JP6865985B1 - Resonance isolated DC-DC converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce switching loss and switching noise because a resonance current can flow in a resonance operation having a magnitude corresponding to a load current and a switch can be turned on and off at a time when the resonance current is zero. An isolated DC-DC converter is provided. SOLUTION: A resonant isolated DC-DC converter circuit 200 composed of a voltage square wave inverter 210, an insulated transformer 220, a rectifying circuit 230, an LC resonance circuit 250 and an LC filter circuit 260 with respect to a DC voltage source 100. Therefore, a DC switch circuit is added and a voltage waveform with a certain period width that depends on the resonance period width of the resonance circuit is added to the resonance circuit with respect to the rectified output of the square wave voltage, or the inverter alone maintains positive and negative symmetry. A voltage waveform having the same period width is added to the resonant circuit, and the switching period is changed. [Effect] The DC output voltage can be continuously controlled under a zero-current switching operation with little current circuit loss while preventing demagnetization of the transformer. [Selection diagram] FIG. 8

Description

The present invention is a technique that contributes to miniaturization, light weight, high efficiency, and reduction of switching noise of an isolated DC-DC converter capable of setting a wide range of DC output voltages.

In recent years, coupled with the rapid development of power electronics equipment and the development and widespread use of storage batteries such as lithium-ion batteries, DC power supply equipment with various output voltage levels of small, lightweight, and highly efficient small and medium capacity can be used with large capacity. Demand for DC-DC converters has increased in a wide range of application fields such as frequency conversion power supplies and DC power supplies for inverters for motor drives.

When a large voltage conversion control is required for a DC-DC converter, if voltage control is performed only by switching duty by hard switching, the efficiency will be significantly reduced, and the DC-DC converter will be isolated between the DC power supply and the DC output. If not, there is a problem that the applicable range is limited.

For this reason, as one of the devices that insulate by interposing a transformer, the DC power supply is once converted to AC, converted to a voltage that can obtain the voltage output required by the transformer, and then the rectifier circuit and filter circuit are installed. An isolated DC-DC converter that obtains a DC output via a DC output is used.

A high frequency AC voltage is required to reduce the size and weight of this transformer. However, when a high frequency voltage is generated by an inverter, hard switching that switches regardless of the flowing current causes switching loss, switching noise, etc. Causes the problem of.

For this reason, various DC-DC converters using soft switching control that switches in a state where the voltage or current is zero or close to zero have been proposed instead of the problematic hard switching control, but vibration due to LC resonance action. There are problems such as an increase in current loss and an increase in element withstand voltage, and partial resonance has been proposed as a countermeasure, but the circuit configuration and control system tend to become complicated.

Japanese Unexamined Patent Publication No. 1-157273 Japanese Unexamined Patent Publication No. 1-218352 Japanese Unexamined Patent Publication No. 4-368464 Japanese Unexamined Patent Publication No. 2011-2111886 Japanese Unexamined Patent Publication No. 2013-201833 International Publication No. 2017/090118 Japanese Unexamined Patent Publication No. 2010-4724 Japanese Patent Application Laid-Open No. 2003-2596343 Japanese Patent Application No. 2016-181995 Patent No. 6667750

Among the prior art documents relating to the resonance soft switching control method so far, the prior art documents characteristic of the isolated DC-DC converter are classified into the circuit form and the control method. It differs from the DC converter in the following points.

The present invention uses a zero-current switch action, and among the prior art documents, (Patent Document 1) to (Patent Document 8) use the zero-current switch (ZCS) action, but (Patent Document 9) has a zero voltage. Due to the switch (ZVS) action, the basic control means of the soft switch itself is different from that of the present invention.

Next, since both (Patent Document 1) and (Patent Document 2) have a forward converter configuration, the circuit configuration is different from that of the present invention, and the voltage of the resonant capacitor is lowered to zero voltage every cycle even in the control principle. It is also a big difference in that it is.

Further, from (Patent Document 3) to (Patent Document 6), the main circuit is composed of an inverter, a transformer, a resonant inductor, a diode bridge rectifying circuit, a resonant circuit using a resonant capacitor, and an LC filter circuit. Although it is similar to the circuit configuration of the present invention, it is described in that the control means of the zero current switch is taken by connecting a switch circuit for performing resonance operation in series or in parallel with the resonance capacitor. The circuit configuration and control means are different from the invention.

