JP2005327035A - Starting circuit and power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a starting circuit and power supply circuit capable of quickly starting a reference voltage generating circuit. <P>SOLUTION: In the starting circuit 20 for starting the reference voltage generating circuit 1, the starting circuit comprises a bipolar transistor Q5 in which a collector is connected with power supply and an emitter is connected with the reference voltage generating circuit 1, a resistor R4 connected between the power supply and a base of the bipolar transistor Q5, and a base voltage retaining means (a resistor R5 and diodes D1 and D2) connected between the base of the bipolar transistor Q5 and a ground and dividing voltage Vcc of the power supply so as to attain base voltage stabilizing the bipolar transistor Q5 at a non-operation point when emitter voltage reaches the reference voltage of the reference voltage generating circuit 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a startup circuit and a power supply circuit for starting up a reference voltage generation circuit, and more particularly, to supply a reference current to the reference voltage generation circuit with a start-up current depending on the capability of the bipolar transistor without designing a troublesome circuit constant. Thus, the present invention relates to a start circuit and a power supply circuit that can achieve a high speed start of the reference voltage generating circuit.

Conventionally, for example, a band gap type reference voltage generation circuit is known as a reference voltage generation circuit that supplies a stable reference voltage to a semiconductor device or the like. For example, see Patent Document 1. This band gap type reference voltage generation circuit is difficult to self-start to stabilize at a desired designed reference voltage, and requires a separate start circuit for supplying a start current from the outside.
JP-A-6-75649

Conventionally, there is an activation circuit 50 shown in FIG. 7 as an example of the activation circuit. Explaining this operation, when the power supply voltage V _CC is turned on, the gate-source voltage of the P-type MOS transistor MP3 exceeds the threshold value, and the P-type MOS transistor MP3 is turned on. As a result, the N-type MOS transistors MN1 and MN2 whose gates are connected to the drain of the P-type MOS transistor MP3 are turned on.

  As a result, the gates of the P-type MOS transistors MP4 and MP5 become low level, and the P-type MOS transistors MP4 and MP5 are turned on. As a result, the starting current is supplied from the power source to the reference voltage generating circuit 1 through the P-type MOS transistor MP5 that is turned on.

  The start-up current is supplied as a base current to each base of the bipolar transistors Q1 to Q4, and the bipolar transistors Q1 to Q4 are turned on, whereby the gates of the P-type MOS transistors MP1 and MP2 become low level and these P-type MOSs. The transistors MP1 and MP2 are turned on. Therefore, after the start-up by the start-up current, the current from the power supply is supplied to the reference voltage generation circuit 1 through the P-type MOS transistor MP1.

When the voltage of the output terminal of the reference voltage generating circuit 1 becomes constant reference voltage Vref, the gate of the P-type MOS transistor MP3 of the activation circuit 50 - source voltage becomes smaller than immediately after V _CC turned, N-type MOS transistor MN1 MN2 and P-type MOS transistors MP4 and MP5 are turned off, and the starting current is not supplied from the starting circuit 50 to the reference voltage generating circuit 1. Further, when the gate of the N-type MOS transistor MN3 becomes Vref, the N-type MOS transistor MN3 is turned on.

After the reference voltage generating circuit 1 is activated, the P-type MOS transistor MP3 is not completely turned off depending on the value of the power supply voltage V _CC . That is, even after the reference voltage generating circuit 1 is activated, the gates of the N-type MOS transistors MN1 and MN2 are in a high impedance state, so that a minute current flows through the path of power source → P-type MOS transistor MP3 → NP-type MOS transistor MN3 → ground. to continue.

  Since the above-described conventional starting circuit 50 is composed of a constant current circuit and a current mirror circuit, the capacitor C1 is connected between the output terminal of the reference voltage generating circuit 1 and the ground in order to prevent oscillation. However, depending on the capacitance of the capacitor C1, there is a problem that the time until the output voltage of the reference voltage generating circuit 1 rises to the reference voltage becomes extremely slow.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a starter circuit and a power supply circuit that can achieve a fast start-up of a reference voltage generating circuit.

