JP4315958B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device such as a series regulator or a constant voltage power supply, and a semiconductor integrated circuit device constituting the power supply device.

FIG. 6 is a circuit diagram showing the internal configuration of a power supply device conventionally used. This conventional power supply device includes switches 1 and 2, constant current sources 3, 4, 5 and a resistor R 1 to which a power supply voltage V _CC is applied via a switch 2, and pnp transistors Tr 1, Tr 2, Tr 3, Tr 6, It comprises TR8, npn transistors Tr4, Tr5, Tr7, an output terminal 6, and resistors R2, R3 for dividing the output voltage of the output terminal 6.

  In the transistor Tr1, the switch 1 is connected to the base, the emitter is connected to the constant current source 3, and the collector is grounded. Transistors Tr2 and Tr3 have their emitters connected to constant current source 4, the emitters of transistors Tr1 and Tr6 connected to their respective bases, and the collectors of transistors Tr4 and Tr5 connected to their respective collectors. Transistors Tr4 and Tr5 have their emitters grounded and their bases connected to each other. The collector of the transistor Tr4 is connected to the base, and the collector of the transistor Tr5 is connected to the base of the transistor Tr7.

The transistor Tr6 has an emitter connected to the constant current source 5, a base connected to the connection node of the resistors R2 and R3, and a collector grounded. The transistor Tr7 has a collector connected to the resistor R1 and an emitter grounded. In the transistor Tr8, the power supply voltage V _CC is applied to the emitter via the switch 2, the base is connected to the resistor R1, and the collector is connected to the output terminal 6. The resistor R2 is connected to the output terminal 6, and the resistor R3 is grounded. When the contact a of the switch 1 is connected, the base of the transistor Tr1 is grounded. When the contact b of the switch 1 is connected, the voltage _VBG is applied to the base of the transistor Tr1. Further, a capacitor Co serving as a phase compensation capacitor with the other end grounded is connected to the output terminal 6.

In such a power supply device, the constant current sources 3, 4, 5 and the transistors Tr 1, Tr 2, Tr 3, Tr 4, Tr 5, Tr 6 make the base of the transistor Tr 1 the positive phase input, the base of the transistor Tr 6 the reverse phase input, and the transistor Tr 3. , Tr5, the comparator 11 is formed in which the connection node where the collectors of the transistors Tr5 are connected is the output. In other words, negative voltage feedback in which the voltage _VBG is applied to the positive phase input of the comparator 11 via the switch 1 and the voltage obtained by dividing the output voltage of the output terminal 6 by the resistors R2 and R3 is fed back to the negative phase input. It is a circuit.

In this power supply device, the switch 2 is connected, and the power supply voltage V _CC is applied to the constant current sources 3, 4, 5, the resistor R 1 and the emitter of the transistor Tr 8. At the same time, the switch 1 is connected to the contact b, and the input voltage V _BG is applied to the base of the transistor Tr1. In this way, by setting the base potential of the transistor Tr1 to V _BG , the transistor Tr1 becomes non-conductive, and when the current does not easily flow from the base of the transistor Tr2 to the emitter of the transistor Tr1, the emitter current of the transistor Tr3 is changed to the transistor Tr2. Larger than the emitter current. Since the transistors Tr4 and Tr5 form a current mirror circuit, the collector currents of the transistors Tr4 and Tr5 are equal to the emitter current of the transistor Tr2.

Therefore, a current flows from the comparator 11 to the base of the transistor Tr7, and a collector current obtained by amplifying the base current flows through the transistor Tr7. Therefore, the base voltage of the transistor Tr8 is lowered by the resistor R1. Therefore, an emitter current flows through the transistor Tr8, and the output voltage Vo is output from the output terminal 6.
Japanese Patent Laid-Open No. 10-293617 JP-A-9-154275 JP-A-6-163803 Japanese Patent Laid-Open No. 2-113314 JP-A-6-110567

In this way, the output voltage Vo is output from the output terminal 6 of the power supply device as shown in FIG. 6, but since the output voltage Vo rises after several milliseconds, a charging current (1 A or more at start-up) (capacitor 1) is supplied to the capacitor Co. Hereinafter, this will be referred to as “inrush current”. Since this inrush current flows up to the current capability limit of the output transistor of the power supply device, when the output voltage suddenly rises like the conventional power supply device, the characteristics of the power supply device deteriorate due to the heat generated by the large inrush current. Or in some cases it could be destroyed. Further, for example, when the V _CC input source is DC / DC, the power supply voltage V _CC drops due to the inrush current, so that there is a possibility that all the circuits used in parallel with the power supply device may become defective in starting.

