JP2000134794A - Power supply equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overvoltage protective means which surely cuts off the current, when 200 V is input to a 100 V power supply by mistake and which can use a varistor of a small capactance at the optimum voltage and secures the maximum margin at low cost. SOLUTION: An overcurent cut-off overvoltage protective section 101 is a series combination of a fuse 102, an overcurrent cut-off means, and a metal oxide varistor 103 and is inserted between the AC power lines immediately after a breaker 203 or between the lines at the shunt nodes from which current is branched for each AC load, just after a line filter 205. The fuse 102 has a characteristic that surge energy is smaller than Joule integral. The Joule- integral is set so that the fuse will not melt with energy caused by instantaneous current. The current rating of the fuse 102 is set to not more than the on-state current, when the varistor 103 is in an on-state with overvoltage, for example, 6.3 A. A connection node between the fuse 102 and the varistor 103 may be set as the input position of an AC/DC converter 207.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having overvoltage protection means for various devices using a commercial AC power supply such as an LBP (laser beam printer) as an input power supply.

[0002]

2. Description of the Related Art Conventionally, one commercial AC such as LBP is used.
(AC) In a power supply device that inputs power from a power supply line and supplies voltage to multiple AC loads in parallel, protection of the device including operation from transient overvoltage such as lightning surge generated by lightning and power line noise An AC power supply input unit as shown in FIG.

[0003] The prior art will be described below with reference to FIG.
Reference numeral 201 denotes a commercial AC power supply.
There are two types of power supplies: 00-120V / 50-60Hz (hereinafter referred to as 100V system) and single-phase 220-240V / 50-60Hz (hereinafter referred to as 200V system). 2
A power switch SW (switch) 02 switches the current from the AC power supply line to 0N / 0FF. A breaker 203 monitors the current of the entire apparatus, and cuts off the current when the current exceeds the rated current. A metal oxide varistor 204 is connected between the AC power supply lines. A line filter 205 suppresses passage of a common mode high-frequency current.

[0004] 206 is a converter fuse, 207 is an AC / DC converter for converting AC to DC, and 208 is a control unit. The AC / DC converter 207 is a control unit 2
08 to supply a DC voltage to the converter fuse 206.
When the AC current supplied to them exceeds the rated current,
Cut off AC current. Reference numeral 209 denotes a heater control circuit, which is one of the AC loads, and controls the energization of a halogen heater disposed in, for example, a fixing unit (not shown) in the LBP.

In the above configuration, the metal oxide varistor 204 inserted between the AC power supply lines is a varistor 0N
A function as an overvoltage limiting means of conducting when a voltage higher than the voltage is applied between the AC power supply lines, and limiting a rise in the voltage between the AC power supply lines to a varistor ON voltage by the supplied current and the line impedance. Demonstrate.

Further, the metal oxide varistor 204 has a property of being deteriorated by repeated application of a surge current, and has a certain life. Further, the metal oxide varistor 204 may fail due to an overcurrent such as the application of a different voltage as in the case where a 200 V power supply is turned on to a 100 V power supply.
In the event of a short-circuit failure in No. 4, safety measures are taken to shut off the current and prevent a fire by an abnormal current cut-off means such as a breaker 203 arranged on the AC input section upstream of the short-circuit mode.

[0007]

However, for example, with recent LBP colorization, it is necessary to increase the power of the fixing heater, thereby increasing the current capacity of the breaker 203 of the AC power supply input section. In this case, the ratio between the residual impedance when the varistor is ON and the ON current decreases, and the breaker cutoff time relatively increases.

As a result, by the time of production of the device,
In the case where a 200 V power input is applied to a 0 V power supply, if the breaker cutoff time is long as described above, the power input is stopped before the breaker is cut off, and an overvoltage stress is applied to the varistor. There was a risk that the product could be shipped without detecting the fact.

When a varistor with a high varistor ON voltage is used to avoid the above-mentioned problem, the problem of overvoltage stress deterioration of the varistor can be avoided, but the overvoltage limiting performance is reduced by that much, and a primary smoothing capacitor or the like is used. There is a problem to be solved that overvoltage stress on other components cannot be avoided.

