Abstract: A system and method for operating a power transistor. Parasitic impedances naturally present in a circuit board or other interconnect structures exhibit a parasitic impedance effective to generate a parasitic voltage signal in response to operating the power transistor. The parasitic voltage signal is monitored in order to better control the power transistor. In particular, the threshold voltage of the power transistor can be determined and used to more optimally control the power transistor.

Abstract: A system and method for operating a power transistor. Parasitic impedances naturally present in a circuit board or other interconnect structures exhibit a parasitic impedance effective to generate a parasitic voltage signal in response to operating the power transistor. The parasitic voltage signal is monitored in order to better control the power transistor. In particular, the threshold voltage of the power transistor can be determined and used to more optimally control the power transistor.

Abstract: A switching control system and method is provided that optimizes switching efficiencies for power switching applications including automotive ignition systems, solenoid drivers, motor drivers and power regulation systems. In an ignition system, a coil current switching magnitude is controlled at the start of ignition coil charging, thereby avoiding an untimely spark event. When the transistor threshold voltage is reached, the collapse rate of the ignition system transistor collector voltage is reduced by reducing the gate charging current. The reduced collector voltage slew rate results in a reduced primary and secondary coil output voltage. After the collector voltage collapses, a continued rapid charge is provided to place the transistor in a hard saturation bias condition. In an aspect, the present invention dynamically determines the threshold voltage of a power transistor.

Abstract: An analog, duty cycle replicating frequency converter extracts duty cycle information from an input, pulse width modulated signal and generates an output pulse width modulated signal of the same duty cycle at a different frequency without regard to the frequency of the input signal. It uses bipolar transistor based circuitry, adaptable to an application specific integrated circuit, to derive voltages representing the on-time and period durations of the input signal, convert these voltages to currents representing the logarithms thereof, generate a voltage representing the difference between the currents, exponentially convert the voltage to a current representing the duty cycle and control an oscillator to generate an output pulse width modulated signal at a predetermined frequency with the duty cycle of the input signal.

Abstract: An analog, duty cycle replicating frequency converter extracts duty cycle information from an input, pulse width modulated signal and generates an output pulse width modulated signal of the same duty cycle at a different frequency without regard to the frequency of the input signal. It uses bipolar transistor based circuitry, adaptable to an application specific integrated circuit, to derive voltages representing the on-time and period durations of the input signal, convert these voltages to currents representing the logarithms thereof, generate a voltage representing the difference between the currents, exponentially convert the voltage to a current representing the duty cycle and control an oscillator to generate an output pulse width modulated signal at a predetermined frequency with the duty cycle of the input signal.

Abstract: A switching control system and method is provided that optimizes switching efficiencies for power switching applications including automotive ignition systems, solenoid drivers, motor drivers and power regulation systems. In an ignition system, a coil current switching magnitude is controlled at the start of ignition coil charging, thereby avoiding an untimely spark event. When the transistor threshold voltage is reached, the collapse rate of the ignition system transistor collector voltage is reduced by reducing the gate charging current. The reduced collector voltage slew rate results in a reduced primary and secondary coil output voltage. After the collector voltage collapses, a continued rapid charge is provided to place the transistor in a hard saturation bias condition. In an aspect, the present invention dynamically determines the threshold voltage of a power transistor.

Abstract: Drive current stabilization is achieved through the management of a drive current. The drive current may include a control current that is provided to a control terminal of a switch, a current limit input current that is provided to a current limit circuit associated with the switch and a stabilization current. The switch carries a load current responsive to a control signal on the control terminal. The magnitude of the control current is monitored and a magnitude of the stabilization current is increased responsive to a decrease in the magnitude of the control current to substantially maintain a magnitude of the drive current.

