Application and Circuit Diagram Analysis of BL8530 in Boost Power Conversion

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BL8530 is a domestic DC-DC booster circuit. Compared with similar products abroad. Has the advantage of being cheap. Because it is a fixed output voltage. When we need some non-standard voltage, we can achieve this by adding peripheral circuits.

The circuit in Figure 1 can boost the lower output voltage. But this circuit can only rise below 7V. This is because the Lx terminal inside the BL8530 has overvoltage protection, limiting the maximum output voltage to less than 7V.

D1 provides a starting operating voltage for the BL8530. Can use 2AP, IN60, 1N5817 and other diodes, R1 provides a stable operating current for the DW1 Zener diode. Generally it is greater than 1mA. For example: when DW1 uses TL431. The output voltage is Vo=3+2.5=5.5V, and different voltage regulators are used. The required voltage can be obtained.

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

L2 uses a Φ0.08mm enameled wire only to reduce the volume of the inductor. The number of turns of the step-up winding can be wound according to your own needs. According to the data in the figure, 4V lithium battery is used, D3 is not connected, and the output voltage exceeds 40V when the load current is 1mA.

Figure 2 can also be designed as a self-shutdown boost circuit 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 changed, the circuit can be automatically turned off. The current after shutdown is extremely small. Almost impossible to detect.

Use a 1.2V rechargeable battery. The output current is greater than 10mA. Use a 4V lithium battery. The output current can exceed 30mA and can be used in equipment that consumes a lot of power. Lithium batteries should use a battery with a protective plate. In order to avoid over-discharge damage to the battery or danger!

Using the TV tuner to make an FM full-band receiver, when using AC power, moving is inconvenient. If you use three 5th rechargeable batteries or a lithium battery, it is very convenient to carry. The 5V operating voltage required by the tuner and the 33V tuning voltage circuit are shown in Figure 4.

The above circuit is to increase the output voltage through the Zener diode, which is a fixed output. If the Zener diode is replaced by TLA31 or LM285, LM385. The output voltage can be continuously adjusted. The circuit is shown in Figure 5.

LM285 and LM385 are micropower voltage reference circuits. Compared with TL431, the efficiency of boost circuit can be improved, but R1 should be replaced by 240kΩ.

There are many boost circuits similar to BL8530, such as QX2301, AIC1642, ML63, etc., refer to the use of BL8530. Various output voltages are available flexibly.

See the PDF document for more details.