Power supply circuit

Abstract

To provide a power supply circuit for generating two or more output voltages smaller than an input voltage with an inexpensive configuration without newly adding an FET (switching element) or a transformer.SOLUTION: The first step-down chopper circuit includes a D1, a L1, and a C1, an anode of the D1 is connected to the common line, a cathode of the D1 is connected to one end of the L1, the other end of the L1 is connected to one end of the C1, and the other end of the C1 is connected to the common line, and the second step-down chopper circuit includes a, a, a, and a, C2 C3 L2 D2, in the power source circuit, one of the terminals of the C2 is connected to the cathode of the D1, the other of the terminals of the C2 is connected to the cathode of the D2, the anode of the D2 is connected to the other of the terminals of the L1, one of the terminals of the L2 is connected to the cathode of the D2, the other of the terminals of the L2 is connected to one of the terminals of the, and the other of the terminals of the is connected to a common line, and a first voltage is generated across the and a second voltage, which is higher than the first voltage, is generated across the under the control of the. C3 C3 C3 C1 Q1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply circuit. [Background technology]

[0002] In recent years, various electrical appliances have become popular, and most of them are equipped with power supply circuits. However, the voltages used by these products are diverse, such as +3.3V, +5V, and +12V, and the number of components that require multiple drive voltages is increasing. For this reason, there is a demand for a power supply circuit with a simple configuration that can generate multiple output voltages that are smaller than the input voltage.

[0003] As a power supply circuit that generates a plurality of output voltages, for example, Patent Document 1 discloses a multi-output DC / DC converter that converts an input DC voltage to output different DC voltages, and is characterized by comprising: a chopper DC / DC converter unit composed of at least a coil, a switching element, a rectifying element, and a voltage smoothing element; a voltage doubler generation circuit composed of a plurality of rectifying elements and voltage smoothing elements that obtains a plurality of different DC output voltages from the DC output voltage output from the chopper DC / DC converter unit; and control means that chopper-controls the switching element based on the output voltage of at least one of the chopper DC / DC converter unit and the voltage doubler generation circuit.

[0004] Furthermore, Patent Document 2 discloses a multi-output DC chopper circuit that boosts the input voltage of one DC power supply to n output voltages that drive n (n≧2) loads, characterized in that a coil on the DC power supply side and a switching element on the branch point side are arranged in series on one main wiring extending from the DC power supply to a branch point, and n sub-wirings extending in parallel from the branch point to the n loads each have a rectifying element on the branch point side and a capacitor on the load side arranged in series.

[0005] Furthermore, Patent Document 3 discloses a multi-output DC / DC converter that generates a plurality of output voltages from a single input voltage using a single switch circuit and supplies the plurality of output voltages to a corresponding plurality of loads, wherein when the plurality of loads are all light loads, the multi-output DC / DC converter operates in a discontinuous current mode, and when the plurality of loads are all heavy loads, the multi-output DC / DC converter operates in a continuous current mode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 09-93914 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-274935 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-311780 Summary of the Invention [Problem to be solved by the invention]

[0007] However, Patent Document 1 requires a voltage doubler circuit, and looking at Figures 1 to 5 of the embodiment, it seems that three or more diodes and three or more capacitors must be added for each additional output. Patent Document 2 also requires a rectifier element on the branch point side and a capacitor on the load side to be added for each additional output, and the rectifier element on the branch point side specifically uses a FET. Patent Document 3 also uses two switches (SL1, SL2) for two outputs, and it seems that an additional switch is required for each additional output.

[0008] Therefore, conventional power supply circuits such as those disclosed in Patent Documents 1 to 3 have the problem of high costs due to the large number of components that must be added to generate multiple output voltages and the high unit costs of the added components.

[0009] On the other hand, a non-isolated step-down chopper circuit (also called a step-down converter) as shown in Fig. 12 is known as an inexpensive power supply circuit that generates a single output voltage. Fig. 13 shows an example of an actual power supply circuit that uses the step-down chopper circuit of Fig. 12.

[0010] The advantage of a step-down chopper circuit is that it can be configured with a small number of components, using the inexpensive drum-type choke coil 100 with a single winding. Therefore, it would be ideal if a simple circuit could be added to it to generate multiple output voltages, but this has not been possible in the past.

