Active OR controller powers up to 400V
- Author:Ella Cai
- Release on:2017-04-14
Diode’s ZXGD3112N7 active ORing mosfet controller supports redundancy power systems with rail voltages up to 400V.
The chip controls an n-channel mosfet so that the mosfet behaves like a low-drop diode “providing a highly efficient power system that is well-suited for target applications in telecoms systems, data centres and servers, where OR’ing two or more power supplies together provides redundancy,” said the firm.
Dropping less than a diode also cuts local power dissipation.
The turn‑off threshold voltage of <5mV is claimed to improve light-load stability, and the controller can implement turn off in <600ns to cut reveres current flow – 5A sink current is available to discharge of the gate, or the gates of paralleled mosfets.
Diodes ZXGD3112The chip will work with mosfets in either the positive or negative rail.
The chip works from voltages up to 20V, and only the mosfet drain connection pin is 400V capable, which means one or more auxilary supplies are needed in applications with rails over 20V – to create +10V relative to the switched rail, in both positive and negative rail switching.
No auxiliary supply is needed with negative rail ORing up to 20V.
A note of caution here, and I apologies in advance if I am wrong, but the auxiliary supply circuits (reproduced below) in the data sheet DS37739 rev1-2 appear to be wrong in that the power supplies have ended up directly-ORed in the positive rail example (left), and there only needs to be one aux supply in the negative rail example.
The chip controls an n-channel mosfet so that the mosfet behaves like a low-drop diode “providing a highly efficient power system that is well-suited for target applications in telecoms systems, data centres and servers, where OR’ing two or more power supplies together provides redundancy,” said the firm.
Dropping less than a diode also cuts local power dissipation.
The turn‑off threshold voltage of <5mV is claimed to improve light-load stability, and the controller can implement turn off in <600ns to cut reveres current flow – 5A sink current is available to discharge of the gate, or the gates of paralleled mosfets.
Diodes ZXGD3112The chip will work with mosfets in either the positive or negative rail.
The chip works from voltages up to 20V, and only the mosfet drain connection pin is 400V capable, which means one or more auxilary supplies are needed in applications with rails over 20V – to create +10V relative to the switched rail, in both positive and negative rail switching.
No auxiliary supply is needed with negative rail ORing up to 20V.
A note of caution here, and I apologies in advance if I am wrong, but the auxiliary supply circuits (reproduced below) in the data sheet DS37739 rev1-2 appear to be wrong in that the power supplies have ended up directly-ORed in the positive rail example (left), and there only needs to be one aux supply in the negative rail example.
