Power conversion device, DC voltage detection system, and DC voltage detection method

Abstract

This power conversion device enables a DC voltage level to be detected by using specific light. The power conversion device comprises a power converter, a capacitor, and a circuit board. The power converter converts DC power. The capacitor stores DC power converted by the power converter. The circuit board is mounted with a light emitter that emits specific light and a drive circuit that modulates the specific light emitted by the light emitter. If the voltage of the capacitor is higher than a prescribed voltage, the drive circuit causes current to flow through the light emitter to emit the specific light. The power conversion device makes it possible to distinguish that the voltage of the capacitor is higher than the prescribed voltage by causing a detection device to detect the specific light.

Description

Power converter, DC voltage detection system and DC voltage detection method

[0001] Embodiments of the present invention relate to a power converter, a DC voltage detection system, and a DC voltage detection method.

[0002] There is a power converter equipped with a capacitor that smoothes direct current. Generally, before starting inspection work on a power converter, voltage detection work is performed to discharge the above capacitor and confirm that the terminal voltage of the capacitor has decreased. However, when the capacitor is disposed at a position distant from the inspector of the power converter, the above voltage detection work has not been easy.

[0003] Japanese Unexamined Patent Application Publication No. 2020-112363

[0004] An object of the present invention is to provide a power converter, a DC voltage detection system, and a DC voltage detection method that facilitate voltage detection work for the power converter.

[0005] The power converter of the embodiment enables detection of a DC voltage level using specific light. The power converter includes a power converter, a capacitor, and a circuit board. The power converter converts DC power. The capacitor stores DC power converted by the power converter. The circuit board includes a light emitting body that emits specific light and a drive circuit that modulates the specific light emitted by the light emitting body. The drive circuit supplies current to the light emitting body to emit the specific light when the voltage of the capacitor is higher than a predetermined voltage. The power converter enables identification that the voltage of the capacitor is higher than the predetermined voltage by causing a detection device to detect the specific light.

[0006] A diagram showing an example of a power conversion system to which the DC voltage detection system of the embodiment is applied. An overhead view showing an example of a cell unit of the embodiment. A cross-sectional view showing a mounted state of the power conversion system of the embodiment. A diagram showing an example of an electrical configuration of a power conversion system to which the DC voltage detection system of the embodiment is applied. A diagram showing an example of an electrical configuration of a cell unit of the embodiment. Diagrams for explaining an example of an internal configuration of a cell unit of the embodiment. Diagrams for explaining an example of an internal configuration of a cell unit of the embodiment. A configuration diagram of a circuit board of the embodiment. A configuration diagram of a detection device of the embodiment.

[0007] The power converter, DC detection system, and DC detection method of the embodiments will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplication of these components may be omitted. For the sake of clarity, the drawings referenced below may omit illustrations of control gate wiring and other components.

[0008] The power converter of this embodiment forms a multi-cell type power converter. The multi-cell type power converter comprises a plurality of cell units. Here, we first define the "positive electrode P" and "negative electrode N" within the plurality of cell units. "Positive electrode P" refers to the part of the cell unit that is at a positive potential when the power converter 1 is operating. "Negative electrode N" refers to the part of the cell unit that is at a negative potential when the power converter 1 is operating. Each cell unit is provided with a capacitor to smooth the potentials of the respective "positive electrode P" and "negative electrode N". The following will explain with specific examples.

[0009] Referring to Figures 1A to 5, a power converter 1 to which the DC voltage detection system 100 of the embodiment is applied will be described. Figure 1A is a diagram showing an example of a power converter 1 to which the DC voltage detection system 100 of the embodiment is applied. Figure 1B is an overhead view showing an example of a cell unit 6 of the embodiment. Figure 1C is a cross-sectional view showing the mounted state of the power converter 1 of the embodiment. Figure 2A is a diagram showing an example of the electrical configuration of the power converter 1 to which the DC voltage detection system 100 of the embodiment is applied. Note that in Figure 2A above, the electrical circuit system is shown with a single line, and switches and other components are omitted from the illustration. Figure 2B is a diagram showing an example of the electrical configuration of the cell unit 6 of the embodiment.

[0010] The power supply side of the power converter 1 is connected to the AC power source 2, for example, via a circuit breaker. The power converter 1 converts the AC power supplied from the AC power source 2 into DC power, and then converts the converted DC power back into AC power of a desired frequency and voltage and supplies it to the motor 3. The motor 3 is, for example, a three-phase induction motor, but is not limited to this.

