Abstract: A linear voltage regulator provides a selectable output voltage to a load. The linear voltage regulator includes: a regulating circuit including an input terminal for receiving an input voltage, an output terminal for providing an output voltage to a load, and an adjusting terminal; a first resistor and a second resistor connected between the output terminal and ground for receiving the output voltage; and a voltage sampling control circuit electrically connected to a node between the first resistor and the second resistor for receiving logic signals from a controlling chip, and generating a reference current to the adjusting terminal of the regulating circuit to provide the selectable output voltage.

Abstract: In one preferred embodiment, a power indicator circuit for a computer comprises a light-emitting diode (LED) indicating power management states of a computer; a first resister connected between one pole of the LED and a power source; a second resistor connected between the other pole of the LED and a power source, a first branch circuit connected between the one pole and ground; and a second branch circuit connected between the other pole and ground. Wherein the first resistor and the second resistor control a current through the LED. Because the LED emits lights of different colors or turns off according to the different power management states, it is easy for users to see what the power management state of the computer is.

Abstract: In one preferred embodiment, an indicating circuit for a computer includes a microcontroller receiving a plurality of signals from the computer, and transforming the signals into a plurality of control signals; and an indicator having at least two light-emitting diodes (LEDs), and controlled by the control signals, wherein the at least two LEDs have different colors. The at least two LEDs emit lights of various colors according to the various usage states of hard disk, or power states of the computer. So it is easy for users to see the states of the computer.

Abstract: A self-startup circuit for a DC fan includes a voltage sampling device receiving a first control signal, a comparator, and a self-startup device. The comparator includes two input terminals and an output terminal. One input terminal is connected to an output terminal of the voltage sampling device. The self-startup device has a switching device and a diode connected in parallel. The self-startup device has an input terminal connected to the output terminal of the comparator, and outputs a second control signal for keeping the DC fan rotating even when the first control signal has a very low duty cycle.

Abstract: A power supply switching circuit includes an input terminal (2) for receiving a signal from a motherboard, an output terminal (4) to output a control signal, a first Bipolar Junction Transistor (BJT) (5), and a second BJT (7). A base of the first BJT is connected to the input terminal via a base bleeder circuit. A collector of the first BJT is connected to a stand-by power supply terminal (10) via a collector resistor. A base of the second BJT is connected to the collector of the first BJT. A collector of the second BJT is connected to a system power supply terminal (12) via a collector resistor. The collector of the second BJT is connected to the output terminal. Emitters of the first and second BJTs are grounded.

Abstract: A method for testing a card reader includes the steps of: identifying a logical drive corresponding to the card reader; determining whether the card reader matches a portable storage device connected to the card reader; displaying error information if the card reader does not match the portable storage device; obtaining a control code of the portable storage device if the card reader matches the portable storage device; testing the performance of the card reader by means of reading and writing data in the portable storage device through the card reader according to the control code.

Abstract: The present invention provides a computer-based method for selecting MOSFETs suitable for a circuit design. The method includes the steps of: providing a database (18) that stores specifications and product information of various MOSFETs; receiving specifications of a circuit design; analyzing the circuit design specifications and determining whether the circuit design specifications satisfy the predetermined requirements for a normal circuit design; computing specifications of proper MOSFETs for the circuit design according to the specifications, and determining if the circuit design specifications satisfy the predetermined requirements; and searching the database for the proper MOSFETs according to the specifications of the proper MOSFETs. A related system is also provided.

Abstract: A linear voltage regulator provides a selectable output voltage to a load. The linear voltage regulator includes: a regulating circuit including an input terminal for receiving an input voltage, an output terminal for providing an output voltage to a load, and an adjusting terminal; a first resistor and a second resistor connected between the output terminal and ground for receiving the output voltage; and a voltage sampling control circuit electrically connected to a node between the first resistor and the second resistor for receiving logic signals from a controlling chip, and generating a reference current to the adjusting terminal of the regulating circuit to provide the selectable output voltage.

Abstract: A card for simulating peripheral component interconnect (PCI) loads is disclosed. The card in accordance with a preferred embodiment of the invention includes an interface configured for electrically connecting to a motherboard; and a load circuit for simulating the different loads, wherein the load circuit comprises at least one power module receiving a voltage from the interface; and the power module dissipates various loads. Because that the card may dissipates various power according to testing requirement, the stability of the motherboard can be tested in various load power without connecting actual PCI loads to the motherboard.

Abstract: A start-up circuit which decreases a start-up current and stabilizes running of a DC fan. The start-up circuit includes a digital-analog converter for convert a digital control signal from a control chip to an analog control signal, a comparator, a switching device for controlling start-up of the DC fan, and a feedback device adjusting current passing through the switching device. The comparator includes two input terminals and an output terminal. One input terminal is connected to an output terminal of the digital-analog converter. The switching device is connected to the output terminal of the comparator. An output signal of the switching device is inputted to the other input terminal of the comparator via the feedback device.

Abstract: An apparatus for automatic testing of a PS/2 interface includes a micro controller unit, a PS/2 port, and a plurality of LEDs. The micro controller unit is coupled with both a data pin and a clock pin of the PS/2 interface. The LEDs coupled to the micro controller unit simulate functions of a keyboard. A related method for testing the PS/2 interface is also provided.

