JP2014036573A - Rectifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and low-loss rectifier circuit capable of improving power factor.SOLUTION: Power outputted from an AC power supply AC is caused to be stored in inductors L1 and L2 as magnetic energy via a switch SW1 (or SW2) in an on-state. When the switch SW1 (or SW2) is turned off, the magnetic energy is stored in a capacitor CM as electrostatic energy. The electrostatic energy in the capacitor CM is discharged to a load, after the completion of the discharging, the switch SW1 (or SW2) is turned on again. The on/off frequency and on-time of the switch are constant, thereby achieving current sensor-less and ideal PFC.

Description

  The present invention relates to a rectifier circuit.

  A bridgeless PFC (Power Factor Correction) circuit is known as a circuit that rectifies alternating current with a high power factor. By combining this with a booster circuit or a step-down circuit, an AC voltage can be converted into various DC voltages.

  As a booster circuit, for example, Patent Document 1 discloses a pulse power supply device capable of boosting a DC or AC voltage with low loss. This pulse power supply device has a configuration in which a power supply is connected in series to a unidirectional MERS (Magnetic Energy Recovery Switch).

Japanese Patent No. 4382665

  When an AC power supply is used for the pulse power supply device described in Patent Document 1, if another circuit is further used for rectification or PFC, there is a problem that the entire device becomes large or loss increases.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a small-sized and low-loss rectifier circuit that can improve the power factor. Another object of the present invention is to provide a rectifier circuit capable of continuously controlling the step-up / step-down voltage.

In order to achieve the above object, a rectifier circuit according to an aspect of the present invention includes:
A control terminal to which a signal for controlling on / off is input; when off, current from one end to the other end is cut off and current from the other end to the one end is conducted; First and second switch portions for conducting current in both directions from the other end to the one end;
An inductor having one end connected to one end of the AC power source and the other end connected to one end of the first switch unit;
A first diode having an anode connected to the other end of the inductor and one end of the first switch unit;
A second diode having an anode connected to the other end of the AC power source and one end of the second switch unit;
A capacitor having one end connected to the cathode of the first diode and the cathode of the second diode, and the other end connected to the other end of the first switch unit and the other end of the second switch unit When,
A control unit for controlling on / off of the first and second switch units by supplying a signal for controlling on / off to the control ends of the first and second switch units;
With
The control unit periodically controls on / off of the first and second switch units at a frequency higher than the output frequency of the AC power supply,
The capacitor generates a DC voltage having a period in which the voltage is substantially zero at least once in one cycle of the AC power source.
It is characterized by that.

  According to the present invention, it is possible to provide a small and low-loss rectifier circuit that can improve the power factor. It is also possible to provide a rectifier circuit capable of continuously controlling the step-up / step-down.

1 is a circuit diagram showing a configuration of a rectifier circuit according to a first embodiment of the present invention. It is a figure for demonstrating the operation | movement of the ON period of the rectifier circuit shown in FIG. It is a figure for demonstrating the operation | movement of the OFF period of the rectifier circuit shown in FIG. FIG. 2 is a waveform diagram showing currents and voltages of respective parts of the rectifier circuit shown in FIG. 1. It is a circuit diagram which shows the structure of the rectifier circuit which concerns on the 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the rectifier circuit which concerns on the 3rd Embodiment of this invention. It is a circuit diagram which shows the application circuit of the rectifier circuit of FIG. It is a circuit diagram which shows the basic part of the rectifier circuit of FIG. It is a wave form diagram which shows the relationship between a capacitor | condenser voltage and power supply voltage and electric current.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment: Configuration)
The rectifier circuit 100 according to the embodiment of the present invention is connected between an AC power supply AC and a load LD. The rectifier circuit 100 includes inductors L1, L2, and L3, diodes D1, D2, and D3, switches SW1, SW2, and SW3, a capacitor CM, a capacitor Cs, and a control unit 150.

The switches SW1 to SW3 include gates G1 to G3 for controlling on / off.
When the off signal is input to the gates G1 to G3, the switches SW1 to SW3 cut off the current from one end to the other end, but the current from the other end to the one end is conducted by the internal diode. When an ON signal is input to the gates G1 to G3, the switches SW1 to SW3 conduct current in both directions.
Hereinafter, the switches SW1 to SW3 are assumed to be n-channel MOSFETs having parasitic diodes.

