Voltage conversion circuit

Abstract

To provide a voltage conversion circuit with extremely high reliability. [Solution] The voltage conversion circuit comprises a plurality of capacitive elements connected in series between a first pair of terminals, a plurality of first photorelays whose output sides are inserted on both ends of each capacitive element, a plurality of second photorelays whose output sides are inserted between each terminal of a second pair of terminals and each end of each capacitive element, and a switching control unit that switches the input sides of the plurality of first and second photorelays so that when the output sides of the plurality of first photorelays are non-conductive, the output sides of the plurality of second photorelays are conductive, and when the output sides of the plurality of first photorelays are conductive, the output sides of the plurality of second photorelays are non-conductive.

Description

Technical Field

[0001] The present invention relates to a voltage conversion circuit used in, for example, electric vehicles and the like.

Background Art

[0002] In order to supply appropriate power from a power source such as a lithium-ion secondary battery to a load, a circuit for converting voltage is used.

[0003] As such a voltage conversion circuit, a technique is disclosed in which a plurality of capacitors are connected in parallel and charged, and at the time of supply (discharge), they are switched so as to be connected in series (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The power for driving an electric vehicle or the like is extremely large compared to that of a smartphone or the like, and extremely high reliability is required. However, in the technique described in Patent Document 1, for example, due to a failure of a switch circuit that switches between parallel and series connections of capacitors, a large current may flow to the control side, resulting in a risk of losing control.

[0006] In order to solve such problems, an object of the present invention is to provide a voltage conversion circuit having extremely high reliability.

Means for Solving the Problems

[0007] The voltage conversion circuit according to the present invention comprises: a plurality of capacitive elements connected in series between a first pair of terminals; a plurality of first photorelays whose output sides are inserted on both ends of each of the capacitive elements; a plurality of second photorelays whose output sides are inserted between each terminal of a second pair of terminals and each end of each of the capacitive elements; and a switching control unit that switches the input sides of the plurality of first and second photorelays so that when the output sides of the plurality of first photorelays are non-conductive, the output sides of the plurality of second photorelays are conductive, and when the output sides of the plurality of first photorelays are conductive, the output sides of the plurality of second photorelays are non-conductive.

[0008] In this invention, since the voltage conversion system, which includes a plurality of capacitive elements that can be connected in series, and the control system, which includes a switching control unit, are separated into the output side and the input side of the photorelay, a voltage conversion circuit with extremely high reliability can be constructed without a large current flowing to the control side in the event of a failure in the voltage conversion system.

[0009] In the voltage conversion circuit according to the present invention, the first pair of terminals are output terminals, and the second pair of terminals are connected to a power source such as a lithium-ion secondary battery. Alternatively, in the voltage conversion circuit according to the present invention, the first pair of terminals may be connected to a power source, and the second pair of terminals may be output terminals. This allows for the configuration of a step-down circuit for reducing voltage.

[0010] The voltage conversion circuit according to the present invention includes a switching control unit having a third photorelay whose output side is connected to the input side of the plurality of first photorelays, and a fourth photorelay whose output side is connected to the input side of the plurality of second photorelays, wherein one of the third photorelay and the fourth photorelay is of type a and the other is of type b, and a common charge / discharge switching signal is input to the input side of the third photorelay and the input side of the fourth photorelay.

[0011] This invention allows switching control to be performed with a simpler configuration, thereby improving reliability.

[0012] The voltage conversion circuit according to the present invention includes a changeover control unit which has a changeover switch and a control power supply that output a common charge / discharge switching signal to the input side of the third photorelay and the input side of the fourth photorelay.

[0013] The voltage conversion circuit according to the present invention includes a switching control unit which has a circuit element and a control power supply that outputs a common charge / discharge switching signal to the input side of the third photorelay and the input side of the fourth photorelay.

