In this project a high voltage application specific integrated circuit was developed in order to drive a number of piezoelectric MEMS-based actuators. The goal was to demonstrate the benefit of a high voltage ASIC development with respect to space, weight, cost and power consumption while providing the full performance in terms of functionality.
In today’s green aircraft technology development active flow control techniques are used to reduce noise, COx/ NOx emission and fuel consumption. MEMS based piezoelectric actuators for active flow control have strong requirements with respect to the actuation voltage level and the capacitive load which has to be controlled. Commercial high voltage amplifier components are mostly large and heavy or can only drive moderate capacitive loads. This work was carried out within the 7th Framework program of the JTI Clean Sky. An integrated high-voltage circuit (HV-ASIC) consisting of six high-voltage amplifier stages together with integrated electronics for temperature monitoring and phase shift control had been developed and characterised.
1. Design Approach and Implementation
The focus of this development was the demonstration of the actuation of micro-pulsed jet actuator (µPJA) elements by integrated high voltage amplifier stages. An output stage design based on high-voltage PMOS and DMOS devices had been implemented in a 1 µm technology- XDH10 of XFAB foundry AG. Each output stage was able to drive capacitive loads up to 100 nF at a level of 300 V with an operation frequency of 500 Hz or 2.5 nF with 20 kHz, respectively. In order to reduce the maximum peak current a phase shift circuitry had been implemented whereas the output signal of each HV stage can be shifted by 60 °. In a first iteration three different HV output stage topologies had been designed, simulated, fabricated and measured on a test chip in order to judge the performance of these output stages. The best approach could be identified with the PMOS/ DMOS output stage (Figure 1). The evaluation had been carried out using CoB (Chip on Board) assemblies of two different carrier materials (FR4/ Aluminum). Based on the results of the test chip a final HV ASIC could be developed and fabricated. The methodology of this HV ASIC design follows the ideas of:
- Accessibility to each relevant subcircuit in order to enable a single characterization
- Decoupling of subsystem functionalities by turn_off features in order to ensure full system functionality even in case of single malfunctions which may be fixed by external circuitries.
- Each HV stage can be powered separately and can drive a maximum load of 100 nF parallel to 50 kOhm.
- Energy saving/ Power management by phase shift unit
- HV operation emergency stop in case of excessive heating by integrated temperature control with automatic turn_off
- Simulations were done with respect to save start-up, technology tolerances, temperature range and functionalities.
The mock-up panel consisted of three basic modules whereas the HV ASIC module and the actuator module were the main elements. The third module was designed to provide a useful common 230 V AC/ 24 V DC and 24 V DC/ HV DC conversion for easy use and demonstration by SFWA partners. In a final aircraft implementation it may be easy to be replaced by an optimised solution with respect to the board voltage supply capabilities. Exemplary the results of all six HV output stages with applied full load of 100 nF with 300 V/ 500 Hz and the related output signals could be shown.
An integrated high voltage circuit had been developed in order to drive high capacitive loads up to 600 nF and enable operation voltages up to 300 V. Due to the reduction of space, weight and power consumption this solution enabled active flow control by MEMS based piezoelectric actuators for aircraft applications.