JPS644287Y2 - - Google Patents

Description

[Detailed description of the invention] This invention detects the voltage difference between the output voltage of the constant voltage circuit and the battery power supply voltage, and when the voltage difference becomes less than a predetermined value, an inverted signal is sent to warn of battery life. This invention relates to a power supply circuit that outputs .

Conventionally, in various systems that use batteries as a power source,
Power supply circuits have been proposed that can generate a signal warning of battery life. For example, as shown in Figure 1, an N-channel MOS FET transistor is used, and the gate voltage of transistor Tr ₁ is obtained by dividing the voltage between resistors R ₁ and R ₂ , and the gate voltage decreases as the battery voltage decreases. Transistor Tr ₁ based on the change
The output signal is inverted by switching from ON to OFF. Here, _R3 is a pull-up resistor. As shown in FIG. 1, the resistance R ₁ ,
A circuit for detecting a drop in battery voltage, which includes R ₂ , R ₃ and transistor Tr ₁ , is provided before the constant voltage circuit 1 . The above transistor Tr ₁ is connected to the battery B
If is above a constant voltage, it is ON, and as the voltage of battery B decreases, it is turned OFF as described above. The output To at this time is connected to a warning device (not shown) to issue a warning. Further, the output Ts of the constant voltage circuit 1 is connected to the system load.

However, in this method, the battery voltage detection circuit does not directly depend on the constant voltage circuit, so as the voltage of battery B decreases, the point at which constant voltage circuit 1 stops operating, that is, its output Ts, changes to the above detection circuit. It is not directly related and cannot make a determination according to the output Ts, so it is necessary to perform detection by the detection circuit itself. Therefore, the operating point of the detection circuit (the point at which the voltage of battery B drops below the constant voltage output by constant voltage circuit 1) is:
For system safety, the system is set with a considerable amount of battery life remaining, which has the disadvantage of extremely low battery efficiency.

In addition, in the conventional circuit shown in FIG. 2, in order to eliminate the drawbacks of the circuit shown in FIG. 1, the battery voltage detection circuit is
This is an example in which it is connected to the output Ts of the constant voltage circuit 1 to have a relationship between the two. In this case, the transistor
The point at which Tr ₁ is reversed from ON to OFF and the warning device connected to its output To is activated is when the output Ts to which the system load is connected becomes even lower than the set voltage. Therefore, since the system is driven at a voltage lower than the constant voltage, there is a risk of malfunctions due to voltage drop, and it is no longer possible to prevent the risk that, for example, the contents of the storage section will not be protected. Therefore, the conventional circuit shown in FIG. 2 is also inappropriate as a detection circuit.

The power supply circuit of the present invention has been developed in view of the above-mentioned points, and its purpose is to immediately issue a warning when the battery power supply voltage falls below the system voltage, that is, below the constant voltage provided by the constant voltage circuit. An embodiment of the present invention that achieves this object will be described with reference to the drawings. FIG. 3 shows an embodiment of the present invention. In the figure, B is a battery, Tr ₁ is an N-channel junction FET transistor, R ₁ and R ₂ are dividing resistors, and the configuration of Tr ₁ and R ₁ R ₂ is as follows. is a so-called constant voltage circuit 1 that utilizes the constant current characteristics of FET transistors.
E ₀ represents the battery voltage, E ₁ represents the constant voltage power supply, and E ₂ represents the battery life warning signal voltage. Also, RL ₁ is a system load, and RL ₂ is a warning load.

The feature of the present invention is particularly that a P-channel type junction FET having a polarity opposite to that of the FET transistor is added to the constant voltage circuit 1. That is, the source electrode S ₂ of the FET transistor Tr ₂ is connected to the output electrode S ₁ of the FET Tr ₁ , and the gate electrode G ₂ of Tr ₂ is connected to the drain electrode D ₂ of Tr ₁ , that is, the battery output terminal. Here, if the pinch-off voltage between the gate and source of transistor Tr ₂ is V _GS (off), then transistor Tr ₂ is OFF when there is no battery voltage drop and E ₀ - E ₁ > |V _GS (off)| From _E2 the voltage level is zero. Then, as the battery voltage decreases (nearing the end of its life), the E ₀ level decreases, and E ₀ −E ₁ < |V _GS (off) |
Then, the transistor Tr ₂ is turned on, and the E ₂ voltage level becomes approximately equal to the E ₁ level, that is, the system power supply level. In other words, the operating point of the battery voltage detection circuit is the pinch-off voltage V _GS of transistor Tr ₂ .
It depends on the value of (off). therefore,
If the transistor Tr ₂ with the lowest V _GS (off) value is selected, the battery voltage detection circuit can be operated when the battery voltage E ₀ becomes approximately equal to the constant voltage power source E ₁ .

