Automatic voltage switching circuit

Abstract

To provide an automatic voltage switching circuit capable of meeting commercial power supply voltage in every country and applicable to electronic products with large power consumption.SOLUTION: An automatic voltage switching circuit 1A is provided with: a power transformer 10 to whose primary windings 11 a commercial power supply V is connected; an intermediate tap 11a placed on the primary windings 11; a change-over switch of which a normally-closed terminal 13nc is connected to the intermediate tap and a normally-opened terminal 13no is connected to the commercial power supply V to output a specific voltage by changing over between the normally-closed terminal 13nc and the normally-opened terminal 13 no; an AC / DC converter 14 connected to a secondary windings 12; a regulator 15 connected to the AC / DC converter 14; a voltage dividing circuit 16 dividing output voltage of the AC / DC converter 14; and a comparator 17 comparing an output voltage of the regulator 15 with an output voltage of the voltage dividing circuit 16. When a result of comparison with the comparator indicates that the output voltage of the voltage dividing circuit is lower than the output voltage of the regulator, the change-over switch is to be changed over to the commercial power supply side, and when higher the change-over switch is to be changed over to the intermediate tap side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an automatic voltage switching circuit that takes into account differences in commercial power supply voltages between countries and enables electrical appliances that meet the power supply voltage specifications of the country of manufacture to be connected to a commercial power supply in the country of use. [Background technology]

[0002] Commercial power supply voltages vary from country to country. For example, in Japan it is AC 100V, while in Korea and China it is AC 220V, in the United States it is AC 120V, and in Europe it is AC 220V to 240V.

[0003] With the spread of switching power supplies, it has become easy to use common electrical appliances both domestically and overseas, even if the commercial power supply voltage is different. However, large home appliances and electrical appliances that require control of heaters and cooling fans often use the commercial power supply voltage as is, and users of overseas electrical appliances have had to prepare a separate voltage transformer.

[0004] Furthermore, when manufacturers export electrical products overseas, they must adapt the products to the power supply voltage specifications of each country, which means that they have had to develop electrical products with different specifications for Japan and overseas.

[0005] One solution to this problem is the AC adapter described in Patent Document 1. This AC adapter has a center tap at a predetermined winding ratio on the primary winding of a power transformer, 220V plugs connected to both ends of the power transformer, and a 100V plug connected to the center tap and one end of the power transformer, and by artificially selecting between the 220V plug and the 100V plug, a constant voltage (for example, 10V) is output from the secondary winding. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-148012 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the AC adapter described in Patent Document 1 has the inconvenience of requiring manual selection of the plug, and also has the problem that only products with low-power DC power supplies can be used because the AC output voltage from the secondary winding of the power transformer is converted to DC and supplied to the electrical appliance.

[0008] Therefore, an object of the present invention is to provide an automatic voltage switching circuit that can accommodate commercial power supply voltages in various countries, automatically and efficiently supply commercial power supply voltage to electrical appliances, and can also be used for products that consume a large amount of current and are directly connected to a commercial power source. [Means for solving the problem]

[0009] In order to solve the above problem, the invention of claim 1 is an automatic voltage switching circuit that is compatible with a plurality of types of commercial power supply voltages and outputs a predetermined voltage even when different commercial power supply voltages are input, comprising: a power transformer having a commercial power supply connected to a primary winding; a center tap provided on the primary winding of the power transformer; a changeover switch having one contact connected to the commercial power supply and the other contact connected to the center tap, and selectively switching between the one contact and the other contact to output the predetermined voltage from a common terminal; an AC / DC converter connected to a secondary winding of the power transformer; The power supply comprises a regulator that outputs a constant voltage, a voltage divider circuit that divides the output voltage of the AC / DC converter, and a comparator that compares the output voltage of the regulator with the output voltage of the voltage divider circuit, the intermediate tap being formed at a position where the predetermined voltage is output, and when the comparison by the comparator shows that the output voltage of the voltage divider circuit is lower than the output voltage of the regulator, the changeover switch is switched to the commercial power supply side, and when the output voltage of the voltage divider circuit is higher than the output voltage of the regulator, the changeover switch is switched to the intermediate tap side, thereby controlling the predetermined voltage to be output from the changeover switch. death , A safety switch is provided on the common terminal side of the changeover switch, and the safety switch is turned on after the changeover switch is controlled. It is characterized by:

[0010] The invention of claim 2 is characterized in that in the automatic voltage switching circuit of claim 1, the changeover switch has a normally closed terminal, and the normally closed terminal is connected to the center tap.

