Analog Filter for Ignition Coil Insulation Fault Detection

When insulation fault occurs in the ignition coil partial secondary winding discharges. Random pulses with various amplitudes appear in primary current and secondary voltage waveforms simultaneously. Moreover the secondary voltage may distort if the fault is serious. Traditional methods are difficult to identify the discharge pulses. This paper examines a measure to overcome the shortages of traditional methods though analog filer. We design an eighth order Butterworth high pass filter in order to separate random pulses from primary current and secondary voltage signals. Then random pulses detection circuit converts the separated pulses’ width to 10μs or more. These pulses are processed and judged by the microprocessor to give the test results. Our method applies in insulation fault detection of five different types’ ignition coils. The experimental results reveal that the detection success rate of each type is greater than 91%. Our method could implement rapid ignition coil insulation fault detection on production line.