JP4924499B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device configured to extract a switching output obtained by switching a DC input voltage to an output winding of a power conversion transformer.

  Generally, in an electric vehicle, a low-voltage DC voltage of, for example, about 14 volts is used as a power source for driving vehicle-mounted equipment (auxiliary equipment) such as wipers, headlights, room lights, audio equipment, air conditioners, and various instruments. Is mounted as a power source for driving the motor, and a high voltage battery (main battery) that outputs a high DC voltage of about 350 to 500 V, for example, is mounted. Usually, such a low-voltage battery is charged by rectifying an AC output voltage from an AC generator driven by the rotation of the engine to obtain a high-voltage DC voltage, and using this DC input voltage as a switching power supply ( DC / DC converter) is used to convert to a lower voltage DC voltage and then supply to the low voltage battery. Note that the high-voltage battery is charged by supplying the DC input voltage from the engine side to the high-voltage battery. In this switching power supply device, as described in Patent Document 1, for example, a DC input voltage is once converted into an AC voltage by an inverter circuit, and then the AC voltage is transformed by a voltage conversion transformer and is again DC by a rectifier circuit or the like. Voltage conversion is performed by converting the voltage.

  Further, for example, Patent Document 1 and Patent Documents 2 and 3 disclose a switching power supply device having a function of charging a high voltage battery by inputting an AC voltage from a so-called commercial power supply. According to such a switching power supply device, for example, when applied to an electric vehicle, the high voltage battery can be charged even when the engine is stopped and the DC input voltage is not supplied to the high voltage battery. It is considered to be.

JP-A-8-317508 Japanese Patent Laid-Open No. 5-284748 Japanese Patent No. 2919363

  Here, in this type of switching power supply device (charger), in order to remove ripples based on the commercial frequency in parallel with an inverter circuit (for example, a bridge circuit) composed of switching elements, a relatively large capacitor ( Smoothing capacitor) is connected. Therefore, when a commercial power supply is supplied, a relatively large inrush current flows into the capacitor via the inverter circuit or the like, thereby possibly damaging the switching element or the like in the inverter circuit. In addition, if there is a risk of such element breakage, the reliability of the apparatus is also lowered.

  Therefore, as a technique for solving such a problem, for example, as shown in Patent Documents 2 and 3, it is considered that a resistor for suppressing inrush current is arranged on a path through which inrush current flows. It is done. However, this method requires a switch circuit for bypassing the resistor when the capacitor is charged and the inrush current stops flowing, or the resistor itself is burned by a relatively large inrush current. There was still room for improvement, such as having to use a high-rated one so that it would not run out.

  The present invention has been made in view of such problems, and an object thereof is to provide a switching power supply device capable of improving the reliability of the device with a relatively simple configuration.

  A switching power supply apparatus according to the present invention includes a transformer including a first transformer coil and a second transformer coil that are magnetically coupled to each other, and is disposed between the first transformer coil and the first DC power supply. Are arranged between the second transformer coil and the AC voltage input terminal, and the pair of switches are connected in series. A bidirectional type second switching circuit configured such that connected switch rows are connected in parallel to each other, and a second switching circuit disposed between the second switching circuit and the AC voltage input terminal. 1, a smoothing capacitor disposed between the second switching circuit and the first rectifier circuit, and a control unit. Here, when the first DC power source is charged based on the AC input voltage input from the AC voltage input terminal, the control unit performs the original charging for the first DC power source based on the AC input voltage. Before performing, the operation of the first and second switching circuits is controlled so that predetermined smoothing is performed on the smoothing capacitor from the first DC power source in accordance with the charge amount in the smoothing capacitor. is there. The “AC input voltage” includes a voltage used as a power supply voltage for electrical equipment, and is preferably used for a so-called commercial power supply.

  In the switching power supply of the present invention, when the first DC power supply is charged based on the AC input voltage input from the AC voltage input terminal, the original charging of the first DC power supply is performed based on the AC input voltage. Before being performed, the operations of the first and second switching circuits are controlled so that a predetermined preliminary charge is performed from the first DC power supply to the smoothing capacitor in accordance with the amount of charge in the smoothing capacitor. Specifically, the preliminary charging is performed as follows. That is, a DC input voltage is supplied from the first DC power supply, the DC input voltage is converted into a pulse voltage by the first switching circuit, and the pulse voltage is transformed by a transformer. The transformed pulse voltage is rectified by the second switching circuit, and the smoothing capacitor is precharged based on the rectified voltage. Moreover, the original charge with respect to a 1st DC power supply is performed as follows. That is, an AC input voltage is input from the AC voltage input terminal, and the AC input voltage is rectified and smoothed by the first rectifier circuit and the smoothing capacitor, and then converted into a DC voltage, and then a pulse based on the DC voltage is used. A voltage is generated in the second switching circuit and transformed by a transformer. Then, the transformed pulse voltage is rectified by the first switching circuit, and the direct-current output voltage is supplied to the first direct-current power supply, whereby the original charge to the first direct-current power supply is performed. In this way, since the smoothing capacitor is preliminarily charged before the original charging of the first DC power supply is performed, the AC input voltage is changed to the original voltage of the first DC power supply. As a result, the occurrence of an inrush current flowing into the smoothing capacitor is suppressed. Further, unlike the prior art, there is no need to separately provide a resistor for suppressing inrush current and a switch circuit (dedicated component for suppressing inrush current) for bypassing it, so that the apparatus configuration is not complicated.

  The switching power supply device according to the present invention includes a first detection unit that detects a charge amount in the smoothing capacitor, and the control unit performs preliminary charging according to the charge amount in the smoothing capacitor detected by the first detection unit. And it is preferable to control to perform the original charging. When configured in this manner, preliminary charging can be performed in consideration of the amount of charge in the smoothing capacitor, and an efficient charging operation can be performed.

  In this case, the control unit controls to perform preliminary charging when the amount of charge in the smoothing capacitor is less than a predetermined first threshold, and performs original charging when the amount of charge in the smoothing capacitor is equal to or greater than the first threshold. It is possible to control as follows. In such a configuration, preliminary charging is performed only when necessary (when the amount of charge in the smoothing capacitor is small), so that an efficient charging operation can be performed while suppressing the occurrence of inrush current. In this case, it is more preferable that the first threshold value is set so as to change according to the charge amount in the first DC power supply. When configured in this way, preliminary charging and original charging in consideration of the amount of charge in the first DC power supply become possible, so that the occurrence of inrush current is suppressed while avoiding overdischarge in the first DC power supply. It becomes possible.

  In the switching power supply device of the present invention, a second detection unit that detects a charge amount in the first DC power supply is provided, and the control unit is charged in the first DC power supply detected by the second detection unit. It is preferable to perform control so that preliminary charging is performed according to the amount. When configured in this way, precharging can be performed in consideration of the amount of charge in the first DC power supply, so that it is possible to suppress the occurrence of inrush current while avoiding overdischarge in the first DC power supply. Become. Further, in this case, the control unit performs control so that preliminary charging is not performed when the charge amount in the first DC power source is less than the predetermined second threshold, and the charge amount in the first DC power source is the second charge amount. It is possible to perform control so that preliminary charging is performed when the threshold value is exceeded. When configured in this way, it is avoided that the pre-charging is performed beyond the allowable amount in the first DC power supply, so that the occurrence of inrush current is suppressed while avoiding overdischarge in the first DC power supply. Is possible.

  The switching power supply device of the present invention includes a third detection unit that detects whether or not the AC input voltage is supplied from the AC voltage input terminal, and the control unit is based on a detection result by the third detection unit. When it is determined that the AC input voltage is supplied, it is preferable to perform control so that preliminary charging and original charging are performed. When configured in this manner, it is possible to avoid malfunction (failure of charging operation) when a commercial power source or the like is not connected to the AC voltage input terminal. In this case, it is more preferable that the control unit determines whether or not to perform preliminary charging and original charging in consideration of a plurality of detection results obtained by the third detection unit. When configured in this manner, malfunction (failure of charging operation) can be avoided more reliably.

  In the switching power supply device of the present invention, when the controller performs precharging based on the DC input voltage supplied from the first DC power supply, the first switching circuit performs a DC / AC conversion operation. When the second switching circuit is controlled to perform a rectifying operation and the original charging is performed based on the AC input voltage, the rectifying circuit performs a rectifying operation and the second switching circuit performs a DC / AC conversion operation. And the first switching circuit can be controlled to perform a rectifying operation. In this case, the first switching circuit may be configured to rectify in synchronization with the second switching circuit.

  In the switching power supply device of the present invention, the first rectifier circuit is constituted by a bidirectional third switching circuit including at least one switch row in which a pair of switches are connected in series, and the AC voltage The input terminal may function as an AC voltage input / output terminal. In such a configuration, during the original charging of the first DC power supply, an AC input voltage is input from the AC voltage input / output terminal, and this AC input voltage is rectified and smoothed by the third switching circuit and the smoothing capacitor. After being converted to a DC voltage, the pulse voltage based on this DC voltage is generated in the second switching circuit and transformed by the transformer. Further, it is possible to output an AC output voltage from the AC voltage input / output terminal while performing preliminary charging based on the DC input voltage supplied from the first DC power supply.

