JPS5831215Y2 - Power supply control circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a power supply control circuit that eliminates the influence of noise on other circuits on a power supply line.

Logic circuits in small electronic calculators and the like can be roughly divided into a plurality of circuit blocks according to their functions.

These circuit blocks are a mixture of circuit blocks that tend to generate noise due to their functions, circuit blocks that hardly generate noise, circuit blocks that may cause noise but have no problem, and circuit blocks that have problems.

By the way, Figure 1 shows a conventional configuration in which such various circuit blocks are mixed, and the configuration is based on a system that has been developed in recent years and is being put into practical use in order to prevent power battery consumption due to forgetting to turn off the power switch, etc. This is a case where the device has an automatic power-off function (hereinafter referred to as an auto-power-off function) that automatically turns off the power if no key operation is performed for a predetermined period of time while the power switch is on.

That is, 1 in the figure is a large-scale integrated circuit (LSI), and externally connected in parallel is a capacitor 2 that prevents noise generated when a power switch (not shown) is turned on or off, etc., and supplies power to each circuit described later. A power supply battery 3 for performing the operations, a key input section 4 for inputting various data, and a display section 5 for displaying entered numbers, calculation results, etc. are provided.

Further, inside this LSII, there is a central processing unit that performs numerical arithmetic processing according to the key data supplied from the key human power section 4 and supplies the processing results to the display section 5, or stores and holds various data. (hereinafter abbreviated as FCPU) 6.
An oscillation circuit T that outputs a clock signal to drive the display section 5 and the CPU 6, a power supply control circuit 8, and P-channel and N-channel transistors 9a.

9b is provided with a switching circuit 9 having an 0MO8 configuration, and is connected directly from the power supply battery 3 to the key power section 4 and from the display section 5. CPU6. Power is supplied to the oscillation circuit 7 via the switching circuit 9 described above.

The power supply control circuit 8 detects that no key operation has been performed for a predetermined period of time in the key manual section 4, and the output signal of this power supply control circuit 8 is supplied to the switching circuit 9. The power supply battery 3 also controls the power supply to each circuit.

By the way, the CPU6. The oscillation circuit 7 uses a CMO 8 having the same configuration as the switching circuit 9 described above in order to reduce power consumption in these circuits.
In this case, in a transient state of switching of two transistors, either they are both turned on at the same time and conductive, and their output becomes an intermediate level, or both of them are turned on and off unstable, and their output level reaches the ground potential in an extremely fast cycle. It is known to repeatedly output a driving potential.

When comparing the respective circuit blocks of the CPU 6, oscillation circuit 7, and power supply control circuit 8, it is found that the oscillation circuit 7
Since it is always operating, it is easy to output the above-mentioned intermediate level output or so-called noise that repeats the ground potential and drive potential, and this noise is transmitted to the CPU 6 via the power supply line.
etc., etc.

That is, if the above-mentioned noise enters the power supply line as shown in FIG. 2a, in the CPU 6, as shown in FIG.
In order to prevent such malfunction, a capacitor 10 is provided on the output side of the switching circuit 9 as shown in FIG.

That is, as shown in the two circuits in FIG. 3, the switching circuit 9 has an element resistance 9' (so-called on-resistance), so the noise generated in the oscillation circuit γ cannot be prevented by the capacitor 2.
A capacitor 10 had to be provided outside the LSII to prevent noise.

Therefore, it is necessary to add LSII pins and attach capacitors, which increases the number of parts and requires work to attach them, resulting in disadvantages such as a very high manufacturing standard.

The present invention was developed in view of the above circumstances, and provides a power supply control circuit that eliminates the influence of noise output from a given circuit block on other circuit blocks without providing a capacitor outside the LSI. It is.

An embodiment of the present invention will be described below with reference to FIG.

In addition, in FIG. 4, the same parts as in FIG. 1 are given the same reference numerals.

That is, in this embodiment, power is supplied to the CPU 6, the oscillation circuit γ, and the display unit 5 from the power source battery 3 separately for each circuit block via switching circuits 11 to 13 having the same configuration as the switching circuit 9. It is designed so that it can be carried out.

These switching circuits 11 to 13 are each composed of P-channel MO8 type field effect transistors lla to 13a and N-channel MO3 type field effect transistors 11b to 13b.

Therefore, the transistor Ila of the switching circuit 11
The drain side electrode of the transistor 11b is grounded, the source side electrode of the transistor 11b is connected to the power supply battery 3, and the source side electrode of the transistor 11a and the drain side electrode of the transistor 11b are connected to the CPU 6 to supply power.

Furthermore, the gate side electrodes of the transistors lla and llb are connected to a power supply control circuit 8 and are controlled to open and close by the output of this power supply control circuit 8.

Similarly, in the switching circuits u12 and u13, the transistor 12a.

The drain side electrode of the transistor 13a is grounded, and the transistor 12
The source electrodes of transistors b and 13b are connected to the power supply battery 3, the source electrodes of the transistor 12a and the drain electrode of the transistor 12b are connected to the oscillation circuit 7, and the source electrodes of the transistor 13a and the drain electrode of the transistor 13b are connected to the oscillation circuit 7. The transistors 12a and 12b or the transistor 13a are connected to the display section 5, respectively.
.

