JPH10145208A - Electronic circuit device and voltage level detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly detect low supply voltage so as to make low voltage forbidding operation performed and to reduce current consumption by setting an application circuit to a low-voltage forbidden state, together with a bias circuit corresponding to a detection state of a voltage level detecting circuit. SOLUTION: A voltage level detecting circuit 4 is an autonomous level- detecting circuit, which operates without referring to an external reference voltage Vr generated in a bias circuit 2, and it binary-discriminates lowering of the level of the supply voltage Vcc which is detecting input voltage. A forbid output circuit 5 sets the application circuit 2 to the low-voltage forbidden (cutoff) state, together with the bias circuit 2 corresponding to the detection state of that autonomous voltage level-detecting circuit 4. Thus, if the supply voltage Vcc lowers to smaller than the prescribed level, the application circuit 1 and also the bias circuit 2 can stop operating and automatically set to the cutoff state of current interrupt, regardless of the operating state of the bias circuit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology effective when applied to an electronic circuit device, and more particularly to an electronic circuit device with a low voltage prohibition function for preventing malfunction at a low power supply voltage and reducing current consumption. And for example regulator I
The present invention relates to a technology that is effective when used in an electronic circuit device formed as a semiconductor integrated circuit such as C or power IC.

[0002]

2. Description of the Related Art For example, in a watchdog system, a regulator system, a power IC system, or the like, there is a risk that a device or a system is destroyed due to a malfunction of a circuit due to a drop in power supply voltage. This destruction includes not only physical destruction of the circuit device itself but also software destruction such as destruction of stored data.

In order to avoid such a danger, for example, “Transistor technology (Jan.
Monthly) ”on page 305, when the power supply voltage of an application circuit such as a power circuit or a digital circuit falls below a specified level, the operation of the application circuit is cut off and current cutoff is cut off. It has been practiced to attach a low-voltage prohibition circuit for performing control.

In this low voltage prohibition circuit, the input voltage obtained by dividing the power supply voltage with a resistor is compared with a constant reference voltage generated by a bias circuit, so that the power supply voltage level falls below a specified level. Whether a voltage level below a specified level is detected or not, the operating current of the application circuit that operates by the power supply voltage is cut off, and the operation is forcibly set to the operation prohibited state.

[0005]

However, it has been clarified by the present inventors that the above-described technology has the following problems.

That is, in the above-described electronic circuit device, a bias circuit for generating a constant reference voltage for detecting a decrease in the power supply voltage with a decrease in the power supply voltage includes:
Normal operation may not be possible due to the decrease in the power supply voltage. Therefore, if the detection level of the low power supply voltage is lowered, the bias circuit cannot operate normally before the low power supply voltage is detected, and the operation of the low voltage prohibition circuit itself cannot be realized.

In order to solve the above problem, a bias circuit that can operate even under a low power supply voltage is required, but it is difficult to configure such a bias circuit.

Further, in the above-described electronic circuit device, even if a bias circuit capable of generating a predetermined reference voltage even under a low power supply voltage is obtained, only the application circuit is cut off under the low power supply voltage. Therefore, the bias circuit must continue to operate even in the setting state where the low voltage is prohibited.

Therefore, even in the setting state (cut-off state) where the low voltage is prohibited, a current for operating the bias circuit is required. In low-voltage prohibition, it is necessary to reduce the current consumption as much as possible in order to prevent the power supply voltage from dropping. However, in the above-described device, the current consumption by the bias circuit is allowed for detecting the low power supply voltage. I had to do it.

SUMMARY OF THE INVENTION It is an object of the present invention to be able to reliably detect a low power supply voltage and to inhibit low voltage even when the detection level of the low power supply voltage is low, and to greatly reduce the current consumption when the low voltage is prohibited. It is to provide a technology to reduce the number of times.

The above and other objects and features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, in an electronic circuit device having an application circuit whose operation is guaranteed at a power supply voltage higher than a predetermined level and a bias circuit for generating a predetermined reference voltage from the power supply voltage, reference is made to an external reference voltage. An autonomous type voltage level detecting circuit for discriminating the level drop of the power supply voltage into two levels by an internal threshold voltage independently formed in a circuit, and an application circuit according to a detection state of the voltage level detecting circuit. A prohibition output circuit for setting a low voltage prohibition state is provided together with the bias circuit.

