JP5166101B2 - Three-phase power factor correction circuit - Google Patents

Description

The present invention relates to a multiphase AC power factor correction circuit that improves a power factor when converting multiphase AC power to DC power.

  Conventionally, as this type of three-phase AC power factor correction circuit, there is, for example, one shown in FIG.

  The three-phase AC power factor correction circuit of FIG. 10 is configured by connecting the single-phase power factor correction circuits 100-1, 100-2, and 100-3 in a delta manner to form a three-phase AC power factor correction circuit. In the power factor correction circuits 100-1, 100-2, 100-3, taking the power factor correction circuit 100-1 as an example, a boost chopper 104 is provided following the full-wave rectification circuit 102. The full-wave rectifier circuit 102 is delta-connected to three-phase AC input terminals R, S, and T.

  The step-up chopper 104 includes a choke coil 106, an inverter element 108 using an FET, a rectifier diode 110, a smoothing capacitor 112, an output transformer 114, rectifier diodes 116 and 118, and a smooth choke coil 120. The inverter element 108 is subjected to switching control so as to approximate the current phase to the phase of the rectified input voltage, and the power factor is improved to approach 1.

  Furthermore, an inverter element 126 constituting a DC-DC converter for stabilizing the DC output voltage is provided, and the inverter element 126 is switched so as to stabilize the DC output voltage to a predetermined voltage by a separately provided control unit 128. I have control. In this case, the inverter element 126 performs a forward operation of transmitting energy to the secondary side when turned on.

Furthermore, a current detection circuit 130 is provided on the output side, and control is performed to balance the current by mutually controlling the control units 128 of each phase.
JP-A-9-271172 Japanese Patent Laid-Open No. 9-149642

  However, such a conventional single-phase power factor correction circuit is delta-connected to form a three-phase, and three power control units 124 are required for the power factor correction operation, and the current balance of each phase is adjusted. A circuit to be taken is also required, and the configuration becomes complicated.

  Moreover, since the ground potential GND of each phase is different, it is necessary to prepare a DC-DC converter, and since it cannot be shared by one DC-DC converter, three DC-DC converter control units 128 are also required. become.

  In order to prevent an input inrush current at the time of power input, an inrush current prevention circuit must be provided for each phase power factor correction circuit. In addition, an insulated sub power supply is required for the internal power supply of each phase. Furthermore, there is a problem that interference occurs due to variations in the switching frequency of each phase, resulting in output ripple.

It is an object of the present invention to provide a polyphase AC power factor correction circuit that shares a control system for power factor improvement when converting polyphase AC to DC to improve performance, reduce size, and reduce costs. And

The present invention is a multiphase AC power factor correction circuit,
Full-wave rectifier circuit, inverter element, inverter element drive circuit, output transformer and output rectifier circuit, and an inverter circuit for the number of phases of the multi-phase AC power supply that performs separately-excited flyback operation;
An input connection circuit that star-connects the full-wave rectifier circuit of the inverter circuit for the number of phases to the polyphase AC power source,
An output connection circuit for connecting each output rectifier circuit of the inverter circuit for the number of phases in parallel and connecting to a single smoothing circuit to output DC power; and
In order to maintain the predetermined voltage by inputting the DC output voltage obtained by the output connection circuit, the inverter circuit for the number of phases is changed at a constant frequency and with respect to one cycle of the AC frequency while maintaining the discontinuous mode. A control circuit that operates as a constant resistance by driving with a small duty ratio;
Is provided.

  Here, the control circuit is a single drive transformer having a primary winding for inputting a switching signal and secondary windings for the number of phases connected to each drive circuit provided in the inverter circuit for the number of phases. Thus, the inverter elements of the inverter circuits corresponding to the number of phases are commonly controlled.

  The inverter circuit having the number of phases includes a current transformer having the number of phases for detecting the inverter current, and the control circuit includes an overcurrent protection circuit that performs a protection operation with respect to the maximum current among the inverter currents detected by each phase current transformer.

  The control circuit sets a frequency response gain that does not respond to a low frequency fluctuation of the DC output voltage that is within the period of the input AC voltage.

  In the multiphase AC power factor correction circuit of the present invention, a single DC-DC converter that stabilizes the output voltage at a predetermined voltage may be connected to the output connection circuit of the inverter circuit for the number of phases.

  The multiphase AC power factor correction circuit according to the present invention further includes a switching circuit that switches the full-wave rectifier circuits of the plurality of inverter circuits between a star connection and a delta connection to the multiphase AC power supply.

