High-density dc/dc converters come in numerous combinations of input voltage, output voltage, and power levels. Modules such as these small PC-board-mounted packages provide output power to 150W. Resonant and quasi-resonant dc/dc converters are becoming more widely used because they are less expensive and more efficient than equivalent linear supplies. Not long ago, efficiency hinged on the converter's switching devices that wasted most of the power budget during relatively low-frequency transitions — typically 20 to 30 kHz — between on and off states. Improving efficiency by increasing the speed of these converters while using the same type of switching devices, however, peaked out at about 66 kHz. But because newer high-speed switching devices operate at 100 kHz and more while dissipating much less power during transitions, converter efficiency has increased dramatically. In a simplified diagram showing a single-ended forward converter, for example, the energy transfers from source to load during the "on" time of a single solid-state switch cycle.The circuit shown is quasi-resonant because the energy stored in capacitor Cr does not return to the inductor Lr as is done in a full-resonant converter. When the main switch, Q1, turns on, about a half cycle of current flows through the switch, transferring the energy from the input source to an LC circuit composed of Lr and Cr. The transformer here provides voltage scaling, electrical isolation from primary to secondary, and magnetic storage in the leakage inductance. The leakage inductance of transformer T1, is modeled as the inductor Lr in series with the secondary, and the capacitor Cr is across D2. The inductor stores energy as current, ), and the capacitor stores energy as voltage, Both diodes, D1 and D2, transfer energy from the input to the output. Diode D1 conducts when the main switch conducts and transfers energy from the leakage inductance
Products & Services
Switching Power Supplies
Switching power supplies are DC sources that use a switching element (normally a power transistor) to generate the desired voltage. Switching power supplies are also called switch-mode products or switching mode power supplies (SMPS).
DC-DC Converter Chips
DC-DC converter chips provide a regulated DC voltage output from a different, unregulated input voltage.
Board Mount Transformers
Board mount transformers are transformers designed to be embedded in or mounted on computer boards.
IC Switching Voltage Regulators
IC switching voltage regulators are integrated circuits (ICs) that store energy in an inductor, transformer, or capacitor and then use this storage device to transfer energy from the input to the output in discrete packets over a low-resistance switch.
IC Voltage Regulators
IC voltage regulators are three-terminal devices that provide a constant DC output voltage that is independent of the input voltage, output load current, and temperature. IC voltage regulators are used in power supplies that hold their output voltage constant over a wide range of load variations.
Topics of Interest
One of the primary goals when designing dc/dc conversion circuits is to get a high conversion efficiency. Without careful design, it is easy to dissipate as much energy in the conversion circuit as...
Inductor-based, step-up switching regulators offer high efficiency, small size and lower cost than isolated switching regulators (DC/DC converters). They are used to amplify (step up) the voltage of a...
Chapter 9: The Step Down Converter
Chapter 10: The Step Up or Boost Converter
Chapter 11: The Buck Boost dc to dc Converter
Chapter 12: The CUK dc to dc Converter
So far, we have discussed duty ratio control of PWM converters, in which the converter output is controlled by direct choice of the duty ratio d( t). We have therefore developed expressions...
As described in Chapter 3, all power DC/DC converters are treated as a second-order-hold (SOH) element in digital control systems. We will discuss this model in various circuits in this chapter.