JP5287561B2 - Stabilized power circuit - Google Patents

Description

  The present invention relates to a stabilized power supply circuit, for example, a stabilized power supply circuit of a control circuit section of an electric cooking appliance used in a general household.

  Conventionally, this type of stabilized power circuit is configured as shown in FIG. 7 (see, for example, Patent Document 1). Hereinafter, the configuration will be described. As shown in FIG. 7, the stabilized power supply circuit has a collector connected to a positive output terminal of a DC power supply unit (not shown) that outputs a DC voltage Vi, and a base connected to the DC power supply unit via a first resistor 71. A NPN first transistor 72 connected to a positive output terminal, a Zener having a cathode connected to the base of the NPN first transistor 72 and an anode connected to a negative output terminal of the DC power supply unit via a second resistor 73 A diode 74, an emitter connected to the negative output terminal of the DC power supply unit, a base connected to the anode of the Zener diode 74, and an emitter connected to the emitter of the NPN first transistor 72 The base is connected to the NPN-type second transistor 75 via a third resistor 76 and the NPN-type first is connected via a fourth resistor 77. Are those comprising a PNP-type third transistor 78 connected to the emitter of the transistor 72, the output voltage Vo from the collector of the PNP-type third transistor 78 is taken out.

  The operation of the conventional stabilized power supply circuit configured as described above will be described. When the output voltage Vi of the DC power supply unit is a sum of the Zener voltage Vz74 of the Zener diode 74 and VBE75 that is the base-emitter voltage of the NPN-type second transistor 75, that is, a voltage lower than Vz74 + VBE75, the first resistor 71 and the Zener diode 74 Since no current flows through the base of the NPN-type second transistor 75 through the NPN-type second transistor 75, the NPN-type second transistor 75 becomes non-conductive. At this time, since the base current of the PNP type third transistor 78 does not flow, the PNP type third transistor 78 is also turned off. When the input power supply voltage Vi becomes higher than VZ74 + VBE75, a current flows through the first resistor 71 and the Zener diode 74 to the base of the NPN second transistor 75, so that the NPN second transistor 75 becomes conductive. As a result, the base current of the PNP third transistor 78 flows through the third resistor 76, and the PNP third transistor 78 is also turned on. At this time, if the potential difference in the first resistor 71 is VR71, Vi = VR71 + Vz74 + VBE75. The emitter voltage VE72 of the NPN first transistor 72 is VE72 = Vz74 + VBE75−VBE72, where the base-emitter voltage of the NPN first transistor 72 is VBE72. The collector voltage VC78 of the PNP third transistor 78 is the collector-emitter voltage of the PNP third transistor 78 as Vce78, and VC78 = VE72-Vce78.

Japanese Unexamined Patent Publication No. 1-155411

However, in the conventional configuration, the Zener voltage Vz74 of the Zener diode 74, the VBE72 of the NPN first transistor 72, the VBE75 of the NPN second transistor 75, the VCE78 of the PNP third transistor 78, and the output of the DC power supply unit. Due to the variation in the voltage Vi, the emitter voltage VE72 of the NPN first transistor 72 and the collector voltage VC78 of the PNP third transistor 78 also have a problem. For example, in an induction heating rice cooker that performs power control by detecting an input power supply voltage or an input power supply current using an AD converter circuit that uses VE72 or VC78 as a reference voltage, power control at the time of rice cooking or heat retention Variation, that is, variation in electric power used for cooking and heating, and as a result, variation in the taste of rice.

  The present invention solves the above-described conventional problems, and in a stabilized power circuit, for example, a stabilized power circuit of a control circuit unit of an electric cooking appliance or the like used in a general household, a stabilized power circuit with less variation in output voltage. The purpose is to provide.

