the second energy application period. FIG. 16 is a diagram showing another example of the second energy application period.

[0009] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0010] The embodiments described below are all comprehensive or specific examples, and the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0011] First Embodiment A power conversion device 1 according to a first embodiment will be described with reference to FIGS. 1 to 6. FIG.

[0012] FIG. 1 is a configuration diagram showing an example of a power conversion device 1 according to the first embodiment.

[0013] The power conversion device 1 is a device that boosts or drops an input voltage to a predetermined voltage and outputs the voltage. Here, a step-down converter will be described as an example of the power conversion device 1. The power conversion device 1 drops an input voltage applied between an input / output terminal t1 and an input / output terminal t2 and outputs the voltage from an input / output terminal t3. The input / output terminal t1 is an example of a first input / output terminal, the input / output terminal t2 is an example of a second input / output terminal, and the input / output terminal t3 is an example of a third input / output terminal. The power conversion device 1 may also be a step-up converter.

[0014] The power conversion device 1 includes switches SW1 and SW2, an inductor L1, a current detection circuit 11, a resonance period detection circuit 21, and a correction circuit 31. The switch SW1 is an example of a first switch, the switch SW2 is an example of a second switch, the inductor L1 is an example of a first inductor, the current detection circuit 11 is an example of a first current detection circuit, the resonance period detection circuit 21 is an example of a first resonance period detection circuit, and the correction circuit 31 is an example of a first correction circuit.

[0015] The switch SW1 is provided on a path P1 connecting the input / output terminal t1 and the input / output terminal t2. The path P1 is an example of a first path. The switch SW1 is, for example, an N-channel metal oxide semiconductor field effect transistor (MOSFET). In FIG. 1, the parasitic capacitance of the switch SW1 is represented by a capacitor C1, which is connected in parallel with the switch SW1 in the equivalent circuit.

[0016] The switch SW2 is provided on the path P1 and is connected in series with the switch SW1. The switch SW2 is, for example, an N-channel MOSFET. In FIG. 1, the parasitic capacitance of the switch SW2 is represented by a capacitor C2, which is connected in parallel with the switch SW2 in the equivalent circuit.

[0017] The power conversion device 1 may have a function of controlling the on and off of the switches SW1 and SW2. Alternatively, the on and off control of the switches SW1 and SW2 may be performed by a device separate from the power conversion device 1.

[0018] The inductor L1 is provided on a path P2 that connects a connection node N1 between the switch SW1 and the switch SW2 on the path P1 and the input / output terminal t3. The path P2 is an example of a second path.

[0019] There is a growing need to miniaturize power conversion devices such as on-board chargers and AC adapters, particularly passive components such as inductors and capacitors, which account for a large portion of the power conversion device's size. When miniaturizing passive components, if the drive frequency remains the same as before the passive components were miniaturized, current ripple increases, so the power conversion device must be driven at a high frequency. However, high-frequency drive generates switching losses with each switching operation, so soft switching is required. Here, zero-voltage switching (ZVS) is explained as an example of soft switching, using FIG. 2 .

[0020] FIG. 2 is a diagram for explaining zero voltage switching.

[0021] During period I, the switch SW1 is turned on and the switch SW2 is turned off, so that a forward current flows through the inductor L1, and while energy is stored in the inductor L1, power is transmitted to the input / output terminal t3.

[0022] In period II, the switch SW1 is turned off, and after the voltage of the capacitor C1 rises to the input voltage applied between the input / output terminal t1 and the input / output terminal t2 due to resonance, the switch SW2 is turned on.

[0023] In period III, a forward current flows through inductor L1, the energy stored in inductor L1 is released, and power is transmitted to input / output terminal t3. After the energy stored in inductor L1 has been released, if switch SW2 is then turned on, a reverse current flows through inductor L1.

[0024] In period IV, the switch SW2 is turned off, and after the voltage of the capacitor C1 drops to 0 V due to resonance, the switch SW1 is turned on.

[0025] The period IV during which the switches SW1 and SW2 are off before the switch SW1 is turned on is called the dead time of the switches SW1 and SW2. When operating in critical conduction mode (CRM), the switch SW1 must be turned on when the voltage of the capacitor C1 has fallen to 0 V during this dead time. This is because if the dead time is short and the switch SW1 is turned on before the voltage of the capacitor C1 has fallen to 0 V, the turn-on loss will be large. However, if the dead time is long and the switch SW1 is turned on after a certain period of time has passed since the voltage of the capacitor C1 fell to 0 V, the conduction loss will be large due to excessive diode mode. Therefore, to achieve highly efficient and stable operation of the power conversion device 1, the dead time must be appropriately adjusted. The period until the voltage of capacitor C1 drops to 0 V is derived from the resonance period of the resonance phenomenon (also called the first resonance phenomenon) caused by the capacitance of capacitors C1 and C2 (i.e., the parasitic capacitance of switches SW1 and SW2) and the inductance of inductor L1, and zero voltage switching can be performed by adjusting the dead time according to this resonance period.

[0026] In order to detect the resonance period of the first resonance phenomenon and adjust the dead time of the switches SW1 and SW2 in accordance with this resonance period, the power conversion device 1 is equipped with a current detection circuit 11, a resonance period detection circuit 21, and a correction circuit 31.

[0027] The current detection circuit 11 detects the current flowing through the inductor L1. For example, the current detection circuit 11 includes a shunt resistor, a reference power supply, and a comparator. The shunt resistor is provided on the path P2 and connected in series with the inductor L1. Specifically, the shunt resistor is provided on the path P2 between the inductor L1 and the input / output terminal t3. One end of the shunt resistor is connected to the inductor L1, the reference power supply, and the negative input terminal of the comparator, and the other end of the shunt resistor is connected to the input / output terminal t3, ground, and the positive input terminal of the comparator. For example, the ground of the switches SW1 and SW2 is separated from the ground of the current detection circuit 11. A comparison signal 1 is output from the output terminal of the comparator. The current detection circuit 11 may detect the current flowing through the inductor L1 in a non-contact manner by using a magnetic core, a Hall element, or the like.

[0028] The current detection circuit 11 is configured to change the magnitude of the voltage generated from the resonant current relative to a reference voltage at the timing when the resonant current flowing through the inductor L1 changes from positive to negative due to the first resonance phenomenon. The function of the current detection circuit 11 will be described in detail later.

[0029] The resonance period detection circuit 21 detects the resonance period of the first resonance phenomenon that occurs due to the switching operations of the switches SW1 and SW2 and the parasitic capacitance of the switches SW1 and SW2 and the inductance of the inductor L1. As described above, the resonance period detection circuit 21 detects the resonance period of the first resonance phenomenon due to the zero-voltage switching of the switches SW1 and SW2. Here, the resonance period detected due to the zero-voltage switching will be described with reference to FIG. 3 .

[0030] FIG. 3 is a diagram showing an example of a resonance period detected for zero voltage switching.

[0031] As shown in Fig. 3, energy is stored in inductor L1 during a first energy application period in which switch SW2 is off and switch SW1 is on. The first resonance phenomenon occurs due to the energy stored in inductor L1 during the first energy application period. As shown in Fig. 3, after energy is stored in inductor L1, switch SW1 is turned off, causing the first resonance phenomenon and a resonant current to flow through inductor L1.

[0032] For example, the reference voltage of the reference power supply in the current detection circuit 11 is approximately half the voltage of the control power supply voltage of the comparator in the current detection circuit 11. A current flows through the shunt resistor in the same manner as the resonant current flowing through inductor L1, and the shunt resistor generates a voltage from the resonant current. This voltage is shown as the measurement voltage in Figures 1 and 3. When the resonant current flowing through inductor L1 switches between positive and negative, the voltage applied to the positive input terminal of the comparator (i.e., the measurement voltage) switches in magnitude relative to the voltage applied to the negative input terminal (i.e., the reference voltage). Figure 3 also shows that the voltage generated from the resonant current switches in magnitude relative to the reference voltage at the timing when the resonant current flowing through inductor L1 switches in positive and negative. As a result, the comparator outputs a comparison signal 1 corresponding to the change in magnitude of the voltage generated from the resonant current relative to the reference voltage.

[0033] The resonance period detection circuit 21 detects the resonance period of the first resonance phenomenon based on a comparison result (specifically, comparison signal 1) between a reference voltage and a voltage generated from the resonance current flowing through the inductor L1 due to the first resonance phenomenon, which is the current detected by the current detection circuit 11. As shown in FIG. 3 , the resonance period of the first resonance phenomenon is the period from when the comparison signal 1 rises to when it subsequently falls and rises again. The resonance period detection circuit 21 can detect the resonance period of the first resonance phenomenon by measuring this period. In this way, the resonance period required for zero-voltage switching of the switches SW1 and SW2 can be easily detected simply by detecting the timing at which the voltage generated from the resonance current switches between high and low relative to the reference voltage.