[0011] In this embodiment, an example is described in which the power converter 1 is equipped with multiple cell units 6s. The number of cell units 6 can be arbitrarily determined, and there is no restriction that it must be multiple; it may be just one unit.

[0012] The power conversion device 1 includes, for example, a transformer 5, a plurality of cell units 6s, a control device 7, and a current sensor AM.

[0013] AC power is supplied to the transformer 5 from the AC power source 2. The transformer 5 transforms the voltage of the AC power supplied from the AC power source 2 (primary voltage) to a desired secondary voltage and supplies the AC power of the secondary voltage to each of the multiple cell units 6s. The transformer 5 has a primary winding and multiple groups of windings (secondary windings) that are insulated from each other. The primary winding and the secondary windings are also insulated from each other.

[0014] The multiple cell units 6s include, for example, three first-phase load cell units 6A1, 6A2, and 6A3 (labeled U1, U2, and U3 in the figure), three second-phase load cell units 6B1, 6B2, and 6B3 (labeled V1, V2, and V3 in the figure), and three third-phase load cell units 6C1, 6C2, and 6C3 (labeled W1, W2, and W3 in the figure). The cell units 6A1, 6A2, 6A3, 6B1, 6B2, 6B3, 6C1, 6C2, and 6C3 have the same circuit configuration, and when describing them without distinction, they are simply referred to as cell unit 6. For example, multiple cell units 6s are an example of multiple slave stations, and cell unit 6 is an example of a slave station. Each cell unit 6 converts the three-phase AC power supplied from the secondary winding of the transformer 5 into DC power, and then converts the converted DC power back into AC power of the desired frequency and voltage for output.

[0015] For example, the first group of secondary wires of transformer 5 is connected to the input of cell unit 6A1. The second group of secondary wires of transformer 5 is connected to the input of cell unit V1. The third group of secondary wires of transformer 5 is connected to the input of cell unit W1. The fourth group of secondary wires of transformer 5 is connected to the input of cell unit 6A2. The fifth group of secondary wires of transformer 5 is connected to the input of cell unit 6B2. The sixth group of secondary wires of transformer 5 is connected to the input of cell unit 6C2. The seventh group of secondary wires of transformer 5 is connected to the input of cell unit 6A3. The eighth group of secondary wires of transformer 5 is connected to the input of cell unit 6B3. The ninth group of secondary wires of transformer 5 is connected to the input of cell unit 6C3.

[0016] In this embodiment, the outputs of cell units 6A1, 6A2, and 6A3 are electrically connected in series with respect to each other in the order shown. The output terminal of cell unit 6A3 that is not connected to cell unit 6A2 is connected to the first phase (U phase) of the motor 3. The output terminal of cell unit 6A1 that is not connected to cell unit 6A2 is connected to the neutral point. In this embodiment, the outputs of cell units 6B1, 6B2, and 6B3 are electrically connected in series with respect to each other in the order shown. The output terminal of cell unit 6B3 that is not connected to cell unit 6B2 is connected to the second phase (V phase) of the motor 3. The output terminal of cell unit 6B1 that is not connected to cell unit 6B2 is connected to the neutral point. In this embodiment, the outputs of cell units 6C1, 6C2, and 6C3 are electrically connected in series with respect to each other in the order shown. The output terminal of cell unit 6C3 that is not connected to cell unit 6C2 is connected to the third phase (W phase) of the motor 3. The output terminals of cell unit 6C1 that are not connected to cell unit 6C2 are connected to the neutral point. This allows the power converter 1 to supply a large amount of AC power to the motor 3.

[0017] Current sensors AM1 and AM2 are examples of current sensors AM, and they detect the load current (phase current) flowing between the inverter 13 (Figure 2) of the power converter 1 and the motor 3. Note that if the system has a configuration for generating an estimated value of the load current, the current sensors AM may be omitted.

[0018] The control device 7 controls or protects each cell unit 6. The control device 7 includes, for example, a storage unit 71 and an operation control unit 72.

[0019] The storage unit 71 stores various data related to the control of the multiple cell units 6s. These various data include, for example, command values ​​and detected values ​​of various control signals.