  One end of the AC power supply AC is connected to one end of the inductor L1. The other end of the AC power supply AC is connected to one end of the inductor L2. The AC power supply AC outputs an AC voltage of 100 V and 50 Hz.

The other end of the inductor L1 is connected to the anode of the diode D1 and one end of the switch SW. The other end of the inductor L2 is connected to the anode of the diode D2 and one end of the switch SW.
The inductors L1 and L2 are 2.5 mH coils.

  Both the diodes D1 and D2 have cathodes connected to one end (positive electrode) of the capacitor CM.

  The other ends of the switches SW1 and SW2 are both connected to the other end (negative electrode) of the capacitor CM.

  One end of the capacitor CM is connected to one end of the switch SW3, and the other end is connected to the anode of the diode D3. The capacitor CM is, for example, a film capacitor having a capacity of 12 nF.

  The other end of the switch SW3 and the cathode of the diode D3 are connected to one end of the inductor L3.

The other end of the inductor L3 is connected to one end of the load LD, and the other end of the load LD is connected to the anode of the diode D3. The capacitor Cs is connected in parallel with the load LD. The inductor L3 and the capacitor Cs function as a low pass filter.
The load LD is, for example, a light emitting diode. In this case, one end corresponds to the anode and the other end corresponds to the cathode.

The control unit 150 supplies control signals SG1, SG2, and SG3 to the gates G1, G2, and G3 of the switches SW1, SW2, and SW3.
The control signals SG1 to SG3 are the same signal composed of an on signal and an off signal. By changing the frequency and duty of the control signals SG1 to SG3, the rectifier circuit 100 performs an operation described later, and adjusts the voltage supplied to the load LD.
In the present embodiment, the initial state of the control signals SG1 to SG3 is 10 kHz, and the ON period (time for supplying the ON signal during one period) is 40 microseconds (25% in terms of duty). To do.

(Operation)
Hereinafter, the operation of the rectifier circuit 100 will be described with reference to FIGS. 2A and 2B. In FIGS. 2A and 2B, the arrows indicate the direction of current flow, and the letters ON or OFF indicate the ON / OFF state of the switch.
Assume that the initial state is that the switches SW1 to SW3 are off and the capacitor CM is charged.
In order to facilitate understanding, the following description will be made assuming that the output voltage of the AC power supply AC is positive (the voltage at one end is higher than the other end). The same reference numerals as those in FIG. 1 are omitted.

"On period"
When the control unit 150 outputs the control signals SG1 to SG3 as ON signals, all the switches SW1 to SW3 are switched from OFF to ON so as to conduct current in both directions from one end to the other end and from the other end to the other end. become.

  Then, as shown in FIG. 2A, the current that flows from one end of the AC power supply AC flows from one end of the switch SW1 to the other end and from the other end of the switch SW2 to the other end of the AC power supply AC.

  On the other hand, the electric charge accumulated in the capacitor CM is discharged, and a current flows from one end of the switch SW3 to the other end, the inductor L3, and the load LD.

In the ON period, a current proportional to both the length of the ON period and the voltage Vs of the AC power supply AC during that period flows through the inductors L1 and L2. When current flows, magnetic energy is accumulated in the inductors L1 and L2.
On the other hand, when the capacitor CM is discharged, the electrostatic energy accumulated in the capacitor CM is released, and power is supplied to the inductor L3 and the load LD. In this embodiment, the capacitor CM completes discharging. After the discharge is completed, the magnetic energy stored in the inductor L3 is supplied to the load LD. Current flows from the other end of the inductor L3 through the load LD and the diode D3 to one end of the inductor L3. Since the capacitor CM completes discharging and its voltage becomes zero, the voltage applied to the switches SW1 to SW3 becomes substantially zero.

"Off period"
When the above-described on period expires, control unit 150 switches control signals SG1 to SG3 from the on signal to the off signal. Then, the switches SW1 to SW3 are switched from on to off, and current is cut off from one end to the other end.
In the aforementioned “on period”, the capacitor CM completes discharging and its voltage becomes zero, so that the voltage applied to the switches SW1 to SW3 becomes substantially zero. That is, this switching is a zero voltage switch.