[0014] The voltage conversion circuit according to the present invention comprises: a plurality of capacitive elements that can be connected in series between output terminals; a plurality of MOSFETs or a plurality of IGBTs inserted on both ends of each of the capacitive elements, with the source-drain or collector-emitter connections between them; a plurality of first photorelays whose output side is connected to the gate of each MOSFET or the gate of each IGBT; a plurality of second photorelays whose output side is inserted between each terminal of a second pair of terminals and each end of each of the capacitive elements; and a switching control unit that switches the input sides of the plurality of first and second photorelays so that when the output sides of the plurality of first photorelays are non-conductive, the output sides of the plurality of second photorelays are conductive, and when the output sides of the plurality of first photorelays are conductive, the output sides of the plurality of second photorelays are non-conductive.

[0015] In this invention, series-parallel switching is performed using MOSFETs or IGBTs, and the switching of these MOSFETs or IGBTs is performed using photorelays. Therefore, it is possible to handle loads that carry large currents exceeding the current rating of the photorelays, and reliability can be improved.

[0016] The high-voltage conversion circuit according to the present invention is configured such that the first pair of terminals or the output terminals of the above-mentioned voltage conversion circuit are connected in parallel to a supercapacitor with respect to a load.

[0017] According to the findings of the present inventors, it has been found that a power supply with extremely small voltage fluctuations with respect to the load can be provided by the above configuration. This is presumably because the switching between series and parallel by the voltage conversion circuit according to the present invention is performed by a photo relay, and the power supply is provided with a square-wave voltage with suppressed voltage fluctuations during charging and discharging.

Effects of the Invention

[0018] According to the present invention, a voltage conversion circuit having extremely high reliability can be provided.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 15 is a circuit diagram showing a voltage conversion circuit according to another embodiment of the present invention. [Figure 2] FIG. 18 is a circuit diagram showing a voltage conversion circuit according to another embodiment of the present invention. [Figure 3] FIG. 21 is a circuit diagram showing a high-voltage conversion circuit according to another embodiment of the present invention. [Figure 4] In FIG. 3, it is a graph of the measurement result of the output voltage of the high-voltage conversion circuit connected in parallel with the supercapacitor. [Figure 5] FIG. 27 is an enlarged graph of a part of FIG. 4. [Figure 6] FIG. 30 is a graph of the measurement result of the output voltage of the voltage conversion circuit before being connected in parallel with the supercapacitor. [Figure 7] FIG. 33 is a circuit diagram according to a modification of the present invention.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0021] FIG. 1 is a circuit diagram showing the configuration of a voltage conversion circuit according to an embodiment of the present invention.

[0022] As shown in Figure 1, the voltage conversion circuit 1 consists of multiple capacitors C1, C2, and C3 connected in series between the output terminals 10, which are a first pair of terminals; multiple first photorelays 11 to 14 inserted on both ends of each series-connected capacitor C1, C2, and C3 (between each capacitor C1, C2, and C3, between capacitor C1 and output terminal 10, and between capacitor C3 and output terminal 10); and the + and - terminals of the charging power supply E1, which are the terminals of the second pair of terminals. The system includes a plurality of second photorelays 21-26 inserted between the capacitors C1, C2, and C3 and their respective ends, and a switching control unit 30 that switches the input sides of the plurality of first and second photorelays 11-14 and 21-26 so that the output sides of the plurality of second photorelays 21-26 are conductive when the output sides of the plurality of first photorelays 11-14 are non-conductive, and the output sides of the plurality of second photorelays 21-26 are non-conductive when the output sides of the plurality of first photorelays 11-14 are conductive.

[0023] More specifically, this voltage conversion circuit 1 is configured to allow three capacitors C1, C2, and C3, which are capacitive elements, to be connected in series. Capacitive elements are used for charging and discharging, and are not limited to three; any number is acceptable.

[0024] Output terminals 10 of this voltage conversion circuit 1 are provided at both ends of capacitors C1, C2, and C3, which are connected in series.

[0025] The output sides of first photorelays 11-14, which switch between charging and discharging modes, are interposed on both sides of each capacitor C1, C2, and C3. In this embodiment, the first photorelays 11-14 are of type b (normally closed). By sharing the first photorelays 12-13 inserted between each capacitor C1, C2, and C3 with adjacent capacitors, the number of photorelays can be reduced from the original six to four, thereby reducing the number of components and enabling the construction of a circuit with reduced power loss.

