Pulse width modulated controller for high temperature power conversion

Abstract

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.

Dependencies are inferred from the claim text.