Time sequence circuit for power supply unit
View Patent ↗A time sequencing circuit for a power supply unit to ensure the correct sequencing of system voltages for a computer from a power supply unit includes first to ninth resistors, first to fifth electronic switches, and a capacitor. Each of the first to fifth electronic switches includes first to third terminals. When the power supply unit outputs all required voltages, the power supply unit outputs a high-voltage level indicating power good and the computer can start up. If any one of the required voltages is not being outputted, the power supply unit outputs a low-voltage level good signal until any non-output of voltage is cured.
1. A time sequence circuit, comprising:
a first to ninth resistor;
a first to fifth electronic switch each comprising a first terminal, a second terminal, and a third terminal; and
a capacitor;
wherein the first terminal of the first electronic switch is coupled to a first power terminal through the first resistor, connected to ground through the second resistor, and the second terminal of the first electronic switch is connected to ground; the first terminal of the second electronic switch is coupled to a second system power terminal through the third resistor, and is connected to ground through the fourth resistor, the second terminal of the second electronic switch is coupled to the third terminal of the first electronic switch, the first terminal of the third electronic switch is coupled to a third system power terminal through the fifth resistor, and is connected to ground through the sixth resistor, the second terminal of the third electronic switch is coupled to the third terminal of the second electronic switch, and the third terminal of the third electronic switch is coupled to a stand-by power terminal through the seventh resistor, and is coupled to the first terminal of the fourth electronic switch; the second terminal of the fourth electronic switch is connected to ground, and the third terminal of the fourth electronic switch is coupled to the stand-by power terminal through the eighth resistor, and is connected to ground through the capacitor; the third terminal of the fourth electronic switch is used to output a power good signal, the first terminal of the fifth electronic switch receives a power on signal, the second terminal of the fifth electronic switch is connected to ground, and the third terminal of the fifth electronic switch is coupled to the third terminal of the fourth electronic switch through the ninth resistor; when the first terminals of the first to fifth electronic switches are at a low-voltage level, the second and third terminals of each electronic switch are disconnected from each other; when the first terminals of the first to fifth electronic switches are at a high-voltage level, the second and third terminals of each electronic switch are connected to each other.
2. The time sequence circuit of claim 1 , further comprising a tenth resistor, wherein the first terminal of the fifth electronic switch receives the power on signal through the tenth resistor.
3. The time sequence circuit of claim 2 , wherein the first to fifth electronic switches are n-channel metal oxide semiconductor field effect transistors (NMOSFETs), and the first terminals, second terminals, and the third terminals of the first to fifth electronic switches are gates, sources, and drains of the NMOSFETs, respectively.