Then, as shown in FIG. 2B, the current flowing from one end of the AC power supply AC flows from the anode of the diode D1 to the one end of the capacitor CM through the cathode. The flowing energy includes the magnetic energy stored in the inductors L1 and L2 during the above-described “on period”.
The current flowing from the other end of the capacitor CM flows from the other end of the switch SW2 to the other end of the AC power supply AC.
When the voltage of the capacitor CM becomes equal to or higher than the output voltage of the AC power supply AC and the magnetic energy of the inductors L1 and L2 is lost, this current does not flow.

  On the other hand, the magnetic energy stored in the inductor L3 continues to flow through the load LD and the diode D3. The current stops flowing as soon as the magnetic energy is lost.

  In the next switching period, the control unit 150 switches the control signals SG1 to SG3 from the off signal to the on signal, and the circuit enters the above-described “on period” again. Since no current flows through the switches SW1 to SW3 in the “off period”, this switching is zero current switching.

  Thereafter, the rectifier circuit 100 repeats the above “on period” and “off period” at the switching frequency set by the control unit 150. As a result, magnetic energy proportional to the voltage Vs output from the AC power supply AC at that time is accumulated in the inductors L1 and L2 during the “on period”, and is recovered by the capacitor CM during the “off period”. Accumulation as energy is repeated alternately. The electrostatic energy accumulated in the capacitor CM is supplied to the inductor L3 and the load LD during the “on period”, and the current is held by the magnetic energy remaining in the inductor L3 even after the “off period”. .

  Note that the operation is substantially the same even if the polarity of the voltage of the AC power supply AC is reversed. The switch SW1 and the switch SW2 only replace the diode D1 and the diode D2.

  As described above, when the switch is turned off, the magnetic energy accumulated in the inductor is collected in the capacitor and accumulated as electrostatic energy. When the switch is turned on, the electrostatic energy accumulated in the capacitor is supplied to the load. Therefore, it can be said that this circuit has the same principle as MERS described in Patent Document 1 and the like.

  Thereby, the peak of the current flowing through the AC power supply AC is proportional to the voltage VS output from the AC power supply AC (whether the voltage VS is positive or negative). Therefore, the current waveform is a sine wave having the same phase as the power supply voltage, and an ideal PFC can be realized.

Further, the amount of electrostatic energy at the peak of the capacitor CM corresponds to at least the amount of magnetic energy accumulated in the recovered inductors L1 and L2. In addition, since a substantial rectifier circuit is included, the voltage peak of the capacitor CM is higher than the peak of the voltage Vs output from the AC power supply AC.
Further, the switch SW3, the inductor L3, and the diode D3 have the same configuration as a general step-down chopper circuit. Therefore, the voltage supplied to the load LD is stepped down by the capacitor CM. (It is not always stepped down from AC power supply AC.)

Compared to the pulse power supply disclosed in Patent Document 1, the circuit configuration is only increased by one diode and one switch.
In addition, a capacitor having a smaller capacity is used as compared with a conventional bridgeless PFC. Therefore, switching is possible at a capacitor voltage of 0 or a voltage lower than the voltage generated in the capacitor of the conventional bridgeless PFC circuit (soft switching). That is, the switching loss can be kept low.

In the present embodiment, as shown in FIG. 3, the output voltage of the AC power supply AC is 100 Vac, whereas the voltage peak of the capacitor CM exceeds 360V. The voltage of the load LD is about 2-13V.
Also, so-called soft switching is realized in which the switches SW1 to SW3 are turned on when the current flowing through the capacitor CM is substantially zero, and the switches SW1 to SW3 are turned off when the voltage of the capacitor CM is substantially zero. Has been.
It should be noted that by adjusting circuit constants, on-time, etc., this circuit can be operated even if it is not completely soft switching, and the voltage of the load LD can be made higher than the voltage of the AC power supply AC.
Note that the shorter the on-time, the smaller the amount of stored magnetic energy, and thus the voltage of the capacitor CM becomes smaller. However, if the on-time is too short, the capacitor CM cannot be completely discharged and hard switching may occur. Therefore, the voltage of the load LD may be reduced by reducing the switching frequency and reducing the amount of magnetic energy per time.

