JP2010136479A - Vehicle power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle power supply wherein it is possible to reduce noise arising from the leading edge/trailing edge of pulse waveform by PWM control of power to such a level that it is inaudible to humans and even when a load current is small, a heat release value is low and thus favorable power efficiency is obtained. <P>SOLUTION: The vehicle power supply includes a means 12 for detecting the output voltage of a battery B and supplies electrical loads 1, 2, ... to be supplied with power with voltage PWM-controlled with a duty ratio corresponding to the output voltage detected by the detecting means 12. The power supply is provided with: current detecting means A1, A2, ... for detecting the values of currents passed through the electrical loads 1, 2, ...; and adjusting means C1, C2, ... for adjusting the leading time/trailing time of each pulse in PWM control in accordance with the current values detected by the current detecting means A1, A2, .... <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle power supply device that detects an output voltage of a battery and applies a voltage that is PWM (Pulse Width Modulation) controlled with a duty ratio corresponding to the detected output voltage to an electric load to be fed.

In recent years, the types of electric loads mounted on vehicles and their power consumption tend to increase dramatically. Therefore, in a vehicle power supply device having a limited power source such as a battery and an alternator (on-vehicle generator, AC generator), securing power is an important issue.
In a vehicle power supply device, the output voltage of a battery is, for example, a nominal value of 12V, and an electric load is often operated at 12V. However, since the power generation voltage of the generator is a high voltage of 14 to 12.5 V in order to charge the battery, the electric load is often operated with a voltage exceeding 12 V, which is wasteful. Power consumption.

Therefore, recently, when the output voltage of the battery exceeds 12V, it has been proposed to provide each electric load with power corresponding to the supplied power when PWM control is not performed at 12V. At that time, PWM control is performed at a constant cycle and the same duty ratio.
In addition, in order to maintain power supply to high-priority electric loads (electric brakes, electric power steering devices, etc.), power to low-priority electric loads (heaters, etc.) may be limited by PWM control. Proposed.

However, when power is PWM controlled, if the pulse waveform is square, there is a problem that noise is generated due to a sudden change in current. Therefore, conventionally, by controlling the resistance value of a switching element such as a semiconductor relay, the pulse waveform has a slope in the rise / fall of the current as shown in FIG. 5 (rise time / rise). There was a fall time).
Here, the rise time is the time required for the pulse voltage to rise from 10% to 90% of the specified voltage, and the fall time is the time required for the pulse voltage to fall from 90% to 10% of the specified voltage. is there.

In Patent Document 1, PWM control means for outputting a pulse signal that is pulse-modulated with a desired duty ratio, and a fluctuation portion of the pulse signal so as to change with time at a predetermined slope that suppresses noise generation at the load. A power control apparatus for an automobile is disclosed that includes a trapezoidal wave generation circuit that generates a trapezoidal wave signal modified in the above. It is equipped with an output control circuit that controls the load current that is driven by the trapezoidal wave signal and flows to the load, and a trapezoidal wave control circuit that controls the trapezoidal wave generation circuit according to the state of the load and appropriately controls the inclination, and makes the load state The noise is reduced by controlling the trapezoidal wave signal accordingly.
JP 2001-54298 A

  As described above, when the power is subjected to PWM control so that the rise / fall of the pulse waveform has a slope, the rise time / fall time has not been changed as shown in FIG. Therefore, when the load current is large, the rise / fall slope increases and noise increases. When the load current is small, the rise / fall slope decreases and noise decreases. There is a problem that unnecessary heat generation occurs and power efficiency is lowered.

In the automotive power control device described in Patent Document 1, in order to reduce noise, when the load is reduced, the slope of the trapezoidal wave signal is moderated, and when the load is increased, the slope of the trapezoidal wave signal is increased. It is steep (paragraph number 0017).
However, noise that occurs when the current is large is often a problem. When the maximum current is PWM controlled and the rise time / fall time is designed to be fixed so that the generated noise is kept below a certain standard. You will have room. That is, when the current decreases, the noise reference value can be satisfied even if the rise time / fall time is shortened. By the way, since the loss of energy increases when the rise and fall times are long, in the design in which the maximum current is taken into consideration, when the current is small, an unnecessary loss occurs while suppressing noise more than necessary.

