JP4612855B2 - Power supply apparatus provided with AC overvoltage protection means for cutting off AC voltage input when overvoltage is input - Google Patents

Description

  The present invention is a power supply apparatus that uses an AC power supply as an input, and switches by a first rectifier element, a smoothing circuit including a capacitor, a current flowing in a transformer winding based on a voltage from the capacitor, and a switching element. The present invention relates to a power supply device that blocks input of an AC voltage by an AC overvoltage protection circuit when an overvoltage is input as a voltage.

  2. Description of the Related Art Conventionally, a power supply device having overvoltage protection means for various devices using a commercial AC power supply as an input power source such as an LBP (laser beam printer) or a copying machine has been proposed. For example, the power supply device described in Patent Document 1 can be reliably cut off with a varistor energization capacity in a power supply device that inputs AC power from one commercial AC power supply line and supplies voltage to one or more loads in parallel. A dedicated fuse with a proper rating is used as overcurrent interrupting means, and this overcurrent interrupting means is connected in series to a varistor as overvoltage limiting means to constitute an overcurrent interrupting overvoltage protection circuit.

  Further, for example, Patent Document 2 discloses an example in which an aluminum electrolytic capacitor is used as a power supply device and attention is paid to the problems of the aluminum electrolytic capacitor. This patent document 2 describes a large aluminum electrolytic capacitor used for a rectifying and smoothing circuit in a relatively large capacity switching power supply device used for a system device having both a control system and a drive system such as a copying machine. It is possible to extend the service life of the battery and to provide means for enabling the management of the service life of these.

  FIG. 1 is a configuration diagram for explaining a conventional power supply device having an overvoltage protection means. In the figure, reference numeral 101 is an AC inlet, 102 is a fuse, 103 is a common mode coil, 104 is a rectifier diode bridge, and 105 is 1 The next smoothing electrolytic capacitor, 106 is a starting resistor, 107 is a switching FET, 108 is a transformer, 109 is a power supply IC, 110 is a choke coil, 111 is a smoothing capacitor, 112 is a photocoupler, and 113 is a shunt regulator.

  As a normal operation, the AC power input from the AC inlet 101 is full-wave rectified through the rectifier diode bridge 104 and charged to the primary smoothing electrolytic capacitor 105. Further, the power supply IC 109 is started through the starting resistor 106, the switching FET 107 is operated, and the operation is started by passing a current through the transformer 108. When the transformer 108 is operated, the power supply of the power supply IC 109 created by the auxiliary winding of the transformer is supplied, the power supply IC 109 can continue to operate, and the switching FET I07 can be switched. Thus, the transformer 108 can continue to operate stably.

  Further, the secondary side voltage transformed by the transformer 108 is smoothed by the choke coil 110 and the smoothing capacitor 111 to output a stable DC output. In the DC output voltage control, a feedback signal is generated by the shunt regulator 113 and the photocoupler 112, fed back to the power supply IC 109, and the switching duty of the switching FET 107 is changed, so that the stable DC output voltage can be controlled.

  In such a conventional power supply device, it is assumed that AC overvoltage input is performed. For example, when the primary smoothing electrolytic capacitor 105 uses a DC200V product and an AC input voltage of 240V is applied from the AC inlet 101, the primary smoothing electrolytic capacitor 105 is charged with DC336V. The power supply device mainly operates in the following patterns (1) to (3).

  (1) Before the primary smoothing electrolytic capacitor 105 is opened due to breakdown withstand voltage, the switching FET 107 undergoes thermal destruction due to overcurrent, and the fuse 102 is blown by breaking in the short mode, and the AC input voltage is cut off. If

  (2) The case where the opening of the primary smoothing electrolytic capacitor 105 and the short-circuit breakdown of the switching FET 107 occur almost simultaneously, and the AC input voltage is cut off by the fuse 102 being blown accordingly.

