Torque sensor for vehicle steering system

A torque sensor for a vehicle steering system, comprising:

• a power source that supplies power;
• an oscillator that oscillates by receiving a voltage from said power source;
• an offset voltage circuit part that generates an offset voltage by using said voltage supplied from said power source;
• a current amplifier that outputs an alternating current voltage which is in-phase with a voltage outputted from said oscillator;
• first and second coils that are in series and connected at both ends thereof to output terminals of said current amplifier and said offset voltage circuit part, respectively;
• first and second resistances that are in series and connected in parallel to said first and second coils;
• first and second waveform selecting parts that receive an alternating current voltage from a contact part of said first and second resistances and from a contact part of said first and second coils, respectively, and then select and output a half-period of said alternating current voltage;
• first and second peak detectors that detect a peak value of each output voltage of said first and second waveform selecting parts;
• a first differential amplifier that executes differential amplification by receiving voltages outputted through said first and second peak detectors;
• a first voltage-current converter that outputs a torque signal by converting a voltage, which is outputted from said first differential amplifier, into a current;
• and
• third and fourth resistances being in series and connected in parallel to said first and second coils;
• third and fourth waveform selecting parts that receive an alternating current voltage from a contact part of said third and fourth resistances and from a contact part of said first and second coils, respectively, and then select and output a half-period of said alternating current voltage;
• third and fourth peak detectors that detect a peak value of each output voltage of said third and fourth waveform selecting parts;
• a second differential amplifier that executes differential amplification by receiving voltages outputted through said third and fourth peak detectors;
• and a second voltage-current converter that outputs a fail-safe torque signal by converting a voltage, which is outputted from said second differential amplifier, into a current.