DC/DC Converter ON-Time Control for Stable Switching Frequency
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Solution Overview
Problem
Existing DC/DC converters face challenges in maintaining constant ON-time control with reduced variations in switching frequency, particularly when operating conditions deviate from a steady state, such as during startup or fault conditions.
Innovation Solution
A control circuit for DC/DC converters incorporating a driver circuit, monitoring circuit, and ON-timer circuit that adjusts the reference voltage based on the operational state (steady or abnormal) to maintain constant ON-time control by using either a variable or fixed reference voltage depending on the converter's state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If constant ON-time control is used in DC/DC converter, then switching frequency can be maintained at high frequency, but switching frequency variations occur when operating conditions deviate from steady state
Solution Approach 1:
The patent applies dynamics by making the reference voltage adjustable based on operating conditions. The control circuit switches between a fixed reference voltage (for steady state) and an adjustable reference voltage (for transient states), allowing the system to adapt its characteristics dynamically to maintain stable switching frequency across different operating conditions
Solution Approach 2:
The patent changes the reference voltage parameter based on the operational state of the DC/DC converter. By detecting whether the converter is in steady state or transient state and adjusting the reference voltage accordingly, the system maintains constant ON-time control with reduced switching frequency variations
2Stability of the object's composition
If conditions for terminating ON interval are changed to prevent switching frequency variations, then switching frequency stability improves, but control complexity increases
Solution Approach 1:
The patent uses feedback by detecting the operational state (steady state or transient state) of the DC/DC converter and adjusting the reference voltage accordingly. The control circuit monitors operating conditions and automatically switches between different reference voltage modes, providing closed-loop control that maintains switching frequency stability without requiring complex manual intervention
Solution Approach 2:
The control circuit is designed to perform multiple functions: it operates in constant ON-time mode during steady state and switches to adjustable reference voltage mode during transient states. This multi-functional approach allows a single control circuit to handle both normal operation and abnormal conditions, reducing the need for separate control mechanisms
Data Source
AI summary
A driver circuit is configured to operate the switching elements using constant ON-time control. A monitoring circuit generates a first control signal indicating whether the DC/DC converter is in a steady state or in an abnormal state. An ON-timer circuit generates a second control signal based on the first control signal, and send the second control signal to the driver circuit, the second control signal provided for terminating a partial interval of each switching cycle of the switching elements, the partial interval being defined such that energy is stored to the inductor in the partial interval. The ON-timer circuit generates the control signal using a first reference voltage varying according to a duty ratio of the switching elements, when the DC/DC converter is in the steady state. The ON-timer circuit generates the control signal using a second reference voltage being fixed, when the DC/DC converter is in the abnormal state.