CPU Voltage Regulator
A voltage regulator generates fixed output voltages of a present magnitude that remain constant regardless of changes to its input voltage or load conditions. There are two types of voltage regulator linear and switching.
A linear regulator employs an active pass device controlled by a high gain differential amplifier. It compares the output voltages with a precise references voltage and adjusts the pass device to maintain a constant output voltage.
A switching regulator converts the DC input voltage to a switched voltage applied to a power MOSFET or BJT switch. The filtered power switch output voltage is fed back to a circuit that controls the power switch on and off times so that the output voltage with a precise references remains constant regardless input voltages or load current changes.
There are three common topologies buck, boost, and buck-boost. Other topologies include the flyback bridge topologies.
Higher switching frequencies mean the voltage regulator can use smaller inductors and capacitor. It also means higher switching losses and greater noise in the circuit.
Losses occur as a result of the power needed to turn the MOSFET on and off which are associated with the MOSFET gate driver. Also, MOSFET power losses occur because it takes a finite time to switch to from the conduction to non-conduction states. Losses are also due to the energy needed to charge and discharge the capacitance of the MOSFET gate between the threshold voltage and gate voltage.
The linear regulator power dissipation is dissipation is directly proportional to its output current for a given input and output voltage so typical eff can be 50% or even lower. Using the optimum components a switching regulator can achieve efficiency can be 90% range. However the noise output from a linear regulator much lower than a switching regulator with the same output voltage and current requirements. Typically the switching regulator can drive higher current loads than a linear regulator.
Among the basic parameters are input voltage output voltage and output current. Depending on the application other parameters other parameters may be important such as output ripple voltage load transient response output noise and efficiency. Important parameters for the linear regulator are dropout voltage PSRR and output noise.
CPU Power Section Block Diagram
Switching Regulator Topologies
Switching Regulator Topologies
The term topology refers to the different forms of switching and energy storage elements combination that are possible for the transmission control and regulations of an output voltage or current from an input voltage source.
The many different topologies for the switching regulator can be divided into two main groups.
.Non isolated converts in which the input source and the output load share a common current path during operation.
.Isolated converts in which the energy transferred via mutually coupled magnetic components wherein the coupling between the supply and the load is achieved solely via an electromagnetic field.
Non Isolated DC/DC Converter
The selection from the variety of available topologies is based on such consideration such as cost performance and control characteristics which are determined by the application requirement. No topology is better or worse than the other. Each topology has an advantage as well as a disadvantage and so the choice is a question of the needs of the user and the system application
1. Buck or Step down converters
2. Boost or Step upconverts
3. Buck-boost or Step up-down converters
4. Two-stage inverting buck-boost
5.Two-stage non-inverting buck-boost.
The subsequent explanation assumes that the PWM control circuit has a feedback control circuit has a feedback control circuit and the correct duty cycle is chosen for the desired output voltage. Also ideal switched as well as ideal capacitor and inductor are assumed to better demonstrate the transmission properties of each topology but before we look at the topologies, a few words about driving switching transistor are opportune.
a device that will go into saturation if the drive voltage VNS>>VTH and switch off if VNS < VTH. One commonly used solution for an N-Channel high side driver is to use the square wave signal at VX to boost the supply voltage to the high side driver via a bootstrap capacitor and diode.
The capacitor CBOOT is charged.
Thus the high side driver has a higher voltage supply that can drive the gate of the high side N-FET above the input voltage.
The disadvantage of this simple bootstrap circuit is that at high PWM duty cycle the bootstrap capacitor does not have enough time to charge up the CDRIVE capacitor. Thus operation at close to 100% duty cycle is not possible. This restricts the input voltage and load range of the converters.
One solution to this problem is to use a separate charge pump oscillator to keep CDRIVE charged up to above over the whole duty cycle range. Such charge pump circuit are often integrated to the controller or high side driver
In the following topologies, the switching elements are represented as simple switches. In reality, they can be a transistor with or without drivers according to the detailed design requirements.
As the name suggests the step-down or buck converter a higher input voltage into a stabilized lower output voltage. A simplified circuits diagram and the main current and voltage waveforms are shown
The simplest way to understand this circuit is to think of L1 and C1 form a low pass filter. When switch S1 is closed the voltage across the load slowly ramps up as the capacitor C1 charges up through L1. The average output voltage is then the mark-space ratio of the PWM control signal multiplied by the input voltage.
Buck Converters Application
The advantage of a buck converter is that the losses are very low efficiencies are readily achievable especially in a synchronous the output voltage can be set anywhere from very large. Also, the switching frequency can be several hundred of KHz to give a very compact construction with a small inductor and fast transient response. Finally, if the switching FET is disabled the output is zero so the no-load power consumption becomes negligible. For all of these reasons the buck regulator makes a very attractive alternative to the linear regulator in many applications.
As the name suggests the step up or boost converters a lower input voltage into a stabilized higher output voltage. A simplified diagram and the main current and voltage waveform
CPU Power Section Component
CPU Core Power IC:-
The processor is the entire chipset including all the cores. Cores are like 2 the processors that do parallel processing which helps in multitasking without causing much strain on the processors. Each core itself is a processor technically. But the chipset is manufactured in such a way that the different cores work with coordination and not individually. An analogy is dividing a large hall into several identical bedrooms so that there is no overcrowding. Each bedroom is like a Core that does the same function of keeping the guests but is different physically.
