JPS60143610A - Solenoid driving circuit - Google Patents

Abstract

PURPOSE:To obtain a solenoid driving circuit suitable for control using a microcomputer, and enabled to perform easily start-quickened driving by a method wherein when the microcomputer receives the output signal of a current detecting circuit, a solenoid driving transistor is controlled intermittently, and a current to flow in an exciting coil is changed over a holding current value from an excessive current value. CONSTITUTION:A solenoid driving transistor 4 is held in an ON condition, and it is awaited that a driving current Ic to reach the current value to satisfy sufficiently the high speed starting condition of a solenoid. When a current detecting circuit 12 detects the fact that an excessive current enabled to perform sufficiently high speed starting is flowed, a microcomputer 1 makes a solenoid driving signal A to ON and OFF at the prescribed period. The solenoid driving transistor 4 is also made to perform ON and OFF action corresponding thereto, and electric power to be applied to an exciting coil 2 from an electric power source +V is made to be intermittent. A current to flow in the exciting coil 2 is made to a current to pulsate at the part sufficiently lower than the excessive current value at initial action starting time, and the average value thereof is made so as to satisfy the holding current value of the solenoid.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a drive circuit for driving a solenoid, and more particularly to a treed drive circuit for high-speed starting.

BACKGROUND ART Solenoids drive controlled parts using a actuator that moves by a magnetic field generated by energization, and are often used in parts that convert electrical control signals into mechanical movements.

In this case, in order to quickly start the solenoid and perform quick control, it is necessary to sharply increase the generated magnetic field at the start of energization. For this reason, when high-speed starting is required, the solenoid drive circuit is configured to allow a large current to flow at the start of energization.

However, if such a large current continues to flow, the coil may generate heat and burn out, so after the solenoid has started, it is necessary to control the current flowing to the solenoid's rated holding current value. Become.

On the other hand, in recent years, with the rapid development of electronic technology, there is a tendency for microcomputers to be incorporated into control units of various devices. In this case, when controlling the solenoid with a microcomputer, if you want to start the solenoid earlier, you must supply a large current only when energization starts by driving the above-mentioned solenoid drive circuit with the output signal of this microcomputer. Therefore, the circuit configuration becomes complicated and expensive.

On the other hand, it is conceivable to control the drive current supplied to the solenoid in an analog manner using the output signal of the microcomputer so that it is large at the start of startup and reaches the rated current after completion of startup, but in this case, In this case, the microcomputer becomes exclusive to the solenoid and cannot perform other controls, and the drive current control part becomes complicated.

DISCLOSURE OF THE INVENTION Accordingly, an object of the present invention is to provide a solenoid drive circuit that is suitable for control using a microcomputer and that can easily perform driving with early start-up.

In order to achieve such an object, the present invention hastens the operation by turning on the solenoid drive transistor in response to a control output signal from a microcomputer and causing an excessive current to flow through the excitation coil of the solenoid. By switching the solenoid drive transistor to intermittent control at a predetermined cycle in response to the output of a current detection circuit that detects when the current has reached a value that satisfies the high-speed operation of the solenoid, the average current flowing through the solenoid's excitation coil is maintained as a current. This is to prevent the excitation coil from burning out.

Therefore, in the solenoid drive circuit configured in this way, the control by the microcomputer is only on/off control, which makes the control suitable for the microcomputer, and it also has the advantage of controlling the current value itself directly It has various superior effects such as greatly simplifying the circuit configuration.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 is a circuit diagram showing one embodiment of a solenoid drive circuit according to the present invention. In the figure, 1 is a microcomputer, which outputs a solenoid control signal A from an output port 01*01 in response to a control input signal supplied to an input terminal IN.
,B are generated. 2 and 3 are solenoid excitation coils, 4
is a solenoid drive transistor which is turned on by a solenoid control signal supplied via a resistor 5, and connects the excitation coil 2 between the power supply +V and ground via a current detection resistor 6.

Reference numeral 7 denotes a solenoid drive transistor, which is turned on by a solenoid control signal B supplied via a resistor 8, and connects the excitation coil 3 between the power supply +■ and ground via a resistor 9 for current detection. 10.11 is the excitation coil 2.
Diodes 12.13 and 12.13 are connected in parallel with each other in parallel to 3 and have opposite polarity to the power supply +■.
This current detection circuit generates an output signal C1D when it detects that the current flowing through the excitation coil 2.3 has reached a set value, and supplies the output signal C1D to the input ports Fp, jp of the microcomputer 1, respectively. And this current detection circuit 1
2.13 is composed of comparators 12b and 13b that compare input signals supplied through resistors 12a and 12b, respectively, with a reference value Vr, and diodes 12c and 13C that absorb negative polarity input signals.

In the solenoid drive circuit configured in this way, when a control signal is supplied to the input terminal IN of the microcomputer 1 from the outside (not shown), the microcomputer 1 identifies the content of this input signal and determines the object to be controlled. do. For example, upon receiving an instruction to drive the solenoid of the excitation coil 2, the microcomputer 1, as shown in step Sl in FIG. 3, outputs a solenoid drive signal A generated from the output port O1 as shown in FIG. When the solenoid drive signal A becomes H", the solenoid drive transistor 4 is turned on and the current supplied from the power supply +■ flows into the exciting coil 2. In this case, since the excitation coil 2 has inductance, the on-resistance of the solenoid drive transistor 4 is rTON, the value of the resistor 6 provided for current detection is ae, the internal resistance of the excitation coil 2 is rL, and the excitation coil Assuming that the inductance Ll is 2, the drive current Ic increases as shown in FIG. 2 1al under the following condition.