In (Patent Document 7) and (Patent Document 8), a resonance circuit is configured by using an inverter, a transformer, a resonance inductor, a diode bridge rectifier circuit, and a resonance capacitor, and the resonance capacitor is connected in series with the AC circuit. The main circuit configuration and the control method are different from those of the present invention because the configuration is such that only the smoothing capacitor is connected to the main circuit.

For these, (
In), the non-feeding period required for the LC resonance current to switch off at zero or a value close to zero to continue the LC resonance operation is set to the zero voltage period at the output of the voltage square wave inverter, and the resonance operation is performed. Since the control method is adopted in which the switch is turned on again while maintaining the voltage of the resonance capacitor so that it is not lowered so much, the voltage difference between the power supply voltage and the resonance capacitor at the time of turning on the switch can be reduced. A major feature is that the vibration current can be reduced.

For this reason, the DCDC converter using this current resonance type soft switching control method has a transformer interposed in the DC voltage source, so that a large voltage control can be performed with high efficiency and the DC output voltage can be controlled. It can be said that it is a very useful DCDC conversion control technology that can be expected to be compact, lightweight, and highly efficient while suppressing switching noise in applications that do not necessarily require it.

However, as an output voltage control method, a method of controlling the output of the LC filter circuit by lowering the voltage of the resonance capacitor by providing a non-feeding period for the feeding resonance operation mode from the power supply that performs the soft switching operation. Because of this, a large current may flow in when the power supply switch is turned on from the operation during the non-power supply period, and because the transformer is used, the symmetry of the positive and negative voltages of the voltage applied to the transformer is broken even a little. There is a risk that a large current will flow due to the demagnetization of the transformer, and countermeasures against this will be an issue in practical use.

Figure 1 shows (
) Is the main circuit configuration of the isolated DC-DC converter, and is composed of a voltage square wave inverter, a transformer, a diode full-wave rectifier circuit, an LC resonance circuit, and an LC smoothing circuit.

In addition, (
) Also shows the configuration of FIG. 2 in which the resonant inductor constituting the LC resonant circuit is arranged on the AC circuit side of the diode full-wave rectifier circuit, and the basic operation is the same as that of FIG.

FIG. 3 shows an operation waveform when switching control is applied so that the switching timing of the voltage square wave inverter corresponds to the resonance period of the LC resonance circuit.

FIG. 3A shows an operating waveform when a voltage square wave inverter generates a square wave voltage at a frequency corresponding to the resonance frequency of the LC resonance circuit, and the voltage esw applied to the switch element and the current isw flowing through the element. From the waveform of, when the switch element is turned on, the vibration current starts to flow from zero current by the resonance circuit, and after returning to zero current again, the switch element can be turned off. Zero current soft switching (ZCS: zero current switching) operation Is shown to be feasible.

Further, the figure shows the AC voltage ea and the AC current ia, the resonant inductor current ir of the resonant circuit, and the resonant capacitor voltage er at this time.

Whereas the conventional one using the resonance operation discharges the voltage er of the resonance capacitor to zero voltage every week, (
In this circuit due to), the decrease in the voltage waveform er of the resonant capacitor is suppressed especially when the load becomes light.

Therefore, when the switch is turned on and the voltage is applied, the difference voltage between the power supply voltage and the resonance capacitor voltage becomes small, so that the resonance vibration current ir can be suppressed to a small value. Unlike, the resonance current loss can be suppressed.

In the present invention, the zero current switching operation can be performed by turning off the switch after the period TW in which the resonance current flows ends, but if the switch is switched in a cycle shorter than this period, the soft switching operation cannot be realized. This is a detailed study of the output voltage control method of interest.

The zero current soft switching operation is possible as long as the period TW in which the resonance current flows ends, and the square wave voltage having a positive and negative symmetric waveform with a certain period width until the resonance current flowing in the LC resonance circuit returns to zero. If is generated, not only the LC resonance period width but also the square wave voltage of positive and negative voltage with a fixed period width of an integral multiple of the period width unit is generated, and the zero current switching operation is performed. It can be realized.

