JP2001054298A - Power control apparatus for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power control apparatus for automobile which generates little noise. SOLUTION: This power control apparatus for an automobile is equipped with a PWM control means 11, outputting a pulse signal, which is pulse- modulated with a desired duty ratio, a trapezoidal wave forming circuit 20 forming a trapezoidal wave signal wherein a changing part of the pulse signal is corrected, so as to time-change with a prescribed gradient to restrain noise generation in a load, an output control circuit 30 controlling a current which is driven by the trapezoidal wave signal and flows into the load, and a trapezoidal wave control circuit 50 which controls the trapezoidal wave forming means, in response to the state of the load and controls adequately the gradient. By controlling the trapezoidal wave signal in response to the state of the load, noise reduction mores satisfactory than that in the conventional technique can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control device for an automobile, which is provided between a DC power supply and a load and controls the power supplied from the power supply to the load by pulse width modulation (PWM).

[0002]

2. Description of the Related Art Conventionally, a means for dimming a lamp mounted on an automobile or adjusting the number of revolutions of a motor is provided with a power transistor between the lamp and the motor, that is, a load and its power supply. A technique for PWM controlling a power transistor is generally known. However, in this technology, the noise generation due to a sudden change in the load current is large,
There is a possibility that the vehicle-mounted radio, the ECU and the like may be adversely affected.

In order to suppress such noise generation,
In the prior art, a pulse signal input to the output control circuit was converted from a square wave to a trapezoidal wave. The output control circuit detects the load current based on the trapezoidal wave and feeds back the load current, so that the time change rate (gradient) of the current or voltage at the rising and falling portions of the trapezoidal wave is always constant. Had gone.

[0004] Specifically, as shown in FIG. 6, an output control circuit 30 is provided between a load 40 and a battery B or a power generator as a DC power supply. The output control circuit 30 is connected to the feedback control current detection circuit 31
It has an SFET 32 and a gate voltage control circuit 33. The PWM control means 11 serving as the PWM means supplies the trapezoidal wave generation circuit 20 with a pulse signal whose voltage is periodically turned on and off so as to have a predetermined duty ratio. The trapezoidal wave generation circuit 20 generates a trapezoidal wave signal having a duty ratio based on the supplied pulse signal and having a constant slope, and supplies the trapezoidal wave signal to the gate voltage control circuit 33.
Then, the feedback control current detection circuit 31 supplies a load current signal proportional to the current flowing through the load to the gate voltage control circuit 33.

Next, the gate voltage control circuit 33 generates a control signal in which the load voltage is proportional to the supplied trapezoidal wave signal, and supplies the control signal to the gate of the MOSFET 32.

That is, in the prior art, the MOSFET 3
The load current is feedback-controlled so that the slope of the trapezoidal wave current flowing through the load through the gate voltage of No. 2 becomes constant to suppress the generation of electromagnetic noise.

[0007]

However, the value of the load current varies depending on a change in the load state due to a change in the state of the load or a change in the optional electric components or the like. The slope of the trapezoidal wave that controls the temperature was fixed. Therefore, the slope of the trapezoidal wave has been determined to be optimal when the maximum load current value is assumed. In other words, when the current value increases or the slope of the trapezoidal wave becomes gentle, the MOS
Since the heat generated from the FET increases, the slope of the trapezoidal wave is made as large as possible in accordance with the maximum value of the load current in order to suppress the heat generated.

In this case, in the conventional power control apparatus for a vehicle, even when the actual load is small and the value of the load current is small, the slope of the trapezoidal wave is unnecessarily large, so that the noise generation cannot be sufficiently suppressed. There was a case.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power control apparatus for an automobile which generates less noise even when the load changes.

[0010]

The present invention has been made to solve the above problems, and the inventors have invented the following means.

(First Means) A first means of the present invention is a power control device for a vehicle according to the first aspect.

According to the present invention, there is provided an electric power control apparatus for a vehicle having a PWM means, a trapezoidal wave generating means and an output control means, further comprising a trapezoidal wave controlling means.

