JP2000311020A - Voltage generation circuit and current monitoring circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly precisely generate a primary function voltage of a power source voltage by a simple circuit structure by grounding a corrector of a third transistor and connecting an emitter to a power source line by way of a serial circuit consisting of a first and second resistors. SOLUTION: In a primary function voltage generation circuit 3, a corrector of a transistor Q1 is connected to a power source line 6, the emitter is connected to a corrector of an NPN transistor Q2 and is connected to a base of a PNP transistor Q3. A base of the transistor Q2 is connected to a corrector of a transistor Q15 and an emitter is grounded. A corrector of the transistor Q3 is grounded and an emitter is connected to a power source line by way of the serial circuit consisting of resistors R1 and R2. A connection point of the resistors R1 and R2 is connected to a base of an NPN transistor Q42a of a buffer circuit 4 by way of a resistor R42a. Thus, it is possible to obtain a primary function voltage V0 of a power source voltage VB outputted from a power source part 20 by a simple electronic circuit without using an operation amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage generating circuit for generating a linear function voltage of a power supply voltage output from a power supply unit, and a current monitoring circuit including the voltage generating circuit.

[0002]

2. Description of the Related Art FETs, IGBTs,
The use of such semiconductor devices is increasing.
Advantages of using semiconductor devices include (1) high reliability because there is no mechanical contact such as a relay, (2) no clicking noise or noise at the time of contact, and (3) power control utilizing high-speed switching. Possible (4) It can be downsized compared to relays and switches. Recently, the self-protection function detects the current level flowing in the semiconductor device itself and the temperature rise caused by the current, and shuts off the current circuit before the device is destroyed by the overcurrent to protect itself. An integrated circuit having the following has been put to practical use.

However, the conventional integrated circuit having a self-protection function interrupts a current circuit when there is a risk of destruction of the semiconductor device itself. Anything that prevents deterioration has not been put to practical use.

[0004] The reason is that when the element itself is a protection target, the judgment level for preventing destruction of the element is constant irrespective of the fluctuation of the power supply voltage. The determination level for determining whether or not there is a need to vary according to the variation of the power supply voltage.

[0005] For example, as a power source for an automobile, generally a rated DC is used.
A 12 (V) lead storage battery (hereinafter referred to as "battery") is used, but in an actual use environment, the output voltage of the battery fluctuates in a range of about 6 to 16 (V). The load current also changes according to the voltage. Therefore, when the battery voltage fluctuates in this way, even if the load current is at the same level, it may be necessary to determine the overcurrent in consideration of the battery voltage level. It may be necessary to determine that

Namely, for example, in FIG. 4, when the detected load current with a relatively small current I _A, when the battery voltage V _B is 6 (V) and low, proper current corresponding to the voltage since the smaller, the current I _a is within the normal range, i.e. it should be determined that the abnormality is not occurring in the circuit, if the battery voltage V _B is high and 16 (V) is to the voltage takes up more appropriate current corresponding, current I _a range smaller than the normal current, i.e. it should be determined that abnormality has occurred in the circuit. Conversely, when the load current is relatively large current I _B, the battery voltage V _B
If There 6 (V) and low, due to the large current I _B than the appropriate current according to the voltage, but it should be determined to be overcurrent, the battery voltage V _B is the 16 (V) If it is, it should be determined that it is within the normal current range.

As described above, the determination level serving as a threshold for determining whether or not the load current is within the range of the normal current needs to be changed according to the battery voltage, that is, the power supply voltage. Here, when the determination level is formed by a voltage signal, for example, a reference voltage of a certain level is generated based on the power supply voltage, and the difference between the reference voltage and the power supply voltage is used to determine the primary level of the power supply voltage. It is conceivable to generate a linear function voltage which is a voltage corresponding to a function.

The reference voltage is preferably independent of the ambient temperature because the ambient temperature fluctuates greatly in the range of −40 ° C. to 125 ° C. in a vehicle environment. 2. Description of the Related Art A band gap reference circuit is conventionally known as a reference voltage generation circuit generated based on a power supply voltage. However, the bandgap reference circuit, in principle, since the reference voltage V _R to be generated is a problem that is fixed to 1.2 (V), is necessary to amplify the reference voltage V _R the voltage amplifying circuit occurs.