[0034] The resonance period detection circuit 21 may detect the resonance period of the first resonance phenomenon by using the time from the timing when the resonant current flowing through the inductor L1 due to the first resonance phenomenon switches between positive and negative for the first time to the timing when the resonant current switches between positive and negative for the second time. This will be described with reference to FIG. 4 .

[0035] FIG. 4 is a diagram showing another example of a resonance period detected for zero voltage switching.

[0036] 4 , the first resonance phenomenon gradually decays. Therefore, if the resonance period of the first resonance phenomenon is detected after a certain amount of time has passed since the first resonance phenomenon occurred, the detection accuracy may be poor. In contrast, if the resonance period of the first resonance phenomenon is detected using the time from the first time the positive / negative polarity of the resonance current flowing through inductor L1 switches to the next time (i.e., the half cycle), the resonance period can be detected before the first resonance phenomenon has decayed much. Therefore, the resonance period required for zero-voltage switching of switches SW1 and SW2 can be detected with high accuracy.

[0037] The correction circuit 31 performs a first correction of the set value for zero-voltage switching of the switches SW1 and SW2 using the resonance period of the first resonance phenomenon detected by the resonance period detection circuit 21. This set value is a value for adjusting the dead time of the switches SW1 and SW2. For example, this set value can be determined from the nominal values ​​of the inductance of the inductor L1 and the parasitic capacitances of the switches SW1 and SW2. However, the inductance of the inductor L1 may deviate from the nominal value depending on the situation, resulting in an inappropriate dead time that is too long or too short. Therefore, the correction circuit 31 performs the first correction when the inductance of the inductor L1 changes to a certain extent. The timing of the set value correction will now be described with reference to FIGS. 5 and 6.

[0038] FIG. 5 is a diagram showing an example of the timing for correcting the set value for zero voltage switching.

[0039] Since the capacitance of capacitors C1 and C2 changes depending on the input voltage, for example, if the voltage (input voltage) between input / output terminal t1 and input / output terminal t2 has changed by more than a predetermined percentage of the input voltage from the input voltage when the first correction was last performed, the correction circuit 31 performs the first correction again.

[0040] As shown in FIG. 5 , the dashed lines drawn above and below the input voltage at time T0 represent voltages that are a predetermined percentage (e.g., plus or minus 10%) of the input voltage. If the current input voltage exceeds these voltages, the first correction is performed. At time T1, the current input voltage is lower by a predetermined percentage from the input voltage at time T0, so the first correction is performed. Next, at time T2, the current input voltage is lower by a predetermined percentage from the input voltage at time T1, when the first correction was previously performed. Next, at time T3, the current input voltage is higher by a predetermined percentage from the input voltage at time T2, when the first correction was previously performed. Next, at time T4, the current input voltage is lower by a predetermined percentage from the input voltage at time T3, when the first correction was previously performed, so the first correction is performed.

[0041] In this way, since the capacitance of capacitors C1 and C2 changes depending on the input voltage, the first correction is performed every time the input voltage changes to a certain extent, thereby making it possible to maintain the optimal dead time of switches SW1 and SW2.

[0042] FIG. 6 is a diagram showing another example of the timing for correcting the set value for zero voltage switching.

[0043] The inductance of inductor L1 changes according to the effective value of the current flowing through inductor L1 when the effective value is equal to or greater than a predetermined threshold. Therefore, for example, the correction circuit 31 performs the first correction again when the effective value of the current flowing through inductor L1 has changed by more than a predetermined percentage from the effective value of the current flowing through inductor L1 when the first correction was last performed.

[0044] As shown in Fig. 6, the effective value of the current flowing through inductor L1 exceeds a predetermined threshold value, and a first correction is performed at time T1. At time T2, the current effective value increases by a predetermined percentage (e.g., 10%) from the effective value at time T1, and so the first correction is performed again. Next, at time T3, the current effective value increases by a predetermined percentage from the effective value at time T2, and so the first correction is performed again. Next, at time T4, the current effective value decreases by a predetermined percentage from the effective value at time T3, and so the first correction is performed again. Next, at time T5, the current effective value decreases by a predetermined percentage from the effective value at time T4, and so the first correction is performed again.

[0045] In this way, since the inductance of inductor L1 changes according to the effective value of the current flowing through inductor L1, the first correction is performed each time the effective value changes to a certain extent, thereby maintaining the optimal dead time of switches SW1 and SW2.

[0046] As described above, the resonant period required for zero-voltage switching of switches SW1 and SW2 is detected based on the resonant current flowing through inductor L1, rather than the voltage across inductor L1. Specifically, the resonant period can be detected by detecting the direction of the resonant current flowing through inductor L1. This allows for a single current detection circuit 11, thereby reducing the circuit size. Furthermore, when operating in CRM mode, a current detection circuit 11 may already be provided. In such cases, the resonant period can be detected using the existing current detection circuit 11, thereby reducing the circuit size. Furthermore, because the resonant current, which fluctuates more slowly than the resonant voltage, is used to detect the resonant period, noise is less likely to be superimposed when detecting the resonant period. Thus, the power conversion device 1 of the present disclosure can suppress noise and achieve a compact design.

[0047] Second Embodiment A power conversion device 2 according to a second embodiment will be described with reference to FIGS. 7 to 12. FIG.

[0048] FIG. 7 is a configuration diagram showing an example of a power conversion device 2 according to the second embodiment.

[0049] Power conversion device 2 further includes switches SW3 and SW4 and an inductor L2, and is a two-phase converter, which is different from power conversion device 1 according to embodiment 1. Since the other points are basically the same as those in embodiment 1, the following description will mainly focus on the differences.

[0050] The switch SW3 is an example of a third switch, the switch SW4 is an example of a fourth switch, and the inductor L2 is an example of a second inductor.

[0051] The switch SW3 is provided on a path P3 that connects the input / output terminal t1 and the input / output terminal t2, and that is different from the path P1. The path P3 is an example of a third path. The switch SW3 is, for example, an N-channel MOSFET. In FIG. 7, the parasitic capacitance of the switch SW3 is represented by a capacitor C3, and the capacitor C3 is connected in parallel with the switch SW3 in the equivalent circuit.

[0052] The switch SW4 is provided on the path P2 and is connected in series with the switch SW3. The switch SW4 is, for example, an N-channel MOSFET. In FIG. 7, the parasitic capacitance of the switch SW4 is represented by a capacitor C4, which is connected in parallel with the switch SW4 in the equivalent circuit. Between the input / output terminal t1 and the input / output terminal t2, the series circuit of the switches SW1 and SW2 and the series circuit of the switches SW3 and SW4 are connected in parallel.

[0053] The power conversion device 2 may have a function of controlling the on and off of the switches SW3 and SW4. Alternatively, the on and off control of the switches SW3 and SW4 may be performed by a device separate from the power conversion device 2.

[0054] The inductor L2 is provided on a path P4 that connects a connection node N2 between the switch SW3 and the switch SW4 on the path P3 and the input / output terminal t3. The path P4 is an example of a fourth path.

[0055] Inductors L1 and L2 are magnetically coupled. When inductors L1 and L2 are magnetically coupled, the effective inductances of inductors L1 and L2 change due to the influence of the currents flowing through inductors L1 and L2, that is, change due to the switching operations of switches SW1 to SW4 that control the currents flowing through inductors L1 and L2. Specifically, the effective inductances of inductors L1 and L2 change due to the relationship between the voltages across inductors L1 and L2, which is determined by the switching operations of switches SW1 to SW4.

[0056] In the second embodiment, the first resonance phenomenon occurs due to the parasitic capacitances of the switches SW1 and SW2 and the effective inductance (self-inductance and mutual inductance) of the inductor L1 coupled to the inductor L2, which is generated by the switching operations of the switches SW1 to SW4. Here, zero voltage switching when the inductors L1 and L2 are coupled will be described with reference to FIG.

[0057] 8 is a diagram illustrating zero voltage switching when two inductors L1 and L2 are coupled. In a graph showing the on / off states of switches SW1 and SW2 (H and L gate voltages), switch SW1 is shown by a solid line and switch SW2 is shown by a dashed line. In a graph showing the on / off states of switches SW3 and SW4 (H and L gate voltages), switch SW3 is shown by a solid line and switch SW4 is shown by a dashed line. The same applies to FIGS. 9 to 12 and 14 to 17, which will be described later.

[0058] During period I, the switch SW1 is turned on and the switch SW2 is turned off, so that a forward current flows through the inductor L1, and while energy is being stored in the inductor L1, power is transmitted to the input / output terminal t3. At this time, the switch SW3 is turned off and the switch SW4 is turned on, and the effective inductance (L ｅｑ１) is expressed by the following equation 1. Note that the self-inductance of inductors L1 and L2 is L, the mutual inductance is M, the duty ratio is d, and 1-d is d'.

