JPS59111417A - Power supply circuit - Google Patents

Abstract

PURPOSE:To attain power supply by providing the 1st and 2nd FFs supplying power to a load circuit at set state and controlling the state of the FFs in response to the state of a power switch and an output state of an oscillating signal from the load circuit. CONSTITUTION:When a power switch 1 is depressed, a power supply switch state signal 4 of an output of an inverter 3 goes to high. The 1st FF7 is set at the leading of the high signal via a gate 5, a Q output 11 goes to high and a Q' output goes to low. On the other hand, the 2nd FF8 keeps the preceding state. A Q output of the 1st FF7 is a power supply output 14 to the load circuit 15 via a gate 13. When the power supply is started to the load circuit 15, an oscillating signal output 20 is outputted from an oscillating circuit 16 and applied to gates 21, 22. An output of the gate 22 is high continuously when a hand is detached from the power switch 1 to be OFF, while an output of an inverter 24 is low continuously, then the 3rd FF23 is triggered to be set, and its output Q goes to high. Thus, the 2nd FF8 is set.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power supply circuit that controls power supply to a load circuit using a single momentary switch.

[Technical background of the invention and its problems]

Conventionally, various electronic devices have used a toggle switch or a combination of a momentary switch and a latching fritz flop as a power switch. Although toggle switches have excellent reliability, they are unsuitable for relatively shaped devices such as electronic thermometers due to the space they occupy and operability, and it is also difficult to make them waterproof.

Therefore, in a plate device such as a waterproof electronic body temperature IL, it is desirable to use a momentary switch such as a rubber switch as a power switch. When using a momentary switch, separate switches are normally used for powering on and powering off, but in that case, there are naturally two switch knobs, which saves space. Therefore, it is conceivable to use a single montage switch and use a logic circuit mainly consisting of flip-flops to alternately turn the power on and off each time the switch is pressed. However, momentary switches such as rubber switches are generally prone to chattering, so it is difficult to turn the power on and off reliably with a single switch. There is a risk of failure. The same goes for turning off the power; even if you press the switch and it turns off temporarily, the power will turn back on again when you release your hand.

[Object of the Invention] An object of the present invention is to provide a power supply circuit that can reliably turn on and off the power supply using a single momentary switch without being affected by chattering.

[Summary of the invention]

The present invention is directed to a load circuit that includes an oscillation circuit, or a circuit that has a function of outputting an oscillation signal when a smear source is supplied, and supplies power to this load circuit when in a set state. 1st. By providing a second flip-frog and controlling the states of these flip-frogs according to the state of the power switch and the state of the oscillation signal output from the load circuit, the third flip-frog can eliminate the influence of chattering of the power switch. It was absorbed.

That is, when the power switch is turned on for the first time, the first flip-frog is set and power supply to the load circuit begins, and then, after chattering, when the power switch is continuously turned off, the third flip-frog is set. The flip-flop and the second 7 lip-flops are sequentially set. On the other hand, when the power switch is turned on again to stop the power supply, the first 7 flip-flops and the third flip-flop are sequentially reset, and then, after chattering, the power switch is continuously turned off. The third flip-flop is in the set state, the second flip-flop is in the reset state, and the power supply is stopped. .

〔Effect of the invention〕

According to this invention, since a momentary switch with a power supply switch is sufficient, it is suitable for small devices such as electronic thermometers or pocket calculators, and is also suitable for turning on and off the power supply without being affected by chattering. It becomes possible to perform the off operation reliably.

Since the power supply circuit according to the present invention uses the output of the flip-flop as the power supply output, it cannot obtain a large amount of power, but it can be sufficiently used as a power supply circuit for 0M08 circuits and the like.

[Embodiments of the invention]

In FIG. 1, 1 is a power switch, and a momentary switch, for example, a rubber switch as shown in FIG. 2, is used. This has electrodes 31 and 32, which serve as contacts 1h and lb, formed on a substrate 30, and a rubber knob 33 placed above them. 31 and 32, and the switch is turned on.

One contact 1b of switch 1 is grounded, and the other contact 1b
Connected to power supply +VceK via aFi resistor 2,
The state signal of the switch 1 is taken as the output 4 of the inverter 3, and this signal 4 is passed through the NAND gates 5, 6 to the first . This becomes the input to the second 7-lip flop f7,8. 1st
The flip-flop 7 is constituted by a NAND gate 7ae7b, and the second 7-rig float f8 is constituted by a NAND gate 8a*8b, and the @power clear circuit 9, which is an R-8 type fritz, 1. It generates an initial power clear signal 10 to reset the second flip-flop circuits 7 and 8 when a battery is attached.