  The starting circuit of the present invention includes a bipolar transistor having a collector connected to a power supply and an emitter connected to a reference voltage generating circuit, a resistor connected between the power supply and the base of the bipolar transistor, and between the base and the ground. And a base voltage holding means for dividing the voltage of the power supply so that the bipolar transistor becomes a base voltage that stabilizes at a non-operating point when the emitter voltage becomes the reference voltage of the reference voltage generating circuit.

  A power supply circuit according to the present invention includes the start-up circuit and a reference voltage generation circuit started by the start-up circuit.

  In the bipolar transistor, a large output current can be taken out by flowing a small base current, the latter stage driving capability is large, and the latter stage (the reference voltage generating circuit in the present invention) can be started at high speed. That is, until the reference voltage generating circuit is started, it is ensured that the base-emitter voltage of the bipolar transistor is sufficient to supply the starting current to the reference voltage generating circuit. The reference voltage generating circuit can be started up at high speed with the dependent current.

  In the base of the bipolar transistor, the power supply voltage is divided by a resistor connected between the power supply and the base, and a base voltage holding means connected between the connection point of the resistor and the base and the ground. A voltage is applied. Therefore, a constant voltage lifted from the ground by the base voltage holding means is applied to the base, and the base voltage is held at the constant voltage. The emitter of the bipolar transistor is connected to the reference voltage generation circuit, and the emitter voltage increases as the output voltage of the reference voltage generation circuit rises. When the output voltage of the reference voltage generation circuit stabilizes to a constant reference voltage, the emitter voltage also increases. Stable to the reference voltage. Therefore, after the start-up of the reference voltage derivation circuit (after the output voltage becomes the reference voltage), the base-emitter voltage of the bipolar transistor is stabilized at a constant value. This constant value is a voltage sufficiently smaller than a voltage for flowing a large current in the diode characteristics between the base and the emitter. That is, after the start-up of the reference voltage circuit, only a very small collector current (emitter current) flows. It is held at the emitter-to-emitter voltage. Therefore, after the start-up of the reference voltage circuit is completed, only a very small current flows through the start-up circuit, and current consumption can be reduced.

  The resistance value of the resistor connected between the power source and the base determines the current flowing in the starting circuit after starting the reference voltage generating circuit, and the current determined by the resistance value flows through the base voltage holding means, A voltage is generated across the base voltage holding means.

  As an example of the configuration of the base voltage holding unit, a configuration including only a resistor can be considered. However, increasing the base voltage to the desired value (relative to the ground) by reducing the current consumption of the starting circuit after starting the reference voltage generating circuit as much as possible requires a large resistor, and the area of the resistor built into the wafer There is a possibility that the start-up time may be delayed due to the increase in charge time or the parasitic capacitance. Further, the current flowing through the resistor is highly dependent on the power supply voltage, and thus the voltage raised by the resistor is likely to fluctuate. On the other hand, if a diode whose forward direction is the direction from the base to the ground is used as the base voltage holding means, even if the forward current slightly fluctuates, the forward drop voltage fluctuation is very small. Since the silicon diode is stably held at around 0.7 V, the base voltage can also be stably held at a desired value.

For example, when the reference voltage generation circuit and the diode are monolithically formed on a silicon substrate, the reference voltage of the reference voltage generation circuit is about 1.25 V, and the forward voltage drop VF of the diode is about 0.7. Here, if three diodes connected in series are used as the base voltage holding means, the base voltage is held at 3VF = 2.1V, and the base voltage when the output voltage of the reference voltage generating circuit settles to 1.25V− The emitter-to-emitter voltage is V _BE = 2.1V-1.25V = 0.85V, and the startup current continues to be supplied from the startup circuit after startup of the reference voltage generation circuit due to the diode characteristics between the base and the emitter. If there is only one diode, the holding voltage of the base voltage is VF = 0.7V, and the starting current is supplied only when the output voltage of the reference voltage generating circuit, that is, the emitter voltage is near the ground potential.