In another form of the multiphase AC power factor correction circuit according to the present invention,
Following the full-wave rectifier circuit, a plurality of inverter elements, a plurality of drive circuits provided for each inverter element, a plurality of output transformers driven by the plurality of inverter elements, and an output rectifier circuit provided for each of the plurality of output transformers , An inverter circuit for the number of phases of the multiphase AC power supply that performs separately excited flyback operation,
An input connection circuit that star-connects the full-wave rectifier circuit of the inverter circuit for the number of phases to the polyphase AC power source,
An output connection circuit that outputs DC power by connecting each output rectifier circuit of the inverter circuit for the number of phases in parallel and connecting to the smoothing circuit;
In order to maintain the predetermined voltage by inputting the DC output voltage obtained in the output connection circuit, a plurality of inverter elements provided in the inverter circuit for the number of phases are divided by 360 ° by the number of inverter elements. A control circuit that operates as a constant resistance by driving at a constant frequency and a duty ratio with little fluctuation with respect to one cycle of the AC frequency while maintaining a discontinuous mode by a plurality of switching signals having,
Is provided.

  Here, when the number of inverter elements is n, the control circuit performs switching control of n inverter elements provided in each inverter circuit by n types of switching signals having a phase difference of 360 ° / n.

In another aspect of the present invention, a single-phase AC power factor correction circuit is provided. The single-phase AC power factor correction circuit of the present invention is
A full-wave rectifier circuit that inputs a single-phase alternating current and full-wave rectifies, an inverter element, a drive circuit of the inverter element, an output transformer, an output rectifier circuit, and a smoothing circuit, and an inverter circuit that performs a separate excitation flyback operation;
In order to maintain the predetermined voltage by inputting the DC output voltage obtained by the inverter circuit, it is fixed by driving at a constant frequency and a duty ratio with little fluctuation for one cycle of the AC frequency while maintaining the discontinuous mode. A control circuit that operates as a resistor;
Is provided.

  According to the present invention, in order to improve the power factor of a multiphase alternating current with a single control system, an inverter circuit that performs a separately-excited flyback operation with a full-wave rectifier is star-connected to the multiphase alternating current power source, and after output rectification This is combined and smoothed, and switching control is performed so that the DC output voltage is maintained at a predetermined voltage. As this switching operation, a separately excited flyback type inverter circuit is maintained at a constant frequency while maintaining a discontinuous mode. In addition, it is operated as a constant resistance by driving at a duty ratio with little fluctuation with respect to one cycle of the AC frequency. As a result, an input current proportional to the input voltage flows, and the power factor can be improved.

That is, when a separately-excited flyback inverter circuit is driven at a constant frequency while maintaining a discontinuous mode and with a duty ratio with little fluctuation with respect to one cycle of the AC frequency, the peak current is I and the input voltage is V When the on-duty time Ton and the inductance of the output transformer are L,
I = V × (Ton / L)
Since (Ton / L) is constant, an input current I proportional to the input voltage V flows, and the same operation as the constant resistance is performed, thereby improving the power factor.

  In addition, since the inverter circuits for the number of phases connected in a star are switched and controlled by a single control unit, there is no interference between the phases, the control system can be simplified, and the control system is driven. The internal power supply (sub-power supply) of the power supply may be one system, and the circuit can be reduced in size and cost.

  In addition, since the rectifier circuit of each phase on the transformer secondary side of the inverter circuit for the number of phases connected in a star is combined and smoothed, the low frequency ripple of each phase is canceled by the synthesis, and the low frequency ripple Can be reduced.

  Also, because the inverter circuit uses an isolated flyback method, there is no restriction that the power factor correction operation will not occur unless the output voltage is higher than the input voltage in the case of a boost chopper, and the DC output voltage can be set arbitrarily. it can.

  In addition, the inverter current of each phase is detected by a current transformer, and the overcurrent protection circuit provided in the control unit common to each phase that is insulated from the inverter element of each phase performs overcurrent protection operation. The inrush current becomes a value limited by a common overcurrent protection circuit, and it is not necessary to provide an inrush current holding circuit for each phase individually.

  In addition, a disadvantage of the flyback inverter circuit is that the voltage applied to the inverter element is the sum of the power supply voltage and the flyback voltage, so that the inverter must have a high withstand voltage. By using a star connection, the power supply voltage becomes 1 / √3 even in the case of three-phase AC, which is advantageous in terms of breakdown voltage.

  In addition, since the multi-phase inverter circuit connected in a star is composed of an insulating switching power supply using an output transformer, the potentials of the DC outputs can be combined into one, so that the DC− connected to the output stage Only one DC converter is required, and stabilization of the DC output voltage can be achieved with a simple circuit configuration.

  Also, if necessary, it is possible to switch from star connection to delta connection. In the case of three-phase AC, for example, in the case of AC440V, the input voltage is suppressed to 1 / √3 as a star connection, and the withstand voltage of the inverter element is advantageous. In the case of AC220V, the input current can be suppressed to 1 / √3 as a delta connection to reduce the current loss of the inverter element and the transformer.

Further, in each phase inverter circuit connected in delta, for example, three inverter elements and output transformers are provided for each phase inverter circuit, and the phase of the switching signal is 0 [deg], 120 [deg], and 240 [deg]. By driving with a shift, the high-frequency ripple component can be reduced by cancellation by phase shift.

