INTERNATIONAL Rectifier has released the IR1150 family of µPFC ICs for ac-dc power factor correction (PFC) circuits. The SO-8-packaged device cuts PFC control board space in half, and enables a simplified and flexible high density solution for computing, consumer electronics and home appliances from 75W to 4kW.
IR's One Cycle Control (OCC) approach delivers the performance of continuous conduction mode (CCM) PFC with the simplicity, reliability and low component count of a discontinuous current mode (DCM) circuit for PFC applications.
Power factor (PF) is the relationship between ac voltage and current waveforms and is a measure of power quality that affects the efficiency of electrical transmission networks. With unity PF as the ultimate goal, the IR1150 enables 0.999 PF with only 4% total harmonic distortion, enabling ac-dc applications to conform to international legislative requirements.
The One Cycle Control method used in the IR1150 controller does not have an analogue multiplier, input voltage sensing or fixed oscillator ramp, simplifying circuitry and reducing component count. Instead it uses an integrator with a reset circuit. The output of the error amplifier is integrated over each clock cycle to generate a variable-slope ramp. This variable ramp is compared with the error voltage and subtracted from the current sense signal to generate the PWM gate drive.
Traditionally, continuous conduction mode PFC offers high performance for applications above 250W. However, solutions using multiplier techniques are complex and require many design stages and a high component count, making CCM solutions very expensive and inappropriate for low-power, price-sensitive applications like laptop power adapters.
In low-power applications from 75W to 250W, discontinuous current mode systems are used for their simplicity and low system cost. However, as system power increases to 100W and above, DCM systems can be very large due to high peak currents and EMI filter requirements.
In addition, a dedicated over voltage protection pin offers greater protection for high power systems and the IC has enable and micro-power startup and sleep mode for compliance with energy efficiency standards such as 1W standby, Blue Angel and Energy Star.
It meets the requirements of legislation such as IEC 1000-3-2 in Europe, JIC C 61000-3-2 in Japan and the China Compulsory Certificate (CCC) for products using more than 75W.