JP2009276876A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit for outputting both a reference voltage source and a voltage higher than the reference voltage source from a single reference voltage source in the power supply circuit generating a plurality of DC voltages by using a commercial AC voltage. <P>SOLUTION: The collector of a first NPN transistor 6 is connected to a positive terminal 3 of an AC-DC power source 2 converting the voltage of a commercial AC power source 1 into a DC voltage, the base thereof is connected to the collector through a first resistor 4 and the emitter thereof is connected to a first load 5, the collector of a second NPN transistor 9 is connected to the emitter of the first NPN transistor 6, the base thereof is connected to the first resistor 4 through a second resistor 7 and the emitter thereof is connected to a second load 8, and a reference voltage source 11 is connected to the second resistor 7 and the negative terminal 10 of the power source 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply circuit that uses a commercial AC voltage to obtain a plurality of DC voltages.

  Conventionally, this type of power supply circuit connects a plurality of constant voltage circuits to the output of a rectifier circuit that converts commercial AC voltage into DC voltage, and a Zener diode breakdown voltage is used as a reference voltage source from one constant voltage circuit terminal. Is used to obtain a stabilized voltage, and a voltage stabilized by a voltage obtained by resistively dividing the breakdown voltage of the Zener diode is obtained from a terminal of another constant voltage circuit (for example, Patent Documents). 1).

In addition, a plurality of Zener diodes are connected in series as a reference voltage source, and a voltage stabilized with reference to the voltage obtained by the sum of breakdown voltages is obtained from the terminals of one constant voltage circuit, and other constant voltage circuits From these terminals, a voltage stabilized with reference to a voltage obtained from a connection point between the Zener diodes is obtained (for example, see Patent Document 2).
Japanese Utility Model Publication No. 4-93310 Japanese Unexamined Patent Publication No. 6-70537

  However, in such a conventional configuration, since the output of the reference voltage source and the voltage obtained by dividing the output voltage of the reference voltage source are used as the reference voltage source, a power supply circuit having an output voltage higher than that of the reference voltage source is configured. The problem is that it is not possible or a plurality of reference voltage sources are required.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to obtain a reference voltage source and a power supply circuit that outputs a voltage higher than the reference voltage source with a single reference voltage source.

  In order to achieve the above object, according to the present invention, the collector of the first NPN transistor is connected to the + terminal of an AC-DC power supply that converts the voltage of the commercial AC power supply into a DC voltage, and the base thereof is connected via the first resistor. The collector is connected to the first load, the emitter is connected to the first load, the collector of the second NPN transistor is connected to the emitter of the first NPN transistor, and the base is connected to the first resistor via the second resistor. In addition, the emitter is connected to the second load, and the reference voltage source is connected to the second resistor and the negative terminal of the AC-DC power supply.

  Thereby, it is possible to obtain a power supply circuit that outputs a reference voltage source and a voltage higher than the reference voltage source with a single reference voltage source without preparing a plurality of reference voltage sources.

  The power supply circuit of the present invention can obtain a power supply circuit that outputs a reference voltage source and a voltage higher than the reference voltage source with a single reference voltage source.

In the first invention, a collector is connected to a positive terminal of an AC-DC power supply that converts a commercial AC power supply voltage into a DC voltage, a base is connected to the collector via a first resistor, and an emitter is connected to a first load. A first NPN transistor, a second NPN transistor having a collector connected to the emitter of the first NPN transistor, a base connected to the first resistor via a second resistor, and an emitter connected to a second load And a reference voltage source connected to the negative terminal of the AC-DC power source, and a first resistor 4, a second resistor 7 and a reference voltage source connected in series. 11, thereby obtaining a reference voltage source and a power supply circuit that outputs a higher voltage than the reference voltage source with a single reference voltage source.

  According to a second invention, in the first invention, the reference voltage source is constituted by a Zener diode, and a power supply circuit having a simple structure can be constructed at a low cost.

