JP2800720B2 - Starting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting circuit, and more particularly to a starting circuit which can be operated from a low voltage, can be set with high accuracy, and has little influence on a circuit to be started.

[0002]

2. Description of the Related Art A conventional starting circuit (st
As an art-up circuit, as shown in FIG. 17, one transistor (output side) constituting a simple current mirror circuit composed of a diode-connected first transistor and a second transistor having a base connected in common with the transistor Widlar current mirror in which a resistor R70 is inserted into the emitter of Q70
ror) circuit (for example, literature: “IEEE Jo
urnal of Solid-State Circuits, VOL.28, NO.6, pp.66
7-670, June 1993, or IEEE Journal of Solid-
State Circuits, VOL.26, pp.1817-1824, December, 19
91 ”).

[0003] In FIG. 17, the transistor Q80 is (also referred to as "reference current") I ₁ is the current supplied from the power supply VCC through a resistor R81, also referred to as a current draw of the transistor Q70 (sinkcurrent) I ₂ ( "mirror current" ) is a non-linear current mirror circuit increases monotonically with increasing current I ₁ by the emitter resistor R70.

[0004]

In the non-linear current mirror circuit of Figure 17 The object of the invention is to solve the above-originally current I ₂ can be set to very small current as compared to the current I _1, if increased power supply voltage, as described above the current value of the current I ₂ also can not be ignored with respect to circuit current of the starting circuit, appears the influence of the starting circuit to this for the starting circuit.

In particular, in the Widlar current mirror circuit, the current I ₂ has a positive temperature characteristic with respect to the current I ₁ ,
It is called a TAT (proportional to absolute temperature) circuit. Therefore, when the Widlar current mirror circuit is used as a starting circuit, the effect on the activated circuit is that the temperature characteristic is changed.

As described above, the conventional starting circuit can operate at a low voltage, but has a problem that it is difficult to reduce the influence on the circuit to be started so that it can be ignored.

Accordingly, the present invention provides a semiconductor integrated circuit comprising:
It is an object of the present invention to provide a start-up circuit which operates from a low voltage and can be made so small that the influence on a circuit to be started can be ignored.

[0008]

In order to achieve the above object, the present invention has a current mirror circuit to which a current is supplied from a power supply via a resistor. , The first with zero circuit current
In the starting circuit for making the first operating point impossible to obtain for the operating points of the activated circuit having a plurality of operating points including the operating point, the mirror current of the current mirror circuit approaches zero as the power supply voltage increases. A startup circuit characterized by the above configuration is provided.

Further, the present invention has a current mirror circuit to which a current is supplied from a power supply via a resistor, and a first operating point of at least a power supply voltage of zero and a circuit current of zero by a mirror current of the current mirror circuit. in starting circuit which does not take the first operating point for the operating point of the starting circuit having a plurality of operating points including a mirror current of the current mirror circuit is substantially constant electrode regardless the increase of the supply voltage Provided is a startup circuit characterized by a small current.

The present invention is preferably characterized in that a mirror current of the current mirror circuit is set to an operating point exceeding a maximum circuit current of the activated circuit.

Further, the present invention provides a starting circuit for making it impossible to obtain the first operating point with respect to an operating point of a started circuit having a plurality of operating points including at least a first operating point of zero power supply voltage and zero circuit current. , An input terminal has a current mirror circuit connected to a power supply side via a resistor, the current mirror circuit includes a resistor between the input terminal and a first signal terminal of the input-side transistor, An actuation circuit is provided, wherein the actuated circuit can be set to the operating point even when the mirror current output from the end exceeds the peak point of the circuit current for the actuated circuit. .

The present invention is preferably characterized in that a second signal terminal of the output stage transistor of the current mirror circuit is connected to a second power supply via a resistor.

In the present invention, preferably, the mirror current of the current mirror circuit becomes a substantially constant extremely small current irrespective of an increase in the power supply voltage after setting the activated circuit to the operating point. It is characterized by the following.

