Abstract: A protection circuit includes an electronic switch and a comparator. The comparator includes a positive input connected to a first power supply, a negative input connected to an output power supply, and an output connected to a first terminal of the electronic switch through a first resistor. A second terminal of the electronic switch is connected to a device. A third terminal of the electronic switch is connected to the output power supply. When a voltage on the positive input is greater than a voltage on the negative input, the comparator outputs a high level signal to turn on the electronic switch, the output power supply powers the device. When the voltage on the positive input is less than the voltage on the negative input, the comparator outputs a low level signal to turn off the electronic switch, the output power supply does not power the device.

Abstract: A protection circuit includes a power supply, a resistor-capacitor (RC) parallel circuit, an inverter, first and second electronic switches. The RC parallel circuit is connected to the power supply through a first resistor. An input terminal of the inverter is connected to the power supply through the first resistor. A first terminal of the first electronic switch is connected to an output terminal of the inverter. A second terminal of the first electronic switch is grounded. A third terminal of the first electronic switch is connected to the power supply through a second resistor. A first terminal of the second electronic switch is connected to the third terminal of the first electronic switch. A second terminal of the second electronic switch is connected to an electronic device. A third terminal of the second electronic switch is connected to an output power supply.

Abstract: A reset circuit includes a power supply, a metal-oxide-semiconductor field-effect transistor (MOSFET) that has a gate, a drain, and a source, a capacitor, a Schmitt trigger; and an inverter. When a voltage of the power supply is applied to the gate and turns on the MOSFET, the power supply charges the capacitor. After a predetermined delay time, a voltage of the capacitor reaches a threshold voltage of the Schmitt trigger and turns on the Schmitt trigger, and the capacitor discharges through the Schmitt trigger to correspondingly generate a reset signal output by the inverter to reset an electronic device.

Abstract: A control circuit for a USB connector includes a first electronic switch. Before a universal serial bus (USB) device is plugged into the USB connector, a ground pin of the USB connector is idle. A control terminal of the first electronic switch receives a high level signal and first and second terminals of the first electronic switch are disconnected. When the USB device is plugged into the USB connector, the ground pin of the USB connector is grounded. The control terminal of the first electronic switch then receives a low level signal and the first and second terminals of the first electronic switch are connected. A power supply connected to the first terminal of the first electronic switch supplies power to the power pin of the USB connector through the first electronic switch.

Abstract: An indication circuit includes a network port, a detecting microchip, a first NOT AND (NAND) gate, a second NAND gate, a NOT gate, a first AND gate, and a second AND gate. The network port receives a network connector of a network cable therein, and includes a first light-emitting diode (LED) L1 and a second LED L2. The detecting microchip is electronically connected to the network port to detect a LAN speed, and accordingly output a group of logic control signal. The first NAND gate, the NOT gate, and the first AND gate are electronically connected between the first NAND gate and an anode of the first LED and a cathode of the second LED. The second NAND gate and the second AND gate are electronically connected between the first NAND gate and a cathode of the first LED and an anode of the second LED.

Abstract: A fan control circuit includes a first switch element, a second switch element, and a fan connector. A first control terminal of the first switch element is connected to a fan control terminal to receive a pulse width modulation signal. A first terminal of the first switch element is connected to a first voltage source. A second control terminal of the second switch element is connected to the first terminal of the first switch element. A fourth terminal of the second switch is connected to a second voltage source via a NTC resistor. A first pin of the fan connector is connected to ground. A second pin of the fan connector is connected to a third terminal of the second switch element. A third pin of the fan connector is connected to a signal receiving terminal. The third pin is configured to receive a feedback signal indicating a rotating speeding of the fan.

Abstract: A reset circuit includes a power supply, a metal-oxide-semiconductor field-effect transistor (MOSFET) that has a gate, a drain, and a source, a capacitor, a Schmitt trigger; and an inverter. When a voltage of the power supply is applied to the gate and turns on the MOSFET, the power supply charges the capacitor. After a predetermined delay time, a voltage of the capacitor reaches a threshold voltage of the Schmitt trigger and turns on the Schmitt trigger, and the capacitor discharges through the Schmitt trigger to correspondingly generate a reset signal output by the inverter to reset an electronic device.

Abstract: A protection circuit includes an electronic switch and a comparator. The comparator includes a positive input connected to a first power supply, a negative input connected to an output power supply, and an output connected to a first terminal of the electronic switch through a first resistor. A second terminal of the electronic switch is connected to a device. A third terminal of the electronic switch is connected to the output power supply. When a voltage on the positive input is greater than a voltage on the negative input, the comparator outputs a high level signal to turn on the electronic switch, the output power supply powers the device. When the voltage on the positive input is less than the voltage on the negative input, the comparator outputs a low level signal to turn off the electronic switch, the output power supply does not power the device.

Abstract: A power switch circuit includes first and second power switches, first to fourth inverters, first and second diodes. An input of the first inverter is connected to a first positive terminal of the first power switch. An input of the second inverter is connected to an output of the first inverter. A cathode of the first diode is connected to an output of the second inverter. An anode of the first diode is connected to a power-on terminal of a motherboard. An input of the third inverter is connected to a second positive terminal of the second power switch. An input of the fourth inverter is connected to an output of the third inverter. A cathode of the second diode is connected to an output of the fourth inverter. An anode of the second diode is connected to the power-on terminal.

Abstract: A voltage detection circuit is used for determining whether a voltage of a power supply is less than a preset voltage. The circuit includes a Zener diode, a first electronic switch, a second electronic switch, and a controller. When the controller receives a high level signal, the controller warns the users that the voltage of the power supply is less than 3.3 volts.

