JP2010263734A - Safety protection circuit, as well as power supply device with the same and electric apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety protection circuit where a fuse reliably melts by a breakdown of a surge absorber in a short mode when overvoltage (200 V AC voltage, for example) is erroneously input and the surge absorber does not break down in a lightning surge of not more than a prescribed level (low lightning surge of a degree where a power supply device with the safety protection circuit must not cause an operation failure, for example). <P>SOLUTION: The safety protection circuit is arranged in the power supply device having a rectifier R1 and a smoothing capacitor C1 for smoothing pulsating flow voltage output from the rectifier R1. The safety protection circuit includes a series circuit which is connected to the smoothing capacitor C1 in parallel and is formed of a ferrite bead or a coil L1 and the surge absorber SA1, a capacitor C2 connected in parallel to the surge absorber SA1 and the fuse F1. When the surge absorber SA1 breaks down in the short mode, current is supplied to the surge absorber SA1 through the fuse F1 in the safety protection circuit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a safety protection circuit that protects an electrical device from an excessive voltage, and a power supply device and electrical device including the safety protection circuit.

  A power supply device provided in an electric device designed to Japanese specifications is for commercial 100V AC voltage input. If a 200V AC voltage is erroneously input to this commercial 100V AC voltage input power supply, there is a risk that the smoothing capacitor at the input of the power supply will burst.

  As a conventional power supply device that can prevent such danger, there is a power supply device including an input unit shown in FIG. 4, for example. 4 includes a rectifier (a diode bridge circuit is shown as an example in the drawing) RE1, a fuse F1 provided on the input side of the rectifier RE1, and a smoothing for smoothing a pulsating voltage output from the rectifier RE1. A capacitor C1, a surge absorber SA1 connected in parallel to the smoothing capacitor C1 (a zener diode is shown as an example in the drawing), and an inrush current reducing resistor R1 inserted between the surge absorber SA1 and the rectifier RE1. Yes. A surge absorber that operates at about 200 V is used as the surge absorber SA1.

  When a 200V AC voltage is erroneously input to the power supply apparatus having the input unit shown in FIG. 4, a voltage of about 280V appears in the smoothing capacitor C1, and a large current flows in the surge absorber SA1 connected in parallel to the smoothing capacitor C1. The surge absorber SA1 is broken in the short mode. Thereby, since a short circuit current flows into the fuse F1 and the fuse F1 is melted, it is possible to prevent a risk that the smoothing capacitor C1 is ruptured.

Japanese Utility Model Publication No. 6-80383 JP-A-6-181553 JP 2000-134794 A

  However, in the input unit shown in FIG. 4, if the smoothing capacitor C1 is a large-capacitance capacitor, once a 200V AC voltage is erroneously input to the power supply device including the input unit shown in FIG. The surge absorber SA1 short-circuits the smoothing capacitor C1, and a large current flows to the surge absorber SA1 due to the electric charge stored in the smoothing capacitor C1, and the surge absorber SA1 may be opened before the fuse F1 is melted. In this case, since the fuse F1 is not blown, a 200V AC voltage is continuously applied to the power supply device having the input unit shown in FIG. 4, and the risk of the smoothing capacitor C1 bursting cannot be prevented. There is a problem (first problem).

  In addition, when a lightning surge occurs in an actual use state, there is a problem (second problem) that the surge absorber SA1 is broken by the lightning surge.

  As a conventional power supply device that can solve the first problem, for example, there is a power supply device including an input unit shown in FIG. 5 that are the same as those in FIG. 4 are given the same reference numerals, and detailed descriptions thereof are omitted. The input unit shown in FIG. 5 has a configuration in which the inrush current reducing resistor R1 inserted between the surge absorber SA1 and the rectifier RE1 in the input unit shown in FIG. 4 is inserted between the surge absorber SA1 and the smoothing capacitor C1. is there. According to such a configuration, since the inrush current reducing resistor R1 limits the short-circuit current from the smoothing capacitor C1, the surge absorber SA1 is prevented from being opened, and the first problem can be solved.

