JPS61277068A - Voltage detection circuit - Google Patents

Abstract

PURPOSE:To widen an operation voltage range and to dispense with a circuit for generating reference voltage, by determining the magnitude of voltage by utilizing that the logical threshold voltage of a logical NOT gate is dependent on the voltage of a power source. CONSTITUTION:An integrating circuit 1' is held to an OFF-state during a period when a signal 100 is at a 'H' level and a transistor switch 8 is turned ON. In this state, the logical NOT gate input in a judge circuit 2' is fixed to a 'L' level and judge output 4' does not change. When the signal 100 comes to the '1' level, the transistor switch 8 is turned OFF and, at the same time, a constant current source control transistor 5 is turned ON and, therefore, the voltage with definite inclination determined by a constant current source 6 and the capacity value of a capacitor 7 is applied to the logical gate input in the judge circuit 2'. When a logical NOT gate logical threshold voltage level exceeds the terminal voltage of the capacitor 7, the logical gate output of the judge circuit 2' is reversed and a state is written in a D-latch 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage detection circuit in the field of MO8 semiconductor integrated circuits.

[Conventional technology]

Conventionally, there have been circuits for the purpose of voltage detection.

However, since most of them are configured with a reference voltage circuit, a detection voltage dividing resistor, and a comparator, there are problems such as an increase in circuit scale, an inability to lower the operating power supply voltage, and a complicated circuit.

Furthermore, today there is a trend toward lower power consumption in all electronic devices, and while devices with as little current consumption as possible are preferred, there are limits to how low power consumption can be achieved with conventional methods.

[Problem that the invention seeks to solve]

The present invention aims to solve two of the problems of the above-mentioned prior art, particularly the complication of the circuit and the restriction of the operating voltage.

[Means for solving problems]

It has three elements: a logic inversion gate, a constant current source composed of a single depletion controlled MOSFET, and a capacitor, and the MO8
IFI! ! A transistor for controlling the on/off operation of a single constant current source is connected in series between a power supply and one end of the constant current source, and the other end of the constant current source is grounded at one end and connected to the other end of the capacitor. Then, the capacitor and the constant 1! The input end of the logic NOT gate is connected to the connection point with the light source, and a transistor switch for the purpose of discharging the capacitor is connected between the logic NOT gate input end and the ground, and when in operation, the constant current source control transistor By turning on the capacitor discharging transistor switch and turning off the capacitor discharging transistor switch at the same time, the capacitor with an initial charge of zero is charged by the constant current source, and after a certain period of time, the terminal voltage of the capacitor reaches the logic level of the logic NOT gate. The logical NOT gate output is determined by whether it exceeds the value voltage or not, and the capacitor discharging transistor switch is turned on during the non-operating period, and the constant current source control transistor is turned off at the same time as the charging voltage is discharged. The output of the logical NOT gate is forcibly determined in one direction, and the magnitude of the voltage is determined by utilizing the fact that the logical single value voltage of the logical NOT gate depends on the power supply voltage. do.

[Function/Example]

The basic concept of the present invention is shown in FIG. 1 in the figure is an integral circuit,
2 is a determination circuit, 5 is a control circuit, and 4 is an output terminal. The present invention will be described in detail below based on specific examples.

FIG. 2 shows a specific embodiment of the present invention. In the figure, 1' is an integrating circuit, 6 is a depletion-controlled MOSFET constant current source, and 5 is a depletion-controlled MOSFET constant current source.
60 is an on/off control transistor, and 7 is a capacitor. 2' is a judgment circuit, 9 is a P channel MOS
FET 10 is an N-channel MO8IFKT and constitutes a logic NOT gate. Reference numeral 8 denotes a discharging transistor switch which has the role of setting the gate input constituted by 9 and 10 to the "0" level and discharging the charge charged in the capacitor 7. 11 is a D latch, and 4' is a judgment output terminal.

Reference numeral 3' denotes a control signal generating section required for the operation of this system, that is, a control circuit.

Next, the operation of each part will be explained based on an embodiment.

In the figure, φM to φD are digital signal inputs. Here -
For example, φmuwIHz, φBx512H2, φ0=2K
Hz,φD! The case of 4KHz will be explained.

The relationship between the signals 100 to 104 obtained by each signal is shown in FIG.

The integrating circuit 1' is in an off state while the signal 100 is at the "R" level, and the transistor switch 8 is on. From this, the input to the logic negation gate in the foot circuit 2' is fixed at the L'' level, and the judgment output 4' does not change.

However, when the signal 100 goes to the "L" level, the transistor switch 8 turns off and at the same time the constant current source control transistor 5 turns on. A voltage with a constant slope determined by the capacitance value of the capacitor V (t) = t / C
(11 is applied. Here, I is the output current t of the constant current source 6 is the time during which the signal 100 is L'', and C is the capacitance value of the capacitor 7.6 The constant current source output voltage aU, Il'1!!Tl1iil value voltage is v?8.
If the shape current coefficient is β;
・+2) and does not depend on the power supply voltage at all. Yo,
Therefore, V (t) in equation (1) can be written as the following equation.

