Abstract: A fan control system includes a temperature detecting circuit and a rotation rate control circuit. The detecting circuit includes a first amplifier, a second amplifier, and a thermistor. The control circuit includes a first terminal, a second terminal, and a third terminal. The detecting circuit detects temperature and outputs a voltage signal. The control circuit receives the voltage signal and controls the rotation rate of the fan according to the voltage signal.

Abstract: An ignition circuit includes a system power supply, an ignition coil, a delay unit, a first switch unit, and a second switch unit. When the system power supply is powered on, the second switch unit is turned on, the ignition coil is powered on. After a delay time, the delay unit controls the first switch unit to be turned on, the second switch unit is turned off, the ignition coil is powered off. Therefore an ignition operation is accomplished.

Abstract: A fan drive circuit for driving a fan used in an electronic device to rotate includes a heat detector, a control unit, an integrating circuit, a regulating circuit; and a power supply. The power supply cooperates with the regulating circuit to drive the fan to rotate, the control unit detects the temperature of the one or more components of the electronic device using the heat detector and cooperates with the integrating circuit to generate a speed control voltage that changes with change of the temperature, and the speed control voltage is input to the regulating circuit to regulate a rotation rate of the fan.

Abstract: A printed circuit board includes a power layer, a ground layer, a signal layer, and a backboard. The backboard is arranged below the signal layer opposite to the ground layer. A number of vias are formed from the backboard through the signal layer, and then connected to the ground layer.

Abstract: A regulating system includes an input port, an output port; and an overvoltage protection circuit. The an overvoltage protection circuit includes a fuse, a semiconductor controlled rectifier (SCR), a first resistor, and a voltage regulator. The fuse includes a first end and a second end. The SCR includes a gate, an anode, and a cathode. The regulator includes a cathode and an anode. The first end of the fuse is connected to the input port, the second end of the fuse is connected to the anode of the SCR, the cathode of the SCR is connected to the ground, the gate of the SCR is connected to the anode of the regulator through the first resistor, the cathode of the regulator is connected to the output port.

Abstract: A printed circuit board includes a reference layer configured to connect to a power or a ground and a dielectric layer stacked on the reference layer. The dielectric layer includes a component surface opposing the reference layer. The component surface forms a differential pairs, a protection runner, and a power runner. The differential pairs include a substantially linear part. The protection runner is intervened between the linear part and the power runner, and is substantially parallel to the differential pairs. The length of the protection runner is approximately equal to that of the linear part. Each of the two ends of the protection runner forms a via that electrically connects the protection runner to the reference layer.

Abstract: A layout method of a differential pair generates the differential pair between a differential signal sender and a differential signal receiver in a printed circuit board (PCB). Differential signal is transmitted via two wires. A plurality of vertical lines are created at a breakout section and a trace section of the differential pair. Junctions of the vertical lines and the two wires are defined as pair of points. A first distance between one pin of the differential signal sender and a corresponding point of each pair of points and a second distance between the other pin of the differential signal sender and the other corresponding point of each pair of points are calculated. If a difference between the first distance and the second distance does not fall within an allowable range, the two wires are adjusted.

Abstract: A fan control system includes a linear adjustor, an input/output controller, and a temperature sensor. A first terminal of the linear adjustor is connected to a first power supply. A second terminal of the linear adjustor is connected to a fan and grounded via a first resistor and a second resistor in series. A third terminal of the linear adjustor is connected to a node between the first resistor and the second resistor. A first terminal of the input/output controller is connected to the third terminal of the linear adjustor via a third resistor. A second terminal of the input/output controller is connected to the temperature sensor.

Abstract: A voltage measuring circuit includes an under-voltage measuring circuit and an over-voltage measuring circuit. The under-voltage measuring circuit includes a first voltage comparator, a first zener diode, and a first light emitting diode. An inverting input of the first voltage comparator is connected to a cathode of the first zener diode. An output of the first voltage comparator is connected to a cathode of the first light emitting diode. The over-voltage measuring circuit includes a second voltage comparator, a second zener diode, and a second light emitting diode. A non-inverting input of the second voltage comparator is connected to the cathode of the second zener diode. An output of the second voltage comparator is connected to a cathode of the second light emitting diode.

Abstract: An overcurrent protection circuit connected between a voltage input and a voltage output of an electronic device to protect against excessive current is disclosed. The overcurrent protection circuit includes first to fifth resistors, a relay comprising a coil and a normally closed switch, a pnp transistor, and a break-over element. When a current between the voltage input and the voltage output is greater or equal to a rated current of the electronic device, the npn transistor is turned on, while the coil is powered on to control the switch to be opened, therefore the voltage output cannot output voltage, which can protect against excessive current damaging the electronic device.