FIG. 3B shows the operation waveform when a square wave voltage is generated with a period slightly exceeding twice the period width of the resonance period of the LC resonance circuit as a half period, and the voltage esw applied to the switch element. From the waveform of the current isw flowing through the element, it can be seen that the zero current switching operation is possible.

In this isolated DC-DC converter, if the positive / negative symmetry of the voltage waveform output from the inverter is broken in the control of the output voltage, there is a concern that the transformer will be demagnetized and a large DC current will flow.

As a means to solve this problem, 1) After applying a positive / negative symmetric square wave voltage to the transformer with a voltage square wave inverter, the output voltage is controlled by another switch circuit, which is necessary for resonance control. A method of output control of a period width voltage and a method of 2) a voltage square wave inverter that outputs and controls a square wave voltage of a positive and negative symmetric waveform with a certain period width required for resonance control with respect to output voltage control. Can be considered.

FIG. 4 shows the main circuit configuration of the isolated DC-DC converter in the basic circuit of the resonance control DC-DC converter shown in FIG. 1 in which the DC output of the diode full-wave rectifier circuit is connected to the resonance circuit via a DC switch. Shown.

In the figure, the free foiling diode Df shown by the broken line at the output end of the added DC switch is normally unnecessary to turn off the DC switch when the current flowing through the resonant inductor is zero, but it is not necessary for other operations. The circuit diagram in the case of bypassing the current of the resonant inductor at the time of the occurrence and connecting as necessary for protection to suppress the occurrence of overvoltage is shown.

Also, if there is an inductor in the AC line, if the DC switch is turned off when the current flowing through the DC switch is not zero, an overvoltage will be generated, so it is conceivable to connect a small capacitor to the output terminal of the diode full-wave rectifier circuit. In this case, a backflow prevention series diode may be connected as necessary for protection so that the reverse voltage from the resonance capacitor is not applied to the DC switch.

As a result, the symmetry of the positive and negative voltages is maintained in the transformer regardless of the output voltage control, so that the problem of the demagnetization of the transformer can be solved.

Here, a specific output voltage method of the resonant insulation type DCDC converter by the circuit of FIG. 4 will be described.

FIG. 5 is a DC switching operation waveform when the output is almost 100% without voltage control.

In the voltage type inverter, the square wave voltage is output by the DC switching signals P1 and P2, and the square wave voltage ea is applied to the AC input of the diode full-wave rectifier circuit via the transformer without causing the problem of polarization, which is shown in the figure. _{By turning off the DC switch SW after the period T W in which the} resonance current flows due to the switching signal Psw, the illustrated resonance current ir flows, and the AC current ia is the waveform in which the resonance current ir is switched between positive and negative every half cycle. It becomes the current of.

Since the square wave inverter and the DC switch move to the off operation after the resonance current becomes zero, the zero current switching operation can be realized.

FIG. 6 shows an operation waveform when the switching period Ts of the square wave inverter is long and the frequency fs is lowered under the same resonance circuit constant and the pulse width Tw of the switching signal Psw is constant.

At this time, since a square wave voltage having positive and negative symmetry is applied to the transformer, there is no problem of deviation due to the asymmetry of the positive and negative voltage waveforms, and the DC switch Sw is controlled on and off by the switching signal Psw, so that the resonance current is resonated. Although ir flows, it shows that the interval between pulses becomes wider and the period of the alternating current ia becomes longer.

FIG. 7 is an enlarged display of these operation waveforms. In contrast to the operation waveform at almost 100% output in FIG. 7A, FIG. 7B shows that the pulse width Tw is constant and constant. It is an operation waveform when the switching period Ts of is lengthened.

From the figure, it can be seen that by lengthening the switching cycle Ts, the discharge period of the terminal voltage of the resonant capacitor is lengthened, so that the average voltage is lowered and the output voltage can be controlled.

When the output voltage is controlled by lowering the resonance capacitor voltage, even if the resonance frequency of the resonance circuit is the same, if the capacitance value of the resonance capacitor Cr is large, the voltage of the resonance capacitor drops when the switching cycle is lengthened. Since the inductance value of the resonant inductor Lr is small, a large current will flow in when the DC switch is turned on again.

