High Voltage Thick Film Resistor In Voltage Regulation Applications

What Is A Voltage regulator?

A voltage regulator protects sensitive components from over voltage conditions. The device delivers a fixed output voltage that remains constant regardless of any changes in the input voltage or load conditions. DC voltage regulators are the most common but, depending on the design, voltage regulators may be used to regulate AC or DC voltages.

The two main types of voltage regulators are linear and switching. Linear regulators drop a voltage across some resistive element (active or passive) to maintain the output voltage at the required level. They often employ a negative feedback loop to compare the actual output voltage to a reference voltage.

Switching regulators turn on and off rapidly to control the output voltage. They require several control elements and charge storage elements (Capacitors). Switching regulators may be step up, step down or inverter voltage type.

Linear voltage regulators may be series or shunt. The shunt type is the simplest but also the most inefficient. The series voltage regulator is, therefore, more common.

Discrete vs Integrated Circuit Solutions

Voltage regulator circuits may be constructed using discrete components or a combination of an integrated circuit and discrete components. The most common choice is the use of an integrated circuit as it has several potential advantages. Using an I.C simplifies system manufacture, reduces on board connections (and therefore improves reliability) and reduces the system board area required compared with the equivalent circuit manufactured using discrete components.

The discrete approach is used in more specialist applications delivering improved performance. and superior ripple reduction at a potentially lower cost. The discrete approach also delivers improved power handling as discrete resistors (particularly when combined with a heatsink) may dump excess energy as heat.

Resistor Applications

In linear shunt regulators, a high voltage thick film resistor is used to dissipate current to ground whereas in Linear series regulators a resistor is used to bias the base of a series voltage element (usually a FET)

In switching regulators a variety of resistors are used as voltage divider, biassing and feedback elements in comparator, integrator and amplifier circuitry.

Given the dimensional constraints in many systems thick film resistor technology is the ideal choice when employing a discrete solution. Thick film resistor technology offers high power handling capability per unit area, long term stability and relatively low cost making it an ideal choice for the demands of both linear and switching regulator circuits.