Ac / DC converter

Abstract

To effectively suppress a rush current by a simple and inexpensive means.SOLUTION: An AC / DC converter 6 includes a PFC circuit 20. The PFC circuit 20 includes a reactor Linv, first and second thyristors SR1 and SR2, switching elements S1 and S2, and a capacitor Cdc. A control unit 14 performs soft start by changing timing for turning on each of thyristors S1, S2 to adjust a pulse width at the time of ON based on phase angles θ ac. x, θ ac. y obtained by processing a volts alternating current eac by predetermined phase-locked circuits 43a, 43b in a state where functions of switching elements SR1, SR2 are disabled at the start of input of the volts alternating current eac.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The disclosed technology relates to an AC / DC converter including a PFC circuit, which is suitable for an on-board charger. [Background technology]

[0002] In recent years, the use of electric vehicles, such as hybrid vehicles and electric vehicles, has become increasingly common. These types of vehicles are equipped with high-voltage batteries as a power source for their operation. To charge the batteries by connecting them to external charging equipment, the vehicles are equipped with chargers (known as OBCs: On Board Chargers).

[0003] For example, the on-board charger converts AC power output from an external charging facility into DC power compatible with the battery. On-board chargers are required to handle high voltages and currents, while also being small, highly efficient, and with low loss.

[0004] Generally, an on-board charger is equipped with a PFC circuit to improve the power factor (for example, reference numeral 440 in FIG. 2 of Patent Document 1). In order to suppress a large current (so-called inrush current) that may flow momentarily when charging begins, the circuit of Patent Document 1 is provided with a precharge circuit (inrush current prevention circuit 420) configured by connecting a resistor and a relay in parallel.

[0005] This type of precharge circuit tends to be large, which goes against the demand for smaller on-board chargers. In addition, the relay may deteriorate over time and fail.

[0006] In response to this, circuits have been proposed that can avoid such problems and suppress inrush currents by using semiconductor elements.For example, Patent Document 2 discloses a rectifier circuit that includes a first series circuit consisting of two thyristors, a second series circuit consisting of two transistors with diodes connected in anti-parallel, and a capacitor connected in parallel, with the midpoint of the second series circuit connected to one side of an AC power supply via a reactor and the midpoint of the first series circuit connected to the other side of the AC power supply.

[0007] The rectifier circuit in Patent Document 2 adjusts the magnitude of the input current by switching thyristors depending on whether the AC voltage is positive or negative, and by controlling the on / off timing of transistors. At startup, the inrush current is suppressed by controlling the firing phase of each thyristor.

[0008] However, with a technique such as that of Patent Document 2, when the frequency of the AC power fluctuates, a difference may occur between the actual value and the expected value of the AC voltage at the start of ignition (false ignition). When false ignition occurs, there is a risk that inrush current will not be sufficiently suppressed. Patent Document 3 discloses a technique for preventing false ignition.

[0009] That is, the technology of Patent Document 3 detects the zero-crossing point where the AC voltage value is zero, and controls the timing of firing the thyristor based on this zero-crossing point. If the frequency of the AC power fluctuates, the thyristor is controlled not to fire for a predetermined period based on the zero-crossing point until the frequency returns to normal. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-103976 [Patent Document 2] Japanese Patent Application Publication No. 1-164273 [Patent Document 3] Japanese Patent Publication No. 2020-28160 Summary of the Invention [Problem to be solved by the invention]

[0011] The technology of Patent Document 3 requires the detection of zero-crossing points. However, in the case of commercial power supplies, the distortion factor of the AC voltage may be high. If the distortion factor of the AC voltage is high, errors are likely to occur in the detection of zero-crossing points. This may result in deviations in the timing of thyristor firing, which may result in insufficient suppression of inrush current.

[0012] Furthermore, the technology of Patent Document 3 executes a series of controls in response to fluctuations in the frequency of the AC current. This has the disadvantage of being prone to chattering, which is particularly likely to cause malfunctions when the harmonic distortion rate is high.

[0013] Therefore, this specification discloses a technology that can appropriately deal with cases where the distortion rate of the commercial power supply voltage is high, and can solve such problems using simple and inexpensive means. [Means for solving the problem]

[0014] The disclosed technology relates to an AC / DC converter including a PFC circuit.

[0015] The PFC circuit has one reactor, two thyristors, first and second, which are switched on and off in response to the alternating positive and negative half cycles of the input AC voltage, at least one switching element which includes a freewheel diode and is switched on and off to convert the AC voltage into a predetermined DC voltage and output it, and one capacitor arranged between a pair of DC output wirings on the output side of the reactor, the thyristor, and the switching element.

[0016] The inverter further includes a control unit for controlling the on / off of the thyristors and the switching elements. When the AC voltage starts to be input, the control unit executes a soft start by varying the timing at which each of the thyristors is turned on and adjusting the pulse width when the thyristors are turned on, based on a phase angle obtained by processing the AC voltage using a predetermined phase locked loop, while disabling the functions of the switching elements.

[0017] That is, in such an AC / DC converter, when the input of the AC voltage begins, the control unit disables the function of the switching elements and, based on the phase angle obtained by processing the AC voltage in a predetermined phase-locked loop, changes the timing at which each thyristor is turned on to adjust the pulse width when it is turned on.