It should be noted that the present invention is applicable not only to PWM but also to pulse amplitude modulation (PAM) and pulse density modulation (PD).
M) can also be applied to noise reduction. This is because, in the PAM and the PDM, a steep pulse-like current change occurs with the power control similarly to the PWM.
Therefore, in this specification, “PWM” means “PA
M "and" PDM ".

The PWM means is a means for supplying a pulse signal pulse-modulated at a desired duty ratio to the trapezoidal wave generating means to drive the load. On the other hand, the trapezoidal wave control means is a means for generating a control signal for controlling the trapezoidal wave generation means and supplying the control signal to the trapezoidal wave generation means. The trapezoidal wave generating means is a means for generating a trapezoidal wave having a predetermined inclination based on a pulse signal input from the PWM means and a control signal from the trapezoidal wave control means. The output control means has a power transistor and is a means for controlling a current flowing through the load or a voltage applied to the load so as to have power corresponding to the supplied trapezoidal wave signal.

The PWM means supplies the trapezoidal wave generating means with a pulse signal pulse-modulated at a desired duty ratio to drive the load. As a method of generating the pulse signal, a known method can be applied. For example, a triangular wave comparison method or a pattern method is used. Here, the method of changing the duty ratio is not particularly limited. Therefore, if it is a method that can change the duty ratio of the pulse signal output from the PWM means by other methods as well as a known method,
Either method can be adopted.

The trapezoidal wave control means generates a trapezoidal wave control signal for controlling the trapezoidal wave generation means, and supplies the trapezoidal wave control signal to the trapezoidal wave generation means. The trapezoidal wave control signal is generated based on the state of the load to be controlled. The trapezoidal wave control signal has a predetermined gradient of a time change rate of a voltage or a current (hereinafter, collectively referred to as “gradient”) at a rising portion and a falling portion of the trapezoidal wave generated by the trapezoidal wave generating means. Control signal.
Here, the predetermined slope is a slope that is appropriately controlled so that the amount of noise generated by the current flowing through the load is reduced.

That is, the power control apparatus for a vehicle according to the present invention makes the slope of the trapezoidal wave signal gentle when the load becomes small. When the load increases, the slope of the trapezoidal wave signal is made steep.

As a method of obtaining the load state, for example, a method of directly or indirectly measuring a load voltage, a load resistance, or a load current, obtaining the average value or an integrated value over a certain period of time, or indirectly obtaining other parameters. A method of determining the magnitude of the load, a method of determining the magnitude of the load by referring to data of the load measured in advance according to the state of the control, and the like. In this case, the magnitude (output) of the load increases as the load resistance decreases and as the load voltage or the load current increases.

The trapezoidal wave generating means generates a trapezoidal wave having a predetermined inclination based on the pulse signal input from the PWM means and the trapezoidal wave control signal from the trapezoidal wave control means. That is, the width of the trapezoidal wave of the trapezoidal wave signal is generated based on the pulse width of the pulse signal, and the slope of the trapezoidal wave signal is generated based on the trapezoidal wave control signal. Then, the trapezoidal wave generator supplies the generated trapezoidal wave signal to the output controller.

The output control means controls the current flowing through the load or the voltage applied to the load so that the power corresponds to the supplied trapezoidal wave signal.

In this means, the output voltage is adjusted by the output control means so that the value of the load voltage or the load current is proportional to the trapezoidal wave signal. The wave generation means may supply a signal adjusted so that the final load voltage or load current becomes a trapezoidal wave to the output control means as a trapezoidal wave signal.

By controlling the slope of the trapezoidal wave signal for driving the output control means in accordance with the fluctuation of the load, the slope of the trapezoidal wave flowing to the load can be made appropriate. In the present means, by supplying the trapezoidal wave signal thus controlled to the output control means, it is possible to suppress heat generation from the power transistor and to reduce noise.

Therefore, according to the present means, the slope of the trapezoidal wave signal is controlled so that the time change rate of the current flowing through the load or the like according to the state of the load becomes appropriate, so that the generated noise is reduced. effective.

(Second Means) A second means of the present invention is an electric power control apparatus for a vehicle according to the second aspect.

