JPH0570849B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a speed control device for a small DC motor used, for example, to drive audio equipment, and particularly to a speed control device for a bridge detection type DC motor that can be driven and controlled with a single dry battery. This relates to a reference voltage circuit that operates even when the power supply voltage is 1V, which is effective as a reference voltage generation source in a control device or the like.

Conventional technology As a conventional reference voltage circuit, for example, "Voltage Regulator Handbook" May 10, 1972
There is a bandgap reference voltage circuit as shown in Nisseibundo Shinkosha, p. 1, pp. 6-7.

A conventional reference voltage circuit will be described below with reference to the drawings. FIG. 4 is a wiring diagram of a conventional reference voltage circuit. In FIG. 4, the base of a transistor 1 is connected to its collector, and is also connected to one power supply terminal 4 via a resistor 2 and a constant current source 3. The emitter of the transistor 1 is connected to the other power supply terminal 5, and the constant current source 3
The connection point between the resistor 2 and the resistor 2 is connected to the output terminal 6. The base of the transistor 7 is connected to the base-collector connection point of the transistor 1, the emitter is connected to the power supply terminal 5 via a resistor 8, and the collector is connected to the output terminal 6 via a resistor 9.
and to the base of transistor 10. The emitter of the transistor 10 is connected to the power supply terminal 5, and the collector thereof is connected to the output terminal 6.

The operation of the reference voltage circuit configured as above will be explained below. Transistor 7 operates at a lower current density than transistor 1, and the positive temperature coefficient of the base-emitter voltage difference ΔV _BE of the two transistors is equal to the base-emitter voltage of transistor 10.
By adding to the negative temperature coefficient of V _BE10 , a predetermined temperature coefficient can be obtained for the output voltage.

Here, the output voltage V _ref is expressed as the following equation.

V _ref = V _BE10 + ΔV _BE /R ₈ · R ₉ + I _B10 · R ₉ ...(1) Here, R ₈ and R ₉ are the resistance values of resistor 8 and resistor 9, respectively, and I _B10 is the resistance value of transistor 10.
However, if the voltage drop at the resistor 9 due to this current is ignored as it is small, it can be expressed as V _ref =V _BE10 +R ₉ /R ₈ ·kT / qlnJ ₁ /J ₇ (2). where q is the electronic charge, k is the Boltzmann constant, T is the absolute temperature, and J ₁ and J ₇ are the emitter current densities of transistors 1 and 7, respectively.

Also, the fluctuation of the output voltage V _ref based on the change in the ambient temperature T is calculated from equation (2) as follows: ΔV _ref /ΔT=ΔV _BE10 /ΔT+R ₉ /R ₈・k/qlnJ
₁ /J ₇ ...(3)

Now, V _BE10 = 0.71V, R ₉ = 5KΩ, R ₈ = 500Ω,
If J ₁ /J ₇ = 10, T = 298〓 (25℃), V _ref
= 1.30V, and assuming that ΔV _BE10 /ΔT = -2V/°C, ΔV _ref /ΔT0 is obtained from equation (3).

That is, in the conventional reference voltage circuit shown in FIG. 4, a temperature compensated reference voltage of about 1.3V is obtained.

Problems to be Solved by the Invention However, in the above configuration, a single dry cell battery is used as a power source, that is, a power supply voltage of 1.5V (approximately
1V), it was impossible to operate in a reduced voltage state. Also, the temperature compensated output voltage is fixed at approximately 1.3V as mentioned above,
Since it is difficult to independently set the output voltage value and temperature coefficient, the degree of freedom in design is low and this is inconvenient.

The present invention was made in view of the above problems, and can operate stably even at the extremely low voltage of a single dry battery, has extremely small fluctuations with respect to the power supply voltage, and has a stable output voltage value and temperature coefficient. The present invention provides a reference voltage circuit that can independently set the voltage with a certain degree of freedom.

