JP4269420B2 - Automotive power control equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automotive power control apparatus that is provided between a DC power supply and a load and controls power supplied from the power supply to the load by pulse width modulation (PWM).
[0002]
[Prior art]
Conventionally, means for dimming a lamp mounted on an automobile and adjusting the rotational speed of a motor are provided with a power transistor between the lamp and the motor, that is, a load and its power supply, and the power transistor is PWM-controlled. The technology to do is generally known. However, with this technique, noise is greatly generated due to a sudden change in load current, which may adversely affect on-vehicle radios, ECUs, and the like.
[0003]
In order to suppress such noise generation, in the prior art, the pulse signal input to the output control circuit is converted from a square wave to a trapezoidal wave. Based on the trapezoidal wave, the output control circuit detects and feeds back the load current, and controls so that the time rate of change (slope) of the current or voltage at the rising and falling parts 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 B and a battery B, a power generation device, or the like as a DC power source. The output control circuit 30 includes a feedback control current detection circuit 31, a MOSFET 32, and a gate voltage control circuit 33. The PWM control means 11, which is the PWM means, supplies the trapezoidal wave generation circuit 20 with a pulse signal whose voltage is periodically turned on / 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. 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.
[0005]
Next, the gate voltage control circuit 33 generates a control signal that is proportional to the trapezoidal wave signal supplied with the load voltage, and supplies the control signal to the gate of the MOSFET 32.
[0006]
That is, in the prior art, the generation of electromagnetic noise is suppressed by feedback controlling the load current so that the slope of the trapezoidal wave current flowing through the load through the gate voltage of the MOSFET 32 becomes constant.
[0007]
[Problems to be solved by the invention]
However, the value of the load current varies depending on the change of the load due to the change of the state of the load or the change of optional electrical components, etc., but in the conventional automotive power control device, the slope of the trapezoidal wave that controls the load current is constant. It was fixed to. Therefore, the slope of the trapezoidal wave has been determined so as to be optimal when the maximum load current value is assumed. In other words, if the current value increases or the slope of the trapezoidal wave becomes gentle, the heat generation from the MOSFET increases, so the slope of the trapezoidal wave is made as large as possible in accordance with the maximum load current in order to suppress the heat generation. It was.
[0008]
As a result, in the conventional automotive power control apparatus, 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, and thus noise generation may not be sufficiently suppressed. It was.
[0009]
Therefore, an object of the present invention is to provide an automotive power control apparatus that generates less noise even when the load changes.
[0010]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and the inventors have invented the following means.
[0011]
(First means)
The first means of the present invention is the automotive power control apparatus according to claim 1.
[0012]
In this means, the power control apparatus for an automobile having the PWM means, the trapezoidal wave generating means, and the output control means further includes a trapezoidal wave control means. The load current detecting means supplies a load current signal corresponding to the current flowing through the load to the load resistance detecting means.
[0013]
The present invention can be applied to noise reduction not only in PWM but also in pulse amplitude modulation (PAM) and pulse density modulation (PDM). This is because, in PAM and PDM, a pulse-like steep current change occurs with power control as in PWM. Therefore, in this specification, “PWM” includes “PAM” and “PDM”.
[0014]
The PWM means is means for supplying the trapezoidal wave generating means with a pulse signal pulse-modulated with a desired duty ratio to drive the load. On the other hand, the trapezoidal wave control unit is a unit that generates a control signal for controlling the trapezoidal wave generation unit and supplies the control signal to the trapezoidal wave generation unit. The trapezoidal wave generating means is means for generating a trapezoidal wave having a predetermined slope based on the pulse signal input from the PWM means and the control signal from the trapezoidal wave control means. The output control means is a means that has a power transistor and 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.
[0015]
The PWM means supplies a pulse signal pulse-modulated with a desired duty ratio to drive the load to the trapezoidal wave generating means. As a method for generating a pulse signal, a known method can be applied. For example, a triangular wave comparison method or a pattern method. Here, the method of changing the duty ratio is not particularly limited. Therefore, any method can be adopted as long as it is a method that can change the duty ratio of the pulse signal output from the PWM means, as well as a known method.