  (3) When only the primary smoothing electrolytic capacitor 105 is opened and the fuse 102 is not blown and other circuit components continue to operate even when the electrolyte is ejected. In this case, when the primary smoothing electrolytic capacitor 105 is opened, the surroundings are contaminated with the electrolytic solution by ejecting the electrolytic solution.

  Note that when the AC line impedance is high, the current flowing through the power supply circuit is limited, so that the fuse 102 is not blown and the above-described pattern (3) is likely to occur.

  Also, depending on the country, there is an area where 100V and 200V AC voltages are mixed using the same power plug, and an AC voltage that causes a 200V AC input to be applied to a 100V power supply device. It can be said that the overvoltage is sufficiently generated.

  Here, the valve opening operation of the aluminum electrolytic capacitor will be described. An aluminum electrolytic capacitor is composed of an aluminum foil for a cathode, an electrolytic solution, and capacitor paper (electrolytic paper) using an oxide film formed on the surface of a high-purity aluminum foil for an anode as a dielectric. If a voltage exceeding the rated voltage is applied in the forward direction of the aluminum electrolytic capacitor, the leakage current will increase rapidly and heat will be generated, and the dielectric breakdown voltage will decrease due to the heat generation. Flows, and the pressure that is not in a short time rises and the pressure valve is activated. When the pressure valve is activated, the gasified electrolyte is violently discharged from the opened pressure valve portion. Since the energy of the capacitor is proportional to the square of the voltage, the higher the voltage, the more intense the valve opening operation.

JP 2000-134794 A JP 7-184373 A

  When such an aluminum electrolytic capacitor is used, even when an AC overvoltage exceeding the AC input voltage range of the power supply device has been applied, the primary smoothing electrolytic capacitor opens and the electrolyte is ejected. Will occur. It is necessary to solve such problems in consideration of regionality and process management.

  The present invention has been made in view of such problems. The object of the present invention is to add an AC overvoltage protection circuit to a conventional power supply circuit so that an AC overvoltage exceeding the AC input voltage range can be obtained. It is another object of the present invention to provide a power supply apparatus that solves the problem that the primary smooth electrolytic capacitor is opened and the electrolyte solution is ejected even when it is charged.

  The present invention has been made to achieve such an object, and the invention according to claim 1 includes a first rectifier element connected to an AC power input section, the AC power input section, and the first power supply. A power cut-off means that is connected in series between the rectifier element and cuts off an input from the AC power input section; and an AC voltage that is connected to the first rectifier element and is input from the AC power input section. A smoothing capacitor for smoothing, a switching element for switching a current flowing in the winding of the transformer based on a voltage from the smoothing capacitor, and a voltage from a first connection point of the first rectifying element and the smoothing capacitor And based on the voltage from the AC power input section side of the first rectifier element, the switching element is put into an overcurrent state by the power cutoff means from the AC power input section. AC overvoltage protection means for cutting off a force, wherein the AC overvoltage protection means includes a voltage breakdown element that operates based on a voltage from the first connection point, a voltage via the voltage breakdown element, and the first A time constant circuit for charging the voltage via the voltage breakdown element based on a voltage from the AC power supply input side of the rectifier element of the rectifier element to bring the switching element into an overcurrent state, and connected to the time constant circuit And when the overvoltage is input as the AC voltage input from the AC voltage input unit, before the smoothing capacitor is opened, the AC power cutoff means opens the AC rectifier. The input from the voltage input unit is cut off.

