LAYOUT OF GATE DRIVER CIRCUIT FOR HIGH-SPEED SWITCHING DEVICES

Abstract

A switching circuit includes a first switch; a second switch connected in series with the first switch; a first isolated driver connected to a gate terminal of the first switch; a second isolated driver connected to a gate terminal of the second switch; and a transformer including a primary winding connected to an auxiliary power supply, a first secondary winding to supply a first voltage to the first isolated driver, and a second secondary winding to supply a second voltage to the second isolated driver.

Claims

1. A switching circuit comprising: a first switch; a second switch connected in series with the first switch; a first isolated driver connected to a gate terminal of the first switch; a second isolated driver connected to a gate terminal of the second switch; and a transformer including a primary winding connected to an auxiliary power supply and a secondary winding to supply a voltage to the first isolated driver; wherein a length of a first gate line connected between the first isolated driver and the gate terminal of the first switch is equal to or shorter than a distance between the first isolated driver and the second isolated driver.

2. The switching circuit of claim 1, wherein a distance between the first isolated driver and the second isolated driver is greater than a distance between the first switch and the second switch.

3. The switching circuit of claim 1, wherein the length of a first gate line connected between the first isolated driver and the gate terminal of the first switch is different from a length of a second gate line connected between the second isolated driver and the gate terminal of the second switch.

4. The switching circuit of claim 1, further comprising a substrate.

5. The switching circuit of claim 4, wherein the first switch is on a first side of the substrate; and the first isolated driver is on a second side of the substrate opposite to the first side.

6. The switching circuit of claim 4, wherein the first isolated driver and the second isolated driver are located on a same side of the substrate.

7. The switching circuit of claim 1, wherein the primary winding and the secondary winding are wound on a common magnetic core.

8. A switching circuit comprising: a first switch; a first isolated driver connected to a gate terminal of the first switch; and a transformer including a primary winding connected to an auxiliary power supply and a secondary winding to supply a first voltage to the first isolated driver; wherein the transformer and the first isolated driver at least partially overlap when viewed in a top plan view.

9. The switching circuit of claim 8, wherein the transformer is provided on a single circuit board or a single substrate.

10. The switching circuit of claim 9, wherein the transformer and the first switch are provided on a same side of the single circuit board or the single substrate.

11. The switching circuit of claim 8, further comprising: a second switch; and a second isolated driver connected to a gate terminal of the second switch.

12. The switching circuit of claim 11, wherein a distance between the transformer and the first isolated driver is less than a distance between the transfer and the second isolated driver.

13. The switching circuit of claim 11, wherein a thickness of the transformer is greater than at least one of a thickness of the first isolated driver or a thickness of the second isolated driver.

14. The switching circuit of claim 11, wherein a thickness of the transformer is greater than at least one of a thickness of the first switch or a thickness of the second switch.

15. The switching circuit of claim 11, wherein a distance between the first isolated driver and the second isolated driver is a straight-line distance in the top plan view.

16. The switching circuit of claim 8, wherein the transformer and the first isolated driver overlap by at least 50%.

17. The switching circuit of claim 8, wherein the primary winding and the secondary winding are wound on a common magnetic core.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a block diagram of a known gate driver circuit.

[0021] FIG. 2 is a block diagram of a gate driver circuit with a transformer located between isolated drivers and an auxiliary power supply.

[0022] FIG. 3 shows a top view of a component layout of a substrate with a gate driver circuit.

[0023] FIG. 4 is a schematic view showing components on the top and the bottom surfaces of the substrate of FIG. 3.

[0024] FIG. 5 shows a bottom view of a component layout of the substrate of FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] FIG. 2 shows that gate driver circuitry with a transformer T.sub.1 provided between the gate driver circuitry and the auxiliary power supply AUX, where the gate driver circuity and an auxiliary power supply AUX can be placed far apart, e.g., the gate driver and the auxiliary power supply AUX and may be located on different PCBs. The gate driver circuitry includes a controller 10, isolated drivers IC.sub.1 and IC.sub.2 that receive signals from the controller 10, and switches Q.sub.1 and Q.sub.2 connected in series and including gates terminals G1 and G2 connected to the isolated drivers IC.sub.1 and IC.sub.2. The gate driver circuitry can include a gate resistor RgH connected between the controller 10 and to the gate terminal G1 of switch Q.sub.1 and a gate resistor RgL connected between the controller 10 and to the gate terminal G2 of switch Q.sub.2. Switches Q.sub.1 and Q.sub.2 can be high-power and/or fast-switching transistors such as GaN HEMTs. Terminals of an input voltage V.sub.in can be provided across a drain terminal D.sub.1 of the switch Q.sub.1 and the source terminal S.sub.2 of the switch Q.sub.2. The gate driver circuitry includes the transformer T.sub.1 respectively connected to the isolated drivers IC.sub.1 and IC.sub.2 via rectifiers REC.sub.1 and REC.sub.2. The transformer T.sub.1 is also connected to the auxiliary power supply AUX. The controller 10 can be any suitable controller, including, for example, a digital signal processor (DSP) or a microcontroller. The controller 10 can include a single controller or can include multiple controllers. Transformer T.sub.1 can be any suitable transformer. Rectifiers REC.sub.1 and REC.sub.2 can be any suitable rectifiers, including, for example, small signal Schottky diodes. The isolated drivers IC.sub.1 and IC.sub.2 can be any suitable isolated drivers that provide enough source/sink current and high-speed switching to turn on/off the switches Q.sub.1 and Q.sub.2. The auxiliary power supply AUX may be a pulse-voltage power supply.

