JP5732842B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device used for a power supply circuit of an electronic device.

  In a conventional switching power supply device, in order to obtain a plurality of output voltages, a secondary winding for receiving power transmitted from the primary winding of the transformer is constituted by a plurality of windings or a DC-DC converter is provided for output. It was necessary to convert the voltage of the voltage. For example, in order for the switching power supply device to obtain an output voltage of 5V and an output voltage of 10V, the secondary winding of the transformer is constituted by a winding for 5V and a winding for 10V, or DC- It was necessary to provide a DC converter and convert the output voltage to 5V and 10V. Patent Document 1 discloses a switching power supply device in which a secondary winding of a transformer is composed of two windings.

Japanese Utility Model Publication No. 4-121181

  In order for the switching power supply device to obtain a plurality of output voltages, when the secondary winding of the transformer is constituted by a plurality of windings as in Patent Document 1, it depends on the number of windings, the length of the windings, etc. Thus, the number of pins around which a plurality of windings are wound, the number of slits through which the windings pass, and the like increase. However, because the number of pins, the number of slits, etc. that can be secured in the transformer are limited, the number of windings constituting the secondary winding, the length of the winding, etc. are restricted, and the output voltage obtained by the switching power supply device There is a problem that the number of output and the magnitude of the output voltage are limited.

  In addition, since the secondary winding is formed by stacking a plurality of windings in multiple layers, the secondary winding becomes thick and it may be difficult to insert the core for forming the transformer. Further, when the secondary winding becomes thick, there is a problem that the transformer becomes large.

  The present invention has been made in view of such circumstances, and the size of the transformer can be reduced without limiting the number of output voltages obtained by the switching power supply device, the magnitude of the output voltage, and the like due to restrictions in the transformer. It aims at providing a switching power supply device.

  In order to achieve the above object, a switching power supply according to a first aspect of the present invention includes a transformer having at least a primary winding and a secondary winding, and is connected to the primary winding and controls on / off by controlling the on / off. A switching element for transmitting power from the primary winding of the transformer to the secondary winding and an AC voltage connected to the secondary winding and output from the secondary winding to a first output voltage A switching power supply comprising: a first rectifying / smoothing circuit configured to output; and an output voltage generating circuit connected to the secondary winding and generating a second output voltage from an AC voltage output from the secondary winding. The output voltage generation circuit is connected to the secondary winding and generates a rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding. And one end connected to the rectangular wave generating circuit. A capacitor for transmitting the rectangular wave, connected to the other end of the capacitor, a potential setting diode for setting a reference potential of the rectangular wave transmitted by the capacitor, and connected to the other end of the capacitor, a reference potential And a second rectifying / smoothing circuit for smoothing the voltage of the rectangular wave set to the second output voltage.

  In the first invention, a rectangular wave generating circuit connected to the secondary winding and generating a rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding, and the rectangular wave generation Connect one end to the circuit, a capacitor that transmits a rectangular wave, the other end of the capacitor, a potential setting diode that sets the reference potential of the rectangular wave transmitted by the capacitor, and the other end of the capacitor Since the output voltage generating circuit having the second rectifying / smoothing circuit for smoothing the rectangular wave voltage set to the second output voltage is provided, the secondary winding of the transformer is constituted by a plurality of windings. A plurality of output voltages can be obtained, and the number of output voltages and the magnitude of the output voltage obtained by the switching power supply device are not limited by restrictions on the transformer. In addition, since it is not necessary to configure the secondary winding of the transformer with a plurality of windings in order to obtain a plurality of output voltages, the transformer can be reduced in size.

  The switching power supply according to a second aspect of the present invention is the switching power supply device according to the first aspect, wherein the output voltage generation circuit includes the rectangular wave generation circuit, the plurality of capacitors, the plurality of potential setting diodes, and the plurality of the second settings. A plurality of capacitors, one end of which is connected to the rectangular wave generation circuit so that each of the capacitors is in parallel, and the other end of each capacitor is connected to the potential setting diode and the second A rectifying / smoothing circuit is connected.

  In the second invention, the output voltage generation circuit includes a rectangular wave generation circuit, a plurality of capacitors, a plurality of potential setting diodes, and a plurality of second rectification smoothing circuits, and each of the plurality of capacitors is in parallel. Since one end is connected to the rectangular wave generating circuit so that the potential setting diode and the second rectifying / smoothing circuit are connected to the other end of each capacitor, the rectangular wave generated by one rectangular wave generating circuit Based on this, a plurality of second output voltages can be output.

