Electronic transformer and its three-phase four-wire power supply system

Abstract

To provide an electronic transformer.SOLUTION: The electronic transformer includes a first forward rectifier circuit connected between a first phase power supply and a first output terminal, a second forward rectifier circuit connected between a second phase power supply and the first output terminal, a third forward rectifier circuit connected between a third phase power supply and the first output terminal, and a reverse rectifier circuit connected between a neutral line and a second output terminal. The first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit are so arranged as to each perform half-wave rectification on the first phase power supply, the second phase power supply, and the third phase power supply, generate rectified first through third-phase power supplies, and overlap the rectified first through third-phase power supplies onto the first output terminal to form an output voltage.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an electronic transformer, and more particularly to an electronic transformer and its three-phase four-wire power supply system. [Background technology]

[0002] An electronic transformer, or coil-type transformer, is a device that combines power electronic conversion technology with high-frequency electrical energy conversion technology based on the principle of electromagnetic induction to convert electrical energy of one power characteristic into electrical energy of another power characteristic. However, when converting three-phase AC voltage to DC voltage, traditional coil-type transformers have drawbacks such as high heat loss, high power consumption, difficult installation, low efficiency, and inconvenient transportation. In light of this, the industry is working to develop a compact electronic transformer that can replace traditional coil-type transformers. Summary of the Invention

[0003] One aspect of the present disclosure is an electronic transformer comprising: a first forward rectifier circuit connected between a first-phase power supply and a first output terminal; a second forward rectifier circuit connected between a second-phase power supply and the first output terminal; a third forward rectifier circuit connected between a third-phase power supply and the first output terminal; and a reverse rectifier circuit connected between a neutral conductor and a second output terminal, wherein the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit perform half-wave rectification on the first-phase power supply, the second-phase power supply, and the third-phase power supplies to generate rectified first-phase power supply, rectified second-phase power supply, and rectified third-phase power supply, and the rectified first-phase power supply, the rectified second-phase power supply, and the rectified third-phase power supply are superimposed on the first output terminal to form an output voltage.

[0004] Another aspect of the present disclosure is a three-phase, four-wire power system comprising: a power supply arranged to provide first, second, and third phase power sources and including a neutral conductor; a load; and an electronic transformer as described above connected between the power supply and the load and arranged to convert the first, second, and third phase power sources into an output voltage for the load.

[0005] The electronic transformer and its three-phase, four-wire power supply system disclosed herein use three forward rectifier circuits to perform half-wave rectification on the three-phase power supply, generating evenly distributed output currents at the first output terminals. The return current generated in the load is rectified by a reverse rectifier circuit and then returned to the power supply device via the neutral line. This forms a complete current loop between the power supply device, the electronic transformer, and the load. The forward output current and the reverse return current are symmetrically balanced, improving the operating efficiency of the three-phase, four-wire power supply system. This solves the problem of uneven current distribution, which can quickly damage certain components. Furthermore, the electronic transformer disclosed herein does not require a three-phase, three-wire configuration for use in subsequent products, and the electronic transformer disclosed herein has a simpler design than conventional electronic transformers. The electronic transformer and its three-phase, four-wire power supply system disclosed herein have the following advantages: (1) a stable output voltage; and (2) evenly balanced output current. (3) The circuit design is simplified, the layout area is small, and the cost is low. (4) The operating temperature is stable and does not increase over time. [Brief explanation of the drawings]

[0006] For a more complete understanding of the embodiments and their advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [Figure 1] 1 is a schematic diagram of a three-phase, four-wire power supply system. [Figure 2] 2 is a waveform diagram of the three-phase input voltage and three node voltages of the electronic transformer of FIG. 1. [Figure 3] 2 is a waveform diagram of an output current at a first output terminal of the electronic transformer of FIG. 1. [Figure 4] 1 is a schematic diagram of a three-phase, four-wire power system according to an embodiment of the present disclosure. FIG. [Figure 5] FIG. 1 is a schematic diagram of an electronic transformer according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a waveform diagram of the output voltage of the electronic transformer shown in FIG. 5. [Figure 7] FIG. 6 is a waveform diagram of the output current of the electronic transformer shown in FIG. 5. [Figure 8] 6 is a temperature change diagram of the electronic transformer shown in FIG. 5 under operating conditions of 100% load and 150% load. [Figure 9] FIG. 1 is a schematic diagram of an electronic transformer according to an embodiment of the present disclosure. [Figure 10] FIG. 1 is a schematic diagram of an electronic transformer according to an embodiment of the present disclosure. [Figure 11] FIG. 11 is a layout schematic diagram of the electronic transformer and the three-phase four-wire power supply system shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] Exemplary embodiments of the present disclosure are discussed in detail below. However, it will be understood that the exemplary embodiments provide many applicable concepts that can be implemented in a variety of specific contexts.

