JPH0469398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving circuit for a sounding body, and its purpose is to provide a sounding driving circuit for synthesizing and producing chords smoothly or attenuatedly.
By incorporating it into a CMOS integrated circuit, the number of external parts can be reduced, reducing costs and allowing for further miniaturization of microelectronic devices such as watches and the addition of new performance.

A detailed explanation will be given below based on the drawings. FIG. 1 shows an example of a sounding body drive circuit conventionally used in a timepiece, in which a piezoelectric buzzer using a piezoelectric element is used as the sounding body. To explain the configuration of this circuit, P channel MOS transistor 1 (hereinafter referred to as
The output terminal A of the gate circuit composed of a N-channel MOST 2 and an N-channel MOST 2 is led out to an external terminal 4 via a resistor 3, and a bipolar transistor 5 is connected to the external terminal 4 outside the integrated circuit. connected to the base of The emitter of the bipolar transistor 5 is connected to the low potential side _Vss of the power supply,
The collector is connected via a resistor 6 to one terminal of each of a coil 7 and a piezoelectric buzzer 8, one terminal of which is connected to the high potential side V _dd of a power supply.

When a pulse signal having a musical scale frequency is applied to the input terminal I of this gate circuit, its inverted signal appears at the output terminal A as shown in FIG.

In FIG. 2, when the potential of the output terminal A is _Vdd, the bipolar transistor 5 is in an on state,
A current flows through the coil 7. When the potential of the output terminal A becomes _Vss , the bipolar transistor 5
is in the off state, the current flowing through the coil 7 is cut off, and at this time, a back electromotive voltage is generated in the positive direction at the output terminal O, but the piezoelectric buzzer 8 responds to this voltage with a capacitive Since it becomes a load, a voltage waveform as shown in FIG. 2 is generated at the output terminal O. The maximum peak value of this voltage waveform is about 6V. That is, the coil 7 is used for boosting the signal.

The first drawback of this conventional circuit is that the frequency range that can be used for sound generation is narrow. In other words, the waveform at the output terminal A in FIG. 2 is not arbitrary, but has a limited period and duty cycle. That is, during the period when the potential of the output terminal A is _Vdd , the current flowing through the coil 7 gradually increases due to the inductance. The back electromotive force generated when the current is interrupted depends on the magnitude of the current flowing immediately before the interruption, so in order to maintain the volume of the piezoelectric buzzer 8 at a certain value, the current flowing through the coil 7 must be adjusted. It is necessary to keep the current flowing until the magnitude of is a sufficient value.

Therefore, the minimum value of the period during which the potential of the output terminal A should be _Vdd is determined.

Next, the period when the potential of output terminal A should be _Vss is:
The minimum value is determined by the time it takes for the voltage waveform at the output terminal O to reach the maximum value, and the maximum value is within the range in which the piezoelectric buzzer 8 does not generate natural vibration and generate sound at a frequency different from the drive frequency. limited to.

Furthermore, the maximum value of the period during which the output terminal A is at V _dd has a limit value in relation to power consumption. In this way, due to the restrictions on the voltage waveform at the output terminal A, the frequency range in which sound can be produced is within an extremely limited range.

The second drawback is that it is difficult to pronounce chords for the same reason as mentioned in the first drawback above. That is, since a chord is composed of two or more different frequency components, the voltage waveform at the output terminal A cannot satisfy the above-mentioned constraints.

The third drawback is the external bipolar transistor 5
, and this cost is relatively high. However, instead of using an external bipolar transistor,
When attempting to set the MOST, the high voltage generated when the piezoelectric buzzer 8 receives a mechanical shock causes
This was not possible due to the latch-up phenomenon caused by CMOS integrated circuits.

Next, FIG. 3 shows an example of a single-tone integrated attenuated sound generation circuit according to the prior art, with P channel MOST9.
The drain of the bipolar transistor 5 is connected to a connection point B with the base of the bipolar transistor 5 via a resistor r12.

