JP2011139587A - Multi-current resonant converter and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-current resonant converter having simple circuit and reducing a peak current to reduce power consumption. <P>SOLUTION: The multi-current resonant converter 50 includes: a MOSFET 2 and a MOSFET 3 connected in series and provided between an output terminal 30 and a GND terminal 31 of a DC voltage source; a leakage inductor 4 which receives a current by being alternatively turned ON/OFF by signals VG 1 and VG 2 at a mid point (A) between the MOSFET 2 and the MOSFET 3; an excitation inductor 5; a series resonant capacitor 6 serially connected to the excitation inductor 5; secondary side inductors 7, 8 in which voltages are induced by resonance operation; output rectifying diodes 9, 10; and an output rectifying capacitor 11 which rectify the output. In the converter, a resonant circuit 33 for harmonics is provided which is constituted by inserting an inductor 16 between the output terminal 30 of the DC voltage source and the MOSFET 2, connecting capacitors 14, 15 in series between the output from the inductor 16 and the GND terminal 31, and connecting the mid point B between the capacitors 14 and 15 to one end of the capacitor 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multiple current resonance type converter and an image forming apparatus, and more particularly to a power supply control device in electronic equipment products such as home appliances and office equipment, and in particular, low power consumption of an LLC current resonance type converter. Is related to the technology.

  In recent years, a shift from a mass-consumption society to an energy-saving society has been eagerly desired in order to cope with environmental problems caused by global warming. As part of such efforts, power consumption of electronic devices such as home appliances and office equipment used in general households and businesses has been reduced. Therefore, there is a strong demand for higher power conversion efficiency in the power supply devices used in these devices, and in particular, current resonance converters with low switching loss are attracting attention. As a typical example of this current resonance type converter, there is an LLC current resonance type converter introduced in Non-Patent Document 1.

FIG. 9 is a basic circuit diagram of a conventional LLC current resonant converter, and FIG. 10 is a timing chart showing the operation of the LLC current resonant converter under heavy load.
VG1 is a gate signal of the MOSFET 102, VG2 is a gate signal of the MOSFET 103, VT1 is a voltage across the series circuit of the transformer primary side inductances 104 and 105, and the series resonant capacitor 106, Icr is a current flowing through the series circuit, and Id1 and Id2 are output rectification A current VT2 flowing through each of the diodes 109 and 110 is a voltage across the transformer secondary side inductances 107 and 108.
In the switching operation, MOSFETs 102 and 103 are alternately turned ON / OFF, and dead times 201 and 202 (FIG. 10) in which both MOSFETs 102 and 103 are OFF are provided between the switching operations. Current supply to the transformer during this dead time is performed by the body diode of the MOSFET 102 or 103, and the transformer primary side voltage VT1 is clamped to Vin + Vf or 0-Vf (Vf is the forward voltage of the body diode). The In this state (the drain-source voltage is Vf), the MOSFET 102 or the MOSFET 103 is turned on, so that the voltage loss due to the MOSFET can be extremely reduced (ZVS indicated by 203 and 204 in FIG. 10).

Further, as shown in FIG. 9, the resonance state of the current resonance waveform Icr of the LLC current resonance type converter changes depending on the resonance by the leakage inductance 104, the excitation inductance 105 and the series resonance capacitor 106, and the state of the secondary output circuit. The resonance component due to the leakage inductance 104 and the DC resonance capacitor 106 as basic components is transmitted to the secondary side inductances 107 and 108. Therefore, the current waveforms Id1 and Id2 of the output rectifier diodes 109 and 110 are close to a half wave of a sine wave (see FIG. 10). Therefore, the loss due to the polarity inversion of the diode can be extremely reduced (ZCS). In addition, since the current waveform is close to a sine wave, low noise characteristics are also a significant factor.
As a conventional technique using such a current resonance type converter, there is Patent Document 1 or the like. In Patent Document 1, an output voltage is reduced at no load, and loss at no load is reduced. The aim is to reduce power consumption in standby mode.