[0059]

[0060] In period II, the switch SW1 is turned off, and after the voltage of the capacitor C1 rises to the input voltage applied between the input / output terminal t1 and the input / output terminal t2 due to resonance, the switch SW2 is turned on. At this time, the switch SW3 is turned off, the switch SW4 is turned on, and the effective inductance (L ｅｑ２ ) is expressed as the following Equation 2:

[0061]

[0062] In period III, a forward current flows through inductor L1, the energy stored in inductor L1 is released, power is transmitted to input / output terminal t3, and then a negative current flows through inductor L1. When switch SW3 is turned on and switch SW4 is turned off, the effective inductance (L ｅｑ３ ) is expressed as the following equation 3.

[0063]

[0064] In period IV, the switch SW2 is turned off, and after the voltage of the capacitor C1 drops to 0 V due to resonance, the switch SW1 is turned on. At this time, the switch SW3 is turned off, the switch SW4 is turned on, and the effective inductance (L ｅｑ４ ) is expressed as the following equation 4.

[0065]

[0066] A period IV during which the switches SW1 and SW2 are off before the switch SW1 is turned on is the dead time of the switches SW1 and SW2. When operating in CRM mode, the switch SW1 must be turned on when the voltage of the capacitor C1 has dropped to 0 V during this dead time. The period until the voltage of the capacitor C1 drops to 0 V is derived from the resonance period of the first resonance phenomenon caused by the parasitic capacitances of the switches SW1 and SW2 and the effective inductance of the inductor L1. Zero-voltage switching can be achieved by adjusting the dead time according to this resonance period. However, in the second embodiment, the inductors L1 and L2 are magnetically coupled, and therefore the first resonance phenomenon is a resonance phenomenon caused by the parasitic capacitances of the switches SW1 and SW2 and the self-inductance and mutual inductance of the inductor L1 coupled to the inductor L2. Therefore, in the second embodiment, the dead time required for zero-voltage switching of the switches SW1 and SW2 is determined by the effective inductance (L ｅｑ４ ) is adjusted.

[0067] In order to adjust such dead time, the resonance period detection circuit 21 detects the resonance period of the first resonance phenomenon during the first resonance period detection period. Here, the first resonance period detection period will be described with reference to FIGS. 9 and 10.

[0068] FIG. 9 is a diagram showing an example of the first resonance period detection period.

[0069] The resonance period of the first resonance phenomenon varies depending on the effective inductance of inductor L1 coupled to inductor L2, and the effective inductance of inductor L1 varies depending on the on / off states of switches SW1 to SW4. The resonance period of the first resonance phenomenon is detected in order to adjust the dead time of switches SW1 and SW2, so it is necessary to detect the resonance period of the first resonance phenomenon when the on / off states of switches SW1 to SW4 are the same as the on / off states of each switch during the dead time of switches SW1 and SW2. The on / off states of each switch during the dead time of switches SW1 and SW2 are a state in which switches SW1 and SW2 are off, one of switches SW3 and SW4 is on, and the other is off. In this state, the effective inductance of inductor L1 is equal to L ｅｑ４ In other words, the effective inductance of the inductor L1 is ｅｑ４ The condition for this to occur is that the switches SW1 and SW2 are off, one of the switches SW3 and SW4 is on, and the other is off. Therefore, during the first resonance period detection period, the switches SW1 and SW2 must be off, one of the switches SW3 and SW4 must be on, and the other must be off.

[0070] 9, for example, the period during which the switches SW1 and SW2 are off, the switch SW3 is on, and the switch SW4 is off corresponds to the first resonance period detection period. Alternatively, the period during which the switches SW1 and SW2 are off, the switch SW3 is off, and the switch SW4 is on may correspond to the first resonance period detection period.

[0071] FIG. 10 is a diagram showing another example of the first resonance period detection period.

[0072] 7, because the power conversion device 2 is a two-phase converter, in order to detect the resonance period of the first resonance phenomenon, power can be transmitted to the input / output terminal t3 by the switches SW3 and SW4 and the inductor L2 even while power transmission to the input / output terminal t3 is not being performed by the switches SW1 and SW2 and the inductor L1. When power is transmitted to the input / output terminal t3 by the switches SW3 and SW4 and the inductor L2, as shown in FIG. 10, the switches SW3 and SW4 are repeatedly turned on and off at an arbitrary duty ratio, and there exists a state in which one of the switches SW3 and SW4 is on and the other is off.

[0073] Therefore, the first resonance period detection period may be the on-time of whichever of the switches SW3 and SW4 has the longer on-time when power is transmitted to the input / output terminal t3 via the switches SW3 and SW4 and the inductor L2. For example, as shown in Fig. 10, if the on-time of the switch SW3 is longer than the on-time of the switch SW4, the first resonance period detection period may be the on-time of the switch SW3 when power is transmitted.

[0074] By setting the on time of the switch SW3 or SW4 that has the longer on time as the first resonance period detection period, the period for detecting the resonance period of the first resonance phenomenon can be lengthened, and therefore the resonance period required for zero voltage switching of the switches SW1 and SW2 can be detected with high accuracy.

[0075] Next, the first energy application period will be described with reference to FIGS.

[0076] FIG. 11 is a diagram showing an example of the first energy application period.

[0077] If there is a large gap between the first energy application period and the first resonance period detection period, the first resonance period detection period will not include at least one cycle of the resonant current, and the resonant period of the first resonance phenomenon will not be detected during the first resonance period detection period. Therefore, the first energy application period is set so that at least one cycle of the resonant current flowing through inductor L1 due to the first resonance phenomenon is included during the first resonance period detection period. Figure 11 shows an example in which the first energy application period is set so that at least one cycle of the resonant current is included during the first resonance period detection period. As shown in the circled area, it can be seen that four cycles of the resonant current are included during the first resonance period detection period.

[0078] By setting the first energy application period so that at least one period of the resonant current is included in the first resonant period detection period, the resonant period required for zero voltage switching of the switches SW1 and SW2 can be detected in the first resonant period detection period.

[0079] FIG. 12 is a diagram showing another example of the first energy application period.

[0080] For example, the first energy application period may be set so that the first resonance period detection period includes the first cycle of the resonant current that flows through inductor L1 due to the first resonance phenomenon. Fig. 12 shows an example in which the first energy application period is set so that the first resonance period detection period includes the first cycle of the resonant current, and it can be seen that the first cycle of the resonant current is included in the first resonance period detection period, as shown in the circled portion.

[0081] Since the resonant current for the first cycle is hardly attenuated, by setting the first energy application period so that the resonant current for the first cycle is included in the first resonant cycle detection period, the resonant cycle required for zero voltage switching of switches SW1 and SW2 can be accurately detected in the first resonant cycle detection period.

[0082] The operations of the current detection circuit 11, the resonance period detection circuit 21, and the correction circuit 31 are basically the same as those in the first embodiment. The resonance period detection circuit 21 detects the resonance period of the first resonance phenomenon using the comparison signal 1 output from the current detection circuit 11 during the first resonance period detection period. The correction circuit 31 performs the first correction at the correction timing described in the first embodiment. Specifically, the correction circuit 31 applies energy to the inductor L1 while the switch SW1 is on and the switch SW2 is off, detects the resonance period of the first resonance phenomenon while the switch SW1 is off, one of the switches SW3 and SW4 is on, and the other switch is off, and performs the first correction by correcting the set values ​​for zero voltage switching of the switches SW1 and SW2 using the resonance period.

[0083] As described above, in the second embodiment, the power conversion device 2 is a two-phase converter, and the inductor L1 and the inductor L2 are magnetically coupled, thereby enabling a faster response to load fluctuations (specifically, fluctuations in the current flowing through the load). Furthermore, when the inductors L1 and L2 are magnetically coupled, there are portions that can be shared between the inductors L1 and L2, allowing the overall sizes of the inductors L1 and L2 to be reduced.

[0084] Furthermore, by detecting the resonance period of the first resonance phenomenon when switches SW1 and SW2 are off, one of switches SW3 and SW4 is on, and the other switch is off, it is possible to accurately detect the resonance period required for zero-voltage switching of switches SW1 and SW2 even when inductor L1 and inductor L2 are coupled.

[0085] Third Embodiment A power conversion device 3 according to a third embodiment will be described with reference to FIGS. 13 to 17. FIG.

[0086] FIG. 13 is a configuration diagram showing an example of a power conversion device 3 according to the third embodiment.