[0008] In this disclosure, a description of "connected" generally refers to an element being indirectly connected to another element through another element, or an element being directly connected to another element without any intervening elements.

[0009] FIG. 1 is a schematic diagram of a three-phase four-wire power system (hereinafter simply referred to as the system) 1. The system 1 includes a power supply device VS, an electronic transformer 10, and a load LD. The power supply device VS transmits three-phase power sources R, S, and T to the electronic transformer 10 via three live lines. The electronic transformer 10 rectifies the first-phase power source R, the second-phase power source S, and the third-phase power source T via three bridge rectifier circuits, respectively, and supplies power to the load LD. The electronic transformer 10 includes a bridge transformer circuit in the front stage and a six-phase inverter in the rear stage. In operation, before the nodes L1, L2, and L3, a bridge transformer circuit is used to perform rectification conversion for the first phase power supply R, the second phase power supply S, and the third phase power supply T, and after the nodes L1, L2, and L3, a six-phase inverter performs secondary rectification, and a capacitor 15 is connected between the first output terminal OUT1 and the second output terminal OUT2 and is used to store power and smooth the rectified voltage, providing a smoothed (i.e., smoothed) voltage to the load LD.

[0010] However, in the electronic transformer 10, the design of the bridge transformer circuit causes uneven voltage distribution. Specifically, two bridge rectifier circuits receiving the first and second phase power supplies R and S are connected to node L1, while the bridge rectifier circuit receiving the third phase power supply T is connected to node L2. The neutral conductor N is directly connected to node L3. Therefore, the converted voltages from the first and second phase power supplies R and S are simultaneously transmitted to the six-phase inverter via node L1, the converted voltage from the third phase power supply T is transmitted to the six-phase inverter via node L2, and the neutral conductor N is connected to the six-phase inverter via node L3. However, the power supply VS does not provide any power to the neutral conductor N. When unevenly distributed voltages are transmitted to the six-phase inverter and rectified, uneven currents are generated. As the electronic transformer 10 operates, certain components (e.g., the diode connected to node L1) are frequently exposed to large currents, generating heat and being damaged more quickly than other components. In addition, the wiring for the three-phase power supplies R, S, and T in a power system may not be connected in order, which means that the elements that are exposed to large currents and generate heat will not be consistent, making it more difficult to repair the product if it breaks down in the future.

[0011] FIG. 2 is a voltage waveform diagram of the three-phase power sources R, S, and T and nodes L1, L2, and L3 of the electronic transformer 10 of FIG. 1. The three-phase power sources R, S, and T are AC voltages of equal magnitude, the same frequency, and a phase difference of 120 degrees. The line voltage may be, for example, 380 volts, and the phase voltage may be, for example, 220 volts, but not limited to these. The converted voltages from the first-phase power source R and the second-phase power source S are simultaneously transmitted through node L1, resulting in double current stress at node L1. The converted voltage from the third-phase power source T is transmitted through node L2, resulting in normal current stress at node L2. Because the power supply VS does not provide power to the neutral line N, the voltage at node L3 is the reverse voltage from the load LD. As can be seen from FIG. 2, the voltages and currents allocated to nodes L1, L2, and L3 are not equal.

[0012] FIG. 3 is a waveform diagram of currents at the first output terminal OUT1 of the electronic transformer 10 of FIG. 1. Currents I31, I32, and I33 flow from nodes L1, L2, and L3, respectively, through diodes to the output terminal OUT1. At the first output terminal OUT1, current I31 is generated based on the converted voltages of the first and second phase power supplies R and S, and therefore has a two-phase sawtooth waveform. Current I32 is generated based on the converted voltage of the third phase power supply T, and therefore has a one-phase sawtooth waveform. Current I33 is generated based on the converted voltage of the neutral conductor N, and therefore remains zero and has no sawtooth waveform for any phase. As can be seen from the above, electronic transformer 10 suffers from a problem of current nonuniformity during operation. During long-term use of electronic transformer 10, certain components generating current I31 are frequently exposed to large currents, which causes them to heat up and be damaged more quickly than other components. Furthermore, the electronic transformer 10 of FIG. 1 requires a large layout area since it is necessary to arrange many electronic elements.

