In the above figure, we circled some key components, namely, PWM controller chip (PWM Controller), MOSFET driver chip (MOSFET Driver), MOSFET of each phase, choke of each phase (Choke), electrolytic capacitors for output filtering (Electrolytic Capacitors), electrolytic capacitors for input filtering and protective choke, etc. Let's look at them separately.
(Figure) PWM Controller IC
The central nervous system that controls the CPU power supply circuit can be found near the CPU socket, which is the PWM main control chip. The main control chip is controlled by VID and transmits PWM square wave signals to each phase driver chip to control the generation of the final core voltage Vcore.
MOSFET Driver
MOSFET driver chip (MOSFET Driver). This small chip with 8 pins is commonly found in the CPU power supply circuit, usually equipped with one per phase. The driver chip in each phase is controlled by the PWM main control chip, driving the upper and lower bridge MOS tubes in turn. Many PWM control chips integrate a three-phase driver, so you can't see the independent driver chip on the motherboard.
This 14-pin driver chip is commonly seen in earlier motherboards. Each of them is responsible for receiving the two-phase drive signal from the PWM control chip and driving the switch of the two-phase MOSFET. In other words, it is equivalent to two 8-pin driver chips, one such driver chip is used for each two-phase circuit.
The small square with three pins below is a common MOSFET package, called D-PAK (TO-252) package, which is commonly known as a three-pin package. The middle pin is the drain, which is also connected to the metal bottom on the back of the MOS tube and is directly soldered to the PCB through a large area pad, so the middle pin is often cut off. This package can pass a large current, has good heat dissipation capacity, is low cost and easy to purchase, but the lead resistance and inductance are high, which is not conducive to achieving a switching frequency of more than 500KHz.
The smaller black square below is also a MOSFET, which belongs to the SO-8 series derivative package. The original SO-8 package is a plastic package with a long lead inside. The thermal resistance from the PN junction to the PCB is large, and the lead resistance and inductance are also high. Existing CPU, GPU and other chips require MOSFET devices to operate at higher currents and higher switching frequencies. Therefore, major manufacturers such as Renesas, Infineon, Philips, ON Semiconductor, Vishay, etc. have made a series of improvements to the SO-8 package, evolving into WPAK, LFPAK, LFPAK-i, POWERPAK, POWER SO-8 and other packaging forms. By changing the structure, using copper clamps instead of leads, integrating heat sinks on the top or bottom, etc., the heat dissipation is improved and the parasitic parameters are reduced, so that the SO-8 size can pass a current similar to that of D-PAK, and it can also save space and obtain better electrical performance. This derivative type is currently common in motherboard and graphics card power supplies. In the players' opinion, the SO-8 series is more YY than D-PAK, but the actual effect should be judged based on circuit design, device indicators and heat dissipation. The original SO-8 is no longer suitable for high-current applications due to its poor heat dissipation performance.
In addition, IR's DirectFET package has also appeared on some motherboards recently. It is also a package with excellent performance and looks very YY. I will add it after I find the actual large picture.
Output choke, also known as inductor. Each phase is generally equipped with a choke, under its action, the output current is continuous and smooth. A few motherboards use two chokes in parallel per phase, and two chokes are equivalent to one. Commonly used output chokes for motherboards are toroidal magnetic powder inductors, DIP ferrite inductors (fully enclosed or semi-enclosed in appearance) or SMD ferrite inductors. The above picture shows a semi-enclosed DIP ferrite power inductor.
The two ferrite inductors above are both enclosed. The left one is a DIP package with a wire-wound structure inside, and an inductance of 0.80 microhenry ("R" is equivalent to a decimal point). The right one is an SMD package with only about one turn of wire inside, and the inductance is much smaller at 0.12 microhenry.
The above are three types of toroidal inductors. The magnetic circuit of toroidal inductors is closed in the toroidal core, so the magnetic leakage is very small. The core material is iron powder (first from the left) or other materials such as Super-MSS. With the increase in board space restrictions and the increase in power supply switching frequency, ferrite inductors with open magnetic circuits and even small-sized SMD ferrite power inductors with few turns have increasingly replaced toroidal inductors with their low losses in the high-frequency region. However, toroidal inductors are still widely used in power supplies due to various application characteristics.
