JP3392915B2 - Power supply for electronic equipment - Google Patents

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 for use in electronic equipment such as office automation equipment and the like, which converts alternating current into direct current, and more particularly, to destroy an electric circuit fed from the power supply device by an internal or external surge voltage. The present invention relates to a surge voltage absorption circuit for preventing.

[0002]

2. Description of the Related Art A general surge voltage absorption circuit is disclosed in FIG. 1 of Japanese Utility Model Laid-Open No. 63-198384.
Varistors are inserted between the AC input terminals or between the AC input terminal and ground.

[0003] This kind of service - di voltage absorbing circuit will be described with reference to the prior art shown in FIG. For convenience of description, the hot line H will be described as a line L and the varistor ZNR1 will be described as B1. The power supply for electronic equipment such as office automation equipment is downsized,
A switching regulator system has been adopted to meet the demands for weight reduction and high efficiency. The switching regulator is smaller, lighter, and more efficient than the conventional dropper type because the converter transformer T1 is driven at a high frequency (50KHz to 200KHz) and the loss is small due to intermittent control. In recent years, most of the power supplies for electronic equipment such as office automation equipment adopt the switching regulator method.

[0004]

However, even such a switching regulator has the following problems. For example, there is an intrusion of an induced surge voltage due to a lightning strike, an intrusion of a surge voltage due to turning on and off of a high power electronic device such as a machine tool and an air conditioner. If these surge voltages enter between the AC input line L / neutral N, line L / frame ground FG (ground), and neutral N / frame ground FG, the surge voltage may reach 10 KV in some cases. As a result, there is a risk that semiconductor elements such as switching transistors will be destroyed.

Further, the switching regulator itself generates noise. Although a snubber circuit (D1, R1, C5) is provided near the switching element that generates noise to reduce the noise, it is also necessary to reduce noise at the AC input section in order to suppress noise flowing from the AC input terminal to the outside of the power supply. is there. In order to reduce these, a noise filter (across the line capacitor C1, a common mode choke coil L1, a line bypass capacitor C2,
C3 and a metal oxide varistor B1) arranged between the AC inputs L / N are provided to absorb and reduce inflow / outflow noise and surge voltage. The noise filter arranged in this way not only suppresses conduction noise (noise terminal voltage), radiation noise (electric field, magnetic field) and surge voltage that flow out from the switching power supply to the outside, but also suppresses noise and surge voltage from the outside. It also has the role of protecting electronic devices against intrusion. The energy of the normal mode surge voltage that has entered between the lines L / N connected to the AC input terminal is clamped by each element of these noise filter elements, and particularly by the varistor voltage of the metal oxide varistor B1 which is a bidirectional element. Most of the surge voltage energy is absorbed inside the varistor. Arranged to be in parallel with the line bypass capacitors C2 and C3 of the noise filter unit and with respect to the common mode surge voltage that enters between the AC input line L / frame ground FG and between the AC input neutral N / frame ground FG. The metal oxide varistors ZNR2 and ZNR3 thus produced are expected to have a surge voltage absorption effect. However, these elements (line bypass capacitors C2, C3, zinc oxide varistors ZNR2, ZNR3) have a large leak current, which may cause problems such as exceeding the leak current standard and increasing the risk of electric shock. Moreover, if the external surge voltage energy is applied within more than tolerance of the metal oxide varistor ZNR2, ZNR3, because failure in metal oxide varistor is short mode, in the conventional case shown in FIG. 3, only the failure of the power supply circuit Instead, it becomes a ground fault of the primary line, which poses a serious problem in terms of safety and reliability of electronic equipment including the power supply circuit, such as fire and electric shock.

An object of the present invention is to provide a power supply device for electronic equipment such as OA equipment which is highly safe and reliable without damage to semiconductors or the like even if an internal and external surge voltage is intruded by a lightning strike or the like. It is what More specifically, common mode,
The purpose is to improve the withstand voltage of external surge voltage in normal mode.