[0012] Claim 3 The invention described in claim 1 is an electrical product. or 2 The invention is characterized in that the automatic voltage switching circuit described in [Effects of the Invention]

[0013] According to the invention of claim 1, the level of the commercial power supply voltage is judged from the level of the output voltage of the secondary winding of the power transformer, and it is decided whether to output the commercial power supply voltage as is or as a voltage stepped down by an intermediate tap provided on the primary winding of the power transformer, so that the commercial power supply voltage can be supplied to electrical appliances automatically and efficiently. In addition, a safety switch is provided on the common terminal side of the changeover switch, and the safety switch is set to the ON state after the changeover switch is controlled. Therefore, voltage is not supplied until the appropriate voltage (rated voltage) for the electrical appliance is reached, and therefore an incorrect voltage is not supplied, preventing breakdown or malfunction of the electrical appliance.

[0014] According to the invention described in claim 2, the normally closed terminal of the changeover switch is connected to an intermediate tap provided on the primary winding of the power transformer. Therefore, when the automatic voltage changeover circuit is connected to a commercial power source, the voltage can only be lower than the commercial power source voltage. For example, even if it is connected to an AC 220V commercial power source, AC 220V will not be supplied to the electrical appliance, preventing damage to the electrical appliance.

[0016] Claim 3 According to the invention described above, when importing or exporting electrical products, users in the export destination do not need to prepare a transformer to convert the commercial power supply voltage, and manufacturers do not need to design or develop products taking into account the commercial power supply voltage of the export destination, thereby eliminating a lot of waste. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a circuit diagram of an electric potential therapy device using an automatic voltage switching circuit according to Embodiment 1 of the present invention. [Figure 2] FIG. 10 is a circuit diagram of an electric potential therapy device using an automatic voltage switching circuit according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 and 2 illustrate the embodiments of the present invention, which are applied to an electric potential treatment device P using automatic voltage switching circuits 1 and 1A according to the present invention. 1, the automatic voltage switching circuits 1 and 1A are shown as the main circuit diagrams, and in reality, the automatic voltage switching circuits 1 and 1A are built into the electric potential treatment device P as one of its components.

[0019] The electric potential treatment device P is known to perform treatment by boosting a commercial power source V to, for example, AC 9000V using a step-up transformer and generating an electric field around an insulated human body.

[0020] (Embodiment 1) 1 is a circuit diagram of an electric potential therapy device P using an automatic voltage switching circuit 1 according to embodiment 1. This automatic voltage switching circuit 1 is intended to enable an electric potential therapy device P of AC 100V specification (Japanese specification) to be used in countries where the commercial power supply voltage is AC 220V (for example, Korea).

[0021] The automatic voltage switching circuit 1 comprises a power transformer 10, a commercial power source V which serves as the input side of the power transformer 10, a changeover switch 13 which selectively connects the commercial power source V and an intermediate tap 11a of the primary winding 11 of the power transformer 10 to supply power to the electric potential therapy device P, an AC / DC converter 14 connected to the secondary winding 12 of the power transformer 10, a regulator 15 connected to the output side of the AC / DC converter 14 and outputs a constant voltage, a voltage divider circuit 16 connected to the output side of the AC / DC converter 14 and divides the voltage, and a microcomputer 17 which compares the constant voltage output by the regulator 15 with the output voltage of the voltage divider circuit 16 and sends various control signals.

[0022] In the power transformer 10, both end taps of the primary winding 11 are connected to a commercial power supply V, and either 220V AC or 100V AC is input. The primary winding 11 is also provided with a center tap 11a, which is located at a turn ratio of 45:55, so that when 220V AC is input to the primary winding 11, the output voltage of the center tap 11a becomes 100V AC.

