JP2011229270A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent generation of a leak current in a device, electric shock when insulation is broken down inside the device, and occurrence of fire when the device is broken, even in the case where means for easily performing protective grounding is provided.SOLUTION: The present invention relates to a power supply unit 10 for converting an AC power source provided by a power supply plug 1 including a protective grounding terminal 1c into a DC power source and supplying the converted DC voltage to a load device. Potential dividing resistors R1 and R2 are provided between an active wire 3a and a neutral wire 3b, the protective grounding terminal 1c of the power supply plug 1 is connected to potential dividing terminals of the potential dividing resistors R1 and R2 and when it is determined that a voltage V1 in the potential dividing terminals becomes about 0 V, the power source is supplied to the load device 20.

Description

  The present invention relates to a grounding technique for information processing equipment and the like equipped with a power supply unit.

  In information processing equipment, office equipment, AV equipment, home appliances, etc., the insulation class is determined by the safety standard to which each product belongs, and is classified into Class I equipment, Class II equipment, Class III equipment, and the like.

  And in a device with an insulation class classified as a class I device such as a washing machine or a refrigerator, if it becomes a dangerous voltage when the basic insulation becomes defective as "equipment where protection against electric shock is achieved by the following" It is said that it comprises means for connecting possible conductive parts to a protective ground conductor in the building wiring, and it is essential to provide protective grounding means.

  For this reason, a grounding wire that can be grounded by screwing to the housing of the apparatus is attached and sold so that protective grounding is possible with the grounding wire. Then, there is a technique for detecting by the controller that protective grounding is not performed due to the grounding of the device and controlling so that power is not supplied to the load device when the protective grounding is not performed (see, for example, Patent Document 1). .

Japanese Patent Application Laid-Open No. 07-083976

  However, the work of screwing and grounding the device casing is troublesome for an unfamiliar user, and in recent years, a two-pole power cord set with a ground wire and a ground terminal have been used to simplify the protective ground connection. It has become common to provide a means for easily providing protective grounding with a three-pole power cord set attached.

  Even in this case, 2-pole outlets with no grounding terminal are the mainstream for household outlets. The 2-wire power cord with a ground wire does not connect the ground wire, or the 3-pole power cord with a ground terminal has 3-pole-2-pole. In some cases, a conversion plug was used without connecting the protective earth terminal.

  As a result, it may be impossible to prevent the occurrence of leakage current of the device, electric shock when breakdown occurs inside the device, and fire when the device is damaged.

  The present invention employs the following configuration in order to solve the above-described problems. That is, in a power supply unit that converts AC power supplied from a power plug having a protective ground terminal into DC power and supplies the load device, a voltage dividing resistor is provided between the live wire and the neutral wire, and the voltage dividing resistor A protective ground terminal of the power plug is connected to the voltage dividing terminal, and when it is determined that the voltage of the voltage dividing terminal is substantially 0 V, power is supplied to the load device.

  According to the power supply unit of the present invention, in the power supply unit that converts the AC power supplied from the power plug having the protective ground terminal into the DC power and supplies the load to the load device, the voltage dividing resistor is provided between the live wire and the neutral wire. A protective ground terminal of the power plug is connected to the voltage dividing terminal of the voltage dividing resistor, and when it is determined that the voltage of the voltage dividing terminal is substantially 0 V, power is supplied to the load device. Therefore, even when providing a means for simple protective grounding, it is possible to reliably prevent the occurrence of leakage current of the device, electric shock when breakdown occurs inside the device, and fire when the device is damaged. it can.

1 is a configuration diagram of a power supply unit and an apparatus main body according to a first embodiment. FIG. 3 is a circuit example and an operation explanatory diagram of a switching control unit of the power supply unit according to the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. Elements common to the drawings are given the same reference numerals.

(Constitution)
FIG. 1 shows a configuration diagram of an apparatus main body on which the power supply unit according to the first embodiment of the present invention is mounted. As shown in the figure, the apparatus main body 30 on which the power supply unit 10 according to the first embodiment is mounted is an information processing device such as a PC (personal computer) or ATM (automatic teller machine). In this example, the switching power supply device includes a switching control unit 7 and converts an AC voltage into a DC voltage.

  Further, in the building 40 in which the apparatus main body 30 is provided, an outlet 8 is provided as shown in the lower left of the figure. The live terminal 8a of the outlet 8 is connected to the live wire 9a in the building 40, the ground terminal 8c of the outlet 8 is connected to the ground wire 9c of the building 40, and the neutral terminal 8b of the outlet 8 is connected to the ground 40 The neutral wire 9b and the ground wire 9c and the neutral wire 9b are grounded.

  On the other hand, the power plug 1 serving as an input to the power supply unit 10 is a three-pole AC power plug having a protective ground terminal 1 c, and the protective ground terminal 1 c of the power plug 1 is connected to the ground wire 3 c of the power supply unit 10. The live terminal 1a of the power plug 1 is connected to the live wire 3a of the power unit 10, and the neutral terminal 1b of the power plug 1 is connected to the neutral line 3b of the power unit 10.

  Then, when the power plug 1 is inserted into the outlet 8, the ground wire 3 c of the apparatus body 30 and the ground wire 9 c of the building 40 are connected via the protective ground terminal 1 c of the power plug 1 and the ground terminal 8 c of the outlet 8. The live wire 3a of the device main body 30 and the live wire 9a in the building 40 are connected via the live terminal 1a and the live power terminal 8a of the outlet 8, and the device main body is connected via the neutral terminal 1b and the neutral terminal 8b of the outlet 8. The 30 neutral wires 3b are connected to the neutral wire 9b in the building 40.