[0026] One end of each capacitor C1, C2, and C3 is connected to the positive terminal of the DC charging power supply E1, and the other end of each capacitor C1, C2, and C3 is connected to the negative terminal of the charging power supply E1. The charging power supply E1 is typically a lithium-ion secondary battery, but can also be a lead-acid battery or other power source.

[0027] The output side of a second photorelay 21-26 is interposed between one end of each capacitor C1, C2, C3 and the + terminal of the charging power supply E1, and between the other end of each capacitor C1, C2, C3 and the - terminal of the charging power supply E1, so that when capacitors C1, C2, C3 are in charging mode, the connection between one end of each capacitor C1, C2, C3 and the + terminal of the charging power supply E1, and between the other end of each capacitor C1, C2, C3 and the - terminal of the charging power supply E1 is made conductive, and when capacitors C1, C2, C3 are in discharge mode, the connection between one end of each capacitor C1, C2, C3 and the + terminal of the charging power supply E1, and between the other end of each capacitor C1, C2, C3 and the - terminal of the charging power supply E1 is made non-conductive. These second photorelays 21-26 are also of type b.

[0028] The switching control unit 30 controls the system so that in charging mode the output sides of the first photorelays 11 to 14 are de-conductive and the output sides of the second photorelays 21 to 26 are conductive, and in discharge mode the output sides of the first photorelays 11 to 14 are conductive and the output sides of the second photorelays 21 to 26 are de-conductive.

[0029] For example, the switching control unit 30 includes a control power supply E2, third and fourth photorelays 31 and 32, and a changeover switch 33. The third photorelay 31 is type a (normally open), and the fourth photorelay 32 is type b. Alternatively, the third photorelay 31 may be type b and the fourth photorelay 32 may be type a.

[0030] The control power supply E2 is connected to one end of the input side of each of the first photorelays 11-14, with the output side of the third photorelay 31 interposed between them. The other end of the input side of the first photorelays 11-14 is grounded.

[0031] The control power supply E2 is connected to one end of the input side of each of the second photorelays 21-26, and the output side of the fourth photorelay 32 is interposed between them. The other end of the input side of the second photorelays 21-26 is grounded.

[0032] A control power supply E2 is connected to one end of the input side of the third and fourth photorelays 31 and 32, with a changeover switch 33 interposed between them. The other ends of the input sides of the third and fourth photorelays 31 and 32 are grounded.

[0033] A resistor R is interposed at one end of the input side of each of the first to fourth photorelays 11 to 14 to set a threshold voltage for switching between conduction and non-conductivity on the output side.

[0034] The changeover switch 33 is a switch that switches between charging mode and discharging mode.

[0035] In charging mode, the changeover switch 33 is turned off. When the changeover switch 33 is turned off, the output side of the third photorelay 31 becomes non-conductive, and the output side of the fourth photorelay 32 becomes conductive. As a result, the output sides of the first photorelays 11-14 become non-conductive, and the output sides of the second photorelays 21-26 become conductive. This allows the charging power supply E1 to charge each of the capacitors C1, C2, and C3.

[0036] In discharge mode, the changeover switch 33 is turned on. When the changeover switch 33 is turned on, the output side of the third photorelay 31 becomes conductive and the output side of the fourth photorelay 32 becomes non-conductive, so the output sides of the first photorelays 11 to 14 become conductive and the output sides of the second photorelays 21 to 26 become non-conductive. As a result, a power supply converted to a high voltage is output from the output terminal 10. In this embodiment, since the three capacitors C1, C2 and C3 are connected in series, this voltage conversion circuit 1 converts the voltage of the charging power supply E1 to approximately three times the voltage.

[0037] Figure 2 is a circuit diagram showing another embodiment of the voltage conversion circuit.

[0038] The voltage conversion circuit 2 shown in Figure 2 differs from the one shown in Figure 1 in the following respects.