Therefore, in a start circuit for a silicon bandgap reference voltage generation circuit which is generally widely used, if two diodes connected in series are used as the base voltage holding means, the base voltage becomes 2VF = 1.4V. The base-emitter voltage is V _BE = 1.4V-1.25 after being stabilized and capable of supplying a sufficient starting current for the reference voltage generation circuit to stabilize to the desired reference voltage 1.25V. V = 0.15V, which is a base-emitter voltage that stabilizes the bipolar transistor at the non-operating point and substantially stops the supply of the starting current.

  Further, as the base voltage holding means, if the resistor connected between the base and the anode of the silicon diode connected to the base side of the two silicon diodes is added to the two silicon diodes, The base voltage holding voltage is increased by the added resistance, and the base-emitter voltage until the output voltage of the reference voltage generation circuit becomes constant can be increased accordingly, and a larger starting current can be generated. Supply to the circuit for faster startup.

In addition, for example, a silicon bandgap type reference voltage generation circuit has a characteristic that the output tends to be stable in the vicinity of 0.9 V in addition to 0 V and the reference voltage of about 1.25 V. Therefore, a forward drop of only two diodes. If the base voltage is held at 1.4V, when the output voltage of the reference voltage generation circuit rises to 0.9V, the base-emitter voltage V _BE = 1.4V-0.9V = 0.5V. Due to the diode characteristics between the emitters, a sufficient starting current may not be supplied. Therefore, in order to stably start the reference voltage generation circuit up to a desired designed reference voltage of about 1.25 V, the base voltage is changed to the base voltage when the emitter voltage becomes 0.9 V by adding the above resistor. -It is preferable to raise it with respect to the ground so that the emitter-to-emitter voltage V _BE ≥ 0.7V.

  According to the start-up circuit of the present invention, by utilizing the diode characteristics of the bipolar transistor, that is, by utilizing the fact that a large forward current flows through the diode, the capability of the bipolar transistor can be achieved without requiring a troublesome circuit design. In other words, a large current can be supplied to the reference voltage generating circuit to start up at high speed.

  According to the power supply circuit of the present invention, the capability of the bipolar transistor can be obtained by utilizing the diode characteristics of the bipolar transistor, that is, by utilizing the fact that a large forward current flows through the diode without requiring a troublesome circuit design. In addition, it is possible to start up the reference voltage generating circuit at high speed by supplying a large current from the starting circuit. As a result, the rise time of the entire power supply circuit can be increased, and the circuits and components that receive power supply from the power supply circuit can also be started up quickly.

  FIG. 1 shows a power supply circuit according to an embodiment of the present invention. The power supply circuit includes a reference voltage generating circuit 1 and a starting circuit 20 for starting the reference voltage generating circuit 1.

  The reference voltage generating circuit 1 is, for example, a silicon bandgap type reference voltage generating circuit. The reference voltage generation circuit 1 includes two P-type MOS transistors MP1 and MP1, four bipolar transistors Q1, Q2, Q3, and Q4, and three resistors R1, R2, and R3. Bipolar transistors Q1, Q2, Q3 and Q4 are all npn type.

  The source of the P-type MOS transistor MP1 is connected to the power source. The drain of the P-type MOS transistor MP1 is connected to one end of the resistor R1. The other end of the resistor R1 is connected to the collector of the bipolar transistor Q1. The emitter of the bipolar transistor Q1 is connected to the ground. The base of the bipolar transistor Q1 and the base of the bipolar transistor Q2 are connected to a connection point between the resistor R1 and the collector of the bipolar transistor Q1.

  The source of the P-type MOS transistor MP2 is connected to the power source. The drain of the P-type MOS transistor MP2 is connected to the collector of the bipolar transistor Q4. The gate of the P-type MOS transistor MP1 and the gate of the P-type MOS transistor MP2 are connected to a connection point between the drain of the P-type MOS transistor MP2 and the collector of the bipolar transistor Q4.

  The emitter of the bipolar transistor Q4 is connected to the collector of the bipolar transistor Q3. The emitter of the bipolar transistor Q3 is connected to the ground.