[0020] The operation control unit 72 generates control signals for controlling the switching elements 13S (Figure 2A) included in each cell unit 6 based on the data stored in the memory unit 71. The operation control unit 72 controls each cell unit 6 by sending the generated control signals to each cell unit 6. The operation control unit 72 may also acquire a signal indicating the control status of the electric motor 3 (for example, a rotational speed feedback signal) and control each cell unit 6 based on this feedback signal. Alternatively, the control device 7 may acquire a control command signal for the electric motor 3 from another device and control each cell unit 6 based on this control command signal.

[0021] Next, we will explain the cell unit 6.

[0022] The cell unit 6 includes, for example, a single-phase cell inverter 6IV and a cell unit control unit 6CUC.

[0023] The single-phase cell inverter 6IV is, for example, a single-phase AC output type inverter. The single-phase cell inverter 6IV includes, for example, a diode converter 12, an inverter 13, a capacitor 14, and resistors 15 and 16. The DC output of the diode converter 12 and the DC input of the inverter 13 are electrically connected to each other via a DC link, with their positive (P) terminals to each other and their negative (N) terminals to each other. The capacitor 14 is provided on the DC link, and the terminals of the capacitor 14 are electrically connected to the positive and negative terminals of the DC link.

[0024] The following explanation uses cell unit 6A1 as an example to illustrate the connection relationship with the outside world. The same applies to the other cell units 6.

[0025] The diode converter 12 is a three-phase AC input type forward converter, and its input section is electrically connected to one group on the secondary side of the transformer 5. The diode converter 12 converts the AC power input from the transformer 5 into DC power by rectifying the AC. The capacitor 14 smooths the DC voltage after conversion.

[0026] The inverter 13 is a single-phase AC output type reverse converter. The inverter 13 includes, for example, a switching element 13S that converts DC power on the DC side into AC power, and a reverse-connected diode 13D connected in antiparallel to the switching element 13S. The switching element 13S is an example of a semiconductor switching element. The inverter 13 is connected so that the DC side is connected to the DC output of the diode converter 12, and the AC side is connected in series with the output of the motor 3 or another cell unit 6. The inverter 13 outputs the converted AC power to the first phase of the motor 3, for example.

[0027] The cell unit control unit 6CUC generates signals to control the switching elements constituting the diode converter 12 and inverter 13 based on the control from the control device 7. The cell unit control unit 6CUC uses the generated signals to control the switching elements constituting the diode converter 12 and inverter 13.

[0028] For example, the inverter 13, although its detailed internal connection configuration is omitted, is equipped with one or more switching elements, which convert power through switching. The type of switching element may be an IGBT (Insulated Gate Bipolar Transistor), IEGT (Injection Enhanced Gate Transistor), MOSFET (metal-oxide-semiconductor field-effect transistor), etc. The inverter 13 functions as an inverter that generates AC power through control, and works in conjunction with other inverters connected to its output to supply current to the windings of the motor M.

[0029] For example, the power conversion device 1 of this embodiment enables the detection of a DC voltage level using a specific light. The power conversion device 1 comprises an inverter 13 (power converter), a capacitor 14, and a circuit board 6CB.

[0030] As described above, the inverter 13 converts DC power to AC power and uses that AC power to operate the motor 3. The inverter 13 (power converter) and the capacitor 14 are connected by a DC bus 6w. The capacitor 14 stores the DC power that the inverter 13 converts to AC power. The capacitor 14 smooths the DC voltage applied to the DC bus 6w. The circuit board 6CB is equipped with a light-emitting element 6LM that emits a specific light and a modulation unit 64 that modulates the specific light emitted by the light-emitting element 6LM. The modulation unit 64 causes the light-emitting element 6LM to emit a specific light by supplying current to it when the voltage of the capacitor 14 is higher than a predetermined voltage. The power converter 1 causes the detection device 20 to detect the above-mentioned specific light, thereby identifying that the voltage of the capacitor 14 is higher than a predetermined voltage.

[0031] The DC voltage detection system 100 may be configured by combining the power conversion device 1 and the detection device 20 described above. The detection device 20 detects light emitted or reflected by the light emitter 6LM. The detection device 20 is designed to be portable by a worker. During the work, the worker supports the device facing the panel surface 6FS of the cell unit 6 to be detected and detects that the light emitted or reflected by the light emitter 6LM is reaching it. Since the light emitter 6LM of the cell unit 6 emits light when it detects the charge state of the capacitor 14, the detection of the above light identifies the presence of a charged capacitor 14.

[0032] The detection device 20 of this DC voltage detection system 100 identifies when the voltage across the capacitor 14 is higher than a predetermined voltage without electrically connecting the detection device 20 to the circuit inside the inverter 13. The detection device 20 can indicate that the voltage is higher than the predetermined voltage by displaying the result on a display unit or by outputting an alarm sound.

