JPH0823673A - Switching power unit and its insulating method - Google Patents

Abstract

PURPOSE:To prevent the copper loss without requiring any intense high-frequency alternating field by supplying high-frequency power generated from a high-frequency switching power source circuit to a load through an insulation circuit composed of capacitors. CONSTITUTION:An insulation circuit is composed of capacitors C. and C2. Insulating barriers are constituted between primary-side terminals A and B and secondary-side terminals C and D. Because of the barriers 45 constituted of the capacitors, the terminals C and D are electrically floated from the terminals A and B. The terminal A is connected to the connecting point A1 between the capacitors CS1 and CS2 of a high-frequency switching power source circuit 1 and the terminal B is connecting to the connecting point B1 between switching elements S1 and S2. The terminals C and D are connected to a frequency converting circuit 7. Then the high-frequency power inputted to the primary side of the insulation circuit 20 is transmitted to the secondary side of the circuit 20 through an electric field passing through dielectric substances in the capacitors C1 and C2.

Description

The present invention relates to a switching power supply device and an insulating method thereof. More specifically, the present invention relates to a switching power supply device for connecting a load to a high-frequency switching power supply circuit that outputs high-frequency power through an insulation circuit, and an insulating method thereof.

[Prior Art] Conventionally, in order to prevent annoying noise from being generated in a switching power supply device using a high frequency switching power supply circuit that outputs high-frequency power, its operating frequency (switching frequency) must be equal to or higher than the audible frequency, that is, Generally, it is selected to be about 20 kHz or more. At present, operating frequencies have been achieved up to several MHz with the breakthrough of semiconductor switching elements for electric power. Such improvement in operating frequency enables the switching power supply to be smaller and lighter, and has the advantages of reducing the number of windings of the high frequency transformer for insulation and reducing the capacity of the passive elements such as reactors and capacitors. . Therefore, increasing the operating frequency has become an essential technology for reducing the size and weight of switching power supply devices.

 FIG. 3 is a diagram showing an example of a conventional switching power supply device. Referring to FIG. 3, a DC power supply E is connected to the high frequency switching power supply circuit 1.

The high-frequency switching power supply circuit 1 is a self-extinguishing high-speed switching circuit in which first and second capacitors CS1 and CS2 are connected in series and are connected in series and are connected in parallel to the capacitors CS1 and CS2. It is composed of elements S1 and S2. Each of the switching elements S1 and S2 is composed of a power MOSFET having a built-in freewheeling diode. A control pulse is applied from a control circuit (not shown) to the control terminals (gates) of the switching elements S1 and S2.

 Primary terminals A and B of the insulation circuit 2 are connected to a connection point A1 between the capacitors C S1 and CS2 and a connection point B1 between the switching elements S1 and S2 of the high frequency switching power supply circuit 1. The insulating circuit 2 is composed of a high frequency transformer T. A frequency conversion circuit 7 consisting of a high speed diode is connected to the secondary side terminals C and D of the insulating circuit 2, and a load circuit 4 is connected to the output side of the frequency conversion circuit 7.

The high frequency transformer T described above forms the insulating barrier 44 between the primary side terminals A and B and the secondary side terminals C and D.

 Next, the operation of the conventional switching power supply device shown in FIG. 3 will be described. When a control pulse is alternately applied to the control terminals of the switching elements S1 and S2, these switching elements S1 and S2 are alternately conducted, and the voltage applied between the primary side terminals A and B of the insulating circuit 2 is alternated. It is inverted and high frequency power is generated. This high frequency power is transmitted to the secondary side terminals C and D by using the magnetic field as a medium inside the high frequency transformer T of the insulating circuit 2. That is, the high frequency power is transmitted to the frequency conversion circuit 7 side via the magnetic field passing through the insulating barrier 44. This high frequency power is frequency converted into DC power by the frequency conversion circuit 7 and supplied to the load circuit 4.

[Problems to be Solved by the Invention] As described above, the high frequency transformer T is exclusively used for the insulation circuit 2 of the conventional high frequency switching power supply device. However, when the high frequency transformer T becomes excited at a high frequency, the loss of the transformer increases. The loss of this transformer consists of iron loss due to magnetic materials, copper loss due to windings, etc., and due to the increase of these losses with higher frequencies, the power conversion efficiency of high-frequency switching power supply units decreases. Not only that, but measures to dissipate the heat due to the loss are becoming a problem.

