Ripple noise refers to the fluctuations in AC current and voltage caused by the switching action of switching devices and the periodic storage and release of capacitor and inductor energy in power electronic equipment. It is also called AC noise. It will cause interference to the circuit and affect the performance and stability of the equipment. It needs to be reduced through appropriate design and control measures.
A DC-DC converter is a power converter that converts a DC voltage into another DC voltage. It is commonly found in various electronic devices. In a DC-DC converter, ripple noise is an important consideration. To reduce the ripple noise of a DC-DC converter, the following methods can be used:
Choose the right components: Choose switching devices, capacitors and CA3140T inductors with low switching loss and low internal resistance to reduce the generation of ripple noise.
Reasonable PCB layout: Reasonable PCB layout can reduce electromagnetic interference and ripple noise. Try to shorten the connection length between the input and output capacitors and inductors and the DC-DC chip to reduce parasitic inductance and resistance. Avoid parallel arrangement of signal lines and power lines to reduce electromagnetic coupling. Ground isolation, shielding and other measures can be used to reduce interference.
Use filters: Adding appropriate filter circuits, such as LC filters, Pi filters, etc., to the input and output of the DC-DC converter can effectively filter out ripple components and reduce ripple noise.
Control the switching frequency: Control the switching frequency of the DC-DC converter so that the ripple frequency does not overlap with the key signal frequency, which can avoid the impact of ripple noise on system performance. At the same time, soft switching technology can also be used, which can reduce the switching loss and electromagnetic interference of the switch tube, thereby reducing ripple noise. For example, zero voltage switching (ZVS) and zero current switching (ZCS) technologies can enable the switch tube to achieve zero voltage or zero current switching during the switching process, reducing the voltage and current spikes at the switching moment.
Use appropriate feedback control strategies: Using appropriate feedback control strategies, such as voltage mode control, current mode control, etc., can effectively reduce ripple noise and improve system stability and response speed.
Circuit design
Input capacitor selection:
Choosing a suitable input capacitor can help smooth the fluctuation of the input voltage. Generally speaking, it is better to use ceramic capacitors and electrolytic capacitors with larger capacitance in parallel. Ceramic capacitors have low equivalent series resistance (ESR) and low equivalent series inductance (ESL), which can respond quickly to high-frequency ripples, while electrolytic capacitors can provide larger capacitance for handling low-frequency ripples.
Note that the withstand voltage of the capacitor should be higher than the input voltage to ensure the reliability of the circuit.
Output capacitor selection:
The output capacitor also has an important impact on ripple noise. You can choose capacitors with high capacitance, low ESR and low ESL, such as solid capacitors or tantalum capacitors. These capacitors can better smooth the output voltage and reduce ripple.
According to the output current and ripple requirements, reasonably calculate the required output capacitance. Generally speaking, the larger the capacity of the output capacitor, the smaller the ripple, but it will also increase the cost and volume.
Through the comprehensive application of the above methods, the ripple noise level of the DC-DC converter can be effectively reduced, and the performance and reliability of electronic equipment can be improved.
