Coin Cell Charge Pump Circuit for Transmitter Peak Current
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Solution Overview
Problem
Coin cell batteries in IoT devices face challenges in supplying the high current peaks required for short signal transmissions due to the large voltage difference between the battery's output and the transmitter's voltage, necessitating the use of very large capacitors that increase device cost and size.
Innovation Solution
A system comprising a coin cell, an external capacitor, a charge pump, and a regulator that charges the external capacitor to a higher voltage during non-transmission periods, allowing it to supply the required current during transmission periods, using a charge pump capacitor with lower capacitance and multiple charging iterations to reduce the size of the external capacitor needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If very big capacitors are used to supply peak current to the transmitter, then the current requirement is met, but the device cost and footprint dramatically increase
Solution Approach 1:
The power supply system is segmented into multiple components: a small coin cell battery, a charge pump circuit with a small charge pump capacitor, and a larger energy storage capacitor. This segmentation allows each component to perform its specific function efficiently, avoiding the need for a single large capacitor to handle all power requirements.
Solution Approach 2:
The charge pump circuit performs preliminary action by pre-charging the energy storage capacitor to a voltage higher than the coin cell battery voltage before transmission events occur. This pre-charging process accumulates energy in advance, enabling the capacitor to supply peak current during transmission without requiring the capacitor to be extremely large.
2Power
If very big capacitors are used to handle transmission peak, then the current peak requirement is met, but the device cost increases
Solution Approach 1:
The power supply system is divided into functional segments: the coin cell battery provides baseline power, the charge pump circuit multiplies voltage, and the energy storage capacitor delivers peak current. This segmentation allows the use of smaller, less expensive capacitors compared to a single large capacitor solution.
Solution Approach 2:
The charge pump circuit acts as an intermediary between the coin cell battery and the energy storage capacitor. It multiplies the battery voltage to a higher level, enabling the capacitor to be charged to a voltage significantly higher than the battery voltage, thereby reducing the required capacitance value and cost.
3Device complexity
If the voltage difference between coin cell output and transmitter voltage is small, then the system is simple, but very big capacitors are required
Solution Approach 1:
The charge pump circuit dynamically changes the voltage parameter by multiplying the coin cell battery voltage to a higher voltage level. This parameter transformation allows the energy storage capacitor to be charged to a voltage significantly higher than the battery voltage, reducing the required capacitance from C=ITX*tTX/dV where dV is the voltage difference.
Solution Approach 2:
The charge pump circuit serves as an intermediary that transforms the voltage parameter between the coin cell battery and the energy storage capacitor. By introducing this intermediate voltage multiplication stage, the system avoids the need for extremely large capacitors that would be required if charging directly from the battery at its lower voltage.
4Device complexity
If coin cell battery directly supplies transmitter, then the system is simple, but the battery cannot supply the required current peak
Solution Approach 1:
The charge pump circuit and energy storage capacitor act as intermediary components between the coin cell battery and the transmitter. The charge pump multiplies the battery voltage, and the capacitor stores energy at this higher voltage, enabling the system to deliver high peak current to the transmitter during transmission events while maintaining system simplicity.
Solution Approach 2:
The charge pump circuit performs preliminary voltage multiplication and the capacitor performs preliminary energy storage before transmission events. This pre-preparation of energy at high voltage enables the battery to continue using its simple architecture while the intermediary components handle the peak current delivery requirement.
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
This solution enables efficient power supply to IoT device transmitters during peak current demands while minimizing the size and cost of capacitors, effectively prolonging battery life and reducing the footprint of IoT devices.
Implementation Method 1
a charge pump capacitor (35) to a charged voltage that exceeds a voltage of a cell coin
Implementation Method 2
an external capacitor (90) that is charged to a charged voltage that exceeds a voltage of the coin cell
Data Source
AI summary
A coin cell powered device includes a regulator, a transmitter and a charge pump. The transmitter is configured to transmit signals during a transmission period while receiving power from the regulator, the power originated from an external capacitor. The charge pump is configured to perform, during a charging period, a charging process for charging the external capacitor to a charged voltage that exceeds a voltage of a cell coin, wherein the charging process may include iterations of (a) charging a charge pump capacitor by the coin cell, and (b) discharging the charge pump capacitor thereby charging the external capacitor. The capacitance of the charge pump capacitor is a fraction of a capacitance of the external capacitor. The duration of the charging period exceeds a duration of the transmission period.