PWM Startup Circuit for Power Converters With Pre-Biased Output
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Solution Overview
Problem
Power converters face challenges in starting up when connected to a pre-biased output voltage, as conventional PWM methods cannot accommodate negative current flow during discontinuous conduction mode, leading to potential damage and inefficiency.
Innovation Solution
The implementation of a power converter system that includes an error amplifier with a feedback network and a differential difference amplifier, a multiplexer, and delay cells controlled by a trigger, allowing the system to manage the pulse width modulation based on a reference voltage and prevent negative current flow by disabling the converter until the output voltage reaches a safe level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PWM methods are used to start power converters, then the converter can be controlled during normal operation, but the converter cannot accommodate negative current flow during discontinuous conduction mode at startup
Solution Approach 1:
The patent applies preliminary action by implementing a soft-start mechanism that gradually enables the power converter. A startup controller progressively adjusts the PWM duty cycle from zero to the target value, allowing the converter to accommodate pre-biased voltage conditions before full operation begins. This prevents negative current flow during discontinuous conduction mode by controlling the ramp-up phase.
Solution Approach 2:
The patent applies dynamics by making the PWM controller adaptive during startup. The controller dynamically adjusts the duty cycle based on the pre-biased voltage level detected at the output. This dynamic adaptation allows the converter to handle varying startup conditions including negative current flow, transitioning from a static conventional PWM approach to a dynamic controlled startup sequence.
2Loss of time
If the power converter starts up with pre-biased output voltage, then the converter can begin operation faster, but negative current flow may occur causing potential damage and inefficiency
Solution Approach 1:
The patent applies preliminary anti-action by implementing protective control logic that anticipates and prevents negative current flow during startup. The controller detects pre-biased voltage conditions before full power application and adjusts the PWM signal accordingly. This preliminary protective measure counteracts the potential harmful effect of negative current flow while still enabling relatively fast startup through controlled duty cycle adjustment.
Solution Approach 2:
The patent applies feedback by implementing a startup controller that monitors the output voltage and current conditions during the startup phase. The controller uses this feedback information to dynamically adjust the PWM duty cycle, preventing negative current flow while maintaining efficient startup timing. The feedback mechanism ensures safe operation by continuously adapting the control signal based on actual converter state.
3Device complexity
If conventional PWM control is used, then the control circuit is simple, but it cannot prevent negative current flow during discontinuous conduction mode
Solution Approach 1:
The patent introduces an intermediary startup controller that sits between the conventional PWM control and the power converter switches. This intermediary component adds minimal complexity by implementing soft-start logic and pre-bias detection, while providing essential protection against negative current flow. The intermediary layer maintains compatibility with existing PWM control structures while adding the necessary protective functionality.
Data Source
AI summary
Methods, apparatus, systems and articles of manufacture are disclosed to start converter into a pre-biased voltage. The disclosed methods, apparatus, systems and articles of manufacture provide an apparatus comprising: an error amplifier including a feedback network and a differential difference amplifier (DDA), the DDA coupled to a power converter, a voltage generator, and the feedback network coupled to the third input of the DDA, the fourth input of the DDA, and the output of the DDA; a multiplexer coupled to the voltage generator, the second input of the DDA, and the first input of the DDA; a first switch coupled in parallel to the feedback network; a second switch coupled to a delay cell and an oscillator; and a trigger including an output, the trigger coupled to the voltage generator, the power converter, and the output of the trigger coupled to the multiplexer, first switch, and the second switch.