[0009] In this manner amplifies the reference voltage V _R, furthermore,
Conventionally, an operational amplifier O as shown in FIG. 5 has been used as a circuit for obtaining a linear function voltage of a power supply voltage using the amplification reference voltage.
A circuit using P1 and OP2 is known. 5, operational amplifier OP1 functions as a voltage amplifier for outputting an amplified reference voltage V _P by amplifying the reference voltage V _{R,
V P = (1 + R 92} / R 91) is a · V _R. However, _R92 is a resistor R9
2 of the resistance value, R ₉₁ is the resistance of resistor R91.

Further, the operational amplifier OP2 is intended to function as a voltage follower, the input impedance is extremely high, since the output impedance is very low, the power supply voltage V _B
The constant voltage _VP is output without being affected by the inflow current from the inverter. Resistor and the output voltage V _P and the power supply voltage V _B R93, R
By dividing by a series circuit consisting of 94, the resistance R9
3, as the output voltage V _OUT from the connection point of _{R94, V OUT = V B ·} R 93 / (R 93 + R 94) + V P · R 94 / (R 93 + R 94) is output, whereby the power supply voltage V _B Linear function voltage V
_OUT is obtained.

[0011]

However, in the conventional circuit using the operational amplifier shown in FIG. 5, if the power supply voltage of the operational amplifier fluctuates, the amplification factor consequently fluctuates and the amplification reference voltage fluctuates. As a result, a highly accurate linear function voltage cannot be obtained. In addition, since the circuit scale becomes large when an operational amplifier is used, it is desired to configure a circuit with a small number of elements without using an operational amplifier.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a voltage generating circuit capable of accurately generating a linear function voltage of a power supply voltage with a simple circuit configuration.

Another object of the present invention is to provide a current monitoring circuit capable of suitably monitoring a current level using the above-mentioned voltage generating circuit.

[0014]

According to the present invention, there is provided a reference voltage generating circuit for generating a reference voltage of a predetermined level based on a power supply voltage output from a power supply section to a power supply line, a plurality of transistors and a plurality of resistors. A voltage amplifying circuit that outputs an amplified reference voltage obtained by amplifying the reference voltage to an output unit; and one of the power supply voltages based on the amplified reference voltage and the power supply voltage.
1 for generating a linear function voltage that is a voltage corresponding to a linear function
A linear function voltage generating circuit, wherein the reference voltage generating circuit includes a band gap reference circuit, and the linear function voltage generating circuit includes a first transistor including an NPN transistor and a first transistor including an NPN transistor. A third transistor comprising a two-transistor and a PNP transistor, and having a base-emitter voltage substantially equal to the first transistor; a first resistor; and a second resistor. The first transistor is connected to the power supply line, and the first transistor is connected to the power supply line;
The emitter of the transistor is connected to the collector of the second transistor and the base of the third transistor, a predetermined bias voltage is applied to the base of the second transistor, and the emitter of the second transistor is grounded. , The collector of the third transistor is grounded, and the emitter of the third transistor is connected to the power supply line through a series circuit including the first resistor and the second resistor. The linear function voltage is generated at the connection point of the two resistors.

According to this configuration, the reference voltage generation circuit generates a reference voltage of a predetermined level from the power supply voltage output from the power supply unit to the power supply line, and the voltage amplification circuit
An amplified reference voltage obtained by amplifying the reference voltage is output to the output unit. Here, since the reference voltage generation circuit is configured by a band gap reference circuit, it is possible to obtain a reference voltage with little dependency on power supply voltage fluctuation and temperature fluctuation. Further, since the reference voltage is amplified by the voltage amplifier circuit, it is possible to use a bandgap reference circuit that can generate only a low-level reference voltage in principle.

In the linear function voltage generating circuit, since the predetermined bias voltage is applied to the base of the second transistor, the second transistor functions as a constant current source,
Thus, the base potential of the third transistor becomes a potential lower than the base potential of the first transistor by the voltage between the base and the emitter of the first transistor. Also, the third
The emitter potential of the transistor is higher than the base potential of the third transistor by the base-emitter voltage of the third transistor.