  However, since the smoothing capacitor C1 is not directly parallel to the surge absorber SA1 in the power supply device including the input unit illustrated in FIG. 5, compared with the power supply device including the input unit illustrated in FIG. When a lightning surge occurs, the surge absorber SA1 is easily broken by the lightning surge.

  Here, Patent Document 1 states that “in an electric device using either AC 100V or 200V as a power source, a voltage detection device that detects a power supply voltage and a power supply voltage applied by a signal from the voltage detection device. There is disclosed a power supply device for an electric device comprising a connection switching device for switching connection to a primary winding terminal of a corresponding transformer. The power supply device for an electric device disclosed in Patent Document 1 is to prevent the electric device from causing heat generation, burning, short circuit, disconnection, etc., regardless of whether a power supply voltage of AC 100V or 200V is applied. However, it does not include a safety protection circuit that blows the fuse when the surge absorber is broken in the short mode when an excessive voltage is input by mistake.

  Further, Patent Document 2 states that “in a power supply circuit corresponding to two power supply voltages, a rectified DC voltage of a standby sub-power supply is a relay drive circuit configured by a dividing resistor, a Zener diode, and a transistor, and a 100 V system. The television receiver is characterized in that the main power supply circuit is operated by switching the relay so as to double rectify the power supply voltage of the power supply and bridge rectify the power supply voltage of the 200V system. ing. The television receiver disclosed in Patent Document 2 realizes automatic switching for two power supply voltages with an inexpensive circuit, but when an excessive voltage is accidentally input, the surge absorber is in a short mode. It does not have a safety protection circuit that blows the fuse when it breaks.

  Patent Document 3 states that “in a power supply apparatus that inputs from one commercial AC power line and supplies a voltage to one or more loads in parallel, an overcurrent blocking means is connected in series to the overvoltage limiting means. There is disclosed a power supply device comprising overcurrent cutoff overvoltage protection means, wherein the overcurrent cutoff overvoltage protection means is disposed between current shunt nodes or upstream lines thereof. In the power supply device disclosed in Patent Document 3, when the overvoltage limiting means (metal oxide varistor) is turned on, the overcurrent cutoff means (fuse) cuts off the current, but when an excessive voltage is input by mistake. However, it does not have a safety protection circuit that blows the fuse when the surge absorber breaks in the short mode.

  In view of the above situation, the present invention ensures that the fuse is surely blown by the surge absorber being broken in the short mode when an excessive voltage is accidentally input, and that the lightning surge (safety protection circuit is less than a predetermined level). An object of the present invention is to provide a safety protection circuit in which a surge absorber is not broken in a lightning surge that is low enough not to cause an abnormal operation of the power supply device provided, and a power supply device and an electric device including the safety protection circuit.

  In order to achieve the above object, a safety protection circuit according to the present invention is a safety protection circuit provided in a power supply device including a rectifier and a smoothing capacitor for smoothing a pulsating voltage output from the rectifier, A parallel circuit connected to the smoothing capacitor, comprising a series circuit comprising a ferrite bead or a coil and a surge absorber, a capacitor connected in parallel to the surge absorber, and a fuse, and when the surge absorber breaks in a short mode A current is supplied to the surge absorber through a fuse.

  According to such a configuration, even if an excessive voltage is accidentally input to the power supply device and the surge absorber is broken in a short mode, the ferrite beads or the coil and the capacitor are subjected to a sudden surge current to the surge absorber. Prevent inflow. Therefore, when the surge absorber is broken in the short mode, a large current does not flow to the surge absorber due to the charge stored in the smoothing capacitor, and the surge absorber is not opened. As a result, when an excessive voltage is erroneously input, the fuse is surely blown by the surge absorber being broken in the short mode.

  In addition, according to such a configuration, when a lightning surge occurs in an actual use state, the ferrite beads or the coil and the capacitor prevent a surge current from flowing suddenly into the surge absorber. The surge absorber will not be broken by lightning surges (lightning surges that are low enough that the power supply with a safety protection circuit should not malfunction).