[0011] For example, if an attempt was made to provide two outputs based on the step-down chopper circuit of FIG. 12, it was necessary to simply create two step-down chopper circuits 101 and 102 by dividing the step-down chopper circuit into two stages as shown in FIG. 14, or to use a transformer 111 with multiple windings instead of a drum-type choke coil as shown in FIG. 15.

[0012] First, in the configuration of Figure 14, although it is good that there are two coils 100, which are inexpensive drum-type choke coils with one winding, the cost inevitably increases when there are two FETs 104, which are switching elements. In this way, the number of FETs 104 (or switching elements) increases every time an output is increased, as in Patent Documents 2 and 3 mentioned above, and an increase in cost due to the addition of an FET (switching element or switch) is unavoidable.

[0013] Next, in the configuration of FIG. 15, the multi-winding transformer 111 is a custom product, which is expensive and difficult to procure.

[0014] Therefore, the two-stage configuration shown in FIG. 14, which can be configured using only general-purpose components without using custom components, has been mainly used in the past.

[0015] Here we will explain an example to give an idea of ​​the increased cost that comes with dual outputs. For example, when using a microcontroller with peripheral devices and an OPAMP, you may need two outputs, with a power supply of about 5V 1A for the microcontroller and 12V 0.1A for the peripheral devices. In this case, the additional cost for both the circuits in Figure 14 and Figure 15 will be 20% or more compared to the circuit in Figure 12.

[0016] In the example mentioned above, the output power used by having two outputs increased by about +10%, but the additional cost was +20% or more, which seemed expensive.

[0017] Furthermore, if an attempt is made to create a two-stage configuration as shown in Figure 14 based on the conventional circuit of Figure 13, the question arises as to whether the control IC 112 of Figure 13 can be used as is. If the FET 104 of Figure 12 is configured within the control IC 112 of Figure 14, and the FET 104 for the second-stage step-down chopper circuit 102 of Figure 14 cannot also be accommodated within the control IC 112, it may be necessary to replace it with a different control IC or add a new control IC.

[0018] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a power supply circuit that generates at least two output voltages smaller than the input voltage with an inexpensive configuration that does not require the addition of new FETs (switching elements) or transformers. [Means for solving the problem]

[0019] In order to solve the above-described problems, a power supply circuit according to the present disclosure is a power supply circuit that generates, with respect to an input voltage, at least two output voltages that are smaller than the input voltage, and includes a first step-down chopper circuit that generates a first output voltage with a common line as a reference, and a second step-down chopper circuit that generates a second output voltage with the common line as a reference, the first step-down chopper circuit including a first diode, a first coil, and a first capacitor, the anode of the first diode being connected to the common line, the cathode of the first diode being connected to one terminal of the first coil, the other terminal of the first coil being connected to one terminal of the first capacitor, and the other terminal of the first capacitor being connected to the common line, and the second step-down chopper circuit including a second and a third capacitor, a second diode, and a second coil, one terminal of the second capacitor being connected to the cathode of the first diode, the other terminal of the second capacitor being connected to the cathode of the second diode, the anode of the second diode being connected to the other terminal of the first coil, one terminal of the second coil being connected to the cathode of the second diode, the other terminal of the second coil being connected to one terminal of the third capacitor, and the other terminal of the third capacitor being connected to the common line, and by control of a switching element, the first output voltage is generated across both ends of the first capacitor, and the second output voltage larger than the first output voltage is generated across both ends of the third capacitor.

[0020] In such a power supply circuit, by adding second and third capacitors, a second diode, and a second coil as a second step-down chopper circuit to the first step-down chopper circuit, the first step-down chopper circuit generates a first output voltage that is smaller than the input voltage, and the second step-down chopper circuit generates a second output voltage that is smaller than the input voltage and larger than the first output voltage, so it is possible to generate at least two output voltages that are smaller than the input voltage with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0021] Preferably, the first and second coils are single-winding coils.

[0022] Such a single-winding coil is certainly cheaper than a multi-winding transformer, and therefore can generate at least two output voltages smaller than the input voltage with an inexpensive configuration.