Therefore, if the base-emitter voltages of the first transistor and the third transistor are equal to each other, the emitter potential of the third transistor becomes equal to the base potential of the first transistor. On the other hand, since the base of the first transistor is connected to the output of the voltage amplifier circuit, the emitter potential of the third transistor becomes equal to the amplification reference voltage.

Further, since the series circuit composed of the first resistor and the second resistor is connected between the emitter of the third transistor and the power supply line, the difference between the amplification reference voltage and the power supply voltage is equal to the first resistance and the power supply voltage. The voltage is divided by the second resistor, and a linear function voltage of the power supply voltage is generated at a connection point between the first resistor and the second resistor. This makes it possible to generate a linear function voltage of the power supply voltage with a simple circuit configuration.

The first, second, and third transistors are:
Functioning as a voltage follower, the emitter potential of the third transistor is not affected by current flowing from the power supply line to the emitter of the third transistor via the second resistor and the first resistor. Thus, the amplification reference voltage generated at the emitter of the third transistor is accurately maintained at a constant level.

Further, the reference voltage generating circuit, the voltage amplifying circuit and the linear function voltage generating circuit may be constituted by an integrated circuit formed on a semiconductor wafer. The accuracy of the linear function voltage depends on the resistance ratio between the first resistor and the second resistor and also depends on the equal degree of the base-emitter voltage of the first transistor and the third transistor. Is constituted by an integrated circuit formed on a semiconductor wafer, and therefore, the one in which the relative characteristics of the resistor and the transistor accurately match can be easily obtained. That is, it is possible to easily make the resistance ratio and the base-emitter voltage equal with high accuracy. As a result, a linear function voltage of the power supply voltage can be obtained with high accuracy.

The power supply unit may be a parallel circuit of a vehicle-mounted battery and an alternator, or may be a vehicle-mounted battery alone.

Further, the present invention provides the above-mentioned voltage generating circuit, and whether or not the level of the load current flowing to the load is an overcurrent based on a judgment level according to the linear function voltage outputted from the voltage generating circuit. And an overcurrent judging means for judging.

According to this configuration, it is determined whether or not the level of the load current is an overcurrent based on the determination level corresponding to the linear function voltage output from the voltage generation circuit, so that the power supply unit determines When the output power supply voltage fluctuates, the determination level also fluctuates, so that it is appropriately determined whether or not an overcurrent occurs.

[0024]

FIG. 1 is a circuit diagram of an embodiment of a voltage generating circuit according to the present invention, and FIG. 2 is a circuit diagram showing a configuration of a reference voltage generating circuit 5 of FIG.

As shown in FIG. 1, the voltage generation circuit 10 includes a current bias circuit 1, a voltage amplification circuit 2, a linear function voltage generation circuit 3, a buffer circuit 4, and a reference voltage generation circuit 5, it is intended to generate a linear function voltage VO of the power supply voltage V _B output from the power supply unit 20 to the power supply line 6 to the output terminal 11.

In the current bias circuit 1, the collector of the NPN transistor Q11a is connected to the power supply line 6, the base is connected to the base of the NPN transistor Q11b, the emitter is connected to the base of the NPN transistor Q12, and via the resistor R11. Grounded. The collector of the transistor Q11b is connected to the base while being connected to the power supply line 6 via the resistor R12, and the emitter is connected to the collector of the transistor Q12 and the base of the NPN transistor Q13. The emitter of the transistor Q12 is grounded.

The emitter of PNP transistor Q14a is connected to power supply line 6, the base is connected to the collector, and the base of PNP transistor Q14b and the collector of transistor Q13. The emitter of the transistor Q13 is grounded via the resistor R13. The emitter of transistor Q14b is connected to power supply line 6, and the collector is NP via resistor R14.
It is connected to the collector and base of N transistor Q15. The emitter of the transistor Q15 is grounded.

In the voltage amplifier circuit 2, the emitter of the PNP transistor Q21a is connected to the power supply line 6 via the resistor R21a, the base is connected to the collector, the base is connected to the base of the PNP transistor Q21b, and the NPN transistor Q22a Connected to collector. The base of the transistor Q22a is a resistor R
The emitter is connected to the output terminal 51 of the reference voltage generating circuit via 22a, the emitter is connected to the emitter of the NPN transistor Q22b, and is grounded via the resistor R23.

