GB2572951A

GB2572951A - A method of manufacture of a gate drive circuit and a gate drive circuit

Info

Publication number: GB2572951A
Application number: GB1806056.6A
Authority: GB
Inventors: Young George; Tue Vu Trong
Original assignee: Icergi Ltd
Current assignee: Icergi Ltd
Priority date: 2018-04-12
Filing date: 2018-04-12
Publication date: 2019-10-23
Also published as: GB201806056D0

Abstract

A high side driver suitable for providing a drive signal to a gate of a semiconductor switch comprises a transformer, a printed circuit board (PCB) substrate (Fig.4, 120), driver circuitry, and switch contacts including at least a gate contact for connecting to the gate of a high side driver switch. The transformer, which includes primary and secondary side windings and a magnetic core 128, typically provides isolation between a control circuit and the high side switch being controlled. The PCB substrate has first and second opposing surfaces 404 & (Fig.4, 402) with a side wall there between, and a first section of the magnetic core material (Fig.4, 124) extends inwardly into the PCB substrate from the side wall such that at least part of the magnetic core is located in the substrate between the first and second surfaces. Input contacts are provided on the first surface of the substrate for receiving an input drive signal, and the driver circuitry transfers the input drive signal through the primary and secondary side windings to the gate contact. Other arrangements include a switching circuit comprising the semiconductor switch and high side driver, and a module comprising a plurality of switching circuits on the same PCB substrate which may be used together with a switched capacitor arrangement to provide a multi-level switching module (Figure 12).

Description

A METHOD OF MANUFACTURE OF A GATE DRIVE CIRCUIT AND A GATE DRIVE CIRCUIT

Field of the Application

The present application relates to drive circuits for driving a switch and in particular to drive circuits employing a transformer to provide an isolation barrier between control circuity and a switch being controlled by the control circuitry.

Background

Switching power supply circuits conventionally employ a controller to ensure that the switching devices of the power supply are switched appropriately. These controllers conventionally operate at relatively low voltages (5Volts or less). At the same time, depending on the topology of the switching circuit and the operating voltage of the power supply, the voltages presented at the switches being switched can be significantly higher. Accordingly, to drive such switches it is necessary to generate a drive signal which is at a higher potential than the reference (ground) voltage of the control circuit. Circuits which provide for this are referred to as high side drivers. They may also be considered as floating or isolated drivers. Similarly, the switches may be considered to be floating switches.

High side drivers also have application in other situations. For example, in a circuit using a ground referenced current sensor positioned between ground and the switch, a high side driver may be employed to isolate the gate control from the effects of any voltage drop across the current sensor (which may vary with current). It will be appreciated that in this context, the voltage across the current sensor may be relatively small.

There are several different approaches to providing high side driver circuits. A first is to implement the driver in silicon (i.e. an integrated circuit) using level shifting circuitry. The advantage of these devices is that they are presented as a single component and thus may be readily employed in a circuit. As a result, they are convenient for use in power supply design. They are however relatively expensive, inefficient and limited in terms of the voltages they may be employed with.

An alternative approach is to employ a transformer to provide an isolation barrier between the control circuitry generating the switching signals for a switch and the gate of the switch being controlled. An exemplary high side driver using such a transformer based approach is described in US Patent No. 9,590,621 which is assigned to the assignee of the present application and the entire contents of this patent are herein enclosed by reference. The disadvantage of this approach is that there is a multitude of components in addition to the transformer that are required to implement the driver. The selection and arrangement of which require that careful consideration must be given to the implementation of the high side driver by the power supply designer.

Summary

The present application provides a solution to the problems of the transformer based high side drivers by presenting a transformer based high side driver as a single component. This single component may be mounted conventionally on a circuit board using conventional surface mounting techniques.

In one aspect, the present application provides a method of manufacturing a circuit component. The component comprises a transformer. The method comprises the steps of:

forming a winding using a multi-layer printed circuit board construction, the printed circuit board construction comprising a top surface, a bottom surface, with at least one side surface extending between the top and bottom surfaces the winding comprising a first series of tracks provided in a first layer of the printed circuit board; defining a first space within the printed circuit board construction; and inserting a first section of magnetic material into the first space through an opening in the at least one side surface to form at least in part a magnetic core of the transformer.

A second section of magnetic material may be provided to complete the magnetic core of the transformer. In this context, the second section may be inserted into recess defined in the top or bottom surface. The second section of magnetic material is suitably a C or E shaped core. The defined recess is suitably shaped to match the shape of the second section of magnetic material.

The first section of magnetic material may be a flat section of magnetic material.

Alternatively, the first section of magnetic material may be a C or E shaped core. In this case, the second section of magnetic material may be a C or E shaped core or flat shaped section of magnetic material. The second section is suitably inserted into a recess that has been formed for receiving it.

Contacts may be formed on the printed circuit board to allow the transformer to be mounted as a discrete component on an application circuit board.

Further components may be mounted on the top surface of the multi-layer printed circuit board. For example, a semiconductor switch may be mounted on the top surface.

The circuit component being manufactured suitably comprises a high side driver. The circuit component may comprise a high side driver in combination with a semiconductor switch being controlled by the high side driver.

