Resonance current control type DC power

Abstract

To further simplify a circuit configuration and improve efficiency in a resonance type DCDC converter requiring at least a resonant switch and an output control switch.SOLUTION: In a resonance current control type DCDC converter 200, a flyback DCDC converter 230-2 starts a subsequent resonance current operation by a common current control operation of shifting current from a resonance capacitor Cr to OFF, while flowing current from charging voltage of the resonance capacitor Cr to an inductor Ld when a switch S is ON, and flowing the current of the inductor Ld to a load side continuously by an OFF signal. By performing both a resonance operation and an output control operation, a circuit configuration is further simplified and efficiency is improved, and by using a full-wave rectified output of AC power for DC power, an AC current waveform improvement and a power-factor improvement are improved.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] This invention is a technology that contributes to improving the power quality and reducing the size, weight, and cost of DC power supplies for loads that consume electrical energy in relatively large-capacity application fields, such as power supplies for LED lighting fixtures as light sources and relatively large-capacity inverter air conditioners. [Background technology]

[0002] In addition to its inherent characteristics of low power consumption and long life, LED lighting is expected to save energy and has improved control functions, and has therefore become widely used along with the recent decline in prices of lighting fixtures.

[0003] Since LED lighting power supplies are loads that consume electrical energy unilaterally according to demand, they can be put to practical use with an extremely simple circuit configuration. However, because there are a huge number of units on the market, there is a demand for relatively simple circuit configurations that have the required characteristics.

[0004] General power supplies for LED lighting rectify AC power, smooth it with an electrolytic capacitor, and then control dimming with a switch circuit. In addition to issues such as hard switching loss, switching noise, and the lifespan of electrolytic capacitors, adding a PFC (Power Factor Correction) rectifier circuit as a power factor improvement measure increases the operating voltage for LED lighting driving power supplies, and requires a two-stage configuration in which a DC-DC converter is connected in the subsequent stage to reduce the voltage, further complicating the circuit configuration.

[0005] On the other hand, in the configuration of DC power supplies for inverters such as inverter air conditioners, the operating voltage and operating current are relatively high compared to power supplies for LED lighting, so the impact of current waveform distortion during rectification operation on peripheral devices is also large.

[0006] For this reason, PFC converters are also used in the DC power supply configuration for inverter air conditioners. This not only complicates the main circuit configuration, but also poses issues such as switching loss and high-frequency noise, so various improvement measures are being implemented.

[0007] To address these issues, a resonant AC-DC power supply (Patent Document 7) has been invented that combines resonant rectification control operation using soft switching technology, which is effective in reducing switching loss and switching noise, with current control operation by a DCDC converter connected to it.Although it has an extremely simple circuit configuration, it has excellent inflow current characteristics and can achieve output voltage current control by switching control using two switching elements, addressing the issues with DCDC converters.

[0008] This power supply can charge the resonant capacitor with zero-current soft switching by turning on the first switching element, and by applying current width control by turning on and off the second switching element of the DC-DC converter connected to the resonant capacitor, it is possible to control the output voltage current of the rectifier circuit and improve the inflow current waveform at a constant switching frequency.

[0009] The present invention relates to moreover Without using the first switching element, the resonant capacitor is charged by the resonant current and the output voltage current of the DC-DC converter is controlled only by the on / off control of the second switching element. What we are trying to achieve This will enable further simplification of the main circuit configuration and elimination of current loss in the switching elements, and is expected to result in further improvements in efficiency. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent application 1990-97272: "Single-switch resonant converter" [Patent Document 2] Patent application 1995-213050: "Resonant converter" [Patent Document 3] Patent application 2007-28829: "Resonant current control method" [Patent Document 4] Patent No. 6667750: "DC-DC converter" [Patent Document 5] Patent No. 6775745: "AC-DC converter" [Patent Document 6] Patent No. 7137260: “AC-DC power supply” [Patent Document 7] Patent application 2023-0470731: “Resonant type AC-DC power supply”

[0011] Power electronics equipment, in principle, does not involve losses if ideal switching control is achieved. Therefore, development has progressed toward faster switching elements. In recent years, SiC semiconductors and GaN semiconductors have become available in place of conventional silicon semiconductors, and this trend is expected to continue rapidly in the future.

