Power Supply Controller Artificial Hysteresis Circuit
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Solution Overview
Problem
Hysteretic power supply controllers face challenges in maintaining duty cycle stability and reducing audible noise due to high or low equivalent series resistance (ESR) capacitors, leading to ripple voltage issues and inaccurate output voltage detection.
Innovation Solution
A power supply controller that includes an oscillator circuit, a pulse circuit, and a current source to form a modulated feedback signal with a decreasing value, which helps regulate the output voltage and reduce pulse skipping and audible noise, operating with a range of capacitors including both low and high ESR capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor with high equivalent series resistance (ESR) is used in a hysteretic power supply controller, then the switching frequency and duty cycle are determined by a sequential switching circuit with two states, but the output voltage has high ripple voltage which causes improper operation or damage to the load
Solution Approach 1:
The patent introduces an artificial hysteresis circuit as an intermediary component between the feedback amplifier and the power switch control. This circuit generates a hysteresis voltage that modifies the feedback signal, creating an effective hysteresis effect without relying on the high ESR of the output capacitor. The intermediary circuit decouples the duty cycle stability function from the capacitor's ESR property, allowing use of low ESR capacitors while maintaining stable operation.
2Object-affected harmful factors
If a capacitor with low equivalent series resistance (ESR) is used, then the ripple on the output voltage is reduced, but the low ripple voltage causes inaccurate detection of the output voltage value which results in irregular duty cycle and pulse skipping or cycle skipping
Solution Approach 1:
The artificial hysteresis circuit acts as a mediator that adds a controlled voltage offset to the feedback signal. This offset creates sufficient voltage difference between switching states, enabling reliable detection even when the actual output voltage ripple is minimal. The intermediary circuit compensates for the lack of natural hysteresis in low ESR capacitor applications, ensuring regular duty cycle operation without pulse skipping.
3Productivity
If a hysteresis power supply controller is used with sequential switching circuit with two states, then the switching frequency and duty cycle are determined, but pulse skipping or cycle skipping occurs which causes undesirable audible noise
Solution Approach 1:
The artificial hysteresis circuit serves as an intermediary that ensures continuous and regular switching transitions by providing a stable voltage reference with inherent hysteresis. This prevents the feedback amplifier from entering undefined states that cause pulse skipping or cycle skipping. By mediating the feedback signal, the circuit eliminates irregular switching behavior that generates audible noise, while maintaining precise switching frequency and duty cycle control.
Data Source
AI summary
In one embodiment, a power supply controller forms a compensation current modulates a value of the feedback signal responsively to a value of a timing control signal used to form a clock signal.