The connection point B has multiple resistors R113, R214...
via multiple N channels MOST10,11
Connected to V _ss . The plurality of N channels
The gate terminals C1 and C2 of the MOSTs 10 and 11 are given signals in a selective combination, and the P channel
When MOST9 is turned on, the high potential level at the connection point B changes between the resistor _r and the resistor R1.
The voltage is divided by the parallel resistance value of R2.

Therefore, with time, the gate terminals C1, C2
By changing the signal given to the connection point B so that the high potential level at the connection point B gradually decreases,
The current flowing through the coil 7 gradually becomes smaller, and the current flowing through the coil 7 becomes smaller.
The sound volume decreases.

This method is simple, but unless the number of resistor divider combinations is increased to a certain extent, the envelope of the attenuated sound will be stepped and unnatural.On the other hand, if the resistor divider combination is increased, the degree of integration of the integrated circuit will be adversely affected. do. Furthermore, the control signal generation circuit for controlling the resistance division becomes complicated because it requires a timer and a decoder.

Therefore, the circuit in Figure 3 can be used to obtain a single envelope as shown in Figure 4a, but
This becomes difficult to implement when a plurality of envelope circuits are required to independently generate envelopes for sounds of different scales, as shown in FIG. 4b.

Therefore, the present invention has been made to improve the various drawbacks mentioned above.

First, FIG. 5 is a circuit diagram showing an embodiment of the present invention, and its configuration can be roughly divided into an envelope cell 20.
(individually shown as 20A, 20B... in the figure),
Boost circuit 30, level detector 40, driver 5
0 and a protection circuit 60.

Describing the configuration of the envelope cell 20A, N
The drain of the channel MOST 21 is connected to V _dd , the source and substrate are connected to the drain of the N channel MOST 22 and grounded to V _dd via the capacitor 23, and further connected to the gate of the P channel MOST 24, and the gate is connected to the common input terminal _J1 . The gate of the N-channel MOST 22 is connected to the individual input terminal _K1 , and the source and substrate are connected to _Vss . Said P channel MOST24
The source of is connected to the drain of P-channel MOST 25, the drain of P-channel MOST 24 is connected to common output terminal N, and the substrate is grounded to V _dd . The gate of the P-channel MOST 25 is connected to the individual input terminal _L1 , the source is connected to the common terminal M, and the substrate is grounded to _Vdd .

A thin whisker signal is supplied to the common terminal _J1 from a whisker generating circuit to be described later. Said individual input terminal L ₁
Different scale signals are applied to the respective input terminals, and a sound generation signal is applied to the individual input terminal _K1 . The common terminal M is connected to V _dd via a resistor 26, and the common output terminal N is connected to the output terminal of the booster circuit 30 via a resistor 27, and also connected to the level detection circuit 40 and the driver. 50.

FIG. 6 is a diagram showing operating waveforms of the envelope cell, in which a scale signal is applied to the individual input terminal _L1 , but when the gate terminal P of the P channel MOST 24 is at a high voltage level _Vx. is the P
Since the channel MOST 24 is in the off state, the output terminal N is pulled down to the level of the output terminal V _L of the booster circuit 30 by the resistor 27 .

Here, when a sound generation signal is applied to the individual input terminal K ₁ and the individual input terminal K ₁ becomes V _dd level for a short time,
During this time, the N-channel MOST 22 is on, so the potential at the gate end P becomes _Vss . As a result, the P-channel transistor 24 is turned on, and the scale signal appears at the output terminal N.
The whisker signal is applied to the common input terminal _J1 , and the whisker signal causes the N channel to be connected to the common input terminal J1.
When the MOST 21 is turned on for a short time, part of the charge held in the capacitor 23 is released during this period, and the potential at the gate end P rises in the direction of V _dd .

Therefore, the on-state of the P channel MOST 24 is weakened and the on-resistance increases, so that the peak value of the scale signal appearing at the output terminal N decreases. This operation is repeated every cycle of the whisker signal, but since the source of the N-channel MOST 21 is connected to the gate end P, as the potential of the gate end P rises, the N-channel MOST 21
The on state of the MOST 21 is gradually weakened, and therefore the amount of charge released from the capacitor 23 by the whisker signal is also gradually reduced. Therefore, as time passes, the potential change at the gate end P gradually becomes more gradual.

