Hot swap decoupling for noise reduction and failure prevention

1. An apparatus, comprising:

a capacitive load having first and second terminals, the first terminal configured to be in electrical connection with a first conductor of a power bus;

a switching device having first and second terminals and a control input, the first and second terminals being in electrical connection when the switching device is in a closed state and being in electrical isolation from each other when the switching device is in an open state, wherein:

the first terminal of the switching device is in electrical connection with the second terminal of the capacitive load; and

the second terminal of the switching device is configured to be in electrical connection with a second conductor of the power bus; and

a hot swap control circuit configured to be in electrical connection with a load that is powered by the first and second conductors of the power bus, wherein the load is separate from the capacitive load; and

wherein:

the hot swap control circuit monitors an electrical state of the load while the load transitions from an unpowered state to a fully powered state in response to the load being connected to the first and second conductors of the power bus, wherein:

the hot swap control circuit outputs a first signal indicative of the electrical state of the load meeting a first threshold during the transition from the unpowered state to the fully powered state, and outputs a second signal indicative of the electrical state of the load not meeting a first threshold during the transition from the unpowered state to the fully powered state; and

the input of the switching device receives the output of the hot swap control circuit and is in the closed state when the first signal is output by the hot swap control circuit to connect the capacitive load in parallel with the load so that the capacitive load forms a decoupling capacitor in parallel with the load, and is in the open state when the second signal is output by the hot swap control circuit so the capacitive load is not connected to the second conductor of the power bus while the load is connected to the first and second conductors of the power bus.

2. The apparatus of claim 1 , wherein the switching device is a field effect transistor.

3. The apparatus of claim 1 , wherein the capacitive load is a capacitor.

4. The apparatus of claim 1 , wherein the first conductor of the power bus is a power supply conductor and the second conductor of the power bus in a power return.

5. The apparatus of claim 1 , wherein the first threshold is a powered state that is less than a fully powered state and greater than an unpowered state.

6. The apparatus of claim 1 , further comprising a resistor in serial connection with the capacitor.

7. An apparatus, comprising:

a server rack configured to receive computer servers and electrically connecting each computer server to a power bus that includes a first conductor and a second conductor;

a capacitive load having first and second terminals, the first terminal be in electrical connection with the first conductor of the power bus;

a switching device having first and second terminals and a control input, the first and second terminals being in electrical connection when the switching device is in a closed state and being in electrical isolation from each other when the switching device is in an open state, wherein:

the first terminal of the switching device is in electrical connection with the second terminal of the capacitive load;

the second terminal of the switching device is in electrical connection with a second conductor of the power bus; and

the control input is configured to be in electrical connection with an output of a control circuit when a computer server is received in the server rack, the control circuit in electrical connection with server, wherein the server is separate from the capacitive load; and

wherein:

the control circuit monitors an electrical state of the server while the server transitions from an unpowered state to a fully powered state in response to being connected to the first and second conductors of the power bus, wherein:

the control circuit outputs a first signal indicative of the electrical state of the server computer meeting a first threshold during the transition from the unpowered state to the fully powered state, and outputs a second signal indicative of the electrical state of the computer server not meeting a first threshold during the transition from the unpowered state to the fully powered state; and

the switching device, in response to the output of the control circuit, is in the closed state when the first signal is output by the control circuit to connect the capacitive load in parallel with the server so that the capacitive load forms a decoupling capacitor in parallel with the server, and is in the open state when the second signal is output by the control circuit so the capacitive load is not connected to the second conductor of the power bus while the server is connected to the first and second conductors of the power bus.

8. The apparatus of claim 7 , wherein the switching device is a field effect transistor.

9. The apparatus of claim 7 , wherein the capacitive load is a capacitor.

10. The apparatus of claim 7 , wherein the control circuit is a hot swap control circuit.

11. The apparatus of claim 7 , wherein the first threshold is a powered state that is less than a fully powered state and greater than an unpowered state.

12. A method, comprising:

monitoring, by a hot swap control circuit, an electrical state of load that is powered by the first and second conductors of a power bus, the monitoring occurring at least while the load transitions from an unpowered state to a fully powered state in response to the load being connected to the first and second conductors of the power bus;

in response to the monitoring, generating, at an output conductor:

a first signal indicative of the electrical state of the load meeting a first threshold during the transition from the unpowered state to the fully powered state;

a second signal indicative of the electrical state of the load not meeting a first threshold during the transition from the unpowered state to the fully powered state;

coupling the output conductor to a switching device that receives the outputs of the hot swap control circuit and is in a closed state when the first signal is output by the hot swap control circuit and is in an open state when the second signal is output by the hot swap control circuit;

while the load is connected to the first and second conductors of the power bus:

coupling a capacitor, by the switch, between the first and second conductors of the power bus when the switch is in the closed state to connect the capacitor in parallel with the load so that the capacitor forms a decoupling capacitor in parallel with the load; and

decoupling the capacitor, by the switch, from the first and second conductors of the power bus when the switch is in the open state so the capacitor is not connected to the second conductor of the power bus while the load is connected to the first and second conductors of the power bus.

13. An apparatus, comprising:

a hot swap control circuit configured to be in electrical connection with a load that is powered by first and second conductors of the power bus, and that monitors an electrical state of the load while the load transitions from an unpowered state to a fully powered state in response to the load being connected to the first and second conductors of the power bus, wherein:

the hot swap control circuit outputs a first signal indicative of the electrical state of the load meeting a first threshold during the transition from the unpowered state to the fully powered state, and outputs a second signal indicative of the electrical state of the load not meeting a first threshold during the transition from the unpowered state to the fully powered state; and

means for connecting a capacitive coupling between the first and second conductors of the power bus when the second signal is output to connect the capacitive coupling parallel with the load so that the capacitive coupling forms a decoupling capacitor in parallel with the load and for disconnecting the capacitive coupling between the first and second conductors of the power bus when the first signal is output so the capacitive coupling is not connected to the second conductor of the power bus while the load is connected to the first and second conductors of the power bus.