 It has also been pointed out that the electromagnetic field radiated from the high frequency transformer T causes problems in the electromagnetic environment, such as causing interference noise to other electronic devices. Therefore, in order to remove the interference noise radiated from the high frequency transformer T, a magnetic shield may be used. However, magnetic shields are generally harder to achieve a higher shield effect than electric field shields, and they are often very difficult to shield the interference noise from high-frequency transformer T, which is very difficult. Has become one of the problems.

 Furthermore, in principle, heavy objects such as the core and winding conductor of the high frequency transformer T made of magnetic material such as ferrite or cobalt-based amorphous material are required, and these are a major obstacle to downsizing and weight saving of the switching power supply. ing.

 Therefore, a main object of the present invention is to provide a switching power supply device and a method of insulating a switching power supply device that can reduce loss.

 Another object of the present invention is to provide a switching power supply device and a method of insulating a switching power supply device that can improve an electromagnetic environment without giving a fault noise to other electronic devices.

 Still another object of the present invention is to provide a switching power supply device suitable for reduction in size and weight and a method of insulating the switching power supply device.

[Means for Solving the Problems] The invention according to the first aspect provides a load to an output of a high-frequency switching power supply circuit which switches power from a power supply and outputs high-frequency power higher than an audible frequency, through an insulation circuit. In the connected switching power supply unit, the insulation circuit consists of an insulation barrier composed of a capacitor.

 According to a second aspect of the present invention, a DC power supply, a high frequency switching power supply circuit that outputs high frequency power based on the DC power from the DC power supply in response to a pulse signal having a frequency equal to or higher than an audible frequency, and In the switching power supply device having the insulation circuit connected between the output of the high-frequency switching power supply circuit and the load, the insulation circuit is composed of a capacitor.

 According to a third aspect of the present invention, an AC power supply, a high frequency switching power supply circuit that outputs a high frequency power based on the AC power from the AC power supply in response to a pulse signal having a frequency equal to or higher than an audible frequency; In a switching power supply device having an insulating circuit connected between the output of a high frequency switching power supply circuit and a load, the insulating circuit is composed of a capacitor.

 The invention according to a fourth aspect includes a frequency conversion circuit that is connected between the load and the capacitor according to any one of the first to third aspects of the invention and that frequency-converts high-frequency power.

 The invention according to claim 5 is a switching power supply device for supplying electric power to a load, and a high frequency switching power supply circuit for switching electric power from the power supply to output electric power of a frequency higher than the electric power from the power supply, the high frequency An insulating circuit that is connected between the switching power supply circuit and the load and that forms an insulating barrier between the high-frequency switching power supply circuit and the load, and a common that passes through the insulating barrier. It includes a filter circuit connected to suppress or block the mode current.

 The invention according to claim 6 is a switching power supply device according to claim 5, wherein the filter circuit includes a common mode choke for suppressing a common mode current passing through the insulation barrier.

 The invention according to claim 7 is the switching power supply device according to claim 5, wherein the filter circuit includes a reactor for suppressing a common mode current passing through the insulating barrier.

 The invention according to claim 8 is a switching power supply device for supplying power to a load, the high-frequency switching power supply circuit switching power from the power supply and outputting high-frequency power having a frequency higher than the power from the power supply. A frequency conversion circuit connected to the output of the high-frequency switching power supply circuit for frequency-converting the high-frequency power output from the high-frequency switching power supply circuit to supply power having a frequency lower than the high-frequency power to a load; and the high-frequency switching circuit. An insulating circuit which is connected between the output of the power supply circuit and the input of the frequency conversion circuit, and which comprises a capacitor that forms an insulating barrier between the output of the high frequency switching power supply circuit and the input of the frequency conversion circuit; and Connected to suppress or cut off the common mode current passing through the insulation barrier Including the filter circuit.

 The invention according to claim 9 is a switching power supply device according to claim 8, wherein the filter circuit is connected so as to suppress a common mode current passing through the insulation barrier. Comprising ku.

 The invention according to claim 10 is the switching power supply device according to claim 8, wherein the filter circuit includes a reactor connected to suppress a common mode current passing through the insulation barrier. .

 According to an eleventh aspect of the present invention, there is provided a step of performing a frequency conversion by switching electric power from a power source into electric power having a frequency higher than that of the electric power from the power source, and supplying the electric power of the high frequency with an electric field as a medium in an insulating barrier. And the step of passing it.

