JPS6053445B2 - Plunger solenoid coil current limiting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current limiting circuit for a plunger solenoid coil (hereinafter referred to as a solenoid).

Generally, as shown in Fig. 1, a solenoid has a small suction force when the stroke is large (point A on the first day), and a very large suction force when the stroke is small (particularly after suction, point B in Fig. 1).

However, in devices that do not require such a large suction force after suction, as shown in FIGS. The full power supply voltage is supplied to both ends to give a large attraction force to the solenoid, and after attraction, the power supply voltage is divided by the high power resistor 2 or the high power transistor 4 to reduce the voltage applied to both ends of the solenoid 1 for several minutes. 1, the current flowing through the solenoid was limited to the current value (called the holding current) necessary to maintain the holding force required for the solenoid after suction (point 1 in Figure 1). .

Furthermore, this post-suction current restriction reduces the power consumption of the solenoid after suction and prevents the solenoid from burning out due to temperature rise. The curve a in Figure 1 shows the relationship between the stroke and attraction force when the solenoid is fully energized, and the curve shows the relationship between the stroke and attraction force when the voltage applied to the solenoid is reduced (current limitation). , c curve is the load on the device.

According to Figure 1, the suction force required for this solenoid is 2.7 regardless of the stroke (the load is constant regardless of the stroke). If you keep moving up to 4 points, it will be 2.
Although the suction force was 8 to 9, the 8 point had a suction force of 7 to 9.

Therefore, the current is limited after attraction by the method shown in FIGS. 1-2 and 3, and the holding force required to hold the load at point C is obtained. On the other hand, in order to limit the current of solenoid 1, a holding current flows through resistor 2 and transistor 4, which are connected in series. This results in consumption of electricity.

For example, if the resistance value (r) connected in series is twice the resistance value (R) of the solenoid, the power supply voltage is (■), the power consumed by the solenoid after suction is (Ps), and the power consumed by the series resistor is (Pr) (however, the voltage drop due to the switching operation of the transistor is ignored), the resistor 2 will consume twice as much power as the power consumed by the solenoid 1. In addition to requiring a resistor for high power, consideration must also be given to heat generation.

The same thing can be said about the transistor 4 as in the case of the resistor 2, and the transistor 4 needs to be designed for high power use, and consideration must also be given to heat generation. Therefore, in order to eliminate this wasteful power consumption and to limit the current, the present invention uses a semiconductor circuit to provide two power sources for the current supplied to the solenoid, and to supply a high voltage during suction and a low voltage after suction. This solenoid performs switching so that almost all the power consumed after suction is consumed only by the solenoid. The present invention aims to provide a current limiting circuit for a noid.

Hereinafter, embodiments of the circuit of the present invention will be explained in detail with reference to the drawings.

In Fig. 4, the current ■1 required during suction and the power V2 required after suction (V1>V2=brow, ~↓V1) are supplied from the outside, and V1 is applied to the emitter of the PNP transistor q and the bias resistor. , V2 are connected to the collector of NPN transistor Q3.

The collector of Q2 and the emitter of α are directly connected to one side of the solenoid 1, and the other side of the solenoid 1 is connected to a common ground. Further, the other side of R1 is connected to the base of q and the control circuit of the circuit 3 (not directly related to the current limiting circuit, so a switch like the one shown in the figure is used instead), and the switch of control circuit 3 is set to 0N (closed). The capacitor C1 is connected to a capacitor C1 which is discharged when the voltage is set (0FF) and charged when the voltage is 0FF. The other side of C1 is connected to the base of Q1 such that it becomes 0N while C1 is charging, and the collector of Q1 is connected to R, so that when Q1 is 0N, Q2 is also 0N.
It is connected to the base of Q2 such that In addition, Dl, R2
is a diode and resistor for circuit protection, and D
2 is a diode for protecting the circuit and rapidly discharging the capacitor C1.

Next, the operation of the circuit of the present invention constructed as above will be explained. Control circuit 3 for making the circuit 0N10FF
When the switch is 0N and connected to the ground circuit, the base of Q3 and the base of Q1 are DC connected to the ground potential, and Q is 0FF. ．． Q1 is also OFF. ．． Q2, which is connected from the collector of Q1 to the base via R3, is also 0.
It is FF. Therefore, solenoid 1 is the emitter of O,
They are cut off from their respective power sources by the Q2 collector. Next, when the switch 3 becomes 0FF (opened), ■ R1 connected to 1 → C1 → base of Q1 → emitter of Q1 → charging begins in C1 through earth, and at the same time Q1 becomes 0N and the collector current of Q1 (=Base current of Q2) is V, → Emitter of Q2 → Base of Q2 →
It flows through R3 → Q1 collector → Q1 emitter → ground, and Q2 becomes 0N, and V is applied to the solenoid.
1 → Q2 emitter Q2 collector → solenoid →
Current flows through the ground and the solenoid is attracted.

At this time, the emitter potential of Q3 is approximately V1 (actually Q
The saturation voltage between collector and emitter of 2 (0.1V
~0.5■) is subtracted), and although the charging voltage of C1 is applied to the base potential of Q3, it never becomes larger than ■1, and Q3 is in the 0FF state. The solenoid is then completely suctioned by V1. Furthermore, as the charging of C1 by R1 progresses and the charging current sufficient to set Q1 to 0N begins to flow, the collector current of Q1, that is, Q
The base current of Q2 also begins to decrease, and the collector current of Q2 also begins to decrease. Then, Q2 can no longer maintain the ON state and starts to become 0FF. This means that the voltage drop between the collector and emitter of Q2 begins to increase, and the voltage across the solenoid begins to decrease.