  According to a second aspect of the present invention, there is provided a first rectifier element connected to an AC power input unit, and the AC power source connected in series between the AC power input unit and the first rectifier element. Based on the power supply cutoff means for cutting off the input from the input unit, the smoothing capacitor connected to the first rectifying element and smoothing the AC voltage input from the AC power supply input unit, and the voltage from the smoothing capacitor A switching element for switching a current flowing through the winding of the transformer, a voltage from a second connection point on the first rectifying element side of the power cut-off means, and the AC power input side of the first rectifying element AC overvoltage protection means for shutting off the input from the AC power supply input section by the power shutoff means by setting the switching element to an overcurrent state based on the voltage from The voltage protection means is based on a voltage breakdown element that operates based on a voltage from the second connection point, a voltage via the voltage breakdown element, and a voltage from the AC power supply input side of the first rectifier element. A time constant circuit for charging the voltage via the voltage breakdown element to bring the switching element into an overcurrent state, and a second rectifier element connected to the time constant circuit, and the AC When an overvoltage is input as an AC voltage input from the voltage input unit, the input from the AC voltage input unit is cut off by the power cut-off means before the smoothing capacitor opens.

  The invention according to claim 3 further includes a shut-off means connected in series between the first rectifying element and the smoothing capacitor, and the AC overvoltage protection means causes the switching element to pass through. The input to the smoothing capacitor is cut off by the cut-off means when the current state is set.

  According to a fourth aspect of the present invention, the power shut-off means and the shut-off means are a fuse or a breaker.

  The invention according to claim 5 is characterized in that the voltage breakdown element is a varistor or a Zener diode.

  According to the present invention, even when an AC overvoltage exceeding the AC input voltage range is applied by adding an AC overvoltage protection circuit to a conventional power supply circuit, the primary smoothing electrolytic capacitor opens and the electrolyte solution Can be solved. In addition, even if the AC overvoltage protection circuit is detachable and the AC overvoltage protection circuit is removed, the AC overvoltage protection function is lost, but the power supply device has a feature of operating normally, so AC overvoltage protection is required. When shipping to a region, the AC overvoltage protection circuit is attached, and when unnecessary, it is possible to ship with the AC overvoltage protection circuit removed. For this reason, it is easy to manage the process, and it is possible to obtain a cost merit because the power supply device does not become overspec.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the first embodiment, an AC overvoltage protection circuit is added to a conventional general power supply device, so that the problem that the primary smoothing electrolytic capacitor opens and the electrolyte solution is ejected when the AC overvoltage is applied is prevented. It is.

  FIG. 2 is a circuit configuration diagram for explaining the first embodiment of the power supply device of the present invention, in which reference numeral 200 is an AC overvoltage protection circuit, 201 is a varistor, 202, 203, 207, 208 and 209 are resistors, 204 Indicates an electrolytic capacitor, 205 indicates a diode, and 206 indicates a capacitor. The other reference numerals 101 to 113 are the same as those shown in FIG. Note that DCH and DCL in the figure indicate a bipolar pattern of the primary smoothing capacitor 105 and are connected to DCH and DCL in the AC overvoltage protection circuit 200.

  The power supply apparatus according to the first embodiment includes an AC power input unit (AC inlet) 101, a rectifier diode bridge 104 that is a first rectifier connected to the AC power input unit 101, an AC power input unit 101, and the like. A fuse 102, which is a first overcurrent interrupting means inserted in series with the first rectifier element 104, a smoothing circuit connected to the first rectifier element 104 and composed of a capacitor 105, and The power supply circuit includes a switching FET 107 that performs current switching from the capacitor 105 through a transformer winding 108 using the capacitor 105 as a supply source.

  In addition, an AC overvoltage protection circuit 200 is connected to a first connection point a between the first rectifying element 104 and the capacitor 105, and the AC overvoltage protection circuit 200 is connected to a control input unit of the switching FET 107.

  The AC overvoltage protection circuit 200 includes a voltage breakdown element 201 connected to the first connection point a, time constant filters 202, 203, and 204 connected to the voltage breakdown element 201, and the time constant filter 202, A series connection circuit including a diode 205 which is a second rectifying element connected to 203 and 204 is provided.

  3A and 3B are diagrams showing an outline of a sequence of circuit operations in the power supply device shown in the first embodiment. FIG. 3A shows an output waveform of the diode bridge 104, FIG. 3B shows a voltage of the primary smoothing electrolytic capacitor 105, and FIG. ) Shows the voltage of the electrolytic capacitor 204, and (d) shows an enlarged view of the voltage of the electrolytic capacitor 204.