  According to a third aspect of the present invention, there is provided the switching power supply device according to the first aspect, wherein the output voltage generation circuit includes a plurality of the rectangular wave generation circuits, a plurality of the capacitors, a plurality of the potential setting diodes, and a plurality of the potential setting diodes. A second rectifying and smoothing circuit, and the plurality of rectangular wave generating circuits are connected to the secondary winding so that each of the rectangular wave generating circuits is in parallel, and each of the rectangular wave generating circuits includes one or a plurality of rectangular wave generating circuits. One end of the capacitor is connected, and the other end of each capacitor is connected to the potential setting diode and the second rectifying / smoothing circuit.

  In the third invention, the output voltage generation circuit includes a plurality of rectangular wave generation circuits, a plurality of capacitors, a plurality of potential setting diodes, and a plurality of second rectification smoothing circuits. Are connected to the secondary winding so that each is in parallel, one end of one or more capacitors is connected to each rectangular wave generating circuit, and a potential setting diode and a second diode are connected to the other end of each capacitor. Since the two rectifying / smoothing circuits are connected, a plurality of second output voltages can be output based on the rectangular waves generated by the respective rectangular wave generating circuits.

  According to a fourth aspect of the present invention, there is provided the switching power supply device according to any one of the first to third aspects, wherein one end of the potential setting diode is connected to the other end of the capacitor and the other end is connected to a ground potential wiring. To do.

  In the fourth invention, when one end of the potential setting diode is connected to the other end of the capacitor and the other end is connected to the ground potential wiring, the second output voltage having the same voltage as the first output voltage can be output. .

  A switching power supply according to a fifth aspect of the present invention is the switching power supply device according to any one of the first to third aspects, wherein one end of the potential setting diode is connected to the other end of the capacitor, and the other end is connected to the first output voltage. Connect to the output wiring.

  In the fifth aspect of the invention, when one end of the potential setting diode is connected to the other end of the capacitor and the other end is connected to the wiring for outputting the first output voltage, the second of the voltage obtained by doubling the first output voltage. Output voltage can be output.

  According to a sixth aspect of the present invention, there is provided the switching power supply device according to any one of the first to third aspects, wherein one end of the potential setting diode is connected to the other end of the capacitor and the other end is connected to an external power source.

  In the sixth aspect of the present invention, when one end of the potential setting diode is connected to the other end of the capacitor and the other end is connected to the external power supply, a second output voltage obtained by adding the output voltage of the external power supply to the first output voltage is obtained. Can be output.

  The switching power supply according to a seventh aspect of the present invention is the switching power supply device according to any one of the first to sixth aspects, wherein the rectangular wave generating circuit has one end of the secondary winding and the other end of the capacitor. And a transistor having a base terminal connected to the secondary winding and one end of the diode and a ground potential connected between a collector and an emitter, and the transistor outputs from the secondary winding. The output voltage of the diode is controlled according to the AC voltage to generate the rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding.

  In the seventh invention, the rectangular wave generating circuit includes a diode having one end connected to the secondary winding and one end connected to the other end of the capacitor, a base terminal connected to the secondary winding, and one end of the diode and the ground potential. Is connected between the collector and the emitter, and the transistor controls the output voltage of the diode according to the AC voltage output from the secondary winding, and the amplitude is output from the ground potential and the secondary winding. Since a rectangular wave that is a potential difference between the AC voltage and the positive voltage is generated, a circuit configuration for generating a rectangular wave whose amplitude is the potential difference between the ground potential and the AC voltage that is output from the secondary winding is generated. It can be realized with a simple circuit configuration of a diode and a transistor.

  According to the above configuration, the rectangular wave generating circuit is connected to the secondary winding and generates a rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding. Connect one end to the generator circuit, a capacitor that transmits a square wave, the other end of the capacitor, a potential setting diode that sets the reference potential of the rectangular wave transmitted by the capacitor, and another end of the capacitor. Since the output voltage generating circuit having the second rectifying / smoothing circuit that smoothes the voltage of the rectangular wave with the potential set to the second output voltage is provided, the secondary winding of the transformer is configured by a plurality of windings. A plurality of output voltages can be obtained without any limitation, and the number of output voltages and the magnitude of the output voltage obtained by the switching power supply device are not limited by restrictions on the transformer. In addition, since it is not necessary to configure the secondary winding of the transformer with a plurality of windings in order to obtain a plurality of output voltages, the transformer can be reduced in size.

