Application of BL8530 boost power conversion

BL8530 is a domestically produced DC-DC boost circuit. Compared with similar foreign products, it has the advantage of being cheaper. Since it has a fixed output voltage, when we need some non-standard voltages, we can achieve this by adding peripheral circuits.

The circuit in Figure 1 can boost the lower output voltage. However, this circuit can only boost it to below 7V. This is because the Lx terminal inside the BL8530 has overvoltage protection, which limits the maximum output voltage to below 7V.

D1 provides a startup voltage for BL8530. You can use diodes such as 2AP, IN60, 1N5817, etc. R1 provides a stable working current for DW1 voltage regulator diode. Generally, it is sufficient to be greater than 1mA. For example, when DW1 uses TL431, the output voltage Vo=3+2.5=5.5V. By replacing different voltage regulator diodes, you can get the required voltage.

To get an output voltage higher than 7V, a boost winding should be added to the inductor. The circuit is shown in Figure 2.

L2 uses Φ0.08mm enameled wire just to reduce the volume of the inductor. The number of turns of the boost winding can be wound according to your needs. According to the data in the figure, using a 4V lithium battery, without connecting D3, when the load current is 1mA, the output voltage exceeds 40V.

Figure 2 can also be designed into a boost circuit that can shut down automatically to replace the 9V battery in the digital multimeter. The circuit is shown in Figure 3. Directly replace the 9V battery, the digital meter does not need to be modified, and the circuit can shut down automatically. The current after shutdown is extremely small and almost unmeasurable.

Use a 1.2V rechargeable battery. The output current is greater than 10mA. Use a 4V lithium battery. The output current can exceed 30mA, which can be used for devices with high power consumption. Lithium batteries should be equipped with a protective board to avoid over-discharge to damage the battery or cause danger!

When using a TV tuner to make an FM full-band receiver, it is inconvenient to move when using AC power. If it is powered by three AA rechargeable batteries or one lithium battery, it is very convenient to carry. The 5V working voltage and 33V tuning voltage circuit required by the tuner are shown in Figure 4.

The above circuits all use Zener diodes to increase the output voltage, and all have fixed outputs. If the Zener diodes are replaced with TLA31 or LM285, LM385, the output voltage can be continuously adjusted. The circuit is shown in Figure 5.

LM285 and LM385 are micro-power voltage reference circuits. Compared with TL431, they can improve the working efficiency of the boost circuit, but R1 needs to be replaced with 240kΩ.

There are many boost circuits similar to BL8530, such as QX2301, AIC1642, ML63, etc. Refer to the usage of BL8530. Various output voltages can be obtained flexibly.