Cascaded DC-DC Converters for Battery Pulse Load Ripple Isolation
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Solution Overview
Problem
Battery-powered electronic devices face issues with voltage transients caused by pulsed loads, leading to undesirable effects such as audible noise and disruption to other subsystems, which existing power system designs struggle to mitigate effectively.
Innovation Solution
The implementation of a cascaded DC-DC converter system, where a second bidirectional DC-DC converter with higher bandwidth isolates loads from transients by supplying transient energy requirements, while a first DC-DC converter handles average power needs, significantly reducing voltage ripple on the power bus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single DC-DC converter is used to power loads, then the device complexity is reduced, but voltage transients from pulsed loads cannot be effectively isolated, causing audible noise and disruption to other subsystems
Solution Approach 1:
The power conversion system is segmented into two distinct DC-DC converters: a first converter connected to the battery and a second converter connected to the pulsed load. This segmentation allows each converter to specialize - the first converter handles average power delivery with lower bandwidth to minimize output ripple, while the second converter handles transient current demands with higher bandwidth, thereby isolating voltage transients from affecting other subsystems
Solution Approach 2:
The first DC-DC converter acts as an intermediary between the battery and the second converter. By placing this converter in between, the system mediates the interaction between the battery and pulsed loads, preventing direct coupling of transient currents from the battery and thereby reducing voltage ripple and audible noise while maintaining stable power delivery
2Volume of moving object
If ceramic capacitors are used for energy storage in small portable devices, then the device size is reduced, but mechanical resonance occurs at audio frequencies causing audible noise
Solution Approach 1:
The system employs dynamic control with two converters operating at different bandwidths. The second converter operates at high bandwidth to rapidly respond to load transient demands, dynamically supplying or absorbing current as needed. This dynamic response prevents large current changes from reaching the ceramic capacitors, thereby avoiding excitation of their mechanical resonance at audio frequencies while maintaining compact device size
3Device complexity
If voltage transients are allowed to propagate on the power bus, then the power delivery is simplified, but complex and expensive regulators are required to protect other loads
Solution Approach 1:
The second DC-DC converter extracts and handles the transient current demands locally at the load side. By taking out the transient management function from the main power bus and placing it at the second converter, the system prevents voltage transients from propagating along the power bus to affect other subsystems, thereby protecting loads without requiring additional complex regulators
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 configuration effectively minimizes voltage transients on the power bus, reducing audible noise and the need for complex regulators, thereby enhancing the stability and efficiency of power delivery in battery-powered devices.
Implementation Method 1
a second DC-DC converter cascaded with the first DC-DC converter... The second DC-DC converter may have a higher bandwidth than the first DC-DC converter so as to isolate the one or more loads from transients
Implementation Method 2
The second DC-DC converter may be a bidirectional converter having first terminals coupled to the output of the first DC-DC converter and second terminals coupled to an energy storage capacitor
Data Source
AI summary
A battery powered electronic device can include a battery to power one or more loads, a first DC-DC converter having an input coupled to the battery and an output, and a second DC-DC converter cascaded with the first DC-DC converter and coupled to a second load subject to pulsed operation. The first and second converters may be configured so as to isolate the one or more loads from transients associated with the pulsed operation of the second load. The second converter may have an input coupled to the output of the first converter and an output coupled to the second load. Alternatively, the second converter may be a bidirectional converter having first terminals coupled to the output of the first converter and second terminals coupled to an energy storage device.