Abstract: This invention includes a charging circuit employing an off-the-shelf battery protection circuit. The invention offers an improvement to the battery protection circuit by providing means to accommodate trickle charging during undervoltage conditions. A pass transistor is provided with a trickle resistor coupled in parallel. The pass transistor is driven by a drooping voltage circuit that causes the pass transistor to open in undervoltage conditions, thus forcing charging current through the trickle resistor. Indicating means are also included to tell the user whether the circuit is in trickle mode or normal charging mode.

Abstract: This invention includes a charging circuit employing an off-the-shelf battery protection circuit. The invention offers an improvement to the battery protection circuit by providing means to accommodate trickle charging during undervoltage conditions. A pass transistor is provided with a trickle resistor coupled in parallel. The pass transistor is driven by a drooping voltage circuit that causes the pass transistor to open in undervoltage conditions, thus forcing charging current through the trickle resistor. Indicating means are also included to tell the user whether the circuit is in trickle mode or normal charging mode.

Abstract: An apparatus for indicating data transfer between a personal electronic device and a host device includes a common node that connects at least one data line to the personal electronic device and at least one data line to the host device. A high impedance amplifier has an input electrically coupled to the common node and generates an amplified signal corresponding to a signal value present on the common node. A monostable circuit is responsive to the amplified signal and generates a plurality of electrical pulses when the amplified signal exhibits changes in value corresponding to a data transfer through the common node. A lamp driver circuit, that is responsive to the plurality of electrical pulses, generates pulses of light correspond to the electrical pulses. Each of the plurality of electrical pulses is of sufficient duration so that each of the pulses of light is of sufficient duration to be perceived by a human eye.

Abstract: A series-resonant power converter (10) featuring a tap winding (106) on a transformer (100) that is coupled to a resonant capacitor (124) in a resonant tank circuit (122). An output voltage is taken at a secondary (104) of the transformer (100) via a rectifier (110). A control circuit (140) is coupled to the output voltage to monitor the output voltage with respect to a reference to determine load conditions and to generate a control signal representative thereof. An energy recirculation circuit (180) is coupled to the control circuit (140) and to the voltage source (12) and comprises a switch (186) coupled to the tap winding (106) of the transformer (100).

Abstract: A series-resonant power converter (10) comprising a transformer (100), a resonant tank circuit (120) having a piezo-electric crystal (122) as the resonant element and a series-connected resonant capacitor (124). First and second switches (132 and 134) are connected to the transformer (100) and are driven by voltages at windings of the transformer so as to alternately turn on. The piezo-electric crystal (122) self-oscillates to store and release energy and thereby charge and discharge the capacitor (124). Moreover, as a result of the self-oscillation of the resonant circuit (120), the switches (132 and 134) are alternately driven in synchronism with the charging and discharging cycle of the capacitor (122) through windings of the transformer (100). No additional switching circuitry is needed to achieve proper oscillation of the resonant tank circuit (120).