What is the difference between normal transformer and planar transformer

Also, could you advise how does one limit current at the output? I'm guessing R19 resistor will play a role in it, right? For instance, the RDR circuit was designed to limit current to 2. What is the input voltage range for your design? Is it universal input or high line only. The reference design uses kHz as nominal switching frequency.

In your design you are using only 66 kHz. The output capacitance also very low. Please re-visit your transformer design using Piexpert online tool.

The tool still doesn't have ER25 core but you can add core details manually or consider the core area equal to ER Your bias voltage seems very high, please follow design parameters form PIexpert tool. Hi, VAC euro mains? What about my questions? Can someone help with them here? I don't think output capacitance is the issue here And if someone could answer why there's 5. Hi, You are correct. I overlooked the C15 value. The output capacitance is correct.

The absolute control pin C maximum voltage is 9V. Your schematic shows that F pin connected to source. That forces IC to kHz operation instead of 66 kHz operation. All Rights Reserved. Start Designing. Your answer has been taken into account.

Thank-you for your help. Subscribe to our newsletter. Thank you for subscribing. There was a problem with your request. Extend the search. Search by manufacturer. Average score: 4.

With DirectIndustry you can: Find the product, subcontractor or service provider you need Find a nearby distributor or reseller Contact the manufacturer to get a quote or a price Examine product characteristics and technical specifications for major brands View PDF catalogues and other online documentation.

They exclude delivery charges and customs duties and do not include additional charges for installation or activation options. Prices are indicative only and may vary by country, with changes to the cost of raw materials and exchange rates. The traces can all be connected in series to form a winding where each trace is a separate turn of the winding.

In this example, the terminal ends of each trace are offset from the traces on the adjacent levels, so that the plated through holes in each level do not intersect. Two or more traces can also be connected in parallel to decrease the impedance of a particular turn of the winding. In yet another alternate embodiment, one or more of the traces can be formed as separate windings.

In each case, the resultant winding or windings is a function of the way in which the conductive traces on each layer of the multi-layer PCB are connected together and coupled to external circuits, to thereby create a planar transformer. The inductance of a winding formed using a multi-layer PCB can be increased by introducing a core of a magnetic material through an aperture formed in the PCB layers that extends through a central non-conducting region of each layer.

Alternatively, the core can be configured to surround the PCB. The core is typically included as part of a housing for the multi-layer PCB winding.

Conductive leads or vias are included on one or more of the PCB layers to enable the efficient electrical connection of the PCB winding to an external circuit, for example, by surface mounting and reflow soldering of the PCB winding to another PCB having other circuit components. This use of a multi-layer PCB to fabricate electromagnetic components results in smaller, more easily manufactured, and more reproducible components than is possible using a winding formed from a wire wrapped about a core.

In order to achieve better coupling and to reduce the leakage inductance of the transformer, the primary and secondary windings of the transformer are typically placed in close proximity to one another. One drawback of this arrangement is that it increases the capacitive coupling between the primary and secondary windings, which results in the generation of increased electromagnetic interference EMI. That is, due to the inter-winding capacitance of the transformer, common mode noise will be injected into the secondary.

In a planar, low profile transformer required for low profile packaging, this inter-winding capacitance is larger and, as a result, the common mode noise injection via this parasitic capacitance is larger.

This drawback is especially significant for a two switch forward converter. Unlike in a single switch forward converter, the primary winding in a two switch forward converter is not connected to either the positive or the return side of the converter's input voltage. The converter 10 has an input terminal 14 to which an input DC voltage, V in , is coupled, relative to a ground potential at an input terminal 16 , and an output terminal 32 where the output DC voltage, V OUT , is provided relative to ground.

Converter 10 includes a transformer 42 having primary winding 2 and a secondary winding 6. Each winding has a first and second end. A first power switch 34 is coupled between the first end of primary winding 2 and input terminal A second power switch 36 is connected between the second end of primary winding 2 and input terminal Power switch 34 is connected in series with primary winding 2 and power switch 36 across the input DC voltage terminals.

A diode 18 is connected between the second end of primary winding 2 and input terminal The diode 22 is connected between the first end of primary winding 2 and input terminal A controller not shown preferably provides a control signal, e. On the secondary side of the forward converter 10 , transformer 42 has a secondary winding 6 having a second end connected to output terminal, Converter 10 includes an inductor 24 connected in series with a diode 26 between output terminal 32 and the first end of secondary winding 6.

A capacitor 28 is connected across the output terminals 32 , A diode 44 is connected between the junction of the cathode of diode 26 and inductor 24 and output terminal As shown in FIG. Primary winding terminal 7 is connected to the source terminal of switch Primary winding terminal 9 is connected to the drain terminal of switch For the two switch forward converter 10 , the voltage swing at primary winding terminals 7 and 9 is at a maximum during normal operation.

If primary winding terminals 7 and 9 are located near the secondary winding 6 of transformer 42 , a significant amount of common mode noise is coupled from the primary side to the secondary side of the transformer 42 due to the capacitance between primary winding 2 and secondary winding 6. This coupled common mode noise increases EMI for converter The ' patent discloses a transformer wherein all of the primary and secondary windings are integrated in a PCB. The ' patent teaches that the top winding 72 connected to the input voltage source is the quiet area of the primary winding since it exhibits a lower voltage swing, and that therefore it is logical to locate the secondary in the vicinity of winding However, due to reasons of symmetry, the secondary winding 80 in ' is positioned between primary windings 74 and Unlike in the single switch forward converter for which the ' patent teachings were directed, the primary winding in a two switch forward converter is not connected to either the positive or the return side of the converter's input voltage.

One drawback of the ' patent, therefore, is that it does not address the unique problems in reducing common mode noise for a two switch forward converter. The ' patent does not disclose, for instance, the optimum location for the secondary winding in a two switch forward converter.

A need therefore exists to reduce common mode noise for a planar transformer. The need especially exists to reduce common mode noise for a planar transformer designed for use in two FET forward converters and which can also be used in single ended, half bridge converters and push pull converters.

The present invention solves the problems of prior art devices by providing a method of construction of a planar transformer that minimizes capacitively coupled common mode noise from the primary winding to the secondary winding of the transformer. An advantage of the present invention is improved EMI performance by reducing common mode noise coupled from the primary winding to the secondary winding in a power transformer.

Another advantage of the present invention is that it reduces the common mode noise coupled to the secondary winding without increasing the leakage inductance. Still another advantage of the present invention is that is readily implemented in a planar transformer using PCB windings, which enables the number of turns of the primary winding in the contact surface between the primary and the secondary winding to be reduced to one turn for minimizing noise coupling.

Another advantage of the present invention is that it can be applied for both regular planar transformers and matrix planar transformer. The forgoing aspects and the attendant advantages of the present invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:.

Converter has an input terminal 14 to which an input DC voltage, V in , is coupled, relative to a ground potential at an input terminal 16 , and an output terminal 32 where the output DC voltage, V OUT , of the converter is provided relative to ground.

Converter includes a transformer having a primary winding and a secondary winding 6. Primary winding comprises a first winding 4 and a second winding 8. The second end of the first winding 4 is connected to the first end of second winding 8 , at a node 5.