JPH073689Y2 - Load control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for controlling a load such as a power amplifier used in, for example, an in-vehicle audio device.

2. Description of the Related Art FIG. 4 is a block diagram showing a typical configuration example of the vehicle-mounted acoustic device 1. The on-vehicle audio device 1 includes a reproducing unit 2 such as a magnetic tape reproducing device, a signal processing unit 3 that performs various kinds of processing on a reproduced acoustic signal, and a speaker 4 that produces sound by the output of the signal processing unit 3. Is included. Signal processing unit 3
Is provided with a miuteing circuit 6 for performing a miuteing operation for eliminating residual noise when the power source 5 of the on-vehicle audio device 1 is de-energized. Drive voltage is applied.

A voltage drop detection circuit 10 is connected to the power supply 5, and the power supply voltage V is level discriminated with respect to a predetermined reference voltage V1. The output is given to the switching circuit 11 and is cut off when the voltage drops. When the switching circuit 11 is in the conducting state, its output is input to the constant voltage circuit 12 to generate a predetermined constant voltage V2. This output voltage V2 is, for example, a chip enable terminal of the microcomputer 13.
While input to CE and the constant voltage V2 is supplied to the chip enable terminal CE, the microcomputer 13 is in an operable state. This Micro Computer 13
Output terminal PO for controlling start / stop of the signal processing unit 3
The output terminal PON is connected to the muting circuit 6 of the signal processing unit 3.

In such a configuration, when the power is turned off or the power supply voltage V drops, the voltage drop detection circuit 10
This state is detected, the switching circuit 11 is cut off, the output of the constant voltage circuit 12 becomes low level, the microcomputer 13 stores the internal data, and indicates the stop of the signal processing unit 3 from the output terminal PON. The operation is stopped after processing such as outputting a signal. Power supply voltage V of power supply 5
When returns to the normal state, the switching circuit 11 becomes conductive and the microcomputer 13 becomes operable.
After that, the microcomputer 13 outputs a signal indicating the activation of the signal processing unit 3 from the output terminal PON, cancels the muting operation of the muting circuit 6, and activates the signal processing unit.

FIG. 5 is an electric circuit diagram showing a configuration example of the voltage detection circuit 10, the switching circuit 11 and the constant voltage circuit 12 in the conventional example. A conventional example will be described with reference to FIG. The voltage drop detection circuit 10 includes a series circuit of a Zener diode 15 and a resistor 16 which are connected in parallel to a signal line 14 to which the power supply voltage V is input. The anode of the Zener diode 15 is connected to the base of the transistor 18 via the resistor 17, and the pull-down resistor 19 is connected to this base. The emitter of the transistor 18 is grounded, and the collector is connected to the base of the transistor 20 which constitutes the switching circuit 11 via the resistor 21.

The emitter of the transistor 20 is connected to the signal line 14 via a resistor 22, and the collector is connected to the chip enable terminal of the microcomputer 13 via a signal line 26.
Connected to CE. A capacitor 23, a zener diode 24 and a resistor 25 are connected in parallel to the signal line 26 from the transistor 20 side, and these constitute a constant voltage circuit 12.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above-described conventional technique, first, the following problems are caused in the voltage drop detection circuit 10, the switching circuit 11 and the constant voltage circuit 12 which generate the chip enable signal to the microcomputer 13. In the voltage drop detection circuit 10, the level of V of the power supply voltage is a single reference voltage V1 (transistor 18
The threshold voltage related to the operation of the switching circuit 11 is used to discriminate the level. Therefore, when the power supply voltage V fluctuates in the vicinity of the reference voltage V1 due to the inclusion of noise in the signal line 14, the switching circuit 11 is turned on / off. The cutoff state is repeated, and accordingly, the microcomputer 13 repeats the operating state / non-operating state, and the sound generation operation and various display operations of the vehicle-mounted audio device 1 controlled by the microcomputer 13 are intermittent. The operation quality is extremely deteriorated.

Further, the activation / stop of the signal processing unit 3 is controlled by the signal from the output terminal PON of the microcomputer 13, but when the power supply voltage drops and the output of the constant voltage circuit 12 becomes low level, , It takes time (about 50 milliseconds) until the signal processing unit 3 is stopped by the output of the output terminal PON detected by the microcomputer 13, and noise is generated during that time. Particularly, when the operation / non-operation of the microcomputer 13 as described above is repeatedly performed, noise is generated each time, and the operation quality is further deteriorated.

An object of the present invention is to provide a load control device that solves the above technical problems.