It is a circuit diagram which shows the structure of the switching power supply device which concerns on Embodiment 1 of this invention. It is a figure which shows the voltage waveform for demonstrating operation | movement of the output voltage generation circuit which concerns on Embodiment 1 of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows another structure of the switching power supply device which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows another structure of the switching power supply device concerning Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a circuit diagram showing a configuration of a switching power supply apparatus according to Embodiment 1 of the present invention. The switching power supply device 1 shown in FIG. 1 includes an input circuit 2, a transformer 3 that converts an input voltage from the input circuit 2, and a primary winding 3a to a secondary winding 3b of the transformer 3 by controlling on / off. Switching element 4 for transmitting electric power, connected to secondary winding 3b, a first rectifying / smoothing circuit 5 for smoothing an AC voltage output from secondary winding 3b into a first output voltage, and a secondary winding The output voltage generation circuit 6 is connected to 3b and generates a second output voltage from the AC voltage output from the secondary winding 3b.

  The input circuit 2 includes a diode bridge 21 that inputs an AC voltage from an AC power source (not shown) through the input terminal 20 and rectifies the input AC voltage, a filter 22 that removes noise, and a fuse 23. Yes.

  The transformer 3 includes a primary winding 3a, a secondary winding 3b, and a drive winding 3c. The primary winding 3a, the secondary winding 3b, and the drive winding 3c each consist of one winding. A capacitor 31 connected between the input circuit 2 and the primary winding 3 a of the transformer 3 smoothes the voltage rectified by the diode bridge 21 of the input circuit 2.

  The switching element 4 has a drain terminal connected to the primary winding 3 a of the transformer 3 and a source terminal connected to the input circuit 2. A resistor 41 is connected between the gate terminal and the source terminal of the switching element 4. A power transmission control circuit 42 is connected to the gate terminal of the switching element 4. A phototransistor phototransistor 43 is connected to the power transmission control circuit 42, and the power transmission control circuit 42 sets the on-time or on-duty ratio of the switching element 4 according to the detection voltage of the phototransistor 43. Yes. That is, the power transmission control circuit 42 sets the on-time or on-duty ratio of the switching element 4 according to the feedback control signal input via the phototransistor 43 of the photocoupler. The phototransistor 43 and a light emitting diode 72 described later constitute a photocoupler.

  A rectifying / smoothing circuit including a diode 32 and a capacitor 33 is connected between both ends of the drive winding 3c. A voltage that is opposite in polarity to the voltage generated in the primary winding 3a during the ON period of the switching element 4 and proportional to the turn ratio is generated in the drive winding 3c. The capacitor 33 is charged with a voltage generated in the drive winding 3 c during the OFF period of the switching element 4. In addition, a power transmission control circuit 42 is connected to the capacitor 33, and a charged voltage is supplied as a drive voltage for the power transmission control circuit 42.

  The first rectifying / smoothing circuit 5 includes a diode 51 having an anode terminal connected to the output side of the secondary winding 3 b of the transformer 3, and a capacitor 52 connected to the cathode terminal of the diode 51. The first rectifying / smoothing circuit 5 smoothes the AC voltage output from the secondary winding 3b and outputs a first output voltage (for example, 8V). The output voltage control circuit 7 is connected to the wiring 53 that outputs the first output voltage.

  The output voltage control circuit 7 includes a series circuit of a resistor 71 connected between a wiring 53 and a ground wiring (ground potential wiring) 54, a light-emitting diode 72 of a photocoupler, and a shunt regulator 73 that is a voltage regulator, A resistance voltage dividing circuit composed of resistors 74 and 75 connected between the wiring 53 and the ground wiring 54, a resistor 76 connected between the voltage control terminal and the reference terminal of the shunt regulator 73, and a capacitor 77 The negative feedback circuit comprised by these. Note that the divided voltage output of the resistance voltage dividing circuit is input to the reference terminal of the shunt regulator 73. The output voltage control circuit 7 generates a feedback control signal based on the first output voltage output from the first rectifying and smoothing circuit 5, and controls the generated feedback control signal via the light emitting diode 72 of the photocoupler. It outputs to the circuit 42.

  The output voltage generation circuit 6 is connected to the secondary winding 3b, and generates a rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding 3b. And one end connected to the rectangular wave generating circuit 61, a capacitor 62 for transmitting the generated rectangular wave, and a cathode terminal connected to the other end of the capacitor 62, and a potential setting for setting a reference potential of the transmitted rectangular wave A diode 63 and a second rectifying / smoothing circuit 64 that is connected to the other end of the capacitor 62 and smoothes a rectangular-wave voltage with a reference potential set to a second output voltage. The output voltage generation circuit 6 generates and outputs a second output voltage different from the first output voltage from the AC voltage output from the secondary winding 3b. The second output voltage may be the same voltage as the first output voltage or a different voltage.