When a sufficient amount of time has elapsed, the potential at the gate end P reaches a level _Vx , which is _Vdd minus the threshold voltage of the N-channel MOST 21. Here, the N channel MOST21 and the P channel
If the threshold voltages of the MOST 24 are approximately the same, the P channel MOST 24 is almost off, and therefore no scale signal appears at the output terminal N.

In this method, the potential at the gate end P approaches the threshold voltage of the P channel MOST 24 very slowly, so the sound attenuates in a very natural manner, unlike the conventional built-in attenuated sound generating circuit. There is no step phenomenon where the sound suddenly disappears in the middle, which is often the case. Also, the potential change at the gate end P is
By appropriately selecting the width of the whisker signal, the value of the capacitance 23, the conductance value of the N-channel MOST 21, and the period of the whisker signal, practically no step difference can be achieved without increasing the number of elements. It can be made so smooth that you won't even feel it.

In the waveform diagram of the output terminal N in FIG.
The value _VH changes depending on the on-resistance of the P channel MOSTs 24 and 25, the value of the resistor 26, and the value of the resistor 27.

Now, to explain the whisker signal generation circuit, FIG. 7 shows the whisker signal generation circuit.
One input terminal R of the gate 81 is the NOR gate 83
The output terminal B is connected to one input terminal of the
It is connected to the other input terminal of the NOR gate 83 and also connected to one input terminal of the NOR gate 82, and the remaining input terminal is connected to the other input terminal of the NOR gate 83.
It is connected to output terminal A of 2. Said NOR gate 8
The output terminal Q of No. 3 is connected to the remaining input terminal of the NOR gate 82.

FIG. 8 shows an operational waveform diagram of this whisker signal generation circuit. When the potential of the input terminal R is V _dd , the output terminal Q is
V _ss , output terminal A is at the level of V _dd , and output terminal B is at the level of V _ss . When the potential at the input terminal R shifts from V _dd to V _ss , it passes through the transmission level shown by the dashed line in FIG. 8, and from this point on, the output terminal Q begins to rise toward V _dd . When the level of the output terminal Q reaches the transmission level, the output terminal A starts to fall toward _Vss , and when the potential of the output terminal A reaches the transmission level, the output terminal B
begins to rise toward V _dd , and when the level of the output terminal B reaches the transfer level, the output terminal Q begins to fall.

Therefore, the signal appearing at the output terminal Q becomes a thin whisker-like signal. As is clear from the above explanation of the operation of this whisker signal, it is guaranteed that at least its peak value rises to the transmission level. However, it is necessary that the peak value of the whisker signal required by the envelope cells 20A, 20B, . . . of the present invention shown and explained in FIG. 5 rise to _Vdd .

To satisfy this point, the sum of the falling time of the output terminal A and the rising time of the output terminal B should be longer than the rising time of the output terminal Q.

Therefore, the rise time of the output terminal Q in the actual integrated circuit is calculated, and each NOR gate 81, The conductance of the transistors composing 82 and 83 is selected, and if necessary, the capacitance 8 is selected as shown by the broken line in FIG.
Measures such as providing 4,85 are taken.

Now, in FIG. 5, the driver 50 is a P channel whose source is connected to V _dd by a resistor 52.
MOST 51 has a common drain with the P channel MOST 51 and has a source connected to the output terminal V _L of the booster circuit 30 via a resistor 54.
Consists of channel MOST53. The gate of the N-channel MOST 53 is connected to the output terminal N of the envelope cells 20A, 20B, . The envelope cell 20
A, 20B, . This will result in a damped sound. At this time, if the sounding body load 70 is of a current-driven type, no more special configuration is required in principle. However, if the sounding body load 70 is capacitive, such as a piezoelectric buzzer, a discharge circuit is required to discharge the accumulated charge.

In FIG. 5, the P-channel MOST51 is the above-mentioned discharge transistor, and the N-channel MOST51 is the above-mentioned discharge transistor.
If MOST53 is mostly off, the P channel
The MOST 51 is turned on and short-circuits both ends of the sounding body load 70. In this case, it is necessary to detect the strength of the on-state of the N-channel MOST 53, and the level detector 40 performs this.