[0010] An object of the present invention is to solve the above-mentioned problems, for example, by increasing the fixing heater power, increasing the current capacity of the breaker in the AC power input section, and increasing the residual impedance at the time of varistor 0N during overvoltage. The present invention provides a power supply device equipped with an overvoltage ON current interrupting means that is optimal for a varistor to be used even in a situation where the ratio of the ON current to the varistor decreases and the breaker interrupting time relatively increases. is there.

A further object of the present invention is to realize a low-cost power supply device which allows the use of a small-capacity varistor at an optimum voltage and has a high degree of design freedom.

A further object of the present invention is to ensure that even if a 200 V power supply is input to a 100 V power supply unit by mistake during the production of the device, the current is reliably interrupted and the varistor is subjected to overvoltage stress. An object of the present invention is to surely avoid the risk that has occurred in the prior art that a product is shipped without being able to detect the fact of adding the above.

A further object of the present invention is to provide a low-cost and maximum margin in an apparatus using a low-voltage power supply having a small capacity (6.3 A or less) in comparison with a large-capacity heater control circuit. It is another object of the present invention to provide a power supply device provided with an overcurrent interruption overvoltage protection means. That is, one of the objects of the present invention is to provide safe and inexpensive overcurrent protection and overvoltage protection for an apparatus that combines a plurality of loads such as a fixing heater power supply control unit and a switching power supply unit.

[0014]

To achieve the above object, according to the present invention, there is provided a power supply apparatus for inputting from one commercial AC power supply line and supplying a voltage to one or a plurality of loads in parallel. The overcurrent cutoff means is connected in series to the overvoltage limit means to constitute overcurrent cutoff overvoltage protection means, and the overcurrent cutoff overvoltage protection means is disposed between the current shunt node or the upstream line thereof. .

Here, the connection position of the overcurrent interruption means of the overcurrent interruption overvoltage protection means can be different from the current path of the load.

In order to achieve the above object, a third aspect of the present invention is a power supply apparatus which receives an input from one commercial AC power supply line and supplies a voltage to a plurality of loads in parallel. The overcurrent cutoff overvoltage protection means is constituted by connecting in series, the overcurrent cutoff means of the overcurrent cutoff overvoltage protection means is partially used as a load overcurrent cutoff means, and the overcurrent cutoff overvoltage protection means is connected to a current shunt node. It is characterized by being arranged between lines.

Preferably, the overcurrent cutoff means of the overcurrent cutoff overvoltage protection means has a surge energy <
It is a time lag fuse that is a Joule integral value.

[0018] Preferably, the overvoltage limiting means is a metal oxide varistor.

Preferably, the power supply device is a power supply device for a device using a combination of a low-voltage power supply having a small capacity as compared with a large-capacity heater control circuit.

Preferably, the device is a device obtained by combining a plurality of loads such as a fixing heater power supply control unit and a switching power supply unit.

Preferably, the device is a color L
BP.

[0022]

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

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
1 shows a schematic configuration of an AC input unit according to the first embodiment, and the components having the same functions as those in FIG. 2 of the above-described conventional example are denoted by the same reference numerals, and redundant description thereof will be omitted.

Here, reference numeral 101 denotes an overcurrent cutoff overvoltage protection section (overcurrent cutoff overvoltage protection means) which is the most important configuration of the present invention.
2 is connected in series to the metal oxide varistor 103 and is connected between the AC power supply lines immediately after the breaker 203.

The metal oxide varistor 103 is a ceramic containing zinc oxide as a main component, for example, NV470D10 manufactured by NEC Corporation. The fuse 102 has a characteristic of surge energy <Joule integral value, and the Joule integral value of the fuse is set so as not to be blown by energy due to instantaneous current such as lightning surge. The current rating of the fuse 102 is set to be equal to or less than the ON current of the metal oxide varistor 103 when the overvoltage is ON.