[0023] In the following explanation of the automatic voltage changeover switches 1 and 1A according to the first and second embodiments, only one side (one side) of the commercial power supply V will be described for the sake of simplicity, and the other side (the other side) will be omitted, but it is assumed that the output of the common terminal 13com of the changeover switch 13 is directly connected to the electric potential treatment device P (electrical appliance) connected in the subsequent stage.

[0024] The changeover switch 13 is a c-contact switch, with a common terminal 13com connected to the electric potential treatment device P, a normally open terminal 13no connected to the commercial power supply V, and a normally closed terminal 13nc connected to the center tap 11a.

[0025] The turns ratio between the primary winding 11 and the secondary winding 12 of the power transformer 10 is, for example, 11:1, so that when AC 220V is input to the primary winding 11, AC 20V is output to the secondary winding 12, and when AC 100V is input to the primary winding 11, approximately AC 9V is output to the secondary winding 12.

[0026] The AC / DC converter 14 converts the output of the secondary winding 12 from AC to DC, and is connected to a regulator 15 and a voltage divider circuit 16 in the subsequent stage.

[0027] Regardless of the output voltage of the AC / DC converter 14, the regulator 15 outputs a constant voltage (for example, DC 3V) to the microcomputer 17 as a reference voltage for a comparator, which will be described later.

[0028] Voltage divider circuit 16 divides the output voltage of AC / DC converter 14. For example, when the input voltage of AC / DC converter 14 is AC 9V and the output voltage is approximately DC 12V, that is, when AC 100V is input to primary winding 11, the divided voltage is set to be smaller than DC 3V output from regulator 15 (for example, DC 2V).

[0029] The microcomputer 17 has a comparator, compares the output voltage of the regulator 15 (this voltage serves as a reference voltage) with the voltage divided by the voltage divider circuit 16, and controls the changeover switch 13.

[0030] Next, the operation of the automatic voltage switching circuit 1 will be described.

[0031] First, when the voltage of the commercial power supply V is AC 220V (for example, when used in Korea), AC 220V is input to both end taps of the primary winding 11 of the power transformer 10, and AC 220V is applied to the normally open terminal 13no of the changeover switch 13.

[0032] Furthermore, AC 100V is output from a center tap 11a of a primary winding 11 of a power transformer 10, and AC 100V is applied to a normally closed terminal 13nc of a changeover switch 13.

[0033] A voltage of 20V AC is output to both end taps of the secondary winding 12 of the power transformer 10, and for example, the output voltage of the AC / DC converter 14 is about 26V DC, and the voltage divided by the voltage divider circuit 16 is, for example, 4.5V DC.

[0034] In response to this, the microcomputer 17 compares the output voltage DC3V of the regulator 15 with the divided voltage DC4.5V of the voltage divider circuit 16, and since the divided voltage is higher, a control signal is sent to the changeover switch 13 so that its movable element 13m contacts the normally closed terminal 13nc, and the changeover switch 13 maintains a state in which the common terminal 13com and the normally closed terminal 13nc are connected.

[0035] As a result, the output voltage AC 100V from the intermediate tap 11a is supplied to the electric potential treatment device P via the changeover switch 13.

[0036] Next, when the voltage of the commercial power supply V is AC 100V (for example, when used in Japan), AC 100V is input to both end taps of the primary winding 11 of the power transformer 10, and AC 100V is applied to the normally open terminal 13no of the changeover switch 13.

[0037] Furthermore, AC 45.5V is output from center tap 11a of primary winding 11 of power transformer 10, and AC 45.5V is applied to normally closed terminal 13nc of changeover switch 13. Incidentally, at this time, AC 45.5V is supplied to electric potential therapy device P from common terminal 13com of changeover switch 13, but this does not cause a problem because the time it takes for movable element 13m in changeover switch 13 to switch from normally closed terminal 13nc to normally open terminal 13no after connection to commercial power source V is short, and furthermore, the input voltage is below the rated voltage.

[0038] A secondary winding 12 of a power transformer 10 has a voltage of AC 9V output to both ends of the secondary winding 12, and the voltage divided by a voltage divider circuit 16 becomes, for example, DC 2V.

