Currently, there are many solar chargers available in the market, but their performance is often not satisfactory. They are often sold in combination with power banks. The reason for their poor performance might be the low conversion rate. Considering that the solar panels have a small surface area, the charging process is not very fast. The general principle of solar cells is as follows: when using solar cells, due to the large changes in sunlight and relatively high internal resistance, the output voltage is unstable, and the output current is small. This requires using a DC converter circuit to convert the voltage to charge the mobile battery. It is a single-ended flyback converter circuit.

From the simple principle above, it can be seen that, in essence, a solar charger is just a voltage stabilizer and a TVS diode conversion process, and someone with a little knowledge of electronics can design it. Therefore, there are many chips available for selection. Below are two examples of chips:

1. CN3063 is a single-cell lithium battery charging management chip that can be powered by solar cells. The device internally includes a power transistor, eliminating the need for external current sensing resistors and current control diodes in application. The internal 8-bit analog-to-digital conversion circuit can automatically adjust the charging current based on the current output capability of the input voltage source, so users do not need to consider the worst-case scenario. It is very suitable for lithium battery charging applications that use voltage sources with limited current output capabilities, such as solar cells. CN3063 requires very few peripheral components and complies with the USB bus technology specifications, making it very suitable for portable applications. The thermal modulation circuit can control the chip temperature within a safe range when the device has relatively high power consumption or the ambient temperature is relatively high. The internally fixed constant voltage charging voltage is 4.2V, which can also be adjusted through an external resistor. Charging current is set through an external resistor. When the input voltage is powered off, CN3063 automatically enters a low-power sleep mode, during which the battery current consumption is less than 3μA. Other functions include input undervoltage lockout, automatic recharge, battery temperature monitoring, and charging status/charging completion status indication, etc.

2. LT3652 supports multiple chemical composition batteries and is a medium-power single-chip buck-type charging management chip using average current mode buck topology. The special input voltage regulation loop can easily set the minimum input voltage through a voltage divider.

LT3652 can set a maximum charging current of up to 2A, and its internal constant frequency of 1 MHz high-frequency switch can improve charging efficiency. The chip has a wide input voltage range from 4.95V to 32V, and its float charging voltage VBAT (FLOAT) can be conveniently set by a voltage divider, up to 14.4V at most, which meets the charging requirements of most rechargeable batteries.

In the context of increasingly scarce non-renewable energy sources, the development of clean energy will become faster and more widespread. The technology and materials will also become more advanced. In time, we will be surrounded by solar energy products.