JPH08251818A - Reverse-current preventive device, rectifying device and photovoltaic power generation system - Google Patents

Abstract

PURPOSE: To enhance a reverse-current preventive function and to reduce the power loss of a forward current. CONSTITUTION: A diode 4, for prevention of a reverse current, which is connected across a power supply 1 and a load 7 and a switching means 5 whose loss power in an ON state is smaller than that of the diode 4 are connected in parallel. A low-loss current detection means 6 which makes and breaks the switching means 5 is provided with a DC current detection part 6A and with a comparator IC1 which compares a detected current value with an operating- current threshold value. The switching means 5 is constituted so as to be made and broken by the output signal of the comparator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar power generation system configured to use, for example, a solar cell as a power source and the electric power generated therein to a load, and a single power source such as an RV vehicle or an electric vehicle. In a multi-battery system that is configured to supply power from a power source to multiple batteries, in order to prevent current from flowing back to the power source side such as the solar cell due to a drop in the output voltage from the power source, The present invention relates to a backflow prevention device in which a backflow prevention diode is interposed in series between a battery and a load (battery), a rectification device that can effectively apply the backflow prevention device, and a photovoltaic power generation system.

[0002]

2. Description of the Related Art In a system in which a diode for preventing backflow is interposed as described above, for example, in the case of the photovoltaic power generation system shown in FIG. 21, a solar cell 50 which is a power source and has a large amount of sunlight like daytime. When the current Is in the forward direction is flowing to the load 51 side, the current Is passes through the diode 52, resulting in a power loss due to a voltage drop of about 1 V, and This will cause a decline.

As a means for solving this, conventionally, as disclosed in Japanese Patent Application Laid-Open No. 2-168819, it is possible to suppress the occurrence of power loss when a current flows in the forward direction as much as possible. A possible power supply has been proposed. Here, when the proposed power supply device is replaced with a solar power generation system and schematically illustrated, the configuration is as shown in FIG. In FIG. 22, reference numeral 50 denotes a solar cell, and a relay contact 53 is connected in parallel to a backflow prevention diode 52 interposed in series between the solar cell 50 and a load 51. When the output voltage of the solar cell 50 is large, the diode 52 is bypassed to supply electric power to the load 51 side through the relay contact 53 which is in a closed state. The relay contact 53 is opened via the detection circuit 54 to prevent backflow to the solar cell 50 side.

[0004]

However, according to the backflow prevention device having the above-mentioned conventional configuration, the relay contact 53 is opened by detecting a decrease in the output voltage of the power source such as the solar cell 50. When the output voltage exceeds the specified value and the voltage drops below the terminal voltage on the battery side, a reverse current phenomenon occurs in which a reverse current flows from the battery side to the power supply side. Such a backflow phenomenon cannot be detected by the voltage detection circuit 54. Therefore, in the conventional backflow prevention device, the original backflow prevention function due to the use of the backflow prevention diode 52 may not be achieved, and new power loss is generated.

A main object of the present invention is to provide a backflow prevention device capable of improving the backflow prevention function and reducing the power loss of the forward current.

Another object of the present invention is to provide a rectifying device capable of exhibiting a predetermined rectifying function under a low voltage by utilizing the effect of reducing the power loss by the backflow prevention device.

Still another object of the present invention is to provide a solar power generation system capable of improving power generation efficiency and downsizing the entire system by utilizing the effect of reducing the power loss by the backflow prevention device. It is in.

[0008]

In order to achieve the above main object, a backflow prevention device according to the invention of claim 1 is a backflow prevention diode connected between a power supply and a load, and is turned on more than this diode. The low-loss current detecting means for connecting and disconnecting the switching means with a small loss power at the time of opening and closing the switching means includes a direct current detecting portion and a comparator for comparing the detected current value with the operating current threshold value. The switching means is opened / closed by an output signal of the comparator.

As the switching means, a power MOSFET or a voltage relay is used as in claims 2 and 4, and the backflow prevention diode can be a parasitic diode of the power MOSFET as in claim 3. . Further, the power MOSFET may be a P-channel type as claimed in claim 5 or an N-channel type as claimed in claim 6.

The DC current detector may be any one of claims 7 to 11.
Such as those using an input resistance, a Hall element and a magnetoresistive element, a means for detecting the voltage across the element that carries a forward current, or both ends of a switching element that is opened and closed by the output signal of the overcharge pressure detection circuit. It may be a means for detecting a voltage.

A backflow prevention device according to a twelfth aspect of the present invention is a backflow prevention device in which a power supply and a battery for storing and discharging the power generated and supplied by the power supply are connected through a backflow prevention diode. A switching means having a smaller loss power at the time of ON than the diode is connected in parallel to the diode, and a low loss current detection means for opening and closing the switching means is connected in series to the diode and the switching means connected in parallel. And a relay contact that disconnects the power supply to the battery when the terminal voltage on the battery side exceeds a predetermined value, in series with the backflow prevention diode, and in parallel with the switching means. It is characterized by being connected to.