[0023] Furthermore, the power supply circuit of the present disclosure is a power supply circuit that generates at least three output voltages smaller than an input voltage in response to the input voltage, and includes a third step-down chopper circuit that generates a third output voltage with the common line as a reference, and the third step-down chopper circuit includes fourth and fifth capacitors, a third diode, and a third coil, one terminal of the fourth capacitor is connected to the cathode of the first diode, the other terminal of the fourth capacitor is connected to the cathode of the third diode, the anode of the third diode is connected to the other terminal of the second coil, one terminal of the third coil is connected to the cathode of the third diode, the other terminal of the third coil is connected to one terminal of the fifth capacitor, and the other terminal of the fifth capacitor is connected to the common line, and preferably generates the third output voltage larger than the second output voltage across the fifth capacitor by controlling a switching element.

[0024] In such a power supply circuit, by adding fourth and fifth capacitors, a third diode, and a third coil as a third step-down chopper circuit, a third output voltage that is smaller than the input voltage and larger than the second output voltage is generated, so that at least three output voltages smaller than the input voltage can be generated with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0025] Preferably, the first, second and third coils are single-winding coils.

[0026] Such a single-winding coil is certainly cheaper than a multi-winding transformer, and therefore provides an inexpensive configuration for generating at least three output voltages that are smaller than the input voltage.

[0027] The power supply circuit of the present disclosure is a power supply circuit that generates, in response to an input voltage, at least N (where N is an integer of 4 or more) output voltages that are smaller than the input voltage, and includes N step-down chopper circuits that generate first to N-th output voltages with the common line as a reference, and the N-th step-down chopper circuit includes 2N-2 and 2N-1 capacitors, an N-th diode, and an N-th coil, and one terminal of the 2N-2 capacitor is connected to the cathode of the first diode, and the other terminal of the 2N-2 capacitor is connected to the N-th The Nth output voltage, which is greater than the N-1th output voltage, can be generated across the 2N-1th capacitor by controlling a switching element.

[0028] In such a power supply circuit, by adding 2N-2 and 2N-1 capacitors, an N-th diode, and an N-th coil as an N-th step-down chopper circuit, an N-th output voltage that is smaller than the input voltage and larger than the N-1 output voltage is generated, so at least N output voltages smaller than the input voltage can be generated with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0029] Furthermore, it is preferable that the first to Nth coils are single-winding coils.

[0030] Such a single-winding coil is certainly cheaper than a multi-winding transformer, and therefore can generate at least N output voltages that are smaller than the input voltage with an inexpensive configuration. [Effects of the Invention]

[0031] As described above, with the power supply circuit of the present disclosure, by adding the second and third capacitors, the second diode, and the second coil as a second step-down chopper circuit to the first step-down chopper circuit, the first step-down chopper circuit generates a first output voltage that is smaller than the input voltage, and the second step-down chopper circuit generates a second output voltage that is smaller than the input voltage and larger than the first output voltage, so it is possible to generate at least two output voltages that are smaller than the input voltage with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0032] Furthermore, if a capacitor, diode, and coil are added as the second step-down chopper circuit, but no transformer is added, it can be configured using only general-purpose parts without using custom parts, making it easier to procure.

[0033] Furthermore, when improving a circuit in which the switching element is included in the control IC, such as a conventional single-stage step-down chopper circuit (see Figure 13), there is no need to replace it with a different control IC or add a new control IC.The original control IC (its switching element) can be used as is to configure a power supply circuit that generates at least two output voltages, making it possible to realize an inexpensive configuration with extremely little increase in cost. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic diagram of a power supply circuit using a step-down chopper circuit according to a first embodiment of the present disclosure. [Figure 2] 2 is a diagram illustrating the configuration of a power supply circuit to which a step-down chopper circuit according to the embodiment is applied. FIG. [Figure 3]3A to 3C are diagrams illustrating the operation of a step-down chopper in the embodiment. [Figure 4] 4 is a graph illustrating the operation of a step-down chopper in the embodiment. [Figure 5] 10 is a graph of vL1 of the step-down chopper in the same embodiment. [Figure 6] 10 is a graph of vL2 of the step-down chopper in the same embodiment. [Figure 7] 10 is a graph related to C2 of the step-down chopper in the embodiment. [Figure 8] 10 is a graph related to C2 of the step-down chopper in the embodiment. [Figure 9] FIG. 10 is a schematic diagram of a power supply circuit using a step-down chopper circuit according to a second embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating the configuration of a power supply circuit to which a step-down chopper circuit according to a third embodiment of the present disclosure is applied. [Figure 11] FIG. 10 is a diagram illustrating the configuration of a power supply circuit to which a step-down chopper circuit according to a fourth embodiment of the present disclosure is applied. [Figure 12] FIG. 1 is a schematic diagram of a power supply circuit using a conventional step-down chopper circuit. [Figure 13] FIG. 1 is a diagram illustrating the configuration of a power supply circuit to which a conventional step-down chopper circuit is applied. [Figure 14] FIG. 1 is a schematic diagram of a conventional power supply circuit with two step-down choppers. [Figure 15] This is a schematic diagram of a conventional two-stage power supply circuit using a transformer in a step-down chopper. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present disclosure will be described in detail below, but the present disclosure is not limited thereto.