[0033] The details will be explained below with more specific examples, referring to Figures 3A and 3B.

[0034] Figures 3A and 3B are diagrams illustrating an example of the internal configuration of the cell unit in the embodiment. The difference between Figure 3A and Figure 3B is that the position where light from the light-emitting element 6LM is reflected is different.

[0035] First, let's explain the first example shown in Figure 3A. The enclosure 6F (frame) forms a roughly rectangular housing space inside it. For example, the enclosure 6F (frame) houses at least a circuit board 6CB. In this example shown in Figure 3A, the enclosure 6F (frame) also houses a capacitor 14 in addition to the above. The positional relationship between the capacitor 14 and the circuit board 6CB inside the enclosure 6F is such that the position of the capacitor 14 is further back (Y-axis: positive direction) than the position of the circuit board 6CB.

[0036] The panel surface of the housing 6F is located on the side of the work area (Y-axis: negative direction) for inspection work of the power converter 1. Electrodes used for inspection work are provided on this panel surface. There is an opening OP in a part of this panel surface. The panel surface of the housing 6F in this embodiment has an opening facing the work area for inspection work of the power converter.

[0037] The circuit board 6CB, mounted inside the enclosure 6F, is equipped with various electrical components. Some of these electrical components (referred to as line-of-sight obstructions OBJ) are positioned between the opening OP and the light-emitting element 6LM. Depending on the worker's position, the position of the opening OP, the position of the light-emitting element 6LM, and the position and shape of the line-of-sight obstructions OBJ, the worker may not be able to directly see the light-emitting element 6LM even when looking through the opening OP.

[0038] In this embodiment, the inner surface of the side plate of the housing 6F is used as a reflective surface. A light-emitting element 6LM and a line-of-sight obstruction OBJ are fixed to the component side (component mounting side) of the circuit board 6CB. For example, the intensity of the light emitted by the light-emitting element 6LM is determined by the direction of its optical axis and a standard light distribution pattern determined based on the optical axis. If a line-of-sight obstruction OBJ exists between the position of the light-emitting element 6LM and the aperture OP, the light emitted by the light-emitting element 6LM will not reach the aperture OP as direct light. Therefore, in this embodiment, the configuration is set so that the reflected light emitted by the light-emitting element 6LM reaches the aperture OP. With this configuration, even if the arrangement prevents direct light from reaching the aperture OP, it becomes possible to detect the lighting state of the light-emitting element 6LM from outside the aperture OP.

[0039] For example, as shown in Figure 3A, the inner surface 6FIS of the side plate of the housing 6F may be used as a reflective surface. In this case, the intensity of light directed toward the inner surface 6FIS may be configured to be in a direction that is relatively large within the light distribution pattern of the light emitter 6LM.

[0040] Next, we will explain the second example shown in Figure 3B. Here, we will focus on explaining the differences from the first example described above. In the first example, we exemplified the use of the inner surface 6FIS of the side panel of the housing 6F as a reflective surface. In this second example, instead of the inner surface 6FIS mentioned above, we use the surface of some components mounted on the component side of the circuit board 6CB or the surface of a dedicated reflective material.

[0041] Although the position of the reflective surface differs between the first and second examples, similar effects can be obtained.

[0042] An example of the circuit board 6CB and detection device 20 of the embodiment will be described with reference to Figures 4 and 5. Figure 4 is a configuration diagram of the circuit board 6CB of the embodiment. The circuit board 6CB is an example of a drive circuit for the light-emitting element 6LM.

[0043] The circuit board 6CB includes, for example, resistors 61 and 62, a stabilization circuit 63, a modulation section 64, and a light emitting body 6LM. The resistors 61 and 62, the stabilization circuit 63, the modulation section 64, and the light emitting body 6LM are examples of components mounted on the circuit board 6CB. The resistors 61 and 62 are connected in series with each other, and constitute a voltage dividing resistor that divides a voltage according to a ratio of resistance values.

[0044] The stabilization circuit 63 stabilizes a voltage lower than the voltage divided by the voltage dividing resistor. The stabilization circuit 63 includes a constant voltage diode. Stabilization is performed with a voltage obtained by applying a reverse bias to the constant voltage diode.

