JP4983677B2 - Surge absorption circuit - Google Patents

Description

  The present invention relates to a surge absorption circuit that is mounted on a power supply device such as a power converter and protects the power supply device from surges such as lightning surge and switching surge applied to the power supply device from a power supply line of a power distribution system.

  In distributed power sources such as photovoltaic power generation that are operated in conjunction with the power distribution system, discharge gap type surge absorbers and semiconductors are used to protect power equipment from lightning surges and switching surges. A surge absorption circuit provided with a protection element such as a varistor using non-linearity is generally used. In the surge absorbing circuit, in order to ensure the protection of the power supply device against the surge, it is desired to set the operating voltage of the surge absorber or the like during the protection operation to be low.

  On the other hand, since it is necessary to maintain the insulation resistance of the power supply device, an insulation withstand voltage test is performed to confirm the insulation resistance of the system when the power supply device is shipped as a product. It is common for high voltage AC at commercial frequency to be applied to power supply equipment during the dielectric strength test, but surge absorbers etc. connected mainly between the power line and ground do not work during the dielectric strength test Thus, it was necessary to select a higher operating voltage such as a surge absorber according to the dielectric strength test voltage. For this reason, the protection voltage level of the power supply device against a surge such as a lightning surge cannot be sufficiently lowered.

  In order to solve such a problem, in the conventional surge absorption circuit, the ground and the surge absorber are separated from each other by using a switching element such as a high breakdown voltage relay during the withstand voltage test (see, for example, Patent Document 1). In addition, without using an active element such as a switch, a capacitor is connected in parallel to one of two discharge gap elements connected in series, and an inductor is connected in parallel to the other, and only a passive element is used (for example, Patent Document 2). reference).

Japanese Patent Laid-Open No. 2001-286057 (pages 3 to 4, FIG. 1) JP 2004-185982 A (pages 5 to 8, FIG. 1)

  In a conventional surge absorption circuit, when a switching element such as a relay is used, the operating voltage of the surge absorber can be set low, but by installing a switching element such as a high breakdown voltage relay and a drive circuit for operating the switching element There is a problem that the apparatus size increases and the manufacturing cost also increases. Further, when the surge absorbing circuit is configured only by passive elements, although the circuit configuration is simple, there is a problem that harmonic leakage current increases due to series resonance of the inductor and the capacitor.

  The present invention has been made to solve the above-described problems. The entire circuit is miniaturized, the manufacturing cost is reduced, and when a lightning surge is applied, the circuit operates at a voltage value lower than the withstand voltage test voltage. A surge absorbing circuit that does not operate during a withstand voltage test is obtained. In addition, a surge absorption circuit capable of maintaining high impedance characteristics in all frequency regions and suppressing harmonic leakage current is obtained.

  The surge absorbing circuit according to the present invention is a surge absorbing circuit connected between a power supply line and ground, and is connected to the first surge absorber and the second surge absorber connected in series, and the first surge absorber. A first resistor connected in parallel; a second resistor connected in parallel to the second surge absorber; and a capacitor connected in parallel to the second resistor. is there.

  Since the surge absorption circuit according to the present invention includes the capacitor connected in parallel to the second surge absorber and the second resistor, a voltage lower than the withstand voltage test voltage when a lightning surge is applied without using a switch element. This circuit operates with values and does not operate during the dielectric strength test, and the entire circuit can be reduced in size. In addition, high impedance characteristics can be maintained in the entire frequency region, and harmonic leakage current can be suppressed.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram of a surge absorption circuit showing a first embodiment for carrying out the present invention. FIG. 2 shows a current path when a high-frequency voltage such as a lightning surge is applied, and FIG. 3 shows a current path when a low-frequency voltage used in a dielectric strength test is applied. In FIG. 1, a surge absorbing circuit 10 includes a first surge absorber 1 and a second surge absorber 2 connected in series, a first resistor 5 connected in parallel to the first surge absorber 1, and a second surge. The second resistor 6 is connected in parallel to the absorber 2, and the first capacitor 7 is a capacitor connected in parallel to the second resistor 6. The surge absorbing circuit 10 is connected between the power supply line 3 and the ground 4. That is, the first surge absorber 1 and the second surge absorber 2 are connected in series between the power supply line 3 and the ground 4.