  In this case, when the control unit outputs the AC output voltage from the AC voltage input / output terminal while performing preliminary charging based on the DC input voltage supplied from the first DC power supply, When the switching circuit 3 performs a DC / AC conversion operation and the second switching circuit performs a rectification operation, the original charging is performed based on the AC input voltage input from the AC voltage input / output terminal. Can be controlled such that the third switching circuit performs an AC / DC conversion operation, the second switching circuit performs a DC / AC conversion operation, and the first switching circuit performs a rectification operation. . The “AC output voltage” includes a voltage used as a power supply voltage for an electric device, and is preferably used for a so-called commercial power supply.

  Moreover, when the said control part inputs alternating current input voltage from an alternating voltage input / output terminal, it is preferable to control so that a 3rd switching circuit also performs power factor improvement operation | movement. When comprised in this way, the power factor at the time of converting the voltage of an alternating current input voltage is improved, and a ripple voltage becomes small.

  In the switching power supply device of the present invention, the transformer has a third transformer coil magnetically coupled to the first transformer coil and the second transformer coil, and the third transformer coil and the second DC power source A second rectifier circuit may be further provided between them. In such a configuration, the pulse voltage generated in the first switching circuit based on the DC input voltage or the pulse voltage generated in the second switching circuit based on the AC input voltage is transformed by the transformer, The pulse voltage thus input is input to the rectifier circuit via the third transformer coil. Then, the transformed pulse voltage is rectified by a rectifier circuit, whereby a DC voltage is supplied to the second DC power supply in addition to the first DC power supply. That is, based on the DC input voltage from the first DC power supply, in addition to the precharging operation to the smoothing capacitor, the DC voltage conversion (DC / DC converter) operation to the second DC power supply is performed. The charging operation is performed on at least one of the first DC power source and the second DC power source by the DC voltage based on the AC input voltage from the AC voltage input terminal.

  According to the switching power supply device of the present invention, when charging the first DC power source based on the AC input voltage input from the AC voltage input terminal, the original power source for the first DC power source is based on the AC input voltage. Before charging, the operation of the first and second switching circuits is controlled so that a predetermined preliminary charge is performed from the first DC power source to the smoothing capacitor according to the amount of charge in the smoothing capacitor. Therefore, it is possible to suppress the occurrence of an inrush current that flows into the smoothing capacitor due to the AC input voltage during the original charging of the first DC power supply without providing a separate dedicated component for suppressing the inrush current as in the prior art. Can do. Therefore, it is possible to improve the reliability of the apparatus with a relatively simple configuration.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a circuit configuration of a switching power supply apparatus according to the first embodiment of the present invention. The switching power supply device is applied to, for example, an automobile, and includes a transformer 2, a capacitor C <b> 1 provided between the transformer 2 and a main battery 10 described later, a voltage detection unit 13, and a bidirectional switching circuit. 11 and a PFC (Power Factor Correction) circuit including a bidirectional switching circuit 41, a voltage detector 42, and a capacitor C3 provided between the transformer 2 and AC voltage input terminals T5 and T6 described later. 43, a rectifier circuit 44, a relay unit 45, and a voltage detection unit 46.

  The switching power supply further includes a SW drive circuit 12 for driving the switching circuit 11, a SW drive circuit 491 for driving the switching circuit 41, and a SW drive circuit 492 for driving the PFC circuit 43. The control unit 6 that controls the SW drive circuits 12, 491, 492, a transformer 5, an isolation amplifier 53, and a differential amplifier 47 are provided.

  The capacitor C1 is disposed between the high voltage line LH1 and the low voltage line LL1, and functions as a smoothing capacitor. One end of the high voltage line LH1 is connected to the input / output terminal T1, one end of the low voltage line LL1 is connected to the input / output terminal T2, and the main battery 10 is disposed between the input / output terminals T1 and T2. The main battery 10 is for supplying a DC input voltage Vdcin between the input / output terminals T1 and T2. For example, when this switching power supply is applied to an automobile, it is connected to a driving inverter or a step-up / down converter. For example, it functions as a high voltage battery of about 350 to 500V.

  The voltage detection unit 13 is disposed between the capacitor C1 and a switching circuit 11 to be described later. The voltage detection unit 13 detects the DC voltage V1 between both ends of the capacitor C1, and the voltage corresponding to the detected DC voltage V1 is an isolation amplifier. 53 is output. As a specific circuit configuration of the voltage detection unit 13, for example, the DC voltage V1 is detected by a voltage dividing resistor (not shown) disposed between the high voltage line LH1 and the low voltage line LL1. The thing which produces | generates the voltage according to it etc. are mentioned.

  The switching circuit 11 is a full bridge type switching circuit having four switching elements Q1 to Q4 and four diodes D1 to D4. Specifically, one end of the switching element Q1 is connected to the high voltage line LH1, and the other end is connected to one end of the switching element Q2 and one end of a winding 21 of the transformer 2 described later. One end of the switching element Q3 is connected to the high voltage line LH1, and the other end is connected to one end of the switching element Q4 and the other end of the winding 21 of the transformer 2. The other end of switching element Q2 and the other end of switching element Q4 are each connected to low voltage line LL1. The diodes D1 to D4 are connected in parallel in opposite directions between both ends of the switching elements Q1 to Q4 (the cathode of each diode is connected to the high voltage line LH1 side, and the anode of each diode is connected to the low voltage line LL1 side. It is connected). That is, one switching element and one diode constitute one bidirectional switch, whereby the switching circuit 11 functions as a bidirectional switching circuit. Specifically, as will be described in detail later, the switching circuit 11 functions as a DC / AC inverter circuit or a rectifier circuit that performs DC / AC conversion (DC to AC conversion). The switching elements Q1 to Q4 are configured by, for example, a bipolar transistor, an IGBT (Insulated Gate Bipolar Transistor), a field effect transistor (MOS-FET), or the like. When these switching elements Q1 to Q4 are respectively constituted by MOS-FETs and have parasitic diode components, these parasitic diode components may be used instead of the diodes D1 to D4.

  The SW drive circuit 12 generates switching control signals S1 to S4 under the control of the control unit 6 described later, and thereby controls the switching operations of the switching elements Q1 to Q4 in the switching circuit 11, respectively. Specifically, although details will be described later, the switching circuit 11 is controlled to perform the above-described DC / AC conversion operation and rectification operation.

  The transformer 2 has one winding 21 provided on the main battery 10 side and one winding 22 provided on the input terminals T5 and T6 described later, and the windings 21 and 22 are mutually connected. They are magnetically coupled so that their polarities are in the same direction. Winding 21 is arranged between the other end of switching element Q1 and one end of switching element Q4. Both ends of the winding 22 are connected to a switching circuit 41 described later.

The switching circuit 41 is a full-bridge type switching circuit having four switching elements Q5 to Q8 and four diodes D5 to D8. Specifically, one end of the switching element Q5 is connected to the high voltage line LH4, and the other end is connected to one end of the switching element Q6 and one end of the winding 22 of the transformer 2. One end of the switching element Q7 is connected to the high voltage line LH4, and the other end is connected to one end of the switching element Q8 and the other end of the winding 22. The other end of switching element Q6 and the other end of switching element Q8 are each connected to low voltage line LL4. The diodes D5 to D8 are connected in parallel in opposite directions between both ends of the switching elements Q5 to Q8 (the cathode of each diode is connected to the high voltage line LH4 side, and the anode of each diode is connected to the low voltage line LL4 side. It is connected). That is, one switching element and one diode constitute one bidirectional switch, whereby the switching circuit 41 also functions as a bidirectional switching circuit. Specifically, although the details will be described later, the switching circuit 41 functions as a rectifier circuit or a DC / AC inverter circuit. The switching elements Q5 to Q8 are also configured by, for example, bipolar transistors, IGBTs, or MOS-FETs. However, when the switching elements Q5 to Q8 are each configured by a MOS-FET and have a parasitic diode component, the diode D5 These parasitic diode components may be used instead of .about.D8.

The SW drive circuit 491 generates switching control signals S5 to S8 under the control of the control unit 6 described later, and thereby controls the switching operations of the switching elements Q5 to Q8 in the switching circuit 41, respectively. Specifically, although details will be described later, the switching circuit 41 is controlled to perform the above-described rectification operation and DC / AC conversion operation.

  The voltage detector 42 is disposed between the switching circuit 41 and a PFC circuit 43 described later, detects the voltage V3 across the capacitor C3, and supplies the voltage corresponding to the detected voltage V3 to the controller 6. Output. As a specific circuit configuration of the voltage detection unit 42, the voltage V3 is detected by, for example, a voltage dividing resistor (not shown) arranged between the connection lines LH4 and LL4, similarly to the voltage detection unit 13. In addition, there is a device that generates a voltage corresponding to this.

  The PFC circuit 43 includes an inductor 43L, a diode 43D, a switching element Q9, and a capacitor C3. One end of the inductor 43L is connected to the anode of the diode 43D and one end of the switching element Q9, the other end of the switching element Q9 is connected to the low voltage line LL4, and the capacitor C3 is connected to the high voltage line LH4 (the diode 43D and the voltage detection unit 42). Between the other end of the switching element Q9 and the voltage detector 42). Moreover, the switching element Q9 is comprised by IGBT, MOS-FET, etc., for example. Although the details will be described later in the PFC circuit 43, the input voltage V43 to the PFC circuit 43 is boosted and stabilized to improve the power factor. Note that only the capacitor C3 functioning as a smoothing capacitor may be provided instead of the PFC circuit 43. However, when the PFC circuit 43 of the present embodiment is provided, the switching operation of the switching element Q9 over the entire input frequency. This is preferable because the peak current is reduced and the ripple voltage is smaller than that of a smoothing capacitor of the same capacity.