As an example, circuit operation will be described under the following conditions.
・ AC input voltage: 240V
Primary smoothing capacitor 105: DC 200V withstand voltage, abnormal voltage compatible product (in this case, the abnormal voltage compatible product is an example in which the valve does not open within 30 seconds when DC 350V is applied)
-Varistor 201: Varistor voltage DC270V product When assuming that the AC voltage 240V exceeding the rated voltage range of this power supply device is applied to the inlet 101, the primary smoothing electrolytic capacitor 105 starts to be charged to DC336V. Here, when the varistor 201 exceeds DC 270 V, which is a varistor voltage, conduction starts and charging of the electrolytic capacitor 204 is started. When the charged voltage exceeds the gate ON voltage of the switching FET 107, the drain-source of the switching FET 107 continues to conduct, resulting in an overcurrent state, the primary smoothing electrolytic capacitor 105 is opened, and the electrolyte is Before the ejection, the fuse 102 is blown to cut off the AC power supply.

  In this case, an indispensable condition as a time to be set in circuit constants and component selection is “a time until the AC overvoltage protection circuit 200 operates and the fuse 102 is blown <a valve opening time of the primary smoothing capacitor 105”. .

  The time setting until the fuse 102 is blown after the AC overvoltage protection circuit 200 is operated mainly includes the varistor voltage of the varistor 201, the resistance values of the resistors 202, 203, 207, and 208, the capacitance of the electrolytic capacitor 204, and the fuse. It is determined by the fusing time of 102 alone.

For example,
・ AC input voltage: Eac
-Varistor voltage of varistor 201: Ev
-Resistance value of resistor 202: R1
-Combined resistance value of resistors 203, 207, 208, and 209: R2
The combined resistance value of the resistors 202, 203, 207, 208, and 209: R
Electrostatic capacitor 204 capacitance value: C
-Voltage that the electrolytic capacitor will eventually charge: Ec
・ Gate ON voltage of switching FET107: Eg
・ Gate ON time of switching FET 107: tg
-Fusing time of fuse 102 alone: tf
Time until the AC overvoltage protection circuit 200 operates and the fuse 102 is blown: t
Assuming
Eg = Ec (1−exp ^ (− tg / (C × R)))
To tg = C × R × ln (Ec / (Ec−e))
It becomes.
That is, the time t until the AC overvoltage protection circuit 200 operates and the fuse 102 is blown is:
t = C × R × ln (Ec / (Ec−e)) + tf.

  Incidentally, since Ec = (Eac × 1.4−Ev) × (R2 / (R1 + R2)), constant setting of each component can be performed.

  It is necessary to determine the constant of each element so that this time t is shorter than the time when the primary smoothing capacitor opens. However, if the gate ON time tg of the switching FET 107 is set too short, the gate of the switching FET 107 is turned ON due to intrusion of noise or the like even if the power supply device is used with the AC power supply voltage within the rated range. Care must be taken in setting the time of tg. It is preferable to set the time mainly by adjusting the capacitance value of the electrolytic capacitor 204.

  Note that the fusing time of a single fuse varies depending on the fuse used. For example, EN 60127-2 S. S. If the fuse shows a time lag characteristic that conforms to 5 standards, when 4 times the current (25.2A) flows, 0.15 seconds to 5 seconds, and when 10 times the current (63A) flows, It is a standard that blows out in 0.02 seconds to 0.1 seconds.

  In addition, EN 60127-2 S. S. If the fuse shows fast-breaking characteristics conforming to 1 standard, when 4 times the current (25.2A) flows, 0.003 seconds to 0.3 seconds and 10 times the current (63A) flowed. It is a standard that blows out within 0.02 seconds. For this reason, since the fusing time varies depending on the selected fuse, it is necessary to be careful because the selection of the fuse greatly depends on the time until the fuse is blown after the AC overvoltage protection circuit operates.