In one aspect, the present application provides a circuit component configured for mounting on a circuit board. The circuit component suitably comprises a laminate body formed as a plurality of layers between a first surface and an opposing second surface, with at least one side wall extending between the first and second surfaces;

a transformer comprising a magnetic core, wherein the magnetic core is formed from a first section of magnetic material and a second section of magnetic material; wherein the first section of magnetic material is received laterally through the at least one side wall into a space formed in the laminate body.

A winding of the transformer may be formed at least in part using a track provided in a first layer of the printed circuit board.

The second section of magnetic material may be positioned within a recess in the first or second surface.

The first section of magnetic material may be a flat section of magnetic material. In which case, the second section of magnetic material is suitably a legged (for example C or E shaped) core.

The first section of magnetic material may be a legged core (for example a C or E shaped core). In which case, the second section of magnetic material may be a C or E shaped core or flat shaped section of magnetic material (l-core).

Contacts may be provided to form connections with an underlying application circuit board.

Discrete components may be surface mounted on the second surface of the circuit component.

The circuit component may be a high side driver or a combined high side driver and switch driven by the high side driver.

In a further aspect, the present application provides a high side driver for providing a drive signal to the gate of a switch. The high side driver suitably comprises at least one transformer having a primary side winding, a secondary side winding and a magnetic core. The high side driver comprises a substrate having a first surface and a second surface opposite the first surface with at least one side wall there between. Input contacts are provided for receiving an input drive signal, wherein the input contacts are provided on the first surface of the substrate. Driver circuitry is provided comprising a plurality of components configured to transfer the input drive signal using the transformer to the gate of the switch. The magnetic core of the at least one transformer is formed at least partially in the substrate between the first and second surfaces.

A switching circuit may be provided by combining the switch and the high side driver together with the high side driver providing a drive signal to the gate of the switch. In this arrangement, the switch may be mounted on the second surface. Thus a floating switch may be provided.

A plurality of switches and associated high side drivers may be commonly provided on the same substrate. With such an approach, a multi-level switching module comprising a switched capacitor arrangement consisting of a plurality of floating switches to switch the capacitors. In this arrangement, the capacitors may be provided as components in the module, for example mounted on the same surface as the switches. The switches may be package-less semiconductor switches mounted on the surface with wire bonds used to form electrical connections.

These and other aspects will become apparent from the detailed description which follows and the accompanying drawings.

Description of Drawings

Figure 1 is a perspective top view of an exemplary approach to constructing a transformer using a printed circuit board and a two section magnetic core known in the art in which the first of the two sections is shown;

Figure 2 is a side perspective view of Figure 1 with both sections shown;

Figure 3 is an alternative approach in which the second section is recessed into the bottom of the printed circuit board;

Figure 4 is a side view of a first aspect according to the present application;

Figure 5 is a bottom perspective view of the aspect of Figure 4;

Figure 6 is an exemplary track layout for a PCB layer employed in the aspect of Figure 4;

Figure 7 is a side view of a circuit board construction in accordance with a second aspect of the present application;

Figure 8 is a top perspective view of a first section of a magnetic core for use with the circuit board construction of Figure 1;

Figure 9 is an exemplary track layout for a first PCB layer employed in the aspect of Figure 7;

Figure 10 is an exemplary track layout for a second PCB layer for use with a layer as shown in Figure 9;

Figure 11 is an exemplary transformer based high side driver package in which the transformer is formed in PCB material with the remaining components provided as components onto the PCB;

Figure 12 is an exemplary arrangement providing a plurality of isolated switches and capacitors as might be employed in a multi-level switching circuit;

Figure 13 is a process flow chart for a first exemplary method which may be employed for example to form the constructions of Figures 4 or 7;

Figure 14 is a process flow chart for a second exemplary method;

Figure 15 is a top view of an exemplary arrangement of a module which may be employed as a pair of switches in a half bridge switching arrangement; and

Figure 16 is a side view of the exemplary arrangement of Figure 15.

Detailed Description of Drawings

The present application seeks to provide an arrangement for a transformer which may be used to advantage in switching circuits. The arrangement is particularly suited to providing a driver circuit for a switch or an integrated driver circuit and switch in a switching circuit.

The arrangements described below implement the windings of a transformer using printed circuit board techniques of tracks (traces) and vias. The arrangements provide a component which in turn may then be positioned on and connected as a discrete component to an application circuit board.

It is known to form transformers and inductors by incorporating magnetic elements along with conventional electronic components in a printed circuit board assembly. More particularly, the technology of “planar magnetics” is known where the windings associated with an inductor or transformer are implemented partially or completely as printed circuit board traces, and a magnetic circuit is formed using pieces of magnetic material - typically ferrite. In the case of a transformer, the magnetic path is conventionally selected to be a closed magnetic path to constrain the magnetic flux developed to the magnetic material.

A relevant example of a magnetic component is as shown in figures 1 and 2, where a transformer 100 is shown. The transformer comprises a first section 102 of magnetics material (an E-core) provided on a substrate 104. The substrate is suitably formed as a section of printed circuit board.

Openings are formed through the printed circuit board from the top surface through to the bottom surface to accommodate the legs of the E-core.

The windings of the transformer (not shown) are formed using conductive tracks defined in one or more layers of the printed circuit board. Connections to the windings may be formed using vias or interconnects.