  The SW drive circuit 492 generates a switching control signal S9 under the control of the control unit 6, and thereby controls the switching operation (PFC operation) of the switching element Q9 in the PFC circuit 43.

  The rectifier circuit 44 is disposed between the PFC circuit 43 and the relay unit 45, and constitutes a bridge circuit including diodes 44D1 to 44D4. Specifically, the anode of the diode 44D1 and the cathode of the diode 44D2 are connected to the input terminal T6 via the connection line L42, and the anode of the diode 44D3 and the cathode of the diode 44D4 are connected to the input terminal T5 via the connection line L41. It is connected. The cathode of the diode 44D1 and the cathode of the diode D44D3 are connected to one end of the high voltage line LH4 (one end of the inductor 43L in the PFC circuit 43), and the anode of the diode 44D2 and the anode of the diode 44D4 are connected to one end of the low voltage line LL4. It is connected. A commercial power supply 40 is connected between the input terminals T5 and T6 so that an AC input voltage Vacin (so-called commercial voltage) is input.

  The relay unit 45 is disposed between the rectifier circuit 44 and a voltage detection unit 46 described later, and has a pair of relays 451 and 452. Specifically, the relay 451 is inserted and arranged on the connection line L41, and the relay 452 is inserted and arranged on the connection line L42. The relays 451 and 452 are supplied with switching control signals S14 and S15 from the control unit 6, respectively, so that the main battery 10 can be charged by the original charging using the commercial power source 40. Become.

  The voltage detection unit 46 is disposed between the relay unit 45 and the input terminals T5 and T6, and detects an AC voltage (specifically, an AC input voltage Vacin) between the input terminals T5 and T6. A voltage corresponding to the detected AC input voltage Vacin is output to the differential amplifier 47. As a specific circuit configuration of the voltage detection unit 46, as with the voltage detection units 13 and 42, a voltage dividing resistor (not shown) arranged between the connection line L41 and the connection line L42 is used. Examples include detecting the AC input voltage Vacout and generating a voltage corresponding to the AC input voltage Vacout.

  The isolation amplifier 53 amplifies the voltage corresponding to the DC voltage V1 detected by the voltage detector 13 while being electrically insulated between the winding 21 side and the winding 22 side in the transformer 2, and the amplification The output voltage is output to the control unit 6.

  The differential amplifier 47 amplifies the AC input voltage Vacin detected by the voltage detection unit 46 and outputs the amplified voltage to the control unit 6.

  The transformer 5 includes one winding 51 provided on the main battery 10 side (winding 21 side of the transformer 2) and one winding provided on the input terminals T5 and T6 side (winding 22 side of the transformer 2). The windings 51 and 52 are magnetically coupled so that their polarities are in the same direction. The transformer 5 supplies the control signal of the SW drive circuit 12 by the control unit 6 to the SW drive circuit 12 while being electrically insulated between the winding 21 side and the winding 22 side in the transformer 2. belongs to.

  Based on the DC voltage V1 detected by the voltage detection unit 13, the DC voltage V3 detected by the voltage detection unit 42, and the AC input voltage Vacin detected by the voltage detection unit 46, the control unit 6 491 and 492 and the relay unit 45 are respectively controlled. Accordingly, switching control signals S1 to S9, S14, and S15 are output from the SW drive circuits 12, 491, 492 and the relay unit 45, and the switching elements Q1 to Q4 in the switching circuit 11 and the switching elements Q5 to Q8 in the switching circuit 41 are output. The switching operations of the switching element Q9 in the PFC circuit 43 and the relays 451 and 452 in the relay unit 45 are controlled.

  Here, the winding 21 corresponds to a specific example of “first transformer coil” in the present invention, and the winding 22 corresponds to a specific example of “second transformer coil” in the present invention. The main battery 10 corresponds to a specific example of “first DC power source” in the present invention. The transformer 2 corresponds to a specific example of “transformer” in the present invention. Further, the switching circuit 11 corresponds to a specific example of “first switching circuit” in the present invention, and the switching circuit 41 corresponds to a specific example of “second switching circuit” in the present invention. The rectifier circuit 44 corresponds to a specific example of “first rectifier circuit” in the present invention, and the control unit 6 and the SW drive circuits 12, 491, and 492 correspond to a specific example of “control unit” in the present invention. To do. The capacitor C3 corresponds to a specific example of “smoothing capacitor” in the present invention. The voltage detection unit 42 corresponds to a specific example of “first detection unit” in the present invention, and the voltage detection unit 13 corresponds to a specific example of “second detection unit” in the present invention. The unit 46 corresponds to a specific example of a “third detection unit” in the present invention. Further, the input terminals T5 and T6 correspond to a specific example of “AC voltage input terminal” in the present invention.

  Next, the operation of the switching power supply having the above configuration will be described in detail.

  In this switching power supply device, based on the AC input voltage Vacin supplied from the commercial power supply 40, the relay unit 45, the rectifier circuit 44, the PFC circuit 43, the switching circuit 41, the transformer 2, and the switching circuit 11, as described below, The main battery 10 is charged.

  At this time, if the commercial power source 40 is connected to the rectifier circuit 44 and the PFC circuit 43 via the relay unit 45 without considering anything, for example, FIG. 2A (a state in the positive half-wave period) and FIG. 2 (B) (the state of the negative half-wave period), relatively large inrush currents I101 and I102 may flow into a relatively large capacitor C3 functioning as a smoothing capacitor. In such a case, the diodes 44D1 to 44D4 in the rectifier circuit 44 may be damaged. In addition, if there is a risk of such element damage, the reliability of the apparatus will also be reduced.

  Here, in the conventional switching power supply device, a resistor (see FIG. 2) on the path (for example, the high voltage line LH4, the low voltage line LL4 or the connection lines L41 and L42 in FIG. 2) through which such an inrush current flows. Not shown; dedicated parts for inrush current suppression) are arranged. However, this method requires a switch circuit (dedicated component for suppressing inrush current) for bypassing the resistor when a smoothing capacitor (for example, capacitor C3 in FIG. 2) is charged and no inrush current flows. And a resistor having a high rating must be used so that the resistor itself does not burn out due to a relatively large rush current, and the member cost increases.

  Therefore, in the switching power supply device of the present embodiment, for example, as shown in FIG. 3, the control operation of charging by the control unit 6 is performed. Specifically, when the main battery 10 is charged based on the AC input voltage Vacin input from the input terminals T5 and T6, before the main battery 10 is originally charged based on the AC input voltage Vacin. The operations of the switching circuits 11 and 41, the PFC circuit 43, and the relay unit 45 are controlled so that the main battery 10 performs predetermined preliminary charging described below on the capacitor C3 according to the amount of charge in the capacitor C3.

  Hereinafter, with reference to FIGS. 3 to 8 in addition to FIG. 1, the charging control operation by the control unit 6 will be described in detail.

  Here, FIG. 4 is a circuit diagram for explaining the precharging operation according to the present embodiment. FIG. 5 is a timing waveform diagram showing an example of the precharging operation. (A) shows the switching control signals S1 and S4, (B) shows the switching control signals S2 and S3, and (C). Is the voltage V22 generated across the winding 22 of the transformer 2, (D) is the switching control signal S5, S8, (E) is the switching control signal S6, S7, (F) is the voltage across the capacitor C3. The voltage V3 is represented. FIG. 6 is a circuit diagram for explaining the original charging operation according to the present embodiment. FIGS. 7 and 8 are timing waveform diagrams showing an example of the original charging operation. Specifically, FIG. 7 shows an operation waveform until the voltage V3 across the capacitor C3 is generated based on the AC input voltage Vacin. (A) shows the AC input voltage Vacin, and (B) shows the operation waveform. The input voltage to the PFC circuit 43 (output voltage from the bridge circuit by the diodes 44D1 to 44D4) V43, (C) the switching control signal S9, (D) the current I43L flowing through the inductor L43, (E) the capacitor A voltage V3 between both ends of C3 is shown. FIG. 8 shows operation waveforms until the capacitor C1 is charged (charging the main battery 10) based on the voltage V3. (A) shows the switching control signals S5 and S8, and (B) shows the switching control. Signals S6 and S7, (C) the voltage V21 generated across the winding 21 of the transformer 2, (D) the switching control signals S1 and S4, (E) the switching control signals S2 and S3, ( F) represents the voltage V1 across the capacitor C1, respectively. For the voltages V1, V21, V22, V3, V43, Vacin and the current I43L, the direction of the arrow shown in FIG. 1 represents the positive direction.

  First, the control unit 6 controls the relay unit 45 with the switching control signals S14 and S15 so that the relays 451 and 452 are turned off, for example, as shown in FIG. 1 (step S101 in FIG. 3).

  Next, the control unit 6 determines whether or not the AC input voltage Vacin is input between the input terminals T5 and T6, that is, whether or not the commercial power supply 40 is connected to the input terminals T5 and T6. Judgment is made based on the detected voltage (step S102). Specifically, when it is determined that the commercial power supply 40 is connected to the input terminals T5 and T6 based on the detected voltage (step S102: Y), the process proceeds to the next step S104. On the other hand, if it is determined that the commercial power source 40 is not connected to the input terminals T5 and T6 (step S102: N), it is determined that the subsequent preliminary charging and the original charging are not performed, and the AC unconnected flag is set. Generated (step S103), and the entire process ends.

