Abstract: A system for providing basic system control functions upon failure of a management processor in a computer system. During normal system operation, a management processor monitors system sensors that detect system power, temperature, and cooling fan status, and make necessary adjustments. The management processor normally provides an output signal indicating that it is operating properly. A high-availability controller monitors each of these signals to verify that there is at least one operating management processor. When none of the processors indicate that they are operating properly, the high-availability controller monitors the system sensors and updates system indicators. If a problem develops, such as failure of a power supply or a potentially dangerous increase in temperature, the high-availability controller sequentially powers down the appropriate equipment to protect the system from damage.

Abstract: A DC-DC voltage converter comprises a controller, two switches, a transformer and two rectifying diodes. The transformer has a first winding, a second winding and a center tap. Input voltage in connected between the center tap and ground. An anode of each diode is connected to the outer ends of the two windings and the cathodes of the two diodes are connected together to provide a positive output with respect to ground. Each switch is connected between an outer end of one windings and ground. The controller generates control signals to turn the switches on and off for limited periods of time in phase opposition to alternately connect the outer ends of the first and second winding to ground to cause current to flow alternatively in one of the windings and induce a voltage in the other winding that is additive to the input voltage, thereby providing an output voltage greater than the input voltage.

Abstract: A method and apparatus for controlling the speed of a voltage-controlled fan by locking the pulse-width modulated speed control voltage to a tachometer signal of the fan is presented. By triggering the off time of the PWM pulse to the detection of the tachometer signal and ensuring the off time is less than one tachometer period, no phase and frequency information is lost.