  According to a third invention, in the first invention, the reference voltage source is constituted by a shunt regulator, and a highly accurate power supply circuit can be constituted.

  According to a fourth invention, in the third invention, the reference voltage of the shunt regulator is obtained from the emitter of the first NPN transistor, and the output voltage accuracy of the first NPN transistor can be improved. A highly accurate power supply circuit can be configured.

  According to a fifth invention, in the third invention, the reference voltage of the shunt regulator is obtained from the emitter of the second NPN transistor, and the output voltage accuracy of the second NPN transistor can be improved. A highly accurate power supply circuit can be configured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 shows a partial block diagram of a power supply circuit according to Embodiment 1 of the present invention, and FIG. 2 shows a sectional view of a rice cooker equipped with the power supply circuit.

  As shown in FIG. 1, the AC-DC power source 2 converts the voltage of the commercial AC power source 1 into a DC voltage, and the collector of the first NPN transistor 6 is connected to the + terminal 3 of the AC-DC power source 2. The base is connected to the collector via the first resistor 4, and the first load 5 including voice notification means (not shown) for performing voice notification to the emitter of the first NPN transistor 6 is provided. Connected. The collector of the second NPN transistor 9 is connected to the emitter of the first NPN transistor 6, the pace of the second NPN transistor 9 is connected to the first resistor 4 through the second resistor 7, and the emitter A second load composed of control means (not shown) for cooking rice by controlling the heating means for heating the pot in the pot and the temperature detection means for detecting the pot temperature in accordance with a previously stored sequence 8 is connected, and a Zener diode 12 is connected as a reference voltage source 11 between the second resistor 7 and the negative terminal 10 of the AC-DC power supply 2.

  The rice cooker including the power supply circuit configured as described above is configured as shown in FIG. That is, as shown in FIG. 2, an openable / closable lid 22 is provided on the upper surface of the body 21, and a heating coil 24 is disposed on the bottom and side surfaces of the storage portion 23 of the body 21. A ferrite core 25 is disposed on the outer peripheral side of 24. The heating coil 24 is a winding having a center substantially directly below the center of the bottom of the pan 21.

  The pan 21 is formed of a magnetic material such as stainless steel, iron, copper, etc., has a flange 26 protruding outward at the upper end opening, and is placed in a state where the flange 26 is lifted from the upper end of the storage portion 23. The storage unit 23 is detachably stored.

Although not shown, the first circuit board 27 includes input means such as a switch, display means such as an LCD, and control means. The second circuit board 28 constitutes the power supply circuit shown in FIG. 1, the voice notification means (not shown), the IGBT constituting the switching means, the resonance capacitor connected in series or in parallel with the heating coil 24, and the rectification means. It consists of a diode bridge, a choke coil, a smoothing capacitor, a current transformer that constitutes the input current detection means, an analog IC that constitutes the on-time setting means, etc., and the winding power cord 29 is electrically connected via a lead wire. It is connected.

  The temperature detection means 30 is composed of a thermistor or the like, and is arranged at the approximate center of the bottom of the pan 21. The cooling means 31 is constituted by a fan motor in which a fan is attached to a rotor of a DC brushless motor. The first circuit board 27 and the second circuit board 28 are electrically connected by lead wires, and an input current setting configured inside a microcomputer which is one of the components of the first circuit board 27. The on-time setting means mounted on the second circuit board 28 receives the signal from the means and the setting current fluctuation means, controls the IGBT on / off, and allows the high-frequency current to flow through the heating coil 24. The heating coil 24 generates an alternating magnetic field when a high-frequency current flows, and an eddy current flows through the pan 21 by the alternating magnetic field, and the pan 21 generates heat.

  As mentioned above, the rice cooker of this Embodiment induction-heats the pot 21, and cooks the food in the pot 21 with heat. Here, the cooked product is rice before cooking rice, water, cooked rice, or the like.