According to a thirteenth aspect of the present invention, there is provided a vehicle battery backflow prevention device which is interposed in at least an electric power supply system for an engine battery among a plurality of electric power supply systems for a vehicle from a single power source. The backflow prevention device according to any one of claims 1 to 11 is used in place of the backflow prevention diode described above.

In order to achieve the above-mentioned other object, the rectifying device according to the invention of claim 14 constitutes a rectifying circuit interposed between a power supply and a load to which electric power generated by the power supply is supplied. The backflow prevention device according to any one of claims 1 to 11 is used instead of the plurality of rectifying diodes.

Further, in order to achieve the above-mentioned another object, the solar power generation system according to the invention of claim 15 is characterized in that the solar cell and the solar inverter are provided between the solar cell and the solar inverter.
It is characterized in that the backflow prevention device according to any one of 1 is arranged.

In the solar power generation system according to claim 16, a plurality of the backflow prevention devices and breakers are mounted on a single board provided with a connection terminal block or a connector between the solar cell and the solar inverter. It is preferable to interpose a connection box formed by the above.

Further, in the solar power generation system according to claim 16 or 17, the backflow prevention device according to any one of claims 1 to 11 is used in place of the protective diode interposed in the solar inverter. Is preferably used.

[0017]

According to the inventions of claims 1 to 11, when the output voltage of the power source is equal to or higher than a predetermined value, a forward current flows from the power source side to the load side. Since it reaches the load side through a switching means, such as a power MOSFET or a contact of a voltage relay, which is connected in parallel to the backflow prevention diode and has a smaller power loss than a diode in a closed state, the current flows through the diode. The power loss due to the voltage drop is much less than in the case. In addition, when the output voltage of the power source becomes a predetermined value or less, or when the load is a battery and the terminal voltage on the battery side exceeds the output voltage of the power source, the reverse current flows from the battery side to the power source side. However, at this time, the switching means is opened based on the low-loss current detection means, for example, the shunt resistance, the Hall element, and the current detection by the magnetoresistive element.
The reverse current is blocked by the diode, and the reverse current is surely prevented. Further, here, the resistance loss due to the current detecting means is also very small, and the power loss under the condition that the terminal voltage on the battery side exceeds the output voltage of the power source is very small.

In particular, when an N-channel type power MOSFET is used as the switching means, it is possible to remarkably reduce power loss when a forward current is flowing.

According to the twelfth aspect of the invention, the power loss is reduced due to the voltage drop when the forward current is flowing and the terminal voltage on the battery side exceeds the output voltage of the power source. In addition to achieving the backflow prevention function of the above, in order to prevent overcharge, the switching element for overcharge prevention, which is one of the factors that causes power loss due to being interposed in series downstream of the diode for backflow prevention, is generally used. The function can be replaced by a relay contact for low-loss current, and it is possible to reduce power loss in total while having both a backflow prevention function and an overcharge prevention function.

According to the thirteenth aspect of the invention, in order to keep the engine battery in a vehicle such as an RV vehicle or an electric vehicle always fully charged, a power supply system from the power source to the engine battery is used. By using the above-described backflow prevention device instead of the intervening backflow prevention diode, it is possible to greatly reduce the power loss when the forward current is flowing, that is, at the time of charging. At the same time, it is possible to prevent electric discharge when the engine is stopped.

According to the fourteenth aspect of the present invention, by using the above-described backflow preventing device instead of the rectifying diode, the power loss of the rectifying circuit as a whole can be reduced.

Further, according to the invention of claims 15 to 17, by utilizing the above-described backflow prevention device effective for reducing power loss in a solar power generation system, power generation efficiency can be improved and the entire system can be improved. Can be miniaturized. In particular,
As the configuration of the junction box used to connect the solar inverter and the solar cells, which are the components of this photovoltaic power generation system, by combining multiple backflow prevention devices and breakers on a single board, As compared with the case where the conventional connection box is used, the number of assembling steps of the entire system can be reduced and the size can be reduced. When the above-mentioned backflow prevention device is used in place of the protection diode interposed in the solar inverter, which is a component of this solar power generation system, to protect the capacitor by reverse connection and prevent electric shock to the operator It is possible to contribute to the improvement of power generation efficiency by reducing the power loss by the protection diode while performing the above-mentioned capacitor protection function and electric shock prevention function as required.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram showing a basic configuration when the backflow prevention device of the present invention is applied to a photovoltaic power generation system. In FIG. 1, 1 is a solar battery serving as a power source, 2
Is a battery that stores and discharges the electric power generated in the solar cell 1, 7 is a load connected in parallel to the battery 2, and the load 2 and the battery 7 connected in parallel and the solar cell 1 are They are connected in series via the backflow prevention device 3. The backflow prevention device 3 includes a backflow prevention diode 4, a switching unit 5 which has a smaller power loss when turned on than the diode 4 and is connected in parallel to the diode 4, the switching unit 5 and the diode. 4 and a current detecting means 6 which is connected in series with the solar cell 1 to detect the current generated by the solar cell 1 to open and close the switching means 5.

