JPS63294004A - Speaker driving circuit - Google Patents

Abstract

PURPOSE:To obtain an inexpensive and miniaturized speaker driving circuit by switching an input signal to the phase inverted signal in accordance with its polarity to input it to an amplifier and inputting the output of the amplifier to one or the other end of a speaker. CONSTITUTION:The signal from a signal source 1 switches a switch 6 to the side of a contact (a) and switches a switch 7 to the side of contacts (d) and (f) if the discrimination signal of a discriminating circuit 8 is '1'. Said signal switches the switch 6 to the side of contact (b) and switches the switch 7 to the side of contacts (c) and (e) if said discrimination signal is '0'. Consequently, the signal from the signal source 1 is in-phase and is amplified by an amplifier 2 and is supplied to a terminal P of a speaker 3 if the discrimination signal is '1'. The signal from the signal source 1 is inverted to the opposite phase through an inverter 4 having one voltage gain and is inputted to the amplifier 2 if the discrimination signal is '0'. Consequently, the input signal of the amplifier 2 is given as a positive potential, and it is amplified and is inputted to a terminal Q of the speaker 3 through the contact (e) of the switch. Thus, a maximum speaker driving output power is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a speaker drive circuit.

[Summary of the Invention] The present invention determines the polarity of a signal from an input signal source using a determination circuit, and according to the determination result, a signal from the input signal source and a signal obtained by determining the phase of the signal from the input signal source. A first switch is used to select and output one of the signals, the output is amplified by an amplifier, and a second switch is used to input the output of the amplifier to one end or the other end of the speaker, according to the judgment result of the judgment circuit. It is distinctive in that it is made into

[Prior Art] As a conventional speaker drive circuit, as shown in FIG.
It is known that a signal from an input signal source 1 is amplified by a power amplifier 2 and input to a speaker 3.

In this case, the maximum output power Po is determined by the impedance RL of the speaker 3 and the DC bias V applied to the amplifier 2.
Determined by CC. That is, if VQ is the effective value of the output of the amplifier 2 (FIG. S), it is expressed by the first-order equation (1).

RL RL As can be seen from equation (1), the maximum output power po is
Power supply voltage VCC and impedance RL of speaker 3
determined by Therefore, if the power supply voltage VCC and the impedance RL of the speaker 3 are fixed, the maximum output power Po cannot be increased any further.

For this reason, it is conventionally known to use the TL method as shown in FIG. 6 to increase the maximum output power PO. That is, the signal from the signal source 1 is input to the power amplifier 2, and the signal is input to the power amplifier 5 via the inverter 4.
The outputs of these power amplifiers 4 and 5 (FIG. 7) are input to both ends of the speaker 3.

[Problems to be Solved by the Invention] In such a TL type speaker drive circuit, the maximum output power Pot is as follows (2), and four times the power can be obtained compared to the example shown in FIG. However, such a conventional circuit has the drawback of requiring two power amplifiers.

An object of the present invention is to provide a speaker drive circuit that is extremely inexpensive and can be miniaturized.

[Means for solving the problem] In order to achieve such an object, in the present invention, a signal from an input signal source and a signal obtained by passing this signal through a phase inversion circuit are changed to have the polarity of the input signal. The present invention is characterized by the provision of a switch which switches the input signal to the amplifier according to the input signal and inputs the output of the amplifier to one end or the other end of the speaker depending on the polarity of the input signal.

[Function] In the present invention, by simply adding simple circuits such as a polarity determination circuit and a switch, it is possible to significantly increase the maximum output power with one power amplifier. A speaker drive circuit with high maximum output power can be realized.

[Example] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the speaker drive circuit according to the present invention, where 6 and 7 are switches, respectively.

8 is a determination circuit.

FIG. 2 is a signal waveform diagram of each part in FIG. Input signal waveform of (d)
indicates a signal waveform applied to the speaker 3.

The operation shown in FIG. 1 will be explained below with reference to FIG.

In FIG. 1, a signal from a signal source 1 is input to a determination circuit 8. The signal at this time is as shown in Figure 2 (,).

The determination circuit 8 determines whether the input signal is positive or negative, and uses the determination output to control the switches 6 and 7.The determination circuit 8 determines whether the input signal is positive or negative, and uses the determination output to control the switches 6 and 7. In the case of a signal of negative polarity, a determination signal of "l l 11" is obtained, and in the case of a signal of negative polarity, a determination signal of "□ jl" is obtained, and the switches 6 and 7 are controlled by this output signal. The positive polarity signal at this time is
It is shown between t□→tif t and →t4 in FIG. 2(a), and the negative polarity signal is shown between t2→t3t in FIG. 2(a).
t.

