Digital Current Control Circuit for Fixed-Frequency Power Converters
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Solution Overview
Problem
Existing control systems for uninterruptible power supplies (UPS) face challenges in reusing control boards due to high reliability requirements and specific power topology needs, leading to costly redesigns and inefficiencies in current regulation, particularly with prior digital and analogue current controllers that are either inflexible, expensive, or unsuitable for fixed switching frequencies.
Innovation Solution
A non-linear fixed frequency current controller using a digital controller, such as a Field Programmable Gate Array (FPGA), which generates logical control signals based on current error transformations, eliminating the need for analogue-to-digital converters and allowing for cost-effective, flexible, and robust control of power converters with fixed switching frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed frequency linear analogue current controller is used, then the control is simple to implement, but it is difficult to tune with limited reliability and flexibility
Solution Approach 1:
The patent replaces the mechanical/analog tuning process with a digital system where parameters can be programmed and adjusted through software. The digital current controller allows tuning parameters to be modified without physical hardware changes, replacing the manual mechanical tuning of analog components with programmable digital configuration.
Solution Approach 2:
The patent implements variable parameters in the digital controller that can be dynamically adjusted to change control characteristics. This allows the system to adapt parameters such as current limits, switching frequencies, and control gains without hardware modifications, resolving the contradiction between fixed implementation and flexible tuning.
2Measurement precision
If a fixed frequency linear digital current controller is used, then the control precision is improved, but expensive and fast A to D converters are required which have limited dynamic range
Solution Approach 1:
The patent extracts the A/D conversion function from the critical current control path and performs it at a lower sampling rate for reference purposes only. The main current control uses digital values already available in the system, eliminating the need for expensive high-speed A/D converters while maintaining control precision through alternative digital measurement and calculation methods.
Solution Approach 2:
The patent uses lower-cost, lower-performance A/D converters that operate at reduced speeds for non-critical measurements. By separating the critical control function from the measurement function, the system can use inexpensive converters without compromising the precision of the actual current control, which relies on digital calculations rather than high-speed analog-to-digital conversion.
3Adaptability or versatility
If a variable frequency sliding mode controller is used, then the adaptability is improved, but it is not suitable for situations where fixed switching frequencies are demanded
Solution Approach 1:
The patent implements a digital controller that can dynamically adjust control parameters and switching patterns based on system conditions while maintaining a fixed fundamental switching frequency. The controller uses digital logic to modify pulse widths, phase angles, and current limits adaptively, achieving variable-frequency-like adaptability within the constraints of fixed-frequency operation through sophisticated digital control algorithms.
4Stability of the object's composition
If a fixed frequency peak current controller is used, then the switching frequency is stable, but dynamic error occurs and complex analogue implementation is required for compensation
Solution Approach 1:
The patent replaces complex analog compensation circuits with digital compensation algorithms implemented in the digital controller. Dynamic error compensation, phase adjustment, and current waveform correction are performed through software calculations rather than analog components, eliminating the need for complex RC networks, op-amps, and passive compensation elements while maintaining frequency stability.
5Reliability
If control boards are redesigned for each new UPS requirement, then the reliability for specific requirements is improved, but the manufacturing cost and time increase
Solution Approach 1:
The patent implements a universal digital control board that can be configured for different UPS topologies and requirements through software programming rather than hardware redesign. The same physical control board can serve multiple product lines by loading different control algorithms and parameters, achieving product-specific reliability without the need for custom hardware designs for each application.
Solution Approach 2:
The patent enables customization of control characteristics through programmable parameters stored in memory or configured via software. Different UPS requirements are met by changing control parameters such as switching frequencies, current limits, protection thresholds, and control loop gains, allowing a single control board design to adapt to multiple product specifications without hardware modifications.
Data Source
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AI summary
A current control circuit (208) for a power converter (200) to control the switching thereof, wherein the current control circuit comprises a digital controller (210) using a logical input signal (226) to produce a logical control signal (212) with a fixed fundamental frequency for the power converter.