[0016]
The trapezoidal wave control unit generates a trapezoidal wave control signal for controlling the trapezoidal wave generation unit, and supplies the trapezoidal wave control signal to the trapezoidal wave generation unit. The trapezoidal wave control signal is generated based on the controlled load current . This trapezoidal wave control signal has a predetermined slope of the rate of time change (hereinafter collectively referred to as “tilt”) of the voltage or current at the rising and falling parts of the trapezoidal wave generated by the trapezoidal wave generating means. It is a signal to control as follows. 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.
[0017]
That is, the vehicle power control apparatus of this means 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.
[0018]
As a method for determining the load current, the current is measured directly or indirectly, the method obtains the average value or the integration value or the like of the fixed time, a method for determining the size of the indirect load from other parameters, previously Examples include a method of determining with reference to load data measured according to the control state. The magnitude of the load in this case (output) becomes larger as the load current is large.
[0019]
The trapezoidal wave generating means generates a trapezoidal wave having a predetermined slope 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 signal is generated based on the pulse width of the pulse signal, and the trapezoidal wave slope of the trapezoidal wave signal is generated based on the trapezoidal wave control signal. Then, the trapezoidal wave generating means supplies the generated trapezoidal wave signal to the output control means.
[0020]
The output control means controls the current flowing through the load or the voltage applied to the load so that the power corresponding to the supplied trapezoidal wave signal is obtained.
[0021]
In this means, the value of the load voltage or load current is adjusted by the output control means so as to be proportional to the trapezoidal wave signal, but other than that, the trapezoidal wave generating means is adapted to the input / output characteristics of the output control means. However, a signal adjusted so that the final load voltage or load current becomes a trapezoidal wave may be supplied to the output control means as a trapezoidal wave signal.
[0022]
Thus, by controlling the slope of the trapezoidal wave signal that drives the output control means in accordance with the fluctuation of the load, the slope of the trapezoidal wave flowing through the load can be made appropriate. In this means, by supplying the trapezoidal wave signal controlled in this way to the output control means, heat generation from the power transistor can be suppressed and noise can be reduced.
[0023]
Therefore, according to this means, since 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 is appropriate according to the load current , there is an effect that the generated noise is reduced.
[0024]
(Second means)
The second means of the present invention is the automotive power control apparatus according to claim 2.
[0025]
In this section, the trapezoidal wave control means comprises a load resistance detection means to generate the detected trapezoidal wave control signal the resistance value of the load current signal is supplied load.
[0026]
Load resistance detecting means detects the load resistance value based on the supplied load current signal, to produce a trapezoidal wave control signal. As a method for detecting the load resistance, for example, there is a method of obtaining it from the average of load current signals at regular intervals. This trapezoidal wave control signal is supplied to the trapezoidal wave generating means.
[0027]
Therefore, according to this means, in addition to the effect of the first means described above, the actual load state is fed back, so that it is possible to cope with frequent changes in the state of the load controlled by the power, so that the noise is further reduced. There is an effect that.
[0028]
(Third means)
The third means of the present invention is the automotive power control apparatus according to claim 3.
[0029]
In this means, the trapezoidal wave control means has a memory for storing a load state in advance as load data. The memory 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.
[0030]
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 microcomputer memory. This memory is preferably a rewritable nonvolatile memory for the purpose of continuously storing data and setting the slope of a trapezoidal wave corresponding to the optional electrical component.
[0031]
Therefore, according to this means, in addition to the effects of the first means described above, the load current detecting means and the like are not necessary, and the cost can be reduced.
[0032]
(Fourth means)
According to a fourth aspect of the present invention, there is provided an automotive power control apparatus according to the fourth aspect.
[0033]
Trapezoidal wave controlling means in the automotive power control apparatus of the present unit includes a memory for storing the state of the pre-load as the load data, and the load resistance detection means for detecting the resistance value of the load based on the load current of that, the memory Load determination means for updating the stored load data.