In this way, the power supply circuit for generating the battery life warning signal of the present invention generates a constant voltage power supply E ₁ (E ₁ <E ₀ ) from the battery voltage E ₀ and calculates the potential difference between the two (E ₀ −E ₁ ).
Connect the drain terminal _D1 of the N (or P) channel junction field effect transistor (FET) Tr ₁ to the positive (or negative) electrode of the battery terminal as a circuit that generates an inverted signal when the voltage drops below a predetermined voltage. and the source terminal of Tr ₁ and the negative (or positive) of the battery
By connecting two series resistors R ₁ and R ₂ between the electrodes and connecting the connection point of these resistors R ₁ and R ₂ to the gate terminal G ₁ of transistor Tr ₁ , the source terminal of Tr ₁
A circuit where S ₁ becomes the output terminal of a constant voltage power supply, and a P (or N) channel type junction FET (Tr ₂ )
By connecting the source terminal S ₂ of this Tr ₂ to the source terminal S ₁ of Tr ₁ and connecting the gate terminal G ₂ of Tr ₂ to the positive (or negative) electrode of the battery, the transistor Tr ₂ is This is achieved by coupling circuits whose drain terminal _D2 serves as an output terminal for an inverted signal.

FIG. 4 is a characteristic curve diagram showing the voltage relationship among the battery voltage E ₀ , the constant voltage power supply E ₁ and the battery life warning signal voltage E ₂ , with the output voltage on the vertical axis and the system operating time on the horizontal axis. Here, the characteristics of the battery voltage E ₀ are those of the most commonly used dry battery (manganese battery).

In the embodiment shown in FIG. 3, the explanation has been made on the assumption that the voltages E ₀ , E ₁ , and E ₂ are positive, but the same can be achieved in the case of negative voltages. is shown in FIG.

Furthermore, although the constant voltage circuit was explained using junction type FET transistors in the above embodiment,
It can be realized with any circuit. Junction type
By using a FET transistor, a highly accurate battery life warning signal can be obtained by simply adding one transistor to a constant voltage circuit, and there is no increase in power consumption due to the addition of the above FET, making it a highly practical power supply circuit. can be obtained.

As explained above, according to the power supply circuit of the present invention, when the power source of the battery power source falls below the predetermined voltage value of the system, this condition can be immediately detected and the warning device can be activated, thereby increasing the efficiency of battery usage. In addition, the system can always operate in a normal state without malfunctioning.

In addition, it is sufficient to use only FET transistors for the configuration of the detection circuit, etc., making the configuration extremely simple, almost eliminating power consumption, and making more effective use of battery power, resulting in a highly practical and inexpensive power supply circuit. be able to.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an example of a conventional power supply circuit, FIG. 3 is a circuit configuration diagram showing an example of the power supply circuit of the present invention, and FIG. 4 is a voltage characteristic diagram of the circuit shown in FIG.
FIG. 5 is a circuit configuration diagram showing another embodiment of the power supply circuit of the present invention. In the figure, 1: Constant voltage circuit, Tr ₁ , Tr ₂ : Junction type FET transistor, R ₁ R ₂ : Resistor, E ₀ :
Battery voltage, E ₁ : Constant voltage power supply, E ₂ : Battery life warning signal voltage.

Claims (1)

[Claims for Utility Model Registration] A power supply battery that outputs a voltage E ₀ , and an output voltage of the power supply battery that is connected to the above power supply battery.
A constant voltage circuit that outputs a constant voltage E ₁ with respect to E ₀ and supplies a constant voltage to the load of the system, and a constant voltage circuit that includes an FET transistor and outputs a constant voltage E ₁ of the above power supply battery and an output voltage E ₁ of the above constant voltage circuit. For the voltage difference (E ₀ − _{E 1} ), the pinch-off voltage between the gate and source of the above FET transistor is
Connect the gate terminal of the above transistor to the output voltage E ₀ , the source terminal to the output voltage E ₁ , and the drain terminal of the transistor to turn it OFF or ON.
A power supply circuit comprising: a voltage detection circuit connected to a warning device as an OFF or ON inverted output terminal;