  The operation and action of the power supply circuit configured as described above will be described below.

The output voltage V _CC (20 VDC) of the AC-DC power supply 2 is applied to the first resistor 4 (1.6 kΩ) and the second resistor 7 (2 kΩ) connected in series and the Zener diode 12 as the reference voltage source 11. Thus, the output voltage V _REF of the reference voltage source 11 becomes 5.6 VDC due to the current flowing through the Zener diode 12. The emitter voltage V ₂ of the second NPN transistor 9 is 5.0 VDC because it is a voltage obtained by subtracting the base-emitter voltage V _BE2 (0.6 VDC) of the second NPN transistor 9 from the base voltage, ie, V _REF . . Similarly, the emitter voltage V ₁ of the first NPN transistor 6 is determined from the base voltage, that is, the contact voltage V _R2 (13.6 VDC) of the first resistor 4 and the second resistor 7, to the base emitter of the first NPN transistor 6. This is a voltage obtained by subtracting the intermediate voltage V _BE1 (0.6 VDC). A first resistor 4 contact voltage _{V R2} of the second resistor 7 becomes 13.0VDC.

  As described above, in the present embodiment, the collector of the first NPN transistor 6 is connected to the + terminal 3 of the AC-DC power supply 2 that converts the voltage of the commercial AC power supply 1 into a DC voltage, and the base thereof is the first. 1 is connected to the collector via the resistor 4 and the emitter is connected to the first load 5, the collector of the second NPN transistor 9 is connected to the emitter of the first NPN transistor 6, and the base is connected to the second resistor 7 is connected to the first resistor 4, the emitter is connected to the second load 8, and the reference voltage source 11 is connected to the second resistor 7 and the negative terminal 10 of the AC-DC power supply 2. A reference voltage is obtained from the connected first resistor 4, second resistor 7, and reference voltage source 11, whereby the reference voltage can be obtained from the same reference voltage source without preparing a separate reference voltage source. Source and reference voltage source There voltage can be obtained a power supply circuit for outputting.

  In addition, since the reference voltage source 11 is constituted by the Zener diode 12, an inexpensive and simple power supply circuit can be configured.

Further, since the second NPN transistor 9 does not step down from V _CC to V ₂ but lowers from V ₁ to V ₂ lower than V _CC , power consumption in the second NPN transistor 9 is reduced. by this, the second NPN transistor 9 as compared to the case of step-down from _{V CC} to _{V 2,} it is possible to use a small NPN transistor.

  In the present embodiment, the output voltage of the AC-DC power supply 2 is 20 VDC, the first resistor 4 is 1.6 kΩ, the second resistor 7 is 2 kΩ, and the reference voltage source 11 output voltage is 5.6 VDC. This is an example, and the present invention is not limited to this.

(Embodiment 2)
FIG. 3 shows a circuit diagram in which the power supply circuit according to the second embodiment of the present invention is partially formed into blocks.

  As shown in FIG. 3, the reference voltage source 11 includes a shunt regulator 15. A third resistor 16 and a fourth resistor 17 are connected in series between the emitter of the first NPN transistor 6 and GND, and a contact voltage between the third resistor 16 and the fourth resistor 17 is used as a shunt regulator. The reference voltage of the shunt regulator 15 is obtained from the emitter of the first NPN transistor 6. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  The operation and action of the power supply circuit configured as described above will be described below.

Output voltage _{V CC} of the AC-DC power supply 2 20 VDC, the reference voltage of the shunt regulator 15 is 2.495VDC, partial de-emitter voltage of the first NPN transistor 6 and the third resistor 16 and fourth resistor 17 The cathode voltage is output so that the pressed value becomes the reference voltage of 2.495 VDC. Here, when the third resistor 16 is 16 kΩ and the fourth resistor 17 is 4.7 kΩ so that the emitter voltage V _{1 of} the first NPN transistor 6 is about 11 VDC, the emitter voltage of the first NPN transistor 6 is set. V ₁ becomes 11.0 VDC, and a desired output voltage can be obtained.

