JPH032521B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a load voltage switching circuit that is most suitable for portable appliances such as hair dryers.

(b) Conventional technology Commercial voltages in various countries around the world currently vary, but they can generally be divided into countries with a rated voltage of 100V and countries with a rated voltage of 200V.

In addition, the number of overseas travelers has increased recently, and these travelers have come to carry small hair dryers, irons, etc. as necessities. has the disadvantage that it cannot be used in countries such as Europe where the commercial voltage is different. For this reason, for example, as disclosed in Japanese Utility Model Publication No. 18804/1988 filed by the same applicant, when the commercial voltage is 100V, multiple loads (heaters) can be connected using a changeover switch.
are connected in parallel to the power supply, and in the case of 200V, multiple loads are connected in series.
As a specific switching means, as shown in FIG. 2 of the above-mentioned prior art, a changeover switch 11 is provided with a V-shaped movable contact piece (no figure number), and each load is connected in parallel to the power supply ( 100V), two movable contacts are used to connect both ends of each load to the power supply, and when connecting a pair of loads in series, one movable contact is used.

Although the switching means described above can easily connect multiple loads in parallel or in series with a single changeover switch,
It is necessary to manually operate the changeover switch after confirming whether it is 100V or 200V, which makes checking and operation troublesome, and if the AC voltage is connected to an AC power source without sufficiently confirming the AC voltage. There were drawbacks such as not being able to generate enough heat, or conversely, the heater overheating, creating a risk of fire or the like, or the heater wire breaking.

(C) Problems to be Solved by the Invention The present invention automatically changes the combined resistance value of the load connected between the AC power supply terminals in accordance with the commercial AC voltage supplied to the AC power supply terminals. It is designed to generate heat that matches the rated value, and in particular to change the combined resistance value of the load in sufficient response even when the AC voltage supplied to the AC power supply terminal fluctuates higher or lower than the rated voltage. purpose.

(d) Means for Solving the Problems The present invention provides at least two or more sets of loads connected between AC power supply terminals, and a voltage between the AC power supply terminals depending on the voltage applied between the AC power supply terminals. an actuation circuit that changes the combined resistance value of the two sets of loads connected to the AC power supply terminal, and the actuation circuit includes a DC circuit that converts AC power applied between the AC power supply terminals into DC; An SCR connected between a DC power source, a series circuit of multiple voltage dividing resistors connected in parallel to the SCR, and a constant voltage conduction connected between the gate of the SCR and the connection part of each of the voltage dividing resistors. and a switching element that increases the combined resistance value of the load when the SCR is conductive and decreases the combined resistance value of the load when the SCR is not conductive.

(E) Effect If the commercial AC voltage supplied between the AC power supply terminals is, for example, rated voltage 200V, the SCR of the operating circuit
becomes conductive and increases the combined resistance value of the load.If the rated voltage is 100V, the SCR becomes non-conductive and reduces the combined resistance value, making it possible to set the load to an appropriate value according to the supplied AC voltage.

(f) Examples Examples of the present invention will be described based on the drawings. FIG. 1 is a side view of the device installed in a hair dryer. Reference numeral 1 designates a hair dryer main body consisting of a pair of cases 2a and 2b, and is provided with a handle 4 having a cavity 3, an intake port 5, and a discharge port 7 consisting of a discharge grille 6. 8 is a motor for driving a fan 9 provided on the side of the intake port 5 in the main body, 10 is a heater unit provided on the side of the discharge port 7 in the main body, and as shown in FIG. The first heater 11 is divided into two parts: a heater 11a for heating and a heater 11b for reducing the voltage of the motor 8. ing. 13 is a printed circuit board stored and fixed in the space 3 of the handle 4; 14 is the space 3;
A mounting board for the relays 15a and 15b stored in the lower part of the interior, 16 a push-button power switch disposed between the printed circuit board 13 and the mounting board 14 in the space 3, 17 a power cord, and 18 the power cord. It is a code protector.

Figure 2 shows the basic electrical circuit diagram, 19
a, 19b are power supply terminals, 20 is a first switching element, 21 is a second switching element having a movable contact piece 21a, a first fixed contact 21b, and a second fixed contact 21c, which is electrically connected to the first switching element 20. It is linked to. The first heater 11 has one end connected to one terminal 19a of the power supply terminals, and the other end connected to the movable contact piece 2 of the second switching element 21.
Connected to 1a. On the other hand, one end of the second heater 12 is connected to the other terminal 19b of the supply terminals, and the other end is connected to the second fixed contact 21c of the second switching element 21. Further, the first fixed contact 21b from the second switching element is connected to the other terminal 19b of the supply terminals, and the first switching element 20 is connected to one terminal 19a of the supply terminals.
and the other end of the second heater 12.

Next, the operation will be described based on the basic electrical circuit diagram shown in FIG. For example, if the AC power that is currently being supplied is
If the voltage is 100V, the first and second switching elements 20 and 21 are switched to the positions indicated by solid lines. This switching operation is performed by operating the actuating circuit 22 as shown by the broken line. Switching element 2 as described above
0 and 21, the first heater 11 is connected to the supply terminals 19a and 19b via the movable contact piece 21a of the second switching element 20 and the first fixed contact 21b, and the second heater 12 is connected to the closed first The supply terminals 19a, 1 via the switching element 20
Connected to 9b. That is, the respective heaters are connected in parallel, and the supply terminals 19a,
A commercial power supply with a rated voltage of 100V is applied via 19b.

Power consumption P ₁ in this case is the resistance value R ₁ of the first heater 11, the resistance value R ₂ of the second heater 12, and the commercial current power source E, P ₁ = E ₂ /R ₁ +E ₂ /R ₂ =E ₂ (R ₁ + R ₂ )/R ₁・R ₂ .

