JPS6037077A - Multiplying circuit - Google Patents

Abstract

PURPOSE:To obtain an output being proportional to the product of a pulse frequency and a DC voltage by scanning an output voltage by a prescribed period, whenever a pulse is inputted, comparing a scanning output and an input DC voltage, and integrating its output. CONSTITUTION:The output pulse S1 of a feed water sensor 9 is converted to the output pulse S2 of single width by a monostable multivibrator 12, and provided to a voltage scanning circuit 43. The output signal S3 of the circuit 43 is compared with a DC voltage Vdeg generated by a temperature difference detecting circuit 30 by a comparator 44, and its output signal obtains the shape which repeats an inversion between the first level and the second level. When the output signal Vy of the comparator 44 is inputted to an average value circuit 14, an average output voltage signal Vy (avg.) is obtained in an output terminal T0. For instance, when a flow rate, and a temperature difference between a set temperature and a feed water temperature are denoted as L and DEG, respectively, Vy (avg.)proportional L.DEG is obtained, and the average output voltage signal Vy (avg.) is proportional to the product of the flow rate L and the temperature difference DEG.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a multiplier circuit, and more particularly to a multiplier circuit that obtains an output proportional to the product of a q-independently variable frequency and a direct current voltage.

The need to obtain an output signal proportional to the product of the input frequency and DC voltage can be seen, for example, in the combustion amount control of instantaneous water heaters and water heaters.

In conventional water heaters of this type, the temperature of the hot water actually dispensed, that is, the hot water temperature, can be controlled to be equal to the set temperature set by the user. , k6'lJJ temperature is detected and compared with the set temperature to perform a predetermined calculation, and based on the resulting signal value, a proportional control electromagnetic-f placed in the fuel supply path is activated.
There was a j method to control t.

However, if the control method is based solely on the difference between the hot water supply temperature and the set temperature, the hot water supply temperature will increase and when the hot water supply capacity of the water heater is exceeded, the hot water supply temperature will drop significantly. Further, there is a drawback that if the amount of hot water to be supplied changes rapidly, the temperature of the hot water to be supplied also fluctuates considerably, which can lead to a dangerous situation, especially when using a shower or the like.

Therefore, in order to eliminate this defect, instead of simply monitoring the hot water temperature, the flow rate and temperature of the water entering the water heater, that is, the values of both the water supply amount and the water supply temperature, are separately detected. From these two values, the combustion amount = (water supply amount) Products that attempt to control water temperature and reduce the drop and fluctuation of hot water temperature are beginning to appear on the market. In addition, water supply; 1
: and the amount of hot water supplied are substantially the same, so in the above equation, the amount of water supplied may be read as the amount of hot water supplied.

However, in such products, the above-mentioned hot water supply, III
A speed-to-frequency conversion type detector is generally used to detect the water supply amount, while a temperature-to-resistance value or voltage conversion type detector such as a thermistor is used to detect the water supply temperature, similar to general temperature detection. used. Therefore, as mentioned at the beginning, a frequency and DC potential multiplier circuit is required in this type of combustion amount control circuit device.

The present invention has been accomplished with the object of making such a multiplication circuit inexpensive, simple, and easy to adjust. Here, a conventional example will be explained.

FIG. 1 shows a schematic diagram of a hot water supply apparatus. Water to be circulated is supplied into the apparatus from a water supply port 1, passes through a heat exchanger 2, and is supplied from a hot water supply port 3. The gas in this case as fuel is supplied from the gas pipe 4 to the gas proportional control solenoid valve 5.
The heat exchanger 2 is heated by the heat exchanger 2. The water supply amount is detected by a water supply amount sensor 9 and is generally converted into the form of a pulse frequency. On the other hand, the water supply temperature is detected by the water supply temperature sensor 11 of the resistance value to voltage value conversion type, such as the above-mentioned thermistor. Further, the temperature of the hot water that is actually dispensed is detected by a hot water supply amount sensor 7.

The combustion amount control circuit 8 issues a control signal according to the control mode already described, and controls the gas proportional electromagnetic control valve 5 and the hot water supply amount adjusting valve 10 provided in the hot water supply path.

