JP2575092B2 - Power supply stabilization circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply stabilizing circuit, and is particularly suitable for application to a semiconductor integrated circuit (hereinafter referred to as an IC) that requires good voltage reduction characteristics. is there.

[Conventional technology]

A power supply stabilizing circuit is used in various electronic devices. The circuit configuration of the power supply stabilization circuit is diverse, one example of which is “Design of the power supply stabilization circuit” (February 10, 1977
It is described in the 15th edition, CQ Publisher, p24, Fig. 2.6). The outline is to divide the output voltage to get the error voltage,
The output voltage is stabilized by driving the control transistor by the error amplifier.

The present inventors have studied reducing the voltage drop of the power supply stabilizing circuit itself. The following is not a known technique, but is a technique studied by the present inventor, and its outline is as follows.

[Problems to be solved by the invention]

That is, if we describe the known example, the transistor Tr ₂ controls the control transistor Tr ₁ so that the voltage base voltage is determined by Vz + VbeTr _2.

If unstable power supply Ei drops below a voltage which is determined by the Vz + VbeTr _2, Tr ₂ is turned off, the output voltage Eo Ei-V
be reduced to a voltage level determined by BETR ₁ is revealed by the study of the present inventor. Assuming that Ei is 1.5V, the output voltage Eo drops to 0.8V.

On the other hand, the power supply used for the electronic device is not always at or above a predetermined voltage level. For example, some electronic telephones use a DC power supply of a telephone line as a power supply. In this case, if the distance between the exchange and the telephone is large,
The voltage supplied to the telephone will also drop. Furthermore,
Since the electronic telephone has a low input impedance, the voltage drop is large.

However, it is very difficult to normally operate not only the electronic telephone IC but also the general IC with the power supply voltage of about 1V. Considering such a situation, it can be understood that the reduction of the voltage drop in the power supply stabilization circuit is important for stably operating the IC. In other words, taking the above voltage relationship as an example, if there is no voltage drop of 0.7 V in the power supply stabilization circuit, the power supply voltage of 1.5 V will be supplied to the IC, and the operating range of the IC will be expanded. Become.

The present inventor has repeatedly studied to reduce the voltage drop of the power supply stabilizing circuit itself, and has come to propose the present invention.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply stabilizing circuit capable of obtaining a stable output voltage with respect to fluctuations in the power supply voltage and reducing a voltage drop when the power supply voltage drops.

The above and other objects and novel features of the present invention are as follows.
It will be apparent from the specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

In other words, a control transistor is composed of a PNP transistor, an unstable voltage is supplied to an emitter as an input terminal, an output voltage is obtained from a collector as an output terminal, and the output voltage is supplied to a feedback terminal of a voltage follower.
A power supply stabilizing circuit that controls the control transistor by an output signal that is 100% negative feedback and is compared with a reference voltage formed by a constant voltage element including a plurality of forward-connected diodes connected in series. By making the common impedance means provided at the emitter common connection point of the differential pair transistors constituting the follower particularly a resistor, when the unstable voltage is equal to or less than the reference voltage, a plurality of serially connected devices as the constant voltage element are connected. When the forward diode is cut off, the differential transistor on the reference voltage side is turned on, and the control transistor saturates, the unstable voltage is generated as it is as the output voltage. The operation is such that the unstable voltage is the base-emitter voltage of the differential transistor on the reference voltage side. It is intended to continue until.

[Action]

According to the above means, when the unstable voltage is higher than the reference voltage, the output follower voltage is controlled to the reference voltage level by the operation of the voltage follower, and when the unstable voltage is equal to or lower than the reference voltage, the voltage is lower than the reference voltage. If the voltage is equal to or higher than the base-emitter voltage of the
The control transistor is saturated and the unstable voltage becomes the output voltage, and the voltage drop of the power supply stabilization circuit itself is prevented.

Embodiment 1 Hereinafter, a first embodiment of a power supply stabilizing circuit to which the present invention is applied will be described with reference to FIGS. 1 and 2. The first
FIG. 2 is a circuit diagram of a power supply stabilizing circuit formed as an IC, and FIG. 2 is a voltage characteristic diagram showing a relationship between an unstabilized voltage and an output voltage.

Transistor Q ₁ is, which corresponds to a control element in the present invention, the transistors Q _2, Q _3, Bol presented follower is constituted by a resistor R _2. The diodes D _{1 to} D ₃ are for obtaining the reference voltage Va according to the present invention, and are set to Va = 2, 1 V in this embodiment.

First, the circuit operation when the unstable voltage is 2.1 V or more will be described.