According to the above-described means, it is not necessary to guarantee the operation of the bias circuit under a low power supply voltage, and the operation current of the bias circuit can be cut off when the low voltage is prohibited.

Thus, even when the detection level of the low power supply voltage is low, the low power supply voltage can be reliably detected and the low voltage prohibition can be performed, and the current consumption when the low power supply voltage is prohibited is greatly reduced. Is achieved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides an application circuit (1) whose operation is guaranteed at a power supply voltage (Vcc) of a predetermined level or more, and a predetermined reference based on the power supply voltage (Vcc). Bias circuit for generating voltage (Vr) (2)
And a low-voltage prohibition circuit (3) for performing cut-off control of the application circuit (1) when the power supply voltage (Vcc) becomes lower than a specified level, thereby preventing malfunction at low power supply voltage and reducing current consumption. And an internal threshold voltage (Vp) that is independently formed in the circuit without referring to the reference voltage (Vr) as the low-voltage prohibition circuit (3). An autonomous voltage level detection circuit (4) for discriminating the level drop of the power supply voltage into two values, and the application circuit (1) is connected to the bias circuit (2) according to the detection state of the voltage level detection circuit (4). ) Together with a prohibition output circuit (5) for setting a low-voltage prohibition state, whereby it is not necessary to guarantee the operation of the bias circuit under a low power supply voltage. Effect that can be the operating current of the road (2) is cut off is obtained.

According to a second aspect of the present invention, in addition to the first aspect, a time constant circuit (6) for delaying the setting of the low voltage inhibition for the bias circuit (2) from that of the application circuit (1).
This allows the cutoff control of the application circuit (1) to be performed under the operating conditions of the bias circuit (2).
An effect is obtained that the operation can be performed smoothly without causing a malfunction.

According to a third aspect of the present invention, in addition to any one of the first and second aspects, the setting of the low-voltage prohibition for the non-power circuit section (12) is delayed more than that of the power circuit section (11). A time constant circuit (6) is provided, whereby the cutoff control of the power circuit unit (11)
Under the operating conditions of the non-power circuit section (12), the operation can be smoothly performed without generating large transient noise.

The invention according to claim 4 is the invention according to claims 1 to 3
And a current mirror circuit (Q25, Q2) forming first and second two current paths having a constant current ratio relationship as the voltage level detection circuit (4).
6)), a first transistor (Q23) to which a collector current is supplied from the first current path (Q25), and an emitter area larger than that of the first transistor (Q23) and a second current path (Q26). ), The collector current is supplied from the second transistor (Q24), the emitter of the first transistor (Q23) and the second transistor (Q2).
4) First resistor (R22) connecting between the emitters
A second resistor (R23) connecting between the emitter of the first transistor (Q23) and the reference potential (GND);
A resistor voltage dividing circuit (R24, R25) for dividing the power supply voltage (Vcc) and applying the divided voltage to the bases of the first and second transistors (Q23, Q24);
24), the base current (I
b) a third transistor (Q27) connected so as to be turned on / off by the third transistor (Q27). The on / off state of the third transistor (Q27) causes the power supply voltage (Vcc) to fall below a specified level. A detection output for detecting whether or not the power supply voltage has been detected is taken out, so that the power supply voltage can be obtained by an internal threshold voltage (Vp) formed independently in a circuit without referring to the reference voltage (Vr). The effect is obtained that the level decrease of (Vcc) can be autonomously binary-discriminated.

