Abstract: An adjustable resistor device includes a first pin, a second pin, a resistance-adjusting branch circuit, and a resistance display circuit. The first and second pins are configured to connect to an external circuit. The resistance-adjusting branch circuit is connected between the first pin and the second pin, and provides resistors for testing the external circuit. The resistance display circuit displays a resistance of the resistance display circuit.

Abstract: A voltage measuring apparatus electrically connected to buck circuits includes the same number of RC circuits as there are buck circuits, an analog/digital (A/D) convertor, a controller, and a display unit. Each RC circuit is configured to be electrically connected in parallel with an inductor of one corresponding buck circuit. The A/D convertor selectively obtains an analog voltage of one of the buck circuits, and converts the analog voltage signal into a digital voltage signal. The controller controls the A/D convertor and receives the digital voltage signal from the A/D convertor. The display unit displays a decimal voltage value based on the digital voltage signal.

Abstract: A control circuit includes a power controller, a comparator, and first to fifth electronic switches. When an electronic device is operating with light load, a voltage received by the inverting terminal of the comparator is less than a voltage received by the non-inverting terminal of the comparator, such that the first and fourth electronic switches are turned on, and the second, third, and fifth electronic switches are turned off. A first power supply is output to the switching power supply. When the electronic device is operating with heavy load, the voltage received by the inverting terminal of the comparator is greater than the voltage received by the non-inverting terminal of the comparator, such that the first and fourth electronic switches are turned off, and the second, third, and fifth electronic switches are turned on. A second power supply is output to the switching power supply.

Abstract: A motherboard includes a processor socket, a platform controller hub (PCH), a power circuit, a switch unit, and a memory slot. The PCH is connected to the memory slot and output a bus signal to a serial advanced technology attachment dual in-line memory module (SATA DIMM) when a SATA DIMM is inserted in the memory slot and when the switch unit is in a first state. When a memory module is in the memory slot the power circuit outputs a voltage to the memory module in response to a second state of the switch unit.