JPS6041111A - Constant voltage device - Google Patents

Abstract

PURPOSE:To prevent the excessive application of voltage in an LSI and to reduce the number of external parts by providing an impedance circuit changing its impedance in accordance with the detected voltage of a voltage detecting part and fixing power supply voltage to the LSI on the same chip. CONSTITUTION:The ON resistance of a transistor (TR) 21 is changed from a signal ¦VGS¦ analogically changed by the voltage detecting part 18, a closed loop is constituted between the voltages VDD and VSS through a resistor 22 and current is made to flow into the loop. When VDD potential is increased through a terminal 13 by the high intensity of illumination of a solar battery 11, the signal ¦VGS¦ is increased and the impedance value of the impedance circuit 20 is reduced, so that the load of the LSI is equivalently increased and the voltage VDD shows the tendency to be decreased. Consequently, the signal ¦VGS¦ is reduced, the impedance value of the impedance circuit 20 is increased and the load is reduced. Therefore, the voltage VDD is kept at a fixed level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a constant voltage device using a solar cell as a power supply means.

[Technical background of the invention and its problems]

With the recent development of LSIs (Large Scale Integrated Circuits), small electronic computers, electronic clocks, etc. have come to have a CMOS structure, and their current consumption is now on the order of several μA at 1.5V.

Furthermore, with the reduction in power consumption of LSIs, solar cells have come to be used as a power supply means. When using this solar cell as a power supply source, if the illuminance of the light irradiated to the solar cell is extremely high due to the characteristics of the solar cell, the LS
In order to prevent excessive voltages from being applied to I, light emitting diodes are attached in such a way that they form a closed loop.

FIG. 1 is a circuit diagram of a small electronic computer using a solar cell. The negative side of solar cell 1 is connected to LSI through resistor 2.
The positive electrode side is directly connected to the supply terminal 5 of the reference voltage V8B of LS1, 9. A capacitor 6 and a light emitting diode 7 are connected in parallel between the terminals 4 and 5. The light emitting diode 7 is used to prevent excessive voltage from being applied to the LSI and 9 by forming a power supply closed loop by passing current through the diode 7 when the illuminance of the light irradiated to the solar cell 1 is extremely high. It is something.

The resistor 2 and the capacitor 6 are a smoothing circuit for preventing sudden changes in the voltage applied to the LSIJ due to sudden changes in the power supply voltage. 8 is a key, and 9 is a liquid crystal display device.

FIG. 2 shows general solar cell characteristics per cell using illuminance [LuX) as a parameter. The open-circuit voltage of a solar cell is determined by the semiconductor elements (silicon single crystal, 8i-I
n! 03, 5nO1) etc., 1.5v system LfS
When driving I, 4 to 5 solar cells are connected in series and used. Figure 3 shows the characteristics of a solar cell when several cells are connected in series.

As mentioned above, the standard operating voltage of LSI is 1.5V,
A power supply circuit is constructed by connecting 4 to 5 cells in series. As a countermeasure against excessive applied voltage during high illuminance due to this configuration,
Conventionally, an external light emitting diode 2 has been used, and external components tend to be large in number.

[Purpose of the invention]

As mentioned above, in the past, an external light emitting diode was used as a measure to prevent excessive applied voltage, but the external light emitting diode was used to reduce the number of components, and the circuit operation was similar to that of the light emitting diode.
This is what we are trying to achieve within I.

[Summary of the invention]

In order to achieve the above object, the present invention provides solar power.

A voltage detection section that detects the voltage of the battery and an impedance circuit that is provided in parallel with the LSI and whose impedance changes according to the detected voltage of the voltage detection section to keep the power supply voltage to the L8I constant are installed on the same chip as the LSI. It was designed to be installed in

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Fourth
In the figure, 11 is a solar cell, 12 is an LSI area, 13 is a solar cell supply power terminal, 14 is an LSI power supply terminal, 15 is a reference potential power supply terminal, 16 is a smoothing capacitor, and 17 is a smoothing resistor. Terminals 14 and 15 supply power supply voltages VDD and vss to the LSI, respectively. Between the power supply terminals 14 and 15, there is an N-channel MO as a voltage detection section 18.
An S transistor 919 and a capacitor C1°Ct are connected in series, and the r-to of the transistor 19 is connected to the A point. Impedance circuit 2 is connected between power terminals 14 and 15.
N-channel type MO8) transistor 21 and closed-loop load resistor 22 are connected in series, and the transistor 21
(1:)'l-) is connected to point B between:yy7-', yfc1, and C.