On the contrary, if the capacitance value of the resonant capacitor Cr is small and the inductance value of the resonant inductor Lr is increased, the voltage drop of the capacitor during the non-feeding period becomes large, the voltage control becomes easy, and the DC switch is turned on again. The current from the power supply can be kept small.

By passing the DC output voltage through the LC smoothing circuit with respect to the resonance capacitor voltage, the load current fluctuation can be suppressed by the smoothing inductor, and the voltage fluctuation of the resonance capacitor is suppressed by the smoothing capacitor to obtain a voltage waveform with less pulsation. Can be done.

FIG. 8 shows a configuration example of a control system for a main circuit configuration in which the main control unit of a resonance-isolated DCDC converter based on this control principle is composed of a voltage-type square wave inverter and a DC switch circuit.

As shown in the figure, the switching pulses P1 and P2 are used as the switching control signal of the square wave inverter in the switching signal generator, and the switching signal Psw having a constant switching pulse width Tw determined by the resonance circuit constant is used as the switching signal of the DC switch Sw. , The DC output voltage can be controlled by changing the switching frequency or the switching cycle.

On the other hand, in the main circuit configuration of FIG. 1 or 2 in which the DC switch circuit is not connected, the voltage square wave inverter is operated by a switching signal that outputs a positive / negative symmetric voltage waveform having a constant switching pulse width Tw determined by the resonance circuit constant. The DC output voltage can be controlled by changing the switching frequency or the switching cycle.

Resonates by turning off the switch signal or adding a switching signal that outputs zero voltage to the square wave switching signal except during the period when the voltage type square wave inverter outputs a positive / negative symmetric voltage waveform with a constant switching pulse width Tw. It is possible to generate the voltage waveform required for operation.

FIG. 9 shows a configuration example of a control system for a main circuit configuration in which the main control unit of the resonance-insulated DCDC converter based on this control principle is composed only of a voltage-type square wave inverter.

In the figure, a zero voltage period is added at the switching signal generator so that a positive or negative symmetric voltage having a period of a constant switching pulse width Tw determined by the resonance circuit constant can be output as a signal to the voltage square wave inverter. The switching pulses P 1 _SW and P ₂ sw are used as the switching control signals of the square wave inverter, and are shown together with the operating waveform of the control system that controls the DC output voltage by changing the switching frequency or switching cycle.

As described above, in the resonance-insulated DCDC converter of the present invention, the resonance operation can flow a resonance current with a magnitude corresponding to the load current, and when the resonance current is zero, the switch can be turned on and off, so that switching can be performed. Loss and switching noise can be reduced (
) Has a major feature.

(
), In response to the concern about demagnetization due to the use of a transformer, in the present invention, after applying a positive / negative symmetric square wave voltage to the transformer with a voltage square wave inverter, By controlling the voltage applied to the resonance circuit via the DC switch, the output voltage can be easily controlled by the switching frequency control while solving the problem of the demagnetization of the transformer.

Further, in the present invention, in the voltage type square wave inverter, the main circuit configuration is changed by a method of applying a square wave voltage having a positive / negative symmetric waveform with a certain period width required for resonance control to the control of the output voltage. It is possible to control the output voltage by switching frequency control while solving the problem of the demagnetization of the transformer.

In the present invention, when the output voltage is controlled by controlling the voltage of the resonance capacitor, if the capacitance value of the resonance capacitor Cr is reduced and the inductance value of the resonance inductor Lr is selected as a constant of the resonance circuit, no power supply is supplied. It was clarified that since the decrease in the capacitor voltage during the period becomes large, the voltage control becomes easy and the current from the power supply when the DC switch is turned on again can be suppressed to a small value.

Further, in the present invention, the zero current soft switching operation is possible as long as the period TW in which the resonance current flows ends, and the positive and negative of a certain period width until the resonance current flowing in the LC resonance circuit returns to zero. If a square wave voltage with a symmetric waveform is generated, not only the LC resonance period width but also a square wave voltage with a fixed period width of an integral multiple of the period width unit can be generated. For example, it was shown that zero current switching operation can be realized.