Abstract: A protection circuit includes a power supply, a resistor-capacitor (RC) parallel circuit, an inverter, first and second electronic switches. The RC parallel circuit is connected to the power supply through a first resistor. An input terminal of the inverter is connected to the power supply through the first resistor. A first terminal of the first electronic switch is connected to an output terminal of the inverter. A second terminal of the first electronic switch is grounded. A third terminal of the first electronic switch is connected to the power supply through a second resistor. A first terminal of the second electronic switch is connected to the third terminal of the first electronic switch. A second terminal of the second electronic switch is connected to an electronic device. A third terminal of the second electronic switch is connected to an output power supply.

Abstract: A current suppression circuit for an electronic device and includes a main power supply and a standby power supply. The current suppression circuit includes a voltage comparator and an electronic switch. The voltage comparator includes a non-inverting input, an inverting input, and an output. The non-inverting input and the inverting input are respectively connected to the main power supply and the standby power supply, and the output is connected to the electronic switch. Whether the electronic switch is turned on or off by virtue of by the voltage comparator, such that when the electronic device itself is powered off, the comparator outputs a voltage signal to the electronic switch to turn it off, and the standby power supply is disconnected from the components.

Abstract: A voltage sequence output circuit includes input terminals of a NOR gate connected to first and second input terminals. An output terminal of the NOR gate connected to a first terminal of a first electrical switch. A third terminal of the first electrical switch connected to a power source. A first terminal of a second electrical switch connected to the first input terminal and the power source through a first resistor. A second terminal of the second electrical switch connected to a second terminal of the first electrical switch. A third terminal of the second electrical switch connected to a first output terminal and a second terminal of a third electrical switch. A first terminal of the third electrical switch connected to a second input terminal and the power source through a second resistor. A third terminal of the third electrical switch connected to a second output terminal.

Abstract: A voltage sequence output circuit includes input terminals of a NOR gate connected to first and second input terminals. An output terminal of the NOR gate connected to a first terminal of a first electrical switch. A third terminal of the first electrical switch connected to a power source. A first terminal of a second electrical switch connected to the first input terminal and the power source through a first resistor. A second terminal of the second electrical switch connected to a second terminal of the first electrical switch. A third terminal of the second electrical switch connected to a first output terminal and a second terminal of a third electrical switch. A first terminal of the third electrical switch connected to a second input terminal and the power source through a second resistor. A third terminal of the third electrical switch connected to a second output terminal.

Abstract: A fan control circuit includes a first switch element, a second switch element, and a fan connector. A first control terminal of the first switch element is connected to a fan control terminal to receive a pulse width modulation signal. A first terminal of the first switch element is connected to a first voltage source. A second control terminal of the second switch element is connected to the first terminal of the first switch element. A fourth terminal of the second switch is connected to a second voltage source via a NTC resistor. A first pin of the fan connector is connected to ground. A second pin of the fan connector is connected to a third terminal of the second switch element. A third pin of the fan connector is connected to a signal receiving terminal. The third pin is configured to receive a feedback signal indicating a rotating speeding of the fan.

Abstract: A power switch circuit includes first and second power switches, first to fourth inverters, first and second diodes. An input of the first inverter is connected to a first positive terminal of the first power switch. An input of the second inverter is connected to an output of the first inverter. A cathode of the first diode is connected to an output of the second inverter. An anode of the first diode is connected to a power-on terminal of a motherboard. An input of the third inverter is connected to a second positive terminal of the second power switch. An input of the fourth inverter is connected to an output of the third inverter. A cathode of the second diode is connected to an output of the fourth inverter. An anode of the second diode is connected to the power-on terminal.

Abstract: A compatible circuit for integrated circuits (ICs) includes three input terminals coupled to corresponding pins of an IC, and three function terminals corresponding to the three input terminals. Each input terminal coupled to the three function terminals via three transmission lines, each transmission line has an open segment, and each input terminal is electrically coupled to a corresponding function terminal by selectively mounting a connection component on the open segment of the corresponding transmission line according to a specification of the IC.

Abstract: A voltage sequence output circuit includes a sequence control circuit and a number of voltage output circuits. The sequence control circuit includes a first NOR gate, and the first NOR gate includes a number of the input terminals. The voltage output circuits each includes an input terminal, an output terminal, and a positively enabled tristate buffer connected between the input terminal and the output terminal thereof. The input terminals of the voltage output circuits is connected to the input terminals of the first NOR gate. If all of input terminals of the voltage output circuits are connected with electronic devices, the positively enabled tristate buffer of the voltage output circuits are enabled. The output terminals of the voltage output circuits sequentially output a voltage.

Abstract: A voltage converting circuit for converting a first voltage signal into a second voltage signal for supplying voltage for an electronic component includes a photoelectric coupler and a connector. The photoelectric coupler includes a light-emitting element and a photosensor. The light-emitting element includes a first terminal configured for receiving the first voltage signal. The photosensor includes a first terminal connected to a power supply, and a second terminal configured for outputting the second voltage signal. The connector configured for connecting the photosensor and the electronic component. When the first voltage signal is at a high level, the light-emitting element emits light to turn on the photosensor, the power supply makes the voltage level of the second voltage signal sent out by the photosensor to satisfy a voltage demand of the electronic component.

Abstract: A voltage converting circuit for converting a first voltage signal into a second voltage signal for supplying voltage for an electronic component includes a photoelectric coupler and a connector. The photoelectric coupler includes a light-emitting element and a photosensor. The light-emitting element includes a first terminal configured for receiving the first voltage signal. The photosensor includes a first terminal connected to a power supply, and a second terminal configured for outputting the second voltage signal. The connector configured for connecting the photosensor and the electronic component. When the first voltage signal is at a high level, the light-emitting element emits light to turn on the photosensor, the power supply makes the voltage level of the second voltage signal sent out by the photosensor to satisfy a voltage demand of the electronic component.