Means for Solving the Problems The present invention compares a level of a power supply voltage with a first reference level and a second reference level, and discriminates when the power supply voltage changes across both of the first and second reference levels. A level discriminating means for switching the level, and a control means for detecting that the discriminating signal level of the level discriminating means has switched and performing a process associated with a power supply fluctuation and then outputting a load start / stop control signal. A load control device comprising: a discriminating means for inputting a discriminating signal of the level discriminating means and a control signal of the control means, and performing start / stop control of the load according to the logic of the discriminating signal and the control signal. Is.

The level discriminating means of the present invention switches the discrimination signal level only when the power supply voltage level changes over both the first reference level and the second reference level.

Therefore, even when the power supply voltage level undesirably fluctuates in the vicinity of the first reference level or the second reference level, the width of the fluctuation causes the level difference between the first reference level and the second reference level. In the range that does not exceed, the discrimination signal level is held, and the discrimination signal level can be held stably despite the undesired fluctuation of the input signal.

The control signal of the control means for detecting the switching of the discrimination signal level and outputting the load start / stop control signal after performing the processing associated with the power supply fluctuation and the start / stop of the load according to the logic of the discrimination signal. Stop control was performed. Therefore, the start / stop control of the load due to the power supply fluctuation can be performed with good timing.

Embodiment FIG. 1 is a block diagram showing the basic construction of an on-vehicle audio device 30 according to an embodiment of the present invention. Referring to FIG. 1, the vehicle-mounted acoustic device 30 has a reproducing unit 31 such as a magnetic tape reproducing device or a compact disc (CD) reproducing device, and the reproduced acoustic signal is input to the signal processing unit 32. Is output to the speaker 34 via the amplifier circuit 33 and is converted into sound. Such a signal processing unit 32 includes a meeting drive circuit 35 and receives a signal from a voltage conversion circuit 36 having a configuration described later. The voltage conversion circuit 36 detects the power supply operation for performing the level discrimination operation for two different discrimination levels V11, V12 V11 <V12 (1) for the power source voltage V of the power source 37 such as a vehicle battery as described later. The circuit 38 and the power stop detection circuit 39 are connected.

The voltage conversion circuit 36 is connected to a signal generation circuit 40, and the output thereof is a chip enable terminal of a microcomputer 41.
Input to CE.

Here, FIG. 2 is an electric circuit diagram showing a specific structural example of the present embodiment. This embodiment will be described with reference to FIG. A series circuit of a zener diode 42 and a resistor 43 is connected in parallel to a power supply line 41 from a power supply 37.
The anode of the Zener diode 42 is connected to the base of the transistor 45 via the resistor 44, and is also connected to the base of the transistor 47 via the resistor 46. The bases of these transistors 45 and 47 are pull-down resistors 48 and
49 is connected and the emitter is grounded. The collector is also connected to the second power supply voltage B via pull-up resistors 50 and 51.

The collector of the transistor 45 is input to the 2-input NAND circuit 52, and the collector of the transistor 47 is input to the NAND circuit 24 of the input via the inverting circuit 53. The output of the NAND circuit 52 is input to the NAND circuit 54, and the output of the NAND circuit 54 is input to the chip enable terminal CE of the microcomputer 41 via the inverting circuit 55 and also to the NAND circuit 42. Here, the RS flip-flop circuit (hereinafter, abbreviated as FF circuit) including the NAND circuits 52 and 54 and the inverting circuits 53 and 55.
70 are composed.

Further, the zener diode 42, the resistor 43, and the transistor 45 constitute the power supply operation detection circuit 38, and the zener diode 42, the resistor 43, and the transistor 47 constitute the power supply stop detection circuit 39. Further, the voltage conversion circuit 36 is configured to include the resistors 50 and 51, and the signal generation circuit 40 is configured to include the FF circuit 70.
Is configured.

The output of the NAND circuit 54 is input to the meeting drive circuit 35. This miuteing drive circuit 35 includes a resistor 57 connected to the base of a transistor 56,
The output of the NAND circuit 54 is input. A pull-down resistor 58 is connected to the base of the transistor 56, and the emitter is grounded. The collector is connected to the startup control signal output terminal PON of the microcomputer 41 via the resistor 59,
A wire and gate 60 is constructed.

The collector output of the transistor 56, that is, the output of the start control signal output terminal PON of the microcomputer 41 is the amplifier circuit 3
The so-called standby terminal S of the power amplifier 61 which constitutes 3
Connected to B. That is, when the signal of either the output terminal PON or the collector of the transistor 56 becomes low level, the power amplifier 61 performs the muting operation. Therefore, after the power is turned on, the microcomputer 41 is activated, and the initialization of the volume etc. is completed, the output terminal PON
It is possible to prevent unnecessary noise from being reproduced until the level becomes high. The power amplifier 61 includes the reproducing unit.
The acoustic signal from 31 is input, and its output is supplied to the speaker 34 as a + input signal, and is also input to the power amplifier 63 via the inverting circuit 62. The power amplifier 63 produces the-input signal of the speaker 34. A signal obtained by dividing the output of the power amplifier 61 by the resistors 64 and 65 is input to the inverting circuit 62.