[0034]
Load resistance detecting means detects the load resistance value based on the supplied load current signal, to generate a load signal indicative of the load resistance. The load determination means calculates new load data and stores it in the memory when it is determined that the load has changed by comparing the load signal supplied with the load signal and the corresponding load data stored 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.
[0035]
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 change in load characteristics with time after shipment.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
The embodiments of the power control apparatus for automobiles of the present invention will be described clearly and sufficiently in the following examples so that a person skilled in the art can understand which can be implemented.
[0037]
<Example 1>
(Configuration of Example 1)
The power control apparatus for automobiles according to the first embodiment of the present invention is a power control apparatus for dimming an automobile interior light 40 having the configuration shown in FIG.
[0038]
That is, the automotive power control apparatus of this embodiment includes a CPU 10, a trapezoidal wave generation circuit 20 as a trapezoidal wave generation unit, an output control circuit 30 including a power transistor, and a current detection circuit 51 as a load current detection unit. Consists of. The CPU 10 implements, as logic, PWM control means 11 as PWM means and load detection means 52 as load resistance detection means.
[0039]
The PWM control means 11 is a logic in the CPU 10 that generates a pulse signal having a duty ratio so that the brightness of the automobile 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 can be changed according to the usage state of the automobile and the user's desire by the variable voltage generation circuit and the logic of the CPU 10.
[0040]
The CPU 10 is a dedicated microcomputer for the light control circuit of the automobile 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.
[0041]
The current detection circuit 51 is a circuit that detects a current flowing through the load 40 to generate a load current signal, and supplies the load current signal to the load detection unit 52 via an A / D converter built in the CPU 10. . The current detection circuit 51 includes a shunt resistor (not shown) and an operational amplifier (not shown) that amplifies the 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. An input terminal of an operational amplifier is connected to both ends of the shunt resistor.
[0042]
The load detection means 52 is means for detecting a resistance of the load based on the load current signal supplied from the current detection circuit 51 and generating a trapezoidal wave control signal that is a signal for controlling the slope of the trapezoidal wave.
[0043]
The trapezoidal wave generation circuit 20 is an analog circuit that generates a trapezoidal wave signal to be supplied to the output control circuit 30 based on the pulse signal supplied from the PWM control unit 11 and the trapezoidal wave control signal supplied from the load detection unit 52. It is.
[0044]
The output control circuit 30 is an analog circuit that supplies 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 whose load current is proportional to the trapezoidal wave signal and supplies the control signal to the gate of the MOSFET 32.
[0045]
(Operational effect of Example 1)
Since the power control device for dimming an automobile interior light according to the present embodiment is configured as described above, the following operational effects are exhibited.
[0046]
The PWM control unit 11 supplies a pulse signal to the trapezoidal wave generation circuit 20 at a duty ratio appropriately set so that the automobile interior light 40 has a desired brightness. Here, the duty ratio is changed by the user operating the variable resistor or the like in the variable voltage generator described above so that the desired brightness of the vehicle interior light is obtained.
[0047]
The pulse signal is generated by the logic in the CPU 10 based on the duty ratio by the PWM control means 11.
[0048]
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 with the operational amplifier. The generated load current signal is supplied to the load detection means 52.
[0049]
Then, the load detection means 52 detects the resistance of the load based on the load current signal supplied from the current detection circuit 51 and generates a trapezoidal wave control signal. That is, the load detection unit 52 calculates an average value of the load current signal over a certain period of time, calculates the load size 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.
[0050]
The trapezoidal wave generation circuit 20 generates a trapezoidal wave signal based on the pulse signal generated by the PWM control unit 11 and the trapezoidal wave control signal generated by the load detection circuit 52. The duty ratio of the generated trapezoidal wave signal is the same as the duty ratio of the pulse signal. 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 and falling portions of a pulse signal that is a square wave to an appropriate slope in accordance with the trapezoidal wave control signal. The trapezoidal wave generation circuit 20 supplies the generated trapezoidal wave signal to the output control circuit 30.