In the present invention, the trapezoidal wave control means detects a load current flowing through the load and generates a load current signal, and detects a load current signal supplied thereto and detects a resistance value of the load to obtain a trapezoidal waveform. Load resistance detecting means for generating a wave control signal.

The load current detecting means supplies a load current signal corresponding to the current flowing through the load to the load resistance detecting means.
The load resistance detection means detects a load resistance value based on the supplied load current signal, and generates a trapezoidal wave control signal. As a method of detecting the load resistance, for example, there is a method of obtaining the load resistance from an average of the load current signals at predetermined time intervals. This trapezoidal wave control signal is supplied to trapezoidal wave generation means.

Therefore, according to this means, in addition to the effect of the above-mentioned first means, it is possible to cope with frequent changes in the state of the power-controlled load by feeding back the actual state of the load. This has the effect of being further reduced.

(Third Means) A third means of the present invention is an electric power control apparatus for a vehicle according to the third aspect.

In this means, the trapezoidal wave control means comprises:
It has a memory for storing the load status as load data in advance. The memory then provides load data to the trapezoidal wave control means. Here, the load data is data indicating a load state such as a load current value and a load resistance value corresponding to the load.

The trapezoidal wave control means generates a trapezoidal wave control signal to be supplied to the trapezoidal wave generation means based on the provided load data. The memory can be, for example, a memory of a microcomputer. It is preferable that this memory is a rewritable non-volatile memory for the purpose of continuously storing data and setting a trapezoidal wave slope corresponding to the optional electric component.

Therefore, according to this means, in addition to the effect of the above-mentioned first means, there is an effect that the load current detecting means and the like are not required and the cost can be reduced.

(Fourth Means) A fourth means of the present invention is an electric power control apparatus for a vehicle according to the fourth aspect.

The trapezoidal wave control means in the vehicle power control apparatus according to the present invention includes a memory for storing a load state as load data in advance, a load current detecting means for detecting a load current flowing through the load, and a load current detecting means for detecting the load current. Load resistance detecting means for detecting the resistance value of the load, and load determining means for updating the load data stored in the memory.

The load current detecting means supplies a load current signal corresponding to the current flowing through the load to the load resistance detecting means.
The load resistance detecting means detects a load resistance value based on the supplied load current signal, and generates a load signal indicating the load resistance value. The load determining means compares the load signal supplied with the load signal with the corresponding load data stored in the memory, and when it is determined that the load has changed, calculates new load data and stores the new load data in the memory. That is, the load data stored in the memory is updated with new load data derived from the load current detected by the load current detecting means. The trapezoidal wave control means generates a trapezoidal wave control signal supplied to the trapezoidal wave generation means based on the load data.

Therefore, according to this means, in addition to the noise reduction effect of the third means, there is an effect that it is possible to flexibly cope with a temporal change in load characteristics after shipping and the like.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the power control device for a vehicle according to the present invention will be clearly and fully described in the following embodiments so that those skilled in the art can understand the present invention.

<Embodiment 1> (Configuration of Embodiment 1) A power control device for a vehicle according to a first embodiment of the present invention has a configuration as shown in FIG. It is.

That is, the power control apparatus for a vehicle according to the present embodiment includes a CPU 10, a trapezoidal wave generation circuit 20 as trapezoidal wave generation means, an output control circuit 30 including a power transistor, and a current detection as load current detection means. And a circuit 51. The CPU 10 implements a PWM control unit 11 as a PWM unit and a load detection unit 52 as a load resistance detection unit as logic.

The PWM control means 11 is a logic in the CPU 10 for generating a pulse signal having a duty ratio such that the brightness of the vehicle interior light desired by the user is obtained. Here, the PWM control means 11 is connected to the trapezoidal wave generation circuit 20. The duty ratio is controlled by a variable voltage generator or CPU.
With the logic of 10, it can be changed according to the use condition of the automobile and the desire of the user.

The CPU 10 is a dedicated microcomputer for a dimming circuit of the vehicle interior light 40. However, the CPU 10 may also be used as a CPU of a microcomputer that controls other electrical components of the automobile.

