JP2007325340A - Rectifying circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectifying circuit which can accurately detect a DC current that flows pulsatingly to the primary side of a current transformer, even when the current flows in either direction. <P>SOLUTION: The current transformer 21 is inserted into a DC part 20, where the direction of DC changes between the time of charge to a battery 14 and the time of discharge from the battery 14, within the circuit of a bidirectional DC/DC converter. A full-bridge type of rectifying circuit 22 is connected to the secondary side of the current transformer 21. In the rectifying circuit 22, a series circuit comprising a switching element Q1 and diodes D1 and D3 and a series circuit comprising a switching element Q2 and diodes D2 and D4 are connected in parallel, and the cathodes of the diodes D1, D2, D3 and D4 are positioned downstream of the flow of a secondary current. The switching elements Q1 and Q2 is so constituted that a selection means selects a current path that is along the flow of the secondary current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rectifier circuit, and more particularly to a rectifier circuit used when current detection is performed using a current transformer.

  As a method for detecting the amount of alternating current, there is a method using a current transformer. When the current transformer is used, as shown in FIG. 4A, a rectifier circuit having one diode D connected to the secondary side of the current transformer CT is provided, and the shunt resistor 41 is connected to the secondary winding of the current transformer CT. Connect to the line in parallel.

  Conventionally, in an inverter that converts a direct current obtained from an alternating current power supply through a rectifier circuit and a smoothing circuit into an alternating current of a desired frequency and voltage by an inverse conversion circuit and feeds the motor, an input current from the alternating current power supply to the inverter An input current detection method for adjusting the AC output from the inverter so that the detected value does not exceed a specified value has been proposed (see, for example, Patent Document 1). In the input current detection method of Patent Document 1, a value obtained by rectifying and smoothing a secondary current of a current transformer inserted in a line (wiring) from an AC power supply to the rectifier circuit, and an output value of the smoothing circuit are used. The calculated value based on this is used as the input current detection value. A full-wave rectifier is used when rectifying the secondary current of the current transformer.

In a current detection circuit using a current transformer, a load current is supplied to the primary side of the current transformer, the output voltage on the secondary side is rectified to direct current, A / D converted by an A / D converter, and the output There is a method for detecting the magnitude of the load current based on data (see, for example, Patent Document 2). Also in this current detection circuit, a full-wave rectifier circuit is used on the secondary side of the current transformer.
JP 2000-2725 A JP 2001-356140 A

  The current transformer can detect a direct current flowing in a pulsed manner even if it is a direct current. If the circuit is such that the direct current always flows in a certain direction, the direction of the current flowing on the primary side of the current transformer CT matches the direction of the diode D even in the half-wave rectification of FIG. If the direction is set, current can be detected without any problem. However, direct current does not always flow in a certain direction. For example, in a direct current section of a bidirectional power converter used in a hybrid vehicle, the direction of direct current flowing in a pulse is different between charging and discharging. In this case, in the current transformer CT, as shown in FIG. 4B, when the primary voltage V1 is positive (when the current generated on the secondary side flows in the forward direction of the diode D), the shunt resistor 41 The secondary voltage V2 generated on the secondary side can be detected. However, when the primary voltage V1 is negative, the secondary voltage V2 cannot be detected. Therefore, in the half-wave rectifier, two rectifiers are required for each direction.

  On the other hand, if a full-wave rectifier is used as in Patent Literature 1 and Patent Literature 2, unlike the case of a half-wave rectifier, the current value can be detected even when the current flows not only in one direction but also in the opposite direction. . However, in the case of Patent Document 1 and Patent Document 2, it is assumed that an AC current value is detected, and it is insufficient to accurately measure a DC value flowing in a target direction. .

  The present invention has been made in view of the above-described conventional problems, and the purpose thereof is an amount of current flowing in a target direction regardless of which direction of direct current flowing in a pulsed manner on the primary side of the current transformer flows. It is an object of the present invention to provide a rectifier circuit capable of accurately detecting the current.

  In order to achieve the above object, the invention according to claim 1 is a full-bridge type rectifier circuit connected to the secondary side of the current transformer, wherein the selection means selects a current path along the flow of the secondary current. It has.