However, the structure of the multiplication part in the combustion amount control circuit 8, which is related to the above-mentioned conventional improvements, is as shown in the second figure.

The output pulse of the water supply amount sensor 9, which is supplied with power from the power source 13, is shaped into a waveform by the monostable multivibrator 12, and is made into a stable output pulse with a single width. This pulse frequency F (Hz) is therefore proportional to the water supply amount L (17 minutes).

Focl, (1) This pulse frequency signal is manually input to the subsequent average value circuit 14, and is made into a temporally averaged DC potential signal Vl. The configuration of the average value circuit 14 is a common integration configuration, and includes an operational amplifier 25 as an integral part having a resistor 23 and a capacitor 24 as time constant elements, and an amplifier that appropriately amplifies the output signal potential. It consists of an operational amplifier 28.

Therefore, this average value circuit output voltage v1 is proportional to the input pulse and, of course, also proportional to the flow rate.

VlocF --- (2) VlocL --- (3) This output voltage v1 is then input to the analog multiplier IC 32.

On the other hand, the difference between the set temperature set by the user and the feed water temperature detected by the feed water temperature sensor 11 is detected by the temperature difference detection circuit 30, changed to a DC voltage, and outputted.
2. It is given to the power of others ■. Assuming that this voltage is Vdeg and the temperature difference between the set temperature and the water supply temperature is DEC, the following equation is naturally satisfied.

Vdeg father DEG (4) Note that the proportional constant in equation (4) is the potentiometer (29,
31).

As is well known, the analog multiplier 1032 is provided with a group of variable resistors 33', 34, 35, etc. for off-cent adjustment, and by appropriately adjusting these, the output terminal TO of the analog multiplier IC 32 can be An output voltage Vx appears that is proportional to the product of the voltages applied to the input terminals.

VxccVdeg-Vl ---...-(5) Therefore,
The voltage Vz generated at the control signal output terminal To is as described in (3) above.
, (4), it is proportional to the water supply amount (hot water supply amount) L and the temperature difference DEC between the set temperature and the water supply temperature.

VzecL-DEG ---・--(8) Once the desired signal is obtained in this way, use the operational amplifier 36 as appropriate.
Process this signal to an appropriate voltage value range through
It can be used for control as described above.

In such conventional circuits, by using an analog multiplication TO, the offset adjustment and gain adjustment are performed with variable resistors, so the calculation accuracy is relatively good and the number of parts is small. The disadvantage is that the work of adjusting the variable resistor to achieve accuracy is extremely troublesome, and the unit cost of the analog multiplication IC is extremely high.

As mentioned earlier, the present invention was made to eliminate the drawbacks of these conventional circuits, and it makes the multiplication circuit itself necessary for this type of component with advanced control capabilities inexpensive, and it can be used in various applied products. The objective is not only to popularize the system, but also to provide a circuit configuration that can avoid troublesome adjustment work as much as possible.

FIG. 3 shows a preferred embodiment of the present invention applied to the combustion amount control of the water heater described above. The same reference numerals as in FIGS. 1 and 2 indicate components that are the same or functionally equivalent to the corresponding components in the conventional example.

In the circuit of the present invention, the circuit operates every cycle synchronously with respect to the output of the monostable multivibrator 12 that generates a single-width output pulse synchronized with the output pulse of the water supply amount sensor 9. One of the features is that it includes a voltage scanning circuit 43 that changes the amplitude with respect to time. For example, a typical example of such a circuit is a tornado wave generation circuit. That is, it is a circuit that increases or decreases the output voltage from a reference potential to another potential at a predetermined speed every time it is triggered. This circuit will also be used in this embodiment of the invention for simplicity.

FIG. 4 shows the waveform of the main part of the circuit shown in the third diagram, while (A) shows the waveform of the water supply amount signal S1 detected by the water supply amount sensor 9, and (B) shows the waveform of the water supply amount signal S1 detected by the water supply amount sensor 9. converted into a sufficiently narrow trigger pulse shape by the stable multivibrator 12,
However, the frequency information is the same signal S2 as that of the water supply amount sensor.
The waveform is shown.