[0036] As described above, there has been a demand for a power supply circuit that can generate at least two output voltages that are smaller than the input voltage, with an inexpensive configuration that does not require the addition of new FETs (switching elements) or transformers.

[0037] As a result of extensive research, the inventors have discovered that by adding a second step-down chopper circuit having second and third capacitors, a second diode, and a second coil to a first step-down chopper circuit having a first diode, a first coil, and a first capacitor, the first step-down chopper circuit can generate a first output voltage that is smaller than the input voltage, and the second step-down chopper circuit can generate a second output voltage that is smaller than the input voltage and larger than the first output voltage, thereby completing the present disclosure.

[0038] That is, the present disclosure provides a power supply circuit for generating at least two output voltages smaller than an input voltage, the power supply circuit including a first step-down chopper circuit for generating a first output voltage with a common line as a reference, and a second step-down chopper circuit for generating a second output voltage with the common line as a reference, the first step-down chopper circuit including a first diode, a first coil, and a first capacitor, the anode of the first diode being connected to the common line, the cathode of the first diode being connected to one terminal of the first coil, the other terminal of the first coil being connected to one terminal of the first capacitor, and the other terminal of the first capacitor being connected to the common line, the second step-down chopper circuit including second and third capacitors, and the second diode a third capacitor and a second coil, wherein one terminal of the second capacitor is connected to the cathode of the first diode, the other terminal of the second capacitor is connected to the cathode of the second diode, the anode of the second diode is connected to the other terminal of the first coil, one terminal of the second coil is connected to the cathode of the second diode, the other terminal of the second coil is connected to one terminal of the third capacitor, and the other terminal of the third capacitor is connected to the common line, and wherein, by control of a switching element, the first output voltage is generated across the first capacitor and the second output voltage larger than the first output voltage is generated across the third capacitor.

[0039] The following description will be made with reference to the drawings.

[0040] [First embodiment] FIG. 1 is a schematic diagram of a power supply circuit using a step-down chopper circuit according to a first embodiment of the present disclosure, and FIG. 2 is a configuration diagram of a power supply circuit to which the step-down chopper circuit according to this embodiment is applied.

[0041] The power supply circuit of FIG. 1 is a power supply circuit that generates at least two output voltages smaller than an input voltage (input DC voltage VDC1: 400V), and includes a first step-down chopper circuit 11 that generates a first output voltage with a common line 10 as a reference, and a second step-down chopper circuit 12 that generates a second output voltage with the common line 10 as a reference. The first step-down chopper circuit 11 includes a first diode D1, a first coil L1, and a first capacitor C1. The anode of the first diode D1 is connected to the common line 10, the cathode of the first diode D1 is connected to one terminal of the first coil L1, the other terminal of the first coil L1 is connected to one terminal of the first capacitor C1, and the other terminal of the first capacitor C1 is connected to the common line 10. The second step-down chopper circuit 12 includes a , second and third capacitors C2 and C3, a second diode D2, and a second coil L2, one terminal of the second capacitor C2 is connected to the cathode of the first diode D1, the other terminal of the second capacitor C2 is connected to the cathode of the second diode D2, the anode of the second diode D2 is connected to the other terminal of the first coil L1, one terminal of the second coil L2 is connected to the cathode of the second diode D2, the other terminal of the second coil L2 is connected to one terminal of a third capacitor C3, the other terminal of the third capacitor C3 is connected to a common line 10, and by controlling a switching element Q1, a first output voltage is generated across both ends of the first capacitor C1, and a second output voltage greater than the first output voltage is generated across both ends of the third capacitor C3.