  In the present invention, the current path along the flow of the current flowing on the secondary side corresponding to the direction of the direct current to be detected flowing on the primary side of the current transformer is selected by the selection means. Therefore, even if an electromotive force is generated in the current transformer when a current with a different direction flows to the primary side as noise, it cannot flow in the current path selected by the selection means. The noise current is prevented from flowing through the current path. Therefore, it is possible to accurately detect the direct current flowing in a pulsed manner on the primary side of the current transformer in any direction.

  According to a second aspect of the present invention, in the first aspect of the present invention, the selection unit includes a transistor, and the rectifier circuit includes two series circuits of the selection unit and a diode connected in parallel, and the diode The cathode is downstream of the secondary current flow. In the present invention, the current path along the flow of current generated on the secondary side of the current transformer is selected by controlling on / off of the transistor.

  According to a third aspect of the present invention, in the second aspect of the present invention, the transistor is a MOSFET, and the selection unit further includes a diode connected in series in the opposite direction to the parasitic diode of the MOSFET. In the present invention, by controlling on / off of the MOSFET, a current path along the flow of current generated on the secondary side of the current transformer is selected. Further, since the MOSFET includes a parasitic diode, it is not necessary to provide an antiparallel diode in order to avoid the possibility of damage when a reverse bias voltage is applied to the MOSFET.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the current transformer is a direct current whose direction of direct current is changed in a circuit of a bidirectional power converter. Inserted in the part. In the present invention, the rectifier circuit is used in a state where an appropriate current path is selected by the selection means corresponding to the direction of the direct current flowing in the direct current portion of the power conversion device.

  According to the present invention, it is possible to accurately detect the amount of current flowing in the target direction regardless of the direction of direct current flowing in a pulsed manner on the primary side of the current transformer.

Hereinafter, an embodiment in which the present invention is embodied in a current detection circuit of a DC / DC converter of a hybrid vehicle will be described with reference to FIGS.
As shown in FIG. 1 (a), the hybrid vehicle includes a generator 11 that is rotationally driven by an engine (not shown), and a converter 12 that converts AC from the generator 11 into DC is electrically connected to the generator 11. Has been. The smoothing capacitor 13 is connected in parallel to the output terminals 12a and 12b of the converter 12, and the battery 14 is connected to the output terminals 12a and 12b in a bidirectional DC for voltage conversion as a bidirectional power converter. / DC converter 15 is connected in parallel. An inverter 17 that supplies an alternating current to a motor 16 that drives a wheel (not shown) inputs a direct current from the converter 12 and the battery 14 and converts it into an alternating current for the motor. In this hybrid vehicle, the engine drives the generator 11, the electric power generated by the generator 11 or the electric power of the battery 14 drives the motor 16 that drives the wheels, and the electric power generated by the generator 11 is left. This is a so-called series-type hybrid vehicle that charges the battery 14 with electric power.

  The bidirectional DC / DC converter 15 is switched by the control device 18 between a state in which the output of the converter 12 is charged in the battery 14 and a state in which the electric power of the battery 14 is supplied to the inverter 17. The bidirectional DC / DC converter 15 includes a current detection circuit 19. The current detection circuit 19 is provided for detecting the current of the direct current section in which the direct current direction is changed in the circuit of the bidirectional DC / DC converter 15.

  As shown in FIG. 1B, the current detection circuit 19 is a part of the bidirectional DC / DC converter 15 in which the direction in which the direct current flows changes between when the battery 14 is charged and when the battery is discharged. That is, a current transformer 21 is provided which is inserted into the DC unit 20 whose DC direction is changed. A full-bridge rectifier circuit 22 is connected to the secondary side of the current transformer 21. The rectifier circuit 22 includes four diodes D1, D2, D3, and D4. The four diodes D1, D2, D3, and D4 include a diode D1 and a diode D3, a diode D2 and a diode D4 connected in series, a connection point between the diode D1 and the diode D3, and a connection point between the diode D2 and the diode D4. Are connected to the secondary coil 21a of the current transformer 21, respectively. The cathodes of the diodes D3 and D4 are connected to the output terminal 22a of the rectifier circuit 22. The shunt resistor R1 for current detection has one end connected to the output terminal 22a and the other end grounded. A resistor R2 is connected in parallel with the secondary coil 21a of the current transformer 21.