  FIG. 1 is a circuit block diagram showing a first embodiment of a power factor correction circuit according to the present invention, taking a three-phase alternating current as an example.

  In FIG. 1, the power factor correction circuit according to the present embodiment includes separately-excited flyback inverter circuits 10-1, 10-2, and 10-3 corresponding to the number of phases of a three-phase AC power supply = 3. , Diode bridges (full wave rectifier circuits) 12-1, 12-2, 12-3 for full wave rectification provided in respective input stages are connected to three-phase AC power input terminals R, S, T. Connected.

  The star connection to the three-phase AC power supply terminals R, S, and T of the separately excited flyback inverter circuits 10-1 to 10-3 is apparent from FIG. 2 showing the outline of the embodiment of FIG.

  When the inverter circuits 10-1 to 10-3 are described as a representative of the inverter circuit 10-1, an inverter element 14-1 using an FET is arranged on the plus side of the diode bridge 12-1, and the inverter element 14-1 Are connected in series to the primary winding 20-1 of the output transformer 18-1, and further connected to the negative side of the diode bridge 12-1 via the current transformer primary winding 35-11.

  The inverter element 14-1 is driven by the drive circuit 16-1, and the drive secondary winding 34-1 of the drive transformer 30 is connected to the drive circuit 16-1, and the control circuit 36 side to be clarified in the following description. The switching signal is input from. A rectifier diode 24-1 is provided on the secondary side of the output transformer 18-1.

  The remaining inverter circuits 10-2 and 10-3 have the same circuit configuration as the inverter circuit 10-1. One output of the rectifier diodes 24-1, 24-2, 24-3 provided on the secondary side of the inverter circuits 10-1 to 10-3 is combined, and a single smoothing capacitor 26 is connected. A direct current output terminal 28 is provided on the output side to output direct current power converted from three-phase alternating current.

  One control circuit 36 is provided for the inverter circuits 10-1 to 10-3. The control circuit 36 includes a control IC 38 and a drive circuit 40. A DC output voltage output from the smoothing capacitor 26 is input to the control IC 38 via a voltage dividing circuit of resistors 41, 42, and 44. The control IC 38 controls the inverters 10-1 to 10-3 in common so that the DC output voltage is stabilized at a predetermined voltage.

  The response to the DC output voltage of the control IC 38 can be adjusted by a time constant circuit including a resistor 46 and a capacitor 48. In this embodiment, this time constant is responded in one cycle of the input AC power supply. The frequency response gain is set so that there is no noise.

  The drive circuit 40 supplies a switching signal generated based on the control signal output from the control IC 38 to the drive transformer primary winding 32 of the drive transformer 30.

  The drive transformer 30 is provided with three drive secondary windings 34-1 to 34-3 for one primary winding 32, and each of the secondary windings 34-1 to 34-3 is an inverter circuit 10-. It is input-connected to the drive circuits 16-1 to 16-3 provided in 1 to 10-3. Thereby, the single control circuit 36 controls the switching of the three inverter circuits 10-1 to 10-3 in common at the same frequency.

  The control IC 38 has a built-in current protection circuit, and overcurrent detection circuits 50-1, 50-2, 50- provided for the current protection terminal 45 corresponding to the inverter circuits 18-1 to 18-3. 3 is connected.

  Overcurrent detection circuits 50-1 to 50-3 are current transformer secondary windings 35 coupled to current transformer primary windings 35-11 to 35-13 provided in inverter circuits 10-1 to 10-3. -21, 35-22, and 35-23 are input-connected, and the inverter current in each inverter circuit is detected.

  The detection outputs of the overcurrent detection circuits 50-1 to 50-3 are connected to the overcurrent protection terminal 45 of the control IC 38 through a diode OR by diodes 52-1, 52-2 and 52-3.

  For this reason, the overcurrent protection circuit built in the control IC 38 is the largest of the overcurrent detection signals detected by the overcurrent detection circuits 50-1 to 50-3 in the three inverter circuits 10-1 to 10-3. The overcurrent detection signal is input and the overcurrent protection operation is performed.

  In the circuit block diagram of FIG. 2 showing the circuit configuration of FIG. 1, the secondary sides of the output transformers 18-1 to 18-3 are extracted from the inverter circuits 10-1 to 10-3 of FIG. The next side is shown as one block of the inverter circuits 10-1 to 10-3, and the diode bridges 12-1 to 12-3 provided in the inverter circuits 10-1 to 10-3 are connected to the AC power supply terminals R and S. , T clearly shows the circuit configuration star-connected to T.

  In FIG. 1, the terminal N is taken out at the midpoint of the star connection in FIG. 2, but there is no problem even if the terminal N is not provided.

