Motor Drive Circuit Reverse Current Inhibition
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Solution Overview
Problem
Existing motor drive circuits face inefficiencies in heat generation and power consumption due to reverse currents and regenerative currents, particularly when synchronous rectification is performed, leading to instability in motor rotation speed and increased power consumption.
Innovation Solution
A motor drive circuit with a synchronous rectification control circuit that includes a detection circuit to identify reverse currents, a disable circuit to inhibit synchronous rectification during specific time periods, and inhibit circuits to manage PWM signal duty periods and frequencies, ensuring efficient synchronous rectification and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If synchronous rectification is performed by turning on the off-state source-side transistor when the sink-side transistor is turned off according to PWM signal, then power consumption is reduced and efficiency is improved, but reverse currents occur causing heat generation and instability in motor rotation speed
Solution Approach 1:
The control circuit detects reverse current occurrence in advance and preemptively inhibits synchronous rectification by controlling the source-side transistor to remain in the off-state during conditions that would generate reverse current, thereby preventing the harmful effect before it occurs
Solution Approach 2:
The control circuit continuously monitors current flow direction and magnitude, using this feedback information to dynamically adjust the synchronous rectification control strategy, enabling the system to adapt to changing operating conditions and maintain stable motor rotation speed
2Loss of energy
If synchronous rectification is performed to reduce heat generation, then energy efficiency is improved, but reverse currents cause additional heat generation that counteracts the benefit
Solution Approach 1:
The control circuit identifies operating conditions where synchronous rectification would generate harmful reverse currents and heat, then converts this knowledge into a beneficial control strategy by selectively disabling synchronous rectification only when necessary, thereby eliminating the harmful heat generation while preserving the energy efficiency benefits during safe operating conditions
3Productivity
If the source-side transistor is turned on during synchronous rectification to improve efficiency, then power consumption is reduced, but reverse currents occur when PWM on-duty period is short causing instability
Solution Approach 1:
The control circuit dynamically adjusts the synchronous rectification strategy based on real-time PWM on-duty period conditions, transitioning between enabling and disabling synchronous rectification as operating conditions change, thereby maintaining both efficiency and stability across varying operating scenarios
Data Source
AI summary
A motor-drive circuit includes a detection circuit to detect a reverse current to flow in a direction from a first sink-side transistor to a second source-side transistor or in a direction from a second sink-side transistor to a first source-side transistor, a disable circuit to disable a detection output of the detection circuit during a predetermined time period from a start of detection of the reverse current performed by the detection circuit, a first inhibit circuit to inhibit synchronous rectification according to a detection output of the detection circuit when the predetermined time period has elapsed from a start of detection of the reverse current performed by the detection circuit, and a second inhibit circuit.