  In order to solve the above-described conventional problems, a stabilized power supply circuit according to the present invention includes a first NPN transistor having a collector connected to a positive output terminal of a DC power supply that is a DC voltage source, and a first NPN transistor. A first resistor connected to a base and a positive output terminal of the DC power supply unit; a second resistor connected to the first resistor and a third resistor connected to the negative output terminal of the DC power supply unit; and an emitter Is connected to the negative output terminal of the DC power supply unit, the base is connected to the connection point of the second resistor and the third resistor, and the emitter is the emitter of the first NPN transistor. A PNP transistor having a base connected to the emitter of the first NPN transistor via a fourth resistor and a collector connected to the collector of the second NPN transistor via a fifth resistor. A voltage detector that divides and outputs the voltage of either the emitter of the first NPN transistor or the collector of the PNP transistor, and the base of the first NPN transistor and the output of the voltage detector A stabilized power supply circuit including a voltage adjusting unit that is connected to a negative output terminal of the DC power supply unit and adjusts an output voltage so that an output voltage of the voltage detection unit becomes a first predetermined voltage is provided. .

  As a result, it is possible to provide a stabilized power supply circuit with high output voltage accuracy by reducing output voltage variations caused by component variations.

  The stabilized power supply circuit of the present invention includes a voltage adjustment unit that adjusts the output voltage so as to obtain a predetermined output voltage, thereby suppressing the output voltage variation of the stabilized power supply circuit due to the characteristics of components or manufacturing variations. Therefore, it is possible to provide a stabilized power supply circuit with high output voltage accuracy.

Circuit diagram of the stabilized power supply circuit according to the first embodiment of the present invention Circuit diagram of the stabilized power supply circuit according to the second embodiment of the present invention Circuit diagram of a stabilized power supply circuit according to Embodiment 3 of the present invention Circuit diagram of a stabilized power supply circuit according to Embodiment 4 of the present invention Circuit diagram of the stabilized power supply circuit according to the fifth embodiment of the present invention Circuit diagram of the stabilized power supply circuit according to the sixth embodiment of the present invention Circuit diagram of conventional stabilized power supply circuit

  The first invention can suppress voltage variations caused by variations in the reference voltage section, the first NPN transistor, the second NPN transistor, the PNP transistor, the DC power supply section, etc., and achieve high-accuracy stabilization A power supply circuit can be provided.

In particular, the voltage regulator of the first invention is connected to the base of the first NPN transistor and the anode is connected to the negative output terminal of the DC power supply unit. Since the reference is configured by the shunt regulator connected to the output of the voltage detection unit, the voltage adjustment unit can be configured with a small number of components, and a compact stabilized power supply circuit can be provided.

  According to a third aspect of the invention, in particular, in any one of the first and second aspects of the invention, a voltage limiting unit that limits the base voltage of the first NPN transistor to be equal to or lower than the second predetermined voltage is provided. The emitter voltage of the first NPN transistor can be suppressed to less than the absolute rated voltage of the load, the load can be prevented from being broken or broken, and a highly reliable device can be provided.

  According to a fourth aspect of the invention, in particular, the voltage limiting section of the third aspect of the invention is constituted by a first Zener diode having a cathode connected to the base of the first NPN transistor and an anode connected to the negative output terminal of the DC power supply section. As a result, the voltage limiting unit can be provided with only one component.

  In particular, in the fifth invention, in any one of the first to fourth inventions, the start-up voltage limiting unit which turns on the second NPN transistor only when the output voltage of the DC power supply unit is equal to or higher than a predetermined voltage. Since the PNP transistor can be brought into a conducting state only when the output of the DC power supply unit is equal to or higher than a predetermined voltage, it is possible to start the power supply after the DC power supply unit is in a sufficiently stable output state. Become.

