JP2023141472A - AC-DC power supply - Google Patents

Abstract

To provide an AC-DC power supply that can control a waveform proportional to an AC current waveform from an AC power supply.SOLUTION: A main circuit 200 of an AC-DC power supply charge-controls a resonant capacitor Cr with resonant pulse current proportional to the magnitude of the full-wave rectified voltage by periodically controlling the output of a full-wave rectifier circuit 220 with a constant on-period determined by the LC resonance period using a switch S1, and an AC current waveform is controlled to be proportional to an AC power supply voltage waveform by controlling the DC output voltage vo by controlling the switching period, and controlling the inductor current by periodically controlling the voltage charged in the resonant capacitor with a constant on period during the off period of a first switch in a circuit consisting of an inductor, a switch S2, and a diode.SELECTED DRAWING: Figure 12

Description

The present invention aims to improve the power quality of DC power supplies for loads that consume electrical energy in relatively large-capacity application fields, such as power supplies for LED lighting equipment as light sources, and inverter air conditioners with relatively large capacity. This is a technology that contributes to lower prices.

In addition to its inherent characteristics of low power consumption and long life, LED lighting has expectations for energy savings and improved control functions, and has become widely popular as lighting equipment has become cheaper in recent years.

LED lighting power supplies are loads that consume electrical energy unilaterally according to demand requirements, so they can be put to practical use even with extremely simple circuit configurations, and because there are extremely large numbers of them on the market, they are low-cost power supplies. There are many issues that need to be resolved for further popularization and development in the future.

A typical power supply for LED lighting rectifies the AC power and smoothes it with an electrolytic capacitor, and then controls the dimming with a switch circuit. Products with a PFC (Power Factor Correction) rectifier circuit added as a power factor improvement measure have a high operating voltage as a drive power source for LED lighting, and a DC-DC converter is connected to the subsequent stage to lower the voltage. There were issues such as a two-stage configuration, which made the circuit configuration even more complicated.

On the other hand, as a DC power source for an inverter air conditioner, the operating voltage of the inverter is high, so voltage doubler rectification is used depending on the connected commercial power supply voltage, so the operating voltage is higher than that of an LED lighting power source, but the capacity is also larger. The operating characteristics when obtaining the rectified power supply have a large effect on peripheral equipment due to current waveform distortion.

For this reason, PFC converters are also used in power supplies for inverter air conditioners, which not only complicates the circuit configuration but also poses problems such as switching loss and high frequency noise, so various improvement measures have been taken.

The present invention combines soft switching control technology, which is effective in reducing switching loss and switching noise, with a simple circuit configuration using newly developed soft switching technology, and technology to improve the waveform of AC power supply current, resulting in high performance, small size, and light weight. Therefore, it is a technology that is expected to be applied in a wide range of applications, from power supplies for LED lighting to DC power supplies for inverter air conditioners.

Patent application 2018-219842: “PFC converter” Patent No. 6667750: “DC-DC converter” Patent No. 6775745: “AC-DC converter”

Power supplies for LED lighting are required to have high conversion efficiency and high power factor drive in addition to dimming function.
Although the output of DC power supplies for inverter air conditioners can be controlled by a PWM inverter in the latter stage, the converter that obtains the DC power in the front stage is also required to improve the power factor and reduce harmonics, both of which require countermeasures against current harmonics of AC power supplies. is required, and the introduction of PFC converters is progressing,
There are problems such as switching loss and switching noise, and a complicated circuit configuration, and various improvement measures have been taken.

Many of these countermeasures rely on hard switching, so not only switching losses but also the effects of switching noise become a problem.
) has proposed a method of adjusting the switching frequency for the purpose of reducing EMI noise and for the purpose of reducing noise in the reactor section associated with switching.

As a method to solve the problem of hard switching noise, there are soft switching methods such as zero voltage switching and zero current switching.

(
) is a DC-DC converter with soft switching control using a new zero-current switching method, and ( ) is an AC-DC converter that applies the switching method to AC-DC conversion operation from an AC power source, and has the feature that it can be configured with a single switching element.