[0013] 4 is a schematic diagram of a three-phase four-wire power supply system 4 according to an embodiment of the present disclosure. The three-phase four-wire power supply system 4 includes a power supply device VS, an electronic transformer 40, and a load LD. The electronic transformer 40 is connected between the power supply device VS and the load LD, and is used to receive the first-phase power supply R, the second-phase power supply S, and the third-phase power supply T from the power supply device VS and perform rectification conversion. The power is stored and smoothed by a capacitor before being supplied to the load LD.

[0014] Structurally, the electronic transformer 40 includes a first forward rectifier circuit 41, a second forward rectifier circuit 42, a third forward rectifier circuit 43, a reverse rectifier circuit 44, and a capacitor 45. The first forward rectifier circuit 41 is connected between a first phase power supply R of the power supply device VS and a first output terminal OUT1. The second forward rectifier circuit 42 is connected between a second phase power supply S of the power supply device VS and the first output terminal OUT1. The third forward rectifier circuit 43 is connected between a third phase power supply T of the power supply device VS and the first output terminal OUT1. The reverse rectifier circuit 44 is connected between a neutral line N of the power supply device VS and a second output terminal OUT2. The capacitor 45 is connected between the first output terminal OUT1 and the second output terminal OUT2. The second output terminal OUT2 is grounded.

[0015] In operation, the first forward rectifier circuit 41, the second forward rectifier circuit 42, and the third forward rectifier circuit 43 perform half-wave rectification on the first phase power supply R, the second phase power supply S, and the third phase power supply T, respectively, to generate rectified first phase power supply R', rectified second phase power supply S', and rectified third phase power supply T', which are then superimposed on the first output terminal OUT1. The capacitor 45 smoothes the voltage superimposed on the first output terminal OUT1 and provides it to the load LD as an output voltage Vdc. Because the first forward rectifier circuit 41, the second forward rectifier circuit 42, and the third forward rectifier circuit 43 perform half-wave rectification on the first phase power supply R, the second phase power supply S, and the third phase power supply T, respectively, current distribution is uniform. Therefore, the electronic transformer 40 and its three-phase four-wire power supply system 4 of the present disclosure solve the problem that certain elements are quickly damaged due to frequent exposure to large currents (i.e., uneven current distribution).

[0016] Subsequently, after the load LD receives the output voltage Vdc, the return current Ire generated in the load LD further flows to the electronic transformer 40 via the second output terminal OUT2. The reverse rectifier circuit 44 is arranged to perform half-wave rectification on the return current Ire to generate a rectified return current Ire' and send it back to the power supply device VS via the neutral conductor N.

[0017] In brief, the electronic transformer 40 performs half-wave rectification on the first-phase power supply R, the second-phase power supply S, and the third-phase power supply T using the first forward rectifier circuit 41, the second forward rectifier circuit 42, and the third forward rectifier circuit 43, respectively, and superimposes the rectified first-phase power supply R', the rectified second-phase power supply S', and the rectified third-phase power supply T' at the first output terminal OUT1. The capacitor 45 then smooths (i.e., smooths) the voltage superimposed at the first output terminal OUT1 and provides the output voltage Vdc to the load LD. Next, the reverse rectifier circuit 44 performs half-wave rectification on the return current Ire generated in the load LD and sends the rectified return current Ire' back to the power supply device VS via the neutral wire N.

[0018] In other words, the three-phase power supplies R, S, and T generated by the power supply VS are rectified by the three forward rectifier circuits 41, 42, and 43 of the electronic transformer 40, respectively, and then collected as the output current Iout via the first output terminal OUT1 and flow to the load LD. Subsequently, the return current Ire generated in the load LD is rectified by the reverse rectifier circuit 44 of the electronic transformer 40 and then returned to the power supply VS via the neutral wire N. In this way, a complete current loop is formed between the power supply VS, the electronic transformer 40, and the load LD, and the forward output current Iout and the reverse return current Ire are operated symmetrically and evenly, thereby improving the operating efficiency of the three-phase four-wire power supply system 4.