  The rectangular wave generating circuit 61 includes a diode 61a having an anode terminal connected to the output side of the secondary winding 3b, a cathode terminal connected to one end of the capacitor 62, an emitter terminal connected to the cathode terminal of the diode 61a, and a ground wiring (ground potential). And a transistor 61b having a collector terminal and a base terminal connected to the output side of the secondary winding 3b. A resistor 61c is connected between the cathode terminal of the diode 61a and the emitter terminal of the transistor 61b, and between the output side of the secondary winding 3b and the base terminal of the transistor 61b. The transistor 61b controls the output voltage of the diode 61a according to the AC voltage output from the secondary winding 3b, and the amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding 3b. Generate a square wave. The rectangular wave generating circuit 61 is not limited to the circuit configuration having the diode 61a and the transistor 61b, and the amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding 3b. Any circuit configuration capable of generating a rectangular wave may be used. For example, there is a circuit configuration in which a diode 61a and a transistor 61b are used as switching elements, and a rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding 3b can be generated.

  The capacitor 62 transmits the rectangular wave generated by the rectangular wave generation circuit 61. The rectangular wave transmitted by the capacitor 62 is an 8V rectangular wave whose amplitude is the potential difference between the ground potential (0V) and the positive voltage (8V) of the AC voltage output from the secondary winding 3b. Not set. Therefore, the potential setting diode 63 sets the reference potential of the rectangular wave transmitted by the capacitor 62. The potential setting diode 63 can set the reference potential of the rectangular wave transmitted by the capacitor 62 to a desired potential by connecting the anode terminal to a wiring having the desired potential. In the output voltage generation circuit 6 shown in FIG. 1, the anode terminal of the potential setting diode 63 is connected to the wiring 53 that outputs the first output voltage, so that the rectangular wave reference potential transmitted by the capacitor 62 is changed to the first output voltage. It is set. Specifically, when the first output voltage is 8V and the positive voltage of the AC voltage is 8V, the potential setting diode 63 sets the rectangular wave reference potential to 8V and generates a rectangular wave with an amplitude of 8V to 16V. To do.

  The second rectifying / smoothing circuit 64 smoothes the rectangular wave voltage set with the reference potential to the second output voltage. The second rectifying / smoothing circuit 64 includes a diode 64a having an anode terminal connected to the other end of the capacitor 62, and a capacitor 64b connected to the cathode terminal of the diode 64a. Specifically, the second rectifying / smoothing circuit 64 smoothes a rectangular wave voltage having an amplitude of 8V to 16V, and outputs a second output voltage of 16V.

  Next, the operation of the switching power supply device 1 according to Embodiment 1 of the present invention will be described. The operation of the switching power supply device 1 other than the output voltage generation circuit 6 is the same as the operation of the conventional switching power supply device, and thus the detailed description is omitted and the operation of the output voltage generation circuit 6 will be described. FIG. 2 is a diagram showing voltage waveforms for explaining the operation of the output voltage generation circuit 6 according to Embodiment 1 of the present invention. The voltage waveform shown in FIG. 2A is an AC voltage output from the secondary winding 3b, and is an AC voltage with an amplitude ranging from a negative voltage to a positive voltage (8V). The negative voltage of the AC voltage is a voltage (negative voltage) proportional to the input voltage input to the input circuit 2.

  The voltage waveform shown in FIG. 2 (b) is a rectangular wave generated by the rectangular wave generating circuit 61, and the amplitude is the ground potential (0V) and the positive voltage (8V) of the AC voltage output from the secondary winding 3b. It is a rectangular wave of 8V, which is the potential difference. When the AC voltage output from the secondary winding 3b is a positive voltage (8V), the rectangular wave generation circuit 61 outputs a positive voltage (8V) by turning off the transistor 61b and is output from the secondary winding 3b. When the alternating voltage is negative, the transistor 61b is turned on and becomes the ground potential, so that a rectangular wave with an amplitude of 0V to 8V can be generated. The generated rectangular wave is a rectangular wave having an amplitude of 8 V, but no reference potential is set.

  The voltage waveform shown in FIG. 2C is a rectangular wave in which the potential setting diode 63 sets the reference potential to 8V, and is a rectangular wave having an amplitude from 8V to 16V.