This AC-DC converter can continuously control the output by controlling the switching period during soft switching operation using an LC resonant circuit, and by passing the power supply current waveform through a high-frequency switching filter circuit. When a resistive load such as an incandescent light bulb or electric heater is connected, excellent characteristics can be obtained in that it can be controlled to the same sine wave as the AC power supply voltage waveform, which does not contain any low-order harmonic current.

However, when the DC circuit load is an LED, the forward voltage drop is high and current flows only when the output voltage of the AC-DC converter is higher than this voltage. Since no current flows near the voltage, the AC power waveform is no longer a sine wave.

Furthermore, in the case of LED lighting, unlike incandescent light bulbs, the brightness changes in proportion to the current flow, so flicker at a frequency twice the AC power frequency is also a concern.

Therefore, when a smoothing capacitor is connected to the output terminal, current will not flow unless the output voltage of the AC-DC converter exceeds the voltage of the smoothing capacitor, so the current waveform becomes an operating waveform similar to that of LED lighting.

For this reason,(
) AC-DC converter alone has a high fundamental wave power factor as a DC power source for LED lighting power supplies and inverter air conditioners, but the overall power factor is low, although the distortion of the AC current waveform is suppressed compared to a capacitor input type rectifier circuit. It is not sufficient as a DC power source, and cannot function as a constant DC power source with no output voltage pulsations.

(
), the AC-DC converter's excellent soft switching characteristics can be used to obtain a constant DC output voltage and current as a DC output, while the input current can be sufficiently suppressed to generate harmonics and be made almost sinusoidal. It is necessary to use an AC-DC power supply with a waveform improvement circuit added.

On the other hand, a general PFC converter has the characteristic of being able to obtain a constant DC output and at the same time control the AC current waveform into a sinusoidal waveform.

Current control means for this PFC converter include a continuous current type called CCM (continuous conduction mode), a current discontinuous type called DCM (discontinuous conduction mode), and a type called CRM, each of which has its own advantages. Along with its features, issues are also pointed out.

In addition, except in the case of DCM control, multiplication processing or the like is required to generate a reference waveform for current control, which complicates the configuration of the control circuit.

In addition, since these are all based on hard switching, there are also problems with the generation of switching loss and switching noise mentioned above, noise in the reactor section for controlling the current waveform, and countermeasures against EMI noise.

In addition, the PFC converter can only operate at a DC operating voltage that is higher than the peak value of the AC power supply voltage, so when adding a DC-DC converter to obtain a low voltage output, the main circuit configuration becomes even more complex. do.

(
) is better than using a PFC converter circuit alone in improving the AC-DC converter into an AC-DC power supply that can obtain a constant DC output in addition to the sine wave AC current waveform. The challenge is whether it can be provided with characteristics and control functions.

FIG. 1 shows a basic circuit configuration diagram of a single-phase AC-DC converter section using soft switching control of an AC-DC power supply according to the present invention.

Figure 2 shows the basic operating waveforms when a resistor is connected as the DC load of this AC-DC converter. By turning on the switch S for a period longer than the LC resonance period and then turning it off, the AC power supply voltage is converted to a diode. Since a resonant current ir proportional to the amplitude value of the output voltage waveform eas of the bridge rectifier circuit flows, the AC power supply current waveform ias shows that a sine wave current waveform ia flows by passing through the power supply filter circuit.

At this time, since the switch S is turned on and off when the resonance current ir is zero current, it can be seen that a zero current soft switching operation can be realized.

Note that the current io when a resistive load is applied is a current proportional to the absolute value of the average sine wave of the resonant current ir, which is proportional to the terminal voltage of the resonant capacitor Cr.

FIG. 3 shows a circuit diagram when the output of a three-phase full-wave rectifier circuit is connected to an AC-DC converter for a three-phase power supply voltage.

