JPH0326036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a drive circuit for a bell motor used in a clock alarm or the like.

[Prior art and its problems]

For example, in a clock that generates an alarm sound by driving a bell with a DC motor, if the battery voltage drops below the starting voltage of the motor, the alarm will stop ringing, which may cause inconvenience to the user. Conventionally, as a countermeasure against this problem, there is a method of detecting whether or not the induced voltage of the motor exceeds a set voltage, and increasing the driving power of the motor if it does not exceed the set voltage. According to this, noise is often included in the induced voltage of the motor, and parts that should be driven with low power are sometimes driven with high power.

〔the purpose〕

The present invention provides a bell motor drive circuit that accurately detects when the DC motor cannot rotate sufficiently due to a drop in battery voltage and reliably switches drive pulses.

〔Example〕

In FIG. 1, reference numeral 1 denotes a pulse generation circuit, and motor drive pulses shown in FIGS. 2A and 2B are generated from output terminals a and b, respectively. A selection circuit 2 selects one of the drive pulses described above. 3 and 4 are one-shot circuits that generate one pulse depending on the rising edge of the pulse; 5 and 6 are flip-flop circuits;
7 to 10 are gate circuits. One-shot circuit 4, flip-flop circuit 5, and gate circuits 9 and 10 constitute a selection signal generation circuit. 11 is an alarm switch, 12 is a transistor serving as a drive circuit, and 13 is a DC motor for driving a bell (not shown). 14 is a switch constituting a switching circuit that opens and closes in conjunction with the rotation of the motor 13, and 15 is a counter that counts the number of times the switch 14 is opened and closed.

Next, the operation will be explained. While the alarm switch 11 is open, the flip-flop circuit 5
has been reset, and the drive pulse shown in FIG. 2A from the terminal a is selected by the selection circuit 2 and supplied to the gate circuit 7. The gate circuit 7 is closed because the output Q of the flip-flop circuit 6 is "1", and the drive pulse does not pass therethrough.

When the alarm switch 11 is closed, the reset of the flip-flop circuit 5 is released and the output Q of the flip-flop circuit 6 becomes "0" due to the rise of the pulse from the pulse generating circuit 1, and the gate circuit 7 is opened. Therefore, selection circuit 2
The pulses shown in FIG. 2A from . On the other hand, the one-shot circuit 3 generates the pulse shown in FIG. 2D to clear the contents of the counter 15, and the one-shot circuit 4 generates the pulse shown in FIG. 2C.

Now, when the motor 13 is rotated by the first pulse, the switch 14 opens and closes as the motor 13 rotates, and a pulse proportional to the rotational speed of the motor 13 is generated from the terminal e as shown in FIG. 2E. This pulse is supplied to the counter 15 via the gate circuit 8, and if the rotational speed of the motor 13 is sufficient, the output Qn of the counter 15 reaches the second level before the fall of the pulse shown in FIG. 2C from the one-shot circuit 4. It becomes "1" as shown in Figure F. Therefore, the one-shot circuit 14
The output "0" of the gate circuit 9 is written into the flip-flop circuit 5 by the fall of the pulse shown in FIG. Pulse is still selected.

If the battery voltage drops and sufficient rotation cannot be obtained with the pulses shown in FIG. The output "1" is written into the flip-flop circuit 5.
Therefore, the output Q of the flip-flop circuit 5 becomes "1" as shown in FIG. 2G, and the selection circuit 2 selects the pulse shown in FIG. 2B from the terminal b, and is thereafter driven by this pulse.

Note that a Hall element or the like may be used instead of the switch 14.

Furthermore, in the above embodiments, instead of switching the width of the motor drive pulse, it is sufficient to switch the average effective drive power per unit time, such as pulse period, duty, voltage, current value, etc.

Further, the number of drive pulses is not limited to two types, but more types may be prepared and switched.

〔effect〕

According to the present invention, the rotational state of the DC motor is detected by counting the pulses synchronized with the rotation of the DC motor, and the effective driving power of the drive pulses is switched, so that it is less susceptible to the effects of noise etc. The rotational state can be detected accurately.
Furthermore, it is possible to prevent the motor bell from suddenly ceasing to ring, and since the volume, manner of ringing, etc. change depending on the battery voltage, it is possible to predict the battery life. Furthermore, since the drive pulses are sequentially driven starting from the lowest effective drive power, current consumption can be reduced, which is effective in extending the life of the battery.

[Brief explanation of the drawing]

FIG. 1 is a logic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation. 1... Pulse generation circuit, 2... Selection circuit, 4...
... one shot circuit, 5 ... flip-flop circuit, 9, 10 ... gate circuit, 12 ... drive circuit, 13 ... DC motor, 14 ... switching circuit, 15 ... counter.

Claims (1)

[Scope of Claims] 1. A DC motor 13 that drives a bell, a pulse generation circuit 1 that generates a plurality of types of drive pulses each having a different effective driving power for intermittently driving this DC motor, and the above DC motor. a switching circuit 14 that generates pulses synchronized with the rotation of the DC motor; a counter 15 that is reset each time the drive pulse is generated and counts the pulses from the switching circuit; and a counter 15 that is initialized by the start command signal of the DC motor. a first selection signal, and determines this when the count value of the counter becomes equal to or less than a preset value after a certain period of time after the reset, and thereafter generates a second selection signal. A first selection signal from circuits 4, 5, 9, and 10 and this selection signal generation circuit selects the drive pulse with the minimum effective drive power among the drive pulses, and a second selection signal selects the drive pulse having the minimum effective drive power. A drive circuit for a bell motor, comprising a selection circuit 2 for selecting a drive pulse with a larger effective drive power, and a drive circuit 12 for driving the DC motor in response to the drive pulse selected by the selection circuit.