  Next, the control unit 6 determines whether or not to perform preliminary charging in step S107, which will be described later, in consideration of the amount of charge in the capacitor C3. Specifically, it is determined whether or not the DC voltage V3 detected by the voltage detector 42 is a value equal to or higher than a predetermined threshold voltage Vth3 (one specific example of the first threshold) (step S104). When it is determined that the DC voltage V3 is equal to or higher than the threshold voltage Vth3 (step S104: Y), it is determined that there is no possibility that an excessive inrush current flows, so that it is not necessary to perform preliminary charging, and step S109 described later is performed. Proceed to On the other hand, when it is determined that the DC voltage V3 is lower than the threshold voltage Vth3 (step S104: N), it is determined that precharging needs to be performed because an excessive input current may flow, and the next step Proceed to S105.

  Next, the control unit 6 considers the amount of charge in the main battery 10 and determines whether to perform preliminary charging in the next step S107. Specifically, it is determined whether or not the DC voltage V1 detected by the voltage detector 13 is a value equal to or higher than a predetermined threshold voltage Vth1 (one specific example of the second threshold) (step S105). When it is determined that the DC voltage V1 is lower than the threshold voltage Vth1 (step S105: N), if the preliminary charging is performed as it is, the main battery 10 may be in an overdischarged state, so that the preliminary charging is performed. If not, a main battery overdischarge flag is generated (step S106), and the entire process is terminated. On the other hand, when it is determined that the DC voltage V1 is equal to or higher than the threshold voltage Vth1 (step S105: Y), it is determined that the main battery 10 is in an overdischarged state, so that the preliminary charging is performed. The process proceeds to step S107.

  Next, the control unit 6 controls the operation of the switching circuits 11 and 41 so that predetermined preliminary charging is performed from the main battery 10 to the capacitor C3 (step S107). Specifically, for example, as shown in FIG. 4 and the energy transmission path 71 shown in FIG. 4, preliminary charging is performed.

  First, when the DC input voltage Vdcin is input from the main battery 10 via the input / output terminals T1 and T2, as indicated by the timings t1 to t8 in FIG. 5, the switching control signals S1 to S4 (FIG. 5 (A), Based on (B)), an alternating pulse voltage is generated in the switching circuit 11 and supplied to the winding 21 of the transformer 2. At this time, a transformed AC pulse voltage V22 is extracted from the winding 22 of the transformer 2 (FIG. 5C). Note that the degree of transformation in this case is determined by the turn ratio between the winding 21 and the winding 22.

  Next, the transformed AC pulse voltage is rectified by the diodes D5 to D8 in the switching circuit 41 functioning as a rectifier circuit. As a result, a rectified output (DC voltage V3) as shown in FIG. 5F, for example, is generated between the high-voltage line LH4 and the low-voltage line LL4 (between both ends of the capacitor C3). The switching elements Q5 to Q8 perform the PWM operation based on the switching control signals S5 to S8 (FIGS. 5D and 5E), and the synchronous rectification operation is performed in the switching circuit 41. This is to reduce the switching loss at ~ Q8.

  In this way, when the DC input voltage Vdcin is supplied from the main battery 10, the switching circuit 11, the SW drive circuit 12, the windings 21, 22 </ b> A and 22 </ b> B of the transformer 2 are switched based on the DC input voltage Vdcin. A DC voltage V3 is generated by a DC / DC converter including the circuit 41 and the capacitor C3, and the capacitor C3 is precharged.

  Returning to FIG. 3, next, the control unit 6 sequentially determines whether or not to continue the preliminary charging in step S <b> 107 in consideration of the charge amount in the capacitor C <b> 3. Specifically, it is determined again whether or not the DC voltage V3 detected by the voltage detector 42 is a value equal to or higher than the threshold voltage Vth3 (step S108). When it is determined that the DC voltage V3 is equal to or higher than the threshold voltage Vth3 (step S108: Y), it is determined that there is no possibility of excessive rush current flowing, so that it is not necessary to continue the preliminary charging, and a step described later Proceed to S109. On the other hand, when it is determined that the DC voltage V3 is less than the threshold voltage Vth3 (step S108: N), it is determined that it is necessary to continue the preliminary charging because there is still a possibility that an excessive input current flows. Proceed to step S107.

  Next, as shown in FIG. 6, for example, the control unit 6 controls the relay unit 45 with the switching control signals S14 and S15 so that the relays 451 and 452 are turned on (step S109). As a result, the commercial power supply 40 is connected to the rectifier circuit 44, the PFC circuit 43, and the like via the relay unit 45.

  Next, the control unit 6 performs the charging operation from the commercial power source 40 to the capacitor C3 (step S110) and performs the original charging operation to the main battery 10 by the energy accumulated in the capacitor C3 (step S110). S111), the operations of the PFC circuit 43 and the switching circuits 11 and 41 are controlled. Specifically, for example, as shown in the energy transmission path 72 shown in FIG. 6 and FIGS.

  First, when an AC input voltage Vacin (commercial voltage) as shown in FIG. 7A is input from the commercial power supply 40 via the input terminals T5 and T6, the AC input voltage Vacin is a bridge circuit composed of diodes 44D1 to 44D4. The voltage V43 as shown in FIG. 7B is generated and input to the PFC circuit 43. At this time, the switching element Q9 repeats the on / off operation as shown in FIG. 7C (for example, the on state from timing t11 to t12, t13 to t14, and the off state from timing t12 to t13). As a result, the current I43L flowing through the inductor 43L becomes a triangular wave as shown in FIG. 7D, and the timing of the voltage at the apex thereof is indicated by reference numeral G1, and the timings t11 to t16, t16 to t18,. A half-wave sine wave with one period is shown. Note that a current I43L (ave) illustrated in FIG. 7D represents an average current of the current I43L. Thus, the voltage V3 across the capacitor C3 becomes a DC voltage having a constant value as shown in FIG. 7F by the action of the PFC circuit 43.

  Next, the main battery 10 is originally charged based on the voltage V3 accumulated across the capacitor C3. Specifically, the switching circuit 41 functions as an inverter circuit, and the switching elements Q5 to Q8 are turned on / off as shown at timings t21 to t28 in FIGS. 8A and 8B. An alternating pulse voltage is generated in the winding 22 of the transformer 2. Then, according to the turn ratio of the winding 22 and the winding 21, a transformed AC pulse voltage V21 as shown in FIG. Next, the switching circuit 11 functions as a rectifier circuit, and the switching elements Q1 to Q4 are turned on / off as shown in FIGS. 8D and 8E, whereby the AC pulse voltage V21 is rectified, A constant DC voltage V1 as shown in FIG. 8F is applied across the capacitor C1. Thus, the main battery 10 is originally charged based on the DC voltage V1.

  In this way, the main battery 10 is charged based on the AC input voltage Vacin (commercial voltage) input from the commercial power supply 40, and the charging control operation by the control unit 6 is completed.

  As described above, in the present embodiment, when the main battery 10 is charged based on the AC input voltage Vacin input from the input terminals T5 and T6, the original charging of the main battery 10 based on the AC input voltage Vacin is performed. Before performing the operation, the operation of the switching circuits 11, 41, etc. is controlled so as to perform a predetermined preliminary charge from the main battery 10 to the capacitor C3 according to the amount of charge in the capacitor C3. In this case, it is possible to suppress the occurrence of an inrush current flowing to the capacitor C3 due to the AC input voltage Vacin when the main battery 10 is originally charged without separately providing a dedicated component for suppressing the inrush current. Therefore, it is possible to improve the reliability of the apparatus with a relatively simple configuration.

  In addition, a voltage detection unit 42 for detecting a charge amount (DC voltage V3) in the capacitor C3 is provided, and preliminary charging and original charging are performed according to the charge amount in the capacitor C3 detected by the voltage detection unit 42. As a result, preliminary charging can be performed in consideration of the amount of charge in the capacitor C3, and an efficient charging operation can be performed.

  Specifically, preliminary charging is performed when the amount of charge (DC voltage V3) in the capacitor C3 is less than a predetermined threshold voltage Vth3, and when the amount of charge (DC voltage V3) in the capacitor C3 is greater than or equal to the threshold voltage Vth3. Since the original charging is performed, the preliminary charging is performed only when necessary (when the amount of charge in the capacitor C3 is small), and an efficient charging operation can be performed while suppressing the occurrence of inrush current. It becomes possible.

  In addition, a voltage detection unit 13 for detecting a charge amount (DC voltage V1) in the main battery 10 is provided, and preliminary charging is performed according to the charge amount (DC voltage V1) in the main battery 10 detected by the voltage detection unit 13. Since it performed, the preliminary charge which considered the charge amount in the main battery 10 was attained, and generation | occurrence | production of an inrush current can be suppressed, avoiding the overdischarge in the main battery 10. FIG.

  Specifically, when the amount of charge (DC voltage V1) in the main battery 10 is less than a predetermined threshold voltage Vth1, preliminary charging is not performed, and the amount of charge (DC voltage V1) in the main battery 10 is equal to the threshold voltage Vth1. Since the preliminary charging is performed at the above time, it is possible to avoid the preliminary charging exceeding the allowable amount in the main battery 10, and to suppress the occurrence of the inrush current while avoiding the overdischarge in the main battery 10. It becomes possible to do.

