Reference Current Source Circuit Startup Power Optimization
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Solution Overview
Problem
The reference current source circuit in semiconductor integrated circuits experiences persistent currents after startup, which are undesirable in battery-powered devices where power consumption needs to be minimized.
Innovation Solution
A reference current source circuit design that includes a constant current circuit and a starting circuit with specific transistor configurations, impedance circuits, current mirrors, and threshold voltage-controlled current sources to manage and reduce currents post-startup, ensuring minimal power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a starting circuit is provided to enable the constant current circuit to transition to a normal stable operating point, then the circuit can be reliably started, but persistent currents continue to flow after startup completing increasing power consumption
Solution Approach 1:
The starting circuit is designed to perform its function only during the startup phase. A detection circuit monitors the power supply voltage and disables the starting circuit once startup is complete, preventing persistent current flow. This preliminary action ensures reliable startup while eliminating unnecessary power consumption during normal operation.
Solution Approach 2:
A detection circuit acts as an intermediary between the power supply voltage and the starting circuit. This intermediary monitors the voltage level and controls the enabling/disabling of the starting circuit, ensuring that the starting function is activated only when needed during startup and deactivated afterward to minimize power consumption.
2Ease of operation
If the starting circuit remains active after startup, then the circuit maintains its starting function, but unnecessary current flow increases power consumption in battery-powered devices
Solution Approach 1:
The detection circuit performs a preliminary check of the power supply voltage to determine whether startup is complete. Based on this preliminary assessment, it selectively enables or disables the starting circuit, ensuring the starting function is available only when necessary and preventing energy waste during normal operation.
Solution Approach 2:
The starting circuit transitions from a static always-on design to a dynamic design where its activation state changes based on operational conditions. The detection circuit monitors voltage levels and dynamically controls the starting circuit's enabling state, allowing the circuit to adapt between startup and normal operation modes to minimize energy loss.
3Power
If multiple current mirrors are used in the starting circuit to generate and multiply starting current, then adequate starting current is provided, but circuit complexity increases
Solution Approach 1:
The detection and control function is extracted from the starting circuit itself and implemented as a separate detection circuit. This separation allows the starting circuit to focus solely on current generation while the detection circuit manages the enabling/disabling logic, simplifying the overall system architecture and reducing complexity.
Solution Approach 2:
The detection circuit serves multiple functions: it monitors power supply voltage, determines startup completion status, and controls the enabling/disabling of the starting circuit. This multi-functionality reduces the need for separate control circuits, thereby managing complexity while maintaining adequate starting current generation.
Data Source
AI summary
A first current mirror circuit is provided between a first transistor and a power supply line to return a current that flows to the first transistor. A second current mirror circuit returns an output current from the first current mirror circuit, and generates a starting current. An inverter has an input connected to a node, and an output connected to a control terminal of the first transistor. A first current source generates a first current when a power supply voltage has exceeded a first threshold value. A third current mirror circuit draws a current proportional to the first current from an input side of the second current mirror circuit. A second current source supplies a second current to the node when the power supply voltage has exceeded a second threshold value.