Current Mirror Calibration Circuit for PWM Controller Error Amplifier
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Solution Overview
Problem
Conventional DC-DC converting controllers face issues with current mirror errors, leading to incorrect voltage drops and output errors when the load line switches from light to heavy load, as they fail to accurately replicate input currents.
Innovation Solution
A current mirror calibration circuit and method that includes a first and second voltage generation unit, a calibration unit, and a current mirror circuit coupled to a PWM controller's error amplifier, which generates default voltages and currents to compare and adjust the reference voltage, using switches and a compensation unit to pump or sink current and eliminate errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current mirror circuit is used to replicate input current for load line droop function, then the load line protection function is provided, but current mirror errors cause incorrect mirror current output leading to erroneous voltage drop and output errors
Solution Approach 1:
The patent applies preliminary action by performing current mirror calibration during an initial period before normal operation. The calibration unit adjusts the reference voltage to compensate for current mirror errors in advance, ensuring accurate current replication from the start without affecting subsequent load line protection functionality
Solution Approach 2:
The patent implements feedback through the calibration unit that compares the mirror current with the original current and adjusts the reference voltage accordingly. This closed-loop feedback mechanism eliminates current mirror errors by continuously monitoring and correcting the reference voltage based on the actual current replication accuracy
2Manufacturing precision
If current mirror calibration is performed during initial period only, then manufacturing precision is improved, but additional circuit components and control logic increase device complexity
Solution Approach 1:
The patent merges the calibration function with the existing current mirror circuit by integrating the calibration unit directly into the current mirror structure. The same nodes and currents are utilized for both calibration and normal operation, reducing the need for separate calibration circuitry and minimizing overall device complexity
Solution Approach 2:
The current mirror circuit performs self-calibration through the calibration unit that uses the circuit's own internal currents and voltages to adjust its reference voltage. The calibration process is autonomous, requiring no external calibration equipment or additional control signals, thereby simplifying the overall system architecture
Data Source
AI summary
A current mirror calibration circuit, coupled to an error amplifier of a pulse-width modulation controller, includes a first voltage generation unit, a second voltage generation unit, a calibration unit and a current mirror circuit. During an initial period, the first voltage generation unit and second voltage generation unit provide a first default voltage and a second default voltage respectively. The current mirror circuit includes a first current unit and a second current unit. The first current unit receives an original current. The second current unit generates a mirror current having a proportional relationship with original current. The first current unit has a first node coupled to the first voltage generation unit and a second node coupled to a third default voltage. The second current unit has a third node coupled to the second voltage generation unit and calibration unit and a fourth node coupled to calibration unit and an output terminal of error amplifier.