[0051]
The output control circuit 30 supplies a current proportional to the supplied trapezoidal wave signal to the automobile interior light 40. That is, the trapezoidal wave signal is input to the gate voltage control circuit and compared with the magnitude of the load current supplied from the feedback control current detection circuit so that the magnitude of the load current is proportional to the trapezoidal wave signal. Is feedback controlled.
[0052]
In other words, the automotive power control apparatus according to the present embodiment detects the state of the load 40 and controls the trapezoidal wave generation circuit 20, so that an appropriate load is suppressed so as to suppress a steep current change according to the state of the load 40. Since it is possible to make the current gradient, it is possible to further reduce noise generation during power control.
[0053]
Therefore, according to the automobile power control apparatus of the present embodiment, there is an effect that noise generation can be further reduced as compared with the prior art.
[0054]
<Example 2>
(Configuration of Example 2)
The power control apparatus for a vehicle according to the second embodiment of the present invention is a power control apparatus that performs light control of the vehicle interior light 40 having a configuration as shown in FIG. That is, the automobile power control apparatus of this embodiment includes a CPU 10, an EEPROM 54 as a memory, a trapezoidal wave generation circuit 20, and an output control circuit 30.
[0055]
The EEPROM 54 is connected to the CPU 10 and is arranged in an address space where 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, and is for controlling the trapezoidal wave generation circuit 20 so as to have the optimum slope of the trapezoidal wave according to the type and number of the vehicle interior lights 40. Control data.
[0056]
The CPU 10 is the same as that described in the first embodiment. The CPU 10 implements the PWM control unit 11 and the load detection unit 52 as logic, and the PWM control unit 11 is the same as that described in the first embodiment. However, unlike the first embodiment, the load detection 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.
The trapezoidal wave generation circuit 20 and the output control circuit 30 are the same as those described in the first embodiment.
[0057]
(Effect of Example 2)
Since the automobile power control apparatus of the present embodiment is configured as described above, the following operational effects are exhibited.
[0058]
The operations of the PWM control unit 11, the trapezoidal wave generation circuit 20, and the output control circuit 30 are the same as those described in the first embodiment.
[0059]
The load detection means 52 reads the load data from the EEPROM 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.
[0060]
As a result, the power control apparatus for a vehicle according to the present embodiment appropriately suppresses the slope of the current flowing through the load according to the load, that is, suppresses a steep change in the current flowing through the load, thereby reducing noise generation. And since the electric power control apparatus for motor vehicles of a present Example does not need to provide a current detection circuit, cost reduction is attained. Further, it is possible to cope with a change in load due to a difference in optional electrical components by rewriting the contents of the EEPROM 54. Even if it is necessary to change the load data, if the system is equipped with an interface such as an in-vehicle LAN, it is possible to rewrite the data in the EEPROM 54 in the vehicle assembly process or at the dealer according to the vehicle option. It is.
[0061]
Therefore, according to the automotive power control apparatus of the present embodiment, there is an effect that the cost can be reduced compared to the first embodiment.
[0062]
<Example 3>
(Configuration of Example 3)
The power control apparatus for a vehicle according to the third embodiment of the present invention is a power control apparatus that performs the dimming of the vehicle interior light 40 having a configuration as shown in FIG.
[0063]
The automotive power control apparatus of this embodiment includes a CPU 10, an EEPROM 54, a current detection circuit 51, a trapezoidal wave generation circuit 20, and an output control circuit 30.
[0064]
The CPU 10 is the same as that described in the first embodiment, but its logic is different from that of the first embodiment. That is, the CPU 10 implements the PWM control unit 11, the load detection unit 52, and the load determination unit 53 as logic. The PWM control means 11 is the same as that described in the first embodiment. 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 the load resistance value of the load.
[0065]
The current detection circuit 51 is connected to the CPU 10 via an A / D converter (not shown).
[0066]
The load detection means 52 is a logic on the digital circuit of the CPU 10 that detects the actual load resistance based on the load current signal and generates a load signal.