 According to a twelfth aspect of the present invention, the step of switching the electric power from the power source to frequency-convert it into electric power of a frequency higher than the electric power from the power source, and passing the electric power of the high frequency through an insulating barrier composed of a capacitor The method comprises the steps of: switching the high frequency power that has passed through the insulation barrier and converting the high frequency power into a low frequency power.

 The invention according to claim 13 is an insulation method according to claims 11 and 12, characterized in that it further comprises the step of suppressing a common mode current passing through the insulation barrier.

 The invention according to claim 14 is an insulation method according to claims 11, 12, and 13, characterized in that the power of the high frequency is power of an audible frequency or higher.

 The invention according to claim 15 is an insulation method according to claims 13 and 14, wherein the common mode current is suppressed by using a common mode choke.

 The invention according to claim 16 is an insulation method according to claims 13 and 14, wherein the common mode current is suppressed by using a reactor.

[Operation] According to the present invention, the high-frequency power generated by the high-frequency switching power supply circuit is supplied to the load through the insulating circuit including the capacitor. Therefore, the insulating circuit is made of a magnetic material as in the conventional case. Compared with the case, high frequency alternating magnetic field is not required, and therefore iron loss and copper loss caused by winding current and winding resistance do not occur.

 Further, since a winding coil for insulation that forms high-frequency magnetic flux can be eliminated, substantially no high-frequency leakage magnetic flux is generated from the insulating circuit.

[Embodiment of the Invention] FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention. Referring to FIG. 1, the DC power supply E, the high frequency switching power supply circuit 1, the load circuit 4 and the frequency conversion circuit 7 are constructed in the same manner as in FIG. The insulation circuit 20 is composed of the capacitors C1 and C2, and the insulation barrier 45 is composed between the primary side terminals A and B and the secondary side terminals C and D. Due to the insulating barrier 45 formed by this capacitor, the secondary side terminals C and D are electrically floated with respect to the primary side terminals A and B. The primary side terminal A is connected to the connection point A1 between the capacitors CS1 and CS2 of the high frequency switching power supply circuit 1, and the primary side terminal B is connected to the connection point B1 between the switching elements S1 and S2. The secondary side terminals C and D are connected to the frequency conversion circuit 7. Then, the high frequency power input to the primary side of the insulating circuit 20 is transmitted to the secondary side through the electric field passing through the dielectric inside the capacitors C1 and C2 as a medium.

The dielectric material inside the capacitors C1 and C2 is made of an insulating material. That is, high frequency power is transmitted to the frequency conversion circuit 7 side through the electric field in the insulating barrier 45. The high frequency power that has passed through the insulating barrier 45 is frequency-converted into DC power by the frequency conversion circuit 7 and supplied to the load circuit 4.

 Next, the operation of the embodiment shown in FIG. 1 will be described. Now, in order to supply high frequency power to the frequency conversion circuit 7, a control pulse of, for example, a switching frequency of 400 kHz is applied to the control terminals of the first switching element S1 and the second switching element S2 of the high frequency switching power supply circuit 1. Can be given alternately. In response to this control pulse, the switching elements S1 and S2 are alternately conducted, and the primary terminals A and B of the insulating circuit 20 are supplied with a somewhat or almost square wave AC voltage of 400 kHz. .

 Here, the inverter operation of the high frequency switching power supply circuit 1 will be described in more detail. First, the control terminal of the switching element S 1 is turned on and the control terminal of the switching element S 2 is turned off for a time of 1 μsec. To be done. When the switching element S1 is turned on and the switching element S2 is turned off in response to the control pulse of the control terminal, the voltage of the capacitor CS1 is output between the connection point A1 and the connection point B1. It

 Next, when the control terminal of the switching element S1 is turned off and the control terminal of the switching element S2 is turned on, the polarity of the output voltage is inverted, but before that, 0.25 μsec is applied to prevent arm short circuit. During this period, a dead time is provided to turn off the control terminals of all the switching elements S1 and S2.