  Further, a voltage detection unit 46 for detecting whether or not the AC input voltage Vacin is supplied from the input terminals T5 and T6 is provided, and it is determined that the AC input voltage Vacin is supplied based on the detection result by the voltage detection unit 36. In this case, since preliminary charging and original charging are performed, it is possible to avoid malfunction (failure of charging operation) when the commercial power supply 40 is not connected to the input terminals T5 and T6.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  FIG. 9 illustrates a circuit configuration of the switching power supply device according to the present embodiment. In this figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The switching power supply according to the present embodiment is different from the switching power supply according to the first embodiment in that a winding 23 (consisting of a pair of windings 23A and 23B) is added to the other side of the transformer 2 instead of the transformer 2. A transformer 2A is provided, and a rectifier circuit 31, a smoothing circuit 32, and a voltage detector 33 are provided between the transformer 2A and the auxiliary battery 30.

  Both ends of the windings 23A and 23B of the transformer 2A are connected to the rectifier circuit 31, respectively.

  The rectifier circuit 31 has two diodes 31D1 and 31D2. The anode of the diode 31D1 is connected to one end of the winding 23A, the anode of the diode 31D2 is connected to one end of the winding 23B, and the cathodes of the diodes 31D1 and 31D2 are commonly connected to the high voltage line LH3. The other ends of the windings 23A and 23B are commonly connected to each other and connected to the low voltage line LL3. That is, the rectifier circuit 31 is a cathode common type rectifier circuit.

  The smoothing circuit 32 includes an inductor 32L and a capacitor 32C. The inductor 32L is inserted and disposed on the high voltage line LH3, one end is connected to the cathodes of the diodes 31D1 and 31D2, and the other end is connected to the output terminal T3 via the voltage detection unit 33. The capacitor 32C is disposed between the high voltage line LH3 (the other end portion of the inductor 32L) and the low voltage line LL3, and the other end of the low voltage line LL3 is connected to the output terminal T4. An auxiliary battery 30 for driving an auxiliary machine (not shown) such as a power window is connected between the output terminals T3 and T4 so that a DC output voltage Vdcout2 (for example, about 14V) is supplied. It has become.

  The voltage detector 33 detects the DC output voltage Vdcout2 supplied between the output terminals T3 and T4, and outputs a voltage corresponding to the detected DC output voltage Vdcout2 to the controller 6. As a specific circuit configuration of the voltage detector 33, for example, the DC output voltage Vdcout2 is detected by a voltage dividing resistor (not shown) disposed between the high voltage line LH3 and the low voltage line LL3. For example, a device that generates a voltage corresponding to this.

  Here, the transformer 2A corresponds to a specific example of “transformer” in the present invention. Further, the winding 23 (23A, 23B) corresponds to a specific example of “third transformer coil” in the present invention. The auxiliary battery 30 corresponds to a specific example of “second DC power supply” in the present invention. The rectifier circuit 31 corresponds to a specific example of “second rectifier circuit” in the present invention.

  Also in the switching power supply device of the present embodiment, the charging control operation by the control unit 6 is performed in the same manner as in the first embodiment. That is, when charging the main battery 10 based on the AC input voltage Vacin input from the input terminals T5 and T6, the capacitor C3 is charged before the main battery 10 is originally charged based on the AC input voltage Vacin. The operations of the switching circuits 11 and 41, the PFC circuit 43, and the relay unit 45 are controlled so that a predetermined preliminary charge is performed from the main battery 10 to the capacitor C3 according to the amount of charge at.

  Specifically, for example, preliminary charging is performed in the same manner as in the first embodiment by the energy transmission path 71 illustrated in FIG. 10, and at this time, in the present embodiment, the battery is supplied from the main battery 10. The auxiliary battery 30 is charged by the energy transmission path 73 in the figure based on the DC input voltage Vdcin.

  Hereinafter, charging of the auxiliary battery 30 by the energy transmission path 73 will be described. First, when the DC input voltage Vdcin is input from the main battery 10 via the input / output terminals T1 and T2, the switching circuit 11 functions as a DC / AC inverter circuit, and the AC pulse voltage is generated by switching the DC input voltage Vdcin. It is generated and supplied to the winding 21 of the transformer 2A. An AC pulse voltage that has been transformed (here, stepped down) is extracted from the windings 23A and 23B of the transformer 2A. In this case, the degree of transformation is determined by the turn ratio between the winding 21 and the windings 23A and 23B.

  Next, the transformed AC pulse voltage is rectified by the diodes 31D1 and 31D2 in the rectifier circuit 31. As a result, a rectified output is generated between the high pressure line LH3 and the low pressure line LL3.

  Next, in the smoothing circuit 32, the rectified output generated between the high-voltage line LH3 and the low-voltage line LL3 is smoothed, and thereby the DC output voltage Vdcout2 is output from the output terminals T3 and T4. The DC output voltage Vdcout2 is supplied to the auxiliary battery 30 and an auxiliary machine (not shown) is driven. At this time, the DC output voltage Vdcout2 is detected by the voltage detection unit 33, and switching control signals S1 to S4 are output from the control unit 6 and the SW drive circuit 12 to the switching circuit 11 based on the detected DC output voltage Vdcout2. Thus, the switching elements Q1 to Q4 in the switching circuit 11 are controlled by PWM (Pulse Width Modulation) so that the switching circuit 11 performs a DC / AC conversion operation and the DC output voltage Vdcout becomes constant.

  In this way, the DC input voltage Vdcin supplied from the main battery 10 is DC output by the switching circuit 11 functioning as a DC / DC converter, the windings 21, 23A, 23B of the transformer 2, the rectifier circuit 31, and the smoothing circuit 32. DC voltage is converted to voltage Vdcout2 and output from output terminals T3 and T4. As a result, the auxiliary battery 30 is charged at a constant voltage, and an auxiliary machine (not shown) is driven.

  In the present embodiment, for example, the original charging is performed in the same manner as in the first embodiment by the energy transmission path 72 illustrated in FIG. 11, and at this time, the AC input supplied from the commercial power supply 40 is performed. Based on the voltage Vacin, the auxiliary battery 30 is charged by the energy transmission path 74 in the figure.

  Hereinafter, charging of the auxiliary battery 30 through the energy transmission path 74 will be described. First, as described in the first embodiment, when an AC pulse voltage is generated in the winding 22 of the transformer 2A during the original charging, the windings 22A and 23B of the transformer 2A are also connected to the winding 22 and the winding 22A. A transformed AC pulse voltage determined by the turn ratio between the windings 23A and 23B is taken out. Therefore, the transformed AC pulse voltage is rectified by the rectifier circuit 31 and smoothed by the smoothing circuit 32, so that the auxiliary battery 30 is also charged with a constant voltage (DC output voltage Vdcout2). The DC output voltage Vdcout2 is detected by the voltage detection unit 33, and switching control signals S5 to S8 are output from the control unit 6 and the SW drive circuit 12 to the switching circuit 41 based on the detected DC output voltage Vdcout2. Thus, the switching elements Q5 to Q8 in the switching circuit 41 are PWM controlled so that the switching circuit 41 performs a DC / AC conversion operation and the DC output voltages Vdcout1 and Vdcout2 are constant.

  As described above, also in this embodiment, it is possible to obtain the same effect by the same operation as that of the first embodiment. That is, it is possible to suppress the occurrence of an inrush current that flows to the capacitor C3 due to the AC input voltage Vacin when the main battery 10 is originally charged without separately providing a dedicated component for suppressing the inrush current as in the prior art. it can. Therefore, it is possible to improve the reliability of the apparatus with a relatively simple configuration.

  The transformer 2A includes windings 23A and 23B magnetically coupled to the windings 21 and 22, and a rectifier circuit 31 is further provided between the windings 23A and 23B and the auxiliary battery 30. Therefore, based on the DC input voltage Vdcin from the main battery 10, it is possible to perform the charging operation to the auxiliary battery 30 in addition to the preliminary charging operation to the capacitor C3, and from the input terminals T5 and T6. It is possible to perform a charging operation on at least one of the main battery 10 and the auxiliary battery 30 by the DC output voltages Vdcout1 and Vdcout2 based on the AC input voltage Vacin.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.

  FIG. 12 shows a circuit configuration of the switching power supply device according to the present embodiment. In this figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The switching power supply of this embodiment is the same as the switching power supply of the first embodiment except that the switching circuit 481, the smoothing circuit 482, and the SW drive circuit 493 are replaced with the rectifier circuit 44, the PFC circuit 43, and the SW drive circuit 492. In addition to providing them, output terminals T7 and T8 for outputting the AC output voltage Vacout are provided in parallel with the input terminals T5 and T6 (specifically, connected to the connection points P1 and P2 in the figure). It is a thing.

  The switching circuit 481 is a full-bridge type switching circuit having four switching elements Q10 to Q13 and four diodes D10 to D13. Specifically, one end of the switching element Q10 is connected to the high voltage line LH4, and the other end is connected to one end of the switching element Q11 and one end of an inductor 482L1 in the smoothing circuit 482 described later. One end of the switching element Q12 is connected to the high voltage line LH4, and the other end is connected to one end of the switching element Q13 and one end of an inductor 482L2 in the smoothing circuit 482 described later. The other end of switching element Q11 and the other end of switching element Q13 are each connected to low voltage line LL4. The diodes D10 to D13 are connected in parallel in opposite directions between both ends of the switching elements Q10 to Q13 (the cathode of each diode is connected to the high voltage line LH4 side, and the anode of each diode is connected to the low voltage line LL4 side. It is connected). That is, one switching element and one diode constitute one bidirectional switch, whereby the switching circuit 481 also functions as a bidirectional switching circuit. Specifically, although details will be described later, the switching circuit 481 functions as a DC / AC inverter circuit or an AC / DC converter circuit that performs AC / DC conversion (conversion from AC to DC). . The switching elements Q10 to Q13 are also configured by, for example, bipolar transistors, IGBTs, or MOS-FETs. However, when the switching elements Q10 to Q13 are each configured by a MOS-FET and have a parasitic diode component, the diode D10 These parasitic diode components may be used instead of -D13.

