JPH04344178A - Switching power supply and its insulating method - Google Patents

Abstract

PURPOSE:To provide a switching power unit and its insulating method which does not contaminate an electromagnetic environment by suppressing the generation of electrical obstructive noise produced when switching is made. CONSTITUTION:This switching power supply is constituted of a DC power source E, a switching element S1 connected to the power source E through a reactor L, the first capacitor C1 connected to one terminal of the reactor L, the second capacitor C2 connected to the other terminal of the reactor L, and an insulating barrier 45 composed of the first and second capacitors C1 and C2 for insulating a load 4 from the DC power source E.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply and a method of insulating the same. More specifically, the present invention relates to a switching power supply device in which a load is connected to a switching power supply circuit that generates high-frequency power via an insulation circuit, and an insulation method thereof.

0002

2. Description of the Related Art FIG. 2 is a diagram showing an example of a conventional switching mechanism capable of controlling a minimum number of units, that is, a switching power supply device consisting of one switching element. Referring to FIG. 2, a DC power supply E is connected to switching power supply circuit 5 via insulation circuit 2. Referring to FIG. The switching power supply circuit 5 includes a self-extinguishing high-speed switching element S.
Consists of 1. Switching element S1 is power MO
It is composed of SFET. A control pulse is applied to the control terminal (gate) of the switching element S1 from a control circuit (not shown). The insulation circuit 2 is constituted by a transformer T. A frequency conversion circuit 7 consisting of a 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 transformer T described above forms an insulating barrier 44 between the primary terminals A, B and the secondary terminals C, D. Next, the operation of the conventional switching power supply shown in FIG. 2 will be explained. When a control pulse is applied to the control terminal of the switching element S1, the switching element S1 is turned on and off. Then, the voltage between the secondary side terminals C and D of the insulating circuit 2 is alternately reversed, and an alternating current voltage is generated. This AC voltage is frequency-converted into DC power by the frequency conversion circuit 7 and supplied to the load circuit 4 .

0003

As described above, the insulation circuit 2 of the conventional switching power supply device uses a transformer T for insulation. Therefore, switching noise accompanying the high-frequency switching operation is radiated from the transformer T, causing a large amount of interference noise to other electronic devices. In recent years, this has become a major problem in the electromagnetic environment because it induces malfunctions in other electronic devices. In order to remove interference noise consisting of various frequency components caused by switching noise emitted from the transformer T, magnetic shielding may be used. However, magnetic shielding is generally difficult to achieve a high shielding effect compared to electric field shielding, and shielding interference noise from transformer T is particularly difficult in switching power supplies that perform high-frequency switching operations. . In addition, in a switching power supply device consisting of the smallest unit, that is, one switching element, the current flowing through the transformer T is abruptly interrupted by switching, so the transformer T forming the insulation circuit 2 generates a surge voltage and the switching element There is a serious problem where excessive voltage is applied and the switching elements are destroyed due to overvoltage resistance.

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide a switching power supply device and a method for insulating the same, which less pollutes the electromagnetic environment and suppresses interference noise from being caused to other electronic devices. Another object of the present invention is to provide a switching power supply device that has a minimum number and size of components and has high power conversion efficiency, and a method for insulating the same. Still another object of the present invention is to provide a switching power supply device and its insulation method that avoids the risk of damage to switching elements due to surge voltage generated by an insulation circuit.

[0005]

[Means for Solving the Problem] The invention according to claim 1 is a switching power supply device for supplying power to a load, which includes an input power source, a switching element connected to the input power source via a reactor, and a reactor. A first capacitor connected to one terminal, a second capacitor connected to the other terminal of the reactor, and an insulation barrier configured by the first and second capacitors to isolate the input power source from the load. It consists of

The invention according to claim 2 is a switching power supply device for supplying power to a load, which includes an input power source, a switching element connected to the input power source via a reactor, and a switching element connected to one terminal of the switching element. The first
, a second capacitor connected to the other terminal of the switching element, and an insulation barrier configured by the first and second capacitors to insulate the input power source from the load.

The invention according to claim 3 is a switching power supply device for supplying power to a load, which comprises an input power supply, a switching power supply circuit comprising a minimum unit switching mechanism connected to the input power supply via a reactor, and a switching power supply. An insulation circuit consisting of a capacitor connected between the circuit and the load and forming an insulation barrier between the switching power supply circuit and the load, and an excessive current passing through the insulation barrier in order to maintain the insulation function of the insulation circuit. includes a filter circuit connected to suppress or block.

[0008] The invention according to claim 4 is a switching power supply device according to claim 3, in which the filter circuit includes a common mode choke that suppresses common mode current passing through the insulation barrier.