This is because the switching elements S1 and S2 above and below the arm are turned on at the same time regardless of the control pulse signal from the control terminal due to the storage time of the switching elements S1 and S2, etc., and arm short circuit does not occur. is there. Therefore, during this dead time period, the control terminals of all the switching elements S1 and S2 are turned off. Of course, the length of this dead time must be longer than the switching time of the switching element used. In the case of this embodiment, a finite time width required for switching the switching elements S 1 and S 2 from on to off and from off to on, that is, a so-called switching time is set to about 0.15 μsec. The output voltage is a non-controlled period during the dead time, and the polarity of the output voltage is determined by the switching characteristics of the switching elements S1 and S2, the load current, etc., and can be said to be indeterminate. This dead time period is one of the causes of the generation of the low frequency component voltage of the output voltage.

 After the dead time period ends, the control terminal of the switching element S1 is turned off and the control terminal of the switching element S2 is turned on for a time of 1 μsec. When the switching element S1 is turned off and the switching element S2 is turned on, the voltage of the capacitor CS2 is applied between the connection point A1 and the connection point B1, and the connection point A1 is connected to the connection point B1. On the contrary, it becomes negative. After that, a dead time period of 0.25 μsec is provided again.

 By repeating the above operation, a high frequency voltage of 400 kHz is output to the connection points A1 and B1. This high frequency voltage is supplied to the frequency conversion circuit 7 through the insulating barrier 45 constituted by the capacitors C1 and C2. The high frequency power input to the frequency conversion circuit 7 is frequency-converted by the frequency conversion circuit 7 into power having the smallest frequency, that is, DC power. Here, the capacitors C1 and C2 have a low impedance with respect to the high frequency voltage of 400 kHz output between the connection points A1 and B1, and the installation of the capacitors C1 and C2 hardly affects the transmission of high frequency power. It won't come.

 However, the insulating barrier 45 formed by the capacitors C1 and C2 exhibits an infinite impedance with respect to frequency zero, that is, direct current. Further, these capacitors C1 and C2 exhibit extremely high impedance with respect to the commercial power frequency (50 Hz or 60 Hz). That is, the impedance value indicated by the capacitors C1 and C2 is inversely proportional to the frequency. Therefore, the value at 50 Hz is as high as 400 kHz / 50 Hz = 8000 times the impedance value at 400 kHz. Therefore, for low frequencies, leakage of electric energy that is as weak as a signal can be substantially ignored as a switching power supply device. Therefore, due to higher frequencies, the insulation circuit can be used effectively as an insulation circuit as a switching power supply device not only for direct currents but also for power frequencies around commercial frequencies.

That is, it can be used as an insulating circuit for the electric power of the DC power supply and the commercial power supply. This was achieved by increasing the frequency of the switching power supply, and if the output frequency of the high-frequency switching power supply circuit is not very high compared to the commercial power supply frequency, for example, at frequencies below the audible frequency of about 400 Hz. Since the frequency ratio to the commercial frequency is as small as 400Hz / 50Hz = 8 times, the capacitors C1 and C2 that compose the barrier inevitably have extremely large capacities, and in principle, they are used as the power supply insulation circuit for the commercial power supply. It's difficult.

 As described above, the high frequency power is transmitted to the frequency conversion circuit 7 through the insulating barrier 45 that electrically floats the frequency conversion circuit 7 or the load circuit 4 with respect to the high frequency switching power supply circuit 1.

 On the other hand, due to the insulating barrier 45, DC power and low-frequency power of about commercial frequency can hardly pass through the insulating barrier 45.

 FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In the embodiment shown in FIG. 2, an AC power supply EAC having a commercial frequency is used in place of the DC power supply E on the input side shown in FIG. 1, and then a rectifying circuit 8 for rectifying the AC power supply EAC is used. Is added to the input side of the high frequency switching power supply circuit 10, and the other configurations are the same as those in FIG. Further, in this embodiment, the operation is the same as that of FIG. 1 described above except that the AC power supply EAC on the input side is subjected to full-wave shunting, and therefore detailed description thereof will be omitted.

 In the embodiment shown in FIG. 1, the high frequency switching power supply circuit 1 is configured by the capacitors CS1 and CS2 and the switching elements S1 and S2, but the high frequency switching power supply circuit is not limited to this. May be used. Similarly, the frequency conversion circuit 7 and the load circuit 4 are not limited to those shown in FIG.

