JP6028474B2 - Capacitor circuit, DC-DC converter circuit, and DC power supply device - Google Patents

Description

  The present invention relates to a capacitor circuit using a four-terminal capacitor, a DC-DC converter circuit, and a DC power supply device.

  Conventionally, a four-terminal capacitor has been used as a noise countermeasure component. For example, Patent Document 1 discloses a noise filter using a four-terminal capacitor. This noise filter (4-terminal capacitor) is inserted between the reference side wiring and the hot side wiring of the AC input portion. That is, the reference-side wiring is wired via a pair of lead wires sharing one electrode of the 4-terminal capacitor, and the hot-side wiring is wired via a pair of lead wires sharing the other electrode of the 4-terminal capacitor. . Further, a ferrite bead is provided in the lead portion of the four-terminal capacitor, and an inductor component is added to a circuit including the four-terminal capacitor.

Japanese Utility Model Publication No. 59-174716

  By the way, in recent years, as a switching power supply device for driving a DC load such as an LED, for example, a DC-DC converter that boosts or steps down a DC voltage to a desired voltage is provided at a subsequent stage of a circuit that converts an AC power input to DC. Those with a circuit installed are widespread. In such a switching power supply device, it is desired to take noise countermeasures more effectively. However, it has been found that in a switching power supply device including a DC-DC converter circuit, it is difficult to obtain a desired noise reduction effect even if a four-terminal capacitor is connected as disclosed in Patent Document 1. Therefore, a technique that can more effectively reduce noise using a four-terminal capacitor has been desired.

  The present invention has been made to solve the above problems, and provides a capacitor circuit, a DC-DC converter circuit, and a DC power supply device that can more effectively reduce noise using a four-terminal capacitor. The purpose is to do.

  A capacitor circuit according to the present invention includes a four-terminal capacitor having a first pair of lead wires sharing one electrode and a second pair of lead wires sharing the other electrode, and is a direct current input from an input wiring A capacitor circuit that transforms the voltage and supplies the load to the load via the output wiring. The inductor element has one end connected to the input wiring, the input terminal is connected to the other end of the inductor element, and the inductor element is connected during the conduction period. A switching element that allows current to flow from the input wiring to the reference potential wiring, and one end is connected to the other end of the inductor element, and the power stored in the inductor element is loaded via the output wiring while the switching element is non-conductive. The other end of the rectifying element and the output wiring are connected via a first pair of lead wires of a four-terminal capacitor, and the switching element Characterized in that the output terminal and the reference potential wiring is connected via the second pair of leads 4 terminal capacitor.

  According to the capacitor circuit of the present invention, current flows to the load side through the first pair of lead wires of the four-terminal capacitor when the switching element is out of circuit. At that time, according to the four-terminal capacitor, the ESL (equivalent series inductor) of the lead wire is reduced, so that the insertion loss can be further increased. Therefore, it is possible to effectively exhibit the noise reduction action by the four-terminal capacitor. In this case, since a four-terminal capacitor is connected after the rectifying element, a large current that is instantaneously generated when the switching element performs a switching operation can be suppressed.

  A DC-DC converter circuit according to the present invention is a DC-DC converter circuit that transforms a DC voltage input from an input wiring and supplies it to a load via an output wiring. The DC-DC converter circuit includes an inductor element and an inductor element during a conduction period. A switching element that allows current to flow from the input wiring to the reference potential wiring via the rectifier, a rectifying element that supplies power stored in the inductor element to the load via the output wiring during the non-conducting period of the switching element, and one electrode And a four-terminal capacitor having a second pair of lead wires sharing the other electrode, and the rectifying element and the output wiring are the first pair of leads of the four-terminal capacitor. The switching element and the reference potential wiring are connected via a second pair of lead wires of a four-terminal capacitor.

  According to the DC-DC converter circuit of the present invention, when the switching element is out of circuit, current flows to the load side through the first pair of lead wires of the four-terminal capacitor. At that time, according to the four-terminal capacitor, the ESL (equivalent series inductor) of the lead wire is reduced, so that the insertion loss can be further increased. Therefore, it is possible to effectively exhibit the noise reduction action by the four-terminal capacitor. In this case, since a four-terminal capacitor is connected after the rectifying element, a large current that is instantaneously generated when the switching element performs a switching operation can be suppressed.