The configuration of the level detector 40 is as follows. N
The source and substrate of the channel MOST 41 are connected to the output terminal V _L of the booster circuit 30, the gate is connected to the common output terminal N of the envelope cells 20A, 20B, and the drain is connected to V _dd via the resistor 42. It is connected to the input terminal of the inverter 43. The output terminal of the inverter 43 becomes the output terminal S of the level detector 40. N in the N channel MOST 41 and the driver 50
Since the channel MOSTs 53 are manufactured within the same chip, their electrical characteristics are similar.

Therefore, the value of the resistor 42 and the conductance of the N-channel MOST 41 can be set so that the output of the inverter 43 is inverted to the _Vss level at a level at which the N-channel MOST 53 is almost considered off.

FIG. 9 shows the waveform at the common output terminal N of the envelope cell 20A, the waveform at the output terminal S of the level detector 40, and the waveform at the external terminal 64 when the sounding body load 70 is a piezoelectric buzzer. The approximate condition is shown below.

In FIG. 5, the protection circuit 60 must be strong enough to prevent the integrated circuit from malfunctioning or latch-up against the high voltage generated when the piezoelectric buzzer receives an impact as described above. Therefore, in the present invention, the conventional idea of a protection circuit using diodes has been abandoned and a protection circuit using transistors has been adopted.

10a and 10b show a conventional protection circuit structure and its conceptual equivalent circuit, and FIGS. 11a and 11b show a protection circuit structure and its equivalent circuit in the present invention.

In FIG. 11, the bipolar transistor 61 is
The transistor 62 is a horizontal PNP transistor with the N ^- substrate as the base, the P ⁺ diffusion layer as the emitter, and ^the P ^- diffusion layer as the collector.
It is a vertical NPN bipolar transistor with a P ^- diffusion layer as the base and an N ^- diffusion layer as the collector. The external terminal IN of the protection circuit is connected to one terminal of the polysilicon resistor 63. The other terminal of the polysilicon resistor 63 is connected to the emitters of the PNP bipolar transistor 61 and NPN bipolar transistor 62, and serves as an internal terminal OUT. The collector of the PNP bipolar transistor 61 is connected to _Vss , and the base of the NPN bipolar transistor 62 is connected to _VL .

This protection circuit is extremely powerful, and has proven to be more than 10 times more powerful than conventional protection circuits. Therefore, the piezoelectric buzzer (capacitance
It had sufficient protection ability against high voltages of 100V or more generated by 50NF), and the effect of its implementation was extremely large.

Next, regarding the booster circuit 30 in FIG. 5, the embodiment shown here uses a coil 33, one end of which is connected to _Vss , and the other end connected to an external terminal. P channel via 32
Drain of MOST31 and N channel MOST3
Connected to 4 sources. Said P channel
The source and board of MOST31 are connected to V _dd ,
A boosting signal is applied to the gate T. The gate and drain of the N-channel MOST 34 are commonly connected to a capacitor 36 via an external terminal 35, and serve as an output terminal _VL . The boosting signal T becomes low level, and the P channel MOST3
1 is turned on, current flows through the coil 33.

Next, when the boost signal T becomes V _dd , the P channel MOST31 is turned off, and the coil 3
The current flowing through 3 is cut off. At this time, a large negative voltage appears at the external terminal 32. Since the N-channel MOST 34 functions as a diode, the capacitor 36 is charged in a negative direction through this diode.

The voltage appearing at the output terminal _VL of the booster circuit 30 varies depending on the inductance value of the coil 33, the state of the booster signal, the conductance of the P channel MOST 31, the size of the N channel MOST 34, etc. Approximately - at no load
8V, about -4V at maximum load. Boost circuit 3
Of course, the output voltage of 0 has no meaning unless it is designed to be lower than _Vss , and conversely, during normal booster circuit operation, _VL is always smaller than _Vss .

Therefore, the boost signal is obtained by converting a V _dd -V _ss level signal into a V _dd -V _L level signal using a level shifter that is very commonly used in watch electronic circuits. It is better to leave the P channel
The dimensions of MOST31 can be made smaller.