[0019] 5 is a schematic diagram of an electronic transformer 50 according to an embodiment of the present disclosure. The electronic transformer 50 may be used in the three-phase, four-wire power supply system 4 of FIG. 4 and may replace the electronic transformer 40. Structurally, the electronic transformer 50 includes a first forward rectifier circuit 51, a second forward rectifier circuit 52, a third forward rectifier circuit 53, a reverse rectifier circuit 54, and a capacitor 55. The first forward rectifier circuit 51 includes diodes D1 and D2, the second forward rectifier circuit 52 includes diodes D3 and D4, the third forward rectifier circuit 53 includes diodes D5 and D6, and the reverse rectifier circuit 54 includes diodes D7 and D8.

[0020] In this embodiment, each of the rectifier circuits 51, 52, 53, and 54 includes two diodes connected in parallel (for example, the diodes D1 and D2 in the rectifier circuit 51 are connected in parallel). The cathodes of the diodes D1 and D2 in the first forward rectifier circuit 51 are connected to the first-phase power supply R, the cathodes of the diodes D3 and D4 in the second forward rectifier circuit 52 are connected to the second-phase power supply S, the cathodes of the diodes D5 and D6 in the third forward rectifier circuit 53 are connected to the third-phase power supply T, and the anodes of the diodes D1, D2, D3, D4, D5, and D6 in the first forward rectifier circuit 51, the second forward rectifier circuit 52, and the third forward rectifier circuit 53 are connected to the first output terminal OUT1. The anodes of the diodes D7 and D8 in the reverse rectifier circuit 54 are connected to the neutral line N, and the cathodes of the diodes D7 and D8 in the reverse rectifier circuit 54 are connected to the second output terminal OUT2. A capacitor 55 is connected between the first output terminal OUT1 and the second output terminal OUT2. The operation methods of the electronic transformers 50 and 40 are similar and will not be repeated here.

[0021] It should be noted that if each rectifier circuit 51, 52, 53, 54 has K identical diodes D1, D2, ..., DK, the total current I_TOTAL, total power P_TOTAL, and total resistance R_TOTAL after the K diodes D1, D2, ..., DK are connected in parallel may be expressed by the following functions (1), (2), and (3) (where "*" represents the multiplication symbol). TIFF0007772302000001.tif20129Let I_D denote the currents I_D1, I_D2, ..., I_DK flowing through the diodes D1, D2, ..., DK, respectively, and R_D denote the resistivity of the diodes D1, D2, ..., DK. In each rectifier circuit, as can be seen from functions (1), (2), and (3), the total power P_TOTAL is inversely proportional to the number K of diodes (since the total current remains constant). That is, the total power loss of the rectifier circuit decreases as the number K of diodes connected in parallel increases.

[0022] The magnitude of the current flowing through each diode after K diodes are connected in parallel may be expressed in Table 1 below. TIFF0007772302000002.tif54167

[0023] As can be seen from Table 1, the difference between the two currents corresponding to the number K of 5 and 6 is 3%, and the current drop is not significant. Considering the specifications of the electronic transformer 50, such as the power consumption and layout area, in some embodiments, the number K of parallel-connected diodes in each rectifier circuit 51, 52, 53, 54 may be 2 to 5. Furthermore, compared to the electronic transformer 10 shown in FIG. 1, which has many electronic elements (i.e., three bridge rectifier circuits and a six-phase inverter), the electronic transformer 40 shown in FIG. 4 has fewer electronic elements, which can save layout area.

[0024] In one embodiment, each of the diodes D1, D2, D3, D4, D5, D6, D7, and D8 is a PN junction diode or a fast rectifying diode.

[0025] Figure 6 is a waveform diagram of the output voltage Vdc of the electronic transformer 50 shown in Figure 5. In an architecture where voltage and current are equal, selecting an appropriate capacitor 55 for storing and smoothing power has the advantage that the output voltage is still relatively stable compared to the conventional electronic transformer with two-stage rectification.

