JP2023110887A - Ac insulating circuit and ac power supply circuit using the same - Google Patents

Abstract

To provide a small and light-weighted AC insulating circuit.SOLUTION: An AC insulating circuit 1 includes a synchronous rectification circuit 10, an insulated DC-DC conversion circuit 20, and a synchronous synthesis circuit 30. The synchronous rectification circuit has first switching circuits Q1, Q2, and turns on/off the first switching circuits Q1, Q2 in synchronization with a first frequency f when a first AC voltage having the first frequency f is input to generate and output first DC voltages Vi1, Vi2 that is obtained by rectifying the first AC voltage. The insulated DC-DC conversion circuit is controlled by a second frequency fs that is higher than the first frequency f and converts the first DC voltages Vi1, Vi2 into second DC voltages Vo1, Vo2 insulated from the first DC voltages Vi1, Vi2 to output them. The synchronous synthesis circuit has second switching circuits Q3, Q4 and generates a second AC voltage Vac insulated from the first AC voltage from the second DC voltages Vo1, Vo2 by turning on/off the second switching circuits Q3, Q4 in synchronization with the first frequency f.SELECTED DRAWING: Figure 1

Description

The present invention relates to an AC isolation circuit and an AC power supply circuit using the same.

As an AC isolation circuit, a commercial voltage isolation transformer as schematically shown in FIG. 16 is generally used. The commercial voltage isolation transformer of FIG. 16 is designed for a commercial voltage frequency f, for example, 50 Hz. In general, transformer cores must be used below the saturation magnetic flux density.

FIG. 17 shows the relationship between the applied commercial voltage V, the magnetic flux density B of the core of the commercial voltage isolation transformer, and the phase θ=ωt (ω is the angular frequency of the commercial voltage V, ω=2πf, and t is time). Since the magnetic flux density varies from -B to +B with respect to the voltage application on the positive electrode side, the maximum magnetic flux density can be obtained by integration up to 1/4 period (π/2). The maximum magnetic flux density Bm is obtained by (Equation 1).

... (Formula 1)

Here, E is the effective voltage of the commercial voltage V, N is the number of turns of the primary winding of the transformer, and S is the cross-sectional area of the core of the transformer.

FIG. 18 is a diagram schematically showing a conventional example of a commercial voltage isolation transformer circuit for converting a single-phase two-wire commercial voltage into a single-phase three-wire AC voltage. In such a commercial voltage isolation transformer, when an AC voltage having an effective voltage of 100 V and a frequency f of 50 Hz is input to the primary winding Lp as a commercial voltage AC, the terminal of the first secondary winding Ls1 An AC voltage with an effective value voltage of 100 V and a frequency f of 50 Hz is output between certain red and white terminals (Vo1) and between white and black terminals (Vo2) that are terminals of the second secondary winding Ls2. , an AC voltage with an effective voltage of 200 V and a frequency f of 50 Hz is output between the red and black terminals (Vo1+Vo2).

JP 2020-129922 A Japanese Patent No. 6564102

At the commercial voltage V used in the commercial voltage isolation transformer, since the frequency f is as small as 50 Hz, it can be seen from (Equation 1) that the magnetic flux density B has a very large value. In order to deal with this problem, commercial voltage isolation transformers generally use a silicon steel sheet with a high saturation magnetic flux density as a core. Therefore, the commercial voltage isolation transformer is very large and heavy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact and lightweight AC insulating circuit and an AC power supply circuit using the same.

An AC isolation circuit according to an aspect of the present invention includes a first switching circuit, and when a first AC voltage having a first frequency is input, the first switching is performed in synchronization with the first frequency. By turning on and off the circuit, a synchronous rectification circuit that generates and outputs a first DC voltage obtained by rectifying the first AC voltage, and a second frequency that is higher than the first frequency. An insulated DC-DC conversion circuit that is controlled and converts the first DC voltage into a second DC voltage that is insulated from the first DC voltage and outputs the second DC voltage, and a second switching circuit, By turning on/off the second switching circuit in synchronization with the first frequency, the second DC voltage has the first frequency isolated from the first AC voltage. a synchronous synthesizing circuit for generating and outputting an alternating voltage;

According to the present invention, it is possible to provide a compact and lightweight AC insulating circuit and an AC power supply circuit using the same.

FIG. 1 is a circuit diagram of an AC insulation circuit according to the first embodiment. FIG. 2 is a time chart showing waveforms of each part of the AC insulation circuit. FIG. 3 is a circuit diagram of an isolated DC-DC converter used in an AC isolation circuit. FIG. 4A is a time chart showing waveforms of each part in the isolated DC-DC converter of FIG. 3 when the input voltage Vi=E and there is a load at the output end. FIG. 4B is a time chart showing waveforms of respective parts in the isolated DC-DC converter of FIG. 3 when the input voltage Vi=E and there is no load at the output terminal. FIG. 4C is a time chart showing waveforms of respective parts in the isolated DC-DC converter of FIG. 3 when the input voltage Vi=E/2 and there is a load at the output terminal. FIG. 4D is a time chart showing waveforms of respective parts in the isolated DC-DC converter of FIG. 3 when the input voltage Vi=E/2 and there is no load at the output terminal. FIG. 5 is a circuit diagram showing an isolated DC-DC converter of a first modified example. FIG. 6 is a circuit diagram showing an isolated DC-DC converter of a second modification. FIG. 7 is a circuit diagram showing an isolated DC-DC converter of a third modification. FIG. 8 is a circuit diagram showing an isolated DC-DC converter of a fourth modification. FIG. 9 is a circuit diagram showing an isolated DC-DC converter of a fifth modification. FIG. 10 is a circuit diagram of an AC insulation circuit according to the second embodiment. FIG. 11 is a time chart showing waveforms of respective parts of the AC insulation circuit according to the second embodiment. FIG. 12 is a circuit diagram of an AC insulation circuit according to a modification of the second embodiment. FIG. 13 is a circuit diagram of a single-phase three-wire AC power supply circuit according to the third embodiment. FIG. 14 is a time chart showing waveforms of respective parts of the single-phase three-wire AC power supply circuit according to the third embodiment. FIG. 15 is a circuit diagram of a single-phase three-wire AC power supply circuit according to a modification of the third embodiment. FIG. 16 is a schematic diagram showing the configuration of a conventional AC insulation circuit (commercial voltage insulation transformer). FIG. 17 is a graph showing the relationship between the phase of the applied commercial voltage and the phase of the magnetic flux density of the core of the commercial voltage isolation transformer in the commercial voltage isolation transformer. FIG. 18 is a diagram schematically showing a conventional example of a commercial voltage isolation transformer circuit for converting a single-phase two-wire commercial voltage into a single-phase three-wire AC voltage.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Elements having the same function are denoted by the same reference numerals, and overlapping descriptions are omitted. The invention is not limited to the embodiments described below.

(First embodiment)
FIG. 1 is a circuit diagram of an AC insulation circuit 1 according to the first embodiment. The AC isolation circuit 1 converts an AC voltage of a commercial AC power supply AC as a first AC voltage into an output voltage Vac as a second AC voltage insulated from the commercial AC power supply AC and outputs the output voltage Vac.

As the commercial alternating current power supply AC, for example, a power supply having a first frequency of f=50 Hz and an effective value voltage of 100 V, which is supplied from an electric power company, is used. The AC isolation circuit 1 converts the AC voltage of the commercial AC power supply AC into an output voltage Vac which is insulated from the commercial AC power supply AC and has the same standard as the commercial AC power supply AC, the frequency f = 50 Hz and the effective value voltage = 100 V. and output. The effective value voltage of the commercial AC power supply AC and the effective value voltage of the output voltage Vac can be set to different values.

The AC isolation circuit 1 includes a synchronous rectification circuit 10, an insulated DC-DC conversion circuit 20, and a synchronous synthesis circuit 30.

The synchronous rectifier circuit 10 includes a first synchronous rectifier Q1 and a second synchronous rectifier Q2 for rectifying and outputting the AC voltage of the commercial AC power supply AC. The first synchronous rectifier Q1 and the second synchronous rectifier Q2 form a first switching circuit.

The first synchronous rectifier Q1 and the second synchronous rectifier Q2 are composed of semiconductor switching elements and have regenerative diodes. In the first embodiment, the first synchronous rectifier Q1 and the second synchronous rectifier Q2 are composed of N-channel MOSFETs.

A first rectification control circuit CT1 capable of outputting a gate signal Vg1 for turning on the first synchronous rectifier Q1 is connected between the gate and source of the first synchronous rectifier Q1. A second rectification control circuit CT2 capable of outputting a gate signal Vg2 for turning on the second synchronous rectifier Q2 is connected between the gate and source of the second synchronous rectifier Q2.

The insulation type DC-DC conversion circuit 20 includes a first insulation type DC-DC converter (hereinafter abbreviated as the first DC-DC converter) 21 and a second insulation type DC-DC converter (hereinafter, the second DC-DC abbreviated as a converter) 22. The first DC-DC converter 21 and the second DC-DC converter 22 are high-frequency switching bidirectional DC-DC converters with a substantially constant conversion ratio between the input voltage and the output voltage, and the input side and the output side are insulated. ing. In the first embodiment, the first DC-DC converter 21 and the second DC-DC converter 22 use the same circuit configuration, but the first DC-DC converter 21 and the second DC-DC converter 22 Different circuit configurations may be used as long as their performance is equivalent. Although it is possible to configure the first DC-DC converter 21 and the second DC-DC converter 22 with one DC-DC converter, in the first embodiment, two DC-DC converters are used for circuit simplification. DC converters 21 and 22 are used.

The positive input terminal of the first DC-DC converter 21 is connected to the drain of the first synchronous rectifier Q1, and the source of the first synchronous rectifier Q1 is connected to the positive output terminal of the commercial AC power supply AC. A negative input terminal of the first DC-DC converter 21 is connected to a negative output terminal of the commercial AC power supply AC.

A positive input terminal of the second DC-DC converter 22 is connected to a negative output terminal of the commercial AC power supply AC. The negative input terminal of the second DC-DC converter 22 is connected to the source of the second synchronous rectifier Q2, and the drain of the second synchronous rectifier Q2 is connected to the positive output terminal of the commercial AC power supply AC.

In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (positive voltage) (between t11 and t12 in FIG. 2), the first synchronous rectifier Q1 is connected to the first rectification control circuit CT1. is turned on by Similarly, when the commercial AC power supply AC is negative (negative voltage) (between t12 and t13 in FIG. 2), the first synchronous rectifier Q1 is turned off by the first rectification control circuit CT1. As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the first positive voltage Vi1 of the first DC voltage.

In synchronization with the frequency f of the voltage of the commercial AC power supply AC, the second synchronous rectifier Q2 is turned off by the second rectification control circuit CT2 when the commercial AC power supply AC is positive (between t11 and t12 in FIG. 2). Similarly, when the commercial AC power supply AC is negative (between t12 and t13 in FIG. 2), the second synchronous rectifier Q2 is turned on by the second rectification control circuit CT2. As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the first negative voltage Vi2 of the first DC voltage.

A pulsating first positive voltage Vi1 is input to the first DC-DC converter 21 as shown in (4) of FIG. A pulsating first negative voltage Vi2 is input to the second DC-DC converter 22 with its polarity reversed as shown in FIG. 2(5).

The first DC-DC converter 21 outputs a second positive voltage Vo1 (second DC voltage) insulated from the input first positive voltage Vi1 according to the voltage conversion ratio. The second positive voltage Vo1 becomes a pulsating voltage, as indicated by (6) in FIG. If the voltage conversion ratio of the first DC-DC converter 21 is set to 1, the first positive voltage Vi1 and the second positive voltage Vo1 have the same waveform. The second DC-DC converter 22 outputs a second negative voltage Vo2 (second DC voltage) insulated from the input first negative voltage Vi2 according to the voltage conversion ratio. The second negative voltage Vo2 becomes a pulsating voltage as shown in (7) of FIG. If the voltage conversion ratio of the second DC-DC converter 22 is set to 1, the first negative voltage Vi2 and the second negative voltage Vo2 have the same waveform.

