JPS626664Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a solenoid drive device for driving a solenoid.

Generally, a solenoid has a characteristic that the rising speed at the time of starting energization is slow. Therefore, when a solenoid is used to drive the printing wire of a dot printer, it is necessary to increase the startup time of the solenoid in order to increase the printing speed of the dot printer.

Conventionally, solenoid drive devices used in dot printers take the above-mentioned characteristics of the solenoid into consideration, and when driving the solenoid, superimpose it on the normal operating voltage (rated voltage) of the solenoid to temporarily raise the operation starting voltage. By applying this operation start voltage, the solenoid is started up at high speed. The operation start voltage is selected to be considerably higher than the rated voltage in order to prevent the solenoid from slowing down even if the power supply voltage drops.

However, with this configuration, if the power supply voltage increases for some reason, a voltage higher than necessary is applied to the solenoid, resulting in an increase in the operating noise associated with the operation of the solenoid. Additionally, the solenoid may burn out.

An object of the present invention is to provide a solenoid drive device that can prevent the solenoid from burning out even when the power supply voltage becomes higher than necessary.

According to the present invention, there is provided a solenoid drive device that includes a series circuit in which a plurality of Zener diodes are connected in series, and a transistor that selectively applies an operation start voltage to the solenoid, and that the series circuit is connected to the base of the transistor. It will be done.

With this configuration, when a control voltage is applied to the common connection point of the Zener diodes, the base voltage of the transistor can be maintained constant. Voltage can be prevented from being applied to the solenoid.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a solenoid drive device according to an embodiment of the present invention is connected to a transformer 10 that forms part of a power supply circuit, and is used to drive a solenoid 11. This solenoid drive device converts an AC voltage from a transformer 10 into a first DC voltage V 1 through a rectifier 12 and a smoothing capacitor ₁₃ , and further supplies this first DC voltage V ₁ to the solenoid 11 through a diode 14. have. The first DC voltage V ₁ is the solenoid 1
1 rated voltage, for example, 8V.

Further, the solenoid drive device has a configuration in which a rectifier 16 and a smoothing capacitor 17 convert the AC voltage from the transformer 10 into a second DC voltage V ₂ . The second DC voltage _V2 is set to be an acceleration voltage, for example 25V, at the time of starting the solenoid operation.

A second DC voltage V ₂ is applied to the collector of a transistor 18 that selectively applies an output voltage to the solenoid 11 . The transistor 18 is of the type described later and is connected to the solenoid 1 through a diode 19.
Sends the output voltage to 1. Two Zener diodes 2 are connected between the base of the transistor 18 and ground.
A series circuit in which 1 and 22 are connected in series is connected. Furthermore, there is a resistor 23 between the base and collector.
is connected.

A first control signal S ₁ is applied from the control circuit 25 to the common connection point of the Zener diodes 21 and 22, as will be described later. In addition, the control circuit 2
5 sends a second control signal S ₂ to the base of a solenoid control transistor 26 connected between the solenoid 11 and ground.

Next, referring also to FIG. 2, the operation of the solenoid drive device shown in FIG. 1 will be explained. The control circuit 25 outputs a first control signal (H) when the solenoid 11 starts operating.
level) S ₁ is sent to the common connection point of Zener diodes 21 and 22. When the first control signal _S1 is at H level, the base voltage is the Zener diode 2.
The voltage is the sum of the Zener voltages of 1 and 22,
An output voltage V ₀ corresponding to this base voltage is applied to the solenoid 11 via the emitter of the transistor 18 and the diode 19 .

A transistor 26 connected to the solenoid 11
The second control signal S2 is applied to the base of _{the transistor 26 simultaneously} with the first control signal S1, so that the transistor 26 is in a conductive state.

As described above, when both the first and second control signals S ₁ and S ₂ are at H level, the output voltage V ₀ of the transistor 18 is added to the first DC voltage V ₁ as an accelerating voltage. The superimposed driving voltage V _D is applied to the solenoid 11, and the solenoid 11 enters the suction state. Output voltage of transistor 18 V ₀
Since the base voltage is substantially constant, it is maintained constant during the H level period of the first control signal _S1 .
Furthermore, since the output voltage V ₀ is higher than the first DC voltage V ₁ , even if the power supply voltage fluctuates, the voltage supplied to the solenoid 11 is controlled by the output voltage V ₀ of the transistor 11. . Therefore, the drive voltage V _D applied to the solenoid 11 is kept stable even if the power supply voltage increases.

If the Zener voltage of the Zener diodes 21 and 22 is selected in consideration of the optimum operating voltage of the solenoid 11, the solenoid 1 at the start of operation can be
1 burnout etc. can be completely eliminated.

Next, the first control signal _S1 becomes low level L,
When the second control signal S ₂ maintains a high level H, the first DC voltage V ₁ is applied to the solenoid 11 through the diode 14 . first DC voltage
If V ₁ is selected as the operating voltage of the solenoid 11, that is, the optimum voltage for the solenoid 11 to maintain the suction state, even after the first control signal S ₁ becomes low level L, the solenoid 11 remains A suction state can be maintained.

When the first control signal S ₁ becomes low level, the connection point between the Zener diodes 21 and 22 is equivalently grounded, and the base voltage of the transistor 18 is kept at the Zener voltage of the Zener diode 21 . If the operating point and Zener voltage of the transistor 18 are set so that the transistor 18 can conduct current even with this base voltage, even if the first DC voltage V ₁ decreases when the solenoid 11 is in the suction state, the transistor 18 The output voltage V ₀ of is supplied to the solenoid 11 as a compensation voltage, and the suction state of the solenoid 11 can be maintained.

Further, when the second control signal S ₂ becomes low level L, the transistor 26 becomes non-conductive and the solenoid 11 stops operating.

As described above, in the present invention, it is possible to stabilize the accelerating voltage applied when the solenoid starts operating, to prevent excessive voltage from being applied to the solenoid, and to reduce the power consumption of the solenoid. Moreover, the operating noise of the solenoid can be reduced, and burnout of the solenoid can also be prevented.

In the above embodiment, two Zener diodes are used.
Although the case where one Zener diode is connected has been described, it goes without saying that more Zener diodes may be connected.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a solenoid drive device according to an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of FIG. 1. Explanation of symbols, 10: Transformer, 11: Solenoid, 12, 16: Rectifier, 13, 17: Capacitor, 14, 19: Diode, 18, 26: Transistor, 21, 22: Zener diode,
23: Resistor, 25: Control circuit.

Claims (1)

[Scope of utility model registration request] a first circuit connected between a power source and a solenoid for supplying a first voltage to the solenoid as required during normal operation of the solenoid; a second circuit that superimposes a voltage on the first voltage and supplies it to the solenoid, and the second circuit includes a transistor connected between the power source and the solenoid, and a plurality of and a series circuit in which Zener diodes are connected in series via a common connection point, and the control signal is applied to the common connection point of the series circuit.