According to a fifth aspect of the present invention, in addition to any one of the first to fourth aspects, as the voltage level detection circuit (4), the first and second two currents having a constant current ratio relationship are provided. Current mirror circuit forming a path (Q25, Q26)
A first transistor (Q23) to which a collector current is supplied from a first current path (Q25); and a second transistor having a larger emitter area than the first transistor (Q23) and a second transistor (Q23).
A second transistor (Q24) to which a collector current is supplied from a current path (Q26), an emitter of the first transistor (Q23), and a second transistor (Q24).
A first resistor (R22) connecting between the emitters of the first transistor (Q22) and a reference potential (G
ND), and a second resistor (R23) that connects between the first and second transistors (Q23) by dividing the power supply voltage (Vcc).
23, Q24) and a resistive voltage dividing circuit (R24, R25) commonly applied to the base of the second transistor (Q24).
A third transistor (Q27) and a second transistor (Q24) connected so as to be turned on / off by a base current (Ib) supplied through the collector of the second transistor (Q24)
Are connected in parallel between the collectors and the emitters, so that a fourth transistor (Q22) having a differential relationship with the second transistor (Q24) and a base of the fourth transistor (Q22) A diode (Q21) connected so as to be forward with respect to the reference potential (GND), and a current (If) for generating a forward voltage (Vf) across the diode (Q21).
Has a resistor (R21) for supplying current from the power supply voltage supply path,
The fourth transistor (Q22) is turned on when the second transistor (Q24) cannot maintain the on state due to a decrease in the power supply voltage (Vcc). Even if Vcc) drops much lower than the specified level, the effect of being able to maintain the detection state below the specified level can be obtained.

According to the present invention, the input voltage (Vc
c) a current mirror circuit (Q25, Q2) forming first and second two current paths having a constant current ratio relationship.
6), a first transistor (Q23) to which a collector current is supplied from the first current path (Q25), and an emitter area larger than that of the first transistor (Q23) and a second current path (Q26). (Q24) supplied with a collector current from the second transistor (Q24), the emitter of the first transistor (Q23) and the second transistor (Q2).
4) First resistor (R22) connecting between the emitters
A second resistor (R23) connecting between the emitter of the first transistor (Q23) and the reference potential (GND);
A resistor voltage dividing circuit (R24, R25) for dividing the input voltage (Vcc) and applying the divided voltage to the bases of the first and second transistors (Q23, Q24) and a collector of the second transistor (Q24). A third transistor (Q27) connected so as to be turned on / off by a base current (Ib) supplied through the third transistor (Q27). The on / off state of the third transistor (Q27) changes the input voltage. A detection output for detecting whether (Vcc) has fallen below a specified level is taken out, whereby an internal threshold voltage () independently formed in a circuit without reference to an external reference voltage is formed. Vp) has the effect that an autonomous voltage level detection circuit can be formed that discriminates the level drop of the input voltage (Vcc) into binary values.

According to a seventh aspect of the present invention, in addition to the sixth aspect, the second transistor (Q24) is connected in parallel between the collectors and the emitters, so that the second transistor (Q24) has the second transistor (Q24).
The fourth transistor having a differential relationship with the transistor (Q24)
(Q22), a diode (Q21) connected from the base of the fourth transistor (Q22) in a forward direction with respect to the reference potential, and a forward voltage (V) across both ends of the diode (Q21). Vf) to generate a current (Vf) from the input voltage (Vcc) supply path, and the second transistor (Q24) cannot be kept on due to a decrease in the input voltage (Vcc). At this time, the fourth transistor (Q22) is turned on, so that even if the input voltage (Vcc) further drops below the specified level, the detection state below the specified level is maintained. The effect that it can be obtained is obtained.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows a schematic configuration of an electronic circuit device to which the technology of the present invention is applied.

The electronic circuit device 100 shown in FIG. 1 is formed as a semiconductor integrated circuit on a single semiconductor substrate, and includes an application circuit 1, a bias circuit 2, a low voltage prohibition circuit 3
Etc.

First, the application circuit 1 is a circuit that forms functions such as a watchdog system, a regulator system, and a power IC system, and operates by the power supply voltage Vcc and the reference voltage Vr generated by the bias circuit 2. . The bias circuit 2 operates at the power supply voltage Vcc, generates a predetermined reference voltage Vr from the power supply voltage Vcc, and supplies the generated reference voltage Vr to each unit in the application circuit 1. The low voltage prohibition circuit 3 performs the operation prohibition of the application circuit 1 and the cutoff control of the current cutoff when the power supply voltage Vcc falls below the specified level. As a result, an electronic circuit device for preventing malfunction at low power supply voltage and reducing current consumption is formed.

The low-voltage prohibiting circuit 3 prohibits a voltage level detecting circuit 4 for detecting a low voltage and a cut-off control for stopping operation and interrupting current in accordance with a detection state of the voltage level detecting circuit 4. The output circuit 5 is configured.

