JPH0810977Y2 - Power on / off circuit - Google Patents

Description

[Detailed Description of the Invention] <Industrial application field> The present invention relates to a power / on / off circuit for turning on / off electric power, and more particularly to a power / on / off circuit for turning on / off a portable instrument using a momentary switch and a microcomputer. On / off circuit.

<Prior Art> There is a configuration shown in FIG. 3 as a first conventional example in the case of turning on / off a power source of a battery-operated portable instrument.

FIG. 3 discloses a switch circuit for supplying electric power from the battery E ₁ via the switch SW ₁ to the electric circuit ECT of the instrument.

The switch used here is a normal switch such as a toggle switch or a slide switch whose position physically changes when operated.

The method of turning on / off the power using such a switch is high in cost, and it is difficult to use a closed structure for use in a place where the operating environment is bad such as an instrument, and it is not suitable for a small instrument. Has the problem that it is difficult to make it thin.

Therefore, as shown in FIG. 4, there is a configuration using a momentary switch in which an electric contact is turned on only while the switch is pressed.

A transistor-type switch SW ₂ is connected between the battery E ₁ and the electric circuit ECT of the instrument, and this switch SW ₂ is connected to the battery E ₁
It is opened / closed by a high / low binary control signal V ₁ output from an on / off logic circuit LGC connected in parallel with. The logic of the logic circuit LGC is configured such that the control signal V ₁ is inverted every time the momentary switch SW ₃ connected to the logic circuit LGC is turned on.

Next, the operation of the switch circuit configured as described above will be described using the waveform chart shown in FIG.

When the momentary type switch SW ₃ ON (FIG. 5 (b)), the logic circuit LGC sets the control signal V ₁ by detecting the rise in the low level (FIG. 5 (b)). As a result, the transistor type switch SW ₂ is turned on (FIG. 5 (c)) to supply a voltage to the electric circuit ECT. Therefore, every time the switch SW ₃ is turned on, the logic circuit LGC
Is supplied with voltage.

<Problems to be solved by the invention> However, a switch circuit for turning on / off a voltage by using such a momentary switch can be made thin as seen in, for example, a thin keyboard switch such as a card calculator. Although it has the advantage of being able to use a sealed structure, it has the disadvantage that the current will flow to the logic circuit LGC even when the power is turned off, and the battery will run down. Further, a battery-operated on / off logic circuit needs to be operated at, for example, about 2 to 3 V, and making such a logic circuit for a small-volume product causes a cost increase.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides an internal structure in which power is supplied from a DC power source (E ₁ ) through an input / output terminal of a first switch element (Q ₁ ). The circuit power supply (RGR) that supplies a specified power supply voltage (V _CC ) to the circuit and the first switch element (Q
A momentary switch (SW ₄ ) that is connected in series between the control end of ₁ ) and the common potential point to turn on and off the first switch element (Q ₁ ) by pressing it, and this momentary switch (SW ₄ ) Second switch element (Q ₂ ) that is connected in parallel with the switch and is turned on and off by the control signal (V _B ).
And a state monitoring means for scanning the ON / OFF state of the momentary switch (SW ₄ ) to monitor and store this state signal (V _A ), and the power supply voltage (V _CC ) is not applied. Under the condition, the previous momentary switch (S
W ₄₎ pressed by the state to which the internal circuit second switching element of the preceding detects that power is supplied to the (Q ₂₎ was set to ON destination of the power supply voltage (V _CC) is applied Below, the previous control signal that turns off the second switch element (Q ₂ ) after confirming the state change of the previous momentary switch (SW ₄ ) from on to off with the previous state signal (V _A ). A control means for outputting (V _B ) is provided, and these means are realized by a microcomputer (CPU).

<Operation> The momentary switch is turned on to bring the switch element into conduction to operate the circuit power supply, thereby supplying a voltage to the internal circuit. The microcomputer operates with this voltage and applies a control signal to the control switch to ensure the conduction of the switch element. Therefore, even if the momentary switch is turned off in this state, the switch element itself maintains the on state.

The microcomputer stores the on / off state of the momentary switch. When the momentary switch is turned on and then turned off, the microcomputer detects this change in state and sends a control signal that turns off the control switch to the control switch. Then, the switch element is turned off via this control switch.

Therefore, every time the momentary switch is turned on, the circuit power supply is repeatedly turned on and off.