Means for Solving the Problems In order to solve the above problems, the reference voltage circuit of the present invention has a base and a collector connected to each other and to one power supply line via a first power supply means, and an emitter is connected to the other power supply line, the base is connected to the base of the first transistor, the collector is connected to the one power supply line via a second power supply means, and the emitter is connected to the first power supply line. a second transistor connected to the other power supply line through one resistor and driven with a smaller emitter current density than the first electric transistor; a third transistor whose collector is connected to the connection point between the second power supply means and whose base is connected to the other power supply line; The other terminal of the second resistor, which is co-connected to the connection point with the resistor, is connected to the third resistor, one terminal of which is connected to the base of the second transistor.
means for dividing the base-emitter voltage of the second transistor by the second and third resistors by connecting the resistor to the other terminal of the resistor; The added voltage of the base-emitter voltage difference of the first and second transistors and the divided voltage of the base-emitter voltage of the second transistor generated across the second resistor is The output is provided between the voltage dividing point of the second and third resistors and the other feed line.

Effects According to the above-described configuration, the present invention adds a divided voltage of the base-emitter voltage of the second transistor to the base-emitter voltage difference of the first and second transistors.
The output voltage can be approximately mV, and
By adding the positive temperature coefficient of the base-emitter voltage difference of the two transistors to the negative temperature coefficient of the divided voltage of the base-emitter voltage of the second transistor 2, the output voltage is set to a predetermined value. Since the temperature coefficient can be obtained, a reference voltage circuit that can operate even with a power supply voltage of 1V can be realized.
Further, since the collector potential of the second transistor is clamped by the emitter-base voltage of the third transistor, there is little change in the collector potential of the second transistor regardless of fluctuations in the power supply voltage. The transistor is less susceptible to the Early effect, and the output voltage has good power supply voltage characteristics. Furthermore, the base-emitter voltage difference of the fourth and fifth transistors operating at different current densities and their Since the current corresponding to the reference current determined by the fourth resistor to which the voltage is applied flows, the output voltage value and the temperature coefficient can be independently set with a certain degree of freedom.

Embodiment A reference voltage circuit according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a wiring diagram of a reference voltage circuit in one embodiment of the present invention. In Figure 1,
The base of transistor 11 is connected to the collector thereof, and also to the collector of transistor 12. The emitter of the transistor 12 is connected to one feed line 15 via a resistor 13. Further, the emitter of the transistor 11 is connected to the other power supply line 16. here,
Reference numeral 14 constitutes a power supply means for supplying current to the transistor 11. transistor 17
Its base is connected to the base-collector connection point of the transistor 11, its emitter is connected to the feed line 16 via a resistor 21, its collector is connected to the collector of the transistor 18, and the emitter of the transistor 24. has been done. The base of the transistor 18 is connected to the base of the transistor 12, and the emitter of the transistor 18 is connected to the power supply line 15 via a resistor 19. Here, 20 constitutes a power supply means for supplying current to the transistor 17. Further, the base of the transistor 24 is connected to the power supply line 16, and the collector thereof is grounded. A series circuit of a resistor 23 and a resistor 22 is connected between the base and emitter of the transistor 17,
An output line 2 is connected to the voltage dividing point between the resistor 23 and the resistor 22.
5 is connected.

In addition, a transistor 26 whose emitter is grounded
The base of is connected to the collector of transistor 37 and to the bases of transistors 29 and 35, respectively. The collector of the transistor 26 is connected to the base of the transistor 29 via a resistor 27, and is also connected to the base of a transistor 28 whose collector is grounded. The emitter of the transistor 28 is connected to the base of the transistor 29. The emitter and collector of the transistor 29 are commonly connected to the transistor 31, the emitter common connection point is grounded via a resistor 30, and the collector common connection point is connected to the collector-base connection point of the transistor 39. The collector-base connection point of the transistor 39 is connected to the transistors 12, 18 and 3.
7, the emitter of the transistor 37 is connected to the power supply line 15 through the resistor 38, and the emitter of the transistor 39 is connected to the power supply line 15 through the resistor 40.
The transistors 12, 18, 37 and 39 constitute a current mirror circuit based on the current flowing through the transistor 39. The base of the transistor 31 is connected to the power supply line 15 via a resistor 32, and the emitter is connected to the collector of a transistor 33 whose emitter is grounded. The base of the transistor 33 is grounded via a resistor 34, and the emitter is connected to the collector of a transistor 41 connected to the power supply line 15. The base of the transistor 41 is connected to the base-collector connection point of a transistor 42 whose emitter is connected to the feed line 15. The collector of the transistor 35 is connected to the base-collector connection point of the transistor 42, and its emitter is grounded via a resistor 36.