On the other hand, the logical single-value voltage vb of the internal logic/failure gate in the judgment circuit 2' is expressed as V'rP, , βP11 e vT'10 p/"1
If it is set to 0, it can be given by the formula. Here, VDD represents the power supply voltage. As is clear from equation (3), logic 1l
The llIlt voltage vb changes depending on the value of the power supply voltage VDD.

Therefore, the essential condition for the judgment circuit 2' to perform the detection operation is
V (t)≦vb・・・・・・・・・＋4+・・・(
4) is given by.

The state change at this time is the signal t02, 105°1 in Fig. 5.
06 and 105. In the figure, 102 is the output waveform of the 1' integration circuit that is transmitted to the 2I judgment circuit, and 106 is (
3) The logical NOT gate logic single value voltage level expressed by the equation (2), 105 is the change in the terminal voltage of the capacitor 7 corresponding to the equation (2). When 105 exceeds the level of 106, the logic gate output of the judgment circuit 2' is inverted by nine as signal 105,
The D latch 11 is activated by the inverted clock (signal 101).
The status is written to.

The above is the operation of each part in the embodiment of the present invention.

〔Effect of the invention〕

According to the present invention, the following advantages are produced.

+11 6 The operating voltage range becomes wider. In particular, since the basic configuration is made of logic circuits, in the 0M08 circuit, P channel M
OSFET, 1! Channel MO8IPI! : Can be operated in a power supply voltage range that is greater than the sum of the gate threshold voltages of 'r.

(2) A circuit for generating a reference voltage becomes unnecessary.

In reality, it may be better to configure a reference voltage circuit that is extremely less affected by voltage fluctuations. However, the circuit configuration for this purpose becomes complicated, and if it becomes possible to operate at a low voltage, it tends to become even more complicated. In the present invention, in order to obtain a voltage reference that is as simple as possible, a method is adopted in which it can be determined only by the product of the constant current value and the operating period, and the capacitor capacity. This greatly simplifies the process, and also has the advantage that the detection voltage can be changed simply by changing the operating time.

It is also important to note that as long as the gate threshold voltage is controlled during the manufacturing process, the constants of analog operating parts can be determined only by the constant current value, the shape and dimensions of the constituent elements such as capacitors, etc. Furthermore, by making the constant current source FET into a P-channel type, the P-channel side of the logic NOT gate for judgment? ]
! ! It also has the advantage that variations in the gate threshold voltage of T are canceled out.

(3) It is advantageous for integration due to the circuit occupation area and freedom in layout.

In conventional voltage detection circuits, dividing resistors for detection are formed by impurity diffusion or the like. However, in order to keep the resistance division ratio accurate, it was necessary to arrange it as straight as possible and reduce the number of bent parts. In addition, in order to reduce the current, it is necessary to increase the resistance value itself, which tends to be disadvantageous due to constraints due to the shape.

On the other hand, if the present invention is used, although the capacitor becomes larger in area, it is not subject to any shape restrictions, so the circuit itself can be treated as one compact block. Therefore, when integrating the circuit, it is possible to layout the circuit in a well-balanced manner with other circuits.

The advantages of the present invention as described above can be applied to electronic watches, for example. In particular, if it is used in a voltage detection circuit for a solar-powered watch where the power supply voltage constantly increases or decreases, a single circuit can set a large number of voltage detection levels and can be used in a wide range of ways, such as displaying battery voltage.

[Brief explanation of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIG. 2 is a diagram showing a specific embodiment, and the ggs diagram is a diagram showing the operation relaxation pressure of the valley. 1.1'...Integrator circuit 2.2'...Judgment circuit 3.5/...II control circuit 4.4'...Judgment output terminal or higher

Claims (1)

[Claims] It has three elements: a logic negative gate, a constant current source composed of a single depletion controlled MOSFET, and a capacitor, and the MOS
An on/off operation control transistor of a constant current source composed of a single FET is connected in series between a power source and one end of the constant current source,
The other end of the constant current source is connected to the other end of the capacitor which is grounded, and the input end of the logic NOT gate is connected to the connection point between the capacitor and the constant current source, and the logic NOT gate input A transistor switch for the purpose of discharging the capacitor is provided between the end and ground, and during operation, the constant current source control transistor is turned on and the capacitor discharging transistor switch is turned off at the same time.
the capacitor with an initial charge of zero is charged by the constant current source;
After a certain period of time has elapsed, the logic NOT gate output is determined depending on whether the terminal voltage of the capacitor exceeds or does not exceed the logic threshold voltage of the logic NOT gate, and the capacitor discharging transistor switch is turned off during the non-operating period. The configuration is such that the constant current source control transistor is turned off and the constant current source control transistor is turned off to force the output of the logic NOT gate to go in one direction, and the logic single value voltage of the logic NOT gate is set to the power supply voltage. A voltage detection circuit characterized in that the magnitude of a voltage is determined by utilizing the dependence on the voltage.