Simplify DC-DC Converter Characterization

DC-DC converters are widely used components that convert DC power from one voltage to another, producing a regulated output voltage. These devices are used in many electronic products, including laptops, mobile phones, and instrumentation. Like any device, DC-DC converters need to be characterized by manufacturers and by engineers evaluating them for a design.
Given the increased pressure to develop products that consume less power, design engineers are looking for ways to increase power conversion efficiencies. Thus, numerous measurements are required to characterize the electrical parameters of DC-DC converters. Tests include:

  • line regulation,
  • load regulation,
  • input and output voltage accuracy,
  • quiescent current,
  • efficiency,
  • turn-on time,
  • ripple, and
  • transient response.

Some of these tests require DC test instruments for sourcing input voltage or current and measuring output voltage and current. You also often need an oscilloscope as well. Figure 1 illustrates a typical DC-DC converter test configuration using an SMU (source-measure unit) and an oscilloscope.
Simplify DC-DC Converter Characterization
The DC-DC Converter
DC-DC converters can product output voltage that are either higher or lower than their inputs voltages. A step-down (buck) converter produces an output voltage lower than the input voltage while a step-up (boost) converter produces an output voltage higher than the input. Ideally, this conversion should be performed with high efficiency to avoid wasting energy.
Figure 2 is a simplified diagram of a DC-DC converter. The VIN terminal is the input voltage node of the device, which is referenced to the common GND terminal. The VOUT terminal is the regulated voltage output with respect to the common terminal.
DC-DC Converter Parameter Testing
Typically, electrical characterization of DC-DC converters involves sourcing and measuring input voltage (VIN ), measuring input current (IIN ), measuring the output voltage (VOUT ), and sinking a load current (IOUT ). From these measurements, you can calculate the efficiency and other parameters. The efficiency of a converter is the output power divided by the input power.
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