The emitter of the transistor Q21b is a resistor R
21b, the collector is connected to the power supply line 6, and the collector is connected to the collector of the transistor Q22b.
It is connected to the base of NPN transistor Q23.
The collector of the transistor Q22a and the transistor Q22
b, a capacitor C2 for preventing oscillation.
1 is connected.

The base of the transistor Q22b is connected to a resistor R2.
2b, and the other end of the resistor R22b is connected to a resistor R22.
24, and is connected to the emitter (output unit) of the transistor Q23 via a resistor R25. That is, the other end of the resistor R22b is connected to a connection point of the resistors R24 and R25 connected in series. The emitter (output section) of the transistor Q23 is further connected to the base of an NPN transistor (first transistor) Q1 of the linear function voltage generation circuit 3, and the collector of the transistor Q23 is connected to the power supply line 6.

In this voltage amplifying circuit 2, transistors Q21a, Q21b, Q22a, Q22b and a resistor R2
1a, R21b, R22a, R22b, and R23 form a differential amplifier 21, and the transistor Q23 and the resistors R24 and R25 form a resistance amplifier 22. Transistor Q21a and transistor Q2
1b, transistor Q22a and transistor Q22b
Employ elements having the same characteristics. Further, the resistors R21a and R21b and the resistor R22a
Elements each having the same resistance value are adopted as the resistance R22b.

In the linear function voltage generating circuit 3, the collector of the transistor Q1 is connected to the power supply line 6, and the emitter is an NPN transistor (second transistor) Q2.
And the base of a PNP transistor (third transistor) Q3.
The base of transistor Q2 is connected to the collector of transistor Q15, and the emitter is grounded. The collector of the transistor Q3 is grounded, and the emitter is a resistor (first
The power supply line 6 is connected to a power supply line 6 via a series circuit including a resistance R1 and a resistance (second resistance) R2. Resistance R1,
The connection point of R2 is connected to the buffer circuit 4 via the resistor R42a.
Is connected to the base of the NPN transistor Q42a.

In the buffer circuit 4, the emitter of the PNP transistor Q41a is connected to the power supply line 6 via the resistor R41a, the base is connected to the collector, and the base of the PNP transistor Q41b is connected to the collector of the transistor Q42a. It is connected. The emitter of transistor Q42a is connected to the emitter of NPN transistor Q42b.
It is connected to the collector of PN transistor Q43.
The emitter of transistor Q41b is connected to power supply line 6 via resistor R41b, and the collector is connected to the collector of transistor Q42b and to the base of NPN transistor Q44. A capacitor C41 for preventing oscillation is connected between the collector of the transistor Q42a and the collector of the transistor Q42b. The base of the transistor Q42b is a resistor R42.
The other end of the resistor R42b is connected to the emitter of the transistor Q44, the collector of the NPN transistor Q45, and the output terminal 11. The bases of the transistors Q43 and Q45 are both connected to the collector of the transistor Q15, and the emitters are both grounded. The collector of the transistor Q44 is connected to the power supply line 6.

In FIG. 2, the reference voltage generation circuit 5
NP transistor Q51, NPN transistor Q52 ~
A known bandgap reference circuit is provided with Q55 and a diode D51, and the like.
1 and outputs a predetermined level of reference voltage V _R.

The bandgap reference circuit uses the energy bandgap voltage of the semiconductor (generally silicon) as a reference voltage because the energy bandgap voltage is determined by the material. The energy bandgap voltage of silicon is 1.205V. Yes, this by, V _R = 1.205V
It has become.

Transistor Q51 of reference voltage generating circuit 5
Is connected to the power supply unit 20 and the anode of the diode D51 via a resistor, and the base is connected to the diode D5.
1 and grounded via a resistor, and the collector is connected to the base of transistor Q52 and the collector of transistor Q55. The transistor Q51 forms a constant current source by a bias voltage circuit including a series circuit of a diode D51 and a resistor.