At this time, the voltage level detection circuit 4
An autonomous level detection circuit that operates without reference to the external reference voltage Vr generated by the bias circuit 2, and has an internal threshold voltage (V
According to b), the level drop of the power supply voltage Vcc, which is the detection input voltage, is discriminated by binary. The prohibition output circuit 5 sets the application circuit 1 together with the bias circuit 2 to a low-voltage prohibition (cutoff) state according to the detection state of the autonomous voltage level detection circuit 4.

According to the above configuration, when the power supply voltage Vcc falls below the specified level, the operation of both the application circuit 1 and the bias circuit 2 is stopped and the cutoff of current cutoff is performed regardless of the operation state of the bias circuit 2. The state can be automatically set. That is, it is not necessary to guarantee the operation of the bias circuit 2 under a low power supply voltage, and it is also possible to cut off the operation current of the bias circuit 2 when the low voltage is prohibited. Thus, even when the detection level of the low power supply voltage is low, the low power supply voltage can be reliably detected and the low voltage prohibition can be performed, and the current consumption when the low power supply voltage is prohibited can be greatly reduced. .

FIG. 2 shows a specific circuit configuration example of the voltage level detection circuit 4 suitable for the electronic circuit device of FIG.

In the figure, the voltage level detection circuit 4
npn type bipolar transistors Q21 to Q24, p
It comprises np type bipolar transistors Q25 to Q27 and resistors R22 to R25.

Here, the pnp transistors Q25 and Q2
Reference numeral 6 denotes that the emitter current is connected to the power supply voltage supply path, and the collector and base of Q25 are connected in common and connected to the base of Q26. A current mirror circuit for transferring at a ratio is formed.

In this case, the current transfer ratio of Q25 and Q26, that is, the mirror ratio is set by the electrode size ratio of Q25 and Q26. Here, it is assumed that the current transfer ratio is set to 1: 1. It is assumed that the same currents Ioq, Ioq flow through the path.

The collector of the npn transistor Q23 is connected to a first current path formed on the collector side of the pnp transistor Q25, so that a collector current is supplied from the first current path. I have. Similarly, the collector of the npn transistor Q24 is connected to a second current path formed on the collector side of the pnp transistor Q26, so that the collector current is supplied from the second current path. I have. The bases of the two npn transistors Q23 and Q24 are commonly connected.

The resistor R22 is connected between the emitters of the transistors Q23 and Q24. Also,
The resistor 23 is connected between the emitter of the transistor Q23 and the reference potential GND.

The pnp transistor Q27 has an emitter connected to the power supply voltage supply path, a base connected to the collector of the npn transistor Q24, and a collector connected to the prohibited output circuit 5 described later.

The resistors R24 and R25 form a resistor voltage dividing circuit for dividing a power supply voltage (Vcc) which is a detection input voltage. The output of this voltage dividing circuit is connected to transistors Q23 and Q24.
Are applied to a common base.

The transistor Q22 includes a transistor Q2
4 is connected in parallel between the collectors and the emitters, so that the transistor Q24 has a differential relationship.

The transistor Q21 has a collector and a base connected so as to be diode-connected, and is further connected from the base of the transistor Q22 so as to be forward with respect to the reference potential GND.

The resistor R21 is connected to the diode (Q21)
At both ends of the base of a normal bipolar transistor
A current If for generating a forward voltage Vf corresponding to an emitter-to-emitter voltage is supplied from a power supply voltage supply path.

The prohibition output circuit 5 includes an npn transistor Q
28. This transistor Q28
Has its base connected to the collector of the pnp transistor Q27, and is turned on by a detection output current Io supplied when the Q27 is turned on. Then, the ON state of Q28 is output as a cutoff control signal Co for stopping the operation of the application circuit 1 and the bias circuit 2 (see FIG. 1) and cutting off the current.

Next, the operation will be described.

In FIG. 2, transistors Q25 and Q2
Reference numeral 6 denotes a current mirror circuit having the same emitter area and a current ratio of 1: 1 between the input side (Q25) and the output side (Q26). This 1: 1 current mirror circuit (Q25, Q26) allows the transistors Q23, Q2
4 are supplied with the same collector current Iqo, Iqo.