Abstract: An ignition control circuit (12) is responsive to a control signal (ESTC) to apply a drive signal (GD) to a power switching device (22) to conduct ignition coil current (IC) therethrough. A resistor (RS) included within the circuit (12) receives, and dissipates heat generated by, the coil current (IC). The circuit (12) includes a first transistor (QHOT) positioned adjacent to the resistor (RS) such that an operating temperature thereof is near that of the resistor (RS), and a second transistor (QREF) positioned remote from the resistor (RS) and having an operating temperature defining a reference temperature. The first and second transistors (QHOT, QREF) are configured to produce an output voltage (VOUT) proportional to a difference in operating temperatures thereof, and a latch circuit (L1) disables the control signal (ESTC) to thereby turn off the power switching device (22) when the output voltage (VOUT) difference exceeds a reference voltage (VREF).

Abstract: Thermal overload protection circuitry 14 for an automotive ignition system includes a gate drive circuit (18) responsive to a control signal (ESTB) to produce a drive signal (VGD) for driving a power switching device (22) separate from the protection circuitry (14), and a thermal overload protection circuit (40) configured to supply a first current (I1) to a thermal sensing component (38) associated with, and having an operating temperature defined by, the power switching device (22), wherein the first current (I1) has a magnitude defined by the operating temperature of the thermal sensing component (38). The first current is multiplied by a current controlled current source (60) to produce a second current (I2), and the second current is used to limit the drive signal (VGD) to thereby maintain the operating temperature of the power switching device (22) below an operating temperature limit.

Abstract: A technique for reducing input currents associated with a comparator circuit during certain events includes minimizing bias currents associated with the comparator circuit when a magnitude of an input signal at a signal input of the comparator circuit is a predetermined value from a magnitude of a reference signal applied to a reference input of the comparator circuit. The bias currents are increased when the magnitude of the input signal is within the predetermined value of the magnitude of the reference signal.

Abstract: An interface for providing thermal overload protection includes a switching device, a temperature indicating device, a drive circuit and a thermal monitoring circuit. The thermal monitoring circuit is coupled across the temperature indicating device and provides a shutdown signal to the drive circuit when the temperature of the switching device is above a predetermined temperature level as indicated by a temperature signal provided by the temperature indicating device. The drive circuit responds to the shutdown signal by removing current sources and current sinks from a control terminal of the switching device at which point leakage currents cause the switching device to reduce a drive current to an inductive load.

Abstract: An automotive ignition diagnostic system includes an ion current detection circuit producing a buffered representation of an ion current flowing across an electrode gap of an ignition plug in response to a bias voltage applied thereto. An ignition diagnostic circuit is responsive to the buffered representation of the ion current to charge a single integration capacitor. The diagnostic circuit is operable to produce an output signal having a pulse width defined by the amount of charge on the capacitor. When the ion current flows following a combustion event, the width of the output signal is controlled as a function of the quality of combustion in the corresponding cylinder. However, if sufficient ion current flows prior to combustion, the width of the output signal is controlled to indicate a fouled ignition plug.

Abstract: An integrated circuit (10) includes a thermal sensing device (20) and a power-switching device (12) such as an IGBT. The power device (12) is fabricated in a conventional manner on a semiconductor substrate, and the thermal sensing device (20) is fabricated on an electrical insulation layer (74) formed over the substrate. The thermal sensing device (20) may be provided in the form of a number of series-connected polysilicon diodes (D1-D3) positioned adjacent to the power device (12) such that the operating temperature of the thermal sensing device (20) is near that of the power device (12). In response to an input current IC, the thermal sensing device (20) produces an output voltage (VD) that is substantially linear with surface die temperature, and which reacts rapidly to changes in surface die temperature. The thermal sensing device (20) is completely electrically isolated from the power device, thereby eliminating any electrical interaction therebetween.

Abstract: In an ignition coil assembly of an ion sensing ignition system having an ignition coil output, a buffered ion-sense current source circuit is provided and includes a current sensing circuit, the current sensing circuit being disposed so as to be communicated with the ignition coil output and an active current source circuit, the active current source circuit being disposed so as to be communicated with the current sensing circuit and a current measuring device.