Current resonance type soft switchon control basic circuit example 1 Current resonance type soft switchon control basic circuit example 2 Basic operating waveform and resonance frequency of switching control Current resonance type soft switchon control circuit with a DC switch added Combination control operation waveform with DC switch Combination frequency control operation waveform with DC switch DC voltage control operation waveform by resonance capacitor voltage control Combination with DC switch Soft switching control system (A type) Soft switching control system using only basic circuits (B type) DC voltage control system (A type) DC current control system (A type) DC voltage current control system (A type) DC voltage control system (B type) DC current control system (B type) DC voltage current control system (B type) DC voltage control system with transformer demagnetization suppression (B type) A type simulation analysis circuit Soft switching operation waveform in A type Frequency control operation waveform in A type A type DC voltage control operation waveform A type DC current control operation waveform B type simulation analysis circuit Soft switching operation waveform in B type Soft switching operation waveform when controlling the resonance period width twice Frequency control operation waveform in B type B type DC voltage control operation waveform B type DC current control operation waveform Demagnetization suppression characteristics during B-type DC current control

As a DCDC converter control system for carrying out the present invention, 1) A type (FIG. 8) in which a switch control unit is added and controlled by a main circuit configuration, and 2) B type in which configuration control is performed only by a basic circuit (FIG. 8). A specific configuration example of the frequency control system for the two basic control systems of 9) is shown below.

FIG. 10 shows a configuration example of a DC voltage control system using the A type, which detects a DC output voltage and controls the switching frequency via a voltage controller so that the average voltage eo matches the DC reference voltage Edr. Then, while operating the voltage inverter with the clock from the voltage control oscillator, it is possible to configure a concrete control system by applying a voltage with a constant switching pulse width Tw determined by the resonance circuit constant in the DC switch circuit to the resonance circuit. it can.

FIG. 11 shows a configuration example of a DC current control system using the A type, which detects a DC load current or a smoothing inductor current and switches the current through a current controller so that the average current matches the DC reference current Idr. It controls the frequency.

FIG. 12 shows a configuration example of a DC voltage / current control system using the A type. The DC output voltage is detected, and the DC reference current Idr is set via the voltage controller so that the average voltage eo matches the DC reference voltage Edr. The switching frequency is controlled via a current controller so that the average current of the generated DC load current or the current of the smoothing inductor matches this DC reference current Idr.

In this control system, if it is within the controllable range, the DC voltage and the DC current can be controlled so as to match the respective reference values, and the current is provided by providing a limiter in the amount of generating the reference current. You can put restrictions.

FIG. 13 shows a configuration example of a DC voltage control system using the B type. Similar to the A type, the DC output voltage is detected and switched via the voltage controller so that the average voltage eo matches the DC reference voltage Edr. The frequency can be controlled.

_{In the B type, switching pulses P1 SW} and P2sw with a zero voltage period are generated at the switching signal generator so that positive and negative symmetric voltages having a period of a constant switching pulse width Tw determined by the resonant circuit constant can be output. Then, it is input as a drive signal of the inverter.

FIG. 14 is a configuration example of a DC current control system using the B type, and the configuration can be controlled in the same manner as the A type.

FIG. 15 is a configuration example of a DC voltage / current control system using the B type, and the configuration can be controlled in the same manner as the A type.

FIG. 16 shows a B-type DC voltage control system that detects the primary current from the inverter to the transformer and prevents the DC component current from flowing during the switching pulse width Tw of the _{switching pulse signal P 1SW} or P _{2 sw.} The control system which added the part which suppresses the eccentricity of the transformer which adjusts is shown.

As an example of the resonant insulation type DCDC converter of the present invention, first, the basic control operation of the A type voltage-current control system is confirmed from the simulation analysis result.

FIG. 17 is a simulation circuit of an A type voltage / current control system, FIG. 17A is a circuit in which a resonant inductor is connected to the DC output side of a diode full-wave rectifier circuit, and FIG. 17B is a diode full-wave rectifier circuit. The circuit connected to the AC side of the rectifying circuit is shown.

FIG. 18 shows a soft switching control operation waveform in the A type according to the present invention, in which a combination of an AC voltage waveform ea of an inverter via a transformer and a DC switch with a switching signal psw a voltage controlled by a switch is applied to a resonance circuit. The operating waveforms of the resonance inductor current ir and the resonance capacitor voltage er, and the waveforms of the voltage esw1 and current isw1 applied to the switch element of the square wave inverter and the voltage vs. the flowing current ie applied to the DC switch are shown.