[0018] The phase angle is obtained by processing the AC voltage with a phase-locked loop, which provides a highly accurate phase angle that always follows the phase of the input AC voltage. This allows for proper control even if the frequency fluctuates slightly, as with commercial power supplies. The pulse width when the thyristor is turned on, i.e., the conduction time, is then adjusted based on this phase angle, allowing for proper soft starting. Inrush current can be effectively suppressed.

[0019] Moreover, since it can be executed by on / off control using an I / O pin, the control program is simple and can be realized using an inexpensive control microcomputer.

[0020] Specifically, the phase locked loop may be composed of a first phase locked loop corresponding to the negative phase of the AC voltage and a second phase locked loop corresponding to the positive phase of the AC voltage, and the control unit may have a first comparator that compares a first phase angle output from the first phase locked loop with a comparison phase angle that is set in advance for executing the soft start and outputs a first control signal, and a second comparator that compares a second phase angle output from the second phase locked loop with the comparison phase angle and outputs a second control signal, and may control on / off of the second thyristor based on the first control signal and control on / off of the first thyristor based on the second control signal.

[0021] Since a transfer function and a phase locked loop are provided for each phase, even if the AC voltage changes between a positive phase (positive voltage) and a negative phase (negative voltage) every half cycle, it can respond appropriately to each of these changes. Therefore, soft starting can be performed appropriately. Inrush current can be effectively suppressed.

[0022] The control unit may have a first transfer function that converts the distorted wave of the AC voltage into a negative-phase sine wave and a second transfer function that converts the distorted wave of the AC voltage into a positive-phase sine wave, and the first phase locked loop may output the first phase angle based on the negative-phase AC voltage obtained by the first transfer function, and the second phase locked loop may output the second phase angle based on the positive-phase AC voltage obtained by the second transfer function.

[0023] Even if the AC voltage is distorted, it can be converted into a distortion-free sine wave using each transfer function.The phase angle is then obtained based on this clean AC voltage, so even if the AC voltage has a high distortion rate, it can be handled appropriately.As a result, soft starting can be performed appropriately.Inrush current can be effectively suppressed.

[0024] The control unit may have a first transfer function that converts a distorted wave of the AC voltage into a negative-phase sine wave, and the first phase locked loop may output the first phase angle based on a negative-phase AC voltage obtained by the first transfer function, and the second phase locked loop may output the second phase angle based on a positive-phase AC voltage obtained by inverting the negative-phase AC voltage obtained by the first transfer function.

[0025] This will reduce the number of transfer functions by one, simplifying the control program and reducing the processing load on the control unit.

[0026] The disclosed technology can also be applied to three-phase AC voltages.

[0027] That is, the AC voltage may be composed of three phases with different phases, and the PFC circuit may include the reactor, the three thyristors consisting of first, second, and third thyristors that are switched on and off corresponding to alternately repeated positive and negative half cycles of the AC voltage of each phase that is input, three diodes consisting of first, second, and third diodes that are connected in series with the same current direction as each of the thyristors, the switching element, and the capacitor that is arranged between a pair of DC output wirings on the output side of the reactor, the thyristors, the diodes, and the switching element, and the control unit may include three phase locked loops corresponding to the AC voltage of each phase, and three comparators provided for each phase to compare a phase angle output from each of the phase locked loops with a comparison phase angle that is set in advance to execute the soft start, and output a control signal, and control the on and off of the first to third thyristors based on the control signal of each phase.

[0028] An AC / DC converter with this configuration can perform an appropriate soft start and effectively suppress inrush current, even with a three-phase AC voltage.

[0029] The control unit may have a gate driver that receives the error amount of the AC voltage obtained from the phase locked loop together with the control signal and outputs a drive signal to turn each of the thyristors on and off, and the gate driver may not output the drive signal when the absolute value of the error amount of the AC voltage is equal to or greater than a predetermined threshold, and may output the drive signal when the absolute value of the error amount of the AC voltage is smaller than the threshold.

[0030] This makes it possible to effectively suppress inrush current and appropriately control the on / off of each thyristor during soft start. [Effects of the Invention]

[0031] The disclosed technology makes it possible to effectively suppress inrush current using simple and inexpensive means, thereby enabling the realization of a compact AC / DC converter with excellent performance at low cost. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a diagram for explaining an application example (OBC) of the disclosed technology (AC / DC converter). [Figure 2] FIG. 1 is a diagram illustrating an example of a PFC circuit that may be included in an AC / DC converter. [Figure 3] FIG. 1 is an image diagram of the change in state of the DC bus voltage at startup. [Figure 4] FIG. 2 is a control block diagram relating to control of a thyristor. [Figure 5] FIG. 10 is a diagram for explaining the flow of processing using a first transfer function. [Figure 6] FIG. 2 is a control block diagram of a phase locked loop circuit. [Figure 7] 10 is an example of setting information relating to control of turning on and off a thyristor. [Figure 8] FIG. 10 is an image diagram of a time chart at startup. [Figure 9] FIG. 10 is an image diagram of a time chart in a steady state. [Figure 10] FIG. 2 is a control block diagram of a PFC circuit. [Figure 11A] FIG. 10 is a diagram showing the results of verification of the effect by simulation. [Figure 11B] FIG. 10 is a diagram showing the results of verification of the effect by simulation. [Figure 11C] FIG. 10 is a diagram showing the results of verification of the effect by simulation. [Figure 12] 10 is a diagram (corresponding to FIG. 4) of another form of AC / DC converter. [Figure 13A] FIG. 10 is a diagram for explaining an example of application to a three-phase PFC circuit. [Figure 13B] FIG. 10 is a diagram for explaining an example of application to a three-phase PFC circuit. DETAILED DESCRIPTION OF THE INVENTION

[0033] The disclosed technology will be described below. However, the following description is essentially merely exemplary. Circuit components are assigned specific symbols along with alphanumeric codes that identify them. For convenience, explanations or illustrations may be made using only those symbols. An uppercase symbol such as "I" represents its maximum value (amplitude value), and a lowercase symbol such as "i" represents its instantaneous value.

