Pseudo Constant On Time Control Circuit for Step-Down Regulator
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Solution Overview
Problem
Existing step-down regulators with pseudo constant on time (PCOT) control require an output voltage pin, frequency setting pin, and external frequency setting resistor, increasing package size and cost, as the switching frequency varies with output power in constant-on-time (COT) control.
Innovation Solution
A pseudo constant on time control circuit that eliminates the need for an output voltage pin and external frequency setting components by using an on-time generator, feedback control circuit, and logic control circuit to maintain a constant switching frequency, integrated within the step-down regulator chip, reducing chip size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pseudo constant on time control circuit uses output voltage pin and external frequency setting resistor, then frequency setting and on-time control can be achieved, but package size and cost increase
Solution Approach 1:
The patent extracts the frequency setting function from external components (output voltage pin and external resistor) and integrates it into the chip's internal pseudo constant on time control circuit. The on-time generator now receives only a switching signal and generates the on-time signal internally based on the feedback signal, eliminating the need for external frequency setting components and reducing package size.
Solution Approach 2:
The patent merges the frequency setting function and on-time control function into the integrated pseudo constant on time control circuit on the chip. The on-time generator, feedback control circuit, and logic control circuit work together as an integrated unit that automatically maintains constant switching frequency without requiring external components, thus reducing both package size and cost.
2Measurement precision
If pseudo constant on time control circuit uses output voltage pin and frequency setting pin, then on-time proportionality and frequency control are achieved, but device complexity increases
Solution Approach 1:
The patent implements self-service by enabling the on-time generator to automatically generate the on-time signal proportional to Vout/Vin based on the feedback signal, without requiring external voltage pins or frequency setting pins. The logic control circuit internally adjusts the on-time to maintain constant switching frequency, making the circuit self-sufficient and reducing device complexity.
Solution Approach 2:
The integrated pseudo constant on time control circuit performs multiple functions using a single feedback signal input: it generates the on-time signal, maintains constant switching frequency, and regulates output voltage. This multi-functional design eliminates the need for separate output voltage pin and frequency setting pin, reducing device complexity while maintaining measurement precision.
Data Source
AI summary
A step-down regulator comprising a pseudo constant on time control circuit is disclosed, comprising an on-time generator configured to receive a switching signal provided by the step-down regulator and a control signal provided by the pseudo constant on time control circuit, and generates an on-time signal; a feedback control circuit configured to receive a feedback signal representative of the output voltage of the step-down regulator and generate an output signal; and a logic control circuit coupled to the on-time generator and the feedback control circuit to receive the on-time signal and the output signal and generating the control signal, and a power stage configured to receive an input voltage and the control signal and generate the switching signal.