The conversion efficiency of electronic transformer is a key index to measure its performance, which directly affects the energy consumption and operating cost of electronic equipment. The following are some ways to improve the conversion efficiency of electronic transformers:

1. Magnetic core material
1. ** Select the right core material **
- ** Ferrite core **
- For high-frequency electronic transformers, ferrite cores are a common choice. For example, manganese zinc ferrite, which has high permeability, is able to produce a large magnetic flux at a small magnetic field strength, which helps to reduce the number of turns in the primary and secondary windings. According to voltage transform formula of the transformer \ (V_2 = \ frac {n_2} {n_1} V_1 \] (\ (n_1 \) as the primary winding circle number, \ (n_2 \) as the secondary winding circle number, \ (V_1 \) as the primary voltage, \ (V_2 \) as the secondary voltage), the decrease of number of turns can reduce the loss of winding resistance.
Ferrite core also has low loss characteristics at high frequencies, especially its eddy current loss is relatively small. This is because the resistivity of ferrite is higher, according to the eddy current loss formula \ [P_e = k \ frac {B ^ 2 f ^ 2 d ^ 2} {\ rho} \] (\ (P_e \) as the eddy current loss, \ [k \], with constant \ [B \] for the magnetic flux density, \ [f \) for frequency, \ \ (d) as the thickness of the material, \(\rho\) is resistivity, high resistivity \(\rho\) can effectively reduce eddy current loss, thereby improving conversion efficiency.
- ** Amorphous alloy core **
- Amorphous alloy cores can also be used to improve conversion efficiency in some cases. This magnetic core has excellent soft magnetic properties, such as high permeability and low coercivity. Low coercivity means that the core consumes less energy during magnetization and demagnetization. In some low-frequency or medium-frequency electronic transformer applications, amorphous alloy core can reduce hysteresis loss, hysteresis loss formula \(P_h=\eta fB^nV\) (\ (P_h\) is the hysteresis loss, \(\eta\) is the hysteresis coefficient, \(f\) is the frequency, \(B\) is the magnetic flux density, \(n\) is the exponent. \(V\) is the core volume), which improves the overall efficiency of the transformer by reducing the hysteresis loss.

2. ** Optimized core structure **
- ** Reduced core gap **
- Minimize the core gap as much as possible. Magnetic core clearance can increase the magnetic resistance of magnetic circuit, according to the magnetic circuit ohm's law \ \ Phi (= \ frac {NI} {R_m} \] (\ (\ Phi \) as the flux, \ [N \] for winding circle number, \ [I \] for current \ [R_m \) for magnetic resistance), magnetic resistance \ [R_m \) increases, To obtain the same magnetic flux \(\Phi\), a larger ampere-turns \(NI\) is required, which causes the winding current to increase, thereby increasing the winding loss. Reducing the magnetic core gap can reduce the reluctance, reduce the current demand, and improve the conversion efficiency.
- ** Using ring core **
- Annular magnetic core has better magnetic circuit closure than other shapes (such as E, U, etc.). In the ring core, the magnetic field is mainly concentrated inside the core, and the magnetic leakage is less. This can improve the utilization rate of the magnetic core, so that the magnetic coupling between the primary winding and the secondary winding is closer, so as to reduce the loss of energy in the magnetic coupling process and improve the conversion efficiency.

Two, winding design
1. ** Reasonable selection of winding wire **
- ** High frequency transformer Leeds wire **
- In high frequency electronic transformers, due to skin effect (high frequency current tends to flow on the wire surface), Leeds wire should be used as the winding wire. Litz wire is composed of multiple strands of thin wire, which can increase the effective conducting area of the wire. = delta according to the skin depth formula \ (\ \ SQRT {\ frac {2 \ rho} {\ mu \ PI f}} \] (\ delta (\ \) as the skin depth, \ \ rho (\) for wire resistivity, \ (\ mu \) as the conductor magnetic permeability, \ [f \) for frequency), in the high frequency fixation of the skin depth is small, The Leeds wire can overcome the problem of increased resistance caused by skin effect, reduce the DC resistance of the winding, reduce the copper loss of the winding (\(P_{cu}=I^2R\), \(P_{cu}\) is the copper loss, \(I\) is the current, \(R\) is the winding resistance), thus improving the conversion efficiency.
- ** Consider current density and wire specifications **
- When selecting the winding wire, the current density should be reasonably determined according to the rated current of the transformer. If the current density is too high, the resistance loss of the conductor will increase. If the current density is too low, the wires will be too thick, increasing the volume and cost of the transformer. Through accurate calculation and experimental verification, the appropriate current density and wire specification are selected, so that the winding can meet the current carrying capacity and reduce the resistance loss to the minimum.
2. ** Optimize winding structure **
- ** Multilayer winding **
- Multi-layer winding structure can reduce magnetic leakage. For example, in a planar transformer, the primary winding and the secondary winding are arranged in layers, which makes the magnetic field generated by the primary winding pass through the secondary winding more, and improves the magnetic coupling efficiency. According to the formula of magnetic flux leakage \ (\ Phi_ = k \ frac {leak} {I} {r} \] (\ (\ Phi_ {leak} \) for leakage flux, \ \) (k is constant, \ [I \] for current \ \ (r) for winding radius), reduce the magnetic flux leakage can increase the energy conversion efficiency of transformer.
- ** Tightly coupled winding **
- When designing windings, the tight coupling of primary and secondary windings should be achieved as far as possible. For example, the mutual inductance coefficient between primary and secondary windings can be maximized by adjusting the spacing and direction of the windings. According to the equivalent circuit theory of transformers, tightly coupled windings can reduce leakage induction and equivalent series resistance, thereby improving conversion efficiency.