FIG. 12 shows an example of a circuit diagram of a level shifter.

This concludes the basic explanation of the present invention shown in FIG. 5, but chord pronunciation will be further explained.

As shown in the time chart of FIG. 13, when a chord is generated, two or more signals with different periods and amplitudes are combined at the common output terminal N of the envelope cell. At this time, for example, the first scale signal N ₁ is
Even if it is below the detection level of the level detector 40 described above, other scale signals such as
If it matches _N2 , only that portion may exceed the level of the level detector 40 and the sounding body is driven again. That is, in FIG. 13, time t ₁
At this point, the _N1 waveform has already fallen below the detection level of the level detector 40 (indicated by a dashed line), so the sounding element is not driven.

However, at time _t2 , as a result of combining _N1 and _N2 , the signal component of _N1 rises to the detection level again, and the sounding body is driven. As a result, the sounding body is driven by a signal different from the scale signal, and noise is generated. In order to further improve this point, the present invention provides the envelope cells 20A and 20B.
...improvements have been made.

FIG. 14 shows another embodiment of the envelope cell, in which the same parts as shown in FIG.
It is 8. The drain of the P channel MOST28 is connected to the gate end P, and the source and substrate are
Connected to V _dd . The gate is connected to the output Q of the data type flip-flop 29. The data input terminal D of the data type flip-flop 29 is connected to the output terminal S of the level detector 40, the positive clock input terminal φ is connected to the scale signal input terminal _L1 , and the set input terminal SE is connected to the scale signal input terminal L1. It is connected to the input terminal _K1 .

The operation of this circuit is relatively simple; when the sound signal applied to the individual input terminal _K1 reaches _Vdd , the data type flip-flop 29 is set, and the output terminal Q is set. Since the V _dd level appears and therefore the P channel MOST 28 is off, the MOST 24 is fully turned on, and therefore, when the scale signal applied to the individual input terminal L ₁ is at the V _ss level, the common output terminal N is Since a sufficiently high output level is obtained and the output terminal S of the level detector 40 is at the V _dd level, even if the scale signal changes from V _ss to V _dd , the data type flip-flop The state of the output terminal of 29 does not change.

After a certain period of time, the potential at the gate end P approaches V _dd as described above, and therefore the P channel
As the on-resistance value of MOST24 increases,
Even if the scale signal reaches the level of _Vss , the potential of the common output terminal N does not rise to a sufficient level, and therefore the output terminal S of the level detector 40 remains at the level of _Vss , Here, when the scale signal shifts from _Vss to _VDD , the level of the output terminal Q of the data type flip-flop 29 becomes the level of _Vss . Then the P channel MOST
28 is turned on, and the gate end P is completely pulled to the level of V _dd , so the N-channel MOST 2
4 is turned off, and this state is maintained until the next sound generation signal applied to the individual input terminal _K1 reaches the _Vdd level. That is, for a scale that is detected to be below the sound generation level by the level detector 40 even once, the output is completely prohibited until the next sound generation signal arrives, so that the above-mentioned problem does not occur.

FIG. 15 is a circuit diagram showing an example of improvement of the envelope cell from a different point of view, and in the envelope cell shown in FIG. 5 or 14, the N channel MOST 21 and the P channel MOST
Although it is required that the thresholds of 24 are substantially the same, this may not always be satisfied depending on the manufacturing conditions of the integrated circuit. Therefore, an improvement was made to allow for variation in the threshold voltages between the two. That is, the drain of the N-channel MOST 21 whose gate is connected to the common input terminal J ₁ is not directly connected to the gate end P, but is connected to the gate end P via a diode constituted by the new P-channel MOST 201. In addition, the source of the P channel MOST 25 is not directly connected to the common terminal M, but is connected to the common terminal M through a diode constituted by the new N channel MOST 202, so that the gate terminal P by the whisker signal is The level at which the potential of
The level of the gate terminal P at which the MOST turns off is both the threshold voltage of the N-channel MOST and the P level.
It is equal to the sum of the channel MOST threshold voltages, and can eliminate the influence of manufacturing variations.