[0012] Furthermore, by increasing the switching frequency, inductors, capacitors, transformers, etc. can be made smaller, leading to rapid improvements in efficiency and reductions in the size and weight of devices.

[0013] On the other hand, although hard switching control can speed up the switching characteristics, problems such as switching loss and switching noise that accompany switching remain.

[0014] On the other hand, if it were possible to control switching when the voltage or current applied to the switching element was zero, these problems could be solved, and this is put to practical use as soft switching control. However, there is an issue with the circuit configuration and control system required for soft switching control becoming complicated.

[0015] (Patent Document 1) aims to solve the problem of magnetic flux reset of a transformer by performing resonant operation on the secondary side of the transformer of a flyback DCDC converter. The circuit configuration is simple and can be controlled with a single switch, but the control of the switching frequency is difficult. It is necessary, this This becomes a challenge.

[0016] (Patent Document 2) is a DC-DC converter method that controls the switching timing between two switching elements used for LC resonance control and output control. It has the feature that the switching frequency for resonance operation can be kept constant, but the switching timing control Complexity There are challenges such as:

[0017] (Patent Document 3) uses an LC resonant circuit and two switching elements and is similar to (Patent Document 2), but is characterized in that the magnitude of the resonant current can be changed depending on the load.

[0018] (Patent Document 4) is an isolated DC-DC converter with soft switching control using a high-frequency square wave voltage type inverter. Since the resonant current changes according to the load current, it is possible to suppress the current loss due to the resonant current under light load like (Patent Document 3). However, the main circuit configuration becomes complicated.

[0019] The above is a control method when resonant control technology is applied to a DC-DC converter. However, in the case of an AC-DC converter that obtains DC power from an AC power source, it is necessary to improve the inflow current characteristics of the rectifier circuit.

[0020] (Patent Document 5) applies the resonant circuit operation of (Patent Document 4) that makes use of the fact that the resonant current changes according to the load current to an AC-DC converter. Since the amplitude of the resonant current is proportional to the AC power supply voltage, the inflow current waveform can be made sinusoidal simply by connecting a high-frequency filter.

[0021] However, when an LED having a certain forward voltage drop is used as a DC load, or when a smoothing capacitor is connected to the DC output, the waveform is not sinusoidal.

[0022] In order to overcome this problem, Patent Document 6 uses a resonant capacitor and a smoothing capacitor. BetweenBy inserting a step-up DC / DC converter and controlling the switching, the inflow current waveform can be improved to be almost a sine wave even when a load such as an LED is connected. It is designed to .

[0023] but, In (Patent Document 6), output Voltage control In order to , it becomes necessary to change the switching operating frequency, Especially significant Voltage and current control becomes an issue.

[0024] In order to overcome this problem, (Patent Document 7) inserts a buck-boost type DCDC converter between the resonant capacitor and the DC load, and controls the switch current width of the buck-boost type DCDC after the resonant current that charges the resonant capacitor becomes zero, thereby achieving a constant switching operating frequency for the DC output voltage and current control. of , possible with nearly sinusoidal inrush current This is what .

[0025] Also In (Patent Document 7), by using a flyback converter in a DCDC converter, any isolated output voltage can be obtained by adjusting the transformation ratio of the transformer.

[0026] moreover, The drive circuit can also be simplified by configuring two switches as a charge pump. It has characteristics . Summary of the Invention [Problem to be solved by the invention]

[0027] The present invention aims to further simplify and improve the efficiency of the resonant AC-DC power supply having such excellent features (Patent Document 7).

[0028] (Patent Document 7) is configured and controlled by a first switch circuit having a backflow prevention function for resonating the LC resonant circuit, and a second switch circuit for supplying power to a DC load via a DCDC converter for the voltage charged in the resonant capacitor by the resonant current, and for controlling the DC output voltage and current, and therefore has issues such as the main circuit configuration and the drive circuits for the two switches being somewhat complicated.

[0029] Furthermore, since the first switch is soft-switched at zero current by the resonant current, the switching loss is kept low. However, the conduction loss proportional to the magnitude of the resonant current leads to a decrease in efficiency. [Means for solving the problem]

[0030] The present invention does not use the first switch, but uses only the second switch. This configuration overcomes these challenges. In addition to the excellent features of (Patent Document 7), Since the first switching element can be omitted, the main circuit configuration and control system can be simplified, and unnecessary switching control noise caused by the first switching element and current loss can be eliminated, enabling further noise reduction and efficiency improvement. A resonant current controlled DC power supply can be realized.