  In addition, since the valve opening time and the valve opening voltage differ depending on the primary smoothing electrolytic capacitor having the same rated voltage, care must be taken when selecting components. Generally, if the product is listed as an abnormal voltage product in the manufacturer's catalog, the oxide film formed on the surface of the high-purity aluminum foil for the anode is thicker than the product that is not compatible with different voltage. Even when the voltage is 200V, the valve opens at a higher voltage. In the first embodiment, it is assumed that an abnormal voltage compatible product is used.

  Further, a Zener diode may be used as a voltage breakdown element in place of the varistor 201, and the same effect as in the first embodiment can be obtained even if a current breaker is used in place of the fuse 102.

  FIG. 4 is a circuit configuration diagram for explaining a second embodiment of the power supply device of the present invention, in which reference numeral 114 denotes a fixing device, and 115 denotes a fuse which is a second overcurrent interruption means. In addition, the same components as those in FIG. 2 are denoted by the same reference numerals. In addition to the fuse 102 connected in series with the AC inlet 101, a fuse 115 serving as a second overcurrent blocking means inserted in series between the rectifier diode bridge 104 and the primary smoothing electrolytic capacitor 105 is provided. . Reference numeral 114 denotes an AC input type heating fixing device used in an electrophotographic printer or the like.

  Also in the case of the circuit configuration in the second embodiment, as in the first embodiment, when an AC overvoltage is input, the primary smoothing electrolytic capacitor 105 starts to be charged, and when the varistor 201 exceeds the varistor voltage, conduction is started. The capacitor 204 starts to be charged. When the charged voltage exceeds the gate ON voltage of the switching FET 107, the drain and source of the switching FET 107 continue to conduct, and as a result, an overcurrent state occurs and the primary smoothing electrolytic capacitor 105 opens, and the electrolyte solution Is blown out, the fuse 115 or the fuse 102 is blown to cut off the AC power supply.

  In such a case, the fuse conforming to the safety standard required for the ITE equipment (information technology equipment; information technology equipment, information processing equipment, etc.) is constituted by the fuse 102, and the fuse 115 is provided by the AC overvoltage protection circuit 200. It is possible to select parts considering only the operation. For this reason, the fuse 115 can be selected with cost-effective parts such as a fuse resistor.

  Further, even if a Zener diode is used as a voltage breakdown element in place of the varistor 201 or a current breaker is used in place of the fuse 102, the same effect as in the second embodiment can be obtained. Other configurations are the same as those of the first embodiment described above.

  FIG. 5 is a circuit configuration diagram for explaining a third embodiment of the power supply device of the present invention, in which the connection from the varistor 201 of the AC overcurrent protection circuit unit 200 is connected to one end (connection point b) of the fuse 102. Is. In addition, ACH connected to one end (connection point b) of the fuse 102 in the figure and ACH in the AC overvoltage protection circuit 200 are connected.

  That is, the AC overvoltage protection circuit 200 includes a voltage breakdown element 201 connected to the second connection point b, time constant filters 202, 203, and 204 connected to the voltage breakdown element 201, and the time constant filter 202, A series connection circuit including a diode 205 which is a second rectifying element connected to 203 and 204 is provided.

  Even if a Zener diode is used as a voltage breakdown element in place of the varistor 201, or a current breaker is used in place of the fuse 102, the same effect as in the third embodiment is obtained. Other configurations and effects are the same as those of the first embodiment described above.

  FIG. 6 is a circuit configuration diagram for explaining a power supply device according to a fourth embodiment of the present invention. In addition to the fuse 102 connected in series with the AC inlet 101, a rectifier diode bridge 104 and a primary smoothing electrolytic capacitor 105 are shown. Is provided with a fuse 115 which is a second overcurrent interruption means inserted in series.