  The switching circuit 481 also functions as a PFC (Power Factor Correction) circuit that performs a power factor correction operation when functioning as an AC / DC inverter circuit. As a result, the input voltage to the switching circuit 481 as a PFC circuit is boosted and stabilized, and the power factor can be improved.

  The SW drive circuit 493 generates switching control signals S10 to S13 under the control of the control unit 6, and thereby controls the switching operations of the switching elements Q10 to Q13 in the switching circuit 481, respectively. Specifically, although details will be described later, the switching circuit 481 is controlled to perform the above-described DC / AC conversion operation, AC / DC conversion operation, and PFC operation.

  The smoothing circuit 482 includes two inductors 482L1 and 482L2 and a capacitor 482C. The inductor 482L1 is inserted and arranged on the connection line L41, one end is connected to the other end of the switching element Q10 and one end of the switching element Q11, and the other end is connected to the input terminal T5 via the relay unit 45 and the voltage detection unit 46. It is connected. The inductor 482L2 is inserted and arranged on the connection line L42, and one end is connected to the other end of the switching element Q12 and one end of the switching element Q13, and the other end is connected to the input terminal T6 via the relay unit 45 and the voltage detection unit 46. It is connected. Capacitor 482C is arranged between connection line L41 (the other end portion of inductor 482L1) and connection line L42 (the other end portion of inductor 482L2).

  Here, the switching circuit 481 corresponds to a specific example of the “third switching circuit” in the present invention, and the control unit 6 and the SW drive circuits 12, 491, 493 correspond to a specific example of the “control unit” in the present invention. Correspond. The input terminals T5, T6 and the output terminals T7, T8 correspond to a specific example of “AC voltage input / output terminal” in the present invention.

  Also in the switching power supply device of the present embodiment, the charging control operation by the control unit 6 is performed in the same manner as in the first and second embodiments. That is, when charging the main battery 10 based on the AC input voltage Vacin input from the input terminals T5 and T6, the capacitor C3 is charged before the main battery 10 is originally charged based on the AC input voltage Vacin. The operations of the switching circuits 11, 41, 481 and the relay unit 45 are controlled so that a predetermined preliminary charge is performed from the main battery 10 to the capacitor C3 in accordance with the amount of charge at.

  Specifically, for example, as shown in FIG. 14 and FIG. 15 by the energy transmission path 71 shown in FIG. 13, preliminary charging is performed in the same manner as in the first embodiment. In the embodiment, the AC output voltage Vacout is generated by the energy transmission path 75 in the figure based on the DC input voltage Vdcin supplied from the main battery 10. FIG. 14 is a timing waveform diagram showing an example of the operation for generating and outputting the AC output voltage Vacout based on the DC voltage V3 across the capacitor C3. FIG. (B) to (E) represent the switching control signals S10 to S13, respectively, and (F) represents the AC output voltage Vacout. For the voltages V3 and Vacout, the direction of the arrow shown in FIG. 12 represents the positive direction.

  Hereinafter, the generation operation of the AC output voltage Vacout based on the DC voltage V3 will be described. First, the switching circuit 481 functions as a DC / AC inverter, and the switching elements Q10 to Q13 switch the voltage V3 according to the switching control signals S10 to S13 (see FIGS. 14B to 14E) from the SW drive circuit 493. To do.

  Specifically, for example, in the period from timing t31 to t32 (positive half-wave period Δ75A), the switching control signal S13 is always “H” (FIG. 14E), and the switching element Q13 is always in the on state. At the same time, the switching control signal S12 is always “L” (FIG. 14D), and the switching element Q12 is always in the OFF state. Then, an equivalent circuit of the switching circuit 481 and the smoothing circuit 482 in this period is as shown in FIG. Here, in this period, as shown in FIG. 14B, the switching control signal S10 gradually increases in pulse width in the first half of the timings t31 to t32, and the latter half of the timings t31 to t32. The pulse width gradually decreases. Further, as shown in FIG. 14C, the switching control signal S11 is always “L”. That is, during this period, the switching element Q11 is always in an off state, the diode D11 is conducted, and the switching element Q10 is in an on / off state by PWM control. Therefore, in this positive half-wave period Δ75A, output is performed from the output terminals T7 and T8 by the switching operation by the switching elements Q10 to Q13 and the smoothing process by the smoothing circuit 482 in the energy path 75A shown in FIG. The AC output voltage Vacout is an upwardly convex sine waveform as shown in FIG. In the positive half-wave period Δ75A, the switching element Q11 may be always turned on to perform the synchronous rectification operation. Such a case is preferable because the switching loss in the switching element Q11 is reduced.

  Next, the period from timing t32 to t33 is a dead time Td in which the switching elements Q10 to Q13 are all turned off (FIGS. 14B to 14E).

  Next, in the period from timing t33 to t34 (negative half-wave period Δ75B), the switching control signal S11 is always “H” (FIG. 14C), and the switching element Q11 is always turned on and switching is performed. The control signal S10 is always “L” (FIG. 14B), and the switching element Q10 is always off. Then, the equivalent circuit of the switching circuit 481 and the smoothing circuit 482 in this period has a configuration upside down from that shown in FIG. 15A in the smoothing circuit 482 as shown in FIG. It becomes. Here, in this period, as shown in FIG. 14D, the switching control signal S12 gradually increases in pulse width at the first half of the timing t33 to t34 and at the latter half of the timing t33 to t34. The pulse width gradually decreases. Further, as shown in FIG. 14E, the switching control signal S13 is always “L”. That is, during this period, the switching element Q13 is always in an off state, the diode D13 is conducted, and the switching element Q12 is in an on / off state by PWM control. Therefore, in the negative half-wave period Δ75B, the output from the output terminals T7 and T8 is performed in the energy path 75B shown in FIG. 15B by the switching operation by the switching elements Q10 to Q13 and the smoothing process by the smoothing circuit 482. As shown in FIG. 14F, the AC output voltage Vacout is a sine waveform that protrudes downward. In this negative half-wave period Δ75B, the switching element Q13 may be always turned on to perform the synchronous rectification operation. Such a case is preferable because the switching loss in the switching element Q13 is reduced.

  Next, the period from the timing t34 to t35 thereafter is the dead time Td in which the switching elements Q10 to Q13 are all turned off (FIGS. 14B to 14E). Further, the operation state at the timing t35 is equivalent to the operation state at the timing t31, and thereafter, the operation at the timings t31 to t35 is repeated. The AC output voltage Vacout output from the output terminals T7 and T8 is detected by the voltage detection unit 46, and the switching control signals S10 to S13 are transmitted from the SW drive circuit 493 to the switching circuit 481 based on the detected AC output voltage Vacout. Is output, the pulse width of the switching elements Q10 to Q13 in the switching circuit 481 is controlled so that the switching circuit 481 performs the DC / AC conversion operation and the AC output voltage Vacout is stabilized. Further, when the AC output voltage Vacout is supplied between the output terminals T7 and T8, the so-called commercial voltage functions as a power supply voltage for the electrical equipment.

  Further, in the present embodiment, the original charging is performed, for example, as shown in FIGS. 17 to 19 through the energy transmission path 76 shown in FIG. 16, for example. FIG. 17 and FIG. 19 show the operation waveforms in this case in timing waveform diagrams. Specifically, FIG. 17 shows an operation waveform until the voltage V3 across the capacitor C3 is generated based on the AC input voltage Vacin. (A) shows the AC input voltage Vacin. (E) represents the switching control signals S10 to S13, and (F) represents the voltage V3 across the capacitor C3. FIG. 19 shows operation waveforms until the capacitor C1 is charged (charging the main battery 10) based on the voltage V3, (A) shows the switching control signals S5 and S8, and (B) shows the switching control. Signals S6 and S7, (C) the voltage V21 generated across the winding 21 of the transformer 2, (D) the switching control signals S1 and S4, (E) the switching control signals S2 and S3, ( F) represents the voltage V1 across the capacitor C1, respectively. For the AC input voltage Vacin and the voltages V3, V21, and V1, the direction of the arrow shown in FIG. 12 represents the positive direction.

  First, when the AC input voltage Vacin (commercial voltage) as shown in FIG. 17A is input from the commercial power supply 40 via the input terminals T5 and T6, a smoothing process for removing noise components in the smoothing circuit 482 is performed. Then, the data is input to the switching circuit 481. Then, the switching circuit 481 functions as a step-up AC / DC converter using the inductor components of the inductors 482L1 and 482L2, and the switching control signals S10 to S13 from the SW drive circuit 493 (FIGS. 17B to 17E). ), Switching elements Q10 to Q13 switch AC input voltage Vacin. Note that the SW drive circuit 491 is controlled based on the output voltage from the switching circuit 481.

