JP3073670U - Power supply - Google Patents

Abstract

(57) [Summary] When switching from a high output to a low output in a power supply device that outputs a DC voltage of a plurality of potentials, the power supply line on the low potential side discharges excessively, and the power supply device temporarily outputs the low potential side. The DC voltage sometimes dropped too much. A power supply device includes a transformer, a first DC conversion circuit, a second DC conversion circuit, and a first DC voltage output unit provided for each power supply line.
A feedback circuit 50 for modulating an AC voltage input to the transformer 10 so as to make the output voltage of 1a constant,
The first DC voltage output unit 21a is configured to include a conduction circuit capable of flowing a current from the first DC voltage output unit 21a to the second DC voltage output unit 22a at the time of low output when the output voltage decreases. Then, the power supply line 22b of the low potential side DC voltage
To prevent excessive discharge, thereby preventing a temporary voltage drop at the time of low output in the power supply line 22b.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a power supply device, and more particularly to a power supply device capable of outputting a plurality of DC voltages and selecting a high output or a low output.

[0002]

[Prior art]

 An electric device such as a television is provided with a power supply device that generates a plurality of DC voltages and supplies the DC voltages to an internal circuit such as a microcomputer. Then, the power supply supplies a plurality of DC voltages to the internal circuit with the output voltage set to a low output in order to perform the operation during standby at the time of standby. This type of power supply uses a transformer that outputs a secondary voltage of a plurality of potentials by using an input AC voltage, and converts the secondary voltage of a plurality of potentials output from the transformer into DC and outputs the DC. It is composed of a plurality of DC circuits and a feedback circuit that modulates the AC voltage input to the transformer according to the highest DC voltage so as to keep the DC voltage constant. The input terminal of the feedback circuit is connected to a high-resistance resistor circuit connected to the power supply line of the highest potential DC voltage. The output voltage is reduced. Then, a power supply line corresponding to each DC voltage is provided, and the microcomputer and the like are connected to the power supply line on the lower potential side and supplied with the DC voltage, so that the entire electric device is controlled even at the time of low output.

[0003]

[Problems to be solved by the invention]

 The conventional power supply device described above has the following problems. At the time of low output when the output voltage of the DC voltage decreases, the discharge time of the power supply line on the lower potential side may be shorter than the discharge time of the power supply line at the highest potential. In this case, since the feedback circuit performs feedback control to keep the highest potential DC voltage constant, excessive discharge occurs on the power supply line on the low potential side, and the DC voltage on the low potential side temporarily drops too much. There is. Therefore, when switching to the low output, the microcomputer or the like sometimes malfunctioned. Also, power supply devices disclosed in Japanese Patent Application Laid-Open No. Hei 2-223378 and Japanese Utility Model Application Laid-Open No. 59-81283 are known. It cannot prevent the voltage drop of the power line on the low potential side. The present invention has been made in view of the above problems, and has as its object to provide a power supply device capable of preventing a temporary voltage drop of a power supply line on a low potential side during a low output.

[0004]

[Means for Solving the Problems]

 In order to achieve the above object, the invention according to claim 1 includes a transformer that outputs a high-potential and a low-potential secondary voltage by using an input AC voltage, and a high-potential output from the transformer. The DC voltage of the secondary side is converted to DC and the first DC voltage output from the first DC voltage output section, and the low-potential secondary voltage output from the transformer is converted to DC. A second DC conversion circuit that outputs from the DC voltage output unit, a high output and a low output can be selected, and the output voltage is made constant according to the output voltage of the first DC voltage output unit. A feedback circuit that modulates an AC voltage input to the transformer so as to output the second DC voltage from the first DC voltage output unit when the output voltage of the first DC voltage output unit decreases. Equipped with a conductive circuit that can supply current to the output unit That it is constituted.