[0026] FIG. 7 is a waveform diagram of the output current Iout of the electronic transformer 50 shown in FIG. 5, where currents I71, I72, and I73 are currents output from the forward rectifier circuits 51, 52, and 53, respectively. The currents I71, I72, and I73 converge at the first output terminal OUT1 to form the output current Iout of the electronic transformer 50. As can be seen from FIG. 7, the three-phase power sources R, S, and T pass evenly through the forward rectifier circuits 51, 52, and 53 and are half-wave rectified, thereby generating evenly distributed currents I71, I72, and I73. Therefore, the electronic transformer 50 of the present disclosure solves the problem of certain elements being quickly damaged due to frequent exposure to large currents (i.e., uneven current distribution).

[0027] FIG. 8 is a graph showing temperature changes of the electronic transformer 50 shown in FIG. 5 under operating conditions of 100% load and 150% load, with curves 81 and 82 corresponding to the temperature changes under 100% load and 150% load, respectively. As can be seen from FIG. 8, apart from the instantaneous maximum temperature rise at the initial power-on, over time, the temperature of the electronic transformer 50 under full load (100% load) operating conditions can be maintained within a predetermined range (e.g., 71°C to 77°C) without gradually increasing over time. Furthermore, under overload (150% load) operating conditions, the temperature of the electronic transformer 50 can be maintained within a predetermined range (e.g., 78°C to 84°C) without gradually increasing over time. Therefore, the electronic transformer 50 of the present disclosure has the advantage of being stable and not increasing over time.

[0028] The test conditions and results for the electronic transformer 50 can be summarized in Table 2 below. TIFF0007772302000003.tif23167

[0029] 9 is a schematic diagram of an electronic transformer 90 according to an embodiment of the present disclosure. The electronic transformer 90 may be used in the three-phase, four-wire power supply system 4 of FIG. 4 and may replace the electronic transformer 40. Structurally, the electronic transformer 90 includes a first forward rectifier circuit 91, a second forward rectifier circuit 92, a third forward rectifier circuit 93, a reverse rectifier circuit 94, and a capacitor 95. The first forward rectifier circuit 91 includes a diode D91, the second forward rectifier circuit 92 includes a diode D92, the third forward rectifier circuit 93 includes a diode D93, and the reverse rectifier circuit 94 includes diodes D94, D95, and D96.

[0030] In some embodiments, the ratio of the number of diodes in one forward rectifier circuit to the number of diodes in one reverse rectifier circuit is 1:3. That is, each of the first, second, and third forward rectifier circuits includes K diodes connected in parallel, and the reverse rectifier circuit includes three sets of K diodes connected in parallel. For example, in this embodiment, the forward rectifier circuit 91 (or 92 or 93) includes one diode D91 (or D92 or D93), and the reverse rectifier circuit 94 includes three diodes D94, D95, and D96, so the ratio of the number of diodes is 1:3. In other words, the number of diodes included in the three forward rectifier circuits 91, 92, and 93 (i.e., the three forward-biased diodes D91, D92, and D93) is equal to the number of diodes included in one reverse rectifier circuit 94 (i.e., the three reverse-biased diodes D94, D95, and D96).

[0031] 9, over the long term, the average current flowing through each of the three forward diodes D94, D95, and D96 is (1 / 3)*Iout, and the average current flowing through each of the three reverse diodes D94, D95, and D96 is (1 / 3)*Ire. Therefore, the output current Iout is evenly distributed among the three forward diodes D94, D95, and D96, and the return current Ire is also evenly distributed among the three reverse-biased diodes D94, D95, and D96. This solves the problem of certain elements being frequently exposed to large currents (i.e., unequal current distribution) and being quickly damaged, thereby making the operating temperature of the electronic transformer 90 more stable.

[0032] 5, as the number K of parallel-connected diodes increases, the current through each diode decreases, and the loss through each diode decreases. Thus, in some embodiments, when the number K of parallel-connected diodes is 2, the forward rectifier circuits 91, 92, and 93 each include two diodes connected in parallel, and the reverse rectifier circuit 94 includes six diodes connected in parallel, and so on.

