JPH0560103A - Driving circuit of duty valve - Google Patents

Abstract

PURPOSE:To perform stable opening and closing operation of a valve and also to reduce noise generation by magnetizing a solenoid quickly at the start of supplying a steady state magnetizing current through utilizing counter electromotive force energy induced in the solenoid due to break of an initial magnetizing current. CONSTITUTION:A magnetization compensating circuit C is made of a booster coil S1 and a switching circuit SW. The booster coil S1 stores the counter electromotive force energy produced in a solenoid S during the stopped period of the drive of a first switching element Q1. The switching circuit SW is driven by the energy stored in the booster coil S1 at the start of driving a second switching element Q2, and feeds an initial magnetizing current ia, which exceeds a steady state magnetizing current ib, into the solenoid S temporarily. Thus, the counter electromotive force is utilized effectively, and stable driving of the solenoid S is performed at the start of supply of the steady state magnetizing current ib, and in addition, since the counter electromotive force is absorbed and utilized by the booster coil S1, generation of noise is also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved duty valve drive circuit.

[0002]

2. Description of the Related Art Duty valves have been developed and used in which the flow rate of gas or liquid is finely controlled by adjusting the opening / closing duty ratio of the valve. Since a high-speed valve opening / closing control is required as compared with a conventional solenoid valve that performs control at a low speed, a unique driving method is adopted for energizing and driving a solenoid that opens / closes a valve.

FIG. 4 shows an example of such a duty valve drive circuit. As shown in the waveform diagrams of FIGS. 5A to 5C, the open duty t of the valve in one cycle T is shown. In the period ta in which the drive pulse A is output in the period of 1), the transistor Q1 that is the first switching element is turned on, the power source voltage V is directly applied to the solenoid S, and the initial excitation current ia is passed to output the drive pulse A. During the period tb during which the drive pulse B is output and the drive pulse B is output, the transistor Q2, which is the second switching element, is turned on so that the power source voltage V is applied to the solenoid S via the resistor R to supply the steady excitation current ib. In the initial stage of the valve opening duty t, the solenoid is rapidly excited by the initial exciting current ia to open the valve, and thereafter the valve is opened. Together thereby opening and closing the valve at a high speed by energizing the constant excitation current ib for lifting, is adapted to reduce power consumption to prevent burnout of the solenoid.

By the way, in such a duty valve drive circuit, a large counter electromotive force is induced in the solenoid S when the initial exciting current ia and the steady exciting current ib are cut off, as shown in FIG. Since the back electromotive force may destroy the drive transistors Q1 and Q2,
Normally, as shown in FIG. 6, a configuration in which a diode D for absorbing a back electromotive force is connected in parallel to a solenoid S is adopted. In this way, when the counter electromotive force absorbing diode D is connected, the counter electromotive force induced in the solenoid S is short-circuited via the diode D, as shown in (a) to (c) of FIG. The back electromotive force can be clamped to the forward voltage of the diode D (about 0.6 V for the junction type diode) to prevent the breakdown of the transistors Q1 and Q2.

However, in the circuit configuration shown in FIG. 6, every time the exciting current is interrupted, a part of the energy due to the exciting current becomes a counter electromotive force in the solenoid S, and as a result, a large current is instantaneously applied to the diode D. , The excitation energy of the solenoid S is unnecessarily lost, and the large current flowing through the diode D easily radiates noise.

In addition, since the current is limited by the current limiting resistor R when the steady exciting current is applied, the initial exciting current ia
When switching from to the steady excitation current ib, it takes time to excite the solenoid, and the level of the steady excitation current ia required to stably hold the once opened valve in the open state cannot be lowered. It was inconvenient and made circuit design difficult.

[0007]

SUMMARY OF THE INVENTION The present invention proposed in view of the above circumstances effectively utilizes the counter electromotive force energy induced in the solenoid when the exciting current is cut off, thereby stably and rapidly opening and closing the valve. It is an object of the present invention to provide a duty valve drive circuit that can be driven and that reduces noise generation.

[0008]

DISCLOSURE OF THE INVENTION The present invention, which is proposed to achieve the above object, provides a first exciting current.
Second switching element and a second energizing steady excitation current
In the duty valve drive circuit that switches the switching element of and drive the solenoid by energizing,
A boost coil that stores the counter electromotive force energy induced in the solenoid when the driving of the first switching element is stopped, and a boost coil that is driven by the stored energy of the boost coil when the driving of the second switching element starts to exceed the steady excitation current. It is configured such that an excitation compensating circuit including a switching circuit for temporarily energizing the solenoid with an exciting current is additionally connected.

[0009]

In the present invention, when the first switching element is turned on, the solenoid is supplied with an initial exciting current, and when the first switching element is cut off, the solenoid is cut off from the initial exciting current. The solenoid induces a back electromotive force, and this back electromotive force energy is stored in the boost coil of the excitation compensation circuit. On the other hand, at the same time when the conduction of the first switching element is cut off, the second switching element is conducted and the solenoid is energized with a steady exciting current. At this time, due to the energy accumulated in the boost coil of the excitation compensation circuit, When the switching circuit is driven and the initial excitation current is energized temporarily, and when the driving of the switching circuit is stopped, the steady excitation current is energized. As a result, the back electromotive force is effectively used, the solenoid is rapidly excited at the start of energization of the steady exciting current to perform stable solenoid drive, and the back electromotive force induced in the solenoid is absorbed and used in the boost coil. Noise is also reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit example of a duty valve drive circuit of the present invention. In the figure, a transistor Q1 which is a first switching element, a transistor Q2 which is a second switching element, and a duty valve (not shown) are opened and closed. Since the solenoid S to be driven is the same as the conventional one, the same reference numeral is given. S1 is a boost coil for storing the counter electromotive force energy of the solenoid S, and the transistors of Q3 and Q4 form a switching circuit SW that conducts by the stored energy of the boost coil S1 and supplies the power supply voltage V directly to the solenoid S. The boost coil S1 and the switching circuit SW form an excitation compensation circuit C. The diode D1 is provided to prevent the exciting currents ia and ib for the solenoid S from flowing to the boost coil S1 side, and to supply the current ir due to the counter electromotive force of the solenoid S through the boost coil S1. The diode D
Reference numeral 2 is a protection diode for preventing the back electromotive force of the solenoid S from being destroyed by being applied between the emitter and the base of the transistor Q3.