The synchronous synthesizing circuit 30 synthesizes the second positive voltage Vo1, which is the output voltage of the first DC-DC converter 21, and the second negative voltage Vo2, which is the output voltage of the second DC-DC converter 22. A first synchronous synthesizer Q3 and a second synchronous synthesizer Q4 are provided for output. The first synchronous synthesizer Q3 and the second synchronous synthesizer Q4 constitute a second switching circuit.

The first synchronous synthesizer Q3 and the second synchronous synthesizer Q4 are composed of semiconductor switching elements and have regenerative diodes. In the first embodiment, the first synchronous synthesizer Q3 and the second synchronous synthesizer Q4 are composed of N-channel MOSFETs.

A first synthesis control circuit CT3 capable of outputting a gate signal Vg3 for turning on the first synchronous synthesizer Q3 is connected between the gate and source of the first synchronous synthesizer Q3. A second synthesis control circuit CT4 capable of outputting a gate signal Vg4 for turning on the second synchronous synthesizer Q4 is connected between the gate and source of the second synchronous synthesizer Q4.

The positive output terminal of the first DC-DC converter 21 is connected to the drain of the first synchronous synthesizer Q3, and the source of the first synchronous synthesizer Q3 is connected to the positive output terminal of the AC isolation circuit 1. there is A negative output terminal of the first DC-DC converter 21 is connected to a negative output terminal of the AC insulation circuit 1 .

A positive output terminal of the second DC-DC converter 22 is connected to a negative output terminal of the AC insulation circuit 1 . The negative side output terminal of the second DC-DC converter 22 is connected to the source of the second synchronous synthesizer Q4, and the drain of the second synchronous synthesizer Q4 is connected to the positive side output terminal of the AC isolation circuit 1. An output capacitor Cac is connected between the positive output terminal and the negative output terminal of the AC insulation circuit 1 .

In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive, the first synchronous combiner Q3 is turned on by the first synthesis control circuit CT3, and the second synchronous combiner Q4 is switched to the second It is turned off by the synthesis control circuit CT4. Similarly, when the commercial AC power supply AC is negative, the second synchronous synthesizer Q4 is turned on by the second synthesis control circuit CT4, and the first synchronous synthesizer Q3 is turned off by the first synthesis control circuit CT3. As a result, the output voltage Vo1 of the first DC-DC converter 21 and the voltage obtained by inverting the polarity of the output voltage Vo2 of the second DC-DC converter 22 are combined to generate the output voltage Vac. The output voltage Vac of the AC isolation circuit 1 is insulated from the commercial AC power supply AC.

Next, waveforms of each part of the AC insulating circuit 1 will be described with reference to the time chart of FIG.

(1) of FIG. 2 shows the waveform of the commercial alternating current power supply AC input to the alternating current isolation circuit 1 . If the effective value voltage of the commercial AC power supply AC input to the AC insulation circuit 1 is 100 V and the frequency is 50 Hz, the peak voltage on the positive side of the sine wave is +141 V, which is √2 times the effective value voltage, and the peak voltage on the negative side is +141 V. is -141 V, and one period of the sine wave is 20 ms.

(2) of FIG. 2 shows the gate signal Vg1 applied between the gate and source of the first synchronous rectifier Q1 from the first rectification control circuit CT1 of the first synchronous rectifier Q1. When the voltage of the commercial AC power supply AC is positive (between t11 and t12), the gate signal Vg1 is output from the first rectification control circuit CT1 at t11, the first synchronous rectifier Q1 is turned on, and the gate signal Vg1 is turned on at t12. becomes 0, the first synchronous rectifier Q1 is turned off. As a result, as shown in (4) in FIG. 2, the positive side of the voltage of the commercial AC power supply AC is half-wave rectified to generate the first positive voltage Vi1 that is input to the first DC-DC converter 21. be.

(3) of FIG. 2 shows the gate signal Vg2 applied between the gate and source of the second synchronous rectifier Q2 from the second rectification control circuit CT2 of the second synchronous rectifier Q2. When the voltage of the commercial AC power supply AC is negative (between t12 and t13), the gate signal Vg2 is output from the second rectification control circuit CT2 at t12, the second synchronous rectifier Q2 is turned on, and the gate signal Vg2 is turned on at t13. becomes 0, the second synchronous rectifier Q2 is turned off. As a result, as shown in (5) in FIG. 2, the negative side of the voltage of the commercial AC power supply AC is half-wave rectified to generate the first negative voltage Vi2 that is input to the second DC-DC converter 22. be. Since the first negative voltage Vi2 is input to the second DC-DC converter 22 with its polarity reversed, it fluctuates from 0 to the positive direction as shown in FIG. 2(5).

When the voltage conversion ratio of the first DC-DC converter 21 is 1, the second positive voltage Vo1, which is the output voltage of the first DC-DC converter 21 to which the first positive voltage Vi1 is input, is 2(6), the waveform is similar to that of the first positive voltage Vi1 shown in FIG. 2(4). The second negative voltage Vo2, which is the output of the second DC-DC converter 22 input by inverting the polarity of the first negative voltage Vi2, is obtained when the voltage conversion ratio of the second DC-DC converter 22 is 1. In some cases, a waveform similar to that shown in FIG. 2(7) is obtained by reversing the polarity of the first negative voltage Vi2 shown in FIG. 2(5).

(8) in FIG. 2 shows the gate signal Vg3 applied between the gate and source of the first synchronous synthesizer Q3 from the first synthesis control circuit CT3 of the first synchronous synthesizer Q3. When the voltage of the commercial AC power supply AC is positive (between t11 and t12), the gate signal Vg3 is output from the first synthesis control circuit CT3 at t11, the first synchronous synthesizer Q3 is turned on, and the gate signal is generated at t12. When Vg3 becomes 0, the first synchronous synthesizer Q3 is turned off. Note that (8) in FIG. 2 has the same waveform as (2) in FIG. (9) in FIG. 2 shows the gate signal Vg4 applied between the gate and source of the second synchronous synthesizer Q4 from the second synthesis control circuit CT4 of the second synchronous synthesizer Q4. When the voltage of the commercial AC power supply AC is negative (between t12 and t13), the gate signal Vg4 is output from the second synthesis control circuit CT4 at t12, the second synchronous synthesizer Q4 is turned on, and the gate signal is turned on at t13. When Vg4 becomes 0, the second synchronous synthesizer Q4 is turned off. Note that (9) in FIG. 2 has the same waveform as (3) in FIG. As a result, the voltage on the positive electrode side and the voltage on the negative electrode side of the output voltage Vac shown in (10) in FIG. 2 are generated.

In this way, the voltage waveform of the commercial AC power supply AC as shown in (1) in FIG. 2 is isolated at a constant voltage conversion ratio and output as the output voltage Vac of the AC isolation circuit 1 as shown in (10) in FIG. be.

Next, the first DC-DC converter 21 and the second DC-DC converter 22 will be explained.

In the first embodiment, the first DC-DC converter 21 and the second DC-DC converter 22 have the same circuit configuration and the same operation, so here only the first DC-DC converter 21 A detailed description will be given, and the description of the second DC-DC converter 22 will be omitted.

FIG. 3 is a circuit diagram of the first insulation type DC-DC converter 21 used in the AC insulation circuit 1. As shown in FIG. 4A shows the input voltage Vi=E with a load RL; FIG. 4B shows the input voltage Vi=E without the load RL; FIG. 4C shows the input voltage Vi=E/2 with the load RL; FIG. 4D shows waveforms of each part of the DC-DC converter 21 when the input voltage Vi=E/2 and no load RL.

As shown in FIG. 3, the DC-DC converter 21 is a high frequency transformer having a core for high frequency voltage, a primary winding Lp, a first secondary winding Ls1 and a second secondary winding Ls2. T, a half bridge circuit as a primary side circuit connected to the primary winding Lp of the high frequency transformer T, and a first secondary winding and a second secondary winding of the high frequency transformer T connected to A full-wave rectification type synchronous rectification circuit is provided as a secondary side circuit.

A high-frequency transformer T includes a core, a primary winding Lp, and a first secondary winding Ls1 and a second secondary winding Ls2 coupled to the primary winding Lp by the core. It is designed for high-frequency AC voltage of about several hundred kHz. A high-frequency transformer T has a primary winding Lp insulated from a first secondary winding Ls1 and a second secondary winding Ls2.

The primary side circuit of the DC-DC converter 21 is a series circuit composed of a primary side first switching element Q11 and a primary side second switching element Q12 for an input voltage Vi (first positive voltage Vi1). , and a series circuit (current resonance capacitance) composed of the first capacitor C11 and the second capacitor C12 are connected in parallel to form a half bridge circuit.

The primary side first switching element Q11 and the primary side second switching element Q12 are composed of semiconductor switching elements and have regenerative diodes. In the first embodiment, the primary side first switching element Q11 and the primary side second switching element Q12 are composed of N-channel MOSFETs.

In the series circuit of the primary side first switching element Q11 and the primary side second switching element Q12, the drain of the primary side first switching element Q11 is connected to the positive electrode side of the input voltage Vi. The source of the primary side first switching element Q11 is connected to the drain of the primary side second switching element Q12, and the source of the primary side second switching element Q12 is connected to the negative electrode side of the input voltage Vi. there is

A first voltage pseudo-resonant capacitor Cv11 is connected in parallel to the primary side first switching element Q11, and a second voltage pseudo-resonant capacitor Cv12 is connected in parallel to the primary side second switching element Q12. there is

Between the connection point of the primary side first switching element Q11 and the primary side second switching element Q12 and the connection point of the first capacitor C11 and the second capacitor C12, the primary winding Lp of the high frequency transformer T and the current A series circuit of resonant inductance Lr is connected.

A primary side control circuit CT10 is connected between the gate and source of the primary side first switching element Q11 and between the gate and source of the primary side second switching element Q12. The primary side control circuit CT10 can output a gate signal Vg11 for turning on the primary side first switching element Q11 and a gate signal Vg12 for turning on the primary side second switching element Q12.

On the secondary side of the high frequency transformer T, a first secondary winding Ls1 and a second secondary winding Ls2 are connected in series. The secondary side circuit of the DC-DC converter 21 includes a secondary side first switching element Q21 connected to both ends of a series circuit of a first secondary winding Ls1 and a second secondary winding Ls2, and a secondary side switching element Q21. A full-wave rectification type synchronous rectification circuit comprising a series circuit of the side second switching element Q22.

The secondary side first switching element Q21 and the secondary side second switching element Q22 are composed of semiconductor switching elements and have regenerative diodes. In the first embodiment, the secondary side first switching element Q21 and the secondary side second switching element Q22 are composed of N-channel MOSFETs. Snubber capacitors C21 and C22 are connected in parallel to the first secondary switching element Q21 and the second secondary switching element Q22, respectively, for suppressing surge currents when the switches are turned off.

The source of the secondary side first switching element Q21 is connected to the first secondary winding Ls1 side of the series circuit of the first secondary winding Ls1 and the second secondary winding Ls2. The source of the secondary side second switching element Q22 is connected to the second secondary winding Ls2 side of the series circuit of the first secondary winding Ls1 and the second secondary winding Ls2.

The drain of the first secondary switching element Q21 and the drain of the second secondary switching element Q22 are connected to the positive output terminal of the DC-DC converter 21 via one end of the output smoothing capacitor Co.

A connection point between the first secondary winding Ls1 and the second secondary winding Ls2 is connected to the negative side output terminal via the other end of the output smoothing capacitor Co.

