DC-DC Converter Circuit Reducing Switch Voltage Stress
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Solution Overview
Problem
Existing DC-DC converter designs that generate split rail supplies from a single input voltage using a single inductor face challenges in integrating with larger signal processing functions due to excessive voltage stress on switches, impacting reliability and cost.
Innovation Solution
A DC-DC converter circuit with a switching network and controller that implements alternating charging cycles using a single inductor, ensuring that no switch experiences voltages higher than the input voltage, thereby reducing stress and allowing integration with larger signal processing functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a buck-flyback converter design is used to generate split rail supply from a single supply using a single inductor, then the number of external components is reduced, but the voltage stress on switches becomes excessively high
Solution Approach 1:
The patent segments the voltage conversion function into two separate converters: a first DC-DC converter generates an intermediate voltage from the input supply, and a second DC-DC converter generates the final output voltage from the intermediate voltage. This segmentation allows each converter to operate at lower voltage stress levels, improving reliability while maintaining component integration.
Solution Approach 2:
The patent introduces an intermediate voltage as a mediator between the input supply and the final output. The first DC-DC converter creates this intermediate voltage, which then serves as the input for the second DC-DC converter. This intermediary approach distributes the voltage conversion stress across two stages rather than concentrating it in a single high-stress converter.
2Device complexity
If a buck-flyback converter design is used to generate split rail supply from a single supply using a single inductor, then component count is minimized, but circuit reliability and process selection are impacted
Solution Approach 1:
The patent divides the voltage conversion function into two separate DC-DC converter circuits, each operating at manageable voltage levels. This segmentation enables standard integrated circuit fabrication processes to be used without requiring specialized high-voltage process steps, improving ease of manufacture and integration with signal processing functions.
Solution Approach 2:
The patent changes the operating parameters of the converter system by introducing an intermediate voltage stage. This parameter change allows each converter stage to operate within standard voltage ranges compatible with conventional IC manufacturing processes, avoiding the need for specialized high-voltage fabrication.
3Reliability
If alternating charging cycles are implemented using a single inductor, then switch voltage stress is reduced, but the complexity of the switching network increases
Solution Approach 1:
The patent segments the switching function into two separate DC-DC converter circuits, each with its own switching network. The first converter's switching network manages switching between input and intermediate voltage, while the second converter's switching network manages switching between intermediate and output voltage. This segmentation distributes the switching complexity across two manageable units rather than requiring a single complex high-voltage switching network.
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
The solution enables efficient generation of split rail supplies with reduced switch stress, improving reliability and cost-effectiveness by maintaining output voltages within predetermined bounds while minimizing the number of external components.
Implementation Method 1
an inductor; a switching network comprising a plurality of switches for: (a) in a first type of charging cycle (i) connecting the inductor in a first phase between the input terminal and the first output terminal to build current in the inductor and (ii) connecting the inductor in a second phase across the first capacitor to transfer energy from the inductor to the first capacitor
Implementation Method 2
a first capacitor connected between the first output terminal and the common terminal; a second capacitor connected between the second output terminal and the common terminal
Data Source
AI summary
Electrical power from an input voltage supply is converted to first and second output voltages of opposite polarities using a single inductor (L) and only four principal switches (S1, S2, S4, S6). In contrast to known circuits, none of the switches is exposed to voltages greater than the input voltage (V1). In a first type of charging cycle (FIG. 5(a)-(c)), the first output voltage (V2+) is obtained from the input voltage supply through the inductor. In a second type of charging cycle (FIG. 5 (d)-(f)), the second output voltage (V2−) is obtained from the first output voltage via the intermediate step of storing energy in the same inductor as is used in the first type of charging cycle. Auxiliary switches (S7a, S7b) can be operated in wait states between cycles of the first and second type.