  In the DC-DC converter circuit according to the present invention, the inductor element is a choke coil having one end connected to the input wiring, the rectifier element is a diode, and the input terminal of the switching element and the anode terminal of the diode are other than the choke coil. The cathode terminal of the diode and the output wiring are connected via a first pair of lead wires of the four-terminal capacitor, and the output terminal of the switching element and the reference potential wiring are a second pair of the four-terminal capacitor. It is preferable that they are connected via a lead wire.

  In this way, it is possible to obtain a noise reduction effect in a step-up type circuit configuration while maintaining the small characteristics of the non-insulated DC-DC converter.

  In the DC-DC converter circuit according to the present invention, the inductor element is a transformer having one end of the primary winding connected to the input wiring, the rectifier element is a diode, and the input terminal of the switching element is the primary winding of the transformer. Connected to the other end, the anode terminal of the diode is connected to one end of the secondary winding of the transformer, the cathode terminal of the diode and the output wiring are connected via a first pair of lead wires of a four-terminal capacitor, and switching The output terminal of the element and the reference potential wiring are preferably connected via a second pair of lead wires of a four-terminal capacitor.

  In this way, it is possible to obtain a noise reduction effect even in an isolated flyback converter that can be stepped up or stepped down and has high versatility.

  A DC power supply device according to the present invention includes an input circuit that rectifies an AC input voltage and supplies a DC voltage to an input wiring, and any one of the DC-DC converter circuits described above.

  According to the DC power supply device according to the present invention, since any one of the DC-DC converter circuits described above is provided, a DC power supply device with a low noise level can be provided.

  According to the present invention, it is possible to more effectively reduce noise using a four-terminal capacitor.

1 is a circuit diagram of a DC power supply device including a DC-DC converter circuit according to an embodiment. It is a figure explaining a 4-terminal capacitor. It is a figure for demonstrating operation | movement of the DC-DC converter circuit of FIG. It is a figure for demonstrating operation | movement of the DC-DC converter circuit of FIG. It is a graph which shows the insertion loss characteristic of the capacitor | condenser of embodiment and a 3rd comparative example. It is a circuit diagram of the direct-current power supply device concerning the 1st comparative example. It is a circuit diagram of the direct-current power supply device concerning the 2nd comparative example. It is a circuit diagram of the DC power supply device concerning the 3rd comparative example. It is a circuit diagram of the DC power supply device concerning the 4th comparative example. It is a graph which shows the radiation noise level of embodiment, a 1st comparative example, and a 3rd comparative example. It is a graph which shows the electric current which flows into the switching element which comprises the 4th comparative example. It is a circuit diagram of the direct-current power supply device concerning the 1st modification. It is a circuit diagram of the direct-current power supply device concerning the 2nd modification.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  First, the configuration of a DC power supply device 1 including a capacitor circuit according to the embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram of the DC power supply device 1. The DC power supply device 1 includes an input circuit 10 that rectifies an input AC voltage to convert it to DC, and a DC-DC converter circuit 20 that steps down the input voltage from the input circuit 10 and supplies the voltage to a load 2. In addition, although LED was used as the load 2 in this embodiment, the load 2 may be any load as long as it is a DC-driven load.

  The input circuit 10 includes a full wave rectifier 11, a smoothing capacitor 12, a filter coil 13, and a filter capacitor 14. Full-wave rectifier 11 performs full-wave rectification on the AC input voltage input from input terminals T1 and T2, and smoothing capacitor 12 smoothes the full-wave rectified output. In other words, the input AC power supply is converted to DC by the full-wave rectifier 11 and the smoothing capacitor 12, and a DC voltage is supplied to the reference potential wiring 31 (ground) and the high potential side wiring (input wiring) 32. The filter coil 13 and the filter capacitor 14 form a noise filter, which mainly attenuates normal mode noise.