Figure 4 shows the switching operation waveforms of the three-phase AC-DC converter.As a resonant current ir with an amplitude proportional to the output voltage waveform eas of the three-phase full-wave rectifier circuit flows due to the on/off control of the switch S, the alternating current As shown in the figure, a current waveform ia in which this resonant current waveform is switched in every 120 degree section flows.

The AC current waveform differs between single-phase and three-phase cases, but in either single-phase or three-phase operation, the AC-DC converter's AC current waveform is equivalent to a resistor at the output end of the full-wave rectifier circuit. This shows that a current proportional to the current waveform when the load is connected flows, and the output is controlled by the switching cycle control of the switch S.

Next, the operation when a load such as an LED is connected as a DC load of the AC-DC converter will be described.

Figure 5 shows an equivalent circuit when a smoothing capacitor Cd and an LED load are connected as the load of a single-phase AC-DC converter, and the forward voltage drop V _F of the LED is made to correspond to the electromotive force E _B. It shows.

Figure 6 shows the operating waveform when a load including such an electromotive force source is connected. Since the output voltage of the AC-DC converter is higher than the voltage of this electromotive force source, the AC No current flows near the zero voltage of the power supply waveform, and the current waveform only flows near the center.

FIG. 7 shows the main circuit configuration of the AC-DC power supply of the present invention, in which a switch circuit using switch S2 is added between the output of the LC resonance circuit of the AC-DC converter and the load, and By periodically controlling the switch S2 on and off in synchronization with the switch S1, the problems that arise when only the AC-DC converter is used alone are solved.

FIG. 8 shows the switching operation of the AC-DC power supply according to the present invention, and shows the switching timing of the soft switching switch S1 of the AC-DC converter and the switch S2 of the additional circuit for improvement, and the resonance circuit current ir due to these switchings. It shows the waveform id of the current flowing to the inductor Ld, which also includes the current i _d0 from the resonant capacitor Cr and the current of the free-wheeling diode D3.

Here, the switch S1 is turned on for approximately the LC resonance period (Tw1), then turned off, and repeats switching at the period Ts, thereby performing a zero current soft switching operation and changing the amplitude of the full-wave rectified output voltage waveform. By turning on the switch S2 for a short period of time (Tw2) in synchronization with the off period of the switch S1, the amplitude of the voltage vr of the resonant capacitor Cr charged by the resonant current is approximately equal to that of the voltage vr. The operation is to repeat the operation of flowing a proportional current id.

Note that even if the on-period Tw2 of the switch S2 is lengthened, the current flowing through the inductor Ld will not increase during the period when the voltage vr of the resonant capacitor is zero, and if there is no circuit loss, the current will flow at an almost constant level. When the switch S2 is turned off, the current id rapidly decreases to zero current due to the voltage of the smoothing capacitor of the load.

Therefore, the off period (Ts-Tw1) of the switch S1 needs to be a period until the current id returns to zero, including the on and off periods of the switch S2.

The current id control described above performs current control similar to the discontinuous mode operation of a PFC converter, and the resonant current ir and current id0 are complementary and perform current control in a short period of time. It is necessary to set the inductor Ld to a certain value.

FIG. 9 shows the above switching operation in terms of the AC power supply cycle period. Even when a load including an electromotive force source connected to a smoothing capacitor is connected to the load, the circuit shown in FIG. By the switching operation of S2 and S2, the resonant current ir and current id0 can be synchronized in each switching cycle and flow at almost the same average current, and the alternating current waveform passing through the filter circuit can be controlled to be the same sine wave as the power supply voltage waveform. be able to.

Then, the DC output voltage can be continuously controlled by controlling the switching period Ts of the soft switching control switch S1 from the sine wave AC power supply, and in a single-phase system, the AC power supply current ia is Although the DC voltage vo or the DC current io has a sinusoidal waveform, the DC voltage vo or the DC current io can have a constant waveform that does not change over time, and it can also be operated as a DC stabilized power source with a constant output.

In addition, in a three-phase system, the DC output voltage can be continuously controlled by controlling the switching period Ts of the switch S1, and the three-phase AC power supply current is 120% proportional to the DC output voltage waveform of the three-phase full-wave rectifier circuit. Although the current waveform is not a sine wave because it is a waveform in the energized section, it can be operated with a fundamental wave power factor of 1.

