1. Reasonable selection of voltage conversion chip
To achieve efficient and stable voltage conversion of the power circuit on the Circuit Board, the voltage conversion chip must be reasonably selected first. For step-down conversion, such as the commonly used DC-DC step-down chip, it should be selected according to the input voltage range, output voltage and current requirements. If the input voltage fluctuates greatly, a chip with a wide input voltage range needs to be selected. For example, the input voltage of the power circuit in some automotive electronics may vary between 9-36V. At this time, a chip that can adapt to this range should be selected.
At the same time, the conversion efficiency of the chip is a key indicator. Compared with the asynchronous step-down chip, the synchronous step-down chip can greatly reduce the conversion loss and improve the efficiency because it uses a low on-resistance MOSFET tube inside. For boost conversion, there are also special boost chips to choose from. When selecting, its switching frequency, minimum starting voltage and other parameters should be considered. For example, in some portable devices powered by lithium batteries and requiring boost output, a boost chip with a low starting voltage and high efficiency in a wide load range should be selected.
2. Optimize circuit layout and wiring
Good circuit layout and wiring are essential for the stability of voltage conversion. In terms of layout, the voltage conversion chip should be placed close to the power input and output filter capacitors to reduce the influence of line parasitic inductance and resistance. For power supply circuits with higher power, the heat dissipation pad of the chip should be well grounded, and sufficient space should be reserved near it to avoid being close to other heating components to prevent excessive temperature from affecting the conversion efficiency.
In terms of wiring, the input and output power lines should be as thick as possible to reduce line resistance and power loss. For high-frequency switching power supply circuits, high-frequency wiring rules should be followed, such as reducing the loop area and avoiding signal crossing. For example, in a step-down circuit, the wiring at the switch node should be short and straight, and the line connecting the inductor should be as close to the output pin of the chip as possible, which can reduce electromagnetic interference and improve the stability of voltage conversion.
3. Use high-quality filter circuits
Filter circuits play a key role in the voltage conversion of power supply circuits. On the input side, large-capacity electrolytic capacitors and high-frequency ceramic capacitors are usually connected in parallel. Electrolytic capacitors are used to filter low-frequency ripples, while ceramic capacitors are used to suppress high-frequency noise. For example, in a 5V to 3.3V power supply circuit, a 10uF electrolytic capacitor and a 0.1uF ceramic capacitor can be connected in parallel on the input side.
On the output side, in addition to capacitor filtering, an LC filter network consisting of inductors and capacitors can be added as needed. Inductors can further smooth the current and reduce ripple. For circuits with extremely high requirements for voltage stability, such as power supply circuits in precision instruments, multi-stage filtering, including complex filtering structures such as π-type filtering, can also be used to ensure the purity and stability of the output voltage.
4. Implement effective feedback and control mechanisms
In order to achieve stable voltage conversion, the power supply circuit needs to implement effective feedback and control mechanisms. In terms of voltage feedback, a high-precision voltage divider network is usually used to feed back the output voltage to the feedback pin of the voltage conversion chip. The error amplifier inside the chip compares the feedback voltage with the internal reference voltage, adjusts the on-time of the switch tube according to the difference, and thus accurately controls the output voltage.
For some circuits that need to dynamically adjust the output voltage, such as power supplies that automatically adjust the voltage according to load changes, digital control chips can be used. Through communication between the microcontroller and the power chip, the reference voltage or other control parameters of the voltage conversion chip can be changed in real time to achieve flexible and accurate voltage control, ensuring efficient and stable voltage conversion under various load conditions.