[0033] FIG. 10 is a schematic diagram of an electronic transformer 99 according to an embodiment of the present disclosure. Electronic transformers 99 and 90 include the same elements and have the same interconnections between them. The difference between electronic transformers 99 and 90 is that diodes D91 and D94, D92 and D95, and D93 and D96 are adjacently arranged. For each forward and reverse diode, the forward current (1 / 3)*Iout and the reverse current (1 / 3)*Ire are equal in magnitude but opposite in direction. When one forward diode and one reverse diode are adjacently arranged, a differential pair is formed, which can improve the power transmission efficiency of a three-phase power supply.

[0034] FIG. 11 is a schematic layout diagram of the electronic transformer 99 and three-phase four-wire power supply system 11 shown in FIG. 10. The three-phase four-wire power supply system 11 includes a circuit board 110 formed on an XY plane and having a first surface SF1 and a second surface SF2. Structurally, the power supply device VS, the diode D91 of the forward rectifier circuit 91 (diodes D92 and D93 of the forward rectifier circuits 92 and 93 are not shown), a live line for transmitting the first power source R (live lines for transmitting the second-phase power source S and the third-phase power source T are not shown), and the load LD are provided on the first surface SF1, while the diode D94 of the reverse rectifier circuit 94 (diodes D95 and D96 are not shown) and the neutral conductor N are provided on the second surface SF2. A first through-hole 111 is formed in the circuit board 110 and extends in the Z direction to connect the power supply device VS and the neutral conductor N. The second through-hole 112 is formed in the circuit board 110, extends in the Z direction, and is arranged to connect the load LD and the neutral wire N. In one embodiment, a connector may be provided on the circuit board 110 to connect the power supply VS, and another connector may be provided on the circuit board 110 to connect the load LD, so that the power supply VS and the load LD may be external devices.

[0035] In the structure of Figure 11, the forward current (1 / 3)*Iout generated in the forward diode D91 is provided to the load LD via the live line, and then the reverse current (1 / 3)*Ire generated in the load LD is provided to the reverse diode D94 and then returned to the power supply device VS via the neutral line N. In this way, a complete current loop CL is formed between the power supply device VS, the electronic transformer 99, and the load LD, and the operation of the forward output current and the reverse return current is symmetrical and equal, thereby improving the operating efficiency of the three-phase four-wire power supply system 11.

[0036] In one embodiment, the projection onto the XY plane of the live wires and forward diodes (including D91, D92, and D93) for transmitting the three-phase power supplies R, S, and T provided on the first surface SF1 and the projection onto the XY plane of the neutral wire N and reverse diodes (including D94, D95, and D96) provided on the second surface SF2 overlap each other. In this structure, the area of ​​the current loop CL approximates the thickness of the circuit board 110 in the Z direction and the length of the neutral wire N (or live wire) in the X direction, and by minimizing the area of ​​the current loop CL, electromagnetic radiation (i.e., energy loss) generated in the current loop CL is minimized. In another embodiment, when the circuit board 110 is a multi-layer board (e.g., four layers, six layers, or more layers), at least one of the live wires and neutral wires N for transmitting the three-phase power supplies R, S, and T may be formed on an inner layer of the circuit board 110, which can further reduce the area of ​​the current loop CL and provide electromagnetic shielding on the surface layer of the circuit board 110 so as to reduce the electromagnetic radiation (i.e., energy loss) generated in the current loop CL.

[0037] In summary, the electronic transformer and its three-phase four-wire power supply system disclosed herein use three forward rectifier circuits to perform half-wave rectification on the three-phase power supply, respectively, generating evenly distributed output currents at the first output terminals. This solves the problem of certain components being rapidly damaged due to frequent high currents (i.e., uneven current distribution). Furthermore, the return current generated in the load is rectified by the reverse rectifier circuit and then returned to the power supply device via the neutral line, forming a complete current loop between the power supply device, the electronic transformer, and the load. The forward output current and the reverse return current are symmetrically and evenly distributed, thereby improving the operating efficiency of the three-phase four-wire power supply system. The electronic transformer and its three-phase four-wire power supply system disclosed herein have the following advantages: (1) stable output voltage; (2) uniform output current distribution; (3) simplified circuit design, small layout area, and low cost; and (4) stable operating temperature that does not increase over time.