・・・（式１）
ここで、Ｖｉｎは直流入力電圧振幅、Ｔｓｗは矩形波の周期（スイッチング周期）、ｎは整数である。
電流共振型コンバータのトランス１次側から２次側へのエネルギーの伝達は、式１の基本波成分である正弦波（Ｓｉｎ波）となる。このため、電流共振型コンバータの２次側インダクタンスの出力電流は、図１０のＩｄ１・Ｉｄ２のように正弦波の半波となり、また出力電流の休止期間もあるため、電流波形のピーク電流は、負荷電流に対して、√２×（出力電流周期）／（出力電流供給期間×２）となる。 As described above, the conventional current resonance type converter has an excellent point that the voltage loss due to the MOSFET and the loss due to the polarity inversion of the diode are extremely reduced, but includes the problems described below.
That is, the transformer primary-side voltage VT1 of the conventional current resonance converter shown in FIG. 9 is a rectangular wave and can be expressed as Equation 1.

... (Formula 1)
Here, Vin is a DC input voltage amplitude, Tsw is a rectangular wave period (switching period), and n is an integer.
Transmission of energy from the transformer primary side to the secondary side of the current resonance type converter becomes a sine wave (Sin wave) which is a fundamental wave component of Equation 1. For this reason, the output current of the secondary inductance of the current resonance type converter is a half wave of a sine wave like Id1 and Id2 in FIG. 10, and there is also a pause period of the output current, so the peak current of the current waveform is For the load current, √2 × (output current cycle) / (output current supply period × 2).

However, when the peak current of the current waveform increases, energy loss at the output rectifier diode and output smoothing capacitor increases, and the ripple voltage on the output voltage also increases. Will occur.
The prior art disclosed in Patent Document 1 is a technique for reducing the output voltage at no load and reducing the loss at no load, and does not contribute much to reducing the loss at heavy load. There is a problem.
The present invention has been made in view of such a problem, and by simplifying the circuit by superimposing a harmonic current on the peak current of the basic component of the current resonance waveform or biasing a voltage having a characteristic opposite to that of the peak current, It is an object of the present invention to provide a multiple current resonance type converter in which current is reduced to reduce power consumption.

  In order to solve this problem, the present invention provides a first switch element and a second switch element connected in series between an output terminal and a GND terminal of a DC voltage source, and the first switch element, A primary winding to which a current is supplied by alternately turning on and off the first switch element and the second switch element at a midpoint between the switch element and the second switch element; and A current resonance circuit including a first capacitor connected in series to the primary winding; a secondary winding in which a voltage is induced by a resonance operation of the current resonance circuit; and A multi-current resonant converter having a smoothing circuit for smoothing an output, wherein an inductor is inserted between an output terminal of the DC voltage source and the first switch element, and an output from the inductor and the GND terminal In between A harmonic resonance circuit configured by connecting a sensor and a third capacitor in series, and connecting a midpoint of the second capacitor and the third capacitor to the current resonance circuit, the resonance current of the current resonance circuit The peak current of the resonance current is reduced by superimposing the resonance current of the harmonic resonance circuit on the resonance current.

  According to a second aspect of the present invention, the first switch element and the second switch element connected in series between the output terminal and the GND terminal of the DC voltage source, and the midpoint of the first switch element and the second switch element The primary winding to which a current is supplied by alternately turning on and off the first switching element and the second switching element in the first winding, and the first winding connected in series to the primary winding and the primary winding. And a secondary winding in which a voltage is induced by the resonance operation of the current resonance circuit, and a smoothing circuit that smoothes the output of the secondary winding. A multiple current resonance type converter, wherein a second capacitor and a third capacitor are connected in series between an output terminal and a GND terminal of the DC voltage source, and a midpoint of the second capacitor and the third capacitor is Connect to current resonance circuit Further, a third switch element and a fourth switch element are connected in series between the output terminal and the GND terminal of the DC voltage source, and the midpoint of the third switch element and the fourth switch element are connected to the second switch element. An inductor is connected between the middle point of the capacitor and the third capacitor, and a bias current is applied to the current resonance circuit by alternately turning on and off the third switch element and the fourth switch element, The peak current of the resonance current is reduced.

According to a third aspect of the present invention, the ON / OFF timing of the third switch element and the fourth switch element is obtained by dividing the ON / OFF timing signal of the first switch element and the second switch element by n. Control is performed at an arbitrary timing between n minutes.
According to a fourth aspect of the present invention, the multiple current resonance type converter according to any one of the first to third aspects is provided as a power supply control device.