  In view of the above problems, the present invention provides a soft start function for gradually increasing the output voltage by gradually increasing the voltage input at the start-up in order to reduce the inrush current at the start-up. An object of the present invention is to provide a power supply apparatus.

In order to achieve the above object, a power supply apparatus according to the present invention compares a detection voltage obtained by dividing an output voltage from an output circuit with a reference voltage by a comparator, and uses the comparison output of the comparator to output the output circuit. In the power supply device that controls the detection voltage output from the reference voltage to be equal to the reference voltage, a voltage that gradually increases at start-up is output, and the reference voltage until the output voltage reaches a predetermined voltage that exceeds the reference voltage. A soft start circuit that operates so as not to apply a voltage to the comparator; the comparator includes a first current source, a second current source, and a third current source to which a first voltage is applied; A first current source is connected, the first transistor having the reference voltage applied to the base, the emitter of the first transistor connected to the base, and the second current source connected to the emitter. And the third transistor having the emitter connected to the second current source, the emitter connected to the third current source and the base of the third transistor, and the output from the output circuit to the base. A fourth transistor to which the detection voltage obtained by dividing the voltage is applied, and outputs the comparison output from the collector side of the third transistor to the output circuit, and the soft start circuit includes the first current source. And a capacitor having one end connected to a connection node between the emitter of the first transistor and the base of the second transistor and the second voltage applied to the other end. .

  According to such a power supply device, the voltage output from the soft start circuit at the time of starting the power supply device gradually increases until reaching a predetermined voltage, and until the output voltage from this soft start circuit reaches a predetermined voltage, The reference voltage input to the comparator is not applied. Therefore, the change in the voltage input to the comparator becomes gradual, and the transient response of the output voltage of the output circuit at startup can be suppressed.

Then, the current flowing from the front Symbol first current source to charge the capacitor, after gradually increasing the emitter voltage of the first transistor, wherein by the reference voltage and the base-emitter voltage of the first transistor second The emitter voltage of one transistor can be limited.

Further, the detection voltage obtained by dividing the output voltage from the output circuit is compared with a reference voltage by a comparator, and the detection voltage output from the output circuit by the comparison output of the comparator becomes equal to the reference voltage. In the power supply device to be controlled, a soft start that outputs a voltage that gradually increases at start-up and that does not apply the reference voltage to the comparator until the output voltage reaches a predetermined voltage that exceeds the reference voltage A circuit is provided, wherein the comparator is connected to a first current source, a second current source, and a third current source to which a first voltage is applied, and an emitter connected to the first current source; The first transistor applied, the emitter of the first transistor connected to the base, the second transistor having the emitter connected to the second current source, and the emitter connected to the first transistor A third transistor to which a current source is connected, a third current source and a base of the third transistor are connected to an emitter, and the detection voltage obtained by dividing the output voltage from the output circuit is applied to the base. 4 transistors, and outputs the comparison output from the collector side of the third transistor to the output circuit. The soft start circuit includes a fourth current source to which a first voltage is applied and one end of the third transistor. A capacitor to which the second voltage is applied at the other end, an emitter of the first transistor is connected to an emitter, and a connection node between the capacitor and the fourth current source is connected to a base. A fifth transistor connected to the collector and applied with the second voltage, and connected between a base of the first transistor and a base of the fifth transistor; And a clamp circuit for limiting the base voltage of the fifth transistor so as not to exceed a predetermined voltage, and charging the capacitor with the current flowing from the fourth current source, After gradually increasing the base voltage of the fifth transistor to gradually increase the emitter voltage of the first transistor, the base voltage of the fifth transistor is limited by the reference voltage and the clamp circuit. The emitter voltage can be limited.

  In the power supply device described above, the comparator includes a collector of the second transistor connected to a collector and a base, a sixth transistor having the emitter applied with the second voltage, and a collector connected to the collector of the three transistor. A seventh transistor having a base connected to the base of the sixth transistor and the second voltage applied to an emitter of the sixth transistor, and when the operation of the power supply device is stopped, the capacitor It is possible to provide a discharge circuit for discharging and initializing.