[0034] <AC / DCコンバータ> 1 shows an on-board charger 3 (OBC) as a preferred application example of the disclosed technology (AC / DC converter). The on-board charger 3 is mounted on a vehicle 1, such as an electric vehicle or a hybrid vehicle, together with a high-output battery 4 that serves as a power source for driving the vehicle.

[0035] The upper diagram in Figure 1 shows the vehicle 1 being charged and the commercial power source 2. The commercial power source 2 is a high-voltage AC commercial grid voltage such as 100V or 200V (AC voltage e ac The battery 4 is charged by connecting the commercial power supply 2 to the vehicle 1 with a cable. The on-board charger 3 is interposed between the battery 4 and the commercial power supply 2 and outputs an AC voltage e ac The DC voltage corresponding to the battery 4 e dc '.

[0036] As shown in the center diagram of Fig. 1, the on-board charger 3 is composed of a DC / DC converter 5, an AC / DC converter 6, etc. The AC / DC converter 6 converts the input AC voltage e ac DC voltage e dc The disclosed technology is applied to this AC / DC converter 6.

[0037] The DC / DC converter 5 is a device that converts a DC voltage into a different DC voltage. dc A given DC voltage e dc ' and output to the battery 4 side.

[0038] 1, the AC / DC converter 6 includes a converter mechanism 13 including a current sensor 10, an input voltage sensor 11, an output voltage sensor 12, a PFC circuit 20, etc., and a controller 14 that controls the converter mechanism 13. The controller 14 is an example of a "control unit."

[0039] The current sensor 10 is a Hall element type sensor. There are two current sensors 10, and they are installed at predetermined positions in the PFC circuit 20. The first current sensor 10 detects the AC current i input to the AC / DC converter 6. ac The second current sensor 10 directly measures the value of the current (reactor current i inv ) is directly measured and output to the controller 14.

[0040] An input voltage sensor 11 and an output voltage sensor 12 are also installed at predetermined positions in the PFC circuit 20. The input voltage sensor 11 detects the AC voltage e input from the commercial power supply 2 to the AC / DC converter 6. ac The output voltage sensor 12 directly measures the value of the DC voltage e output from the AC / DC converter 6 and outputs it to the controller 14. dc (DC bus voltage e dc ) is directly measured and output to the controller 14.

[0041] Based on these measurement values, the controller 14 outputs drive signals to the thyristors 25 (SR1, SR2) and switching elements 26 (e.g., S1, S2) of the PFC circuit 20 to control their on / off. That is, the controller 14 switches the thyristors 25 and switching elements 26 between a conducting state (on) in which current flows and a non-conducting state (off) in which current does not flow at predetermined timing.

[0042] (PFC circuit) 2 illustrates two PFC circuits 20 that may be included in the AC / DC converter 6. Type A PFC circuit 20 is a bridgeless type. Type B PFC circuit 20 is a bridge type. Both PFC circuits 20 have the same basic structure.

[0043] That is, the inverter includes a pair of AC input wirings 21, 21, a pair of DC output wirings 22, 22, and a plurality of relay wirings 23 (23a, etc.) connecting the pair of DC output wirings 22, 22, as well as one reactor 24, two thyristors 25 consisting of first and second thyristors, at least one switching element 26, and one smoothing capacitor 27 arranged on the output side of the reactor 24, the thyristor 25, and the switching element 26.

[0044] The switching element 26 is a power semiconductor device such as an IGBT, and includes a diode (freewheel diode) connected in antiparallel. The thyristor 25 is a commonly used electronic component similar to the switching element 26, and can maintain a conductive state in a certain direction by turning it on (so-called ignition), and can maintain a non-conductive state by turning it off (so-called extinction).

[0045] The pair of DC output wirings 22, 22 have a DC bus voltage e dc The rectifier has a pair of output terminals (a grounded N terminal and a non-grounded P terminal) from which the following is output:

[0046] In the bridgeless PFC circuit 20, a first relay wiring 23a in which first and second switching elements S1 and S2 are arranged in series, a second relay wiring 23b in which two thyristors SR1 and SR2 are arranged in series, and a third relay wiring 23c in which a smoothing capacitor 27 (Cdc) is arranged are arranged in parallel in this order from the input side to the output side between a pair of DC output wirings 22, 22.

[0047] In the bridge-type PFC circuit 20, between a pair of DC output wirings 22, 22, a first relay wiring 23a in which one thyristor 25 (SR2) and one diode 28 (D2) are arranged in series in this order from the non-grounded side, a second relay wiring 23b in which one thyristor 25 (SR1) and one diode 28 (D1) are arranged in series in this order from the non-grounded side, a fourth relay wiring 23d in which one switching element 26 (S1) is arranged, and a third relay wiring 23c in which a smoothing capacitor 27 (Cdc) is arranged are arranged in parallel in this order from the input side to the output side.