According to the present invention, the third harmonic of the fundamental wave of energy propagation is generated by the inductor and the two capacitors, and the harmonic is superimposed on the fundamental wave, so that the peak current can be reduced with a simple circuit.
In addition, in synchronization with the ON / OFF timing of the two switching elements, a signal with a characteristic opposite to that of the fundamental wave is created and superimposed on the fundamental wave, reducing peak current without being affected by load conditions. can do.
In addition, since the ON / OFF timing of the two switching elements is arbitrary, the peak current can be reduced under optimum conditions.

1 is a basic circuit diagram for explaining a multiple current resonance type converter according to a first embodiment of the present invention. It is a figure which shows the relationship between a fundamental wave, a 3rd harmonic, and a superimposed wave. It is a timing chart of the multiple current resonance type converter concerning a 1st embodiment of the present invention. It is a basic circuit diagram for demonstrating the multiple current resonance type | mold converter which concerns on the 2nd Embodiment of this invention. It is a timing chart of the multiple current resonance type converter concerning a 2nd embodiment of the present invention. It is a timing chart of the multiple current resonance type converter concerning a 3rd embodiment of the present invention. It is a figure which shows the Example of the converter using the multiple current resonance type | mold converter which concerns on 1st Embodiment. 1 is a schematic diagram showing a schematic structure of an image forming apparatus using a multiple current resonance type converter of the present invention as a power supply control device. It is a basic circuit diagram of a conventional LLC current resonance type converter. It is a timing chart which shows operation | movement of the conventional LLC current resonance type | mold converter with heavy load.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

  FIG. 1 is a basic circuit diagram for explaining a multiple current resonance type converter according to a first embodiment of the present invention. The multiple current resonance type converter 50 includes a MOSFET 2 (first switch element) and a MOSFET 3 (second switch element) provided in series between the output terminal 30 and the GND terminal 31 of the DC voltage source, MOSFET 2, A leakage inductor 4 (hereinafter simply referred to as an inductor) and an excitation inductor 5 (hereinafter simply referred to as an inductor) to which current is supplied by turning on and off the MOSFETs 2 and 3 alternately by signals VG1 and VG2 from the middle point A of FIG. ) (Primary winding), inductor 4, inductor 5, and series resonance capacitor 6 (hereinafter simply referred to as a capacitor) (first capacitor) connected in series to the current resonance circuit 32. And secondary inductors 7 and 8 (hereinafter simply referred to as inductors) in which a voltage is induced by the resonance operation of the current resonance circuit 32. (Secondary winding), output rectifier diodes 9, 10 (hereinafter simply referred to as diodes) for smoothing the outputs of the inductors 7 and 8, and output smoothing capacitor 11 (hereinafter simply referred to as a capacitor) (smoothing circuit 34). ), The inductor 16 is inserted between the output terminal 30 of the DC voltage source and the MOSFET 2, and the capacitor 14 (second output) is connected between the output from the inductor 16 and the GND terminal 31. And a capacitor 15 and a capacitor 15 (third capacitor) are connected in series, and a harmonic resonance circuit 33 configured by connecting the midpoint B of the capacitors 14 and 15 to one end of the capacitor 6 (current resonance circuit 32) is provided. The peak current of the resonance current is reduced by superimposing the resonance current of the harmonic resonance circuit 33 on the resonance current of the current resonance circuit 32.

That is, the secondary side of the high frequency transformer 13 forms a center tap by the secondary side inductors 7 and 8, the output rectifier diodes 9 and 10, and the output smoothing capacitor 11. On the primary side of the high-frequency transformer 13, the transformer primary-side inductors 4, 5 and the series resonance capacitor 6 constitute a current resonance circuit equivalent to the conventional one.
Further, in the present invention, capacitors 14 and 15 are connected to MOSFETs 2 and 3 in a half-blit configuration, and an inductor 16 that performs voltage resonance together with capacitors 14 and 15 is inserted into the Vin line. The values of the capacitors 14 and 15 and the inductor 16 are set to be the third harmonic of the resonance frequency of the leakage inductance 4 and the series resonant capacitor 6.