The operation of the reference voltage circuit of this embodiment configured as described above will be described below.

First, since transistors 12 and 18 constitute a current mirror circuit with transistor 39, a current corresponding to the current flowing through transistor 39 flows through transistors 12 and 18. Assuming that the emitter area of the transistor 17 is larger than that of the transistor 11 and the emitter current density of the transistor 17 is smaller than that of the transistor 11, the base-emitter voltage difference ΔV _BE of the transistors 11 and 17 is larger than that of the resistor 21. It is applied as the terminal voltage of . Further, a voltage dividing circuit consisting of a resistor 23 and a resistor 22 is connected between the base and emitter of the transistor 17. Therefore, the output voltage V _REF is expressed as follows.

V _REF = R ₂₂ / R ₂₂ + R ₂₃ · V _BE17 + ΔV _BE ... (4) Here, R ₂₂ and R ₂₃ are the resistance 2, respectively.
2 and the resistance value of the resistor 23, V _BE17 is the base-emitter voltage of the transistor 17. Further, if q is the electronic charge, k is the Boltzmann constant, T is the absolute temperature, and J ₁₁ and J ₁₇ are the emitter current densities of the transistors 11 and 17, respectively, then
Equation (4) can be rewritten as the following equation.

V _REF =R ₂₂ /R ₂₂ +R ₂₃・V _BE17 +kT/qlnJ ₁₁ /J ₁₇ ……
(5) Now, V _BE17 = 0.68V, R ₂₂ = 2KΩ, R ₂₃ =
Assuming 13KΩ, J ₁₁ /J ₁₇ = 10, T = 293〓 (20℃), from equation (5), V _REF = 2/2 + 13 x 0.68 + 1380 x 10 ^-23
×293/1602×10 ^-19 ×ln10=0.149(V).

Now, the function of the transistor 24 will be explained here. The emitter of the transistor 24 is connected to the collector of the transistor 17, and the base thereof is connected to the power supply line 16, so that the collector potential of the transistor 17 is clamped to the emitter-base voltage of the transistor 24. Therefore, even if the power supply voltage Vcc of the feed line 15 increases, the collector potential of the transistor 17 hardly changes. In general, even under conditions where the base current is constant in the active region of a transistor, when the voltage applied between the collector and emitter increases, the collector current increases slightly, which is the so-called Early effect, and this type of reference voltage circuit This is the cause of deterioration of power supply voltage characteristics. However, in this embodiment, the collector voltage of the transistor 17 is fixed to approximately the same voltage as the diode-connected forward voltage of the transistor 11 due to the action of the transistor 24, so the transistors 11 and 17 are connected to the power source. The reference voltage circuit of this embodiment exhibits good power supply voltage characteristics because it operates in a balanced operating state regardless of the voltage or ambient temperature, and the transistor 17 is not easily affected by the Early effect.

Now, this example will be explained in more detail using actually measured data. Now transistor 1
Assuming that the current flowing through resistors 13 and 18 is 100 μA, and the resistance value of resistors 13 and 19 is 500Ω, the resistor 13
and 19 is 0.05V, reducing the saturation voltage of transistors 12 and 18 to about 0.2V
If the collector voltage of transistor 11 and transistor 17 is about 0.65V, a stabilized output voltage can be obtained if the power supply voltage is about 0.9V or more. FIG. 2 is an actual measurement characteristic diagram, showing that the output voltage V _REF was sufficiently stabilized at a power supply voltage Vcc of 1V, and almost no fluctuation was observed with respect to the power supply voltage Vcc, and good actual measurement results were obtained.

Further, the fluctuation of the output voltage V _REF based on the change in the ambient temperature T is expressed by the following equation from equation (5).

