Efficiency of a corona charger

A method of charging a photoreceptor to a desired voltage level comprising:

• providing a first corona charging unit having a first corona electrode, a first shell electrode, and a first high voltage power supply;
• connecting the first high voltage power supply to the first corona electrode;
• raising the potential of the first shell electrode to at least one tenth the magnitude of the potential of the first corona electrode;
• providing a second corona charging unit having a second corona electrode, a grid electrode, and a second shell electrode;
• connecting the grid electrode to the second shell electrode;
• sensing a first corona current from the first high voltage power supply to the first corona electrode;
• sensing a return current from the first shell electrode to ground;
• adjusting a voltage on the first high voltage power supply to maintain a constant difference between the first corona current and the return current;
• wherein the first corona charging unit charges the photoreceptor to at least 63% of the desired voltage;
• and
• wherein the second corona charging unit charges the photoreceptor to within 10% of the desired voltage.

A method of charging a photoreceptor to a desired voltage level comprising:

• providing a first corona charging unit having a first corona electrode, a first shell electrode, a first grid electrode, and a first high voltage power supply;
• connecting the first shell electrode through a resistor to ground;
• connecting the first grid electrode to the first shell electrode;
• connecting the first high voltage power supply to the first corona electrode;
• providing a second corona charging unit having a second corona electrode, a second grid electrode, and a second shell electrode;
• connecting the second grid electrode to the second shell electrode;
• sensing a first corona current from the first high voltage power supply to the first corona electrode;
• sensing a return current from the first shell electrode to ground;
• adjusting a voltage on the first high voltage power supply to maintain a constant difference between the first corona current and the return current;
• wherein the first corona charging unit charges the photoreceptor to at least 63% of the desired voltage;
• and
• wherein the second corona charging unit charges the photoreceptor to within 10% of the desired voltage.