[0048] The pair of AC input wirings 21, 21 have an AC voltage e ac The AC input wiring 21 has a pair of input terminals (a grounded N terminal and a non-grounded L terminal) to which a voltage is input. The other output ends of the pair of AC input wirings 21 are connected to the midpoints of the first and second relay wirings 23a and 23b, respectively. A relay capacitor 29 (Cinv) is connected between the pair of AC input wirings 21 for the purpose of reducing noise. Note that the relay capacitor 29 is not essential.

[0049] In the case of the bridgeless PFC circuit 20, the reactor 24 (Linv) is arranged in a portion of the ungrounded AC input wiring 21 closer to the output side than the relay capacitor 29. In contrast, in the case of the bridge-type PFC circuit 20, the reactor 24 (Ldc) is arranged in a portion between the second relay wiring 23b and the fourth relay wiring 23d in the ungrounded DC output wiring 22. In the case of the bridge-type PFC circuit 20, the third diode 28 (D3) is arranged in a portion between the fourth relay wiring 23d and the third relay wiring 23c in the ungrounded DC output wiring 22.

[0050] (Normal operation) In the steady state of AC / DC converter 6, the DC bus voltage e dc The controller 14 controls the AC voltage e so that it is constant at a predetermined value. dcThe first and second thyristors SR1 and SR2 are switched on and off in response to the alternating positive and negative half cycles of the DC bus voltage e dc The on / off of the corresponding switching elements S1 and S2 is controlled so that the voltage Vcc is constant at a predetermined value.

[0051] Specifically, in the case of a bridgeless PFC circuit 20, the first thyristor SR1 is turned off and the second thyristor SR2 is turned on during the positive half cycle. In this state, the second switching element S2 is controlled to be turned on and off. Although known, the current path CR1 when the second switching element S2 is on and the current path CR2 when the second switching element S2 is off in this case are shown in FIG. 2.

[0052] During the negative half cycle, the first thyristor SR1 is turned on and the second thyristor SR2 is turned off. In this state, the first switching element S1 is controlled to be turned on and off. The current path in this case is not shown.

[0053] In the case of a bridge-type PFC circuit 20, during the positive half cycle, the first thyristor SR1 is turned off and the second thyristor SR2 is turned on. In this state, the on / off of the switching element S1 is controlled. Although known, the current path CR3 when the switching element S1 is on and the current path CR4 when the switching element S1 is off in this case are shown in the figure.

[0054] During the negative half cycle, the first thyristor SR1 is turned on and the second thyristor SR2 is turned off. In this state, the on / off of the switching element S1 is controlled. The current path in this case is not shown.

[0055] (soft start) When the power is turned on, AC / DC converter 6 receives AC voltage e acWhen a voltage Vcc is input, a large current (so-called inrush current) flows into the PFC circuit 20 to charge the smoothing capacitor Cdc. Conventionally, to prevent this inrush current, a precharge circuit has generally been implemented in an AC / DC converter.

[0056] The precharge circuit generates AC voltage e ac This limits the amount of current that flows into the PFC circuit when input begins, thereby suppressing inrush current (soft start). A typical precharge circuit is one in which a resistor and a relay are connected in parallel, but this tends to make the circuit larger. There is also the risk of the relay deteriorating over time and failing.

[0057] In contrast, in this AC / DC converter 6, a precharge circuit is configured by using a thyristor 25 in the PFC circuit 20. Note that, hereinafter, the AC / DC converter 6 will be described as including the bridgeless PFC circuit 20 described above.

[0058] Figure 3 shows the DC bus voltage e at startup with soft start. dc The period from the start of startup to t1 corresponds to the soft start.

[0059] The upper table shows the DC bus voltage e dc The first gate block signal (SGB) and the second gate block signal (SGB.CTL) are set in response to the state changes of the two thyristors SR1 and SR2. The first gate block signal is a control signal for the gate block of the two switching elements S1 and S2.

[0060] During the soft start, the first gate block signal is enabled, and the functions of the two thyristors SR1 and SR2 are valid. After the soft start is completed, the first gate block signal is enabled, and the functions of the two thyristors SR1 and SR2 are valid.

[0061] On the other hand, during the soft start, the second gate block signal is disabled, and the functions of the two switching elements S1 and S2 are disabled. After the soft start is completed, the second gate block signal is enabled, and the functions of the two switching elements S1 and S2 are enabled.

[0062] As a result, the PFC circuit 20 receives the AC voltage e ac When the input of AC voltage e starts, the controller 14 disables the functions of the switching elements S1 and S2, as will be described in detail later. ac Based on the phase angle obtained by processing this in a predetermined phase locked loop, the timing at which each of the thyristors SR1 and SR2 is turned on is changed to adjust the pulse width when the thyristors are turned on. This allows soft start to be performed.

[0063] This results in a DC bus voltage e dc gradually increases, and the smoothing capacitor Cdc is gradually charged. Then, the DC bus voltage e dc is AC voltage e ac The maximum value of (E ac.max ) (timing t1), the soft start ends.

[0064] When the soft start is completed, the two thyristors SR1 and SR2 and the two switching elements S1 and S2 are enabled and driven. dc is the target DC bus voltage command value (e dc * ) is boosted until it reaches the DC bus voltage command value. After that, the DC bus voltage e dc is maintained at that voltage value (steady state).

