DC to DC pulse width modulation (PWM) circuit diagram for motherboard

This is a three-phase power supply diagram. Q1 and Q2 form one phase, Q3 and Q4 form one phase, and Q5 and Q6 form one phase. Each phase is controlled by the PWM control IC ( CS5301) and conducts current in turn, rather than being turned on at the same time. CS5301 controls the on and off of Q1 through the Gate1 (H) pin output, and controls the on and off of Q2 through the Gate2 (L) output. When Gate1 (H) outputs, Q1 is turned on, and Q2 is turned off (Gate1 (L) has no output). The energy stored in the +12V terminal L4 and the filter capacitors C15 and C16 is released through Q1 and charged to L1 and the filter capacitors connected in parallel afterwards , and L1 stores energy. When Q1 is turned off and Q2 is turned on, the energy stored on L1 is charged to the filter capacitor through Q2 . After one phase completes a turn-on and turn-off period, the next phase will work again. The advantage of multi-phase work in turn is that the power tube has more rest time, which reduces heat generation. In order to reduce heat generation, some motherboards also connect a MOS tube in parallel to each phase, or reserve a parallel position. (The boards sent to the media for evaluation have parallel tubes welded on, but the retail ones have cancelled them and reserved parallel positions.) Because the CPU power supply voltage is low voltage (1.1-1.8V), and the voltage of the power supply for the CPU is relatively high (P4 is +12V, most AMD is +5V, and now AMD is increasingly using +12V power supply), the current passing through Q1 is smaller than that of Q2, and Q1 can have a smaller index. Similarly, the index of the energy storage inductor L4 is also smaller than that of the following L1 (L2, L3). We can see in the motherboard that if it is a ring-shaped L4 (same appearance as L1, L2, L3), the wires wound on it are also sparser than those on L1, etc. This is also the situation where we see different sizes of MOS tubes on some motherboards. For the convenience of procurement and production, most motherboards have the same model of Q1 and Q2. The above is essentially a DC-DC conversion, L4 and C15-16 form the front stage DC. L1 (L2, L3 and parallel filter capacitors) form the rear stage DC. Through the above introduction, we know that the PWM power supply circuit must include the front stage circuit of the front DC-DC and the circuit composed of each phase of the DC-DC rear stage. Based on this feature, it is easier for us to distinguish how many phases the motherboard is powered.