The collector of the transistor Q52 is connected to the power supply 2
0 and the emitter is connected to the output terminal 51. The collector of the transistor Q53 is connected to the base, connected to the output terminal 51 via a resistor, the base is connected to the base of the transistor Q54, and the emitter is grounded. The collector of the transistor Q54 is connected to the base of the transistor Q55, connected to the output terminal 51 via a resistor, and the emitter is grounded via a resistor. The emitter of transistor Q55 is grounded.

Next, the operation of the voltage generation circuit 10 configured as described above will be described with reference to FIG.

In the current bias circuit 1, the power supply voltage V _B
A reference current I ₀ that does not depend on the level of
Currents I ₁ , I ₂ , and I ₃ at the same level also flow through the collectors of transistors Q 2, Q 43, and Q 45 that form a current mirror circuit together with transistor Q 15. That is, I ₀ =
I ₁ = I ₂ = I ₃ .

On the other hand, in the differential amplifying section 21 of the voltage amplifying circuit 2, the resistances of the resistors R21a and R21b are equal, and the transistors Q21a and Q21b form a current mirror circuit. the relationship between the emitter current I ₂₂ of ₂₁ and the transistor Q21b will I ₂₁ = I _22. Further, the collector current I ₂₁ is determined by the emitter current I _{23 of the} transistor Q22a determined by the base potential V ₂₁ of the transistor Q22a.
Is determined, and I ₂₃ ≒ I ₂₁ .

Here, as shown in FIG.
The base potential of Q22b is V_{twenty two}, Connection of resistors R24 and R25
Set the potential at the connection point to V_{twenty three}, The emitter voltage of the transistor Q22b
Flow I _{twenty four}From the collector of the transistor Q21b.
The current flowing through the base of the_{twenty five}And

At this time, if V ₂₁ > V ₂₂ , then I ₂₃ > I ₂₄ , so that the current I ₂₅ increases. Therefore, transistor Q
Since the emitter current of 23 increases, the voltage drop at the resistor R24 increases the potential V ₂₃ rises, whereby the potential V ₂₂ rises.

On the other hand, when V ₂₁ <V ₂₂ , the transistor Q
The emitter current I ₂₃ is greater than the current of 22a since the transistor Q22b is going to draw in the collector current, current I
₂₅ is reduced. Therefore, since the emitter current of the transistor Q23 decreases, the voltage drop across the resistor R24 and the potential V ₂₃ is lowered due to the reduced, whereby the potential V ₂₂ is lowered.

By the above operation, the adjustment is always made so that V ₂₁ = V ₂₂ . Here, since the resistance values of the resistors R22a and R22b are equal to each other, V _R = V ₂₃ . Therefore,
The other end of the resistor R22b, i.e. the connecting point of the resistors R24, R25, the voltage V _R of the same level as the output terminal 51 of the reference voltage generating circuit 5 is generated.

Accordingly, the reference voltage V _R as shown in the following equation (1) is applied to the emitter (output section) of the transistor Q23.
Is output as the amplified reference voltage _VA . V _A = V _R · (R ₂₄ + R ₂₅ ) / R ₂₄ (1) where R ₂₄ and R ₂₅ are resistance values of the resistors R ₂₄ and R ₂₅ .

A constant voltage is constantly applied to the base of the transistor Q2.
2, operating as a constant current source for supplying a constant current I _1.
Therefore, the voltage V _A input to the base of the transistor Q1
From the base-emitter voltage V _{BE1 of} the transistor Q1
The voltage (V _A -V _BE1 ) dropped by the amount is applied to the base of the transistor Q3. Therefore, the potential of the emitter of the transistor Q3 is higher than the base potential by the base-emitter voltage.
Since it is higher by V _BE3, it becomes (V _A −V _BE1 + V _BE3 ).

Here, the transistor Q3 whose base-emitter voltage V _{BE3 satisfies} V _BE3 = V _BE1 is employed, so that the emitter potential of the transistor Q3 is the same level as the base of the transistor Q1. Become _A.
This relationship is obtained when the transistors Q1 and Q3 are operating in a linear region where the base-emitter voltage is constant, and is not affected by the absolute value of the transistor amplification factor.

On the other hand, the buffer circuit 4 is for improving the current supply capability from the output terminal 11 to the external circuit, and operates in the same manner as the differential amplifier 21 of the voltage amplifier circuit 2 described above. The output voltage V _O of the resistor R
It becomes equal to the potential of the connection point between R1 and R2.