Abstract: A method for identifying Peripheral Component Interconnect (PCI) device information can identify information on all PCI devices coupled to a PCI bus. The method includes the steps: (a) initializing an address parameter and an address offset to a predetermined first number; (b) writing a first address value to a configuration port; (c) reading data from a data port based on the address value; (d) determining whether there is a corresponding PCI device coupled to the PCI bus based on the data; (e) adding a predetermined second number to the address parameter if there is no corresponding PCI device coupled to the PCI bus, so as to allocate an address for a next PCI device; (f) determining whether all the PCI devices have been searched; and (g) repeating step (b) to step (f) till all the PCI devices have been searched. A related system is also disclosed.

Abstract: A method for displaying debug codes of a BIOS includes the steps of: initializing a host electronic system and sending out a debug code corresponding to the initialization of the host electronic system to a debug card; displaying the debug code on an LED-display screen of the debug card; transmitting the debug code displayed on the LED-display screen to an application software; choosing the BIOS file corresponding to the debug code displayed, then acquiring and displaying the information via the application software. A system implementing this method includes a host electronic system with a BIOS for sending out a debug code during the initialization; a debug card connected electrically to the host electronic system for receiving and displaying the debug code sent out by the host electronic system; an application software for acquiring and displaying the information corresponding the debug code displayed on the debug card.

Abstract: A linear voltage regulator includes an error amplifier receiving an operational voltage and provided a control signal, a pass device controlled by the control signal and providing a load voltage from a power supply, and a leakage circuit controlled by the control signal and consuming a drive-back current. Since the linear voltage regulator includes the leakage circuit, a drive-back current created can be grounded via the switch transistor of the leakage circuit. Thereby an impedance calibration of termination transistors will be normal, and a life span of electronic components will be protected.

Abstract: A control circuit for command signals of a clock generator includes a power supply end, an output end, a control end, a diode, a first resistor and a second resistor. The first resistor, the diode, and the second resistor are connected in series between the power supply end and the ground. The diode has an anode connected to the first resistor and a cathode connected to the second resistor. The control end is connected to a node between the diode and the second resistor; the output end is connected to a node between the diode and the first resistor. The output end outputs the command signals to the clock generator.

Abstract: A pulse width modulation (PWM) generating circuit includes a first comparator, a first resistor, a second resistor, a third resistor, a fourth resistor, a capacitor, and a diode. The first resistor and the second resistor are connected in series between a voltage input and ground. The third resistor, the fourth resistor, and the capacitor are connected in series between the voltage input and ground. The first comparator has a non-inverting input connected to a node between the first resistor and the second resistor, an inverting input connected to a node between the fourth resistor and the capacitor, and an output connected to a node between the third resistor and the fourth resistor. The diode is connected between the non-inverting input and the output. The inverting input of the first comparator provides triangular wave signals to a second comparator by which PWM signals are generated.

Abstract: A voltage providing circuit for a central processing unit (CPU) includes a power supply, three voltage regulation modules, and a pulse width modulation (PWM) controller. The power supply provides three voltages respectively to the three voltage regulation modules. The PWM controller outputs three signals to the three voltage regulation modules. The three voltage regulation modules regulate the voltages from the power supply according to the signals from the PWM controller, and output a regulated voltage to the CPU. The voltage providing circuit also includes three resettable fuses, which are respectively connected between the three voltage regulation modules and the power supply. The resettable fuses automatically shut off the voltage providing circuit when a current is overloading the circuit and turn on the voltage providing circuit when the current is normal.

Abstract: A power supply for a bus interface is provided. The power supply comprises: an input terminal; an output terminal; a fuse providing over-current protection; a diode providing over-voltage protection, a reverse breakdown voltage of the diode not less than a maximal voltage difference of the output terminal and the input terminal, the diode connected to the fuse in series between an input terminal and an output terminal; and a plurality of capacitors filtering noise, one end of each of the capacitors connected to a node between the fuse and an anode of the diode, and another end of each of the capacitors is grounded. The power supply can provide effective over-voltage protection because a reverse breakdown voltage of the diode is not less than a maximal voltage difference of the output terminal and the input terminal. In addition, the power supply has a low cost of manufacture.

Abstract: A frequency double circuit includes an input terminal, a first voltage source, a multiplier, a second voltage source, and an output terminal. The input terminal receives an input signal and outputs to the first voltage source. The first voltage source filters out a direct current signal of the input signal. The multiplier includes two input ends receiving the input signal from the first voltage source for linear multiplication and gets a double frequency signal. The double frequency signal is output to the second voltage source for filtering out a direct current signal of the double frequency signal. The output terminal outputs the double frequency signal from the second voltage source.

Abstract: An LCD backlight driving circuit is provided for providing protection to LCD backlight lamps. In a preferred embodiment, the driving circuit for LCD backlight lamps comprises: a PWM controller sending control signals; two transistors receiving the control signals and sending two low-voltage pulse signals; an inverter converting the two low-voltage pulse signals to a high-voltage AC (Alternating Current) power; two lamps; two overvoltage protection circuits connected to the two lamps respectively; a voltage feedback module connected to the two lamps, a current feedback module connected to one of the two lamps; and a double-bridge circuit connected between the two lamps, and connected to the current feedback module for controlling the PWM controller to turn-on or turn-off. The driving circuit is capable of providing defective connection protection and open-circuit protection to LCD backlight lamps, and proportionately adjusting current flowing through the lamps.