At this time, C1 is almost fully charged and the potential of C1 is V.
It's getting close to 1. When the potential of C1 becomes larger than the voltage applied to the solenoid, in other words, the base voltage of Q3 becomes higher than the emitter voltage of Q3 (approximately 0.7V).
Then, Q3 suddenly becomes 0N, and Ql and Q2 become 0FF. Therefore, the solenoid is separated from V1 by J-! After suction, it is connected to V2.
241, the current value of the terminal is maintained.

24 After this, if you want to stop driving the solenoid, turn switch 3 to 0N so that Ql, Q2, and q are all 0.
Since the solenoid is FF, the solenoid is cut off from the power supply.

Further, C1 in a charged state is rapidly discharged via switch 3 and D2. Furthermore, when Q3 becomes 0N, Q
l, Q2 become 0FF because Q3 is used as an emitter follower, so when O becomes 0N, the emitter potential of Q3 immediately becomes V2, and the base voltage of q becomes ■2+0
．． It becomes 7V.

This means that while Q2 was 0N, C1 was charged to almost V1, but due to Q3 being 0N, it was discharged to V2 + 0.7V, and the negative side of C1, that is, the base of Q1, has -(V1-( A negative voltage of V2+0.7)) appears and immediately sets Ql and Q2 to 0FF, but in reality, to prevent Q1 from being destroyed by this negative voltage, D
A diode 2 is inserted to bypass this negative voltage through D2, and a reverse bias of approximately 10.7 cm due to the voltage drop of D2 is applied to the base of Q1. Q from this Q2ON,
The process of switching to ON takes place in an instant, and all the transistors used are switched on! Since the switching operation is performed, the time for Q2 and q to pass through the active region is instantaneous, and there is no breakage or heat generation due to transistor runaway, which is often seen when the transistors take a long time to pass through the active region. Therefore, Q2 and Q2 can be sufficiently covered by transistors with small power dissipation, and there is no need to consume power with a high-power resistor or a high-power transistor instead of reducing the power consumed by the solenoid as in the past. This circuit is characterized by the fact that the power consumption of the entire system can be reduced by a fraction.

Further, in the circuit according to the present invention, D
2 is provided, and the switch 3 is turned ON for a short time, . 0FF
C1 is completely discharged even if Therefore, it is possible to prevent the solenoid from not being driven. The features of the circuit according to the present invention will be further explained below while comparing the conventional circuit and the circuit according to the present invention.

In order to make the conditions the same, the solenoid resistance of the conventional circuit and the inventive circuit is set to R1, the power supply voltage is 1 (the inventive circuit uses the higher power supply required during suction), and the current after suction is the current during suction. Assuming that the current is limited to a certain number of people, in FIG. 2, the resistance value r of the resistor 2 in order to make the current after attraction A is r=. Therefore the current 1 during attraction.

:V1/R current after suction or power consumption of solenoid during suction Turn off solenoid YF after suction! Power consumption of the resistor after excessive force suction The total power consumption after suction becomes the total power consumption after suction, and the power consumption of the solenoid after suction becomes Δ during suction.

Nevertheless, the resistance also consumes power, and the system as a whole consumes the power of A during suction. In Figure 3, in order to make the current after attraction A, it is necessary to cause a voltage drop in transistor 4 of about 100 Ω. The power consumed by the solenoid is Δ during suction, and the power consumed by the transistor is A in total.

(The voltage drop of the transistor during switching is ignored for both A and b.) In the circuit of the present invention, in order to make the current after attraction the same, V2 becomes V2=1!1. Therefore, the current during suction is 1/R.The power consumption of the solenoid during suction after suction is PO=POR=10V1.The power consumption of the solenoid after suction is the power consumption of the entire system, and compared to the conventional circuit. The power during suction does not change at all, but after suction, the solenoid has the same power as during suction, but the conventional circuit uses an extra resistor or transistor, which is twice the power required for the solenoid. This consumes power, and as a whole, it consumes three times as much power as the circuit of the present invention.

In this way, the circuit of the present invention eliminates unnecessary power consumption, and by limiting the power supply, two power supplies are supplied to the solenoid, so that a high voltage is supplied during suction, and a low voltage is supplied after suction. This circuit performs switching so that the power consumption after suction is done almost exclusively by the solenoid, and is extremely effective as a power supply limiting circuit for a solenoid.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the stroke of the plunger solenoid coil and the attraction force, Figs. 2 and 3 are circuit diagrams of the current limiting circuit of the plunger solenoid coil that has been generally used in the past, and Fig. 4 is a diagram of the current limiting circuit of the plunger solenoid coil that is generally used in the past. FIG. 3 is a circuit diagram of a current limiting circuit of a plunger solenoid coil in an embodiment. 1... Plunger solenoid coil, Q2, Q
,...Transistor, C1...Capacitor, D
2...Diode.

Claims (1)

[Claims] 1. First and second power supplies that supply currents of different values to the plunger solenoid coil, and first and second power supplies that are connected to the first and second power supplies and turn on and off the power supplies supplied to the plunger solenoid coil, respectively. a capacitor connected between the control electrodes of the first and second transistors; and a discharging means connected between one end of the capacitor and a return line of the power supply, for rapidly discharging the capacitor. When the capacitor is charged, the first transistor is turned on to supply the first power to the plunger solenoid coil, and when the capacitor is charged, the second transistor is turned on and the second transistor is turned on. A current limiting circuit for a plunger solenoid coil in which a first transistor is turned off and a second power source is supplied to the plunger solenoid coil so that a limited current flows.