Hi-c Cap
In addition, you can also see tantalum capacitors and tantalum-polymer capacitors (Figure: Sanyo POSCAP series), which have much better performance than ordinary aluminum electrolytic capacitors. Tantalum-polymer capacitors have better ESR, high-frequency characteristics and smaller size than ordinary solid capacitors. There are already very detailed introductions on the Internet.
The capacitor in the center of the socket is called a multilayer ceramic capacitor (MLCC). Its single-piece capacity is much smaller than that of an electrolytic capacitor, but its high-frequency characteristics are much better and its ESR is very low. Electrolytic capacitors have poor high-frequency characteristics, so there are dozens of MLCCs around and inside the CPU socket of the motherboard for high-frequency decoupling, and they are paired with large-capacity electrolytic capacitors to provide better filtering effects and dynamic performance. In recent years, the digital power supply circuits of high-frequency switching high-end boards have taken advantage of the good high-frequency characteristics of MLCC and directly used many MLCCs for filtering, but the total capacity cannot be increased, and it is only suitable for use at very high switching frequencies. [page]
The input circuit is sometimes connected in series with a choke. The function of this choke is to prevent transient changes in the load current from affecting the upper circuit. It may be in the form of a coil wound on a rod or a coil wound on a toroidal core.
It may also be a closed type. Many motherboards do not have this choke, or there is a soldering position but it is omitted. In addition, we can also see some small parts in the power supply part that play a role of protection and buffering.
Okay, now that we have learned about these main components, let’s take a look at how to identify the number of phases in the CPU power supply circuit.
GIGABYTE EP45-UD3 with six-phase power supply. We can see six chokes and a total of 18 MOSFETs, with three MOSFETs for every output choke. We can also see the small MOSFET Driver chip next to each phase. Finally, we also see the square PWM main control chip in the corner of the CPU socket, which is the intersil ISL6336, which supports up to 6-phase power supply. From this we can confirm that this is a 6-phase power supply, and each phase MOSFET uses a motherboard with one up and two down configurations. The three MOS tubes used in each phase belong to the SO-8 derivative package, which is a MOSFET with low on-resistance (Low Rds-on).
The Gigabyte EP43-DS3L has four-phase power supply, and each phase has a choke, a driver, and three MOSFETs. The main control chip is the Intersil ISL6334, which supports up to 4 phases, so it has a 4-phase power supply.
Biostar Tforce 945P, three-phase power supply, uses the Intersil ISL6566 master controller with integrated three-phase MOS driver, three MOSFETs per phase. Again, we do not see any input chokes.
Biostar TA790GX 128M, four-phase power supply, uses Intersil ISL6322 master controller with integrated three-phase MOS driver, three MOSFETs per phase, and the MOSFET Driver for the fourth phase is placed next to the MOSFET (circled). Similar is Biostar TP43D2-A7, which is also an ISL6322 solution.
Onda Magic Sword P35 (same as Colorful C.P35 X7) has five-phase power supply, with two MOSFETs in each phase. It uses Richtek's main control chip RT8802 and two RT9619 MOSFET Drivers. RT8802 is a PWM controller that supports 2~5 phases and integrates three-phase MOSFET Driver. The fourth and fifth phases require external Driver chips.
Older MOSFET Driver chips use a single integrated two-phase MOS driver chip like HIP6602, which means that the two-phase drivers are integrated into one chip. Its appearance may be dual-row 14 pins (SSOP-14) or four-sided 16 pins (QFN-16). Here are a few examples.
Soyo SY-15P-FG, four-phase power supply, three MOS tubes per phase, PWM main control chip is Intersil ISL6561, and a 14-pin driver is used for each two phases (circled)
Abit AN8, four-phase power supply, MOS tubes covered under the heat sink. We can also see a driver (circled) used for every two phases. The HIP6602 is replaced by the Intersil ISL6614 chip. A certain Intersil PWM master controller is labeled μGURU here, so we can't see the model number.
