One-Cycle PFC Control in Main DSP Chip
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional Power Factor Correction (PFC) circuits are complex, costly, and require specific high-cost one cycle control chips, which is inefficient when integrated with main control chips like DSP in systems, such as air conditioner power supplies.
Innovation Solution
A one cycle control method for PFC integrated into a main control chip, utilizing a simple boost circuit with an AC input, rectifying circuit, inductor, diodes, capacitor, inductive current sampling, output voltage sampling, and a switch transistor, eliminating the need for a specific PFC chip by calculating sampling triggering instants to ensure accurate PWM control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PFC circuit is used, then power factor correction function is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines the PFC control function with the existing main control chip (DSP) by integrating the one-cycle control algorithm into its software. This merging eliminates the need for separate PFC control circuits and dedicated PFC chips, reducing overall system complexity while maintaining the power factor correction function. The control chip simultaneously manages both the compressor motor control and PFC operations.
Solution Approach 2:
The main control chip is made multi-functional by programming it to perform both compressor control and PFC operations. The single control chip handles multiple tasks including sampling inductor current and output voltage, calculating duty ratios for both PFC and motor control, and generating PWM signals for both the PFC switch and inverter switches, thereby eliminating dedicated PFC control hardware.
2Measurement precision
If specific one cycle control chip for PFC is used, then control precision is improved, but system cost increases
Solution Approach 1:
The patent merges the sampling and control functions into the existing main control chip. The DSP samples the inductor current and output voltage using its existing ADC resources, eliminates the need for separate sampling circuits and dedicated PFC chips, while maintaining precise one-cycle control through software implementation of the control algorithm.
3Productivity
If sampling around switching instant is performed, then real-time control is achieved, but sampling accuracy deteriorates due to transient effects
Solution Approach 1:
The patent calculates and determines the sampling triggering instant in advance based on the PWM duty ratio and switching cycle timing. By pre-calculating when to sample (at a fixed offset from the switching instant rather than exactly at it), the system avoids the transient effects and voltage spikes that occur during switching, ensuring accurate sampling while maintaining real-time control through the one-cycle control methodology.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A one-cycle controlled power factor correction method. The method is used for a boost converter and is realized by a system main control chip. A bus voltage sampling value Uo and an inductor current sampling value ig are detected at A/D sampling trigger time according to the method. Voltages u1(t) and u2(t) are calculated according to the following formulas. The duty cycle of a PWM signal is calculated according to the calculated voltages. The PWM signal is output and the next A/D sampling trigger time is calculated according to the duty cycle (I). Wherein, Rs is a current sensing resistor, um is a voltage which is achieved by controlling the difference between the voltage Uo and a reference value Uref by using a PI controller, and T is a switching period.