Switching power supply using the resonance of a capacitor and a coil

Abstract

To provide a compact and lightweight switching power supply that is noise-free by generating a resonance state by using a coil together with power transmission by a capacitor and switching at a point where the current becomes zero.SOLUTION: In an electric energy transmission circuit (switching power supply 1), electric energy is transmitted to the load side through an LC tank circuit 3 that resonates in series with a coil. The switching timing is timing in which switching is performed at a current zero point on the basis of an LC resonant circuit constant (1 / (2π√LC)). In order to reduce the ratio of an input voltage to an output voltage, the voltage dividing capacitor capacity of a half-bridge inverter is set smaller than the capacitor capacity used for an LC resonance tank, and at the same time, a multiple of the half cycle of the sine wave determined by the LC tank resonance frequency is controlled so as to become an ON time of an inverter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a switching power supply that utilizes resonance between a capacitor and a coil. [Background technology]

[0002] Currently, magnetic coupling (transformer coupling) is used in power converters (DC / DC or AC converters), and in order to prevent the generation of switching noise, a resonant circuit is formed between the L component of the transformer and a capacitor C, and switching occurs at the zero-cross point (or a state close to it) of the voltage and current, thereby preventing the generation of switching noise (commonly known as LLC).

[0003] With the magnetic coupling (transformer coupling) that has been used up until now, it would be desirable to increase the switching frequency in order to make the transformer smaller, but the magnetic materials (ferrite, amorphous, etc.) that are used do not exist that can handle frequencies above several hundred kHz, making it difficult to reduce weight.On the other hand, the "capacitor coupling method" that was considered in the past has not yet been put to practical use because when the inverter performs hard switching (simply turning the capacitor on and off), a short-circuit current is generated in the capacitor (low impedance), resulting in increased switching noise.

[0004] Patent Document 1 describes an uninterruptible power supply that includes a rectifier circuit, a rectifier conduction control signal generating circuit, an inverter circuit, and an inverter conduction control signal generating circuit, a plurality of input-side reactors each connected in series to the AC input terminals of the rectifier circuit, a plurality of output-side reactors each connected in series to the AC output terminals of the inverter circuit, a plurality of input-side capacitors each connected at one end to the AC power supply side terminals of the plurality of input-side reactors and at the other end to a common line, and a plurality of output-side capacitors each connected at one end to the load side terminals of the plurality of output-side reactors and at the other end to a common line, but the uninterruptible power supply does not have an isolated inverter-converter configuration, and only a coil (L) is used, so resonance (zero current switching, etc.) is not achieved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-295623 Summary of the Invention [Problem to be solved by the invention]

[0006] Advances in power devices are making it possible to switch at frequencies of several MHz or even several tens of MHz, but as mentioned above, advances in magnetic materials have not kept pace, limiting the ability to make power supplies smaller and lighter. Therefore, the present invention aims to create a noiseless, small, lightweight power supply by using a capacitor as the main power transmission method, in combination with a coil to create a resonant state, and switching at the point where the current becomes zero. [Means for solving the problem]