PANZHEN 8RDA3I PRO has two-phase power supply, each phase is equipped with three MOS tubes and two parallel chokes (we will mention this later). Its power supply uses the intersil HIP6302 (left side of the above picture) main control with a HIP6602 driver chip to control the two-phase power supply. Although there are a total of four output chokes, since the main control only supports 2-phase HIP6302, there is only one two-phase driver, and the total of 6 MOS tubes can only be divided into two phases instead of four phases. We know that this is a two-phase power supply solution instead of a four-phase one.
We don't know what technical reasons manufacturers have for using two inductors in parallel instead of one inductor. Two inductors can allow twice the current to pass through, and the same amount of loss is shared by two inductors, so the temperature rise of each inductor is smaller, but compared with the real two-phase split, the ripple is still a little worse.
(Photo: GIGABYTE DQ6)
(Photo: Soyo OC3P45-GR)
- The PWM main control chip and driver numbers both indicate that this is a two-phase power supply solution;
- With 6 MOSFETs, there can only be two phases, 3 in each phase, and it is impossible to have 4 phases.
ASL
P45T
The following one is trickier, the ASL P45T. 8 chokes and 8 pairs of MOS tubes, it looks like an 8-phase power supply! But wait, we can find that its main control chip is the ISL6312 that supports 4-phase control, and there is also a MOSFET Driver (circled) next to it. This is a typical four-phase circuit controlled by 3 built-in driver groups and one external driver. Two chokes are connected in parallel for each phase, and 4 MOSFETs are connected in parallel in groups of two.
Similarly, there is the Gigabyte DQ6 series. This "12-phase" power supply is driven by the ISL6327/ISL6336 control chip that supports 6-phase control and 6 ISL6609 driver chips. Through the specifications of the main control chip and the number of drivers, we can know that it is a 6-phase power supply. Gigabyte has officially admitted that the design of the DQ6 series is a "virtual 12-phase". The early DQ6 motherboard was equipped with 4 MOSFETs per phase, and on the EX48-DQ6, each phase was equipped with 5, so the number of MOSFETs can automatically exclude the possibility of 12 phases.
The easily confused input choke (Input Choke) As mentioned earlier, there may be a choke at the input of the power supply. Usually it is next to the 4-pin/8-pin socket of the +12V input.
This choke often appears in the form of a magnetic bar.
Since this type of inductor is quite different from an output choke, it is not usually confused with an inductor. Some people may not even realize that it is an inductor.
However, sometimes it also looks like a closed inductor.
As shown in the picture above, if it is close to the output choke, it is easy to be mistaken. However, generally speaking, the inductance of the input choke is slightly different from that of the output choke, which will be reflected in the marking. At the same time, because the current of the input choke is smaller, the appearance size will also be slightly different.
Sometimes it is a donut-shaped choke, in which case it is easier to mistake.
Qingyun PX915 SLI
In this picture, we can see that the output choke and input choke of the power supply are both ring-shaped with green magnetic cores, but the number of windings of the input choke is less than that of the output choke. If you notice this difference, you will not mistake it for a four-phase power supply motherboard.
Is it three-phase power supply? No, it is two-phase. The core and winding sheath of the input choke are slightly different in color. Many editors would regard this motherboard as three-phase power supply.
EPOX 8RDA+
The once very popular EPOX 8RDA+. Although the input choke looks and is similar to the output choke, it can be distinguished from the output choke by its position and the total number of MOS tubes.
I believe that no one will mistake the power supply of the Soyo SY-15P-FG as a 5-phase power supply. As long as you pay attention to the difference in position and appearance, it is not difficult to identify the input choke.
How is the true 8-phase and true 16-phase power supply achieved? ("True 8-phase/16-phase" voltage regulators) Mainstream PWM control chips support up to 6 phases (before this article was completed, Taiwan uPI has launched a native 12/8-phase VR11 controller uP6208). However, ASUS has loudly declared that their motherboards have true 8-phase or even true 16-phase power supply. How is this done?