The commercial power supply being supplied is at the rated voltage.
If the voltage is 200V, the movable contact 21a of the second switching element 21 is connected to the second fixed contact 21c by the operating circuit 22, and the first switching element 20 is connected to the second fixed contact 21c.
release. Due to the operation of the switching element as described above, the first heater 11 and the second heater 12 are connected in series via the movable contact piece 21a of the second switching element 21 and the second fixed contact 21b, and the supply terminal 19a is connected to this series circuit. , 19b, 200V commercial power is applied.

Power consumption P ₂ in this case is P ₂ =E ₂ /R ₁ +R ₂ .

Therefore, if R ₁ = 200Ω and R ₂ = 20Ω, P ₁
=P ₂ =1000W, even if the supply voltage is 100V
The same goes for 200V.

FIG. 3 embodies the operating circuit 22 shown in FIG. 2, and the electrical circuit diagram and its operation will be briefly explained. 23 and 24 are step-down resistors and diodes connected in series, 25 is a resistor connected to the diode 24, 26 is a constant voltage Zener diode, and 27 is a smoothing capacitor connected in parallel to the diode.

The first and second relays 15a and 15b are connected in parallel, and the first relay 15a, when energized, opens the first switching element 20, and the second
When the relay 15b is energized, the movable contact 21a of the second switching element 21 is connected to the second fixed contact 21c, and the switching element SW is connected to the second fixed contact 21c.
Configure. The parallel circuit of the first relay 15a and the second relay 15b is connected in series to the SCR 28,
This series circuit is connected in parallel to the smoothing capacitor 27. 29 and 30 are the diode 2
They are connected in series through a voltage dividing resistor connected between the cathode side of No. 4 and the other power supply terminal 19b. 3
1 is the gate of the SCR 28 and the resistor 29, 3
This is a constant voltage conduction element connected to the connection point P with 0, and is set to a value such that it becomes conductive depending on the potential of the connection point P when the supplied AC power supply voltage is about 150 to 160V. A full-wave rectifier 32 applies a DC voltage to the motor 8, and is connected to both ends of the step-down heater 11b. Reference numeral 33 designates an overtemperature rise preventer connected to the power supply terminals 19a and 19b via the power switch 16, and is provided at a suitable location in the heater unit 10.

If the currently supplied commercial power is 100V, the potential of the connection point P between the voltage dividing resistors 29 and 30 is low and the constant voltage conduction element 31 does not conduct, so the SCR
28 is non-conductive, and the first and second relays 15a,
The contact points of the first switching element 20 and the second switching element 21 of 15b are at the solid line positions shown in FIG. 19a and 19b. Here, when the power switch 16 is closed, each heater is
When a voltage of 100V is applied, the motor 8 rotates and the fan 9 blows air.

When the commercial power supply is 200V, the potential at the connection point P between the voltage dividing resistors 29 and 30 becomes high, and when it reaches the Zener voltage value of the constant voltage conduction element 31 or higher, the conduction element becomes conductive and the SCR 28 becomes conductive. Each of the first and second relays 15a, 15b is energized. With this activation, the first switching element 20
is opened and the movable contact piece 21a of the second switching element 21 is switched from the first fixed contact 21b to the second fixed contact 21c, so the first heater 11 and the second heater 12 are connected in series, and the combined resistance of the entire heater is The value increases.

Incidentally, in the present invention, an operating circuit has been described in which the first switching element is opened and closed and the second switching element is electrically interlocked.
The same applies to mechanical switching using one or more contact pieces. Further, the first heater and the second heater may not be switched in series and parallel, but one of the two heaters connected in series may be short-circuited depending on the voltage.

(G) Effects of the Invention As described above, the present invention automatically changes the combined resistance value of the load connected between the AC power supply terminals in accordance with the commercial AC voltage supplied to the AC power supply terminals, and always maintains the rated value. (from 100V to 200V), especially when the AC voltage supplied to the AC power supply terminal is rated 100V or 200V, the voltage fluctuation is higher or lower than the rated voltage. Even if there is a
The timing of conduction and non-conduction is determined.
Therefore, even if the rated voltage increases due to voltage fluctuations when a rated voltage of 100V is being supplied, the circuit will switch to a rated 200V circuit, or if the rated voltage decreases due to voltage fluctuations when the rated voltage is supplied to 200V. Since the operating circuit operates accurately, there is no inconvenience that would occur if the circuit switches to the rated 100V side due to malfunction, and dangers such as fire can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a side view of a hair dryer equipped with the load voltage switching circuit of the present invention with one case removed, Fig. 2 is a basic electric circuit diagram of the present invention, and Fig. 3 is a specific electric circuit diagram of the same. be. 11...First load, 12...Second load, 19a, 1
9b... AC power supply terminal, 22... Operating circuit, 28
...SCR, 29,30...Voltage dividing resistor, SW...Switching element.

Claims (1)

[Claims] 1 at least two connected between AC power supply terminals
at least one set of loads, and an operating circuit that changes a combined resistance value of the two sets of loads connected between the AC power supply terminals according to a voltage applied between the AC power supply terminals, the operating circuit is a DC circuit that converts the AC power applied between the AC power supply terminals into DC, an SCR connected to the DC power supply side of the DC circuit, and a series of multiple voltage dividing resistors connected in parallel to the SCR. A circuit, a constant voltage conduction element connected between the gate of the SCR and the connection portion of each of the voltage dividing resistors, and a combined resistance value of the load when the SCR is conductive, and a combined resistance value of the load when the SCR is conductive. A load voltage switching circuit comprising a switching element that reduces a combined resistance value.