Switching Power Supply Control Circuit for Load Transient Response
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Solution Overview
Problem
Existing switching power-supply devices face challenges in rapidly responding to sudden load changes, leading to output voltage drops that can result in abnormal operations, necessitating large and costly output capacitors to prevent these drops.
Innovation Solution
A control circuit that includes a first A/D converter, a control signal generation unit, a regeneration completion sensing unit, and a sampling clock generation unit, which samples and converts the output voltage multiple times during a switching cycle using both a first and second sampling clock, allowing for timely adjustments in switching control to minimize voltage drops without requiring large capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the output voltage is sampled only once during a switching cycle, then the device complexity is reduced, but the response time to sudden load changes increases causing output voltage drops
Solution Approach 1:
The patent implements periodic sampling of the output voltage at multiple time points within each switching cycle. The sampling unit samples the output voltage at a first time point during the switching operation and at a second time point during the regeneration period, creating multiple periodic measurement opportunities per cycle. This allows the control system to detect voltage changes more rapidly in response to load transitions while maintaining a structured, predictable sampling rhythm that doesn't overly complicate the device architecture.
Solution Approach 2:
The patent performs voltage sampling at a first time point during the switching operation before the regeneration period begins. This preliminary sampling allows the control system to detect voltage drops caused by sudden load changes earlier in the cycle, enabling faster corrective action. By anticipating potential voltage issues before the regeneration phase completes, the system can respond more quickly than waiting for end-of-cycle sampling.
2Reliability
If a large output capacitor is used to prevent output voltage drops, then the reliability is improved, but the device size and cost increase
Solution Approach 1:
The patent implements a feedback control mechanism where the sampling unit continuously monitors the output voltage at multiple time points during each switching cycle. The control unit compares the sampled voltage values against reference levels and adjusts the switching duty ratio in real-time to maintain voltage stability. This active feedback control allows the system to maintain reliable output voltage without requiring oversized capacitors, as the control system dynamically compensates for voltage fluctuations caused by load changes.
Solution Approach 2:
The patent replaces the passive mechanical approach of using large output capacitors to physically store energy and suppress voltage drops with an active electronic control approach. Instead of relying on the physical size of capacitive elements, the system uses digital or analog control circuits to sense voltage changes and dynamically adjust switching parameters. This substitution of passive energy storage with active control logic reduces the required capacitor size while maintaining voltage stability and reliability.
3Speed
If multiple sampling points are used during a switching cycle, then the response time to load changes is improved, but the device complexity increases
Solution Approach 1:
The patent combines the sampling function with the existing switching control architecture. The sampling unit is integrated into the switching control circuitry, sharing common components such as the voltage divider network and control logic. By merging the sampling function with the existing control structure rather than adding completely separate sampling hardware, the patent achieves multiple sampling points per cycle while minimizing the increase in overall device complexity. The same control unit that manages switching also processes sampling data and generates control signals.
Data Source
AI summary
A control circuit of a switching power-supply device that converts a first DC voltage supplied from an input power source to a second DC voltage, includes: a first A/D converter that converts the second DC voltage into a first digital value, in response to a sampling clock depending on a first sampling clock and a second sampling clock; a control signal generation unit that generates a control signal for controlling on-and-off of the switching element based on of a difference between the first digital value and a target value; a regeneration completion sensing unit that senses completion of regeneration of the inductor and outputs a regeneration completion signal; and a sampling clock generation unit that: generates the first sampling clock, in response to the control signal to turn on the switching element, and generates the second sampling clock, in response to the regeneration completion signal.