  In a sixth aspect of the present invention, in particular, in any one of the fifth aspects of the present invention, the starting voltage limiting unit has a cathode connected to a contact point between the first resistor and the base of the first NPN transistor, and an anode Since the second Zener diode connected to the second resistor is used, the voltage limiting unit can be provided with only one component.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a circuit diagram of a stabilized power supply circuit according to the first embodiment of the present invention. In FIG. 1, the first NPN transistor 1 has a collector connected to a positive output terminal of a DC power supply unit 3 that is a DC voltage source that converts a commercial AC power supply 2 into a DC voltage VCC and outputs the converted voltage. The first resistor 4 is connected to the base of the first NPN transistor 1 and the positive output terminal of the DC power supply unit 3. The second resistor 5 is connected to the first resistor 4 and the third resistor 6 connected to the negative output terminal of the DC power supply unit 3. The second NPN transistor 7 has an emitter connected to the negative output terminal of the DC power supply unit 3 and a base connected to a connection point between the second resistor 5 and the third resistor 6. The PNP transistor 8 has an emitter connected to the emitter of the first NPN transistor 1, a base connected to the emitter of the first NPN transistor 1 via the fourth resistor 9, and a second resistor via the fifth resistor 10. It is connected to the collector of the NPN transistor 7. The voltage detection unit 11 includes a first voltage dividing resistor 11a and a second voltage dividing resistor 11b. The first voltage dividing resistor 11a is connected to the collector of the PNP transistor 8 and the second voltage dividing resistor 11b. The other end of the second voltage dividing resistor 11 b is connected to the negative output terminal of the DC power supply unit 3. The collector voltage VB of the PNP transistor 8 divided by the voltage dividing resistor 11 a and the second voltage dividing resistor 11 b is output to the voltage adjusting unit 11. The voltage adjustment unit 12 is connected to the base of the first NPN transistor 1, the output of the voltage detection unit 11, and the negative output terminal of the DC power supply unit 3.

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

When a DC voltage VCC is output from the DC power supply unit 3, a base current flows through the first NPN transistor 1 via the first resistor 4 to be turned on, and the first NPN transistor generates VDD from the emitter. VDD is applied to the collector of the second NPN transistor 7 through the fourth resistor 9 and the fifth resistor 10. A base current flows through the base of the second NPN transistor 7 via the first resistor 4 and the second resistor 5. At this time, if VCC is equal to or higher than a predetermined voltage, the second NPN transistor 7 is turned on. When the second NPN transistor is turned on, the base current of the PNP transistor 8 flows through the fifth resistor 10 and the second NPN transistor 7, and the PNP transistor is turned on. When the PNP transistor is turned on, the voltage detection unit 11 divides the output voltage VB by the first voltage dividing resistor 11a and the second voltage dividing resistor 11b and outputs the divided voltage to the voltage adjusting unit 12. The voltage adjustment unit 12 outputs its output voltage, that is, the base voltage of the first NPN transistor 1 so that the collector voltage VB of the PNP transistor 7 becomes a first predetermined voltage (for example, 5 V) in response to the input from the voltage detection unit 11. Vb1 is adjusted. That is, when VB is lower than the first predetermined voltage, Vo is increased, and when VB is higher than the first predetermined voltage, adjustment is performed so that VB becomes the first predetermined voltage by decreasing Vo. .

  Since the emitter voltage VDD of the first NPN transistor 1 is lower than the output voltage Vo of the voltage adjustment unit 12 by its own base-emitter voltage VBE1, VDD is VDD = Vo−VBE1. Further, since the collector voltage VB of the PNP transistor 7 is lower than its own collector-emitter voltage VCE8 by VDD, VB can be expressed as VB = VDD−VCE8 or VB = (Vo−VBE1) −VCE8. it can.

  The base-emitter voltage VBE1 of the first NPN transistor and the collector-emitter voltage VCE8 of the PNP transistor fluctuate due to various causes such as variations due to manufacturing of the element itself, a load state, and an ambient temperature. However, since the voltage adjustment unit 12 adjusts the output voltage Vo according to the output voltage of the voltage detection unit 11, that is, VB, the influence of changes in VBE1 and VCE8 can be suppressed. Furthermore, since the voltage adjusting unit 11 adjusts the output without depending on the output voltage VCC of the DC power supply unit 3, the influence on the VB due to the output variation of the DC power supply unit 3 can be suppressed.

  As described above, in the present embodiment, the voltage adjustment unit 12 adjusts the output voltage, that is, the base voltage of the first NPN transistor, in accordance with the input from the voltage detection unit 11, and therefore the first NPN transistor 1 Since the output voltage variation caused by the variation of the second NPN transistor 7, the PNP transistor 8, and the DC power supply unit 3 can be suppressed, the detection voltage of the voltage detection unit 11 can always be kept at the first predetermined voltage. A highly accurate stabilized power supply circuit can be supplied.