<Embodiment> FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

E ₁ is a battery having a voltage of about 2 V, and one end is connected to the common potential point COM and the other end is connected to the emitter of the PNP transistor Q ₁ . Its collector is connected to the regulator circuit RGR. Also, the base of transistor Q ₁ is a resistor
It is connected to the emitter via R ₁ and is also connected to the common potential point COM via a series circuit of a resistor R ₂ , a diode D ₁ and a momentary switch SW ₄ . Further, the base of the transistor Q ₁ is connected to a common potential point COM via a resistor R ₃ and a series circuit of a collector and an emitter of an NPN transistor Q ₂ whose base and emitter are connected by a resistor R ₄ .

The regulator circuit RGR boosts the voltage of the battery E _{1 serving} as a power source of the internal circuit between the common potential point COM and outputs the voltage as a circuit voltage V _CC of 5 V, for example.

The microcomputer CPU operates by being supplied with the circuit voltage V _CC . Voltage V _A at the connection point C ₁ from the connection point C ₁ of the diode D ₁ and the momentary switch SW ₄ via the diode D ₂ is inputted to the terminal T _1. Note that this connection point C ₁
Is pulled up to the circuit voltage V _CC through a resistor R ₅ .

The terminal T ₂ of the microcomputer CPU outputs a control signal V ₂ to the base of the transistor Q ₂ through a series circuit of a diode D ₃ and a resistor R ₆ to control the conduction of the transistor Q ₂ .

The diodes D ₂ and D ₃ are for preventing current from flowing into the circuit when the power is off.

ANC is an abnormality monitoring circuit, and this abnormality monitoring circuit ANC receives a control signal from the microcomputer CPU via the control line l ₁ l ₂ . The abnormality monitoring circuit ANC has its terminal T ₃ has an internal watchdog timer circuit WDT is connected to the connection point C ₂ of a diode D ₃ through a diode D ₄ and the resistor R _4. This abnormality monitoring circuit ANC monitors the movement of software in the microcomputer CPU by hardware and resets (restarts) the microcomputer CPU when the software becomes abnormal.

Next, the operation of the switch circuit configured as described above will be described with reference to the waveform chart shown in FIG.

First, when the switch SW ₄ shown in FIG. 2 is off and the circuit power supply V _{CC is}
The low level "L" state in which the is turned off will be described.

In this state, the circuit power supply V _CC is low level “L” of zero.
(Fig. 2 (e)), the voltage V _{B at the} connection point C ₂ is also low level "L" (Fig. 2 (f)), and the momentary switch SW ₄ is off (Fig. 2 (e)). B)), the voltage V _{C at} the base of the transistor Q ₁ is the same as the voltage V _n of the battery E ₁ (FIG. 2 (c)).

Therefore, the transistor Q ₁ is in the off state, and the collector voltage V _D is in the low level “L” state (FIG. 2 (d)).

Next, the state 1 in which the circuit power is turned on will be described.

When the momentary switch SW ₄ is turned on (Fig. 2 (a)), the voltage V _{A at the} connection point C ₁ becomes low level "L" (Fig. 2 (b)), the battery E ₁ to the resistor R ₁ , R ₂ , diode
A current flows through D ₁ and the momentary switch SW ₄ , which causes a potential drop in the resistor R ₁ and the base of the transistor Q ₁ becomes low level “L” (Fig. 2 (c)). ₁ is turned on.

Therefore, the voltage V _{D of} its collector is equal to the voltage V _{n of the} battery E _1.
(Fig. 2 (d)). Therefore, the regulator circuit RGR boosts the voltage V _n (about 2 V) to the circuit voltage V _CC of the high level “H” of 6 V (FIG. 2 (e)).

This rising circuit voltage V _CC causes the microcomputer CPU to start operating. In this case, if the voltage V _B appearing at the terminal T ₂ of the microcomputer CPU is programmed to the high level “H”, The voltage V _{B at the} connection point C ₂ becomes high level “H” (Fig. 2 (f)), and the transistor Q ₂
Turns on.

When the transistor Q ₂ turns on, a base current flows through the transistor Q ₁ through the resistor R ₃ to keep the transistor Q ₁ on.