When this driving current ■c increases, the voltage generated across the resistor 6 also increases as shown in FIG. 2 1al, so the input signal to the current detection circuit 12 also increases Become. Here, when the input signal level of the current detection circuit 12 corresponding to the drive current Ic exceeds the excessive current value that satisfies the high-speed starting of the solenoid, that is, the reference value Vr, the output signal 0 of the comparator 12b becomes ), it is reversed from L'' to H''. The microcomputer 1 determines the state of the output signal C supplied from the current detection circuit 12 to the input port P1 in step S2 shown in FIG.
Then, the microcomputer 1 sets the solenoid drive signal A to L'' as shown in FIG. Start counting 11 seconds and %T1
When the second is reached, the solenoid drive signal A is set to ``H'' in step S11, and after t, the process moves to step S6.In step s6, the solenoid drive signal A is set to ``H'' in step S6. Start timing the
When the time reaches 13 seconds, the process moves to step S7, the content of the control signal is identified, and the process moves to step S8. step s
In step 8, the solenoid drive signal determines the instruction to the person, and if the solenoid drive signal is instructing to drive the solenoid having the excitation coil 2, steps Ss to S
Execute loop processing returning to step 3. Further, if the determination in step Ss is YES, that is, the drive instruction for the solenoid having the excitation coil 2 has been released, step S is performed.

At this point, set the solenoid drive signal A to "L".

In other words, when starting to drive the target solenoid, the solenoid drive transistor 4 is held in the on state, and the drive current Ic, which increases exponentially, reaches a current value that sufficiently satisfies the high-speed starting conditions of the solenoid. wait. If this state continues, a large current for high-speed starting will continue to flow through the excitation coil 2, causing the coil to burn out. For this purpose, when the current detection circuit 12 detects that an excessive current that is sufficient for high-speed starting has flowed and notifies the microcomputer 1, the microcomputer 1 turns on and off the solenoid drive signal A at predetermined intervals. . When the solenoid drive signal A is turned on and off, the solenoid drive transistor 4 is also turned on and off accordingly, so that the power applied to the excitation coil 2 from the power supply +■ is interrupted. When the solenoid drive transistor 4 is turned off, a back electromotive force is generated in the excitation coil 4, and a flywheel current flows through the closed loop consisting of the excitation coil 2 and the diode 10, causing the excitation coil itself to flow. The flowing current does not suddenly become zero even when the solenoid drive transistor 4 is turned off, but gradually decreases as shown in FIG. 2(d). Then, when the solenoid drive transistor 4 is turned on again, the power supply +■ is applied, so that the voltage gradually increases again. In this way, when the power applied to the excitation coil 2 is interrupted, the current flowing through the excitation filter 2 is reduced as shown in FIG.
As shown in 1, the current pulsates in a portion sufficiently lower than the excessive current value at the start of startup, and the average current satisfies the holding current value of the solenoid. In other words, the microcomputer 1 can control the current flowing through the excitation coil from an excessive current value for high-speed drive at startup to a holding current value by simply controlling the solenoid drive transistor 4 intermittently.

In the above embodiment, only the drive control of the solenoid having the excitation coil 2 has been described, but it goes without saying that the drive control of the solenoid having the excitation coil 3 can be performed in the same manner.

As explained above, the solenoid drive circuit according to the present invention speeds up the operation by turning on the solenoid drive transistor in response to a control output signal from a microcomputer and causing an excessive current to flow through the excitation coil of the solenoid.
When the current at the start of startup reaches a value that satisfies the high-speed operation of the solenoid, the solenoid drive transistor is turned on and off at predetermined intervals to lower the average current flowing through the excitation coil and use it as a holding current. It becomes suitable for solenoid control by computer, and
It has various excellent effects such as a simplified configuration and low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the solenoid drive circuit according to the present invention, FIG. 2 tal to ldl are operational waveform diagrams of each part of the circuit shown in FIG. 1, and FIG. It is a figure which shows the flowchart which shows operation|movement. 1...Microcomputer, 2.3...
... Excitation coil, 4.7 ... Solenoid drive transistor, 5, 6, 8.9 ... Resistor, 12.
13... Current detection circuit. Applicant: NEC Home Electronics Co., Ltd. No. 2
Figure 3

Claims (1)

[Claims] (1) a microcomputer that generates a solenoid control signal from an output port in response to an external input signal; a solenoid drive transistor that is turned on by the solenoid control signal and supplies power to the excitation coil of the solenoid;
A diode connected in parallel to the excitation coil of the solenoid and with opposite polarity to the power supply detects that the current flowing through the excitation coil has reached an excessive current value that satisfies high-speed operation conditions. and a current detection circuit that supplies an output signal to the microcomputer, and when the microcomputer receives the output signal of the current detection circuit, it controls the solenoid drive transistor intermittently to maintain the current flowing through the exciting coil from an excessive current value. A solenoid drive circuit characterized by executing control for switching to a current value.