Next, an embodiment based on the basic structure shown in FIG. 1 will be described. Embodiment 1 FIG. 2 shows a P-channel type power MOSFE as the switching means 5 in the backflow prevention device 3.
While using T, the input resistance R is used as the current detection means 6.
DC current detector 6A composed of s, shunt resistors R1 to R
4 and the comparator IC1 are used, and the shunt resistors R1 to R4 are set so that the current detecting means 6 exhibits the circuit characteristics shown in FIG. Specifically, when the generated current Is of the solar cell 1 is small, the output V1 of the comparator IC1 becomes Hi (V3 ≧ V2), and when the generated current Is of the solar cell 1 is large, the input resistance voltage Vs is large. Then, the output V of the comparator IC1
R4 / (R3 +) so that 1 becomes Lo (V2> V3)
R4)> R2 / (R1 + R2) is set. Figure 2
Since other configurations are the same as those in FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

Next, the operation of the first embodiment will be described. When the amount of sunshine is large and the power generation current Is of the solar cell 1 is large, such as during daytime in fine weather, the input resistance voltage Vs is large.
Becomes larger, the output V1 of the comparator IC1 becomes Lo, and the output of the current detecting means 6 becomes Lo, so that the P-channel power MOSFET is maintained in the closed (ON) state. As a result, the generated current Is does not flow through the diode 4, bypasses it, and flows through the FET having a small resistance to the battery 2 side, and the power loss due to the diode 4 is reduced.

On the other hand, the generated current I of the solar cell 1 is small when the amount of sunshine is small, or when there is no sunshine, such as at night or in rainy weather.
When s becomes a predetermined value or less, the output V of the comparator IC1
Since 1 becomes Hi and the output of the current detecting means 6 becomes Hi, the P-channel type power MOSFET is in an open (off) state, and a backflow from the battery 2 side to the solar cell 1 side is prevented. Furthermore, at night, the comparator IC1
Since the output of will use the open collector output,
When the output V1 is Hi, the output current of the comparator IC1 is 0A, and the input resistance Rs and the comparator I
C1 does not consume the charging power of the battery 2.

Embodiment 2 In FIG. 4, an N-channel power MOSFET is used as the switching means 5 in the backflow prevention device 3, while the current detecting means 6 is a DC current detecting section 6A composed of an input resistor Rs and a shunt. The resistors R1 to R4, the comparator IC1 and the switching transistor Tr1 are used, and the positive and negative electrodes of the circuit of the first embodiment are replaced to prevent backflow on the negative electrode side.

According to the above construction, when the generated current Is of the solar cell 1 is large, the input resistance voltage Vs becomes large and the output V1 of the comparator IC1 becomes Hi as shown in FIG. Since the output is Hi, the N-channel type power MOSFET is maintained in the closed (ON) state. In addition, the generated current I of the solar cell 1
When s becomes a predetermined value or less, the output V of the comparator IC1
Since 1 becomes Lo and the output of the current detecting means 6 becomes Lo, the N-channel type power MOSFET is in an open (OFF) state, and backflow from the battery 2 side to the solar cell 1 side is prevented. Since the other configurations are the same as those of the first embodiment shown in FIG. 2, corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

By the way, as the discharge path from the battery 2 at night, the paths indicated by arrows a and b in FIG. 4 can be considered. Among them, the discharge current of the a path is not reacted by the current detecting means 6 at all, so that the FET is maintained in the open state and blocked by the diode 4. Also, b
Since the current detection means 6 does not react to the discharge current of the path, the transistor Tr1 is turned off and the FET
Is kept open, no current flows, and there is no discharge of the battery 2 at night.