  Further, the rectifier circuit 100 realizes PFC without using a current sensor or the like that is necessary for a conventional PFC circuit. In addition, since soft switching is possible, high frequency can be easily achieved, and thus miniaturization is possible.

(Summary)
As described above, according to the rectifier circuit 100 according to the present invention, the switches SW1 to SW3 are turned on when the current flowing through the capacitor CM is substantially zero, and the switch SW1 when the voltage of the capacitor CM is substantially zero. SW3 is turned off to realize soft switching. As a result, the voltage of the capacitor CM is boosted from the power supply voltage. Further, by passing this through the switch SW3, the diode D3, and the inductor L3, a voltage that is stepped up or stepped down from the power supply voltage can be supplied to the load LD.
Further, by making the duty constant in this configuration, an ideal PFC in which the current waveform is a sine wave even if sensorless is realized. Of course, it is possible to apply PFC in which the current waveform is not a sine wave by modulating the duty. Soft switching is possible and the number of parts is small.
That is, according to the present invention, it is possible to provide an ideal rectifier circuit having a PFC function capable of step-up / step-down with a small number of parts, a small size, and a relatively small switching loss.

(Second Embodiment)
In the rectifier circuit 100 according to the first embodiment described above, the voltage of the load LD pulsates between 2V and 13V with a period of 120 Hz. This is not preferable particularly when the load LD is illumination. In addition, non-insulation may be required.
In the following, a second embodiment of the present invention that is insulated and has a configuration with little load voltage pulsation will be described.

  In the rectifier circuit 200 according to the second embodiment, as shown in FIG. 4, the inductor L3 of the rectifier circuit 100 of the first embodiment is replaced with a transformer 210, and further, a rectifier 220 and a filter 230 before the load LD. It is equipped with.

  The rectifier circuit 200 is connected to the primary side of the transformer 210 instead of the inductor L3 of the rectifier circuit 100. The secondary side of the transformer 210 is connected to the load LD via the rectifier 220 and the filter 230.

  The rectifier 220 has an AC input and a DC output. The AC input is connected to the secondary side of the transformer 210, and the DC output is connected to the filter 230. The rectifier 220 rectifies the power input from the AC input and outputs it from the DC output. In this embodiment, the rectifier 220 is a full-wave rectifier circuit.

  The filter 230 smoothes the load current / load voltage. In this embodiment, the inductor 231 is connected in series and the capacitor 232 is connected in parallel. One end of the inductor 231 is connected to the positive side of the DC output of the rectifier 220, and the other end is connected to one end of the capacitor 232 and one end of the load LD. The other end of the capacitor 232 is connected to the other end of the load LD and the negative side of the DC output of the rectifier 220.

  The load LD is organic EL (ElectroLuminescence) illumination in the present embodiment. The power flowing from one end to the other is converted into light and output.

The filter 230 reduces the pulsation of the current flowing through the load LD. As a result, the load LD can output light with less flicker.
Moreover, since it is insulated by the transformer 210, safety is high.

(Third embodiment)
Synchronous rectification may be performed using the diodes D1 to D3 of the rectifier circuits 100 and 200 described above as switches. Hereinafter, a third embodiment of the present invention with less loss in which each diode is replaced with a switch will be described with reference to FIG.

  The rectifier circuit 300 according to the third embodiment is obtained by replacing the diode D1 of the rectifier circuit 100 with a switch 310, the diode D2 with a switch 320, and the diode D3 with a switch 330, as shown in FIG.

  The configurations of the switches 310, 320, and 330 are the same as those of the switches SW1 to SW3, respectively.

The switches may be turned on at the timing when current flows from one end to the other. For example, with respect to the switches 310 and 320, the discharge of the capacitor CM is completed while the switches SW1 and SW2 are on.
Alternatively, the switches 310 to 330 may be turned on when the switches SW1 to SW3 are on.