Furthermore, the present invention is preferably characterized in that the mirror current of the current mirror circuit approaches zero as the power supply voltage increases.

The present invention is preferably characterized in that the current mirror circuit is constituted by a bipolar transistor.

Further, the present invention is preferably characterized in that the current mirror circuit is constituted by a MOS transistor.

[0017]

The principle and operation of the present invention will be described below. A started circuit having a plurality of operating points including an operating point of zero power supply voltage and zero circuit current (for example, the circuit is at a stable operating point when power is not turned on) is autonomous, for example, simply by turning on the power. Does not shift to the desired operating point (stable operating point), and is bootstrapped by a predetermined starting circuit so as to reach the operating point. According to the present invention, by configuring such a starting circuit as a current mirror circuit having a predetermined circuit configuration (also referred to as “Nagata current mirror circuit”), the influence on the activated circuit is minimized, and the peak of the activated circuit is minimized. It has been completed based on the inventor's knowledge that it can be configured to operate stably at an operating point beyond the point. The effect can be made negligible.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

[0019]

Embodiment 1 FIG. 1 is a block diagram for explaining a configuration of an embodiment of the present invention. FIG. 2 shows a current mirror circuit according to the present embodiment (current mirror circuit 103 in FIG. 1).
FIG. 3 is a diagram showing the configuration of FIG.

Here, assuming that the matching of the elements is good and ignoring the base width modulation, an exponential law is established in the relation between the base-emitter voltage V _{BE of} the transistor and the collector current, and the collector of the transistor Q1 in FIG. The current is given by the following equation (1).

[0021]

(Equation 1)

Here, V _T is a thermal voltage, and V _T = kT /
It is represented as q. Here, k is Boltzmann's constant, T is absolute temperature, and q is unit electron charge. _IS is the saturation current of the transistor.

Similarly, the collector current of transistor Q2 is given by the following equation (2).

[0024]

(Equation 2)

Referring to FIG. 2, transistor Q
The base-emitter voltage V _BE1 of the transistor ₁ is the transistor Q2
_Is equal to the _sum of the base-emitter voltage V _BE2 and the potential drop R2 × I ₁ of the resistor R2. Therefore, the following equation (3) holds as the base-emitter voltage difference ΔV _BE .

[0026]

(Equation 3)

Here, for the sake of simplicity, the current amplification factor α _F of the transistor is set to 1.

Therefore, the following equation (4) is derived from the above equation (3) as the relationship between the collector currents I ₁ and I ₂ of the transistors Q1 and Q2.

[0029]

(Equation 4)

The differential temperature coefficient TC _F of the mirror current I ₂ in the current mirror circuit in FIG. 2 is obtained by the following equation (5).

[0031]

(Equation 5)

In the above equation (5), when dR ₂ / dT = 0, the differential temperature coefficient TC _F of the mirror current I ₂ is apparently obtained.
(I ₂ )> 0, and the mirror current I ₂ is proportional to the absolute temperature.

FIG. 3 shows the relationship between the collector currents I ₁ and I ₂ of the transistors Q1 and Q2 in FIG. In FIG. 3, the horizontal axis represents I ₁ and the vertical axis represents I ₂ . The temperature coefficient of the resistor R2 is set to zero. Referring to FIG. 3, at room temperature (25 ° C.)
When the collector current I ₁ is V _T / R _{2, the} mirror current I ₂ has a value of 1 / e (= 1 / 2.71828) (= V _T / (e × R 2)) of I ₁ as a peak point.

The reference current I ₁ input to the input terminal of the current mirror circuit 103 (ie, the collector current of the transistor Q1 in FIG. 2) is given by the following equation (6) as the power supply voltage VCC from FIG.

[0035]

(Equation 6)

The base-emitter voltage V _BE1 of the transistor Q1 is logarithmically compressed with respect to the value of the collector current I _1, close to a constant value in the order of 0.7 V. That is, the mirror current I ₂ is almost proportional to the power supply voltage.