Unstable voltage Ve is applied to the emitter of the transistor Q _1, it is applied to the diode D ₁ and via the resistor R _1. 3 times the voltage Va of the forward voltage Vf of the diode D ₁ to D ₃ is applied to the base of the transistor Q _2, the transistor Q ₂ is turned on,
Transistor Q ₃ is turned off. By the transistor Q ₂ is performed suction of the base current of the transistor Q _1, the voltage level of the output voltage Vcc becomes high level close to the unstable voltage Ve.

Transistor Q ₃ is operated to the ON state, the voltage level equal to the output voltage Vcc to a reference voltage Va by the operation of the Bol presentation follower, i.e. allowed to drop to 2.1V.

As a result of the above-described circuit operation, when the unstable voltage Ve is 2.1 V or more, the output voltage Vcc is also stabilized at 2.1 V as shown in FIG.

Next, a circuit operation when the unstable voltage Ve fluctuates between 2.1V>Ve> 0.7V will be described.

Diode D ₁ to D ₃ will cut off, the reference voltage Va becomes the voltage level of the unstable voltage Ve. When unregulated voltage Ve is to 1V to temporary, it means that a bias voltage is applied to the transistor Q _2, it operates on state transistor
The Q ₁ allowed to saturation. Output voltage Vcc is obtained, the transistor Q ₃ is operated to the ON state to stabilize the output voltage Vcc to 1V by Bol presented follower operation. In other words, no voltage drop 0.7V by transistor Q ₁ is, the voltage level of the unstable voltage Ve directly becomes the voltage level of the output voltage Vcc.

The above-described stabilizing operation is performed while the unstable voltage Ve is in the range of 2.1V>Ve> 0.7V, so that the IC shown as the load Z1 is supplied with the unstable voltage Ve as a power supply. Assuming that the power supply voltage for normally driving the IC is 2.1 V, the voltage drop of 0.7 V does not occur even if a sufficient circuit operation is not performed when the unstable voltage Ve drops to 2.1 V or less. The operation is not completely stopped, and the voltage reduction characteristics are improved.

Next, a circuit operation when the unstable voltage Ve changes to 0.7V> Ve will be described.

In this case, since the reference voltage Va is also lowered below 0.7V, the transistor Q ₂ is turned off, does not control the transistor Q _1. Accordingly, as shown in FIG. 2, the output Vcc also drops sharply, and the IC as a load also becomes inactive.

The power supply stabilizing circuit shown in the above embodiment has the following effects.

(1) By controlling a control transistor that is supplied with an unstable voltage and controls an output voltage by a voltage follower that compares the reference voltage with the output voltage, the output voltage is controlled when the unstable voltage is equal to or higher than the reference voltage. The effect is obtained that the voltage can be stabilized at the same level as the reference voltage.

(2) According to the above (1), when the unstable voltage changes to a level at which the voltage follower can be driven below the reference voltage, the control transistor can be saturated to make the unstable voltage an output voltage, thereby stabilizing the output voltage. The effect of reducing the voltage drop of the circuit itself is obtained.

(3) According to the above (2), the power supply range in which the load can be driven even when the unstable voltage decreases is expanded, and the voltage reduction characteristics of the load such as an IC to which power is supplied are improved. The effect is obtained.

(4) Since the circuit configuration is simple, it is suitable for IC implementation.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

It should be noted that the difference between the present embodiment and the first embodiment resides in the provision of the resistor R ₃ in place of the control transistor, identical to those forming the same circuit operation as in the first embodiment Are attached to avoid duplication of description.

When unregulated voltage Ve is above 2.1V, the reference voltage Va of the voltage 2.1V provided by the diode D ₁ to D _3. Output voltage Vcc
Although obtained via a resistor R _3, before the transistor Q ₃ is operated is equal to the unregulated voltage Ve. But transistors
As the voltage follower operation by Q ₂ and Q ₃ is performed, the voltage drop of the resistor R ₃ increases, and the voltage level of the output voltage Vcc is stabilized at 2.1V.

On the other hand, when the unstable voltage Ve changes to 2.1V>Ve> 0.7V, the output voltage Vcc changes in level corresponding to the unstable voltage Ve.

Further, when the unstable voltage Ve becomes 0.7V> Ve, the voltage follower operation is not performed, and the output voltage Vcc changes in level according to the unstable voltage Ve.

Therefore, in the circuit configuration shown in this embodiment, the stabilizing operation is performed when Va> Va, and when Va> Ve, the unstable voltage Ve becomes the output voltage Vcc, and the voltage drop of the stabilizing circuit is reduced.