  In the present embodiment, the voltage detection unit 11 detects the collector voltage VB of the PNP transistor 8 and outputs the divided voltage VB to the voltage adjustment unit 12 so that VB becomes the first predetermined voltage. However, the voltage detection unit 11 detects the emitter voltage VDD of the first NPN transistor 1 and outputs the divided voltage of VDD to the voltage adjustment unit 11 so that VDD becomes the first predetermined voltage. May be.

(Embodiment 2)
FIG. 2 is a circuit diagram of a stabilized power supply circuit according to the second embodiment of the present invention. In FIG. 2, the same components as those in FIG. 1 are given the same numbers as in FIG.

The voltage adjustment unit 12 includes a shunt regulator 12a. The cathode of the shunt regulator 12 a is connected to the base of the first NPN transistor 1. The anode of the shunt regulator 12 a is connected to the negative output terminal of the DC power supply unit 3. The reference of the shunt regulator 12a is connected to the connection point between the voltage dividing resistor 11a and the second voltage dividing resistor 11b of the voltage detection unit 11. The resistance values of the voltage dividing resistor 11a and the second voltage dividing resistor 11b are set to resistance values that are equal to the reference voltage of the shunt regulator 12a when the detection voltage of the voltage detection unit 11 is the first predetermined voltage.

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

  When a DC voltage VCC is output from the DC power supply unit 3, a base current flows through the first NPN transistor 1 via the first resistor 4 to be turned on, and the first NPN transistor generates VDD from the emitter. VDD is applied to the collector of the second NPN transistor 7 through the fourth resistor 9 and the fifth resistor 10. A base current flows through the base of the second NPN transistor 7 via the first resistor 4 and the second resistor 5. At this time, if VCC is equal to or higher than a predetermined voltage, the second NPN transistor 7 is turned on. When the second NPN transistor is turned on, the base current of the PNP transistor 8 flows through the fifth resistor 10 and the second NPN transistor 7, and the PNP transistor is turned on. When the PNP transistor is turned on, the voltage detection unit 11 divides the output voltage VB by the first voltage dividing resistor 11a and the second voltage dividing resistor 11b and outputs the divided voltage to the voltage adjusting unit 12. The voltage adjustment unit 12 outputs its output voltage, that is, the base voltage of the first NPN transistor 1 so that the collector voltage VB of the PNP transistor 7 becomes a first predetermined voltage (for example, 5 V) in response to the input from the voltage detection unit 11. Vb1 is adjusted. That is, when VB is lower than the first predetermined voltage, the output voltage of the voltage detection unit is smaller than the reference voltage Vref of the shunt regulator 12a, so that the shunt regulator 12a increases the output voltage. On the other hand, when VB is higher than the first predetermined voltage, the output voltage of the voltage detector is higher than Vref, so that the shunt regulator 12a decreases the output voltage. With the above operation, the voltage adjustment unit 11 adjusts the output voltage so that VB becomes the first predetermined voltage. That is, when VB is lower than the first predetermined voltage, Vo is increased, and when VB is higher than the first predetermined voltage, adjustment is performed so that VB becomes the first predetermined voltage by decreasing Vo. . Since the emitter voltage VDD of the first NPN transistor 1 is lower than the output voltage Vo of the voltage adjustment unit 12 by its own base-emitter voltage VBE1, VDD is VDD = Vo−VBE1. Further, since the collector voltage VB of the PNP transistor 7 is lower than its own collector-emitter voltage VCE8 by VDD, VB can be expressed as VB = VDD−VCE8 or VB = (Vo−VBE1) −VCE8. it can. The base-emitter voltage VBE1 of the first NPN transistor and the collector-emitter voltage VCE8 of the PNP transistor fluctuate due to various causes such as variations due to manufacturing of the element itself, a load state, and an ambient temperature. However, since the shunt regulator 12a adjusts the output voltage Vo according to the output voltage of the voltage detection unit 11, that is, VB, the influence of changes in VBE1 and VCE8 can be suppressed. Furthermore, since the shunt regulator 12a adjusts its output without depending on the output voltage VCC of the DC power supply unit 3, the influence on the VB due to the output variation of the DC power supply unit 3 can be suppressed.