N Channel Mosfet:-
The N-Channel Mosfet has N channel region between the source and drains it is a four terminal device such as gate drain-source Body. This type of MOSFET the drain and source are heavily doped region and the substrate with a repulsive force. The depletion region is populated by the bound negative chargers which are associated with the acceptor atoms. The electron reach channel is formed. The positive voltage also attracts an electron from the n+source and drain region into the channel. Now if a voltage is applied between the drain and source the current flows freely between the source and drain and the Gate voltage control the electron in the channel. Instead of positive voltage if we apply negative voltage a hole channel will be formed under the oxide layer.
Tantalum capacitor is a subtype of electrolytic capacitor. They are made of tantalum metal which acts as an anode covered by a layer of oxide which acts as the dielectric surrounded by a conductive cathode. The use of tantalum allows for a very thin dielectric layer. This result in a higher capacitance value per volume superior frequency characteristics compared to many other types of capacitor and excellent stability over time. Tantalum capacitor is generally polarized which means that they may only be connected to a DC supply observation the correct terminal polarity. The downside to using tantalum capacitor is their unfavorable failure mode which may be lead to thermal runaway fires and small explosion, but this can be prevented through the use of external failsafe devices such as current limiters or thermal fuses. Technology advances allow tantalum capacitors to be used in a wide variety of circuit often found in laptop, automatic industry cell phones and other surface mounted devices.
An inductor is a circuit elements that is a wire wound into a coil to create a magnetic field.
An inductor resist change in the flow of electric current through it because generated a magnetic field that acts to oppose The flow of current through it. When two inductor are connected in series as shown above then their total inductance equals the sum of individual inductance. An inductor is a circuit element that is a wire wound into a coil to create a magnetic field.
The standard unit of inductance is the Henry, abbreviated. This is a large unit. More common units are the microhenry abbreviated and the diligently, abbreviated mH.
A switched mode power supply is an electronic circuit the converts power using switching devices that are turned on and off at high frequencies and strong component such as inductor or capacitor to supply power when the switching devices is its non-conductive state. Switching power supplies have high efficiency and are widely used in a variety of electronic equipment including computer and others sensitive equipment requiring stable and efficient power supply. A switched mode power supply is also known as a switch mode power supply or switching mode power supply.
A resistor is an electrical component with two terminals that is used to limit or regulate the flow of electrical current in an electronic circuit. Its purpose is to reduce current flow as well as lower then voltage levels in its general vicinity or portion of the circuit. A resistor is an electrical component with two terminals that are used to limit or regulate the flow of electrical current in electronic circuits. Its purpose is to reduce current flow as well as lower the voltage levels in its general vicinity or portion of the circuit. A resistor is meant to regulate the actual load on the system meaning that it uses up electricity and dissipates it as heat, thereby effectively the amount of electricity flowing out of it by specific amounts.
Components Identification CPU Power Section
A power supply is an electronic circuit that converts an ac voltage to dc voltage. It is basically consisting of the following elements transformer rectifier filter and regulator circuit. Power supply units are in computer amateurs radio transmitter and receiver and all other electronic equipment that use DC voltage as an input. Uninterruptible power supply is a must for computer which holds volatile data from time to time. This prevents corruption of data due to power failure system from and low voltage.
The transformer is a static device that transfer electrical energy from the primary winding to the secondary winding without affecting the frequency. It is used to step up or Step down the ac voltage level and isolates the remainder of the electronic system from the ac power.
The primary winding of the transformer is connected to an ac voltages sources that produces alternating current while the secondary is connected to a load. The primary and secondary winding are not physically connected to each other but due to electromagnetic induction following Faraday’s law, there is an induced voltage in the secondary winding. There are three main function of transformer namely stepping the voltage down and providing isolation between the primary and secondary circuit.
Rectifier:- The rectifier is a device used to change the AC power into Pulsating DC. The basic rectifier is the diode. This diode is a unidirectional device that operates as a rectifier in the forward direction. The three basic rectifier circuit using diodes is the half-wave full wave center tapped and full wave bridge type.
Filter :- The filter of the copy supply is used to keep the ripple components from appearing in the output. It is designed to convert pulsating DC from rectifier circuit into a suitable smooth DC level. The C filter is the simplest and most economical filter available. On the other hand RC filter is used to reduce the amount of ripple voltage across a capacitor filter.
Ripple and Ripple factor
Ripple is the unwanted ac components of the signal after rectification. It is unwanted because it can destroy or damage the load. This is the main reason why filter is installed in the power supply to prevent high ripples. The job of the filter is to smoother the signal and suppers the ac components or variations. Ripple factor is the ratio of the root mean square of the ripple voltage to the value of DC components at the output voltage. It is sometimes expressed in percentage or in peak to peak value.
A voltage regulator is designed to provide a very steady as well regulated DC output. It is always ideal to have a steady output voltage so that the load will operate properly. The output level is maintained regardless of the variation of the input voltages. The commonly used transistor voltage regulators are the series voltage regulator and the shunt voltage regulator.
Series voltage regulator
The series element control the amount of the unregulated input voltage that goes to the output as a regulated output. The regulated output voltage is sampled by a circuit that provides a feedback to the comparative circuit and is compared to a reference voltage.
Shunt voltages regulator
The shunt voltage regulator provides regulation by shunting current away from The load to regulate the output voltage
IC voltage Regulators: A regulator integrated circuit unit contain the circuitry the reference source comparator amplifier control device and the overload protector inside a single IC. There is also adjustable voltage regulator which allow the user to set the desired output level. Other IC regulator has fixed output values. It is said that IC regulators are superior compared to a transistor voltage regulator when it comes to the linearity of the output voltage.