Here, assuming that the emitter area of the transistor Q24 is n times that of the transistor Q23, Q23
Is the base-emitter voltage Vbe23 of the equation (1)
24 is expressed by equation (2)
Can be represented by

The voltage difference Δ between Vbe23 and Vbe24
Vbe can be expressed by equation (3).

[0047]

(Equation 1) Here, if the current amplification factor of Q24 is sufficiently large, the current flowing through the resistor R22 can be regarded as the collector current Iqo of Q24. Thereby, the collector current I of Q24
qo is given by equation (4). In this equation (4), if the temperature T is constant, the collector current Iqo is defined by the resistor R22 and the emitter area ratio n of Q24 to Q23.

The collector currents Iqo and Iqo of the transistors Q24 and Q23 merge and flow through the resistor R23. At this time, the collector current Iqo of Q24 becomes Q25, Q26
Assuming that the collector current Iqo of Q24 follows 1: 1 by the transfer operation by the current mirror circuit, the condition of the base voltage Vb of Q23 and Q24 at that time is given by equation (5).

[0049]

(Equation 2) On the other hand, the voltage Vp divided by the resistors R24 and R25 is applied to the common base of Q23 and Q24, and the applied voltage Vp satisfies the condition for forming the base voltage Vb given by the equation (5). (Vp ≧
Vb), all of the collector current Iqo of the transistor Q24 is supplied from the transistor Q26. That is, there is no room for the collector of the transistor Q24 at this time to flow a current other than that supplied from the transistor Q26. Therefore, transistor Q27, which is connected so that the base current flows through the collector of Q24, maintains the off state because there is no room for the collector of Q24 to flow the base current Ib of Q27.

However, the voltage Vp applied to the common base of Q23 and Q24 is equal to the base voltage Vb given by equation (5).
If the magnitude is not large enough to satisfy the formation condition of (5), that is, if it is smaller than the base voltage Vb given by the equation (5) (Vp <Vb), the same base voltage is given to Q23 and Q24. Is larger than that of Q23, Q24 draws more collector current than Q23. However, the collector currents of Q23 and Q24 are Q25, Q2
The current mirror circuit 6 forms a 1: 1 ratio. As a result, the collector of Q24 has Q
An extra current other than that supplied from 26 flows in. That is, there is room for the collector current of Q24 to be larger than that of Q23. As a result, the transistor Q27, which is connected so that the base current flows through the collector of the transistor Q24, turns on when the base current Ib of the transistor Q27 flows as the collector current of the transistor Q24.

As described above, the voltage Vp divided by the resistors R24 and R25 and applied to the common base of Q23 and Q24 depends on whether the voltage Vp is equal to or higher than the base voltage Vb given by the equation (5). , Q27 are turned on / off. Thereby, the divided voltage V given from the resistors R24 and R25
Let p be the detection input voltage and Vb given by equation (5)
Is detected as a detection threshold value, and the detection output is output in the form of ON / OFF of Q27.

In this case, when Vp as the detection input voltage falls below Vb as the detection threshold value, the transistor Q28 of the prohibition output circuit 5 is turned on. The operation stop and the current cutoff (cutoff) of the circuit 1 and the bias circuit 2 are set.

It should be noted here that the above-mentioned voltage level detection circuit 4 does not use the external reference voltage Vr for detection, but instead has an internal threshold voltage (Vb) formed independently in a circuit. Is autonomously detecting the voltage level. Moreover, the internal threshold voltage (Vb) as a reference for the detection does not depend on the power supply voltage Vcc, as shown in Expression (5). Thus, high-precision low-voltage detection can be performed without externally applying the reference voltage Vr.

Next, the operation of the above-described voltage level detection circuit 4 in consideration of the temperature characteristics will be described.

In equation (5), Q which forms the detection threshold
When the temperature characteristics of the base voltage Vb of 24 and Q25 are obtained,
Equation (6) is obtained.