[0042] In such a power supply circuit, by adding second and third capacitors C2 and C3, a second diode D2, and a second coil L2 as a second step-down chopper circuit 12 to the first step-down chopper circuit 11, the first step-down chopper circuit 11 generates a first output voltage that is smaller than the input voltage, and the second step-down chopper circuit 12 generates a second output voltage that is smaller than the input voltage and larger than the first output voltage, so that at least two output voltages that are smaller than the input voltage can be generated with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0043] Although not particularly limited, the first and second coils L1 and L2 are preferably single-winding coils.

[0044] Such a single-winding coil is certainly cheaper than a multi-winding transformer, and therefore can generate at least two output voltages smaller than the input voltage with an inexpensive configuration.

[0045] Details will be given later, but a chopper circuit is formed by a diode and a coil, and the charge in the capacitor is released or stored by switching the switching element Q1.

[0046] Although not particularly limited, the first capacitor C1 and the third capacitor C3 of the output stage can be electrolytic capacitors to obtain a stabilized output.

[0047] Furthermore, although not particularly limited, by using the configuration of Figure 1, when the input voltage is 400 V DC, it is possible to generate a first output voltage of 5 V DC across the first capacitor C1, and a second output voltage of 10 V DC, which is greater than the first output voltage, across the third capacitor C3.

[0048] Furthermore, as described above, only a capacitor, a diode, and a coil are added as the second step-down chopper circuit, and no transformer is added. This means that the circuit can be configured using only general-purpose parts without using custom parts, making it easier to procure.

[0049] Furthermore, although not particularly limited, the power supply circuit configuration of FIG. 2 of this embodiment is an improvement on the conventional single-output power supply circuit configuration of FIG. 13. Therefore, the switching element Q1 in FIG. 1 can be used as is in the control IC 112 of FIG. 2 (the same as the control IC 112 of FIG. 13). This means that when changing from one output to two outputs (changing FIG. 13 to FIG. 2), there is no need to replace it with a different control IC or add a new control IC. A power supply circuit that generates at least two output voltages can be configured using the original control IC 112 (its switching element), making it possible to realize an inexpensive configuration with extremely little increase in cost.

[0050] From here, a specific circuit operation will be described.

[0051] In FIG. 1, when the switching element Q1 is turned ON, current flows from the first coil L1 to the first capacitor C1, and from the second capacitor C2 to the second coil L2 to the third capacitor C3, storing energy in the first coil L1 and the second coil L2.

[0052] If the second capacitor C2 is set to a small capacity, charging will be completed in a short time. Once charging is complete, current will no longer flow toward C2, and it will be disconnected.

[0053] When switching element Q1 is turned OFF, the current supply from the power supply is cut off, and a back electromotive force is generated in the first coil L1 and the second coil L2. At this time, the current due to the back electromotive force generated in the first coil L1 branches toward the first capacitor C1 and the second diode D2, and the current flowing toward the second diode D2 further flows toward the second coil L2 and the second capacitor C2, becoming a current that charges the second capacitor C2 in the opposite direction to when Q1 is ON.

[0054] Furthermore, since the electromotive force of the second coil L2 is superimposed on the first coil L1, the sum of the electromotive forces of the first coil L1 and the second coil L2 is generated in the third capacitor C3.

[0055] Further details will be explained with reference to the drawings.

[0056] FIG. 3 is a circuit diagram that schematically explains the operation (particularly the current flow) of the step-down chopper in this embodiment, and FIGS. 4 to 8 are graphs that show the operation of the step-down chopper as changes in voltage and current.

[0057] (1) Switching element Q1-ON Current flows along the route indicated by arrow A1 in Figure 3, that is, from the second capacitor C2 to the second coil L2 to the load (on the side of the third capacitor C3). This charges the second capacitor C2, but the charging current is suppressed by the second coil L2 (current iC2 flowing through the second capacitor C2 = current iL2 flowing through the second coil L2).