Figure (a) shows the operating waveforms when the DC load resistance value is R = 10Ω, and Figure (b) shows the operating waveforms when the DC load resistance value is R = 50Ω. In each case, the switch elements circled in the figure. The zero-current switching operation is confirmed from the voltage and current waveforms applied to.

From the terminal voltage waveform eo of the capacitor, it can be seen that when the load becomes lighter, the resonance capacitor voltage fluctuation becomes smaller, and as a result of having a DC component, the magnitude of the resonance current becomes smaller according to the load state.

FIG. 19 shows an operation waveform when the switching operation frequency is halved from 40 kHz to 20 kHz. The resonance capacitor voltage er decreases, and the DC output voltage eo, which is the average value thereof, also decreases, depending on the switching frequency. It can be confirmed that the DC voltage can be controlled.

FIG. 20 shows an analysis operation waveform in a DC voltage control system using the A type, and FIG. 20A shows a reference voltage when Edr = 50V as a reference voltage at which the DC output voltage becomes 100%. The operation waveform when the voltage is set to 30V is shown.

When the reference voltage becomes low, the flow width of the switching signal Psw to the DC switch is controlled, and as a result, the voltage of the resonance capacitor drops, and the output voltage eo, which is the average value, drops. It can be seen that can be controlled with a voltage value that matches the reference value.

FIG. 21 shows the analysis operation waveform when the resonant inductor is connected to the AC side in the A type DC current control system.

Fig. (A) shows the operating waveform when Idr = 5A as the reference current for which the DC current is 100%, and Fig. (B) shows the operating waveform when the reference current is set to 3A. In both cases, the DC current It can be seen that can be controlled with a current value that matches the reference value.

Next, as an example of the resonance-insulated DCDC converter of the present invention, the basic control operation of the B-type voltage-current control system will be confirmed from the simulation analysis results.

FIG. 22 is a simulation circuit of a B-type voltage-current control system, FIG. 22A is a circuit in which a resonant inductor is connected to the DC output side of a diode full-wave rectifier circuit, and FIG. 22B is a diode full-wave rectifier circuit. The circuit connected to the AC side of the rectifying circuit is shown.

FIG. 23 shows a B-type soft switching control operation waveform according to the present invention, and the inverter outputs a voltage waveform having positive and negative symmetry of a constant switching pulse width Tw, but the same result as the A type is obtained. There is.

FIG. 24 shows an operation waveform when the frequency of the switching operation is halved from 40 kHz to 20 kHz, and it can be confirmed that the same result as in the case of the A type is obtained.

FIG. 25 shows an analysis operation waveform in the DC voltage control system by the B type, and is an operation waveform when the DC reference voltage is set to Edr = 50V and Edr = 30V, and matches the reference value as in the case of the A type. The output voltage is obtained.

FIG. 26 is an analysis operation waveform in the DC current control system by the B type, and is an operation waveform when the DC reference currents are set to Idr = 5A and Idr = 3A, and matches the reference values as in the case of the A type. It can be seen that the current control is performed.

FIG. 27 shows a circuit including an excitation circuit of a transformer in a B-type DC voltage control system, in which compensation control of the pulse width of the output voltage of the inverter is applied based on the DC component current of the primary current of the transformer. The comparison of the operation waveforms based on the simulation analysis results when the voltage is applied and when the voltage is not applied is shown.

Fig. (A) shows the control result when the demagnetization compensation control of the transformer is not applied, and Fig. (B) shows the control result when the demagnetization compensation control of the transformer is added. In im, the former contains a DC component current, whereas the latter contains almost no DC component current, and the demagnetization compensation control effect can be confirmed.

Finally, FIG. 28 shows a case where the resonance period is halved by halving both the resonance inductance and the resonance capacitance of the LC resonance circuit while the switching frequency is constant at 40 kHz in the resonance insulation type DCDC converter according to the present invention. The simulation analysis result of is shown. ..

Fig. (A) shows the operating waveforms of the A type and Fig. (A) shows the operating waveforms of the B type. In both cases, the resonance current flows at twice the frequency, but the vibration current is zero at the switching timing. It can be confirmed from the voltage and current waveforms of the switch that zero-current soft switching control is realized.