[0031] FIG. 1 shows a resonant current control type DCDC converter circuit configured with an LC resonant circuit section of a resonant AC-DC power supply of (Patent Document 7) and a step-up / step-down DC-DC converter section.

[0032] The voltage of the resonant capacitor Cr charged by the resonant current of the LC resonant circuit controlled by the first switch circuit having a reverse current prevention function is controlled by controlling the conduction width Ton of the second switch of the buck-boost type DCDC converter, thereby controlling the DC output voltage and current for the DC power source Es.

[0033] Figure 2 shows the waveforms of the resonant current ir and the resonant voltage er of the resonant capacitor in response to switching signals of the first switch and the second switch, the current id1 flowing from the resonant capacitor Cr to the second switch, and the current id2 flowing to the load circuit when the second switch is off.

[0034] Here, the resonant current ir is ofA resonant current ir flows that is proportional to the difference voltage ΔE between the DC power supply voltage Es and the charging voltage of the resonant capacitor Cr.

[0035] For this reason, when the load current is small, the voltage drop across resonant capacitor Cr is small, so the differential voltage ΔE is small and the resonant current ir is also small. However, when the load current increases, the voltage drop across resonant capacitor Cr increases, reaching zero voltage, and the resonant current ir reaches its maximum.

[0036] FIG. 3 is a circuit diagram of a one-switch resonant current control type DC-DC converter in which a first switch S1 is turned on and a second switch is controlled to control the conduction width in synchronization with the resonant period of an LC resonant circuit.

[0037] FIG. 4 shows switching operation waveforms of each part in this DC-DC converter circuit when the first switch S1 is in an on state and the conduction width of the second switch S2 is controlled.

[0038] In the same figure, it is shown that by turning on the second switch S2, the voltage of the resonant capacitor Cr drops, and a resonant current ir proportional to the difference voltage ΔE between the DC power supply voltage Es and the voltage er of the resonant capacitor Cr at the time when the switch is turned off after the current width Ton flows.

[0039] Although the timing at which the resonant current begins to flow in the LC resonant circuit differs, it can be seen that a resonant current ir flows that is proportional to the differential voltage ΔE generated by the magnitude of the load current due to the conduction width control of the second switch S2.

[0040] That is, without relying on the resonant current control by the first switch S1, the resonant current control and the output voltage current control can be performed only by the second switch S2 without using the first switch. Therefore, compared to the case where the first switch is used, not only can the main circuit configuration be simplified, but also the conduction loss in the first switch S1 and the soft switching operation can be reduced. by It is possible to eliminate switching loss and switching noise.

[0041] Figure 5 shows the DC-DC converter section of Figure 3 replaced with a flyback converter that uses a transformer. By using a transformer, the limitations on the voltage control range can be eliminated by setting the transformation ratio, and a DC output isolated from the DC power source can be obtained.

[0042] Next, FIG. 6 shows a resonant current control type step-down DCDC converter circuit in which the step-up / step-down DCDC converter circuit in FIG. 3 is replaced with a step-down DCDC converter circuit.

[0043] Figure 7 shows a resonant current control type forward converter circuit in which the flyback DCDC converter in Figure 5 is replaced with a forward DCDC converter.

[0044] In these resonant current control type DCDC converters, whether they are step-up / step-down DCDC converters, step-down DCDC converters, flyback DCDC converters or forward DCDC converters, the current flows from the charging voltage of the resonant capacitor Cr to the inductor Ld during the on period of the switch S, and the current of the inductor Ld continues to flow to the load side by the off signal, but the current from the resonant capacitor Cr is turned off. At this point, Next resonant current operation can be started. .

[0045] FIG. 8 shows the basic circuit configuration of a resonant current control type DCDC converter, which is a schematic diagram showing the basic operation of a DCDC converter that controls the current from the resonant capacitor Cr on and off.