Abstract: A computer includes a display assembly, a base, a stand, and a keyboard. The base includes a supporting board and an engaging board. The stand is located on the base supporting the display assembly. The keyboard includes a main body and an extension board extending from the main body. The main body has a key area. The extension board is fixed to the engaging board to help stabilize the display assembly.

Abstract: A connecting device for connecting pins of a DIP chip to a test device comprises two each of half frames, columns of testing pins, connecting screws, fixing screws, and four holding plates. The two columns of testing pins are arranged respectively on the two half frames parallel to the lengthways direction of the half frame. The distance between two adjacent testing pins in the same column is equal to that between the two adjacent pins in the same column of the DIP chip. The two connecting screws screw into the half frames perpendicular to the lengthways direction of the half frame. Two of the holding plates extend down from each of the half frames and are aligned with short sides of the corresponding half frame. The fixing screws fix the two holding plates on the same half frame along a direction parallel to the lengthways direction of the half frame.

Abstract: A low voltage warning circuit includes an input terminal configured to receive a supply voltage, a reference voltage connected to the input terminal for providing a reference voltage, a transistor connected to the reference voltage circuit and the input terminal, and a silicon controlled rectifier connected to the transistor and the input terminal via a indicating device, the low voltage warning circuit raise a warning through the indicating device when the supply voltage is below the reference voltage.

Abstract: A regulating system includes an input port having a first input terminal and a second input terminal, an output port having a first output terminal and a second output terminal, a regulating circuit, an over-current protection circuit, and an overvoltage protection circuit. The overvoltage protection circuit includes a regulating diode, a first bipolar transistor and a second bipolar transistor. The first output terminal is connected to the base of the first bipolar transistor via the regulating diode and grounded via first bipolar transistor. A base of the second bipolar transistor connects to the collector of the first bipolar transistor. The second output terminal is grounded via the second transistor.

Abstract: A protecting device includes a power plug, a switch circuit, and a power supply circuit. The switch circuit is connected to the power plug. The power supply circuit is connected to the switch circuit and the power plug. When the temperature of the protecting device is higher than a predetermined temperature, a voltage at a node between a thermo-sensor and a variable resistor is higher than a turn-on voltage of a second electrical switch to turn on the second electrical switch, a first electrical switch is turned off, the power supply circuit is disconnected from the power plug to stop the electronic device from working.

Abstract: A temperature control device is used to control a temperature of an electronic component. The temperature control device includes a temperature sensing circuit, a controlled unit, a caution circuit, and a microcontroller. The microcontroller is used to sense the temperature of the electronic component, and determine whether the sensed temperature is higher than a predetermined high temperature stored in the microcontroller. If the sensed temperature is higher than a predetermined high temperature, the microcontroller controls the controlled unit to cool the electronic component and count the number of times the electronic component is cooled. The microcontroller determines whether the count of cooling the electronic component is equal to a predetermined cooling count. If the count of cooling the electronic component is equal to the predetermined cooling count, the microcontroller starts the caution circuit.

Abstract: A circuit for controlling time sequence of an electronic device, the circuit comprises a delay unit to receive a first control signal, a first switch unit connected to the delay unit to receive the first control signal after a rising edge of the first control signal, a second switch unit to promptly receive the first control signal in response to a falling edge of the first control signal, and a voltage output unit connected to the first and second switch units. The voltage output unit is selectively controlled by the first or the second switch unit to output a second or a third control signal to turn on or off the electronic device.

Abstract: A temperature controlling alarm circuit includes a power source including a high level terminal and a low level terminal, the low level terminal being grounded; a thermal diode including an anode and a cathode, the anode connected to the high level terminal; a resistor connected to the thermal diode in series; another resistor parallelly connected in parallel to the thermal diode and the said resistor which connected in series; a pnp-type transistor including a base, an emitter and a collector, the base and the emitter being respectively connected to two terminals of the another resistor; and an alarm connected between the collector of the PNP-type transistor and the low level terminal of the power source.

Abstract: A power supply control circuit includes a first switch unit comprising an input terminal to receive a control signal, and a number of second switch units. The second switch units are each connected between an input power source and a power output terminal. The first switch unit controls the number of second switch units to be turned on in response to the control signal being in a first status, so as to control the number of power output terminals to output corresponding power sources. The first switch unit controls the number of second switch units to be turned off in response to the control signal being in a second status, so as to direct the power output terminals to not output the corresponding power sources.

Abstract: A fan circuit controls a speed of a fan. A control chip outputs a pulse width modulation (PWM) signal that changes with the temperature of an electronic device that the fan is mounted in. An input circuit converts the PWM signal into a continual voltage signal. An amplifier circuit amplifies the voltage signal and outputs a control signal. When the control signal is less than a threshold voltage, the control circuit is turned on and the fan receives current which is less than preset current. When the control signal is greater than the threshold voltage, the control circuit is turned off and the fan receives current which is greater than the preset current.