  One end of the resistor R2 is connected to a line L1 connecting one end of the resistor R1, the base of the bipolar transistor Q4, and the output terminal B of the reference voltage generating circuit 1. The other end of the resistor R2 is connected to the collector of the bipolar transistor Q2. A connection point between the resistor R2 and the collector of the bipolar transistor Q2 is connected to the base of the bipolar transistor Q3. The emitter of the bipolar transistor Q2 is connected to the ground via a resistor R3.

  An oscillation preventing capacitor C1 is connected between the output terminal B of the reference voltage generating circuit 1 and the ground. The capacitor C1 is externally attached to the reference voltage generation circuit 1, but may be incorporated in the reference voltage generation circuit 1.

  Next, the activation circuit 20 according to the present embodiment will be described. The starting circuit 20 includes a bipolar transistor Q5, a resistor R4, a resistor R5, a diode D1, and a diode D2.

  A resistor R4, a resistor R5, a diode D1, and a diode D2 are connected in series from the power source side between the power source and the ground. That is, one end of the resistor R4 is connected to the power source, and the other end is connected to one end of the resistor R5. The other end of the resistor R5 is connected to the anode of the diode D1. Both the diodes D1 and D2 are connected in the forward direction from the power supply to the ground. The cathode of the diode D1 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the ground.

  The bipolar transistor Q5 is an npn-type bipolar transistor, the collector of which is connected to the power supply, and the emitter of which is connected to the reference voltage generating circuit 1. Specifically, the emitter is connected to a line L1 connecting one end of the resistor R1, one end of the resistor R2, the base of the bipolar transistor Q4, and the output terminal B of the reference voltage generating circuit 1. The base of the bipolar transistor Q5 is connected to the connection point between the resistor R4 and the resistor R5.

  The line L1 functions as an input line through which the reference voltage generating circuit 1 receives the input of the starting current from the starting circuit 20 and an output line for outputting the output of the reference voltage generating circuit 1 to the output terminal B.

  The resistor R5, the diode D1, and the diode D2 connected between the base of the bipolar transistor Q5 and the ground constitute base voltage holding means according to the present embodiment. The base voltage holding means gives the divided value of the power supply voltage Vcc as the base voltage of the bipolar transistor Q5, which is determined by the sum of the drop voltage in the resistor R5, the forward drop voltage of the diode D1, and the forward drop voltage of the diode D2. That is, when a current flows through the resistor R5, the diode D1, and the diode D2 (the direction of this current is a direction in which a forward current flows through the diodes D1 and D2), the base voltage (the potential at the node A) is a predetermined potential (with respect to the ground). The sum of the drop voltage at the resistor R5, the forward drop voltage of the diode D1, and the forward drop voltage of the diode D2).

  Next, operations of the starting circuit 20 and the reference voltage generating circuit 1 will be described.

On power up, it is supplied to the base via a resistor R4 base current I _B from the power supply, the base - the operation of the bipolar transistor Q5 applied forward voltage is started between the emitters. Immediately after the power is turned on, since the emitter of the bipolar transistor Q5 is at the ground potential, the potential V _{A of the} node A shown in FIG. 1 is V _A = V as shown in the diode characteristic between the base and the emitter shown in FIG. _BE (Base-emitter voltage) ≒ 0.7V.

Since the collector of the bipolar transistor Q5 is connected to the power supply, the bipolar transistor Q5 starts operation at an operating point of a point in V _CE -I _C characteristic diagram shown in FIG. 3, the reference voltage generating circuit 1 line L1 Is supplied with an emitter current I _E = (I _B + I _C ) as a starting current. This starting current is a current value determined by the current supply capability of the bipolar transistor Q5, and an extremely large current can be supplied as compared with the conventional example shown in FIG.

  The starting current from the starting circuit 20 is supplied as a base current to the bipolar transistors Q1 to Q4 of the reference voltage generating circuit 1 via the line L1, thereby turning on the bipolar transistors Q1 to Q4. When the bipolar transistors Q1 to Q4 are turned on, the gates of the P-type MOS transistors MP1 and MP2 become low level, and the P-type MOS transistors MP1 and MP2 are turned on. Therefore, as will be described later, even if the supply of the starting current from the starting circuit 20 is cut off, the current from the power supply is supplied to the reference voltage generating circuit 1 via the P-type MOS transistor MP1.