[0046] Figure 9 shows the operating waveforms when the conduction width Ton1, Ton2 (> Ton1) of the switch S of the resonant current control type DCDC converter is changed, and shows that the resonant current ir flows into the resonant capacitor Cr from the point at which the conduction width is turned off, and a) when the conduction width is small, the differential voltage ΔE due to the voltage drop in the resonant capacitor Cr is small, and the resonant current ir and the pulse current id2 and average current io flowing into the load side when the switch S is turned off are also small, but b) when the conduction width becomes large, both the resonant current ir and the load current Io become large. Effect of the Invention

[0047] The resonant current controlled DC power supply of the present invention has a circuit configuration in which the power supply is connected to the DC / DC converter not directly but via an LC resonant circuit. The effects of this configuration will now be described.

[0048] FIG. 10 shows a schematic diagram of a resonant current controlled DC power supply that converts a DC power supply into the required DC voltage, and FIG. 11 shows the waveforms of the voltage Es on the DC power supply side, the resonant current ir, and the power supply current waveform is.

[0049] By using an LC resonant circuit, a pulse-like current does not flow to the power supply side, and the LC resonant circuit Smooth waveform Resonant current ir flows To , DC power filter with small LC Insert So the inflow current is Low noise This is the average current of the resonant oscillation current.

[0050] FIG. 12 shows a schematic diagram of a resonant current controlled DC power supply that rectifies an AC power supply and converts it into the required DC voltage, and FIG. 13 shows the waveforms of the voltage es on the AC power supply side, the resonant current ir, and the power supply current waveform is.

[0051] In this case, the rectified voltage waveform becomes the absolute value waveform of the sine wave AC power supply voltage, and a resonant current ir proportional to the voltage amplitude flows. However, the current is on the AC side is filtered by a small LC AC power supply filter, It is possible to make the current sinusoidal with the same waveform as the AC power supply voltage without using special PFC control.

[0052] If the voltage rectified from the AC power supply is directly connected to a DCDC converter without passing through an LC resonant circuit, a pulsed current caused by the switching control of the DCDC converter will flow directly into the AC line.

[0053] Figure 14 is a schematic diagram of a resonant current controlled DC power supply that rectifies a three-phase balanced AC voltage with a three-phase bridge circuit and converts the voltage output through a small LC filter circuit into the required DC voltage. In this case, the AC power supply current is has a current waveform close to a square wave with a 120-degree conduction width as shown in the figure.

[0054] In addition, by using an LC resonant circuit, a current proportional to the difference voltage between the DC power supply voltage and the voltage of the resonant capacitor is generated. flow, Excessive current can be suppressed to a current determined by the power supply voltage and the LC resonant circuit constant.

[0055] Furthermore, the voltage applied to the switching element of the DCDC converter can be expected to be kept low because the switch is turned off when the voltage of the resonant capacitor becomes low.

[0056] As described above, in addition to the excellent features of (Patent Document 7), the present invention can be configured without using a resonant switch, thereby eliminating the loss and noise generation associated with a switch, and further simplifying the main circuit configuration and drive circuit configuration.

[0057] The features of the resonant current controlled DC power supply according to the present invention will now be summarized.

[0058] 1) By simply controlling the switch conduction width at a fixed frequency using one switch, it is possible to control any DC output voltage and current while improving the power supply current waveform and characteristics. 2) The control system, including the main circuit configuration and drive circuit, is extremely simple. 3) Compared to a power supply that is configured and controlled by two switches (Patent Document 7), switching noise and switching loss can be significantly reduced. 4) If the DC-DC converter is a step-up / step-down type DC-DC converter, the voltage control range is wide, so it can easily accommodate worldwide AC power supply voltages. 5) Furthermore, in a configuration using a flyback type DCDC converter, a transformer is used, so an isolated DC output can be obtained. 6) Depending on the design of the transformation ratio, it can be easily used as a low-voltage, high-current small switching power supply. 7) By passing the current through the LC resonant circuit, it is possible to prevent the sharp switching component current in the DC-DC converter from flowing to the power supply, which is also effective in suppressing EMI noise. 8) The switching of the DC-DC converter can be controlled to switch off when the resonant capacitor voltage is discharged and reduced, so the withstand voltage of the switch element can be reduced. 9) An LC resonant circuit is used in the DC power supply, so excessive current can be suppressed by the characteristic impedance of the LC resonant circuit. 10) If the DCDC converter section is a step-down DCDC converter, the output voltage control range will be restricted, but the current peak value in the DCDC converter section will be suppressed, and improved efficiency can be expected. [Brief description of the drawings]