A first secondary control circuit CT21 capable of outputting a gate signal Vg21 for turning on the first secondary switching element Q21 is connected between the gate and source of the first secondary switching element Q21.

A secondary-side second control circuit CT22 capable of outputting a gate signal Vg22 for turning on the secondary-side second switching element Q22 is connected between the gate and source of the secondary-side second switching element Q22.

Next, the operation of the DC-DC converter 21 will be explained in detail.

The primary-side first switching element Q11 and the primary-side second switching element Q12 are driven by gate signals Vg11 and Vg12 generated by the primary-side control circuit CT10 to operate at a high frequency of about several hundred kHz (eg, 100 kHz). 2 at a switching frequency fs. The gate signals Vg11 ((5) in FIGS. 4A-4D) and Vg12 ((6) in FIGS. 4A-4D) always turn off the primary side first switching element Q11 and the primary side second switching element Q12 at the same time. (see waveforms immediately after t21, t22, t23 in (5) and (6) of FIGS. 4A-4D).

The gate signal Vg21 of the secondary side first switching element Q21 ((5) in FIGS. 4A to 4D) generated by the secondary side first control circuit CT21 is the same as the gate signal Vg11 of the primary side first switching element Q11. is a timing signal.

The gate signal Vg22 ((6) in FIGS. 4A to 4D) of the secondary side second switching element Q22 generated by the secondary side second control circuit CT22 is the same as the gate signal Vg12 of the primary side second switching element Q12. is a timing signal.

When the input voltage Vi is applied to the DC-DC converter 21, the first capacitor C11 and the second capacitor C12 are charged and the potential difference becomes 1/2 Vi. Since the primary side first switching element Q11 and the primary side second switching element Q12 are alternately turned on and off, the voltages of +1/2Vi and -1/2Vi are alternately applied to the primary winding Lp of the high frequency transformer T. is applied to That is, the primary winding Lp of the high-frequency transformer T is applied with an AC voltage having a switching frequency fs that fluctuates between +1/2Vi and -1/2Vi.

When the load RL is not connected to the output terminal of the DC-DC converter 21 (output side release), the primary side first switching element Q11 is turned on by the gate signal Vg11 after the dead time period (( Immediately after t21 in 5)). Then, a current flows through the path of Vi->Q11->Lr->Lp->C12->Vi and the path of C11->Q11->Lr->Lp->C11. The resonance frequency fr of the primary side circuit at this time is given by (Equation 2).

…（式２）

... (Formula 2)

Here, if the value of the inductance is set as primary winding Lp>>current resonance inductance Lr, and if the switching frequency of all the switching elements Q11, Q12, Q21, Q22 is fs, fr<<fs. . The waveform of the drain current Id (Q11) when the primary side first switching element Q11 is turned on becomes the resonance frequency fr. However, in the waveform of this drain current Id (Q11), since the resonance frequency fr is much lower than the switching frequency fs, a part of the sine wave of the resonance frequency fr appears as a linear waveform rising to the right (( 2) Between t21 and t22 of Id (Q11)). This current waveform is also the waveform of the excitation current of the high-frequency transformer T. As shown in FIG.

The energy ε stored in the primary winding Lp and the current resonance inductance Lr due to the switching current (drain current) Id (Q11) when the primary side first switching element Q11 is turned off is given by (Equation 3). Become.

…（式３）

... (Formula 3)

The energy ε accumulated in the primary winding Lp and the current resonance inductance Lr is transferred between the first voltage pseudo-resonance capacitor Cv11 and It is discharged to the second voltage pseudo-resonant capacitor Cv12 (voltage pseudo-resonant capacitor circuit). The relationship with the energy ε at this time is as shown in (Equation 4).

…（式４）

... (Formula 4)

The capacitance value of Cv11+Cv12 and the inductance value of Lp+Lr are determined so that the voltage V in (Equation 4) is greater than or equal to the input voltage Vi. In order to achieve the voltage pseudo-resonance during the dead time period, the 1/4 period of the voltage pseudo-resonant frequency fv is set to be equal to or shorter than the dead time period of the primary side first switching element Q11 and the primary side second switching element Q12. set to be Here, the voltage quasi-resonant frequency fv is given by (Equation 5).

…（式５）

... (Formula 5)

Further, when the load RL is connected to the output terminal of the DC-DC converter 21, the primary side first switching element Q11 is turned on by the gate signal Vg11 after the dead time period (t21 in (5) of FIG. 4A). immediately after). Then, in the primary side circuit, current flows through the path of Vi->Q11->Lr->Lp->C12->Vi and the path of C11->Q11->Lr->Lp->C11. At the same time, since the secondary side first switching element Q21 is turned on by the gate signal Vg21, current flows in the secondary side circuit through the high frequency transformer T in the route of Ls1→Q21→RL→Ls1. The resonance frequency fr at this time is given by (Equation 6).

…（式６）

... (Formula 6)

The values of the current resonance inductance Lr, the first capacitor C11, and the second capacitor C12 are set so that the resonance frequency fr in (Equation 6) is approximately equal to the switching frequency fs. Then, during the period when the first switching element Q11 on the primary side is ON, a sine wave current with a half cycle of the switching frequency fs is applied to the output terminal of the DC-DC converter 21 when the load RL is not connected. The drain current Id(Q11) is superimposed on the rising linear waveform (between t21 and t22 in (2) of FIG. 4A).

Further, when the load RL is not connected to the output terminal of the DC-DC converter 21 (output side release), the primary side second switching element Q12 is turned on by the gate signal Vg12 after the dead time period. Then (immediately after t22 in (6) of FIG. 4B), current flows through the paths of C12→Lp→Lr→Q12→C12 and Vi→C11→Lp→Lr→Q12→Vi. The resonance frequency fr of the primary side circuit at this time is given by (Equation 7).

…（式７）

... (Formula 7)

Here, if the value of the inductance is set as primary winding Lp>>current resonance inductance Lr, and if the switching frequency of all the switching elements Q11, Q12, Q21, Q22 is fs, fr<<fs. . The waveform of the drain current Id (Q12) when the primary side second switching element Q12 is turned on becomes the resonance frequency fr. However, in the waveform of this drain current Id (Q12), since the resonance frequency fr is much lower than the switching frequency fs, a part of the sine wave of the resonance frequency fr appears as a linear waveform rising to the right (( 4) between t22 and t23). The waveform of the drain current Id (Q12) is also the waveform of the excitation current of the high-frequency transformer T. As shown in FIG.

The energy ε stored in the primary winding Lp and the current resonance inductance Lr due to the switching current (drain current) Id (Q12) when the primary side second switching element Q12 is turned off is given by (Equation 8). Become.

…（式８）

... (Formula 8)

The energy ε accumulated in the primary winding Lp and the current resonance inductance Lr is transferred between the first voltage pseudo-resonance capacitor Cv11 and It is discharged to the second voltage pseudo-resonant capacitor Cv12 (voltage pseudo-resonant capacitor circuit). The relationship with the energy ε at this time is as shown in (Expression 9).

…（式９）

... (Formula 9)

The capacitance value of Cv11+Cv12 and the inductance value of Lp+Lr are determined so that the voltage V in Equation 9 is equal to or higher than the input voltage Vi. In order to achieve voltage pseudo-resonance during the dead time period of the primary-side first switching element Q11 and the primary-side second switching element Q12, the 1/4 period of the voltage pseudo-resonant frequency fv is set to the primary side first switching element Q12. It is set to be equal to or less than the dead time period of the switching element Q11 and the second primary side switching element Q12. The voltage pseudo-resonant frequency fv is given by (Equation 10).

…（式１０）

... (Formula 10)

Further, when the load RL is connected to the output terminal of the DC-DC converter 21, the primary side second switching element Q12 is turned on by the gate signal Vg12 after the dead time period. Then, in the primary side circuit, current flows through the path of C12→Lp→Lr→Q12→C12 and the path of Vi→C11→Lp→Lr→Q12→Vi. At the same time, since the secondary side second switching element Q22 is turned on by the gate signal Vg22, current flows through the high frequency transformer T in the secondary side circuit in the route of Ls2→Q22→RL→Ls2. The resonance frequency fr at this time is given by (Equation 11).

…（式１１）

... (Formula 11)

The values of the current resonance inductance Lr, the first capacitor C11, and the second capacitor C12 are set so that the resonance frequency fr in (Equation 11) is approximately equal to the switching frequency fs. Then, during the period when the primary-side second switching element Q12 is on, a sinusoidal current with a half cycle of the switching frequency fs is applied to the output terminal of the DC-DC converter 21 when the load RL is not connected. The drain current Id(Q12) is superimposed on the rising linear waveform (between t22 and t23 in (4) of FIG. 4A).

Next, the waveforms of each part when there is a load RL at the output terminal of the DC-DC converter 21 and when there is no load RL will be described with reference to FIGS. 4A to 4D.

4A-4D, (1) is the drain-source voltage Vds (Q11) of the primary side first switching element Q11, and (2) is each waveform of the drain current Id (Q11) of the primary side first switching element Q11. is shown. (3) shows the waveforms of the drain-source voltage Vds (Q12) of the second primary side switching element Q12, and (4) shows the waveforms of the drain current Id (Q12) of the second primary side switching element Q12. there is (5) is the gate signal Vg11 of the primary side first switching element Q11 and the gate signal Vg21 of the secondary side first switching element Q21, and (6) is the gate signals Vg12 and 2 of the primary side second switching element Q12. Each waveform of the gate signal Vg22 of the secondary side second switching element Q22 is shown. Similarly, (7) is the drain current Id (Q21) of the secondary side first switching element Q21, (8) is the drain current Id (Q22) of the secondary side second switching element Q22, and (9) is DC-DC Each waveform of the output voltage Vo of the converter 21 is shown.

As can be seen from FIGS. 4A-4D, with or without load RL, the drain current of each switching element (2) Id(Q11) and (7) Id(Q21) between t21 and t22, (4) Id(Q12) and (8) the presence or absence of sinusoidal current between t22 and t23 of Id(Q22).

The drain-source voltage Vds (Q11) of the primary side first switching element Q11 and the drain-source voltage Vds (Q12) of the primary side second switching element Q12 vary depending on the magnitude of the input voltage Vi. Then, the drain current Id (Q11) of the first switching element Q11 on the primary side and the drain current Id (Q12) of the second switching element Q11 on the primary side, which are the exciting currents of the high-frequency transformer T, also increase or decrease, and the output voltage Vo also increases or decreases. . That is, when the input voltage Vi changes, the corresponding output voltage Vo is generated. It has a voltage conversion ratio determined by the turns ratio of the primary winding Lp of the high frequency transformer T to the first secondary winding Ls1 and the second secondary winding Ls2. Further, in the DC-DC converter 21, the drain current Id (Q21) of the secondary side first switching element Q21 and the drain current Id (Q22) of the secondary side second switching element Q22, which are the output currents, are sinusoidally resonant. It is a current, and its amplitude changes according to the output current. The starting and ending points of this sinusoidal resonance current are substantially constant regardless of the output current. In other words, regardless of the output current, the start point and end point of the current when the primary side first switching element Q11 or the primary side second switching element Q12 is turned off are the same, and the voltage pseudo-resonance is maintained. In addition, the drain currents Id (Q11) and Id (Q12), which are the exciting currents of the high-frequency transformer T, also vary with the magnitude of the input voltage Vi, and voltage pseudo-resonance is maintained. Furthermore, since the DC-DC converter 21 is a synchronous rectification circuit in which the switching element on the secondary side turns on and off at exactly the same timing as the switching element on the primary side, bidirectional operation is possible. The DC-DC converter 21 similarly maintains resonant operation even in the case of reverse operation.

That is, the DC-DC converter 21 can constitute an insulated bidirectional DC-DC converter with a substantially constant voltage conversion ratio.

