Abstract: A battery backup system using a power factor correction (PFC) front end as a DC-to-DC converter of a power supply for supplying a regulated DC input signal to a main power converter. The battery backup system includes a battery backup for supplying power, a switch circuit for connecting the battery in the event of loss of the AC input signal and a detection circuit for detecting the presence or absence of AC power for controlling the switch circuit. The PFC front end preferably receives either a pulsing DC voltage from a bridge rectifier or the battery voltage and switches this voltage through a series inductor for providing the regulated DC input voltage to the main power converter. The battery is switched in to replace the AC source and rectifier in the event of loss of the AC signal. In the preferred embodiment, the PFC circuit includes a series inductor and diode, a switching transistor and a control circuit for providing the regulated DC input voltage.

Abstract: A communication system for allowing a master to send commands to one or more slave devices across a normally static digital signal line of a bus. The master includes command logic for asserting a sequence of digital pulses according to a predetermined protocol with inherent timing to clock each data bit into a slave device. The master transmits several data bits to form each command, where each data bit is combined with clocking pulses to implement the self-clocking scheme. In particular, an initial data pulse incorporates a data bit to initiate a data phase. Each slave device includes a state machine which detects the data pulse and enables a sample and hold or latch circuit to capture the data bit. Then a clock pulse followed by a reset pulse is sent to clock the data into the slave device and reset the state machine. The slave also includes shift register logic to hold a command bit and address bits for each command.

Abstract: A fan speed monitoring system for interfacing a fan, including a fan drive and sensing circuit for maintaining the voltage of the fan's TFSC pin above a minimum voltage level, thus maintaining continuous power to the fan. The fan drive and sensing circuit includes a control loop having an isolation resistor for enabling superposition of fan pulses asserted by the fan on the TFSC pin. The fan speed monitoring system also includes a filter circuit for filtering and amplifying the fan pulses and providing corresponding filtered pulse signals. The fan drive and sensing circuit includes an active control loop for maintaining the voltage of the TFSC pin at an average level above the minimum voltage level, while also enabling inclusion of the fan pulses. The filter circuit preferably includes an AC amplifier for amplifying the fan pulses and a level transition comparator for converting the amplified fan pulses to the filtered pulse signals having the desired form.

Abstract: A circuit for determining and reporting the energy consumed by an electronic device having a microprocessor and power supply lines for supplying power to the device is disclosed. The circuit comprises a voltage divider connected for sensing the voltage across the power supply lines and generating a voltage signal indicative of the sensed voltage. A current sense resistor is connected in series with a power supply line for sensing the current passing through the power supply lines and generating a current signal indicative of the sensed current. An analog multiplier is connected for receiving and computing the product of the voltage and current signals, and for generating a power signal indicative of the product of the voltage and current signals, the power signal being indicative of the power consumed by the device.

Abstract: A configuration system including a processor having memory for storing operating parameters and configuration logic for retrieving the operating parameters and configuring a computer system to achieve a desired performance level. The configuration logic preferably includes programmable regulators, such as a voltage regulator and a clock synthesizer, for asserting an operating voltage and clock signal, respectively, to the processor. These operating signals are asserted at nominal levels at start up to allow the processor to operate at a reduced, yet adequate performance level. The stored operating parameters are asserted onto a processor data bus by the processor during start up and stored in corresponding data latches. The parameters are further provided to the programmable regulators, such as a voltage regulator, a clock synthesizer, for example, which convert the operating signals from the nominal levels to optimal levels corresponding to the retrieved parameters.

Abstract: A last power state apparatus including a power supply controller having a battery-backed memory bit for retaining the power state of an electronic device during a failure of a primary power source. The battery is preferably a lithium type battery and the power supply preferably provides a flea power signal when primary power is available to maintain the state of the memory bit even if the power supply is off. The controller asserts a power status signal to the power supply based on the state of the memory bit, so that the power supply remains off or powers up as appropriate when primary power is next available. A momentary power switch is used to manually turn on and off the power supply and the electronic device by toggling the memory bit. The electronic device, which is typically a computer system, provides signals to the power supply controller to turn off the device. Further, the computer can enable an interrupt to prevent the user from turning off the device until after vital functions are completed.

Abstract: A power supply includes circuitry implementing a self-testing method in which the power supply is first disconnected from its source and the system which it supplies. The power supply testing method then applies an external power source to the supply, insures that the power supply planar is disconnected from the application system and applies a simulated full load to the power supply output. The power supply output voltages are then tested for compliance with predetermined specifications and a test result signal is given to the user. The power supply is then shut off and available for re-connection to the application system.