[0007]

One embodiment of the present invention is
Overcurrent protection fuse connected to AC input terminals (L, N)
(F ₁₎ and, the Fyn -'s and (F ₁₎ for rectifying smoothing an AC input via a rectifying and smoothing circuit (D), DC-DC converter for converting the unstable DC rectified smoothed stabilized direct current output And a noise filter circuit (2) including a surge voltage absorption circuit arranged between the AC input terminals (L, N) and the rectifying and smoothing circuit (D).
In the power supply device for electronic equipment including, the surge voltage absorbing circuit, one end is electrically continuous to the line to which the fuse (F ₁ ) for overcurrent protection is connected, and the other end is a frame. A first series circuit of a constant voltage element (A ₅ ) and a metal oxide varistor (B ₄ ) that are electrically continuous to the ground (FG) and are composed of discharge electrodes, and a pair of AC input terminals in electrically continuous at one end to the other one there is electrically continuous and the other end to the frame ground
And in series with the first series circuit between the pair of AC input terminals
Is connected, a second series circuit between the metal oxide varistor (B ₅₎ constant voltage element (A ₆₎ consisting of separate discharge electrodes and the elements of the first series circuit, and the pair of AC input Another metal oxide varistor (B ₁ ) disposed between the ends. The symbols in parentheses refer to corresponding elements in the embodiments shown in the drawings.

[0008]

[Function] One of the AC input terminals L / frame ground FG
If a common-mode surge voltage invades between the AC input terminals or another N / frame ground FG,
Line L / first series circuit of constant voltage element (A ₅ ) and metal oxide varistor (B ₄ ) / path of frame ground FG,
Alternatively, the surge energy is absorbed through the path of the second series circuit of the line N / constant voltage element (A ₆ ) and the metal oxide varistor (B ₅ ) / frame ground FG. Since the metal oxide varistor (B ₄ ) and (B ₅ ) of each series circuit conducts at a low voltage, most of the common mode surges are generated by the constant voltage element (A
₅ ) and (A ₆ ) are absorbed. Therefore, the metal oxide varistor (B ₄ ) and (B ₅ ) in each series circuit is light but there is no possibility of damage. In addition, these metal oxide varistors (B ₄ ) and (B ₅ )
Is a constant voltage device (A ₅ ) and (A ₆ ) after the surge voltage is absorbed
Since the follow current due to is cut off in a short time, only excessive surge voltage can be absorbed efficiently, reliably and safely.

Normal mode surge between lines L and N
If a voltage comes in, surge response as a constant voltage element
The varistor voltage of a metal oxide varistor (B ₁ ) with excellent characteristics
Lamp, and more surge energy is applied to the metal oxide bar.
Absorbed inside the Lister (B ₁ ).

[0010]In addition, the constant voltage element (A ₅ ), (A ₆ ), Metal oxide
Barista (B _Four ), (B ₅ ) Is connected in series between lines L and N.
Therefore, a surge voltage is applied between lines L and N.
If this occurs, this is the metal oxide varistor (B ₁ ) In addition to the above
4 parties (A ₅ ), (A ₆ ), (B _Four ), (B ₅ ) By the series circuit
Be absorbed. Therefore, the normalizer applied between the lines L / N
It is also effective in absorbing surge voltage in
The withstand capability is improved. Metal oxide varistor B _Four And B
₅ After the normal mode surge voltage is absorbed,
Gas tube arrester A ₅ And A ₆ No discharge due to
Prevents the continuous flow of the mal mode in a short time.

Therefore, the surge withstand capability is greatly improved against the common mode internal / external surge voltage applied between the AC input terminal (L) / frame ground FG and between the AC input terminal (N) / frame ground FG. Also,
Normal mode applied between current input terminals (L) / (N)
Surge withstand voltage is improved.

Other objects and features of the present invention as well as other embodiments will become apparent from the following description of embodiments with reference to the drawings.

[0013]

EXAMPLES Example 1 FIG. 1 shows a first example of the present invention. In the circuit shown in FIG. 1, the same or corresponding elements as those of the conventional example are designated by the same reference numerals. In FIG. 1, a switching regulator type power supply device for electronic equipment such as office automation equipment is composed of an input unit 1, a noise filter unit 2, a rectifying / smoothing unit 3 and a converter unit 4, and the input AC voltage is a rectifying / smoothing unit. A DC output Vout that is rectified and smoothed by 3, converted by the converter unit 4 and stabilized is output. Stabilized DC output Vout
Is used as a control power source or a driving power source for electronic equipment such as office automation equipment. The detailed operation of the switching regulator is general and is omitted here.