ΔV _REF /ΔT=R ₂₂ /R ₂₂ +R ₂₃・ΔV _BE17 /ΔT+k/q
lnJ ₁₁ /J ₁₇ ...(6) Therefore, if the positive temperature coefficient of the second term on the right side of equation (6) is offset by the negative temperature coefficient of the first term on the right side, the temperature compensated output voltage V _REF is obtained. Furthermore, a predetermined temperature coefficient can be provided by adjusting the partial pressure ratio R ₂₂ /R ₂₂ +R ₂₃ in the first term on the right side or the current density ratio in the second term on the right side.

Furthermore, in this embodiment, the temperature coefficient of the constant current flowing through the transistors 12 and 18 for supplying current to the transistors 11 and 17 can be set without being restricted by the value of the output voltage V _REF . _REF and its temperature coefficient ΔV _REF /ΔT can be set independently with a certain degree of freedom.

Next, reference current generating means, which serves as a reference for the current flowing through the transistors 12 and 18, will be explained. Transistor 29 operates with a smaller emitter current density than transistor 26, and the base-emitter voltage difference of transistors 26 and 29 is applied as the terminal voltage of resistor 30. Therefore, said transistors 26 and 2
9 emitter current densities as J ₂₆ and J ₂₉ , respectively.
Assuming that the resistance value of the resistor 30 is R ₃₀ and the current flowing therein is I ₃₀ , the following equation holds true.

I ₃₀ = 1/R ₃₀・kT/qlnJ ₂₆ /J ₂₉ ...(7) The current determined by the above equation (7) is
9 and serves as a reference current for the currents flowing through the transistors 12 and 18. From equation (7), the temperature coefficient of the reference current is ΔI ₃₀ /ΔT=1/R ₃₀・k/q・lnJ ₂₆ /
_J29 (1-1/ _R30・_ΔR30 /ΔT・T)...(8) It is expressed as follows. Therefore, by adjusting the value of the resistor 30 or the emitter area of the transistors 26 and 29, the temperature coefficient of the reference current can be arbitrarily set. That is, the constant currents flowing through the transistors 12 and 18 can have an arbitrary temperature coefficient, thereby making it possible to adjust the temperature coefficient of the output voltage V _REF .

FIG. 3 shows the reference voltage circuit in the embodiment of the present invention shown in FIG. 1 applied to the reference voltage generation source of a speed control device for a bridge detection type DC motor. explain. In FIG. 3, components similar to those of the embodiment of the present invention shown in FIG. 1 are designated by the same figure numbers. In the figure, 43 is a reference voltage circuit in the embodiment of the present invention. 50 is a controlled DC motor, and the equivalent internal resistance of this DC motor 50, a resistor 51, a resistor 52, and a resistor 53 constitute a bridge circuit 59 having each side as each side. A voltage follower 56 is connected to the output line 25 of the reference voltage circuit.
The output terminal of is connected to the power supply line 16 and one detection terminal a of the bridge circuit 59 through a series circuit of a resistor 54 and a resistor 55. The resistor 5
4 and the resistor 55 is connected to one input terminal of a differential amplifier 57, and the other detection terminal b of the bridge circuit 59 is connected to the other input terminal of the differential amplifier 57. The differential amplifier 57
The output terminal of is connected to the base of a power supply control transistor 58 whose emitter-collector path is connected between the power supply and the power supply terminal d of the bridge circuit 59.

The operation of the embodiment of the present invention configured as described above will be described below.

Now, if the equivalent internal resistance of the DC motor 50 is Ra, and the resistance values of the resistor 51, 52, and 53 are _R51 , _R52 , and _R53 , respectively, then the bridge equilibrium condition is _R51・_R52 =Ra・_R53 ...When (9) holds true, the voltage between the detection terminals a and b of the bridge circuit 59 depends only on the rotation speed,
It is not related to load torque, that is, armature current Ia. Therefore, this voltage and the reference voltage are compared in a differential amplifier 57, and the difference voltage is amplified and the power supply control transistor 58 inserted between the power supply and the bridge circuit 59 is controlled to control the DC motor 50. When the rotational speed of the bridge circuit 59 increases, the bridge circuit 59
The rotational speed can be kept constant by decreasing the current I supplied to the motor and increasing the current I when the rotational speed decreases.