  FIG. 2 is a diagram showing the relationship between the fundamental wave, the third harmonic, and the superimposed wave. As is apparent from this figure, when the third harmonic 37 is superimposed on the fundamental wave 35, a superimposed wave 36 is generated.

FIG. 3 is a timing chart of the multiple current resonance type converter according to the first embodiment of the present invention. This timing chart is assumed under the same conditions as the conventional current resonance type converter shown in FIG. 9, and the operation timing is also the same. VG1 is a gate signal of MOSFET2, VG2 is a gate signal of MOSFET3, VT1 is a voltage waveform of transformer primary side inductances 4 and 5, Icr is a current flowing in a series circuit composed of inductors 4, 5 and capacitor 6, Id1 and Id2 Is a current flowing through each of the output rectifier diodes 9 and 10, and VT2 is a voltage across the transformer secondary side inductances 7 and 8.
In the circuit configuration of FIG. 1, the resonance current from the inductor 16 and the capacitor 14 or the capacitor 15 is superimposed on the current Icr flowing through the transformer 13. For this reason, the third-order harmonic current is also superimposed on the secondary output currents Id1 and Id2, and a current waveform integrated by the transformer is obtained, and a current having a smaller peak current than that of the sine wave can be obtained.

  FIG. 4 is a basic circuit diagram for explaining a multiple current resonance type converter according to a second embodiment of the present invention. The same components will be described with the same reference numerals as in FIG. The multiple current resonant converter 51 includes a MOSFET 2 (first switch element) and a MOSFET 3 (second switch element) provided in series between the output terminal 30 and the GND terminal 31 of the DC voltage source, MOSFET 2, 3 to the inductors 4 and 5 (primary winding) to which current is supplied by alternately turning ON / OFF the MOSFETs 2 and 3 by the signals VG1 and VG2 and the inductors 4 and 5 and the inductors 4 and 5 A current resonance circuit 32 including a capacitor 6 (first capacitor) connected in series, inductors 7 and 8 (secondary windings) whose voltage is induced by the resonance operation of the current resonance circuit 32, and an inductor A multiple current resonance type converter 51 having diodes 9 and 10 and a capacitor 11 (smoothing circuit 34) for smoothing the outputs of 7 and 8. The capacitor 14 (second capacitor) and the capacitor 15 (third capacitor) are connected in series between the output terminal 30 and the GND terminal 31 of the DC voltage source, and the midpoint d of the capacitors 14 and 15 is connected to the current resonance circuit 32. Further, a MOSFET 17 (third switch element) and a MOSFET 18 (fourth switch element) are connected in series between the output terminal 30 and the GND terminal 31 of the DC voltage source, and the midpoint b of the MOSFETs 17 and 18 and the capacitor 14 are connected. , 15 is connected to the midpoint d, and MOSFETs 17 and 18 are alternately turned ON / OFF by signals VG3 and VG4, whereby a bias current is applied to the current resonance circuit 32 and a peak current of the resonance current is obtained. Reduce.

That is, the secondary side of the high frequency transformer 13 forms a center tap by the secondary side inductors 7 and 8, the output rectifier diodes 9 and 10, and the output smoothing capacitor 11.
On the primary side of the high-frequency transformer 13, a leakage inductance 4, an excitation inductance 5, and a series resonance capacitor 6 constitute a current resonance circuit equivalent to the conventional one, and, like FIG. 1, are connected to MOSFETs 2 and 3 in a half-blit configuration. Further, an inductor 16 for applying a bias current is connected to the midpoint d of the capacitors 14 and 15, and the inductor 16 is driven by ON / OFF control of the MOSFETs 17 and 18.

