Abstract: A protection circuit (100) for use with a battery operated device (50) which includes an over temperature detector (110), a controller (130), and a voltage divider circuit (102 and 106). The voltage divider circuit includes a multi-use thermistor (102) for monitoring a temperature of a battery cell (104), a battery charger, or a battery operated device. Further, the thermistor can be operatively connected to the over temperature detector. An input voltage at the input (114) of the over temperature detector can vary relative to a variance in the monitored temperature. The temperature detector can signal the controller to terminate the charging of the battery cell if the temperature exceeds a predefined value. The device discharge detector can signal the controller to terminate the discharging of the battery cell if the battery operated device determines a specific event such as water intrusion, circuit failure or a software problem.

Abstract: This invention includes a thermally stable, low-cost charging circuit for rechargeable batteries. The circuit includes a thermal control circuit that employs a temperature dependent component such as a thermistor or positive temperature coefficient device. The temperature dependent device is thermally coupled to a charging pass element, which is typically a power transistor. When the transistor enters a danger zone, which is a region of operation characterized by elevated power dissipation in the pass element, the thermal control circuit is actuated to regulate the pass element in a constant power mode until the circuit exits the danger zone.

Abstract: This invention includes a thermally stable, low-cost charging circuit for rechargeable batteries. The circuit includes a thermal control circuit that employs a temperature dependent component such as a thermistor or positive temperature coefficient device. The temperature dependent device is thermally coupled to a charging pass element, which is typically a power transistor. When the transistor enters a danger zone, which is a region of operation characterized by elevated power dissipation in the pass element, the thermal control circuit is actuated to regulate the pass element in a constant power mode until the circuit exits the danger zone.

Abstract: This invention includes a memory device having exactly three external terminals: a power external terminal; a ground or return external terminal; and a one-wire data communication external terminal. The memory is preferably employed in a rechargeable battery pack having exactly four terminals. The power external terminal is coupled to a battery terminal traditionally used for a thermistor. When a host device desires to read data from the memory, the host device closes a switch coupled between a power source and the thermistor battery terminal, thereby actuating the memory. The host then reads data by way of a communication channel established between a microprocessor in the host device and the data communication external terminal of the memory.

Abstract: This invention offers an improved hands-free device for coupling to radio devices having mute and audio inputs. The invention couples serially between the radio and a portable electronic device such as a mobile telephone. The invention facilitates the delivery of appropriate audio signals to the radio. The invention also senses the activity of the portable electronic device and actuates a mute signal upon sensing such activity. The mute signal causes the radio to switch the input to its loudspeakers from a received signal to the audio being delivered by the invention from the portable electronic device. In so doing the invention offers an easy to install, inexpensive hands-free unit that takes advantage of the high fidelity loudspeakers in the automotive stereo system.

Abstract: This invention includes a circuit for the prevention of acoustic feedback between an electronic device and an audio accessory. In a preferred embodiment, the circuit prevents audio feedback between a cellular telephone and a speakerphone accessory. The circuit includes a current limiting device coupled serially in the receive (Rx) line. The current limiting device is actuated via a delay circuit coupled between the current limiting device and the transmit (Tx) line. When a bias current is presented to the Tx line, the bias propagates through the delay circuit, thereby actuating the current limiting device a predetermined time after the presentation of the bias. The circuit keeps the Rx line open long enough for the phone to deactivate its internal microphone.

Abstract: A clamp circuit for limiting output voltage from a power supply secondary inductor to a ground when a first secondary node has a first secondary node voltage above a predetermined value relative to ground includes a silicone controlled rectifier and a control circuit. The silicone controlled rectifier has a first anode that is electrically coupled to the first secondary node of the secondary inductor, a first cathode that is electrically coupled to the secondary ground, and a first gate. The control circuit is electrically coupled to the first secondary node and to the gate of the silicon controlled rectifier. The control circuit senses the first secondary node voltage and applies a control voltage to the gate of the silicon controlled rectifier when the first secondary node voltage is above the predetermined value.

Abstract: An isolation circuit for isolating a load node from a power supply secondary inductor includes a Zener diode and a PTC thermistor. The Zener diode electrically couples the load node to a ground and is capable of being in a substantially conductive state when the voltage between the load node and the ground exceeds a predetermined threshold and is also capable of being in a substantially non-conductive state when the voltage between the load node and the ground does not exceed the predetermined threshold. The Zener diode has a non-conductive temperature corresponding to when the Zener diode is in the substantially non-conductive state and a conductive temperature corresponding to when the Zener diode is in the substantially conductive state. The PTC thermistor electrically couples the power supply secondary inductor to the load.

Abstract: This invention combines linear charging techniques with ionic relaxation pulse charging to rapidly charge lithium ion batteries to full capacity. The preferred embodiment incorporates a blocking diode and series resistor to multiplex an ionic relaxation control circuit with a linear regulated charging circuit, thereby utilizing a single, common, shared power transistor.

Abstract: A battery charger (100) suitable for sub-miniaturization and connection to a wall transformer power supply (20) to charge a battery (30). The battery charger (100) features a switch (130) that controls flow of current from the transformer (20) either to output terminals for charging the battery (30) or to ground, a voltage regulator (120), a microprocessor (110), a current sensing resistor (150) and a Schottky diode (140). The microprocessor (110) is coupled to the switch (130) to control whether the switch is open or closed. The secondary leakage inductance of the wall transformer (20) is exploited to control charging of the battery. The microprocessor (110) is programmed to initiate a charging mode comprising oscillation between a conduction interval and a flyback interval. A charging pulse is delivered to the battery (30) during the flyback interval.

Abstract: A battery charger system (10) consisting of a power supply unit (20) and a battery charger unit (70). The power supply unit (20) features a current profile generator (26) that defines a current profile of the output current of the power supply unit (20). The battery charger system (10) provides a unique way of communicating charging current demand between the battery charger unit (70) and the power supply unit (20). The power supply unit (20) is capable of determining the charging current demand by detecting specific logical operating states of the battery charger unit (70), and comparing the current to a set threshold. The battery charger unit (70) communicates charging current demand to the power supply unit (20), and the power supply unit (20) responds by adjusting its output current to meet the required demand.

Abstract: A battery charging system 100 is provided which comprises a charger 101 and a battery pack 102. The battery pack 102 comprises a battery cell or cells 150, memory means 140, temperature sensing means 147, and a high accuracy, high impedance voltage sensing means 112 that senses voltage directly at the battery cell terminals 151, 149. By sensing directly at the cell terminals 151, 149, charging error due to parasitic conductor impedances 132, 138 can be eliminated. The voltage sensing means 112 allows memory 140 and thermistor 147 data to be multiplexed, allowing the system to operate with four or fewer battery terminals.

Abstract: A charging technique (200) charges a battery pack (102) by taking into account the additional internal circuit impedance of the battery pack. An optimum pack voltage value for the battery pack is calculated (208) based on the rated internal cell voltage as well as the charge current and the internal battery pack circuitry impedance. The battery pack can now be charged such that the internal battery cell voltage is maintained at the rated voltage throughout the charging process. The optimum pack voltage is also updated (220) to account for variations in the battery pack circuitry impedance over temperature (216, 218) as well as variations in charge current (222, 224) during the charging process.

Abstract: A method for charging a battery or battery pack (206) provides a scheme for terminating a rapid charging regime only after both a temperature and voltage threshold are exceeded. This allows a battery to continue to receive a rapid charge even when battery temperatures are rising rapidly due to external (non-charge related) conditions.

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.