JPS60100936A - Electronic hemomanometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic blood pressure monitor that piezoelectrically converts the pressure of a cuff for ischemia.

Recently, it has become common for individuals to routinely measure blood pressure at home. For this reason, in place of conventional devices that measure blood pressure using a mercury pressure gauge and a stethoscope, electronic blood pressure monitors have been commercialized that can measure blood pressure by signal processing using an electronic circuit using a piezoelectric transducer and a microphone. However, conventional electronic blood pressure monitors are large in volume and weight and cannot be easily carried by individuals.In order to meet these demands, it is necessary to further reduce the size and weight of electronic blood pressure monitors.

By making full use of current integrated circuit technology, the number of parts can be reduced, and the circuit system can be made low-power and low-voltage. This means that the circuit can be powered by a small battery, making electronic blood pressure monitors even smaller and smaller.
It is possible to make it lighter.

However, in blood pressure measurement systems that use batteries and are driven at low voltage, the inrush current that occurs when the power switch is turned on to perform measurements causes the battery voltage to drop momentarily, causing malfunctions in the blood pressure detection function and logic operations. Problems such as malfunction or stoppage of functions occur. In particular, in blood pressure measurement systems that reduce the number of batteries and drive at low voltages with the aim of reducing size and weight, the permissible range of power supply voltage fluctuations is narrow, so the adverse effects of the above-mentioned inrush current appear more prominently.

The present invention has been made in view of the above-mentioned problems, and is intended to prevent the rush current that occurs when the power switch is turned on, and to solve problems such as malfunctions and inoperability of electronic blood pressure monitors.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a block diagram showing a conventional blood pressure measurement system of an electronic blood pressure monitor. Battery 1 is used as the power source for the circuit. A silver battery, a lithium battery, or a small alkaline manganese battery is used as the battery 1, which is small and lightweight. 2 is a Korotkoff sound discrimination circuit, based on the Rybarotchi-Korotkoff method, which discriminates only Korotkoff sounds from the pulse sounds, Korotkoff sounds, and noises collected by microphone 3 on the distal side of the area of ischemia caused by the cuff, and shapes the waveform. give a signal. A piezoelectric conversion element 5 piezoelectrically converts the pressure of a blood ischemia cuff (not shown) wrapped around the upper arm of the subject and outputs it as an analog electrical signal.

The output of the piezoelectric transducer 5 is input to the blood pressure measurement circuit 4, where it is amplified and then A/D converted and output as a digital signal.

Reference numeral 6 has a logical operation circuit, into which the output signals of the Korotkoff sound discrimination circuit 2 and the blood pressure measurement circuit 4 are input, performs predetermined logical operations, outputs information such as systolic and diastolic blood pressure values, pulse rate, etc., and receives this information. It is displayed on the display section 7.

The Korotkoff sound discrimination circuit 2, blood pressure measurement circuit 4, logic operation circuit 6, and display section 7 described above are connected to the battery 1 via a power switch circuit 9. In the following description, the power switch circuit 9 is implemented using a bipolar transistor, but it may also be a MOS transistor, another switch element, or a bipolar transistor.
It can also be configured by a combination of these.

The base of the bipolar transistor 9 for the power switch is connected to one terminal of a switch 11 via a current limiting resistor 10. The other terminal of switch 11 is connected to the battery. In the following explanation, the terminal of the switch 11 is connected to the positive side of the battery, but the terminal of the switch 11 is connected to the positive terminal of the battery.
It may be connected to the negative electrode side of the battery, depending on the polarity of the element used for this purpose and whether the power switch circuit 9 is placed on the positive or negative electrode side of the battery.

The capacitor 8 is connected between the power supply terminals of the circuits, as shown, in order to absorb the power supply noise applied to the various circuits of the Korotkoff sound discrimination circuit 2, the blood pressure measurement circuit 4, the logic operation circuit 6, and the display section 7. To avoid cluttering the diagram, only one capacitor is shown, but it is preferable to connect one capacitor to each circuit.

When using an electronic blood pressure monitor with the above circuit configuration,
First, when the switch 11 is turned on to power on the circuit, the base current of the bipolar transistor 90 flows through the current limiting resistor 10, and the bipolar transistor 9
becomes conductive. The bias between the collector and emitter of the bipolar transistor 9 is caused by the short-circuit current of the capacitor 8 and the Korotkoff sound discriminator circuit 2 at the moment it becomes conductive.
The blood pressure measurement circuit 4 and the logic circuit B become unsaturated due to the current flowing through them, etc. After that, the capacitor 8 is charged, and when there is no more current flowing through the circuit, the circuit enters a saturated state. 5- It stabilizes at a predetermined bias value.

The inrush current that instantaneously flows between the power supplies in the follicle state described above is a large current that is 10 to 100 times the normal operating current, considering the variation in the constants of the circuit elements used. Furthermore, since batteries have internal impedance (several ohms to several 100 ohms),
The output voltage of the stain pond decreases significantly due to the rush current.

FIG. 2 shows the experimental results of battery output voltage fluctuations before and after turning on the power switch. The battery is a lithium battery (open circuit voltage 3.
The normal operating current of the blood pressure monitor was about 500 μA, and the peak value of the rush current was about 50 mA.

When the switch 11 was turned on at time T1, the amount of voltage drop was about 0.5V, and the voltage recovery time was about 0.5μ.