  Furthermore, the power supply device may be a one-chip semiconductor integrated circuit device.

  The charging time may be set so that the output current at the time of startup is within 10 times the normal output current.

  The power supply device may be configured such that the capacitor is provided outside and the circuit other than the capacitor is a one-chip semiconductor integrated circuit device.

  Further, in the soft start circuit, when the capacitor is discharged and initialized, a clamp circuit is provided for shortening the discharge time.

  According to the power supply device of the present invention, the voltage input to the comparator is gradually increased, and a soft start circuit that cuts off the reference voltage until this voltage exceeds a predetermined voltage is provided. The output does not change rapidly, and when a capacitive load is connected to the output side of the comparator, the start-up charging current flowing through this load can be reduced to suppress a decrease in the comparison output. Further, since the capacitor is provided so as to be connected to the outside of the one-chip semiconductor integrated circuit device, the magnitude of the charging current at startup can be set by changing the capacitance of the capacitor.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the internal structure of the power supply device of this embodiment. In the power supply apparatus of FIG. 1, the same elements and portions as those of the power supply apparatus of FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

The power supply device of FIG. 1 includes pnp transistors Tr1, Tr2, Tr3, Tr6, Tr8, npn transistors Tr4, Tr5, Tr7, resistors R1, R2, R3, switches 1, 2, constant current sources 3, 4, 5 and an output terminal 6, a constant current source 7 to which a power supply voltage V _CC is applied via a switch 2, a pnp transistor Tr 9, a capacitor Cs, and a discharge circuit 8 The switch 9 and the clamp circuit 10 are newly provided power supply devices.

  The transistor Tr9 has an emitter connected to the emitter of the transistor Tr1, a base connected to the capacitor Cs, and a collector grounded. The capacitor Cs has one end grounded and the other end connected to the switch 9. The switch 9 has a contact c connected to the constant current source 7 and a contact d connected to the discharge circuit 8. The clamp circuit 10 is connected between the base of the transistor Tr9 and the base of the transistor Tr1. Similarly to the power supply device of FIG. 6, the output terminal 6 is connected to a capacitor Co serving as a phase compensation capacitor with the other end grounded.

  Similar to the power supply device of FIG. 6, the comparator 11 is constituted by the transistors Tr1, Tr2, Tr3, Tr4, Tr5, Tr6 and the constant current sources 3, 4, 5. The constant current source 7, the discharge circuit 8, the switch 9, the clamp circuit 10, the transistor Tr9, and the capacitor Cs constitute a soft start circuit 12.

  The operation of the power supply device having such a configuration will be described. Now, it is assumed that this power supply device is already in an initial state with the contact d of the switch 9 connected and the capacitor Cs discharged. Switch 9 is switched to contact c, switch 1 is switched to contact b, and switch 2 is connected. The ON (state in which the power supply device is turned on) shown in FIG. 2 means that the switches 1, 2 and 9 are connected as described above, and OFF (state in which the power supply device is turned off) shown in FIG. Means when the switches 1, 2 and 9 are reversed. In FIG. 2A, the broken line represents the state of the power supply voltage, and the solid line represents the state of the output voltage Vo. Further, in FIG. 2B, the broken line represents the base voltage of the transistor Tr1, and the solid line represents the base voltage of the transistor Tr9.

In this way, the power source voltage V _CC is applied to the constant current sources 3, 4, 5, 7, the resistor R1, and the emitter of the transistor Tr8, and the voltage V _BG is applied to the base of the transistor Tr1. Further, since the contact c of the switch 9 is connected, a current flows from the constant current source 7 to the capacitor Cs, and the capacitor Cs is charged. Thus, at the moment when each switch is switched to switch from the initial state to the ON state, as shown in FIG. 2B, the base voltage of the transistor Tr9 is 0, so that the transistor Tr9 becomes conductive and the transistor Tr2 Is the base voltage V _BE (the voltage V _BE is the base-emitter voltage of the transistor Tr9).