[0009] The invention according to claim 5 is a switching power supply device according to claim 3, in which the filter circuit includes a reactor that suppresses a common mode current passing through an insulating barrier.

[0010] The invention according to claim 6 includes the steps of: generating power at a higher frequency than the power from the power supply by switching one switching element using the power from the power supply via magnetic energy; It consists of a step of passing high frequency power through an electric field as a medium.

[0011] The invention according to claim 7 includes the step of switching the power from the power supply through one switching element to generate power of a higher frequency than the power from the power supply, and the step of converting the power of the high frequency to an insulating barrier composed of a capacitor. and a step of converting the high frequency power passed through the insulation barrier into low frequency power.

The invention according to claim 8 is an insulation method depending on claims 6 and 7, further comprising the step of suppressing or interrupting excessive current passing through the insulation barrier.

[0013]

[Operation] According to the present invention, high frequency power is supplied to the load via an insulated circuit consisting of a capacitor.
Unlike conventional technology, high-frequency current does not flow through the transformer windings, so there is no electromagnetic field radiated from the transformer. That is, switching noise is not radiated into the atmosphere from the transformer windings. In addition, as in the past, an insulated circuit does not require a strong high-frequency alternating magnetic field for insulation, which eliminates the need for primary and secondary windings that form a strong high-frequency magnetic flux, making the insulated circuit essentially No strong high-frequency leakage flux is generated. In addition, an isolation circuit can be constructed in which there is no leakage inductance of an isolation transformer. As a result, no surge voltage is generated from the insulated circuit. Furthermore, according to the present invention, in order to configure a low-power pollution switching power supply with a minimum number of components, the problem is pointed out that a switching power supply cannot be constructed with only a capacitor insulation circuit and one switching element. In order to solve the problem, the minimum number of parts, that is,
Added one reactor.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an electrical circuit diagram showing a first embodiment of the present invention. Referring to FIG.
connected to. The switching power supply circuit 5 consists of one controllable switching element S1, and a power MOSFET, which is an extremely high-speed self-extinguishing switching element, is used as the switching element S1. A control pulse is applied to the control terminal (gate) of the switching element S1 from a control circuit (not shown), and the switching element S1 is turned on and off in response to the control pulse. The negative side of the DC power supply E is connected to one terminal (source) of the switching element S1, and the primary side terminal B of the insulating circuit 20 is connected to the other terminal (drain) of the switching element S1. Further, the positive side of the DC power supply E is connected to the primary side terminal A of the insulation circuit 20. Between the switching element S1 and the insulation circuit 20, a reactor L is connected to the primary side terminals A and B of the insulation circuit 20.
connected between. The isolation circuit 20 includes capacitors C1 and C2.
The insulating barrier 45 is composed of primary side terminals A and B.
and 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 floating with respect to the primary side terminals A and B. A load 4 is connected to secondary side terminals C and D of the insulated circuit.

Next, the operation of the embodiment shown in FIG. 1 will be explained. Now, in order to supply high frequency power to load 4,
A control pulse with a switching frequency of 500 kHz is applied to the control terminal of the switching element S1 of the switching power supply circuit 5. First, the control terminal of the switching element S1 is turned on for a period of 1 μsec. In response to a control pulse from the control terminal, the switching element S1 becomes conductive (on). When the switching element S1 is turned on, current flows from the DC power supply E to the load 4 via the capacitors C1 and C2, and power is supplied from the DC power supply E to the load 4. Thereby, capacitors C1 and C2 are charged. Moreover, during that time, the voltage of the DC power supply E is applied to the reactor L, and the current flowing through the reactor L increases. Next, the control terminal of switching element S1 is turned off for a period of 1 μsec. In response to the control pulse at the control terminal, the switching element S1 becomes non-conductive (off state). When the switching element S1 is turned off, the current flowing through the reactor L flows through the capacitor C2, the load 4, and the capacitor C1. The current causes capacitors C1 and C2 to be discharged. Further, the reactor L supplies power to the load 4 based on the magnetic energy stored in the reactor L. Meanwhile, the current flowing through reactor L decreases. As described above, by repeating the switching operation (on/off operation) of the switching element S1, the DC power of the DC power source E is converted into 500 kHz high frequency power, and the 500 kHz high frequency power is supplied to the load 4.

