Investigation Into Digital Control Of Multi-Output Full-Regulated DC-DC Converter For Spacecraft

Compared with civilian products, aerospace DC-DC modules are high-end power suppliers, so they must be provided with more stringent reliability. Actually, the most urgent demand now is breaking away from traditional custom-built power development mode and establishing a step-by-step design flatform for customers to decrease repetitiveness and shorten developping cycle. Designing a multi-output converter with precise regulation is the key solution for this challenge, and the core technology is digital power controller.The digital converter can not only regulate its outputs on-line smartly, but also can compensate component distortions resulted from aging and parameter drifting which will cause unstable loop oscillations. In recent years, international dominant IC companies have developed their own digital power products. Domestic researches on digital power supply are most focused on DSP (Digital Signal Processor) and ready digital IC platform. There's still a wide gap between top level in ASIC (Application Specific Integrated Circuit) development.The main researching object is to develop a dedicated digital power controller, and apply it to a multi-outputs isolated DC-DC converter. Furthermore, efficiency optimalization, modelling method, DPS (Distributed Power Supply) stability are studied deeply. The digital controller will be integrated into an ASIC. The main investigative works in this thesis include:An IBA-based (Intermediate Bus Architecture) DC-DC converter and a digital controller with multiple PWM outputs are designed. The topology, control method and the feedback loop of the DC-DC converter are analyzed for later research.For the limitations of spacecraft application, an isolated IBA-based digital DC-DC solution is proposed. The primary-side is controlled in open-loop and the secondary-side is regulated with closed-loop, and the intermediate bus voltage level and transformer ratios are optimized to improve the efficiency.A compound DPWM (Digital Pulse Width Modulator) structure including comparator-counter and dither is designed for high-precision control and reducing the amplitudes of low-frequency noise and switching ripple in the outputs. The reasons of limiting cycle oscillation in DPWM, improving method and dither bits are analyzed.The voltage transfer models of Buck, Boost, Buck/Boost converters are built by EF method. The relationships between conversion efficiency, damping time constant and EF are investigated; and the influnces of damping time constant on output voltage dynamic response are analyzed. A theoretical method based on EF(Energy Factor) is proposed for designing DC-DC converter step-by-step.Based on the conclusions drawn form a single sync-Buck DC-DC converter, optimal rules are proposed for source converter design in a cascade DPS system. By analyzing the variations of closed-loop output impedance with input voltage and power and the influence of capacitors'on steady and dynamic performance, filter design principles are proposed for a cascade power system. A cascade DC-DC power is tested by voltage disturbance injection, and the impedance criterion is verified effective for stability analysis.Based on a three-dimension thermal model for operating temperature simulation, several methods are proposed to impove PCB layout and heat revomal of DC-DC module, thermal design solutions are applied to alleviate local overheat and avoid components failure, so the reliability of DC-DC module is improved.The electrial performance indexes and fuctions have all been tested to meet the design targets in the aforementioned multi-output digital DC-DC converter. The digital controller IC has been in tape-out testing, and the DC-DC module has begun to be produced in thick film technology now.