[0058] (2) Switching element Q1-OFF When Q1 is turned off, the cathode potential of the first diode D1 drops to the forward voltage vf of the first diode D1. Since the voltage vL1 of the first coil is approximately equal to the voltage vC1 of the first capacitor, current flows from the first coil L1 and the first capacitor C1 through the second diode D2, charging the second capacitor C2 in the reverse direction (arrow A2).

[0059] (3) Charging of (2) is completed. The back electromotive force of the first coil L1 passes through the second diode D2 and then flows via the second coil L2 toward the load (the third capacitor C3 side). This is the route indicated by the arrow A3 in Figure 3. At this time, the voltage caused by the back electromotive force of L2 is superimposed.

[0060] Here, if the output voltage (second output voltage) across the third capacitor C3 is vout2, the voltage of the first coil is vL1, and the voltage of the second coil is vL2, then: vout2=vL1+vL2-(vf of D1+vf of D2) This becomes:

[0061] Figure 4 shows the current and voltage waveforms for each part in (1) to (3) above. However, for ease of viewing, the current iL2 of the second coil and other currents are displayed with the GND shifted. Figure 4 also shows the current iC1 of the first capacitor, the current iC2 of the second capacitor, the current iD2 of the second diode, the current iL1 of the first coil, the current iL2 of the second coil, the voltage vC2 of the second capacitor, and the voltage vL1 of the first coil.

[0062] Next, because the horizontal axis in Figure 4, particularly part (2), was difficult to see, the current and voltage shown have been reduced and shown in Figures 5 and 6. Figure 5 is a graph explaining the voltage vL1 of the first coil of the step-down chopper, and Figure 6 is a graph explaining the voltage vL2 of the second coil of the step-down chopper. Also shown are the voltage Q1Vds, which indicates the ON / OFF status of the switching element, and the currents iL1 and iL2 of the first and second coils.

[0063] Here, the voltage vL1 of the first coil and the voltage vL2 of the second coil, which are close to 400V, are due to the input voltage (400V).

[0064] Next, the current and voltage related to the second capacitor C2 are shown in graphs in Figures 7 and 8. In particular, Figure 8 is an example where the horizontal axis of Figure 7 has been enlarged to make it easier to see.

[0065] When switching element Q1 is turned ON, current flows through the route indicated by arrow A1 in Figure 3, but due to the presence of second coil L2, a large current does not flow (it is approximately the output current + α). Next, when switching element Q1 is turned OFF, current flows in the opposite direction through the route first coil L1 → second diode D2 → second capacitor C2. Due to the current continuity of the first coil L1, the current at this time is nearly the same as the output current. For reference, Figures 7 and 8 show the current iC2 and voltage vC2 of the second capacitor, the current iC1 of the first capacitor, and the voltage Q1Vds, which indicates the ON / OFF state of the switching element.

[0066] [Second embodiment] FIG. 9 is a schematic diagram of a power supply circuit using a step-down chopper circuit according to the second embodiment of the present disclosure.

[0067] The power supply circuit of FIG. 9 is a power supply circuit that generates at least three output voltages smaller than an input voltage (input DC voltage VDC1: 400V), and has a third step-down chopper circuit 13 that generates a third output voltage with a common line 10 as a reference, and the third step-down chopper circuit 13 includes fourth and fifth capacitors C4 and C5, a third diode D3, and a third coil L3, one terminal of the fourth capacitor C4 is connected to the cathode of the first diode D1, and the other terminal of the fourth capacitor C4 is The second coil L2 has an anode connected to the cathode of a third diode D3, the anode of the third diode D3 is connected to the other terminal of the second coil L2, one terminal of the third coil L3 is connected to the cathode of the third diode D3, the other terminal of the third coil L3 is connected to one terminal of a fifth capacitor C5, and the other terminal of the fifth capacitor C5 is connected to a common line 10. By controlling the switching element Q1, a third output voltage greater than the second output voltage is generated across the fifth capacitor C5.