[0007] The present invention, which solves the above problems, is as follows. (1) A switching power supply characterized by including a circuit in which an inverter circuit, two sets of LC (coil-capacitor) tank circuits, and a rectifier circuit are connected in this order. That is, it is a switching power supply characterized in that two sets of series circuits of a capacitor and a coil are provided at the inverter output configured with a high-side switch and a low-side switch, and are connected to a rectifier circuit. (2) The switching power supply according to (1), wherein the inverter circuit is composed of a power semiconductor. That is, the capacitor and the coil are preset to have current resonance during the ON pulse time (width) of the switching, and the switching power supply is characterized in that the switching is always performed at the zero crossing point. (3) In the switching power supply described in (1) or (2), the LC resonance is utilized, and the switching of the inverter circuit is operated in relation to the switching frequency of the inverter circuit so that the capacitor current becomes the zero point. That is, the switching power supply is characterized in that the resonant current can be plural within the ON pulse (plural sine waves are included within the ON pulse). Switching of the inverter circuit means turning the switch of the inverter circuit ON / OFF. do. (4) In the switching power supply described in (1) or (2), the voltage output from the switching power supply is adjusted by adding or thinning out a sine wave (half cycle) as the minimum unit, and the switching of the inverter circuit is operated in relation to the switching frequency of the inverter circuit so that the capacitor current becomes the zero point. (5) In the switching power supply described in (1) or (2), the voltage output from the switching power supply is adjusted by stepping down the input voltage using a capacitor capacity that divides the input voltage and a capacitor capacity that is used in an LC tank. (6) In the switching power supply according to any one of (1) to (3), the inverter circuits are connected in parallel and the control signal is multiphased (interleaved). (7) A power supply circuit characterized in that, in the switching power supply described in any one of (1) to (3), a plurality of (n) units are used and the units are operated with a phase difference of 1 / n electrical angle. (8) The power supply circuit according to (7) is characterized in that the input sections of the plurality of (n) units are connected in series and the output sections are connected in parallel to form a multi-stage connection, and an input power supply and short circuit are provided in the input section. (9) A power supply method using the power supply circuit described in (8), characterized in that when at least one of the multiple (n) units has an open circuit fault, the input power supply short circuit is turned on. [Effects of the Invention]

[0008] Because a capacitor is used to transmit electrical energy, it is possible to achieve smaller size and lighter weight in the high frequency range (above several hundred kHz) compared to when a transformer is used.Inverter switching is always performed at the point of zero current, so there is no need to add noise suppression components, and a small, lightweight power supply can be constructed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an electrical energy transfer circuit using a capacitor according to one embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing the energization timing of switching devices (S1 to S2) of two half-bridge inverters when the electrical angle phase is 0 to 2π. [Figure 3] (a) A diagram showing the inverter switching waveform (□) and capacitor current (◇). (b) A diagram showing the ON / OFF control signal for the power device (S1) and the inverter output simultaneously. (c) A diagram showing the ON / OFF control signal for the power device (S2) and the inverter output simultaneously. (d) A diagram showing the voltage waveform (□) and load current waveform (◇) of the inverter output after full-bridge diode rectification. The switching timing is at the timing of zero current. [Figure 4] FIG. 4 is an enlarged view of FIG. [Figure 5] (a) and (b) are diagrams showing a method of pausing the operation of the inverter in a half-cycle or one cycle of the sine wave and reducing the output voltage. (a) The inverter operates in the entire section (full output state). (b) The inverter is in a paused operation during one cycle of the sine wave (the operation of the inverter is paused in one cycle of the sine wave). [Figure 6] (a) to (f) are diagrams showing that the output voltage of the inverter can be adjusted by selecting a smaller power supply side capacitor (power supply voltage dividing capacitor (「C1」 in Fig. 1)) for the half-bridge inverter and setting (C1, C2 < Cin) for the coupling capacitor. Also, it is a diagram showing that two or more sine waves can be generated within the inverter ON pulse at the same time. [Figure 7] It is a diagram showing the configuration of the three-phase interleaved method. [Figure 8] It is a diagram showing the inverter control signal during three-phase interleaved operation. [Figure 9] It is a diagram showing the voltage and current waveforms of each unit during three-phase interleaved operation. [Figure 10] (a) and (b) are diagrams showing that the output voltage ripple and current ripple during three-phase interleaved operation are reduced to 1 / 3. [Figure 11] It is a diagram showing examples of series and parallel connections of units, showing (a) input parallel, output parallel, and (b) input series, output parallel. [Figure 12] With C1, C2 < Cin and the switching waveforms during three-phase interleaved operation. (a) shows the switch signal of unit 1 and the LC tank (resonance) circuit current, (b) shows the switch signal of unit 2 and the LC tank (resonance) circuit current, and (c) shows the switch signal of unit 3 and the LC tank (resonance) circuit current. [Figure 13] (a) A power supply circuit with a multi-stage connection by connecting the input parts of 4 units in series and the output parts in parallel, and an input power supply and a short-circuit circuit provided in the input part. (b) A power supply circuit in which one of the units constituting the power supply circuit in (a) has failed, are diagrams showing them respectively. [Figure 14] FIG. 10 is a diagram showing a change in voltage at the output section when a power supply circuit having five units changes from a five-unit operation to a four-unit operation. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

