Charge Injection Circuit for Instantaneous Transient Support

A method of regulating a load, the method comprising:

• regulating a voltage applied to the load via a voltage regulator electrically coupled to the load through an output inductor;
• discharging energy stored in an output capacitor to the load during step-up transient events at the load, the output capacitor being electrically coupled to a node between the inductor and the load;
• absorbing energy from the load via the output capacitor during step-down transient events at the load;
• injecting charge onto the output capacitor during the step-up transient events via a charge injection circuit capacitively coupled to the node;
• and
• absorbing charge from the output capacitor during the step-down transient events via the charge injection circuit.

A charge injection circuit for a voltage regulator circuit electrically coupled to a load through an output inductor and having an output capacitor electrically coupled to a node between the inductor and the load, the charge injection circuit comprising:

• a first switch;
• a second switch;
• an auxiliary capacitor having a first terminal electrically coupled to the node without using an inductor and a second terminal switchably coupled to a first voltage rail though the first switch and to a second voltage rail different than the first voltage rail through the second switch;
• and
• a bias voltage applied to the second terminal of the auxiliary capacitor,
• wherein the first switch is configured to electrically couple the second terminal of the auxiliary capacitor to the first voltage rail during step-up transient events at the load,
• wherein the second switch is configured to electrically couple the second terminal of the auxiliary capacitor to the second voltage rail during step-down transient events at the load.