  Next, a basic operation function as a power factor correction circuit in the embodiment of FIG. 1 will be described. In the control circuit 36 of the present embodiment, the separately excited flyback inverter circuits 10-1 to 10-3 are subjected to switching control so that the DC output voltage is stabilized at a constant voltage under the following three conditions. Yes.

  (1) Operates while maintaining the discontinuous mode by reducing the on-duty of the switching control.

  (2) The inverter circuit of each phase is driven at a constant frequency.

  (3) Drive with a duty ratio with little variation (the duty is not changed within the cycle) for one cycle of the AC frequency (50 Hz or 60 Hz).

  When switching control of the inverter circuits 10-1 to 10-3 of each phase is performed under the conditions (1) to (3), each of the inverter circuits 10-1 to 10-3 can be operated as a constant resistance. it can.

That is, assuming that the peak current in the inverter circuits 10-1 to 10-3 of each phase is I, the input voltage is V, the on-duty time is Ton, and the inductance of the output transformers 18-1 to 18-3 is L, The relationship is obtained.
I = V (Ton / L) (1)
When switching control is performed so that (Ton / L) is kept constant according to the conditions (1) to (3) from the equation (1), an input current I proportional to the input voltage V flows, which is a constant resistance. Thus, each of the inverter circuits 10-1 to 10-3 according to the present embodiment causes the power factor to approach 1 in switching control when converting three-phase AC power to DC power. Power factor improvement can be performed.

  FIG. 3 is a circuit block diagram showing details of the drive circuits 16-1 to 16-3 and the drive circuit 40 provided in the inverters 10-1 to 10-3 and the control circuit 36 of FIG.

  In FIG. 3, the drive circuit 40 provided following the control IC 38 of the control circuit 36 includes an NPN transistor 54 and a PNP transistor 56 connected in series via a resistor 58 following the output terminal from the control IC 38. Connected to the base of the connected drive transformer driving transistor circuit.

  A resistor 60 is connected between the transistor 54 and a control power source used as an internal power source. The resistor 60 is provided to adjust the speed at which the inverter element provided in the inverter circuit rises from OFF to ON.

  Following the transistors 54 and 56, a series circuit of a capacitor 62 and a resistor 64 is provided. This circuit is a CR series provided to prevent parasitic oscillation when the NPN transistor 54 in the drive transformer driving transistor circuit is turned on. The circuit is configured.

  Subsequently, the diode 66 is connected in the reverse direction, and the diode 66 constitutes a circuit for protecting the transistors 54 and 56 of the drive transformer driving transistor circuit from being applied with a reverse voltage or a forward high voltage. Yes.

  Subsequently, the drive transformer secondary winding 32 is connected via a capacitor 68 for preventing DC superimposition with respect to the drive transformer 30. A zener diode 70 is connected in parallel to the capacitor 68. The zener diode 70 applies an abnormal voltage to the gates of the inverter elements 14-1 to 14-3 provided in the inverter circuit when the duty changes in the switching control. Provided to prevent.

  The drive circuits 16-1 to 16-3 provided on the inverter circuits 18-1 to 18-3 side have the same circuit configuration. For example, when the drive circuit 16-1 corresponding to the inverter circuit 18-1 is taken as an example, A circuit including a transistor 72-1, diodes 74-1, 80-1 and resistors 76-1, 78-1 is provided between the transformer secondary winding 34-1 and the inverter element 14-1.

  The transistor 72-1 is a transistor for speeding up when the inverter element 14-1 is turned off from on. That is, in a lay-fly-back type inverter circuit, energy is stored in the primary winding of the output transformer when the inverter element 14-1 is turned on, and then the primary winding is turned on when the inverter element 14-1 is turned off. Since the operation of transmitting the energy stored in the line to the secondary side is performed, the speed at which the inverter element 14-1 is switched off when transmitting the energy to the secondary side is determined by the operation of the transistor 72-1. Speeding up and increasing energy transfer efficiency.

  The diode 74-1 connected between the drive transformer secondary winding 34-1 and the emitter of the transistor 72-1 has priority over the transistor 72-1 when the inverter element 14-1 is switched from on to off. This is a diode for causing the base current to flow through and promoting the speed-up operation.

  A resistor 76-1 connected to the base side of the transistor 72-1 is a resistor for limiting the base current of the transistor 72-1. Further, the resistor 78-1 is a gate resistor for preventing oscillation of the inverter element 14-1.

  As shown in the above (1) to (3), the control circuits 36 of one system as shown in FIG. The power factor can be improved by driving in a continuous mode at a low frequency and with a duty ratio with little variation with respect to the cycle of the AC frequency, and operating the inverter circuit of each phase as a constant resistance.

  FIG. 4 is a circuit block diagram showing details of the overcurrent protection circuit system of FIG. In FIG. 4, on the control circuit 36 side, the circuit configuration of the overcurrent protection circuits 50-1 to 50-3 of each phase connected to the overcurrent protection terminal 45 of the control IC 38 is shown. Drive circuits 16-1 to 16-3, inverter elements 14-1 to 14-3, and current transformer primary windings 35-11 to 35-35 provided on the inverter circuits 10-1 to 10-3 side of the respective phases. 13 is shown.