  The first and second surge absorbers 1 and 2 are discharge tube types, and when a voltage higher than the discharge start voltage (hereinafter referred to as an operating voltage) of the discharge tube type surge absorber is applied to both ends of the surge absorber. Discharge occurs and short-circuits. The connection point between the power line 3 and the first surge absorber 1 is a, the connection point between the first surge absorber 1 and the second surge absorber 2 is b, and the connection point between the second surge absorber 2 and the earth 4 Is c. As described above, the first resistor 5 is connected in parallel to both ends of the first surge absorber 1 (between ab), and the second resistor 6 and the second resistor 6 are connected to both ends of the second surge absorber 2 (between bc). The first capacitors 7 are respectively connected in parallel.

  Here, the operating voltage V2S of the second surge absorber 2 is set to be equal to or lower than the operating voltage V1S of the first surge absorber 1. When the voltage Vac is applied between the power supply line 3 and the ground 4, the voltage applied to both ends of the first surge absorber 1 and both ends of the second surge absorber 2 is determined by the ratio of the impedances at both ends. Is done. Assuming that the voltage at both ends of the first surge absorber 1 is Vab, the impedance is Zab, the voltage at both ends of the second surge absorber 2 is Vbc, and the impedance is Zbc, the above-mentioned voltage and impedance are expressed by the relations of the expressions Will have.

  First, a case where a lightning surge is applied between the power supply line 3 and the ground 4 will be described. Generally, the voltage rise of lightning surge is set to 1.2 μs (microseconds). If a quarter period of the high-frequency voltage corresponds to this voltage rise, the frequency of the lightning surge is about 208.3 kHz. When such a high-frequency voltage is applied, the capacitor has a low impedance, and thus the impedance ZC of the first capacitor 7 becomes small. For this reason, when the specification is determined so that the impedance ZC of the first capacitor 7 at the lightning surge frequency is sufficiently small, for example, 1/10 or less of the impedance ZR2 of the second resistor 6, the first The impedance ZR2 of the second resistor 6 connected in parallel to the capacitor 7 is ignored and passes between the power line 3 and the ground 4 through the path 21 as shown by the arrow line in FIG. Surge current flows through

  As a result, since the impedance Zbc becomes very small, almost all of the voltage caused by the lightning surge is applied to the first surge absorber 1 if the impedance Zab is set to a value that is much larger than the impedance Zbc. become. For this reason, the protection voltage level of the power supply device against the lightning surge is determined by the operating voltage V1S of the first surge absorber 1.

  When a voltage higher than the operating voltage V1S of the first surge absorber 1 is applied between the power supply line 3 and the ground 4 due to a lightning surge, and the first surge absorber 1 operates, FIG. A surge current flows through the path 22 as shown by the arrow line. For this reason, the impedance Zab is substantially 0, and almost all surge voltages are applied to both ends of the second surge absorber 2. Since the operating voltage V2S of the second surge absorber 2 is set to be equal to or lower than the operating voltage V1S of the first surge absorber 1, the second surge absorber 2 operates immediately, as shown by the arrow line in FIG. A current flows through the path 23. That is, since the second surge absorber 2 also operates promptly following the operation of the first surge absorber 1, the reaction time to lightning surge is not inferior to the case where the surge absorber is used alone. .

  Next, voltage application in the dielectric strength test will be described. In the withstand voltage test, a commercial frequency alternating current is generally used. The frequency is 50 Hz or 60 Hz. At such a low frequency, the impedance ZC of the first capacitor 7 becomes very large. For this reason, the impedance ZC of the first capacitor 7 connected to the second surge absorber 2 can be ignored with respect to the flow of current between the power supply line 3 and the ground 4, and the arrow shown in FIG. A current flows through a path 24 like a line.

  At this time, since the voltage applied to the surge absorbing circuit 10 is divided by the resistance ratio between the first resistor 5 and the second resistor 6, the first resistor 5 and the second resistor 6 is a voltage applied to both ends of the first surge absorber 1 and both ends of the second surge absorber 2 if the maximum value of the test voltage used in the withstand voltage test is VINS. Is half the value of VINS. For this reason, if a voltage value between half of VINS and VINS is selected as the operating voltage of the first surge absorber 1 and the second surge absorber 2, the surge absorbing circuit 10 will operate in the dielectric strength test. Disappear. For this reason, it is not necessary to select a surge absorber having an operating voltage equal to or higher than VINS as in the prior art, and the protection voltage level of the power supply device against the lightning surge can be lowered.