The leakage inductance of the high-frequency transformer T can be used as the current resonance inductance Lr. It is also possible to connect a voltage quasi-resonant capacitor in parallel with the switching elements Q21 and Q22 of the secondary side circuit.

In the AC isolation circuit 1 according to the first embodiment, the AC voltage of the commercial AC power supply AC applied to the input terminal is isolated and output to the output terminal as the output voltage Vac at a certain voltage ratio. A synchronous rectification circuit 10 rectifies an AC voltage of an input commercial AC power source AC, an insulation type DC-DC conversion circuit 20 isolates and converts the voltage, and a synchronous synthesis circuit 30 restores the AC voltage. All of them are bidirectionally operable, and can flow from a high voltage to a low voltage with respect to phase lag, lead, etc. peculiar to AC circuits. That is, the same operation as the conventional commercial frequency transformer shown in FIG. 16 is possible. In addition, since the insulation type DC-DC converter 21 used in the AC insulation circuit 1 can have a switching frequency of several hundred kHz, the transformer (high frequency transformer) that performs voltage conversion with insulation is greatly reduced in size. can do. The isolated DC-DC converter 21 is capable of resonant operation under almost all input/output conditions, and because of so-called soft switching, switching noise is low and efficiency is high.

Conventionally, a voltage conversion transformer made of a large and heavy silicon steel plate as shown in FIG. 16 was used to support 50/60 Hz. , it becomes possible to use a compact and lightweight high-frequency transformer. In addition, by adopting a resonance type switching power supply configuration that is extremely small in the effects of switching loss and switching noise, it is highly efficient with little noise and is compact and lightweight. A capable high frequency modulated commercial frequency transformer can be provided.

(First modification)
FIG. 5 is a circuit diagram showing the configuration of the DC-DC converter 21A of the first modified example. The DC-DC converter 21A of the first modification differs from the DC-DC converter 21 of FIG. 3 in that the secondary side circuit is a full-bridge type synchronous rectification. The circuit is composed of the same half-bridge circuit as the DC-DC converter 21 in FIG. Therefore, only the configuration of the secondary side circuit will be described, and the description of the configuration of the primary side circuit will be omitted.

In the DC-DC converter 21A of the first modified example, one secondary winding Ls is connected to the secondary side of the high frequency transformer T. As shown in FIG.

That is, the high-frequency transformer T includes a core, a primary winding Lp, and a secondary winding Ls coupled to the primary winding Lp and the core, and is designed for high-frequency AC voltages of several kHz to several hundred kHz. It is In addition, the high-frequency transformer T is insulated between the primary winding Lp and the secondary winding Ls.

A series circuit of a secondary-side first switching element Q21 and a secondary-side second switching element Q22 and a secondary-side third switching element Q21 are connected to both ends of the secondary winding Ls as a synchronous rectification circuit of the DC-DC converter 21A. A series circuit of the element Q23 and the secondary side fourth switching element Q24 is connected in parallel.

Each of the switching elements Q21, Q22, Q23, Q24 of the secondary side circuit is composed of a semiconductor switching element and has a regenerative diode. In the first modification, each switching element Q21, Q22, Q23, Q24 of the secondary side circuit is composed of an N-channel MOSFET. Snubber capacitors C21, C22, C23 and C24 for suppressing surge currents when the switches are turned off are connected in parallel to the switching elements Q21, Q22, Q23 and Q24 of the secondary circuit, respectively.

The source of the secondary side first switching element Q21 is connected to the positive side of the secondary winding Ls, the source of the secondary side second switching element Q22 is connected to the negative side of the secondary winding Ls, and the secondary side is connected to the negative side of the secondary winding Ls. The drain of the first switching element Q21 and the drain of the secondary side second switching element Q22 are connected.

The drain of the secondary side third switching element Q23 is connected to the positive side of the secondary winding Ls, the drain of the secondary side fourth switching element Q24 is connected to the negative side of the secondary winding Ls, and the secondary side is connected to the negative side of the secondary winding Ls. The source of the third switching element Q23 and the source of the fourth secondary side switching element Q24 are connected.

A connection point between the first secondary switching element Q21 and the second secondary switching element Q22 is connected to the positive output terminal of the DC-DC converter 21A via one end of the output smoothing capacitor Co.

A connection point between the secondary side third switching element Q23 and the secondary side fourth switching element Q24 is connected to the negative side output terminal of the DC-DC converter 21A via the other end of the output smoothing capacitor Co.

A first secondary control circuit CT21 capable of outputting a gate signal Vg21 for turning on the first secondary switching element Q21 is connected between the gate and source of the first secondary switching element Q21.

A secondary-side second control circuit CT22 capable of outputting a gate signal Vg22 for turning on the secondary-side second switching element Q22 is connected between the gate and source of the secondary-side second switching element Q22.

A third secondary control circuit CT23 capable of outputting a gate signal Vg23 for turning on the third secondary switching element Q23 is connected between the gate and source of the third secondary switching element Q23.

A fourth secondary control circuit CT24 capable of outputting a gate signal Vg24 for turning on the fourth secondary switching element Q24 is connected between the gate and source of the fourth secondary switching element Q24.

The gate signal Vg21 of the secondary side first switching element Q21 generated by the secondary side first control circuit CT21 and the gate signal Vg24 of the secondary side fourth switching element Q24 generated by the secondary side fourth control circuit CT24 are , are signals of the same timing as the gate signal Vg11 of the first switching element Q11 on the primary side. That is, it is similar to waveform (5) in FIGS. 4A-4D.

The gate signal Vg22 of the secondary side second switching element Q22 generated by the secondary side second control circuit CT22 and the gate signal Vg23 of the secondary side third switching element Q23 generated by the secondary side third control circuit CT23 are , are signals of the same timing as the gate signal Vg12 of the second switching element Q12 on the primary side. That is, it is similar to waveform (6) in FIGS. 4A-4D.

In the DC-DC converter 21A of the first modified example configured in this manner, the primary side first switching element Q11 is turned on. Then, on the primary side, current flows through two paths of Vi->Q11->Lr->Lp->C12->Vi and C11->Q11->Lr->Lp->C11. → A current flows through the path of Ls. Further, when the primary side second switching element Q12 is turned on, on the primary side, current flows through two paths of Vi→C11→Lp→Lr→Q12→Vi and C12→Lp→Lr→Q12→C12. In the secondary circuit, current flows through the route of Ls→Q22→RL→Q23→Ls.

Even if the DC-DC converter 21A of the first modified example is used, the same operation as the DC-DC converter 21 of FIG. 3 can be performed.

The DC-DC converter 21 of FIG. 3 has two switching elements in the secondary circuit, whereas the DC-DC converter 21A of the first modification requires four switching elements in the secondary circuit. Become. However, while the DC-DC converter 21 of FIG. 3 requires two secondary windings Ls1 and Ls2, the DC-DC converter 21A of the first modified example requires only one secondary winding Ls. Therefore, the number of secondary windings can be reduced.

(Second modification)
FIG. 6 is a circuit diagram showing the configuration of a DC-DC converter 21B of the second modification. The DC-DC converter 21B of the second modification differs from the DC-DC converter 21 of FIG. 3 in that the primary side circuit is a full bridge circuit, and the secondary side circuit is It is the same full-wave rectification type synchronous rectification circuit as the DC-DC converter 21 in FIG. Therefore, only the configuration of the primary side circuit will be described, and the description of the configuration of the secondary side circuit will be omitted.

The high-frequency transformer T includes a core, a primary winding Lp, and a first secondary winding Ls1 and a second secondary winding Ls2 coupled to the primary winding Lp by the core. It is designed for high-frequency AC voltages on the order of 100 kHz. In addition, the high-frequency transformer T has the primary winding Lp insulated from the first secondary winding Ls1 and the second secondary winding Ls2.

In the DC-DC converter 21B of the second modification, the series circuit of the primary side first switching element Q11 and the primary side second switching element Q12 and the primary side third switching element Q13 are connected to the input voltage Vi. and a series circuit of the primary side fourth switching element Q14 are connected in parallel.

Each of the switching elements Q11, Q12, Q13, Q14 on the primary side is composed of a semiconductor switching element and has a regenerative diode. In the second modification, each switching element Q11, Q12, Q13, Q14 of the primary side circuit is composed of an N-channel MOSFET.

In the series circuit of the primary side first switching element Q11 and the primary side second switching element Q12, the drain of the primary side first switching element Q11 is connected to the positive electrode side of the input voltage Vi. The source of the primary side first switching element Q11 is connected to the drain of the primary side second switching element Q12, and the source of the primary side second switching element Q12 is connected to the negative electrode side of the input voltage Vi. there is

In the series circuit of the primary side third switching element Q13 and the primary side fourth switching element Q14, the drain of the primary side third switching element Q13 is connected to the positive electrode side of the input voltage Vi. The source of the fourth primary side switching element Q13 is connected to the drain of the fourth primary side switching element Q14, and the source of the fourth primary side switching element Q14 is connected to the negative electrode side of the input voltage Vi. there is

A first voltage pseudo-resonant capacitor Cv11 is connected in parallel to the primary side first switching element Q11. A second voltage pseudo-resonant capacitor Cv12 is connected in parallel to the primary side second switching element Q12. A first voltage pseudo-resonant capacitor Cv13 is connected in parallel to the primary side third switching element Q13. A fourth voltage pseudo-resonant capacitor Cv14 is connected in parallel with the primary side fourth switching element Q14.

A high-frequency transformer T A series circuit of a primary winding Lp, a current resonance inductance Lr, and a current resonance capacitance C12 is connected. Here, the current resonance capacitance C12 is obtained by integrating the first capacitor C11 and the second capacitor C12 of the primary side circuit of the DC-DC converter 21 in FIG.

Between the gate and source of the primary side first switching element Q11, between the gate and source of the primary side second switching element Q12, between the gate and source of the primary side third switching element Q13, and between the gate and source of the primary side fourth switching element Q13. A primary side control circuit CT10 is connected between the gate and source of the switching element Q14. The primary side control circuit CT10 outputs a gate signal Vg11 for turning on the primary side first switching element Q11, a gate signal Vg12 for turning on the primary side second switching element Q12, and a primary side third switching element Q12. A gate signal Vg13 for turning on the element Q13 and a gate signal Vg14 for turning on the primary side fourth switching element Q14 can be output.

The gate signal Vg11 for the first switching element Q11 on the primary side and the gate signal Vg14 for the fourth switching element Q14 on the primary side generated by the primary side control circuit CT10 are signals of the same timing, and are shown in FIGS. It becomes the same as the waveform of (5).

The gate signal Vg12 of the primary side second switching element Q12 and the gate signal Vg13 of the primary side third switching element Q13 generated by the primary side control circuit CT10 are signals of the same timing, and are shown in FIGS. It becomes the same as the waveform of (6).

Next, the operation of the DC-DC converter 21B will be described.

The primary side first switching element Q11, the primary side second switching element Q12, the primary side third switching element Q13, and the primary side fourth switching element Q14 are connected to the gate signal Vg11 generated by the primary side control circuit CT10. , Vg12, Vg13, and Vg14 at a high frequency of about several hundred kHz (for example, 100 kHz). Here, the primary side first switching element Q11 and the primary side fourth switching element Q14 are turned on/off at the same time (see waveforms (5) in FIGS. 4A to 4D), and the primary side second switching element Q12 and The primary side third switching element Q13 is controlled to turn on and off at the same time (see waveform (6) in FIGS. 4A-4D). The gate signals Vg11, Vg12, Vg13, and Vg14 must be controlled by the primary side first switching element Q11, the primary side second switching element Q12, the primary side third switching element Q13, and the primary side fourth switching element Q14. It has a slight dead time period that turns off at the same time (see the waveforms immediately after t21, t22 and t23 in (5) and (6) of FIGS. 4A-4D).