[0065] (Thyristor control block) 4 shows an example of a control block related to the control of the thyristors SR1 and SR2 executed by the controller 14. The example control block is composed of a first transfer function 41a and a second transfer function 41b, first and second phase locked loops 43a and 43b, a first comparator 45a and a second comparator 45b, a first gate driver 46 for the thyristors, and the like.

[0066] The first transfer function 41a and the second transfer function 41b are configured, for example, by a plurality of first-order low-pass filters. The first transfer function 41a is a function of the AC voltage e ac This converts the distorted wave of the AC voltage e into a negative-phase sine wave. ac Form a signal.

[0067] 5 illustrates the flow of processing by the first transfer function 41a. As shown in the upper diagram of FIG. 5, the AC voltage e ac The waveform of a signal is often distorted due to noise and other factors (distorted wave). If the distortion rate is high, it can affect the determination of zero-crossing points, making it difficult to properly control the signal.

[0068] Therefore, in this AC / DC converter 6, in order to eliminate the influence of distortion, the AC voltage e is converted into a waveform (sine wave) without distortion using the first transfer function 41a. ac Specifically, as shown in FIG. 4, the first transfer function 41a processes the AC voltage e ac and its angular frequency (ω ac ).

[0069] As shown in the middle diagram of Figure 5, the input AC voltage e ac The first transfer function 41a processes the portion (solid line portion) that is delayed in phase by 180 degrees relative to the input AC voltage e. ac For , the AC voltage e consists of a sine wave with an inverse phase (negative phase) ac Here, we consider this to be an AC voltage e with no phase lag. ac By doing so, the actual input AC voltage eac A sine wave (e ac.y ) is obtained (here, the reverse phase is distinguished by adding y).

[0070] Similarly, the second transfer function 41b is ac For example, the input AC voltage e is converted into a sine wave with the same phase (positive phase). ac The second transfer function 41b may be used to process the portion that is delayed in phase by 360 degrees relative to the actual input AC voltage e. ac AC voltage e consisting of a positive-phase sinusoidal wave that is in phase with ac signal (e ac.x ) is obtained (here, the positive phase is distinguished by adding an x).

[0071] The first phase locked loop 43a receives an AC voltage e ac The second phase locked loop 43b receives a positive AC voltage e ac The first phase locked loop 43a receives the AC voltage signal e of the opposite phase obtained by the first transfer function 41a. ac,y and AC voltage e ac Angular frequency ω ac and the first phase angle θ ac.y The second phase locked loop 43b outputs a positive-phase AC voltage signal e obtained by the second transfer function 41b. ac.x and AC voltage e ac Angular frequency ω ac and the second phase angle θ based on ac.x Output.

[0072] These phase locked loop circuits 43a and 43b generate positive and negative phase AC voltage signals e ac.x ,e ac,y is the AC voltage e input to the AC / DC converter 6. ac and synchronize the phase angle θ ac.x ,θ ac.y Therefore, the highly accurate phase angle θ ac.x ,θ ac.y is obtained.

[0073] 6 shows the control blocks of these phase locked loop circuits 43a and 43b. The control blocks are composed of a transfer function 51, which is a predetermined low-pass filter, an integral element 52, and the like. Note that the control blocks are identical in content except for the difference between the positive and negative phases to be processed, so for convenience, the symbols "ac.x, ac.y" will be replaced with "in".

[0074] The positive and negative phase AC voltage signals (e in ) is the predetermined feedback value for the phase angle: Cos(θ in ) / E in.max This results in the AC voltage error (Δe in ) is obtained and processed by the transfer function 51.

[0075] where e in is E in.max *Sin(θ a ) is equivalent to θ a is the AC voltage e ac is the phase angle of (θ a : the phase angle of the actual commercial grid voltage, actual phase angle). Therefore, e in By multiplying the feedback value by Sin(θ a )*Cos(θ). This is Δe in And, θ a = θ, the phase is locked, and the AC component is cut by the transfer function 51, leaving only the DC component, that is, the angular frequency of the actual commercial grid voltage and the angular frequency (fixed angular frequency) ω ac The deviation value (angular frequency deviation value) from this is output.

[0076] fixed angular frequency ω ac After subtracting the output value (angular frequency deviation value) of the transfer function 51 from the phase angle θ in is output from the phase locked loop 43a. The feedback value is the phase angle θ in This can be obtained from the equations shown at the bottom of Figure 6. Note that Tac is the AC voltage e acfac is the AC voltage e ac is the frequency.

[0077] As shown in FIG. 4, the first comparator 45a detects the first phase angle θ output from the first phase locked loop 43a. ac.y and the comparison phase angle (θ comp ) and outputs a first control signal Sy to the first gate driver 46. The comparison phase angle is a setting value that is set in advance to execute a soft start, and is implemented in the memory of the controller 14.

[0078] The comparative phase angle is set to change constantly from the 2π side toward the π side within a range (conduction width) of 180 degrees (π) or more and 360 degrees (2π) or less. As will be described later, the comparative phase angle determines the timing at which each thyristor SR1, SR2 is turned on, and the pulse width at the time of turning on is adjusted. The time corresponding to the conduction width when soft starting is performed may be set appropriately when designing the circuit constants. For example, the time corresponding to the conduction width may be set to 1 second.

[0079] Similarly, the second comparator 45b also detects the second phase angle θ output from the second phase locked loop 43b. ac.x and the comparison phase angle, and outputs a second control signal Sx to the first gate driver 46. The first control signal Sy corresponds to the second thyristor SR2. The second control signal Sx corresponds to the first thyristor SR1.