Therefore, in this state, even if the momentary switch SW ₄ is turned off (FIG. 2 (a)), the transistor Q ₁ is kept in the on state and the circuit voltage V _CC is in the high level “H” state (second
Figure (e)) is maintained. At this time, when the momentary switch SW ₄ is turned off, the voltage V _{A at the} connection point C ₁ becomes high level “H” (Fig. 2 (b)), and this state change
Read into microcomputer CPU via T ₁ .

With the above operation, the state 1 in which the circuit power is turned on in FIG. 2 ends.

After that, the level change (high / low) of the terminal T ₁ is scanned by the regular scan and read into the microcomputer CPU to monitor the state of the momentary switch.

Next, when the momentary switch SW ₄ is turned on again (Fig. 2 (a)), the microcomputer CPU is set to the voltage V _A
(Fig. 2 (b)) becomes low level "L" and it is memorized, and then the momentary switch SW ₄ is turned off (Fig. 2 (a)) and the voltage V _A (Fig. Microcomputer CPU indicates that the high level "H" in Figure 2 (b))
Confirm. At this time, if the software of the microcomputer CPU is programmed so that the voltage V ₂ of the terminal T ₂ becomes low level “L”, the transistor Q ₂ is turned off and the base current supply of the transistor Q ₁ is stopped. The transistor Q ₁ is turned off (Fig. 2 (f)).

When the operation of the microcomputer CPU becomes abnormal, the abnormality monitoring circuit ANC outputs a high level “H” voltage to the terminal T ₃ and keeps the transistor Q ₂ on, thereby turning off the power due to the runaway of the microcomputer CPU. To prevent.

In the switch circuit shown in FIG. 1, the circuit operates even without the regulator circuit RGR and the diodes D ₂ , D ₃ and D ₄ .

Also, the transistors Q ₁ and Q ₂ function similarly in devices such as field effect transistors (FETs).

Further, in a battery-operated instrument, an automatic power-off circuit that protects the decrease in battery capacity due to forgetting to turn off the power is often required. Even in such a case, according to the present embodiment, the terminal T _{2 in} FIG. The automatic power-off can be easily realized by holding the voltage of the low level "L".

Since the circuit shown in FIG. 1 is made up of transistors, it can operate at a low voltage of about 1.5V. Also,
In this case, the regulator circuit RGR can boost the voltage V _n of the battery E ₁ of 1.5 V to a large voltage V _CC such as 5 V, so that the electric circuit and the microcomputer are
The one that operates at 5V can be used, which contributes to cost reduction.

<Effects of Device> As described above in detail with the embodiments, according to the present invention, almost no current flows in the circuit when the power is off, and the circuit element (diode, diode, Leakage current of transistor etc. (μA order)
This is a big advantage in battery-operated instruments.

Particularly, in the present invention, since the microcomputer is provided with the state detecting means for detecting and storing the on / off state of the momentary switch and the control means for outputting the control signal based on the on / off state, the momentary switch is Even if it is pressed for a long time, the microcomputer can detect this, so that the power can be surely turned off without causing malfunction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention, FIG. 2 is a waveform diagram explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a configuration of a conventional first switch circuit. Circuit diagram,
FIG. 4 is a circuit diagram showing the configuration of a conventional second switch circuit, and FIG. 5 is a waveform diagram for explaining the operation of the switch circuit shown in FIG. ECT ...... electrical circuit, E ₁ ...... battery, LGC ...... logic circuit, RGR
...... Regulator circuit, CPU …… Microcomputer, WDT …… Watchdog timer, ANC …… Abnormality monitoring circuit, V _CC …… Circuit voltage.

Claims (1)

[Scope of utility model registration request] 1. A circuit power supply for supplying electric power from a DC power supply through an input / output terminal of a first switch element to supply a predetermined power supply voltage to an internal circuit, and a control terminal of the first switch element and a common potential point. A momentary switch connected in series between and to operate the first switch element by turning on and off, and a second switch element connected in parallel to the momentary switch and turned on and off by a control signal.
State monitoring means for scanning the on / off state of the momentary switch to monitor and store the state signal, and to supply power to the internal circuit by pressing the momentary switch when the power supply voltage is not applied. Is detected, the second switch element is set to the ON state, and under the condition that the power supply voltage is applied, the momentary switch changes from ON to OFF. A power / on / off circuit comprising control means for outputting the control signal for turning off the two-switch element, and implementing these means by a microcomputer.