Capacitor assisted low voltage write circuit

A write circuit in a disc drive for writing data to a magnetic disc based on a data signal received by the write circuit, the data signal having positive and negative going edges, the write circuit comprising:

• delay means for delaying the data signal and producing a delayed data signal;
• a transition circuit, connected to the delay means, producing a transition voltage based on the delayed data signal;
• H-switch control means, connected to the transition circuit, producing at least one H-switch control signal based on the transition voltage;
• an H-switch, connected to the H-switch control means, producing a write head current based on the H-switch control signal;
• a magnetic write head, connected to the H-switch, producing a magnetic field based on the write head current;
• and
• a write assistance circuit, connected to the H-switch control means and the H-switch, producing a write assistance voltage, the write assistance circuit including:
• a capacitor for providing voltage pulses to the H-switch;
• charging means, connected to the capacitor, for charging and discharging the capacitor;
• and
• ground current restriction means, connected to the capacitor and to ground, for preventing current flow from ground.

A write circuit in a disc drive for receiving a data signal and writing data represented by the data signal to a magnetic disc, the data signal having positive and negative going edges, the write circuit comprising:

• a delay circuit for receiving the data signal, for delaying the data signal, and for providing a delayed data signal;
• a transition circuit, connected to the delay circuit, for producing a voltage transition based on the delayed data signal;
• H-switch control means, connected to the transition circuit, for producing at least one H-switch control signal based on the transition voltage;
• an H-switch, connected to the H-switch control means, for producing a write head current based on the H-switch control signal;
• a magnetic write head connected to the H-switch, for producing a magnetic field based on the write head current;
• a one-shot circuit producing a one-shot signal based on the data signal;
• a capacitor driver circuit, connected to the one-shot circuit, for producing a capacitor voltage based on the one-shot signal;
• a headroom assistance capacitor, connected to the capacitor driver circuit, the H-switch, and the H-switch control means, for providing additional switching voltage across the magnetic head;
• and
• ground current restriction means, connected to the headroom assistance capacitor, the H-switch, the H-switch control means and ground, for restricting current flow from ground.

A write circuit receiving a write signal having differing voltage values therein for representing write data and providing differing magnetic fields corresponding to these differing voltage values, the differing magnetic fields having values capable of magnetizing selected portions of a magnetic medium positioned proximate the write circuit, the write circuit comprising:

• current switch control means for receiving the write signal and for providing a current switch control signal having changes of voltage values therein based on the differing voltage values of the write signal;
• a current switch having a first terminal and a second terminal and being responsive to the changes in voltage values of the current switch control signal to change between a first mode and a second mode, the current switch providing a write head current having alternatively a first flow direction from the first terminal to the second terminal when the current switch is operating in the first mode and a second flow direction from the second terminal to the first terminal when the current switch is operating in the second mode;
• a magnetic write head electrically coupled between the first and second terminals of the current switch and responsive to the write head current to provide the differing magnetic fields, the write head current establishing a voltage drop at the write head relative to a voltage at a reference node;
• a capacitor having a first terminal and a second terminal, the second terminal being electrically coupled to the reference node;
• and
• charging control means electrically coupled to the first terminal of the capacitor for controlling charging and discharging of the capacitor based on the differing voltage values of the write signal to provide voltage pulses to selectively change the voltage at the reference node.