Digital power converter input current control circuit

• US 4,678,984 A
• Filed: 04/21/1986
• Issued: 07/07/1987
• Est. Priority Date: 04/21/1986
• Status: Expired due to Term

• Current Assignee: Sperry Corporation
• Original Assignee: Sperry Corporation
• Inventors: Henze, Christopher P.
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/854,243
• Time in Patent Office: 442 Days
• Field of Search: 323/282, 323/283, 323/284, 323/285, 323/286, 323/276, 323/277, 361/57, 361/58, 361/93, 361/111
• US Class Current: 323/285
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A digital power converter input current control circuit is connected between a power converter and a power source. This circuit monitors, and controls if necessary, the current that flows between the power source and the power converter in a manner that protects the power source, the input current control circuit, and the power converter from the catastrophic effects of excessive current flow. The input current control circuit operates similar to an electronic circuit breaker with an automatic reset feature, in that the power delivered to the power converter is maintained low during fault conditions. Thus, if a power transistor in the power converter should fail, a current limit circuit in the input current control circuit will prevent additional damage to the power converter. The operation of the input current control circuit, however, is different than that of a circuit breaker in that a control circuit in the current limit circuit allows for current limiting during start-up, transient conditions which prevents the generation of "gliches" or voltage spikes on energized input power lines when the power converter is suddenly activated.

Claims

1. An input current control having a normal operating range, coupled between an input power supply means connectable to a source of electrical power and output means connectable to a load, comprising current limit means comprising control means, current regulating means having a control terminal and a current path coupled between said input power supply means and said output means which may be selectively opened and closed in response to a control signal applied to said control terminal wherein said control signal determines whether said current path is opened or closed, and said control signal controls the magnitude of current flowing in said current path when said path is closed, inrush/normal, operation circuit means coupled to said input power supply means constructed to supply said control signal to said control terminal so as to cause said regulating means to close said current path between said input power supply means and said output means when said control signal reaches a predefined threshold magnitude, and so as to cause said regulating means to control the current flowing in said current path during normal operation of said input current control circuit, current sensing means for sensing the current flowing through said current path and signal-control means coupled to said current sensing means and to said control terminal for assuming control of said current regulating means in response to said current sensing means such that said current path will be opened upon the sensing by said current sensing means of a current flowing through said current path which is greater than a predefined overcurrent magnitude.

2. An input current control circuit as claimed in claim 1 further comprising timing means coupled to said inrush/normal operation circuit means and to said current sensing means for switching control of said current regulating means from said current sensing means to said inrush/normal operation circuit means after a predetermined period of time following each opening of said current path in response to said sensing of said overcurrent magnitude by said current sensing means.

3. An input current control circuit as claimed in claim 1 wherein said current regulating means comprises transistor means that comprises two load terminals and said control terminal, wherein said current path is between said two load terminals and said current path comprises, in the absence of an overcurrent condition, a high impedance path of gradually decreasing impedance after said current path has been connected to said input power supply means until such time that a normal operation low impedance path which is substantially constant in a magnitude is obtained.

4. An input current control circuit as claimed in claim 3 further comprising timing means coupled to said inrush/normal operation circuit means and to said current sensing means for switching control of said current regulating means from said current sensing means to said inrush/normal operation circuit means after a predetermined period of time following each opening of said current path in response to said sensing of said overcurrent magnitude by said current sensing means.