Peak Current Mode Control with Dual-DAC Slope Compensation
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Solution Overview
Problem
Existing peak current mode (PCM) control systems face challenges with high-resolution and high-speed Digital to Analogue Converters (DACs), which are expensive and difficult to integrate, leading to layout and digital isolation issues, especially when digital control processing is separate from analogue circuit elements.
Innovation Solution
The implementation of a PCM controller using two DACs to generate analogue control and slope compensation voltages, which are integrated and subtracted to produce an analogue output voltage, allowing for a comparator to compare with an analogue current sense signal, eliminating the need for high-speed quantization and reducing the complexity of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution fast DAC is used to provide accurate control voltage, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The control voltage generation is segmented into two separate DACs: one for the control component and one for the slope compensation component. This segmentation allows each DAC to operate at lower resolution and speed requirements compared to a single high-performance DAC, thereby reducing overall device complexity while maintaining control precision through the combining of the two components in the differential integrator.
Solution Approach 2:
Instead of requiring a single DAC to provide the complete high-resolution control signal, the system uses two DACs that each provide partial control signals (control component and slope compensation component). The differential integrator combines these partial signals to achieve the required overall precision, allowing each individual DAC to operate with reduced specifications.
2Reliability
If a high-speed DAC is used to avoid quantisation effects, then control stability is improved, but manufacturing cost increases
Solution Approach 1:
The control signal is segmented into control and slope compensation components generated by separate DACs. This segmentation allows each DAC to operate at lower sampling rates and resolutions, avoiding the need for expensive high-speed DACs while maintaining control stability through proper timing and integration of the two components.
Solution Approach 2:
The system uses periodic sampling and updating of the control and slope compensation signals through the two DACs. By synchronizing the update rates of the two DACs with the switching frequency of the power converter, the system achieves stable control without requiring continuously high-speed conversion, thereby reducing manufacturing cost.
3Adaptability or versatility
If separate digital control processing and analogue circuit elements are used, then design flexibility is improved, but layout difficulty and digital isolation problems increase
Solution Approach 1:
The patent merges the digital control processing and analogue circuit elements into a single integrated device. The two DACs and differential integrator are co-integrated with the digital control logic, eliminating the need for separate components and reducing layout complexity. This integration maintains design flexibility while solving the isolation and layout problems associated with separate implementations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient PCM control with reduced hardware requirements, avoiding quantization effects and allowing for stable operation at lower sampling rates, thus simplifying the layout and improving digital isolation.
Implementation Method 1
a first digital to analogue converter 'DAC' arranged to receive the series of digital control values and output a corresponding analogue control voltage
Implementation Method 2
a second DAC arranged to receive the digital slope compensation value and output a corresponding analogue slope compensation voltage
Implementation Method 3
an analogue differential integrator arranged to: receive the analogue control voltage and the analogue slope compensation voltage; integrate the analogue slope compensation voltage
Data Source
AI summary
A peak current mode ‘PCM’ controller comprising control logic arranged to produce a series of digital control values derived from a voltage sense signal, control logic arranged to produce a digital slope compensation value, a first digital to analogue converter ‘DAC’ arranged to receive the series of digital control values and output a corresponding analogue control voltage, a second DAC arranged to receive the digital slope compensation value and output a corresponding analogue slope compensation voltage, an analogue differential integrator arranged to receive the analogue control voltage and the analogue slope compensation voltage, integrate the analogue slope compensation voltage, subtract the integrated slope compensation voltage from the analogue control voltage, and output the result of the subtraction as an analogue output voltage, a comparator arranged to compare the analogue output voltage to a voltage of an analogue current sense signal and produce an output signal when the analogue current sense signal voltage is equal to or exceeds the analogue output voltage, and control logic arranged to produce a drive signal in response to the output signal.