  As shown in FIG. 2A, when the voltage output from the output terminal 6 is 0, the voltages input to the bases of the transistors Tr1 and Tr6 are equal. Thereafter, when the capacitor Cs is charged, the base voltage of the transistor Tr9 gradually increases and the emitter voltage of the transistor Tr9 also increases. Therefore, the base voltage of the transistor Tr2 becomes higher than the base voltage of the transistor Tr3, and the emitter current flowing through the transistor Tr2 becomes smaller than the emitter current flowing through the transistor Tr3.

  Since the collector current flowing through the transistors Tr4 and Tr5 is the same current value as the emitter current flowing through the transistor Tr2, the output current from the comparator 11 flows through the transistor Tr7. The transistor Tr7 lowers the base voltage of the transistor Tr8 by the resistor R1 by flowing a collector current obtained by amplifying the output current. An emitter current corresponding to the voltage drop due to the resistor R1 flows through the transistor Tr8, and this emitter current flows through the resistors R2 and R3, thereby generating an output voltage Vo.

At this time, as the base voltage of the transistor Tr9 gradually increases as shown in FIG. 2B, the base voltage of the transistor Tr2 gradually increases, so that the base current flowing through the transistor Tr7 also gradually increases. Therefore, as shown in FIG. 2A, the output voltage Vo also gradually increases according to the base voltage of the transistor Tr9. When the base voltage of the transistor Tr9 is more than higher becomes the voltage V _BG Thus, beginning many emitter current flows through the transistor Tr1 than transistor Tr9, the base voltage of the transistor Tr2 is determined by the transistor Tr1.

  Thus, since the base voltage of the transistor Tr2 is determined by the transistor Tr1, the base voltage of the transistor Tr2 becomes constant. Therefore, the output current flowing through the transistor Tr7 is constant, and the output voltage Vo is constant as shown in FIG. In addition, the capacitor Cs tries to continue to flow current from the constant current source 7, but the clamp circuit 10 restricts the base voltage of the transistor Tr9 from exceeding a predetermined value, so that the charging operation of the capacitor Cs is stopped. As a result, the base voltage of the transistor Tr9 also becomes constant at a predetermined value as shown in FIG.

The clamp circuit 10 can be realized by using a pnp transistor having an emitter connected to the base of the transistor Tr9, a base connected to the base of the transistor Tr1, and a collector grounded. That is, assuming that the base-emitter voltage of the transistor used in the clamp circuit 10 is V _BE , when the base voltage of the transistor Tr9 becomes V _BG + V _BE , the current that is going to flow from the constant current source 7 to the capacitor Cs. It flows to the transistor of the clamp circuit 10. Therefore, the charging operation of the capacitor Cs is stopped, and the base voltage of the transistor Tr9 is held at V _BG + V _BE .

With this power supply to ON, as shown in FIG. 2 (a), the output voltage Vo is gradually increased with the base voltage of the transistor Tr9, after the base voltage of the transistor Tr9 exceeds voltage V _BG constant It becomes. The time τ until the output voltage Vo becomes constant can be obtained by using the following equation. Cs is a capacitance value of the capacitor Cs, and i is a charging current charged in the capacitor Cs.
τ = Cs × V _BG / i

Therefore, the charging current I flowing through the capacitor Co can be obtained from the following equation using the time τ obtained using the above equation. Co is a capacitance value of the capacitor Co, and Vmax is a value when the output voltage Vo is constant.
I = Co × Vmax / τ

  From the above equation, the charging current I becomes smaller as the time τ becomes longer. Therefore, in order to keep the charging current I within the same level or 10 times as the normal output current, the time τ is about 100 msec to several tens msec. You can do it. Further, this time τ can be lengthened by increasing the capacity of the capacitor Cs or decreasing the charging current i flowing from the constant current source 7. In this way, by increasing the rise time of the output voltage, the charging current at the time of startup can be reduced to the same level or within 10 times the normal output current. Hereinafter, the charging current at start-up set to such a value is referred to as “start-up charging current”. Therefore, the starting charging current I flows when the output voltage Vo is rising as shown in FIG.

  Then, after the output voltage Vo becomes constant, the switch 1 is connected to the contact a and the switch 9 is connected to the contact d, and the switch 2 is disconnected, and the power supply device is turned off. At this time, the capacitor Cs is discharged by the discharge circuit 9, and the base voltage of the transistor Tr9 becomes zero as shown in FIG. Further, the capacitor Co is discharged through the resistors R2 and R3, and the output voltage Vo is lowered as shown in FIG.