As described above, since the operating voltage V2S of the second surge absorber 2 needs to be equal to or lower than the operating voltage V1S of the first surge absorber 1 for protection from lightning surge, the operating voltage V1S and the operating voltage V2S are required. Is set as follows.
VINS> V1S ≧ V2S> VINS / 2

  Assuming that the capacitance of the first capacitor 7 is 100 [pF], the impedance of the first capacitor 7 is 7.6 [kΩ] at the lightning surge frequency 208.3 [kHz], and the commercial frequency ( 50 [Hz]), 32 [MΩ]. Here, as an example, if the resistance values of the first resistor 5 and the second resistor 6 are selected to be 1 [MΩ], the above-described conditions for ignoring the impedance are satisfied, and the dielectric strength test is performed to 1500 [V. ], The leakage current generated in the surge absorbing circuit 10 can be reduced to about 0.75 [mA].

  In the above description, when a low-frequency voltage is applied between the power supply line 3 and the ground 4, the first capacitor 7 is selected so that the impedance of the first capacitor 7 can be ignored. By using the high impedance of the first capacitor 7 and selecting the first resistor 5 and the second resistor 6 having higher resistance values, the impedance at both ends of the surge absorbing circuit 10 is increased, It is also possible to further suppress the leakage current. In addition, since no inductor is used, impedance reduction between lines does not occur in the resonance frequency region, and the impedance at both ends of the surge absorption circuit 10 is high impedance in the entire frequency region due to the presence of the first resistor 5. Thus, the leakage current with respect to the harmonic can be reduced.

  As described above, by providing the first capacitor 7 connected in parallel to the second surge absorber 2, the following surge absorbing circuit 10 can be obtained. When a voltage is applied between the power supply line 3 and the ground 4, the applied voltage is divided by the impedance ratio between both ends of the first surge absorber 1 and both ends of the second surge absorber 2, so that a lightning surge occurs. When a high frequency voltage is applied, the impedance of the second resistor 6 can be ignored because the first capacitor 7 connected in parallel to the second surge absorber 2 has a low impedance. Since the first resistor 5 connected to the first surge absorber 1 has a sufficiently larger impedance than the first capacitor 7 connected in parallel to the second surge absorber 2, the lightning surge is First, it is applied to both ends of the first surge absorber 1, and the surge absorbing circuit 10 operates when the voltage value of the lightning surge rises above the operating voltage of the first surge absorber 1.

  When a low-frequency voltage used for the dielectric strength test is applied, the first capacitor 7 connected to the second surge absorber 2 has a high impedance, and the impedance is that of the second resistor 6. Since the impedance is sufficiently larger than the impedance, the impedances of the first and second resistors 5 and 6 connected to the first and second surge absorbers 1 and 2 are both ends of the first surge absorber 1 and the second surge absorber. 2 dominates the impedance of both ends. For this reason, since the low frequency voltage is divided by the impedance ratio between the first resistor 5 and the second resistor 6, the operating voltages of the first and second surge absorbers 1 and 2 are isolated. Even if the voltage is lower than the maximum voltage applied in the withstand voltage test, the operation of the surge absorbing circuit 10 during the withstand voltage test can be prevented and the withstand voltage test of the power supply device can be performed.

  Thus, without using a switching element, a surge that operates at a low voltage when a high-frequency voltage such as a lightning surge is applied, and does not operate when a low-frequency voltage used in a dielectric strength test is applied. Since the absorption circuit 10 can be obtained, the entire circuit can be reduced in size. Further, by selecting a resistor having a high resistance value for the first resistor 5 and the second resistor 6, the circuit maintains a high impedance characteristic in the entire frequency region. Leakage current can be suppressed.

  In the present embodiment, the case where the second surge absorber 2 and the second resistor 6 to which the first capacitor 7 is connected in parallel is provided on the ground 4 side has been described. As shown in FIG. The second surge absorber 2 and the second resistor 6 with the first capacitor 7 connected in parallel are provided on the power supply line 3 side, and the first surge absorber 1 and the first resistor 5 are provided on the ground 4 side. The same effect can be obtained in the surge absorbing circuit 20.