  Reference numeral 114 denotes an AC input type heating fixing device used in an electrophotographic printer or the like. Further, the connection from the varistor 201 of the AC overcurrent protection circuit unit 200 is connected to one end of the fuse 102. In addition, ACH connected to one end (connection point b) of the fuse 102 in the figure and ACH in the AC overvoltage protection circuit 200 are connected.

  Also in the case of the circuit configuration of the fourth embodiment, when the AC overvoltage is inputted as in the first embodiment, the primary smoothing electrolytic capacitor 105 starts to be charged, and when the varistor 201 exceeds the varistor voltage, the conduction is started. The capacitor 204 starts to be charged. When the charged voltage exceeds the gate ON voltage of the switching FET 107, the drain and source of the switching FET 107 continue to conduct, and as a result, an overcurrent state occurs and the primary smoothing electrolytic capacitor 105 opens, and the electrolyte is ejected. Before the operation, the fuse 115 or the fuse 102 is blown to cut off the AC power supply.

  Also in this case, as in the second embodiment, the fuse conforming to the safety standard required for the ITE device is configured by the fuse 102, and the fuse 115 can be selected in consideration of only the operation of the AC overvoltage protection circuit 200. Become. For this reason, the fuse 115 can be selected with cost-effective parts such as a fuse resistor.

  Further, even if a Zener diode is used as a voltage breakdown element instead of the varistor 201, or a current breaker is used instead of the fuse 102, the same effect as in the fourth embodiment can be obtained. Other configurations are the same as those of the first embodiment described above.

  7 to 9 are configuration diagrams for explaining a fifth embodiment of the power supply device of the present invention, in which the AC overvoltage protection circuit 200 is detachable as an independent sub board. It is assumed that the AC overvoltage protection function is lost even when the AC overvoltage protection circuit 200 is removed, but the power supply device operates normally.

  That is, in the power supply device of the fifth embodiment, only the series connection circuit portion including the voltage breakdown element 201, the time constant filters 202, 203, and 204 and the second rectifier element 205 is mounted as a sub board, In this case, the connection with the daughter board can be attached and detached, and the operation can be performed regardless of whether the daughter board is attached or detached.

  By doing in this way, it ships with the AC overvoltage protection circuit 200 attached to an area where AC overvoltage protection is required, and ships without attaching the AC overvoltage protection circuit 200 to an area where AC overvoltage protection is unnecessary. As a result, it is possible to provide a power supply device that matches the local power supply state. From this, it is excellent also in process management, and the cost can be reduced by making the AC overvoltage protection function removable.

  FIG. 7 is a configuration diagram showing an example in which a child board of an AC overvoltage protection circuit is mounted on a power supply device with solder terminals. In this way, mounting the sub-boards upright also leads to space saving. However, as a matter of course, when the space is sufficient, the embodiment in which the sub-board is mounted without standing is also applied in this embodiment.

  FIG. 8 is a configuration diagram showing an example in which a child board of an AC overvoltage protection circuit is connected to the power supply device by a board-to-board connector. In this way, the child board is raised and connected to the power supply device through a connector, which leads to space saving. However, as a matter of course, when there is a sufficient space, the embodiment in which the power supply device and the connector are connected without standing the sub board is also applied in the fifth embodiment.

  FIG. 9 is a configuration diagram showing an example in which a sub-board of the AC overvoltage protection circuit is connected using a power supply device and a harness connector. Even when there is no space for placing the sub board in the power supply device, it can be placed in another space as shown in FIG.

It is a block diagram for demonstrating the power supply device provided with the conventional overvoltage protection means. It is a circuit block diagram for demonstrating Example 1 of the power supply device of this invention. FIG. 3 is a diagram illustrating an outline of a sequence of circuit operations in the power supply device illustrated in the first embodiment. It is a circuit block diagram for demonstrating Example 2 of the power supply device of this invention. It is a circuit block diagram for demonstrating Example 3 of the power supply device of this invention. It is a circuit block diagram for demonstrating Example 4 of the power supply device of this invention. It is a block diagram for demonstrating Example 5 of the power supply device of this invention, and is the block diagram which showed the example which mounted the child board | substrate of the AC overvoltage protection circuit on the power supply device with the solder terminal. It is a block diagram for demonstrating Example 5 of the power supply device of this invention, and is the block diagram which showed the example which connected the sub board | substrate of the AC overvoltage protection circuit to the power supply device with the board to board connector. It is a block diagram for demonstrating Example 5 of the power supply device of this invention, Comprising: It is the block diagram which showed the example which connected the subunit | substrate of the AC overvoltage protection circuit using the power supply device and the harness connector.

