Power supply system for an optical inspection apparatus

For use in a stabilized light supply system subject to battery voltage variation, power supply system comprising:

• (a) a battery having an output voltage subject to variation over a period of time;
• (b) a voltage tracking circuit connected to said battery for following variations in battery voltage, said tracking circuit having an output terminal providing a signal indicative of battery voltage variations;
• and voltage tracking circuit comprising a RC charging circuit serially with a Zener diode, said RC circuit charging more rapidly with increased battery voltage, and also including means for controllably discharging said RC circuit periodically;
• (c) timing circuit means connected to said voltage tracking circuit terminal, said timing circuit means forming a timed duty cycle control signal having a duty cycle varied with battery voltage variations, said timing circuit means having a voltage dependent input connected thereto from said voltage tracking circuit means;
• (d) electronic switch means having a control input connected to said timing circuit means for control by the control signal therefrom;
• and
• (e) a lamp serially connected to said battery to be powered thereby, said lamp also being connected with said electronic switch means to control current flow from said battery through said lamp and further subject to control by the timed duty cycle control signal for adjusting current flow to thereby adjust light output notwithstanding battery voltage variations.