Abstract: A reduced noise power converter is provided with a transformer having primary, secondary, and auxiliary windings (22, 24, and 46). An electrostatic shield (26) having a shield termination (32) is disposed between the primary and secondary windings. The auxiliary winding has the opposite polarity of the primary winding, and is coupled between the shield termination and the input voltage source (12). By appropriate selection of the number of turns of the auxiliary winding, noise coupled from the primary side to the secondary side through the stray device capacitance (34) is neutralized.

Abstract: A battery charger (10) is provided with a power supply (26) which is energized by a main winding (22) and a bias winding (24) on the secondary side (18) of an input transformer (14). The charger switches a main voltage level provided at a main voltage output (28) according to a pulse width modulation scheme, and has an output section (36) for filtering the switched voltage. A power switch (38) is coupled between the output section and the main voltage output, and is driven by a bias switch (48) coupled between the control terminal (50) of the power switch, and a bias voltage output (30), which provides a bias voltage level that is higher then the main voltage level by a minimum delta.

Abstract: A battery charger (12) is used for recharging a battery pack (10) when the battery pack is placed in a charging pocket (14). The battery pack generates heat upon being recharged, which is collected by a probe (22). The probe senses the temperature and changes in temperature of the battery pack by means of a temperature sensing element disposed (54) therein. The temperature sensing element provides an electrical signal indicative of the temperature of the battery pack to a charging circuit (58). The charging circuit, upon sensing sufficient temperature conditions, modifies the operation of the charger such that only low rate currents are thereafter applied to the battery pack.