FIG. 5 is a timing chart of the multiple current resonance type converter according to the second embodiment of the present invention. This timing chart is assumed under the same conditions as the conventional current resonance type converter shown in FIG. 9, and the operation timing is also the same. VG1 is the gate signal of MOSFET2, VG2 is the gate signal of MOSFET3, VG3 is the gate signal of MOSFET17, VG4 is the gate signal of MOSFET18, a is the voltage waveform at the points shown in FIG. 4, and b is the voltage at the points shown in FIG. Waveform, b 'is a current waveform at the point shown in FIG. 4, Icr is a current flowing through the transformer primary inductors 4 and 5 and the series resonant capacitor 6, Id1 is a current waveform of the output diode 9, and is indicated by c in the figure. The dotted line is the current waveform of the conventional LLC current resonance type converter and is shown for comparison.
In FIG. 4, the ON / OFF control timing of the MOSFETs 17 and 18 is controlled by 90 ° from the timing of the MOSFETs 2 and 3. As a result, the voltage applied to the inductor 16 becomes b, and the flowing current becomes b '. Further, at point d in FIG. 4, the current Icr flowing through the transformer 13 and the current flowing through the inductor 16 are combined. Here, the voltage at the point d becomes higher than the conventional voltage value due to an increase in the current flowing through the inductor 16, and as a result, the voltage across the transformer primary inductors 4 and 5 and the series resonant capacitor 6 is inversely proportional to b '. Thus, the peak current of the inductor 16 is suppressed, and the peak currents of the secondary output currents Id1 and Id2 are also reduced.

FIG. 6 is a timing chart of the multiple current resonance type converter according to the third embodiment of the present invention. The basic circuit diagram according to the present invention is the same as that shown in FIG. That is, the ON / OFF timing of the MOSFETs 17 and 18 is controlled by an arbitrary timing between 16-minute periods obtained by dividing the ON / OFF timing signals of the MOSFETs 2 and 3 by n (n = 16 in this embodiment).
VG1 is the gate signal of MOSFET2, VG2 is the gate signal of MOSFET3, VG3 is the gate signal of MOSFET17, VG4 is the gate signal of MOSFET18, a is the voltage waveform at the points shown in FIG. 4, and b is the voltage at the points shown in FIG. Waveform, b 'is a current waveform at the point indicated in FIG. 4, Icr is a current flowing through the transformer primary inductors 4 and 5 and the series resonant capacitor 6, Id1 and Id2 are current waveforms of the output diodes 9 and 10, c in the figure The dotted line written in is a current waveform of a conventional LLC current resonance type converter, and is shown for comparison.
In the third embodiment, the switching resolution of the MOSFETs 2, 3, 17, and 18 is made finer, and a current bias is applied to the pinpoint of the timing at which the peak current is generated by the MOSFETs 17 and 18, so that the transformer primary inductors 4, 5 And the voltage across the series resonant capacitor 6 is reduced.

<Example>
FIG. 7 is a diagram showing an example of a converter using the multiple current resonance type converter according to the first embodiment. The second embodiment and the third embodiment are the same as those of the first embodiment except for the characteristic configuration.
In the present invention, the conventional LLC current resonance type converter is added with the harmonic resonance capacitors 14 and 15 and the harmonic resonance inductor 16, and the switching control IC 25 can be implemented by a conventional general purpose IC.
The circuit shown in FIG. 7 receives a commercial AC power supply (AC 100 V), is full-wave rectified by the diode bridge 26, and obtains a DC voltage (DC 141 V) by the input smoothing capacitor 1.
In the LLC current resonance type converter, the DC voltage is alternately turned on / off by the two MOSFETs 2 and 3 to apply a rectangular wave voltage to the series circuit of the primary inductor 5 and the current resonance capacitor 6 to cause current resonance. At this time, the MOSFETs 2 and 3 are controlled by the switching control IC 25. The switching control IC 25 controls dead time in which the MOSFETs 2 and 3 are not turned ON at the same time (this enables a conduction period by the body diode and enables ZVS operation). The switching frequency is adjusted according to the feedback signal from the output voltage.
Further, the feedback signal from the output amplifies the difference between the reference voltage of the shunt regulator 23 added to the output and the voltage obtained by the voltage dividing resistors 20 and 21, and is added to the photodiode of the photocoupler 24. , And transmitted as the ON resistance of the phototransistor. By this feedback control, it is possible to obtain a constant voltage arbitrarily set regardless of the load.

