Switching Converter Over-Current Detection with Extended ON-Time

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Solution Overview

Problem

Existing switching converters face challenges in reliably detecting over-current conditions due to short ON durations of high-side switches, which can lead to damage if not managed promptly.

Innovation Solution

The solution involves extending the ON duration of the high-side switch to a second magnitude to allow for reliable detection of current through the switch, using an over-current management block that includes a current comparator and HS-off-time comparator to determine actual over-current conditions, and taking remedial actions if necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the ON duration of the high-side switch is kept short, then the switching converter operates efficiently and responds quickly to load changes, but the over-current detection becomes unreliable and may miss actual over-current conditions

Engineering Contradiction:

Improveswitching response speedVSAvoidover-current detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system performs preliminary over-current detection during the low period before the high-side switch turns on. By detecting potential over-current conditions in advance using the low-side switch current and timing circuits, the system can prepare remedial actions before the actual current flow occurs during the high-side switch ON period, thus resolving the contradiction between short ON duration and reliable detection

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces intermediary circuits including a timing circuit, current comparator, and over-current management block that mediate between the switch control and load monitoring. These intermediary components enable indirect detection of potential over-current conditions through the low-side switch and timing relationships, allowing reliable over-current management without requiring extended high-side switch ON duration

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the ON duration of the high-side switch is extended to enable reliable current detection, then over-current conditions can be detected accurately, but the switching efficiency decreases and response time increases

Engineering Contradiction:

Improveover-current detection reliabilityVSAvoidswitching converter efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system performs preliminary detection during the low period before the high-side switch activates. By using the timing circuit to detect potential over-current conditions in advance through the low-side switch current characteristics, the system achieves reliable over-current detection without extending the high-side switch ON duration, thus avoiding additional energy losses

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces direct mechanical/current measurement during the high-side switch ON period with an indirect electrical measurement system using the low-side switch and timing circuits. This substitution enables reliable over-current detection through electrical signal processing rather than direct current measurement during the critical ON period, maintaining switching efficiency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If the system continuously monitors current during the high-side switch ON period, then accurate over-current detection is achieved, but the circuit complexity and power consumption increase

Engineering Contradiction:

Improvecurrent monitoring accuracyVSAvoidmonitoring circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses periodic action by monitoring current during the low period when the low-side switch is active, rather than continuously during the high-side switch ON period. The timing circuit enables periodic detection at appropriate intervals in the switching cycle, achieving accurate over-current detection while reducing circuit complexity and power consumption compared to continuous monitoring

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent extracts the current monitoring function from the high-side switch ON period and relocates it to the low period when the low-side switch is active. By separating the detection function from the power switching function, the system achieves accurate monitoring with reduced complexity, as the monitoring circuit only needs to operate during the low period rather than continuously

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS12451798B2Managing over-current condition in a switching converter

Publication Date: 2025.10.21 NINGBO AURA SEMICON CO LTD

AI summary

A switching converter provides an output voltage, and includes a first switch, a gate driver and an over-current management block. The gate driver is operable to drive the first switch with an ON duration of a first magnitude normally to provide the output voltage. The ON duration corresponds to a first phase of each cycle of a sequence of cycles of a periodic clock signal employed in the switching converter. The over-current management block is operable to determine a potential over-current condition when the switch operates with an ON duration of a first magnitude. In response to the determination, the over-current management block is operable to cause the gate driver to increase an ON duration of the first switch to a second magnitude, and examine a magnitude of current through the first switch with ON duration of the second magnitude to determine whether actual over-current condition is present.