In this embodiment, as an example, the voltage of the commercial AC power supply 201 is 100 V, the load of the heater control circuit 209 is 900 W, and the load of the AC / DC converter 207 is 2
The current rating of the breaker 203 through which the current supplied to both loads flows is 16 A. On the other hand, AC
The current rating of the fuse 206 connected immediately before the / DC converter 207 is 6.3 A, and the upper limit value of the abnormal current of the AC / DC converter 207 is kept low.

In such a configuration, the fuse 102 serving as the overcurrent cutoff means of the overcurrent cutoff overvoltage protection unit 101
Is set to 6.3 A, the current rating of the conventional metal oxide varistor 204 (FIG. 2)
The breaking current when the metal oxide varistor is ON can be set low,
In accordance with the ON current of the varistor to be used, the cutoff characteristics can be secured with a margin.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
1 shows a schematic configuration of an AC power input unit according to the embodiment;
Components having the same functions as those of FIG. 2 of the conventional example and FIG. 1 of the first embodiment of the present invention are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 3, reference numeral 301 denotes an overcurrent cutoff overvoltage protection unit (overcurrent cutoff overvoltage protection means) similar to 101 in the first embodiment, and a fuse 102 serving as an overcurrent cutoff means is replaced with a metal oxide varistor. 103 is connected in series.

The feature of the second embodiment is that the overcurrent cutoff overvoltage protection section 301 is connected between the lines of the branch nodes to each AC load immediately after the line filter 205.

The unique effect of this configuration is that the overcurrent cutoff overvoltage protection section 301 is connected to the position closest to the AC load, so that it can be compared with a surge voltage between lines such as a triac used in the heater control circuit 209. In circuits that are weak and generate undesirable phenomena such as false ignition, the effect of flyback voltage due to the residual inductance of the common mode choke of the line filter 205 can be minimized, and the maximum margin can be secured. The point that can be.

(Third Embodiment) FIG. 4 shows a third embodiment of the present invention.
1 shows a schematic configuration of an AC power input unit according to the embodiment;
Components having the same functions as those of the conventional example shown in FIG. 2 and the first and second embodiments of the present invention shown in FIGS. 1 and 3 are denoted by the same reference numerals, and redundant description is omitted.

In FIG. 4, reference numeral 401 denotes an overcurrent cutoff overvoltage protection unit (overcurrent cutoff overvoltage protection means) similar to 301 of the second embodiment, wherein the fuse 102 serving as the overcurrent cutoff means is replaced with a metal oxide varistor. 103 is connected in series.

As a feature of the third embodiment, the overcurrent cutoff overvoltage protection unit 401 is connected immediately after the line filter 205 and at a position between the lines of the shunt nodes of each load similarly to the second embodiment. However, the input position of the AC / DC converter 207 is set to a connection node between the fuse 102 and the metal oxide varistor 103 which are the overcurrent cutoff means.

As a specific effect of this configuration, AC / DC
By setting the input position of converter 207 to the connection node between fuse 102 and the metal oxide varistor 103, which are the overcurrent cutoff means of overcurrent cutoff overvoltage protection unit 401, fuse 206 for AC / DC converter 207 in the conventional example (FIG. 2) can also be used as the fuse 102 of the overcurrent interruption overvoltage protection unit 401, and has a smaller capacity (6.3) than the large capacity heater control circuit 209 like LBP.
A or less) in a device using a low-voltage power supply (AC / DC converter 207)
An advantage of the present invention is that an overvoltage power supply protection unit that secures a maximum margin can be provided as in the embodiment.

(Other Embodiments) In the above embodiment, the power supply device applied to the LBP has been described as an example.
The present invention is not limited to this, and it is needless to say that the present invention can be applied to power supply devices of various devices that input commercial AC power, such as electrophotographic printers other than LBP.

The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.).
The present invention may be applied to a device including two devices (for example, a printer, a copier, a facsimile device, and the like).

[0038]

As described above, according to the present invention,
In a power supply device that inputs AC power from one commercial AC power supply line and supplies a voltage to one or more loads in parallel, a dedicated fuse with a rating that can be reliably cut off with a varistor conduction capacity is used as overcurrent cutoff means. The overcurrent protection circuit is connected in series to a varistor serving as a limiting means, and the overcurrent protection circuit is provided between the current shunt node and the upstream line. As a result, the fixing heater power needs to be increased, the current capacity of the breaker in the AC power input section increases, the ratio of the ON current due to the residual impedance at the time of varistor 0N during overvoltage decreases, and the breaker is relatively cut off. Even in a situation where the time is increased, it is possible to provide an overcurrent ON current interrupting means optimal for a varistor to be used.