Now, since the equivalent internal resistance of the DC motor 50 and the temperature coefficient of the resistor 51 are equal, and the temperature coefficients of the resistors 52 and 53 are equal, the equilibrium condition of the bridge, that is, equation (9), is maintained regardless of the ambient temperature. It is assumed that Further, assuming that the current Ir flowing through the feed line 16 and flowing into one detection terminal a of the bridge circuit 59 is sufficiently small compared to the armature current Ia and can be ignored, the rotational speed N is expressed by the following equation.

N=V _REF /Ka・R ₅₂ +R ₅₃ /R ₅₃・R ₅₅ /R ₅₄ +R ₅₅ ...
(10) Here, R ₅₄ and R ₅₅ are the resistance values of the resistor 54 and the resistor 55, and it is assumed that they are composed of resistance elements having the same temperature coefficient. Further, Ka is the power generation constant of the DC motor 50, and its temperature coefficient is approximately -0.04%/°C when a rare earth magnet is used for the field, and approximately -0.18%/°C when a barium ferrite magnet is used. ℃, so if the rotation speed is to be controlled to be constant regardless of the ambient temperature, it is necessary to set the temperature coefficient of the reference voltage V _REF to match the temperature coefficient of the power generation constant Ka of the DC motor.

The speed control device for the DC motor shown in Figure 3 is
By applying the reference voltage circuit in the embodiment of the present invention as a generation source of the reference voltage that serves as the speed reference, it is possible to operate even when the power supply voltage is 1V, and
The variation in rotational speed with respect to variation in power supply voltage is small, and since the voltage value of the reference voltage and its temperature coefficient can be set independently, it can be applied to various DC motors with different types of field magnets.

Effects of the Invention As described above, the present invention includes a first transistor whose base and collector are connected, a second transistor that operates with a smaller emitter current than the first transistor, and the first and second transistors. a third transistor for clamping the collector potential of the second transistor, and between the base and emitter of the first and second transistors; Since the output voltage is configured to be the sum of the voltage difference and the divided voltage of the base-emitter voltage of the second transistor, it operates stably even when the power supply voltage is as low as 1V. Therefore, it is possible to realize a reference voltage circuit in which the output voltage varies extremely little with respect to variations in the power supply voltage.

The device further includes a fourth transistor, a fifth transistor that operates at an emitter current density different from that of the fourth transistor, and a resistor to which a base-emitter voltage difference of the fourth and fifth transistors is applied. By configuring the first and second power supply means to supply a current corresponding to the reference current flowing through the resistor, the output voltage value and temperature coefficient can be independently set with a certain degree of freedom. Effects can be obtained. Furthermore, by applying the reference voltage circuit in the embodiment of the present invention to the reference voltage source of a speed control device for a bridge detection type DC motor, it can operate even with a power supply voltage of 1V, resulting in power savings and a longer battery life. Not only useful, but also against fluctuations in power supply voltage.
An excellent effect can be obtained in that it is possible to realize a device that is less sensitive to changes in rotational speed than changes in ambient temperature.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of a reference voltage circuit in an embodiment of the present invention, Fig. 2 is an actual measurement characteristic diagram of the embodiment of the present invention shown in Fig. 1, and Fig. 3 is a reference voltage circuit diagram in an embodiment of the present invention. A circuit connection diagram when the voltage circuit is applied to a reference voltage generation source of a bridge detection type DC motor speed control device. FIG. 4 is a connection diagram of a conventional reference voltage circuit. DESCRIPTION OF SYMBOLS 11... First transistor, 14... First power feeding means, 17... Second transistor, 20...
...Second power supply means, 21...First resistor, 22...
...Second resistor, 23...Third resistor, 24...Third transistor, 26...Fourth transistor, 29...Fifth transistor, 30...Fourth transistor
resistance, 50...DC motor, 59...bridge circuit.