  Switching elements Q1, Q2 are connected to the anode sides of the diodes D1, D2, respectively. The switching elements Q1 and Q2 are respectively constituted by p-channel MOSFETs, the drains are the anodes of the diodes D1 and D2, that is, the parasitic diodes of the MOSFETs and the diodes D1 and D2 are connected in the opposite direction, and the sources are grounded. Each of the switching elements Q1 and Q2 receives a control signal from the control device 18 at the gate, and one of the switching elements Q1 and Q2 is on and the other is in correspondence with the direction of the current flowing through the DC unit 20 in response to charging and discharging of the battery 14. It is controlled to be turned off. That is, the selection means for selecting a current path along the flow of the secondary current includes switching elements Q1 and Q2 (transistors). In the rectifier circuit 22, a series circuit of a switching element Q1 and diodes D1 and D3, a series circuit of a switching element Q2 and diodes D2 and D4 are connected in parallel, and the cathodes of the diodes D1, D2, D3, and D4 are secondary currents. It is on the downstream side of the flow. A secondary current flows through the series circuit in which the MOSFET is turned on.

  Next, the operation of the current detection circuit 19 configured as described above will be described. The control device 18 determines whether the bidirectional DC / DC converter 15 is to be charged or discharged from the battery 14 based on the power generation state of the generator 11 and the power necessary for driving the motor 16. The bidirectional DC / DC converter 15 is controlled to a corresponding state.

  When a current flows through the DC unit 20 so that a secondary current flows through the secondary coil 21a of the current transformer 21 in the direction of the solid arrow A1 in FIG. Switching element Q1 is held in the on state, and switching element Q2 is held in the off state. In this state, the secondary side current flows through the path of the switching element Q1 → diode D1 → secondary side coil 21a → diode D4 → shunt resistor R1, and by measuring the terminal voltage of the shunt resistor R1, the current of the current transformer 21 The amount of current flowing on the primary side can be detected.

  Further, when a current flows through the DC unit 20 so that a secondary current flows in the secondary coil 21a of the current transformer 21 in the direction of the two-dot chain line arrow A2 in FIG. By the control signal, the switching element Q2 is held in the on state, and the switching element Q1 is held in the off state. In this state, the secondary side current flows through the path of the switching element Q2, the diode D2, the secondary side coil 21a, the diode D3, and the shunt resistor R1, and the terminal voltage of the shunt resistor R1 is measured to thereby determine the current of the current transformer 21. The amount of current flowing on the primary side can be detected.

  That is, when the voltage V1 of the current flowing on the primary side of the current transformer (CT) 21 changes as shown in FIG. 2, if the on / off of the switching elements Q1 and Q2 is controlled as shown in FIG. The voltage V2 of the current flowing on the secondary side of the current transformer 21 can be detected corresponding to

  For example, if the direction of the current flowing through the DC unit 20 during charging of the battery 14 is the direction in which the current flows through the secondary coil 21a of the current transformer 21 in the direction of the arrow A1, the control device 18 switches the switching element Q1 during charging. A control signal for turning on and turning off the switching element Q2 is output. At the time of discharging, the control device 18 outputs a control signal for turning on the switching element Q2 and turning off the switching element Q1.

  Although direct current flows through the direct current section 20 in both charging and discharging, the switching element Q1 is kept on during charging and the switching element Q2 is kept on during discharging. When current flows in the DC unit 20 as noise in the direction of discharging during charging, an electromotive force in the opposite direction to that of charging is generated in the secondary coil 21a of the current transformer 21. However, since the switching element Q2 constituting the reverse current path is held in the OFF state, no current flows through the shunt resistor R1 even if an electromotive force is generated in the current transformer 21. Accordingly, erroneous detection is prevented.