  In place of the smoothing capacitor 12, a capacitor for forming a π-type filter with the filter coil 13 and the filter capacitor 14 may be connected. Further, when the input power supply is a DC power supply, the input circuit 10 is not necessary, and the DC power supply may be directly connected to the DC-DC converter circuit 20.

  The DC-DC converter circuit 20 includes a choke coil 21 (inductor element), a switching element 22, a rectifying element 23, a four-terminal capacitor 24, a capacitor 25, a resistor 26, a driver 27, and the like. One end of the choke coil 21 is connected to the high potential side wiring 32, and the other end is connected to a drain terminal (corresponding to an input terminal described in claims) of the switching element 22 made of, for example, a MOS FET. The anode terminal of the rectifying element 23 made of a diode is connected to the other end of the choke coil 21 and the drain terminal of the switching element 22.

  The source terminal of the switching element 22 (corresponding to the output terminal described in the claims) and the cathode terminal of the rectifying element 23 are connected to the lead wires 24c and 24a of the four-terminal capacitor 24, respectively, and the lead wire 24d of the four-terminal capacitor 24 is connected. And 24b are connected to the reference potential wiring 31 and the output wiring 33, respectively. That is, the cathode terminal of the rectifying element 23 and the output wiring 33 are connected via a pair of lead wires 24a and 24b, and the source terminal of the switching element 22 and the reference potential wiring 31 are connected via a pair of lead wires 24c and 24d. The

Here, FIG. 2 shows a configuration of the four-terminal capacitor 24 used in the present embodiment. The 4-terminal capacitor 24 is connected to the main body 240 made of a ceramic capacitor, the electrode 241, the electrode 242, the electrode 241 and bent into a hairpin shape, and the electrode 242, connected to the electrode 242 and bent into a hairpin shape. It consists of lead wires 24c and 24d. The ceramic capacitor of the main body 240 is formed by alternately stacking a plurality of dielectric layers formed in a rectangular shape and internal electrodes formed in a rectangular thin film shape. The dielectric layer is made of a dielectric ceramic whose main component is BaTiO ₃ , CaTiO ₃ , CaZrO ₃ or the like. In this dielectric layer, subcomponents such as a Mn compound, Fe compound, Cr compound, Co compound, and Ni compound may be added to the main component.

  Generally, an actual capacitor has an equivalent series inductance (ESL (Equivalent Series Inductance)) and an equivalent series resistance (ESR (Equivalent Series Resistance)) in addition to a capacitance component (ESC (Equivalent Series Capacitance)). The impedance decreases with increasing frequency on the low frequency side with the resonance frequency as a boundary, but tends to increase with increasing frequency on the high frequency side due to the influence of ESL. In the case of a capacitor with a lead wire, since the ESL is relatively large, the impedance in the high frequency band increases, and the four-terminal capacitor reduces the ESL. Attaching two leads to each, by separating these leads to the input side and the output side, it is intended to eliminate the inductance component is inserted in series with the capacitor (ESL).

  Returning to FIG. 1, the capacitor 25 smoothes the output from the rectifying element 23 as necessary. In the present embodiment, the load 2 is an LED, and it is desirable to insert the capacitor 25 in order to reduce the ripple of the light output. However, when the output ripple does not become a problem in the load 2, the capacitor 25 has a small capacity. May be omitted or omitted. The resistor 26 discharges the voltage remaining in the capacitor 25 (voltage less than or equal to the total LED Vf) at the end of the operation of the DC-DC converter circuit 20 so that no voltage is generated between the output terminals T3 and T4 when the load 2 is removed. It is for making.

  Next, the operation of the DC-DC converter circuit 2 will be described with reference to FIGS. A driver 27 is connected to the gate terminal of the switching element 22. The driver 27 performs PWM control of the switching element 22 with an appropriate ON width and drive frequency (for example, several tens of k to several hundreds of kHz).

  First, as shown in FIG. 3, during the conduction period of the switching element 22, the main current is the high potential side wiring 32 → choke coil 21 → switching element 22 → lead wire 24c of the 4-terminal capacitor 24 → electrode 242 (FIG. 2). Reference) → Lead wire 24d → Reference potential wiring 31 flows. That is, during this period, current flows from the high potential side wiring 32 toward the reference potential wiring 31 through the choke coil 21, and energy is accumulated in the choke coil 21. During this period, the rectifying element 23 is in a non-conductive state.