In the invention according to claim 1 configured as described above, the input AC voltage is divided into a high potential voltage and a low potential voltage by a transformer, and is converted into DC. Then, a DC voltage on the high potential side is output from the first DC voltage output section, and a DC voltage on the low potential side is output from the second DC voltage output section. The feedback circuit looks at the DC voltage on the high potential side and modulates the AC voltage input to the transformer so as to keep this DC voltage constant. Then, the high-potential and low-potential secondary voltages are simultaneously modulated so as to keep the high-potential DC voltage constant. Then, the modulated high-potential and low-potential secondary voltages are converted to direct current, and the high-potential and low-potential DC voltages are output. As a result, the output voltage of the first DC voltage output unit on the high potential side is kept constant.

At the time of a low output in which the high-potential-side DC voltage output from the first DC voltage output unit decreases, the low-potential-side DC voltage output through the same transformer is also changed to the high-potential-side DC voltage. It goes down as it goes down. At this time, it becomes possible to flow a current from the first DC voltage output unit to the second DC voltage output unit. Here, if the discharge is completed on the low-potential-side DC voltage power supply line before the discharge is completed on the high-potential-side DC voltage power supply line, the first DC voltage output section is switched to the second DC voltage output section. Apply current to This prevents the power supply line of the low-potential-side DC voltage from being excessively discharged, and prevents a temporary voltage drop at the time of low output on the power supply line of the low-potential-side DC voltage.

Here, the transformer only needs to be able to output a plurality of secondary voltages using the input AC voltage. For example, a configuration having a primary winding wound around a core and secondary windings wound around the core and provided with output units at a plurality of positions having different numbers of turns can be employed. Then, by inputting an AC voltage to the primary winding, a high-potential and a low-potential secondary voltage can be output from a plurality of outputs of the secondary winding. Further, a configuration having independent secondary windings for each of a plurality of output units may be employed, and various configurations are possible. Also, the AC voltage input to the transformer may use a commercial AC power supply as it is, or may be a pulse-like current generated from a DC power supply using a switching element or the like. Things are possible.

[0008] The first DC conversion circuit and the second DC conversion circuit only need to be able to convert the secondary voltage output from the transformer to DC. For example, DC may be obtained by rectifying and smoothing the secondary voltage with a diode and a capacitor, or a silicon bridge using a plurality of diodes and further reducing the voltage fluctuation by combining transistors. Often, the configurations vary.

The feedback circuit only needs to be able to modulate the AC voltage input to the transformer in accordance with the output voltage of the first DC voltage output unit on the high potential side so as to keep this voltage constant. For example, a comparison circuit that compares the output voltage of the first DC voltage output unit with a reference voltage may be provided, and the AC voltage input to the transformer may be modulated according to the output of the comparison circuit, or A / D conversion may be performed. The output voltage of the first DC voltage output unit may be input to a microcomputer having functions, and the microcomputer may perform a predetermined operation to modulate the AC voltage input to the transformer, and the configuration is various. In addition, the modulation of the input AC voltage may change the amplitude of the AC voltage, or may change the pulse width of the AC voltage. It is.

[0010] The conduction circuit may be configured to allow a current to flow from the first DC voltage output section to the second DC voltage output section during low output. As an example of the configuration, the invention according to claim 2 is the power supply device according to claim 1, wherein the conduction circuit includes a high-resistance resistance circuit having one end connected to the first DC voltage output unit. The other end of the resistor circuit is connected to the ground at the time of high output, and the other end of the resistor circuit is disconnected from the ground at the time of low output, and a current flows from the other end of the resistor circuit to the second DC voltage output section. And a directional rectifier circuit.

In the invention according to claim 2 configured as described above, at the time of high output, a minute current flows from the power supply line of the high-potential-side DC voltage to the ground via the high-resistance resistor circuit and the switching circuit, The other end of the resistance circuit is at the ground potential. At the time of low output, this current is cut off, and the voltage is supplied from the power line of the high-potential side DC voltage via the resistor circuit. Here, the rectifier circuit can flow current only from the other end of the same resistance circuit having one end connected to the high potential side DC voltage power supply line to the low potential side DC voltage power supply line. Then, when the voltage at the other end of the resistance circuit supplied with the voltage from the high-potential-side DC voltage power supply line is higher than the voltage of the second DC-voltage output unit, the current is supplied to the low-potential-side DC voltage power supply line. Will flow. That is, no current flows through the rectifier circuit when the other end of the resistor circuit has the ground potential, and no current flows through the rectifier circuit during the low output when the voltage at the other end of the resistor circuit rises. Therefore, with a simple circuit, power is supplied from the high potential side DC voltage power supply line only at the time of low output, and the low potential side DC voltage power supply line is not excessively discharged.