[0087] The power conversion device 3 further includes a current detection circuit 12, a resonance period detection circuit 22, and a correction circuit 32, and is capable of adjusting the dead times of the switches SW1 and SW2 as well as the dead times of the switches SW3 and SW4, which is different from the power conversion device 2 according to the second embodiment. Since the other points are basically the same as those in the second embodiment, the following description will mainly focus on the differences.

[0088] The current detection circuit 12 is an example of a second current detection circuit, the resonance period detection circuit 22 is an example of a second resonance period detection circuit, and the correction circuit 32 is an example of a second correction circuit. Details of the current detection circuit 12, the resonance period detection circuit 22, and the correction circuit 32 will be described later.

[0089] Zero-voltage switching is also performed on switches SW3 and SW4. The period during which switches SW3 and SW4 are off before switch SW3 is turned on is the dead time of switches SW3 and SW4. When operating in CRM mode, switch SW3 must be turned on when the voltage of capacitor C3 has fallen to 0 V during this dead time. This is because if the dead time is short and switch SW3 is turned on before the voltage of capacitor C3 has fallen to 0 V, turn-on loss will be large. However, if the dead time is long and switch SW3 is turned on after a certain period has elapsed after the voltage of capacitor C3 has fallen to 0 V, excessive diode mode will result in large conduction loss. Therefore, to achieve high-efficiency and stable operation of the power conversion device 3, the dead time must be appropriately adjusted. The period until the voltage of capacitor C3 drops to 0 V is derived from the resonance period of the resonance phenomenon (also called the second resonance phenomenon) caused by the parasitic capacitance of switches SW3 and SW4 and the effective inductance of inductor L2, and zero voltage switching can be performed by adjusting the dead time according to this resonance period.

[0090] In order to detect the resonance period of the second resonance phenomenon and adjust the dead time of the switches SW3 and SW4 based on this resonance period, the power conversion device 3 is provided with a current detection circuit 12, a resonance period detection circuit 22, and a correction circuit 32.

[0091] The current detection circuit 12 detects the current flowing through the inductor L2. For example, the current detection circuit 12 has a circuit configuration similar to that of the current detection circuit 11 shown in Fig. 1 and outputs a comparison signal 2. Note that the current detection circuit 12 may detect the current flowing through the inductor L1 in a non-contact manner by using a magnetic core or a Hall element.

[0092] The current detection circuit 12 is configured to change the magnitude of the voltage generated from the resonant current relative to a reference voltage at the timing when the resonant current flowing through the inductor L2 changes from positive to negative due to the second resonance phenomenon. The function of the current detection circuit 12 will be described in detail later.

[0093] The resonance period detection circuit 22 detects the resonance period of the second resonance phenomenon that occurs due to the switching operations of the switches SW3 and SW4 and the parasitic capacitance of the switches SW3 and SW4 and the inductance of the inductor L2. As described above, the resonance period detection circuit 22 detects the resonance period of the second resonance phenomenon due to the zero-voltage switching of the switches SW3 and SW4.

[0094] Energy is stored in the inductor L2 during a second energy application period in which the switch SW4 is turned off and the switch SW3 is turned on. The second resonance phenomenon occurs due to the energy stored in the inductor L2 during the second energy application period.

[0095] For example, the reference voltage of the reference power supply in the current detection circuit 12 is approximately half the voltage of the control power supply voltage of the comparator in the current detection circuit 12. A current flows through the shunt resistor in the same manner as the resonant current flowing through inductor L2, and the shunt resistor generates a voltage from the resonant current. When the resonant current flowing through inductor L2 switches between positive and negative, the voltage applied to the positive input terminal of the comparator (i.e., the measurement voltage) switches in magnitude relative to the voltage applied to the negative input terminal (i.e., the reference voltage). As a result, the comparator outputs a comparison signal 2 corresponding to the change in magnitude of the voltage generated from the resonant current relative to the reference voltage.

[0096] The resonance period detection circuit 22 detects the resonance period of the second resonance phenomenon based on the comparison result (specifically, comparison signal 2) between the reference voltage and a voltage generated from the resonance current flowing through the inductor L2 due to the second resonance phenomenon, which is the current detected by the current detection circuit 12. The resonance period of the second resonance phenomenon is the period from when the comparison signal 2 rises to when it subsequently falls and rises again, and the resonance period detection circuit 22 can detect the resonance period of the second resonance phenomenon by measuring this period. In this way, the resonance period required for zero-voltage switching of the switches SW3 and SW4 can be easily detected simply by detecting the timing at which the voltage generated from the resonance current switches between high and low relative to the reference voltage.

[0097] In addition, the resonance period detection circuit 22 may detect the resonance period of the second resonance phenomenon using the time from the time when the positive and negative polarities of the resonance current flowing through the inductor L2 due to the second resonance phenomenon are first switched to the time when they are next switched.

[0098] Because the second resonance phenomenon gradually decays, detecting the resonance period of the second resonance phenomenon after a certain amount of time has passed since the second resonance phenomenon occurred may result in poor detection accuracy. In contrast, detecting the resonance period of the second resonance phenomenon using the time from the first time the positive / negative polarity of the resonance current flowing through inductor L2 switches to the next time (i.e., the half cycle) allows the resonance period to be detected before the second resonance phenomenon has decayed much. Therefore, the resonance period required for zero-voltage switching of switches SW3 and SW4 can be detected with high accuracy.

[0099] The correction circuit 32 performs a second correction of the set value for zero-voltage switching of the switches SW3 and SW4 using the resonance period of the second resonance phenomenon detected by the resonance period detection circuit 22. This set value is a value for adjusting the dead time of the switches SW3 and SW4. For example, this set value can be determined from the nominal values ​​of the inductance of the inductor L2 and the parasitic capacitances of the switches SW3 and SW4. However, the inductance of the inductor L2 may deviate from the nominal value depending on the situation, resulting in an inappropriate dead time. Therefore, the correction circuit 32 performs the second correction when the inductance of the inductor L2 changes to a certain extent.

[0100] Since the capacitance of capacitors C3 and C4 changes depending on the input voltage, for example, if the voltage (input voltage) between input / output terminal t1 and input / output terminal t2 has changed by more than a predetermined percentage of the input voltage from the input voltage when the second correction was last performed, the correction circuit 32 performs the second correction again.

[0101] In this way, since the capacitance of capacitors C3 and C4 changes depending on the input voltage, the second correction is performed every time the input voltage changes to a certain extent, thereby making it possible to maintain the optimal dead time of switches SW3 and SW4.

[0102] Furthermore, since the inductance of inductor L2 changes according to the effective value of the current flowing through inductor L2 when the effective value is equal to or greater than a predetermined threshold, for example, the correction circuit 32 performs the second correction again when the effective value of the current flowing through inductor L2 has changed by more than a predetermined percentage from the effective value of the current flowing through inductor L2 when the second correction was last performed.

[0103] In this way, since the inductance of inductor L2 changes according to the effective value of the current flowing through inductor L2, the second correction is performed each time the effective value changes to a certain extent, thereby maintaining the optimal dead time of switches SW3 and SW4.

[0104] In the third embodiment, the second resonance phenomenon occurs due to the switching operation of the switches SW1 to SW4, and is a resonance phenomenon caused by the parasitic capacitance of the switches SW3 and SW4 and the effective inductance (self-inductance and mutual inductance) of the inductor L2 coupled to the inductor L1.

[0105] With respect to zero voltage switching when the inductors L1 and L2 are coupled, the effective inductance of the inductor L2 changes in the same manner as the effective inductance of the inductor L1 described in the second embodiment. ｅｑ１ , L ｅｑ２ , L ｅｑ３ , L ｅｑ４ During the dead time of the switches SW3 and SW4, the effective inductance of the inductor L2 changes as follows, as in the dead time of the switches SW1 and SW2. ｅｑ４ This becomes:

[0106] In the third embodiment, since the inductor L1 and the inductor L2 are magnetically coupled, the second resonance phenomenon is a resonance phenomenon caused by the parasitic capacitance of the switches SW3 and SW4 and the self-inductance and mutual inductance of the inductor L2 coupled to the inductor L1. Therefore, in the third embodiment, the dead time required for the zero voltage switching of the switches SW3 and SW4 is the time when the effective inductance of the inductor L2 is equal to L ｅｑ４ The resonance period is adjusted in accordance with the resonance period of the second resonance phenomenon at this time.

[0107] In order to adjust such dead time, the resonance period detection circuit 22 detects the resonance period of the second resonance phenomenon during the second resonance period detection period. Here, the second resonance period detection period will be described with reference to FIGS. 14 and 15.

[0108] FIG. 14 is a diagram showing an example of the second resonance period detection period.

