The UCC28510 series of combination PFC/PWMcontrollers provide complete control functionalityfor any off-line power system requiringcompliance with the IEC1000−3−2 harmonicreduction requirements. By combining the controland drive signals for the PFC and the PWM stagesinto a single device, significant performance andcost benefits are gained. By managing themodulation mechanisms of the two stages(leading-edge modulation for PFC andtrailing-edge modulation for PWM), the ripplecurrent in the boost capacitor is minimized.
Based on the average current mode controlarchitecture with input voltage feedforward of priorPFC/PWM combination controllers, these devicesoffer performance advantages. Two new keyPWM features are programmable maximum dutycycle and the 2x PWM frequency options to thebase PFC frequency. For the PFC stage, thedevices feature an improved multiplier and theuse of a transconductance amplifier for enhancedtransient response.
The core of the PFC section is in a three-inputmultiplier that generates the reference signal forthe line current. The UCC28510 series features ahighly linearized multiplier circuit capable ofproducing a low distortion reference for the linecurrent over the full range of line and loadconditions. A low-offset, high-bandwidth currenterror amplifier ensures that the actual inductorcurrent (sensed through a resistor in the returnpath) follows the multiplier output commandsignal. The output voltage error is processedthrough a transconductance voltage amplifier.
The transient response of the circuit is enhanced by allowing a much faster charge/discharge of the voltageamplifier output capacitance when the output voltage falls outside a certain regulation window. A number ofadditional features such as UVLO circuit with selectable hysteresis levels, an accurate reference voltage for thevoltage amplifier, zero power detect, OVP/enable, peak current limit, power limiting, high-current output gatedriver characterize the PFC section.
The PWM section features peak current mode control (with a ramp signal available to add slope compensation),programmable soft-start, accurate maximum duty cycle clamp, peak current limit and high-current output gatedriver. The oscillator for the combination controller is available in two versions. In UCC28510, UCC28511,UCC28512, and UCC28513, the PWM and the PFC circuits are switched at the same frequency. In theUCC28514, UCC28515, UCC28516, and UCC28517, the PWM stage frequency is twice that of the PFCfrequency. The PWM stage is suppressed until the PFC output has reached 90% of its programmed value duringstartup. During line dropout and turn off, the device allows the PWM stage to operate until the PFC output hasdropped to 47% (UCC28512, UCC28513, UCC28516, and UCC28517) or 71% (UCC28510, UCC28511,UCC28514, and UCC28515) of its nominal value. See available options table on page 1 for a summary ofoptions.
The UCC28510 family also features leading-edge modulation for the PFC stage and trailing-edge modulationfor the PWM stage in order to reduce the ripple current in the boost output capacitor. The current amplifierimplementation associated with this scheme also results in better noise immunity.Available in 20-pin N and DW packages.
Provides Control of PFC and PWM Power Stages In One Device
Leading-Edge PFC, Trailing-Edge PWM Modulation for Reduced Ripple
Built-In Sequencing of PFC and PWM Turn-On
2-A Source and 3-A Sink Gate Drive for Both PFC and PWM Stages
Typical 16-ns Rise Time and 7-ns Fall Time into 1-nF Loads