DC/DC Converter Capacitor Switching for Low-Input Voltage Hold-Up
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Solution Overview
Problem
Conventional step-down DC/DC converters become unstable when the input voltage drops close to the output voltage, leading to insufficient power supply to connected devices, especially during power outages, due to the requirement for a capacitor voltage higher than the input voltage for stable operation.
Innovation Solution
The DC/DC converter configuration is modified by placing a capacitor between the input and output voltages, allowing the capacitor to supply power even when its voltage is lower than the input voltage by adding its voltage to the output voltage, and using a switching unit to connect the capacitor's electrode to either ground or the output node based on input voltage levels, ensuring efficient energy release during 'dying gasp' periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor is placed between input and ground to maintain input voltage, then the input voltage can be stabilized, but the capacitor voltage must be higher than the output voltage which limits operation when input voltage drops
Solution Approach 1:
The patent applies dynamics by making the capacitor configuration adaptive rather than static. The switching unit dynamically reconfigures the capacitor connections based on operating conditions: during normal operation the capacitor is connected between input and ground to stabilize input voltage, while during low input voltage conditions it is reconfigured between output nodes to boost output voltage. This dynamic reconfiguration allows the system to maintain reliability across a wider range of input voltage conditions.
Solution Approach 2:
The patent segments the capacitor functionality into distinct operational modes. Instead of using a single fixed capacitor configuration, the system divides the capacitor's role into: (1) input voltage stabilization mode during normal operation, and (2) output voltage boosting mode during low input voltage conditions. This segmentation is achieved through the switching unit that separates and reconfigures the capacitor connections based on operational needs, resolving the contradiction between stability and adaptability.
2Reliability
If the input voltage is kept sufficiently higher than the output voltage for stable operation, then the output voltage remains stable, but the converter cannot supply power when input voltage drops close to output voltage
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor during normal operation when input voltage is sufficient. The capacitor stores energy in advance during periods when the input voltage is high, so that this stored energy can be utilized during power outages or when input voltage drops. The switching unit enables the capacitor to be charged from the input during normal operation and then reconfigured to discharge to the output during low voltage conditions, extending the duration of power supply.
Solution Approach 2:
The patent changes the electrical parameters of the system by reconfiguring the capacitor connections. During normal operation, the capacitor is connected to the input side with voltage VIN. During low voltage or power outage conditions, the switching unit reconfigures the capacitor to the output side, changing its voltage reference from VIN to VOUT. This parameter change allows the stored energy to be released at the appropriate time, extending power supply duration while maintaining output stability.
3Quantity of substance
If a large external capacitor is used to supply energy during dying gasp periods, then energy storage capacity is sufficient, but the capacitor becomes bulky and expensive
Solution Approach 1:
The patent applies universality by making the existing input capacitor serve multiple functions. Instead of requiring a separate large energy storage capacitor, the system uses the same capacitor for: (1) input voltage stabilization during normal operation, and (2) energy storage and release during dying gasp periods. The switching unit enables this multi-functionality by reconfiguring the capacitor's connection based on operational mode, thereby achieving sufficient energy storage capacity without the need for additional bulky 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 configuration ensures stable output voltage supply to connected devices, such as CPUs, even when the input voltage drops, by efficiently utilizing the stored energy in the capacitor, thereby improving power efficiency and extending the supply duration during power failures.
Implementation Method 1
a capacitor GC2, and a switching unit S1. The capacitor GC2 has one electrode connected to the input node NIN and the other electrode connected to the switching unit S1
Implementation Method 2
The switching unit S1 has one input connected to the other electrode of the capacitor GC2, one output connected to ground, and the other output connected to the output node NOUT
Data Source
Figure 1~2
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Figure 4
AI summary
A DC/DC converter (100) includes a voltage conversion unit (20) having an input node to receive an input voltage and an output node to output an output voltage and configured to convert the input voltage to the output voltage to output the output voltage from the output node, and an electrical energy storage unit (GC2) including a first electrode to be a positive electrode and a second electrode to be a negative electrode. The first electrode is electrically connected to the input node of the voltage conversion converter. The DC/DC converter (100) further includes a switching unit (S1) configured to electrically connect the second electrode of the electrical energy storage unit to one of ground and the output node of the voltage conversion unit alternatively. The switching unit (S1) connects the second electrode of the electrical storage unit (GC2) to the output node when the input voltage is lower than a predetermined voltage.