The gate signal Vg21 of the secondary side first switching element Q21 generated by the secondary side first control circuit CT21 has the same timing as the gate signal Vg11 of the primary side first switching element Q11 (Fig. 4A- See 4D (5) waveform).

The gate signal Vg22 of the secondary side second switching element Q22 generated by the secondary side second control circuit CT22 has the same timing as the gate signal Vg12 of the primary side second switching element Q12 (Fig. 4A- See the waveform of (6) in 4D).

When the load RL is not connected to the output terminal of the DC-DC converter 21B (output side release), after the dead time period, the primary side first switching element Q11 and the primary side fourth switching element Q14 output the gate signal Vg11. , Vg14. Then, current flows through the path of Vi->Q11->Lr->Lp->C12->Q14->Vi. The resonance frequency fr of the primary side circuit at this time is given by (Equation 2).

…（式１２）

... (Formula 12)

Here, if the value of the inductance is set as follows: primary winding Lp>>current resonance inductance Lr, then if the switching frequency of all the switching elements Q11, Q12, Q13, Q14, Q21, Q22 is fs, then fr< <fs. The waveform of the drain current Id (Q11) when the primary side first switching element Q11 and the primary side fourth switching element Q14 are turned on becomes the resonance frequency fr. However, in the waveform of this drain current Id (Q11), since the resonance frequency fr is much lower than the switching frequency fs, a part of the sine wave of the resonance frequency fr appears as a linear waveform rising to the right (( 2) between t21 and t22). This current waveform is also the waveform of the excitation current of the high-frequency transformer T. As shown in FIG.

Energy ε stored in primary winding Lp and current resonance inductance Lr by switching current (drain current) Id (Q11) when primary side first switching element Q11 and primary side fourth switching element Q14 are turned off. is as in (Equation 13).

…（式１３）

... (Formula 13)

The energy ε stored in the primary winding Lp and the current resonance inductance Lr is applied to each voltage pseudo-resonance during the dead time period when the primary side first switching element Q11 and the primary side fourth switching element Q14 are turned off. are discharged to capacitors Cv11, Cv12, Cv13 and Cv14. The relationship with the energy ε at this time is as shown in (Equation 14).

…（式１４）

... (Formula 14)

The capacitance values of the voltage pseudo-resonant capacitors Cv11, Cv12, Cv13, and Cv14 and the inductance value of Lp+Lr are determined so that the voltage V in (Equation 14) is equal to or higher than the input voltage Vi. In order to achieve the voltage pseudo-resonance during the dead time period when the primary side first switching element Q11 and the primary side fourth switching element Q14 are turned off, a quarter cycle of the voltage pseudo-resonant frequency fv is dead. Set to be less than or equal to the time period. Here, the voltage quasi-resonant frequency fv is given by (Equation 15).

…（式１５）

... (Formula 15)

Further, when the load RL is connected to the output terminal of the DC-DC converter 21B, after the dead time period, the primary side first switching element Q11 and the primary side fourth switching element Q14 are switched by the gate signals Vg11 and Vg14. turn on. Then, in the primary side circuit, current flows through the path of Vi->Q11->Lr->Lp->C12->Q14->Vi. At the same time, since the secondary side first switching element Q21 is turned on by the gate signal Vg21, current flows in the secondary side circuit through the high frequency transformer T in the route of Ls1→Q21→RL→Ls1. The resonance frequency fr at this time is given by (Equation 16).

…（式１６）

... (Formula 16)

The values of the current resonance inductance Lr and the current resonance capacitance C12 are set so that the resonance frequency fr in (Equation 16) is approximately equal to the switching frequency fs. Then, during the period when the primary side first switching element Q11 and the primary side fourth switching element Q14 are ON, a sinusoidal current with a half cycle of the switching frequency fs is applied to the output terminal of the DC-DC converter 21. The drain current Id (Q11) is superimposed on the rising linear waveform when RL is not connected (between t21 and t22 in (2) of FIG. 4A).

After the dead time period, when the load RL is not connected to the output terminal of the DC-DC converter 21 (output side release), the primary side second switching element Q12 and the primary side third switching element Q13 are turned on by the gate signals Vg12 and Vg13. Then, current flows through the path of Vi->Q13->C12->Lp->Lr->Q12->Vi. The resonance frequency fr of the primary side circuit at this time is given by (Equation 17).

…（式１７）

... (Formula 17)

Here, if the value of the inductance is set as follows: primary winding Lp>>current resonance inductance Lr, then if the switching frequency of all the switching elements Q11, Q12, Q13, Q14, Q21, Q22 is fs, then fr< <fs. The waveform of the drain current Id (Q12) when the primary side second switching element Q12 and the primary side third switching element Q13 are turned on becomes the resonance frequency fr. However, in the waveform of this drain current Id (Q12), since the resonance frequency fr is much lower than the switching frequency fs, a part of the sine wave of the resonance frequency fr appears as a linear waveform rising to the right (( 4) between t22 and t23). The waveform of the drain current Id (Q12) is also the waveform of the excitation current of the high-frequency transformer T. As shown in FIG.

The energy ε stored in the primary winding Lp and the current resonance inductance Lr due to the switching current (drain current) Id (Q12) when the primary side second switching element Q12 is turned off is given by (Equation 18). Become.

…（式１８）

... (Formula 18)

The energy ε stored in the primary winding Lp and the current resonance inductance Lr is discharged to the respective voltage pseudo-resonance capacitors Cv11, Cv12, Cv13 and Cv14 during the dead time period. The relationship with the energy ε at this time is as shown in (Equation 19).

…（式１９）

... (Formula 19)

The capacitance values of the voltage pseudo-resonant capacitors Cv11, Cv12, Cv13, and Cv14 and the inductance value of Lp+Lr are determined so that the voltage V in Equation 19 is equal to or higher than the input voltage Vi. In order to achieve the voltage pseudo-resonance during the dead time period when the primary side second switching element Q12 and the primary side third switching element Q13 are turned off, a quarter cycle of the voltage pseudo-resonant frequency fv is dead. Set to be less than or equal to the time period. The voltage quasi-resonant frequency fv at this time is given by (Equation 20).

…（式２０）

... (Formula 20)

Further, when the load RL is connected to the output terminal of the DC-DC converter 21B, after the dead time period, the primary side second switching element Q12 and the primary side third switching element Q13 are switched by the gate signals Vg12 and Vg13. turn on. Then, in the primary side circuit, current flows through the route of Vi->Q13->C12->Lp->Lr->Q12->Vi. At the same time, since the secondary side second switching element Q22 is turned on by the gate signal Vg22, current flows through the high frequency transformer T in the secondary side circuit in the route of Ls2→Q22→RL→Ls2. The resonance frequency fr at this time is given by (Equation 21).

…（式２１）

... (Formula 21)

The values of the current resonance inductance Lr and the current resonance capacitance C12 are set so that the resonance frequency fr in (Equation 21) is approximately equal to the switching frequency fs. Then, during the period when the primary side second switching element Q12 and the primary side third switching element Q13 are on, a sinusoidal current with a half cycle of the switching frequency fs is applied to the output terminal of the DC-DC converter 21B. The drain current Id (Q12) is superimposed on the rising linear waveform when RL is not connected (between t22 and t23 in (4) of FIG. 4A).

Even if the DC-DC converter 21B of the second modified example configured in this way is used, the same operation as the DC-DC converter 21 of FIG. 3 can be performed.

The DC-DC converter 21 of FIG. 3 has two switching elements in the primary circuit, whereas the DC-DC converter 21B of the second modification requires four switching elements in the primary circuit. Become. However, in the DC-DC converter 21B of the second modification, the DC-DC The average voltage of the current resonant capacitance C12 of the converter 21B is zero. Therefore, the current resonance capacitance C12 of the DC-DC converter 21B of the second modification can have a low breakdown voltage.

(Third modification)
FIG. 7 is a circuit diagram showing the configuration of a DC-DC converter 21C of the third modification. Unlike the DC-DC converter 21B of the second modification, the DC-DC converter 21C of the third modification has the same full-bridge type synchronous rectification as the secondary circuit of the first modification. The difference is that the primary side circuit is the same full bridge circuit as in the second modification.

The high-frequency transformer T includes a core, a primary winding Lp, and a secondary winding Ls coupled to the primary winding Lp and the core, and is designed for high-frequency AC voltages of several kHz to several hundred kHz. there is In addition, the high-frequency transformer T is insulated between the primary winding Lp and the secondary winding Ls.

Even if the DC-DC converter 21C of the third modified example configured in this way is used, the same operation as the DC-DC converter 21 of FIG. 3 can be performed.

(Fourth modification)
FIG. 8 is a circuit diagram showing the configuration of a DC-DC converter 21D of the fourth modification. The DC-DC converter 21D of the fourth modification is a half-bridge circuit in which the first capacitor C11 and the first voltage pseudo-resonant capacitor Cv11 are omitted in the primary circuit of the DC-DC converter 21 of FIG. The difference is that they are circuits. The secondary side circuit is a full-wave rectification type synchronous rectification circuit, which is the same as the DC-DC converter 21 in FIG. In addition, in the DC-DC converter 21D of the fourth modification, the first capacitor C11 is omitted from the DC-DC converter 21 of FIG. good too. Further, although the first voltage pseudo-resonant capacitor Cv11 is omitted from the DC-DC converter 21 of FIG. 3, the second voltage pseudo-resonant capacitor Cv12 may be omitted instead.

The high-frequency transformer T includes a core, a primary winding Lp, and a first secondary winding Ls1 and a second secondary winding Ls2 coupled to the primary winding Lp by the core. It is designed for high-frequency AC voltages on the order of 100 kHz. In addition, the high-frequency transformer T has the primary winding Lp insulated from the first secondary winding Ls1 and the second secondary winding Ls2.

In the DC-DC converter 21D of the fourth modification, the first capacitor C11 of the DC-DC converter 21 of FIG. 3 is integrated with the second capacitor (current resonance capacitance) C12. The first voltage quasi-resonant capacitor Cv11 of the DC-DC converter 21 of FIG. 3 is integrated with the second voltage quasi-resonant capacitor Cv12.

In the DC-DC converter 21D of the fourth modified example configured in this way, when the primary side first switching element Q11 is turned on, the primary side circuit follows a path of Vi→Q11→Lr→Lp→C12→Vi , and in the secondary circuit, the current flows through the route of Ls1→Q21→RL→Ls1. Further, when the primary side second switching element Q12 is turned on, current flows in the primary side circuit through the path of C12→Lp→Lr→Q12→C12, and in the secondary side circuit, the path is Ls2→Q22→RL→Ls2. A current flows in the path.

Even if the DC-DC converter 21D of the fourth modified example is used, the same operation as the DC-DC converter 21 of FIG. 3 can be performed.

(Fifth modification)
FIG. 9 is a circuit diagram showing the configuration of a DC-DC converter 21E of the fifth modification. The DC-DC converter 21E of the fifth modification has the same full-bridge synchronous secondary circuit as the DC-DC converter 21A of the first modification compared to the DC-DC converter 21D of the fourth modification. The difference is that they are rectified. The primary side circuit is a half bridge circuit omitting the first capacitor C11 and the first voltage pseudo-resonant capacitor Cv11, which is the same as the DC-DC converter 21D of the fourth modification.

The high-frequency transformer T includes a core, a primary winding Lp, and a secondary winding Ls coupled to the primary winding Lp and the core, and is designed for high-frequency AC voltages of several kHz to several hundred kHz. . In addition, the high-frequency transformer T is insulated between the primary winding Lp and the secondary winding Ls.

Even if the DC-DC converter 21E of the fifth modified example configured in this manner is used, it is possible to perform an operation equivalent to that of the DC-DC converter 21 of FIG.