On ASUS 8-phase and 16-phase power supply motherboards, we can indeed find the MOSFET driver chip for each phase, which means that each phase has an independent driver. Unfortunately, the surface of the PWM control chip is covered by ASUS's own number and EPU, so we don't know the specifications of the PWM control chip.
Taiwanese netizen LSI Wolf has analyzed the early model A8N32 SLI Deluxe of 8-phase power supply. The main control chip of A8N32 SLI Deluxe is ADI ADP3186 which supports 4-phase operation, and is matched with ADG333A four-way two-choice switch. According to my analysis, this working method is to let ADP3186 output 4-phase phase signal, and the single-pole double-throw switch transmits the 4-phase signal to the 1st, 2nd, 3rd, and 4th drivers in the first cycle, and transmits the 4-phase signal to the 5th, 6th, 7th, and 8th signals in the second cycle. In this way, the 8-phase driver can stagger the phases and conduct in turn to realize the 8-phase working mode - this is how the first generation of 8-phase power supply motherboards are realized. It is speculated that the true 16-phase method may be two 8-phase alternating switching actions or four 4-phase alternating actions.
In the 8-phase power supply circuit of the P5Q motherboard, we only found a PWM control chip marked with EPU2, and no additional chips similar to electronic switches were seen. In addition to the EPU, there is also a chip called PEM on a motherboard with a 16-phase power supply design like the P5Q Deluxe. We can't find public information about their specific functions. According to ASUS, the EPU is a native 8-phase PWM controller, and the PEM, as a device such as an electronic switch, is responsible for sending the 8-phase signal to the 16-phase driver chip to achieve a 16-phase and 8-phase switchable working mode.
K10's Split-Plane design and "N+1" phase power delivery circuits AMD K10 processor introduced a split power plane design. The split power plane means that the CPU is divided into two parts: the processor core (each core and L2 cache) and the on-chip north bridge (L3 cache, HTT3.0 controller, memory controller, etc.). The processor core uses a power supply called VDD, and the on-chip north bridge uses a power supply called VDDNB. The working voltages of these two power supplies are called core voltage and north bridge voltage respectively. Under different working conditions, the two sets of voltages can be controlled independently to achieve better energy saving effects.
To obtain two independent voltages, two independent power supply circuits are required. On a motherboard with a separate power supply design, a traditional N-phase power supply circuit provides VDD power according to the instructions of the core VID in the VID signal, and an independent single-phase power supply circuit provides independent VDDNB power according to the instructions of the north bridge VID in the VID. This is the so-called "N+1 phase" design. When a motherboard with an N+1 phase power supply design is plugged into a K8 CPU with a single power supply design, only the N-phase VDD power supply works to generate VDD voltage for the CPU.
The power supply requirements of the K10 require a maximum output current of 100A for the VDD power supply, and a maximum TDP of 140W (Phenom 9950 2.6GHz), requiring four-phase power supply support, otherwise the power supply circuit will heat up too much and be unstable. Therefore, the common power supply design of the K10 motherboard is 4+1 phase, and the low-end integrated motherboard often uses a 3+1 phase design, and some overclocking motherboards even have 5+1 phases.
Let's take the power supply of GIGABYTE MA770-DS3H as an example to see how to determine the N+1 phase power supply.
After the release of K10, Intersil launched the corresponding hybrid power management solutions ISL6323 and ISL6324. Both chips support up to 4+1 phase power supply design. If you see this control chip, it is basically an N+1 phase solution.
This is easier to identify. The four chokes are three 0.60 microhenry and one 2.2 microhenry. It is obviously a 3+1 phase power supply. The number of MOS tubes is 14=4*3+2, so there are 4 MOS per phase for VDD power supply and two MOS for VDDNB power supply. The VDD control chip is ISL6312 with three built-in drivers supporting up to 4 phases, which is very common on 775 motherboards. ISL6312 is a PWM control chip with a single power supply design. It cannot support a separate power supply design when used alone. In order to achieve separate power supply, the motherboard uses a Fintek F75125 power supply chip. This chip translates the VDD serial VID (SVI) signal sent by the K10 CPU into a parallel VID (PVI) core voltage VID signal and transmits it to the ISL6312. At the same time, it converts the VDDNB serial VID signal into a signal voltage and drives the 1-phase power supply to generate the north bridge voltage through the F78215 single-phase buck controller. In contrast, the hybrid chip ISL6324 is another separate power supply design. With the popularity of 790GX motherboards, 4+1 phase power supply solutions based on ISL6323 and ISL6324 are very common.