Claims (1)

[Claims] 1. A first base and a collector connected to each other and to one power supply line via a first power supply means, and an emitter connected to the other power supply line.
a transistor whose base is connected to the base of the first transistor, whose collector is connected to the one feed line via a second feed means, and whose emitter is connected to the other feed line via a first resistor. a second transistor connected to the transistor and driven with an emitter current density smaller than that of the first transistor; and a collector is grounded and the emitter is connected to the collector of the second transistor and the second power supply means. a third transistor whose base is connected to the other feed line; and a third transistor whose one terminal is co-connected to the connection point between the emitter of the second transistor and the first resistor. One terminal connects the other terminal of the second resistor to the second resistor.
means for dividing the base-emitter voltage of the second transistor by the second and third resistors by connecting the second resistor to the other terminal of the third resistor connected to the base of the transistor; the base-emitter voltage difference of the first and second transistors occurring across the first resistor; and the second voltage difference occurring across the second resistor.
A reference voltage circuit that outputs a voltage added to a divided voltage of the base-emitter voltage of the transistor between the voltage dividing point of the second and third resistors and the other power supply line. 2 The base and collector are connected to each other and to one feed line via the first feed means, and the emitter is connected to the other feed line.
a transistor whose base is connected to the base of the first transistor, whose collector is connected to the one feed line via a second feed means, and whose emitter is connected to the other feed line via a first resistor. a second transistor connected to the transistor and driven with an emitter current density smaller than that of the first transistor; and a collector is grounded and the emitter is connected to the collector of the second transistor and the second power supply means. a third transistor whose base is connected to the other feed line; and a third transistor whose one terminal is co-connected to the connection point between the emitter of the second transistor and the first resistor. One terminal connects the other terminal of the second resistor to the second resistor.
means for dividing the base-emitter voltage of the second transistor by the second and third resistors by connecting to the other terminal of a third resistor connected to the base of the transistor; a fourth transistor whose collector is connected to each other through a resistor and whose emitter is grounded; and whose base is connected to the base of the fourth transistor so as to be driven with an emitter current density different from that of the fourth transistor. , a fifth transistor whose collector is connected to the first and second power supply means; one terminal is connected to the emitter of the fifth transistor, the other terminal is grounded, and the fourth
and a fourth resistor to which a voltage difference between the base and emitter of the fifth transistor is applied, and a current corresponding to the reference current flowing through the fourth resistor is supplied from the first and second power supply means. By this, the base-emitter voltage difference of the first and second transistors occurring across the first resistor and the base-emitter voltage difference of the second transistor occurring across the second resistor. A reference voltage circuit that outputs a voltage added to a divided voltage between a voltage dividing point of the second and third resistors and the other power supply line. 3 Compare a voltage proportional to the rotational speed of the DC motor obtained from the detection end of the bridge circuit configured with the DC motor as one side with a reference voltage, and amplify the difference voltage and feed it back to the power supply end of the bridge circuit. The source of the reference voltage in the device for controlling the speed of the DC motor by , the first one whose emitter is connected to the other feed line
a transistor whose base is connected to the base of the first transistor, whose collector is connected to the one feed line via a second feed means, and whose emitter is connected to the other feed line via a first resistor. a second transistor connected to the electric transistor and driven with an emitter current density smaller than that of the first electric transistor; and a collector is grounded and the emitter connects the collector of the second transistor to the second power supply means a third transistor whose base is connected to the other feed line; and a third transistor whose one terminal is co-connected to the connection point between the emitter of the second transistor and the first resistor. One terminal connects the other terminal of the second resistor to the second resistor.
means for dividing the base-emitter voltage of the second transistor by the second and third resistors by connecting the second resistor to the other terminal of the third resistor connected to the base of the transistor; the base-emitter voltage difference of the first and second transistors occurring across the first resistor; and the second voltage difference occurring across the second resistor.
A reference voltage circuit that outputs a voltage added to a divided voltage of the base-emitter voltage of the transistor between the voltage dividing point of the second and third resistors and the other power supply line.