[0080] The first gate driver 46 calculates the error amount (Δe ac.x ,Δe ac.y ) along with the first and second control signals Sy and Sx. The first gate driver 46 also receives the first gate block signal (SGB) described above. The first gate driver 46 then outputs drive signals to the first and second thyristors SR1 and SR2 to turn them on and off.

[0081] At this time, the first gate driver 46 supplies an AC voltage eac When the error amount (absolute value) is equal to or greater than a predetermined threshold k, no drive signal is output. On the other hand, for the AC voltage e ac when the error amount (absolute value) is less than the threshold k, a drive signal is output. The threshold k is the limit value at which the phase synchronization circuits 43a and 43b can function.

[0082] Specifically, in the controller 14, a table regarding the control for turning on and off the thyristors SR1 and SR2 shown in FIG. 7 is set. For the positive-phase and negative-phase AC voltages e ac when the error amount (absolute value) is equal to or greater than a predetermined threshold (|Δe in |≧k), the AC current i ac becomes excessive, and phase lock cannot be achieved in each of the phase synchronization circuits 43a and 43b.

[0083] In such a case, when turning on and off the thyristors SR1 and SR2, there is a risk of excessive inrush current flowing. To suppress this, the controller 14 disables the first gate block signal (SGB). Then, a predetermined control signal (L) that renders each of the thyristors SR1 and SR2 inoperable is output. Accordingly, no drive signal is output.

[0084] On the other hand, for the positive-phase and negative-phase AC voltages e ac when the error amount (absolute value) is less than the threshold k (|Δe in |<k), each of the phase synchronization circuits 43a and 43b is determined to be in a phase-locked state, and the phase angle of the measured commercial power system voltage is output. The controller 14 takes into account the first gate block signal. If the first gate block signal is in an enabled state, the first gate driver 46 outputs a drive signal based on the first control signal Sy to control the on and off of the second thyristor SR2, and outputs a drive signal based on the second control signal Sx to control the on and off of the first thyristor SR1.

[0085] In this way, the first and second control signals Sy and Sx that control the on / off of the two thyristors SR1 and SR2 can be obtained using a control block composed of simple logic, and can be realized inexpensively using the I / O pins of a commercially available control microcontroller.

[0086] (Start-up time chart) Figure 8 shows an example of a time chart at startup when a soft start is executed. The top line shows the DC bus voltage e dc The change in the phase angle θ ac.x ,θ ac.y changes periodically within the range of 0 degrees to 360 degrees (2π). At the timing of 0 degrees (360 degrees), the first and second control signals Sy and Sx are turned off. Specifically, the first control signal Sy is turned off at timings t2 and t6, and the second control signal Sx is turned off at timings t4 and t8.

[0087] On the other hand, as described above, the comparison phase angle θcomp is set in the range of 180 degrees (π) to 360 degrees (2π), and this is used as the phase angle θ ac.x ,θ ac.y The timings at which the first and second control signals Sy and Sx are turned on are determined. Specifically, the first control signal Sy is turned on at times t1 and t5, and the second control signal Sx is turned on at times t3 and t7.

[0088] By doing so, the pulse width of the first and second thyristors SR1 and SR2 when they are turned on is adjusted. As a result, the DC bus voltage e dc increases gradually, and the smoothing capacitor Cdc is gradually charged. This allows the soft start to be performed properly and the inrush current to be effectively suppressed.

[0089] (After soft start is complete) After the soft start is completed, the steady state is reached as described above, and the first and second thyristors SR2 are connected to the AC voltage e acThe on / off state corresponds to the alternating positive and negative half cycles of the

[0090] 9 shows a time chart for controlling the first and second thyristors SR1 and SR2 in the steady state. The comparison phase angle θcomp of the first comparator 45a and the second comparator 45b is constant (180 degrees:π). The pulse widths are the same when on and when off, and they switch on and off every half cycle.

[0091] At the same time, the second gate block signal is enabled, enabling the functions of the two switching elements S1 and S2. The first and second switching elements S1 and S2 are then PWM controlled, allowing the PFC circuit 20 to perform its original control.

[0092] (PFC circuit control block) 10 shows a control block of the PFC circuit 20. In order to control the PFC circuit 20, the controller 14 has a DC bus voltage control unit 61, a current control unit 63, a second gate driver 65, and the like.

[0093] The DC bus voltage control unit 61 determines the DC bus voltage command value e dc * and the DC bus voltage e detected by the output voltage sensor 12. dc and input the AC current command value I ac * The AC current command value I ac * , Sin(θ ac.x ) to obtain the AC current command value i ac * is obtained, and the AC current command value i ac * is input to the current control unit 63.

[0094] The current control unit 63 also receives the AC current i detected by the first and second current sensors 10. ac and the reactor current i invand the AC voltage e detected by the input voltage sensor 11 and the output voltage sensor 12. ac and DC bus voltage e dc Then, the current control unit 63 calculates the duty ratio command value d ac * and outputs it to the second gate driver 65.

[0095] The second gate driver 65 receives a duty ratio command value d ac * At the same time, the switching frequency Fs, the dead time Td, and the second gate block signal (SGB.CTL) are input. The second gate driver 65 then performs PWM control based on these values ​​and outputs drive signals to the first and second switching elements S1 and S2 to turn them on and off.