Next, the power loss generated in the backflow prevention device 3 of the first and second embodiments and the power loss when the forward current flows through the diode 4 are compared based on a predetermined calculation formula. Then, it becomes as follows. (1) Assumed conditions Battery voltage VB: 12V Maximum generated current Imax: 3A R1 to R6: Approximately 100KΩ (2) Power loss Pd of the backflow prevention diode is: Pd = Imax × VFM ∴VFM: Diode forward voltage = 3A × 0.55V (ERC80 (5A) made by Fuji Electric) = 1.65W (3) The power loss P1 of Examples 1 and 2 is: P1 = P2 + P3 + P4 + P5 + P6 ∴P2: FET loss P3: Input resistance loss P4: Loss of IC1 P5 : Gate drive loss P6: Current detection resistance loss where P2 = Imax ² × RDS (on) ∴RDS (on): Drain-source ON resistance = (3A) ² × 0.014Ω (2SK1596 manufactured by NEC) ^{= 0.126W P3 = Imax 2 × Rs} ∴Rs: input resistance resistance ^{= (3A) 2 × 0.01Ω =} 0.09W P4 = VB × Icc ∴Icc: circuit current 12V × 0.0006A (μPC277 made NEC) = 0.0072W P5 = {( VB) 2 / R5} + {(VB) 2 / R6} = {(12) 2 / 100KΩ} + {(12) 2 / 100KΩ} = 0.028W P6 = {(VB) ² / R1 + R2} + {(VB) ² / R3 + R4} = {(12) ² / 200KΩ} + {(12) ² / 200KΩ} = 0.0014W. Therefore, P1 = 0.26 + 0.09 + 0.0072 + 0.0028 + 0.0014 = 0.227w, which is compared with (2): P1 / Pd = 0.138 = 1 / 7.3 and the power loss is 7 minutes. It can be reduced to 1 or less.

Embodiment 3 In FIG. 6, a voltage relay X is used as the switching means 5 in the backflow prevention device 3, and its contact La is connected in parallel to the backflow prevention diode 4, while the current detection means 6 receives an input. The direct current detection unit 6A including the resistor Rs, the shunt resistors R1 to R4, and the comparator IC1 are used. The resistance values of the shunt resistors R1 to R4 are set in the same manner as in Example 1, and the other configurations are the same as those in FIG.
Corresponding parts are designated by the same reference numerals and their description is omitted. Also, since the basic operation is almost the same as that of the first embodiment, the description thereof will be omitted.

Next, the power loss generated in the backflow prevention device 3 of the third embodiment is compared with the power loss when the forward current flows through the diode 4 as follows. The assumed conditions are the same as those in the first and second embodiments. The power loss P7 of Example 3 is: P7 = P8 + P3 + P4 + P6 ∴P8: Relay loss (G5C made by OMRON) P3: Input resistance loss P4: IC1 loss P6: Current detection resistance loss = 0.2 + 0.09 + 0.0072 + 0.0014 = 0.30 W, which is P7 / Pd = 0.18 = 1 / 5.5 compared with the power loss Pd of the backflow prevention diode 4 in (2) above, and the power loss is reduced to one fifth or less. can do.

Embodiment 4 In FIG. 7, a P-channel type power MOSFET is used as the switching means 5 in the backflow prevention device 3, while a GaAs Hall element OHD11 (Matsushita Electric Industrial Co., Ltd.) is used as the current detecting means 6. The direct current detector 6A, the comparator IC1 and the variable resistor VR1 are used. Since the other configurations are the same as those in FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted. Further, since the basic operation is almost the same as that of the first embodiment, the description will be omitted.

Next, the power loss generated in the backflow prevention device 3 of the fourth embodiment and the power loss when a forward current flows through the diode 4 are compared as follows. The assumed conditions are: battery voltage VB: 12V maximum power generation current Imax: 3A Hall element consumption current IH: 1.7mA, variable resistance value RVR: 100KΩ. The power loss P9 of the fourth embodiment is P9 = PH + PVR + P2 + P4 + P5 ∴PH: Hall element loss PVR: Variable resistance loss P2: FET loss P4: IC1 loss P5: Gate drive loss = (0.0017 × 12) + (12 ^2/100 · 10 ³⁾ is +0.12 6 + 0.0072 + 0.0028 = 0.158W , when compared to the power loss Pd of the backflow prevention diode in the (2), P9 / Pd = 0.158 / 1. Since 65 = 1 / 10.4, the power loss can be reduced to 1/10 or less.

Embodiment 5: In FIG. 8, a P-channel type power MOSFET is used as the switching means 5 in the backflow prevention device 3, while a DC current detection consisting of a magnetoresistive element (MR element) is used as the current detection means 6. 6A, shunt resistors R2 to R4, and comparator IC
1 is used. Since the other configurations are the same as those in FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted. Further, since the basic operation is almost the same as that of the first embodiment, the description will be omitted.

