Current detection apparatus for a car power source
A current detection apparatus includes a current detection section that detects charging current and discharging current of the car driving battery, a level-shift circuit connected to the output-side of the current detection section that shifts the output of the current detection section, and an A/D converter connected to the output-side of the level-shift circuit. The level-shift circuit shifts the current detection section output signal to unbalance the maximum discharging current and maximum charging current that can be detected.
1. A current detection apparatus for a car power source comprising:
a car driving battery;
a current detection section that detects a charging current and a discharging current of the car driving battery;
a level-shift circuit connected to an output-side of the current detection section, the level-shift circuit being configured to shift both charging current and discharging current output signals of the current detection section; and
an A/D converter connected to an output-side of the level-shill circuit,
wherein the level-shift circuit shifts the current detection section charging current and discharging current output signals to unbalance a maximum discharging current and a maximum charging current to be detected so that a range of the charging current is narrower than a range of the discharging current received by the A/D converter, wherein the level-shift circuit is configured to shift both charging current and discharging current output signals of the current detection section so that a shifted-line of charging/discharging current-to-voltage is parallel to an original line and the shifted-line and the original line have the same slope.
2. The current detection apparatus of claim 1 , further comprising:
a battery ECU configured to control the battery discharging current and the charging current, wherein the battery ECU controls larger discharging currents than charging currents.
3. The current detection apparatus claim 1 wherein the level-shift circuit is a difference amplifier; in the level-shift circuit that is a difference amplifier, current detection section output is input to one input terminal and a DC compensation voltage is input to the other input terminal to shift the current detection section output signal by the compensation voltage and input it to the A/D converter.
4. The current detection apparatus for a car power source as cited in claim 3 wherein the level-shift circuit is a difference amplifier; the current detection section output signal is input to the non-inverting side (+side) input terminal and a compensation voltage is input to the inverting side (−side) input terminal to shift the level of the current detection section output signal.
5. The current detection apparatus for a car power source as cited in claim 4 wherein the level-shift circuit is a difference amplifier with a voltage gain of one.
6. The current detection apparatus of claim 1 , wherein the level-shift circuit is an adder circuit, and a DC bias voltage is input to an input-side of the adder circuit to shift a current detection section output signal by the DC bias voltage and input it to the A/D converter.
7. The current detection apparatus of claim 6 , wherein the level-shift circuit is an adder circuit, and the current detection section output signal and a linear bias voltage are both input through a resistor to an input-side of an amplifier, wherein a sum of the current detection section output signal and the linear bias voltage is output.
8. The current detection apparatus of claim 1 , wherein the current detection section has output characteristics showing an output voltage increase with a discharging current increase, and an output voltage decrease with a charging current increase.
9. The current detection apparatus of claim 1 , wherein the current detection section has output characteristics showing a linear output voltage increase with a battery current increase in a discharging direction.
10. The current detection apparatus of claim 1 , further comprising:
an amplitude adjustment circuit provided at the output-side of the level-shift circuit to adjust an amplitude of a level-shift circuit output voltage to an input range of the A/D converter.
11. The current detection apparatus of claim 10 , wherein the amplitude adjustment circuit is an attenuating circuit.
12. The current detection apparatus of claim 11 , wherein the amplitude adjustment circuit, which is an attenuating circuit, is a resistive voltage divider circuit.
13. The current detection apparatus of claim 10 , wherein the amplitude adjustment circuit is an amplifying circuit.
14. The current detection apparatus for a car power source as cited in claim 10 wherein the level-shift circuit is an op-amp that serves the dual purpose as an amplitude adjustment circuit, and the amplitude of the level-shift circuit output voltage is adjusted to the input range of the A/D converter by the gain of the op-amp.
15. The current detection apparatus of claim 1 , wherein an input voltage range of the A/D converter is 0V to 5V.
16. The current detection apparatus of claim 1 , further comprising:
a computation circuit connected to an output-side of the A/D converter, the computation circuit being configured to compute battery discharging current and charging current from a digital signal input from the A/D converter.
17. The current detection apparatus of claim 16 , wherein the computation circuit has a function stored in a memory to compute current values corresponding to the input digital signal based on the stored function.