  As described above, in the present embodiment, the shunt regulator 12a adjusts the output voltage, that is, the base voltage of the first NPN transistor, in accordance with the input from the voltage detector 11, so that the first NPN transistor 1, Since the output voltage variation caused by the variations of the second NPN transistor 7, the PNP transistor 8, and the DC power supply unit 3 can be suppressed, and the detection voltage of the voltage detection unit 11 can always be kept at the first predetermined voltage. An accurate stabilized power supply circuit can be supplied.

  In the present embodiment, the voltage detection unit 11 detects the collector voltage VB of the PNP transistor 8 and outputs the divided voltage VB to the voltage adjustment unit 12 so that VB becomes the first predetermined voltage. However, the voltage detection unit 11 detects the emitter voltage VDD of the first NPN transistor 1 and outputs the divided voltage of VDD to the voltage adjustment unit 11 so that VDD becomes the first predetermined voltage. May be.

(Embodiment 3)
FIG. 3 is a circuit diagram of a stabilized power supply circuit according to the third embodiment of the present invention. 3, the same components as those in FIG. 1 are given the same reference numerals as those in FIG.

  The voltage limiting means 13 is provided between the base of the first NPN transistor 1 and the negative output terminal of the DC voltage unit 3, and limits the base voltage of the first NPN transistor 1 to be equal to or lower than a second predetermined voltage. It is.

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

  The voltage adjustment unit 12 adjusts the output voltage in accordance with the input from the voltage detection unit 11, but the current supplied to the load connected to VDD or VB suddenly changes, and the commercial power supply 1 flows in. Due to various factors such as sudden fluctuations in the output voltage VCC of the DC power supply unit 3 due to unexpected noise or noise superimposed on the output voltage of the voltage adjustment unit 11, the output voltage Vo rises, and VDD and VB are There is a risk of supplying a voltage exceeding the absolute maximum rating of the connected load. In order to prevent this, the voltage limiting means 12 is provided between the base of the first NPN transistor 1 and the negative output terminal of the DC voltage unit 3 so that the base voltage of the first NPN transistor 1 is equal to or lower than the second predetermined voltage. It is restricted as such. The second predetermined voltage is a voltage lower than any voltage obtained by adding the base-emitter voltage VBE1 of the first NPN transistor 1 to the absolute maximum rating of the load connected to VDD and VB.

  As described above, in the present embodiment, the base voltage of the first NPN transistor is set to the second voltage so that the emitter voltage VDD of the first NPN transistor is lower than the absolute maximum rating of all the connected loads. Since the emitter voltage of the first NPN transistor does not exceed the absolute rated voltage of all the loads, it is possible to prevent the load from being broken or broken. A highly reliable device can be provided.

(Embodiment 4)
FIG. 5 is a circuit diagram of a stabilized power supply circuit according to the fourth embodiment of the present invention. In FIG. 5, the same components as those in FIG. 3 are given the same numbers as in FIG.

  The voltage limiting means 13 is composed of a first Zener diode 13 a having a cathode connected to the base of the first NPN transistor 1 and an anode connected to the negative output terminal of the DC power supply unit 3.

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

The voltage adjustment unit 12 adjusts the output voltage in accordance with the input from the voltage detection unit 11, but the current supplied to the load connected to VDD or VB suddenly changes, and the commercial power supply 1 flows in. Due to various factors such as sudden fluctuations in the output voltage VCC of the DC power supply unit 3 due to unexpected noise or noise superimposed on the output voltage of the voltage adjustment unit 11, the output voltage Vo rises, and VDD and VB are There is a risk of supplying a voltage exceeding the absolute maximum rating of the connected load. In order to prevent this, there is provided voltage limiting means 13 comprising a first Zener diode 13a having a cathode connected to the base of the first NPN transistor 1 and an anode connected to the negative output terminal of the DC power supply unit 3. Yes. By providing this voltage control means 13, even if the base voltage of the first NPN transistor 1 rises, it is clipped by the Zener voltage of the first Zener diode, so it does not exceed the Zener voltage of the first Zener diode 13a. . The Zener voltage of the first Zener diode is the second predetermined voltage, and is lower than any voltage obtained by adding the base-emitter voltage VBE1 of the first NPN transistor 1 to the absolute maximum rating of the load connected to VDD. It is. As a result, no voltage exceeding the absolute maximum rating is applied to all the loads connected to the emitter of the first NPN transistor 1.