100 ... DC voltage source 200 ... Main circuit of resonance-isolated DCDC converter 210 ... Voltage square is inverter 220 ... Transformer 230 ... Diode full-wave rectifier circuit 240 ... DC switch circuit 250 ... LC resonance circuit 260 ... LC smoothing circuit 300 ... Load 400 ... Resonant isolated DCDC converter control circuit unit 410 ... Switching signal generator 420 ... DC current control unit 430 ... DC voltage control unit 440 ... Square wave pulse width control unit

Claims (8)

The output transformed into the required AC voltage via a transformer with respect to the AC output of the voltage square wave inverter connected to the DC voltage source is rectified by a diode full-wave rectifier circuit, and the switch alone or when the switch is turned off if necessary. An LC smoothing circuit composed of a smoothing inductor and a smoothing capacitor is connected to both ends of the resonance capacitor via a DC switch circuit composed of a free foiling diode for protection and connected to an LC resonance circuit composed of a resonance inductor and a resonance capacitor. In a DC-AC-DC conversion circuit that connects and leads to a DC load
In the voltage square wave inverter, a square wave voltage having a constant period width that depends on the resonance period width until the resonance current flowing by applying a voltage to the LC resonance circuit returns to zero or a period width that is an integral multiple of the resonance period width. Is generated, and the DC switch circuit is turned on every half cycle in synchronization with the square wave voltage waveform for a period that substantially matches the resonance cycle width of the LC resonance circuit or a cycle width that is an integral multiple of the resonance cycle width, and then the off period is set. By adding an on / off voltage waveform whose switching cycle is the switching operation to be input to the LC resonant circuit,
The transformer and the transformer by the high frequency switching operation can reduce the switching loss and the switching noise by operating the switching operation at a value where the current flowing through the switching element of the voltage type square wave inverter and the DC switch circuit is zero or almost zero. A resonance-insulated DC-DC converter characterized by being able to reduce the size and weight of an LC resonance circuit, the LC smoothing circuit, and the like. The resonance-insulated DC-DC converter according to claim 1, wherein the DC voltage and the DC current are controlled by changing the switching period of the voltage square wave inverter and the DC switch circuit. DC-DC converter. In the resonance-insulated DC-DC converter according to claims 1 and 2, the DC voltage is controlled by controlling the switching cycle so that the average voltage of the terminal voltage of the DC load or the resonance capacitor matches the reference voltage. A resonant isolated DCDC converter characterized by In the resonance-insulated DC-DC converter according to claims 1 and 2, the DC current is controlled by controlling the switching cycle so that the average value of the current flowing through the DC load or the smoothing inductor matches the reference current. A resonant isolated DCDC converter characterized by In the resonance-insulated DC-DC converter according to claims 1 and 2, a reference current is generated so that the average voltage of the terminal voltage of the DC load or the resonance capacitor matches the reference voltage, and the DC load is combined with the reference current. Alternatively, a resonance-isolated DCDC converter characterized in that a DC voltage and a DC current are controlled by controlling the switching cycle so that the average values of the currents flowing through the smoothing inductor match. In the resonance-isolated DC-DC converter according to claims 1 to 5, the DC switch circuit is removed, and instead of the switching operation during the off period of the DC switch circuit, the square wave switching signal of the voltage square wave inverter is turned off. Or, by operating the voltage square wave inverter with a square wave switching signal including a zero voltage period and controlling the waveform of the positive and negative symmetric square wave voltage, the current flowing through the switching element becomes zero or a value close to zero. A resonance-isolated DC-DC converter characterized in that a switching operation is possible and a DC voltage and a DC current are controlled by changing the switching cycle of the voltage type square wave inverter. The resonance-insulated DC-DC converter according to claims 1 to 6, wherein the resonance inductor connected to the DC side of the diode full-wave rectifier circuit is changed and connected to the AC side for control. Type DC-DC converter. In the resonance-insulated DC-DC converter according to claims 1 to 7, the width of the positive voltage period or the negative voltage period of the voltage square wave inverter is set so that the DC component current due to the demagnetization of the transformer does not flow. A resonance-isolated DC-DC converter characterized by adding a control unit to be adjusted for control.

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