[0109] The resonance period of the second resonance phenomenon varies depending on the effective inductance of inductor L2 coupled to inductor L1, and the effective inductance of inductor L2 varies depending on the on / off states of switches SW1 to SW4. Since the resonance period of the second resonance phenomenon is detected in order to adjust the dead time of switches SW3 and SW4, it is necessary to detect the resonance period of the second resonance phenomenon when the on / off states of switches SW1 to SW4 are the same as the on / off states of each switch during the dead time of switches SW3 and SW4. During the dead time of switches SW3 and SW4, switches SW3 and SW4 are off, one of switches SW1 and SW2 is on, and the other switch is off. In this state, the effective inductance of inductor L2 is equal to L ｅｑ４ In other words, the effective inductance of the inductor L2 is ｅｑ４ The condition for this to occur is that the switches SW3 and SW4 are off, one of the switches SW1 and SW2 is on, and the other is off. Therefore, during the second resonance period detection period, the switches SW3 and SW4 must be off, one of the switches SW1 and SW2 must be on, and the other must be off.

[0110] 14, for example, the period during which the switches SW3 and SW4 are off, the switch SW1 is off, and the switch SW2 is on corresponds to the second resonance period detection period. Alternatively, the second resonance period detection period may correspond to the period during which the switches SW3 and SW4 are off, the switch SW1 is on, and the switch SW2 is off.

[0111] FIG. 15 is a diagram showing another example of the second resonance period detection period.

[0112] 13, because the power conversion device 3 is a two-phase converter, in order to detect the resonance period of the second resonance phenomenon, power can be transmitted to the input / output terminal t3 by the switches SW1 and SW2 and the inductor L1 even while power transmission to the input / output terminal t3 is not being performed by the switches SW3 and SW4 and the inductor L2. When power is transmitted to the input / output terminal t3 by the switches SW1 and SW2 and the inductor L1, as shown in FIG. 15, the switches SW1 and SW2 are repeatedly turned on and off at an arbitrary duty ratio, and there is a state in which one of the switches SW1 and SW2 is turned on and the other is turned off.

[0113] Therefore, the second resonance period detection period may be the on-time of whichever of the switches SW1 and SW2 has the longer on-time when power is transmitted to the input / output terminal t3 via the switches SW1 and SW2 and the inductor L1. For example, as shown in Fig. 15, if the on-time of the switch SW2 is longer than the on-time of the switch SW1, the second resonance period detection period may be the on-time of the switch SW2 when power is transmitted.

[0114] By setting the on time of the switch SW1 or SW2 that has the longer on time as the second resonance period detection period, the period for detecting the resonance period of the second resonance phenomenon can be lengthened, and therefore the resonance period required for zero voltage switching of switches SW3 and SW4 can be detected with high accuracy.

[0115] Next, the second energy application period will be described with reference to FIGS.

[0116] FIG. 16 is a diagram showing an example of the second energy application period.

[0117] If there is a large gap between the second energy application period and the second resonance period detection period, the second resonance period detection period will not include at least one cycle of the resonant current, and the resonant period of the second resonance phenomenon will not be detected during the second resonance period detection period. Therefore, the second energy application period is set so that at least one cycle of the resonant current flowing through inductor L2 due to the second resonance phenomenon is included during the second resonance period detection period. Figure 16 shows an example in which the second energy application period is set so that at least one cycle of the resonant current is included during the second resonance period detection period. As shown in the circled area, it can be seen that four cycles of the resonant current are included during the second resonance period detection period.

[0118] By setting the second energy application period so that at least one period of the resonant current is included in the second resonant period detection period, the resonant period required for zero voltage switching of switches SW3 and SW4 can be detected in the second resonant period detection period.

[0119] FIG. 17 is a diagram showing another example of the second energy application period.

[0120] For example, the second energy application period may be set so that the first cycle of the resonant current flowing through inductor L2 due to the second resonance phenomenon is included in the second resonance period detection period. Fig. 17 shows an example in which the second energy application period is set so that the first cycle of the resonant current is included in the second resonance period detection period, and it can be seen that the first cycle of the resonant current is included in the second resonance period detection period, as shown in the circled portion.

[0121] Since the resonant current for the first cycle is hardly attenuated, by setting the second energy application period so that the resonant current for the first cycle is included in the second resonant cycle detection period, the resonant cycle required for zero voltage switching of switches SW3 and SW4 can be accurately detected in the second resonant cycle detection period.

[0122] The current detection circuit 12, the resonance period detection circuit 22, and the correction circuit 32 operate basically the same as those of the current detection circuit 11, the resonance period detection circuit 21, and the correction circuit 31. The resonance period detection circuit 22 detects the resonance period of the second resonance phenomenon using the comparison signal 2 output from the current detection circuit 12 during the second resonance period detection period. The correction circuit 32 performs the second correction at the correction timing described above. Specifically, the correction circuit 32 applies energy to the inductor L2 while the switch SW3 is turned on and the switch SW4 is turned off, detects the resonance period of the second resonance phenomenon while the switch SW3 is turned off, and turns one of the switches SW1 and SW2 on and the other switch off, and performs the second correction by correcting the set values ​​for zero voltage switching of the switches SW3 and SW4 using the resonance period.

[0123] As described above, in the third embodiment, the resonance period required for the zero-voltage switching of the switches SW3 and SW4 is also detected based on the resonance current flowing through the inductor L2. For example, while power is being transmitted to the input / output terminal t3 by the switches SW1 and SW2 and the inductor L1, the dead time for the zero-voltage switching of the switches SW3 and SW4 can be adjusted. Alternatively, while power is being transmitted to the input / output terminal t3 by the switches SW3 and SW4 and the inductor L2, the dead time for the zero-voltage switching of the switches SW1 and SW2 can be adjusted.

[0124] Furthermore, by detecting the resonance period of the second resonance phenomenon when the switches SW3 and SW4 are off, one of the switches SW1 and SW2 is on, and the other switch is off, it is possible to accurately detect the resonance period required for zero-voltage switching of the switches SW3 and SW4 even when the inductors L1 and L2 are coupled.

[0125] (Other Embodiments) As described above, the embodiments have been described as examples of the technology according to the present disclosure. However, the technology according to the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. For example, the following modifications are also included in one embodiment of the present disclosure.

[0126] For example, in the above embodiment, an example has been described in which the power conversion device includes a correction circuit, but the power conversion device does not necessarily have to include a correction circuit.

[0127] In addition, this disclosure also includes forms obtained by making various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope that does not deviate from the intent of this disclosure.

[0128] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0129] (Technology 1) A first switch provided on a first path connecting a first input / output terminal and a second input / output terminal, a second switch provided on the first path and connected in series with the first switch, a first inductor provided on a second path connecting a connection node on the first path between the first switch and the second switch and a third input / output terminal, a first current detection circuit for detecting a current flowing through the first inductor, and a current detection circuit for detecting a current flowing through the first inductor, the current detection circuit detecting a current flowing through the first inductor and a current generated by a parasitic capacitance of the first switch and the second switch and an inductance of the first inductor due to switching operations of the first switch and the second switch. and a first resonance period detection circuit that detects a resonance period of a first resonance phenomenon occurring when the second switch is turned off and the first switch is turned on, wherein energy is accumulated in the first inductor during a first energy application period in which the second switch is turned off and the first switch is turned on, and the first resonance phenomenon occurs due to the energy of the first inductor accumulated during the first energy application period, and the first resonance period detection circuit detects the resonance period of the first resonance phenomenon based on a comparison result between a voltage generated from a resonance current flowing in the first inductor due to the first resonance phenomenon, which is detected by the first current detection circuit, and a reference voltage.

[0130] The resonant period required for zero-voltage switching of the first switch and the second switch is detected based on the resonant current flowing through the first inductor, rather than the voltage across the first inductor. Specifically, the resonant period can be detected by detecting the direction of the resonant current flowing through the first inductor, thereby requiring only a single current detection circuit and reducing the circuit size. Furthermore, when operating in CRM mode, a current detection circuit may already be provided. In such cases, the resonant period can be detected using the existing current detection circuit, thereby minimizing the increase in circuit size. Furthermore, because the resonant current, which fluctuates more slowly than the resonant voltage, is used to detect the resonant period, noise is less likely to be superimposed when detecting the resonant period. Thus, the power conversion device of the present disclosure can suppress noise and achieve compactness.

[0131] (Technology 2) The power conversion device according to Technology 1 further includes: a third switch provided on a third path connecting the first input / output terminal and the second input / output terminal, the third path being different from the first path; a fourth switch provided on the third path and connected in series with the third switch; and a second inductor provided on the fourth path connecting a connection node on the third path between the third switch and the fourth switch and the third input / output terminal, wherein the first inductor and the second inductor are magnetically coupled, and the first resonance phenomenon is a resonance phenomenon caused by switching operations of the first switch, the second switch, the third switch, and the fourth switch, and is due to parasitic capacitances of the first switch and the second switch, and self-inductance and mutual inductance of the first inductor coupled to the second inductor.