 FIG. 4 is an electric circuit diagram of the third embodiment of the present invention. In the embodiment shown in FIG. 4, a filter circuit 5 composed of a common mode choke is connected to the power line between the insulation circuit 20 and the frequency conversion circuit 7, and other configurations are used. Is the same as the embodiment shown in FIG. The filter circuit 5 basically has an infinite impedance between the ground on the input power supply side and the ground on the output load side, that is, when the input and output grounds are completely electrically independent, basically. Unnecessary. However, when the impedance between the input and output grounds is not high impedance with respect to the switching frequency of the high frequency switching power supply circuit 1, the filter circuit 5 plays an important role. For example, when the impedance between the input and output grounds is low impedance with respect to the switching frequency of the high frequency switching power supply circuit 1 and the filter circuit 5 is not provided, the switching operation of the high frequency switching power supply circuit 1 is performed. As a result, a large impulse-like common mode current flows through the insulating circuit 20 via the input / output ground. As a result, the charge amounts of the capacitors C1 and C2 forming the insulating barrier wall 45 change rapidly. Therefore, a large impulse current flows through the switching elements S1 and S2 that form the high-frequency switching power supply circuit 1, leading to the destruction of these switching elements S1 and S2.

 However, this problem is solved by connecting the filter circuit 5 to the power line as shown in FIG. That is, if the value of the inductance of the common mode choke constituting the filter circuit 5 is high impedance with respect to the switching operation frequency of the high frequency switching power supply circuit 1, the insulating circuit 20 is switched every time the high frequency switching power supply circuit 1 switches. The current flowing between the input and output grounds via the input terminal, that is, the common mode current is effectively suppressed by the filter circuit 5.

 Therefore, the voltage of the capacitor C2 does not abruptly change due to the high frequency current in the common mode by the filter circuit 5, and the voltages of the capacitors C1 and C2 forming the insulation barrier 45 are stabilized. When the common mode choke is completely coupled, the filter circuit 5 theoretically does not act as an impedance with respect to the normal mode. That is, the common mode cheek has zero impedance in the normal mode. Therefore, basically, the normal mode high frequency power output from the high frequency switching power supply circuit 1 is not blocked from being transmitted to the frequency conversion circuit 7.

 In other words, the high-frequency switching power supply circuit 1 outputs a high-frequency voltage of 400 kHz between the connection points A1 and B1 in the normal mode, and the filter circuit 5 has a zero impedance in principle. The installation of the filter circuit 5 does not hinder the transmission of electric power. Moreover, the coupling between the winding coils forming the common mode choke is not a perfect coupling or a tight coupling, and even if some normal mode impedance actually exists in the common mode choke, there is no problem in high frequency power transmission.

 The filter circuit 5 is provided between the DC power supply E and the high frequency switching power supply circuit 1 as shown in FIG. 4A which is a modification of the embodiment shown in FIG. 4 or the embodiment shown in FIG. Alternatively, as shown in FIG. 4B, which is another modified example, the connection may be made between the high frequency switching power supply circuit 1 and the insulating circuit 20. Furthermore, as shown in FIG. 4C, one winding coil of the common mode choke forming the filter circuit 5 is provided between the terminal C of the insulating circuit 20 and the frequency conversion circuit 7, and the other winding coil is provided. May be connected between the high-frequency switching power supply circuit 1 and the terminal B of the insulating circuit 20 to suppress the common mode current passing through the insulating barrier 45.

 FIG. 5 is an electric circuit diagram showing a fourth embodiment of the present invention. In the embodiment shown in FIG. 5, the frequency conversion circuit 7 shown in FIG. 4 is removed, the input power supply side, that is, the DC power supply E is connected to the ground G1, and the output load side, that is, the load circuit 4 is connected. It is connected to the land G2 and further connected between the grounds G1 and G2 via an impedance Z. In the filter circuit 5 in this embodiment, the value of the common mode inductance is high impedance with respect to the switching frequency of the high frequency switching power supply circuit 1 as in the case of FIG.

As a result, in response to the switching of the high frequency switching power supply circuit 1, the voltages of the capacitors C1 and C2 forming the insulating circuit 20 do not change suddenly, and the impedance Z of the input / output grounds G1 and G2 is low. The filter circuit 5 effectively suppresses the common mode current flowing through the impedance Z through the insulating barrier 45 even if the impedance or zero impedance is present. Therefore, the voltage of the capacitor C2 does not suddenly change due to the filter circuit 5, and the voltages of the capacitors C1 and C2 forming the insulating barrier 45 are stabilized.