This battery voltage fluctuation causes malfunctions of the Korotkoff sound discrimination circuit 2 and blood pressure measurement circuit 4, and also causes problems such as malfunctions of the memory and logic circuits inside the logic operation circuit 6, and malfunctions or stoppage of the reference clock. The above-mentioned trouble becomes more and more noticeable as the internal impedance of the battery increases at the end of the battery's life or under low-temperature environments.

FIG. 3 is a block diagram showing one blood pressure measurement system of an electronic blood pressure monitor according to the present invention. Components that are the same as those in FIG. 1 are given the same numbers, and explanations of their operations will be omitted.

In FIG. 3, a capacitor 12 is connected to the base of the bipolar transistor 9 as a measure to prevent inrush current.
Connect between emitters.

As a result of arranging the capacitor 12, the circuit operation will be explained as follows. When the switch 11 is turned on, the base current of the bipolar transistor 9 gradually flows in a large amount with a time constant determined by the resistor 10 and the capacitor 12, and for a time t until it reaches a predetermined value, the bipolar transistor 9 , Since the base current is narrowed to a small value, the collector current is limited and inrush current is suppressed. Then, the transistor 9 slowly charges the capacitor 8 and shifts to a saturated state, and stabilizes at a predetermined bias value at time t3. If the time constant determined by the capacitor 12 and the resistor 10 is selected so that t>ts, the inrush current can be completely prevented.

FIG. 4 is a block diagram showing another blood pressure measurement system according to the present invention. Components that are the same as those in FIG. 1 are given the same numbers, and explanations of their operations will be omitted. FIG. 4 shows an example in which a capacitor 13 for preventing rush current is connected between the base of the bipolar transistor 9 and the positive electrode of the battery 1. The explanation of the operation will be omitted since it is the same as the embodiment shown in FIG.

FIG. 5 is a block diagram showing another embodiment according to the present invention. Components that are the same as those in FIG. 1 are given the same numbers, and explanations of their operations will be omitted.

The embodiment shown in FIG. 5 is a circuit block in which the logic operation circuit 14 performs calculations related to blood pressure and other functions such as a clock.

The logic operation circuit 14 and the display section 15 are connected directly between the positive and negative poles of the battery 1 without going through the power switch circuit 9, since they need to operate at all times in order to perform a clock function, for example. In this case, the logic operation circuit 14 has C! A MOS circuit and a liquid crystal display for the display section 15 are suitable for battery-driven systems that require low voltage and low power.

Further, the switch 16 is connected to one electrode of the battery and one input terminal of the logic operation circuit 14. The switch opening/closing information is subjected to signal processing within the logic operation circuit 14, outputted from one output terminal of the logic operation circuit 14, and transmitted to the base of the bipolar transistor 9 via the current limiting resistor 17.

The inrush current generation mechanism in this circuit is the same as that in the circuit shown in FIG.

To prevent inrush current, the capacitor 18 is a bipolar transistor? connected between the base and emitter of The operation is the same as the embodiment shown in FIG. 3, and will therefore be omitted.

FIG. 6 is a block diagram showing another embodiment according to the present invention. Components that are the same as those in FIG. 5 are given the same numbers, and a description of their operation will be omitted.

The circuit shown in Fig. 6 is a circuit in which the connection position of the capacitor 18 used in Fig. 5 has been changed, and the capacitor 19 for inrush current prevention is
is connected between the base of bipolar transistor 90 and the positive electrode of the battery. Operation Theory-9 = Light is the same as in Figure 5, so it is omitted.

The circuit configuration and rotational operation described above can completely prevent inrush current that occurs when the power is turned on in the blood pressure measurement system of the electronic blood pressure monitor.

As described above, according to the present invention, the inrush current that occurs when the electronic blood pressure monitor is turned on can be completely eliminated with a small number of parts, so low voltage drive is possible, and a small and lightweight electronic blood pressure monitor can be used. Can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional blood pressure measurement system of an electronic blood pressure monitor. FIG. 2 is a diagram showing battery voltage fluctuations before and after power-on. FIG. 3 is a block diagram of a blood pressure measurement system according to the present invention. FIG. 4 is a block diagram showing another blood pressure measurement system according to the present invention. FIG. 5 is a block diagram showing another blood pressure measurement system according to the present invention. -10- FIG. 6 is a block diagram showing another blood pressure measurement system according to the present invention. l't>a2\...Korotkoff sound discrimination circuit 3...Microphone 4...Blood pressure measurement circuit 5...
Piezoelectric conversion element 6...Logic operation circuit 7...Display section
14...Logic operation circuit 15...Display unit 8...Capacitor 10...Current limiting resistor 9...Power switch circuit 17...Current limiting resistor 11...Switch 1
2.13, 18.19 ... 16... Switch
...Inrush current prevention capacitors and above Applicant Seiko Electronics Co., Ltd. Agent Patent attorney Tsutomu Mogami-11- Tadaka Soda

Claims (2)

[Claims] (1) In an electronic blood pressure monitor consisting of a measuring means for electrically measuring blood pressure, a display, and a power switch circuit that supplies power supply voltage to the blood pressure measuring means and display, the power switch circuit when the power is turned on. An electronic blood pressure monitor characterized by gradually increasing conduction current. (2) The electronic blood pressure monitor according to claim 1, characterized in that an integrating circuit consisting of a resistor and a capacitor is connected to the input section of the power switch circuit.