[0056]

(Equation 3) In equation (6), ΔV / ΔT = 0, that is, temperature characteristic 0
In order to be (zero), the first and second terms on the right side must be equal. Since the first term is approximately 2 mV / ° C., if the second term is also 2 mV / ° C., the temperature dependency can be eliminated. In this case, the second term is 2 mV / ° C. × 3
If 00 ° C. (absolute temperature) = 0.6 V, ΔV / Δ
T = 0 can be set. Vb at this time is about 1.3.
V bandgap voltage.

Accordingly, the low voltage prohibition setting voltage (Q27) on the input side of the voltage dividing circuit formed by the resistors R24 and R25.
If Vst is a detection threshold value at which is turned on, this Vs
t is given by equation (7). That is, when the power supply voltage (detection input voltage) Vcc becomes lower than the voltage Vst set by the equation (7), Q27 is turned on to set the low voltage prohibition state.

[0058]

(Equation 4) In the equation (7), if, for example, R25 / R24 = 2, the low voltage prohibition setting voltage Vst is 3 × 1.3V = 3.9.
V, that is, about 4V. Therefore, the power supply voltage Vc
If it is desired to perform low voltage inhibition when c becomes lower than 4 V, R25 / R24 may be set to 2.

Next, the operation of transistor Q22 will be described.

In the voltage level detection circuit 4 described above,
After the power supply voltage Vcc falls below the low voltage prohibition set voltage Vs and Q27 is turned on, if the Vcc further decreases, for example, if Vcc drops to about 1.8 V, the resistors R24 and R25 are reset. As a result, the voltage Vp applied to Q24 drops to about 0.6 V, and the ON state of Q24 cannot be maintained. If Q24 cannot be maintained in the ON state, the base current of Q27 will not be able to flow, and the setting of the low voltage prohibition state will be invalidated.

Here, when the power supply voltage Vcc drops so that the ON state of Q24 cannot be maintained, there is a problem if the application circuit 1 and the bias circuit 2 naturally stop and shut off due to the power supply voltage drop. However, even if such a low power supply voltage does not result in complete shutdown and shut-off, and half-way operation continues, the risk of malfunction or destruction remains. I will.

Therefore, in the circuit 4 shown in FIG. 2, the collector and the emitter are connected in parallel to the transistor Q24, so that the transistor Q22 having a differential relationship with the transistor Q24 and the diode Q24 A transistor Q21 and a resistor R21 for applying a forward voltage Vf (= approximately 0.7 V) are provided. That is, Q22 having a differential relationship with Q24 is provided, and a base voltage (Vf = approximately 0.7 V) required at least to turn on this Q22 is applied.

Thus, even if Q24 cannot be kept on due to a decrease in power supply voltage Vcc, Q2
In place of 4, Q22 turns on and Q27 continues to turn on. This makes it possible to lower the minimum operating power supply voltage for which low voltage is prohibited to the minimum voltage (about 0.7 V) required for the power supply voltage Vcc to turn on Q22. If the power supply voltage Vcc drops further, Q2
2 cannot maintain the ON state, but under such an extremely low power supply voltage (Vcc <0.7 V), most of the transistor circuits are completely stopped and cut off (cut off state). Therefore, there is no need to worry about malfunction or destruction.

The case where the current mirror ratio of Q25 and Q26 is 1: 1 has been described above, but the current mirror ratio may be other than that. For example, the condition when the mirror ratio is set to m: 1 can be obtained by Expressions (8) and (9).

[0065]

(Equation 5) That is, regardless of the mirror ratio, the resistances R24 and R24
With the ratio of 25 and the setting of the emitter area ratio n of Q24 to Q23, it can be considered as if the mirror ratio was 1: 1.

Even if the pnp transistor and the npn transistor are replaced with an npn transistor and a pnp transistor, the same voltage level detection circuit 4 and low voltage inhibition circuit 3 can be formed. Although the input of the voltage dividing circuit resistors R24 and R25 is obtained from Vcc, the input may not be obtained from Vcc but may be set from outside. It may be obtained.

FIG. 3 shows a detailed circuit example near the low-voltage inhibiting circuit and the bias circuit of the electronic circuit device shown in FIG.

In the figure, transistors Q23 to Q2
7 and the resistors R22 to R25 constitute the voltage level detection circuit 4. The voltage level detection circuit 4 shown here is almost the same as that shown in FIG. 2 except that the transistors Q21 and Q22 are omitted. R211 is for starting Q23 to Q26 to enter an equilibrium state, and is turned on / off of Q27.
Apply a small current that does not affect turning off.