[0039] In response to this, the microcomputer 17 compares the output voltage DC3V of the regulator 15 with the divided voltage DC2V of the voltage divider circuit 16, and since the divided voltage is lower, a control signal is sent to the changeover switch 13, and the movable element 13m of the changeover switch 13 operates to connect the common terminal 13com and the normally open terminal 13no.

[0040] As a result, AC 100V directly connected to the commercial power supply V is supplied to the electric potential treatment device P via the changeover switch 13.

[0041] As described above, the automatic voltage switching circuit 1 according to the first embodiment compares the secondary output voltage of the power transformer 10 with a predetermined reference voltage and the voltage divided by the voltage divider circuit 16, By automatically determining whether the voltage input to the transformer 10 is high or low, the output of the intermediate tap 11a or the power supply voltage V can be switched, so that even if the connected commercial power supply V is AC220V or AC100V, a voltage of AC100V can be supplied to the electric potential treatment device P.

[0042] Furthermore, in the automatic voltage switching circuit 1 according to this embodiment 1, the commercial power source V is connected to the normally open terminal 13no of the contacts of the switching switch 13, so that even if the automatic voltage switching circuit 1 is inadvertently connected to the commercial power source V, high voltage AC 220V will not be supplied to the electric potential therapy device P, and damage to electrical appliances can be prevented.

[0043] In this embodiment 1, the normally closed terminal 13nc of the contacts of the changeover switch 13 is connected to the center tap 11a. However, the present invention is not limited to this. The changeover switch may have a mover 13m that is normally not in contact with any of the contacts, and may move so as to contact the center tap 11a or the commercial power supply V upon receiving a control signal from the microcomputer 17.

[0044] (Embodiment 2) FIG. 2 is a circuit diagram of an electric potential therapy device P using an automatic voltage switching circuit 1A according to embodiment 2. This embodiment 2 differs from the above-described embodiment 1 in that a main switch 18 and a safety switch 19 are provided to prevent damage to the electric potential therapy device P even in the event of an unforeseen incident. Components equivalent to those in embodiment 1 will be assigned the same reference numerals and will not be described again.

[0045] The main switch 18 is provided at the rear stage of the commercial power supply V, and unless the main switch 18 is turned on, no voltage is applied to the power transformer 10 and the changeover switch 13.

[0046] The safety switch 19 is provided after the changeover switch 13 and between it and the electric potential treatment device P, and is controlled by the microcomputer 17.

[0047] This safety switch 19 is normally in the OFF state, but after the movable element 13m of the changeover switch 13 is selected to contact the normally open terminal 13no or the normally closed terminal 13nc, a control signal is sent from the microcomputer 17 and the safety switch 19 is turned ON.

[0048] This is to avoid the risk of breakdown or malfunction of the control circuit of electric potential therapy device P if power is supplied to electric potential therapy device P when the supply voltage is not at the rated AC 100V (whether the voltage is high or low) when main switch 18 is turned on. In other words, by supplying power to electric potential therapy device P only after the supply voltage has reliably reached the rated AC 100V, a safer design is achieved.

[0049] As a result, in the automatic voltage switching circuit 1A according to this embodiment 2, after the switching of the switching switch 13 is completed, the safety switch 19 is turned ON when the supply voltage becomes AC 100V, and the rated voltage (AC 100V) can be reliably supplied to the electric potential therapy device P.

[0050] As described above, the automatic voltage switching circuits 1, 1A and the electric potential therapy device P using this automatic voltage switching circuit determine whether the voltage of the commercial power supply V (AC 100V or AC 220V) is high or low (AC 9V or AC 20V) based on the output voltage of the secondary winding 12 of the power transformer 10, and generate an AC / DC converter 14 (DC 12V or DC 26V) and a voltage divider 16 (DC 2V or DC 4.5V). The microcomputer 1 then determines whether the output voltage of the regulator 15 (DC 3V) is high or low. A comparator in 7 determines whether to output the commercial power supply voltage as is or to output a voltage stepped down by an intermediate tap 11a provided on the primary winding 11 of the power transformer 10, so that whether the commercial voltage is AC100V or AC220V, AC100V (rated voltage) is always supplied to the potential treatment device P.

