A pulse width modulated (PWM) controller for high temperature power
conversion application is disclosed. The controller includes following
functional blocks. A bias generator (10) establishes a stable operating
point with Zero- Temperature-Coefficient (ZTC) over operating temperatures
and supply voltage variations. An oscillator (13) using the same bias
resistor for the bias generator (10), produces a precision time base for
the PWM operation. A temperature compensated error amplifier (20) forms a
closed loop regulation of a power converter. Three voltage comparators
(18,33,37) provide direct coupled current mode control, current limit
protection and under voltage lock-out functions. A latch (30) engages the
PWM pulses to an output select circuit (21) for user configurable
single-ended or double-ended switching topology. An on shot discharge
circuit (26) triggered by the under voltage lock-out comparator (37)
allows for proper start-up during input voltage transient. Five voltage
buffers (11,12,16,35,36) with fixed gain setting provide temperature
stabilized voltage thresholds for the oscillator (13) and the comparator
(18,33,37). Soft start is accomplished by controlling the inverting input
of the current limit comparator (33) in a timely fashion, in conjunction
with the one shot discharge circuit (26). In addition, two balanced delay
circuit blocks (40,41) eliminate cross-conduction current over operating
temperatures in two corresponding output drivers (42,43). All of the
disclosed functions are preferably incorporated into an integrated circuit
whose fabrication process is suitable for high temperature applications.