High power DC SSPC with capability of soft turn-on large capacitive loads
Pre-charge circuitry allows capacitive loads connected to a solid state power controller to be gradually charged up by a PWM, generated with a cycle by cycle current limit, switching a single MOSFET in series with an inductor, before the SSPC is turned on. The pre-charge circuitry may require only three additional components, e.g., a MOSFET, an inductor and a diode, along with a designated MOSFET gate driver.
1. A solid state power controller (SSPC) comprising:
a pre-charge circuit connected in parallel with a solid state switching device, wherein the pre-charge circuit includes:
a MOSFET receiving power from a main power bus at an input side of the solid state switching device;
an inductor in series with the MOSFET and to a load side of the solid state switching device; and
a freewheeling diode connected between the MOSFET and the inductor; and
a gate driver integral to a DSP control engine of the power controller, the gate driver coupled to the MOSFET and configured to control a switch of the MOSFET of the pre-charge circuit in a pulse width modulation fashion based on a sampled load voltage measurement to apply an on logic to the MOSFET until the sampled load voltage reaches an input voltage of the SSPC and to apply an off logic to the MOSFET when the sampled load voltage reaches the input voltage of the SSPC.
2. The power controller of claim 1 , wherein the solid state switching device is selected from the group consisting of a MOSFET, an IGBT, a GaN based switching device, and a SiC based VJFET.
3. The power controller of claim 1 , wherein the inductor has an inductor value of about 68 μH.
4. The power controller of claim 1 , wherein the switching device is a normally closed solid state switching device.
5. The power controller of claim 4 , including an electromechanical contactor in series with the switching device.
6. The power controller of claim 5 , wherein a load side of the inductor is electrically connected between the solid state switching device and the electromechanical contactor.
7. A solid state power controller comprising:
a DSP control engine including a coil driver and a pre-charge circuit gate driver;
a solid state switching device receiving power from a main power bus; and
a pre-charge circuit connected in parallel with the solid state switching device, wherein the pre-charge circuit includes:
a MOSFET receiving power from the main power bus at an input side of the switching device;
an inductor in series with the MOSFET and to a load side of the switching device;
a freewheeling diode connected between the MOSFET and the inductor;
a first gate driver is integral to a DSP control engine of the power controller and coupled with the MOSFET, the first gate driver configured to apply:
an on logic to the MOSFET until the sampled load voltage reaches an input voltage of the SSPC,
an off logic to the MOSFET when the sampled load voltage reaches the input voltage of the SSPC, and
an off logic to the MOSFET in response to the load voltage failing to reach the input voltage at a desired rate; and
a second gate driver coupled with the solid state switching device, the second gate driver configured to apply an on logic to the solid state switching device in response to the load voltage reaching the input voltage.
8. The solid state power controller of claim 7 , wherein the inductor has an inductor value from about 50 to about 90 μH.
9. The solid state power controller of claim 7 , including an electromechanical contactor in series with the solid state switching device.