  The overcurrent protection circuits 50-1 to 50-3 corresponding to the respective phases have diodes 86-1, 86-2, 86- for the current transformer secondary windings 35-21, 35-22, 35-23, respectively. 3 are connected in series, a DC voltage proportional to the secondary voltage induced by the inverter current of each phase is generated at both ends of the resistor 88. Each of the resistors 88-1 to 88-3 is a diode OR circuit. Are connected to the overcurrent protection terminal 45 side of the control IC 38 through the diodes 52-1 to 52-3.

  For the connection of the diodes 52-1 to 52-3 to the overcurrent protection terminal 45 of the diode OR, the overcurrent detection voltage divided by the voltage dividing circuit by the resistors 84 and 85 is inputted, and the voltage is supplied through the voltage dividing circuit. By inputting, it is made hard to receive the influence of the noise of the inverter current (drain current) in the inverter circuits 18-1 to 18-3 and the external noise. Of course, you may connect directly to the overcurrent protection terminal 45, without providing a voltage dividing circuit. The capacitor 82 is provided to remove external noise input to the overcurrent protection terminal 45.

  According to the overcurrent protection circuit system provided so as to correspond to the inverter circuits 10-1 to 10-3 of each phase, the control IC for the largest overcurrent in the three inverter circuits 10-1 to 10-3. When the overcurrent detection voltage exceeds the overcurrent threshold set in the overcurrent protection circuit, the inverter circuits 10-1 to 10-3 by the control IC 38 are operated. The switching operation is stopped and overcurrent protection is achieved.

  Also, an inrush current flowing through each of the inverter circuits 10-1 to 10-3 of each phase when the power is turned on is detected by the overcurrent protection circuit, and the control IC 38 provided in the one-system control circuit 36 is excessively detected. Since the protection operation against the inrush current is performed by the current protection circuit, it is not necessary to provide the inrush current protection circuit individually for each phase of the inverter circuits 10-1 to 10-3.

  FIG. 5 is a circuit block diagram showing a second embodiment of the power factor correction circuit according to the present invention for reducing high-frequency ripple by phase-shifted switching control, and FIG. 6 shows the details of the control circuit.

  In FIG. 5, in the second embodiment, the diode bridge 12-provided in the inverter circuits 10-11, 10-12, and 10-13 with respect to the power input terminals R, S, and T of the three-phase AC power source. 1, 12-2 and 12-3 are star-connected, and this is the same as in the first embodiment of FIG.

  The inverter circuits 10-11 to 10-13 have a circuit configuration representatively shown by the inverter circuit 10-11. In the inverter circuit 10-11, when the number of inverter elements n is n = 3, the AC phase angle 360 ° is divided by the number of inverter elements n = 3 (360 ° / n) = 120 ° having a phase difference of 120 °. There are provided n = 3 separately-excited flyback inverter circuit units driven by three kinds of switching signals, that is, three kinds of switching signals having phase differences of 0 °, 120 °, and 240 °.

  That is, the inverter circuit unit driven at phases 0 °, 120 °, and 240 ° includes drive transformer secondary windings 34-11, 34-12, and 34-13, and drive circuits 16-11, 16-12, and 16−. 13, inverter elements 14-11, 14-12, 14-13, primary windings 20-11, 20-12, 20-13 and secondary windings 22-11, 22-12, 22-13 It comprises output transformers 18-11, 18-12, 18-13 and rectifier diodes 24-11, 24-12, 24-13.

  Similarly to the inverter circuit 10-11, the other inverter circuits 10-12 and 10-13 are provided with three inverter circuit portions corresponding to the switching signal phases 0 °, 120 °, and 240 ° in parallel. ing.

  The output circuit side includes 9 rectifier diodes 24-11 to 24-33 connected to secondary windings 22-11 to 22-33 of three output transformers provided in the inverter circuits 10-11 to 10-13. After the two output sides are combined into one, they are connected to a single smoothing capacitor 26 and DC power of a predetermined voltage is supplied to the DC output terminal 28.

  The control circuit 36-1 is provided as one circuit for the inverter circuits 10-1 to 10-13 of each phase, and the control circuit 36-1 is the same as (1) to (3) in the first embodiment of FIG. By driving at the same condition, that is, in a discontinuous mode in which the on-duty is reduced, at a constant frequency and with a duty ratio with little fluctuation with respect to one cycle of the AC frequency, the relationship of the above expression (1) is continued. By operating as a constant resistance, the input current is proportional to the input voltage, and the power factor is improved.