According to this embodiment, the following effects can be obtained.
(1) The rectifier circuit 22 is a full-bridge rectifier circuit that is used by being connected to the secondary side of the current transformer 21 and selecting a current path along the flow of the secondary current of the current transformer 21 Means (switching elements Q1, Q2) are provided. Therefore, when currents with different directions flow as noise on the primary side, no current flows even if an electromotive force is generated on the secondary side of the current transformer 21. Even when it flows in the direction of, it becomes possible to detect accurately.

  (2) The selection means includes transistors (switching elements Q1, Q2), and the rectifier circuit 22 is a series circuit of selection means (switching element Q1) and diodes D1, D3, and selection means (switching element Q2) and diodes D2, D4. Are connected in parallel, and the cathodes of the diodes D1, D2, D3, and D4 are downstream of the flow of the secondary current. A secondary current flows through the series circuit in which the switching elements Q1 and Q2 are turned on in the series circuit. Then, the current path along the flow of the current generated on the secondary side of the current transformer 21 is selected by controlling on / off of the switching elements Q1, Q2 by the control signal from the control device 18. Therefore, the current path corresponding to the direction of the current flowing through the DC unit 20 is surely selected.

  (3) The switching elements Q1, Q2 are composed of MOSFETs. As shown in FIG. 1B, when a positive voltage is applied to the current transformer 21 on the side of the secondary coil 21a connected to the anode of the diode D1, the switching element Q1 is off and the switching element Q2 is on. A voltage is applied to the diode D1 and the switching element Q1 as shown in FIG. When the switching elements Q1 and Q2 are composed of bipolar transistors, a reverse bias voltage is applied to the switching element Q1 and there is a risk of damage. However, when the switching elements Q1 and Q2 are constituted by MOSFETs, reverse bias voltage is prevented from being applied to the switching element Q1 by the action of the parasitic diode Dp provided in the MOSFETs. In addition, since the MOSFET is a gate insulation type, a current for driving the switching element does not flow into the secondary current.

  (4) The current transformer 21 is inserted in the direct current unit 20 in which the direct current direction is changed in the circuit of the bidirectional DC / DC converter 15. The rectifier circuit 22 is used in a state where an appropriate current path is selected by the selection means (switching elements Q1, Q2) corresponding to the direction of the direct current flowing through the direct current section 20 of the bidirectional DC / DC converter 15. Therefore, it is possible to accurately detect the amount of current flowing through the DC unit 20 in the operating state of the bidirectional DC / DC converter 15, that is, in a state corresponding to charging or discharging of the battery 14.

The embodiment is not limited to the above, and may be embodied as follows, for example.
○ Switching elements are used in place of the diodes D3 and D4. The switching element connected in series with the switching element Q1 is controlled to be turned off when the switching element Q1 is turned on and turned on when the switching element Q1 is turned off. The switching element connected in series with the switching element Q2 is Control is performed so that it is off when Q2 is on and on when Q2 is off. Also in this case, it is possible to accurately detect the direct current flowing in a pulsed manner on the primary side of the current transformer 21 in any direction.

  The transistors constituting the switching elements Q1 and Q2 are not limited to MOSFETs but may be other transistors such as bipolar transistors, IGBTs (Insulated Gate Bipolar Transistors), and junction FETs. When using a bipolar transistor or IGBT, an emitter is connected to a portion to which the source of the MOSFET is connected, and a collector is connected to a portion to which the drain is connected. It is possible to use a transistor having no antiparallel parasitic diode, such as a MOSFET, for the switching elements Q1 and Q2. However, when a reverse bias voltage is applied to the switching elements Q1 and Q2, as described above. Since there is a risk of damage, it is preferable to further provide an antiparallel diode.

O When the transistor which does not have a parasitic diode is used as switching element Q1, Q2, and the diode in antiparallel is not provided, diode D1, D2 does not need to be.
The switching elements Q1, Q2 (transistors) may not necessarily be grounded. For example, instead of grounding the sources of the switching elements Q1, Q2, the other end of the shunt resistor R1 may be connected. However, it is preferable to ground the switching elements Q1 and Q2 in order to fix the operating potential.