  The same applies to a two-pole power plug with a ground terminal. In this case, the ground wire provided in the power plug 1 is connected to the ground terminal 8c of the outlet 8.

  The resistors R1 and R2 are resistors for detecting whether or not the protective ground terminal 1c is connected to the ground. The resistors R1 and R2 are resistors having the same electrical rating in order to generate an intermediate voltage between the live wire 3a and the neutral wire 3b. Capacitors C1 and C2 are Y capacitors, that is, line bypass capacitors, which have the same electrical rating, and have a function of smoothing the divided intermediate voltage and removing noise.

  The diode bridge D1 is a diode bridge for full-wave rectification of the AC power supply, and C3 is a smoothing capacitor.

  The switching control unit 7 is a circuit that controls the operation of the power supply unit 10 that turns on and off the FET transistor Q1 and supplies the DC power to the load device 20 via the transformer T1, and is divided by the resistor R1 and the resistor R2 and the capacitor C1. A ground connection detection terminal 8 for monitoring the ground connection detection voltage V1 smoothed by C2 is provided.

(Operation)
With the above configuration, the power supply unit 10 according to the first embodiment operates as follows. This operation will be described in detail below with reference to FIG. In the following description, the AC input voltage is described as AC 100 V, but other AC voltages may be used.

  When the power plug 1 is correctly inserted into the outlet 8 having the grounding terminal 8c, the grounding wire 3c of the main unit 30 is connected to the grounding wire 40 in the building via the grounding terminal 8c provided in the outlet 8 and the protective grounding terminal 1c. Since the neutral line 9b and the ground line 9c of the power line in the building 40 are grounded by the grounding work as described above, the ground line 3c of the power unit 10 becomes 0V and the voltage V1 Becomes almost 0V, and the voltage of the ground connection detection terminal 7a of the switching control unit 7 becomes almost 0V.

  Then, the switching control unit 7 determines that it is safe because the ground connection detection terminal 8 is supplied with almost 0V as the voltage V1, is connected to the protective ground, and starts switching of the FET transistor Q1 to start the power supply unit. 10 is operated normally, power is supplied to the load device 20, and the device main body 30 can be used.

  On the other hand, when the outlet 8 is not provided with the earth terminal 8c, and the protective earth terminal 1c of the power plug 1 is not connected to the earth terminal 8c of the outlet 8, the voltage of the earth wire 3c, that is, the voltage V1 is AC100V. And the voltage at the ground connection detection terminal 7a is also AC50V.

  Then, the switching control unit 7 determines that the protective ground is not connected and is not safe, stops the switching of the FET transistor Q1, stops the power supply to the load device 20, and cannot use the device main body 30. To.

  The determination as to whether or not the protective ground is connected, that is, the determination of whether the voltage of the ground connection detection terminal 7a is (a) AC50V or (b) approximately 0V is shown in FIG. As shown, the voltage input to the ground connection detection terminal 7a of the switching control unit 7 is further divided by about 1/10 through the buffer Q2 and input to the negative terminal of the comparator Q3, Va = 2. About 5V is input to the + terminal of the comparator Q3 as a reference voltage, and the output of the comparator Q3 is referred to by the control unit 7x. When a rectangular wave is obtained as shown in (a), the protective ground is not connected. It may be determined that it is not safe, and as shown in (b), if the voltage is always 5 V, it may be determined that the protective ground is connected.

(Effect of Example 1)
As described above, according to the power supply unit of the first embodiment, in the power supply unit that converts the AC power supplied from the power plug provided with the protective ground terminal into the DC power and supplies it to the load device, between the live wire and the neutral wire Is connected to the voltage dividing terminal of the voltage dividing resistor, and when it is determined that the voltage at the voltage dividing terminal is substantially 0 V, the load device is supplied with power. Even when providing a means for easy protective grounding, it is possible to ensure the occurrence of leakage current in the device, electric shock when breakdown occurs inside the device, and fire when the device is damaged. Can be prevented.

  As described above, the present invention can be widely used for information processing equipment, office equipment, AV equipment, home appliances, and the like equipped with a power supply unit.

DESCRIPTION OF SYMBOLS 1 Power plug 1a Live terminal 1b Neutral terminal 1c Protective ground terminal 3a, 9a Live wire 3b, 9b Neutral wire 3c, 9c Ground wire 7 Switching control part 7a Ground connection detection terminal 8a Live terminal 8b Neutral terminal 8c Ground terminal 10 Power supply unit 20 Load device 30 Device body 40 In the building

Claims (3)

A power supply unit that converts AC power supplied by a power plug having a protective ground terminal into DC power and supplies the power to a load device,
A voltage dividing resistor is provided between the live wire and the neutral wire, a protective ground terminal of the power plug is connected to the voltage dividing terminal of the voltage dividing resistor, and the voltage of the voltage dividing terminal is determined to be approximately 0V. A power supply unit characterized in that power is supplied to a load device. A switching control unit for controlling power supply to the load device;
2. The power supply unit according to claim 1, wherein the switching operation is controlled based on a determination result based on a voltage of the voltage dividing terminal.   The power supply unit according to claim 1, further comprising a capacitor having the same capacity in parallel with the voltage dividing resistor.

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