The current detection circuit 51 detects a current flowing through the load 40 to generate a load current signal, and supplies the load current signal to the load detection means 52 via an A / D converter built in the CPU 10. Circuit. Current detection circuit 51
Is composed of a shunt resistor (not shown) and an operational amplifier (not shown) for amplifying a potential difference between both ends of the shunt resistor. This shunt resistor is inserted in a power supply line connecting the battery B and the load 40. The input terminal of the operational amplifier is connected to both ends of the shunt resistor.

The load detecting means 52 detects the resistance of the load based on the load current signal supplied from the current detecting circuit 51 and generates a trapezoidal wave control signal for controlling the inclination of the trapezoidal wave. .

The trapezoidal wave generation circuit 20 includes a PWM control unit 1
1 and a trapezoidal wave control signal supplied from the load detection means 52.
This is an analog circuit that generates a trapezoidal wave signal to be supplied to 0.

The output control circuit 30 is an analog circuit for supplying a current proportional to the supplied trapezoidal wave signal to the vehicle interior light 40. The output control circuit 30 includes a feedback control current detection circuit, a MOSFET 32, and a gate voltage control circuit. The feedback control current detection circuit is a circuit that detects the magnitude of the load current and supplies the detected magnitude of the load current to the gate voltage control circuit. The gate voltage control circuit is further supplied with a trapezoidal wave signal, and generates a control signal such that the load current is proportional to the trapezoidal wave signal, and supplies the control signal to the gate of the MOSFET 32.

(Operation and Effect of First Embodiment) The power control device for dimming the interior light of the vehicle according to this embodiment has the following operation and effect because it is configured as described above.

The PWM control means 11 includes a vehicle interior light 40
Supplies a pulse signal to the trapezoidal wave generation circuit 20 at a duty ratio appropriately set so that the desired brightness is obtained. Here, the duty ratio is changed by the user operating a variable resistor or the like in the above-described variable voltage generating device so that the brightness of the interior light of the vehicle becomes desired.

The pulse signal is generated by the logic in the CPU 10 by the PWM control means 11 based on the duty ratio.

The current detection circuit 51 generates a load current signal having a voltage value proportional to the current flowing through the load 40 by amplifying the potential difference between both ends of the shunt resistor by the operational amplifier. The generated load current signal is supplied to the load detecting means 52.

The load detecting means 52 detects the resistance of the load based on the load current signal supplied from the current detecting circuit 51 and generates a trapezoidal control signal. That is, the load detecting means 52 calculates an average value of the load current signal over a certain period of time, calculates the magnitude of the load from the average value, and generates a trapezoidal wave control signal. The generated trapezoidal wave control signal is supplied to the trapezoidal wave generation circuit 20.

The trapezoidal wave generation circuit 20 includes a PWM control unit 1
1 and a trapezoidal wave control signal generated by the load detection circuit 52 to generate a trapezoidal wave signal. The duty ratio of the generated trapezoidal wave signal is the same as the duty ratio of the pulse signal. Further, the slope of the trapezoidal wave is determined based on the trapezoidal wave control signal.
That is, the trapezoidal wave generation circuit 20 generates a trapezoidal wave by changing the rising part and the falling part of the square pulse signal to an appropriate slope in accordance with the trapezoidal wave control signal. Then, the trapezoidal wave generation circuit 20 supplies the generated trapezoidal wave signal to the output control circuit 30.

The output control circuit 30 supplies a current proportional to the supplied trapezoidal wave signal to the vehicle interior light 40. That is, the trapezoidal wave signal is input to the gate voltage control circuit,
The gate voltage of the MOSFET 32 is feedback controlled so that the magnitude of the load current is compared with the magnitude of the load current supplied from the feedback control current detection circuit and is proportional to the trapezoidal wave signal.

That is, the power control apparatus for a vehicle according to the present embodiment detects the state of the load 40 and controls the trapezoidal wave generation circuit 20 so as to suppress a sharp current change according to the state of the load 40. Since it becomes possible to make the slope of the load current appropriate, it is possible to further reduce the generation of noise during power control.