As shown in Figure 2, a second section of ferrite 106 (a flat core piece (commonly referred to as an l-core) or a second E-core) is provided in alignment with the first section to complete the magnetic core of the transformer. Tracks on the surface layers, and more commonly on internal layers, of the PCB are used to implement “windings”. The printed circuit board may part of a larger circuit board or it may be formed as a discrete component for placement on an “application” printed circuit board.

Where the arrangement is employed as a discrete component on a printed circuit board, a lead frame is required to allow the component to be mounted directly onto the application circuit board.

Alternatively, a recess (cut-out) may be formed in the application board. This recess is shaped to accommodate the second section of magnetic material with the result that the bottom surface of the printed circuit board comes into contact with the top surface of the application circuit board allowing for connections to be made without an additional lead frame.

An alternative approach is to make the circuit board thicker and to form a channel or slot 110 in the bottom surface of the board to accommodate the second section of magnetic material. In this alternative approach, as shown in Figure 3, the lower section offerrite may be fully recessed within the printed circuit board, thus allowing a flat mounting surface which may be mounted on an underlying application board without the need for a cutout in the “application board”.

An aspect of the present application is to provide a high side driver module, which employs at least one transformer, as a discrete component for placement on an application circuit board.

Whilst the approach of figure 3 provides advantage, in that it allows for flat mounting, an inherent disadvantage is that space to allow for the provision of circuit tracks and for the placement of other components so as to combine the magnetics (transformer) with other components is limited by the presence of the core on the top surface, i.e. the surface opposite the mounting surface.

It will be appreciated that any arrangement that reduces the footprint of a component is desirable.

In the context of the present application, providing a transformer based high side driver or floating switch that has a similar footprint to silicon based high side driver or floating switch is desirable.

An alternative approach (not shown) that has been employed previously to form a transformer in a circuit board is one of embedding a magnetic section to provide a closed magnetic circuit as the printed circuit board lamination steps are taking place, and using vias and tracking to provide the required turns associated with providing the inductance or transformer functionality. Typically this involves placement of a ferrite toroid within the PCB layers during assembly. An advantage of this approach is that the windings may be formed using tracks on surfaces above and below the magnetic core in contrast to the approach of Figure 1 and 2, where the space must be left open to accommodate the positioning of the cores.

A challenge with the embedding approach lies in containment of stresses in the ferrite material. The ferrite possesses magnetostrictive properties. This implies an increase in losses and a reduction in permeability when the ferrite section cannot move freely or is otherwise subject to stresses. Such stresses would be an inherent part of a PCB lamination process. This is particularly the case with relatively small magnetic cores where the inherent strength is less. In the context, of the present application which is directed at relatively low energy transfers of drive signal or snubbers rather than inductors or transformers in the switching topology of a switching circuit, the magnetic cores are relatively small. In this context, the effective cross sectional area of exemplary cores employed is less than or equal to 9mm² and typically of the order of approximately 4mm².

The present application seeks generally to provide an alternative solution and provides an approach that provides the advantages of embedded toroid type cores but avoids the problems associated with PCB lamination techniques.

More generally, the method allows for post-placement offerrite material into previously formed slots or cavities in the printed circuit board. However, in contrast to the prior art approaches of assembling the magnetic core through cut-outs extending between the top and bottom surfaces, the present application enables the insertion of one or both sections of the magnetic core laterally through an opening(s) defined in a side wall which extends between the top and bottom surface. It will be appreciated that such an approach is entirely counter-intuitive since normal manufacturing technique is to pick and place from above.

However, the advantage of this approach is that it means that the ferrite material does not have to undergo the pressure and temperature extremes as associated with PCB lamination, and can be affixed into position by clip and/or glue approaches after fabrication of the PCB laminate (circuit board). This operation may be undertaken in advance of placement of additional electronic components (for example on the top surface) or subsequently.

The slots or cavities in the printed circuit board may be formed using conventional PCB techniques, for example mechanical or laser milling techniques.

It will be appreciated that conventional PCB production techniques may thus be employed to produce the circuit board construction which incorporates the magnetic materials.

In order to position the magnetic materials within the PCB, it is necessary to form a space (cavity within the PCB) into which a corresponding magnetic piece or pieces may be received.

The process to form a space may be applied partially or fully upon completion of the PCB lamination process, as effectively an extension of the normal board routing steps.

Alternatively, some cavities may be formed during build-up of the board. It will be appreciated that if the space is to be formed during the PCB lamination process, it is necessary to create the space and then ensure that the space remains throughout the PCB lamination process.

If a conventional pre-preg was used in which the space was formed (e.g. by laser cutting), it will be appreciated that the pre-preg would flow to at least partially fill the space.

To counter this, a form having a suitable release agent may be placed in the space. The form acts to prevent the pre-preg filling the space during lamination. Once the lamination process has been completed the form may be withdrawn to create the space.

Alternatively, a “no flow prepreg” material may be used so as to maintain the integrity of the cavity.

In this way, the materials in which the space is formed are selected to be no flow materials. Several layers of no flow prepreg may be required, with a first forming the base of the cavity, the second having a space cut-out to define the cavity and the final layer forming the roof of the cavity.

