Virtual Reference Bias Circuit for Low-Current High-Voltage Switching
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Solution Overview
Problem
Existing biasing techniques for high voltage switching devices in integrated circuits face challenges when the device maximum ratings are lower than the supply maximum value, necessitating complex circuitry like cascoded switching stages and LDMOS-based solutions, which require significant quiescent current and large capacitive decoupling.
Innovation Solution
A bias circuit comprising a bias stage, voltage follower, first and second charge pumps, and a switchable buffer, which generates a virtual reference voltage using a transconductor stage with minimal quiescent current, actively maintaining the virtual reference voltage through charge pumps and a switchable buffer to minimize voltage bouncing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex circuitry like cascoded switching stages and LDMOS-based solutions is used, then high voltage switching capability is achieved, but quiescent current consumption increases significantly
Solution Approach 1:
The charge pumps operate periodically to replenish charge on the virtual ground node, rather than requiring continuous high current. The switched buffer activates only during switching transitions to counteract voltage bouncing, enabling low quiescent current operation while maintaining high voltage switching capability when needed.
Solution Approach 2:
A virtual ground node is introduced as an intermediary between the high voltage switching stage and the low voltage baseline circuitry. This virtual ground allows the switching devices to operate at high voltages while the baseline components remain at low voltages, eliminating the need for complex high-voltage baseline circuitry and reducing quiescent current consumption.
2Reliability
If complex circuitry like cascoded switching stages and LDMOS-based solutions is used, then high voltage switching capability is achieved, but device complexity increases
Solution Approach 1:
The virtual ground node serves as a mediator that decouples the high voltage switching domain from the low voltage baseline domain. This allows simple baseline circuitry to be used while still enabling high voltage switching operations, avoiding the complexity of cascoded stages and LDMOS devices.
Solution Approach 2:
The circuit is segmented into distinct voltage domains: a high voltage domain for switching operations and a low voltage domain for baseline processing. The virtual ground node creates an electrical boundary between these domains, allowing each to be optimized independently and reducing overall circuit complexity.
3Stability of the object's composition
If large capacitive decoupling is used, then voltage stability is improved, but device area and power consumption increase
Solution Approach 1:
Instead of using large continuous capacitors, the system uses periodic charge pumping to maintain voltage stability. The charge pumps replenish charge on small capacitors at the virtual ground node during specific phases of the switching cycle, enabling voltage stability with minimal capacitor area.
Solution Approach 2:
The switched buffer provides active feedback to counteract voltage bouncing at the virtual ground node during switching transitions. By detecting voltage deviations and applying corrective current only when needed, the system maintains voltage stability without requiring large passive decoupling capacitors.
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 provides efficient, low-power biasing with minimal quiescent current, reducing the need for large capacitors and enabling integrated switching devices by actively stabilizing the virtual reference voltage during switching activities.
Implementation Method 1
a first charge pump coupled to the voltage follower output; and at least one of a second charge pump coupled to the bias stage voltage output
Data Source
AI summary
A bias circuit for generating a virtual reference voltage is described. The bias circuit may bias a switching device configured to switch a switching device output between a first and second supply voltage. The bias circuit includes a bias stage coupled between the first supply voltage rail and the second supply voltage rail. The bias stage has a bias stage output configured to output a virtual reference voltage value having a value between the first and second supply voltage. The bias circuit further includes a voltage follower coupled to the bias stage. The voltage follower is configured to output the virtual reference voltage. The bias circuit further includes a first charge pump coupled to the voltage follower output; and at least one of a second charge pump coupled to the bias stage voltage output, and a switchable buffer coupled to the bias stage voltage output and the voltage follower output.