Preface
Digital power amplifiers feature low distortion, low noise, and a wide dynamic range. In terms of sound warmth/coolness, resolution, and the impact force of low frequencies, they are incomparable to traditional power amplifiers.
Development of Inductors for Digital Power Amplifiers
The digital power inductor, also known as Class D power inductor, is mainly used for filtering at the output of digital power amplifier circuits to meet the design requirements of high sound quality and low distortion. In the field of power amplifiers, open I-shaped inductors were initially used for output filtering. This type of inductor has poor current resistance and is prone to heating, so it is only used in low-power scheme designs. Due to its open structure, it also has relatively poor anti-radiation interference capability. Subsequently, shielded plug-in inductors were introduced, which improved the anti-interference capability. However, due to the limitations of the core material characteristics, they are extremely prone to saturation and are still limited to some low-power scheme designs. At the same time, high-power output schemes generally use toroidal inductors made of iron powder core materials.Toroidal inductors have been greatly improved in terms of anti-interference capability and power, but due to the relatively low permeability of their materials, many turns need to be wound to meet the design requirements, resulting in a large product volume, occupying a lot of PCB area, and the iron powder core materials have poor linearity, which is easily causes distortion and affects the sound quality.
Therefore, in the design of small-volume and high-power output schemes, the selection of filter inductors has gradually become a key concern for engineers.
Digital Power Inductors
To meet the design requirements of small size, high power, low radiation, and low distortion, CODACA Electronics has designed and developed multiple series of digital power inductors, such as CPD, CSD, CPE, CSAD, etc. A total of 31 series and 160 specifications have been successfully applied to various Class D high-power amplifier scheme designs.
Scheme Design Application
The following is the Infineon EVAL_AUDAMP24 evaluation board, a dual-channel, 225W/ch (4Ω at ±43V) or 250W/ch (8Ω at ±63V) half-bridge digital power amplifier designed for high-end Hi-Fi audio systems. This evaluation board demonstrates the implementation of protection circuits and the design of an optimal PCB layout using IGT40R070D1 E8220 CoolGaN™ gallium nitride transistors and MERUS™ IRS20957SPBF controller ICs.
The scheme design of the EVAL_AUDAMP24 evaluation board adopts CODACA Electronics' digital power inductor series CPD3119 for output filtering. The output inductor features relatively low resistance, and the capacitor exhibits high linearity with respect to load current and voltage. This ensures high fidelity while achieving higher efficiency and greater output power.
[Infineon EVAL_AUDAMP24 Evaluation Board]
1.Schematic Diagram
[Infineon EVAL_AUDAMP24 Simplified Schematic Diagram]
2.Test Conditions:- Vbus = ±43 V- Input Signal: 1 kHz- Load = 4 Ω- Frequency = 500 kHz
[Power vs. THD+N @ 4Ω Load]
[4 Ω load stereo, ±B supply = ±43 V]
CODACA's digital power inductors feature the following characteristics:
1.Stable high saturation magnetic flux density: Resistant to magnetic saturation under high peak currents, effectively filtering out spike noise signals.
2.Excellent shielding effect: Strong electromagnetic interference (EMI) resistance.
3.Oxygen-free copper enameled wire coil design: Superior electrical conductivity enables ultra-fast signal transmission with low distortion.
4. Compact package size: Suitable for various small-volume and high-efficiency scheme designs.
The CPD3119 series of digital power inductors has 9 inductance values, ranging from 5.0μH to 33μH, with saturation currents of 21.5A to 70.0A. It can continuously work in an environment of -40℃ to +125℃.
Electrical Characteristics
Saturation curve：
Temperature rise curve：
Service environment
Operating temperature: -40°C to +125°C (including heat generated by the coil).
Environmental standards
The CPD3119 digital power amplifier inductor complies with environmental protection requirements such as RoHS, REACH, and halogen-free standards.
Production status
Mass production, packaged in blister trays, 9 pieces per tray. A sample application is available.