(Second embodiment)
FIG. 10 is a circuit diagram of an AC insulating circuit 1A according to the second embodiment. FIG. 11 is a time chart showing waveforms of respective parts of the AC insulating circuit 1A according to the second embodiment shown in FIG. An AC insulation circuit 1A according to the second embodiment constitutes a single-phase three-wire AC power supply circuit.

Conventionally, as shown in FIG. 18, from a single-phase two-wire commercial power supply, a single-phase three-wire commercial power supply is generated by a commercial frequency transformer, but an AC isolation circuit 1A according to the second embodiment is used. A single-phase three-wire AC power supply circuit can be realized by configuring as follows.

In the AC insulating circuit 1A according to the second embodiment, another set of circuits similar to the AC insulating circuit 1 according to the first embodiment is prepared. That is, the AC isolation circuit 1A according to the second embodiment includes a circuit set consisting of a first synchronous rectifier circuit 10A, a first isolated DC-DC converter circuit 20A, a first synchronous synthesis circuit 30A, and a first output capacitor Cac1. , a second synchronous rectifier circuit 10B, a second insulated DC-DC converter circuit 20B, a second synchronous combining circuit 30B, and a second output capacitor Cac2.

The first synchronous rectification circuit 10A and the second synchronous rectification circuit 10B are configured similarly to the synchronous rectification circuit 10 of the first embodiment. For convenience of explanation, in the second synchronous rectifier circuit 10B, the third synchronous rectifier Q5 corresponds to the first synchronous rectifier Q1, and the second synchronous rectifier Q2 corresponds to the second synchronous rectifier Q2 in the synchronous rectifier circuit 10 of the first embodiment. A third rectification control circuit CT5 corresponds to the 4-synchronous rectifier Q6, the first rectification control circuit CT1, and a fourth rectification control circuit CT6 corresponds to the second rectification control circuit CT2.

The first insulation type DC-DC conversion circuit 20A and the second insulation type DC-DC conversion circuit 20B are configured similarly to the insulation type DC-DC conversion circuit 20 of the first embodiment. For convenience of explanation, in the second insulation type DC-DC conversion circuit 20B, in the insulation type DC-DC conversion circuit 20 of the first embodiment, the one corresponding to the first insulation type DC-DC converter 21 is replaced with the third insulation type. A fourth insulated DC-DC converter 24 corresponds to the DC-DC converter 23 and the second insulated DC-DC converter 22 .

The first synchronous synthesis circuit 30A and the second synchronous synthesis circuit 30B are configured similarly to the synchronous synthesis circuit 30 of the first embodiment. For convenience of explanation, in the second synchronous synthesizer circuit 30B, the third synchronous synthesizer Q7 and the second synchronous synthesizer Q4 correspond to the first synchronous synthesizer Q3 in the synchronous synthesizer circuit 30 of the first embodiment. A fourth synchronous synthesizer Q8, a third synthesis control circuit CT7 corresponding to the first synthesis control circuit CT3, and a fourth synthesis control circuit CT8 corresponding to the second synthesis control circuit CT4.

Accordingly, detailed description of the circuit configuration of the AC insulating circuit 1A according to the second embodiment is omitted.

Next, the operation of the AC insulation circuit 1A according to the second embodiment will be described using the time chart of FIG.

In synchronization with the frequency f of the voltage of the commercial AC power supply ((1) in FIG. 11), when the commercial AC power supply is positive (between t31 and t32 in (1) in FIG. 11), the first synchronous rectifier Q1 is turned on by the gate signal Vg1 of the first rectification control circuit CT1 (between t31 and t32 in (2) of FIG. 11). Similarly, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the first synchronous rectifier Q1 is turned off by the gate signal Vg1 of the first rectification control circuit CT1 becoming 0. (between t32 and t33 in (2) of FIG. 11). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the positive voltage Vi1 ((4) in FIG. 11). In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t31 and t32 in (1) of FIG. 11), the second synchronous rectifier Q2 is connected to the second rectification control circuit CT2. It is turned off when the gate signal Vg2 becomes 0 (between t31 and t32 in (3) of FIG. 11). Similarly, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the second synchronous rectifier Q2 is turned on by the gate signal Vg2 of the second rectification control circuit CT2 ( (3) between t32 and t33). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the negative voltage Vi2 ((5) in FIG. 11).

A positive voltage Vi1 is input to the first DC-DC converter 21 . A negative voltage Vi2 is input to the second DC-DC converter 22 with its polarity reversed.

The first DC-DC converter 21 outputs a positive voltage Vo1 according to the voltage conversion ratio, which is insulated from the input positive voltage Vi1 ((6) in FIG. 11). If the voltage conversion ratio of the first DC-DC converter 21 is set to 1, the positive voltage Vi1 and the positive voltage Vo1 have the same waveform. The second DC-DC converter 22 outputs a negative voltage Vo2 insulated from the input negative voltage Vi2 according to the voltage conversion ratio ((7) in FIG. 11). If the voltage conversion ratio of the second DC-DC converter 22 is set to 1, the negative voltage Vi2 and the negative voltage Vo2 have the same waveform.

Synchronizing with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t31 and t32 in (1) of FIG. 11), the first synchronous combiner Q3 switches to the first synthesis control circuit CT3. is turned on by the gate signal Vg3 of (during t31-t32 in (2) of FIG. 11). Then, the second synchronous synthesizer Q4 is turned off when the gate signal Vg4 of the second synthesis control circuit CT4 becomes 0 (between t31 and t32 in (3) of FIG. 11). When the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the second synchronous combiner Q4 is turned on by the gate signal Vg4 of the second synthesis control circuit CT4 ( (3) between t32 and t33). Then, the first synchronous synthesizer Q3 is turned off when the gate signal Vg3 of the first synthesis control circuit CT3 becomes 0 (between t32 and t33 in (2) of FIG. 11). As a result, the output voltage Vo1 of the first DC-DC converter 21 and the voltage obtained by inverting the polarity of the output voltage Vo2 of the second DC-DC converter 22 are combined to generate the first output voltage Vac1 ( (8) in FIG. 11). The first output voltage Vac1 is insulated from the commercial AC power supply AC.

In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t31 and t32 in (1) of FIG. 11), the third synchronous rectifier Q5 is connected to the third rectification control circuit CT5. It is turned on by the gate signal Vg5 (between t31 and t32 in (2) of FIG. 11). Further, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the third synchronous rectifier Q5 is turned off by the gate signal Vg5 of the third rectification control circuit CT5 becoming 0. (Between t32 and t33 in (2) of FIG. 11) As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to a positive voltage Vi3 ((4) in FIG. 11). In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t31 and t32 in (1) of FIG. 11), the fourth synchronous rectifier Q6 is connected to the fourth rectification control circuit CT6. It is turned off when the gate signal Vg6 becomes 0 (between t31 and t32 in (3) of FIG. 11). Further, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the fourth synchronous rectifier Q6 is turned on by the gate signal Vg6 of the fourth rectification control circuit CT6 (( 3) between t32 and t33). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the negative voltage Vi4 ((5) in FIG. 11).

A positive voltage Vi3 is input to the third DC-DC converter 23 . A negative voltage Vi4 is input to the fourth DC-DC converter 24 with its polarity reversed.

The third DC-DC converter 23 outputs a positive voltage Vo3 according to the voltage conversion ratio, which is insulated from the input positive voltage Vi3 ((6) in FIG. 11). If the voltage conversion ratio of the third DC-DC converter 23 is set to 1, the positive voltage Vi3 and the positive voltage Vo3 have the same waveform. The fourth DC-DC converter 24 outputs a negative voltage Vo4 according to the voltage conversion ratio, which is insulated from the input negative voltage Vi4 ((7) in FIG. 11). If the voltage conversion ratio of the fourth DC-DC converter 24 is set to 1, the negative voltage Vi4 and the negative voltage Vo4 have the same waveform.

In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t31 and t32 in (1) of FIG. 11), the third synchronizing combiner Q7 operates in the third combining control circuit CT7. is turned on by the gate signal Vg7 (between t31 and t32 in (2) of FIG. 11). Then, the fourth synchronous synthesizer Q8 is turned off when the gate signal Vg8 of the fourth synthesis control circuit CT8 becomes 0 (between t31 and t32 in (3) of FIG. 11). Further, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the fourth synchronous combiner Q8 is turned on by the gate signal Vg8 of the fourth synthesis control circuit CT8 ( (3) between t32 and t33). When the gate signal Vg7 of the third synthesis control circuit CT7 becomes 0, the third synchronous synthesizer Q7 is turned off (between t32 and t33 in (2) of FIG. 11). As a result, the output voltage Vo3 of the third DC-DC converter 23 and the voltage obtained by inverting the polarity of the output voltage Vo4 of the fourth DC-DC converter 24 are combined to generate the second output voltage Vac2 ( (8) in FIG. 11). The second output voltage Vac2 is insulated from the commercial AC power supply AC.

As shown in FIG. 10, the connection point between the negative terminal of the first output voltage Vac1 and the positive terminal of the second output voltage Vac2 is white, and the positive terminal of the first output voltage Vac1 is red. The negative terminal of Vac2 is assumed to be black. From this, if the voltage conversion ratio of the insulated DC-DC converters 21-24 is 1:1, when a single-phase 100 V is input as the voltage of the commercial AC power supply, red and white and white and black A single-phase AC voltage of 100 V, which is insulated from the commercial AC power supply AC, can be taken out from between the terminals ((8) in FIG. 11). A single-phase 200 V AC voltage insulated from the commercial AC power source AC can be taken out from between the red and black terminals ((9) in FIG. 11 (indicated by a dashed line)).

In the second embodiment, the first synchronous rectification circuit 10A and the second synchronous rectification circuit 10B can be shared (see the modified example of the second embodiment).

By adopting a configuration like the AC insulation circuit 1A according to the second embodiment, it is possible to replace the conventional large and heavy single-phase three-wire commercial insulation frequency transformer with a small size and light weight. It is possible to provide an insulated single-phase three-wire AC power supply circuit that can be mounted on a substrate.

Like the AC insulation circuit 1A according to the second embodiment, by combining several AC insulation circuits 1 according to the first embodiment, it is possible to convert from a single-phase two-wire system to a single-phase three-wire system. . Also, the AC insulation circuit 1 according to the first embodiment can be used for three-phase AC by preparing three sets of similar circuits and connecting them in Δ connection or Y connection. This makes it possible to provide a three-phase AC isolation circuit that is compact and lightweight and can be mounted on, for example, one (or a few) substrates instead of a large and heavy three-phase commercial isolation frequency transformer.

Also, the AC insulating circuit 1A according to the second embodiment has the same effects as the AC insulating circuit 1 according to the first embodiment.

(Modification of Second Embodiment)
FIG. 12 is a circuit diagram of a single-phase three-wire AC insulation circuit 1B according to a modification of the second embodiment. Unlike the AC insulating circuit 1A according to the second embodiment shown in FIG. 10, the AC insulating circuit 1B does not include the second synchronous rectification circuit 10B. The drain of the first synchronous rectifier Q1 of the first synchronous rectifier circuit 10A is connected to the positive side input terminal of the third insulation type DC-DC converter 23. As shown in FIG. Also, the source of the second synchronous rectifier Q2 of the first synchronous rectifier circuit 10A is connected to the negative side input terminal of the fourth isolated DC-DC converter . That is, in the AC insulating circuit 1B shown in FIG. 12, the first synchronous rectification circuit 10A is shared by two sets of circuits of the AC insulating circuit 1A shown in FIG. Other configurations of the AC insulating circuit 1B shown in FIG. 12 are the same as those of the AC insulating circuit 1A shown in FIG. That is, the single-phase three-wire AC insulation circuit 1B according to the modification of the second embodiment includes a first synchronous rectification circuit 10A, a first insulation type DC-DC conversion circuit 20A, and a second insulation type DC-DC It comprises a conversion circuit 20B, a first synchronous synthesizing circuit 30A, and a second synchronous synthesizing circuit 30B. The output side of the first synchronous rectification circuit 10A is connected in parallel with the input sides of the first insulation type DC-DC conversion circuit 20A and the second insulation type DC-DC conversion circuit 20B. The input side of the first synchronous synthesizing circuit 30A is connected to the output side of the first isolated DC-DC conversion circuit 20A. The input side of the second synchronous synthesizing circuit 30B is connected to the output side of the second isolated DC-DC conversion circuit 20B. A positive output terminal of the first synchronous synthesizing circuit 30A is connected to the red terminal. The negative output terminal of the first synchronous synthesizing circuit 30A and the positive output terminal of the second synchronous synthesizing circuit 30B are connected to the white terminal. A negative output terminal of the second synchronous synthesizing circuit 30B is connected to the black terminal.