Here, the switching circuit connects the other end of the high-resistance resistor circuit connected to the first DC voltage output section to the ground at the time of high output, and disconnects the other end from the ground at the time of low output. I just want to be able. For example, a changeover switch in which one is connected to ground and the other is open may be used, or a switch element that switches on and off the ground according to a signal for switching between high output and low output may be used. It may have a variety of configurations.

The rectifier circuit only needs to have a direction in which a current flows to the second DC voltage output section at the other end of the high-resistance resistor circuit connected to the first DC voltage output section. As an example of a simple configuration, the invention according to claim 3 is the power supply device according to claim 2, wherein the rectifier circuit has an anode connected to the other end of the resistor circuit, and The voltage output section has a diode connected on the cathode side. In the invention according to claim 3 configured as described above, current can flow from the high-potential-side DC voltage power supply line to the low-potential-side DC voltage power supply line via a high-resistance resistor circuit and a diode. It is. That is, a rectifier circuit is configured with simple components, and at the time of low output, electric charge is supplied from the power supply line of the high potential side DC voltage, and the power supply line of the low potential side DC voltage is not excessively discharged.

Incidentally, the feedback circuit may use a high-resistance resistor circuit to check the voltage of the power supply line of the high-potential-side DC voltage. As an example of the specific configuration, the invention according to claim 4 is described. The power supply device according to claim 2 or 3, wherein the resistance circuit is configured to output the first DC voltage while changing an output voltage depending on whether the other end is connected to the ground. An output terminal that outputs the voltage substantially in proportion to the voltage of the unit, and the output terminal is connected to an input terminal of the feedback circuit.

In the invention according to claim 4 configured as described above, it is determined whether or not the other end of the high-resistance resistor circuit having one end connected to the first DC voltage output unit is connected to the ground. The output voltage at the output terminal changes. The feedback circuit modulates the AC voltage input to the transformer so as to eliminate the change in the voltage at the output terminal. Then, the output voltage of the first DC voltage output unit changes between high output and low output. The output terminal of the resistor circuit outputs a voltage that is substantially proportional to the voltage of the first DC voltage output unit, which is different between high output and low output. Makes the voltage of the first DC voltage output unit constant according to the voltage of the first DC voltage output unit that differs between the high output time and the low output time. In other words, the above-described circuit allows current to flow from the high-potential-side DC voltage power supply line to the low-potential-side DC voltage power supply line only at the time of low output, and between high output and low output. The DC voltage of the power line on the high potential side switches.

The configuration of the circuit is various, and as a specific example of the configuration, the invention according to claim 5 is the power supply device according to claim 4, wherein the resistor circuit has one end of the first circuit. First and second resistors having a high resistance connected to the DC voltage output unit; and an anode connected to the other end of the second resistor and the other end of the first resistor. And a diode connected to the input side of the feedback circuit while the cathode side is connected to the input side of the feedback circuit.

In the invention according to claim 5 configured as described above, the connection terminal between the first resistor and the cathode side of the diode is set as the output terminal of the resistance circuit. At the time of high output in which the other end of the high-resistance second resistor whose one end is connected to the first DC voltage output section is connected to the ground, the second resistor is connected to the second resistor from the high-potential-side DC voltage power supply line. A minute current flows to the ground via the switching circuit, and the other end of the second resistor becomes the ground potential. As a result, the output terminal of the resistor circuit is substantially proportional to the voltage of the first DC voltage output unit, which is obtained by subtracting the voltage drop due to the current flowing only through the first resistor from the voltage of the first DC voltage output unit. Voltage. On the other hand, at the time of the low output in which the other end of the second resistor is cut off from the ground, the current from the first DC voltage output section to the output end of the resistor circuit flows through the first resistor. And those flowing via the second resistor and the diode. Then, the output terminal of the resistor circuit subtracts the voltage drop due to the current flowing through the first resistor and the second resistor connected in parallel from the voltage of the first DC voltage output unit, The voltage is approximately proportional to the voltage of the DC voltage output section. That is, since the output voltage at the output terminal of the resistor circuit changes between high output and low output, the feedback circuit to which this output voltage is input provides high-potential side DC between high output and low output. The output voltage of the voltage power supply line is switched.

By the way, as a specific application example of the present power supply device, the invention according to claim 6 is based on the idea that an AC voltage input to a primary winding wound around a core is converted to a secondary voltage wound around the core. A transformer for outputting high-potential and low-potential secondary voltages from a plurality of output units provided in the winding, and a first terminal connected to the anode side to the high-potential secondary voltage output unit of the transformer. And a first capacitor connected between the cathode of the first diode and the ground, and a low-potential secondary voltage output of the transformer. A second direct-current circuit having a second diode connected to the anode side, a second capacitor connected between the cathode side of the second diode and ground, and one end connected to the second diode. High resistance connected to the cathode side of one diode A first and second resistor, and a third diode having an anode connected to the other end of the second resistor and a cathode connected to the other end of the first resistor. A switching circuit having a changeover switch for connecting the anode side of the third diode to the ground at the time of high output and disconnecting the anode side of the third diode from the ground at the time of low output; A switching transistor connected to a primary winding of the transformer and capable of switching conduction and interruption of an input AC voltage, connected to a cathode side of the third diode, and connected to a cathode of the third diode; A feedback circuit for switching the conduction and interruption of the switching transistor so as to make the voltage of the third diode constant, and an anode connected to the anode of the third diode. Is connected to the side, it is constituted comprising a rectifying circuit having the second diode fourth diode connected to the cathode side to the cathode side of the. That is, the present invention is also effective as a power supply device having the above specific configuration.

[0019]

[Effect of the invention]

 As described above, the present invention prevents the power line of the low potential side DC voltage from being excessively discharged and can prevent a temporary voltage drop of the power line at the time of the low output. Further, according to the invention of the second aspect, with a simple circuit, at the time of low output, power is supplied from the power supply line of the high potential side DC voltage, and the power is not excessively discharged by the power supply line of the low potential side DC voltage. Further, according to the present invention, power is supplied from a high-potential-side DC voltage power supply line at the time of low output with a simple component, and the power is not excessively discharged by a low-potential-side DC voltage power supply line.

Further, according to the invention of claim 4, it is possible to flow a current from the power line of the high-potential-side DC voltage to the power line of the low-potential-side DC voltage only at the time of the low output. It is possible to provide a power supply device in which the output voltage of the power supply line of the high-potential-side DC voltage is switched between at the time of output and at the time of low output. Further, according to the present invention, the output voltage of the power supply line of the high-potential-side DC voltage is switched between the high output and the low output by a simple circuit. Furthermore, according to the present invention, the power supply line of the low-potential-side DC voltage can be prevented from being excessively discharged, and the power supply line can prevent a temporary voltage drop of the power supply line at the time of low output. An apparatus can be provided.

[0021]

[Embodiment of the invention]

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a power supply device according to an embodiment of the present invention. In FIG. 1, a power supply device 100 outputs three types of DC voltages V1, V2, and V3 from an input AC voltage to a power supply line, and reduces the DC voltages V1, V2, and V3 during standby. Has become. In order to output these DC voltages V1, V2, and V3, the power supply device 100 includes a transformer 10 according to the present invention and a first DC conversion circuit 21 provided corresponding to each power supply line. The circuit includes a second DC conversion circuit 22, a third DC conversion circuit 23, a high-resistance resistance circuit 30, a switching circuit 40, a feedback circuit 50, and a rectification circuit 60.

When the present power supply device 100 is applied to a television device, the highest potential DC voltage V1 is used for outputting an electron beam of a picture tube, etc., and has a lower potential DC voltage V2 than the DC voltage V1. Are supplied to a microcomputer or the like. Then, the microcomputer controls the entire television set even when the output is low, and performs the operation at the time of standby. In the present embodiment, three types of DC voltages V1, V2, and V3 are output. However, the present invention is applicable to a power supply device that outputs a plurality of DC voltages. Therefore, in a power supply device that outputs two types of DC voltages, only two DC circuits are required.

The transformer 10 has a substantially annular core 11, and primary windings 12 and 13 and secondary windings 14 and 15 wound around the core 11. An AC voltage is input to one end of the primary winding 12, and the other end is connected to the collector of an npn-type switching transistor 52 in the feedback circuit 50. The base of the switching transistor 52 is connected to one end of the primary winding 13, and the other end of the primary winding 13 is connected to the ground. When an AC voltage is input to one end of the primary winding 12, a current flows to the ground via the primary winding 12, the switching transistor 52, and the primary winding 13.

The secondary winding 14 has one end connected to the ground and the other end connected to a high-potential secondary voltage output end 14 a. In the middle of the secondary winding 14, an output terminal 14b for a low-potential secondary voltage is provided. As a result, the output voltage is lower at the output terminal 14b than at the output terminal 14a. The secondary winding 15 has one end connected to the ground and the other end connected to a low-potential secondary voltage output end 15a. The number of turns of the secondary windings 14, 15 is set so that the voltage at the output terminal 15a is lower than the voltage at the output terminal 14a. Then, when an AC voltage is input to the primary winding 12, three levels of AC voltages are output from the output terminals 14a, 14b, and 15a in the descending order of the output voltage. That is, the transformer 10 outputs a high-potential and a low-potential secondary voltage using the input AC voltage.

The first direct current conversion circuit 21 includes a first diode D1 according to the present invention having an anode connected to the output terminal 14a of the high potential secondary voltage of the transformer 10, and a cathode connected to the diode D1. And the first capacitor C1 according to the present invention connected to the ground. The connecting portion between the diode D1 and the capacitor C1 serves as a first DC voltage output portion 21a, and a DC voltage on the high potential side is supplied from the first DC voltage output portion 21a to the first power supply line 21b. ing.

The second DC conversion circuit 22 and the third DC conversion circuit 23 have the same configuration as the first DC conversion circuit 21. The second direct-current conversion circuit 22 includes a second diode D2 according to the present invention having an anode connected to the low-potential secondary voltage output terminal 14b of the transformer 10, a cathode of the diode D2 and a ground. And the second capacitor C2 according to the present invention connected between them. The third DC conversion circuit 23 includes a diode D12 having an anode connected to the output terminal 15a of a lower potential secondary voltage of the transformer 10, and a capacitor connected between the cathode of the diode D12 and the ground. And C12. The connection portions between the diodes D2 and D12 and the capacitors C2 and C12 are referred to as a second DC voltage output portion 22a and a third DC voltage output portion 23a, respectively. The second DC voltage output portion 22a and the third DC voltage output portion 23a , A DC voltage is supplied to the second power supply line 22b and the third power supply line 23b.

The AC voltages output from the output terminals 14a, 14b, and 15a are rectified by the diodes D1, D2, and D12, respectively, and smoothed by the capacitors C1, C2, and C12. Therefore, the AC voltage is converted into a three-stage DC voltage and output to the outside. That is, these DC conversion circuits convert a plurality of stages of secondary-side voltages output from the transformer 10 into DC and output the DC voltages from the respective DC voltage output units 21a, 22a, and 23a.

The high-resistance resistor circuit 30 has one end as an input terminal 30a and is connected to the first DC voltage output section 21a on the cathode side of the first diode D1 according to the present invention. Device R1 and a second resistor R2. The third diode D3 according to the present invention is connected to the other end of the second resistor R2 on the anode side, and connected to the other end of the first resistor R1 on the cathode side. The connection between the first resistor and the diode D3 is set as the output terminal 30b, and the output voltage of the output terminal 30b is input to the feedback circuit 50.