[0132] By configuring the power conversion device as a two-phase converter and magnetically coupling the first inductor and the second inductor, it is possible to speed up the response to load fluctuations (specifically, fluctuations in the current flowing through the load). Furthermore, when the first inductor and the second inductor are magnetically coupled, there are parts that can be shared between the first inductor and the second inductor, and it is possible to reduce the overall size of the first inductor and the second inductor.

[0133] (Technology 3) The power conversion device described in Technology 2, wherein the first resonance period detection circuit detects the resonance period of the first resonance phenomenon during a first resonance period detection period, and during the first resonance period detection period, the first switch and the second switch are turned off, one of the third switch and the fourth switch is turned on, and the other switch is turned off.

[0134] The resonance period of the first resonance phenomenon varies depending on the effective inductance of the first inductor coupled to the second inductor, and the effective inductance of the first inductor varies depending on the on / off states of the first switch, the second switch, the third switch, and the fourth switch. Since the resonance period of the first resonance phenomenon is detected in order to adjust the dead time of the first switch and the second switch, it is necessary to detect the resonance period of the first resonance phenomenon when the on / off states of the first switch, the second switch, the third switch, and the fourth switch are the same as the on / off states of each switch during the dead time of the first switch and the second switch. The on / off states of each switch during the dead time of the first switch and the second switch are a state in which the first switch and the second switch are off, one of the third switch and the fourth switch is on, and the other switch is off. Therefore, by detecting the resonance period of the first resonance phenomenon when each switch is in this on / off state, it is possible to accurately detect the resonance period required for zero voltage switching of the first switch and the second switch even when the first inductor and the second inductor are coupled.

[0135] (Technology 4) A power conversion device according to Technology 3, wherein the first resonance period detection period is the on time of the switch having the longer on time among the third switch and the fourth switch when power is transmitted to the third input / output terminal by the third switch, the fourth switch, and the second inductor.

[0136] By setting the on time of the switch with the longer on time out of the third switch and the fourth switch as the first resonance period detection period, the period for detecting the resonance period of the first resonance phenomenon can be lengthened, and therefore the resonance period required for zero voltage switching of the first switch and the second switch can be detected with high accuracy.

[0137] (Technology 5) A power conversion device according to Technology 3 or 4, wherein the first energy application period is set so that at least one cycle of resonant current flowing through the first inductor due to the first resonance phenomenon is included in the first resonance period detection period.

[0138] By setting the first energy application period so that at least one period of the resonant current is included in the first resonant period detection period, the resonant period required for zero voltage switching of the first switch and the second switch can be detected in the first resonant period detection period.

[0139] (Technology 6) A power conversion device according to Technology 5, wherein the first energy application period is set so that the first resonance period detection period includes the first period of resonant current flowing through the first inductor due to the first resonance phenomenon.

[0140] Since the resonant current for the first cycle is hardly attenuated, by setting the first energy application period so that the resonant current for the first cycle is included in the first resonant cycle detection period, the resonant cycle required for zero voltage switching of the first switch and the second switch can be accurately detected in the first resonant cycle detection period.

[0141] (Technology 7) A power conversion device according to any one of technologies 1 to 6, wherein the first current detection circuit is configured to switch the magnitude of the voltage generated from the resonant current relative to a reference voltage at the timing when the positive and negative polarities of the resonant current flowing through the first inductor are switched due to the first resonance phenomenon.

[0142] The first current detection circuit is configured so that the timing at which the resonant current flowing through the first inductor switches between positive and negative coincides with the timing at which the voltage generated from the resonant current switches between large and small relative to the reference voltage. This makes it possible to easily detect the resonant period required for zero voltage switching of the first switch and the second switch simply by detecting the timing at which the voltage generated from the resonant current switches between large and small relative to the reference voltage.

[0143] (Technology 8) A power conversion device according to any one of technologies 1 to 7, wherein the first resonance period detection circuit detects the resonance period of the first resonance phenomenon using the time from the timing when the positive and negative polarities of the resonance current flowing through the first inductor due to the first resonance phenomenon are first switched to the timing when they are next switched.

[0144] By detecting the time from the first time when the resonant current flowing through the first inductor switches positive and negative to the next time when it switches, i.e., the first half cycle, it is possible to easily detect the resonant cycle required for zero-voltage switching of the first switch and the second switch. Furthermore, since the resonant cycle is detected when the first resonant phenomenon is barely attenuated, it is possible to accurately detect the resonant cycle required for zero-voltage switching of the first switch and the second switch.

[0145] (Technology 9) Further, a first correction circuit that performs a first correction of a set value for zero voltage switching of the first switch and the second switch using the resonance period of the first resonance phenomenon detected by the first resonance period detection circuit. The power conversion device described in any one of techniques 1 to 8.

[0146] It is possible to correct the set values ​​for zero voltage switching of the first switch and the second switch, specifically the set values ​​for adjusting the dead times of the first switch and the second switch.

[0147] (Technology 10) A power conversion device according to Technology 9, wherein the first correction circuit performs the first correction again when the voltage between the first input / output terminal and the second input / output terminal has changed by a predetermined percentage or more from the voltage between the first input / output terminal and the second input / output terminal when the first correction was previously performed, or when the effective value of the current flowing through the first inductor has changed by a predetermined percentage or more from the effective value of the current flowing through the first inductor when the first correction was previously performed.

[0148] Since the parasitic capacitances of the first switch and the second switch change according to the voltage between the first input / output terminal and the second input / output terminal, the first correction is performed each time the voltage changes to a certain extent, thereby maintaining optimal dead times for the first switch and the second switch. Alternatively, since the inductance of the first inductor changes according to the effective value of the current flowing through the first inductor, the first correction is performed each time the effective value changes to a certain extent, thereby maintaining optimal dead times for the first switch and the second switch.

[0149] (Technology 11) The power conversion device according to Technology 2 further includes: a second current detection circuit that detects a current flowing in the second inductor; and a second resonance period detection circuit that detects a resonance period of a second resonance phenomenon that occurs due to switching operations of the first switch, the second switch, the third switch, and the fourth switch, and is caused by parasitic capacitances of the third switch and the fourth switch and the self-inductance and mutual inductance of the second inductor coupled to the first inductor, wherein energy is accumulated in the second inductor during a second energy application period in which the fourth switch is turned off and the third switch is turned on, and the second resonance phenomenon occurs due to the energy of the second inductor accumulated during the second energy application period, and the second resonance period detection circuit detects the resonance period of the second resonance phenomenon based on a comparison result between a voltage generated from a resonance current flowing in the second inductor due to the second resonance phenomenon, detected by the second current detection circuit, and a reference voltage.

[0150] A resonance period required for zero-voltage switching of the third switch and the fourth switch may also be detected based on the resonance current flowing through the second inductor. For example, while power is being transmitted to the third input / output terminal by the first switch, the second switch, and the first inductor, a dead time for zero-voltage switching of the third switch and the fourth switch can be adjusted. Alternatively, while power is being transmitted to the third input / output terminal by the third switch, the fourth switch, and the second inductor, a dead time for zero-voltage switching of the first switch and the second switch can be adjusted.

[0151] (Technology 12) The power conversion device according to Technology 11, wherein the first resonance period detection circuit detects the resonance period of the first resonance phenomenon during a first resonance period detection period, during which the first switch and the second switch are turned off, one of the third switch and the fourth switch is turned on, and the other switch is turned off; the second resonance period detection circuit detects the resonance period of the second resonance phenomenon during a second resonance period detection period, during which the third switch and the fourth switch are turned off, one of the first switch and the second switch is turned on, and the other switch is turned off.

[0152] The resonance period of the first resonance phenomenon varies depending on the effective inductance of the first inductor coupled to the second inductor, and the effective inductance of the first inductor varies depending on the on / off states of the first switch, the second switch, the third switch, and the fourth switch. Since the resonance period of the first resonance phenomenon is detected in order to adjust the dead time of the first switch and the second switch, it is necessary to detect the resonance period of the first resonance phenomenon when the on / off states of the first switch, the second switch, the third switch, and the fourth switch are the same as the on / off states of each switch during the dead time of the first switch and the second switch. The on / off states of each switch during the dead time of the first switch and the second switch are a state in which the first switch and the second switch are off, one of the third switch and the fourth switch is on, and the other switch is off. Therefore, by detecting the resonance period of the first resonance phenomenon when each switch is in this on / off state, it is possible to accurately detect the resonance period required for zero voltage switching of the first switch and the second switch even when the first inductor and the second inductor are coupled.