[0011] Figure 1 shows one embodiment of an electrical energy transfer circuit (switching power supply 1) of the present invention. Electrical energy is transferred to the load side through an LC tank circuit 3 that resonates in series with the coil. Switching is performed at the current zero point based on the LC resonant circuit constant (1 / (2π√LC)). A DC voltage is applied to the half-bridge inverter 2 from a DC power supply 5, which converts the DC voltage into an AC voltage (pulse) and transmits it to a rectifier circuit (full-bridge rectifier) ​​4 via two sets of resonant tank circuits consisting of series resonant circuits of a capacitor and a coil. The DC power supply 5 and rectifier circuit 4 are connected by a capacitor and are insulated from the DC side.

[0012] The half-bridge inverter 2 operates according to the timing chart shown in Figure 2. Figure 3(a) shows the inverter switching control signal and the current waveform of the LC tank circuit 3. Figures 3(b) and (c) show the inverter output voltage waveform based on the inverter control signal. It can be seen that the inverter is turned ON / OFF when the capacitor current is zero. Figure 3(b) is based on the operation of "semiconductor switch S1" and Figure 3(c) is based on the operation of "semiconductor switch S2".

[0013] The inverter output can be fine-tuned by setting a half-cycle or one cycle of the sine wave of the resonant frequency as a pause (thinned-out operation) section. Figure 5(a) shows the operating waveform with the entire section ON, and Figure 5(b) shows the operating waveform with one cycle OFF.

[0014] The inverter output voltage can be achieved by connecting capacitors with different capacitances in series. Assuming that the capacitances of C1 and C2 in Fig. 1 are smaller than the capacitance of Cin (C1, C2 < Cin), an alternating current can be applied during the inverter operation to adjust the output voltage. As an example, by setting the voltage-dividing capacitors C1 and C2 to "0.005 μF" and Cin to 0.5 μF, a voltage division ratio of approximately 100:5 (output voltage of 5 V for an input of 100 V) can be obtained (see Fig. 6).

[0015] Since the inverter switching timing is performed at the period of the resonance frequency (an integer multiple of one period or half period), the timing for controlling the output voltage becomes dependent and affects the output voltage ripple. However, n unit power supply units shown in Fig. 1 are connected in parallel, and the switching phases of the inverters of each unit are shifted by an electrical angle of 1 / n to drive each unit. Fig. 7 shows an embodiment with n = 3 (three-phase interleaving). Fig. 10 shows the inverter control signal during three-phase interleaving operation (Fig. 8) and the operation waveforms of each unit based on it. Compared with single-phase switching operation, the three-phase interleaving operation reduces the output voltage and current ripple to 1 / 3 or less (Fig. 10). As shown in Fig. 11, each unit can operate in either parallel connection or series connection with respect to the input power supply, and similarly, it can also be connected in parallel or series with respect to the output.

[0016] Fig. 12 shows that by providing a partial pause period (OFF period) and simultaneously providing a phase difference of 120 electrical degrees to the ON signal to perform three-phase leap operation, the output voltage ripple can be reduced (Fig. 12(d)).

[0017] (Variant example) After passing through the LC tank circuit, it is connected to a diode bridge circuit. However, for lower losses, a synchronous rectification circuit can be used, and any power supply circuit that switches at an integer multiple of half the period of the sine wave resonance frequency based on the LC resonance tank is acceptable.

