Igniter and vehicle, and method for controlling ignition coil

Patent metadata

Field	Value
Publication number	US-2016134085-A1
Application number	US-201514935763-A
Country	US
Kind code	A1
Filing date	Nov 9, 2015
Priority date	Nov 11, 2014
Publication date	May 12, 2016
Grant date	—

Abstract

An igniter that includes switch element and switch control device for controlling the switch element depending on ignition signal. The switch control device includes a determination stage that compares voltage associated with the ignition signal with a predetermined voltage to generate a determination signal, a driving stage that controls ON/OFF operations of the switch element depending on the determination signal, a timer circuit that asserts a conduction protection signal when state where the determination signal becomes an assert level corresponding to an ON operation of the switch element continues for predetermined time, a time-varying voltage generating circuit that generates time-varying voltage over time in response to the assertion of the conduction protection signal, and an amplifier that changes the voltage of a control terminal of the switch element such that detection voltage associated with coil current flowing in the switch element is close to the time-varying voltage.

First claim

What is claimed is:

1 . An igniter, comprising:
a switch element connected to a primary coil of an ignition coil; and a switch control device configured to control the switch element depending on an ignition signal from an engine control unit (ECU), wherein the switch control device comprises: a determination stage configured to compare a voltage associated with the ignition signal with a predetermined reference voltage to generate a determination signal; a driving stage configured to control ON/OFF operations of the switch element depending on the determination signal; a timer circuit configured to assert a conduction protection signal when a state where the determination signal becomes an assert level corresponding to the ON operation of the switch element continues for a predetermined conduction protection time; a time-varying voltage generating circuit configured to generate a time-varying voltage which decreases from an initial voltage over time in response to the assertion of the conduction protection signal; and an amplifier configured to change a voltage of a control terminal of the switch element such that a detection voltage associated with a coil current flowing in the switch element is close to the time-varying voltage.

2 . The igniter of claim 1 , wherein the amplifier is configured to sink a current from the control terminal of the switch element.

3 . The igniter of claim 1 , wherein, when the detection voltage is higher than the time-varying voltage, the amplifier is configured to change the voltage of the control terminal of the switch element such that the detection voltage is close to the time-varying voltage.

4 . The igniter of claim 1 , wherein the amplifier comprises:
an output transistor installed between the control terminal of the switch element and a ground line; and a voltage comparator configured to compare the detection voltage with the time-varying voltage, and turn on the output transistor when the detection voltage exceeds the time-varying voltage.

5 . The igniter of claim 1 , wherein the amplifier comprises:
an output transistor installed between the control terminal of the switch element and a ground line; and an error amplifier configured to adjust a voltage of a control terminal of the output transistor depending on a difference between the detection voltage and the time-varying voltage.

6 . The igniter of claim 1 , wherein the time-varying voltage generating circuit comprises:
a first node at which the time-varying voltage is output; a first resistor installed between a first voltage line regulated with a predetermined first voltage level and the first node; and a variable impedance circuit installed between the first node and a ground line, and in which an impedance of the variable impedance circuit decreases from an initial impedance corresponding to the initial voltage over time in response to the assertion of the conduction protection signal.

7 . The igniter of claim 1 , wherein the time-varying voltage generating circuit comprises:
a first node at which the time-varying voltage is output; a third resistor in which a potential of a first end is fixed and a second end is connected to the first node; and a slope current source connected to the third resistor and configured to generate a slope current changed over time in response to the assertion of the conduction protection signal.

8 . The igniter of claim 7 , wherein the slope current source comprises:
a differential transistor pair including a fourth transistor and a fifth transistor; a tail current source connected to the differential transistor pair; a first bias circuit configured to supply a predetermined first bias voltage to a control terminal of the fourth transistor; and a second bias circuit configured to generate a second bias voltage changed over time at a voltage level equal to the first bias voltage and supply the generated second bias voltage to a control terminal of the fifth transistor in response to the assertion of the conduction protection signal, and wherein the slope current source is configured to generate the slope current depending on a current flowing in the fifth transistor.

9 . The igniter of claim 8 , wherein the first bias circuit comprises:
a fourth resistor installed between a second voltage line, to which a predetermined second voltage is supplied, and the control terminal of the fourth transistor; and a fifth transistor installed between the control terminal of the fourth transistor and the ground line, and wherein the second bias circuit comprises: a sixth resistor installed between the second voltage line and the control terminal of the fifth transistor; and a variable impedance circuit installed between the control terminal of the fifth transistor and the ground line, and in which an impedance of the variable impedance circuit decreases from an initial impedance corresponding to the initial voltage toward zero over time, in response to the assertion of the conduction protection signal.

10 . The igniter of claim 7 , wherein the slope current source comprises:
a plurality of variable current sources, wherein each of the variable current sources is configured such that an output current thereof varies between a predetermined minimum value and a predetermined maximum value depending on a control signal; and a current controller configured to control the plurality of variable current sources, wherein the current controller is configured to sequentially select the plurality of variable current sources and change an output current of the selected variable current source between the predetermined maximum value and the predetermined minimum value over time, and wherein the slope current source is configured to output a sum of output currents of the plurality of variable current sources.

11 . The igniter of claim 10 , wherein the current controller comprises:
a second slope voltage source configured to start an operation to periodically and repeatedly generate a second slope voltage changed over time in response to the assertion of the conduction protection signal; and a counter configured to receive a period signal asserted at every period of the second slope voltage to generate an N-bit thermometer code, and wherein the current controller is configured to select one of the variable current sources based on the thermometer code, control an output current of the selected variable current source depending on the second slope voltage, and fix the output current of the selected variable current source as a final value depending on the thermometer code.

12 . The igniter of claim 11 , wherein each of the variable current sources comprises:
a differential transistor pair including a fourth transistor and a fifth transistor; a tail current source connected to the differential transistor pair; a first bias circuit configured to supply a predetermined first bias voltage to a control terminal of the fourth transistor; and a second bias circuit configured to supply a second bias voltage to a control terminal of the fifth transistor depending on the second slope voltage and the thermometer code, and wherein each of the variable current sources is configured to output a current flowing in the fifth transistor.

13 . The igniter of claim 7 , wherein the slope current source comprises:
a sixth transistor, a predetermined voltage being applied to a base/gate of the sixth transistor; and a variable impedance circuit installed between an emitter/source of the sixth transistor and the ground line, and in which an impedance of the variable impedance circuit changes from an init

Assignees

• Rohm Co Ltd

Inventors

• Obe Katsuya
• Tanigawa Hiroyuki

Classifications

• H01T15/00 Primary

  Circuits specially adapted for spark gaps, e.g. ignition circuits (ignition circuits for internal-combustion engines F02P; electric spark ignition for combustion apparatus F23Q; protection circuits using spark gaps H02H9/06) · CPC title

• F02P5/1502

  using one central computing unit · CPC title

• F02P2017/121

  by measuring spark voltage · CPC title

• F02P11/00

  Safety means for electric spark ignition, not otherwise provided for · CPC title

• F02P17/12

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