Therefore, the output voltage V _O is the same as that of the transistor Q3
Of the emitter potential V _A, the power supply line 6 and the power supply voltage V _B,
The value is divided by the resistance (first resistance) R1 and the resistance (second resistance) R2, and is represented by Expression (2). V _O = (V _B −V _A ) · R ₁ / (R ₁ + R ₂ ) + V _A = V _B · R ₁ / (R ₁ + R ₂ ) + V _A · R ₂ / (R ₁ + R ₂ )… (2 Here, R ₁ and R ₂ are resistance values of the resistors R ₁ and R ₂ . According to the equation (2), it is understood that the output voltage V _O depends on the ratio and does not depend on the absolute value unless the resistance values R ₁ and R ₂ are extremely large or small.

By substituting equation (1) into equation (2), Next, as an output voltage V _O, 1 linear function voltage of the power supply voltage V _B can be obtained.

As described above, according to the present embodiment, the linear function voltage V _O of the power supply voltage V _B output from the power supply unit 20 can be obtained by a simple electronic circuit having a transistor and a resistor without using an operational amplifier. Obtainable.

The accuracy of the linear function voltage V _O is determined not by the absolute accuracy of a resistor or a transistor such as a resistance value or a transistor amplification factor but by the relative accuracy between each pair of elements. . That is, as shown in equation (3), the resistance ratio R ₂₄ / R ₂₅ of the resistors R ₂₄ and R ₂₅ and the resistance R
By 1, R2 of the resistance ratio R ₁ / R ₂ with high precision,
And the coefficient of the power supply voltage V _B of the first term of the right side of the equation (3) can be the second term on the right side to those high precision.

As described above, the transistor Q
By making the base-emitter voltages of Q1 and Q3 equal, the base potential of transistor Q1 and
3 can be equalized, whereby the linear function voltage V _O can be made highly accurate.

The power supply section 20 has a rated DC12
(V), but the output voltage is 6 to 16 in actual use environment.
Even when employing a parallel circuit or vehicle battery of the vehicle battery and alternator variation width is large supply voltage that varies in a range of about (V), 1 linear function voltage V of the power supply voltage V _B output from the power supply unit 20 _O can be obtained with high accuracy.

In the above embodiment, the voltage generating circuit 10 shown in FIG. 1 is an integrated circuit (Integrat) in which the resistors and transistors shown in FIGS. 1 and 2 are formed on a semiconductor wafer.
ed Circuit, hereinafter referred to as “IC”. ).

Here, the variation in the characteristics of the elements in the IC will be described. An IC is manufactured by forming a large number of identical circuits on a single wafer cut out of a semiconductor (generally silicon) ingot by a known circuit forming process, and then dicing and molding each circuit (chip). Is done.

Therefore, variations in the characteristics of elements in an IC can be divided into variations occurring between chips within one wafer, variations between wafers, and variations between ingots obtained by cutting wafers.

Variations in the characteristics of elements in an IC are caused by factors such as variations in a circuit forming process, that is, variations in an etching process, variations in an exposure process, variations in the degree of diffusion in an impurity diffusion process, and variations in temperature in each process.

Of these, the steps of etching, exposure, and impurity diffusion, which are the causes of the above-mentioned variations, are performed for each wafer, and the same wafer has the same temperature in each step.
Variations in characteristics are unlikely to occur between chips inside a single wafer. In particular, variations between elements formed close to each other in the same chip can be almost ignored.

Here, in the voltage generation circuit 10 configured by an IC, the relationship between the elements denoted by a and b (for example, the resistors R21a and R21b, the transistor Q
21a and the transistor Q21b) The transistor Q1 and the transistor Q3 in the linear function voltage generating circuit 3
, The resistor R24 and the resistor R2 in the voltage amplifier circuit 2.
5, the resistance in the linear function voltage generation circuit 3 (first
The relationship between the resistor R1 and the resistor (second resistor) R2 corresponds to the relationship between elements formed close to each other on the same chip inside the wafer.