  Specifically, first, for example, in the period from timing t41 to t42 (a positive half-wave period Δ76A in which the AC input voltage Vacin shows a convex sine waveform), the switching control signal S13 is always “H” (FIG. 17 (E)) While switching element Q13 is always on, switching control signal S12 is always “L” (FIG. 17D), and switching element Q12 is always off. Then, an equivalent circuit of the switching circuit 481 and the smoothing circuit 482 in this period is as shown in FIG. Here, during this period, as shown in FIG. 17C, the switching control signal S11 has a pulse width that gradually decreases in the first half of the timing t41 to t42, and the second half of the timing t41 to t42. The pulse width gradually increases. Further, as shown in FIG. 17B, the switching control signal S10 is always “L”. That is, during this period, the switching element Q10 is always in an off state, the diode D12 is conducted, and the switching element Q11 is in an on / off state by PWM control. Therefore, in the positive half-wave period Δ76A, in the smoothing process by the smoothing circuit 482 (energy path 76A shown in FIG. 18A), the smoothing process by the smoothing circuit 482 and the switching operation by the switching elements Q10 to Q13 are performed. Thus, the voltage V3 across the capacitor C3 becomes a DC voltage having a constant value, as shown in FIG. In this positive half-wave period Δ76A, the switching element Q10 may be in a phase opposite to that of the switching element Q11 to perform the synchronous rectification operation. This is preferable because the switching loss and conduction loss in the diode D10 are reduced.

  Next, in a period from timing t42 to t43 (a negative half-wave period Δ76B in which the AC input voltage Vacin shows a downward sine waveform), the switching control signal S11 is always “H” (FIG. 17C). ) The switching element Q11 is always on, and the switching control signal S10 is always “L” (FIG. 17B), and the switching element Q10 is always off. Then, the equivalent circuit of the switching circuit 481 and the smoothing circuit 482 in this period has an upside down configuration as shown in FIG. 18A in the smoothing circuit 482 as shown in FIG. 18B. It becomes. Here, during this period, as shown in FIG. 17E, the switching control signal S11 gradually decreases in pulse width in the first half of timing t42 to t43, and the latter half of timing t42 to t43. The pulse width gradually increases. Further, as shown in FIG. 17D, the switching control signal S12 is always “L”. That is, during this period, the switching element Q12 is always in an off state, the diode D12 is conducted, and the switching element Q13 is in an on / off state by PWM control. Therefore, in this negative half-wave period Δ76B, the voltage between both ends of the capacitor C3 is obtained by the smoothing process by the smoothing circuit 482 and the switching operation by the switching elements Q10 to Q13 in the energy path 76B shown in FIG. V3 is a DC voltage having a constant value as shown in FIG. In this negative half-wave period Δ76B, the switching element Q12 may be in a phase opposite to that of the switching element Q13 to perform the synchronous rectification operation. This is preferable because the switching loss and conduction loss in the diode D12 are reduced.

  At this time, in the switching circuit 481 and the smoothing circuit 482, the power factor is improved as compared with the capacitor input type rectifier for performing the AC / DC conversion operation as described above. As a result, the peak current is reduced, and the ripple voltage is reduced as compared with a smoothing capacitor having the same capacity.

  Next, the main charging of the main battery 10 is performed by the energy transmission path 76 based on the voltage V3 stored across the capacitor C3.

  Specifically, the switching circuit 41 functions as a DC / AC inverter circuit, and the switching elements Q5 to Q8 perform an on / off operation as shown at timings t51 to t58 in FIGS. 19A and 19B. As a result, an AC pulse voltage is generated in the winding 22 of the transformer 2. Then, according to the turn ratio between the winding 22 and the winding 21, a transformed AC pulse voltage V21 as shown in FIG. Next, the switching circuit 11 functions as a rectifier circuit, and the switching elements Q1 to Q4 are turned on / off as shown in FIGS. 19D and 19E, whereby the AC pulse voltage V21 is rectified, A constant DC voltage V1 as shown in FIG. 19F is applied across the capacitor C1. In this manner, the main battery 10 is originally charged with the DC output voltage Vdcout1 based on the voltage V1. The switching elements Q1 to Q4 perform a PWM operation based on the switching control signals S1 to S4, and the PWM operation is synchronized with the PWM operation of the switching circuit 41.

  As described above, also in this embodiment, it is possible to obtain the same effect by the same operation as in the first and second embodiments. That is, it is possible to suppress the occurrence of an inrush current that flows to the capacitor C3 due to the AC input voltage Vacin when the main battery 10 is originally charged without separately providing a dedicated component for suppressing the inrush current as in the prior art. it can. Therefore, it is possible to improve the reliability of the apparatus with a relatively simple configuration.

  In addition, a switching circuit 481, a smoothing circuit 482, and a SW drive circuit 493 are provided in place of the rectifier circuit 44, the PFC circuit 43, and the SW drive circuit 492 in the first embodiment, respectively, and output in parallel with the input terminals T5 and T6. Since the terminals T7 and T8 are provided, the AC output voltage Vacout can be output from the output terminals T7 and T8 while performing preliminary charging.

  Furthermore, since the switching circuit 481 also performs the power factor improving operation, it is possible to improve the power factor when converting the AC input voltage Vacin to reduce the harmonic component.

  In the present embodiment, as in the second embodiment, for example, as shown in FIG. 20, a transformer 2A is provided in place of the transformer 2, and between the transformer 2A and the auxiliary battery 30. The rectifier circuit 31, the smoothing circuit 32, and the voltage detector 33 may be provided. In such a configuration, for example, as shown in FIG. 21, the auxiliary battery 30 is charged by the energy transmission path 73 while performing the preliminary charging by the energy transmission path 71 and the AC output voltage Vacout by the energy transmission path 75. Can be generated and output. Further, for example, as shown in FIG. 22, it is possible to charge the auxiliary battery 30 through the energy transmission path 77 while performing the original charging of the main battery 10 through the energy transmission path 76.

[Modifications 1 and 2]
Next, modifications of the present invention common to the first to third embodiments will be described. Specifically, some modified examples of the charging control operation by the control unit 6 will be described.

  FIG. 23 is a flowchart showing the charging control operation by the controller 6 according to the first modification of the present invention, and corresponds to the modification shown in FIG. In the charging control operation according to the first modification, the control unit 6 considers the detection result of the voltage detection unit 46 a plurality of times (the detection result of whether or not the commercial power supply 40 is connected to the input terminals T5 and T6). Thus, it is determined whether to perform preliminary charging and original charging.

  Specifically, in step S202, after initially setting the variable k = 0, the control unit 6 determines whether or not the AC input voltage Vacin is input based on the voltage detected by the voltage detection unit 46 (the commercial power supply 40 is connected). It is determined whether or not the input terminals T5 and T6 are connected (step S203). If it is determined that the AC input voltage Vacin is input (step S203: Y), the variable k is then incremented to k + 1 (step S205), and whether or not the variable k has reached the predetermined number N. Is determined (step S206). When k = N (step S206: Y), the process proceeds to the subsequent precharging operation and the original charging operation. When k <N (step S206: N), the process returns to step S203 again. It is determined whether or not the AC input voltage Vacin is input.

  Note that other steps in steps S201 to S214 in FIG. 23 are the same as those in FIG. 3 in the first embodiment, and thus the description thereof is omitted.

  In this way, in the present modification, in consideration of the detection result of a plurality of times by the voltage detection unit 46 (detection result of whether or not the commercial power supply 40 is connected to the input terminals T5 and T6), the preliminary charging and the original Since it is determined whether or not to perform charging, it is possible to more reliably avoid malfunction (failure of charging operation).

  Next, FIG. 24 is a flowchart showing the charging control operation by the control unit 6 according to the second modification of the present invention, and corresponds to the modification shown in FIG. In the charge control operation according to the second modification, the threshold voltage Vth3 (first threshold corresponding to the charge amount of the capacitor C3) described in the first embodiment changes according to the charge amount in the main battery 10. It is set to be.

  Specifically, first, in step S305, the amount of charge (DC voltage V1) in the main battery 10 is compared with two threshold voltages Vth11 and Vth12 (Vth11 <Vth12). More specifically, first, when the DC voltage V1 is less than the threshold voltage Vth11 (V1 <Vth11), a main battery overdischarge flag is generated (step S306).

  When the DC voltage V1 is equal to or higher than the threshold voltage Vth11 and lower than the threshold voltage Vth12 (Vth11 ≦ V1 <Vth12), the main battery 10 is precharged to the capacitor C3 (step S307) and the capacitor The amount of charge to C3 (DC voltage V3) is compared with the threshold voltage Vth3a (step S308). When the DC voltage V1 is equal to or higher than the threshold voltage Vth12 (Vth12 ≦ V1), preliminary charging from the main battery 10 to the capacitor C3 is performed (step S309), and the amount of charge (DC voltage) to the capacitor C3 is also made. The magnitudes of V3) and threshold voltage Vth3b are compared (step S310).

  Here, the threshold voltage Vth3 changes (is different from each other) such as the threshold voltage Vth3a and the threshold voltage Vth3b according to the amount of charge to the main battery 10 (here, Vth3b> Vth3a). .

  Other steps in steps S301 to S313 in FIG. 24 are the same as those in FIG. 3 in the first embodiment, and thus the description thereof is omitted.

  In this way, in the present modification, the threshold voltage Vth3 (the first threshold value corresponding to the charge amount of the capacitor C3) is changed according to the charge amount in the main battery 10, so the charge amount in the main battery 10 is Therefore, it is possible to perform the preliminary charging and the original charging in consideration of the above, and thus it is possible to suppress the occurrence of the inrush current while avoiding the overdischarge in the main battery 10.