In the input section 1, an overcurrent protection fuse F ₁ is arranged in a line L connected to one of a pair of AC input terminals. A series circuit of a gas tube arrester A ₅ and a metal oxide varistor B ₄ is arranged between the fuse F ₁ and the frame ground FG. That Gasuchu - Buaresuta end of A ₅ is connected to a line connected to the fuse F _1, one end and the other end to the varistor B ₄ arrester A ₅ is connected, the other end of the varistor B ₄ is frame -
It is connected to the ground FG. Neutral N
And the frame ground FG between the gas tube
Arrangement of series circuit of Lester A ₆ and metal oxide varistor B ₅
Has been done. That is , one end of the gas tube arrester A ₆
There New - connected to Tsentralnyi N, bar the other end of the arrester A ₆
One end of the lister B ₅ is connected and the other end of the varistor B ₅ is connected.
It is connected to the frame ground FG.

A line L connected to each of the AC input terminals
Between the neutral and the neutral N, as in the conventional case, a metal oxide varistor B is provided for absorbing the normal mode surge voltage.
₁ is placed. The conduction voltage (varistor voltage) of the varistor B ₁ is about 200V to 500V depending on the AC input voltage. After that, an Across the Line capacitor C ₁ is arranged between the line L and the neutral N for normal mode noise reduction. After that, for normal mode noise reduction, a common mode choke coil L ₁ is provided between the line L and the neutral N, and also between the line L and the frame ground FG and the neutral N.
And the frame ground FG, line bypass capacitors C ₂ and C ₃ are arranged respectively. The AC input that has passed through the noise filter unit 2 is rectified by the diode bridge D and smoothed by the capacitor C ₄ to become an unstable DC voltage. This unstable DC voltage is the D of the converter unit 4.
It is stabilized by the C-DC converter and becomes a DC voltage Vout, which is output. The stabilized DC output Vout is used as a control power source or a driving power source for electronic devices.

When a normal mode surge voltage invades between the line L and the neutral N, it is clamped by the varistor voltage of the metal oxide varistor B _{1 having} excellent surge response characteristics as a constant voltage element, and the surge energy beyond that is oxidized. It is absorbed inside the metal varistor B ₁ . The surge energy that entered is extremely large, and the metal oxide varistor B ₁
If surge energy exceeding the surge withstand level of ₁ is entered, the metal oxide varistor B ₁ may be destroyed in the short mode, and the fuse F ₁ of the input section ₁ may be blown to bring down the system such as an electronic device. According to the Central Research Institute of Electric Power Industry, the discharge current in the arrester is almost 200A.
It is reported below that 5% exceeds 200A. Specifically, the safety factor is 5 for a discharge current of 200A.
If the metal oxide varistor is selected from those having surge current withstand capacities of 1000 A and 1250 A, the energy resistance will be sufficient, and the system down due to the short mode destruction of the metal oxide varistor B ₁ can be completely eliminated. Particularly when high reliability is required, the reliability can be improved by further increasing the safety factor and selecting the metal oxide varistor B ₁ . Specifically, by selecting a large surge resistance (surge current resistance, energy resistance) of the metal oxide varistor B ₁ , danger can be avoided and reliability can be improved.

In FIG. 1 , gas tube arresters A ₅ and A ₆ have a discharge voltage of 2000 V to 4000 V, and metal oxide varistors B ₄ and B ₅ have a varistor voltage of about 10 V to 500 V. A case where a common mode surge voltage enters between the AC input line L / frame ground FG and between the neutral N / frame ground FG will be described. First, the AC input line L
When a surge voltage enters from the line, the surge energy is absorbed by the gas tube arrester A ₅ and the metal oxide varistor B ₄ in the route of the line L / gas tube arrester A ₅ and the series circuit of the metal oxide varistor B _{4 and} the frame ground FG. . When a surge voltage from the AC input neutral N enters, the neutral N / gas tube arrester A ₆
And a path of the series circuit / frame ground FG of the metal oxide varistor B _5, Gasuchu - a series circuit of Buaresuta A ₆ and the metal oxide varistor B _5, the surge energy is absorbed.

