In an emergency power unit for an alternating current consumer, there are supplied a connection (9) for an alternating current generator (10), a battery (5), which can be charged by rectified current from the alternating current generator (10), a controllable bidirectional converter unit (6), which is located between the said battery and a consumer connection (2), an alternating voltage regulator (13), which stabilizes the alternating voltage on the alternating voltage side (3) of the bidirectional converter unit (6) by means of pulse-width modulation, and a battery voltage regulator (12). The alternating current generator (10) can be connected, in parallel, to the alternating voltage side of the bidirectional converter unit (6), and a current-limiting resistor (8) is located between the alternating voltage side (3) of the bidirectional converter unit (6) and the alternating current generator connection (9). In order to achieve galvanic isolation between the bidirectional converter unit and the alternating current generator, and between the consumer (1) and the alternating voltage generator (10), the current-limiting resistor is designed as a leakage-reactance transformer (8') which has three windings. Of these, one winding (31) is connected directly to the alternating voltage side (3) of the bidirectional converter unit, the second winding (32) is connected to the alternating current generator connections (9, 9a) and the third winding is connected to the consumer connections (2, 2a). The leakage-reactance transformer effects not only galvanic isolation, but at the same time effects the required current-limitation as a consequence of its leakage-inductance.

Emergency power unit

Apparatus for driving a timing device from an external AC power source and, in the event that the AC power source fails, from an auxiliary DC source. The driving apparatus includes a pulse producing circuit which produces periodic pulses in response to timing pulses. A timing pulse circuit, including an oscillator which produces an oscillating voltage having a frequency substantially proportional to the AC power source frequency, applies the timing pulses to the pulse producing circuit. A DC power supply receives the voltage which is supplied by the AC power source and generates a DC energizing voltage to energize the various circuits of the apparatus, including the pulse producing circuit and the oscillator. In the event that the AC power source fails, the voltage produced by the auxiliary DC source is used to energize the various circuits of the apparatus. A storage device is included in the DC power supply for receiving and storing the generated DC energizing voltage so as to maintain a sufficient energizing voltage during the interim between the failure of the AC power source and the time that the auxiliary DC source reaches a satisfactory energizing level. A driving circuit responds to the periodic pulses produced by the pulse producing circuit to supply driving energy to the timing device. The timing device comprises a single clock or clock system or, in the alternative, a master clock which is used to drive and control one or more slave clocks.

Clock drive apparatus

An example relates to a method for accessing data of a first domain that is driven by a first clock via a second clock, comprising at least one of the following: accessing the data of the first domain via the second clock during a time when the first clock is in a first logical state. An edge indicating a transition from a second logical state to the first logical is used to access data via the first clock, or accessing the data of the first domain via the second clock at edges of the first clock that are synchronized with edges of the second clock.

Accessing Data Via Different Clocks

A power system for a master clock motor or the like which includes automatic switching circuitry for enabling instant switch-over from main power operation to standby power operation in the event of a temporary main power loss.

J Baltrush

Papers

Master clock standby switching circuitry