13b is connected to the power supply control circuit 8 to control the power supply.

In this way, in this embodiment, switching circuits 11 to 13 are provided independently for the CPU 6, the oscillation circuit 7, and the display section 5, respectively.
is provided, and the on-resistance of these switching circuits 11 to 13 is used to prevent noise output from one circuit block from entering the power supply line of another circuit block.

Next, the operation of this embodiment will be explained.

That is, while the computer is operating, the power supply control circuit 8 outputs 1" (H
) is output, and the transistors 11a to 13a of each switching circuit 11 to 13 become non-conductive, and the transistors 11b to 13b become conductive.

Therefore, these switching circuits 11 to 13 all output the voltage (+V) of the power supply battery 3, and supply power to the CPU 6, the oscillation circuit 7, and the display circuit 5.

By the way, when each circuit operates in response to power supply, especially the oscillation circuit 1 outputs noise as described above,
This noise is transferred to the output line of the switching circuit 12, that is, the power supply line 12c to the oscillation circuit T.

However, since this switching circuit 12 has an on-resistance similar to that explained in FIG. 3, it becomes an equal circuit as shown in FIG.
2r and the capacitor 2 form an integrating circuit (by forming a closed circuit as shown by the dotted line in the figure), and the noise on the output line 12c is cut by this integrating circuit. Other circuit blocks, i.e. CPU6
And the influence on the display section 5 disappears.

On the other hand, the noise generated in the oscillation circuit 7 and transferred to the output line 12c of the switching circuit 12 is cut off as described above, but the noise is outputted as an oscillation output of the oscillation circuit 70 and applied to the CPU 6.

However, this oscillation output noise does not pose an equivalent problem for the following reasons.

The CPU & sends its basic timing signal to the oscillator circuit 7.
It is created based on the output of the oscillation circuit γ
Even if a pulse is output in a shorter period than the normal output period, the CPU 6 will only speed up the operation cycle slightly at that time, and each part will not lose its synchronization and will not malfunction. .

In addition, each circuit block other than the oscillation circuit 7, the CPU 6, and the display unit 5 also have switching circuits 11 and 130 and on-resistances 11r and 13r, and noise generated in each of these parts (although extremely rare) As above, other circuit blocks are not affected.

Next, the off state will be explained. When each key of the key manual section 4 is not operated for a predetermined period of time or more, the power supply control circuit 8 detects this state and sets its output to "0" (L).

, Therefore, in each switching circuit 11 to 13, transistors 11a to T3a are in a conductive state, and transistors 11b to 13b are in a conductive state.
becomes non-conductive, the ground potential is applied to the CPU 6, the oscillation circuit T, and the display section 5, and their operations are stopped.

As described above, in this embodiment, each switching circuit 11 to 130 and the on-resistance 11r to 13r are used, and the power supply lines 11c to 13c to each circuit block (CPU 6, oscillation circuit I, and display section 5) are connected to each switching circuit 11 to 130. By connecting the on-resistances 11r to 13r in common at the latter stages of the on-resistances 11r to 13r, the on-resistances 11r to 13r of the husband and husband each form an integrating circuit with the capacitor 2, and are directly placed on the own power supply line with their own circuit blocks. Noise will not be introduced into the power supply lines of other circuit blocks and will not affect their operation.

Unfortunately, in the above embodiment, each circuit is functionally divided into blocks, and a switching circuit is provided for each block to supply power. However, the present invention is not necessarily limited to this, and can be applied to circuit blocks that are likely to generate noise. Alternatively, a switching circuit may be provided only.

In addition, in the above embodiment, a case is explained in which an auto power off function is provided, and each of the switch pins and ffl paths 11 to 1
3 is controlled by the output of the power supply circuit 8, but the present invention is not limited to those having an auto power-off function, and each switching circuit JT to 13 can be controlled directly by the power switch. You may also do this.

As explained in detail above, according to the present invention, the influence of noise on other circuit blocks can be reduced by simply providing switching circuits each having an on-resistance independently in a circuit block that tends to generate noise and in other circuit blocks. Since there is no need to provide a capacitor for noise prevention as in the past, the number of pins on the LSI can be reduced, and a large number of manufacturing costs are required, such as making the single screen of the electronic device itself very cheap. It has advantages.

[Brief explanation of the drawing]

Figure 1 is a circuit block diagram of a conventional computer, and Figure 2 is a circuit block diagram of a conventional computer.
In the figure, a diagram showing a level change assuming a malfunction due to noise, Figure 3 is a diagram showing an isometric circuit such as the switching circuit 9 in Figure 1, and Figure 4 is an example of an implementation of the present invention. FIG. 5, a circuit block diagram for explaining an example, is a diagram showing equivalent circuits of the switching circuits 11 to 13, etc. in FIG. 4. 1...LSI, 3...Power battery, 5...Display section,
6...CPU, γ...Oscillation circuit, 8...Power supply control circuit, 11°12.13...Switching circuit.

Claims (1)

[Scope of utility model registration request] In an electronic device in which the power supply to each circuit of the electronic device is controlled by turning on and off a switching circuit, the electronic device is divided into a plurality of circuit blocks according to function. A power supply control circuit characterized in that switching circuits each having an on-resistance are independently provided in at least one circuit block and another circuit block among the divided circuit blocks.