Further, since the signal of the switch S2 according to the present invention can be controlled with a constant pulse field in synchronization with the switch S1, the control circuit configuration can be configured using a sine wave current reference waveform, a current detection circuit for waveform control, and the like. Compared to a general PFC converter that requires a complicated control circuit such as instantaneous value comparison control, it can be configured extremely easily.

Single phase soft switching control AC-DC converter circuit Operating waveform of single-phase soft switching control AC-DC converter Three-phase soft switching control AC-DC converter circuit Basic operating waveform of three-phase soft switching control AC-DC converter Equivalent circuit when driving an LED load with a smoothing circuit Operation waveform when driving LED load operation with smoothing circuit Waveform improvement switch circuit addition basic circuit Current waveform control principle of basic circuit with waveform improvement switch circuit Basic operating waveform of basic circuit with waveform improvement switch circuit Practical circuit example of single-phase AC-DC power supply Simplified circuit configuration of single-phase AC-DC power supply - Example of series connection circuit of switch S1 and switch S2 - Example of series connection circuit of switch S2 and switch S1 Practical circuit example and control system for single-phase AC-DC power supply Practical circuit example of three-phase AC-DC power supply Single-phase AC-DC power supply simulation circuit and circuit constants Soft switching independent control operation waveform of single-phase AC-DC power supply when resistive load is connected Single-phase soft switching independent control operation waveform when connecting a resistive load including a DC voltage source Waveform improvement of single-phase AC-DC power supply Comparison of operating waveforms with and without switch control Switch control characteristics of single-phase AC-DC power supply (fs=40kHz) Switch control characteristics of single-phase AC-DC power supply (fs=20kHz) Combined control switching operation waveform of single-phase AC-DC power switch Simulation circuit and circuit constants of three-phase AC-DC power supply with waveform improvement switch circuit Three-phase soft switching independent control operation waveform when connecting a resistive load including a DC voltage source Switch control characteristics of three-phase AC-DC power supply (fs=40kHz) Switch control characteristics of three-phase AC-DC power supply (fs=20kHz)

In carrying out the present invention, it would be a more desirable embodiment if the drive circuit for the switch S1 and the switch S2 could be simplified with respect to the main circuit configuration of the AC-DC power supply shown in FIG.

In FIG. 7, which shows the basic circuit configuration of the AC-DC power supply of the present invention, in the AC-DC converter circuit, the switch-off period after on-off control with zero current is achieved by turning on the AC-DC converter circuit for a period (Tw1) approximately equal to the LC resonance period. Since the necessary current control can be achieved by turning on the waveform improvement switch S2 for a short period of time (Tw2), the switches S1 and S2 can be connected in series.

FIG. 10 shows a configuration in which switch S2 in FIG. 7 is connected from the output end of switch S1 through diode D3, and from the output of current control inductor Ld through diode D5, so that switch S1 and switch S2 are connected in series. This is an example of the main circuit configuration as an AC-DC power source that can realize the same switching control without affecting the circuit operation.

Moreover, FIG. 11 is an example of a circuit configuration in which two sets of switch circuits are connected in series by changing the arrangement of switches and inductors without adding a new diode. FIG. 3(b) is an example of a main circuit configuration in which the switch S2 and the switch S1 are connected in series.

Note that the series diode D1 of the switch S1 is connected in series to the switch S1 as a circuit by simply changing the connection position of the circuit, but when the switch S1 is directly connected to the DC output end of the full-wave rectifier circuit. From the circuit diagram, it is possible to use a diode in the full-wave rectifier circuit, but since the switching frequency of the switch S1 is high, it is necessary to use a high-speed diode in order to use the switch S1 for the same purpose.