  Next, as shown in FIG. 4, during the period when the switching element 22 is non-conductive, the main current uses the energy stored in the choke coil 21 as a power source and the lead of the choke coil 21 → rectifier element 23 → four-terminal capacitor 24. The current flows through the line 24a → the electrode 241 (see FIG. 2) → the lead wire 24b → the output wiring 33 → the load 2 → the choke coil 21. As a result, the boosted DC power is supplied to the load 2. The operations of FIGS. 3 and 4 are repeated at the drive frequency by the driver 27.

  As described above, during the conduction period of the switching element 22, a current path is formed in the pair of lead wires 24 c and 24 d of the four-terminal capacitor 24. Further, during the non-conduction period of the switching element 22, a current path is formed in the pair of lead wires 24 a and 24 b of the four-terminal capacitor 24. Thereby, the ESL caused by the lead wires 24a to 24d of the four-terminal capacitor 24 can be reduced, and the impedance can be lowered. Therefore, it is possible to further exhibit the noise reduction effect by connecting the four-terminal capacitor 24 between the output wiring 33 and the reference potential wiring 31.

  Here, FIG. 5 shows S21 when the four-terminal capacitor 24 is used and when the two-terminal capacitor 124 (comparative example) shown in FIG. 8 is used. The horizontal axis of the graph shown in FIG. 5 is frequency (MHz), and the vertical axis is S parameter S21 (dB). Note that S21 is a ratio transmitted to point B (port 2) when a signal is input to point A (port 1) in the embodiment (FIG. 1) and the comparative example (FIG. 8), that is, a forward transmission coefficient. is there. Therefore, it can be evaluated that the smaller this S21, the greater the insertion loss and the greater the noise countermeasure effect.

  As shown in FIG. 5, the resonance point of S21 of the two-terminal capacitor 124 in FIG. 8 is less than 10 MHz, whereas the resonance point of S21 of the four-terminal capacitor 24 according to the present embodiment has increased to 20 MHz. Further, on the high frequency side from the resonance point of S21, the magnitude of S21 at the same frequency is 10 dB or more smaller than the two-terminal capacitor 124 in FIG. 8 (that is, the insertion loss is large). ) Was confirmed. Here, since the frequency band in which the radiation noise of LED illumination is easily observed is 30 to 300 MHz, the increase of the resonance point and the reduction of S21 on the high frequency side from the resonance point are preferable in reducing the radiation noise. .

  As described above, according to the connection form of the four-terminal capacitor 24 according to the present embodiment, the noise reduction effect in the DC-DC converter circuit 20 can be reliably obtained.

  Then, the noise reduction effect of this embodiment was confirmed using the circuit of the comparative example. 6 to 9 show DC power supply apparatuses according to first to fourth comparative examples, respectively. As shown in FIG. 6, the DC power supply device 101 of the first comparative example has a circuit configuration that does not include a four-terminal capacitor (and a two-terminal capacitor). Further, as shown in FIG. 7, in the DC power supply device 102 according to the second comparative example, 4 is connected to the input circuit 110 in the previous stage of the DC-DC converter circuit 122, more specifically, to the output terminal of the full-wave rectifier 11. A terminal capacitor 24 is connected.

  As shown in FIG. 8, in the DC power supply device 103 according to the third comparative example, a two-terminal capacitor 124 is connected instead of the four-terminal capacitor 24 in the circuit (this embodiment) in FIG. As shown in FIG. 9, in the DC power supply device 104 of the fourth comparative example, a four-terminal capacitor 24 is inserted on the input side of the rectifying element 23. That is, the connection point between the choke coil 21 and the drain terminal of the switching element 22 and the anode terminal of the rectifying element 23 are connected via the lead wires 24a and 24b.