[0045] When the voltage stabilized by the stabilization circuit 63 exceeds the lower limit value of a predetermined power supply voltage that allows the modulation section 64 to function, a built-in modulation circuit 641 (MOD) of the modulation section 64 is enabled. The modulation circuit 641 (MOD) generates a specific modulation signal. The circuit board 6CB supplies a drive current to the light emitting body 6LM based on the specific modulation signal generated by the modulation circuit 641 (MOD). The light emitting body 6LM is, for example, an LED that emits visible light or infrared light. The light emitted by the light emitting body 6LM is modulated by the aforementioned specific modulation signal.

[0046] Figure 5 is a configuration diagram of the detection device 20 according to the embodiment. The detection device 20 includes a light receiving section 21, a demodulator 22, and a display section 23. The detection device 20 operates using electric power from a battery or a rechargeable battery, which is not illustrated, for example. The light receiving section 21 is a light receiving element having a sensitivity region in the wavelength region of the light emitted by the light emitting body 6LM. The light receiving section 21 is, for example, a phototransistor or a photodiode. The demodulator 22 includes a demodulation section 221 (DEM) and an identification section 222 (ID). The demodulation section 221 (DEM) demodulates the electrical signal photoelectrically converted by the light receiving section 21. The identification section 222 (ID) identifies whether the signal has been modulated by a desired method based on the demodulation result. The display section 23 includes, for example, an LED that emits visible light. The display section 23 displays the identification result from the identification section 222 (ID). This display includes a display for calling attention when the capacitor 14 is in a charged state.

[0047] The modulation scheme of the modulation unit 64 on the circuit board 6CB and the modulation scheme of the signal that can be demodulated by the demodulator 22 of the detection device 20 are a common scheme. Known schemes can be applied to this modulation scheme. For example, the modulation may be based on the light signal intensity, frequency, DUTY of pulses, period, or the like. In the case of code modulation in which a specific code is transmitted using an optical pulse train, it is preferable that the code is shared by both parties.

[0048] Unlike the detection method for identifying the presence or absence of light in the comparative example, in the present embodiment, the influence of external light such as illumination can be reduced by aligning the modulation schemes applied to the modulation unit 64 of the circuit board 6CB on the transmitting side and the demodulator 22 of the detection device 20 on the receiving side.

[0049] According to the above embodiment, the power conversion device 1 enables detection of a DC voltage level using specific light. The power conversion device 1 comprises an inverter 13 (power converter), a capacitor 14, and a circuit board 6CB. The inverter 13 (power converter) converts DC power. The capacitor 14 stores the DC power converted by the inverter 13 (power converter). The circuit board 6CB carries a light-emitting body 6LM that emits specific light and a modulation unit 64 that modulates the specific light emitted by the light-emitting body 6LM. The modulation unit 64 supplies current to the light-emitting body 6LM to emit specific light when the voltage of the capacitor 14 is higher than a predetermined voltage. The power conversion device 1 enables the detection device 20 to detect the specific light, thereby making it possible to identify that the voltage of the capacitor 14 is higher than the predetermined voltage. This makes it possible to identify the state where electric charge remains in the internal circuit of the power conversion device 1 using the detection device 20, thereby facilitating the voltage detection work of the power conversion device 1.

[0050] For example, a DC bus 6w extends on the far side (Y-axis positive direction) of the circuit board 6CB of the power conversion device 1. Since the voltage of the DC bus 6w is a relatively high voltage, it has been difficult to directly draw it out to the outside of the housing 6F even by using an insulated cable or the like. In contrast, in the present embodiment, by using a voltage dividing resistor connected to the DC bus 6w to reduce the voltage to a level applicable to an electronic circuit, it has become possible to modulate the light emitted by the LED.

[0051] Some or all of the functional units of the power converter 1 in the embodiments described above may include a software functional unit that is realized by a program (computer program, software component) stored in the computer's memory (such as a computer's memory) being executed by the computer's processor (hardware processor). Some or all of the above functional units may be realized by hardware such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), or FPGA (Field-Programmable Gate Array), or by a combination of a software functional unit and hardware.

[0052] According to at least one embodiment described above, the power conversion device enables the detection of a DC voltage level using a specific light. The power conversion device comprises a power converter, a capacitor, and a circuit board. The power converter converts DC power. The capacitor stores the DC power converted by the power converter. The circuit board is equipped with a light-emitting element that emits a specific light and a drive circuit that modulates the specific light emitted by the light-emitting element. The drive circuit emits the specific light by flowing current through the light-emitting element when the voltage of the capacitor is higher than a predetermined voltage. The power conversion device enables the detection of the specific light by allowing a detection device to detect the voltage of the capacitor to be identified as being higher than a predetermined voltage. This facilitates the voltage detection work of the power conversion device.