  In order to achieve the above object, a power supply device according to the present invention is a power supply device including a rectifier, a smoothing capacitor for smoothing a pulsating voltage output from the rectifier, and a safety protection circuit, The safety protection circuit includes a series circuit including a ferrite bead or a coil and a surge absorber connected in parallel to the smoothing capacitor, a capacitor connected in parallel to the surge absorber, and a fuse, and the surge absorber is in a short mode. The current is supplied to the surge absorber through the fuse when it breaks.

  According to such a configuration, the same effects as those of the protective safety circuit according to the present invention described above can be obtained.

  Further, in the power supply device having the above configuration, the power supply device is a power supply device for commercial 100V AC voltage input, the rectifier rectifies the input voltage of the power supply device, and the input voltage of the power supply device is 200V AC voltage. The surge absorber may be broken in the short mode.

  As a result, when a 200V AC voltage is erroneously input to the power supply device, the fuse can be surely blown.

  Further, in the power supply device having any one of the above configurations, the fuse is provided on the input side of the rectifier, and an inrush current reduction resistor is provided between the series circuit and the rectifier, or between the series circuit and the smoothing capacitor. You may make it insert.

  In order to achieve the above object, an electric apparatus (for example, a liquid crystal television) according to the present invention is provided with the power supply device having any one of the above structures.

  According to the present invention, when an excessive voltage is erroneously input to the power supply device, the fuse is surely blown by breaking the surge absorber in the short circuit mode in the protective safety circuit.

  Further, according to the present invention, when a lightning surge occurs in an actual use state, in a lightning surge below a predetermined level (a lightning surge that is low enough that the power supply device equipped with the safety protection circuit should not cause an abnormal operation) The surge absorber does not break.

It is a figure which shows an example of the input part of the power supply device which concerns on this invention. It is a figure which shows the other example of the input part of the power supply device which concerns on this invention. It is a figure which shows the example of schematic structure of the liquid crystal television which concerns on this invention. It is a figure which shows an example of the input part with which the conventional power supply device is provided. It is a figure which shows the other example of the input part with which the conventional power supply device is provided.

  Embodiments of the present invention will be described below with reference to the drawings. An example of the input unit of the power supply apparatus according to the present invention is shown in FIG. 1 includes a rectifier (a diode bridge circuit is shown as an example in the drawing) RE1, a fuse F1 provided on the input side of the rectifier RE1, and a smoothing for smoothing a pulsating voltage output from the rectifier RE1. A capacitor C1, a series circuit comprising a ferrite bead or coil L1 connected in parallel to the smoothing capacitor C1 and a surge absorber SA1 (a zener diode is shown as an example in the drawing), a capacitor C2 connected in parallel to the surge absorber SA1, and a ferrite An inrush current reducing resistor R1 is inserted between the series circuit including the bead or coil L1 and the surge absorber SA1 and the rectifier RE1.

  Here, a surge absorber that operates at about 200 V may be used as the surge absorber SA1. As the smoothing capacitor, an electrolytic capacitor having a capacity of about several hundred μF may be used. The capacitor C2 may be a high voltage capacitor such as a ceramic capacitor.

  A fuse F1 provided on the input side of the rectifier RE1, a ferrite bead or coil L1 connected in parallel to the smoothing capacitor C1 and a series circuit composed of the surge absorber SA1 and a capacitor C2 connected in parallel to the surge absorber SA1. A protective safety circuit is configured.

  When a 200V AC voltage is erroneously input to the power supply device having the input unit shown in FIG. 1, a voltage of about 280V appears in the smoothing capacitor C1, and the ferrite beads or coil L1 and the surge absorber connected in parallel to the smoothing capacitor C1. A large current flows through the series circuit composed of SA1, and the surge absorber SA1 is broken in the short mode. Thereby, since a short circuit current flows into the fuse F1 and the fuse F1 is melted, it is possible to prevent a risk that the smoothing capacitor C1 is ruptured.