Abstract: Thermal overload protection circuitry 14 for an automotive ignition system includes a gate drive circuit (18) responsive to a control signal (ESTB) to produce a drive signal (VGD) for driving a power so itching device (22) separate from the protection circuitry (14), and a thermal overload protection circuit (40) configured to supply a first current (I1) to a thermal sensing component (38) associated with, and having an operating temperature defined by, the power switching device (22), wherein the first current (I1) has a magnitude defined by the operating temperature of the thermal sensing component (38). The first current is multiplied by a current controlled current source (60) to produce a second current (I2), and the second current is used to limit the drive signal (VGD) to thereby maintain the operating temperature of the power switching device (22) below an operating temperature limit.

Abstract: An integrated circuit (10) includes a thermal sensing device (20) and a power-switching device (12) such as an IGBT. The power device (12) is fabricated in a conventional manner on a semiconductor substrate, and the thermal sensing device (20) is fabricated on an electrical insulation layer (74) formed over the substrate. The thermal sensing device (20) may be provided in the form of a number of series-connected polysilicon diodes (D1-D3) positioned adjacent to the power device (12) such that the operating temperature of the thermal sensing device (20) is near that of the power device (12). In response to an input current IC, the thermal sensing device (20) produces an output voltage (VD) that is substantially linear with surface die temperature, and which reacts rapidly to changes in surface die temperature. The thermal sensing device (20) is completely electrically isolated from the power device, thereby eliminating any electrical interaction therebetween.

Abstract: An automotive ignition system (50) includes a control circuit (52) operable to drive a coil current switching device (24) connected between an ignition coil (30) referenced at battery voltage (VBATT) and a sense resistor (RS) referenced at ground potential. The control circuit (52) includes a drive circuit (20) and voltage trip circuit (54) defining a reference voltage (VTH) for comparison with a sense voltage (VS) developed across the sense resistor (RS) due to increasing coil current (IC) through the ignition coil (30). As the sense voltage (VS) increases to the reference voltage (VTH), the voltage trip circuit (54) produces a trip voltage signal (VTRIP) to which the drive circuit (20) is responsive to deactivate the coil current switching device (24). The voltage trip circuit (54) is configured such that the reference voltage (VTH) is temperature and battery voltage, and optionally engine speed, dependent.

Abstract: In an ignition coil assembly of an ion sensing ignition system having an ignition coil output, a buffered ion-sense current source circuit is provided and includes a current sensing circuit, the current sensing circuit being disposed so as to be communicated with the ignition coil output and an active current source circuit, the active current source circuit being disposed so as to be communicated with the current sensing circuit and a current measuring device.

Abstract: An automotive ignition diagnostic system includes an ion current detection circuit producing a buffered representation of an ion current flowing across an electrode gap of an ignition plug in response to a bias voltage applied thereto. An ignition diagnostic circuit is responsive to the buffered representation of the ion current to charge a single integration capacitor. The diagnostic circuit is operable to produce an output signal having a pulse width defined by the amount of charge on the capacitor. When the ion current flows following a combustion event, the width of the output signal is controlled as a function of the quality of combustion in the corresponding cylinder. However, if sufficient ion current flows prior to combustion, the width of the output signal is controlled to indicate a fouled ignition plug.

Abstract: An automotive ignition system includes a control circuit (52) operable to drive a coil current switching device (24) connected to an ignition coil (30) referenced at battery voltage. The control circuit (52) includes a drive circuit (20) and ring damping circuit (58) producing an inhibit signal (INH) to which the drive circuit (20) is responsive to control the state of the coil drive signal (GD). In a single pulse ignition system; i.e., an ignition system employing a single coil charging event per combustion cycle, the ring damping circuit (58) is responsive to a spark control signal (ESTBF) to control charging and discharging of a single capacitor (C1) to define the inhibit signal (INH). In a multiple pulse ignition system; i.e.