Therefore, according to the power control apparatus for a vehicle of the present embodiment, there is an effect that noise generation can be further reduced as compared with the prior art.

<Embodiment 2> (Configuration of Embodiment 2) The power control apparatus for a vehicle according to Embodiment 2 of the present invention has a configuration as shown in FIG. Device. That is, the power control device for a vehicle according to the present embodiment includes a CPU 10, an EEPROM 54 as a memory, a trapezoidal wave generation circuit 20,
And an output control circuit 30.

The EEPROM 54 is connected to the CPU 10 and is located in an address space from which the CPU 10 can read and write. The EEPROM 54 stores load data in advance. Here, the load data is control data used for the trapezoidal wave control signal,
This is control data for controlling the trapezoidal wave generation circuit 20 so that the inclination of the trapezoidal wave is optimal according to the type and number of the vehicle interior lights 40.

The CPU 10 is the same as that described in the first embodiment. Then, the CPU 10 implements the PWM control unit 11 and the load detection unit 52 as logic,
The PWM control means 11 is the same as that described in the first embodiment. However, unlike the first embodiment, the load detecting means 52 generates a trapezoidal wave control signal based on the load data stored in the EEPROM 54. The generated trapezoidal wave control signal is supplied to the trapezoidal wave generation circuit 20. And
The trapezoidal wave generation circuit 20 and the output control circuit 30 are the same as those described in the first embodiment.

(Effects of Embodiment 2) The power control device for a vehicle of the present embodiment is constructed as described above, and exhibits the following effects.

PWM control means 11, trapezoidal wave generation circuit 2
0 and the operation of the output control circuit 30 are the same as those described in the first embodiment.

The load detecting means 52 converts the load data into EEP
It reads from the ROM 54 and generates a trapezoidal wave control signal.
Then, the trapezoidal wave control signal is supplied to the trapezoidal wave generation circuit 20 via the D / A converter.

As a result, in the power control apparatus for a vehicle according to the present embodiment, the gradient of the current flowing through the load is appropriately suppressed according to the load, that is, the steep change of the current flowing through the load is suppressed, and the generation of noise is suppressed. Can be reduced. In addition, the power control device for a vehicle according to the present embodiment does not require a current detection circuit, so that the cost can be reduced. Further, it is possible to cope with a change in load due to a difference between optional electrical components by rewriting the contents of the EEPROM 54. Also, even if it becomes necessary to change the load data, if the system is provided with an interface such as an in-vehicle LAN, the EEPRO
It is also possible to rewrite the data of M54 in the vehicle assembling process or at the dealer, with the load data according to the vehicle option.

Therefore, according to the power control apparatus for a vehicle of the present embodiment, there is an effect that the cost can be reduced as compared with the first embodiment.

Third Embodiment (Configuration of Third Embodiment) A power control apparatus for a vehicle according to a third embodiment of the present invention has a configuration as shown in FIG. Device.

The power control apparatus for a vehicle according to the present embodiment has a CP
U10, EEPROM 54, current detection circuit 51,
It comprises a trapezoidal wave generation circuit 20 and an output control circuit 30.

Although the CPU 10 is the same as that described in the first embodiment, its logic is different from that of the first embodiment. That is, the CPU 10 controls the PWM control unit 1
1, the load detecting means 52 and the load determining means 53 are realized as logic. The PWM control means 11 is the same as that described in the first embodiment. Then, the trapezoidal wave generation circuit 20
And the output control circuit 30 are the same as those described in the first embodiment. The EEPROM 54 is the same as that described in the second embodiment. The load data stored in the EEPROM 54 is a load resistance value of the load.

The current detection circuit 51 is connected to the CPU 10 via an A / D converter (not shown).

The load detecting means 52 is a logic on a digital circuit of the CPU 10 for detecting the magnitude of the actual load resistance based on the load current signal and generating the load signal.

The load judging means 53 calculates E based on the load signal.
The logic on the digital circuit of the CPU 10 updates the data in the EPROM 54 and generates a trapezoidal wave control signal based on the magnitude of the load.

(Effects of Embodiment 3) The power control device for a vehicle of the present embodiment is constructed as described above, and exhibits the following effects.