→t, is shown between. Therefore, the output signal waveform of the determination circuit 8 is as shown in FIG. 2(b).

It becomes “1” between t1→tzt t3→t4, and t2
→t31 becomes “0” between t4 and →t.

Next, when the determination signal from the 1 determination circuit 8 is 1'', the switch 6 is turned to the a side, and the switch 7 is turned to the d and f sides.

Further, when the determination signal is 'O'', the switch 6 is turned to the b side, and the switch 7 is turned to the e side and the e side at the same time.

Therefore, when the determination signal is "1"', the signal from the signal source 1 is input to the power amplifier 2 in the same phase as the signal from the signal source 1. The signal waveform at this time is t1→t2t t,→ in FIG. 2(c).
It will be like during t1. The amplifier 2 amplifies this input signal and supplies it to the P terminal of the speaker 3 via the d side of the switch 7. Here, the dynamic range given to the speaker 3 is +Vcc.

Next, when the determination signal is 110 It, the signal from the signal source 1 is passed through the inverter 4 with a voltage gain of 1, inverted to the opposite phase, and input to the amplifier 2. Therefore, since the input signal to the amplifier 2 is given as a positive potential, the signal waveform at this time becomes as shown in FIG. 2(c) between t2→titt4→t5. The amplifier 2 amplifies this signal and supplies it to the Q terminal of the speaker 3 via the e side of the switch 7.

Here, the dynamic range given to the speaker 3 is -VCC. Therefore, the signal applied to the speaker 3 becomes as shown in FIG. 2(d).

From the above, the maximum output power P1 is RL RL This is four times as large as the conventional circuit shown in FIG.

FIG. 3 shows a specific configuration of the inverter 4 shown in FIG. 1, in which 11 is a differential amplifier with high input impedance;
12 is a level shift circuit for shifting down the bias voltage VB of the differential amplifier 11; R1-R8 are resistors;
C1 and C are capacitors.

The inverter 4 must invert the negative voltage of the signal from the signal source 1 to a positive voltage without distortion, but it is generally difficult for semiconductor active devices to handle large negative input voltages. The inverter shown in Figure 3 has no distortion even with a large negative input voltage.
Phase inversion operation can be performed normally.

In FIG. 3, a signal from a signal source 1 is input to a differential amplifier 11 via a coupling capacitor C1 and a resistor R2. Since the input impedance of the differential amplifier 11 is high, the bias voltage VB of the differential amplifier 11 can be applied to the bias voltage VB of the differential amplifier 11 without any voltage loss caused by the resistors R1 to R3.
added to one input. Assuming that the values of the resistors R2 and R4 are equal, the output of the differential amplifier 11 becomes a signal having a phase opposite to that of the signal from the signal source 1, with the voltage VB as the center. The level shift circuit 12 shifts down the voltage vB. Therefore, the inverter can also invert negative polarity input signals without distortion.

Note that as the determination circuit 8, a DC amplifier with a sufficiently large gain or a comparator whose reference point is set at the "0" point of the AC signal can be used.

[Effects of the Invention] As described above, according to the present invention, the following effects can be obtained.

(1) Only one power amplifier is required, and accordingly, only one heat sink is required, making it possible to reduce the cost and space significantly.

(2) A large dynamic range can be obtained even if the power supply voltage is small.

[Brief explanation of the drawing]

1 is a circuit diagram of an embodiment of the speaker drive circuit according to the present invention, FIG. 2 is a signal waveform diagram of each part of FIG. 1, FIG. 3 is a circuit diagram of a specific example of the inverter of FIG. 1, and FIG. 5 and 6 are circuit diagrams of conventional speaker drive circuits, and FIGS. 5 and 7 are speaker input signal waveform diagrams of the circuits shown in FIGS. 4 and 6, respectively. 1... Signal source. 2...Power amplifier. 3... Speaker, 4... Inverter, 6.7... Switch, 8... Judgment circuit. Patent Applicant Clarion Co., Ltd. Agent Patent Attorney Nagai 1) Take 3, Department Figure 1 Figure 3 Figure 4 Figure 6 Figure 5! Figure 7

Claims (1)

[Claims] an input signal source, a determination circuit that determines the polarity of a signal from the input signal source, a phase inversion circuit that inverts the phase of the signal from the input signal source, a signal from the input signal source, and the phase inversion circuit. a first switch that switches and outputs a signal from the circuit according to the determination result of the determination circuit; an amplifier that amplifies the signal outputted via the first switch; The second output signal is configured such that the output signals are input to different terminals.
A speaker drive circuit comprising: a speaker;