3 phase voltage stabilizer: seven key issues with voltage regulators - 3 phase voltage stabilizer

There are two types of voltage regulators: linear and switching.

 

 

Linear regulators use active (BJT or MOSFET) current-passing devices (series or parallel) controlled by a high gain differential amplifier. It compares the output voltage to a precision voltage reference and adjusts the pass device to maintain a constant output voltage.

 

 

A switching regulator converts a DC input voltage to a switching voltage that is applied to a power MOSFET or BJT switch. The filtered power switch output voltage is fed back to a circuit that controls when the power switch is turned on and off, so that the output voltage remains constant regardless of changes in its input voltage or load current.

 

 

 

 

2 What are the topologies of switching regulators?

 

 

There are three common topologies: buck, boost, and buck/boost. Other topologies include flyback, SEPIC, Cuk, push-pull, forward, full-bridge and half-bridge topologies.

 

 

3 How does the switching frequency affect the regulator design?

 

 

Higher switching frequencies mean that regulators can use smaller inductors and capacitors. It also means higher switching losses and greater circuit noise.

 

 

4 What are the losses of switching regulators?

 

 

The power required to turn the MOSFET on and off causes losses and is associated with the MOSFET gate driver. Likewise, switching from a conducting state to a non-conducting state takes a certain amount of time, and therefore generates MOSFET power dissipation. In addition, the energy required to charge and discharge the MOSFET gate capacitance between the threshold voltage and gate voltage also causes losses.

 

 

5 What are the common applications of linear and switching regulators?

 

 

For a given input and output voltage, the power dissipation of a linear regulator is proportional to the output current, so typical efficiency can be 50% or less. By optimizing the device, switching regulators can achieve 90% efficiency. However, the noise output of a linear regulator is much lower than that of a switching regulator for the same output voltage and current requirements. Typically, switching regulators can drive higher current loads than linear regulators.

 

 

6 How does a switching regulator control its output?

 

 

A switching regulator needs to change its output voltage in some way in response to input and output voltage changes. One approach is to use PWM to control the input of the associated power switch, thereby controlling its switching time (duty cycle). During operation, the filtered output voltage of the regulator is fed back to the PWM controller to control the duty cycle. If the filtered output changes, feedback applied to the PWM controller changes the duty cycle to maintain a constant output voltage.

 

 

7 Which design specifications are important for a regulator IC?

 

 

The basic parameters include input voltage, output voltage and output current. Depending on the application, other parameters may also be important, such as output ripple voltage, load transient response, output noise, and efficiency. Important parameters of linear regulators include dropout, PSRR

(power supply rejection ratio) and output noise.