Control Circuit Pin Reduction via Bias Capacitor Current Sensing
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Solution Overview
Problem
Conventional switching power supplies require multiple pins for control circuit integration, which complicates chip packaging and increases manufacturing costs due to the need for separate pins for bias power, detection, and current sensing.
Innovation Solution
A control circuit configuration that includes a power supply circuit with a bias capacitor, a detection circuit, a current feedback circuit, and a control signal generator, where the power supply circuit powers the control circuit via a bias capacitor, and the current feedback circuit generates a feedback signal representing the inductor current by detecting voltage differences during the main power switch's off state, allowing for simplified pin configuration by using the power supply pin as both a power source and a current detection point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pins are used for bias power, detection, and current sensing in control circuit integration, then the control circuit can function properly with dedicated signal paths, but the chip packaging becomes complicated and manufacturing costs increase
Solution Approach 1:
The power supply pin is designed to serve dual purposes: providing bias power to the control circuit and serving as a current detection point. The detection circuit utilizes the voltage at this same pin during the main power switch off-state to sense inductor current, eliminating the need for separate detection and sensing pins while maintaining proper control circuit functionality
Solution Approach 2:
The patent combines the power supply function and current detection function into a single pin configuration. By using the bias capacitor connected to the power supply pin and utilizing the voltage at this pin during switch off-state, the patent merges what would traditionally require separate pins into one integrated function, simplifying chip packaging
2Measurement precision
If multiple pins are used for control circuit integration, then proper signal detection and control can be achieved, but manufacturing costs increase due to more complex packaging requirements
Solution Approach 1:
The power supply pin performs multiple functions including power delivery and current sensing. The detection circuit measures the voltage at this pin during the main power switch off-state, where the voltage reflects the inductor current through the bias capacitor relationship, achieving accurate current detection without requiring additional dedicated sensing pins
Solution Approach 2:
The power supply pin serves itself by providing both power and detection functionality. The voltage at the power supply pin during off-state naturally contains the information needed for current detection, eliminating the need for separate detection infrastructure and reducing manufacturing complexity
Data Source
AI summary
A control circuit can include: a power supply circuit having a bias capacitor coupled between a power terminal and a common node, where the power supply circuit supplies power to the control circuit via the bias capacitor; a detection circuit coupled between the common node and a current output terminal of a main power switch of a power stage circuit, to detect current flowing through the main power switch; a current feedback circuit that generates a feedback signal according to a difference value between a sense value obtained from a voltage at the power terminal during an off state of the main power switch and a present voltage at the power terminal, where the feedback signal represents an inductor current of the power stage circuit; and a control signal generator that generates a control signal according to the feedback signal to control the main power switch.