Abstract: A feedback sensing system including a control circuit for detecting power failure of either power supply, and for controlling first and second switch circuits to modify the feedback sensing path of the other supply to the output load. In this manner, when one power supply fails, the feedback sensing path of the other power supply is rerouted to the output node to directly monitor and regulate the voltage across the load. Each switch circuit preferably operates to switch between two nodes along the respective output paths of the power supply, including a first node located before the current control device and a second node located between the current control device and the load. In one embodiment, each switch circuit includes two switches operated in a mutually-exclusive manner.

Abstract: A programmable resistive network coupled between the regulated output voltage and an error amplifier of a feedback circuit for adjusting the operating voltage for desired performance of a replaceable device. The replaceable device is preferably connected using a ZIF socket to facilitate removal and replacement. In a first embodiment, the resistive network includes a resistor pack having a resistive ratio corresponding to a replaceable device. In a second embodiment, the resistive network includes a mounted programmable potentiometer which is programmed to a new value when the device is replaced or upgraded. In a third embodiment, the resistive network comprises laser trimmed silicon resistors mounted on the same silicon die as the replaceable device, where the silicon resistors are laser trimmed when the device is fabricated. A junction of the silicon device is provided through an external pin to the feedback error amplifier.

Abstract: A power switch detection system for a power supply including an operator-accessible power switch coupled to the secondary ground of the power supply and to one side of an isolation capacitor. The other side of the isolation capacitor is coupled to a switch detection circuit referenced to primary ground for detecting the state of the power switch through the isolation capacitor. The switch detection circuit controls a control circuit on the primary side based on the state of the power switch, where the control circuit correspondingly controls the power state of the power supply and a corresponding electronic device. In this manner, the power switch remains isolated by the isolation capacitor but controls the power state of the device. The control circuit controls conversion of AC power from an AC source coupled to the primary side through a transformer.

Abstract: A universal offline switch mode power supply including an input stage having an input filter inductor and a switch for switching between a first lower AC input voltage or a second higher AC input voltage. A bridge rectifier full-wave rectifies the higher AC voltage when the switch is in a first position, where the filter inductor serves to filter the higher AC voltage. The higher AC voltage is preferably approximately 230 V rms. The bridge rectifier and two bulk capacitors serve to double the lower AC voltage when the switch is in a second position, where the lower AC voltage is preferably approximately 115 V rms. Also, the input filter is bypassed for the lower AC voltage. The switch is preferably an SPST switch. In the preferred embodiment, the inductor is placed between one AC input line and one input of a bridge rectifier circuit. The outputs of the bridge rectifier circuit are placed across two series input bulk capacitors and to the input of a switchmode power converter.

Abstract: A power supply including a detection and switch system for sensing either a uni-plane or a split-plane device connected to a socket and for providing one or two supply voltages, respectively. In one embodiment, a dual output regulator includes first and second regulators with corresponding first and second feedback circuits and comparators for regulating first and second outputs, respectively. A switch circuit connects the second feedback circuit to the comparator of the second regulator in split-plane mode for providing the second output. However, the switch circuit connects the first feedback circuit to the comparator of the second regulator in uni-plane mode where the two outputs are coupled together by a uni-plane device, so that the two outputs are regulated at the same level. A detection circuit monitors the output signals and controls the switch circuit depending upon whether a uni-plane or split-plane device is detected.

Abstract: An isolated low power converter including a low voltage, self-oscillating power converter, which derives power through bleeder current from the relatively high-voltage, input bulk capacitors. A bleeder circuit taps a relatively low voltage current source from the bulk capacitors to supply an oscillator circuit. The bleeder circuit preferably incorporates current limit resistors typically provided according to safety specifications. The oscillator circuit is preferably implemented using the primary of a transformer. A simple regulator circuit coupled to the secondary of the transformer provides a low voltage SELV power signal for powering detection circuitry. In the preferred embodiment, the bleeder circuit includes a relatively large resistive voltage divider for supplying current to charge a capacitor. The voltage of the capacitor is regulated using a constant voltage device, such as one or more Zener diodes.