[0026] Isolated drivers such as isolated drivers IC.sub.1 and IC.sub.2 can be used in applications in which a controller, such as controller 10, is located on a different side of an isolation barrier as the devices to be driven, such as switches Q.sub.1 and Q.sub.2. For example, in a converter with a transformer that provides isolation between a primary side and a secondary side of the transformer, if the controller is located on the primary side of the transformer, then an isolated driver can be used to drive devices on the secondary side of the transformer, while maintaining the isolation barrier between the primary and secondary sides of the transformer. Conversely, if the controller is located on the secondary side of the transformer, then an isolated driver can be used to drive devices on the primary side of the transformer, while maintaining the isolation barrier between the primary and secondary sides of the transformer.

[0027] Because of the isolation between the inputs and the outputs of the isolated driver, each of the input circuitry and the output circuitry of the isolated driver must be independently supplied with power. The output circuitry of the isolated drivers can be powered by an auxiliary power supply that is separate from the power supply circuitry that powers the input circuitry of the isolated drivers. The input circuitry of the isolated drivers can be powered by the same power supply circuitry as the controller (not shown). For example, the power supply that supplies voltage to the controller 10 can also supply power and ground of the isolated drivers IC.sub.1 and IC.sub.2. The isolation in the isolated drivers can be provided by any suitable device, including, for example, a transformer, an opto-isolator, etc.

[0028] In the gate driver circuit of FIG. 2, the transformer T.sub.1 can be relatively small in size, while still being able to supply power to the gate driver circuitry, and the transformer T.sub.1 can be smaller in size than each of the switches Q.sub.1 and Q.sub.2. However, the transformer T.sub.1 decouples the signals between the auxiliary power supply AUX and the switches Q.sub.1 and Q.sub.2, in particular, at the gates G.sub.1 and G.sub.2 of the switches Q.sub.1 and Q.sub.2. Accordingly, the switches Q.sub.1 and Q.sub.2 can be cleanly switched by significantly reducing or preventing any effect of noise from the auxiliary power supply AUX.

[0029] The controller 10 can be any suitable controller. The controller 10 can be an IC chip or suitable device that provides control signals to turn on and off switching devices, such as GaN HEMTs. For example, the controller 10 can provide pulse-width modulation (PWM) signals to control the switches Q.sub.1 and Q.sub.2 based on the output of a converter in which the switches Q.sub.1 and Q.sub.2 are included.

[0030] As shown in FIG. 2, the auxiliary power supply AUX includes two terminals that supply voltages V.sub.p and V.sub.PR to a primary winding of the transformer T.sub.1. The transformer T.sub.1 includes first and second secondary windings that are respectively connected to rectifiers REC.sub.1 and REC.sub.2. The first secondary windings can supply a first voltage to the high-side isolated driver IC.sub.1, and the second secondary winding can supply a second voltage to the low-side isolated driver IC.sub.2. The first and the second voltages can be different, depending on the turns ratio of the first and the second secondary windings. That is, the outputs of the transformer T.sub.1 separately power the isolated drivers IC.sub.1 and IC.sub.2 via the corresponding rectifiers REC.sub.1 and REC.sub.2.

[0031] Rectifier REC.sub.1 is a high-side rectifier that provides a high-side voltage V.sub.ccH to the isolated driver IC.sub.1, and rectifier REC.sub.2 is a low-side rectifier that provides a low-side voltage V.sub.ccL to the isolated driver IC.sub.2. Rectifier REC.sub.1 is also connected to a low-side ground terminal GND.sub.H of the isolated driver IC.sub.1, and rectifier REC.sub.2 is also connected to a low-side ground terminal GND.sub.L of the isolated driver IC.sub.2. The low-side ground terminal GND.sub.H of the isolated driver IC.sub.1 is connected to a source terminal S.sub.1 of the switch Q.sub.1, and the low-side ground terminal GND.sub.L of the isolated driver IC.sub.2 is connected to a source terminal S.sub.2 of the switch Q.sub.2. FIG. 2 shows optional signal ground pins SG.sub.1 and SG.sub.2 that can be used in switches with four pins (i.e., drain, source, gate, and signal ground) to ensure proper gate-source voltage V.sub.gs. An input voltage V.sub.in is provided across a drain terminal D.sub.1 of the switch Q.sub.1 and the source terminal S.sub.2 of the switch Q.sub.2. Gate terminals G.sub.1 and G.sub.2 of the switches Q.sub.1 and Q.sub.2 are respectively driven by voltages V.sub.G1 and V.sub.G2 output from the isolated drivers IC.sub.1 and IC.sub.2 according to control signals provided to the isolated drivers IC.sub.1 and IC.sub.2 by a control device. The switches Q.sub.1 and Q.sub.2 are connected in series, with the source terminal S.sub.1 of the switches Q.sub.1 connected to the drain terminal D.sub.2 of the switch Q.sub.2. The switches Q.sub.1 and Q.sub.2 are preferably transistors, for example.