  The voltage waveform shown in FIG. 2D is a second output voltage smoothed by the second rectifying / smoothing circuit 64, and is a second output voltage of 16V. Since the second output voltage uses the rectangular wave reference potential as the first output voltage, the second output voltage is approximately twice the first output voltage.

  As described above, the switching power supply device 1 according to Embodiment 1 of the present invention is connected to the secondary winding 3b, and the amplitude is the ground potential and the positive voltage of the AC voltage output from the secondary winding 3b. A rectangular wave generating circuit 61 that generates a rectangular wave that is a potential difference; a rectangular wave generating circuit 61 that has one end connected to the rectangular wave generating circuit 61; A potential setting diode 63 for setting the reference potential of the wave, and a second rectifying / smoothing circuit 64 connected to the other end of the capacitor 62 and smoothing the rectangular-wave voltage with the reference potential set to the second output voltage. Since the output voltage generation circuit 6 is provided, a plurality of output voltages can be obtained without configuring the secondary winding 3b of the transformer 3 with a plurality of windings. Is not the size of the number of power voltage and the output voltage is limited. Further, since it is not necessary to configure the secondary winding 3b of the transformer 3 with a plurality of windings in order to obtain a plurality of output voltages, the transformer 3 can be reduced in size.

(Embodiment 2)
FIG. 3 is a circuit diagram showing a configuration of the switching power supply according to Embodiment 2 of the present invention. 3 is the same as the circuit configuration of the switching power supply 1 shown in FIG. 1 because the circuit configuration from the input circuit 2 to the primary winding 3a of the transformer 3 is the same as that of the switching power supply 1 shown in FIG. doing. Moreover, since the switching power supply device 10 is the same as the component of the switching power supply device 1 shown in FIG. 1, detailed description is abbreviate | omitted.

  The switching power supply device 10 does not connect the anode terminal of the potential setting diode 63 to the wiring 53 that outputs the first output voltage, but connects the anode terminal of the potential setting diode 63 to the ground wiring 55. Therefore, the rectangular wave reference potential is set to the ground potential. Specifically, when the positive voltage of the AC voltage is 8V, the potential setting diode 63 sets the reference potential of the rectangular wave to 0V and generates a rectangular wave with an amplitude of 0V to 8V. The second rectifying / smoothing circuit 64 smoothes a rectangular wave voltage having an amplitude of 0V to 8V, and outputs a second output voltage of 8V. The second output voltage is the same voltage as the first output voltage because the rectangular wave reference potential is the ground potential.

  As described above, the switching power supply device 10 according to the second embodiment of the present invention connects the anode terminal of the potential setting diode 63 to the ground wiring 55, and therefore the second output voltage that is the same voltage as the first output voltage. Can be output.

  The potential setting diode 63 is not limited to the case where the anode terminal is connected to the wiring 53 for outputting the first output voltage or the ground wiring 55, and may be connected to an external power source. FIG. 4 is a circuit diagram showing another configuration of the switching power supply apparatus according to Embodiment 2 of the present invention. Note that the switching power supply 11 shown in FIG. 4 has the same circuit configuration from the input circuit 2 to the primary winding 3a of the transformer 3 as the circuit configuration of the switching power supply 1 shown in FIG. doing. Moreover, since the switching power supply device 11 is the same as the component of the switching power supply device 1 shown in FIG. 1, detailed description is abbreviate | omitted.

  The switching power supply device 11 does not connect the anode terminal of the potential setting diode 63 to the ground wiring 55 but connects the anode terminal of the potential setting diode 63 to the external power supply 63a. Therefore, the rectangular wave reference potential is set to the output voltage of the external power supply 63a. Specifically, when the output voltage of the external power supply 63a is 5V and the positive voltage of the AC voltage is 8V, the potential setting diode 63 sets the rectangular wave reference potential to 5V and generates a rectangular wave with an amplitude of 5V to 13V. Generate. The second rectifying / smoothing circuit 64 smoothes a rectangular wave voltage having an amplitude of 5V to 13V, and outputs a second output voltage of 13V. The second output voltage is a voltage obtained by adding the output voltage (5 V) of the external power supply 63a to the first output voltage because the rectangular wave reference potential is the output voltage of the external power supply 63a.

(Embodiment 3)
FIG. 5 is a circuit diagram showing a configuration of a switching power supply according to Embodiment 3 of the present invention. 5 is the same as the circuit configuration of the switching power supply 1 shown in FIG. 1 because the circuit configuration from the input circuit 2 to the primary winding 3a of the transformer 3 is the same as that of the switching power supply 1 shown in FIG. doing. Moreover, since the switching power supply device 12 is the same as the component of the switching power supply device 1 shown in FIG. 1, detailed description is abbreviate | omitted.

  The switching power supply device 12 includes an output voltage generation circuit 6 that can output a plurality of second output voltages. The output voltage generation circuit 6 includes a rectangular wave generation circuit 61, a plurality of capacitors 62 and 66, a plurality of potential setting diodes 63 and 67, and a plurality of second rectifying and smoothing circuits 64 and 68. One end of the plurality of capacitors 62 and 66 is connected to the rectangular wave generating circuit 61 so that each of the capacitors 62 and 66 is parallel, and the other end of the capacitor 62 is connected to the potential setting diode 63 and the second rectifying / smoothing circuit 64. A potential setting diode 67 and a second rectifying / smoothing circuit 68 are connected to the other end of 66.

  The rectangular wave generated by the rectangular wave generating circuit 61 is transmitted to the capacitors 62 and 66, respectively. Each of the capacitors 62 and 66 transmits the rectangular wave generated by the rectangular wave generating circuit 61. The potential setting diode 63 sets the rectangular wave reference potential transmitted by the capacitor 62, and the potential setting diode 67 sets the rectangular wave reference potential transmitted by the capacitor 66. In the output voltage generation circuit 6 shown in FIG. 5, the reference terminal of the rectangular wave transmitted by the capacitor 62 is changed to the first output voltage by connecting the anode terminal of the potential setting diode 63 to the wiring 53 that outputs the first output voltage. It is set. Specifically, when the first output voltage is 8V and the positive voltage of the AC voltage is 8V, the potential setting diode 63 sets the rectangular wave reference potential to 8V and generates a rectangular wave with an amplitude of 8V to 16V. To do. The second rectifying / smoothing circuit 64 smoothes a rectangular wave voltage having an amplitude of 8V to 16V, and outputs a second output voltage of 16V.

  On the other hand, by connecting the anode terminal of the potential setting diode 67 to the wiring 6a that outputs the second output voltage smoothed by the second rectifying and smoothing circuit 64, the rectangular wave reference potential transmitted by the capacitor 66 is second rectified. The second output voltage smoothed by the smoothing circuit 64 is set. Specifically, when the second output voltage smoothed by the second rectification smoothing circuit 64 is 16V and the positive voltage of the AC voltage is 8V, the potential setting diode 67 sets the rectangular wave reference potential to 16V, A rectangular wave having an amplitude of 16V to 24V is generated.

  The second rectifying / smoothing circuit 68 smoothes the rectangular wave voltage set with the reference potential to the second output voltage. The second rectifying / smoothing circuit 68 includes a diode 68a having an anode terminal connected to the other end of the capacitor 66, and a capacitor 68b connected to the cathode terminal of the diode 68a. Specifically, the second rectifying / smoothing circuit 68 smoothes a rectangular wave voltage having an amplitude of 16V to 24V and outputs a second output voltage of 24V.

  As described above, in the switching power supply device 12 according to the third embodiment of the present invention, the output voltage generation circuit 6 includes the rectangular wave generation circuit 61, the plurality of capacitors 62 and 66, and the plurality of potential setting diodes 63 and 67. And a plurality of second rectifying / smoothing circuits 64, 68. The capacitors 62, 66 are connected at one end to the rectangular wave generating circuit 61 so as to be in parallel with each other. Since the potential setting diodes 63 and 67 and the second rectifying / smoothing circuits 64 and 68 are connected to the other end of the second output voltage, a plurality of second output voltages are generated based on the rectangular wave generated by one rectangular wave generating circuit 61. Can be output. In the output voltage generation circuit 6 shown in FIG. 5, one rectangular wave generation circuit 61, two capacitors 62 and 66, two potential setting diodes 63 and 67, and two second rectifying and smoothing circuits 64 are provided. 68, two second output voltages are output. However, one rectangular wave generation circuit 61, three or more capacitors, three or more potential setting diodes, and three The second rectifying / smoothing circuit described above may be used to output three or more second output voltages.

  Further, the output voltage generation circuit 6 is not limited to the configuration having one rectangular wave generation circuit 61, and may have a configuration having a plurality of rectangular wave generation circuits 61. FIG. 6 is a circuit diagram showing another configuration of the switching power supply according to Embodiment 3 of the present invention. 6 is omitted because the circuit configuration from the input circuit 2 to the primary winding 3a of the transformer 3 is the same as the circuit configuration of the switching power supply 1 shown in FIG. doing. Further, the switching power supply device 13 is the same as the components of the switching power supply device 1 shown in FIG.