Although the first to third embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above. With the basic configuration shown in FIG. 7, the essential effects of the present invention can be obtained.
The rectifier circuit 500 of FIG. 7 is an extract of the diodes D1 and D2, the switches SW1 and SW2, the inductors L1 and L2, the capacitor CM, and the controller 150 of the rectifier circuit 100 of FIG.
The load may be connected to both ends of the capacitor CM, or may be connected between the AC power supply AC and the inductor L1. For example, like the rectifier circuit 100, it may be indirectly connected to both ends of the capacitor CM via another circuit (a load may be considered including other circuits), or the AC power supply AC and the inductor L1. A load may be connected via a rectifier (since AC power is supplied to the rectifier, it cannot be said that the entire circuit is a rectifier circuit, but a DC voltage is generated in the capacitor CM. It can be said that this part is a rectifier circuit).

(Relationship between capacitor capacity and ideal PFC)
In the above description, the case where each switch is completely soft-switched has been described as an example. However, if the purpose is to realize an ideal PFC, the switch may not be soft-switched.

  It is of course possible to reproduce an ideal PFC by feeding back current and modulating the duty. However, an ideal PFC can be easily obtained by selecting a capacitor CM having such a capacity that the voltage of the capacitor CM in the rectifier circuit 500 is zero at least near the power supply voltage.

FIG. 8 shows P1.., When the rectifier circuit 500 has the following circuit constants. When the voltage of the capacitor CM does not become zero at all (when it does not become zero voltage), P2. When the voltage of the capacitor CM drops to almost 0 (when it becomes substantially 0 voltage), P3. When the voltage of the AC power supply AC is near 0 and the voltage of the capacitor CM becomes 0 only once (when it becomes 0 voltage once), P4. The voltage / current of the AC power supply AC and the voltage of the capacitor CM when the capacitor CM drops to 0 voltage each time switching (in the case of soft switching) are shown.
Inductors L1 and L2: 2.5 mH
AC power supply AC: 100Vac, 50Hz
Capacitor CM; P1: 12.0 μF, P2: 4.0 μF, P3: 1.2 μF, P4: 12.0 nF

As can be seen from FIG. 8, when the voltage does not become 0 of P1, it is not an ideal PFC. On the other hand, an almost ideal PFC is reproduced at P2 to P4 at which the voltage is substantially zero at least once.
It can also be seen that soft switching can be realized both when the voltage of P3 becomes zero once and when soft switching of P4 is performed.
That is, since the voltage of the capacitor CM becomes substantially zero near the output voltage of the AC power supply AC (the voltage of the capacitor CM becomes substantially zero at least once during one power cycle), An ideal PFC can be realized by control. Since the timing at which the output voltage of the AC power supply AC becomes zero is twice in one cycle, the voltage of the capacitor CM becomes zero at least in both of them (the voltage of the capacitor CM is substantially zero in two cycles or more in one cycle). 0).

  It can also be seen from the waveforms of P3 and P4 that the capacitor voltage is a waveform obtained by rectifying a sine wave.

(Other applications)
For example, electric power may be extracted using the voltage of the capacitor CM as a DC voltage source. Note that the peak voltage of the capacitor CM is higher (boosted) than the voltage of the AC power supply AC.

Alternatively, the voltage across the capacitor CM may be output as an alternating current using an inverter. In the rectifier circuit 400 of FIG. 6, a capacitor CM is connected to the primary side of the transformer 210 of the rectifier circuit 200 via a midpoint grounded inverter 410, and an inductor 420 and diodes 430 and 440 are connected instead of the load LD. The cathodes of the diodes 430 and 440 are respectively connected to the other ends of the inductors L1 and L2.
The inverter 410 converts the DC voltage of the capacitor CM into AC, and the inductor 420, the diodes 430 and 440 smooth the voltage pulsation of the capacitor CM.
When the capacitor CM is used as a DC voltage source, a voltage higher than the output voltage of the AC power supply AC can be provided to the load, which is suitable for use with high power.

  Each switch described above has been described as having an internal diode. However, a diode may be further provided in parallel, or a switch having no internal diode may be provided with a diode in parallel. The switch portion may be configured.

  In the above description, the AC power source AC is connected to the switches SW1 and SW2 via the two inductors L1 and L2. However, only one inductor may be used. In that case, it is only necessary to have an inductor having the total inductance of the two inductors.

In addition, since the ideal PFC can be realized if the on-time described above is constant in one cycle, the ideal PFC can be realized even if the on-time is adjusted for each cycle. In addition, the power supplied to the load can be adjusted by this adjustment.
In other words, if the desired PFC can be achieved, finer control is possible by finely adjusting the on-time.