The stabilizing circuit shown in the present embodiment has the following effects in addition to the same effects as in the first embodiment.

(5) By providing the resistor R ₃ in place of the control transistor, the circuit configuration is simplified, the effect is obtained that.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and may be variously modified without departing from the gist thereof. Needless to say. For example, a MOS transistor can be used instead of a bipolar transistor. In this case, the control transistor may be a P-channel MOS transistor, the transistor forming the voltage follower may be an N-channel MOS transistor, and the diode may be an N-channel MOS transistor.

Further, the reference voltage circuit composed of a diode may be replaced with a constant voltage circuit such as a band-cap reference.

Further, the voltage level of the reference voltage Va is not limited to the above, and can be changed according to the required output voltage Vcc.

In the above description, the invention made mainly by the inventor has been applied to the power supply stabilization circuit as the background of the application, but the invention is not limited to this. For example, at the start of a car, the voltage of the battery drops sharply, so if it is used individually for the power supply circuit of an IC provided to an electronic device for a vehicle, there is no need to provide a power supply stabilization circuit for the entire electronic device. Good. An advantage of such a use method is that even if one of the stabilized power supplies is destroyed by an unexpected situation, the entire electronic device does not become inoperable, and the vehicle can be driven safely.

INDUSTRIAL APPLICABILITY The present invention can be incorporated at least into an IC requiring power supply stability and widely used.

〔The invention's effect〕

The effects obtained by the representative inventions among the inventions disclosed in the present application will be briefly described as follows.

That is, a control element for supplying an unstable voltage to obtain a stabilized output voltage, and a voltage follower for comparing the reference voltage with the output voltage to drive the control element to perform the stabilization operation are provided. When the unstable voltage is higher than the reference voltage, the stabilizing operation is performed, and when the unstable voltage is low, the control element is in a saturated state, and the voltage drop by the control element is reduced, thereby expanding the range of the power supply voltage for driving the load. And the voltage reduction characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a power supply stabilizing circuit to which the present invention is applied, FIG. 2 is a voltage characteristic diagram illustrating circuit operation, and FIG. 3 is a power supply showing a second embodiment of the present invention. FIG. 3 shows a circuit diagram of a stabilization circuit. Q _{1 to} Q ₃ …… Transistor, D _{1 to} D ₃ …… Diode, R ₁ to
R ₃ …… Resistance, Va …… Reference voltage, Ve …… Unstable voltage, Vcc
…… Output voltage.

Continuation of the front page (56) References JP-A-62-281019 (JP, A) Practical application Photograph of the contents of the specification and drawings attached to the application form of Japanese Patent Application No. 56-128368 (Japanese Utility Model Application No. Microfilm (JP, U) Practical application Microfilm (JP, U) photographing the contents of the specification and drawings attached to the application form No. 54-111748 (Japanese Utility Model Application No. 56-32216)

Claims (1)

(57) [Claims] A first transistor of a first conductivity type for supplying an unstable voltage to an emitter and forming an output voltage from a collector; a first transistor connected between the unstable voltage and a ground potential of a circuit; A constant voltage generating circuit that generates a reference voltage by using the direct diode having a plurality of serially connected forward diodes as a constant voltage element, and the reference formed by the constant voltage generating circuit. A second transistor of a second conductivity type to which a voltage is supplied to the base; an emitter connected to the emitter of the second transistor of the second conductivity type; and a collector of the first transistor of the first conductivity type A third transistor of the second conductivity type to which the collector is connected, and a commonly connected emitter of the second transistor and the third transistor of the second conductivity type, and And a common impedance means for connecting the second and third transistors of the second conductivity type to operate as a differential pair transistor. Supplying the output voltage obtained from a common connection point between the collector of the first transistor and the collector of the third transistor of the second conductivity type to the base of the third transistor of the second conductivity type.
A power supply stabilizing circuit for generating a stabilized output voltage substantially equal to the reference voltage as the output voltage when the unstable voltage is equal to or higher than the reference voltage of the constant voltage element by forming a voltage follower having a% negative feedback. When the unstable voltage is equal to or less than the reference voltage of the constant-voltage element, the forward diode of the plurality of series-connected elements as the constant-voltage element is cut off when the unstable voltage is equal to or less than the reference voltage of the constant-voltage element. Then, the second transistor of the second conductivity type operates in an on state, and the first transistor of the first conductivity type operates.
When the first transistor of the conductivity type is saturated, the unstable voltage is generated almost as it is as the output voltage,
A power supply stabilizing circuit, wherein the unstable voltage generating operation is continued until the unstable voltage becomes the base-emitter voltage of the second transistor of the second conductivity type.