[0038] Although the present disclosure has been disclosed as above by way of examples, those skilled in the art may make some changes or modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure is determined by the content specified in the following claims. [Explanation of symbols]

[0039] 1, 4, 11 Three-phase four-wire power system 10, 40, 50, 90, 99 Electronic Transformers 41, 51, 91 1st forward rectifier circuit 42, 52, 92 2nd forward rectifier circuit 43, 53, 93 Third forward rectifier circuit 44, 54, 94 Reverse rectifier circuit 45, 55, 95 capacitors 81, 82 curve 110 Circuit Board CL Current Loop D1, D2, D3, D4, D5, D6, D7, D8, D91, D92, D93, D94, D95, D96 diodes Iout output current Ire,Ire' リターンcurrent L1, L2, L3 ノード LD load N Neutral line OUT1 1st output terminal OUT2 2nd output terminal R, R' Phase 1 power supply S, S' Phase 2 power supply T, T' 3rd phase power supply Vdc output voltage VS power supply unit

Claims

1. a first forward rectifier circuit connected between the first phase power supply and the first output terminal; a second forward rectifier circuit connected between a second phase power supply and the first output terminal; a third forward rectifier circuit connected between a third phase power supply and the first output terminal; a reverse rectifier circuit connected between the neutral line and the second output terminal; a capacitor connected between the first output terminal and the second output terminal, the capacitor being arranged to store power and smooth an output voltage; It consists of the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit are arranged to perform half-wave rectification on the first-phase power supply, the second-phase power supply, and the third-phase power supply, respectively, to generate rectified first-phase power supply, rectified second-phase power supply, and rectified third-phase power supply, and to superimpose the rectified first-phase power supply, the rectified second-phase power supply, and the rectified third-phase power supply at the first output terminal to form an output voltage; an electronic transformer, wherein a plurality of diodes in the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit, and live wires for transmitting the first phase power supply, the second phase power supply, and the third phase power supply are arranged on a first surface of a circuit board, and a plurality of diodes in the reverse rectifier circuit and the neutral wire are arranged on a second surface of the circuit board, the circuit board is formed on a plane, and projections of the live wires and the plurality of diodes arranged on the first surface and projections of the neutral wire and the plurality of diodes arranged on the second surface overlap each other on the plane.

2. 2. The electronic transformer of claim 1, wherein the output voltage is supplied to a load and generates a return current at the second output terminal, the reverse rectifier circuit performs half-wave rectification on the return current to generate a rectified return current, and the rectified return current is transmitted to a power supply device via the neutral conductor.

3. 2. The electronic transformer of claim 1, wherein each of the first forward rectifier circuit, the second forward rectifier circuit, the third forward rectifier circuit, and the reverse rectifier circuit includes two to five diodes connected in parallel.

4. 4. The electronic transformer of claim 3, wherein a cathode of each diode in the first forward rectifier circuit is connected to the first phase power supply, a cathode of each diode in the second forward rectifier circuit is connected to the second phase power supply, a cathode of each diode in the third forward rectifier circuit is connected to the third phase power supply, anodes of each diode in the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit are connected to the first output terminal, an anode of each diode in the reverse rectifier circuit is connected to the neutral line, and a cathode of each diode in the reverse rectifier circuit is connected to the second output terminal.

5. 2. The electronic transformer according to claim 1, wherein a ratio of the number of the plurality of diodes in any one of the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit to the number of the plurality of diodes in the reverse rectifier circuit is 1:

3.

6. 6. The electronic transformer according to claim 5, wherein the plurality of diodes in the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit are respectively arranged adjacent to the plurality of diodes in the reverse rectifier circuit.

7. 6. The electronic transformer according to claim 5, wherein each of the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit includes K diodes connected in parallel, and the reverse rectifier circuit includes three sets of K diodes connected in parallel, where K is a positive integer between 2 and 5.

8. 8. The electronic transformer of claim 7, wherein a cathode of each diode in the first forward rectifier circuit is connected to the first phase power supply, a cathode of each diode in the second forward rectifier circuit is connected to the second phase power supply, a cathode of each diode in the third forward rectifier circuit is connected to the third phase power supply, anodes of each diode in the first forward rectifier circuit, the second forward rectifier circuit, and the third forward rectifier circuit are connected to the first output terminal, an anode of each diode in the reverse rectifier circuit is connected to the neutral line, and a cathode of each diode in the reverse rectifier circuit is connected to the second output terminal.

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