Abstract: A fan test system and method for determining fan bearing friction and available life, including a power controller for changing the fan's power level for at least a predetermined time period and a measuring device for measuring the change in rotation of the fan. A memory is preferably coupled to the power controller for storing a plurality of rotation values for providing a history of fan bearing performance. A current sensor or current limiter is preferably coupled in series with the fan, where the measuring device detects voltage pulses or poles of the fan. The power controller preferably includes a timer for determining the time period and a counter for counting rotation events. The power controller also preferably includes a control circuit for controlling a switch coupled between a power source and the fan.

Abstract: A fail-safe system for monitoring the voltage of a backup battery of a portable computer system to prevent excessive drainage of the backup battery. The backup battery is primarily provided to maintain voltage to the configuration memory of the portable computer during swapping of the main battery. A timing circuit allows the backup battery to provide power to other, low power system components for a limited time, such as two minutes, while the main battery is being replaced. In the fail-safe circuit, a comparator circuit monitors the voltage of the backup battery and asserts a signal in the event its voltage falls to a predetermined minimum level. A switch circuit correspondingly disconnects the backup battery from the other system components, thereby conserving the energy of the backup battery.

Abstract: A synchronous regulator circuit including a transformer having a secondary inductor magnetically coupled to a primary inductor, where the secondary inductor is coupled to control a synchronous power switch. The secondary inductor operates to drive the synchronous power switch using self-regeneration during a flux reversal phase of each cycle. A timing circuit or simple pulse width modulation circuit (PWM) turns on the primary switch and turns off the synchronous switch during a power phase of each cycle, and then turns off the primary switch during the flux reversal phase of each cycle. The flux reversal of the secondary inductor drives the synchronous switch on, thereby achieving synchronous operation without an expensive dual output PWM. The present invention is illustrated using both a buck and a boost topology. A third switch is preferably used to clamp the synchronous switch off during the power phase.

Abstract: The voltage regulator includes two sections, a switching regulator section (12) for regulating a voltage from an input (10) to an intermediate node (14). This voltage on the intermediate node (14) is then regulated with a linear regulator down to a regulated output voltage on an output node (18). The linear regulator includes a pass transistor (16) that is controlled by a linear regulator control (50). Linear regulator control (50) is operable to sense the voltage across the transistor (16) and perform multiple functions. First, it controls the pass element transistor (16) to regulate the voltage from the node (14) to the node (18) in a linear manner. Second, it controls the switching regulator section (12) to provide a regulated voltage on the node (14). Third, it controls the level of the voltage on the intermediate node (14) such that it is at a predetermined voltage level above the voltage on the output node (18), such that the power dissipation through the pass element transistor (16) is minimized.

Abstract: A battery charger including a control system for controlling a linear pass element to maintain relatively constant power dissipation of the linear pass element. In one embodiment, the charge current and the voltage across the linear pass element are provided to a constant dissipation amplifier, which increases the charge current as the voltage of the linear pass element decreases due to charging of the battery. The charge current is increased in such a manner to maintain the power dissipation of the linear pass element to a relatively constant level. In another embodiment, the battery voltage is provided to the amplifier, which increases charge current in response to rising battery voltage to maintain constant power dissipation of the linear pass element. The latter embodiment is in recognition that the voltage across the linear pass element is inversely proportional to the voltage across the linear pass element.

Abstract: A fusible link provided in a power supply of a computer system for providing evidence of an over temperature condition to document a fan failure in the event of catastrophic failure of the power supply. The power supply typically includes a temperature detection circuit often including a thermistor providing a signal indicative of an over temperature condition in the power supply. A latch circuit coupled to the temperature detection circuit shuts the power supply down in an attempt to prevent such catastrophic failure. In a circuit according to the present invention, a fuse is coupled to the temperature detection circuit where the fuse open-circuits when an over temperature condition is detected. Such blown fuse documents the over temperature condition. An external pin provided through a Zener diode and coupled to the fusible link enables external determination of the state of the fuse without disassembling the power supply.

Abstract: A detection system for detecting the insertion or removal of expansion cards having a standard edge connector using one or more capacitive plates coupled to corresponding variable frequency oscillators. The capacitive plates are preferably mounted on an internal layer of the expansion card and preferably aligned with corresponding pins of the edge connector for establishing capacitive loading with respect to the corresponding pins. The frequency of the oscillators change with changes in the capacitive loading of the corresponding plates. The detection circuitry includes a processor which continuously monitors the frequency of the oscillators to thereby detect movement of the expansion card, and preferably includes a control and isolation circuit which electrically isolates the power and data pins during insertion and/or removal as controlled by the processor. The detection circuitry may be mounted to either on the expansion card or the planar of the computer system.