POWER SWITCH

Abstract

The disclosure provides a power switch that can be switched by a logic source in an ON or an OFF state. The switch comprises a component to output an optical signal responsive to the control signal and an optical sensitive device to react to the optical signal and self-conducting JFET in cascode configuration with the optical sensitive device.

Claims

1. A power switch responsive to a control signal from a logic source to switch between an ON and an OFF state, the power switch comprising: an optical component arranged to output an optical signal responsive to the control signal; and a driver device responsive to the optical signals to switch between a non-conductive state and a conductive state.

2. The power switch of claim 1, wherein the driver device comprises an optical sensitive device and a self-conducting JFET in a cascode configuration.

3. The power switch of claim 2, wherein the optical component comprises a light-emitting diode LED

4. The power switch of claim 1, wherein the optical component comprises a light-emitting diode LED.

5. The power switch of claim 2, wherein the optical sensitive device comprises a Darlington isolator or other light sensitive high current low voltage device.

6. The power switch of claim 3, wherein the optical sensitive device comprises a Darlington isolator or other light sensitive high current low voltage device.

Description

BRIEF DESCRIPTON OF THE DRAWINGS

[0010] FIG. 1 is a block diagram of an existing power switch using an IGBT.

[0011] FIG. 2 is a block diagram showing a conventional IGBT integrated power module.

[0012] FIG. 3 is a block diagram of an optical power switch according to the disclosure.

[0013] FIG. 4 is a block diagram of an alternative implementation of an optical power switch according to the disclosure.

DETAILED DESCRIPTION

[0014] Preferred embodiments will now be described by way of example only with reference to the drawings.

[0015] Referring first to FIGS. 1 and 2, a conventional power switch is described briefly. Such switches are in widespread use and would be readily known to a person skilled in the art. Only a very brief overview will, therefore, be given.

[0016] In a conventional power switch such as that shown in FIGS. 1 and 2, power from a power source 1 is to be converted to a drive power for a load by the switch. The power source supplies a power signal to a gate driver 2 such as a push-pull gate driver via a split isolated power supply 3. The gate driver is switched between an on and an off state in response to control signals from a controller such as a logic source 4. An optical isolation component 5 is provided between the logic source and the gate driver. A switch element such as a JFET or an IGBT 6 is either conductive or non-conductive in response to the on and off states of the gate driver 2. Depending on the environment in which the switch is used, the optical isolator component could be omitted but the other components will still be needed.

[0017] FIG. 2 shows how the above-described components might be incorporated in a package for an integrated power module (IPM). There are limitations to the size of the electronic chip 7 on which the components can be mounted. As can be seen, whilst it is possible to mount many of the elements on the chip, this is difficult and not all components can be accommodated on a single chip.

[0018] The present disclosure uses a high speed, high power optical device such as an LED 8 and a light sensitive switch element such as a light sensitive IGBT 9. This then removes the need for the other common circuit elements required by the conventional gate driver arrangement such as the isolating components, drive circuits and floating/split power supplies. The resulting fewer components mean that the entire switch can be easily mounted on a small chip surface.

[0019] FIG. 4 shows an implementation of the optical power switch of the disclosure where the switch element combines a high current low voltage optical switch element (e.g. Darlington or optical MOSFET) 10 and a high voltage JFET 11.

[0020] The optical switch element and the JFET will have to be sized to meet the desired rating of the device in terms of current and voltage rating. Both light sensitive switch element and JFET need to be rated for the current capability of the device. In addition the JFET needs to be able to handle the device's voltage rating. Whereas the voltage rating of the optical device is determined by the voltage the JFET needs, to be blocked, which will be in the range of a 20V.

[0021] The optical device or LED 8 can be located close to the light sensitive switch element or remote from the light sensitive device connected by a optical fiber or similar light carrying device.

[0022] The switch of the present disclosure combining known technologies such as SiC JFET high power optical devices in a cascode configuration enables the manufacture of simple power stages in drive systems and power supplies without the need for optical isolation, gate drives and floating/split power supplies, thus providing small, reliable, light and inexpensive devices.