Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

Martinus Bredius

Hendrik Boezen

Abraham Klaas Van Den Heuvel

Patrick Willem Hubert Heuts

Cecilius Gerardus Kwakernaat

Ruurd Anne Visser

Aloysius Johannes Maria Boomkamp

Peter Michael Buehring

Egon Joehnk

Maarten Teunis Visser

Aloysius J Boomkamp

A fault tolerant air bag system needs a floating supply, which supply conventionally is made by means of a DC-DC converter with a transformer. By splitting the main energy reserve capacitor ( ) into two capacitors ( ), and coupling one of the capacitors ( ) to the other ( ) by means of switches ( ) which open during a crash, no transformer is needed any more.

Fault tolerant air bag bus system without transformer

Bus driver having a P-channel output transistor (T1) for driving a first bus terminal (6) from a positive supply terminal (2), an N-channel output transistor (T2) for driving a second bus terminal (12) from a negative supply terminal (4), a P-channel driver transistor (T3) and an N-channel driver transistor (T4) series connected between the positive (2) and the negative (4) supply terminal. The control electrodes of the P-channel transistors (T1, T3) are interconnected and the control electrodes of the N-channel transistors (T2, T4) are interconnected to obtain a fixed relationship between the currents through the P-channel transistors (T1, T3) and through the N-channel transistors (T2, T4). The conduction of the driver transistors (T3, T4) is controlled by two floating control voltage sources (22, 24) which are connected between the interconnection node (20) of the driver transistors (T3, T4) and the respective control electrodes of the driver transistors. Any difference between the current through the P-channel driver transistor (T3) and the N-channel driver transistor (T4) is compensated for by a change in the voltage level at the interconnection node (20). In this way the currents through the driver transistors (T3, T4), and also through the output transistors (T1, T2) which are scaled copies of the driver transistors, are always equal and a highly symmetrical driving of the two bus wires (8, 14) is obtained. As a result, the electromagnetic radiation of the bus wires is low.

CAN bus driver with symmetrical differential output signals

Growing community of inventors

Santa Clara, CA, United States of America

Martinus Bredius