1. An abnormality diagnosis apparatus for a NOx sensor, characterized in comprising:
a selective reduction NOx catalyst provided in an exhaust passage of an internal-combustion engine;
an after-catalyst NOx sensor for detecting a NOx concentration of exhaust gas at a downstream side of the NOx catalyst;
reducing agent addition means for selectively adding reducing agent to the NOx catalyst;
before-catalyst NOx concentration acquisition means for detecting or estimating a NOx concentration of exhaust gas at an upstream side of the NOx catalyst; and
abnormality determination means for comparing, during the stoppage of an addition of reducing agent by the reducing agent addition means, NOx concentrations detected or estimated by the after-catalyst NOx sensor and the before-catalyst NOx concentration acquisition means respectively to determine an abnormality of the after-catalyst NOx sensor.
2. The abnormality diagnosis apparatus for a NOx sensor according to claim 1, characterized in that:
during an idling operation of the internal-combustion engine, the reducing agent addition means stops an addition of reducing agent and the abnormality determination means performs an abnormality determination of the after-catalyst NOx sensor.
3. The abnormality diagnosis apparatus for a NOx sensor according to claim 1, characterized in comprising:
stoppage request signal generating means for generating a stoppage request signal for stopping the internal-combustion engine; and
stoppage delay means for delaying, when the stoppage request signal is generated by the stoppage request signal generating means, the stoppage of the internal-combustion engine by a predetermined delay time,
wherein:
during the delay time, the reducing agent addition means stops an addition of reducing agent and the abnormality determination means performs an abnormality determination of the after-catalyst NOx sensor.
4. The abnormality diagnosis apparatus for a NOx sensor according to claim 3, characterized in comprising:
forced idling control means for executing a forced idling control for causing the internal-combustion engine to perform an idling operation during the delay time.
5. The abnormality diagnosis apparatus for a NOx sensor according to claim 1, characterized in that:
the reducing agent addition means stops an addition of reducing agent when the NOx catalyst is not within a predetermined temperature range.
6. The abnormality diagnosis apparatus for a NOx sensor according to claim 1, characterized in that:
the before-catalyst NOx concentration acquisition means consists of at least one of estimation means for estimating, based on an operating condition of the internal-combustion engine, a NOx concentration of exhaust gas discharged from the internal-combustion engine and a before-catalyst NOx sensor for detecting a NOx concentration of exhaust gas at an upstream side of the NOx catalyst.
7. The abnormality diagnosis apparatus for a NOx sensor according to claim 6, characterized in that:
the before-catalyst NOx concentration acquisition means consists of both of the estimation means and the before-catalyst NOx sensor, and
the abnormality determination means compares the detected NOx concentration value by the after-catalyst NOx sensor, the detected NOx concentration value by the before-catalyst NOx sensor, and the estimated NOx concentration value by the estimation means to thereby distinctly determine abnormalities of the after-catalyst NOx sensor, the before-catalyst NOx sensor, and the internal-combustion engine.
8. The abnormality diagnosis apparatus for a NOx sensor according to claim 7, characterized in that:
the estimated NOx concentration value by the estimation means is calculated based on a predetermined map and, when the abnormality determination means determines an abnormality of the internal-combustion engine, data in the map is corrected based on at least one of the detection value of the after-catalyst NOx sensor and the detection value of the before-catalyst NOx sensor.
9. The abnormality diagnosis apparatus for a NOx sensor according to claim 1, characterized in that:
the detection of a NOx concentration by the after-catalyst NOx sensor is carried out when a predetermined time has passed since the stoppage of the addition of reducing agent by the reducing agent addition means.
10. The abnormality diagnosis apparatus for a NOx sensor according to claim 1, characterized in that the reducing agent is urea.
11. An abnormality diagnosis method for a NOx sensor, the method is for diagnosing an abnormality of an after-catalyst NOx sensor in an internal-combustion engine in which an exhaust passage includes a selective reduction NOx catalyst and the after-catalyst NOx sensor is provided at the downstream side thereof and reducing agent is selectively added to the NOx catalyst, characterized in comprising:
a step of stopping the addition of reducing agent;
a step of allowing, during the stoppage of the addition of reducing agent, the after-catalyst NOx sensor to detect an after-catalyst NOx concentration and detecting or estimating a before-catalyst NOx concentration at an upstream side of the NOx catalyst; and
a step of making comparison between these after-catalyst NOx concentration and before-catalyst NOx concentration to determine an abnormality of the after-catalyst NOx sensor.
12. The abnormality diagnosis method for a NOx sensor acceding to claim 11, characterized in that:
the step of stopping the addition of reducing agent includes a step of stopping the addition of reducing agent during an idling operation of the internal-combustion engine.