Further, according to the present invention, it is possible to use a small-capacity varistor at an optimum voltage, thereby realizing a low-cost configuration with a high degree of design freedom.

Therefore, according to the present invention, even if the input of the 200V power supply is accidentally applied to the 100V power supply device during the production of the device, the current is reliably cut off.
It is possible to avoid a risk that occurs in the related art, such as the fact that a product is shipped without being able to detect the fact that the varistor has been subjected to overvoltage stress.

Further, according to the present invention, in a power supply device for inputting power from one commercial AC power supply line and supplying a voltage to a plurality of loads in parallel, the overcurrent cutoff means is connected in series to the overvoltage limit means. The overcurrent protection means constitutes overcurrent protection means, and the overcurrent protection means of the overcurrent protection overvoltage protection means also serves as a load overcurrent protection means having a current rating or less, and the overcurrent protection means is connected between the current shunt node lines. By using a low-voltage power supply having a small capacity (6.3 A or less) in combination with a large-capacity heater control circuit such as an LBP, a low-cost and maximum margin is secured. An overcurrent interruption overvoltage protection means can be provided.

Therefore, according to the present invention, the overcurrent protection and the overvoltage protection of an apparatus which combines a plurality of loads such as a fixing heater conduction control section and a switching power supply section, such as an LBP, can be safely and inexpensively configured. Means can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a schematic configuration of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a schematic configuration of a conventional power supply device.

FIG. 3 is a circuit diagram illustrating a schematic configuration of a power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram illustrating a schematic configuration of a power supply device according to a third embodiment of the present invention.

[Explanation of symbols]

101, 301, 401 Overcurrent cutoff overvoltage protection section (overcurrent cutoff overvoltage protection means) 102 Fuse (overcurrent cutoff means) 103 Metal oxide varistor (overvoltage limit means) 201 Commercial AC power supply line 202 Power supply SW 203 Breaker 204 Metal oxidation Object varistor 205 Line filter 206 Converter fuse 207 AC / DC converter 208 Control unit 209 Heater control circuit

Claims (8)

[Claims] 1. An input from one commercial AC power line,
In a power supply device for supplying a voltage to one or a plurality of loads in parallel, an overcurrent cutoff means is connected in series with an overvoltage limit means to constitute an overcurrent cutoff overvoltage protection means, and the overcurrent cutoff overvoltage protection means is provided with a current. A power supply device provided between a branch node and an upstream line thereof. 2. The power supply device according to claim 1, wherein a connection position of the overcurrent cutoff means of the overcurrent cutoff overvoltage protection means is different from a current path of a load. 3. An input from one commercial AC power line,
In a power supply device for supplying a voltage to a plurality of loads in parallel, an overcurrent cutoff means is connected in series with an overvoltage limit means to constitute an overcurrent cutoff overvoltage protection means, and an overcurrent cutoff means of the overcurrent cutoff overvoltage protection means is provided. A power supply device characterized in that some of the power supply devices also function as load overcurrent cutoff means, and the overcurrent cutoff overvoltage protection means is disposed between the current shunt node lines. 4. The overcurrent cutoff means of the overcurrent cutoff overvoltage protection means is a time lag fuse having a surge energy <Joule integral value.
4. The power supply device according to any one of items 3 to 3. 5. The power supply device according to claim 1, wherein the overvoltage limiter is a metal oxide varistor. 6. The power supply device according to claim 1, wherein the power supply device is a power supply device for a device that uses a combination of a low-voltage power supply having a small capacity as compared with a large-capacity heater control circuit.
The power supply device according to any one of the above. 7. The power supply device according to claim 6, wherein the device is a device obtained by combining a plurality of loads such as a fixing heater conduction control unit and a switching power supply unit. 8. The power supply device according to claim 6, wherein the device is a color LBP.