FIG. 3 is a time chart for explaining the operation of this embodiment. The configuration of this embodiment will be described with reference to FIG. First, as shown in (1) of FIG.
Rises from 0 level, the operating voltage of transistor 47 V1
Transistor 47 conducts at the input signal level Vb corresponding to 2. After this, the power supply voltage V further rises, and the transistor
When the input voltage Va corresponding to the operating voltage V11 of 45 is reached, the transistor 45 becomes conductive. In the FF circuit 70, the output rises to the high level at the time t2 only when not only the input signal of the inverting circuit 53 but also the input signal of the NAND circuit 52 goes to the high level. As a result, the micro computer 41 becomes operable. Then, when the microcomputer 41 completes the initialization of the volume and the like and sets the output terminal PON to the high level at time t5, the standby terminal BS of the power amplifier 61 is given a high level signal, and the miute is released. After that, when the power supply voltage V decreases from the operating voltage, for example, 13.2V, when it falls below the voltage Va, the transistor 45 is cut off as shown in FIG. 3 (3). At this time t3, the FF circuit
The output of 70 has not been switched yet. After that, the power supply voltage V
Is decreased, and at time t4 when the input signal level Vb has passed, the transistor 47 is cut off, and at this timing, the FF circuit 70 switches the output to the low level, and at the same time, the standby terminal BS of the power amplifier 61 becomes the low level, and The action is taken. After that, at time t6, the microcomputer
41 output terminal PON goes low.

That is, even when the input signal level undesirably fluctuates in the vicinity of the voltage Va when attempting to energize the microcomputer 41, the flip-flop circuit 70 maintains a constant level as long as the input voltage does not fall below the voltage Vb. Hold.
The same applies to the voltage Vb. In this way, stable operation of the micro computer 41 is guaranteed.

On the other hand, as described above, the standby input terminal SB of the power amplifier 61 is controlled by the logical product of the output of the NAND circuit 54 output via the switching transistor 56 and the output of the output terminal PON of the microcomputer 41. It Therefore, when the power supply voltage V is lowered and the chip enable signal CE of the micro computer 41 is switched to the low level, and the micro computer 41 is stopped, the operation of the power amplifier 61 is performed at the same timing (time t4). Be stopped. When the power supply voltage rises, the power amplifier is activated when the activation of the microcomputer 41 is completed. As a result, not only the generation of undesired noise when the power supply voltage is cut off can be preferably removed, but also a configuration for removing the noise when the system is stopped can be realized very simply. In the present embodiment, the discrimination levels V11 and V12 of the power supply operation detection circuit 38 and the power supply stop detection circuit 39 are set to a common Zener diode 42 and a resistor 44, respectively.
Since it is determined by the resistance ratio of 48 and the resistance ratio of the resistors 46 and 49, the adverse effect due to the variation of the zener diode that occurs when the discrimination level is determined by independent zener diodes is eliminated.

As described above, according to the present invention, the discrimination signal level can be stably maintained even when the level of the power supply voltage changes undesirably near the first reference level or the second reference level. . The load start / stop control due to the power supply fluctuation detects the switching of the discrimination signal level, and after performing the processing associated with the power supply fluctuation, the load start / stop signal output from the control means and the discrimination The operation is performed based on the logical operation with the signal. As a result, it is possible to immediately perform load start / stop control due to power supply fluctuation.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic constitution of an embodiment of the present invention, FIG. 2 is an electric circuit diagram showing a concrete constitution example, FIG. 3 is a time chart for explaining the operation of the embodiment, and FIG. FIG. 5 is a block diagram showing a typical prior art configuration, and FIG. 5 is an electric circuit diagram showing a partial configuration example of the conventional example. 30 …… Vehicle audio equipment, 32 …… Signal processing unit, 33 …… Amplification circuit, 35 …… Muteing drive circuit, 36 …… Voltage conversion circuit, 37 …… Power supply, 38 …… Power supply operation detection circuit, 39… … Power stop detection circuit, 40… Signal generation circuit, 61… Power amplifier, CE… Chip enable signal, SB… Standby input terminal

Claims (1)

[Scope of utility model registration request] 1. A power supply voltage level is compared with a first reference level and a second reference level, and the power supply voltage is the first and second reference levels.
The level discrimination means that the discrimination level is switched when it changes over both reference levels, and the fact that the discrimination level of the level discrimination means is switched is detected, and the load is activated after the processing associated with the power supply fluctuation is performed. / A control means for outputting a stop control signal, a discrimination means for inputting a discrimination signal of the level discrimination means and a control signal of the control means, and performing start / stop control of the load based on the discrimination signal and the logic of the control signal A load control device comprising: