JPS5832979A - Driving circuit for electromagnetic pump - Google Patents

Abstract

PURPOSE:To heighten the accuracy of control, by composing a driving circuit of a semiconductor element connected to an electromagnetic pump, a current detecting resistor, a reference voltage source and a comparator for cutting off an input signal to the semiconductor element. CONSTITUTION:When an input signal Vin is supplied, it is impressed on the inverting input terminal of a voltage comparator U2 through a transistor Q3 so that the comparator sends out an output signal of positive voltage to turn on the transistor Q3. As a result, a transistor Q1 is also turned on to supply a driving current IL to an electromagnetic pump SOP. When the driving current IL has increased over a prescribed value and the output voltage VR of a resistor R1 has exceeded a reference level Vref, the output signal of the voltage comparator U2 is inverted from the positive voltage to negative one to turn off a transistor Q2. Consequently, the transistor Q1 is also turned off.

Description

[Detailed description of the invention] The present invention relates to a drive circuit for an electromagnetic pump.

Conventionally, electromagnetic pumps are often used in devices that supply fluids etc. to match the target value. (2) A current control method that controls the drive current for the electromagnetic pump according to a target value.

However, the former voltage control method has the problem that the resistance value of the electromagnetic pump fluctuates depending on the ambient temperature and its own heat generation, making it impossible to perform highly accurate control. On the other hand, the latter current control method is widely used because it does not have the above-mentioned problems, but if the power supply voltage is increased to overcome the start-up characteristics of the electromagnetic voice pump, the drive current cannot be transmitted. This has disadvantages in that heat is generated in the transistor, the heat dissipation fin becomes larger, and reliability decreases.

That is, an example of conventional current control type driving is shown in FIG.

In FIG. 1, the electromagnetic pump 80F has a transistor Q.
A resistor R1 for detecting the drive current IL is connected between the emitter of the transistor Ql and the ground potential terminal. The base input of the transistor Q1 is supplied with an output signal of a differential amplifier U1 having the input signal Vln and the voltage VB (=IL-&l) between the terminals of the resistor R1 as differential inputs, and the electromagnetic pump 80P
, it is configured to supply a constant drive current It expressed as .

However, in such a drive circuit, the inductance component of the electromagnetic pump causes a delay in the rise time of the drive current, resulting in poor start-up characteristics of the electromagnetic pump and causing errors in control accuracy.

Therefore, if the power supply voltage of the electromagnetic pump is increased to solve this problem, since the transistor Ql is used in the proportional operation region, the multiplication value of the emitter-collector saturation voltage VOIC of the transistor Ql and the drive current IL “V.
OIC and ILJI generate a large amount of heat, the heat dissipation fins become larger, and the reliability decreases.

The present invention has been made in order to solve the above-mentioned drawbacks, and its purpose is to build an electromagnetic pump drive circuit that can suppress heat generation of the transistor that sends the drive current even if the power supply voltage of the electromagnetic pump is increased. Our goal is to provide the following.

For this reason, the electromagnetic pump drive circuit according to the present invention is configured to stop sending out the drive current when the drive current value when driving the electromagnetic pump reaches a predetermined value.

In other words, a semiconductor element that sends out a drive current is turned on and off at high speed in a self-exciting manner within a range in which a drive current value equal to or higher than a certain value is ensured.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 2 is a circuit diagram showing an embodiment of the present invention, and the electromagnetic pump SOP has a transistor Ql that sends out a drive current.
are connected in series, and a current detection resistor R1 that outputs a voltage signal VB proportional to the drive current IL is also connected in series. The output voltage Vm of the resistor Ri is input to the inverting input terminal of the voltage comparison @U2 via the resistor Rs. This voltage comparator U2 detects that the output voltage Vm of the resistor R1 has exceeded a predetermined value and makes the transistor Q1 non-conductive, and has a variable resistor V at its non-inverting input.
A reference voltage Vref set by B is inputted, and its output is inputted to the base of the transistor Qs+. On the other hand, a resistor R8 is connected to the inverting input terminal of the voltage comparator U2.
and a pulsed input signal T through the transistor Qs.
in is supplied. Transistor Q! l is conductive when the output signal of the voltage ratio softener U2 is a positive voltage, making the transistor Qr conductive; conversely, when the output signal of the comparator U2 is a negative voltage, it is non-conductive and makes the transistor Ql conductive. be. Note that a freewheeling diode DI is connected in parallel to the series circuit of the electromagnetic pump 80F and the resistor R1.