The transistors Q28 and Q29 and the resistor R2
6, R27 constitute the prohibition output circuit 5. In the prohibition output circuit 5, the low voltage detection output of the voltage level detection circuit 4 is taken out by two transistors Q28 and Q29, and one of the Q28 is used to prohibit the low voltage prohibition of the bias circuit 2.
In the other Q29, the low voltage of the application circuit 1 is prohibited. Co1 and Co2 are cut-off control signals for inhibiting the low voltage.
It is taken out from each of the 29 collectors.

The bias circuit 2 includes transistors Q11 to Q11.
Q17 and resistors R11 to R15. This bias circuit is a band gap type constant voltage circuit, and Q11 and Q12 operate as a starting circuit.

FIG. 4 shows a further preferred configuration example of the electronic circuit device of the present invention.

In the circuit shown in FIG. 7, when the voltage level detection circuit 4 detects a low power supply voltage, the inhibition output circuit 5 outputs the cutoff control signals Co1 and Co2 output to the application circuit 1 and the bias circuit 2. Among them, a time constant circuit 6 for selectively delaying only the cutoff signal Co1 for the bias circuit 2 is provided. The time constant circuit 6 is formed by connecting a capacitance element C1 in parallel to the base side of a transistor Q28 that is turned on by the detection output of the voltage level detection circuit 4.

With the provision of the time constant circuit 6, the cut-off operation at the time of detecting the low power supply voltage can be performed by first using the application circuit 1
Are cut off, and the cutoff setting of the bias circuit 2 is started a little after the cutoff setting of the application circuit 1 is completed.

As a result, the application circuit 1 is controlled to be cut off under a normal operating condition in which the reference voltage Vr is supplied from the bias circuit 2, and it is possible to reliably prevent a malfunction during a cut-off transition period. Will be able to

FIG. 5 shows a further preferred configuration example of the electronic circuit device of the present invention.

In the circuit shown in the figure, the cut-off setting by the inhibit output circuit 5 is performed by setting the power circuit section 11 which consumes a relatively large amount of current, such as an output circuit, and the bias circuit 2.
As described above, the cutoff control signal Co1 for the non-power circuit section 12 is selectively delayed by the time constant circuit 6 while being divided into the non-power circuit section 12 which consumes relatively little current.

As a result, the cutoff control of the power circuit section 11 is performed under the condition that the non-power circuit section 12 such as the bias circuit 2 operates normally, and it is possible to reduce the noise generation during the cutoff transition period. become able to.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Needless to say.

In the above description, mainly the case where the invention made by the present inventor is applied to the low voltage prohibition system of the electronic circuit device, which is the field of application as the background, is not limited thereto. For example, the present invention can be applied to an overvoltage prohibition system that stops operation when a power supply voltage or an input voltage exceeds a certain level, or a general-purpose voltage level detection circuit that does not require a reference voltage.

[0080]

The following is a brief description of an outline of typical inventions among the inventions disclosed in the present application.

That is, even when the detection level of the low power supply voltage is low, the low power supply voltage can be reliably detected and the low voltage prohibition can be performed, and the current consumption when the low power supply voltage is prohibited is greatly reduced. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an electronic circuit device to which the technology of the present invention is applied.

FIG. 2 is a circuit diagram showing a specific configuration example of a voltage level detection circuit used in the present invention.

FIG. 3 is a circuit diagram showing a detailed configuration example near a low-voltage inhibiting circuit and a bias circuit;

FIG. 4 is a circuit diagram showing a further preferred configuration example of the electronic circuit device of the present invention.