In the AC insulating circuit 1B according to the modification of the second embodiment, an insulating single-phase circuit that operates in the same manner as the AC insulating circuit 1A according to the second embodiment with the time chart of FIG. A three-wire AC power supply circuit can be provided.

That is, in synchronization with the frequency f of the voltage of the commercial AC power supply ((1) in FIG. 11), when the commercial AC power supply is positive (between t31 and t32 in (1) in FIG. 11), the first synchronization The rectifier Q1 is turned on by the gate signal Vg1 of the first rectification control circuit CT1 (between t31 and t32 in (2) of FIG. 11). Similarly, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the first synchronous rectifier Q1 is turned off by the gate signal Vg1 of the first rectification control circuit CT1 becoming 0. (between t32 and t33 in (2) of FIG. 11). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the positive voltage Vi1 ((4) in FIG. 11). In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t31 and t32 in (1) of FIG. 11), the second synchronous rectifier Q2 is connected to the second rectification control circuit CT2. It is turned off when the gate signal Vg2 becomes 0 (between t31 and t32 in (3) of FIG. 11). Similarly, when the commercial AC power supply AC is negative (between t32 and t33 in (1) of FIG. 11), the second synchronous rectifier Q2 is turned on by the gate signal Vg2 of the second rectification control circuit CT2 ( (3) between t32 and t33). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the negative voltage Vi2 ((5) in FIG. 11).

A positive voltage Vi1 is input to the first DC-DC converter 21 . A negative voltage Vi2 is input to the second DC-DC converter 22 with its polarity reversed. At the same time, the third DC-DC converter 23 receives a positive voltage Vi1. A negative voltage Vi2 is input to the fourth DC-DC converter 24 with its polarity reversed. Since the subsequent operation of the AC insulating circuit 1B is the same as the operation of the AC insulating circuit 1A according to the second embodiment, the explanation is omitted.

In the AC insulating circuit 1B according to the modification of the second embodiment, the second synchronous rectification circuit 10B is removed from the AC insulating circuit 1A according to the second embodiment, so that it can be configured with fewer parts. It is possible. However, the first synchronous rectifier Q1 and the second synchronous rectifier Q2 of the AC isolation circuit 1B according to the modified example have a larger voltage than the first synchronous rectifier Q1 and the second synchronous rectifier Q2 of the AC isolation circuit 1A according to the second embodiment. current will flow. Therefore, in the first synchronous rectifier Q1 and the second synchronous rectifier Q2 of the AC isolation circuit 1B according to the modification of the second embodiment, it is necessary to use switching elements with currents larger than those of the AC isolation circuit 1A according to the second embodiment. There is

Even with a configuration like the AC insulation circuit 1B according to the modification of the second embodiment, instead of the conventional large and heavy single-phase three-wire commercial insulation frequency transformer, it is small and lightweight, and for example, one (or a few) It is possible to provide an insulated single-phase three-wire AC power supply circuit that can be mounted on a substrate.

(Third embodiment)
FIG. 13 is a circuit diagram of a single-phase three-wire AC power supply circuit 1C according to the third embodiment. A single-phase three-wire AC power supply circuit 1C uses the AC isolation circuit 1 according to the first embodiment shown in FIG. 1 to configure a non-insulated single-phase three-wire AC power supply circuit. That is, the single-phase three-wire AC power supply circuit 1C includes a synchronous rectification circuit 10, an insulated DC-DC conversion circuit 20, and a synchronous synthesis circuit 30, as in the first embodiment. A single-phase three-wire AC power supply circuit 1C according to the third embodiment has a positive electrode of an output voltage Vac1 corresponding to the output voltage Vac of the AC insulation circuit 1, as opposed to the AC insulation circuit 1 according to the first embodiment. It has a connected red terminal (first terminal), a white terminal (second terminal) connected to the negative electrode, and a black terminal (third terminal). Then, the power supply line to which the positive electrode of the commercial power supply AC is connected (corresponding to the positive side input of the AC insulation circuit 1 according to the first embodiment) and the negative electrode of the output voltage Vac1 (of the AC insulation circuit 1 according to the first embodiment) are connected. corresponding to the negative side output) are connected by the first electric wire 41 . A power supply line to which the negative electrode of the commercial power supply AC is connected and the black terminal are connected by a second electric wire 42 . A first output capacitor Cac1 is connected between the positive and negative electrodes of the output voltage Vac1. A second output capacitor Cac2 is connected between the first wire 41 and the second wire 42 . In the single-phase three-wire AC power supply circuit 1C, the voltage of the commercial AC power supply AC is directly output as the second output voltage Vac2 between the white terminal and the black terminal. Since other configurations of the single-phase three-wire AC power supply circuit 1C are the same as those of the AC insulation circuit 1 according to the first embodiment, description thereof is omitted.

Next, the operation of the single-phase three-wire AC power supply circuit 1C according to the third embodiment will be described using the time chart of FIG.

In synchronization with the frequency f of the voltage of the commercial AC power supply ((1) in FIG. 14), when the commercial AC power supply is positive (between t11 and t12 in (1) in FIG. 14), the first synchronous rectifier Q1 is turned on by the gate signal Vg1 of the first rectification control circuit CT1 (between t11 and t12 in (2) of FIG. 14). When the commercial AC power supply AC is negative (between t12 and t13 in (1) of FIG. 14), the first synchronous rectifier Q1 is turned off by the gate signal Vg1 of the first rectification control circuit CT1 becoming 0. (Between t12 and t13 in (2) of FIG. 14). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the positive voltage Vi1 ((4) in FIG. 14). In synchronization with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t11 and t12 in (1) of FIG. 14), the second synchronous rectifier Q2 is connected to the second rectification control circuit CT2. It is turned off when the gate signal Vg2 becomes 0 (between t11 and t12 in (3) of FIG. 14). When the commercial AC power supply AC is negative (between t12 and t13 in (1) of FIG. 14), the second synchronous rectifier Q2 is turned on by the gate signal Vg2 of the second rectification control circuit CT2 (( 3) between t12 and t13). As a result, the AC voltage of the commercial AC power supply AC is half-wave rectified to the negative voltage Vi2 ((5) in FIG. 14).

A positive voltage Vi1 is input to the first DC-DC converter 21 . A negative voltage Vi2 is input to the second DC-DC converter 22 with its polarity reversed.

The first DC-DC converter 21 outputs a positive voltage Vo1 according to the voltage conversion ratio, which is insulated from the input positive voltage Vi1 ((6) in FIG. 14). If the voltage conversion ratio of the first DC-DC converter 21 is set to 1, the positive voltage Vi1 and the positive voltage Vo1 have the same waveform. The second DC-DC converter 22 outputs a negative voltage Vo2 according to the voltage conversion ratio, which is insulated from the input negative voltage Vi2 ((7) in FIG. 14). If the voltage conversion ratio of the second DC-DC converter 22 is set to 1, the negative voltage Vi2 and the negative voltage Vo2 have the same waveform.

Synchronizing with the frequency f of the voltage of the commercial alternating current power supply AC, when the commercial alternating current power supply AC is positive (between t11 and t12 in (1) of FIG. 14), the first synchronous synthesizer Q3 switches to the first synthesis control circuit CT3. is turned on by the gate signal Vg3 of (between t11 and t12 in (2) of FIG. 14). Then, the second synchronous synthesizer Q4 is turned off when the gate signal Vg4 of the second synthesis control circuit CT4 becomes 0 (between t11 and t12 in (3) of FIG. 14). Further, when the commercial AC power supply AC is negative (between t12 and t13 in (1) of FIG. 14), the second synchronous combiner Q4 is turned on by the gate signal Vg4 of the second synthesis control circuit CT4 ( (3) between t12 and t13). Then, the first synchronous synthesizer Q3 is turned off when the gate signal Vg3 of the first synthesis control circuit CT3 becomes 0 (between t12 and t13 in (2) of FIG. 14). As a result, the output voltage Vo1 of the first DC-DC converter 21 and the voltage obtained by inverting the polarity of the output voltage Vo2 of the second DC-DC converter 22 are combined to generate the first output voltage Vac1 ( (8) in FIG. 14). In the single-phase three-wire AC power supply circuit 1C, the voltage of the commercial AC power supply AC is directly output as the second output voltage Vac2.

In the single-phase three-wire AC power supply circuit 1C, as shown in FIG. 14, the connection point between the negative terminal of the first output voltage Vac1 and the positive terminal of the second output voltage Vac2 is a white terminal. The positive terminal of the output voltage Vac1 is set as a red terminal, and the negative terminal of Vac2 is set as a black terminal. From this, if the voltage conversion ratio of the insulated DC-DC converters 21-22 is 1:1, when a single-phase 100 V is input as the voltage of the commercial AC power supply, red and white and white and black A single-phase AC voltage of 100 V can be taken out from between the terminals ((8) in FIG. 14). A single-phase AC voltage of 200 V can be taken out from between the red and black terminals ((9) in FIG. 14 (indicated by a broken line)).

In the single-phase three-wire AC power supply circuit 1C according to the third embodiment, since the voltage of the commercial AC power supply AC is directly output as the second output voltage Vac2, the commercial AC power supply AC and the single-phase three-wire AC power supply circuit It is not insulated from each output terminal of 1C. However, the single-phase three-wire AC power supply circuit 1C according to the third embodiment can be configured by simply adding the first electric wire 41 and the second electric wire 42 to the AC insulation circuit 1 according to the first embodiment. Therefore, a single-phase three-wire AC power supply circuit can be configured more easily than the AC insulation circuit 1A according to the second embodiment.

By adopting a configuration like the single-phase three-wire AC power supply circuit 1C according to the third embodiment, it is possible to replace the conventional large and heavy single-phase three-wire commercial insulated frequency transformer with a small size and light weight. It is possible to provide a single-phase three-wire AC power supply circuit that can be mounted on one (or a few) substrates.

(Modified example of the third embodiment)
FIG. 15 is a circuit diagram of a single-phase three-wire AC power supply circuit 1D according to a modification of the third embodiment. A single-phase three-wire AC power supply circuit 1D uses the AC isolation circuit 1 according to the first embodiment shown in FIG. 1 to constitute a non-insulated single-phase three-wire AC power supply circuit. That is, the single-phase three-wire AC power supply circuit 1D includes a synchronous rectification circuit 10, an insulated DC-DC conversion circuit 20, and a synchronous synthesis circuit 30, as in the first embodiment. A single-phase three-wire AC power supply circuit 1D has a white terminal ( first terminal), a black terminal (second terminal) connected to the negative electrode, and a red terminal (third terminal). Then, the power supply line to which the negative pole of the commercial power supply AC is connected (corresponding to the negative side input of the AC insulation circuit 1 according to the first embodiment) and the positive pole of the output voltage Vac1 (the AC insulation circuit 1 according to the first embodiment) are connected. corresponding to the positive side output) are connected by the first electric wire 41A. Also, the power line to which the positive electrode of the commercial power supply AC is connected and the red terminal are connected by a second electric wire 42A. A first output capacitor Cac1 is connected between the positive and negative electrodes of the output voltage Vac1. A second output capacitor Cac2 is connected between the first wire 41 and the second wire 42 . In the single-phase three-wire AC power supply circuit 1D, the voltage of the commercial AC power supply AC is directly output as the second output voltage Vac2 between the red terminal and the white terminal. Since other configurations of the single-phase three-wire AC power supply circuit 1C according to the third embodiment are the same as those of the AC insulation circuit 1 according to the first embodiment, description thereof will be omitted.