Next, the power loss generated in the backflow prevention device 3 of the fifth embodiment will be compared with the power loss when the forward current flows through the diode 4 as follows. The assumed conditions are: battery voltage VB: 12V maximum generated current Imax: 3A Resistance value RM of MR element: 100KΩ since it can be arbitrarily changed depending on the film thickness and shape. The power loss P10 of the fifth embodiment is as follows: P10 = PM + P2 + P4 + P5 ∴PM: Loss of the value of MR element and resistors R2 to R4 (≈P6) P2: FET loss P4: IC1 loss P5: Gate drive loss = 0.0014 + 0 .126 + 0.0072 + 0.0028 = 0.137W, which is compared with the power loss Pd of the backflow prevention diode in (2) above. P10 / Pd = 0.137 / 1.65 = 1/12

Example 6: FIG. 9 shows a solar cell 1 as a power source.
And a battery 2 that stores and discharges electric power generated in the solar cell 1 and a load 7 that is connected in parallel to the battery 2 are connected in series via a backflow prevention device 3, and a battery An overcharge pressure detection circuit 8 for detecting the terminal voltage on the second side is provided, and is provided with an overcharge prevention function that cuts off the power supply to the battery 2 when the detected terminal voltage thereby exceeds a predetermined value. Is. As shown in FIG. 10, the specific circuit configuration uses a voltage relay X as the switching means 5 connected in parallel to the backflow prevention diode 4 in the same manner as in the third embodiment, and its contact Xa. Is connected in parallel to the backflow prevention diode 4, and the backflow prevention device 3 is configured by using, as the current detection means 6, the direct current detection unit 6A including the input resistance Rs, the shunt resistors R1 to R4, and the comparator IC1. At the same time, the overcharge pressure detection circuit 8 causes the resistors R7 and R
8, R10, a zener diode (low voltage diode) D and a comparator IC2, and a contact X1a of a voltage relay X1 which is opened / closed via a switching transistor Tr1 by an output VE of the overcharge pressure detection circuit 8.
Is connected in series to the backflow prevention diode 4, and the voltage relay X can be opened via the transistor Tr2 and the comparator IC2. Since other configurations are the same as those in the above-described respective embodiments, corresponding parts are designated by the same reference numerals, and description thereof will be omitted.

In the operation of the sixth embodiment described above, the power loss is reduced due to the voltage drop of the backflow prevention diode 4 when the forward current is flowing, and the terminal voltage on the battery 2 side exceeds the output voltage of the solar cell 1. In addition to achieving the backflow prevention function under such conditions, the overcharge pressure detection circuit 8
When the output VE becomes low, the contacts Xa and X1a of the voltage relays X and X1 are both opened to automatically stop the charging of the battery 2. The contact X of the low-loss current relay X1 has the function of the switching element for overcharge prevention, which has been a cause of generating power loss by being interposed in series on the downstream side.
1a can be substituted, and the total power loss can be reduced while having both the backflow prevention function and the overcharge prevention function.

Embodiment 7: FIG. 11 shows a solar cell 1 serving as a power source, the power generated by the solar cell 1, and
The discharging battery 2 and the load 7 connected in parallel to the battery 2 are connected via the backflow prevention device 3, and the overcharge pressure detecting circuit 8 for detecting the terminal voltage on the battery 2 side is provided. When the detection terminal voltage thereby exceeds a predetermined value, the power supply to the battery 2 is cut off, and an overcharge preventing function is provided. A specific circuit configuration is such that a P-channel type power MOSFET is used as the switching means 5 connected in parallel to the backflow prevention diode 4, and a P-channel type power MOSFET 1 is used as the current detecting means 6. The direct current detection unit 6A, the shunt resistors R1 to R4, and the comparator IC1 are used. When the detection terminal voltage by the overcharge pressure detection circuit 8 becomes a predetermined value or more, the FET1 supplies power to the battery 2. It is configured to cut off. Since other configurations are the same as those in the above-described respective embodiments, corresponding parts are designated by the same reference numerals, and description thereof will be omitted.

In the above configuration, when the detection terminal voltage by the overcharge pressure detection circuit 8 is below a predetermined value, its output V
E is Lo and holds the FET1 in the ON state.
In this state, when the amount of sunlight is large and the power generation current Is of the solar cell 1 is large, as in the daytime in fine weather, the above FET is used.
Since the voltage Vs1 (Va-Vb) across 1 becomes large, the output V1 of the comparator IC1 becomes Lo, and the output of the current detecting means 6 becomes Lo, the FET is maintained in the ON state. As a result, the generated current Is does not flow through the diode 4, bypasses it, and flows through the FET having a small resistance to the battery 2 side, and the power loss due to the diode 4 is reduced.

On the other hand, when the power generation current Is of the solar cell 1 becomes less than a predetermined value, the voltage Vs1 across the FET1 becomes small and the output V1 of the comparator IC1 becomes Hi,
Since the output of the current detection means 6 becomes Hi, the FET is turned off and the backflow from the battery 2 side to the solar cell 1 side is prevented. Further, when the detection terminal voltage by the overcharge pressure detection circuit 8 becomes equal to or higher than a predetermined value, the output VE becomes Hi, the FET 1 is held in the OFF state, and the power supply to the battery 2 is cut off, Charging can be prevented.