After that, when the switches 1, 2 and 9 are switched again to turn on the power supply device, the transistor Tr9 performs the same operation as described above, and gradually, as shown in FIG. When the base voltage increases and exceeds V _BG + V _BE , it becomes constant. At this time, if the output voltage Vo does not reach 0 as shown in FIG. 2A, the base voltage of the transistor Tr3 becomes higher than the base voltage of the transistor Tr2. Not flowing. Therefore, the capacitor Co is discharged through the resistors R2 and R3, and the output voltage Vo continues to decrease. Thereafter, when the base voltage of the transistor Tr2 becomes higher than the base voltage of the transistor Tr3, the output voltage Vo starts to rise again by performing the same operation as described above, as shown in FIG. When the base voltage of the transistor Tr9 exceeds V _BG, the output voltage Vo becomes constant.

  Although an example in which a pnp transistor is used as the clamp circuit 10 is shown, the present invention is not limited to a circuit using this element, and a circuit that performs the same operation using another element may be used. Further, the discharge circuit 8 can be realized by grounding the other end of the resistor whose one end is connected to the contact d of the switch 9, but is not limited to such a circuit. Such a power supply device may be a one-chip semiconductor integrated circuit device. Thus, when it is set as the semiconductor integrated circuit device of 1 chip | tip, the capacity | capacitance can be made variable by attaching the capacitor | condenser Cs externally, and the setting of the magnitude | size of a starting charging current can be changed.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a circuit diagram showing the internal structure of the power supply device of this embodiment. In the power supply device of FIG. 3, the same elements and portions as those of the power supply device of FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The power supply device of FIG. 3 includes pnp transistors Tr1, Tr2, Tr3, Tr6, Tr8, npn transistors Tr4, Tr5, Tr7, resistors R1, R2, R3, switches 1, 2, constant current sources 3, 4 is a power supply device in which a capacitor Cs, a discharge circuit 13 and a switch 14 are newly provided in the power supply device including the output terminals 6 and 5.

  The capacitor Cs has one end grounded and the other end connected to a connection node between the emitter of the transistor Tr1 and the base of the transistor Tr2. The switch 14 is connected to a connection node between the emitter of the transistor Tr1 and the base of the transistor Tr2, the contact e is connected to the constant current source 3, and the contact f is connected to the discharge circuit 13. Similarly to the power supply device of FIG. 6, the output terminal 6 is connected to a capacitor Co serving as a phase compensation capacitor with the other end grounded.

  Similar to the power supply device of FIG. 6, the comparator 11 is composed of the transistors Tr1, Tr2, Tr3, Tr4, Tr5, Tr6 and the constant current sources 3, 4, 5. The constant current source 3, the discharge circuit 13, the switch 14, and the capacitor Cs constitute a soft start circuit 15.

  The operation of the power supply device having such a configuration will be described. Now, it is assumed that this power supply device is already in an initial state with the contact f of the switch 14 connected and the capacitor Cs discharged. Switch 14 is switched to contact e, switch 1 is switched to contact b, and switch 2 is connected. The ON state shown in FIG. 4 (when the power supply device is turned on) refers to the state where the switches 1, 2 and 14 are connected as described above, and the OFF state (state where the power supply device is turned off) shown in FIG. Means when the switches 1, 2 and 14 are in the opposite states. In FIG. 4A, the broken line represents the state of the power supply voltage, and the solid line represents the state of the output voltage Vo. Further, in FIG. 4B, the broken line represents the base voltage of the transistor Tr1, and the solid line represents the base voltage of the transistor Tr2.

In this way, the power source voltage V _CC is applied to the constant current sources 3, 4, 5, the resistor R 1 and the emitter of the transistor Tr 8, and the voltage V _BG is applied to the base of the transistor Tr 1. Further, since the contact e of the switch 14 is connected, a current flows from the constant current source 3 to the capacitor Cs, and the capacitor Cs is charged. Thus, at the moment when each switch is switched to switch from the initial state to the ON state, as shown in FIG. 4B, the base voltage of the transistor Tr2 is 0, so that the base of the transistor Tr2 is grounded. Become.