The single-phase three-wire AC power supply circuit 1D according to the modification of the third embodiment is also the same as the single-phase three-wire AC power supply circuit 1C according to the third embodiment, which has been explained using the time chart of FIG. A single-phase three-wire AC power supply circuit that operates similarly can be provided.

A configuration like the single-phase three-wire AC power supply circuit 1D according to the modified example of the third embodiment is also small and lightweight in place of the conventional large and heavy single-phase three-wire commercial insulated frequency transformer. It is possible to provide a single-phase three-wire AC power supply circuit that can be mounted on one (or a few) substrates.

Further, the isolated DC-DC converters 21A to 21E of the first to fifth modifications shown in FIGS. is also applicable.

1, 1A, 1B AC isolation circuits 1C, 1D Single-phase three-wire AC power supply circuit 10 Synchronous rectification circuit 10A First synchronous rectification circuit 10B Second synchronous rectification circuit 20 Insulated DC-DC conversion circuit 20A First insulated DC- DC conversion circuit 20B Second insulation type DC-DC conversion circuit 21 First insulation type DC-DC converter (insulation type DC-DC converter)
21A, 21B, 21C, 21D, 21E insulation type DC-DC converter 22 second insulation type DC-DC converter 23 third insulation type DC-DC converter 24 fourth insulation type DC-DC converter 30 synchronous synthesis circuit 30A First synchronous synthesis circuit 30B Second synchronous synthesis circuit 41 First wire 42 Second wire AC Commercial AC power supply (first AC voltage)
Co Output smoothing capacitor Cac Output capacitor Cac1 First output capacitor Cac2 Second output capacitor f Frequency of commercial AC power supply (first frequency)
fr resonance frequency fs switching frequency (second frequency)
fv voltage pseudo-resonant frequency Vac output voltage (second AC voltage)
Vi1 first positive voltage (first DC voltage)
Vi2 first negative voltage (first DC voltage)
Vo1 Second positive voltage (second DC voltage)
Vo2 second negative voltage (second DC voltage)

Claims (19)

A first switching circuit is provided, and when a first AC voltage having a first frequency is input, the first switching circuit is turned on and off in synchronization with the first frequency. A synchronous rectification circuit that generates and outputs a first DC voltage obtained by rectifying the AC voltage of
Controlled by a second frequency higher than the first frequency, the insulation converts the first DC voltage into a second DC voltage isolated from the first DC voltage and outputs the second DC voltage. a type DC-DC conversion circuit;
The second switching circuit is insulated from the first AC voltage from the second DC voltage by turning on and off the second switching circuit in synchronization with the first frequency. and a synchronous combining circuit for generating and outputting a second alternating voltage having a frequency of 1. The insulated DC-DC conversion circuit is
an input terminal connected to the output of the synchronous rectification circuit;
a core, a primary winding, and a secondary winding coupled to the primary winding by the core, the primary winding and the secondary winding being insulated; a high frequency transformer operable at
a primary circuit connected between the input terminal and the primary winding;
a secondary circuit connected to the secondary winding;
The primary circuit is controlled by the second frequency, converts the first DC voltage into a third AC voltage having the second frequency, and applies the third AC voltage to the primary winding;
the secondary winding outputs a fourth alternating voltage having the second frequency in response to the third alternating voltage applied to the primary winding;
2. The AC isolation circuit according to claim 1, wherein said secondary circuit is controlled by said second frequency, rectifies said fourth AC voltage, and outputs said second DC voltage. The primary circuit is
a first series circuit of a primary side first switching element and a primary side second switching element connected in parallel to the input terminal;
a current resonance capacitance in which a first capacitor and a second capacitor are connected in series, the current resonance capacitance being connected in parallel with the first series circuit with respect to the input terminal;
A series circuit of a first voltage pseudo-resonant capacitor connected in parallel to the primary side first switching element and a second voltage pseudo-resonant capacitor connected in parallel to the primary side second switching element. a voltage pseudo-resonant capacitor circuit;
a current resonance inductance connected in series with the primary winding;
In the primary circuit, the primary winding is provided between a connection point between the primary side first switching element and the primary side second switching element and a connection point between the first capacitor and the second capacitor. and a series circuit of the current resonance inductance are connected,
3. The AC insulation circuit according to claim 2, wherein said primary side first switching element and said primary side second switching element are synchronously turned on/off by said second frequency. The primary circuit is
a series circuit of a primary side first switching element and a primary side second switching element connected in parallel to the input terminal;
a voltage pseudo-resonant capacitor circuit comprising a voltage pseudo-resonant capacitor connected in parallel to at least one of the primary side first switching element and the primary side second switching element;
a current resonance inductance and a current resonance capacitance connected in series to the primary winding;
In the primary side circuit, a series circuit of the primary winding, the current resonance inductance, and the current resonance capacitance is one of the primary side first switching element and the primary side second switching element. is connected in parallel to
3. The AC insulation circuit according to claim 2, wherein said primary side first switching element and said primary side second switching element are synchronously turned on/off by said second frequency. The primary circuit is
A first series circuit, which is a series circuit of a primary side first switching element and a primary side second switching element, a primary side third switching element, and a primary side fourth switching element, which are connected in parallel to the input terminal. a second series circuit that is a series circuit of switching elements;
a first voltage pseudo-resonant capacitor connected in parallel to the primary side first switching element;
a second voltage pseudo-resonant capacitor connected in parallel to the primary side second switching element;
a third voltage pseudo-resonant capacitor connected in parallel to the primary side third switching element;
a fourth voltage pseudo-resonant capacitor connected in parallel to the fourth primary side switching element;
a current resonance inductance and a current resonance capacitance connected in series to the primary winding;
The primary side circuit includes a connection point between the primary side first switching element and the primary side second switching element and a connection point between the primary side third switching element and the primary side fourth switching element. A series circuit of the primary winding, the current resonance inductance, and the current resonance capacitance is connected between them,
The first switching element on the primary side, the second switching element on the primary side, the third switching element on the primary side, and the fourth switching element on the primary side are turned on/off in synchronization with the second frequency. 3. An AC isolation circuit according to claim 2. The secondary side circuit includes a secondary side first switching element and a secondary side connected in parallel to a series circuit of a first secondary winding and a second secondary winding as the secondary winding. A series circuit of second switching elements,
a connection point between the first secondary switching element and the second secondary switching element is connected to one output terminal of the secondary circuit via one end of an output smoothing capacitor;
a connection point between the first secondary winding and the second secondary winding is connected to the other output terminal of the secondary circuit via the other end of the output smoothing capacitor;
6. The method according to claim 3, wherein said secondary side first switching element and said secondary side second switching element are turned on/off by said second frequency in synchronization with each switching element of said primary side circuit. The alternating current insulation circuit according to any one of claims 1 to 3. The secondary circuit includes a series circuit of a secondary side first switching element and a secondary side second switching element, and a secondary side third switching element and a secondary side secondary switching element connected in parallel to the secondary winding. Equipped with a series circuit of 4 switching elements,
a connection point between the first secondary switching element and the second secondary switching element is connected to one output terminal of the secondary circuit via one end of an output smoothing capacitor;
a connection point between the third secondary switching element and the fourth secondary switching element is connected to the other output terminal of the secondary circuit via the other end of the output smoothing capacitor,
The secondary side first switching element, the secondary side second switching element, the secondary side third switching element, and the secondary side fourth switching element are each switched in the primary side circuit according to the second frequency. 6. The AC insulating circuit according to any one of claims 3 to 5, wherein the switching element is turned on/off in synchronization with the switching element. The insulated DC-DC conversion circuit converts the primary side first switching element and the primary side second switching element to substantially the same ON width, and the primary side first switching element and the primary side second switching element. 5. The AC insulation circuit according to claim 3, further comprising a primary side control circuit for controlling so that two switching elements are turned off at the same time with a dead time and alternately turned on and off at said second frequency. 9. The AC isolation circuit according to claim 8, wherein the voltage pseudo-resonance occurs during the dead time period at the resonance frequency of the inductance of the primary winding and the voltage pseudo-resonance capacitor circuit. 5. A capacitance value of said current resonance capacitance and a value of said current resonance inductance are set so that a resonance frequency of said current resonance capacitance and said current resonance inductance is substantially equal to said second frequency. AC isolation circuit as described in . In the insulated DC-DC conversion circuit, the primary side first switching element, the primary side second switching element, the primary side third switching element, and the primary side fourth switching element are substantially the same. In the ON width, there is a dead time in which the primary side first switching element, the primary side second switching element, the primary side third switching element, and the primary side fourth switching element are turned off at the same time. alternately turned on and off at the second frequency, the primary side first switching element and the primary side fourth switching element are turned on and off at the same time, and the primary side second switching element and the primary side 6. The AC isolation circuit according to claim 5, further comprising a primary side control circuit for controlling the third switching elements to be turned on and off simultaneously. an inductance of the primary winding, a series circuit of the first voltage pseudo-resonant capacitor and the third voltage pseudo-resonant capacitor, and a series circuit of the second voltage pseudo-resonant capacitor and the fourth voltage pseudo-resonant capacitor 12. The AC isolation circuit according to claim 11, wherein the voltage quasi-resonates during the period of the dead time at the resonance frequency with the combined capacitance of the AC isolation circuit. 6. The value of the current resonance capacitance and the current resonance inductance are set so that the resonance frequency of the current resonance capacitance and the current resonance inductance is approximately equal to the second frequency. AC isolation circuit. 3. The AC isolation circuit according to claim 1, wherein said first frequency is equal to the frequency of commercial power supply voltage. 3. The AC isolation circuit according to claim 1, wherein said second AC voltage has a frequency equal to said first frequency. A first AC insulating circuit and a second AC insulating circuit, each being the AC insulating circuit according to claim 1 or 2,
The input terminal of the first AC isolation circuit and the input terminal of the second AC isolation circuit are connected in parallel, and the negative output terminal of the first AC isolation circuit and the positive output terminal of the second AC isolation circuit are connected. A.C. isolated circuit to which is connected. An AC insulation circuit according to claim 1 or 2;
A second insulation type that converts the first DC voltage output by the synchronous rectification circuit controlled by the second frequency into a third DC voltage that is insulated from the first DC voltage and outputs the third DC voltage. a DC-DC conversion circuit;
A third switching circuit is provided, and by turning on/off the third switching circuit in synchronization with the first frequency, the third DC voltage is insulated from the first AC voltage. a second synchronous synthesis circuit for generating and outputting a third AC voltage having a frequency of 1;
An AC isolation circuit to which the negative side output terminal of the synchronous synthesis circuit and the positive side output terminal of the second synchronous synthesis circuit are connected. An AC insulation circuit according to claim 1 or 2;
a first terminal connected to the positive output of the AC isolation circuit;
a second terminal connected to the negative output of the AC isolation circuit;
a third terminal connected to the negative input of the AC isolation circuit;
An AC power supply circuit in which the positive side input and the negative side output of the AC isolation circuit are connected. An AC insulation circuit according to claim 1 or 2;
a first terminal connected to the positive output of the AC isolation circuit;
a second terminal connected to the negative output of the AC isolation circuit;
A third terminal connected to the positive input of the AC isolation circuit,
An AC power supply circuit in which the negative side input and the positive side output of the AC isolation circuit are connected.

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