## MSc thesis project proposal

# Various projects on energy harvesting and power management in collaboration with NOWI

### Project outside the university

NOWI**(Ultra) Low Power PVT Independent MHz-Range CMOS Oscillator**

Oscillators are widely used in modern integrated circuits. They are used for timed tasks (e.g. MPPT), digital control loops (e.g. FSM), driving switching power supplies (e.g. charge pump), digital communication (e.g. RF, I2C) and for many other applications. Crystal oscillators (like the quart-crystal clock) can output a highly accurate and stable frequency, but they cannot be integrated into CMOS technology. Fully integrated structures exist in CMOS, but process variation, supply voltage and temperature (PVT) can greatly influence the behaviour of a circuit. By suppressing this effect one can reduce the variation in the output frequency of the oscillator.

**Cold start for Energy Harvesters with Piezo transducer**

What is the optimal implementation of a cold start system for Piezo applications that operate around humans. Part 1: What are the specifications of such a system and piezo source, Part 2: Design an optimal (low power, small area) cold start for this.

**Capacitive voltage regulator**

Research capacitive voltage regulator techniques and find an optimal design in terms of efficiency and silicon area. What specifications of a voltage regulator suit well with capacitive regulators and where are the challenges?

‘**Empty’ battery maximum power point harvesting**

Non-rechargeable batteries often have energy left in them when normal appliances can no longer use them. How can we harvest this energy optimally (find the maximum power point) without draining the battery too quick?

**Power estimation circuit for a switched-capacitor DC/DC converter**

Measuring or estimating the output power of the DC/DC converter is important for maximum power point tracking operation. One way to measure the output power of a switched-capacitor DC/DC converter is to place a sense resistor at its output and measure the voltage drop across the resistor. If we consider that the converter output voltage is constant during different measurements, we can compare the voltage drops across the resistor and observe if the output power is increasing or decreasing. However, this method leads to considerable additional silicon area. We are looking into alternative ways to measure the power that do not require a sense resistor.

The goal of this project is to design an output power estimation method for a switched-capacitor DC/DC converter. One possible way would be to measure the voltage across the flying capacitors at different instants during the converter operation and use timing information, such as the converter’s switching frequency, to estimate the output power.

## Contact

### prof.dr.ir. Wouter Serdijn

Bioelectronics Group

Department of Microelectronics

Last modified: 2022-05-04