The current detection circuit 51 detects a current flowing through the load and generates a load current signal. The generated load current signal is supplied to the load detecting means 52.

FIG. 4 shows the operation of the load detecting means 52. In step 1 (S1), the load detection means 52 A / D converts the load current signal supplied from the current detection circuit 51. In step 2, the load detecting means 52 calculates the average value of the A / D converted load current signal. As a method of calculating the average value, a known method such as using a fixed number of integration values of the load current signal that has been A / D converted at certain intervals can be applied. Step 3
Then, the load detecting means generates the average value calculated in step 2 as a load signal.

FIG. 5 shows the operation of the load determining means 53. First, in step 4, the load determining means 53
After reading the load signal supplied from the
Reads the load data from the EEPROM 54.
Next, in step 6, the load determination means 53 compares the load signal with the load data, and if a difference equal to or more than a predetermined value occurs, in step 7, the load signal is used as new load data as EEPR.
It is stored in the OM 54. Then, in step 8, the load determining means 53 generates a trapezoidal wave control signal based on the load data and the duty ratio. The load determining means 53
This trapezoidal wave control signal is supplied to a trapezoidal wave generation circuit 20 via a D / A converter.

As a result, in the power control device for a vehicle according to the present embodiment, the gradient of the current flowing through the load is appropriately controlled, and the noise generation can be further reduced. Then, it becomes possible to cope with the temporal change of the load 40 by updating the load data as needed.

Therefore, according to the power control apparatus for a vehicle of the present embodiment, in addition to the effect of the first embodiment, a noise reduction effect is provided immediately after the start of control, and the load characteristics can be flexibly changed over time after shipment. There is an effect that it is possible to respond.

<Modification> In the first to third embodiments, the CPU 10 serves as a PWM control unit, a load determination unit, and a load detection unit.
However, this may be realized as an analog circuit.

On the other hand, the trapezoidal wave generation circuit 20 is connected to the CPU 1
It may be realized as logic 0.

However, A / D converters for transmitting and receiving signals and D / D
It is necessary to install or remove the A converter as needed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a vehicle power control device according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of a vehicle power control device according to a second embodiment.

FIG. 3 is a block diagram illustrating a configuration of a vehicle power control device according to a third embodiment.

FIG. 4 is a flowchart illustrating an operation of a load detecting unit according to a third embodiment.

FIG. 5 is a flowchart illustrating an operation of a load determining unit according to the third embodiment.

FIG. 6 is a block diagram showing a configuration of a conventional vehicle power control device.

[Explanation of symbols]

 10: CPU 11: PWM control means 20: trapezoidal wave generation circuit 30: output control circuit 31: current detection circuit for feedback control 32: MOSFET 33: gate voltage control circuit 40: vehicle interior light (load) 50: trapezoidal wave control means 51: current detection circuit 52: load detection means 53: load determination means 54: EEPROM B: battery

Claims (4)

[Claims] 1. A PWM means for outputting a pulse signal pulse-modulated with a desired duty ratio, and a trapezoidal wave generating means for generating a trapezoidal wave signal in which a variable portion of the pulse signal is modified so as to change with time at a predetermined slope. Means, and an output control means for controlling a load current driven by the trapezoidal wave signal and flowing to a predetermined load. An electric power control device for an automobile, comprising: controlling the trapezoidal wave generating means according to a state of the load; An electric power control device for an automobile, further comprising trapezoidal wave control means for appropriately controlling the inclination. 2. The trapezoidal wave control means includes: load current detection means for detecting the load current flowing through the load; and load resistance detection means for detecting a resistance value of the load based on the load current. The vehicle power control device according to claim 1. 3. The power control apparatus for a vehicle according to claim 1, wherein said trapezoidal wave control means stores load data corresponding to a resistance value of said load, and has a memory for providing said load data. 4. The trapezoidal wave control means includes: a load current detection means for detecting the load current flowing through the load; a load resistance detection means for detecting a resistance value of the load based on the load current; The vehicle power control device according to claim 3, further comprising: a load determination unit that updates the load data stored in the power control unit.