The switching circuit 40 has a switching switch 41 for switching between connection / disconnection between the connection point 30c between the anode of the diode D3, which is the other end of the resistance circuit 30, and the resistor R2, and ground. The changeover switch 41 connects the connection point 30c to the ground at the time of the high output when the power is on, and disconnects the connection point 30c from the ground at the time of the low output which is the standby time. At the time of high output, as shown in the main part circuit diagram of FIG. 2, a minute current flows from the power supply line 21b of the high potential side DC voltage to the ground via the resistor R2, and the voltage at the connection point 30c becomes almost zero. ing. The current flowing in the power supply device 100 is indicated by an arrow. Then, the voltage input to the feedback main circuit 51 is the voltage of the first DC voltage output unit 21a obtained by subtracting the voltage drop due to the current flowing only through the resistor R1 from the voltage of the first DC voltage output unit 21a. A voltage approximately proportional to the voltage is input. On the other hand, at the time of low output, as shown in the main circuit diagram of FIG. 3, this minute current is cut off, and the current flowing through the resistor R2 is also input to the feedback main circuit 51. Then, the voltage input to the feedback main circuit 51 is the first DC voltage output obtained by subtracting the voltage drop due to the current flowing through the resistors R1 and R2 from the voltage of the first DC voltage output unit 21a. A voltage substantially proportional to the voltage of the unit 21a is input.

The feedback circuit 50 includes the switching transistor 52 described above, and a feedback main circuit 51 connected to the base of the switching transistor 52 and the output terminal 30b of the resistance circuit 30. The collector of the switching transistor 52 is connected to the primary winding 12 as described above, and the emitter is connected to ground. The base of the switching transistor 52 is connected to the primary winding 13 as described above, and is also connected to the output of the feedback main circuit 51.

An input terminal 51 a of the feedback main circuit 51 is connected to an output terminal 30 b of the resistance circuit 30. The feedback main circuit 51 looks at the output voltage of the output terminal 30b and changes the conduction / cutoff ratio between the collector and the emitter of the switching transistor 52 so as to keep this output voltage constant. Then, the AC voltage input to the transformer 10 is modulated according to the conduction / interruption ratio, and the three-stage secondary voltages are simultaneously modulated. Then, the modulated secondary voltage is converted to direct current, and each direct current voltage is output. The output voltage of the output terminal 30b of the resistor circuit 30 to which the voltage of the power supply line 21b of the high potential side direct voltage is input is constant. Is to be kept. Then, the voltages of the power supply lines 22b and 23b are also output from the transformer 10 and converted to DC, similarly to the power supply line 21b, and thus change according to the voltage change of the power supply line 21b.

Here, as described above, different voltages are input to the input terminal 51 a of the feedback main circuit 51 at the time of high output and at the time of low output. The voltage of the power supply line 21b is made constant according to the voltage of the power supply line 21b which differs from time to time. In the present embodiment, the input AC voltage is modulated by changing the conduction / cutoff ratio between the collector and the emitter of the switching transistor 52. However, other than this, the secondary voltage may be modulated. Is possible. For example, the input AC voltage may be changed by changing the amplitude, and various methods are possible.

The rectifier circuit has an anode side 60a connected to a connection point 30c of the resistor circuit 30 on the anode side of the third diode D3, and a second DC voltage on the cathode side of the second diode D2. It has a fourth diode D4 according to the present invention in which the cathode side 60b is connected to the output section 22a. That is, the rectifier circuit has a direction in which current flows from the connection point 30c to the second DC voltage output unit 22a. When the voltage of the power supply line 22b becomes lower than the voltage of the connection point 30c, the current flows.