  As described above, in the present embodiment, the base voltage of the first NPN transistor is set to the second voltage so that the emitter voltage VDD of the first NPN transistor is lower than the absolute maximum rating of all the connected loads. Since the emitter voltage of the first NPN transistor does not exceed the absolute rated voltage of all the loads, it is possible to prevent the load from being broken or broken. A highly reliable device can be provided. Further, the voltage limiting means 12 is constituted by a first Zener diode having a cathode connected to the base of the first NPN transistor and an anode connected to the negative output terminal of the DC power supply unit. A voltage limiting means can be realized.

(Embodiment 5)
FIG. 5 is a circuit diagram of a stabilized power circuit according to the sixth embodiment of the present invention. In FIG. 5, the same components as those in FIG. 1 are given the same numbers as in FIG.
The start-up voltage limiting unit 14 is connected to the contact between the first resistor 4 and the base of the first NPN transistor 1 and the second resistor, and turns on the second NPN transistor at a third predetermined voltage or higher. It is possible to flow a base current that can be generated.

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

When a DC voltage VCC is output from the DC power supply unit 3, a base current flows through the first NPN transistor 1 via the first resistor 4 to be turned on, and the first NPN transistor generates VDD from the emitter. VDD is applied to the collector of the second NPN transistor 7 through the fourth resistor 9 and the fifth resistor 10. Then, a base current flows through the base of the second NPN transistor 7 through the first resistor 4, the starting voltage limiting unit 14, and the second resistor 5. At this time, if VCC is at least a third predetermined voltage or more, a base current that is sufficient to turn on the second NPN transistor 7 flows, so that the second NPN transistor 7 is turned on. When the second NPN transistor is turned on, the base current of the PNP transistor 8 flows through the fifth resistor 10 and the second NPN transistor 7, and the PNP transistor is turned on. When the PNP transistor is turned on, the voltage detection unit 11 divides the output voltage VB by the first voltage dividing resistor 11a and the second voltage dividing resistor 11b and outputs the divided voltage to the voltage adjusting unit 12. The voltage adjustment unit 12 outputs its output voltage, that is, the base voltage of the first NPN transistor 1 so that the collector voltage VB of the PNP transistor 7 becomes a first predetermined voltage (for example, 5 V) in response to the input from the voltage detection unit 11. Vb1 is adjusted. That is, when VB is lower than the first predetermined voltage, Vo is increased, and when VB is higher than the first predetermined voltage, adjustment is performed so that VB becomes the first predetermined voltage by decreasing Vo. .
Since the emitter voltage VDD of the first NPN transistor 1 is lower than the output voltage Vo of the voltage adjustment unit 12 by its own base-emitter voltage VBE1, VDD is VDD = Vo−VBE1. Further, since the collector voltage VB of the PNP transistor 7 is lower than its own collector-emitter voltage VCE8 by VDD, VB can be expressed as VB = VDD−VCE8 or VB = (Vo−VBE1) −VCE8. it can.
The base-emitter voltage VBE1 of the first NPN transistor and the collector-emitter voltage VCE8 of the PNP transistor fluctuate due to various causes such as variations due to manufacturing of the element itself, a load state, and an ambient temperature. However, since the voltage adjustment unit 12 adjusts the output voltage Vo according to the output voltage of the voltage detection unit 11, that is, VB, the influence of changes in VBE1 and VCE8 can be suppressed. Furthermore, since the voltage adjusting unit 11 adjusts the output without depending on the output voltage VCC of the DC power supply unit 3, the influence on the VB due to the output variation of the DC power supply unit 3 can be suppressed.