[0153] Furthermore, the resonance period of the second resonance phenomenon varies depending on the effective inductance of the second inductor coupled to the first inductor, and the effective inductance of the second inductor varies depending on the on / off states of the first switch, the second switch, the third switch, and the fourth switch. Since the resonance period of the second resonance phenomenon is detected in order to adjust the dead time of the third switch and the fourth switch, it is necessary to detect the resonance period of the second resonance phenomenon when the on / off states of the first switch, the second switch, the third switch, and the fourth switch are the same as the on / off states of each switch during the dead time of the third switch and the fourth switch. The on / off states of each switch during the dead time of the third switch and the fourth switch are a state in which the third switch and the fourth switch are off, one of the first switch and the second switch is on, and the other switch is off. Therefore, by detecting the resonance period of the second resonance phenomenon when each switch is in this on / off state, it is possible to accurately detect the resonance period required for zero voltage switching of the third switch and the fourth switch even when the first inductor and the second inductor are coupled.

[0154] (Technology 13) A power conversion device according to Technology 12, wherein the first resonance period detection period is the on-time of one of the third switch and the fourth switch having a longer on-time when power is transmitted to the third input / output terminal by the third switch, the fourth switch, and the second inductor, and the second resonance period detection period is the on-time of one of the first switch and the second switch having a longer on-time when power is transmitted to the third input / output terminal by the first switch, the second switch, and the first inductor.

[0155] By setting the on time of the switch with the longer on time out of the third switch and the fourth switch as the first resonance period detection period, the period for detecting the resonance period of the first resonance phenomenon can be lengthened, and therefore the resonance period required for zero voltage switching of the first switch and the second switch can be detected with high accuracy.

[0156] Furthermore, by setting the on time of the switch with the longer on time out of the first switch and the second switch as the second resonance period detection period, the period for detecting the resonance period of the second resonance phenomenon can be lengthened, and therefore the resonance period required for zero voltage switching of the third switch and the fourth switch can be detected with high accuracy.

[0157] (Technology 14) A power conversion device described in Technology 12 or 13, wherein the first energy application period is set so that at least one cycle of resonant current flowing through the first inductor due to the first resonance phenomenon is included in the first resonance period detection period, and the second energy application period is set so that at least one cycle of resonant current flowing through the second inductor due to the second resonance phenomenon is included in the second resonance period detection period.

[0158] By setting the first energy application period so that at least one period of the resonant current is included in the first resonant period detection period, the resonant period required for zero voltage switching of the first switch and the second switch can be detected in the first resonant period detection period.

[0159] Furthermore, by setting the second energy application period so that at least one cycle of the resonant current is included in the second resonant period detection period, the resonant period required for zero voltage switching of the third switch and the fourth switch can be detected in the second resonant period detection period.

[0160] (Technology 15) A power conversion device according to Technology 14, wherein the first energy application period is set so that the first resonance period detection period includes the first cycle of resonant current flowing through the first inductor due to the first resonance phenomenon, and the second energy application period is set so that the second resonance period detection period includes the first cycle of resonant current flowing through the second inductor due to the second resonance phenomenon.

[0161] Since the resonant current for the first cycle is hardly attenuated, by setting the first energy application period so that the resonant current for the first cycle is included in the first resonant cycle detection period, the resonant cycle required for zero voltage switching of the first switch and the second switch can be accurately detected in the first resonant cycle detection period.

[0162] Furthermore, since the resonant current for the first cycle is hardly attenuated, by setting the second energy application period so that the resonant current for the first cycle is included in the second resonant cycle detection period, the resonant cycle required for zero voltage switching of the third switch and the fourth switch can be accurately detected in the second resonant cycle detection period.

[0163] (Technology 16) A power conversion device according to any one of technologies 11 to 15, wherein the first current detection circuit is configured to switch the magnitude of the voltage generated from the resonant current relative to a reference voltage at the timing when the resonant current flowing through the first inductor switches between positive and negative due to the first resonance phenomenon, and the second current detection circuit is configured to switch the magnitude of the voltage generated from the resonant current relative to a reference voltage at the timing when the resonant current flowing through the second inductor switches between positive and negative due to the second resonance phenomenon.

[0164] The first current detection circuit is configured so that the timing at which the resonant current flowing through the first inductor switches between positive and negative coincides with the timing at which the voltage generated from the resonant current switches between large and small relative to the reference voltage. This makes it possible to easily detect the resonant period required for zero voltage switching of the first switch and the second switch simply by detecting the timing at which the voltage generated from the resonant current switches between large and small relative to the reference voltage.

[0165] Furthermore, since the second current detection circuit is configured so that the timing at which the resonant current flowing through the second inductor switches between positive and negative coincides with the timing at which the voltage generated from the resonant current switches between large and small relative to the reference voltage, the resonant period required for zero voltage switching of the third switch and the fourth switch can be easily detected simply by detecting the timing at which the voltage generated from the resonant current switches between large and small relative to the reference voltage.

[0166] (Technology 17) A power conversion device described in any one of Technologies 11 to 16, wherein the first resonance period detection circuit detects the resonance period of the first resonance phenomenon using the time from the timing when the positive and negative signs of the resonance current flowing through the first inductor due to the first resonance phenomenon are first switched to the timing when the current next switches, and the second resonance period detection circuit detects the resonance period of the second resonance phenomenon using the time from the timing when the positive and negative signs of the resonance current flowing through the second inductor due to the second resonance phenomenon are first switched to the timing when the current next switches.

[0167] By detecting the time from the first time when the resonant current flowing through the first inductor switches positive and negative to the next time when it switches, i.e., the first half cycle, it is possible to easily detect the resonant cycle required for zero-voltage switching of the first switch and the second switch. Furthermore, since the resonant cycle is detected when the first resonant phenomenon is barely attenuated, it is possible to accurately detect the resonant cycle required for zero-voltage switching of the first switch and the second switch.

[0168] Furthermore, by detecting the time from the first time when the resonant current flowing through the second inductor switches positive and negative to the next time when the resonant current switches, i.e., the first half cycle, it is possible to easily detect the resonant cycle required for zero-voltage switching of the third switch and the fourth switch. Furthermore, since the resonant cycle is detected when the second resonant phenomenon is barely attenuated, it is possible to accurately detect the resonant cycle required for zero-voltage switching of the third switch and the fourth switch.

[0169] (Technology 18) The power conversion device according to any one of technologies 11 to 17, further comprising: a first correction circuit that performs a first correction of a set value for zero voltage switching of the first switch and the second switch using the resonance period of the first resonance phenomenon detected by the first resonance period detection circuit; and a second correction circuit that performs a second correction of a set value for zero voltage switching of the third switch and the fourth switch using the resonance period of the second resonance phenomenon detected by the second resonance period detection circuit.

[0170] It is possible to correct the set values ​​for zero voltage switching of the first switch and the second switch, specifically the set values ​​for adjusting the dead times of the first switch and the second switch.

[0171] Furthermore, it is possible to correct the set values ​​for zero voltage switching of the third switch and the fourth switch, specifically the set values ​​for adjusting the dead times of the third switch and the fourth switch.

[0172] (Technology 19) The power conversion device according to Technology 18, wherein the first correction circuit performs the first correction again when the voltage between the first input / output terminal and the second input / output terminal has changed by a predetermined percentage or more from the voltage between the first input / output terminal and the second input / output terminal when the first correction was previously performed, or when the effective value of the current flowing through the first inductor has changed by a predetermined percentage or more from the effective value of the current flowing through the first inductor when the first correction was previously performed; and the second correction circuit performs the second correction again when the voltage between the first input / output terminal and the second input / output terminal has changed by a predetermined percentage or more from the voltage between the first input / output terminal and the second input / output terminal when the second correction was previously performed, or when the effective value of the current flowing through the second inductor has changed by a predetermined value or more from the effective value of the current flowing through the second inductor when the second correction was previously performed.

[0173] Since the parasitic capacitances of the first switch and the second switch change according to the voltage between the first input / output terminal and the second input / output terminal, the first correction is performed each time the voltage changes to a certain extent, thereby maintaining optimal dead times for the first switch and the second switch. Alternatively, since the inductance of the first inductor changes according to the effective value of the current flowing through the first inductor, the first correction is performed each time the effective value changes to a certain extent, thereby maintaining optimal dead times for the first switch and the second switch.

[0174] Furthermore, since the parasitic capacitances of the third switch and the fourth switch change depending on the voltage between the first input / output terminal and the second input / output terminal, the second correction is performed each time the voltage changes to a certain extent, thereby maintaining optimal dead times for the third switch and the fourth switch. Alternatively, since the inductance of the second inductor changes depending on the effective value of the current flowing through the second inductor, the second correction is performed each time the effective value changes to a certain extent, thereby maintaining optimal dead times for the third switch and the fourth switch.