  Further, as shown in FIG. 4A, since the voltage output from the output terminal 6 is 0, the transistor Tr6 becomes conductive and the base of the transistor Tr3 is grounded. Therefore, the voltages input to the transistors Tr2 and Tr3 are in the same state. Thereafter, when the capacitor Cs is charged, the base voltage of the transistor Tr2 gradually increases, so that the base voltage of the transistor Tr2 becomes higher than the base voltage of the transistor Tr3, and the emitter current flowing through the transistor Tr2 flows into the transistor Tr3. Smaller than current.

  The collector current flowing through the transistors Tr4 and Tr5 is equal to the emitter current flowing through the transistor Tr2, and the output current from the comparator 11 flows through the transistor Tr7. The transistor Tr7 lowers the base voltage of the transistor Tr8 by the resistor R1 by flowing a collector current obtained by amplifying the output current. An emitter current corresponding to the voltage drop due to the resistor R1 flows through the transistor Tr8, and this emitter current flows through the resistors R2 and R3, thereby generating an output voltage Vo.

At this time, since the base voltage of the transistor Tr2 gradually increases as shown in FIG. 4B, the base current flowing through the transistor Tr7 also gradually increases. Therefore, as shown in FIG. 4A, the output voltage Vo also gradually increases according to the base voltage of the transistor Tr2. Thus, when the base voltage of the transistor Tr2 increases and exceeds V _BG + V _BE (V _BE is the base-emitter voltage of the transistor Tr1), the transistor Tr1 becomes conductive, and the emitter current begins to flow through the transistor Tr1. As shown in FIG. 4B, the base voltage of the transistor Tr2 is constant at V _BG + V _BE .

Thus, when the base voltage of the transistor Tr2 becomes constant, the output current flowing through the transistor Tr7 becomes constant, and the output voltage Vo becomes constant as shown in FIG. When the power supply device is turned on in this way, the output voltage Vo gradually increases with the base voltage of the transistor Tr2 as shown in FIG. 4A, and after the base voltage of the transistor Tr2 exceeds the voltage V _BG + V _BE. Is constant. The time τ until the output voltage Vo becomes constant can be obtained by using the following equation. Cs is a capacitance value of the capacitor Cs, and i is a charging current charged in the capacitor Cs.
τ = Cs × (V _BG + V _BE ) / i

Therefore, the starting charging current I flowing in the capacitor Co can be obtained from the following equation using the time τ obtained using the above equation. Co is a capacitance value of the capacitor Co, and Vmax is a value when the output voltage Vo is constant.
I = Co × Vmax / τ

  From the above equation, the start-up charging current I decreases as the time τ becomes longer. Therefore, in order to keep the start-up charging current I within the same range as that of the normal output current or within 10 times, the time τ is about 100 msec to What is necessary is just about several tens of milliseconds. Further, this time τ can be lengthened by increasing the capacitance of the capacitor Cs or decreasing the charging current i flowing from the constant current source 3. In this way, by increasing the time for the output voltage to rise, the startup charging current can be reduced to the same level as the normal output current or within 10 times. Therefore, the starting charging current I flows when the output voltage Vo is increasing as shown in FIG.

  After the output voltage Vo becomes constant, the switch 1 is connected to the contact a and the switch 14 is connected to the contact f, and the switch 2 is disconnected to turn the power supply device OFF. At this time, the capacitor Cs is discharged by the discharge circuit 13, and the base voltage of the transistor Tr2 becomes 0 as shown in FIG. Further, the capacitor Co is discharged through the resistors R2 and R3, and the output voltage Vo is lowered as shown in FIG.

After that, when the switches 1, 2 and 14 are switched again to turn on the power supply device, the transistor Tr2 performs the same operation as described above, and gradually, as shown in FIG. When the base voltage increases and exceeds V _BG + V _BE , it becomes constant. At this time, if the output voltage Vo does not reach 0 as shown in FIG. 4A, the base voltage of the transistor Tr3 becomes higher than the base voltage of the transistor Tr2. Not flowing. Therefore, the capacitor Co is discharged through the resistors R2 and R3, and the output voltage Vo continues to decrease. Thereafter, when the base voltage of the transistor Tr2 becomes higher than the base voltage of the transistor Tr3, the output voltage Vo starts to rise again by performing the same operation as described above, as shown in FIG. When the base voltage of the transistor Tr2 exceeds V _BG + V _BE , the output voltage Vo becomes constant.