Therefore, the relative variations in the characteristics of the transistor Q1 and the transistor Q3, the resistance R24 and the resistance R2
The relative variation of the resistance value of the resistor 5 and the relative variation of the resistance values of the resistor R1 and the resistor R2 can be set to very low levels.

As a result, the characteristics of the transistors Q1 and Q3 can be accurately matched, and the ratio of the resistance values of the resistors R24 and R25 and the ratio of the resistance values of the resistors R1 and R2 can be accurately set to a constant value. It is possible to easily obtain a high-precision voltage generating circuit 10 with small variation.

On the other hand, if the voltage generation circuit 10 is constituted by discrete resistors and transistors to obtain the same accuracy, it is necessary to select each element to make the characteristics such as the resistance value uniform. This requires time and effort, resulting in reduced manufacturing efficiency.

On the other hand, according to the present embodiment, as described above, the voltage generating circuit 10 can be obtained with high accuracy by obtaining the linear function voltage of the power supply voltage by forming the voltage generating circuit 10 by an IC. Can be easily realized. Further, the voltage generation circuit 10 can be downsized.

The circuit configuration of the bandgap reference circuit constituting the reference voltage generation circuit 5 is not limited to the one shown in FIG. 2 of the above embodiment, and another circuit configuration may be adopted.

FIG. 3 is a block diagram showing an embodiment of a current monitoring circuit according to the present invention, and shows an example in which the present invention is applied to a power supply circuit of an automobile.

In FIG. 3, the power supply unit 20 is composed of a vehicle-mounted battery. The power supply unit 20 is connected to an electric connection box 91. The power supply unit 20 is connected to a starter motor 92 and an alternator 93 via the electric connection box 91. ing. The electric connection box 91 houses a fusible link and a small-capacity fuse, and also houses the voltage generating circuit 10, the overcurrent judging means 94, and the current interrupting section 95. Is electrically connected to

The overcurrent judging means 94 includes the voltage generating circuit 10
Has a function of determining whether or not the level of the load current flowing through the load 96 is an overcurrent based on a determination level corresponding to the level of the linear function voltage V _O output from the controller. The overcurrent judging means 94 has a function as a warning signal outputting means for outputting a warning signal when the overcurrent is judged. The current cutoff unit 95 has a function as a load current cutoff unit that cuts off a current flowing through the load 96 by a warning signal output from the overcurrent determination unit 94.

As described above, according to the present embodiment, whether the level of the load current flowing through the load 96 is an overcurrent based on the determination level corresponding to the level of the linear function voltage V _O output from the voltage generation circuit 10 is determined. since determine whether, since the power supply voltage V _B output from the battery 9 varies also determine the level fluctuates, it is possible to suitably determine whether or not the overcurrent.

By forming the voltage generation circuit 10 by an IC, as described above, a voltage generation circuit capable of obtaining a linear function voltage of the power supply voltage with high accuracy can be easily realized. As a result, a current monitoring circuit that can accurately monitor the load current can be realized.
Further, the voltage generation circuit 10 can be reduced in size, thereby reducing the space occupied in the electric junction box 91,
The size of the electric connection box 91 can be reduced.

[0071]

As described above, according to the present invention,
A reference voltage generation circuit that generates a reference voltage of a predetermined level based on a power supply voltage output to a power supply line from a power supply unit;
A voltage amplifier circuit having a plurality of transistors and a plurality of resistors and outputting an amplified reference voltage obtained by amplifying the reference voltage to an output unit; and a linear function of the power supply voltage based on the amplified reference voltage and the power supply voltage. A first-order function voltage generation circuit that generates a first-order function voltage, the reference voltage generation circuit including a band gap reference circuit, and the first-order function voltage generation circuit including an NP
A first transistor including an N transistor, a second transistor including an NPN transistor, and a third transistor including a PNP transistor and having a base-emitter voltage substantially equal to the first transistor; a first resistor; and a second resistor. Wherein the base of the first transistor is connected to the output of the voltage amplifier circuit, the collector of the first transistor is connected to the power supply line, the emitter of the first transistor is the collector of the second transistor, Connected to the base of the third transistor, a predetermined bias voltage is applied to the base of the second transistor, the emitter of the second transistor is grounded, the collector of the third transistor is grounded, The emitter of the third transistor is connected to the first resistor and It is connected to the power supply line via a series circuit composed of a second resistor, and the linear function voltage is generated at a connection point between the first resistor and the second resistor. A linear function voltage of a power supply voltage can be generated by a circuit configuration.