[0067]
The load determination means 53 is a logic on the digital circuit of the CPU 10 that updates data in the EEPROM 54 based on the load signal and generates a trapezoidal wave control signal based on the magnitude of the load.
[0068]
(Effect of Example 3)
Since the automobile power control apparatus of the present embodiment is configured as described above, the following operational effects are exhibited.
[0069]
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 detection means 52.
[0070]
The operation of the load detection means 52 is shown in FIG. 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 detection means 52 calculates the average value of the A / D converted load current signal. As a method for calculating the average value, a known method can be applied, for example, by using a certain number of integral values of the load current signal subjected to A / D conversion at regular intervals. In step 3, the load detecting means generates the average value calculated in step 2 as a load signal.
[0071]
The operation of the load determination unit 53 is shown in FIG. First, in step 4, the load determination means 53 reads the load signal supplied from the load detection means 52, and then reads load data from the EEPROM 54 in step 5. Next, in step 6, the load determination means 53 compares the load signal with the load data and stores a load signal in the EEPROM 54 as new load data in step 7 when a difference of a certain value or more occurs. In step 8, the load determination unit 53 generates a trapezoidal wave control signal based on the load data and the duty ratio. The load determination unit 53 supplies the trapezoidal wave control signal to the trapezoidal wave generation circuit 20 via the D / A converter.
[0072]
As a result, the power control apparatus for a vehicle according to the present embodiment can appropriately control the slope of the current flowing through the load, and can further reduce noise generation. And it becomes possible to cope with the change with time of the load 40 by updating the load data as needed.
[0073]
Therefore, according to the automotive power control apparatus of the present embodiment, in addition to the effects of the first embodiment, there is a noise reduction effect immediately after the start of control, and it is possible to flexibly cope with a change in load characteristics with time after shipment. There is an effect that becomes possible.
[0074]
<Deformation mode>
In the first to third embodiments, the PWM control unit, the load determination unit, and the load detection unit are realized as the logic of the CPU 10, but may be realized as an analog circuit.
[0075]
Conversely, the trapezoidal wave generation circuit 20 may be realized as the logic of the CPU 10.
[0076]
However, it is necessary to install or remove the A / D converter and D / A converter for signal transmission / reception as required.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an automotive power control apparatus according to a first embodiment.
FIG. 2 is a block diagram illustrating a configuration of an automotive power control apparatus according to a second embodiment.
FIG. 3 is a block diagram illustrating a configuration of an automotive power control apparatus according to a third embodiment.
FIG. 4 is a flowchart illustrating the operation of a load detection unit according to the third embodiment.
FIG. 5 is a flowchart illustrating an operation of a load determination unit according to the third embodiment.
FIG. 6 is a block diagram showing a configuration of a conventional automobile power control device.
[Explanation of symbols]
10: CPU
11: PWM control means 20: trapezoidal wave generation circuit 30: output control circuit 31: feedback control current detection circuit 32: MOSFET
33: Gate voltage control circuit 40: Car 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)

PWM means for outputting a pulse signal pulse-modulated at a desired duty ratio;
Trapezoidal wave generating means for generating a trapezoidal wave signal in which the fluctuation part of the pulse signal is corrected to change with time at a predetermined slope;
Output control means for controlling a load current driven by the trapezoidal wave signal and flowing to a predetermined load;
In an automotive power control device having
The has a load current detecting means for detecting the load current flowing through the load, the load current in response to said detected load current by the detecting means and controlling said trapezoidal wave generating means trapezoidal wave control to properly control the tilt A power control apparatus for an automobile, further comprising means. The trapezoidal wave controlling means,
Automotive power control apparatus according to claim 1, wherein with the load resistance detection means to detect the resistance value of the load based on the load current. The trapezoidal wave control means includes
The vehicle power control apparatus according to claim 1, further comprising a memory for storing load data corresponding to the resistance value of the load and providing the load data. The trapezoidal wave controlling means,
A load resistance detection means for detecting the resistance value of the load based on the load current,
Load determination means for updating the load data stored in the memory;
The power control apparatus for automobiles according to claim 3 having

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