  Further, even if a 200V AC voltage is accidentally input to the power supply device including the input unit shown in FIG. 1 and the surge absorber SA1 is broken in the short mode, the ferrite beads or the coil L1 and the capacitor C2 are suddenly applied to the surge absorber SA1. Prevent inflow of excessive surge current. Therefore, when the surge absorber SA1 is broken in the short mode, a large current does not flow to the surge absorber SA1 due to the charge stored in the smoothing capacitor C1, and the surge absorber SA1 is not opened. Thereby, when a 200V type | system | group AC voltage is accidentally input into a power supply device provided with the input part shown in FIG. 1, the fuse F1 can be blown reliably.

  In addition, when a lightning surge occurs in actual use, the ferrite bead or coil L1 and capacitor C2 prevent a surge current from flowing into the surge absorber SA1, so that a lightning surge (safety protection circuit below a predetermined level) The surge absorber SA1 is not broken in the case of a lightning surge that is low enough to prevent the power supply device having a malfunction from occurring.

  Next, another example of the input unit of the power supply device according to the present invention is shown in FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. The input unit shown in FIG. 2 includes an inrush current reducing resistor R1 inserted between the rectifier RE1 and the series circuit composed of the ferrite bead or coil L1 and the surge absorber SA1 in the input unit shown in FIG. This is a configuration inserted between a series circuit composed of L1 and surge absorber SA1 and a smoothing capacitor C1.

  In the power supply device having the input unit shown in FIG. 2, the inrush current reducing resistor R1 is not provided on the front side of the series circuit composed of the ferrite beads or the coil L1 and the surge absorber SA1, but lightning surges are generated in the actual use state. If it occurs, the ferrite bead or coil L1 and the capacitor C2 prevent a surge current from flowing into the surge absorber SA1, so that a lightning surge below a predetermined level (the power supply device with a safety protection circuit causes an abnormal operation). The surge absorber SA1 is not broken in a lightning surge that is low enough to avoid).

  In addition, when a 200V AC voltage is erroneously input to the power supply device including the input unit illustrated in FIG. 2, the fuse F1 can be reliably blown in the same manner as the power supply device including the input unit illustrated in FIG. .

  Various modifications can be made to the configuration shown in FIGS. 1 and 2 without departing from the gist of the invention. For example, Sidac (registered trademark) can be used as the surge absorber SA1. In addition, a configuration in which the inrush current reduction resistor R1 is not provided, or another inrush current reduction element (for example, a thermistor or a thyristor) can be provided in place of the inrush current reduction resistor R1.

  In the configuration shown in FIGS. 1 and 2 described above, in the series circuit including the ferrite beads or coil L1 and the surge absorber SA1, the ferrite bead or coil L1 is the positive polarity side of the smoothing capacitor C1, and the surge absorber SA1 is the smoothing capacitor C1. However, the ferrite bead or coil L1 may be provided on the negative polarity side of the smoothing capacitor C1, and the surge absorber SA1 may be provided on the positive polarity side of the smoothing capacitor C1. In this case also, the capacitor C2 is connected in parallel to the surge absorber SA1.

  Next, an electric device according to the present invention will be described. Here, a liquid crystal television will be described as an example of the electrical apparatus according to the present invention. FIG. 3 shows a schematic configuration example of the liquid crystal television according to the present invention. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  3 includes a fuse F1, a rectifier RE1, an inrush current reducing resistor R1, a ferrite bead or coil L1, a surge absorber SA1, a capacitor C2, a smoothing capacitor C1, a DC / AC circuit 1, a main power circuit 2, and A power supply device having a sub power supply circuit 3, a load 4, a microcomputer (hereinafter referred to as a microcomputer) 10, a remote control light receiving unit 11, an operation key 12, and a switch SW1 are provided.

  The DC / AC circuit 1 converts the DC voltage output from the smoothing capacitor C1 into a stabilized AC voltage and supplies it to the main power supply circuit 2 and the sub power supply circuit 3.