Here, as a filter circuit for the resonant pulse current ir, in addition to the case where it is placed on the AC side of a single-phase full-wave rectifier circuit as shown in Fig. 10, it is also possible to use a filter circuit on the DC side of a single-phase full-wave rectifier circuit or a filter inductor. It is also possible to arrange a capacitor on the AC side of the single-phase full-wave rectifier circuit and on the DC side.

Based on the above, FIG. 12 shows a configuration example of a switching control system for the main circuit configuration example shown in FIG. 10 as an embodiment of the AC-DC converter power supply of the present invention.

The ON period Tw1 of the switch S1 corresponds to the LC resonant circuit constant, and at the same time when the switch S1 is turned off, a signal is generated that turns on the switch S2 for a period Tw2 with a dead time to prevent a short circuit between elements at the time of switching. The control system can be configured extremely easily, and since the switches S1 and S2 can be controlled to be on/off in a complementary manner, charge pump operation is also possible, and the drive circuit can be simplified.

In addition, in the same figure, the output voltage or output current of the DC load circuit is detected, and the switching period Ts (=1/fs) of the first switch circuit is set by the controlled amount compared with the reference value. , it is possible to construct a constant DC voltage control or constant DC current control system.

Figure 13 shows the main circuit configuration of the AC-DC power supply of the present invention for a three-phase power supply, and for a single-phase main circuit configuration, the single-phase full-wave rectifier circuit is simply replaced with a three-phase full-wave rectifier circuit. However, in order to simplify the main circuit configuration, the filter circuit for the resonant pulse current ir is arranged on the DC circuit side.

The following describes the soft switching operation of the AC-DC power supply of the present invention, the current waveform control effect, output control characteristics, etc. when a resistive load, a smoothing capacitor, an LED load including an equivalent electromotive force source, etc. are connected to the load end. Confirm basic operating characteristics through simulation analysis.

FIG. 14 is a simulation circuit of a single-phase AC-DC power supply according to the present invention, and shows circuit constants and operating conditions used in simulation analysis.

In the simulation analysis of the single-phase AC-DC power supply of the present invention, an AC voltage of voltage Ea = 100V and frequency fa = 60Hz is applied, and the DC load is a resistive load R = 50Ω and an LED load (resistance R = 50Ω and voltage Equivalent electromotive force sources of EB=VF==100V are connected in series).

As circuit parameters of the single-phase AC-DC power supply of the present invention, for an LC resonant circuit consisting of Lr = 100uH and Cr = 0.18uF, the pulse width corresponding to the resonance period is 15 usec, and the switching frequency fs of switch S1 were conducted at 20 kHz and 40 kHz, the current control inductance Ld was selected equal to Lr, and the DC smoothing capacitor Cd was Cd = 2000 uF.
1) AC-DC converter operation

First, in order to confirm the basic operation of the soft switching control AC-DC converter, we will show the simulation analysis results when the switch S2 in the additional circuit for improving the current waveform is turned off and does not work in the AC-DC power supply of the present invention. .

Figure 15 shows the voltage and current waveforms of various parts when a resistive load of R = 50Ω is connected as a DC load, and (b) shows the time axis of the waveform in (a) when the time axis near the maximum current is expanded. The waveform is shown.

From the same figure (b), the resonant current ir when the switch signal of the switch S (S1) is turned on and off is zero, confirming the zero current switching operation. When a resistive load is connected, it can be confirmed that a sinusoidal alternating current ia flows.

Figure 16 shows the operating waveform when a load containing an equivalent electromotive force source is connected, and (a) in the same figure shows the case where R = 50Ω and E _B = 100V are connected in series as the equivalent load of the LED. FIG. 5B shows the analysis results for a load in which a smoothing capacitor of Cd=2000 uF is connected in parallel with a resistive load of R=50Ω.

In either case, it is confirmed that the AC power supply current ia flows only near the center of the AC power supply when the voltage vr across the resonant circuit capacitor Cr is equal to or higher than the voltage value of the load circuit.
2) AC-DC power supply operation

FIG. 17 shows the control operation of the AC-DC power supply depending on the presence or absence of switching operation by switch S2 of the additional circuit for improving the current waveform when a smoothing capacitor is connected to an LED load that includes an equivalent electromotive force source as a DC load. Shows a comparison of waveforms.