[0051] Moreover, since the changeover switch 13 operates automatically when the power supply is used, the user does not need to be aware of the commercial voltage and does not feel bothered.

[0052] In each of the above embodiments, the electric potential therapy device P, which generates an electric field by boosting the commercial power source V to a high voltage using a transformer, has been described as an electrical appliance, but the automatic voltage switching circuits 1 and 1A of the present invention can also be applied to other electrical appliances.

[0053] For example, it can be applied to electrical appliances that use commercial power supply voltage as the driving voltage as is, such as motors and heaters as their main components, such as electric blankets, hair dryers, irons, various fans, electric fans, and washing machines, and at the same time, it can also be applied to general electrical appliances such as refrigerators and microwave ovens.

[0054] The automatic voltage switching circuits 1, 1A of the present invention may be incorporated into the electric potential therapy device P as in the above embodiment, but they can also be made into a product that consists solely of an automatic voltage switching circuit. For example, it is conceivable to provide a plug that can be used overseas on the input side of the automatic voltage switching circuits 1, 1A, and a receptacle into which the plugs of desired electrical appliances can be inserted on the output side. In this way, the circuits function as a so-called conversion adapter.

[0055] Although the embodiments of the present invention have been described above, the specific configuration is not limited to the above embodiments, and the present invention also includes design changes and the like within the scope of the gist of the present invention. For example, while the commercial power supply voltages of AC220V and AC100V have been described in the above embodiments 1 and 2, the present invention is not limited to these, and any combination of AC100V, AC120V, AC220V, AC230V, AC240V, etc. is also possible, and the combination of commercial power supply voltages is not limited to two types, but may be three, four, or more.

[0056] Combinations of multiple commercial power supply voltages can be achieved by increasing the number of center taps on the power transformer, the output of the voltage divider circuit, the number of comparisons in the comparator, the number of contacts on the changeover switch, etc.

[0057] In the above-mentioned embodiments 1 and 1A, the microcomputer 17 is provided with a comparator, but the present invention is not limited to this. The selector switch 13 may be operated by comparing a predetermined reference voltage with the voltage divided by the voltage divider circuit using only a comparator, without relying on microcomputer control. [Explanation of symbols]

[0058] V Commercial power supply P Electrical potential therapy device (electrical product) 10 Power transformer 11 Primary Winding 11a center tap 12 Secondary Winding 13. Selector switch 13com common terminal 13no normally open terminal (one contact) 13nc Normally closed terminal (other contact) 14 AC / DC converter 15 Regulator 16 Voltage divider circuit 17 Microcomputer (comparator) 18 Main switch 19 Safety Switch

Claims

1. An automatic voltage switching circuit that supports a plurality of types of commercial power supply voltages and outputs a predetermined voltage even when different commercial power supply voltages are input, a power transformer having a commercial power supply connected to its primary winding; a center tap provided on a primary winding of the power transformer; a changeover switch having one contact connected to the commercial power supply and the other contact connected to the center tap, and configured to selectively switch between the one contact and the other contact to output the predetermined voltage from a common terminal; an AC / DC converter connected to a secondary winding of the power transformer; a regulator connected to the AC / DC converter and outputting a constant voltage; a voltage dividing circuit that divides the output voltage of the AC / DC converter; a comparator that compares the output voltage of the regulator with the output voltage of the voltage divider circuit, the center tap is formed at a position where the predetermined voltage is output, If the comparison result by the comparator indicates that the output voltage of the voltage divider circuit is lower than the output voltage of the regulator, the changeover switch is switched to the commercial power supply side, and if the output voltage of the voltage divider circuit is higher than the output voltage of the regulator, the changeover switch is switched to the intermediate tap side, thereby controlling so that a predetermined voltage is output from the changeover switch; A safety switch is provided on the common terminal side of the changeover switch, The safety switch is set to an ON state after the changeover switch is controlled. An automatic voltage switching circuit.

2. The changeover switch has a normally closed terminal, and the normally closed terminal is connected to the center tap.

2. The automatic voltage switching circuit according to claim 1.

3. 3. A power supply using the automatic voltage switching circuit according to claim 1 or 2. An electrical product characterized by:

Images