[0016] Here, the role of the reactor L will be explained. In FIG. 1, if the reactor L is removed, high frequency power is not supplied to the load 4 even if the switching element S1 is switched. That is, in FIG. 1, if the reactor L is removed, the device in FIG. 1 will not operate as a switching power supply device. That is, the novel switching power supply shown in FIG. 1 always requires one reactor as the minimum unit of the circuit configuration. On the other hand, the conventional switching power supply shown in FIG. 2 does not require the reactor L. From the above, it is understood that a switching power supply device consisting of a minimum unit switching element having an insulating circuit of a capacitor has a unique feature of including at least one reactor.

The role of the insulation circuit 20 will now be explained. 500 output from the switching power supply circuit 5
The capacitors C1 and C2 have low impedance with respect to high frequency power of kHz, and the installation of the capacitors C1 and C2 causes almost no problem in high frequency power transmission. However, the DC component and low frequency component contained in the high frequency power output from the switching power supply circuit 5 are absorbed by the capacitor C.
1, C2 can hardly or never pass through the insulating barrier 45. Therefore, there is no DC power in the power supplied to the load 4, and there is almost no low frequency power. This is because the insulation barrier 45 constituted by the capacitors C1 and C2 exhibits infinite impedance with respect to zero frequency (DC), and at commercial power frequency (50Hz or 60Hz), these capacitors C1 and C2
This is because 2 shows an extremely high impedance. That is, the impedance value shown by the capacitors C1 and C2 is inversely proportional to the frequency. Therefore, for the impedance value at 500kHz, its value at 50Hz is 500
kHz/50Hz=10,000 times higher value. Therefore, for low frequencies, there may be some electrical energy leakage as weak as a signal, but it can be virtually ignored as a switching power supply device. Therefore, due to the increase in frequency, the present insulation circuit can actually be used effectively as an insulation circuit for switching power supplies not only for direct current but also for power frequencies on the order of commercial frequencies. In other words, DC power supply,
It can also be used as an insulating circuit for commercial power supply. This has been achieved by increasing the frequency of the switching power supply, and if the output frequency of the switching power supply circuit is not much higher than the commercial power supply frequency, for example, at frequencies below the audio frequency of about 400Hz, the Frequency ratio is 400Hz/5
Since it is as small as 0 Hz = about 8 times, the capacitors C1 and C2 forming the barrier inevitably have an extremely large capacity, and it is difficult in principle to use it as an insulating circuit for a commercial power supply.

FIG. 3 is a circuit diagram showing a second embodiment of the invention. The embodiment shown in FIG. 3 is one in which a frequency conversion circuit 7 consisting of a full-wave rectifier circuit is newly added between the insulation circuit 20 shown in FIG. 1 and the load 4, and the other configuration is as shown in FIG. is the same as In this embodiment, the operation is the same as in FIG. 1 described above except for full-wave rectification of the high frequency power output from the secondary side terminals C and D of the insulating circuit 20, so a detailed explanation will be omitted.

[0019] Here, problems related to the load 4 shown in FIGS. 1 and 3 will be explained. In the switching power supply devices shown in FIGS. 1 and 3, there is no problem if the load 4 is a pure resistance load. However, if the load 4 is an inductive or capacitive load, there is a problem. In other words, the first problem is
When the load 4 is an inductive load, the moment the switching element S1 is turned off, a surge voltage is generated by the magnetic energy of the reactor L and is applied to the switching element S1. Also, the second problem is that if load 4 is a capacitive load,
At the moment when the switching element S1 is turned on, the insulation circuit 20
A surge current is generated by the electrostatic energy of the capacitors C1 and C2 and flows to the switching element S1. Inventions made to solve these problems are shown in FIGS. 4 and 5 below.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention. In the embodiment shown in FIG. 4, the frequency conversion circuit 7 consisting of the full-wave rectifier shown in FIG. 3 is replaced with a frequency conversion circuit 71, and the load 4 shown in FIG. 3 is replaced with a reactor and a resistor. This is replaced by an inductive load 40 consisting of a series circuit of . Other configurations are shown in Figure 3.
is the same as The frequency conversion circuit 71 consists of one diode, and this diode is connected to the secondary terminal C of the insulation circuit 20.
, D in parallel with the load 4, and more specifically, its cathode is connected to the secondary side terminal C, and its anode is connected to the secondary side terminal D. The frequency conversion circuit 71 then half-wave rectifies the high frequency power output from the secondary side terminals C and D of the insulation circuit 20 and supplies it to the load 4 . Here, the operation of the embodiment shown in FIG. 4 will be explained. First, when the switching element S1 is in the on state for 1 μsec, the voltages of the DC power supply E and the capacitors C1 and C2 are applied to the load 40. During that time, the load is supplied with a DC power supply E.
and a capacitor C1 in which electrostatic energy is stored,
Power is supplied from C2. Furthermore, since the DC power source E is applied to the reactor L, the current flowing through the reactor L increases, and power is supplied to the reactor L from the DC power source E. Next, for 1 μsec, the switching element S
1 is in the off state, the current flowing through the reactor L flows through the capacitor C2, the diode forming the frequency conversion circuit 71, and the capacitor C1. Also, load 40
Since the current flowing through the reactor also flows through the diode of the frequency conversion circuit 71, no power is supplied to the load 40 from the power supply side during that period. In other words, while the switching element S1 is off, the diode of the frequency conversion circuit 71 is in a conductive state, so the voltage applied to the load 40 becomes zero voltage. Furthermore, during this time, the capacitors C1 and C2 are charged by the current flowing through the reactor L, and the energy stored in the reactor L is transferred to the capacitors C1 and C2. Power is supplied to the load through the above-described on/off operation of the switching element S1. At that time, inductive load 40
Regardless, reactor L does not generate surge voltage.