[0039] In the voltage conversion circuit 1 shown in Figure 1, charging of capacitors C1, C2, and C3 from a charging power supply E1 was performed via six second photorelays 21 to 26. However, in this embodiment, the voltage conversion circuit 2 is performed by two second photorelays 41 and 42 and six diodes 43 to 48.

[0040] A second photorelay 41 and diodes 43, 44, and 45, respectively, connected in the forward direction, are inserted between one end of each capacitor C1, C2, and C3 and the + terminal of the charging power supply E1. A second photorelay 42 and diodes 46, 47, and 48, respectively, connected in the forward direction, are inserted between the other end of each capacitor C1, C2, and C3 and the - terminal of the charging power supply E1.

[0041] In the voltage conversion circuit 1 shown in Figure 1, the switching of charging and discharging was performed by a changeover switch 33 in the switching control unit 30. However, in the voltage conversion circuit 2 according to this embodiment, the switching of charging and discharging is performed by a timer IC (model number JRC555D) 49 as a circuit element. Terminal 3 of the timer IC 49 is an output, and the switching of charging and discharging is performed by this output.

[0042] In charging mode, an OFF (Low) signal is output from terminal 3 of timer IC 49. When it is turned OFF, the output side of the third photorelay 31 becomes non-conductive, and the output side of the fourth photorelay 32 becomes conductive. As a result, the output sides of the first photorelays 11-14 become non-conductive, and the output sides of the second photorelays 41 and 42 become conductive. This allows the charging power supply E1 to charge capacitors C1, C2, and C3.

[0043] In discharge mode, a high signal is output from terminal 3 of timer IC 49. When this is activated, the output side of the third photorelay 31 becomes conductive, and the output side of the fourth photorelay 32 becomes non-conductive. Consequently, the output sides of the first photorelays 11-14 become conductive, and the output sides of the second photorelays 41 and 42 become non-conductive. As a result, a high-voltage power supply is output from output terminal 10.

[0044] Figure 3 is a circuit diagram of a high-voltage conversion circuit according to another embodiment of the present invention.

[0045] As shown in Figure 3, the high-voltage conversion circuit 100 is configured by connecting, for example, the output terminal 10 of the voltage conversion circuit 2 and the supercapacitor 102 in parallel to the motor 101, which is the load.

[0046] The supercapacitor used here differs from a typical capacitor in that it is a type of capacitor with extremely high electrical capacity. Unlike typical rechargeable batteries, supercapacitors store electricity electrostatically, allowing for rapid charging and discharging, and enabling them to withstand a very large number of charge-discharge cycles.

[0047] According to the inventors' findings, it has been found that the above configuration can supply a power supply with extremely small voltage fluctuations to loads such as motors. This is thought to be because the series-parallel switching by the voltage conversion circuit according to the present invention is performed by a photorelay, thereby supplying power with a square wave voltage that suppresses voltage fluctuations during charging and discharging.

[0048] Figure 4 is a graph showing the measured output voltage of the high-voltage conversion circuit 100 connected in parallel with the supercapacitor 102. Figure 5 is an enlarged view of a portion of Figure 4 (the part with high voltage values). Figure 6 is a graph showing the measured output voltage of the voltage conversion circuit 2 before it was connected in parallel with the supercapacitor 102.

[0049] The output voltage in Figure 4 is 30.5V, and Figure 5 is an enlarged view for more accurate measurement, showing an output voltage of 30.22~30.55V. The output voltage in Figure 6 is 11.9~32.1V. While a typical smoothing circuit would produce an output of around 22V, the voltage conversion circuit 2 produces 30.5V as shown in Figure 4. We actually constructed a voltage conversion circuit with five capacitors and measured the voltage in the same way, and we were able to confirm a five-fold increase in voltage.

[0050] The present invention is not limited to the embodiments described above, and can be implemented in various modified forms, with the scope of such implementation also falling within the technical scope of the present invention.