[0032] A gate-line current loop (Gate loop H/Gate loop L) of each of the switches Q.sub.1 and Q.sub.2 is defined by a path from the isolated drivers IC.sub.1 and IC.sub.2 to the corresponding gate terminal G.sub.1 and G.sub.2 and to ground GND.sub.H and GND.sub.L of the isolated drivers IC.sub.1 and IC.sub.2. A power-supply current loop (Supply loop H/Supply loop L) of the power supplied to each of the isolated drivers IC.sub.1 and IC.sub.2 is defined by a path from the low-side voltages V.sub.ccH and V.sub.ccL of the isolated drivers IC.sub.1 and IC.sub.2, through the rectifiers REC1 and REC2 and secondary windings of the transformer T.sub.1, and to the high-side voltages +V.sub.ccH and +V.sub.ccL of the isolated drivers IC.sub.1 and IC.sub.2. Accordingly, by including the transformer T.sub.1 between the auxiliary power supply AUX and the isolated drivers IC.sub.1 and IC.sub.2, a length of the gate-line current loop (Gate loop H/Gate loop L) of each of the switches Q.sub.1 and Q.sub.2 and a length of the power-supply current loop (Supply loop H/Supply loop L) to each of the isolated drivers IC.sub.1 and IC.sub.2 can be significantly reduced. Therefore, clean switching can be provided due to the power-supply current loops (Supply loop H/Supply loop L) being less susceptible to EMI and noise caused by large voltage spikes, which provides more ideal switching waveforms with significantly reduced voltage spikes and dips.

[0033] FIGS. 3 and 5 show top and bottom sides of a substrate with an example of a component layout of a gate driver circuit, and FIG. 4 is a schematic view showing components on the top and the bottom surfaces of the substrate. Any suitable substrate can be used, including, for example, a PCB. As shown in FIGS. 3-5, the transformer T.sub.1, rectifiers REC.sub.1 and REC.sub.2, switches Q.sub.1 and Q.sub.2 can be located on the top side of the substrate, and the isolated drivers IC.sub.1 and IC.sub.2 and the gate resistors RgH and RgL can be located on the bottom side of the substrate. By locating the transformer T.sub.1 and the switches Q.sub.1 and Q.sub.2 on different sides of the substrate, the component placement and layout design of the rectifiers REC.sub.1 and REC.sub.2 can be simplified, and an area circumscribed by a current loop from the power supply (e.g., auxiliary power supply AUX) can be significantly reduced. In addition, by locating the isolated drivers IC.sub.1 and IC.sub.2 on the bottom side of the substrate, the gate-line current loop (Gate loop H/Gate loop L) of each of the switches Q.sub.1 and Q.sub.2 can be made relatively short, i.e., an area circumscribed by the gate-line current loop (Gate loop H/Gate loop L) of each of the switches Q.sub.1 and Q.sub.2 can be significantly reduced. For example, the gate-line current loop (Gate loop H/Gate loop L) of the switches Q.sub.1 and Q.sub.2 can be made as short as the width of one of the switches Q.sub.1 and Q.sub.2.

[0034] However, component arrangements other than those described above and shown in FIGS. 3-5 are also possible.

[0035] The auxiliary power supply AUX is not shown in FIGS. 3-5. The auxiliary power supply AUX is not located on the substrate and can be connected to the terminals corresponding to V.sub.p and V.sub.PR shown in FIG. 3. The controller 10, which is not shown in FIGS. 3-5, can be located on a different substrate. The power supply of the controller 10, which is not shown in FIGS. 3-5, can also be located on a different substrate and can provide power to the input circuitry of the isolated drivers IC.sub.1 and IC.sub.2.

[0036] As shown in FIGS. 3-5, each of the switches Q.sub.1 and Q.sub.2, the isolated drivers IC.sub.1 and IC.sub.2, the rectifiers REC.sub.1 and REC.sub.2, and the transformer T.sub.1 can all be provided on a single substrate.

[0037] A line from the transformer T.sub.1 to the rectifier REC.sub.1 can be on a different side of the transformer T.sub.1 than a line from the transformer T.sub.1 to the rectifier REC.sub.2, for example. By providing the lines from the transformer T.sub.1 to the rectifiers REC.sub.1 and REC.sub.2 on different sides of the transformer T.sub.1, the component placement and layout design of the gate driver circuitry and GaN HEMTs connected to the transformer can be simplified. This implementation is particularly advantageous if only the components provided for GaN HEMTs are mounted on a sub-board, and the sub-board is then connected to a main board.

[0038] It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.