An exemplary flowchart 200 for manufacture is shown in Figure 13 which uses conventional multi-layer PCB techniques. The process commences with the formation 202 of one or more inner layers of PCB. It will be appreciated that several devices may be constructed together as part of a panel for reasons of economy.

Where the windings are to be formed as tracks on an inner layer of the PCB, then a series of tracks are suitably formed at this time. Tracks are suitably formed using conventional etching techniques familiar to those in the art. Different series of tracks may be formed on different layers which may then be connected together by interconnects to form an overall winding. During the formation of the inner layers one or more spaces may be defined to subsequently accommodate a section of a magnetic core for the transformer. As an example, three layers of non-flow pre-preg may be assembled one on top of the other. The bottom layer acts as a bottom surface of a cavity or space for the magnetic material. Tracks for the windings may be defined on the bottom layer or a layer beneath this again. A middle layer may be milled or laser cut to create a space for the magnetic material.

To accommodate subsequent lateral insertion of the magnetic material, the space may extend to the border of the device. It will be appreciated that in the case of where the devices are constructed in panel form that this may not be to the edge of the panel merely to the edge of where the device will be de-panneled. Equally, as will become apparent from the discussion of the further method of Figure 14 the space need not extend fully to the edge as the side opening may be opened in a later step.

A top and bottom layer of pre-preg may then be added and the layers then laminated 204 together using a combination of heat and pressure. Thereafter, the conductive tracks for the top and bottom layers may be formed. The board may then be drilled and plated 206 to form plated through holes, interconnects and castellated vias as required. It will be appreciated that the use of contact features such as castellated vias, allows for the device to be mounted directly to an underlying application circuit board.

At this stage, the top surface of the panel may be populated by additional components (for example switches, drivers, capacitors etc.) using conventional surface mount or wire bond techniques.

If the device has been produced in panel form, the device may be de-panneled 208. The depanneling process may be by any suitable cutting means, for example, laser cutting.

The de-panneling process creates an opening in the side wall of the device for the magnetic core (or section thereof) to be inserted into the previously defined space. A second section of magnetic core may then be placed in through a separate opening to a separate connected space so as to complete the formation of the magnetic core (as described above). The separate opening may be in another side wall or in the top or bottom surface. It will be appreciated that for lateral insertion, the simplest approach is to employ an l-core for the laterally inserted piece with a C or E core inserted through openings in the top or bottom surface. In both cases, the openings are suitably shaped to match and receive the core.

An alternative method 300 of construction is shown in Figure 14. In this method, the module is constructed conventionally using PCB processes. During these processes, the tracks, interconnects and vias are formed in the various layers of the PCB. For efficiency, a plurality of modules are formed in a single PCB panel 302. At this juncture, the spaces for the subsequent insertion of magnetic core pieces have not been completed.

Openings may be formed in the top or bottom surfaces to allow for the subsequent insertion of the magnetic core pieces.

A depanneling step 304 is then employed to separate the individual modules from the panel so as to expose the side edges where openings will be subsequently formed (as described below) into which magnetic core pieces can subsequently be inserted.

In this context, it will be appreciated that the modules may be depanneled in strips rather than in individual modules.

The modules or strips of modules are then stacked one on top of the other to form a stack.

The entire stack may then be rotated 306 so that a side wall of each of the modules is then exposed on the top.

A conventional mechanical or laser milling process may then be employed to form cuts through the exposed side wall of each module to define the spaces for receiving sections of the magnetic core through the side wall. The advantage of this approach is that milling/drilling machines employed in PCB manufacturing are generally configured for milling in a vertical operation and so using the stack in which the sides of the modules are presented as a top (or bottom) surface allows for the use of a conventional milling/drill machine set-up in a PCB manufacturing environment.

Once the milling step is finished, the required sections of magnetic core may be inserted into the spaces formed through the openings formed in the exposed side wall of the individual modules. The modules may then be de-stacked and the top surfaces populated with additional components as required. If sections of magnetic core are to be inserted in through openings in the bottom or top surface they may, for example, be inserted at this stage.

In both exemplary processes of manufacture, a fixing means may be employed to retain the magnetic pieces in situ. The fixing may be a tape or suitable adhesive.

Final steps of the process in both processes of manufacture may be to provide a shell about the component so that the component has the appearance of a single discrete device rather than a plurality of individual components assembled on a printed circuit board.

The shell may be of plastic.

Advantageously, the shell suitably comprises at least a top surface of metal to facilitate thermal conduction from the semiconductor components. The shell may be marked with manufacturer and component identifiers as would be familiar to those skilled in the art.

The shell may be configured as walls and a top surface to sit upon the top surface of the module or to sit around the edges of the module. In the latter case and potentially io the first, cut-outs or other accommodation may be made to ensure that the shell walls do not interfere with forming electrical connections to the module.

The application will now be explained in detail with reference to two separate exemplary implementations (configurations) of magnetic cores, where assembly of the core comprises the lateral insertion of a core piece through an opening in a side wall. It will be appreciated that both exemplary implementations may be manufactured using either of the two methods described above.

It will be recognised that these are representative of many possible implementations, including combinations where aspects of both approaches may be used.