  In FIG. 6 showing the details of the control circuit 36-1 in FIG. 5, the input of the DC output voltage to the control IC 38 is the same as that in the embodiment of FIG. 1, and the frequency response gain of the control IC 38 is also the resistor 46 and the capacitor 48. With this time constant circuit, a frequency response gain with a time constant that does not respond to a low frequency fluctuation of the DC output voltage within the cycle of the input AC voltage is set.

  A control signal from the control unit 36 is input to each drive system having a phase of 0 °, 120 °, and 240 ° provided in three systems. The drive circuit 40-1 corresponds to the phase 0 °, and inputs the control signal from the control IC 38 as it is, and outputs the switching signal of the phase 0 ° to the drive transformer secondary winding 32-1.

  The 120 ° shift circuit 90-2 shifts the control signal by 120 ° in phase, and the drive circuit 40-2 outputs a switching signal shifted in phase by 120 ° to the drive transformer primary winding 32-2. Further, in the 240 ° shift circuit 90-3, a control signal shifted in phase by 240 ° is input to the drive circuit 40-3, and a switching signal shifted in phase by 240 ° is supplied to the drive transformer secondary winding.

  As a circuit configuration for shifting the phase of the switching duty in the 120 ° shift circuit 90-2 and the 240 ° shift circuit 90-3, a delay circuit using an analog circuit or a digital circuit is used.

  For the overcurrent protection terminal 45 of the control IC, the current transformer secondary corresponding to the nine current transformer primary windings of the inverter circuit provided in the inverter circuits 10-11 to 10-13 in FIG. The windings 35-211 to 35-233 are provided and converted into overcurrent detection voltages by the overcurrent detection circuits 50-11 to 50-33, respectively, and then the control IC 38 via the diode OR by the diodes 52-11 to 52-33. Therefore, the maximum overcurrent detection signal among the total of nine overcurrent detection signals provided in the three-phase inverter 10-11 is incorporated in the control IC 38. The overcurrent protection circuit that is over will perform overcurrent protection operation.

  According to the second embodiment shown in FIGS. 5 and 6, the three systems provided in the inverter circuits 10-11 to 10-13 corresponding to the respective phases are arranged in parallel corresponding to the phases 0 °, 120 °, and 240 °. By switching the three-phase AC voltage to DC power by performing general switching control, the ripple voltage shifts by 0 °, 120 °, and 240 ° and is combined into one on the output side, thereby shifting by 120 ° The high frequency ripple can be reduced by canceling the three ripple voltages.

  In the second embodiment shown in FIGS. 5 and 6, the case where the number of inverter elements is n = 3 and three inverter circuit portions are provided in each of the inverter circuits 10-11 to 10-13 is taken as an example. However, when the number of inverter elements is n = 2 and two inverter circuit units are provided, switching control is performed so that the respective phases are shifted by 0 ° and 180 °, so that two ripple voltages shifted by 180 ° are obtained. By canceling out, high-frequency ripple can be reduced.

  FIG. 7 is a circuit block diagram showing a third embodiment of the present invention capable of switching between star connection and delta connection. FIG. 7 (A) shows the inverter circuit portion on the primary side of the block 10 shown in FIG. 7 (B) as inverters 10-1 to 10-3 as one block, and the three-phase AC power supply terminals R, S , T, the inverters 10-1 to 10-3 of each phase can be switched from the star connection to the delta connection by switching the three changeover switches 94-1, 94-2, 94-3.

  The change-over switches 94-1 to 94-3 have a star connection contact a and a delta connection contact b, and can be switched as interlocked switches. In the connection positions of the star connection terminals a of the illustrated changeover switches 94-1 to 94-3, the inverters 10-1 to 10-3 are connected to the three-phase alternating current R as in the first embodiment shown in FIG. , S, T are star-connected.

  On the other hand, when the changeover switches 94-1 to 94-3 are switched to the delta connection terminal b side, the three inverters 10-1 to 10-3 are delta connected to the three-phase AC power input terminals R, S, and T. be able to.

  The switching between the star connection and the delta connection in the embodiment of FIG. 7 can be used for the following usage.

  First, in the star connection of the illustrated inverter circuits 10-1 to 10-3, the AC voltage input to each of the inverter circuits 10-1 to 10-3 can be reduced to 1 / √3. An element having a low withstand voltage can be used as the element 14. For example, in the case of an AC 400 volt system as a three-phase alternating current, the applied voltage can be reduced to 1 / √3 by switching to the star connection, and the withstand voltage of the inverter element can be made advantageous.

  On the other hand, in the case of the delta connection in which the inverter circuits 10-1 to 10-3 are switched to the delta connection terminal b side by switching the changeover switches 94-1 to 94-3, the current flowing through the inverter circuits 10-1 to 10-3 Can be reduced to 1 / √3. In such a case, for example, an AC 400 volt system to which a star connection is applied is switched to a delta connection for an AC 200 volt system three-phase alternating current, and the inverter circuits 10-1 to 10-10. By reducing the current flowing through −3 to 1 / √3, it is possible to reduce the current loss of the inverter element and the output transformer.

