Method and circuitry for reliably controlling the state of a transistor switch under high voltage conditions are disclosed. The present invention monitors the level of an external signal applied to one terminal of the switch. If the level of the external signal is lower than a reference voltage such as the power supply voltage of the integrated circuit that comprises the switch, the control of the switch is passed to a digital signal internal to the integrated circuit. If the level of the external signal exceeds the reference voltage, then the present invention operates to allow the switch to be controlled by the external signal. This ensures that the switch is turned off, and remains off when it interfaces with voltages with absolute magnitudes higher than the highest internal voltage. The invention further ensures that the switch is turned off when no power is applied to the switch control circuit.
A synchronous rectifier MOSFET control circuit which overcomes many of the shortcomings of the prior art employs MOSFET for supplying voltage to a load when the MOSFET is in the forward biased condition (i.e., when an input voltage level exceeds the threshold voltage level by a pre-determined amount). The MOSFET control circuit is configured to turn off the MOSFET when the input voltage level dips below that pre-determined level required to maintain the MOSFET in the forward biased condition. When the MOSFET is turned off, the diode internal to the MOSFET device prevents current flow in the reverse bias direction (i.e., the internal diode prevents current flow from the output to the input), effectively isolating the load from the input voltage source, thereby allowing the capacitors to discharge their energy to the load to maintain a voltage supply to the load which is at or above the output load threshold voltage level. Thus, although a diode is still employed to prevent current flow in the reverse direction, the diode need not function to supply the current to the load when the MOSFET is in the forward biased direction. Rather, current flows through the MOSFET channel (as opposed to flowing through the diode) when the MOSFET is in the forward biased condition.
An apparatus and method for automatic shut-off of a combustion engine driving a fluid pump of a fluid displacement unit is presented. The apparatus and method are designed to protect the fluid displacement unit form damage due to excessively high running speeds by shutting off the combustion engine and to automatically reset the combustion engine for manual restart subsequent to the combustion engine spinning down to a rest.
A voltage clamp circuit is disclosed and claimed. The voltage clamp circuit includes a bypass device and a differential sense amplifier or comparator adapted to control operation of the bypass device. The bypass device is activated in response to the differential sense amplifier or comparator sensing a voltage above a predetermined level.