Both implementations use E- cores. However, in the intended gate drive application, the E core (when combined with a flat section or other E-core) in effect provides two separate magnetic (loops) circuits. In other words, the E-core may be configured to be dual-chamber usage with two separate transformers defined by appropriately placed windings. It will be appreciated that a C-core may also be used to provide a single transformer.

As referenced above, the cross sectional area of the core in the applications outlined below is suitably of the order of 9mm² or less. Suitably, the cross sectional area of the core is of an order of 4mm² or less. In the context of an E-core, an exemplary core may be an E 6.3 core which would have a length of 6.3mm with a width of 2mm along the primary axis.

An initial implementation for making a circuit component uses a constructional approach as shown in figure 4. This approach illustrates a laminate body 120. The laminate 120 body is made up of a plurality of layers extending from a first planar surface to a second planar surface, i.e. top 402 and bottom 404 surfaces. Suitably, the laminate body is formed as a multi-layer printed circuit board construction using a combination of conventional PCB manufacturing techniques, for example as described above.

The bottom surface may be employed as a mounting surface which is intended in use to sit upon an application circuit board. The circuit component may have individual discrete components surface mounted on the top surface of the printed circuit board. Side walls extend between the top and bottom surfaces. A side wall may also be employed as a mounting surface if the circuit component is placed vertically on an application circuit board. In this case, it is advantageous to have all the connections 406 formed on the mounting surface or the edge of the top and bottom surfaces adjoining the edge.

A slot 122 is defined transverse to the axis between the top and bottom surfaces. The slot has an opening defined in a side wall in the section of printed circuit board material to accommodate a first section of magnetic material 124. In the exemplary arrangement shown, the section of magnetic material is an l-core. It will be appreciated that the slot and l-core shapes generally correspond. The dimensions of the slot may be selected to accommodate the insertion of the l-core without using undue pressure.

In contrast to the prior art, at least one piece of the magnetic material is slid laterally into the printed circuit board through a side wall rather than through openings in the top or bottom surface.

The slot may be a full width slot extending between two side walls of the section of printed circuit board. Alternatively, the slot may extend from just one side wall with a “stop” preventing the magnetic material being inserted past a point. The use of a stop allows for more defined positioning of the “l-piece” 124 with an associated Epiece for an “El” type magnetic core structure. It is also appropriate where the length of the core piece is short relative to the inter wall distance of the PCB section.

Openings are also defined through the PCB from either the bottom or top surface to allow the insertion of the legs of a second section of magnetic material, i.e. the previously referenced associated E-core to contact the l-piece in the slot.

As described above, these openings may be formed by a conventional PCB, for example milling, process. It will be appreciated that the space into which the I piece is inserted may be partially formed at the time of creating the space for the E core (i.e. the section of the space where the l-core will abut the legs of the E-core. Thus the required space for receiving the l-piece may be formed in different stages of the manufacturing process rather than as a single step.

A recess may be formed in the same surface to receive the body of the E-core so that the surface of the E-core is substantially flush or recessed with respect to the surface of the E-core. Thus a recess may be formed which is shaped to receive the entire E-core with the legs extending inwardly from the opening of the recess.

In the exemplary arrangement shown, the bottom surface of the section of printed circuit board has a deeper milling 126 for the E-core legs as well as more shallow milling for the “body” of the E-core 122, as will be evident from figure 5 where two limbs 410 of PCB material are shown remaining between the spaces for the legs of the E-core. The windings are partially formed by tracks which pass through the limbs. Thus the slots and milling for accommodating the legs of the E-core are such as to allow tracking to effect “windings” 128 around the legs of the E-core with usage of vias 130 for interconnect. The available turns count is a function of the allowed track-gap spacing, board cutout spacing, as well as layer count. Representative winding layer tracking is as shown in figure 6. The windings shown are for a single (e.g. a primary or secondary) winding of each of two transformers with further windings provided on separate layers of printed circuit board. It will be appreciated that this includes suitable tracks on the limbs 410 of the PCB material interposed between the legs of the core 122.

Connections (such as for example castellated vias 406 or edge plating) may be employed to provide electrical contacts to corresponding contacts on an underlying printed circuit board.

The approach is particularly suited because of the size of the transformers required to forming a high side driver of the type described in US Patent No. 9,590,621, the entire contents of which are herein incorporated by reference, by mounting the additional components required on the top surface of the board in which the transformer is formed. Additionally, the switch to be controlled by such a high side driver may be accommodated on the top surface of the board.

The switch mounted on the top surface may for example be a package-less transistor to save space.

An advantage of the present approach is that a floating switch combined with a driver for the floating switch may be constructed having a similar form factor to a transistor switch. Allowing for a circuit designer to effectively design-in an isolated or high side switch as if it was a ground referenced switch having a drain and source. Or alternatively stated, a circuit designer can employ the same approach in laying out a switching circuit to effect control of the power switches irrespective of their position in the circuit thus simplifying the design process.

The modules comprising a high side driver and an associated switch may be formed as a singular combination.