As described above, FIG. 4 shows a switching power supply device suitable for an inductive load. In other words, FIG. 4 shows a switching power supply device composed of the minimum unit switching elements that solves the first problem in FIG. 3, that is, the reactor L generates a surge voltage when the load is an inductive load. .

FIG. 5 is a circuit diagram showing a fourth embodiment of the invention. In the embodiment shown in FIG. 5, the load 40 shown in FIG. 4 is replaced with a load 41 consisting of a parallel circuit of a capacitor and a resistor, and the frequency conversion circuit 71 shown in FIG. 4 is replaced with a frequency conversion circuit 710. It is something. Then, a new reactor LL is connected between the secondary terminals of the insulating circuit 20. Other configurations are the same as in FIG. 4. Here, the operation of the embodiment shown in FIG. 5 will be explained. First, for 1 μsec, the switching element S
1 is on, DC power supply E is applied to reactor L, so the current flowing through reactor L increases,
Power is supplied to the reactor L from a DC power supply E. Further, since the DC power source E is applied to the reactor LL via the insulation circuit 20, the current flowing through the reactor LL increases, and power is supplied from the DC current source E to the reactor LL. During that time, the capacitors C1 and C2 are charged by the current flowing through the reactor LL. Next, 1μse
During c, when the switching element S1 is in the off state, the current flowing through the reactor L flows through the capacitor C2, the diode that constitutes the frequency conversion circuit 710, the load 41, and the capacitor C1, and the current flowing through the reactor LL. Also flows through the frequency conversion circuit 710 and the load 41. During this time, the capacitors C1 and C2 are discharged by the current flowing through the reactor L. Power is supplied to the load through the above-described on/off operation of the switching element S1. At this time, despite the capacitive load 41, no surge current is generated in the switching element S1 via the insulating circuit 20.

FIG. 6 is a circuit diagram showing a fifth embodiment of the invention. In the embodiment shown in FIG. 6, the frequency conversion circuit 710 shown in FIG. 5 is replaced with a frequency conversion circuit 711. The other configurations are the same as in FIG. 5. Further, since the operation is basically the same as that in FIG. 5 described above, detailed explanation will be omitted.

As described above, FIGS. 5 and 6 show switching power supply devices suitable for capacitive loads. That is, FIGS. 5 and 6 solve the second problem of FIG.
This is a switching power supply device configured with a minimum unit switching element that solves the problem of surge current flowing through the switching element S1 when the load is a capacitive load.

FIG. 7 is an electrical circuit diagram showing a sixth embodiment of the present invention. In the embodiment shown in FIG. 7, the installation locations of the switching power supply circuit 5 and the reactor L shown in FIG. 1 are replaced. The other configurations are the same as in FIG. In FIG. 7, the switching power supply circuit 5 is composed of one switching element S1 that short-circuits or opens the primary side terminals A and B of the insulating circuit 20. In FIG. One terminal (drain) of the switching element S1 of the switching power supply circuit 5 is connected to the primary side terminal A of the insulation circuit 20, and the other terminal (source) of the switching element S1 is connected to the primary side terminal B.
connected to. Here, the operation of the embodiment shown in FIG. 7 will be explained. First, the control terminal of the switching element S1 is turned on for a period of 1 μsec. Then, in response to a control pulse from the control terminal, the switching element S1 becomes conductive (turned on). When the switching element S1 is turned on, the DC power supply E is short-circuited via the reactor L and the switching element S1, and the voltage of the DC power supply E is applied to the reactor L. Therefore, during that time, the current flowing through the reactor L continues to increase. Furthermore, the charges in the capacitors C1 and C2 are discharged via the switching element S1 and the load. As a result, the electrostatic energy of the capacitors C1 and C2 is applied to the load 4, and power is supplied to the load 4. Next, for a period of 1 μsec, the switching element S
1 control terminal is turned off. Then, in response to a control pulse from the control terminal, the switching element S1 becomes non-conductive (off state). When the switching element S1 is turned off, the magnetic energy stored in the reactor L causes current to flow through the capacitor C1, the load 4, and the capacitor C2. As a result, the magnetic energy stored in the reactor L becomes electrostatic energy in the capacitors C1 and C2 and is simultaneously transferred and consumed in the load 4. Therefore, the current flowing through the reactor L decreases. In this way,
By repeating the switching operation (on-off operation) of the switching element S1, the DC power of the DC power source E is converted into the magnetic energy of the reactor L and the capacitors C1 and C2.
The electrostatic energy is converted into high frequency power of 500 kHz, and the high frequency power is supplied to the load 4.