Figure (a) shows the operating waveforms when the switch S2 is not controlled, and Figure (b) shows the operating waveforms when the control is applied. Due to the control, the DC output voltage vo also increases, and the AC current waveform ia becomes a sine wave. It can be confirmed that improvements have been made.

Next, FIG. 18 shows the analysis results when the switching frequency fs is set to 40 kHz while the on period (Tw1 = 15 usec) of the resonance control switch S1 is constant.

Figure (b) shows the waveform when the time axis near the maximum current of the waveform in figure (a) is expanded. , a sinusoidal alternating current waveform ia can be confirmed.

On the other hand, in FIG. 19, similar operating waveform results are obtained when the switching frequency fs is lowered to 20 kHz, but compared to the results in FIG. 18, the DC output voltage vo is lowered by lowering the frequency. However, the load current io also decreases, and it can be confirmed that the magnitude of the alternating current waveform ia can be nearly controlled.

From the above, it can be seen that in the AC-DC power supply of the present invention, a constant DC voltage control output without pulsation in the DC output voltage can be obtained, and the AC current waveform can be controlled to a sine wave.

FIG. 20 shows switch signals and current waveforms of the resonance switch S1 of the AC-DC power supply of the present invention and the switch S2 of the waveform improvement additional circuit when the switching frequency fs is 40 kHz and 20 kHz, with the time axis enlarged. be.

According to the switch signal and the resonant current waveform, the switch S1 operates as a switch when the resonant current is zero, confirming soft switching operation, but when the current id of the current waveform improvement load circuit is a low value. It can be confirmed that the current value increases when the switch S2 is turned on, and that even when the switch S2 is turned on, it can be switched in a state close to a zero current switch.

When the switch S2 is turned off, the current id of the inductor Ld flowing through the switch can be controlled as a snubber operation in which the current id flowing through the switch can be commutated to the smoothing capacitor Cd of the load, and a noise suppressing effect can be expected.

FIG. 21 is a simulation circuit for confirming the operation of the AC-DC power supply in the three-phase system of the present invention, and shows the circuit constants and operating conditions used in the simulation analysis.

In the simulation analysis of the three-phase AC-DC power supply, the single-phase power supply of the single-phase AC-DC power supply mentioned above was used as a three-phase power supply, and an AC voltage with a line voltage Ea = 200V and a frequency fa = 60Hz of the three-phase power supply was added. , an equivalent LED load (R=50Ω, EB=100V) was connected via a three-phase full-wave rectifier circuit and an LC filter circuit with the same circuit parameters as in the single-phase case.
・AC-DC converter operation

FIG. 22 shows the simulation analysis results when the switch S2 is turned off in the AC-DC power supply circuit. Since the waveform of the three-phase full-wave rectifier circuit flows only when the voltage is higher than the voltage of the smoothing capacitor, the AC current waveform is 120 It can be seen that a discontinuous section occurs in the current with a width of 100 degrees.
・AC-DC power supply operation

FIG. 23 shows the operating waveforms when switch S2 is turned on for a short period of time (Tw2 = 5 usec) after switch S1, which had been turned on, is turned off for a period approximately equal to the LC resonance period (Tw1 = 15 usec). Figure (b) shows the time axis enlarged waveform. As a result of current control of current ir by switch S1 and current id by switch S2, an alternating current waveform ia with a 120 degree conduction width flows as shown in figure (a). It can be confirmed that

FIG. 24 shows operating waveforms when the switching frequency fs is 20 kHz, and the DC output voltage vo decreases with the switching frequency fs as in the single-phase case, and the control effect can be confirmed.

The AC-DC power supply of the present invention operates in a combination of step-down and step-up operations, so when used as a power supply for LED lighting, it can be used to power LEDs connected in series in both single-phase and three-phase systems. The DC output voltage varies over a wide range as the forward voltage drop varies and as the AC supply voltage varies, while the AC supply current varies sinusoidally in single-phase systems and 120 degrees in three-phase systems. It has been confirmed that the waveform has amplitude modulation of the flow width.