Equally, they may be formed in multiple combinations. Thus, as shown in Figures 15 and 16, a pair of components are co-formed in a common component structure. Each component comprising a driver responsive to a control signal delivered to a primary side control circuit with control pulses delivered across primary transformer windings to a switch connected on the secondary side. The transformer windings and core may be as described hereinbefore and hereinafter. Depending on the arrangement of the driver and switch, there may be more than one transformer. Accordingly, in arrangements using a gate drive circuit as described in 9,590,621 there may be a first transformer for switching on a switch (suitably for example a MOSFET) with a second transformer for effecting a turn-off of the switch. Accordingly, as shown in Figure 16, there are two spaces 162 represented for inserting the l-cores. Support functions for the switch, e.g. switch loss management by including snubbers to allow for soft switching may also be included (as represented by cavities 164) as may be desired.

This dual floating switch construction with integrated driver may be employed with half-bridge switching implementations, in which the result is two “cells”, each having a floating MOSFET. A preferred approach is also to allow the connection between the drain terminal of the lower FET and the source terminal of the upper FET to be made externally. If these are joined, then the cell may for example be operated as a conventional half-bridge.

Thus as shown in Figures 15 and 16, the reference-level control devices 174 are used to drive printed circuit board traces which for “windings” around posts of magnetic material inserted in cavities 162 using the approaches as described. The substrate 176 can be of epoxy-glass or ceramic material and may use thick copper layers and affixed or inserted metal pieces so as to optimise thermal transfer. The complementary drives can be provided via drivers 168 to switches 170, using interconnect vias 166. Provision is also made for switching support magnetics to be located within the board using cavities 164 and with interconnect vias 172. The assembly may be connected to its host board using castellated vias 160 and/or edge plating.

Equally, it will be appreciated that multiple switches and associated drivers may be accommodated on a single board with the result that a switching circuit may readily be manufactured by subsequent integration with other components (e.g. power transformer) on an applications printed circuit board. Equally filtering or snubber magnetics may be formed using the technique described above and may be incorporated with the high side driver and switches.

The component may be extended to provide for a full bridge control by integrating four switches and drivers together in a single module.

Advantageously, the present approach may be employed in arrangements using a larger number of switches. In particular, the arrangement may be employed in a multilevel arrangement of the type described in US Patent Application No. 15/500,858 the entire contents of which are incorporated by reference. By way of example, a multi-level switching arrangement of the type shown in Figure 4A of this application (15/500,858) including switches 130-140 and capacitors 144 and 146 may be provided as a single module as shown in Figure 12 of the present application in which a 5 level switching arrangement is shown comprising 8 switches and 3 capacitors.

An alternative construction to provide the magnetic core will now be described. In this alternative approach, a legged core (e.g. E or C) is inserted laterally through the side wall rather than the l-core as described above.

This second aspect of the present application inserts a legged core (e.g. E or C), as shown in figure 8, as a first section of the magnetic core laterally through a first side wall into spaces formed in a printed circuit board 700, as shown in Figure 7. Separate spaces 702 are formed within the printed circuit board to receive each of the legs of the magnetic core 800. In the example shown, the centre leg 804 is larger than the side legs 802. The space/cavity for the centre leg 804 is shown as a slot 704. In this context, it will be appreciated that the centre leg may be exposed to the top or as shown bottom surface of the substrate but the other legs are not as the windings are formed using tracks above and below the legs.

In figure 7, a recess is shown to allow the entire legged section be received and so that the outside wall of the PCB is flush with the legged section. However, it will be appreciated that whilst this is advantageous, it is also possible for the legged section to extend further than the PCB wall either inwardly or outwardly.

The second part of the magnetic core, may be a further legged core inserted from the opposite side of the printed circuit board into corresponding openings defined in the opposite wall. Thus two opposing E cores may be inserted into respective openings formed in opposing side walls abutting in the middle to complete the magnetic core. It will be appreciated that as with the arrangement of Figs 4 and 5 limbs are defined on which the windings are partially defined as a series of tracks.

It will be appreciated that a second E-core is not required. A C-core may be used to provide a gapped center leg.

The second part of the magnetic core may also for example be an I core inserted into a slot of the PCB section. It will be appreciated that the slot may be a vertical slot, i.e. one in which the l-core is inserted through the top or bottom surface or it may be a horizontal slot or recess formed through a side wall. As an example, the I piece may be inserted through a side wall which is perpendicular to the first side wall into a slot that runs transverse to the recesses defined for receiving the legs of the Ecore.

The windings may be formed using a combination of tracks and interconnects, as indicated by the path 708 shown in dashed outline in Figure 7.

This alternative implementation uses a core structure placed coplanar with the printed circuit board, and using vias to effect connection between a layer above the magnetic element and a layer below this magnetic element. This approach may be more demanding on PCB technology, requiring a large number of small vias, and typically the via array needs to be “buried” so that required isolation can be ensured and the electronic components can be connected without the need for large “keepout regions” as would be required if through-hole vias were used for the winding interconnect.

An example of tracking is shown in Figure 9, for the layer above the magnetic elements and in Figure 10 for the layer below the magnetic elements. It will be seen that windings are formed given the track and vias 164 between the two layers. Some of the tracks terminate on external connections 406, and requisite connections to components provided on the top surface (not shown) are effected via blind vias 160. Overall castellated through-hole vias 406 are used at the edge of the board and vias identified 160 may be used for interconnect to allow for the provision of components on the top surface. It will be appreciated that the windings formed by the combination of the two layers represent two transformers, i.e. a first transformer with a magnetic core formed in part by an outer leg and the middle leg and a second transformer formed in part by the other outer leg and the middle leg of the E-core. Thus, the combination of exemplary tracks shown for each of the transformers defines both primary and secondary windings.