FIG. 8 is a circuit diagram showing a seventh embodiment of the invention. The embodiment shown in FIG. 8 is one in which a frequency conversion circuit 7 consisting of a full-wave rectifier circuit is newly added between the insulation circuit 20 shown in FIG. 7 and the load 4, and the other configuration is as shown in FIG. is the same as In this embodiment, the operation is the same as that of FIG. 7 described above except for full-wave rectification of the high frequency power output from the secondary side terminals C and D of the insulating circuit 20, so a detailed explanation will be omitted.

[0027] Here, problems regarding the load 4 shown in FIGS. 7 and 8 will be explained. In the switching power supply devices shown in FIGS. 7 and 8, there is no problem if the load 4 is a pure resistance load. However, if the load 4 is an inductive or capacitive load, there is a problem. In other words, the first problem is
When the load 4 is an inductive load, the moment the switching element S1 is turned off, a surge voltage is generated by the magnetic energy of the reactor L and is applied to the switching element S1. Also, the second problem is that if load 4 is a capacitive load,
At the moment when the switching element S1 is turned on, the insulation circuit 20
A surge current is generated by the electrostatic energy of the capacitors C1 and C2 and flows to the switching element S1. The inventions made to solve these problems are shown in Figures 9 and 10 below.
It is.

FIG. 9 is a circuit diagram showing an eighth embodiment of the present invention. The embodiment shown in FIG. 9 replaces the frequency conversion circuit 7 shown in FIG. 8 with a frequency conversion circuit 70, and replaces the load 4 shown in FIG. This is replaced with the sexual load 40. The other configurations are the same as in FIG. 8. The frequency conversion circuit 70 consists of one diode, and this diode is connected in parallel with the load 40 to the secondary terminals C and D of the insulating circuit 20. More specifically, its anode is connected to the secondary terminal C, and Its cathode is connected to terminal D. The frequency conversion circuit 70 then half-wave rectifies the high frequency power output from the secondary side terminals C and D of the insulation circuit 20 and supplies it to the load 4 . Here, the operation of the embodiment shown in FIG. 9 will be explained. First, when the switching element S1 is on for 1 μsec, the capacitor C1
, C2 are applied to the load 40. Further, the DC power source E is short-circuited to the reactor L via the switching element S1, and the voltage of the DC power source E is applied to the reactor L. Therefore, during that time, the current flowing through the reactor L continues to increase. Then, when the switching element S1 is in the off state for 1 μsec, the current flowing through the reactor L flows through the capacitor C1, the diode that constitutes the frequency conversion circuit 70, the capacitor C2, and the DC power supply E, so the load 40 No electricity will be supplied during that period. In other words, while the switching element S1 is off, the diode of the frequency conversion circuit 70 is conductive, so the voltage applied to the load 40 becomes zero voltage. Also, during that time, the capacitors C1 and C2 are charged by the current flowing through the reactor L, the magnetic energy stored in the reactor L is transferred to the capacitors C1 and C2, and the current flowing through the reactor L is reduced.

As described above, FIG. 9 shows a switching power supply device suitable for an inductive load. In other words, FIG. 9 shows a switching power supply device composed of the smallest unit of switching elements that solves the first problem in FIG. 8, that is, the reactor L generates a surge voltage when the load is an inductive load. .