Further, if the resistance values of the first resistor 4 and the second resistor 7 are selected so that the cathode voltage of the shunt regulator 15 becomes 5.5 VDC, the base of the second NPN transistor 9 is determined by the cathode voltage of the shunt regulator 15. The emitter voltage V2 of the _second NPN transistor 9, which is a voltage obtained by subtracting the voltage (0.6 VDC), can be set to 4.9 VDC. The connection point between the first resistor 4 and the second resistor 7 is the base voltage of the first NPN transistor 6, which is 11.6 VDC because it is 0.6 VDC higher than the emitter voltage V ₁ , and the first resistor 4 Is 1.8 kΩ, and the second resistor 7 is 1.3 kΩ, the current flowing through the first resistor 4 is 4.7 mA. For simplicity, if the current flowing to the base of the first NPN transistor 6 is ignored, the current flowing to the first resistor 4 also flows to the second resistor 7, and the voltage drop across the second resistor 7 is 6 .1VDC.

As a result, the base voltage of the second NPN transistor 9 becomes 5.5 VDC, and the emitter voltage V ₂ of the second NPN transistor 9 becomes 4.9 VDC.

  The power supply circuit configured as described above is mounted on, for example, a rice cooker shown in FIG.

  As described above, in the present embodiment, since the reference voltage source 11 is configured by the shunt regulator 15, a highly accurate power supply circuit can be configured.

  Further, since the reference voltage of the shunt regulator 15 is obtained from the emitter of the first NPN transistor 6, the output voltage of the first NPN transistor, that is, the output voltage to the first load 5 can be made highly accurate. . Further, by obtaining a reference voltage from the first resistor 4 and the second resistor 7 connected in series and the reference voltage source 11, a reference voltage source can be obtained with the same reference voltage source without preparing a separate reference voltage source. A highly accurate power supply circuit that outputs a higher voltage than the reference voltage source can be obtained.

Further, since the second NPN transistor 9 does not step down from V _CC to V ₂ but lowers from V ₁ to V ₂ lower than V _CC , power consumption in the second NPN transistor 9 is reduced. by this, the second NPN transistor 9 as compared to the case of step-down from _{V CC} to _{V 2,} it is possible to use a small NPN transistor.

In the present _embodiment, 20 VDC to _{V CC,} 2.495VDC the reference voltage of the shunt regulator 15, 11VDC to _{V 1,} 4.9VDC and _{V 2,} the first resistor 4 and 1.8Keiomega, the second Although the resistor 7 is set to 1.3 kΩ, the third resistor 16 is set to 16 kΩ, and the fourth resistor 17 is set to 4.7 kΩ, this is an example, and the present invention is not limited thereto.

(Embodiment 3)
FIG. 4 shows a circuit diagram in which a power supply circuit according to the third embodiment of the present invention is partially blocked.

  As shown in FIG. 4, the reference voltage source 11 includes a shunt regulator 15. A fifth resistor 18 and a fourth resistor 17 are connected in series between the emitter of the second NPN transistor 9 and GND, and a contact voltage between the fifth resistor 18 and the fourth resistor 17 is used as a shunt regulator. The reference voltage of the shunt regulator is obtained from the emitter of the second NPN transistor 9. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  The operation and action of the power supply circuit configured as described above will be described below.

Output voltage _{V CC} of the AC-DC power supply 2 20 VDC, the reference voltage of the shunt regulator 15 is 2.495VDC, partial de-emitter voltage of the second NPN transistor 9 and the fifth resistor 18 and fourth resistor 17 The cathode voltage is output so that the pressed value becomes the reference voltage of 2.495 VDC. Here, the emitter voltage _{V 2} of the second NPN transistor 9 and both 10kΩ and fourth resistor 17 a fifth resistor 18 so as to be approximately 5VDC, emitter voltage _{V 2} of the second NPN transistor 9 5 .0VDC and a desired output voltage can be obtained.