Explanation of symbols

101 AC inlets 102 and 115 Fuse 103 Common mode coil 104 Rectifier diode bridge 105 Primary smoothing electrolytic capacitor 106 Starting resistor 107 Switching FET
108 Transformer 109 Power supply IC
110 Choke coil 111 Smoothing capacitor 112 Photocoupler 113 Shunt regulator 114 Fixing device 200 AC overvoltage protection circuit 201 Varistor 202, 203, 207, 208, 209 Resistor 204 Electrolytic capacitor 205 Diode 206 Capacitor

Claims (5)

A first rectifier connected to an AC power input;
A power shut-off means connected in series between the AC power input section and the first rectifying element, and shuts off an input from the AC power input section ;
A smoothing capacitor connected to the first rectifying element and smoothing an AC voltage input from the AC power supply input unit ;
A switching element for switching a current flowing in the winding of the transformer based on the voltage from the smoothing capacitor;
Based on the voltage from the first connection point of the first rectifying element and the smoothing capacitor and the voltage from the AC power input section side of the first rectifying element, the switching element is put into an overcurrent state. AC overvoltage protection means for shutting off the input from the AC power input unit by the power shutoff means,
With
The AC overvoltage protection means includes:
A voltage breakdown element that operates based on a voltage from the first connection point;
When charging the voltage via the voltage breakdown element based on the voltage via the voltage breakdown element and the voltage from the AC power supply input side of the first rectifying element to bring the switching element into an overcurrent state A constant circuit;
A second rectifying element connected to the time constant circuit;
And when the overvoltage is input as the AC voltage input from the AC voltage input unit, before the smoothing capacitor is opened, the input from the AC voltage input unit is input by the power shut-off means. Cut off
A power supply device characterized by that. A first rectifier connected to an AC power input;
A power shut-off means connected in series between the AC power input section and the first rectifying element, and shuts off an input from the AC power input section;
A smoothing capacitor connected to the first rectifying element and smoothing an AC voltage input from the AC power supply input unit;
A switching element for switching a current flowing in the winding of the transformer based on the voltage from the smoothing capacitor;
Based on the voltage from the second connection point on the first rectifying element side of the power shut-off means and the voltage from the AC power supply input side of the first rectifying element, the switching element is placed in an overcurrent state. AC overvoltage protection means for shutting off the input from the AC power input unit by the power shutoff means,
With
The AC overvoltage protection means includes:
A voltage breakdown element that operates based on a voltage from the second connection point;
When charging the voltage via the voltage breakdown element based on the voltage via the voltage breakdown element and the voltage from the AC power supply input side of the first rectifying element to bring the switching element into an overcurrent state A constant circuit;
A second rectifying element connected to the time constant circuit;
And when the overvoltage is input as the AC voltage input from the AC voltage input unit, before the smoothing capacitor is opened, the input from the AC voltage input unit is input by the power shut-off means. A power supply device that is cut off . Furthermore, it comprises a shut-off means connected in series between the first rectifying element and the smoothing capacitor, and the shut-off means causes the switching element to be in an overcurrent state by the AC over-voltage protection means. The power supply device according to claim 1, wherein an input to the smoothing capacitor is cut off . The power supply apparatus according to any one of claims 1 to 3, wherein the power cutoff unit and the cutoff unit are a fuse or a breaker . The power supply apparatus according to claim 1, wherein the voltage breakdown element is a varistor or a Zener diode .

Images