Charge Pump Current Limiter With Adaptive Threshold Tracking
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Solution Overview
Problem
Charge pump regulators face challenges in maintaining a stable current limit threshold due to significant variations in input and output voltage conditions, leading to potential damage from excessive currents, especially in applications requiring wide Vin/Vout ranges.
Innovation Solution
A current limiter is introduced for the charge pump regulator, comprising a sampling block, adaptive tracking block, and voltage clamp block to accurately track and clamp the feedback voltage, ensuring a stable current limit threshold independent of Vin/Vout variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional current mode regulation is used with a fixed current limit threshold, then the circuit structure is simple, but the current limit threshold varies significantly at different Vin/Vout conditions
Solution Approach 1:
The current limit threshold is made dynamic by introducing an adaptive tracking block that continuously adjusts the threshold based on real-time detection of Vin and Vout conditions. The block modifies the reference voltage for the current limit comparator, enabling the threshold to adapt to varying operating conditions rather than remaining fixed.
Solution Approach 2:
A feedback mechanism is implemented where the actual Vin and Vout values are monitored and fed back to the adaptive tracking block. This feedback loop enables the system to automatically adjust the current limit threshold according to the actual operating conditions, ensuring stable protection across different Vin/Vout ratios.
2Reliability
If the current limit threshold is made adaptive to track Vin/Vout variations, then the current limit stability is improved, but the device complexity increases
Solution Approach 1:
An adaptive tracking block is introduced as an intermediary component between the existing current limit circuit and the voltage sensing network. This block receives Vin and Vout information, processes it to generate an adjusted reference voltage, and outputs it to the current limit comparator. The intermediary approach adds functionality while maintaining a clear separation of concerns.
Solution Approach 2:
The reference voltage parameter for the current limit comparator is changed from a fixed value to a dynamically adjustable value. The adaptive tracking block modifies this parameter based on the ratio of Vin to Vout, enabling the current limit threshold to scale appropriately with operating conditions without fundamentally changing the underlying current limit circuit architecture.
3Adaptability or versatility
If a wide Vin/Vout range is supported, then the adaptability is improved, but the current limit accuracy deteriorates due to threshold variations
Solution Approach 1:
The current limit threshold transitions from a static value to a dynamic value that automatically adapts to the Vin/Vout ratio. The adaptive tracking block continuously adjusts the threshold based on real-time voltage conditions, enabling accurate current limiting across the entire operating range from 2.7V to 4V input and various output voltages.
Solution Approach 2:
The reference voltage parameter is dynamically adjusted according to the Vin/Vout ratio. When Vin varies or Vout changes, the adaptive tracking block modifies the reference voltage to maintain a consistent current limit threshold in terms of actual current, rather than in terms of fixed voltage.
Data Source
AI summary
A current limiter and a charge pump regulator including the current limiter are provided. The charge pump regulator converts an input voltage to an output voltage and includes a feedback loop including a first transistor for regulating a discharge current from the charge pump regulator. The current limiter limits the current provided by the charge pump regulator. The current limiter includes a sampling block configured to sample a first drain-source voltage of the first transistor and hold it as a reference drain-source voltage; an adaptive tracking block configured to receive the reference drain-source voltage, and to generate a maximum voltage based on the reference drain-source voltage, so that the maximum voltage tracks the reference drain-source voltage; and a voltage clamp block configured to clamp a feedback voltage to the maximum voltage, and to provide the clamped voltage as a first gate-source voltage of the first transistor.