Periodic Sampling Feedback for DC-DC Converter Power Reduction
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Solution Overview
Problem
Conventional DC-DC converters experience high power consumption due to resistive voltage dividers, which is particularly problematic in low-power applications like energy harvesting systems, where the current through the dividers becomes a significant portion of overall current consumption, diminishing efficiency at small load currents.
Innovation Solution
The implementation of a capacitive feedback network that periodically refreshes a voltage divider, reducing average power consumption by sampling and energizing the resistive voltage divider only when necessary, thereby minimizing parasitic leakage current effects on capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a resistive voltage divider is used in the feedback network of a DC-DC converter, then the output voltage can be regulated, but the current consumption increases significantly, reducing efficiency in low-power applications
Solution Approach 1:
The voltage divider is periodically activated rather than continuously powered. A switch periodically connects the voltage divider to the output voltage, allowing capacitors to charge and store the divided voltage. This periodic activation dramatically reduces average current consumption while maintaining voltage regulation through the stored capacitor voltages during the off periods.
Solution Approach 2:
Capacitors are pre-charged to the divided voltage levels before the voltage divider is deactivated. This preliminary charging action stores the necessary voltage information in the capacitors, allowing the feedback network to function without continuous power consumption from the resistive divider.
2Reliability
If the voltage divider is continuously powered to maintain accurate feedback, then voltage regulation is stable, but average current consumption remains high
Solution Approach 1:
Capacitors are introduced as intermediary energy storage elements between the voltage divider and the feedback network. These capacitors act as mediators that store the divided voltage and provide it to the feedback network, eliminating the need for continuous power supply to the voltage divider while maintaining stable feedback voltage.
Solution Approach 2:
The system transitions from continuous operation to periodic operation. The voltage divider is switched on at regular intervals to recharge the capacitors, maintaining stable feedback voltage while dramatically reducing average current consumption. The switching frequency is chosen to maintain stability while minimizing power loss.
3Use of energy by moving object
If high-value resistors are used in the voltage divider to reduce power consumption, then current consumption decreases, but leakage currents on the PCB become significant
Solution Approach 1:
The voltage divider is pre-charged to the correct voltage levels before being deactivated. This preliminary charging action ensures that the capacitors hold the accurate divided voltage, compensating for any subsequent leakage currents that may occur during the off period.
Solution Approach 2:
The system dynamically switches between high-impedance state (voltage divider off) and low-impedance state (voltage divider on) to optimize performance. During the off state, leakage currents are minimized; during the brief on state, the system quickly recharges the capacitors to maintain accurate feedback levels.
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 approach significantly reduces the overall current and power consumption of the DC-DC converter, making it more efficient for nano-power applications by eliminating constant DC current through the voltage divider, thereby enhancing efficiency and stability.
Implementation Method 1
A first sampling switch has a first terminal coupled to a second terminal of the voltage divider and a second terminal coupled to the output, and a second sampling switch has a first terminal coupled to the feedback conductor and a second terminal coupled to an output of the voltage divider. A timing circuit has a first output coupled to a control terminal of the first sampling switch to periodically energize the voltage divider and a second output coupled to a control terminal of the second sampling switch to periodically refresh the first capacitor
Data Source
AI summary
A converter (10) for converting a first DC voltage (VDD) to a second DC voltage (VOUT) includes an output stage (40) for producing the second DC voltage (VOUT) in response to both the first DC voltage (VDD) and an output of an error amplifier (20). A sampling circuit (15) periodically energizes a voltage divider (R0,R1) by periodically coupling a first terminal thereof to the second DC voltage and periodically coupling an output (14) of the energized voltage divider to a feedback conductor (7) to refresh a feed back capacitor (C0) coupled between the second DC voltage and the feedback conductor. The feedback conductor is coupled to an input of the error amplifier.