[0068] In such a power supply circuit, by adding fourth and fifth capacitors C4 and C5, a third diode D3, and a third coil L3 as a third step-down chopper circuit 13, a third output voltage that is smaller than the input voltage and larger than the second output voltage is generated, so that at least three output voltages smaller than the input voltage can be generated with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0069] Although not particularly limited, the first, second and third coils L1, L2 and L3 are preferably single-winding coils.

[0070] Such a single-winding coil is certainly cheaper than a multi-winding transformer, and therefore provides an inexpensive configuration for generating at least three output voltages that are smaller than the input voltage.

[0071] Although not particularly limited, in this case, the first output voltage can be 5 V, the second output voltage can be 10 V, and the third output voltage can be 15 V. By connecting multiple stages in this way, it is possible to easily generate voltage ratios of integer multiples.

[0072] Although not particularly limited, the control is performed at only one point, the switching element Q1, which is an inexpensive configuration and is easy to control.

[0073] The above embodiment will be expanded to explain a power supply circuit that generates N outputs (not shown).

[0074] A power supply circuit generates at least N (where N is an integer of 4 or more) output voltages smaller than an input voltage, the power supply circuit having N step-down chopper circuits generating first to N-th output voltages with a common line as a reference, the N-th step-down chopper circuit comprising 2N-2 and 2N-1 capacitors, an N-th diode, and an N-th coil, one terminal of the 2N-2 capacitor being connected to the cathode of the first diode, and the other terminal of the 2N-2 capacitor being connected to the cathode of the N-th diode. The Nth diode has an anode connected to the cathode of the Nth diode, an anode of the Nth diode is connected to the other terminal of the N-1th coil, one terminal of the Nth coil is connected to the cathode of the Nth diode, the other terminal of the Nth coil is connected to one terminal of the 2N-1th capacitor, and the other terminal of the 2N-1th capacitor is connected to a common line, and by controlling the switching element, an Nth output voltage greater than the N-1th output voltage is generated across the 2N-1th capacitor.

[0075] In such a power supply circuit, by adding 2N-2 and 2N-1 capacitors, an N-th diode, and an N-th coil as an N-th step-down chopper circuit, an N-th output voltage that is smaller than the input voltage and larger than the N-1 output voltage is generated, so at least N output voltages smaller than the input voltage can be generated with an inexpensive configuration that does not require the addition of any new FETs (switching elements) or transformers.

[0076] Although not particularly limited, the first to Nth coils are preferably single-winding coils.

[0077] Such a single-winding coil is certainly cheaper than a multi-winding transformer, and therefore can generate at least N output voltages that are smaller than the input voltage with an inexpensive configuration.

[0078] [Third embodiment] FIG. 10 is a diagram illustrating the configuration of a power supply circuit to which a step-down chopper circuit according to the third embodiment of the present disclosure is applied.

[0079] The FETs used in the main switches of switching power supplies are often 10V gate voltage types, and may not be able to be fully turned on if the control voltage is 5V. So, is it okay to use a 5V type FET? However, there are few varieties of 5V type FETs, and their characteristics may be insufficient.

[0080] In the present disclosure, the added second output voltage (SUB output) can be set to twice the voltage of the original first output voltage (Main output). Therefore, if the power supply voltage VCC15 of IC14 is taken from the SUB output side (i.e., terminal 16 on the output side of the second step-down chopper circuit 12) as shown in FIG. 10, even if the voltage of the Main output (i.e., the first output voltage of the first step-down chopper circuit 11) is 5 V, VCC (i.e., the second output voltage of the second step-down chopper circuit 12) will be 10 V, and it will be possible to use FETs and control circuits for 10 V as they are.

[0081] This eliminates the need to route the SUB output (10 V) externally, so a chopper with a single 5 V output can also be used. In the example shown in Figure 10 of this embodiment, both VCC and voltage detection are taken from the SUB output side, but this is not particularly limited, and voltage detection can also be done from the 5 V Main output.

[0082] [Fourth embodiment] FIG. 11 is a configuration diagram of a power supply circuit to which a step-down chopper circuit according to the fourth embodiment of the present disclosure is applied.

[0083] This embodiment is an example in which two components in the configuration of FIG. 2 of the first embodiment are combined into one component to reduce the number of components through commonality. Although not particularly limited, the diode D7 and second diode D2 in FIG. 2 can be combined into one diode D9 in FIG. 11, and the capacitor C7 and second capacitor C2 in FIG. 2 can be combined into one capacitor C9 in FIG. 11. By combining components in this way, the number of components can be reduced, thereby achieving further cost reductions.

