Abstract: An uniterruptible power supply is provided that incorporates switching ciitry permitting a path for instantaneous DC backup power to be supplied to a voltage-declining primary power supply bus. Once the instantaneous transition is made, battery power is switched to a low impedance path to provide long-term battery power delivery to the bus. At a point where the backup batteries no longer supply useful power to a load, disabling circuitry disconnects the batteries from the load so that excessive draining of the batteries does not result in irreversible battey damage. The uninterruptible power supply of the invention further includes an automatic battery charging circuitry that seeks to maintain the power supply batteries at optimal charge level. To enable an operator to adequately assess battery charge condition, the invention provides battery test circuitry that causes a simulated load to appear at the power supply batteries. Visual representations are then made as to battery status.

Abstract: A direct current power supply for instantaneously providing tens of kilows of electrical energy for brief periods, such as 100 ms, during momentary power interruptions between a load and an electrical power source having a supply voltage includes a capacitor having an initial voltage charge preferably greater than the supply voltage. The cathode of a zener diode is operably coupled to the capacitor. The anode of a second diode is operably coupled to the anode of the zener diode. A solid state switch has a power input operably coupled between the capacitor and the cathode of the zener diode, a power output operably coupled between the anodes of the zener diode and second diode, and an enabling input, so that the switch may be triggered to conduct electrical power whereby voltage from the capacitor is conducted through the switch to the anode of the second diode when an enabling signal is provided to the enabling input.