As described in the conventional example, most of the metal oxide varistor B ₁ is damaged in the short mode. Metal oxide varistor B ₄ and B used in the first embodiment
_In case of ₅ , it and gas tube arrester A ₅ and A
_From the voltage ratio with respect to ₆ , most of the common mode surges are absorbed by the gas tube arresters A ₅ and A _6, so that the metal oxide varistors B ₄ and B ₅ are lightly loaded and there is no possibility of damage. Also, metal oxide varistors B ₄ and B
_5, after the surge voltage is absorbed, Gasuchu - so to prevent a short time Buaresuta continued flow due to discharge of A ₅ and A _6, Gasuchu - series circuit of Buaresuta A ₅ and the metal oxide varistor B _4, and , Gas tube arrester A ₆
Each of the series circuits of the metal oxide varistor B ₅ and the metal oxide varistor B ₅ reliably and efficiently absorbs an excessive surge voltage.

Further, the gas tube arrester A ₅ , the metal oxide varistor B ₄ , the gas tube arrester A ₆ and the metal oxide varistor B ₅ are connected in series between the line L and the neutral N, so that the line L is connected. And neutral N
When a surge voltage is applied during this, this is absorbed by the four series circuits in addition to the metal oxide varistor B ₁ . Therefore, it is effective for absorbing the normal mode surge voltage applied between the line L and the neutral N, and the surge withstand capability is improved.

According to the first embodiment, the AC input line L /
Between frame grounds FG and AC input Neutral N /
The surge withstanding capability for the common mode internal / external surge voltage applied between the frame grounds FG is greatly improved, and the surge withstanding capability for the normal mode surge voltage applied between the AC input line L / neutral N is also improved. .

[0021] A second embodiment (Embodiment 2) FIG. The difference from the first embodiment shown in FIG. 1 is that the metal oxide varistors B ₄ and B ₅ of the common mode surge voltage absorption circuit in the noise filter unit 2 are replaced by low resistance resistors R ₃ and R ₄ , respectively. It is in the replaced point. Other circuit configurations are the same as the first embodiment shown in FIG. The resistances R ₃ and R ₄ are about 1Ω to 10Ω, and the power is 1 to 10W. When a surge voltage enters from the AC input line L, a series circuit of the line L / gas tube arrester A ₉ and the resistor R ₃ / frame ground FG forms a series circuit of the gas tube arrester A ₉ and the resistor R ₃ . Absorb surge energy. At the time of surge voltage intrusion from AC input neutral N, a series circuit of neutral N / gas tube arrester A ₁₀ and resistor R ₄ / a series circuit of gas tube arrester A ₁₀ and resistor R ₄ via the route of frame ground FG. But absorbs the surge energy.

The resistors R ₃ and R ₄ have low resistance values, and most of the common mode surges are absorbed by the gas tube arrester A ₉ or A _10. Therefore, the load on the resistors R ₃ and R ₄ is light and the possibility of damage is low. There is none. In order to further improve safety, it may be used resistance temperature fuse built - in type. The resistors R ₃ and R ₄ , which substantially contribute to the short-term interruption of their discharge (following current) after the gas tube arrester A ₉ or A ₁₀ has absorbed the surge voltage, and the gas tube arrester A ₉ and A ₁₀ Each of the series circuits of each of A ₁₀ and each of resistors R ₃ and R ₄ reliably and efficiently and safely absorbs an excessive surge voltage.

Further, a gas tube arrester A ₉ and a resistance R
_{3. Since} the gas tube arrester A ₁₀ and the resistor R ₄ are arranged in series between the line L and the neutral N, surge energy is also absorbed in these series circuits and the oxidation arranged between the line L and the neutral N is absorbed. The load on the metal varistor B ₁ is reduced, the effect of absorbing the surge voltage in the normal mode is great, and the surge resistance is improved.

According to the second embodiment, the AC input line L /
Between frame grounds FG and AC input Neutral N /
The surge withstanding capability for the common mode internal / external surge voltage applied between the frame grounds FG is greatly improved, and the surge withstanding capability for the normal mode surge voltage applied between the AC input line L / neutral N is also improved. .

In place of the gas tube arrester described above, a plug
The discharge electrode formed by the conductor pattern of the lint wiring board,
It can be used as a constant voltage element. The inter-electrode gap of the discharge electrodes of the conductor pattern which can be replaced by the gas tube arrester is in the range of 1.5 mm to 4 mm. The conditions for selecting a specific value within this range are the required surge withstand voltage, input voltage and applicable safety standards. Insulating distance between the lines L and neutral N and the frame ground FG of the AC input unit 1, it determines the safety and the like of applying safety standards and intended. What is important here is to set the insulation distance between the AC input lines L and N and the frame ground FG larger than the interelectrode gap by 0.5 mm to 2 mm.
With such a configuration, the circuit elements are simplified,
It can exert almost no damaging that the effects described in or One real施例.