FIG. 2 is an equivalent circuit diagram of the duty valve drive circuit shown in FIG.
Q2 is equivalently shown as a switch that is closed and driven when the drive pulses A and B are input, and transistor Q4 is equivalently shown as a switch that is closed and driven by the energy stored in the boost coil S1. The operation of the drive circuit of the present invention will be described with reference to the drawings and the waveform diagrams of the respective parts shown in FIGS. 1 and 3A to 3H. When the drive pulse A falls to the "L" level for the time ta, the transistor Q1 becomes conductive, the power supply voltage V is applied to both ends of the solenoid S, and the initial exciting current ia is conducted for the time ta. The maximum value iamax of this initial excitation current ia
Is the inductance of the solenoid, and iamax = (V / L) × t from di = (V / L) dt
Therefore, the energy P accumulated in the solenoid S during the time ta is P = (1/2) × L × (iamax) ² = (1 / (2 ×
L)) × (V × ta) ² . ((A) of FIG.
(See (c) and (f)). When the time ta has passed and the conduction of the transistor Q1 is cut off, the solenoid S energizes the current ir through the diode D1 and the boost coil S1 by the counter electromotive force due to the energy P accumulated by the initial exciting current ia, and , Energy P to boost coil S1
Accumulate in. (See (a), (c), and (g) of FIG. 3). When the transistor Q1 is turned off, the transistor Q2 is turned on for a time tb, the power supply voltage V is applied to both ends of the solenoid S via the resistor R, and the steady excitation current ib is applied for a time tb. ((B) of FIG.
(See (d) and (f)). Further, when the steady excitation current ib starts to be energized, the back electromotive force of the energy stored in the boost coil S1 causes the transistors Q3 and Q4 of the switching circuit SW to be conductive for a time t1, and thus the transistor Q1 is conductive for a time t1. As in the case of
Is energized to the solenoid S for rapid excitation, and the time t
When 1 has elapsed and the transistor Q4 is turned off, the steady exciting current ib is entered. Since the impedance on the switching circuit SW side is lower than the impedance seen from the boost coil S1 to the solenoid S side, the stored energy of the boost coil S1 is supplied to the switching circuit SW side to drive the transistors Q3 and Q4 in conduction. To do.
(See (b), (d), (f) to (h) in FIG. 3). Further, when the transistor Q2 is turned off after the lapse of time tb, the energy P2 due to the steady excitation current ib accumulated in the drive coil S is used as the counter electromotive force to generate the boost coil S1.
Is stored in the transistor Q of the switching circuit SW.
3 and Q4 become conductive, and the initial exciting current ia is temporarily passed. (See (f) to (h) in FIG. 3).

As described above, according to the drive circuit of the present invention,
By effectively utilizing the back electromotive force energy induced in the solenoid due to the interruption of the initial excitation current, the solenoid can be rapidly excited at the start of energization of the steady excitation current. It is also possible to effectively reduce the generation of noise due to the back electromotive force.

[0013]

As can be understood from the above description, according to the duty valve drive circuit of the present invention, the counter electromotive force induced in the solenoid when the initial excitation current is cut off is accumulated in the boost coil, and the steady excitation is performed. During current transfer, the energy accumulated in the boost coil drives the switching circuit to temporarily energize the solenoid with the initial excitation current for rapid excitation, so the steady excitation current is current-limited. It is possible to compensate for the gradual rise of the steady excitation current and to effectively use the back electromotive force of the solenoid to reduce noise generation.

[Brief description of drawings]

FIG. 1 is a circuit example diagram of a duty valve drive circuit of the present invention.

FIG. 2 is an equivalent circuit diagram of the duty valve drive circuit shown in FIG.

3 (a) to 3 (h) are waveform diagrams of respective parts of the duty valve drive circuit shown in FIG.

FIG. 4 is a circuit diagram of a conventional duty valve drive circuit.

5 (a) to 5 (c) are waveform diagrams of respective parts of the duty valve drive circuit shown in FIG.

FIG. 6 is a circuit diagram of a conventional duty valve drive circuit provided with a diode for absorbing a counter electromotive force of a solenoid.

7 (a) to 7 (c) are waveform diagrams of respective parts of the duty valve drive circuit shown in FIG.

[Explanation of symbols]

 Q1 1st switching element Q2 2nd switching element ia Initial excitation current ib Steady excitation current C Excitation compensation circuit S Solenoid S1 Boost coil SW Switching circuit

Claims (1)

[Claims] 1. A duty valve drive circuit in which a first switching element for supplying an initial excitation current and a second switching element for supplying a steady excitation current are switchingly driven to electrically drive a solenoid. A boost coil that stores counter electromotive force energy induced in the solenoid when the driving of the first switching element is stopped, and a steady excitation current that is driven by the stored energy of the boost coil when driving of the second switching element is started. A duty valve drive circuit further comprising an excitation compensation circuit, which is additionally connected to a switching circuit for temporarily energizing the solenoid with an initial excitation current exceeding 0.