  The activated reference voltage generating circuit 1 causes a current to flow toward its output terminal B. The current is gradually charged by the capacitor C1, and the voltage at the output terminal B gradually increases as shown in FIG. 4 (d). To go. Along with this, the emitter voltage of the bipolar transistor Q5 connected to the output terminal B also rises.

As the emitter voltage rises, the collector-emitter voltage V _CE of the bipolar transistor Q5 decreases as shown in FIG. 4B, but the base-emitter voltage V _BE is V _BE ≈0.7V. At the beginning of the operation of the bipolar transistor Q5, as shown in FIG. 3, the decrease rate of the collector current, that is, the starting current is very small. Therefore, a large current is supplied to start the reference voltage generating circuit 1 at high speed. Can do.

When the reference voltage generation circuit 1 is activated, as shown in FIG. 4D, the output voltage of the reference voltage generation circuit 1 settles to a predetermined reference voltage. In the bandgap type reference voltage generation circuit, by appropriately setting circuit constants such as the resistance values of the resistors R1, R2, and R3 and the emitter areas of the bipolar transistors Q1 to Q4, the change due to the power supply voltage V _CC and the temperature is changed. A small stable reference voltage Vref can be obtained. For example, in this embodiment, a silicon bandgap type reference voltage generation circuit is used, and the reference voltage is generally about 1.25V.

As the emitter voltage rises, the base voltage also rises, and when the voltage between both ends of the diodes D1 and D2 connected in series is greatly opened, the current I ₁ also flows through the resistor R5 and the diodes D1 and D2. start.

When a current flows through the resistor R5 and the diodes D1 and D2, the potential V _{A of the} node _A is held at V _A = 2VF + I ₁ × R5. Note that VF is a forward drop voltage of each of the diodes D1 and D2. In this embodiment, since the diodes D1 and D2 are both silicon diodes, VF is about 0.7V. R5 represents the resistance value of the resistor R5.

In this embodiment, V _A = 2VF + I ₁ × R5 is about 1.6V, that is, the base voltage is held at about 1.6V as shown in FIG. Since the base voltage is held at a constant value, the base-emitter voltage V _BE is shown in FIG. 4 (a) when the emitter voltage rises as the output voltage of the reference voltage generation circuit 1 rises. gradually decreases as the bipolar transistor Q5 is an operating point at V _CE -I _C characteristic diagram shown in FIG. 3 will move as the point a → b point → c point → d point, the start circuit 20 The starting current supplied gradually decreases.

When the reference voltage generating circuit 1 is completely activated (the output voltage is stabilized at a reference voltage of about 1.25 V), the emitter voltage is also stabilized at about 1.25 V. Therefore, after the reference voltage generating circuit 1 is completely activated, the base voltage and the emitter voltage are settled at a constant voltage, so that the base-emitter voltage V _BE is settled at a constant voltage as shown in FIG. Become. This voltage is sufficiently small with respect to 0.7 V (see FIG. 2) that substantially turns on the bipolar transistor Q5, the base current hardly flows, and the bipolar transistor Q5 is stabilized at the non-operating point. As a result, very little current is supplied from the starting circuit 20 to the reference voltage generating circuit 1. The supply of starting current is substantially stopped.

Incidentally, the bipolar transistor Q5 is also after stable in non-operating point, the resistance R4, R5, diodes D1, D2, current _{I 1 = (Vcc-2VF)} ÷ (R4 + R5) current I ₁ expressed by the continuing flow . Vcc represents the power supply voltage, and R4 represents the resistance value of the resistor R4. Because after activating the reference voltage generating circuit 1 is not necessary to operate the start-up circuit 20, it is possible to reduce the current consumption in the current activation completion after the start circuit 20 of the reference voltage generating circuit 1 as I ₁ is smaller the . For example, in the present embodiment, the resistance value R4 of the resistor R4 is designed so that the current I ₁ is about ₁ μA.