  The present invention has been made in view of the above-described circumstances, and noise caused by rising / falling of a pulse waveform due to PWM control of electric power is adversely affected to surrounding electronic devices such as noise to a radio. An object of the present invention is to provide a vehicular power supply device that is low in heat generation and has high power efficiency even when the load current is small.

  A vehicle power supply device according to a first aspect of the present invention includes a means for detecting an output voltage of a battery, and for a vehicle that applies a voltage PWM-controlled with a duty ratio corresponding to the output voltage detected by the means to an electric load to be fed In the power supply apparatus, current detecting means for detecting a current value flowing through the electric load, and adjusting means for adjusting the rise time / fall time of each pulse of the PWM control according to the current value detected by the current detection means It is characterized by providing.

  In this vehicle power supply device, an output voltage of a battery is detected, and a voltage subjected to PWM control with a duty ratio corresponding to the detected output voltage is applied to an electric load to be fed. The current detection means detects the current value flowing through the electric load, and the adjustment means adjusts the rise time / fall time of each pulse of the PWM control according to the detected current value.

  The vehicular power supply apparatus according to the second invention is characterized in that the current detecting means is configured to detect a current value flowing through the electric load in the middle of the pulse width.

  According to the vehicle power supply device of the present invention, noise caused by the rise / fall of the pulse waveform by PWM control of electric power can be avoided while avoiding adverse effects on surrounding electronic devices such as noise to the radio. Even when is small, it is possible to realize a vehicle power supply device that generates a small amount of heat and has high power efficiency.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a vehicle power supply device according to the present invention.
The vehicle power supply device includes a battery B, and the battery B is charged with electric power generated by an alternator (on-vehicle generator, AC generator) 10. The alternator 10 generates power in conjunction with an engine (not shown), and the generated power is rectified and output in the alternator 10.

The electric power charged in the battery B and the electric power output from the alternator 10 are given to loads (electric loads) 1, 2,... Mounted on the vehicle through the semiconductor switches T1, T2,.
The semiconductor switches T1, T2,... Are on / off controlled from the control unit 11 of the vehicle power supply device through the adjusting units C1, C2,. The semiconductor switches T1, T2,... Are, for example, IPS (Intelligent Power Switch), and the current values flowing through the loads 1, 2,... Detected by the built-in current detection means A1, A2,. Given to part 11. The control unit 11 samples an average current value (for example, a simple average value, a weighted average value, a moving average value) a plurality of times, for example, a current value in the middle (phase) of the PWM control pulse width among the given current values. Etc.).

The control unit 11 is connected to each of the switches S1, S2,... And individually turns on / off the semiconductor switches T1, T2,... According to the given on / off signals of the switches S1, S2,. Control. That is, when it is on, the semiconductor switches T1, T2,... Are individually PWM controlled through the PWM controllers P1, P2,. In addition, the control unit 11 includes voltage detection means 12 that detects the output voltage of the battery B.
For example, the control unit 11 performs PWM control of the semiconductor switches T1, T2,... With a constant period and the same duty ratio in order to adjust the power supply voltage.

  When the control unit 11 performs PWM control on the semiconductor switches T1, T2,..., The rise time / fall time of the PWM control pulse is proportional to the current value detected by the current detection means A1, A2,. Then, the adjustment units C1, C2,. The control unit 11 stores a voltage signal value corresponding to the current value detected by the current detection means A1, A2,... In the memory, and sends a voltage signal corresponding to the current value to the adjustment units C1, C2,. give. The adjustment units C1, C2,... Adjust the rise time / fall time of the PWM control pulse based on the applied voltage signal.

  FIG. 2 is a circuit diagram illustrating a configuration example of the adjustment units C1, C2,. In this circuit, a square wave PWM signal is input to the non-inverting amplifier 21 from the PWM control units P1, P2,. The square wave PWM signal output from the non-inverting amplifier 21 is supplied to, for example, the gate of the semiconductor switch T1 through the transistor T12 and the diode D2 connected in series. Further, the voltage is supplied to the gate of the semiconductor switch T1 through the transistor T11 and the reversely connected diode D1. The cathode of the diode D2 and the anode of the diode D1 are grounded through the capacitor C.