The reference voltage generating circuit, the voltage amplifying circuit and the linear function voltage generating circuit are constituted by an integrated circuit formed on a semiconductor wafer.
A linear function voltage of the power supply voltage can be obtained with high accuracy because a resistor and a transistor whose relative characteristics match accurately can be easily obtained.

Further, according to the present invention, whether or not the level of the load current flowing through the load is an overcurrent is determined based on the determination level according to the linear function voltage output from the voltage generation circuit. Therefore, when the power supply voltage output from the power supply unit fluctuates, the determination level also fluctuates, so that it is possible to appropriately determine whether or not an overcurrent occurs.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of a voltage generation circuit according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a reference voltage generation circuit of FIG.

FIG. 3 is a block diagram showing one embodiment of a current monitoring circuit according to the present invention.

FIG. 4 is a diagram illustrating a conventional problem.

FIG. 5 is a conventional circuit diagram for obtaining a linear function voltage of a power supply voltage using an amplified reference voltage obtained by amplifying a reference voltage.

[Explanation of symbols]

 Reference Signs List 2 voltage amplifying circuit 3 linear function voltage generating circuit 5 reference voltage generating circuit 10 voltage generating circuit 20 power supply section 94 overcurrent judging means Q1 transistor (first transistor) Q2 transistor (second transistor) Q3 transistor (third transistor) R1 Resistance (first resistance) R2 Resistance (second resistance)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Fumiaki Mizuno 1-7-10 Kikuzumi, Minami-ku, Nagoya-shi, Aichi F-term in Harness Research Institute, Inc. (Reference) 5H420 BB12 CC02 DD02 EA11 EB37 FF04 FF22 LL05 NA23 NB02 NB14 NB24 NC02 NC03 NC26 5J091 AA01 AA58 CA00 CA11 CA92 FA02 HA08 HA19 HA25 HA29 KA00 KA01 KA02 KA03 KA09 KA11 KA12 SA07 TA01 TA02

Claims (4)

[Claims] A reference voltage generating circuit for generating a reference voltage of a predetermined level based on a power supply voltage output from a power supply unit to a power supply line; a plurality of transistors and a plurality of resistors; and amplifying the reference voltage. A voltage amplifying circuit for outputting an amplified reference voltage to an output unit; and a linear function voltage generating circuit for generating a linear function voltage corresponding to a linear function of the power supply voltage from the amplified reference voltage and the power supply voltage. Wherein the reference voltage generation circuit comprises a bandgap reference circuit, and the linear function voltage generation circuit comprises: a first transistor comprising an NPN transistor;
A third transistor composed of an N transistor, a third transistor composed of a PNP transistor, and having a base-emitter voltage substantially equal to the first transistor;
A base of the first transistor is connected to an output of the voltage amplifier circuit, a collector of the first transistor is connected to the power supply line, and an emitter of the first transistor is connected to a power supply line. A collector connected to the collector of the second transistor and a base of the third transistor, a predetermined bias voltage is applied to a base of the second transistor, an emitter of the second transistor is grounded, The collector of the transistor is grounded and the third
The emitter of the transistor is connected to the power supply line via a series circuit including the first resistor and the second resistor, and the linear function voltage is generated at a connection point between the first resistor and the second resistor. A voltage generating circuit characterized in that: 2. The voltage generating circuit according to claim 1, wherein
The reference voltage generation circuit, the voltage amplification circuit, and the 1
A voltage generation circuit, wherein the linear function voltage generation circuit is configured by an integrated circuit formed on a semiconductor wafer. 3. The voltage generating circuit according to claim 1, wherein the power supply unit is configured by a parallel circuit of a vehicle-mounted battery and an alternator or a vehicle-mounted battery. 4. The voltage generating circuit according to claim 1, wherein a level of a load current flowing through the load is an overcurrent according to a determination level according to the linear function voltage output from the voltage generating circuit. A current monitoring circuit, comprising: an overcurrent determining unit that determines whether the current monitoring is performed.