  FIG. 10 shows the results of measuring the radiation noise of this embodiment, the first comparative example (FIG. 6), and the third comparative example (FIG. 8). The horizontal axis of the graph shown in FIG. 10 is the frequency (MHz), and the vertical axis is the noise level (dBμV / m). In the graph of FIG. 10, the measurement result of this embodiment is indicated by P, the measurement result of the first comparative example is indicated by C1, and the measurement result of the third comparative example is indicated by C3. Although not shown, the radiation noise of the second comparative example (FIG. 7) was equivalent to the radiation noise (measurement result C1) of the first comparative example described later.

  By connecting the two-terminal capacitor 124 between the output wiring 33 and the reference potential wiring 31, the noise level of the measurement result C3 is lower than the noise level of the measurement result C1 over almost the entire measurement frequency. Further, by connecting the 4-terminal capacitor 24 instead of the 2-terminal capacitor 124 to reduce the ESL of the capacitor, the noise level of the measurement result P is lower than the noise level of the measurement result C3 over almost the entire measurement frequency. . As a result, it has been confirmed that the noise level of the measurement result P is significantly lower than the noise level of the measurement result C1 over almost the entire measurement frequency.

  Moreover, about the 4th comparative example (FIG. 9), it was confirmed that there exists a problem on switching operation before a noise characteristic. Here, FIG. 11 shows a waveform of a current flowing between the drain and source of the switching element 22 in this comparative example. The horizontal axis of the graph shown in FIG. 11 is time (ms), and the vertical axis is current (mA). As shown by a portion X surrounded by a broken line in FIG. 11, in this comparative example, an instantaneous spike current is generated every time the switching element 22 is turned on. Since this spike current may destroy the switching element 22, the fourth comparative example (FIG. 9) cannot be employed.

  As described above, in the DC-DC converter circuit 20, the cathode terminal of the rectifying element 23 and the output wiring 33 are connected via the pair of lead wires 24 a and 24 b of the four-terminal capacitor 24, and the source terminal of the switching element 22 is connected. It has been confirmed that a significant noise reduction effect can be obtained by connecting the reference potential wiring 31 via the pair of lead wires 24c and 24d. Thus, according to the present embodiment, a capacitor circuit that allows the four-terminal capacitor 24 to function effectively in the DC-DC converter circuit 20 can be obtained, and the DC-DC converter circuit 20 can be obtained only by adding the four-terminal capacitor 24. A significant noise reduction effect can be obtained.

  Note that the configuration of the present invention can be applied to various types of DC-DC converter circuits. For example, as a first modification, the present invention can be applied to a step-up DC-DC converter circuit to obtain a circuit configuration as shown in FIG. In the circuit shown in the figure, during the conduction period of the switching element 22, the main current is high potential side wiring 32 → choke coil 21 → lead wire 24c → electrode 242 (see FIG. 2) → lead wire 24d → reference potential wiring 31. Flowing into. On the other hand, during the non-conduction period of the switching element 22, the main current uses the energy stored in the choke coil 21 as a power source, and the choke coil 21 → rectifier element 23 → lead wire 24a → electrode 241 (see FIG. 2) → lead wire. 24b → output wiring 33 → load 2 → reference potential wiring 31. As a result, a voltage obtained by adding the peak voltage generated in the choke coil 21 to the potential difference between the high potential side wiring and the reference potential wiring is output. As a result, a noise reduction effect can be obtained even in the boost converter.

  Further, as a second modification, the present invention can be applied to an insulating flyback DC-DC converter circuit to obtain a circuit configuration as shown in FIG. In the circuit shown in the figure, during the conduction period of the switching element 22, the main current is the high potential side wiring 32 → the primary winding 28a of the transformer 28 (inductor element) → the lead wire 24c → the electrode 242 (see FIG. 2) → It flows from the lead wire 24 d to the reference potential wiring 31. On the other hand, during the non-conduction period of the switching element 22, the main current uses the energy stored in the transformer 28 as a power source, the secondary winding 28 b of the transformer 28 → the rectifying element 23 → the lead wire 24 a → the electrode 241 (see FIG. 2). ) → Lead wire 24b → Output wiring 33 → Load 2 → Secondary winding 28b (At this time, current does not flow to the secondary side and the rectifying element 23 is non-conductive). Note that this modification is a step-up type or a step-down type depending on the turn ratio of the primary winding 28a and the secondary winding 28b of the transformer 28. As described above, it is possible to obtain a noise reduction effect even in an isolated flyback converter that can be stepped up and down and has high versatility.