Embodiment 2. FIG.
FIG. 5 is a circuit diagram of a surge absorption circuit showing a second embodiment for carrying out the present invention. The surge absorbing circuit 30 according to the present embodiment is different from the first embodiment in that a series circuit in which the first resistor 5 and the second capacitor 8 are connected in series is connected in parallel to the first surge absorber 1. Different. In FIG. 5, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and this is common throughout the entire specification. Moreover, the aspect of the component which appears in the whole specification is an illustration to the last, and is not limited to these description.

  When a high-frequency voltage such as a lightning surge is applied, the second capacitor 8 has a low impedance, and the impedance is sufficiently lower than that of the first resistor 5. Since the impedance of 8 can be ignored, the lightning surge can be absorbed by the same operation as in the first embodiment. And when the low frequency voltage used for a withstand voltage test is applied, since the 2nd capacitor | condenser 8 becomes a high impedance, the suppression capability of the leakage current with respect to a harmonic of a low order can be made high.

  In the present embodiment, the case where the series circuit of the first resistor 5 and the second capacitor 8 is connected in parallel to the first surge absorber 1 provided on the power supply line 3 side has been described. This series circuit is connected in parallel to the second surge absorber 2 provided on the ground 4 side, and a parallel circuit of the second resistor 6 and the first capacitor 7 is provided on the power line 3 side. Even if the absorber 1 is connected in parallel, the same effect can be obtained.

Embodiment 3 FIG.
FIG. 6 is a circuit diagram of a surge absorption circuit showing a third embodiment for carrying out the present invention. In the surge absorbing circuit 40 of the present embodiment, a varistor 9 that is a protection element (nonlinear resistance element) that utilizes semiconductor nonlinearity is inserted between the second surge absorber 2 and the ground 4. Different from 1.

  In FIG. 6, a varistor 9 is inserted between the second surge absorber 2 and the earth 4. With such a configuration, the continuation of the surge absorber, which is a discharge tube, can be suppressed. Although the varistor 9 holds a certain amount of capacitance, depending on the capacitance held by the varistor 9 in order to prevent the voltage across the first surge absorber 1 from becoming small when a lightning surge is applied. Alternatively, the varistor capacitor 11 may be connected in parallel to the varistor 9 to increase the capacitance.

  A non-linear resistance element may be inserted between the surge absorbing circuit shown in the second embodiment and the ground as in the present embodiment. With such a configuration, the continuation of the surge absorber, which is a discharge tube, can be suppressed as in the present embodiment.

It is a circuit diagram of the surge absorption circuit in Embodiment 1 of this invention. It is a figure which shows the electric current path | route in case the high frequency voltage in Embodiment 1 of this invention is applied. It is a figure which shows the electric current path | route in case the low frequency voltage in Embodiment 1 of this invention is applied. It is another surge absorption circuit in Embodiment 1 of this invention. It is a circuit diagram of the surge absorption circuit in Embodiment 2 of this invention. It is a circuit diagram of the surge absorption circuit in Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 1st surge absorber, 2nd 2nd surge absorber, 3 power supply line, 4 earth | ground, 5 1st resistor, 6 2nd resistor, 7 1st capacitor, 8 2nd capacitor, 9 Varistor, 10, 20, 30, 40 Surge absorption circuit, 11 Varistor capacitor.

Claims (5)

A surge absorbing circuit connected between the power line and ground,
A first surge absorber and a second surge absorber connected in series;
A first resistor connected in parallel to the first surge absorber;
A second resistor connected in parallel to the second surge absorber;
A surge absorption circuit comprising: a capacitor connected in parallel to the second resistor. A second capacitor connected in series to the first resistor;
2. The surge absorbing circuit according to claim 1, wherein a series circuit including the first resistor and the second capacitor is connected in parallel to the first surge absorber. The surge absorption circuit according to claim 1 or 2, wherein a discharge start voltage of the second surge absorber is equal to or lower than a discharge start voltage of the first surge absorber. The surge according to any one of claims 1 to 3, wherein the first surge absorber is connected to the power supply line side, and the second surge absorber is connected to the ground side. Absorption circuit. 5. The non-linear resistance element is connected between the first surge absorber and the second surge absorber connected in series and the ground, 5. Surge absorption circuit.

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