  The connection order of the diodes D1 and D3 and the switching element Q1 is not limited to the order of the embodiment. For example, the diode D1 and the switching element Q1 are interchanged, the junction between the diode D1 and the switching element Q1 is connected to the current transformer 21, the diode D1 and the switching element Q1 are interchanged, and the diode D3 and the switching element Q1 These junction points may be connected to the current transformer 21. Further, the diode D3 and the switching element Q1 may be interchanged, and the junction point of the diode D3 and the diode D1 may be connected to the current transformer 21. Similarly, the connection order of the diodes D2 and D4 and the switching element Q2 is not limited to the order of the embodiment. For example, the diode D2 and the switching element Q2 are interchanged, the junction between the diode D2 and the switching element Q2 is connected to the current transformer 21, the diode D2 and the switching element Q2 are interchanged, and the diode D4 and the switching element Q2 These junction points may be connected to the current transformer 21. Further, the diode D4 and the switching element Q2 may be interchanged, and the junction point between the diode D4 and the diode D2 may be connected to the current transformer 21.

  ○ Instead of a series-type hybrid vehicle, the wheel may be used for a parallel-type hybrid vehicle that uses both electric energy (electric power) drive and engine-driven mechanical energy drive. Even in a parallel hybrid vehicle, when the engine efficiency is light and the load is low, the motor is charged instead of the generator, and the motor is driven by a battery to assist the driving force when starting or accelerating when the engine is heavily loaded. The bidirectional DC / DC converter 15 is necessary. Further, the present invention may be applied to a split type hybrid vehicle combining a parallel type and a series type.

  The bidirectional DC / DC converter 15 is not limited to the one provided for charging and discharging a battery serving as a power source for a motor that drives wheels in a hybrid vehicle. For example, in a vehicle having an auxiliary battery driven at a high voltage (42V) and an auxiliary battery driven at a low voltage (12V), a direct current is used to complement the 42V system and the 12V system. You may apply to the bidirectional | two-way DC / DC converter corresponding to both the case where voltage is stepped up to the DC voltage of a different voltage, and the case where it steps down.

  ○ Not only for vehicles, but for other applications, such as uninterruptible power supplies, supply commercial power to the load during normal operation, supply battery power to the load during a power failure, and charge the battery during normal operation You may apply to the apparatus performed from above, or a battery combined use solar power generation facility.

O You may apply not only to a vehicle but to the apparatus provided with the some battery from which voltage differs for other uses.
The power converter is not limited to a bidirectional DC / DC converter, and may be a DC / AC inverter. A power supply device such as AC → DC → AC (any bi-directional power supply device having a DC section) may be used.

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to claim 2 or claim 3, the transistor is grounded.

  (2) A current detection circuit comprising the rectifier circuit of the invention according to claim 1 or 2.

(A) is a block diagram which shows the structure of the electric system of the hybrid vehicle in one Embodiment, (b) is a circuit diagram of a current detection circuit. The wave form diagram which shows a detection voltage waveform. The circuit diagram explaining an effect | action. (A) is a circuit diagram which shows a prior art, (b) is a wave form diagram which shows a detection voltage waveform.

Explanation of symbols

  D1, D2, D3, D4 ... Diode, Dp ... Parasitic diode, Q1, Q2 ... Switching element constituting selection means, 15 ... Bidirectional DC / DC converter as bidirectional power converter, 20 ... DC section, 21 ... current transformer, 22 ... rectifier circuit.

Claims (4)

  A full-bridge rectifier circuit connected to a secondary side of a current transformer, comprising a selection means for selecting a current path along a flow of a secondary current.   The selection means includes a transistor, and the rectifier circuit has two series circuits of the selection means and a diode connected in parallel, and the cathode of the diode is downstream of the flow of the secondary current. The rectifier circuit according to 1.   The rectifier circuit according to claim 2, wherein the transistor is a MOSFET, and the selection unit further includes a diode connected in series in a direction opposite to a parasitic diode of the MOSFET.   The said current transformer is a rectifier circuit as described in any one of Claims 1-3 inserted in the direct current | flow part from which the direction of direct current | flow is changed in the circuit of a bidirectional | two-way power converter device.

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