Boost DC/DC Control Circuit With Adaptive ON-Time Frequency Stabilization
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Solution Overview
Problem
Existing DC/DC converters using the ripple control method with bottom detection and constant on time (COT) face challenges in stabilizing the switching frequency and reducing output voltage during overcurrent states.
Innovation Solution
A control circuit for a boost DC/DC converter that includes a main comparator, a timer circuit, an overcurrent detection circuit, and a turn-on inhibition circuit, which together stabilize the switching frequency by adaptively changing the ON time based on input and output voltages, and reduce output voltage during overcurrent states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If constant on time (COT) control is used, then response speed is high and power consumption is reduced, but switching frequency greatly fluctuates
Solution Approach 1:
The patent applies dynamics by making the on-time variable rather than constant. The on-time is dynamically adjusted based on the ratio of input voltage to output voltage, allowing the system to maintain high response speed while stabilizing switching frequency. The control circuit continuously adapts the on-time parameter to changing operating conditions.
Solution Approach 2:
The patent changes the parameter of on-time from a fixed constant value to a variable value that depends on the voltage ratio. By modifying the on-time parameter dynamically according to Vin/Vout conditions, the system resolves the contradiction between fast response and frequency stability.
2Device complexity
If fixed ON time is applied, then design is simple and transient response is excellent, but switching frequency fluctuates significantly
Solution Approach 1:
The patent introduces dynamic adjustment of on-time based on voltage ratio sensing, adding minimal complexity to the control circuit while achieving frequency stabilization. The dynamic parameter adjustment is implemented through simple comparative operations and timing control.
3Use of energy by moving object
If ripple control with bottom detection is used, then power consumption is reduced, but output voltage cannot be reduced during overcurrent states
Solution Approach 1:
The patent implements feedback by detecting the voltage ratio between input and output and using this information to control the on-time. This feedback mechanism enables the system to respond to overcurrent conditions by adjusting the on-time, thereby reducing output voltage when needed while maintaining low power consumption operation.
Data Source
AI summary
A main comparator compares a feedback voltage VFB corresponding to an output voltage VOUT of a DC/DC converter with a reference voltage VREF and asserts a turn-on signal when the feedback voltage VFB falls below the reference voltage VREF. A timer circuit generates a turn-off signal S2 that transitions in level after an ON time TON proportional to (VOUT−VIN/VOUT has elapsed from assertion of the turn-on signal.