FIG. 4 shows that in FIG. 1 and FIG.
80Ω, R2 = 100Ω, temperature characteristic TC of resistance R2
_F (R) = − 300 ppm / ° C., collector voltage V _CE2 =
It shows the actual measurement value of the temperature characteristic of the mirror current I ₂ of 0.5 V,
FIG. 5 shows measured values of the mirror current characteristics when the resistance value of the resistor R1 is changed. The horizontal axis in FIG. 4 and FIG. 5 is a power supply voltage VCC, and the vertical axis shows a mirror current I _2.

The peak value of the mirror current I ₂ is determined so that the voltage drop at the resistor R 2 connected to the collector of the transistor Q 2 is just equal to the thermal voltage V _T , and the peak current value changes in proportion to the temperature; The power supply voltage value at the peak point changes in inverse proportion to the temperature.

Referring to FIG. 5, bias resistor R
By varying the 1, peak current value of the mirror current I ₂ can be varied substantially in proportion to the resistance value of the bias resistors R1 to the supply voltage value VCC at the peak point remains constant.
That is, the peak current value can be set by the resistor R2, and the power supply voltage value at the peak point can be set by the bias resistor R1. At a voltage value that is about five times the power supply voltage value at the peak point, the mirror current value is 1/10 of the peak current value, and the effect on the activated circuit can be almost ignored.

Further, when there are three or more operating points such as when the circuit current of the activated circuit has a peak characteristic (when the power supply voltage VCC = 0, ICC = 0 and other operating points are included). However, by using the starting circuit having the peak characteristics shown in FIGS. 4 and 5 (see FIG. 2), the operating point can be operated at a stable point exceeding the peak point of the activated circuit. .

A specific example will be described using the reference voltage circuit shown in FIG. The circuit shown in FIG.
This is a reference voltage circuit that is self-biased by a simple current mirror circuit composed of Q5 and Q6 to simplify the circuit, and is generally a bandgap reference voltage circuit (bandgap reference voltage circuit).
rence circuit). The output reference voltage _Vref of the bandgap reference voltage circuit is equal to the base-emitter voltage _VBE3 of the transistor Q3 (R3
/ R4) × ΔV _BE , which is given as a voltage.

Referring to FIG. 6, transistors Q5, Q6
The current ratio of the simple current mirror circuit consisting of 1: to 1, the circuit for generating the difference [Delta] V _BE between the base and emitter voltages between the transistors Q3 and Q4 ((R
3 / R4) × ΔV _{BE (referred} to as “ΔV _BE multiplier circuit”), as described above, the emitter area ratio between the transistor Q3 and the transistor Q4 is set to 1
It is necessary to /e(=1/2.71828) (i.e., the mirror current I ₂ at the peak point of the mirror current I ₂ as shown in FIG. 3 is 1 / e next to the current I _1, the collector current I _{To make} the current ratio between ₃ and I ₄ 1: 1, the emitter area ratio of transistor Q4 to transistor Q3 is e).

On the other hand, when the emitter area ratio of the transistor Q4 is an integral multiple of the emitter area of the transistor Q3, the value is somewhat too large even if the emitter area ratio K = 3.

Similarly, if the emitter area ratio of the transistor Q4 is K = 4, the value becomes considerably large. When the emitter area ratio K is 4, as shown in FIG.
For the collector currents I ₃ and I ₄ of Q3 and Q4 (see FIG. 6), I ₃ = I ₄ holds at the peak point (when the current I ₃ is V _T
/ R4) (point of emitter area ratio K
Is 3, the operating point is a. ).

However, in order to reach this operating point (the intersection b between I ₃ = I ₄ and the solid line in FIG. 7), the peak point must be exceeded. the current draw I ₂ of the circuit 101, as long as I ₃ is beyond the peak point can reach the operating point of the I ₃ = I _4.