[0096] <Verification of effects through simulation> A simulation was conducted to verify the effects of the disclosed technology. In the simulation, the AC voltage (effective value) was set to 240 V with a frequency of 60 Hz and a total harmonic distortion (THDv) of 14.3%.

[0097] In Figure 11A, the AC voltage e ac and the AC voltage e after processing by the first transfer function 41a and the second transfer function 41b. ac.x , e ac.y The waveform of the AC voltage before processing is shown. ac is a distorted waveform (distorted wave), whereas the AC voltage e after processing by these transfer functions 41a and 41b is ac.x , e ac.y It was confirmed that a waveform without distortion (sine wave) could be obtained.

[0098] 11B and 11C show time charts at startup and steady state in the simulation corresponding to FIGS. 8 and 9. acEven if input is made, it is possible to adjust the timing of turning on the first and second thyristors SR1 and SR2 without trouble and perform soft start, and it was confirmed that the DC bus voltage e dc can be precharged. Then, it was confirmed that it is possible to smoothly transition to the steady state.

[0099] <Another form of AC / DC converter> In the above-described embodiment, in order to form a non-distorted positive-phase and negative-phase sine wave from the distorted AC voltage e ac the first transfer function 41a and the second transfer function 41b are used for each phase (see FIG. 4). However, the second transfer function 41b for forming the positive-phase sine wave may be omitted or simplified. By doing so, the control program can be simplified and the processing load on the controller 14 can be reduced.

[0100] As shown in FIG. 12, the controller 14 in this alternative form has a first transfer function 41a that converts the distorted wave of the AC voltage e ac into a negative-phase sine wave. And the first phase synchronization circuit 43a outputs a first phase angle θ ac.y based on the negative-phase AC voltage signal e ac.y obtained by the first transfer function 41a. This point is the same as that of the above-described embodiment.

[0101] On the other hand, the controller 14 in this alternative form does not have the second transfer function 41b. Instead, the controller 14 multiplies the signal e c of the AC voltage consisting of the negative-phase sine wave output from the first transfer function 41a by -1 and inverts the signal. By doing so, a signal e ac.y of the AC voltage consisting of the positive-phase sine wave is formed and input to the second phase synchronization circuit 43b. ac.x Then, the second phase synchronization circuit 43b outputs a second phase angle θ

[0102] based on the positive-phase AC voltage signal e ac.x The other configurations of the control block are the same as those of the above-described embodiment. ac.x

[0103] <Other application examples of the disclosed technology> In the above-described embodiment, an example has been described in which the disclosed technology is applied to an AC / DC converter 6 including a single-phase PFC circuit 20. The disclosed technology can also be applied to a three-phase PFC circuit. An application example thereof will be described below. Note that the basic circuit configuration is the same as that of the bridge-type single-phase PFC circuit 20, and the basic control content is the same as that of the above-described embodiment, so a description thereof will be omitted.

[0104] 13A illustrates a three-phase PFC circuit 70 to which the disclosed technology is applied. ac is composed of three phases (U phase, V phase, and W phase) that are 120 degrees out of phase with each other.

[0105] The PFC circuit 70 is composed of one reactor 24, three thyristors 25 (SR1, SR2, SR3) consisting of first, second, and third diodes, four diodes 28 (D1 to D4) consisting of first, second, third, and fourth diodes, one switching element 26 (S1), one smoothing capacitor 27 (Cdc), and three relay capacitors 29 (Cu, Cv, Cw).

[0106] First to fifth relay wirings 23a to 23e are connected in parallel between a pair of DC output wirings 22, 22. As in the bridge-type single-phase PFC circuit 20, a reactor 24 (Ldc) is arranged in the non-contact side DC output wiring 22. A smoothing capacitor Cdc is arranged in the fourth relay wiring 23d, and a switching element S1 is arranged in the fifth relay wiring 23e.

[0107] The AC input wiring 21 is made up of three wirings corresponding to each phase. ac The AC input wirings 21 are provided with input terminals (U terminal, V terminal, W terminal) to which the respective phases of the AC input wirings 21 are input. The other ends of the output sides of these AC input wirings 21 are connected to the midpoints of the first, second, and third relay wirings 23a, 23b, and 23c, respectively. Relay capacitors Cu, Cv, and Cw are connected between these AC input wirings 21, respectively.

[0108] The three thyristors SR1, SR2, and SR3 correspond to the respective phases and are arranged on the first to third relay wirings 23a to 23c. These thyristors SR1, SR2, and SR3 are connected to the AC voltages e of the respective phases to be input. un ,e vn ,e wn The first to third diodes D1 to D3 are connected in series to the ground sides of the thyristors SR1, SR2, and SR3, with the conduction direction of each diode being the same as that of the thyristors SR1, SR2, and SR3.

[0109] 13B illustrates a control block related to the control of the thyristors SR1, SR2, and SR3 executed by the controller 14. The controller 14 has control elements consisting of a transfer function 71, a phase locked loop 73, and a comparator 75 for each of the three phases.

[0110] The function of each of these control elements is to control the input AC voltage e un ,e vn ,e wn The control contents are the same as those of the control block corresponding to the positive phase sine wave shown in Figure 12.

[0111] That is, each control element controls the AC voltage e of each phase. un ,e vn ,e wn and the angular frequency ω of these AC voltages ac is input and processed by a transfer function 71 corresponding to the first transfer function 41a. As a result, an AC voltage signal consisting of a negative-phase sine wave is obtained. The AC voltage signal is multiplied by -1 to invert the signal. By doing so, an AC voltage signal (e un.z ,e vn.y ,e wn.x ) and input to the respective phase locked loop circuits 73.