[0053] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, the configurations of each embodiment may be implemented in combination with each other and can be applied to components that have not been described. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0054] (Note) (1) The power conversion device of the embodiment is a power conversion device that enables detection of a DC voltage level using specific light, comprising: a power converter that converts DC power; a capacitor that stores the DC power converted by the power converter; and a circuit board that mounts a light emitter that emits specific light and a drive circuit that modulates the specific light emitted by the light emitter, wherein the drive circuit flows current through the light emitter to emit the specific light when the voltage of the capacitor is higher than a predetermined voltage, and the detection device detects the specific light, thereby enabling identification that the voltage of the capacitor is higher than a predetermined voltage. (2) The power converter according to (1) above comprises a housing that houses at least the circuit board, and the panel surface of the housing has an opening facing the work area for inspection work of the power converter, and when light emitted by the light emitter or light reflected by the reflective surface on the inside of the housing leaks out of the housing through the opening, the detection device detects the light emitted by the light emitter or the light reflected by the reflective surface on the inside of the housing outside the housing. (3) In the power converter according to (1) or (2) above, the drive circuit for the light emitter comprises a voltage divider resistor that divides the voltage of the capacitor at a predetermined ratio, a stabilization circuit that stabilizes the voltage to a voltage lower than the divided voltage, and a modulation unit that generates a specific modulation signal when the stabilized voltage exceeds a predetermined voltage, and current is passed to the light emitter based on the specific modulation signal. (4) The power converter according to (2) or (3) above comprises a control unit for the power converter inside the housing. Note that the cell unit control unit 6CUC of the cell unit 6 above is an example of a control unit. (5) A DC voltage detection system comprising the power conversion device described in (2) above and a detection device for detecting the light emitted by the light-emitting element or the reflected light.

[0055] 1...Power converter 3...Electric motor 6...Cell unit 6s...Multiple cell units 6IV...Single-phase cell inverter 6CB...Circuit board 6CUC...Cell unit control unit 6F...Housing 20...Detection device 100 DC voltage detection system

Claims

1. A power conversion device that enables detection of a DC voltage level using specific light, comprising: a power converter that converts DC power; a capacitor that stores the DC power converted by the power converter; and a circuit board mounted on a light-emitting element that emits specific light and a drive circuit that modulates the specific light emitted by the light-emitting element, wherein the drive circuit flows current through the light-emitting element to emit the specific light when the voltage of the capacitor is higher than a predetermined voltage, and the detection device detects the specific light, thereby enabling identification that the voltage of the capacitor is higher than a predetermined voltage.

2. The power conversion device according to claim 1, comprising a housing for at least the circuit board, wherein the panel surface of the housing has an opening facing the work area for inspection work of the power conversion device, and when light emitted by the light-emitting element or light reflected by a reflective surface on the inside of the housing leaks to the outside of the housing through the opening, the detection device detects the light emitted by the light-emitting element or the light reflected by a reflective surface on the inside of the housing outside the housing.

3. The power conversion device according to claim 1, wherein the drive circuit for the light-emitting element comprises: a voltage divider resistor that divides the voltage of the capacitor in a predetermined ratio; a stabilization circuit that stabilizes the voltage to a level lower than the divided voltage; and a modulation unit that generates a specific modulation signal when the stabilized voltage exceeds a predetermined voltage, and current is supplied to the light-emitting element based on the specific modulation signal.

4. The power conversion device according to claim 2, further comprising a control unit for the power converter within the housing.

5. A DC voltage detection system comprising a power conversion device according to claim 2, and a detection device for detecting light emitted by the light-emitting body or the reflected light.

6. A DC voltage detection method for a power converter capable of detecting a DC voltage level using a detection device that detects specific light, wherein the power converter comprises: a power converter that converts DC power; a capacitor that stores the DC power converted by the power converter; a circuit board mounted on a light-emitting element that emits specific light and a drive circuit that modulates the specific light emitted by the light-emitting element; and a housing that houses at least the circuit board, wherein the drive circuit is used to flow current through the light-emitting element when the voltage of the capacitor is higher than a predetermined voltage, causing the light-emitting element to emit the specific light, and the detection device detects the specific light to identify that the voltage of the capacitor is higher than a predetermined voltage.

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