  The discharge circuit 13 can be realized by grounding the other end of the resistor having one end connected to the contact f of the switch 14, but is not limited to such a circuit. Such a power supply device may be a one-chip semiconductor integrated circuit device. Thus, when it is set as the semiconductor integrated circuit device of 1 chip | tip, the capacity | capacitance can be made variable by attaching the capacitor | condenser Cs externally, and the setting of the magnitude | size of a starting charging current can be changed.

In the first and second embodiments, the comparator has a circuit configuration as shown in FIG. 1 or FIG. 3, but is not limited to such a circuit configuration. A comparator having a circuit configuration as shown in FIG. 5 may be used. The configuration of the comparator shown in FIG. 5 will be described below. In the comparator of FIG. 5, elements used for the same purpose as the elements constituting the comparator 11 of FIG. 1 or FIG. 3 are given the same symbols, and detailed descriptions thereof are omitted. The comparator of FIG. 5 includes a switch 2 (see FIG. 1 or FIG. 1), which is composed of constant current sources 3, 4, 5, pnp transistors Tr 1, Tr 2, Tr 3, Tr 6, and npn transistors Tr 4, Tr 5. The pnp transistors Tr10 and Tr11 to which the power source voltage V _CC (see FIG. 1 or 3) is applied via the emitter via FIG. 3), the npn transistor Tr12 having the base and collector of the transistor Tr4 connected to the base, and The npn transistor Tr13 having the base and collector of the transistor Tr5 connected to the base is a new comparator.

  Further, in the comparator of FIG. 5, unlike the comparator 11 shown in FIG. 1 or FIG. 3, the bases of the transistors Tr4 and Tr5 are not connected to each other. Furthermore, the emitters of the transistors Tr12 and Tr13 are grounded, the collectors of the transistors Tr10 and T13 are connected to each other, and the collectors of the transistors Tr11 and Tr12 are connected to each other. The base and collector of the transistor Tr10 are connected to the base of the transistor Tr11. As described above, the transistor Tr4 and the transistor Tr12, the transistor Tr5 and the transistor Tr13, and the transistor Tr10 and the transistor Tr11 respectively constitute a current mirror circuit.

  In the comparator shown in FIG. 5, like the comparator 11 shown in FIG. 1 or FIG. 3, the base of the transistor Tr1 is a positive phase input and the transistor Tr6 is a negative phase input. The output is a connection node to which the collectors of the transistors Tr11 and Tr12 are connected. The base of the transistor Tr7 (see FIG. 1 or 3) is connected to the connection node to which the collectors of the transistors Tr11 and Tr12 are connected. .

  In such a comparator, when the voltage applied to the base of the transistor Tr1 becomes higher than the voltage applied to the transistor Tr6, the emitter current flowing through the transistor Tr3 becomes larger than the emitter current flowing through the transistor Tr2. Now, since the emitter current flowing through the transistor Tr2 becomes equal to the collector current flowing through the transistor Tr4, the collector current of the transistor Tr12 that forms the current mirror circuit with the transistor Tr4 is also equal to the emitter current flowing through the transistor Tr2. Further, since the emitter current flowing through the transistor Tr3 is equal to the collector current flowing through the transistor Tr5, the collector current of the transistor Tr13 that forms the current mirror circuit with the transistor Tr5 is also equal to the emitter current flowing through the transistor Tr3.

  Furthermore, since the emitter current flowing through the transistor Tr10 is equal to the collector current of the transistor Tr13, a collector current equal to the emitter current of the transistor Tr3 flows through the transistor Tr10 and the transistor Tr11 that forms a current mirror circuit with the transistor Tr10. Therefore, since the emitter current flowing through the transistor Tr11 is larger than the collector current flowing through the transistor Tr12, the current is output from the comparator of FIG. 5, and the base current flows through the transistor Tr7 (see FIG. 1 or FIG. 3).

These are circuit diagrams which show the internal structure of the power supply device of 1st Embodiment. These are time charts showing the voltages of the respective parts of the power supply device of FIG. These are circuit diagrams which show the internal structure of the power supply device of 2nd Embodiment. Fig. 4 is a time chart showing voltages of respective parts of the power supply device of Fig. 3. These are an example of the circuit diagram which shows the internal structure of a comparator. These are the circuit diagrams which show the internal structure of the conventional power supply device.