The arrangements described herein are particularly suited to the provision of a high side driver circuit. The arrangements can indeed go further and include both the switches to be driven and the drivers as illustrated in Figure 11 in which a module 1100 is shown having a plurality of magnetic cores 124 positioned within a substrate 120 as previously described with a plurality of switches 1102 mounted on the top surface. An advantage of the present construction is that semiconductor devices such as MOSFET or other switches may be mounted directly in bare (non-packaged) form with wire bonding 1106 employed to create electrical connections between the semiconductor devices and connections defined on the top surface of the module 1100. Surface connections 1104 to an underlying application circuit board may be formed using the previously described castellated vias. This has the significant advantage of a significantly reduced footprint on an applications circuit board.

This will now be described with reference to a more detailed exemplary arrangement as shown in Figures 12 and 13 which combines a plurality of high side switches and their associated high side drivers. The arrangement is intended for mounting on an applications circuit board where it may be combined with additional components, e.g. filtering and other elements of a switching circuit including magnetics (inductors/transformers), capacitors and controllers. These components would be mounted separately on the same applications circuit board to which the arrangement is mounted.

The construction techniques as outlined can also be used to implement an overall device assembly, an example of which is illustrated in figure 12. In this case a multilayer substrate 154, with tracking and vias used to implement windings, is as shown. The substrate may be of ceramic and/or glass-epoxy construction. This substrate is equipped with “open” cavities as described. Here cavities 142 are shown for usage with drive magnetics and cavities 144 can also be provided for usage with switching support or “snubber” magnetics.

Advantageously, connections for power and control can be effected to the module using one or either or both castellated vias or edge plating 140. Similarly, bump connections/contacts can be formed on the bottom surface to allow direct solder connections between the module an underlying circuit board.

Positioning of magnetic elements as inserts in the cavities within the substrate allows mounting of electronic devices over the full top face of the substrate. These can include drivers 148, switches 150, capacitors 156 and control drives 158. Blind-via interconnect is used to access gate drive windings and snubber windings that are located within the substrate.

In the context of the present application, it will be appreciated that for a give PCB substrate there is a top surface and a bottom surface. However, depending on the outline shape of the top/bottom surface, the number of side walls may vary. Thus, if the top/bottom surfaces of the PCB are circular in shape, there will be a single wall, whereas if the PCB is rectangular in shape (as is conventional), there will be four side walls.

Whilst the above description has been made with reference to a cavity or space being formed for lateral insertion of a section of magnetic material through a side wall of a PCB construction, the approach is not to be considered so limited. Thus for example, in addition to the use for magnetics, other uses include the post placement of metal pieces to act as heat sinks for semiconductor switches, where a metal piece would be inserted below a semiconductor mounted on the surface to improve thermal dissipation. Such an approach may be used in conjunction with the magnetics described above or on their own.

In the foregoing specification, the application has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended statements. For example, whilst the present application has been described in the context of providing a transformer based drive circuit for driving a switch, it will be appreciated that the application is no so restricted and it may be employed to advantage in any circuit requiring a transformer. It will be understood that the PCB construction described above may employ any suitable materials, for example FR4 type constructions.

Because the apparatus implementing the present application is, for the most part, composed of electronic components and circuits known to those skilled in the art, circuit details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention. It will be understood that whilst particular polarity devices, e.g. PMOS, NMOS, PNP or NPN may be illustrated in the figures shown or referenced, that alternative polarity devices may be employed by appropriate modification of the circuits.

Thus, it is to be understood that the architectures and constructions depicted herein are merely exemplary, and that in fact many other architectures and constructions can be implemented which achieve the same functionality. In an abstract, but still definite sense, any arrangement of components to achieve the same functionality is effectively associated such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as associated with each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being operably connected, or operably coupled, to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundaries between the functionality of the above described operations are merely illustrative. The functionality of multiple operations may be combined into a single operation, and/or the functionality of a single operation may be distributed in additional operations. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.

However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

In the statements, any reference signs placed between parentheses shall not be construed as limiting the statement. The word ‘comprising’ does not exclude the presence of other elements or steps than those listed in a statement. Furthermore, Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the statements should not be construed to imply that the introduction of another statement element by the indefinite articles a or an limits any particular statement containing such introduced statement element to inventions containing only one such element, even when the same statement includes the introductory phrases one or more or at least one and indefinite articles such as a or an. The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different statements does not indicate that a combination of these measures cannot be used to advantage.

The present application also extends to include the following numbered statements.

1. A method of manufacturing a circuit component comprising a transformer, the method comprising the steps of: forming a winding using a multi-layer printed circuit board construction, the printed circuit board construction comprising a top surface, a bottom surface, with at least one side surface extending between the top and bottom surfaces the winding comprising a first series of tracks provided in a first layer of the printed circuit board; defining a first space within the printed circuit board construction; and inserting a first section of magnetic material into the first space through an opening in the at least one side surface to form at least in part a magnetic core of the transformer.

2. A method according to statement 1, further comprising the step of providing a second section of magnetic material to complete the magnetic core of the transformer.