  In any of the modifications, the impedance can be lowered by reducing the ESL of the four-terminal capacitor 24 (lead wires 24a to 24d) as in the above embodiment. Thereby, it becomes possible to further exhibit the noise reduction effect by connecting the four-terminal capacitor 24 between the output wiring 33 and the reference potential wiring 31.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, although the MOS FET is used as the switching element 22 in the above embodiment, for example, a bipolar transistor or the like may be used. When a bipolar transistor is used as the switching element 22, the collector terminal corresponds to the input terminal, the emitter terminal corresponds to the output terminal, and the base terminal serves as the control terminal.

1 DC power supply 10 Input circuit
20 DC-DC converter circuit 21 Choke coil (inductor element)
22 Switching element 23 Rectifier element 24 4-terminal capacitor 24a, 24b, 24c, 24d Lead wire 241, 242 Electrode 28 Transformer (inductor element)
31 Reference potential wiring 32 High potential side wiring (input wiring)
33 Output wiring

Claims (5)

A four-terminal capacitor having a first pair of lead wires sharing one electrode and a second pair of lead wires sharing the other electrode; transforms a DC voltage input from the input wiring; A capacitor circuit for supplying a load via
An inductor element having one end connected to the input wiring;
A switching element in which an input terminal is connected to the other end of the inductor element, and a current flows from the input wiring to the reference potential wiring of the capacitor circuit through the inductor element during a conduction period;
A rectifying element that has one end connected to the other end of the inductor element and supplies the power stored in the inductor element to the load via the output wiring during a period when the switching element is non-conductive,
The other end of the rectifying element and the output wiring are connected via a first pair of lead wires of the 4-terminal capacitor, and the output terminal of the switching element and the reference potential wiring of the capacitor circuit are connected to the 4-terminal capacitor. The capacitor circuit is connected through a second pair of lead wires. A DC-DC converter circuit that transforms a DC voltage input from an input wiring and supplies the voltage to a load via an output wiring,
An inductor element;
A switching element for passing a current from the input wiring to a reference potential wiring of the DC-DC converter circuit via the inductor element during a conduction period;
A rectifying element that supplies power stored in the inductor element to a load via the output wiring during a period in which the switching element is non-conductive;
A four-terminal capacitor having a first pair of lead wires sharing one electrode and a second pair of lead wires sharing the other electrode,
The rectifying element and the output wiring are connected via a first pair of lead wires of the 4-terminal capacitor, and the switching element and a reference potential wiring of the DC-DC converter circuit are connected to the second terminal of the 4-terminal capacitor. A DC-DC converter circuit that is connected through a pair of lead wires. The inductor element is a choke coil having one end connected to the input wiring,
The rectifying element is a diode;
The input terminal of the switching element and the anode terminal of the diode are connected to the other end of the choke coil,
The cathode terminal of the diode and the output wiring are connected via a first pair of lead wires of the 4-terminal capacitor, and the output terminal of the switching element and the reference potential wiring of the DC-DC converter circuit are the 4 3. The DC-DC converter circuit according to claim 2, wherein the DC-DC converter circuit is connected through a second pair of lead wires of the terminal capacitor. The inductor element is a transformer having one end of a primary winding connected to the input wiring,
The rectifying element is a diode;
The input terminal of the switching element is connected to the other end of the primary winding of the transformer,
The anode terminal of the diode is connected to one end of the secondary winding of the transformer,
The cathode terminal of the diode and the output wiring are connected via a first pair of lead wires of the 4-terminal capacitor, and the output terminal of the switching element and the reference potential wiring of the DC-DC converter circuit are the 4 The DC-DC converter circuit according to claim 2, wherein the DC-DC converter circuit is connected via a second pair of lead wires of the terminal capacitor. An input circuit for rectifying an AC input voltage and supplying a DC voltage to the input wiring;
A DC power supply device comprising: the DC-DC converter circuit according to any one of claims 2 to 4.

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