Explanation of symbols

1, 2, 9, 14 Switch 3, 4, 5, 7 Constant current source 6 Output terminal 8, 13 Discharge circuit 10 Clamp circuit 11 Comparator 12, 15 Soft start circuit Tr1-Tr3, Tr6, Tr8, Tr9-Tr11 pnp Type transistor Tr4, Tr5, Tr7, Tr12, Tr13 npn type transistor R1-R3 resistance Cs, Co capacitor

Claims (7)

The detection voltage obtained by dividing the output voltage from the output circuit is compared with a reference voltage by a comparator, and the detection voltage output from the output circuit is controlled to be equal to the reference voltage by the comparison output of the comparator. In the power supply to
A soft start circuit that operates so as not to apply the reference voltage to the comparator until the output voltage reaches a predetermined voltage that exceeds the reference voltage, while outputting a voltage that gradually increases at startup ,
The comparator is
A first current source, a second current source, and a third current source to which a first voltage is applied;
A first transistor having an emitter connected to the first current source and a base applied with the reference voltage;
A second transistor having a base connected to an emitter of the first transistor and an emitter connected to the second current source;
A third transistor having the emitter connected to the second current source;
A fourth transistor having an emitter connected to the third current source and a base of the third transistor, and a base to which the detection voltage obtained by dividing the output voltage from the output circuit is applied;
Have
Outputting the comparison output from the collector side of the third transistor to the output circuit;
The soft start circuit is
The first current source;
A capacitor having one end connected to a connection node between the emitter of the first transistor and the base of the second transistor and the second voltage applied to the other end;
Power and wherein the composed. The detection voltage obtained by dividing the output voltage from the output circuit is compared with a reference voltage by a comparator, and the detection voltage output from the output circuit is controlled to be equal to the reference voltage by the comparison output of the comparator. In the power supply to
A soft start circuit that operates so as not to apply the reference voltage to the comparator until the output voltage reaches a predetermined voltage that exceeds the reference voltage, while outputting a voltage that gradually increases at startup,
The comparator is
A first current source, a second current source, and a third current source to which a first voltage is applied;
A first transistor having an emitter connected to the first current source and a base applied with the reference voltage;
A second transistor having a base connected to an emitter of the first transistor and an emitter connected to the second current source;
A third transistor having the emitter connected to the second current source;
A fourth transistor having an emitter connected to the third current source and a base of the third transistor, and a base to which the detection voltage obtained by dividing the output voltage from the output circuit is applied;
Have
Outputting the comparison output from the collector side of the third transistor to the output circuit ;
The soft start circuit is
A fourth current source to which the first voltage is applied;
A capacitor having one end connected to the fourth current source and the other voltage applied to the other end;
A fifth transistor having an emitter connected to the emitter of the first transistor, a base connected to a connection node between the capacitor and the fourth current source, and a collector applied with the second voltage;
A clamp circuit connected between the base of the first transistor and the base of the fifth transistor for limiting the voltage of the base of the fifth transistor so as not to exceed a predetermined voltage;
Power supplies you characterized in that it is composed of. The comparator is
A sixth transistor in which the collector of the second transistor is connected to a collector and a base, and the second voltage is applied to an emitter;
A seventh transistor having a collector connected to a collector of the three transistors, a base connected to a base of the sixth transistor, and the second voltage applied to an emitter;
Have
The power supply apparatus according to claim 1 or 2 , further comprising a discharge circuit for discharging and initializing the capacitor when the operation of the power supply apparatus is stopped. In the soft start circuit, when initializing discharges the capacitor, the power supply according to any one of claims 1 to 3, characterized in that the clamping circuit for shortening the discharge time is provided apparatus. The power supply device according to any one of claims 1 to 4 , wherein the power supply device is a one-chip semiconductor integrated circuit device. 6. The power supply device according to claim 5 , wherein the charging time is set so that the output current at the time of startup is within 10 times the normal output current. The power supply, together with the capacitor is provided outside power supply apparatus according to any one of claims 1 to 4, wherein the circuitry other than the capacitor is a semiconductor integrated circuit device of one chip.

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