Wireless charging with no cables to connect is convenient and allows the product to be encased completely. This benefit is enormous for wearable and medical devices that might get wet, need to be cleaned, or are implanted. By embedding a battery and with the wireless charging logic, the product is placed on a wireless charging pad and is fully protected.
When we do a design we check all of the items on the checklist, and even more. Often we need to use our engineering judgment on the tradeoff between size, cost, testability, and manufacturability of the product.
- What size and type of battery?
- What is the appropriate battery lifetime?
- What is the maximum current draw? (also determines battery size)
- How fast to charge?
- Does it have overcharge protection?
- Does it have thermal protection?
- Does it meet regulatory requirements and standard compliance?
- What is the efficiency?
- Select parts to minimize power drain
- What subsystems can be powered down?
- How do you detect thermal problems?
- Does the firmware to keep subsystems powered down as much as possible?
- Does it meet regulatory requirements at system level?
- Can the application use a commonly available charging pad? Avoid designing this part if possible to save time and money.
- Are there special mechanical or current requirements?
- Charging times: How fast to charge?
- What is the distance between the charger and the device?
- What is the coil and ferrite sizing?
- Are there any special materials requirements?
- How is coil alignment done?
- How is charger/device detection done?
- Standards compliance: which standards apply?
- Is there an audible or visual signal to indicate the device has been placed correctly on the charger, or does it have a receptacle which makes incorrect placement difficult?