Voltage doubler protection circuit results in large cost savings

Medium to high end colour TVs that are designed for an international market must operate over a wide mains voltage range, which typically ranges from 90 V AC to 276 V AC. To achieve operation over this wide mains voltage range, at the power levels that these sets require, a voltage doubler circuit is required at the front end. The doubler circuit consists of two electrolytic capacitors, which are rated at 400 V in order to comply with IEC65 requirements. This paper proposes an "electrolytic capacitor protection circuit", which enables the voltage rating of the electrolytics to be reduced to 250 V. This patented circuit results in cost savings of more than 50% in the price of the electrolytic filter capacitors. This represents substantial savings, especially for mass produced items like TV sets. Therefore, what may at first appear to be an unnecessary circuit, may from a financial point of view be very desirable.