  As described above, according to the present embodiment, the diode characteristic of the bipolar transistor Q5 is used, that is, the forward current of the diode is used so that a large current flows, so that no complicated circuit design is required. Depending on the capability of the bipolar transistor Q5, a large current can be supplied to the reference voltage generating circuit 1 to start it up at high speed.

  Next, with reference to FIGS. 5 and 6, the result of a comparison simulation with a conventional example will be described.

  FIG. 5 shows simulation results of the starting current, the starting circuit current consumption, and the starting characteristics of the reference voltage generating circuit when the reference voltage generating circuit 1 is started using the starting circuit 20 of the present embodiment shown in FIG. FIG. 6 shows simulation results of the starting current, the starting circuit current consumption, and the starting characteristics of the reference voltage generating circuit when the reference voltage generating circuit 1 is started using the conventional starting circuit 50 shown in FIG.

  In both the present embodiment and the conventional example, the capacitance of the capacitor C1 is 10 nF, and the current consumption of the starting circuit after starting the reference voltage generating circuit 1 (in this embodiment, the current flowing through the path of the resistor R4 → R5 → diode D1 → D2 In the conventional example, it is designed so that the current flowing through the path of the P-type MOS transistor MP3 → N-type transistor MN3) is about 1.0 μA.

  As can be seen from the comparison between FIG. 5A and FIG. 6A, the present embodiment can supply a larger starting current, and as a result, FIG. 5C and FIG. As can be seen from the comparison, the startup time until the output voltage of the reference voltage generating circuit 1 is set to a predetermined reference voltage (about 1.25 V) is about 0.7 seconds in the present embodiment, and about 1.3 seconds in the conventional example. In addition, the present embodiment can be started faster.

  Further, as can be seen from a comparison between FIG. 5B and FIG. 6B, in this embodiment, the current consumption of the starting circuit does not exceed 1.0 μA, and the current consumption can be reduced as compared with the conventional example. ing. Therefore, this is effective for mobile devices such as mobile phones that require low power consumption design.

  As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to this, A various deformation | transformation is possible based on the technical idea of this invention.

  In the above embodiment, the base voltage holding unit is configured by the resistor R5 and the diodes D1 and D2. However, the base voltage holding unit may be configured by only the diodes D1 and D1 by removing the resistor R5. With this configuration, the base voltage is held at the sum of the forward drop voltages of the two diodes D1 and D2, that is, 2VF = 1.4V.

  However, if the resistor R5 is added and the base voltage holding voltage is increased by the amount corresponding to the resistor R5 as in the above embodiment, the base voltage until the output voltage of the reference voltage generating circuit 1 becomes constant is increased accordingly. The emitter-to-emitter voltage can be increased, and a larger starting current can be supplied to the reference voltage generating circuit 1 to perform a faster starting.

Further, a silicon bandgap type reference voltage generating circuit which is generally widely used has a characteristic that the output is easily stabilized in the vicinity of 0.9 V in addition to 0 V and the reference voltage of about 1.25 V. Therefore, the diodes D1 and D2 If the base voltage is held at a forward voltage drop of only 1.4V, the base-emitter voltage V _BE = 1.4V-0.9V = when the output voltage of the reference voltage generating circuit 1 rises to 0.9V = There is a possibility that a sufficient starting current may not be supplied due to the diode characteristics between the base and the emitter shown in FIG. Therefore, in order to stably start the reference voltage generating circuit 1 up to a desired designed reference voltage of about 1.25 V, the base voltage is set to 0.9 V when the emitter voltage becomes 0.9 V by adding the resistor R5. It is preferable to raise the base-emitter voltage V _BE ≧ 0.7 V as much as possible.

If another diode is attached instead of the resistor R5, the base voltage becomes 3VF = 2.1V, and the base-emitter voltage when the output voltage of the reference voltage generating circuit 1 settles to 1.25V is V _BE. = 2.1V−1.25V = 0.85V, and the starting current continues to be supplied from the starting circuit 20 even after the reference voltage generating circuit 1 is started. If there is only one diode, the starting current is supplied only when the output voltage of the reference voltage generating circuit 1, that is, the emitter voltage is near the ground potential.