In FIG. 4 having the above configuration, the N-channel transistor 19 with its dart and drain connected acts as a constant voltage circuit, and the potential of the connection between its dart and drain is determined from the voltage/voltage DD at the terminal 14 of the transistor 19. The level becomes higher by the threshold voltage vTH. Therefore, the voltage vB at point B is VB = (VDD - VTH) ” + / (CH+
C2). This voltage vB is the r-) signal of the N-channel transistor 2. Also transistor 2
The source-to-source voltage IV and SI of the node are 1VGsl=lVDnl-1vBl. As the power supply voltage vDD decreases, l VO2
1 decreases, and the on-resistance of transistor 2 increases. Furthermore, as VDD rises, l Yes l rises, and the on-resistance of the transistor 21 becomes smaller. The power supply voltage VDD can be changed by setting the capacitance value of the capacitor CI+Cff1, the threshold voltage of the transistor 19, etc. Transistor 21 from signal I Vos l which changes in analog quantity by voltage detection unit 18
The on-resistance of VDD and VB2 changes through the resistor 22.
In between, a closed loop is formed and a current is passed. That is, when the solar cell 1 is exposed to high illuminance and the VDD potential increases through the terminal 13, l VGS l increases, and the impedance value of the impedance circuit 2θ decreases, so the load on the LSI increases, and the power supply voltage VDD becomes Shows a decreasing trend. As a result, l Vos l becomes smaller, thereby increasing the impedance value of the impedance circuit 20 and reducing the load. Through the above operations, VDD remains at a constant level.

Note that the present invention is not limited to the above embodiments, and can be applied in various ways. For example, the resistor 22 of the impedance circuit 20 may be omitted. In addition, the voltage detection section 18 is like a voltage dividing circuit or the like, in short, it can detect the voltage of the solar cell and control the impedance value of the impedance circuit 20. [Effects of the Invention] As explained above, according to the present invention, In various arithmetic processing devices that use batteries as electrical voltage supply means, measures to prevent excessive voltage applied due to high illuminance can be implemented within the LSI instead of using light emitting diodes, thereby eliminating the need for external components. It is possible to reduce the

[Brief explanation of drawings]

The first factor is the circuit diagrams showing conventional voltage regulators, Figures 2 and 3.
The figure is a solar cell characteristic diagram, and FIG. 4 is a circuit diagram of an embodiment of the present invention. 11...Solar cell, 12...LSI, 13,14゜15...Power terminal (Yatsud), 16...Smoothing capacitor, 17...Smoothing resistor, 18...Voltage detection Section 20... Impedance circuit, 21.°°transistor. Applicant's representative Patent attorney Takeshi Suzue Syllable 1 Figure 4 Figure 1.2 -1111 stroke

Claims (1)

[Scope of Claims] (11) A solar cell, a power supply section to which the battery voltage is supplied and supplies a power supply voltage to the integrated circuit, and a voltage detection section provided between the electrodes of this power supply section and detecting the voltage of the solar cell. and an impedance circuit that is provided in parallel with the integrated circuit and whose impedance changes according to the voltage detected by the voltage detection section to constantize the power supply voltage to the integrated circuit. (2) The voltage regulator according to claim 1, wherein the power supply section, the voltage detection section, and the impedance circuit are configured on the same chip as the integrated circuit. The voltage regulator according to claim 1, wherein the impedance circuit includes at least an MO8 transistor and changes its source-drain resistance value in accordance with the voltage detected by the voltage detection section. 4) The voltage regulator according to claim 3, wherein the voltage detecting section is a voltage dividing circuit that divides the power supply voltage by 'ε, and applies the voltage to the dart of the MO8) transistor.