13. The abnormality diagnosis method for a NOx sensor according to claim 11, characterized in that:
the step of stopping the addition of reducing agent includes a step of stopping the addition of reducing agent within a predetermined delay time from the generation of a stoppage request sign for stopping the internal-combustion engine to the stoppage of the internal-combustion engine.
14. The abnormality diagnosis method for a NOx sensor according to claim 13, characterized in comprising:
a step of forcedly causing the internal-combustion engine to perform an idling operation during the delay time.
15. The abnormality diagnosis method for a NOx sensor according to claim 11, characterized in that:
the step of stopping the addition of reducing agent includes a step of stopping the addition of reducing agent when the NOx catalyst is not within a predetermined temperature range.
16. The abnormality diagnosis method for a NOx sensor according to claim 11, characterized in that:
the step of detecting or estimating the before-catalyst NOx concentration consists at least one of a step of estimating a NOx concentration of exhaust gas discharged from the internal-combustion engine based on an operating condition of the internal-combustion engine and a step of using a before-catalyst NOx sensor to detect a NOx concentration of exhaust gas at an upstream side of the NOx catalyst.
17. The abnormality diagnosis method for a NOx sensor according to claim 16, characterized in that:
the step of detecting or estimating the before-catalyst NOx concentration consists both of a step of estimating a NOx concentration of exhaust gas discharged from the internal-combustion engine based on an operating condition of the internal-combustion engine and a step of using a before-catalyst NOx sensor to detect a NOx concentration of exhaust gas at an upstream side of the NOx catalyst, and
the step of determining an abnormality of the after-catalyst NOx sensor includes a step of comparing the detected NOx concentration value by the after-catalyst NOx sensor, the detected NOx concentration value by the before-catalyst NOx sensor, and the estimated NOx concentration value by the estimation means to thereby distinctly determine abnormalities of the after-catalyst NOx sensor, the before-catalyst NOx sensor, and the internal-combustion engine.
18. The abnormality diagnosis method for a NOx sensor according to claim 17, characterized in that:
the estimated NOx concentration value is a value calculated from a predetermined map based on an operating condition of the internal-combustion engine, and
the method includes a step of correcting, when an abnormality of the internal-combustion engine is determined, data in the map based on at least one of the detection value of the after-catalyst NOx sensor and the detection value of the before-catalyst NOx sensor.
19. The abnormality diagnosis method for a NOx sensor according to claim 11, characterized in that:
the detection of an after-catalyst NOx concentration by the after-catalyst NOx sensor is carried out when a predetermined time has passed since the stoppage of the addition of reducing agent.
20. The abnormality diagnosis method for a NOx sensor according to claim 11, characterized in that the reducing agent is urea.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A multiphase interleaved voltage regulator for providing a regulated output voltage at an output terminal thereof, the multiphase interleaved voltage regulator comprising:
an input terminal receiving an input voltage;
a compensator in a voltage control loop, coupled to the output terminal, operative to provide a compensation signal; and
a plurality of phase circuits coupled to the input terminal, the output terminal and the compensator, operative to generate a plurality of interleaved phase currents, each said phase circuit having an offset cancellation circuit for increasing a current loop gain thereof, so as to mitigate beat-frequency oscillation of the phase currents.
2. The multiphase interleaved voltage regulator of claim 1, wherein the compensation signal is proportional to a difference between the output voltage and a reference voltage.
3. The multiphase interleaved voltage regulator of claim 2, wherein each said phase circuit comprises a control circuit for current mode control.
4. The multiphase interleaved voltage regulator of claim 3, wherein each said control circuit generates a pulse-width modulation signal in response to the compensation signal and the phase current of the phase circuit it belongs to so as to realize the current mode control.
5. The multiphase interleaved voltage regulator of claim 4, wherein each said control circuit comprises a pulse-width modulator operative to generate the pulse-width modulation signal for the phase circuit it belongs to.
6. The multiphase interleaved voltage regulator of claim 5, wherein each said offset cancellation circuit provides an offset signal to the pulse-width modulator of the phase circuit it belongs to.
7. The multiphase interleaved voltage regulator of claim 6, wherein each said offset signal is generated in response to the compensation signal and a current sense signal representative of the phase current of the phase circuit it belongs to.
8. The multiphase interleaved voltage regulator of claim 7, wherein each said offset cancellation circuit comprises:
a first adder coupled to the compensator, adding the offset signal into the compensation signal and subtracting a bias therefrom to generate a modified compensation signal;
a second adder coupled to the pulse-width modulator, subtracting the current sense signal from the modified compensation signal to generate a difference signal; and
a low-pass filter coupled to the first and second adders, filtering the difference signal to generate the offset signal.
9. The multiphase interleaved voltage regulator of claim 8, wherein the low-pass filter has a gain greater than one below a frequency, and equal to one above the frequency.