  Moreover, although the said embodiment demonstrated each power supply as a single phase alternating current, a three phase may be sufficient. In this case, a pair of diodes and switches (for example, one having the same configuration as the pair of the diode D1 and the switch SW1) may be increased and further connected to both ends of the capacitor CM. Even with this configuration, an ideal PFC can be realized to some extent, but the waveform is far from the sine wave as compared to the single-phase AC described above. If a more ideal PFC is required, it is preferable to adjust the duty by, for example, feeding back current.

On the other hand, the configuration of the control unit 150 in each of the above embodiments can also be realized using a normal computer system.
For example, a program for executing the above-described processing performed by the control unit 150 is stored in a CD-ROM (Compact Disk Read-Only Memory), DVD (Digital Versatile Disk), or other computer-readable recording medium and distributed. And the above-mentioned control part 150 can be constituted by installing this program in a computer.

Further, the program may be stored in a disk device or the like included in a predetermined server device on a communication network such as the Internet, and may be downloaded onto a computer by being superimposed on a carrier wave, for example. Furthermore, the above-described processing can also be achieved by starting and executing a program while transferring it via a communication network.
In addition, when the above functions are realized by sharing an OS (Operating System), or when the functions are realized by cooperation between the OS and an application, only the part other than the OS may be stored in a medium and distributed. Alternatively, it may be downloaded to a computer.

  This application is based on US61 / 680,680 filed on August 7, 2012, filed on October 27, 2008. In this specification, the specification of US61 / 680,680, the claims, and the entire drawing are incorporated by reference.

100, 200, 300, 400, 500 Rectifier circuit AC AC power supply L1-L3 Inductor D1-D3 Diode SW1-SW3 Switch 310, 320, 330 Switch CM Capacitor LD Load 150 Control unit

Claims (6)

A control terminal to which a signal for controlling on / off is input; when off, current from one end to the other end is cut off and current from the other end to the one end is conducted; First and second switch portions for conducting current in both directions from the other end to the one end;
An inductor having one end connected to one end of the AC power source and the other end connected to one end of the first switch unit;
A first diode having an anode connected to the other end of the inductor and one end of the first switch unit;
A second diode having an anode connected to the other end of the AC power source and one end of the second switch unit;
A capacitor having one end connected to the cathode of the first diode and the cathode of the second diode, and the other end connected to the other end of the first switch unit and the other end of the second switch unit When,
A control unit for controlling on / off of the first and second switch units by supplying a signal for controlling on / off to the control ends of the first and second switch units;
With
The control unit periodically controls on / off of the first and second switch units at a frequency higher than the output frequency of the AC power supply,
The capacitor generates a DC voltage having a period in which the voltage is substantially zero at least once in one cycle of the AC power source.
A rectifier circuit characterized by that. The voltage of the capacitor has a period in which at least the output voltage of the AC power supply is 0 voltage near 0,
The rectifier circuit according to claim 1. The control unit switches the first and second switch units on and off substantially simultaneously,
The rectifier circuit according to claim 1 or 2, wherein The control unit holds the ON time of the first and second switch units substantially constant during one cycle of the AC power supply.
The rectifier circuit according to any one of claims 1 to 3. The control unit switches off the first and second switch units after the voltage of the capacitor becomes substantially zero, and the current flowing through the first and second switch units becomes substantially zero. Switching on the first and second switch sections;
The rectifier circuit according to any one of claims 1 to 4, wherein A control terminal to which a signal for controlling on / off is input; when off, current from one end to the other end is cut off and current from the other end to the one end is conducted; A third switch unit that conducts current in both directions from the other end to the one end, and is connected to one end of the capacitor at one end;
A third diode having an anode connected to the other end of the capacitor and a cathode connected to the other end of the third switch unit;
A second inductor having one end connected to the other end of the third diode;
Further comprising
One end of the load is connected to the other end of the second inductor, the other end of the load is connected to the anode of the third diode;
The control unit controls on / off of the third switch unit simultaneously with the first and second switch units;
The rectifier circuit according to any one of claims 1 to 5, wherein:

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