  The main power supply circuit 2 converts the stabilized AC voltage output from the DC / AC circuit 1 into a plurality of DC voltages having different values, and supplies the plurality of DC voltages to the load 4 as various power supply voltages of the load 4. . The load 4 includes a tuner unit 5, a video circuit 6, an audio circuit 7, a liquid crystal display unit 8, and a speaker 9. The tuner unit 5 selects and demodulates a television broadcast signal received from an antenna (not shown). The video circuit 6 performs various processes (for example, luminance correction and gamma correction) on the video signal received from the tuner unit 5, and outputs the video signal subjected to the various processes to the liquid crystal display unit 8. The liquid crystal display unit 8 performs display based on the output signal of the video circuit 6. The audio circuit 7 performs various processes (for example, volume adjustment) on the audio signal received from the tuner unit 5 and outputs the audio signal subjected to the various processes to the speaker 9. The speaker 9 emits sound based on the output signal of the sound circuit 7.

  The sub power supply circuit 3 converts the stabilized AC voltage output from the DC / AC circuit 1 into a DC voltage, and supplies the DC voltage to the microcomputer 10 as the power supply voltage of the microcomputer 10. Further, the remote control light receiving unit 11 and the operation key 12 use a DC voltage of a predetermined value supplied from the microcomputer 10 as a power supply voltage.

  The remote control light receiving unit 11 outputs an instruction signal corresponding to an infrared signal from a remote control transmitter (not shown) to the microcomputer 10. The operation key 12 outputs an instruction signal corresponding to the user's key operation to the microcomputer 10. The microcomputer 10 controls the operation of the load 4 (for example, a channel selection operation by the tuner unit 5 and a volume adjustment operation by the audio circuit 7) based on an instruction signal from the remote control light receiving unit 11 or the operation key 12. Further, the microcomputer 10 controls the switch SW1 for turning on / off the power supply to the main power supply circuit 2 on the basis of the instruction signal from the remote control light receiving unit 11 or the operation key 12, and from the remote control light receiving unit 11 or the operation key 12 If the instruction signal indicates the standby state of the liquid crystal television, the switch SW1 is turned off to reduce power consumption in the main power supply circuit 2 and the load 4.

DESCRIPTION OF SYMBOLS 1 DC / AC circuit 2 Main power supply circuit 3 Sub power supply circuit 4 Load 5 Tuner part 6 Video circuit 7 Audio circuit 8 Liquid crystal display part 9 Speaker 10 Microcomputer 11 Remote control light-receiving part 12 Operation key C1 Smoothing capacitor C2 Capacitor F1 Fuse L1 Ferrite bead or Coil R1 Inrush current reduction resistor RE1 Rectifier SA1 Surge absorber SW1 Switch

Claims (6)

In a power supply device comprising a rectifier, a smoothing capacitor for smoothing a pulsating voltage output from the rectifier, and a safety protection circuit,
The safety protection circuit is
A series circuit composed of a ferrite bead or coil and a surge absorber, connected in parallel to the smoothing capacitor,
A capacitor connected in parallel to the surge absorber;
With fuse,
A power supply device, wherein when the surge absorber is broken in a short mode, a current is supplied to the surge absorber through the fuse. The power supply device is a commercial 100V AC voltage input power supply device,
The rectifier rectifies the input voltage of the power supply;
The power supply apparatus according to claim 1, wherein the surge absorber is broken in a short mode when an input voltage of the power supply apparatus is a 200V AC voltage. Providing the fuse on the input side of the rectifier;
3. The power supply device according to claim 1, wherein an inrush current reduction resistor is inserted between the series circuit and the rectifier, or between the series circuit and the smoothing capacitor.   An electric apparatus comprising the power supply device according to claim 1.   The electric apparatus according to claim 4, wherein the electric apparatus is a liquid crystal television. A safety protection circuit provided in a power supply device including a rectifier and a smoothing capacitor for smoothing a pulsating voltage output from the rectifier,
A series circuit composed of a ferrite bead or coil and a surge absorber connected in parallel to the smoothing capacitor;
A capacitor connected in parallel to the surge absorber;
With fuse,
A safety protection circuit, wherein when the surge absorber is broken in a short mode, a current is supplied to the surge absorber through the fuse.

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