Accordingly, in this embodiment, the waveform of the output signal S3 of the above-mentioned tornado wave generation circuit 43 is triggered every time the output pulse of the monostable multivibrator 12 is generated, and reaches a specific potential Vo consisting of a reference potential of zero. It is of a type that linearly scans and varies the voltage oscillation 111.

This signal S3 is connected to the DC voltage Vdeg generated by the temperature difference detection circuit 30, which may be similar to the conventional example described above, and the comparator 44.
(see FIG. 4(G)), so the comparator 44
As shown in FIG. 4 (II), the output signal waveform Vy of is inverted repeatedly between the first level and the second level depending on the voltage Vdeg at each time. In this case, the first level is zero potential and the second level is voltage vO.

Similarly, the following relationships can be derived from each figure in Figure 4.

Assuming that the period of the output pulse generated by the monostable multivibrator 12 is t, this period is inversely proportional to the frequency F of the input signal pulse, and thus to the flow rate.

tc-:l/F (7) tOc1/L (8) On the other hand, as the temperature difference DEC between the water supply temperature and the set temperature changes, the temperature difference detection circuit 30 DC voltage Vde generated by
If g fluctuates, the inversion threshold Vdeg of the comparator 44 will fluctuate as is obvious from FIG. Become something.

Tlcl: VdegocDEG (8) Therefore, when the output signal VT of the comparator 44 is input to the average value circuit 14 and its time average is taken, the average output voltage signal Vy (avg , ) can be expressed by the following equation, with the peak value of the input signal vy being Vo as described above.

......(lO) By substituting the above-mentioned equations (8) and (9) into this equation (10), we get Vy(avg,)oc L -DEC--・--(11
), and the above (6) was created based on the conventional example circuit system.
A similar result is obtained as in Eq. That is, the signal Vy(avg,) appearing at both ends of the load RL has the same control information as the previous control signal Vx.

In this embodiment, the multiplication circuit of the present invention was applied to the multiplication part necessary for controlling the combustion amount in the water heater.
The pulse frequency signal Sl generated by the sensor 9 is generally treated as a frequency signal whose value fluctuates, and the DC voltage signal PyVdeg generated by the temperature difference detection circuit 30 is also generally treated as a DC voltage signal whose value fluctuates. For example, it can be seen that the multiplier circuit of the present invention is a circuit that can realize an output proportional to the product of a frequency and a DC voltage that vary independently from each other without using an analog multiplier IC that is expensive and difficult to adjust.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a device for controlling the amount of combustion in a water heater as an example of a case where it is necessary to obtain an output proportional to the product of a mutually varying frequency and a DC voltage, and Fig. 2 is a diagram of the device shown in Fig. 1. FIG. 3 is a schematic configuration diagram of the main part of a combustion amount control circuit conventionally used in a combustion amount control circuit, FIG. 3 is a schematic configuration diagram when an embodiment of the present invention is applied to a combustion amount control circuit, and FIG. This is an explanatory diagram of the operation. In the figure, 1 is a water supply port, 2 is a heat exchanger, 3 is a hot water supply port, 5 is a gas proportional control solenoid valve, 6 is a burner, 7 is a hot water supply temperature sensor, 8
9 is a combustion amount control circuit, 9 is a water supply amount sensor, 10 is a flow rate control valve, 11 is a water supply amount sensor, 12 is a monostable multi-pie break, 14 is an average value circuit, 32 is an analog multiplication IC 14
3 is a voltage scanning circuit, and 44 is a comparator.

Claims (1)

[Scope of Claims] A multiplier circuit that receives a frequency signal and a DC voltage signal again and generates an output proportional to the product of the frequency and DC voltage, comprising: ``a multiplier circuit that receives a frequency signal and a DC voltage signal again, and generates an output proportional to the product of the frequency signal and the DC voltage; a monostable multivibrator that outputs a pulse signal of a constant width for each cycle; and -ff of the output pulse of the monostable multivibrator.
A voltage scanning circuit that scans the output voltage at a constant cycle every time address i is input; a comparator that compares the output voltage of the voltage scanning circuit with the input DC voltage; and an average value circuit that integrates the comparator output. A multiplication circuit characterized in that it obtains an output proportional to the product of the frequency and the DC voltage from the output of the average value circuit.