  As described above, in the present embodiment, the voltage adjustment unit 12 adjusts the output voltage, that is, the base voltage of the first NPN transistor, in accordance with the input from the voltage detection unit 11, and therefore the first NPN transistor 1 Since the output voltage variation caused by the variation of the second NPN transistor 7, the PNP transistor 8, and the DC power supply unit 3 can be suppressed, the detection voltage of the voltage detection unit 11 can always be kept at the first predetermined voltage. A highly accurate stabilized power supply circuit can be supplied. In addition, the second NPN transistor can be brought into a conductive state only when the output voltage of the DC power supply unit is equal to or higher than the third predetermined voltage. As a result, the PNP transistor can be turned on only when the output of the DC power supply unit is equal to or higher than a predetermined voltage, and the power supply can be activated after the DC power supply unit is in a sufficiently stable output state.

  In the present embodiment, the voltage detection unit 11 detects the collector voltage VB of the PNP transistor 8 and outputs the divided voltage VB to the voltage adjustment unit 12 so that VB becomes the first predetermined voltage. However, the voltage detection unit 11 detects the emitter voltage VDD of the first NPN transistor 1 and outputs the divided voltage of VDD to the voltage adjustment unit 11 so that VDD becomes the first predetermined voltage. May be.

(Embodiment 6)
FIG. 6 is a circuit diagram of a stabilized power supply circuit according to the sixth embodiment of the present invention.

6, the same components as those in FIG. 5 are given the same numbers as in FIG.
The second Zener diode 14a has a cathode connected to a contact point between the first resistor 4 and the base of the first NPN transistor 1, and an anode connected to the second resistor.

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

  When a DC voltage VCC is output from the DC power supply unit 3, a base current flows through the first NPN transistor 1 via the first resistor 4 to be turned on, and the first NPN transistor generates VDD from the emitter. VDD is applied to the collector of the second NPN transistor 7 through the fourth resistor 9 and the fifth resistor 10. A base current flows through the base of the second NPN transistor 7 via the first resistor 4, the second Zener diode 14 a, and the second resistor 5. At this time, if VCC is at least equal to or higher than the Zener voltage of the second Zener diode 14a, the base current flows through the second NPN transistor 7, so that the second NPN transistor 7 is turned on. When the second NPN transistor is turned on, the base current of the PNP transistor 8 flows through the fifth resistor 10 and the second NPN transistor 7, and the PNP transistor is turned on. When the PNP transistor is turned on, the voltage detection unit 11 divides the output voltage VB by the first voltage dividing resistor 11a and the second voltage dividing resistor 11b and outputs the divided voltage to the voltage adjusting unit 12. The voltage adjustment unit 12 outputs its output voltage, that is, the base voltage of the first NPN transistor 1 so that the collector voltage VB of the PNP transistor 7 becomes a first predetermined voltage (for example, 5 V) in response to the input from the voltage detection unit 11. Vb1 is adjusted. That is, when VB is lower than the first predetermined voltage, Vo is increased, and when VB is higher than the first predetermined voltage, adjustment is performed so that VB becomes the first predetermined voltage by decreasing Vo. .

Since the emitter voltage VDD of the first NPN transistor 1 is lower than the output voltage Vo of the voltage adjustment unit 12 by its own base-emitter voltage VBE1, VDD is VDD = Vo−VBE1. Further, since the collector voltage VB of the PNP transistor 7 is lower than its own collector-emitter voltage VCE8 by VDD, VB can be expressed as VB = VDD−VCE8 or VB = (Vo−VBE1) −VCE8. it can.
The base-emitter voltage VBE1 of the first NPN transistor and the collector-emitter voltage VCE8 of the PNP transistor fluctuate due to various causes such as variations due to manufacturing of the element itself, a load state, and an ambient temperature. However, since the voltage adjustment unit 12 adjusts the output voltage Vo according to the output voltage of the voltage detection unit 11, that is, VB, the influence of changes in VBE1 and VCE8 can be suppressed. Furthermore, since the voltage adjusting unit 11 adjusts the output without depending on the output voltage VCC of the DC power supply unit 3, the influence on the VB due to the output variation of the DC power supply unit 3 can be suppressed.