 As with the embodiment of FIG. 4, many modifications of FIG. 5 are possible. For example, by removing the frequency conversion circuits 7 shown in FIGS. 4A, 4B, and 4C, several kinds of modifications shown in FIG. 5 can be obtained.

 FIG. 6 is an electric circuit diagram showing a fifth embodiment of the present invention. In the embodiment shown in FIG. 6, the connection between the filter circuit 5 and the frequency conversion circuit 7 of the embodiment shown in FIG. 4 is replaced. In this embodiment as well, as in the embodiment shown in FIG. 4, the filter circuit 5 has a high impedance in the common mode inductance with respect to the switching frequency of the high frequency switching power supply circuit 1. As a result, the common mode current passing through the insulation barrier 45 is effectively cut off by the common mode choke forming the filter circuit 5 every time the high frequency switching power supply circuit 1 switches. Therefore, the voltage of the capacitors C1 and C2 does not suddenly change due to the common mode current by the filter circuit 5, and the voltages of the capacitors C1 and C2 forming the insulating barrier 45 are stabilized.

 FIG. 7 is an electric circuit diagram showing a sixth embodiment of the present invention. In the embodiment shown in FIG. 7, a filter circuit 50 composed of reactors L1 and L2 is connected instead of the filter circuit 5 shown in FIG. The filter circuit 50 has a function of suppressing the common mode current, like the filter circuit 5 of the embodiment shown in FIGS. 4 to 6 described above.

That is, if the inductance values of the reactors L1 and L2 forming the filter circuit 50 are high impedance with respect to the switching operating frequency of the high frequency switching power supply circuit 1, the insulating circuit 20 is switched every time the high frequency switching power supply circuit 1 switches. The high frequency common mode current flowing between the input and output grounds via the filter is effectively suppressed by the filter circuit 50.

 Therefore, the voltage of the capacitor C2 does not suddenly change due to the high frequency current in the common mode by the filter circuit 50, and the voltages of the capacitors C1 and C2 forming the insulating barrier 45 are stabilized.

Further, since the filter circuit 50 acts as an impedance in principle with respect to the normal mode, a filter for smoothing the normal mode high frequency power output from the high frequency switching power supply circuit 1 transmitted to the frequency conversion circuit 7. Also acts as.

 The filter circuit 50 may be connected between the DC power source E and the high frequency switching power source circuit 1 as shown in FIG. 7A which is a modification of the embodiment shown in FIG.

 FIG. 8 is an electric circuit diagram showing a seventh embodiment of the present invention. In the embodiment shown in FIG. 8, a filter circuit 5 composed of a common mode choke is connected to the AC power supply line between the AC power supply EAC and the high frequency switching power supply circuit 10 shown in FIG. It was done. Also in this embodiment, the value of the common mode choke has a high impedance with respect to the switching frequency of the high frequency switching power supply circuit 1, so that the voltages of the capacitors C1 and C2 do not fluctuate abruptly and the insulation barrier wall is not changed. The voltage of the capacitor forming 45 is stabilized.

 It should be noted that the filter circuit 5 is not limited to the embodiment shown in FIG. 8, and the filter circuit 5 may be provided between the high frequency switching power supply circuit 10 and the insulation circuit 20, or between the insulation circuit 20 and the frequency conversion circuit 7, and further for the frequency conversion. You may connect between the circuit 7 and the load circuit 4, etc.

 FIG. 8A is a modification of the embodiment shown in FIG. 8, in which the output side of the rectifier circuit 8 is replaced with the input side of the rectifier circuit 8 where the filter circuit 5 shown in FIG. 8 is installed. It is installed, and the configuration on other main circuits is the same. Even when the filter circuit 5 is installed inside the high frequency switching power supply circuit 11 as in this modification, the common mode choke forming the filter circuit 5 suppresses the common mode current as in FIG. The mode current does not cause the voltages of the capacitors C1 and C2 to fluctuate abruptly, and the voltage of the capacitor forming the insulating barrier 45 is stabilized.

 FIG. 9 is an electric circuit diagram showing an eighth embodiment of the present invention. In the embodiment shown in FIG. 9, the filter circuit 5 composed of the reactors L1 and L2 is connected instead of the filter circuit 5 comprising the common mode choke shown in FIG. This filter circuit 50 also has a function of suppressing the common mode current, similarly to the filter circuit 5 shown in FIG.