  FIG. 8 is a circuit block diagram showing a fourth embodiment of the present invention in which inverter circuits are star-connected for a six-phase AC power source. In FIG. 8, the inverter circuits 10-1 to 10-6 have the same circuit configuration as that shown in FIG. 7B, and this is the primary side of the inverter circuit. As shown in the first embodiment, after the output transformers are combined into one via a rectifier diode, the DC output power is taken out by a single smoothing capacitor.

  In other words, the present invention adopts the same star connection configuration for multi-phase AC other than three-phase AC, so that one output smoothing and control system may be used, and each of the inverter circuits 10-1 to 10-6 is provided. The power factor can be improved by controlling with the conditions (1) to (3) to operate with low resistance.

  FIG. 9 is a circuit block diagram showing a fifth embodiment of the present invention in which a DC-DC converter is connected after the power factor correction circuit. In FIG. 9, the power factor correction circuit unit 96 is the same circuit as that of the first embodiment of FIG. 2, and a DC-DC converter 98 is connected to the output stage of the power factor improvement circuit unit 96.

  An appropriate switching regulator can be used as the DC-DC converter 98, and the DC voltage input from the power factor correction circuit unit 96 is stabilized at a predetermined constant voltage and supplied from the DC output terminal 28 to the load. it can.

  Here, the control circuit 36 provided in the power factor correction circuit unit 96 receives not the output voltage from the smoothing capacitor 26 but the DC output voltage of the DC-DC converter 98, and an inverter circuit so as to stabilize it at a predetermined voltage. Although switching control of 10-1 to 10-3 is performed, switching control may be performed by inputting a DC voltage output from the smoothing capacitor 26.

  Further, by adjusting the capacity of the smoothing capacitor 26 provided at the output stage of the power factor correction circuit unit 96 and the setting of the stop voltage of the DC-DC converter, the DC power is maintained against the instantaneous interruption of the three-phase AC power supply. Arbitrary holding time can be secured.

  The configuration in which the DC-DC converter 98 is provided at the output stage of the power factor correction circuit unit 96 in the embodiment of FIG. 9 is the same as that of the embodiment of FIG. 5, the embodiment of FIG. 7, and the embodiment of FIG. The same can be applied.

  In addition, since the separately excited flyback type inverter circuit is used in the inverter circuits 10-1 to 10-3 of the present embodiment, the output voltage must be higher than the input voltage in the case of the boost chop. Unlike the case where the power factor improvement operation cannot be performed, a sufficient power factor improvement operation can be performed even if the output voltage is arbitrarily set.

  Furthermore, the present invention provides a single-phase AC power factor correction circuit, and the embodiment leaves the inverter circuit 10-1 and the inverter circuit 10-2 for the three-phase AC power factor correction circuit of FIG. 10-3, and the control circuit system of only the inverter 10-1 except the overcurrent detection circuits 50-2 and 50-3 and the diodes 52-2 and 52-3 from the control circuit 36 may be used. .

  Even in the single-phase AC power factor correction circuit having such a circuit configuration, as shown in the above (1) to (3), the control circuit 36 is in a discontinuous mode, at a low frequency and a cycle of the AC frequency. In contrast, the power factor when the single-phase AC power is converted to DC power can be improved by driving the inverter circuit 10-1 as a constant resistance by driving with a duty ratio with less fluctuation.

  In the above embodiment, the current transformer primary winding is connected to the minus line, but the same operation can be obtained even if it is connected to the plus line.

  Moreover, although MOSFET is used as an inverter element, the appropriate switch element limited to this can be used.

  Further, instead of the rectifier diode on the output circuit side, a synchronous rectifier circuit using a MOSFET may be used.

  Further, a high frequency filter may be connected before and after the input stack diode constituting the full wave rectifier circuit.

The present invention includes appropriate modifications without impairing the object and advantages thereof, and is not limited by the numerical values shown in the above embodiments.

The circuit block diagram which showed 1st Embodiment of the power factor improvement circuit by this invention Circuit block diagram showing star connection to a three-phase AC terminal in the power factor correction circuit of FIG. Circuit block diagram showing details of drive circuit diameter in FIG. Circuit block diagram showing details of the overcurrent protection circuit system of FIG. A circuit block diagram showing a second embodiment of a power factor correction circuit according to the present invention for performing phase-shifted switching control. The circuit block diagram which showed the detail of the control part of FIG. Circuit block diagram showing a third embodiment of the present invention capable of switching between star connection and delta connection The circuit block diagram which showed 4th Embodiment of this invention which connected the inverter circuit star for 6 phase alternating current power supply object The circuit block diagram which showed 5th Embodiment of this invention which connected the DC-DC converter in the back | latter stage of the power factor improvement circuit Block diagram showing a conventional three-phase AC power factor correction circuit with delta-connected boost chopper