FIG. 10 is a circuit diagram showing a ninth embodiment of the present invention. In the embodiment shown in FIG. 10, the load 40 shown in FIG. 9 is replaced with a load 41 consisting of a parallel circuit of a capacitor and a resistor, and the frequency conversion circuit 7 shown in FIG.
0 is replaced with a frequency conversion circuit 700. Then, a new reactor LL is installed at 2 of the insulation circuit 20.
It is connected between the next side terminals. Other configurations are shown in Figure 9.
is the same as Here, the operation of the embodiment shown in FIG. 10 will be explained. First, when the switching element S1 is on for 1 μsec, the charges in the capacitors C1 and C2 are discharged through the reactor LL, so the current flowing through the reactor LL increases. That is, the electrostatic energy stored in the capacitors C1 and C2 is transferred to the reactor LL as magnetic energy. Next, 1μs
During ec, when switching element S1 is in the off state,
The current flowing through reactor L is DC power supply E and capacitor C.
1, the load 41, and the diode and capacitor C2 that constitute the frequency conversion circuit 700, and the current flowing through the reactor LL also flows through the load 41 and the frequency conversion circuit 710.
flows through. During this time, the capacitors C1 and C2 are charged by the current flowing through the reactor L. Power is supplied to the load through the above-described on/off operation of the switching element S1.

FIG. 11 is a circuit diagram showing a tenth embodiment of the present invention. The embodiment shown in FIG. 11 replaces the frequency conversion circuit 700 shown in FIG.
01. The other configurations are the same as in FIG. 10. Further, since the operation is basically the same as in FIG. 10 described above, detailed explanation will be omitted.

As described above, FIGS. 10 and 11 are switching power supply devices suitable for capacitive loads. In other words, FIGS. 10 and 11 show a minimum system that solves the second problem in FIG. 8, that is, when the load is a capacitive load, a surge current flows to the switching element S1 due to the charges in the capacitors C1 and C2 of the insulated circuit. This is a switching power supply device composed of unit switching elements.

FIG. 12 is an electrical circuit diagram for explaining the unique problem regarding insulation of the invention shown in FIG. In FIG. 12, one side of the DC power supply E and the secondary terminal D of the insulation circuit 20 are grounded to the ground G, and the other configurations are the same as in FIG. In Figure 12, the switching power supply circuit 5
A large impulse-like excessive current flows through the insulating circuit 20 via the ground G in response to the switching operation. That is, the charge in the capacitor C2 is rapidly discharged via the ground G at the same time that the switching element S1 is turned on. Therefore, a large impulse current flows through the switching element S1 constituting the switching power supply circuit 5, leading to destruction of the switching element S1. Further, since the power from the DC power supply E is consumed in the ground G and is hardly transmitted to the load 4, a very serious problem occurs as a switching power supply device. Figures 13, 16, and 18 show solutions to this problem.

FIG. 13 is an electrical circuit diagram of an eleventh embodiment of the present invention. In the embodiment shown in FIG. 13, the DC power source E
A filter circuit FC composed of a common mode choke LC is connected to the power line between the switching power supply circuit 5 and the switching power supply circuit 5, and the other configuration is the same as the embodiment shown in FIG. 1 described above. The problem with Figure 12 mentioned above is
This problem can be solved by using a filter circuit FC. That is, if the value of the common mode inductance of the common mode choke LC constituting the filter circuit FC is high impedance with respect to the switching operation frequency of the switching power supply circuit 5, the power supply through the ground every time the switching power supply circuit 5 switches. The current flowing through the insulation circuit 20, that is, the common mode current, is effectively suppressed by the filter circuit FC. Therefore, filter circuit FC
Due to the common mode high frequency current, capacitor C
Therefore, the voltage of the capacitors C1 and C2 forming the insulation barrier 45 is stabilized. In FIG. 13, when the common mode choke LC is tightly coupled, the filter circuit FC theoretically does not act as an impedance for the normal mode. That is, the common mode choke has zero impedance for normal mode. Therefore, even if the normal mode current changes sharply, the common mode choke L
C does not generate surge voltage. However, if the common mode choke LC is not tightly coupled, the filter circuit FC acts as an impedance with respect to the normal mode. Therefore, when the normal mode current changes sharply due to switching, the common mode choke LC generates a surge voltage. In order to solve this problem, as shown in FIG. 18, it is necessary to install a capacitor CF on the output side of the common mode choke LC of the filter circuit FCC. That is, the capacitor CF has a function of suppressing the surge voltage generated by the common mode choke LC when the common mode choke LC is not tightly coupled.