[0175] The present disclosure can be applied to a boost converter or a buck converter that performs zero voltage switching.

[0176] 1, 2, 3 Power conversion device 11, 12 Current detection circuit 21, 22 Resonance period detection circuit 31, 32 Correction circuit C1, C2 Parasitic capacitance L1, L2 Inductor N1, N2 Connection node P1, P2, P3, P4 Path SW1, SW2, SW3, SW4 Switch t1, t2, t3 Input / output terminal

Claims

1. a first switch provided on a first path connecting the first input / output terminal and the second input / output terminal; a second switch provided on the first path and connected in series with the first switch; a first inductor provided on a second path connecting a connection node between the first switch and the second switch on the first path and a third input / output terminal; a first current detection circuit that detects a current flowing through the first inductor; a first resonance period detection circuit that detects a resonance period of a first resonance phenomenon caused by a parasitic capacitance of the first switch and the second switch and an inductance of the first inductor, the first resonance period detection circuit generating a parasitic capacitance of the first switch and the second switch and a parasitic capacitance of the first inductor; energy is stored in the first inductor during a first energy application period in which the second switch is turned off and the first switch is turned on; the first resonance phenomenon is caused by energy stored in the first inductor during the first energy application period; the first resonance period detection circuit detects a resonance period of the first resonance phenomenon based on a comparison result between a voltage generated from a resonance current flowing through the first inductor due to the first resonance phenomenon and detected by the first current detection circuit, and a reference voltage. Power conversion equipment.

2. moreover, a third switch provided on a third path that connects the first input / output terminal and the second input / output terminal and is different from the first path; a fourth switch provided on the third path and connected in series with the third switch; a second inductor provided on a fourth path connecting a connection node between the third switch and the fourth switch on the third path and the third input / output terminal; the first inductor and the second inductor are magnetically coupled to each other, the first resonance phenomenon is a resonance phenomenon caused by switching operations of the first switch, the second switch, the third switch, and the fourth switch, the resonance phenomenon being caused by parasitic capacitances of the first switch and the second switch, and by self-inductance and mutual inductance of the first inductor coupled to the second inductor; The power conversion device according to claim 1 .

3. the first resonance period detection circuit detects a resonance period of the first resonance phenomenon during a first resonance period detection period; During the first resonance cycle detection period, the first switch and the second switch are turned off, one of the third switch and the fourth switch is turned on, and the other switch is turned off. The power conversion device according to claim 2 .

4. the first resonance period detection period is an on-time of one of the third switch and the fourth switch, which has a longer on-time, when power is transmitted to the third input / output terminal by the third switch, the fourth switch, and the second inductor; The power conversion device according to claim 3 .

5. the first energy application period is set so that at least one period of a resonance current flowing through the first inductor due to the first resonance phenomenon is included in the first resonance period detection period; The power conversion device according to claim 3 .

6. the first energy application period is set so that a first period of a resonant current flowing through the first inductor due to the first resonance phenomenon is included in the first resonance period detection period; The power conversion device according to claim 5 .

7. the first current detection circuit is configured to switch between a magnitude of a voltage generated from the resonant current and a magnitude of a reference voltage at a timing when a resonant current flowing through the first inductor switches between positive and negative due to the first resonance phenomenon; The power conversion device according to any one of claims 1 to 6.

8. the first resonance period detection circuit detects the resonance period of the first resonance phenomenon by using a time from a timing when the positive and negative polarities of a resonance current flowing through the first inductor due to the first resonance phenomenon are first switched to a timing when the resonance current is next switched; The power conversion device according to any one of claims 1 to 6.

9. The power supply voltage detecting circuit further includes a first correction circuit that performs a first correction of set values ​​for zero voltage switching of the first switch and the second switch by using a resonance period of the first resonance phenomenon detected by the first resonance period detection circuit. The power conversion device according to any one of claims 1 to 6.

10. the first correction circuit performs the first correction again when a voltage between the first input / output terminal and the second input / output terminal has changed by a predetermined percentage or more from a voltage between the first input / output terminal and the second input / output terminal when the first correction was previously performed, or when an effective value of a current flowing through the first inductor has changed by a predetermined percentage or more from an effective value of a current flowing through the first inductor when the first correction was previously performed. The power converter according to claim 9.

11. moreover, a second current detection circuit that detects a current flowing through the second inductor; a second resonance period detection circuit that detects a resonance period of a second resonance phenomenon caused by parasitic capacitances of the third switch and the fourth switch and a self-inductance and a mutual inductance of the second inductor coupled to the first inductor, the parasitic capacitances being generated by switching operations of the first switch, the second switch, the third switch, and the fourth switch; energy is stored in the second inductor during a second energy application period in which the fourth switch is turned off and the third switch is turned on; the second resonance phenomenon is caused by energy stored in the second inductor during the second energy application period, the second resonance period detection circuit detects a resonance period of the second resonance phenomenon based on a comparison result between a voltage generated from a resonance current flowing through the second inductor due to the second resonance phenomenon and detected by the second current detection circuit, and a reference voltage. The power conversion device according to claim 2 .

12. the first resonance period detection circuit detects a resonance period of the first resonance phenomenon during a first resonance period detection period; In the first resonance cycle detection period, the first switch and the second switch are turned off, one of the third switch and the fourth switch is turned on, and the other switch is turned off, the second resonance period detection circuit detects a resonance period of the second resonance phenomenon during a second resonance period detection period; During the second resonance cycle detection period, the third switch and the fourth switch are turned off, one of the first switch and the second switch is turned on, and the other switch is turned off. The power converter according to claim 11.

13. the first resonance period detection period is an on-time of one of the third switch and the fourth switch, which has a longer on-time, when power is transmitted to the third input / output terminal by the third switch, the fourth switch, and the second inductor; the second resonance period detection period is an on-time of one of the first switch and the second switch, which has a longer on-time, when power is transmitted to the third input / output terminal by the first switch, the second switch, and the first inductor; The power converter according to claim 12.

14. the first energy application period is set so that at least one period of a resonance current flowing through the first inductor due to the first resonance phenomenon is included in the first resonance period detection period; the second energy application period is set so that at least one period of a resonance current flowing through the second inductor due to the second resonance phenomenon is included in the second resonance period detection period; The power converter according to claim 12.

15. the first energy application period is set so that a first period of a resonance current flowing through the first inductor due to the first resonance phenomenon is included in the first resonance period detection period; the second energy application period is set so that a first period of a resonant current flowing through the second inductor due to the second resonance phenomenon is included in the second resonance period detection period; The power converter according to claim 14.

16. the first current detection circuit is configured to switch between a magnitude of a voltage generated from the resonant current and a magnitude of a reference voltage at a timing when a resonant current flowing through the first inductor switches between positive and negative due to the first resonance phenomenon; the second current detection circuit is configured to switch between a magnitude of a voltage generated from the resonant current and a magnitude of a reference voltage at a timing when a positive / negative sign of a resonant current flowing through the second inductor is switched due to the second resonance phenomenon. The power conversion device according to any one of claims 11 to 15.

17. the first resonance period detection circuit detects a resonance period of the first resonance phenomenon by using a time from a timing when a resonant current flowing through the first inductor due to the first resonance phenomenon first switches between positive and negative to a timing when the resonant current next switches; the second resonance period detection circuit detects the resonance period of the second resonance phenomenon by using a time from a timing when the positive and negative polarities of a resonance current flowing through the second inductor due to the second resonance phenomenon are first switched to a timing when the resonance current is next switched; The power conversion device according to any one of claims 11 to 15.

18. moreover, a first correction circuit that performs a first correction of set values ​​for zero voltage switching of the first switch and the second switch by using the resonance period of the first resonance phenomenon detected by the first resonance period detection circuit; a second correction circuit that performs a second correction of set values ​​for zero voltage switching of the third switch and the fourth switch by using the resonance period of the second resonance phenomenon detected by the second resonance period detection circuit. The power conversion device according to any one of claims 11 to 15.

19. the first correction circuit performs the first correction again when a voltage between the first input / output terminal and the second input / output terminal has changed by a predetermined percentage or more from a voltage between the first input / output terminal and the second input / output terminal when the first correction was previously performed, or when an effective value of a current flowing through the first inductor has changed by a predetermined percentage or more from an effective value of a current flowing through the first inductor when the first correction was previously performed, the second correction circuit performs the second correction again when a voltage between the first input / output terminal and the second input / output terminal has changed by a predetermined percentage or more from a voltage between the first input / output terminal and the second input / output terminal when the second correction was previously performed, or when an effective value of a current flowing through the second inductor has changed by a predetermined value or more from an effective value of a current flowing through the second inductor when the second correction was previously performed.

20. The power converter of claim 18.