Explanation of symbols

10-1 to 10-6: Inverter circuits 12, 12-1 to 12-3: Diode bridges 14, 14-1 to 14-3: Inverter elements 16, 16-1 to 16-3, 16-11 to 16- 13: Drive circuits 18-1 to 18-3, 18-11 to 18-13: Output transformers 20-1 to 20-3, 20-11 to 20-13: Primary windings 22-1 to 22-3, 22-11 to 22-33: secondary windings 24-1 to 24-3, 24-11 to 24-33: rectifier diode 26: smoothing capacitor 28: output terminal 30: drive transformer 32, 32-1 to 32-2. 3: Drive primary windings 34, 34-1 to 34-3, 34-211 to 34-233: Drive secondary windings 35-11 to 35-13: Current transformer primary windings 35-21 to 35-35 23: Current transformer secondary winding 36 36-1: The control unit 38: control IC
40: Drive circuits 41, 42, 44, 46, 58, 60, 64, 76-1 to 76-3, 78-1 to 78-3, 84, 85, 86-1 to 86-3: Resistor 45: Excessive Current protection terminals 48, 62, 82: capacitors 50-1 to 50-3, 50-11 to 50-33: overcurrent detection circuits 52-1 to 52-3, 74-1 to 74-3, 80-1 80-3, 88-1 to 88-3: Diodes 54, 56, 72-1 to 72-3: Transistor 70: Zener diode 90-2: 120 ° shift circuit 90-3: 240 ° shift circuit 94-1 94-3: Changeover switch 96: Power factor correction circuit unit 98: DC-DC converter

Claims (5)

Full-wave rectifier circuit, inverter element, drive circuit of the inverter element, an output transformer and an output rectifier circuit, an inverter circuit for the number of phases of a multiphase AC power source that performs a separate excitation flyback operation;
An input connection circuit that star-connects the full-wave rectifier circuit of the inverter circuit for the number of phases to a multiphase AC power source,
An output connection circuit that outputs DC power by connecting each output rectifier circuit of the inverter circuit for the number of phases in parallel and connecting to a single smoothing circuit;
In order to maintain the predetermined voltage by inputting the DC output voltage obtained by the output connection circuit, the inverter circuits for the number of phases are maintained at a constant frequency and one cycle of the AC frequency while maintaining the discontinuous mode. Provided with a control circuit that operates as a constant resistance by driving with a duty ratio with less fluctuation ,
The control circuit includes a single drive transformer having a primary winding for inputting a switching signal and secondary windings for the number of phases connected to each drive circuit provided in the inverter circuit for the number of phases. Switching control common to each inverter element of the inverter circuit for the number of phases,
The inverter circuit of the phase several minutes with a phase number of the current transformer for detecting the inverter current, the control circuit over protection operation on the maximum current in the inverter current detected in the previous SL-phase minutes of the current transformer Equipped with a current protection circuit,
A multiphase AC power factor correction circuit characterized by   2. The multiphase AC power factor correction circuit according to claim 1, wherein the control circuit has a frequency response gain that does not respond to a low frequency fluctuation of the DC output voltage within a cycle of the input AC voltage. A multiphase AC power factor correction circuit characterized by setting.   2. The multiphase AC power factor correction circuit according to claim 1, further comprising a single DC-DC converter that stabilizes the output voltage at a predetermined voltage following the output connection circuit of the inverter circuit for the number of phases. A multiphase AC power factor correction circuit characterized by that.   2. The multi-phase AC power factor correction circuit according to claim 1, further comprising a switching circuit for switching each full-wave rectifier circuit of the plurality of inverter circuits between a star connection and a delta connection to the multi-phase AC power source. A multiphase AC power factor correction circuit characterized by Following the full-wave rectifier circuit, a plurality of inverter elements, a plurality of drive circuits provided for each inverter element, a plurality of output transformers driven by the plurality of inverter elements, and an output rectifier provided for each of the plurality of output transformers An inverter circuit corresponding to the number of phases of the multiphase AC power source that includes a circuit and performs separately excited flyback operation;
An input connection circuit that star-connects the full-wave rectifier circuit of the inverter circuit for the number of phases to a multiphase AC power source,
An output connection circuit that outputs DC power by connecting each output rectifier circuit of the inverter circuit for the number of phases in parallel and connecting to a smoothing circuit;
A plurality of inverter elements provided in the inverter circuit for the number of phases is divided by 360 ° by the number of inverter elements so that the DC output voltage obtained in the output connection circuit is input and the predetermined voltage is maintained. A plurality of switching signals having a phase difference, and a control circuit that operates as a constant resistance by driving at a constant frequency while maintaining a discontinuous mode at a duty ratio with little variation with respect to one cycle of the AC frequency ;
The control circuit performs switching control of n inverter elements provided in each inverter circuit by n kinds of switching signals having a phase difference of 360 ° / n, where n is the number of inverter elements.
A multiphase AC power factor correction circuit characterized by

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