Patent ID: 8624684
Filing Date: 2014-01-07
Classification: H03K

Abstract:
1. A circuit for starting an oscillator, which is configured to provide an oscillating signal to an inductive heating coil for a fuel injector, the circuit comprising: an oscillator comprising a tank circuit, the tank circuit comprising the inductive heating coil and having a resonant frequency, the oscillator further comprising first and second transistors coupled to the inductive heating coil and configured to conduct current through said inductive heating coil, the transistors being additionally configured to conduct a first predetermined current through the inductive heating coil when the oscillator circuit is oscillating, the transistors configured such that they conduct more than the first predetermined current when the oscillator circuit is not oscillating; a transistor current sensor operatively coupled to the transistors and configured to continuously generate a voltage signal, which is representative of current actually flowing through the first and second transistors; an inductive heating coil current comparator, operatively coupled to the transistor current sensor and a power supply for the transistors, the comparator generating an over-current signal responsive to the current flowing through at least one of the transistors being greater than the first predetermined current; and a transistor disabler coupled to both the comparator and the transistors, the disabler being configured to disable one of the transistors responsive to receipt of the over-current signal from the comparator; whereby disablement of one of the transistors reduces current flowing through the inductive heating element and causes the oscillator to attempt oscillation.