FIG. 14 is an electrical circuit diagram for explaining the unique and serious problem regarding the insulation of the invention shown in FIG.
In FIG. 14, one side of the DC power source E and the secondary side terminal D of the insulation circuit 20 are grounded to the ground G, and the other configurations are the same as those in FIG. 7. In FIG. 14, a large impulse-like excessive current flows through the insulation circuit 20 via the ground G in response to the switching operation of the switching power supply circuit 5. That is, the charge in the capacitor C2 is rapidly discharged via the ground G at the same time that the switching element S1 is turned on. Therefore, a large impulse current flows through the switching element S1 constituting the switching power supply circuit 5, leading to destruction of the switching element S1. Also, the power from the DC power supply E is consumed in the ground G,
Almost no signal is transmitted to load 4. Therefore, a switching power supply device consisting of an insulating circuit using a capacitor has the above-mentioned serious and unique problem. Figures 15, 17, and 19 show solutions to this problem.

FIG. 15 is an electrical circuit diagram of a twelfth embodiment of the present invention. In the embodiment shown in FIG. 15, the DC power source E
A filter circuit FC composed of a common mode choke LC is connected to the power line between the switching power supply circuit 5 and the switching power supply circuit 5, and the other configuration is the same as the embodiment shown in FIG. 7 described above. The problem with Figure 14 mentioned above is
This problem can be solved by using a filter circuit FC. That is, if the value of the common mode inductance of the common mode choke LC constituting the filter circuit FC is high impedance with respect to the switching operation frequency of the switching power supply circuit 5, the power supply through the ground every time the switching power supply circuit 5 switches. The current flowing through the insulation circuit 20, that is, the common mode current, is effectively suppressed by the filter circuit FC. Therefore, filter circuit FC
Due to the common mode high frequency current, capacitor C
Therefore, the voltage of the capacitors C1 and C2 forming the insulation barrier 45 is stabilized.

FIG. 16 is an electrical circuit diagram showing a thirteenth embodiment of the present invention. The embodiment shown in FIG.
In place of the filter circuit FC shown in 3, reactor LF
A filter circuit F consisting of 1, LF2 and a capacitor CF is connected. This filter circuit F has a function of suppressing common mode current like the filter circuit FC of the embodiment shown in FIG. 13 described above. That is,
Reactors LF1 and LF forming the filter circuit F for the switching operation frequency of the switching power supply circuit 5
If the inductance value of 2 is high impedance,
The filter circuit F effectively suppresses the high frequency common mode current flowing between the input and output grounds via the insulation circuit 20 every time the switching power supply circuit 5 switches. Therefore, the filter circuit F prevents the voltage of the capacitor C1 or C2 from fluctuating rapidly due to the common mode high frequency current, and the voltage of the capacitors C1 and C2 forming the insulation barrier 45 is stabilized.

FIG. 17 is an electrical circuit diagram showing a fourteenth embodiment of the present invention. The embodiment shown in FIG.
In place of the filter circuit FC shown in 5, a filter circuit F0 composed of a pair of reactors LF3 and LF4 is connected. This filter circuit F0 is shown in FIG.
Similar to the filter circuit FC of the embodiment shown in 1, it has a function of suppressing common mode current. In other words, if the inductance values of the reactors LF3 and LF4 constituting the filter circuit F0 are high impedance with respect to the switching operation frequency of the switching power supply circuit 5, the input through the insulation circuit 20 each time the switching power supply circuit 5 is switched. The high frequency common mode current flowing between the output grounds is effectively suppressed by the filter circuit F0. Therefore, the filter circuit F0 prevents the voltage of the capacitor C1 or C2 from fluctuating rapidly due to the common mode high frequency current, and the voltage of the capacitors C1 and C2 forming the insulation barrier 45 is stabilized. In FIG. 17, since reactor L is present, one reactor LF4 of filter circuit F0 can be omitted.

FIG. 18 is an electrical circuit diagram showing a fifteenth embodiment of the present invention. The embodiment shown in FIG.
In place of the filter circuit FC shown in FIG. 3, a filter circuit FCC composed of a common mode choke LC and a filter capacitor CF is connected. The filter circuit FCC shown in FIG. 18 solves the problem shown in FIG. 13 described above. The detailed explanation of FIG. 18 overlaps with the operation explanation of FIG. 13, so it will be omitted here.

FIG. 19 is an electrical circuit diagram showing a 16th embodiment of the present invention. The embodiment shown in FIG.
In place of the filter circuit F0 shown in 7, reactor LF
A filter circuit F00 composed of 3, L is connected to the filter circuit F00. The detailed explanation of FIG. 19 overlaps with the explanation of the operation of FIG. 17, so it will be omitted here.

[0041]

Effects of the Invention As described above, according to the present invention shown in FIGS. 1 and 3 to 19, by configuring the insulation barrier with a capacitor, even if the switching element is forcibly turned on and off, there is no excessive No surge voltage will occur. Therefore, a large amount of interference noise is not generated on the power supply line due to leakage inductance of the insulating circuit, and a good electromagnetic environment can be achieved in principle. moreover,
There is no risk of damage to the switching element due to excessive surge voltage caused by leakage inductance of the isolation transformer.