 The connection is not limited to the embodiment shown in FIG. 9 and may be connected between the frequency conversion circuit 7 and the load circuit 4.

 FIG. 9A is a modification of the embodiment shown in FIG. 9, in which the output side of the rectifier circuit 8 is replaced with the input side of the rectifier circuit 8 where the filter circuit 50 shown in FIG. 9 is installed. It is installed, and the other configurations on the main circuit are the same. Even if the filter circuit 50 is installed inside the high-frequency switching power supply circuit 12 as in this modification, the common mode current is suppressed by the reactors L1 and L2 forming the filter circuit 50 as in FIG. The voltage of the capacitors C1 and C2 does not suddenly change due to the common mode current, and the voltage of the capacitor forming the insulating barrier 45 is stabilized.

 FIG. 10 is an electric circuit diagram showing a ninth embodiment of the present invention. The embodiment shown in FIG. 10 is obtained by removing the frequency conversion circuit 7 shown in FIG. 9, and since the other configurations and operations are the same as those in FIG. 9, detailed description thereof will be omitted. To do.

 The present invention is not limited to the specific embodiment shown in FIGS. 1 to 10, but infinite variations and modifications are possible.

 That is, those skilled in the art can use various other complicated or simpler structures of the high frequency switching power supply circuit without departing from the spirit and scope of the present invention. Can be realized.

 For example, increasing the number of switching elements that make up the high frequency switching power supply circuit, or conversely reducing the number of switching elements, and adding another type of passive element such as a reactor to the high frequency switching power supply circuit. Infinite variations of the embodiment are possible.

 Furthermore, the insulation circuit, the frequency conversion circuit, and the load circuit are not limited to the illustrated embodiments, and the invention described above can be implemented using an insulation circuit and a frequency conversion circuit having other structures.

[Advantages of the Invention] As described above, according to the embodiment of the present invention, the high frequency power output from the high frequency switching power supply circuit is supplied to the load through the insulating circuit including the capacitor. Almost no iron or copper loss occurs in the insulation circuit.

 And, the main loss in the insulation circuit is only the dielectric loss, and in principle the loss in the insulation circuit can be reduced. Therefore, if a capacitor with a very low dielectric loss tangent, such as a polypropylene film capacitor, is used as the capacitor forming the insulation barrier, the loss in the insulation circuit can be improved very effectively.

 Further, since a high frequency transformer is not required, it is theoretically unnecessary to form a strong high frequency magnetic field on the insulating barrier in order to transmit high frequency power. Therefore, the disturbing radiation noise of the intensity radiated from the insulation circuit can be reduced, and a good electromagnetic environment can be essentially obtained.

 Furthermore, since the insulating barrier is formed without using a heavy material such as a core made of a magnetic material or a large amount of primary and secondary winding coils, it is possible to reduce the size and weight of the insulating circuit.

 Furthermore, as described above, according to the embodiment shown in FIGS. 4 to 10, the common circuit generated in response to the switching operation of the power switching element inside the switching power supply device by connecting the filter circuit. The mode current is effectively suppressed.

 As a result, even if the impedance between the input and output grounds is zero, in other words, even if the input and output grounds are the same, excessive common mode current cannot pass through the insulation barrier.

 Therefore, the filter circuit does not cause a sudden change in the voltage of the capacitor in the insulation circuit due to the common mode current, and the voltage of the capacitor forming the insulation barrier is stabilized.

 Further, since the common mode current like impulse is suppressed by the filter circuit, destruction of the switching element is avoided.

 Furthermore, it is possible to prevent the high-frequency power of the switching power supply device from significantly leaking through the ground, and prevent the deterioration of the power efficiency of the switching power supply device.

[Brief description of drawings]

 FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention. FIG. 2 is an electric circuit diagram showing a second embodiment of the present invention. FIG. 3 is a circuit diagram showing an example of a conventional switching power supply device. 4, FIG. 4A, FIG. 4B, and FIG. 4C are electrical circuit diagrams showing a third embodiment of the present invention. FIG. 5 is an electric circuit diagram showing a fourth embodiment of the present invention. FIG. 6 is an electric circuit diagram showing a fifth embodiment of the present invention. 7 and 7A are electric circuit diagrams showing a sixth embodiment of the present invention. 8 and 8A are electrical circuit diagrams showing a seventh embodiment of the present invention. 9 and 9A are electric circuit diagrams showing an eighth embodiment of the present invention. FIG. 10 is an electric circuit diagram showing a ninth embodiment of the present invention. In the figure, 1, 10, 11, and 12 are high-frequency switching power supply circuits, 4 are load circuits, 5 and 50 are filter circuits, 7 is a frequency conversion circuit, 8 is a rectifier circuit, 20 is an insulation circuit, and 45 is an insulation barrier. , CS1, CS2, C1, C2 are capacitors, S1, S2 are switching elements, E is a DC power supply, and EAC is an AC power supply.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 1-282245 (32) Priority date Hei 1 (1989) October 30 (33) Priority claim country Japan (JP)