In such a configuration, when the input signal Vin is supplied, this input signal Vin is applied to the inverting input terminal of the voltage comparison @U2 via the transistor Qs. This causes voltage comparator U2 to send out a positive voltage output signal, causing transistor Qs to conduct. As a result, the transistor Ql also becomes conductive, and the drive current IL is supplied to the electromagnetic pump 80F. When the drive current It exceeds a predetermined value and the output voltage Vn of the resistor R11 exceeds the reference voltage Vref, the output signal of the voltage comparator U2 is inverted from a positive voltage to a negative voltage, and the transistor IQs is turned off. Let it be. Along with this, the transistor Ql also becomes non-conductive. 2. In other words, when the input signal Vin holds a voltage value that drives the electromagnetic pump 80F, the voltage comparator U2 outputs an output signal every time the output voltage VB of the resistor R1 reaches the predetermined value Vref. Invert. Then, after the transistor Ql becomes non-conductive, when the drive current IL from the freewheeling diode DIK falls below a predetermined value and the output voltage VB of the resistor R1 falls below the reference value Vref, the voltage comparator U2
The output signal becomes a positive voltage again, making the transistor Ql conductive and sending out the drive current IL. As shown in the waveform diagram of FIG. 3(a), Φ), when the input signal Vin maintains a voltage value that drives the electromagnetic pump 80P, the transistor Ql increases the drive current It.
It is turned on and off in a self-exciting manner every time the current exceeds the current value It,o defined by the reference voltage vref. Note that the on/off period of the transistor Ql is determined by the slew rate of the voltage comparator U2, the inductance component of the electromagnetic pump 80P, and the like. Therefore, compared to the case where the drive current It continues to flow while the input signal Min maintains a predetermined voltage value, the transistor Ql is switched at a high speed, so that heat generation can be suppressed. In this case, there is an advantage that sudden changes in the drive current It can be suppressed due to the inductance component of the electromagnetic pump SOP.

In the embodiment, the drive current IL is transmitted through a low-level transistor, but it may be a Darlington-connected transistor Q4 as shown in FIG. Further, as the transistor in this case, a bipolar transistor or a field effect transistor may be used.

As is clear from the above description, according to the present invention, it is possible to suppress the heat generation of the semiconductor element that sends out the drive current, so it is possible to increase the power supply voltage of the electromagnetic pump and improve the start-up characteristics. , control accuracy can be improved. Furthermore, there are excellent effects such as the ability to miniaturize the heat dissipation fins and miniaturize the circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional electromagnetic pump drive circuit, FIG. 2 is a circuit diagram showing an embodiment of the present invention, FIG. 3 is a waveform diagram for explaining its operation, and FIG. FIG. 3 is a circuit diagram showing another embodiment of the present invention. sop...electromagnetic pump, Ql, Ql, Q8゜Q4・
...Transistor, Rx, Rv, R@...0. resistance,
VB, ・Variable resistor, U2---・Voltage comparator. Patent applicant Yamatake Honeywell Co., Ltd. Agent Masaki Yamakawa (and one other person) Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a semiconductor element connected in series to the electromagnetic pump and supplying a drive current to the electromagnetic pump according to an input signal; and a semiconductor element connected in series to the drive current path of the electromagnetic pump and a voltage proportional to the drive current of the electromagnetic pump. A current detection resistor that outputs a signal, a reference voltage generation source that generates a predetermined reference voltage, and the output voltage of the current detection resistor and the reference voltage are compared, and when the former is greater than the latter, the output voltage for the semiconductor element is determined. An electromagnetic pump drive circuit comprising a comparison circuit that cuts off an input signal.