Assuming that the draw current I ₂ of the starting circuit 101 at the operating point where I ₃ = I ₄ is a very small current that can be ignored, the transistors Q 3, Q 4, Q 5, Q
The current loop composed of 6 constitutes a negative feedback loop, and the operation is stabilized.

[0047]

Embodiment 2 FIG. 8 is a diagram showing a configuration of a current mirror circuit according to a second embodiment of the present invention.

Referring to FIG. 8, in the present embodiment, an emitter resistor R3 is inserted in the current mirror circuit according to the first embodiment shown in FIG.

In the present embodiment, the inserted emitter resistor R3 has a lower peak characteristic than in the first embodiment. That is, flattening characteristics can be provided by the emitter resistor R3.

In general, circuit analysis becomes difficult when an emitter resistor is inserted, but FIG. 9 shows that R2 = 100Ω and R3 = 1.
The calculated value of the temperature characteristics of the collector currents of the transistors Q1 and Q2 when 5 KΩ is set is shown.

The draw-in current of the starting circuit using this current mirror circuit is also proportional to the absolute temperature, as in the first embodiment, but the ratio of I ₁ to I ₂ can be set to 1: several%. Therefore, the influence on the activated circuit 102 (see FIG. 1) can be almost negligible. And the starting circuit 10
Current I ₂ retraction of 1 may be set to a substantially constant value regardless of the supply voltage.

FIG. 10 shows that R2 = 100Ω and R3 = 15K
_{Ω, TC F (R) =} - 300ppm / ℃, the measured value of the temperature characteristics of the mirror current I ₂ in the case where the collector voltage V _CE2 = 0.5V, in FIG. _{11, R2 = 100Ω, TC F} (R2)
= -300 ppm / ° C., V _{CE 2} = 0.5 V, and the emitter resistance R3 is set to 0Ω, 100Ω, 220Ω, 470
The measured values of the input / output current characteristics of the current mirror circuit when Ω, 1 KΩ, 2.2 KΩ, and 15 KΩ are changed are shown.

FIG. 12 shows that R2 = 100Ω and R3 = 1K
Ω, TC _F (R) = − 300 ppm / ° C., V _CE2 = 0.5
V, the bias resistance R1 is set to 280Ω, 560Ω,
The measured values of the current mirror current characteristics when 1 KΩ and 2 KΩ are changed are shown.

[0054] With reference to FIG. 11, by increasing the emitter resistor R3, the current draw I ₂ of the starter circuit can be set to a minute current, yet can be set substantially constant value.

[0055]

Third Embodiment The starting circuit described in each of the above embodiments is not limited to a bipolar element, but may be constituted by a MOS device. MO in the first embodiment
The case where the circuit is constituted by S transistors will be described below.

Assuming that the matching of the elements is favorable, the channel length modulation and the body effect are ignored, and the relationship between the drain current of the MOS transistor and the voltage between the gate and the source follows the square law, the drain current of the MOS transistor becomes , Given by the following equation (7).

[0057]

(Equation 7)

Here, β is a transconductance parameter, and is expressed as β = μ (C _OX / 2) (W / L). Where μ is the effective mobility of the carrier, C _OX is the gate oxide film capacity per unit area, W and L are the gate width and gate length, V _GS is the gate-source voltage, and V _TH is the gate threshold. The voltages are shown respectively.

FIG. 13 shows a current mirror circuit in which the circuit described in the first embodiment is constituted by MOS transistors. The drain currents of the MOS transistors M1 and M2 are given by I ₁ and I ₂ by the following equations (8) and (9).

[0060]

(Equation 8)

[0061]

(Equation 9)

The source of the MOS transistor M1
The drain-to-drain voltage V _GS1 is equal to the source-to-drain voltage V _GS2 of the MOS transistor M2 and the voltage R2 between the terminals of the resistor R2.
× I ₁ (see FIG. 13).
The difference ΔV _GS between the drain voltages is given by the following equation (10).

[0063]

(Equation 10)

From the above equations (8) and (10), the following equation (11) is derived as the mirror current I ₂ .