  Although the present invention has been described with reference to the first to third embodiments and their modifications, the present invention is not limited to these embodiments and the like, and various modifications are possible.

  For example, in the above-described embodiment and the like, the case where the switching circuits 11, 41, and 481 are all full-bridge type switching circuits has been described. However, the configuration of the switching circuit is not limited to this, and the switching circuits 11, 481, for example. May be configured by a half-bridge type switching circuit.

  In the above-described embodiment, the case where the switching circuit 41 performs the PWM operation and the switching circuit 11 is synchronously rectified with the switching circuit 41 has been described. For example, the DC output voltage Vdcout1 is based on the AC input voltage Vacin. When the main battery 10 is charged by generating / outputting, the switching elements Q5 to Q8 in the switching circuit 41 perform switching operation with a variable pulse width, while the switching elements Q1 to Q4 in the switching circuit 11 are fixed. The switching operation may be performed with a pulse width of 1 to adjust the amount of charge to the main battery 10.

It is a circuit diagram showing the structure of the switching power supply device which concerns on the 1st Embodiment of this invention. It is a circuit diagram for demonstrating inrush current when alternating current input voltage is supplied. It is a flowchart showing an example of control operation of charge by a control part. It is a circuit diagram for demonstrating the precharging operation | movement which concerns on 1st Embodiment. FIG. 5 is a timing waveform diagram for explaining the precharging operation shown in FIG. 4. It is a circuit diagram for demonstrating the original charge operation which concerns on 1st Embodiment. FIG. 7 is a timing waveform diagram for explaining the original charging operation shown in FIG. 6. FIG. 8 is a timing waveform diagram for explaining the original charging operation subsequent to FIG. 7. It is a circuit diagram showing the structure of the switching power supply device which concerns on 2nd Embodiment. It is a circuit diagram for demonstrating the precharging operation | movement and charging operation of an auxiliary battery which concern on 2nd Embodiment. It is a circuit diagram for demonstrating the original charging operation and charging operation of an auxiliary battery which concern on 2nd Embodiment. It is a circuit diagram showing the structure of the switching power supply device which concerns on 3rd Embodiment. It is a circuit diagram for demonstrating the precharge operation | movement and generation | occurrence | production operation | movement of alternating current output voltage which concern on 3rd Embodiment. FIG. 14 is a timing waveform diagram for explaining an operation of generating the AC output voltage shown in FIG. 13. FIG. 14 is an equivalent circuit diagram for describing an operation of the switching circuit in the operation of generating the AC output voltage shown in FIG. 13. It is a circuit diagram for demonstrating the original charge operation which concerns on 3rd Embodiment. FIG. 17 is a timing waveform diagram for explaining the original charging operation shown in FIG. 16. FIG. 18 is an equivalent circuit diagram for explaining the operation of the switching circuit during the original charging operation shown in FIG. 17. FIG. 18 is a timing waveform diagram for explaining the original charging operation subsequent to FIG. 17. It is a circuit diagram showing the structure of the switching power supply device which concerns on the modification of 3rd Embodiment. It is a circuit diagram for demonstrating the precharging operation | movement which concerns on the modification of 3rd Embodiment, the charging operation of an auxiliary machine battery, and the production | generation operation | movement of alternating current output voltage. It is a circuit diagram for demonstrating the original charge operation and charge operation of an auxiliary battery which concern on the modification of 3rd Embodiment. It is a flowchart showing the control operation of charge by the control part which concerns on the modification of this invention. It is a flowchart showing the control operation of charge by the control part which concerns on the other modification of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Main battery, 11, 41, 481 ... Switching circuit, 12, 491, 492, 493 ... SW control circuit, 13, 33, 42, 46 ... Voltage detection part, 2, 2A, 5 ... Transformer, 21-23, 51, 52 ... Winding, 30 ... Auxiliary battery, 31, 44 ... Rectifier circuit, 32, 482 ... Smoothing circuit, 40 ... Commercial power supply (AC power supply), 43 ... PFC circuit, 45 ... Relay unit, 451, 452 ... Relay, 47 ... differential amplifier, 53 ... isolation amplifier, 6 ... control unit, 71-77, 75A, 75B, 76A, 76B ... energy transmission path, T1, T2 ... input / output terminals, T3, T4, T7, T8 ... Output terminal, T5, T6 ... Input terminal, Vdcin ... DC input voltage, Vdcout1, Vdcout2 ... DC output voltage, Vacin ... AC input voltage, Vacout ... AC output voltage, Q1-Q13 ... Switching element S1, S15 ... switching control signal, C1, C3, 32C, 482C ... capacitor, D1-D8, D10-D13, 31D1, 31D2, 44D1-44D4 ... diode, 32L, 43L, 482L1, 482L2 ... inductor, LH1, LH3, LH4 ... high voltage line, LL1, LL3, LL4 ... low voltage line, L41, L42 ... connection line, V1, V21, V22, V3, V43 ... voltage, Vth11, Vth12, Vth3, Vth3a, Vth3b ... threshold voltage, I43L ... Current, Td ... dead time, t1-t8, t11-t18, t21-t28, t31-t35, t41-t43, t51-t58 ... timing, Δ75A, Δ76A ... positive half-wave period, Δ75B, Δ76B ... negative half Wave period.

Claims (13)

A transformer including a first transformer coil and a second transformer coil magnetically coupled to each other;
A bidirectional first switching circuit that is arranged between the first transformer coil and the first DC power supply and includes at least one switch row in which a pair of switches are connected in series;
A bidirectional second switching circuit which is arranged between the second transformer coil and the AC voltage input terminal and is configured such that a switch row in which a pair of switches are connected in series is connected in parallel to each other. When,
A first rectifier circuit disposed between the second switching circuit and the AC voltage input terminal;
A smoothing capacitor disposed between the second switching circuit and the first rectifier circuit;
When charging the first DC power source based on the AC input voltage input from the AC voltage input terminal, before performing the original charging of the first DC power source based on the AC input voltage, A controller that controls the operation of the first and second switching circuits so as to perform a predetermined preliminary charge from the first DC power source to the smoothing capacitor according to the amount of charge in the smoothing capacitor. The switching power supply device characterized by the above-mentioned. A first detection unit for detecting a charge amount in the smoothing capacitor;
2. The switching power supply according to claim 1, wherein the control unit performs control so as to perform the preliminary charging and the original charging according to a charge amount in a smoothing capacitor detected by the first detection unit. apparatus. The control unit controls to perform the preliminary charging when the amount of charge in the smoothing capacitor is less than a predetermined first threshold, and performs the original charging when the amount of charge in the smoothing capacitor is equal to or greater than the first threshold. It controls so that it may perform. The switching power supply device of Claim 2 characterized by the above-mentioned. The switching power supply according to claim 3, wherein the first threshold value is set so as to change according to a charge amount in the first DC power supply. A second detection unit for detecting a charge amount in the first DC power supply;
5. The control unit according to claim 1, wherein the controller performs control so as to perform the preliminary charging according to a charge amount in the first DC power source detected by the second detection unit. The switching power supply device according to Item 1. The control unit performs control so that the preliminary charging is not performed when a charge amount in the first DC power supply is less than a predetermined second threshold value, and a charge amount in the first DC power supply is equal to or greater than the second threshold value. The switching power supply according to claim 5, wherein control is performed so that the preliminary charging is performed. A third detector for detecting whether or not the AC input voltage is supplied from the AC voltage input terminal;
The control unit controls to perform the preliminary charging and the original charging when it is determined that the AC input voltage is supplied based on a detection result by the third detection unit. The switching power supply device according to any one of claims 1 to 6. The switching according to claim 7, wherein the control unit determines whether or not to perform the preliminary charging and the original charging in consideration of a plurality of detection results by the third detection unit. Power supply. The controller is
When performing the preliminary charging based on the DC input voltage supplied from the first DC power supply, the first switching circuit performs a DC / AC conversion operation and the second switching circuit performs a rectification operation. Control to do and
When performing the original charging based on the AC input voltage, the rectifier circuit performs a rectification operation, the second switching circuit performs a DC / AC conversion operation, and the first switching circuit rectifies. The switching power supply according to any one of claims 1 to 8, wherein the switching power supply is controlled to perform an operation. The first rectifier circuit is constituted by a bidirectional third switching circuit including at least one switch row in which a pair of switches are connected in series.
The switching power supply according to any one of claims 1 to 9, wherein the AC voltage input terminal functions as an AC voltage input / output terminal. The controller is
When outputting the AC output voltage from the AC voltage input / output terminal while performing the preliminary charging based on the DC input voltage supplied from the first DC power supply, the first and third switching circuits are Performing a DC / AC conversion operation and controlling the second switching circuit to perform a rectification operation;
When the original charging is performed based on the AC input voltage input from the AC voltage input / output terminal, the third switching circuit performs an AC / DC conversion operation and the second switching circuit is DC / DC. The switching power supply according to claim 10, wherein an AC conversion operation is performed and control is performed so that the first switching circuit performs a rectification operation. The control unit controls the third switching circuit to also perform a power factor correction operation when an AC input voltage is input from the AC voltage input / output terminal. 11. The switching power supply device according to 11. The transformer includes a third transformer coil magnetically coupled to the first transformer coil and the second transformer coil;
The switching power supply according to any one of claims 1 to 12, further comprising a second rectifier circuit between the third transformer coil and the second DC power supply.

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