  As described above, in the present embodiment, the voltage adjustment unit 12 adjusts the output voltage, that is, the base voltage of the first NPN transistor, in accordance with the input from the voltage detection unit 11, and therefore the first NPN transistor 1 Since the output voltage variation caused by the variation of the second NPN transistor 7, the PNP transistor 8, and the DC power supply unit 3 can be suppressed, the detection voltage of the voltage detection unit 11 can always be kept at the first predetermined voltage. A highly accurate stabilized power supply circuit can be supplied. Only when the output voltage of the DC power supply unit is equal to or higher than the Zener voltage of the second Zener diode 14a, the second NPN transistor can be made conductive. As a result, the PNP transistor can be turned on only when the output of the DC power supply unit is equal to or higher than a predetermined voltage, and the power supply can be activated after the DC power supply unit is in a sufficiently stable output state. Further, by configuring the starting voltage limiting unit 14 with the second Zener diode 14a, the voltage limiting means can be realized with a single component.

  In the present embodiment, the voltage detection unit 11 detects the collector voltage VB of the PNP transistor 8 and outputs the divided voltage VB to the voltage adjustment unit 12 so that VB becomes the first predetermined voltage. However, the voltage detection unit 11 detects the emitter voltage VDD of the first NPN transistor 1 and outputs the divided voltage of VDD to the voltage adjustment unit 11 so that VDD becomes the first predetermined voltage. May be.

  As described above, the stabilized power supply circuit according to the present invention can output a predetermined voltage regardless of variations in components constituting the stabilized power supply circuit. It can also be applied to applications of stabilized power supply circuits other than equipment.

DESCRIPTION OF SYMBOLS 1 1st NPN transistor 2 Commercial power supply 3 DC power supply part 4 1st resistance 5 2nd resistance 6 3rd resistance 7 2nd NPN transistor 8 PNP transistor 9 4th resistance 10 5th resistance 11 Voltage detection Unit 11a first voltage dividing resistor 11b second voltage dividing resistor 12 voltage adjusting unit 12a shunt regulator 13 voltage limiting unit 13a first Zener diode 14 startup voltage limiting unit 14a second Zener diode

Claims (6)

A first NPN transistor having a collector connected to a positive output terminal of a DC power supply that is a DC voltage source, a base of the first NPN transistor, and a first resistor connected to a positive output terminal of the DC power supply; A second resistor connected to the first resistor and a third resistor connected to the negative output terminal of the DC power supply unit, an emitter connected to the negative output terminal of the DC power supply unit, and a base connected to the second output terminal A second NPN transistor connected to a connection point between the resistor and the third resistor; an emitter connected to the emitter of the first NPN transistor; and a base connected to the emitter of the first NPN transistor via a fourth resistor. And a PNP transistor connected to the collector of the second NPN transistor via a fifth resistor, and an emitter of the first NPN transistor, or A voltage detector that divides and outputs the voltage of one of the collectors of the NP transistor; and a base of the first NPN transistor, an output of the voltage detector, and a negative output terminal of the DC power supply, A stabilized power circuit including a voltage adjustment unit that adjusts an output voltage so that an output voltage of the voltage detection unit becomes a first predetermined voltage. The voltage adjustment unit includes a shunt regulator having a cathode connected to a base of the first NPN transistor, an anode connected to a negative output terminal of the DC power supply unit, and a reference connected to an output of the voltage detection unit. The stabilized power supply circuit according to claim 1. It stabilized power supply circuit according to claim 1 or claim 2, wherein the base voltage with a voltage limiting unit that limits so as to be less than the second predetermined voltage of the first NPN transistor. 4. The stabilized power supply circuit according to claim 3 , wherein the voltage limiting unit is a first Zener diode having a cathode connected to a base of the first NPN transistor and an anode connected to a negative output terminal of the DC power supply unit. And contact with the base of the first resistor and the first NPN transistor, any one of claims 1 to 4 having a starting voltage limiting unit 14 which is connected between the second resistor regulated power supply circuit according to. The starting voltage limiting unit 14 is configured by a second Zener diode 14a having a cathode connected to a contact point between the first resistor and the base of the first NPN transistor and an anode connected to the second resistor. The stabilized power supply circuit according to claim 5.

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