Embodiment 8: In FIG. 12, an N-channel type power MOSFET is used as the switching means 5 in the backflow prevention device 3, while a DC current detecting section consisting of an N-channel type power MOSFET 1 is used as the current detecting means 6. 6A, shunt resistors R1 to R4, and a comparator IC1 are used, and the positive and negative electrodes of the circuit of the seventh embodiment are replaced with each other to prevent backflow and overcharge on the negative electrode side. Since other configurations are the same as those of the seventh embodiment shown in FIG. 11, corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

Next, comparing the power loss generated in the backflow prevention device 3 of the first and second embodiments with the power loss generated in the backflow prevention device 3 of the seventh and eighth embodiments, the input resistance RS , Power MOSFET and FET1
When each resistance value of is 30 mΩ, the former power loss Pd1 when the generated current is 3 A is Pd1 = (3A) ² × (30 mΩ × 3) = 810 mW, whereas the latter power loss Pd2 is , Input resistance R
Since S is unnecessary, Pd2 = (3A) ² × (30 mΩ × 2) = 540 mW, and the power loss Pd2 can be reduced to two-thirds of Pd1.

FIG. 13 shows current-power loss characteristics. As is apparent from FIG. 13, the power loss (characteristic A) of the backflow prevention diode 4 at the rated current 3A is about 2 W, while the relay contacts Xa and X1a shown in FIG.
And the power MOSFETs F and F shown in FIGS. 11 and 12.
The power loss (characteristic B) of ET1 is about 0.17W, which is 1
It is possible to reduce the loss to 1/0 or less.

FIG. 14 shows current-device temperature characteristics at an ambient temperature of 25 ° C. As is apparent from FIG. 14, the junction temperature of the backflow prevention diode 4 at the rated current 3A is 75 ° C., which is a temperature increase of 50 ° C. Since the maximum rated temperature of diode 4 is 150 ° C, the allowable temperature rise is 100 ° C, considering that the temperature inside the housing installed outdoors in summer reaches 50 ° C.
Is. Therefore, the backflow prevention diode 4 needs a heat dissipation measure in order to pass a current of 6 A or more, which hinders size reduction. Further, if the junction temperature is 100 ° C. or higher, the failure rate becomes high and the reliability is lowered. On the other hand, the backflow prevention relay contacts Xa, X1a, MOSFET,
In the case of FET1, the junction temperature at rated current 3A is 2 ° C (about 1/25 of that of diode 4), current 7A
Since the junction temperature at 15 ° C. is a temperature rise of 15 ° C. (about 1/9 of the diode 4), no heat dissipation measures are required, and the size can be reduced and the reliability can be improved.

Embodiment 9: In each of the above embodiments, the backflow prevention diode 4 can also be used as a parasitic diode of a power MOSFET, whereby the backflow prevention device 3 can be miniaturized. it can.

[Embodiment 10] In this embodiment, as shown in FIG. 15, power is supplied to an engine battery 2A for supplying electric power from a generator 11 (power source) to an engine 10 for driving a vehicle and an on-vehicle electric appliance 9. In a vehicle such as an RV or an electric vehicle equipped with a battery 2B for supplying electric products,
In order to ensure that the engine battery 2A is always in a fully charged state, the generator battery 11 is connected to the engine battery 2
This is an application example in which the above-described backflow prevention device 3 is used in place of the backflow prevention diode interposed in the power supply system reaching A. According to this embodiment, a forward current from the generator 11 is generated. While flowing, that is, it is possible to greatly reduce the power loss during charging,
It is possible to prevent discharge from the battery 2A when the engine 10 is stopped. Further, it is possible to eliminate or reduce the heat dissipation plate of the diode which is conventionally required.

Embodiment 11: In this embodiment, as shown in FIG. 16, in order to convert the alternating current input from the alternating-current power supply 12 to direct current, four rectifying diodes are assembled in a rhombus, and one of the pairs is formed. In addition to using the backflow prevention device 3 as described above, instead of each rectifying diode of the bridge-type full-wave rectifier circuit 13 configured to apply an AC voltage to the corner and take out the DC from another diagonal, This is an application example in which the above-described backflow prevention device 3 is used instead of the DC smoothing diode connected to the output side of the full-wave rectification circuit 13 via the transformer 14. According to this embodiment, the rectification is performed. It is possible to reduce the power loss due to the use and smoothing diodes, and improve the rectification efficiency.

Embodiment 12: In this embodiment, as shown in FIG. 17, a solar cell 1 having a solar cell 1 and a solar inverter 15 for DC / AC is provided with a backflow prevention device 3 as described above. This is an application example to a photovoltaic power generation system, and according to this embodiment, it is possible to reduce power loss during power generation,
In addition to improving power generation efficiency, the entire system can be downsized and a backflow prevention function can be secured when the amount of sunlight is small.