1st. Q output of second '7 rig 70 tube 7.8 11.
12 are combined by a NOR gate 13 and become a power supply output 14 to a load circuit 15. The load circuit 15 is, for example, a body temperature measurement circuit in an electronic thermometer using an oscillation frequency comparison method;
It includes an oscillation circuit 16. Note that the output 14 of the NOR gate 13 is also given to the power display LED 19 via the inverter 17 and the LED driver 18.The oscillation signal output 20 of the oscillation circuit 16 is AND ) Through the dart 22, it is logically processed with the state signal of the power switch 1 appearing at the output 4 of the inverter 3, and becomes the trigger input of the third flip-flop 23 of the J- type. This flip flop 2
3, the power switch status signal 4 is applied to the reset terminal via the inverter 24, so that the power switch 1 is activated.
It is set to be reset every time it is turned on.

The AND gate 25 and the NAND gate 26, 27 select the first 7 rigs based on the output of the third 7 rig 70 rig 23. This is for controlling the second 7-lip flop f7.8.

Next, the operation of this embodiment will be explained. In the initial state, as described above, the initial AI power rear signal 10
By 1st. The second flip-flops 7, 8 are reset and their Q outputs 11, 12 are both L'' (low level)
, 100 outputs 28 and 29 are both in the "H" (high level) state. If the power switch 1 is pressed in this state, the power switch state signal 4Fi of the output of the inverter 3
It becomes "H". However, in reality, due to chattering, the power switch status signal 4 irregularly repeats the 'H' and It L' states as shown in period A in FIG. At this time, at the first rise of period A, the first 7
Lip-flop 7 is set and Q output 11 is °'H”
1, -Q output becomes L#. On the other hand, the second flip-flop 8 maintains its previous state. 1st 7 lip 70, f
The Q output (“H”) of 7 becomes the power supply output 14 to the load circuit 15 via the dart 13. Note that during period A, the reset state is maintained because the power switch operation signal 4 is reset via the inverter 24 at the start-up point indicated by the arrow in FIG. 3 (, ).

When the load circuit 15 starts being supplied with power as shown in FIG. 3(b), the oscillation circuit 16 outputs an oscillation signal output 20, which is supplied to darts 21 and 22. When the power switch 1 is removed and turned off and enters the period B shown in FIG. IL continuously
Since the signal becomes L#, the third flip-flop f23 is triggered and becomes set. The output becomes tHH. As a result, the output of the output 25 becomes Hs, the output of the gate 26 becomes '°L#', and the second 7-lip 7-day knob 8 is set. This second 7 trip 0. Q output of step 8 (
PaH”) is the Q of the first flip-flop 7 on dirt 13
Combined with the output, the power supply output to the load circuit 15 and the body temperature measurement are performed.

After the user reads the body temperature measurement result, when the user presses the power switch 1 again, the power switch status signal 4 is displayed as shown in FIG.
), as in period A, ``H#'' and ttL# are repeated due to chattering. In this case, at the first rising edge of the power switch status signal 4, the first 7 Lips 70 and f7 are reset, and the third 7-lip flop 23 is also reset. After period C, when the tab stain source switch 1 is released, the third While the 7 lip flop fzs is in the set state, the Q output ('H') of the 7 lip flop 23 at this time also resets the second 7 lip flop 8 via the gate 27yk. As a result, the output of the gate 13 becomes °'L'', and the load circuit 1
The power supply to s will be cut off.

In this way, even if there is chattering in the power switch 1, each time the power switch 1 is pressed and then released, the power is alternately supplied and turned off correctly.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, the first embodiment. A means for resetting the second seven rigs 70f after a certain period of sowing, such as by a timer, may be added. Furthermore, the power supply circuit according to the present invention is not particularly limited to electronic thermometers, but may be applied to any device that includes a circuit that starts oscillation when power is supplied. Furthermore, as long as the power switch is a momentary type, it is also effective to use something other than a rubber switch.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a power supply circuit according to an embodiment of the present invention, FIG. 2 is a sectional view of a rubber switch used in a power switch, and FIG. 3 is an explanatory diagram of the operation of the embodiment. DESCRIPTION OF SYMBOLS 1...Power switch, 7...First 7-lip flop, 8...Second 7-lip flop, 15...Load circuit, 16...Oscillation circuit, 23...Third flip-flop 70 Tuzo.

Claims (1)

[Claims] In a circuit that uses a single momentary switch as the power switch and supplies power to a load circuit including an oscillation circuit,
The first one supplies power to the load circuit when in the set state. The second FreeResofurotsuno and these first. second 7
A third control unit that controls the state of the trigger according to the state of the power switch and the oscillation signal output state of the load circuit.
The first 7-rig flip-flop is in a set state and a reset state, respectively, depending on whether the second flip-flop is in a reset state or a set state when the power switch is turned on. The second flip-flop is set in the set state and the reset state, respectively, depending on whether the #441 7-lip frog is in the set state or the reset state when the third 7-lip frog is in the set state. The third fritsuno flop is placed in a set state when the power switch is turned off while the load circuit receives power supply and outputs an oscillation signal, and
A power supply circuit characterized in that it is configured to be reset each time a power switch is turned on.