FIG. 5 is a circuit diagram showing a still further preferred configuration example of the electronic circuit device of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Electronic circuit device 1 Application circuit 11 Power circuit section 12 Non-power circuit section 2 Bias circuit 3 Low voltage prohibition circuit 4 Voltage level detection circuit 5 Prohibition output circuit 6 Time constant circuit Vcc Power supply voltage Vr Reference voltage GND Reference potential Q21 to Q24 npn -Type bipolar transistors Q28, Q29 npn-type bipolar transistors Q25 to Q27 pnp-type bipolar transistors R21 to R25 Resistance C1 Capacitor

Claims (7)

[Claims] 1. An application circuit whose operation is guaranteed at a power supply voltage higher than a predetermined level, a bias circuit that generates a predetermined reference voltage from the power supply voltage, and the application circuit when the power supply voltage becomes lower than a specified level. An electronic circuit device configured to prevent malfunction at a low power supply voltage and reduce current consumption by using a low-voltage prohibition circuit that performs cut-off control, wherein the low-voltage prohibition circuit refers to the reference voltage. An autonomous type voltage level detection circuit that discriminates the level drop of the power supply voltage in a binary manner by an internal threshold voltage that is formed independently in a circuit-less manner, and the application circuit according to the detection state of the voltage level detection circuit And a prohibition output circuit for setting a low voltage prohibition state together with the bias circuit. 2. The electronic circuit device according to claim 1, further comprising a time constant circuit for delaying the setting of the low voltage prohibition for the bias circuit from that of the application circuit. 3. The electronic circuit device according to claim 1, further comprising a time constant circuit for delaying the setting of the low-voltage prohibition for the non-power circuit portion from that of the power circuit portion. 4. A current mirror circuit forming first and second current paths having a constant current ratio relationship as a voltage level detection circuit, and a first current path supplied with a collector current from the first current path. And a second transistor having an emitter area larger than that of the first transistor and supplied with a collector current from the second current path, and an emitter connected between the emitter of the first transistor and the emitter of the second transistor. A first resistor that connects between the emitter of the first transistor and a reference potential;
A resistive voltage dividing circuit for dividing the power supply voltage and applying the divided voltage to the bases of the first and second transistors in common and connected so as to be turned on / off by a base current supplied through the collector of the second transistor. And a detection output for detecting whether or not the power supply voltage has fallen below a specified level depending on the on / off state of the third transistor. An electronic circuit device according to any one of the above. 5. A current mirror circuit forming first and second current paths having a constant current ratio relationship as a voltage level detecting circuit, and a first current path supplied with a collector current from the first current path. And a second transistor having an emitter area larger than that of the first transistor and supplied with a collector current from the second current path, and an emitter connected between the emitter of the first transistor and the emitter of the second transistor. A first resistor that connects between the emitter of the first transistor and a reference potential;
A resistive voltage dividing circuit for dividing the power supply voltage and applying the divided voltage to the bases of the first and second transistors in common and connected so as to be turned on / off by a base current supplied through the collector of the second transistor. A third transistor, a fourth transistor having a differential relationship with respect to the second transistor by being connected in parallel between the collector and the emitter with the second transistor, and a fourth transistor A diode connected in a forward direction with respect to a reference potential from the base of the diode, and a resistor for supplying a current for generating a forward voltage from a power supply voltage supply path to both ends of the diode; The fourth transistor is turned on when the second transistor cannot be kept on due to the decrease. Electronic circuit device according to any one of claims 1 to 4 for. 6. A current mirror circuit forming first and second current paths having a constant current ratio relationship from an input voltage, a first transistor supplied with a collector current from the first current path, and , A second transistor having a larger emitter area than the first transistor and supplied with a collector current from a second current path, and a first transistor connecting between the emitter of the first transistor and the emitter of the second transistor. A second resistor connecting between the emitter of the first transistor and the reference potential; a resistor voltage dividing circuit for dividing the input voltage and applying the divided voltage to the bases of the first and second transistors in common; And a third transistor connected so as to be turned on / off by a base current supplied through a collector of the second transistor. A detection output for detecting whether or not the input voltage has fallen below a prescribed level depending on an on / off state of the voltage level detector. 7. When the collector and the emitter are connected in parallel to the second transistor, the second transistor is connected to the second transistor.
A fourth transistor having a differential relationship with respect to the first transistor, a diode connected from the base of the fourth transistor so as to be forward with respect to the reference potential,
The diode has a resistor for supplying a current for generating a forward voltage from the input voltage supply path to both ends of the diode. When the input voltage decreases, the second transistor cannot maintain the ON state. 7. The voltage level detection circuit according to claim 6, wherein the transistor is turned on.