In particular, in the twelfth embodiment, as shown in FIG. 18, a solar inverter 15 which is a constituent element of this solar power generation system and a plurality of sets of solar cells 1 installed in parallel on a roof or the like are provided, for example, in a building. As a configuration of the connection box 16 used for connection in the space under the eaves of the eaves, as shown in FIG.
By using a plurality of backflow prevention devices 3 and breakers 19 mounted on a single board 18 having a large diode, as in the past, a large diode is used, and these diodes are attached to the heat sink by soldering. In addition, the number of assembly steps for the entire system can be reduced, and the size and space can be reduced compared to the case where a wiring box is used and a junction box that is configured to cover the whole with an electric shock prevention cover is used. It is possible.

Furthermore, in the solar inverter 15 which is a constituent element of the solar power generation system shown in the eleventh embodiment,
As shown in FIG. 20, instead of the protection diode, which is connected in series to the PWM 20, the transformer 21, and the capacitor 22, and which is interposed for protection of the capacitor 22 by reverse connection and prevention of electric shock to the worker, It is also possible to use the above-described backflow prevention device 3, and in this case,
It is possible to contribute to the improvement of power generation efficiency by reducing the power loss by the protection diode while performing the above-mentioned capacitor protection function and electric shock prevention function as required.

[0052]

As described above, the claims 1 to 1 are as follows.
According to the first aspect of the present invention, when a forward current flows from the power supply side to the load side, the current is switched to a switching means having a smaller power loss than the backflow prevention diode, for example, a contact of a power MOSFET or a voltage relay. By flowing the current through the diode to the load side, it is possible to significantly reduce the power loss due to the voltage drop, as compared with the case of flowing through the diode. Nevertheless, when the forward current is small, or when the load is a battery and the terminal voltage on the battery side exceeds the output voltage of the power supply, low loss current detection means, such as a shunt resistor, is used. The switching means is opened based on the current detection by the Hall element, the magnetoresistive element, and the reverse current is blocked by the diode, so that the original backflow preventing function can be surely exhibited. Further, the resistance loss due to the current detection means is extremely small, and the power loss under the condition that the terminal voltage on the battery side exceeds the output voltage of the power source can be extremely reduced, which is also an advantage. Is one.

In particular, if an N-channel type power MOSFET is used as the switching means, the power loss when a forward current is flowing can be further remarkably reduced.

According to the twelfth aspect of the present invention, the power loss is reduced due to the voltage drop when the forward current is flowing and the terminal voltage on the battery side exceeds the output voltage of the power source. In addition to achieving the backflow prevention function of, the low-loss current relay contact can replace the function of the overcharge prevention switching element, which has been a cause of generating power loss. It is possible to significantly reduce the total power loss while ensuring the overcharge prevention function.

According to the thirteenth aspect of the present invention, when the forward current is flowing, that is, when the engine battery is charged, the power loss can be greatly reduced, and the discharge can be prevented when the engine is stopped. Therefore, it is possible to prevent the engine battery in a vehicle such as an RV vehicle or an electric vehicle from being constantly maintained in a fully charged state.

According to the fourteenth aspect of the invention, it is possible to reduce the power loss due to the rectifying diode during the rectifying action, and it is possible to improve the rectifying efficiency.

Further, according to the fifteenth to seventeenth aspects of the present invention, by utilizing the above-described backflow prevention device effective for reducing the power loss in the solar power generation system, the power generation efficiency can be improved. The size of the entire system can be reduced. In particular, when connecting the solar inverter, which is a component of this photovoltaic power generation system, and the solar cell using a junction box having a configuration in which a plurality of backflow prevention devices and breakers are assembled on a single board, the entire system is It is possible to reduce the number of assembly steps and reduce the size. When the above-mentioned backflow prevention device is used in place of the protection diode interposed in the solar inverter, which is a component of this solar power generation system, to protect the capacitor by reverse connection and prevent electric shock to the operator Can reduce the power loss and contribute to the improvement of power generation efficiency while performing the capacitor protection function and the electric shock prevention function as predetermined.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a basic configuration when a backflow prevention device of the present invention is applied to a solar power generation system.

FIG. 2 is a circuit diagram showing the configuration of the first embodiment.

FIG. 3 is an explanatory diagram showing a circuit characteristic of a current detection unit in the first embodiment.

FIG. 4 is a circuit diagram showing a configuration of a second embodiment.

FIG. 5 is an explanatory diagram showing the circuit characteristics of the current detection means in the second embodiment.

FIG. 6 is a circuit diagram showing a configuration of a third embodiment.

FIG. 7 is a circuit diagram showing a configuration of a fourth embodiment.

FIG. 8 is a circuit diagram showing a configuration of a fifth embodiment.

FIG. 9 is a block circuit diagram showing the basic configuration of the sixth embodiment.

FIG. 10 is a circuit diagram showing a specific configuration of FIG.