As described above, since the AC-DC power supply of the present invention uses soft switching control, it is effective in reducing switching loss and switching noise, and is expected to be applied in a wide range of fields as a DC power supply with excellent inflow current waveforms. It seems possible.

100 ... AC power supply 200 ... Main circuit of AC-DC power supply 210 ... LC filter for resonance current 220 ... Diode bridge rectifier circuit 230 ... Resonance switch circuit 230-2 ... Switch circuit with resonance switch and waveform improvement switch 240 ... For preventing reverse charging LC resonant circuit with diode 250...Output side LC circuit 250-2...Output side LC circuit including a waveform improvement switch circuit 250-3...Output side LC circuit 300 including a diode switch circuit...DC load 300-2...Resistive load 300- 3...Resistive load 400 including a voltage source equivalent to the forward voltage drop of the LED...Control signal generation circuit

Claims (4)

A full-wave rectifier circuit is connected to an AC power supply, and a first switch circuit is connected to the DC output terminal side of the full-wave rectifier circuit through a first diode with a resonant inductor Lr and a resonant capacitor Cr with a reverse charge prevention diode. A second switch is connected to the resonant capacitor Cr via an inductor Ld and a second diode, and a smoothing capacitor Cd is connected to the resonant capacitor Cr through an inductor Ld and a second diode. In an AC-DC conversion circuit that connects a circuit to the other end of the resonant capacitor Cr, and connects a DC load circuit to both ends of the smoothing capacitor Cd,
After the first switch circuit is turned on for a certain period determined by the resonance period of the LC resonant circuit or a period that is an integral multiple thereof, the first switch circuit is switched periodically at a certain period including an off period necessary to control the DC output voltage. By repeating the operation and controlling the switching of the first switch circuit when the resonant current flowing through the LC resonant circuit is zero current or a value close to zero current, the switching loss is reduced and the generation of switching noise is reduced. By changing the switching frequency, the interval of the pulse train of the resonant current proportional to the absolute value waveform of the voltage waveform of the AC power source is changed, and the magnitude of the DC output voltage smoothed by the smoothing capacitor Cd is changed. The current flowing into the inductor Ld is controlled by synchronously turning on and off the second switch circuit for a certain period of time during the off period of the periodic on/off control of the first switch circuit, and controlling the current flowing into the inductor Ld. By passing the resonant current of the pulse train flowing through the first switch through an LC filter circuit, the waveform is controlled to be proportional to the AC current waveform from the AC power source, regardless of the load circuit state of the DC load circuit. AC-DC power supply. The AC-DC power supply according to claim 1, wherein the first switch circuit and the second switch circuit are connected in series without affecting circuit operation, or the second switch circuit and the first switch are connected in series. By using a main circuit configuration in which circuits are connected in series,
The drive circuit configuration of the two sets of switch circuits can be simplified by enabling bootstrap charging of the drive power supply between the two sets of switch circuits, the first switch circuit and the second switch circuit. AC-DC power supply. In the AC-DC power supply according to claim 1, when the AC power supply is a single-phase power supply, the full-wave rectification circuit is a single-phase full-wave rectification circuit, and when the AC power supply is a three-phase power supply, the When the AC power source is a single-phase sine wave, the full-wave rectifier circuit is a three-phase full-wave rectifier circuit, and the pulse train current of the resonant current is passed through the LC filter circuit. In the case of a phase sine wave, the AC-DC power source is characterized in that it is controlled to an alternating current waveform with a conduction width of 120 degrees of the line voltage waveform. 5. The AC-DC power supply according to claim 1, wherein the first control amount is a comparison control amount between a reference value of the DC output voltage or DC output current to be set and a detected amount of the DC output voltage or DC output current of the DC load circuit. An AC-DC power supply characterized in that the DC output voltage or DC output current of the DC load circuit can be controlled by controlling the switching frequency of the switch circuit.

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