As described above, the present invention incorporates various new technologies such that dispersed chords can be generated with different envelopes and can be built into an integrated circuit, and is superior to conventional methods having similar functions. , it is extremely advantageous in terms of cost, and the ability to provide high-quality products at low prices is very effective.

The gist of the present invention is to first enable a wide range of sounds and the sounding of chords;
Second, a new protection circuit was implemented to strengthen the resulting protection circuit, third, a booster circuit was used to obtain a sufficient sound level, and fourth, it was possible to produce dispersion chords, and The point is that we have created a sounding element drive circuit equipped with a new all-in-one envelope generation circuit that is capable of producing naturally attenuated sound. This envelope circuit includes the MOST21 and the MOST2.
4 have different conduction types, and the MOST2
1 is the source output, the MOST 24 is the drain output, and the main feature is that the MOST 21 is made conductive with a whisker-like ultra-fine pulse that is sufficiently short compared to the period.This allows a natural and smooth attenuation characteristic to be obtained. At the same time, it became possible to incorporate the capacitor 23 into the integrated circuit.

In the above description, the conductivity type of the transistor was limited, but it is clear that the same effect can be obtained even if all the P channels and N channels are replaced.
Of course, in this case, the voltage relationship is reversed. Furthermore, if the polarity of the power source to which the capacitor 23 is connected is changed, "discharging" and "charging" in the above description will be interchanged, but this does not affect the essence of the present invention.
Alternatively, the resistor 26 in FIG. 5 may be deleted, a current limiting resistor may be inserted into the drain or source of the transistor 21, or the transistors 21 and 201 or the transistor 2 may be replaced in FIG.
Changes such as replacing the insertion positions of 02, 25, and 24 are included in the present invention.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional sound generation drive circuit, Fig. 2 is a waveform diagram explaining the circuit operation of Fig. 1, and Fig. 3 is a waveform diagram explaining the circuit operation of Fig. 1.
The figure is a circuit diagram showing a conventional attenuated sound generation method, Figures 4a and 4b are waveform diagrams showing the differences between the conventional attenuated sound and the attenuated sound of the present invention, and Figure 5 is an implementation of the present invention. A circuit diagram showing an example, Fig. 6 is an operating waveform diagram of an envelope cell, Fig. 7 is a circuit diagram showing a whisker signal generation circuit, Fig. 8 is an operating waveform diagram of the circuit in Fig. 7, and Fig. 9 is a level detection diagram. Waveform diagram explaining the action of the device, No. 10
Figures a and 10b are a structural diagram and an equivalent circuit diagram showing a conventional protection circuit, Figures 11a and 11b are a structural diagram and an equivalent circuit diagram showing a protection circuit of the present invention,
Fig. 12 is a circuit diagram showing an example of a level shifter, Fig. 13 is a waveform diagram illustrating the pronunciation situation of dispersed chords,
FIG. 14 is a circuit diagram showing another embodiment of the envelope circuit of the present invention, and FIG. 15 is a circuit diagram showing still another embodiment of the envelope circuit of the present invention. 20... Envelope cell, 30... Boost circuit, 40... Level detector, 50... Driver,
51, 53...MOS transistor, 60...protection circuit, 70...sounding body.

Claims (1)

[Claims] 1. In a sounding element drive circuit having an envelope circuit that controls the charging/discharging characteristics of a capacitor by intermittent operation of a transistor, the envelope circuit is used to simultaneously charge (discharge) the capacitor 23 whose one end is connected to the power supply. and a second MOS transistor 22 for discharging (charging) the capacitor 23 for the time period of the extremely thin pulse signal applied to the gate end.
It has a MOS transistor 21 and a third MOS transistor 24 whose gate end is connected to the other end of the capacitor 23, whose source end is connected to the power supply side, and whose drain end is an output end.
The MOS transistor 21 and the third MOS transistor 24 are of different conductivity types, and the second MOS transistor 24 is of different conductivity type.
The drain end of the MOS transistor 21 is connected to the third
The source of the MOS transistor 24 is connected to the power supply side, and the source end is connected to the source of the transistor 24.
A sounding element drive circuit characterized in that it is connected to the gate side of No. 4.