High voltage power supply with overcurrent protection

Claim 2

A very high voltage power supply for electrostatic spray coating application in which electrostatically charged coating material is sprayed onto a directly electrically grounded object comprising, in combination: a source of DC power with a control input and an output, said source producing a DC voltage at said output, said source including a turnoff means responsive to an externally generated turnoff signal applied to said control input for turning off said source thereby removing said DC voltage from said source output; an inverter circuit with a DC input and an AC output, said inverter circuit input being connected to receive DC power from said DC source output, said inverter circuit producing at its output an intermediate AC voltage at a high frequency; a voltage multiplier circuit with an input and an output, said voltage multiplier input being connected to receive power from said inverter circuit output, said voltage multiplier producing at its output a very high DC voltage for use in electrostatically charging coating material sprayed onto a directly electrically grounded object in electrostatic spray coating; an overcurrent detector with an input and an output, said overcurrent detector input being connected to the input of said voltage multiplier circuit to monitor ground return current from said voltage multiplier aNd producing an overcurrent signal at its output when the current flow from said voltage multiplier circuit to said overcurrent detector exceeds a predetermined selectable maximum value; a power supply shutdown switch activated in response to said overcurrent signal for simultaneously a) generating and applying said turnoff signal to said turnoff means to thereby turnoff said DC source and b) inhibiting power transfer from said DC source to said inverter and thereby removing power from the input of said voltage multiplier circuit; a remotely controlled electronic switch connected between electrical ground and said control input for selectably producing said turnoff signal; and a mechanical switch remotely located with respect to said electronic switch, said mechanical switch being operative to control said electronic switch to selectably produce said turnoff signal.

Claim 3

A power supply for producing a very high DC voltage for application to a probe of an electrostatic spray gun from which electrostatically charged coating material is sprayed onto a directly electrically grounded object comprising, in combination: a source of unregulated DC power including an output power lead and a common ground lead, said power lead having an unregulated voltage thereat relative to said common ground lead, a voltage regulator circuit with a two wire power input, a control input and an output, one input wire of said regulator input being connected to said power lead and the other input wire of said series regulator being connected to said common ground lead, said voltage regulator circuit producing a regulated DC voltage at its output relative to said common ground lead when said control input is at a voltage higher than at said ground lead, said regulator including a turnoff means responsive to an externally generated turnoff signal applied to said control input for turning off said regulator thereby removing said DC voltage from said regulator output; an inverter circuit with a two wire input and a two wire output, one said inverter circuit input wire is connected to said regulator output and the other inverter circuit input wire is connected to said common ground lead, said inverter circuit producing at its two wire output an intermediate AC voltage at a high frequency; a voltage multiplier circuit with a two wire input and a single wire output, said two wire input of said voltage multiplier is connected to said inverter circuit two wire output, said voltage multiplier produces at its single wire output a very high DC voltage which is electrically connected to the spray gun probe for electrostatically charging coating material sprayed onto a directly electrically grounded object; an overcurrent detector connected between one said input wire of said voltage multiplier circuit and said common ground lead to monitor ground return current from said voltage multiplier, said overcurrent detector producing an overcurrent signal at its output when the current flow from the voltage multiplier circuit to said common ground lead exceeds a predetermined selectable maximum value; a power supply shutdown switch activated in response to said overcurrent signal for simultaneously a) generating and applying said turnoff signal to said turnoff means to thereby turnoff said regulator and b) short circuiting to said common ground lead said regulator output and said inverter circuit input to thereby inhibit power transfer from said DC source to said multiplier.

Claim 4

A power supply for producing a very high DC voltage for application to a probe of an electrostatic spray gun from which electrostatically charged coating material is sprayed onto a directly electrically grounded object comprising, in combination: a source of unregulated DC power including an output power lead and a common ground lead, said power lead having an unregulated voltage thereat relative to said common ground lead, a voltage regulator circuit with a two wire power input, a control input and an output, one input wire of said regulator input being connected to said power lead and the other input wire of said series regulator being connected to said common ground lead, said voltage regulator circuit producing a regulated DC voltage at its output relative to said common ground lead when said control input is at a voltage higher than at said ground lead, said regulator including a turnoff means responsive to an externally generated turnoff signal applied to said control input for turning off said regulator thereby removing said DC voltage from said regulator output; an inverter circuit with a two wire input and a two wire output, one said inverter circuit input wire is connected to said regulator output and the other inverter circuit input wire is connected to said common ground lead, said inverter circuit producing at its two wire output an intermediate AC voltage at a high frequency; a voltage multiplier circuit with a two wire input and a single wire output, said two wire input of said voltage multiplier is connected to said inverter circuit two wire output, said voltage multiplier produces at its single wire output a very high DC voltage which is electrically connected to the spray gun probe for electrostatically charging coating material sprayed onto a directly electrically grounded object; an overcurrent detector connected between one said input wire of said voltage multiplier circuit and said common ground lead to monitor ground return current from said voltage multiplier, said overcurrent detector producing an overcurrent signal at its output when the current flow from the voltage multiplier circuit to said common ground lead exceeds a predetermined selectable maximum value; a power supply shutdown switch activated in response to said overcurrent signal for simultaneously a) generating and applying said turnoff signal to said turnoff means to thereby turnoff said regulator and b) short circuiting to said common ground lead said regulator output and said inverter circuit input to thereby inhibit power transfer from said DC source to said multiplier.

Claim 5

The power supply of claim 2 additionally including a mechanical switch located at the spray gun and an electronic switch, said electronic switch being connected between said control input and said common ground for selectably connecting said control input directly to said common ground, said mechanical switch being connected in circuit with said electronic switch so that the voltage appearing across the mechanical switch contacts is relatively small thereby reducing the hazard of arcing at Said mechanical switch, said electronic switch being controlled by said mechanical switch to selectably connect said control input to said common ground.

Claim 6

The power supply of claim 3 wherein said overcurrent detector includes means to prevent generation of said overcurrent signal in response to a transient current flowing from said voltage multiplier circuit to said overcurrent detector.

Claim 7

The power supply of claim 4 additionally including an overvoltage detector connected to said regulator circuit output, said overvoltage detector producing an overvoltage signal when the voltage at the output of said regulator circuit exceeds a predetermined value, said overvoltage signal being operative to activate said power supply shutdown switch.

Claim 8

The power supply of claim 2 additionally including an overvoltage detector connected to said regulator circuit output, said overvoltage detector producing an overvoltage signal when the voltage at the output of said regulator circuit exceeds a predetermined value, said overvoltage signal being operative to activate said power supply shutdown switch.

Claim 9

The power supply of claim 2 wherein said DC source includes a smoothing capacitor and wherein said inverter circuit includes a transformer, and wherein said short-circuiting of said regulator output and said inverter input to said common ground lead discharges electrical energy stored in said smoothing capacitor and in said transformer.