Claims (16)

[Claims] 1. A switching power supply device in which a load is connected to an output of a high-frequency switching power supply circuit that switches power from a power supply to output high-frequency power at an audible frequency or higher, and the insulation circuit is a capacitor. It is characterized by consisting of an insulation barrier composed of. 2. A DC power supply, a high-frequency switching power supply circuit that outputs high-frequency power based on the DC power from the DC power supply in response to a pulse signal having a frequency higher than an audible frequency, and the high-frequency switching power supply. A switching power supply device comprising an insulating circuit connected between the output of the circuit and a load, wherein the insulating circuit comprises a capacitor. 3. An AC power supply, a high-frequency switching power supply circuit that outputs high-frequency power based on the AC power from the AC power supply in response to a pulse signal having a frequency higher than an audible frequency, and the high-frequency switching power supply. A switching power supply device comprising an insulating circuit connected between the output of the circuit and a load, wherein the insulating circuit comprises a capacitor. 4. The switching power supply according to claim 1, further comprising a frequency conversion circuit that is connected between the load and the capacitor and that frequency-converts the high-frequency power. apparatus. 5. A switching power supply device for supplying electric power to a load, the high frequency switching power supply circuit switching the electric power from the power supply to output electric power of a frequency higher than the electric power from the power supply, the high frequency switching power supply An insulation circuit connected between the circuit and the load and forming an insulation barrier between the high frequency switching power supply circuit and the load; and suppressing a common mode current passing through the insulation barrier. Includes a filter circuit connected to shut off. 6. A switching power supply device according to claim 5, wherein the filter circuit includes a common mode choke for suppressing a common mode current passing through the insulation barrier. 7. The switching power supply device according to claim 5, wherein the filter circuit includes a reactor that suppresses a common mode current passing through the insulation barrier. 8. A high-frequency switching power supply circuit for supplying power to a load, the high-frequency switching power supply circuit switching power from a power supply and outputting high-frequency power having a frequency higher than that of the power from the power supply. A frequency conversion circuit connected to the output of the high-frequency switching power supply circuit, for frequency-converting the high-frequency power output from the high-frequency switching power supply circuit to supply power of a frequency lower than the high-frequency power to a load, the high-frequency switching An insulation circuit comprising a capacitor connected between the output of the power supply circuit and the input of the frequency conversion circuit and forming an insulation barrier between the output of the high frequency switching power supply circuit and the input of the frequency conversion circuit, And a filter circuit connected so as to suppress or cut off the common mode current passing through the insulation barrier. Including. 9. A switching power supply device according to claim 8, wherein the filter circuit includes a common mode choke connected to suppress common mode current passing through the isolation barrier. . 10. The switching power supply device according to claim 8, wherein the filter circuit includes a reactor connected to suppress common mode current passing through the insulation barrier. 11. A step of switching power from a power source to perform frequency conversion into power having a frequency higher than that of the power source, and passing the power of the high frequency through an electric field through an insulating barrier as a medium. Insulation method for switching power supply consisting of and. 12. Switching power from a power source to frequency-convert it into power having a frequency higher than that from the power source, and passing the power having a high frequency through an insulating barrier composed of a capacitor, And a step of frequency-converting the high-frequency power that has passed through the insulation barrier into a low-frequency power, thereby isolating the switching power supply device. 13. An insulating method according to any one of claims 11 and 12, further comprising: suppressing a common mode current passing through the insulating barrier. 14. An insulation method according to any one of claims 11, 12, and 13, wherein the power of the high frequency is power of an audible frequency or higher. 15. An insulating method according to claim 13, wherein the common mode current is suppressed by using a common mode choke. 16. An insulating method according to any one of claims 13 and 14, wherein the common mode current is suppressed by using a reactor.