11 is a circuit diagram showing a specific configuration of FIG.

FIG. 12 is a block circuit diagram showing a configuration of an eleventh embodiment.

FIG. 13 is a current-power loss characteristic of the backflow prevention device according to the present invention.

FIG. 14 is a current-element temperature characteristic of the backflow prevention device according to the present invention.

FIG. 15 is a block circuit diagram showing the configuration of the tenth embodiment.

FIG. 16 is a block circuit diagram showing the configuration of the eleventh embodiment.

FIG. 17 is a block circuit diagram showing the configuration of the twelfth embodiment.

FIG. 18 is a block circuit diagram showing a configuration of an application example of the twelfth embodiment.

19 is a schematic perspective view showing one of the components of FIG. 18. FIG.

FIG. 20 is a block circuit diagram showing a configuration of a solar inverter which is one of application examples of the twelfth embodiment.

FIG. 21 is a block circuit diagram showing a schematic configuration of a general solar power generation system.

FIG. 22 is a block circuit diagram showing a schematic configuration of a conventionally proposed solar power generation system.

[Explanation of symbols]

1 Solar Cell (Power Source) 2 Battery 2A Engine Battery 3 Backflow Prevention Device 4 Backflow Prevention Diode 5 Switching Means (Power MOSFET, Voltage Relay, etc.) 6 Low Loss Current Detection Means (Input Resistance, Hall Element, Magnetoresistive Element, Power) 6A DC current detection unit 7 Load 8 Overcharge pressure detection circuit 11 Generator (power supply) 13 Bridge type full-wave rectifier circuit 15 Solar inverter 16 Junction box 18 Single board 19 Breaker IC1 Comparator VS1 Both-end voltage

Claims (17)

[Claims] 1. A low loss current for connecting a backflow prevention diode connected between a power source and a load and a switching means, which has a smaller loss power when turned on than the diode, in parallel and for opening and closing the switching means. The detection means includes a direct current detection unit and a comparator for comparing the detected current value with the operating current threshold value, and the switching means is configured to open and close by the output signal of the comparator. Prevention device. 2. The switching means is a power MOS
The backflow prevention device according to claim 1, comprising a FET. 3. The backflow prevention diode has a power M
The backflow prevention device according to claim 1, which comprises a parasitic diode of an OSFET. 4. The backflow prevention device according to claim 1, wherein the switching means comprises a voltage relay, and a relay contact of the voltage relay is connected in parallel to the backflow prevention diode. 5. The backflow prevention device according to claim 2, wherein the power MOSFET is a P-channel type. 6. The backflow prevention device according to claim 2, wherein the power MOSFET is an N-channel type. 7. The backflow prevention device according to claim 1, wherein the direct current detection unit includes an input resistor. 8. The backflow prevention device according to claim 1, wherein the DC current detector uses a Hall element. 9. The backflow prevention device according to claim 1, wherein the current / current detector uses a magnetoresistive element. 10. The backflow prevention device according to claim 1, wherein the direct current detection unit includes means for detecting a voltage across an element for supplying a forward current. 11. The backflow prevention device according to claim 1, wherein the DC current detection unit includes means for detecting a voltage across a switching element that is opened and closed by an output signal of an overcharge pressure detection circuit. 12. A backflow prevention device comprising a power supply and a battery that stores and discharges the power generated and supplied by the power supply, connected via a backflow prevention diode, wherein the diode is turned on when the diode is on. Connected in parallel to the switching means having a small loss power, the low-loss current detection means for opening and closing the switching means is connected in series to the diode and the switching means connected in parallel, and the terminal voltage on the battery side. Is a predetermined value or more, a relay contact for cutting off power supply to the battery is connected in series to the backflow prevention diode and in parallel to the switching means. Prevention device. 13. A backflow prevention diode interposed in at least an electric power supply system for an engine battery among electric power supply systems for supplying a plurality of batteries in a vehicle from a single power source, in place of any one of claims 1 to 11. A backflow prevention device for a vehicle battery, characterized by using the backflow prevention device according to item 1. 14. The rectifying circuit, which is interposed between a power source and a load to which the power generated by the power source is supplied, is replaced with a plurality of rectifying diodes, and the rectifying circuit is replaced by a plurality of rectifying diodes. A rectifying device characterized by using the backflow prevention device described in 1. 15. A photovoltaic power generation system, comprising the backflow prevention device according to claim 1 connected between a solar cell and a solar inverter. 16. The solar cell and the solar inverter are connected through a connection box formed by assembling a plurality of the backflow prevention devices and a breaker on a single board provided with a connection terminal block or a connector. Item 11. The solar power generation system according to Item 11. 17. The backflow prevention device according to claim 1, in place of the protective diode interposed in the solar inverter.
Or the solar power generation system according to item 16.