[0084] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Explanation of symbols]

[0085] 10... common line; 11... first step-down chopper circuit; 12... second step-down chopper circuit, 13... third step-down chopper circuit, 14...IC, 15...VCC, 16...terminal, 100... Coil (drum type choke coil), 101, 102...Step-down chopper circuit, 104...FET (switching element), 111...Transformer, 112...Control IC. A1, A2, A3...arrows, C1...first capacitor, C2: Second capacitor, C3: Third capacitor, C4...fourth capacitor, C5...fifth capacitor, C7, C9...capacitors, D1...first diode, D2...second diode, D3...third diode, D7, D9...Diodes, iC1, iC2, iD2, iL1, iL2...Current, L1...first coil, L2...second coil, L3...third coil, Q1: switching element Q1Vds, vC1, vC2, vL1, vL2... voltage, VAC1...input AC voltage, VDC1...input DC voltage.

Claims

1. A power supply circuit that generates at least two output voltages that are smaller than an input voltage, a first step-down chopper circuit for generating a first output voltage referenced to a common line; a second step-down chopper circuit for generating a second output voltage with the common line as a reference; the first step-down chopper circuit includes a first diode, a first coil, and a first capacitor; The anode of the first diode is connected to the common line; a cathode of the first diode connected to one terminal of the first coil; the other terminal of the first coil is connected to one terminal of the first capacitor; the other terminal of the first capacitor is connected to the common line; the second step-down chopper circuit includes second and third capacitors, a second diode, and a second coil; one terminal of the second capacitor is connected to the cathode of the first diode; the other terminal of the second capacitor is connected to the cathode of the second diode; the anode of the second diode is connected to the other terminal of the first coil; one terminal of the second coil is connected to the cathode of the second diode; the other terminal of the second coil is connected to one terminal of the third capacitor; the other terminal of the third capacitor is connected to the common line; A power supply circuit characterized in that, by controlling a switching element, the first output voltage is generated across the first capacitor, and the second output voltage larger than the first output voltage is generated across the third capacitor.

2. 2. The power supply circuit according to claim 1, wherein the first and second coils are single-winding coils.

3. A power supply circuit that generates at least three output voltages that are smaller than an input voltage, a third step-down chopper circuit for generating a third output voltage with the common line as a reference; the third step-down chopper circuit includes fourth and fifth capacitors, a third diode, and a third coil; one terminal of the fourth capacitor is connected to the cathode of the first diode; the other terminal of the fourth capacitor is connected to the cathode of the third diode; the anode of the third diode is connected to the other terminal of the second coil; one terminal of the third coil is connected to the cathode of the third diode; the other terminal of the third coil is connected to one terminal of the fifth capacitor; the other terminal of the fifth capacitor is connected to the common line; 2. The power supply circuit according to claim 1, wherein the third output voltage, which is greater than the second output voltage, is generated across the fifth capacitor by controlling a switching element.

4. 4. The power supply circuit according to claim 3, wherein the first, second and third coils are single-winding coils.

5. A power supply circuit that generates, in response to an input voltage, at least N output voltages (where N is an integer of 4 or greater) that are smaller than the input voltage, N step-down chopper circuits are provided to generate first to N-th output voltages based on the common line; the Nth step-down chopper circuit includes (2N-2)th and (2N-1)th capacitors, an Nth diode, and an Nth coil; One terminal of the second N-2 capacitor is connected to the cathode of the first diode, The other terminal of the second N-2 capacitor is connected to the cathode of the N diode, The anode of the Nth diode is connected to the other terminal of the N-1th coil, One terminal of the Nth coil is connected to the cathode of the Nth diode, The other terminal of the Nth coil is connected to one terminal of the second (N-1)th capacitor, The other terminal of the second N-1 capacitor is connected to the common line, 4. The power supply circuit according to claim 3, wherein the Nth output voltage greater than the N-1th output voltage is generated across the 2N-1th capacitor by controlling a switching element.

6. 6. The power supply circuit according to claim 5, wherein the first to Nth coils are single-winding coils.

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