Reference Voltage Generation Circuit with Start-Up Mechanism
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Solution Overview
Problem
Conventional reference voltage generation circuits take a long time to transition from a non-operating stable state to an operating stable state due to the need to increase a control voltage other than the reference voltage, which affects the response characteristics to power supply changes.
Innovation Solution
A reference voltage generation circuit that includes a start-up circuit to directly increase the reference voltage by supplying a start-up current to the output node and differential amplifier, reducing the transition time and power consumption, and allowing for arbitrary adjustment of the start-up current through a current mirror circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bandgap reference circuit is used to generate reference voltage, then the reference voltage has low dependence on power supply voltage and temperature, but the circuit takes a long time to transition from non-operating stable state to operating stable state
Solution Approach 1:
The start-up circuit activates before the main reference voltage generation circuit to pre-charge the output node and differential amplifier to appropriate voltage levels. This preliminary action ensures that when the main circuit activates, it immediately transitions to the operating stable state rather than requiring a lengthy startup period, thus resolving the contradiction between reliability and transition time.
2Loss of time
If the reference voltage is directly increased by supplying start-up current to the output node, then the transition time is reduced, but the power consumption increases
Solution Approach 1:
The start-up circuit operates periodically or temporarily only during the startup phase rather than continuously. The circuit supplies start-up current to accelerate the transition to operating state, then automatically shuts off or reduces current once the reference voltage stabilizes. This periodic operation reduces overall power consumption while maintaining fast transition characteristics.
3Speed
If the start-up current is increased to reduce transition time, then the response characteristics improve, but the circuit area and power consumption increase
Solution Approach 1:
The start-up circuit employs dynamic current control where the start-up current magnitude is adjusted based on the startup phase requirements. The circuit uses voltage-dependent current sources or transistor sizing that provides high current during startup to improve response characteristics, then automatically reduces current as the reference voltage stabilizes, optimizing both speed and area efficiency.
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
The solution reduces the transition time from a non-operating to an operating stable state, improves response characteristics to power supply changes, and minimizes circuit area and power consumption while ensuring accurate reference voltage generation.
Implementation Method 1
a start-up circuit configured to cause, by supplying a start-up current to the output node in response to supply of a power supply voltage, a transition from a first stable state where the reference voltage is stabilized at a voltage level lower than a desired voltage level to a second stable state where the reference voltage is stabilized at the desired voltage level
Implementation Method 2
a differential amplifier configured to output a control voltage corresponding to a difference between a first voltage generated at a connection point of the first rectifying element and the first resistance element and a second voltage generated at a connection point of the second resistance element and the third resistance element
Implementation Method 3
a voltage generation circuit including a first rectifying element, a first resistance element coupled between the first rectifying element and an output node at which the reference voltage is generated, a second rectifying element
Data Source
AI summary
A first resistance element is coupled between a first rectifying element and an output node at which a reference voltage is generated. Second and third resistance elements are coupled in series between a second rectifying element and the output node. A differential amplifier outputs a control voltage corresponding to a difference between a first voltage generated at a connection point of the first rectifying element and the first resistance element and a second voltage generated at a connection point of the second resistance element and the third resistance element. A control circuit supplies a control current corresponding to the control voltage from the differential amplifier. A start-up circuit causes, by supplying a start-up current to the output node in response to supply of a power supply voltage, transition from a first stable state to a second stable state.