[0059] [Figure 1] Resonant current controlled step-up / step-down DC / DC converter circuit [Diagram 2] Switching operation waveforms of a resonant current controlled buck-boost DCDC converter circuit [Diagram 3]One-switch resonant current controlled step-up / step-down DC / DC converter circuit [Figure 4] Switching control operation waveform of one-switch resonant current controlled step-up / step-down DC-DC converter circuit [Diagram 5] Resonant current controlled flyback DCDC converter circuit [Figure 6] Resonant current controlled step-down DC / DC converter circuit [Figure 7] Resonant current controlled forward DCDC converter circuit [Figure 8] Basic circuit of resonant current controlled DC / DC converter [Figure 9] Switching control operation waveforms of a resonant current controlled buck-boost DCDC converter [Figure 10] Main circuit configuration of resonant current control type DC power supply [Figure 11] Current flow waveform of resonant current controlled DC power supply [Figure 12] Main circuit configuration of single-phase resonant current controlled DC power supply [Figure 13] Current flow waveform of single-phase resonant current controlled DC power supply [Figure 14] Main circuit configuration of three-phase resonant DC power supply [Figure 15] Operating waveform of resonant current controlled DC power supply (Es=100V, LED1, Ton=5us) [Figure 16] Operational waveform of step-up / step-down direct control DC power supply (Es=100V, LED1, Ton=5us) [Figure 17] Operating waveforms of resonant current controlled step-down DC power supply (Es=100V, LED2, Ton=5us) [Figure 18] Operating waveforms of resonant current controlled flyback DC power supply (Es=100V, N1 / N2=1, LED1, Ton=5us) [Figure 19] Operating waveforms of single-phase resonant flyback DC power supply (Va=100V, N1 / N2=1, LED1, Ton=5us) [Figure 20] Operating waveforms of single-phase resonant flyback DC power supply (Va=200V, N1 / N2=1, LED1, Ton=3us) [Figure 21] Operating waveforms of a single-phase resonant flyback DC power supply (Va=100V, N1 / N2= 20, R=10 ohm, Ton=3us) [Figure 22] Operating waveforms of three-phase resonant flyback DC power supply (Va=200V, N1 / N2=1, LED1, Ton=3us) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] In implementing the present invention, the input / output control operation of the DC power supply when (1) a buck-boost type DCDC converter, (2) a buck type DCDC converter, (3) a flyback DCDC converter, or (4) a forward converter is applied to the DCDC converter section as the resonant current controlled DC power supply shown in Figure 8 is confirmed by several simulation analysis results for the case where a full-wave rectified power supply of a DC power supply and an AC power supply is connected.

[0061] The simulation analysis was performed under the following operating conditions. DC power supply voltage Es applied to the resonant current controlled DC power supply teeth, Es=100V, When adding AC power, AC power supply of At frequency fa = 60Hz, exchange Voltage (effective value) Es (=Ea) teeth, Es=100 V or 200 V, the LC filter on the power supply side is La=0.5 mH, Ca=2 uF, the resonant inductance Lr is Lr=100 uH, the resonant capacitance Cr is Cr=0.1 uF, and the inductance Ld connected to the DC-DC converter is teeth, Ld=100uH, the inductance Lm of the flyback transformer is Lm=100uH, the transformation ratio of the transformer teeth, N1 / N2=1, resonant operation and The switching frequency of the output control switch is fs=70 kHz. Also, The switch on time Ton is Ton=0 from The setting was 5 usec.

[0062] In addition, the DC load circuit is as follows: Connect to the load endThe smoothing capacitor Cd is Cd=1000 uF. The load is LED1 (resistance r F =10 ohm, voltage drop V F =165 V ) or LED2 (resistor r F =5 ohm, voltage drop V F =86 V) was connected and a simulation analysis was performed.

[0063] In addition, in checking the operation of the low-voltage DC power supply, a simulation analysis was performed with the flyback converter's transformation ratio set to N1 / N2 = 20, the smoothing capacitor Cd set to Cd = 4000 uF, and the resistor R set to R = 10 ohms. EXAMPLES

[0064] (1) Buck-boost DC-DC converter operation Figure 15 shows the operating waveforms when the DC power supply voltage Es(vad) = 100V, the on period of the switch of the resonant current control type DC power supply composed of a buck-boost type DCDC converter is Ton = 5usec, and an LED1 load is connected.