[0065]

[Equation 11]

[0066] by differentiating both sides of the equation (11) with a current I _1, the current I ₁ to give dI ₂ / dI ₁ = 0, the following equation (1
Given in 2).

[0067]

(Equation 12)

[0068] The first value (1 / R _{² 2} β) the mirror current I ₂ = 0 becomes out of the current I ₁ in the above equation (12), the circuit is inappropriate not start.

[0069] Therefore, a peak value of the mirror current I ₂ is given by the following equation (13) in the case of _{I 1 = 1 / (4R 2} 2 β).

[0070]

(Equation 13)

FIG. 14 shows the current characteristics of the MOS type current mirror circuit according to the present embodiment shown in FIG. FIG.
, The expected peaking characteristics appear.

However, in the case of a MOS, the mirror current I ₂ becomes zero at a current four times or more of the current I ₁ (= 1 / (4R ₂ ² β)) giving the peak value.

Therefore, the MOS type current mirror circuit shown in FIG. 13 can be used as a starter circuit having the same characteristics as the bipolar current mirror circuit shown in FIG.

In a MOS device, the mobility μ
Has a temperature characteristic, the temperature dependence of the transconductance parameter β is expressed by the following equation (14).

[0075]

[Equation 14]

Where β ₀ is room temperature (T = T ₀ = 300 K)
Is the value of β at

Therefore, the peak current represented by the above equation (13) is calculated by using β in the above equation (14), when the differential temperature coefficient TC _F (R ₂ ) of the resistor R2 is zero (= 0). It can be seen that it is proportional to 3/2 power of (absolute temperature T).

FIG. 15 shows the 1 / β characteristic. Referring to FIG. 15, the MOS current mirror circuit shown in the above equation (9) has a normal operating region centered at room temperature.
It can be considered approximately proportional to temperature. That is, it can be regarded as PTAT.

The differential temperature coefficient (TC _F ) of the mirror current of the MOS current mirror circuit is approximately 1.5 times the differential temperature coefficient (TC _F ) of the mirror current of the bipolar current mirror circuit. That is, 1 / (R
₂ beta) is understood to correspond to the thermal voltage V _T of a bipolar.

[0080]

[Embodiment 4] The circuit described in the second embodiment is replaced with a MOS transistor.
FIG. 16 shows a circuit including transistors. Referring to FIG. 16, in the MOS current mirror circuit in which source resistance R3 is inserted into MOS transistor M2, the peak value of the mirror current is blunted similarly to the case of the bipolar element,
At the same time as flattening, it can be set to a small current. That is, the effect on the activated circuit can be made so small as to be negligible.

Although the present invention has been described with reference to the above embodiments, it is needless to say that the present invention is not limited to only the above embodiments. For example, the current mirror circuit in the present invention is not limited to an npn-type bipolar transistor, but may be constituted by a pnp-type transistor which outputs a mirror current (source current). In a MOS structure, it is not limited to an n-channel MOS transistor. , P-channel MOS transistors.

[0082]

As described above, according to the starting circuit of the present invention, it is possible to operate from a low voltage and to minimize the influence on the circuit to be started. Also,
According to the present invention, the draw-in current of the start-up circuit can be set to a very small current, and the peak can be flattened and set to a substantially constant value. The actuated circuit can be operated stably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a starting circuit according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a current mirror circuit according to a first example of the present invention.

Figure 3 is a graph showing a characteristic of the current mirror circuit (the relationship of the reference current I ₁ and the mirror current I ₂₎ according to a first embodiment of the present invention.

FIG. 4 is a diagram showing actually measured values of temperature characteristics of the starting circuit according to the first example of the present invention.

FIG. 5 is a diagram showing actually measured values of characteristics with respect to a starting circuit bias resistance according to the first example of the present invention.

FIG. 6 is a diagram showing a reference voltage circuit configured using a current mirror circuit according to the first example of the present invention.