4 chokes, 3 semi-enclosed and 1 enclosed, 3+1 phase power supply, 3 MOS tubes per phase for VDD power supply, 2 MOS tubes for VDDNB. The main control chip is ISL6323, with 1 driver.
Split-Plane power delivery design on Nehalem. Netizens who have been paying attention to the X58 motherboard recently should have noticed that in addition to the power supply around the CPU, the Nehalem motherboard has several more phases of power supply that are not known to whom.
EX58-UD3R
Nehalem/Bloomfield also introduced a separate power supply design. The QPI controller and three-channel DDR3 memory controller in the CPU are called "Uncore" and are powered by an independent power supply. Because the power consumption of this part is not small, coupled with the need for overclocking, the motherboard's Uncore power supply is mostly two-phase. The above motherboard uses a 4+1 phase power supply configuration. The core power supply and Uncore power supply use two independent PWM control chips (lower left and lower right in the picture), and each phase of the core power supply uses double the material.
Memory and Chipset power delivery circuits: In the past, the motherboard's memory VDD/VDDq and chipset VDD power supply were not in high demand. Linear power supply was used to provide power for the chipset or memory. The required voltage was converted from +5V or +3.3V through a device such as LDO (low dropout regulator). The difference was consumed by the regulator and turned into heat. As the memory operating voltage dropped from 3.3V to 2.5V and then to 1.8V and 1.5V, the chipset core voltage also dropped from 1.5V to 1.1V, and the required current increased, the low efficiency and high heat of linear power supply became unacceptable, and the memory and chipset power supply turned to switching power supply.
The iconic component of the switching power supply circuit is the output choke. If there is no output choke, it is definitely not a switching power supply circuit. To determine the power supply method, we have to find these chokes, which I marked with red circles in the previous picture.
Note that the switching power supply of memory and chipset is a single-phase or multi-phase switching power supply circuit. Like the CPU power supply, there will be input and output filter capacitors, and there may also be input chokes to reduce the impact of the output on the upper circuit. On this ABIT GD8 motherboard, we can see that the input end of the memory and chipset power supply has a yellow magnetic core toroidal choke. The output current is larger than the input current, so the output choke uses a three-strand parallel winding method, and the magnetic core is also larger.
The memory power supply uses +5V to convert to the DDR3 operating voltage of 1.5V to 2V, so the capacitor with a voltage of 6V is the input filter capacitor, and the capacitor with a voltage of 4V is the output filter capacitor, which determines that the 2 microhenry choke is the output choke.
The chipset power supply uses +12V to convert to the chipset core voltage of about 1.25V, so the capacitor with a voltage of 16V is the input filter capacitor, and the capacitor with a voltage of 4V is the output filter capacitor, which determines that the 2 microhenry choke is the output choke.
The chipset power supply uses +12V to convert to the chipset core voltage of about 1.25V, so the capacitor with a voltage of 16V is the input filter capacitor, and the capacitor with a voltage of 4V is the output filter capacitor, which determines that the 2 microhenry choke is the output choke.
This is a genuine two-phase power supply, each phase uses a 1.2 microhenry output choke and two SO-8 derivative low internal resistance MOSFETs. The two two-phase power supplies are each controlled by an ISL6312, which is a standard configuration used by 4-phase power supply motherboards! On the chipset power supply side, we can also see a 1.2 microhenry input choke, don't make a mistake.
(Picture: ASUS P5Q Deluxe memory power supply)
This is also a genuine two-phase power supply, with a pair of LFPAK packaged MOSFETs in each phase, and the PWM control chip is uPI's uP6203
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