Synchronous Rectifier Startup Delay for DC-DC Converter Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing DC-DC converters with pre-bias circuits are complex, unreliable, and increase costs and inefficiency due to the need for additional components like MOSFETs to prevent energy recirculation damage during startup and shutdown, especially when multiple converters are connected in parallel with inconsistent power-on and power-off times.
Innovation Solution
A switch-mode DC-DC power converter design that includes a transformer with a primary and secondary winding, a primary switch, and a synchronous rectifier, where the synchronous rectifier's switching operation is controlled by disabling it for a defined time delay upon startup and enabling it after the delay, using a control circuit or pre-bias circuit with RC components to manage energy recirculation without additional power elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a MOSFET hot-plug circuit is added to prevent energy recirculation damage, then component reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent removes the external MOSFET hot-plug circuit from the system and extracts its protective function into the synchronous rectifier's inherent body diode. By utilizing the body diode's natural reverse-blocking capability during startup and shutdown transitions, the design eliminates the need for additional protective components while maintaining component reliability.
Solution Approach 2:
The synchronous rectifier's body diode is made to serve dual functions: its primary rectification function and its secondary function as a protective element during startup and shutdown. This multi-functionality approach allows the same component to provide both power conversion and protection, reducing overall circuit complexity.
2Reliability
If a MOSFET hot-plug circuit is added to prevent energy recirculation, then component reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent eliminates the need for additional MOSFET components by extracting the protective function from a separate hot-plug circuit and integrating it into the synchronous rectifier's existing structure. This reduction in component count directly lowers manufacturing costs while maintaining the protective function.
Solution Approach 2:
The design utilizes the body diode's inherent protective capability during transient states (startup and shutdown) without requiring expensive additional components. The body diode provides adequate protection during these brief transition periods, eliminating the need for costly hot-plug circuits.
3Reliability
If a MOSFET hot-plug circuit is added to prevent energy recirculation, then component reliability is improved, but conversion efficiency decreases
Solution Approach 1:
By removing the external MOSFET hot-plug circuit and utilizing the synchronous rectifier's body diode instead, the patent eliminates the additional conduction losses and switching losses that would be introduced by another active component in the current path, thereby improving overall conversion efficiency.
4Reliability
If pre-bias circuits are used to prevent voltage drops during startup, then component reliability is improved, but device complexity increases
Solution Approach 1:
The patent removes the need for separate pre-bias circuits by extracting the voltage stabilization function into the controlled startup sequence of the synchronous rectifier. The body diode's natural characteristics and the timing control work together to prevent voltage drops without requiring additional pre-bias components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design simplifies the pre-bias circuit, reduces costs, improves efficiency, and allows for parallel startup of multiple converters without damaging components due to energy recirculation, while maintaining a stable output voltage.
Implementation Method 1
a transformer coupled between the input and output terminals. The transformer includes at least one primary winding and at least one secondary winding
Implementation Method 2
a synchronous rectifier coupled to control current through the at least one secondary winding
Data Source
AI summary
A switch-mode DC-DC power converter includes one or more input terminals for receiving an input voltage from a voltage source, one or more output terminals for supplying an output voltage to a load, and a transformer coupled between the input and output terminals. The transformer includes at least one primary winding and at least one secondary winding. The converter also includes a primary switch coupled to control current through the at least one primary winding, a synchronous rectifier coupled to control current through the at least one secondary winding, and means for controlling switching operation of the synchronous rectifier by disabling switching of the synchronous rectifier for a defined time delay in response to receiving an input signal indicative of a startup of the DC-DC power converter, and enabling switching of the synchronous rectifier after the defined time delay has elapsed.