Computer motherboard switching power supply mode

The current production of computer motherboards are using switching power supply mode. Switching power supply mode can be divided into: single-phase power supply, two-phase power supply and multiphase power supply.

(1) Single-Phase power supply

The CPU power supply principle is shown in Figure 1.

CPU Single-Phase power supply principle is: Obtain the host power output +5v or +12v power supply, because the voltage does not meet the CPU core power supply requirements, CPU identification PIN issued voltage identification code (VID) to the PWM (pulsewidthmodulation, pulse width modulation) controller, The PWM controller can control the sequence and frequency of the two field effect tubes to make the output voltage and current reach the CPU core power supply requirement.

As can be seen from fig. 1, the single-phase power supply 耑 to two field effect tubes, and two electrolytic capacitors are needed. In the power supply to the end of the use of large capacitance of electrolytic capacitor ci for decoupling, in the output by using large capacitance electrolytic capacitor filtering, you can obtain a relatively smooth and stable voltage, so that the output voltage reached the CPU supply voltage requirements. The physical figure of the CPU power supply is shown in Figure 2.

The 12V Electric Music of the host power supply is filtered by the first LC circuit (composed of L1 and C1 in Fig. 2), sent to two Fet and PWM control chip circuit, two FET in the PWM control chip under the control of rotating conduction, and then through the second stage LC circuit filter (composed of 12 and C2) Get the working voltage required by the CPU.

Because the field effect tube works in the switch state, the internal resistance of the conduction inch and the leakage current at the cut-off time are smaller, so the electricity consumption is very small.

(2) Two-phase power supply

Single-phase power supply generally provides a maximum of 25A current, and Li before the commonly used CPU power supply is much larger than 25A, single-phase power supply can not provide sufficient and reliable power, so now the main board of power supply circuit using two-phase or multiphase power supply.

CPU two-phase power supply circuit as shown in Figure 3, the circuit is actually two single-phase circuit in parallel, so it can provide double current.

(3) Three-phase or multiphase power supply

Three-phase power supply circuit as shown in Figure 4, the circuit is made up of three single-phase circuits in parallel, so theoretically can provide three times times the current.