[0065] For the switch current waveform id1, when the switch is turned off, a resonant current ir flows due to the resonant operation caused by the difference voltage between the power supply voltage vad and the resonant capacitor voltage vr, the output voltage is controlled by the switch conduction time, and a DC input current is proportional to the output current flows, and the LC resonant circuit In this case The DC output current is 0.87A, while the power supply current has a peak value of 3.14A. (3.61 times the DC output current) It is confirmed that a resonant current of

[0066] For comparison, Figure 16 shows the operating waveforms when the DCDC converter is operated without the LC resonant circuit. When the switch is turned on, the current flows linearly, In this case The DC output current is 0.74A, while the power supply current has a peak value of 4.86A. (6.56 times the DC output current) It is confirmed that a large current flows. EXAMPLES

[0067] (2) Step-down DC-DC converter operation In Fig. 17, the on-period of the switch of the resonant current control type DC power supply composed of a step-down DC-DC converter is set to Ton = 5usec for a DC power supply voltage Es(vad) = 100V, Low operating voltage This is the operating waveform when LED2 load is connected.

[0068] Switch is off and the current waveform id1 becomes zero. At this point, It is confirmed that a resonant current ir flows due to the resonant operation caused by the difference voltage between the power supply voltage vad and the voltage vr of the resonant capacitor. EXAMPLES

[0069] (3) Flyback DCDC converter operation Figure 18 shows the operating waveforms when the switch on period of a resonant current controlled DC power supply composed of a flyback DCDC converter using a transformer with a transformation ratio of N1 / N2=1 for a DC power supply voltage Es(vad)=100V, and an LED1 load is connected with Ton=5usec. EXAMPLES

[0070] (4) Single-phase resonant flyback DC power supply operation In this case, the transformation ratio N1 / N2 is set to 1, which is the same as the result of the buck-boost DC-DC converter operation described above (1). However, a DC output isolated from the DC power supply is obtained.

[0071] Figure 19 shows the operating waveforms of an ACDC converter when a single-phase full-wave rectified voltage waveform is added from an AC power supply with an AC power supply voltage Es(vad) = 100V via an LC filter circuit, the transformation ratio is N1 / N2 = 1, the switch on period is Ton = 5usec, and one LED load is connected.

[0072] Figure 2(a) shows the operating waveform of a resonant current controlled AC / DC converter, and Figure 2(b) shows an enlarged waveform near the maximum value of the AC power supply voltage in order to confirm the switching operation. It can be confirmed that by simply controlling the on-period of a single switch, the resonant current control ir, DC output voltage vo, and current io can be controlled, and at the same time, the power supply current is is a beautiful sine wave.

[0073] FIG. 20 shows the operating waveforms when the output is reduced with the AC power supply voltage Es(vad)=200V and the switch on period Ton=3usec. Since the power supply voltage is increased, the switch current id1 for the same output is reduced, so the voltage drop in the resonant capacitor Cr is small and the ripple width is reduced. At the same time, the amplitude of the resonant current ir is also reduced, the voltage of the resonant capacitor is also reduced, and the voltage applied to the switch element is also reduced. It can be confirmed. EXAMPLES

[0074] (5) Single-phase resonant flyback DC power supply operation FIG. 21 shows the operating waveforms when the AC power supply voltage is set to Es(vad)=100V, the transformation ratio is set to N1 / N2=20, the smoothing capacitor Cd is set to 4000uF, and the switch on period is set to Ton=3usec in order to operate the resonant current controlled DC power supply as a low DC power supply.

[0075] The resonant current controlled DC power supply of the present invention uses only one switch to perform LC resonant operation and control the required DC voltage and current, while also making the waveform of the current flowing into the power supply a sine wave. This means that it can be expected to have excellent characteristics not only as a normal DC power supply, but also as a low-voltage, large-current power supply. EXAMPLES

[0076] (6) Three-phase resonant flyback DC power supply operation Figure 22 shows the operating waveforms of the power supply device with the configuration of Figure 14, in which a three-phase AC power supply with Es = 200V is rectified by a three-phase full-wave rectifier circuit and the voltage is applied to a resonant current control type DCDC converter via an LC filter circuit. In this case, the AC current waveform is close to a square wave with a 120-degree conduction width, similar to the current waveform when a resistive load is connected to the DC output of the three-phase rectifier circuit. Capacitor Input Compared to the case of a rectifier circuit, this circuit can improve the power factor significantly. It can be confirmed that . EXAMPLES

[0077] (7) Forward ACDC converter operation By adding the full-wave rectified output from an AC power source as the DC power supply section of the resonant current control type forward DCDC converter circuit shown in Figure 7, it is possible to operate as a forward ACDC converter, and an isolated output can be obtained by passing it through a transformer.