Next, the operation of the power supply device according to the present embodiment will be described. FIG. 4 is a timing chart showing the state of each of the DC voltages V1, V2, V3 and the like. In the figure, when the power is turned on, the connection point 30c of the resistor circuit 30 is connected to the ground, and the voltage on the anode side 60a of the diode D4 is almost zero. And each DC voltage V1, V2, V3 is a high output. Actually, the DC voltages V1, V2, and V3 slightly fluctuate, and the feedback circuit 50 modulates the AC voltage input to the transformer 10 so as to eliminate the fluctuation of the DC voltage V1. The voltage at the input terminal 51a of the feedback circuit 50 is a voltage substantially proportional to the substantially constant DC voltage V1.

When switching from high output to low output at timing T1, the connection point 30c is cut off from the ground, and the anode 60a of the diode D4 connected to the connection point 30c connects the resistor R2 from the power supply line 21b. Is supplied with voltage. Then, a current flows from the anode side 60a to the output terminal 30b of the resistance circuit 30 via the diode D3, and the resistance between the first DC voltage output unit 21a and the output terminal 30b of the resistance circuit 30 decreases. . As a result, the voltage drop from the first DC voltage output unit 21a decreases, and the voltage input to the input terminal 51a of the feedback circuit 50 increases. The feedback circuit 50 modulates the AC voltage input to the transformer 10 by switching the conduction and interruption of the internal switching transistor 52 so as to keep the voltage of the input terminal 51a constant. Then, when the voltage at the input terminal 51a returns to the original state at the timing T2, the DC voltage V1 is switched to the low output. The voltage on the anode side 60a of the diode D4 rises at the timing T1 because the anode side 60a is cut off from the ground and is connected to the power supply line 21b via the resistor R2. .

Here, similarly to the conventional circuit configuration, when the discharge time of the power supply line 23b of the DC voltage V3 not connected to the rectifier circuit 60 is shorter than that of the power supply line 21b of the DC voltage V1, the feedback circuit 50 Since the feedback control is performed so as to keep the voltage of the power supply line 21b of the DC voltage V1 constant, excessive discharge occurs in the power supply line 23b of the DC voltage V3. Then, the output voltage of the power supply line 23b of the DC voltage V3 temporarily becomes substantially zero.

On the other hand, if the power supply line 22b of the DC voltage V2 connected to the rectifier circuit 60 has a shorter discharge time than the power supply line 21b of the DC voltage V1, the discharge ends first. Here, since the rectifier circuit 60 is connected to the power supply line 22b, when the voltage of the power supply line 22b becomes lower than the voltage of the connection point 30c cut off from the ground at the time of low output, the rectifier circuit 60 is used. Thus, a current flows from the connection point 30c to the power supply line 22b. Then, the power is not excessively discharged in the power supply line 22b, and the DC voltage V2 is slightly lower than the voltage at the time of the low output, but does not become 0. Therefore, a temporary voltage drop at the time of low output in the power supply line of the DC voltage on the lower potential side than the DC voltage V1 is prevented. Further, when the power supply device 100 is supplied to a television device, a malfunction does not occur in the microcomputer of the television device connected to the power supply line 22b. In the present embodiment, the rectifier circuit 60 is not connected to the power supply line 23b of the DC voltage V3. However, if the rectifier circuit 60 is connected to the power supply line 23b, the DC voltage V3 can be connected to a low output. It is possible to prevent a temporary voltage drop.

As described above, in the present invention, by connecting the rectifier circuit to the low-potential-side DC voltage power supply line of the power supply device that outputs the DC voltage in a plurality of stages, the discharge is performed on the low-potential-side DC voltage power supply line. No more overdoing. Therefore, it is possible to provide a power supply device capable of preventing a temporary voltage drop in the power supply line of the low potential side DC voltage at the time of the low output.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a power supply device according to an embodiment of the present invention.

FIG. 2 is a main part circuit diagram illustrating a current flowing in the power supply device at the time of high output.

FIG. 3 is a main part circuit diagram illustrating a current flowing in the power supply device at the time of low output.