  The switching power supply device 13 includes an output voltage generation circuit 6 that can output a plurality of second output voltages. The output voltage generation circuit 6 includes a plurality of rectangular wave generation circuits 61 and 65, a plurality of capacitors 62 and 66, a plurality of potential setting diodes 63 and 67, and a plurality of second rectifying and smoothing circuits 64 and 68. doing. The plurality of rectangular wave generating circuits 61 and 65 are connected to the output side of the secondary winding 3b so that each of them is in parallel. One end of the capacitor 62 is connected to the rectangular wave generating circuit 61, and the other end of the capacitor 62 is connected. The potential setting diode 63 and the second rectifying / smoothing circuit 64 are connected to each other, one end of the capacitor 66 is connected to the rectangular wave generating circuit 65, and the potential setting diode 67 and the second rectifying / smoothing circuit are connected to the other end of the capacitor 66. 68 is connected.

  The rectangular waves generated by the rectangular wave generating circuits 61 and 65 are transmitted to the capacitors 62 and 66, respectively. Each of the rectangular wave generating circuits 61 and 65 generates a rectangular wave whose amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding 3b. The rectangular wave generated by the rectangular wave generating circuit 61 is transmitted to the capacitor 62, and the rectangular wave generated by the rectangular wave generating circuit 65 is transmitted to the capacitor 66. The capacitor 62 transmits the rectangular wave generated by the rectangular wave generation circuit 61, and the capacitor 66 transmits the rectangular wave generated by the rectangular wave generation circuit 65. The potential setting diode 63 sets the rectangular wave reference potential transmitted by the capacitor 62, and the potential setting diode 67 sets the rectangular wave reference potential transmitted by the capacitor 66.

  In the output voltage generation circuit 6 shown in FIG. 6, the anode terminal of the potential setting diode 63 is connected to the wiring 53 that outputs the first output voltage, so that the rectangular wave reference potential transmitted by the capacitor 62 is changed to the first output voltage. It is set. Specifically, when the first output voltage is 8V and the positive voltage of the AC voltage is 8V, the potential setting diode 63 sets the rectangular wave reference potential to 8V and generates a rectangular wave with an amplitude of 8V to 16V. To do. The second rectifying / smoothing circuit 64 smoothes a rectangular wave voltage having an amplitude of 8V to 16V, and outputs a second output voltage of 16V.

  On the other hand, by connecting the anode terminal of the potential setting diode 67 to the wiring 6a that outputs the second output voltage smoothed by the second rectifying and smoothing circuit 64, the rectangular wave reference potential transmitted by the capacitor 66 is second rectified. The second output voltage smoothed by the smoothing circuit 64 is set. Specifically, when the second output voltage smoothed by the second rectification smoothing circuit 64 is 16V and the positive voltage of the AC voltage is 8V, the potential setting diode 67 sets the rectangular wave reference potential to 16V, A rectangular wave having an amplitude of 16V to 24V is generated. The second rectifying / smoothing circuit 68 smoothes a rectangular wave voltage having an amplitude of 16V to 24V, and outputs a second output voltage of 24V.

  As described above, the output voltage generation circuit 6 shown in FIG. 6 includes a plurality of rectangular wave generation circuits 61 and 65, a plurality of capacitors 62 and 66, a plurality of potential setting diodes 63 and 67, and a plurality of second rectifiers. The plurality of rectangular wave generation circuits 61 and 65 are connected to the output side of the secondary winding 3b so as to be parallel to each other, and the respective rectangular wave generation circuits 61 and 65 are provided. In addition, one end of each of the capacitors 62 and 66 is connected, and the potential setting diodes 63 and 67 and the second rectifying / smoothing circuits 64 and 68 are connected to the other ends of the respective capacitors 62 and 66. A plurality of second output voltages can be output based on the rectangular wave generated by the generation circuits 61 and 65.

  In the output voltage generation circuit 6 shown in FIG. 6, two rectangular wave generation circuits 61 and 65, two capacitors 62 and 66, two potential setting diodes 63 and 67, and two second rectifying / smoothing operations. Although the circuit 64, 68 is used to output two second output voltages, three or more rectangular wave generation circuits, three or more capacitors, three or more potential setting diodes, Further, it may be configured to have three or more second rectifying / smoothing circuits and outputting three or more second output voltages. The output voltage generation circuit 6 shown in FIG. 6 has a configuration in which one end of one capacitor 62, 66 is connected to each of the rectangular wave generation circuits 61, 65. A configuration in which one end of a plurality of capacitors connected in parallel may be connected.

