Self-Startup Circuit for Wireless Power Receive Coil
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Solution Overview
Problem
Wireless power systems face challenges in charging batteries when the battery charge is low, as the charging circuitry may not operate effectively, preventing normal system control and power reception due to depleted battery conditions.
Innovation Solution
A self-startup circuit is introduced, which includes a receive coil, a switch circuit with a transistor, and a self-start circuit that provides power to hold the switch in receive mode, allowing wireless power reception and charging even with a dead battery by using a diode-based self-start circuit to power the transistor and enable the receive coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery charge is low or depleted, then the charging circuitry cannot operate effectively to charge the battery, but the system still needs to receive wireless power to restore battery charge
Solution Approach 1:
The self-start circuit is designed to automatically activate the receive coil and switch circuit before the main charging circuitry can operate, creating a preliminary power pathway that restores battery charge from depleted states. The circuit uses the wireless power signal itself to bootstrap the charging process without requiring prior battery power.
Solution Approach 2:
The system uses its own wireless power reception capability to service itself by automatically initiating the charging process through the self-start circuit, eliminating the need for external intervention or pre-charged battery conditions. The receive coil and switch circuit serve themselves by using the incoming power signal to activate the charging pathway.
2Reliability
If the switch circuit is not powered to hold in receive mode, then power cannot be received, but providing continuous power to hold the switch creates energy consumption that depletes the battery further
Solution Approach 1:
The self-start circuit uses the periodic nature of the wireless power transmission signal to periodically activate and hold the switch circuit in receive mode. Rather than continuous power consumption, the circuit synchronizes with the incoming power signal's oscillation to maintain the switching state, consuming energy only when needed to sustain the receive mode.
Solution Approach 2:
The circuit changes the operational parameters of the switch transistor by using the varying voltage levels from the receive coil during wireless power reception to control the switching state. The transistor transitions between conducting and non-conducting states based on the AC power signal parameters, allowing mode control without continuous DC power consumption.
3Adaptability or versatility
If a self-start circuit is added to enable low-battery operation, then battery charging becomes possible from depleted states, but the device complexity increases
Solution Approach 1:
The self-start circuit components serve multiple functions: the receive coil not only receives wireless power but also provides the bootstrap voltage for the self-start circuit; the switch transistor not only controls power reception but also acts as the primary switching element for the entire charging system. This multi-functionality reduces the need for separate dedicated components.
Solution Approach 2:
The self-start circuit acts as an intermediary between the wireless power reception system and the main charging circuitry, using simple diode-based voltage rectification and transistor switching to bridge the gap. This intermediary layer adds minimal complexity while enabling the critical low-battery startup functionality.
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
Enables battery charging and system operation even with a discharged battery by automatically switching to receive mode and providing power to the switch circuit, ensuring continuous power reception and charging functionality.
Implementation Method 1
wireless power transfer involves a transmitter driving a transmit coil and a receiver with a receiver coil placed proximate to the transmit coil. The receiver coil receives the wireless power generated by the transmit coil
Implementation Method 2
a transistor coupled between the receive coil and the second node, the transistor configured to conduct in the receive mode and not to conduct in the transmit mode
Implementation Method 3
The self-start circuit can include a first diode coupled to the receive coil to receive power and a second diode coupled in series with the first diode, the self-start circuit providing power from a node between the first diode and the second diode
Data Source
AI summary
A wireless power circuit is presented that includes a transmit coil coupled to a first node; a receive coil coupled to the first node; a switch circuit coupled to the transmit coil and the receive coil opposite the first node, the switch switching the transmit coil to a second node in a transmit mode and switching the receive coil to the second node in a receive mode; a controller coupled to the first node and the second node, the controller coupled to provide signals to the switch circuit; and a self-start circuit coupled to the receive coil (or Tx coil) that automatically selects one of the coils to be used, the self-start circuit providing power to the switch circuit to hold the switch circuit in the receive mode (or predefined coil to be selected by default).