[0018] 13, power supply circuit 21 includes four units 22 to 25. One unit 22 includes an isolation unit 21a that corresponds to switching power supply 1. It may also include a basic power supply unit 21b electrically connected to isolation unit 21a. Therefore, the following description will be given of a case where the unit includes an isolation unit and a basic power supply unit.

[0019] The input section 32 of the unit 22 is composed of a switch, a resistor, and a diode. The input sections of the units 22 to 25 are connected in series. On the other hand, the output sections of the units 22 to 25 are connected in parallel. Therefore, even if one of the units fails, the output voltage from the power supply circuit 21 maintains the rated voltage. In other words, in the event of an "open fault" in the basic configuration, the basic configuration units can be short-circuited, thereby maintaining the overall power supply function.

[0020] The effects of this are explained below based on Figures 13(a) and 13(b): The operating efficiency is maximized when the isolation unit is set to "1 / 2 voltage."

[0021] 13(b) shows a case in which unit 23 in FIG. 13(a) fails and power supply circuit 21 becomes power supply circuit 21'. In this case, the input voltage (battery voltage (384V)) is applied, but in the case of an open circuit failure, no output voltage can be obtained.

[0022] At this time, by short-circuiting one of the basic configuration units via the input section 33, the input voltage of the basic configuration unit changes from 96V to 128V (384V / 3). In other words, the basic power supply unit can be controlled to a constant voltage of 48V (by step-down converter control).

[0023] Figure 14 shows the change in output voltage when a power supply circuit with five units is changed from operating with five units to operating with four units. With five units operating and an input voltage of 400V, the power supply circuit had an output voltage of 80V (=400V / 5). By changing this to a power supply circuit operating with four units, we found that the output voltage could be increased to 100V (=400V / 4). [Industrial Applicability]

[0024] As described above, switching power supplies that utilize the resonance of a capacitor and coil can achieve DC isolation using a capacitor without using the magnetic coupling of a transformer. Furthermore, commutation (ON / OFF) at the point where the inverter output current is "zero" can suppress switching noise. The output voltage can be adjusted by turning the power ON / OFF in units of half a cycle or full cycle of a sine wave based on the resonance frequency. In particular, when using switching frequencies of several hundred kHz or higher, there are limits to how small and lightweight a transformer can be. However, capacitors can transmit electrical energy, and the use of surface-mount capacitors enables thinner, smaller, and lighter designs, improving the power consumption of products such as aircraft, helicopters, drones, and flying cars. [Explanation of symbols]

[0025] 1: Switching power supply 2: Half-bridge inverter 3: LC tank circuit 4: Rectifier circuit 5:DC power supply 11, 12: Zero current timing 21, 21´: Power supply circuit 22~25: Unit 21a: Isolation unit 21b: Basic power supply unit 32, 33: Input section

Claims

1. An isolated switching power supply comprising a circuit in which a half-bridge inverter circuit, two sets of LC tank series circuits, and a rectifier circuit are connected in this order.

2. 2. The isolated switching power supply according to claim 1, wherein the half-bridge inverter circuit is composed of power semiconductors.

3. 3. The isolated switching power supply according to claim 1, wherein L and C are driven in a state of resonance so that the relationship fc=1 / (2π√LC) is satisfied, and thus the switching of the half-bridge inverter circuit brings the capacitor current to a zero point.

4. An isolated switching power supply, characterized in that in a power supply circuit having a plurality of isolated switching power supplies as described in any one of claims 1 to 3, the inputs of the half-bridge inverter circuits are connected in series and the outputs are connected in parallel.

5. A power supply circuit comprising a plurality of isolated switching power supplies according to any one of claims 1 to 3, the input sections of which are connected in series and the output sections of which are connected in parallel to form a multistage connection, and an input power supply and a short circuit are provided in the input section.

6. 6. The power supply method according to claim 5, wherein when at least one of the plurality of isolated switching power supplies has an open circuit fault, the input power supply short circuit is turned on.

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