Down-hole switching-mode power supply using a remote CA start up pulse

The hydrocarbon industry leans heavily upon advanced technologies to extract oil and gas from greater depths and in harsher environments. The challenge to electronics manufacturers and designers is to make complex electronics work at the high temperatures, vibration, and extreme pressures encountered in these locations. Among the more critical electronic systems required for high temperature down-hole operations is high efficiency switching mode power supplies (SMPS). The use of high frequency switching permits not only decreasing the size of inductors and capacitors in the circuit design, but also obtaining typical power efficiencies up to 90%. Generally a SMPS is composed of a controller, a converter and silicon carbide (SiC) power switches. High temperature down-hole gauges operate with low voltages either 3.3V or 5.0V; however, wire-line surface power equipment utilizes higher voltages above 250 V CD. Hence, SMPS requires efficient power dissipation circuits to reduce the DC input voltage. This work describes a high temperature SMPS that has a DC input range from 150 V CD to 300 V CD, ± 6 V CD output voltages and 12 W total power. The SMPS design uses a CA start up pulse provided by a programmable surface power supply via a mono-conductor wire-line cable; subsequently, the SMPS sustains its operation by powering itself using one of the voltage outputs. The obtained laboratory tests results of the down-hole SMPS, using changes in temperature from 25 °C – 200 °C, provide a firm basis for testing and evaluating the DC-CD power supply in high temperature gauges in the field.