  In the switching power supply devices 10 to 12 according to the first to third embodiments of the present invention, the output voltage can be negative by connecting the diodes and the transistors in reverse polarity. For example, in the switching power supply device 10 illustrated in FIG. 3, the second output voltage can be set to −8V by setting the connection of the potential setting diode 63 and the diode 64a to the reverse polarity. If the first output voltage is a negative output voltage, for example, -8V, the connection between the potential setting diode 63, the diode 61a, and the diode 64a is reversed, and the connection between the collector and emitter of the transistor 61b is reversed. Thus, the second output voltage can be set to -8V.

DESCRIPTION OF SYMBOLS 1, 10, 11, 12, 13 Switching power supply device 2 Input circuit 3 Transformer 4 Switching element 5 1st rectification smoothing circuit 6 Output voltage generation circuit 6a, 53 Wiring 21 Diode bridge 22 Filter 23 Fuse 31, 33, 52, 62 , 64b, 66, 67, 77 Capacitor 32, 51, 61a, 64a, 68a Diode 41, 61c, 61d, 71, 74, 75, 76 Resistor 42 Power transmission control circuit 43 Phototransistor 54, 55 Ground wiring 61, 65 Rectangular Wave generation circuit 63, 67 Potential setting diode 64, 68 Second rectification smoothing circuit 72 Light emitting diode 73 Shunt regulator

Claims (7)

A transformer having at least a primary winding and a secondary winding;
A switching element that is connected to the primary winding and transmits power from the primary winding to the secondary winding of the transformer by controlling on / off;
A first rectifying / smoothing circuit connected to the secondary winding and smoothing an AC voltage output from the secondary winding to a first output voltage;
An output voltage generation circuit connected to the secondary winding and generating a second output voltage from an AC voltage output from the secondary winding;
The output voltage generation circuit includes:
A rectangular wave generating circuit which is connected to the secondary winding and generates a rectangular wave whose amplitude is a potential difference between a ground potential and a positive voltage of the AC voltage output from the secondary winding;
One end connected to the rectangular wave generating circuit, and a capacitor for transmitting the rectangular wave;
A potential setting diode that is connected to the other end of the capacitor and sets a reference potential of the rectangular wave transmitted by the capacitor;
A switching power supply device comprising: a second rectifying / smoothing circuit connected to the other end of the capacitor and smoothing the rectangular wave voltage set with a reference potential to a second output voltage. The output voltage generation circuit includes the rectangular wave generation circuit, the plurality of capacitors, the plurality of potential setting diodes, and the plurality of second rectification smoothing circuits,
The plurality of capacitors have one end connected to the rectangular wave generation circuit so that each of them is in parallel, and the other end of each capacitor is connected to the potential setting diode and the second rectifying and smoothing circuit. The switching power supply device according to claim 1. The output voltage generation circuit includes a plurality of rectangular wave generation circuits, a plurality of capacitors, a plurality of potential setting diodes, and a plurality of second rectification smoothing circuits.
The plurality of rectangular wave generation circuits are connected to the secondary winding so that each of them is in parallel,
One end of one or a plurality of the capacitors is connected to each rectangular wave generation circuit,
2. The switching power supply device according to claim 1, wherein the potential setting diode and the second rectifying / smoothing circuit are connected to the other end of each of the capacitors.   4. The switching power supply device according to claim 1, wherein one end of the potential setting diode is connected to the other end of the capacitor, and the other end is connected to a wiring having a ground potential.   4. The switching according to claim 1, wherein one end of the potential setting diode is connected to the other end of the capacitor, and the other end is connected to a wiring that outputs the first output voltage. 5. Power supply.   4. The switching power supply device according to claim 1, wherein one end of the potential setting diode is connected to the other end of the capacitor, and the other end is connected to an external power source. 5. The rectangular wave generation circuit includes:
A diode having one end connected to the secondary winding and the other end connected to one end of the capacitor;
A base terminal connected to the secondary winding, and a transistor in which one end of the diode and a ground potential are connected between a collector and an emitter;
The transistor controls the output voltage of the diode according to the AC voltage output from the secondary winding, and the amplitude is a potential difference between the ground potential and the positive voltage of the AC voltage output from the secondary winding. The switching power supply according to any one of claims 1 to 6, wherein the rectangular wave is generated.

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