The integrated circuit, including MOS transistors, for driving the step motor of an analog display is substantially reduced in size by boosting the transistor gate voltage above the battery voltage applied to the source-drain terminals.

A miniature electronic timepiece whose analog-display time-indicating hands are driven by the rotor of a stepping motor actuated by low-frequency periodic timing pulses derived by frequency division from a high-frequency crystal-controlled time base. This motor, in addition to a stator coil wound on a core, includes an auxiliary coil wound on the same core to define a transformer whose primary is the auxiliary coil and whose secondary is the stator coil. To power the electronic watch, a voltage at a predetermined level is required, this being supplied by a converter formed by an electronic chopper interposed between the primary of the transformer and a d-c source whose output is at a different voltage level. The d-c voltage applied to the primary is periodically interrupted, the resultant a-c voltage yielded by the secondary being rectified to provide the desired power voltage. The rotor of the motor is braked immediately after the end of each drive pulse by means functioning to momentarily short circuit the stator coil.

A switching circuit that utilizes an N-channel field effect transistor. The circuit can be used in a generator voltage regulator wherein the drain and source of the transistor are connected in series with the field winding of the generator. The circuit includes a capacitor that is repetitively charged and discharged. At the end of the charge period a gate bias voltage is developed that is applied to the gate of the transistor. The magnitude of the gate bias voltage that is developed is the sum of the capacitor voltage and the voltage of a voltage source. The capacitor is allowed to discharge until the gate bias voltage decreases to a value that is high enough to maintain the transistor conductive whereupon the discharge period is terminated and the capacitor is recharged. The system responds to the magnitude of the output voltage of the generator relative to a reference voltage and will cause the transistor to be biased conductive or nonconductive for total time periods that are equal to the sum of a plurality of consecutively occurring timing periods.

A voltage regulator for regulating the output voltage of a diode-rectified alternating current generator that supplies the electrical loads on a motor vehicle including the storage battery. The voltage regulator has an up-down counter which is incremented when the output voltage of the generator is below a desired regulated value and is decremented when the output voltage of the generator is above the desired regulating value. The magnitude of the count in the counter is repeatedly sampled and used to determine the on time of a semiconductor switch that is connected in series with the field winding to thereby control the duty cycle of the field voltage pulses. The counter is incremented at a lower rate when the speed of the engine that drives the generator is below a predetermined speed than it is when the speed of the engine is above the predetermined speed. When the generator is not rotating, the up-count of the counter is limited to a predetermined value that provides a minimum field voltage duty cycle. The system is capable of sensing either battery voltage or rectifier output voltage and is controlled to automatically switch between battery voltage and rectifier voltage under certain operating conditions.