[0051] For example, in the voltage conversion circuit 1 shown in Figure 1 and the voltage conversion circuit 2 shown in Figure 2, the first photorelays 11-14 and the second photorelays 21-26, 41, and 42 are configured as type B, but these photorelays may also be type A.

[0052] Furthermore, in the above embodiment, the output sides of the first photorelays 11-14 were inserted on both ends of the series-connected capacitors C1, C2, and C3. However, as shown in Figure 7, a combination of MOSFETs 51-54 and the first photorelays 11-14 may be used instead of the first photorelays 11-14. That is, the source-drain connections of each MOSFET 51-54 may be inserted on both ends of the series-connected capacitors C1, C2, and C3, and the output sides of each first photorelay 11-14 may be connected to the gates of each MOSFET 51-54. IGBTs may also be used instead of MOSFETs 51-54. This eliminates the dependence of the photorelay's voltage and current ratings on the maximum voltage and current ratings of the voltage conversion circuit. As a result, the voltage and current ratings corresponding to the maximum voltage and current ratings of the voltage conversion circuit can be determined by the performance of the MOSFET or IGBT. [Explanation of symbols]

[0053] 1. Voltage conversion circuit 10 Output terminals 11-14 First Photo Relay 21-26 Second Photo Relay 30 Switching control unit C1, C2, and C3 are capacitors, which are multiple capacitive elements connected in series. Power supply for E1 charging (compatible with lithium-ion batteries, lead-acid batteries, and other power sources).

Claims

1. Multiple capacitive elements that can be connected in series between a first pair of terminals, The output side comprises a plurality of first photorelays inserted on both ends of each of the aforementioned capacitive elements, The output side consists of a plurality of second photorelays inserted between each terminal of the second pair of terminals and each end on both sides of the respective capacitive elements, A switching control unit controls the input sides of the plurality of first and second photorelays such that when the output side of the plurality of first photorelays is not conducting, the output side of the plurality of second photorelays is conducting, and when the output side of the plurality of first photorelays is conducting, the output side of the plurality of second photorelays is not conducting. A voltage conversion circuit equipped with the following.

2. A voltage conversion circuit according to claim 1, The first pair of terminals are output terminals, The second pair of terminals are connected to a power supply. Voltage conversion circuit.

3. A voltage conversion circuit according to claim 1 or 2, The switching control unit includes a third photorelay whose output side is connected to the input side of the plurality of first photorelays, and a fourth photorelay whose output side is connected to the input side of the plurality of second photorelays. Of the third and fourth photorelays, one is of type a and the other is of type b. A common charge / discharge switching signal is input to the input side of the third photorelay and the input side of the fourth photorelay. Voltage conversion circuit.

4. A voltage conversion circuit according to claim 3, The switching control unit includes a changeover switch and a control power supply that output a common charge / discharge switching signal to the input side of the third photorelay and the input side of the fourth photorelay. Voltage conversion circuit.

5. A voltage conversion circuit according to claim 3, The switching control unit has a circuit element and a control power supply that output a common charge / discharge switching signal to the input side of the third photorelay and the input side of the fourth photorelay. Voltage conversion circuit.

6. Multiple capacitive elements that can be connected in series between the output terminals, Multiple MOSFETs or multiple IGBTs are inserted on both ends of each of the capacitive elements, with the source-drain or collector-emitter junctions being the source-drain or collector-emitter junctions. Multiple first photorelays, the output side of which is connected to the gate of each MOSFET or the gate of each IGBT, The output side consists of a plurality of second photorelays inserted between each terminal of the power supply and each end of each of the capacitive elements, A switching control unit controls the input sides of the plurality of first and second photorelays such that when the output side of the plurality of first photorelays is not conducting, the output side of the plurality of second photorelays is conducting, and when the output side of the plurality of first photorelays is conducting, the output side of the plurality of second photorelays is not conducting. A voltage conversion circuit equipped with the following.

7. A voltage conversion circuit in which the first pair of terminals or the output terminals of the voltage conversion circuit according to claims 1 to 6 are connected in parallel with a supercapacitor to a load.

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