The rise time of the square-wave PWM signal output from the non-inverting amplifier 21 is determined in accordance with the on-resistance of the transistor T11 due to the voltage signal from the control unit 11 and the capacitance of the capacitor C. The fall time is determined according to the on-resistance of the transistor T12 and the capacitance of the capacitor C due to the voltage signal from the control unit 11.
The semiconductor switch T1 (T2,...) Is turned on by the PWM signal having the predetermined rise time / fall time, and a current corresponding to the PWM signal is supplied to the load 1 (2,...).

FIG. 3 is a circuit diagram showing another configuration example of the adjusting units C1, C2,. In this circuit, a square-wave PWM signal is input to the base of one transistor T13 of the differential amplifier 22 from the PWM control units P1, P2,. The base of the other transistor T14 is grounded. The difference voltage between the collectors of the transistors T13 and T14 is given to the gate of the semiconductor switch T1 through the limiter 24 as an output signal of the differential amplifier 22.
The voltage signal from the control unit 11 is given to the base of the transistor T15 which is a constant current source of the differential amplifier 22.

The PWM signal output from the differential amplifier 22 has its rise time / fall time determined according to the current flowing through the transistor T15 by the voltage signal from the control unit 11.
The semiconductor switch T1 (T2,...) Is turned on by the PWM signal having the predetermined rise time / fall time, and a current corresponding to the PWM signal is supplied to the load 1 (2,...).

FIG. 4 is an explanatory diagram for explaining the operation of the vehicle power supply device according to the present invention for adjusting the rise time / fall time of the PWM control pulse.
Adjustment control unit 11, when the current detecting means A1, A2, the current value ... detects an I _1, adjuster C1, C2, through ..., the rise time / fall time t _r / t _f Let When current detecting means A1, A2, the current value ... detects an I _2, adjuster C1, C2, through ..., thereby adjusting the rise time / fall time t _r '/ t _f'.

Note that I ₁ / I ₂ = t _r / t _r ′ = t _f / t _f ′.
I ₁ / t _r = I ₂ / t _r ′ = I ₁ / t _f = I ₂ / t _f ′ can be reduced to the extent that noise caused by the rise / fall of the pulse waveform cannot be heard by humans. The value is set so as not to generate heat.
Here, the pulse width is, for example, about 10 to 100 ms, the pulse rise / fall time is, for example, about 10 μs to 1 ms, and the current value is, for example, about 10 to 20 A.

In the above-described embodiment, the rise time / fall time of each pulse of PWM control is adjusted in proportion to the current value, but not limited to proportional, depending on the magnitude of the current value, The rise time / fall time of each pulse may be adjusted to be long / short.
In the above-described embodiment, a semiconductor switch is provided for each load and the power supply is PWM-controlled. However, the power supply of each load may be PWM-controlled by one semiconductor switch.

It is a block diagram which shows schematic structure of embodiment of the vehicle power supply device which concerns on this invention. It is a circuit diagram which shows the structural example of an adjustment part. It is a circuit diagram which shows the other structural example of an adjustment part. It is explanatory drawing for demonstrating the operation | movement in which the vehicle power supply device which concerns on this invention adjusts the rise time / fall time of the pulse of PWM control. It is a wave form diagram which shows the example of the pulse waveform in the case of carrying out PWM control of electric power. It is explanatory drawing which shows the example of the rise time / fall time of the conventional pulse waveform in the case of carrying out PWM control of electric power.

Explanation of symbols

1, 2 Load (electric load)
DESCRIPTION OF SYMBOLS 10 Alternator 11 Control part 12 Voltage detection means 21 Non-inverting amplifier 22 Differential amplifier 24 Limiter A1, A2 Current detection means B Battery C Capacitor C1, C2 Adjustment part (Adjustment means)
D1, D2 Diode P1, P2 PWM controller S1, S2 Switch T1, T2 Semiconductor switch T11-T15 transistor

Claims (2)

In a vehicle power supply device comprising means for detecting an output voltage of a battery, and applying a voltage PWM-controlled with a duty ratio corresponding to the output voltage detected by the means to an electric load to be fed,
Current detection means for detecting a current value flowing through the electric load, and adjustment means for adjusting the rise time / fall time of each pulse of the PWM control according to the current value detected by the current detection means. A power supply device for a vehicle.   2. The vehicle power supply device according to claim 1, wherein the current detection unit is configured to detect a current value flowing through the electric load in the middle of the pulse width. 3.

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