[0112] As a result, the phase angle θ un.z ,θvn.y ,θ wn.x The comparators 75 compare these phase angles with the comparison phase angle θcomp and output control signals Sx, Sy, Sz for each phase to the first gate driver 46. The first gate driver 46 also receives the error amount (Δe un.z ,Δe vn.y ,Δe wn.x ), and a first gate block signal (SGB) are also input.

[0113] Based on these input signals, the first gate driver 46 outputs drive signals to the first, second, and third thyristors SR1, SR2, and SR3, respectively, to control the on / off of the first to third thyristors SR1, SR2, and SR3.

[0114] The disclosed technology is not limited to the above-described embodiment and includes various other configurations. For example, average current mode control is a common control method for PFC circuits. Therefore, the disclosed technology can be applied to PFC circuits that perform average current mode control. However, the disclosed technology may also be applied to PFC circuits that perform peak current mode control. [Explanation of symbols]

[0115] 1 vehicle 2 Commercial power supply 3 On-board charger 4 Battery 5 DC / DC converters 6 AC / DC converters 10 Current Sensor 11 Input voltage sensor 12 Output voltage sensor 13 Converter mechanism 14 Controller (control unit) 20 PFC circuit 21 AC input wiring 22 DC output wiring 23a~23e Relay wiring 24 Reactor 25 Thyristor 26 Switching element 27 Smoothing capacitor 28 Diode 29 Relay capacitor 41a First transfer function 41b Second transfer function 43a First phase locked loop 43b Second phase locked loop 45a 1st comparator 45b 2nd comparator 46 1st gate driver 51 Transfer Function 52 Integral Elements 61 DC bus voltage control unit 63 Current control section 65 Second gate driver

Claims

1. An AC / DC converter including a PFC circuit, The PFC circuit comprises: One reactor, two thyristors, first and second, which are switched on and off in response to alternately repeated positive and negative half cycles of an input AC voltage; at least one switching element including a freewheel diode, which is turned on and off to convert the AC voltage into a predetermined DC voltage and output the DC voltage; a capacitor disposed between a pair of DC output wirings on the output side of the reactor, the thyristor, and the switching element; and a control unit for controlling the on / off of the thyristor and the switching element, the control unit, when input of the AC voltage starts, disables the function of the switching elements, and changes the timing at which each of the thyristors is turned on, based on a phase angle obtained by processing the AC voltage in a predetermined phase locked loop, thereby adjusting a pulse width when the thyristors are turned on, thereby executing a soft start.

2. 2. The AC / DC converter according to claim 1, The phase locked loop circuit a first phase locked loop corresponding to the opposite phase of the AC voltage; a second phase locked loop circuit corresponding to a positive phase of the AC voltage; It consists of The control unit a first comparator that compares a first phase angle output from the first phase locked loop with a comparison phase angle that is preset for executing the soft start and outputs a first control signal; a second comparator that compares a second phase angle output from the second phase locked loop with the comparison phase angle and outputs a second control signal; and An AC / DC converter that controls the on / off of the second thyristor based on the first control signal, and controls the on / off of the first thyristor based on the second control signal.

3. 3. The AC / DC converter according to claim 2, The control unit a first transfer function that converts the distorted wave of the AC voltage into a sine wave of an inverse phase; a second transfer function that converts the distorted wave of the AC voltage into a positive-phase sine wave; and an AC / DC converter in which the first phase locked loop outputs the first phase angle based on a negative-phase AC voltage obtained by the first transfer function, and the second phase locked loop outputs the second phase angle based on a positive-phase AC voltage obtained by the second transfer function.

4. 3. The AC / DC converter according to claim 2, the control unit has a first transfer function that converts the distorted wave of the AC voltage into a sine wave of an inverse phase, an AC / DC converter in which the first phase locked loop outputs the first phase angle based on a negative-phase AC voltage obtained by the first transfer function, and the second phase locked loop outputs the second phase angle based on a positive-phase AC voltage obtained by inverting the negative-phase AC voltage obtained by the first transfer function.

5. 2. The AC / DC converter according to claim 1, The AC voltage is composed of three phases with different phases, The PFC circuit comprises: The reactor; the three thyristors, namely the first, second and third thyristors, which are switched on and off in response to alternately repeated positive and negative half cycles of the AC voltage of each phase to be input; three diodes, namely, first, second, and third diodes, connected in series with the thyristors in the same conduction direction; the switching element; the capacitor disposed between a pair of DC output wirings on the output side of the reactor, the thyristor, the diode, and the switching element; and The control unit three phase locked loops corresponding to the AC voltages of the respective phases; three comparators provided for each phase to compare a phase angle output from each of the phase locked loops with a comparison phase angle that is preset for executing the soft start, and output a control signal; and An AC / DC converter that controls the on / off of the first to third thyristors based on the control signal for each phase.

6. 6. The AC / DC converter according to claim 2, the control unit has a gate driver that receives the error amount of the AC voltage obtained from the phase locked loop together with the control signal and outputs a drive signal that turns on and off each of the thyristors; the gate driver does not output the drive signal when the absolute value of the error amount of the AC voltage is equal to or greater than a predetermined threshold, and outputs the drive signal when the absolute value of the error amount of the AC voltage is smaller than the threshold.

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