3. A method according to statement 2, further comprising the step of defining a recess in the top or bottom surface for receiving the second section of magnetic material.

4. A method according to statement 3, wherein the second section of magnetic material is a C or E shaped core.

5. A method according to statement 3 or statement 4, wherein the recess is shaped to match the shape of the second section of magnetic material.

6. A method according to any one of statements 1 to 5, wherein the first section of magnetic material is a flat section of magnetic material.

7. A method according to any one of statements 2 to 3, wherein the first section of magnetic material is a C or E shaped core.

8. A method according to statement 7, further comprising the step of defining a recess for receiving the second section of magnetic material.

9. A method according to statement 7 or statement 8, wherein the second section of magnetic material is a C or E shaped core or flat shaped section of magnetic material.

10. A method according to any preceding statement, further comprising the step of forming contacts on the printed circuit board to allow the transformer to be mounted as a component on an application board.

11. A method according to any preceding statement, further comprising the step of mounting further components on the top surface of the printed circuit board.

12. A method according to statement 11, wherein the circuit component being manufactured is a high side driver.

13. A circuit component configured for mounting on a circuit board, the circuit component comprising:

a laminate body formed as a plurality of layers of printed circuit board material between a first surface and an opposing second surface, with at least one side wall extending between the first and second surfaces;

a transformer comprising a magnetic core, wherein the magnetic core is formed from a first section of magnetic material and a second section of magnetic material; wherein the first section of magnetic material is received through the at least one side wall into a space formed in the laminate body.

14. A circuit component according to statement 13, wherein a winding of the transformer is formed at least in part using a track provided in a first layer of the laminate body.

15. A circuit component according to statement 14, wherein the winding is formed at least in part using a track provided in a second layer of the laminate body.

16. A circuit component according to any one of statements 13 to 15, wherein the first section of magnetic material is a flat section of magnetic material.

17. A circuit component according to statement 16, wherein the second section of magnetic material is positioned within a recess in the first or second surface.

18. A circuit component according to statement 17, wherein the second section of magnetic material is a C or E shaped core.

19. A circuit component according to any one of statements 13 to 15, wherein the first section of magnetic material is a C or E shaped core.

20. A circuit component according to statement 19, wherein the second section of magnetic material is a C or E shaped core or flat shaped section of magnetic material.

21. A circuit component according to any one of statements 13 to 20, further comprising contacts to form connections with an underlying printed circuit board.

22. A circuit component according to any one of statements 13 to 21, wherein discrete components are surface mounted on the second surface the circuit component.

23. A circuit component according to statement 22, wherein the circuit component is a high side driver.

24. A high side driver for providing a drive signal to the gate of a switch, the high side driver comprising:

a transformer having a primary side winding, a secondary side winding and a magnetic core, a substrate having a first surface and a second surface opposite the first surface with at least one side wall there between, input contacts for receiving an input drive signal, wherein the input contacts are provided on the first surface of the substrate;

driver circuitry comprising a plurality of components to transfer the input drive signal using the transformer to the gate of the switch;

wherein the magnetic core is formed at least partially in the substrate between the first surface and the second surface.

25. A switching circuit comprising a switch and a high side driver according to statement 24, for providing a drive signal to the gate of the switch, wherein the switch is mounted on the second surface.

26. A switching circuit comprising: according to statement 25 wherein there a plurality of switches and high side drivers commonly provided with the substrate.

27. A floating switch incorporating a high side driver of the type statemented in statement 24 and a semiconductor switch driven by the high side driver, wherein the semiconductor switch is mounted on the substrate of the high side driver.

28. A module comprising a plurality of floating switches according to statement io 27, wherein the individual floating switches are commonly provided on the substrate.

29. A multi-level switching module comprising a switched capacitor arrangement consisting of a plurality of switches and capacitors, wherein the switches are provided by a module according to statement 28.

30. A multi-level switching module according to statement 29, wherein the capacitors are provided as components in the module.

Claims

1. A high side driver for providing a drive signal to the gate of a semiconductor switch, the high side driver comprising:

a transformer having a primary side winding, a secondary side winding and a magnetic core, a printed circuit board substrate having a first surface and a second surface opposite the first surface with at least one side wall there between, input contacts for receiving an input drive signal, wherein the input contacts are provided on the first surface of the substrate;

switch contacts including at least a gate contact for connecting to the gate of the high side switch;

driver circuitry comprising a plurality of components to transfer the input drive signal through the primary side winding and the secondary side winding to the gate contact; wherein the magnetic core is formed at least partially in the substrate between the first surface and the second surface by a first section of magnetic core material that extends inwardly from the side wall into the printed circuit board substrate.

2. A switching circuit comprising a semiconductor switch and a high side driver according to claim 1, wherein the switch contacts are provided on the second surface of the substrate and the switch is mounted on the second surface of the high side driver.

3. A module comprising a plurality of switching circuits according to claim 2, wherein the plurality of switching circuits are commonly provided on the same printed circuit board substrate.

4. A multi-level switching module comprising a switched capacitor arrangement consisting of a plurality of switches and capacitors, wherein the switches are provided by the module of claim 3.

5. A multi-level switching module according to claim 4, wherein the capacitors are provided as components on the printed circuit board substrate.