Ignition control circuit with current slope detection

Patent metadata

Field	Value
Publication number	US-9920736-B2
Application number	US-201615012513-A
Country	US
Kind code	B2
Filing date	Feb 1, 2016
Priority date	Feb 3, 2015
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

In a general aspect, a circuit for controlling operation of an ignition circuit including an insulated-gate bipolar transistor (IGBT) device can include a current slope detection circuit configured to detect a slope of a current in a primary winding of an ignition coil included in the ignition circuit and a driver circuit coupled with the current slope detection circuit. The current slope detection circuit can be further configured to, during charging of the ignition coil, if the detected slope is above a first limit, provide a first indication to the driver circuit; and, if the detected slope is below a second limit, provide a second indication to the driver circuit. The driver circuit can be configured to, in response to receiving the first indication or the second indication, modify operation of the ignition circuit.

First claim

What is claimed is:

1. A circuit for controlling operation of an ignition circuit including an insulated-gate bipolar transistor (IGBT) device, the circuit comprising:
a current slope detection circuit configured to detect a slope of a current in a primary winding of an ignition coil included in the ignition circuit; and
a driver circuit coupled with the current slope detection circuit; and
a voltage reference circuit configured to:
provide a first reference voltage corresponding with a first limit; and
provide a second reference voltage corresponding with a second limit,

the current slope detection circuit being further configured to, during charging of the ignition coil:
if the detected slope is above the first limit, provide a first indication to the driver circuit; and
if the detected slope is below the second limit, provide a second indication to the driver circuit,

the driver circuit being configured to, in response to receiving the first indication or the second indication, modify operation of the ignition circuit.

2. The circuit of claim 1 , wherein modifying operation of the ignition circuit includes limiting a current through the IGBT.

3. The circuit of claim 1 , wherein modifying operation of the ignition circuit includes modifying a dwell time of the ignition circuit.

4. The circuit of claim 1 , further comprising a soft-shutdown (SSD) circuit coupled with the driver circuit, wherein modifying operation of the ignition circuit includes the driver circuit instructing the SSD circuit to perform a controlled shutdown of the IGBT device.

5. The circuit of claim 1 , wherein the driver circuit is further configured, in response to receiving the first indication or the second indication, to send a notification of a failure mode to an engine control unit (ECU) coupled with the ignition circuit, the ECU being configured to modify operation of the ignition circuit bused on the notification.

6. The circuit of claim 1 , wherein the current slope detection circuit includes:
a resistive-capacitive circuit configured to produce a signal corresponding with the slope of the current in the primary winding;
a first comparator configured to compare the signal corresponding with the slope of the current in the primary winding with the first reference voltage corresponding with the first limit, the first limit being an upper limit; and
a second comparator configured to compare the signal corresponding with the slope of the current in the primary winding with the second reference voltage corresponding with the second limit, the second limit being a lower limit.

7. The circuit of claim 1 , wherein the current slope detection circuit further includes a timer circuit configured to prevent the current slope detection circuit from indicating that the detected slope is above the first limit during a first portion of a dwell time of the ignition circuit.

8. The circuit of claim 1 , wherein the current slope detection circuit includes:
a first comparator configured to compare a voltage signal corresponding with the slope of the current in the primary winding with the first reference voltage corresponding with the first limit; and
a second comparator configured to compare the voltage signal corresponding with the slope of the current in the primary winding with the second reference voltage corresponding with the second limit.

9. The circuit of claim 8 , wherein the current slope detection circuit further includes a timer circuit configured to prevent the current slope detection circuit from indicating that the detected slope is above the first limit during a first portion of a dwell time of the ignition circuit.

10. The circuit of claim 1 , wherein the current slope detection circuit includes:
a sampling circuit configured to:
store a first digital value corresponding with a first value of a voltage signal corresponding with the slope of the current in the primary winding at a first time; and
store a second digital value corresponding with a second value of the voltage signal corresponding with the slope of the current in the primary winding at a second time, the second time being a period of time after the first time;

a first comparator configured to compare the first digital value with the second digital value to produce an output signal;
a second comparator configured to compare the output signal with the first reference voltage corresponding with the first limit; and
a third comparator configured to compare the output signal with the second reference voltage corresponding with the second limit.

11. The circuit of claim 10 , wherein comparing the first digital value with the second digital value includes comparing a voltage corresponding with the first digital value and a voltage corresponding with the second digital value.

12. The circuit of claim 10 , wherein the first reference voltage and the second reference voltage are scaled based on the period of time between the first time and the second time.

13. An ignition circuit for use in an internal combustion engine, the ignition circuit, comprising:
an ignition insulated-gate bipolar transistor (IGBT) circuit;
an ignition coil coupled with the ignition IGBT circuit;
a spark plug coupled with the ignition coil; and
a control circuit coupled with the ignition IGBT circuit, the control circuit including:
a current slope detection circuit configured to detect a slope of a current in a primary winding of the ignition coil; and
a driver circuit coupled with the current slope detection circuit,
the current slope detection circuit being further configured to, during charging of the ignition coil:
if the detected slope is above a first limit, provide a first indication to the driver circuit; and
if the detected slope is below a second limit, provide a second indication to the driver circuit,

the driver circuit being configured to, in response to receiving the first indication or the second indication, modify operation of the ignition circuit,
the current slope detection circuit including:
a first comparator configured to compare a voltage signal corresponding with the slope of the current in the primary winding with a first reference voltage corresponding with the first limit; and
a second comparator configured to compare the voltage signal corresponding with the slope of the current in the primary winding with a second reference voltage corresponding with the second limit.

14. The ignition circuit of claim 13 , wherein the ignition IGBT circuit includes:
an IGBT device; and
a clamp configured to define a clamping voltage for the IGBT device.

15. The ignition circuit of claim 13 , wherein the current slope detection circuit further includes:
a resistive-capacitive circuit configured to produce the signal corresponding with the slope of the current in the primary winding.

16. The ignition circuit of claim 15 , wherein the current slope detection circuit further includes a timer circuit configured to prevent the current slope detection circuit from indicating that the detected slope is above the first limit during a first portion of a dwell time of the ignition circuit.

17. The ignition circuit of claim 13 , wherein the current slope detection circuit further includes a timer circuit configured to prevent the current slope detection circuit from indicating that the detected slope is above the first limit during a first portion of a dwell time of the ignition circuit.

18. The ignition circuit of claim 13 , wherein the current slope detection circuit includes:
a sampling circuit

Assignees

• Fairchild Semiconductor

Inventors

• Tang Qingquan
• Gillberg James E

Classifications

• F02P3/0453

  Opening or closing the primary coil circuit with semiconductor devices · CPC title

• F02P3/0442 Primary

  using digital techniques (F02P3/0456, F02P3/053, F02P3/0554, F02P3/0558 take precedence) · CPC title

• H03K17/168

  in composite switches · CPC title

• F02P3/053

  using digital techniques · CPC title

• F02P17/12 Primary

  Testing characteristics of the spark, ignition voltage or current (testing of sparking plugs H01T13/60) · CPC title