[0026]

The power supply device for electronic equipment according to the present invention has a good surge response characteristic, can reliably absorb serge energy, and has a high reliability of surge voltage absorption.

In the first embodiment described above, the line L and the new line
When the normal mode surge voltage is applied between the trawl N
If this is absorbed by the metal oxide varistor B ₁ .
It In addition, constant voltage elements A ₅ , A ₆ and gold oxide
Absorbed also by the series circuit of four members of the genus varistor B ₄ , B _5.
To be done. Therefore, join between line L / neutral N
It is also effective in absorbing normal mode surge voltage.
As a result, the surge resistance of normal mode is improved. Metal oxide
Varistors B ₄ and B ₅ are normal mode surge
Discharge of constant voltage elements A ₅ and A ₆ after the pressure is absorbed
Prevents normal mode follow-up current in a short time.

In the second embodiment described above, the line L and the new line
When the normal mode surge voltage is applied between the trawl N
If this is absorbed by the metal oxide varistor B ₁ .
It In addition, constant voltage elements A ₉ and A ₁₀ and resistors
It is also absorbed by the series circuit of four members of R ₃ and R ₄ . Shi
Therefore, normal joining between line L and neutral N
Mode is also effective in absorbing surge voltage,
The surge tolerance of the le mode is improved. Resistors R ₃ and R ₄
Is the constant after the normal mode surge voltage is absorbed.
Normal mode due to discharge of voltage elements A ₉ and A ₁₀
To prevent the follow-up of the flow in a short time.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a second embodiment of the present invention.

FIG. 3 is an electric circuit diagram showing one configuration of a conventional power supply device.

[Explanation of symbols]

A _{5 to} A ₁₀ : Gas tube arrester B _{1 to} B ₅ : Metal oxide varistor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H02M 7/06 H02M 7/06 A

Claims (4)

(57) [Claims] 1. An overcurrent protection fuse connected to one of a pair of alternating current input terminals, a rectifying / smoothing circuit for rectifying and smoothing an alternating current input via the fuse, and a rectified and smoothed unstable direct current. A power supply device for electronic equipment, comprising: a DC-DC converter for converting to a stabilized DC output; and a noise filter circuit including a surge voltage absorbing circuit arranged between the AC input terminal and the rectifying and smoothing circuit, The surge voltage absorption circuit includes a constant voltage element consisting of a discharge electrode and an oxidation element, one end of which is electrically continuous to the line to which the overcurrent protection fuse is connected and the other end of which is electrically continuous to the frame ground. A first series circuit with a metal varistor,
One end is electrically continuous with the other of the pair of AC input ends
And before the other end an electrically continuous to the frame ground
It is connected in series with the first series circuit between the pair of AC input terminals.
That the second series circuit and each element and the constant voltage element consisting of a separate discharge electrode and metal oxide varistors of the first series circuit,
And another disposed between the pair of AC input terminals
A metal oxide varistor according to claim 1, which is a power supply device for electronic equipment. 2. An overcurrent protection fuse connected to one of a pair of AC input terminals, a rectifying / smoothing circuit for rectifying and smoothing an AC input through the fuse, and a rectified and smoothed unstable DC. A power supply device for electronic equipment, comprising: a DC-DC converter for converting to a stabilized DC output; and a noise filter circuit including a surge voltage absorbing circuit arranged between the AC input terminal and the rectifying and smoothing circuit, The surge voltage absorption circuit includes a constant voltage element and a resistor, which are electrically continuous at one end and electrically continuous at the other end to the frame ground with respect to the line to which the fuse for overcurrent protection is connected, and a resistor. , A series circuit of a constant voltage element composed of a discharge electrode and a resistor, one end of which is electrically continuous to the other of the pair of AC input ends and the other end of which is electrically continuous to the frame ground. , and, Serial pair of AC input
A power supply device for electronic equipment, comprising a metal oxide varistor disposed between the force ends . Constant voltage element consisting of 3. A discharge electrode, a power supply device for an electronic device according to claim 1 or claim 2, wherein a gas tube arrester. Constant voltage element consisting of wherein the discharge electrode is printed conductor pattern on the printed wiring board - formed by emissions, claim 1 or claim 2 Power supply for electronic devices according.