Charge Pump Overcurrent Protection Using a Current Mirror
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Solution Overview
Problem
Charge pump circuits face damage risks due to large currents generated by short circuits in capacitors, threatening power switches.
Innovation Solution
An overcurrent protection circuit with a current source and bias transistor forms a current mirror, controlling current flow through a current controlling transistor to prevent damage by adjusting the driving voltage in response to voltage changes at the capacitor terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a charge pump circuit uses a capacitor as an energy storage device that is switched when voltage conversion is required, then the charge pump can convert input voltage to output voltage under different voltage conditions, but when a short circuit occurs in the capacitor, a relatively large current is generated that poses a risk of damaging power switches in the circuit
Solution Approach 1:
The protection circuit proactively monitors the voltage across the capacitor and prepares to limit current flow before damage can occur. When the voltage exceeds a predetermined threshold (indicating potential short circuit), the circuit immediately activates to constrain current through the power switch, preventing damage before it happens.
Solution Approach 2:
The protection circuit continuously monitors the voltage across the capacitor and uses this feedback to control the current flowing through the power switch. When the monitored voltage indicates a short circuit condition, the feedback mechanism automatically adjusts the current limit to protect the power switch, creating a closed-loop protection system.
2Productivity
If the charge pump circuit operates with high current capability to ensure efficient voltage conversion, then productivity is improved, but the circuit becomes more vulnerable to damage from short circuits in the capacitor
Solution Approach 1:
The protection circuit dynamically adjusts the current flowing through the power switch based on real-time voltage monitoring. During normal operation, the circuit allows high current for efficient voltage conversion. When a short circuit is detected (voltage exceeds threshold), the circuit immediately transitions to a protected state, dynamically constraining the current to safe levels.
Solution Approach 2:
The circuit changes the current parameter flowing through the power switch based on the voltage condition across the capacitor. Under normal conditions, the current parameter is set for optimal voltage conversion efficiency. When the voltage parameter exceeds the predetermined threshold, the current parameter is automatically adjusted to a limited value to prevent damage.
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
Prevents damage to transistors by maintaining normal current levels during short circuits, ensuring efficient operation of the charge pump.
Implementation Method 1
An overcurrent protection circuit with a current source and bias transistor forms a current mirror, controlling current flow through a current controlling transistor
Data Source
AI summary
A charge pump having a first capacitor, a current controlling transistor and an overcurrent protection circuit. The first capacitor has a first terminal and a second terminal. The current controlling transistor has a first terminal coupled to the first terminal of the first capacitor, and a second terminal coupled to a ground reference. The overcurrent protection circuit has a current source and a bias transistor. The current source has a first terminal coupled to a power supply. The bias transistor has a first terminal coupled to a second terminal of the current source, a second terminal coupled to the ground reference, and a control terminal coupled to both the first terminal of the bias transistor and a control terminal of the current controlling transistor.