Secondary-Side SMPS Controller for Selectable CV-CC Output

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional switch mode power supplies with primary-side control suffer from poor dynamic response and instability due to coupled analog signals, requiring complex load compensation circuits and being susceptible to noise, especially when providing selectable output voltages and currents.

Innovation Solution

A switch mode power supply with a secondary-side controller that monitors output voltage and current, selecting appropriate reference signals to control the power switch on the primary side, allowing for constant voltage and constant current control without relying on coupling between sides, and operating in either discontinuous or continuous current modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If primary-side control is used with coupled analog signals, then the power supply can provide selectable output voltages, but the dynamic response becomes poor and instability increases

Engineering Contradiction:

Improveselectable output voltagesVSAvoidstability and dynamic response

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent inverts the conventional control architecture by moving the control function from the primary side to the secondary side. The secondary-side controller directly monitors output parameters and controls the primary-side power switch, eliminating the need for analog signal coupling and load compensation circuits. This inversion resolves the contradiction by providing both selectable output voltages and improved stability with better dynamic response.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If load compensation circuitry is added to provide different output voltages, then the power supply can be tuned for fine voltage control, but the circuit becomes complicated and more susceptible to noise

Engineering Contradiction:

Improvefine voltage tuningVSAvoidcircuit complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts the control function from the primary side and places it on the secondary side, eliminating the need for load compensation circuitry. The secondary-side controller directly monitors output voltage and current, and controls the primary-side power switch accordingly. This extraction removes the complicated compensation circuits while maintaining fine voltage tuning capability through digital control.

Inventive Principle:

Principle #2Taking out (Extraction)

3Adaptability or versatility

If analog signals are coupled between primary and secondary sides, then the power supply can provide selectable outputs, but the system becomes susceptible to instability and noise

Engineering Contradiction:

Improveselectable outputsVSAvoidnoise and instability

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical/analog signal coupling system with a digital control system. The secondary-side controller uses digital signal processing to monitor output parameters and generate control signals for the primary-side power switch. This substitution eliminates analog signal coupling and its associated noise and instability problems while maintaining selectable output functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If secondary-side control is implemented, then stability and noise are reduced, but the coupling between primary and secondary sides must be managed

Engineering Contradiction:

Improvestability and noise reductionVSAvoidcontrol architecture

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses the transformer's magnetic coupling as an intermediary to transfer power and control signals between primary and secondary sides. The secondary-side controller monitors output parameters and uses the transformer coupling to communicate control information to the primary side, managing the interaction between sides while maintaining stability and reducing noise.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9893626B2Switching mode power supply with selectable constant-voltage constant-current control

Publication Date: 2018.02.13 BCD (SHANGHAI) MICRO ELECTRONICS LTD

AI summary

A switch mode power supply (SMPS) has a primary-side controller configured to control a power switch for turning on and turning off a current flow in the primary winding. A secondary-side controller is coupled to the secondary winding for providing constant voltage (CV) and constant current (CC) control of the SMPS. The secondary-side controller is configured to receive an output selection signal and, based on the output selection signal, select a voltage reference signal from a plurality of voltage reference signals and select a current reference signal from a plurality of current reference signals. The secondary-side controller is configured to monitor an output voltage and an output current of the SMPS, and is configured to provide a turn-on signal to the primary-side controller for turning on the power switch upon determining that the output voltage is below the selected voltage reference signal and the output current is below the selected current reference signal.