Floating HV Switch Impedance Control for Stable Ron
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing high-voltage semiconductor switches suffer from significant on-impedance (Ron) variations due to process, voltage, and temperature fluctuations, with current solutions failing to effectively control Ron without limiting bandwidth and slew-rate.
Innovation Solution
An open-loop impedance control system using a low-temperature coefficient resistor and current references to calibrate the gate-to-source voltage (Vgs) of floating HV switches, implemented in a low-voltage domain to minimize area and power consumption, while maintaining signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HV switch control is used, then the switch can operate at high voltage, but the on-impedance (Ron) varies significantly (up to 50%) due to PVT variations
Solution Approach 1:
The patent pre-calibrates the gate-to-source voltage (Vgs) at room temperature using a low-voltage calibration circuit before operation. This preliminary calibration establishes a baseline Vgs value that compensates for PVT variations during subsequent high-voltage operation, thereby stabilizing Ron without requiring complex real-time control during switching operations.
Solution Approach 2:
The patent changes the operating voltage domain from high-voltage to low-voltage for the calibration circuit. By performing calibration at low voltage where precision components (low-TCR resistors, precision voltage references) can operate more accurately, the system achieves better Ron control precision. The calibrated Vgs value is then applied during high-voltage operation to maintain stable Ron despite PVT variations.
2Reliability
If closed-loop control with high-voltage opamps is used to control Ron, then Ron stability improves, but the bandwidth and slew-rate of the switch signals are limited
Solution Approach 1:
The patent performs Ron calibration and Vgs optimization in advance at room temperature, before the actual high-voltage switching operation begins. This preliminary calibration eliminates the need for complex real-time closed-loop control during switching, allowing the main switch signals to operate at full bandwidth and slew-rate without being constrained by control loop bandwidth limitations.
Solution Approach 2:
The patent extracts the calibration function into a separate low-voltage domain circuit that operates independently from the high-voltage switching path. This separation allows the high-voltage switch to operate at full speed with unlimited bandwidth and slew-rate, while the calibration circuit operates at low voltage with high precision, eliminating the trade-off between control precision and signal speed.
3Manufacturing precision
If calibration is performed in high-voltage domain, then Ron control accuracy improves, but circuit area and power consumption increase
Solution Approach 1:
The patent extracts the calibration function from the high-voltage domain and relocates it to the low-voltage domain. This allows the use of small-area, low-power components (low-TCR resistors, precision voltage references) that operate accurately at low voltage. The calibration circuit area and power consumption are dramatically reduced compared to using high-voltage components, while still achieving accurate Ron calibration through the subsequent application of calibrated Vgs during high-voltage operation.
Data Source
AI summary
High-voltage (HV) semiconductor switches are used in various applications. On-impedance (Ron) of the HV switches is prone to process, voltage, and temperature (PVT) variations. The present invention discloses system and method embodiments to calibrate a gate-to-source voltage (Vgs) of the switch based on a low temperature coefficient resistor and current references. The Ron of a replica switch transistor is matched to a reference resistor using a feedback to generate the required Vgs voltage. The calibrated Vgs is enforced to the floating HV switch transistor via controlling the bias current of a replica gate driver by feedback. With this approach, a desired input current to the gate driver may be obtained and applied to a main gate driver to control the Ron of the floating HV switches. Simulation results demonstrate a significant improvement in Ron variation.