  Note that the value of the base voltage to be held depends on the desired designed reference voltage value of the reference voltage generating circuit 1, and accordingly, the resistance value of the resistor constituting the base voltage holding means, The number and type of diodes (for example, the forward voltage drop differs between silicon diodes and germanium diodes) are arbitrarily changed.

Further, the base voltage holding means may be composed of only a resistor without including a diode. However, if you try to raise the base voltage to the desired value by reducing the current consumption of the startup circuit after starting the reference voltage generation circuit as much as possible, a large resistance is required, which increases the area of the resistance built into the wafer, and parasitic capacitance The start-up time may be delayed depending on the charging time. In addition, the current flowing through the resistor is highly dependent on the power supply voltage V _CC , so that the voltage raised by the resistor is likely to fluctuate. However, even if the forward current fluctuates somewhat, the diode has little fluctuation in the forward voltage drop. For example, in the case of a silicon diode, since it is stably maintained at around 0.7 V, the base voltage can also be stably maintained at a desired value.

It is a circuit diagram of a starting circuit and a reference voltage generating circuit according to an embodiment of the present invention. A V _BE -I _B characteristic diagram of the bipolar transistor Q5 shown in FIG. A V _CE -I _C characteristic diagram of the bipolar transistor Q5. FIG. 2 is a transient characteristic diagram of each node in the circuit shown in FIG. 1. It is a figure which shows the simulation result of the starting characteristic in this embodiment using the circuit of FIG. 1, the starting current consumption of a starting circuit, and the starting characteristic of a reference voltage generation circuit. FIG. 8 is a diagram illustrating a simulation result of a start-up current, a start-up circuit consumption current, and a start-up characteristic of a reference voltage generation circuit in a conventional example using the circuit of FIG. It is a circuit diagram of the starting circuit and reference voltage generation circuit of a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reference voltage generation circuit, 10 ... Starting circuit, 20 ... Starting circuit, Q5 ... Bipolar transistor, R4, R5 ... Resistance, D1, D2 ... Diode.

Claims (8)

A starting circuit for starting a reference voltage generating circuit,
A bipolar transistor having a collector connected to a power source and an emitter connected to the reference voltage generating circuit;
A resistor connected between the power source and the base of the bipolar transistor;
Base voltage hold connected between the base and ground, and divides the voltage of the power supply so as to become a base voltage that stabilizes the bipolar transistor at a non-operating point when the emitter voltage becomes the reference voltage of the reference voltage generating circuit. Means,
A start-up circuit comprising: The starting circuit according to claim 1, wherein the base voltage holding unit includes a diode whose forward direction is from the base toward the ground. The starter circuit according to claim 2, wherein the diode includes two series-connected silicon diodes. The base voltage holding means includes, in addition to the two silicon diodes, a resistor connected between the base and an anode of a silicon diode connected to the base side of the two silicon diodes. 4. The start-up circuit according to claim 3, wherein A power supply circuit comprising a reference voltage generating circuit and a starting circuit for starting the reference voltage generating circuit,
The starting circuit is
A bipolar transistor having a collector connected to a power source and an emitter connected to the reference voltage generation circuit;
A resistor connected between the power source and the base of the bipolar transistor;
Base voltage hold connected between the base and ground, and divides the voltage of the power supply so as to become a base voltage that stabilizes the bipolar transistor at a non-operating point when the emitter voltage becomes the reference voltage of the reference voltage generating circuit. Means,
A power supply circuit comprising: The power supply circuit according to claim 5, wherein the base voltage holding unit includes a diode whose forward direction is from the base toward the ground. The power supply circuit according to claim 6, wherein the diode includes two silicon diodes connected in series. The base voltage holding means includes, in addition to the two silicon diodes, a resistor connected between the base and an anode of a silicon diode connected to the base side of the two silicon diodes. The power supply circuit according to claim 7, wherein:

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