  FIG. 8 is a schematic diagram showing a schematic structure of an image forming apparatus using the multiple current resonance type converter of the present invention as a power supply control device. The image forming apparatus includes a laser writing unit 121 that writes a latent image on a photoconductor with a laser, a photoconductor 122 that exposes a surface charged by the laser writing unit 121 to form a latent image, and a photoconductor 122 on the photoconductor 122. A cleaner 123 for removing the remaining toner, a charging charger 124 for uniformly charging the photosensitive member 122, a developing device 125 for forming a toner image on the latent image on the photosensitive member, and a transfer for transferring the toner image to a recording sheet. A drum 126, a transfer charger 127 that generates an electric charge for attracting the toner image toward the recording paper, a fixing device 128 that fixes the toner image transferred onto the recording paper, and an information processing unit that controls recording information from the outside 129, a paper feeding device 130 that stores recording paper and feeds the recording paper one by one, a paper discharge tray 131 that discharges the fixed recording paper, and an external interface. A communication port 132 that is in charge of a power supply device 133 according to the present invention, and a. The operation of the image forming apparatus is well known and will not be described.

1 input smoothing capacitor, 2 MOSFET, 3 MOSFET, 4 leakage inductor, 5 excitation inductor, 6 series resonant capacitor, 7 secondary inductor, 8 secondary inductor, 9 output rectifier diode, 10 output rectifier diode, 11 output smoothing capacitor , 12 Load resistance, 13 High-frequency transformer, 14 capacitor, 15 capacitor, 16 inductor, 17 MOSFET, 18 MOSFET, 19 shunt regulator, 20 voltage divider resistor, 21 voltage divider resistor, 24 photocoupler, 25 switching control IC, 26 diode bridge , 30 Output terminal, 31 GND terminal, 32 Current resonance circuit, 33 Harmonic resonance circuit, 34 Smoothing circuit, 50 Multiple current resonance type converter

JP 2006-136047 A Transistor technology special issue “Power supply circuit design 2009” CQ publication pp. 191-204 [Design of LLC Resonant Converter] Koichi Morita

Claims (4)

A first switch element and a second switch element connected in series between the output terminal of the DC voltage source and the GND terminal;
A primary winding to which a current is supplied by alternately turning on and off the first switch element and the second switch element at a midpoint between the first switch element and the second switch element;
A current resonance circuit comprising the primary winding and a first capacitor connected in series to the primary winding;
A secondary winding in which a voltage is induced by the resonant operation of the current resonant circuit;
A multi-current resonant converter having a smoothing circuit for smoothing the output of the secondary winding,
An inductor is inserted between the output terminal of the DC voltage source and the first switch element, and a second capacitor and a third capacitor are connected in series between the output from the inductor and the GND terminal, and the second capacitor A harmonic resonance circuit configured by connecting a middle point of a capacitor and a third capacitor to the current resonance circuit, and superimposing the resonance current of the harmonic resonance circuit on the resonance current of the current resonance circuit; A multiple current resonance type converter that reduces the peak current of the resonance current. A first switch element and a second switch element connected in series between the output terminal of the DC voltage source and the GND terminal;
A primary winding to which a current is supplied by alternately turning on and off the first switch element and the second switch element at a midpoint between the first switch element and the second switch element;
A current resonance circuit comprising the primary winding and a first capacitor connected in series to the primary winding;
A secondary winding in which a voltage is induced by the resonant operation of the current resonant circuit;
A multi-current resonant converter having a smoothing circuit for smoothing the output of the secondary winding,
A second capacitor and a third capacitor are connected in series between the output terminal and the GND terminal of the DC voltage source, and a midpoint of the second capacitor and the third capacitor is connected to the current resonance circuit; A third switch element and a fourth switch element are connected in series between the output terminal and the GND terminal of the DC voltage source, and a midpoint of the third switch element and the fourth switch element, the second capacitor, An inductor is connected to the middle point of the third capacitor, and a bias current is applied to the current resonance circuit by alternately turning on and off the third switch element and the fourth switch element, and the resonance A multi-current resonance converter characterized by reducing a peak current.   The ON / OFF timing of the third switch element and the fourth switch element is an n-minute period obtained by dividing the ON / OFF timing signal of the first switch element and the second switch element by n. The multicurrent resonant converter according to claim 2, wherein the multicurrent resonant converter is controlled at an arbitrary timing.   An image forming apparatus comprising the multiple current resonance converter according to claim 1 as a power supply control device.

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