As described above, according to the inventions shown in FIGS. 13, 15, 16 to 19, the filter circuit composed of the reactor or common mode choke prevents the generation of electricity caused by the switching operation of the switching element inside the switching power supply. The steep common mode current that occurs is cut off. Thereby, common mode current passing through the insulation barrier is suppressed. Therefore, by the filter circuit,
The voltage of the capacitor forming the insulation barrier does not fluctuate rapidly due to the common mode current. Furthermore, since the impulse common mode current is suppressed by the filter circuit, destruction of the switching elements due to excessive common mode current is avoided. Furthermore, the filter circuit can prevent the power output from the switching power supply circuit from leaking significantly to the ground of the switching power supply, thereby significantly deteriorating the power efficiency of the switching power supply.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing an example of a conventional electric circuit.

FIG. 3 is an electrical circuit diagram showing a second embodiment of the invention.

FIG. 4 is an electrical circuit diagram showing a third embodiment of the present invention.

FIG. 5 is an electrical circuit diagram of a fourth embodiment of the present invention.

FIG. 6 is an electrical circuit diagram of a fifth embodiment of the present invention.

FIG. 7 is an electrical circuit diagram of a sixth embodiment of the present invention.

FIG. 8 is an electrical circuit diagram of a seventh embodiment of the present invention.

FIG. 9 is an electrical circuit diagram of an eighth embodiment of the present invention.

FIG. 10 is an electrical circuit diagram of a ninth embodiment of the present invention.

FIG. 11 is an electrical circuit diagram of a tenth embodiment of the present invention.

FIG. 12 is an electrical circuit diagram for explaining the problems of this invention.

FIG. 13 is an electrical circuit diagram of an eleventh embodiment of the present invention.

FIG. 14 is an electrical circuit diagram for explaining the problems of this invention.

FIG. 15 is an electrical circuit diagram of a twelfth embodiment of the present invention.

FIG. 16 is an electrical circuit diagram of a thirteenth embodiment of the present invention.

FIG. 17 is an electrical circuit diagram of a fourteenth embodiment of the present invention.

FIG. 18 is an electrical circuit diagram of a fifteenth embodiment of the present invention.

FIG. 19 is an electrical circuit diagram of a 16th embodiment of the present invention.

[Explanation of symbols]

E is a DC power supply 4 is a load circuit 5 is a switching power supply circuit 7, 70, 700, 701, 71, 710, 711 is a frequency conversion circuit 2, 20 is an isolation circuit S1 is a switching element C1, C2, CF is a capacitor

Claims (8)

[Claims] 1. A switching power supply device that supplies power to a load, comprising: an input power source; a switching element connected to the input power source via a reactor; and a first switching element connected to one terminal of the reactor. A capacitor, a second capacitor connected to the other terminal of the reactor, and an insulation barrier configured by the first and second capacitors and for insulating the input power source and the load. switching power supply. 2. A switching power supply device that supplies power to a load, comprising: an input power source; a switching element connected to the input power source via a reactor; and a first switching element connected to one terminal of the switching element. a second capacitor connected to the other terminal of the switching element; and an insulation barrier configured by the first and second capacitors and for insulating the input power source and the load. A switching power supply device featuring: 3. A switching power supply device that supplies power to a load, the switching power supply circuit comprising an input power supply, a minimum unit switching mechanism connected to the input power supply via a reactor, the switching power supply circuit and the load. an insulating circuit consisting of a capacitor connected between the switching power supply circuit and the load and forming an insulating barrier between the switching power supply circuit and the load, and an excessive current passing through the insulating barrier in order to maintain the insulating function of the insulating circuit. includes a filter circuit connected to suppress or block. 4. A switching power supply according to claim 3, wherein the filter circuit includes a common mode choke that suppresses common mode current passing through the insulation barrier. 5. A switching power supply according to claim 3, wherein the filter circuit includes a reactor that suppresses a common mode current passing through the insulation barrier. 6. Switching power from a power source through magnetic energy to a switching element to generate power at a higher frequency than the power from the power source; A method of insulating a switching power supply comprising the step of passing high frequency power. 7. Switching power from a power source through one switching element to generate power at a higher frequency than the power from the power source; and passing the high frequency power through an insulating barrier formed of a capacitor. and converting the high frequency power that has passed through the insulation barrier into low frequency power. 8. An insulation method for a switching power supply according to claim 6, further comprising the step of suppressing or blocking excessive current passing through the insulation barrier.