[0078] However, because this is a step-down type load, for loads such as LED loads or DC loads with a smoothing capacitor connected, the AC current waveform does not flow in sections where the power supply voltage is low, and a reverse-biased current waveform occurs, but it has been confirmed that the load operates with a high fundamental power factor. [Explanation of symbols]

[0079] 100…power supply 100 -1…DC power supply 100 -2... Single-phase AC power supply 100 -3…Three-phase AC power supply 110 … Filter circuit 110 -1...AC filter 110 -2…DC filter 120 … Diode bridge circuit 120 -1... Single-phase diode bridge circuit 120 -2...Three-phase diode bridge circuit 200 … Resonant DC-DC converter 210 ... Directional switch circuit 210 -1…Switch 210 -2...Diode 220…LC resonant circuit 120 -1…Resonant inductor Lr 120 -2…Resonant capacitor Cr 120 -3…Diode to prevent reverse charging 230 … Inductor current switch circuit 230 -1...Step-up / step-down chopper circuit 230 -2...Flyback DC-DC converter circuit 230 -3...Step-down chopper circuit 230 -4…Forward DC-DC converter circuit 240 … Transformer circuit 240 -1...Transformer 240 -2…Snubber circuit 300 … DC load circuit 300-1...Smoothing capacitor 300-2…DC load (resistance, LED)

Claims

1. A circuit configuration in which an LC resonant circuit in which a resonant inductor Lr and a resonant capacitor Cr to which a reverse charging prevention diode is connected in anti-parallel as required are connected in series is connected to a DC power supply, via a reverse current prevention diode as required, a DC-DC converter using a step-up / step-down chopper circuit or a step-down chopper circuit composed of a switch S, an inductor Ld, and a diode is connected across both ends of the resonant capacitor Cr, and a DC load in which a smoothing capacitor Cd is connected in parallel is connected to the output of the DC-DC converter, A resonant current controlled DC power supply characterized in that the switching pulse width of the switch S is controlled in synchronization with the resonant period of the LC resonant circuit, thereby making it possible to control the LC resonant current and the voltage and current to the DC load using only one switch.

2. The step-up / step-down chopper circuit constituting the DC-DC converter in the resonant current controlled power supply according to claim 1 is configured as a flyback type DCDC converter circuit in which a primary winding of a transformer and the switch are connected in series to both ends of the resonant capacitor Cr, one end of the secondary winding of the transformer is connected to the smoothing capacitor Cd via a backflow prevention diode, the other end of the secondary winding of the transformer is connected to the other end of the smoothing capacitor Cd, and a DC load is connected to both ends of the smoothing capacitor Cd, The step-down chopper circuit has a circuit configuration of a forward type DCDC converter in which a primary winding of a transformer and the switch are connected in series to both ends of the resonance capacitor Cr, one end of a secondary winding of the transformer is connected to a smoothing capacitor Cd via a backflow prevention diode, a free foiling diode and a smoothing inductor Ld, the other ends of the smoothing capacitor Cd and the free foiling diode are connected to the other end of the secondary winding of the transformer, and a DC load is connected to both ends of the smoothing capacitor Cd; A resonant current controlled DC power supply characterized in that, by using a transformer, it is possible to obtain a large voltage control and a DC output isolated from the DC power supply.

3. The DC power supply in the resonant current controlled power supply according to claims 1 and 2 is configured from an AC power supply via a full-wave rectifier circuit, and the switching pulse width is controlled by the switch, When the AC power source is a single-phase sine wave, an AC filter circuit is provided on the AC side of the full-wave rectifier circuit to remove a resonant frequency component of the resonant current, thereby making the AC waveform sinusoidal; When the AC power source is a three-phase balanced sine wave, an AC filter circuit that removes resonant frequency components is provided on the DC output side of the full-wave rectifier circuit to produce a square-wave AC current waveform with a 120-degree conduction width; A resonant current controlled DC power supply capable of controlling the voltage and current applied to the DC load.

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