FIG. 7 is a diagram for explaining characteristics of the reference voltage circuit of FIG. 6;

FIG. 8 is a diagram illustrating a configuration of a current mirror circuit according to a second example of the present invention.

FIG. 9 is a diagram illustrating characteristics (a relationship between an input current I ₁ and a mirror current I ₂ ) of a current mirror circuit according to a second example of the present invention.

FIG. 10 is a diagram illustrating measured values of temperature characteristics of a current mirror circuit according to a second example of the present invention.

FIG. 11 is a diagram showing measured values of flattening characteristics by an emitter resistance of a current mirror circuit according to a second example of the present invention.

FIG. 12 is a diagram showing actually measured values of characteristics of a starter circuit according to a second embodiment of the present invention, which are based on bias resistance.

FIG. 13 is a diagram illustrating a configuration of a current mirror circuit according to a third example of the present invention.

FIG. 14 is a diagram illustrating characteristics of a current mirror circuit according to a third example of the present invention.

FIG. 15 is a characteristic diagram shown to explain the temperature characteristic of the starting circuit according to the third example of the present invention.

FIG. 16 is a diagram illustrating a configuration of a current mirror circuit according to a fourth embodiment of the present invention.

FIG. 17 is a diagram showing a configuration of a conventional circuit.

[Explanation of symbols]

 101 Start circuit 102 Activated circuit 103 Current mirror circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-7149 (JP, A) JP-A-48-54460 (JP, A) JP-A-64-35616 (JP, A) JP-A-62 293326 (JP, A) JP-A-6-59761 (JP, A) JP-A-5-297969 (JP, A) JP-A-6-15113 (JP, U) JP-A 55-22835 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G05F 3/24, 3/26, 3/30 H03F 3/343 G05F 1/56

Claims (9)

(57) [Claims] A current mirror circuit to which a current is supplied from a power supply via a resistor, a plurality of mirrors including a first operating point having at least a power supply voltage of zero and a circuit current of zero by a mirror current of the current mirror circuit; In a starting circuit for making it impossible to obtain the first operating point with respect to an operating point of an activated circuit having an operating point, a mirror current of the current mirror circuit is configured to approach zero as the power supply voltage increases. A starting circuit characterized by: A current mirror circuit to which a current is supplied from a power supply via a resistor, a plurality of mirrors including a first operating point of at least a power supply voltage of zero and a circuit current of zero by a mirror current of the current mirror circuit; in starting circuit which does not take the first operating point for the operating point of the starting circuit having an operating point, the mirror current of the current mirror circuit is substantially constant microfine current regardless the increase of the supply voltage A starting circuit, characterized in that: 3. The mirror current of the current mirror circuit is:
2. The starting circuit according to claim 1, wherein the operating point is set to an operating point exceeding a maximum circuit current of the activated circuit. 4. A first circuit having at least zero power supply voltage and zero circuit current.
An operating point of an actuated circuit having a plurality of operating points including the operating point described in (1), wherein the first operating point cannot be obtained, and a current mirror circuit having an input terminal connected to a power supply via a resistor is provided. The current mirror circuit includes a resistor between the input terminal and the first signal terminal of the input-side transistor, and a mirror current output from an output terminal exceeds a peak point of a circuit current for the activated circuit. A starting circuit which can be set to the operating point with respect to the operating point. 5. The starting circuit according to claim 4, wherein a second signal terminal of an output stage transistor of said current mirror circuit is connected to a second power supply via a resistor. 6. The current mirror circuit according to claim 1, wherein said mirror current becomes a substantially constant extremely small current regardless of an increase in said power supply voltage after said activated circuit is set to said operating point. 4. The starting circuit according to 4. 7. The starting circuit according to claim 4, wherein said mirror current of said current mirror circuit approaches zero as the power supply voltage increases. 8. The current mirror circuit according to claim 1, wherein said current mirror circuit comprises a bipolar transistor.
The starting circuit according to any one of the above. 9. The start-up circuit according to claim 1, wherein said current mirror circuit comprises a MOS transistor.