3. Heat dissipation management
1. ** Thermal design optimization **
- ** Application of heat sink **
- For electronic transformers with large power, installing heat sinks is an effective way to dissipate heat. By increasing the heat dissipation area, the heat generated by the transformer is dissipated to the surrounding environment more quickly. \ according to the heat conduction formula (Q = - kA \ frac {dT} {dx} \) (\ \ (Q) for the heat flow, \ [k \] as the thermal conductivity, \ [A \] for the cooling area, \ (\ frac {dT} {dx} \) for temperature gradient), large heat dissipation area \ [A \) can increase the cooling efficiency. When choosing a heat sink, factors such as its material (such as aluminum heat sink with high thermal conductivity), shape (such as fin fin heat sink with large heat dissipation area) should be considered.
- ** Optimized transformer package **
- In the packaging design of the transformer, packaging materials with good heat conduction properties should be used. For example, some high-performance epoxy resin packaging materials have higher thermal conductivity than ordinary materials. At the same time, it is necessary to reasonably design the packaging structure so that the heat can be smoothly transmitted from the inside of the transformer to the external environment. For example, a heat conduction channel is set up inside the package or a thin package structure is used to reduce thermal resistance, improve heat dissipation efficiency, and prevent the transformer from reducing efficiency due to overheating.

4. Circuit topology and control
1. ** Adopts advanced circuit topology **
- ** Soft switching technology **
In electronic transformer applications in switching power supplies, the use of soft switching technology can significantly improve the conversion efficiency. Soft switching technologies such as zero voltage switching (ZVS) and zero current switching (ZCS) can reduce power losses during switching. In the traditional hard switching circuit, the switching tube will produce a large voltage and current spike at the moment of opening and closing, resulting in switching loss (\(P_{sw}=V_{ds}I_{ds}t_{sw}\), \(P_{sw}\) is the switching loss, \(V_{ds}\) is the drain-source voltage, \(I_{ds}\) is the drain-source current, \(t_{sw}\) is the switching time). The soft switching technology greatly reduces the switching loss by making the voltage or current zero or close to zero when the switching tube is on and off, thus improving the conversion efficiency of the electronic transformer.
- ** Resonant circuit topology **
- Resonant circuit topology is also an effective way to improve the conversion efficiency of electronic transformers. For example, a series resonant circuit and a parallel resonant circuit can enable an electronic transformer to operate in a resonant state, in which the current and voltage waveforms in the circuit are optimized. According to the resonant frequency formula \(f_0=\frac{1}{2\pi\sqrt{LC}}\) (\(f_0\) is the resonant frequency, \(L\) is the inductor, \(C\) is the capacitor), through a reasonable choice of inductor and capacitor values, so that the circuit works near the resonant frequency, can reduce the reactive power in the circuit, improve the power factor, The conversion efficiency of electronic transformer is improved.
2. Accurate control strategy **
- ** Feedback control **
The use of accurate feedback control strategies is essential to improve the conversion efficiency of electronic transformers. For example, in a regulated power supply, through voltage feedback control, the output voltage can be monitored in real time, and the working state of the electronic transformer can be adjusted according to the deviation of the output voltage from the set value. If the output voltage is too high, the feedback control system will reduce the input voltage or adjust the turn ratio of the transformer to reduce the output voltage, thereby avoiding unnecessary energy loss. At the same time, the current feedback control can also be used to optimize the working parameters of the transformer according to the size of the load current, and improve the conversion efficiency.
- ** Intelligent control algorithm **
The application of intelligent control algorithms such as fuzzy control and neural network control can further improve the control accuracy and efficiency of electronic transformers. These intelligent control algorithms can adaptively adjust the working mode of the electronic transformer according to various input parameters (such as input voltage, load current, temperature, etc.). For example, fuzzy control can determine the appropriate control output through fuzzy rule base according to the input fuzzy variables (such as voltage fuzzy set, current fuzzy set, etc.), so that the electronic transformer can maintain a high conversion efficiency under different working conditions.