The base voltage of the second NPN transistor 9, since the base-emitter voltage _V BE2 (0.6VDC) a voltage applied than the emitter voltage _{V 2} second NPN transistor 9, the 5.6VDC.

Next, assuming that the first resistor 4 is 1.6 kΩ and the second resistor 7 is 2 kΩ, the base voltage of the first NPN transistor 6 is divided by the first resistor 4 and the second resistor 7. The voltage is 13.6 VDC. As a result, the emitter voltage V ₁ of the first NPN transistor 6 is a voltage obtained by subtracting the base-emitter voltage V _BE1 (0.6 VDC) of the first NPN transistor 9 and thus becomes 13.0 VDC.

  The power supply circuit configured as described above is mounted on, for example, a rice cooker shown in FIG.

  As described above, in this embodiment, since the reference voltage of the shunt regulator 15 is obtained from the emitter of the second NPN transistor 9, the output voltage of the second NPN transistor 9, that is, the second load 8 The output voltage to can be made highly accurate. Further, by obtaining a reference voltage from the first resistor 4 and the second resistor 7 connected in series and the reference voltage source 11, the reference voltage source can be connected with the same reference voltage source without preparing a separate reference voltage source. A highly accurate power supply circuit that outputs a higher voltage than the reference voltage source can be obtained.

Further, since the second NPN transistor 9 does not step down from V _CC to V ₂ but lowers from V ₁ to V ₂ lower than V _CC , power consumption in the second NPN transistor 9 is reduced. by this, the second NPN transistor 9 as compared to the case of step-down from _{V CC} to _{V 2,} it is possible to use a small NPN transistor.

In the present _embodiment, 20 VDC to _{V CC,} 2.495VDC the reference voltage of the shunt regulator 15, 13VDC to _{V 1,} 5.0 VDC to _{V 2,} the first resistor 4 and 1.6Keiomega, the second The resistor 7 is set to 2.0 kΩ, the third resistor 16 is set to 10 kΩ, and the fourth resistor 17 is set to 10 kΩ. However, this is an example, and the present invention is not limited thereto.

  As described above, the power supply circuit according to the present invention can obtain a reference voltage source and a power supply circuit that outputs a higher voltage than the reference voltage source with a single reference voltage source. It is useful as a power supply circuit for obtaining a direct current voltage.

Circuit diagram in which the power supply circuit according to Embodiment 1 of the present invention is partly blocked Cross section of rice cooker equipped with the same power circuit The circuit diagram which made the power supply circuit in Embodiment 2 of this invention into a partial block The circuit diagram which made the power supply circuit in Embodiment 3 of this invention into a partial block

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial alternating current power supply 2 AC-DC power supply 3 + terminal 4 1st resistance 5 1st load 6 1st NPN transistor 7 2nd resistance 8 2nd load 9 2nd NPN transistor 10-terminal 11 Reference voltage source

Claims (5)

A first NPN transistor having a collector connected to a positive terminal of an AC-DC power source that converts a voltage of a commercial AC power source into a DC voltage, a base connected to the collector via a first resistor, and an emitter connected to a first load; A second NPN transistor having a collector connected to the emitter of the first NPN transistor, a base connected to the first resistor via a second resistor, and an emitter connected to a second load; A power supply circuit comprising a resistor and a reference voltage source connected to a negative terminal of the AC-DC power supply. 2. The power supply circuit according to claim 1, wherein the reference voltage source is constituted by a Zener diode. 2. The power supply circuit according to claim 1, wherein the reference voltage source is constituted by a shunt regulator. 4. The power supply circuit according to claim 3, wherein the reference voltage of the shunt regulator is obtained from the emitter of the first NPN transistor. 4. The power supply circuit according to claim 3, wherein the reference voltage of the shunt regulator is obtained from the emitter of the second NPN transistor.