FIG. 4 is a timing chart showing states of voltages such as DC voltages V1, V2, and V3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Transformer 11 ... Core 12,13 ... Primary winding 14,15 ... Secondary winding 14a, 14b, 15a ... Output terminal 21 ... First DC circuit 21a ... First DC voltage output part 21b ... Power supply line Reference numeral 22: a second DC conversion circuit 22a: a second DC voltage output section 22b: a power supply line 23: a third DC conversion circuit 23a: a third DC voltage output section 23b: a power supply line 30: a resistance circuit 30a: an input terminal 30b: an output terminal Reference numeral 30c: Connection point 40: Switching circuit 41: Switching switch 50: Feedback circuit 51: Feedback main circuit 51a: Input terminal 52: Switching transistor 60: Rectification circuit 60a: Anode side 60b: Cathode side 100: Power supply device D1, D2, D3 , D4: Diode C1, C2: Capacitor R1, R2: Resistor

Claims (6)

[Utility model registration claims] 1. A transformer for outputting a high-potential and low-potential secondary voltage using an input AC voltage, and a high-potential secondary voltage output from the transformer is converted into a direct current. A first DC conversion circuit that outputs from a DC voltage output unit, and a second DC conversion circuit that converts a low-potential secondary voltage output from the transformer to DC and outputs from a second DC voltage output unit And a high output or a low output can be selected, and modulates an AC voltage input to the transformer so as to make the output voltage constant according to an output voltage of the first DC voltage output unit. A feedback circuit, and a conducting circuit capable of flowing a current from the first DC voltage output unit to the second DC voltage output unit during a low output in which the output voltage of the first DC voltage output unit decreases. A power supply device comprising: 2. The power supply device according to claim 1, wherein the conduction circuit has a high-resistance resistor circuit having one end connected to the first DC voltage output section, and a high-resistance resistor circuit having the other end connected to a high level. A switching circuit that is connected to the ground at the time of output, and disconnects the other end from the ground at the time of low output; and a rectifier circuit having a direction in which current flows from the other end of the resistor circuit to the second DC voltage output unit. A power supply device characterized by the above-mentioned. 3. The power supply device according to claim 2, wherein the rectifier circuit has an anode connected to the other end of the resistor circuit, and a cathode connected to the second DC voltage output unit. A power supply device comprising a diode. 4. The power supply device according to claim 2, wherein the resistance circuit changes the output voltage depending on whether or not the other end is connected to the ground. A power supply device comprising: an output terminal that outputs a voltage substantially in proportion to a voltage of a DC voltage output unit; and the output terminal is connected to an input terminal of the feedback circuit. 5. The power supply device according to claim 4, wherein the resistor circuit includes first and second resistors having one end connected to the first DC voltage output unit and having high resistance. An anode is connected to the other end of the second resistor, and a diode is connected to the input of the feedback circuit while the cathode is connected to the other end of the first resistor. A power supply device comprising: 6. An AC voltage input to a primary winding wound on a core is supplied from a plurality of output sections provided on a secondary winding wound on the core to a high potential and low potential secondary side. A transformer for outputting a voltage, a first diode having an anode connected to an output section of a high-potential secondary voltage of the transformer, and a cathode connected between the cathode of the first diode and ground. A first direct-current conversion circuit having a first capacitor, a second diode having an anode connected to the low-potential secondary voltage output section of the transformer, and a cathode of the second diode. A second direct-current circuit having a second capacitor connected between the first diode and the ground; a high-resistance first and second resistor having one end connected to the cathode side of the first diode; The anode side is connected to the other end of the second resistor And a resistor circuit having a third diode having a cathode connected to the other end of the first resistor, and an anode of the third diode connected to the ground at the time of high output, and at the time of low output. A switching circuit having a switching switch for disconnecting the anode side of the third diode from the ground, and a switching transistor connected to the primary winding of the transformer and capable of switching conduction and interruption of an input AC voltage, A feedback circuit that is connected to the cathode side of the third diode and that switches on / off of the switching transistor so that the voltage on the cathode side of the third diode is constant; The anode side is connected, and the cathode side is connected to the cathode side of the second diode. Power apparatus characterized by comprising a rectifying circuit having a fourth diode.