Power limiting regulator

• US 5,604,425 A
• Filed: 08/08/1994
• Issued: 02/18/1997
• Est. Priority Date: 08/08/1994
• Status: Expired due to Fees

• Current Assignee: Thomson Consumer Electronics Incorporated (Vantiva SA)
• Original Assignee: Thomson Consumer Electronics Incorporated (Vantiva SA)
• Inventors: Smith, Lawrence E.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US08/287,591
• Time in Patent Office: 925 Days
• Field of Search: 323/231, 323/267, 323/276, 323/313, 323/907, 363/21, 363/89, 307/11, 307/28, 327/513
• US Class Current: 323/267
• CPC Class Codes: G05F 3/18 using Zener diodes
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control

Abstract

A source of an input supply voltage is coupled via a current limiting resistor to a load. A diode has a first terminal that is coupled to a junction terminal between the resistor and the load. A second terminal of the diode is coupled to an output of a regulated power supply where a regulated supply voltage is developed. The diode clamps a second output supply voltage developed at the first terminal of the diode to the regulated supply voltage. When the power in the load exceeds a predetermined value, the diode ceases conducting. In this way, the conductor that couples the second output supply voltage to the load need not meet the strict 15 watt node spacing requirements.

Claims

1. A power supply, comprising:

a voltage regulator for applying a first regulated supply voltage to a first load;

a power limiting impedance for applying a second supply voltage to a second load; and

a first diode having a first terminal coupled to said impedance and a second terminal coupled to said first regulated supply voltage for regulating said second supply voltage by clamping said second supply voltage to said first supply voltage and for isolating said voltage regulator from said second load to prevent said voltage regulator from energizing said second load.

2. A power supply according to claim 1 further comprising, a second diode that is coupled between said second load and said first diode to provide for temperature compensation with respect to variations in said first diode.

3. A power supply according to claim 1 wherein said impedance comprises a resistor.

4. A power supply according to claim 3 wherein said first diode and said resistor are coupled in series.

5. A power supply according to claim 3 wherein said second diode is coupled in series with said resistor and between said resistor and said second load.

6. A power supply according to claim 1 wherein said regulator comprises series pass regulator.

7. A power supply, comprising:

a voltage regulator for applying a first regulated supply voltage to a first load;

a power limiting impedance for applying a second supply voltage to a second load;

a first diode coupled to said impedance and to said first regulated supply voltage;

said first diode being conductive in a first mode during normal operation of said second load, in which said first diode clamps said second supply voltage to said first regulated supply voltage; and

said first diode being non-conductive in a second mode during abnormal operation of said second load, in which said second supply voltage decreases as current through said power limiting impedance increases due to said abnormal operation, thereby limiting the power delivered to said second load to a predetermined maximum value.

8. A power supply, comprising:

a voltage regulator for applying a first regulated supply voltage to a first load;

a power limiting impedance for applying a second supply voltage to a second load; and

means coupled to said impedance and to said first regulated voltage for clamping said second supply voltage to said first regulated voltage to regulate said second supply voltage such that power transfer from said voltage regulator of said first supply voltage to said second load via said clamping means is prevented.

9. A power supply according to claim 8 wherein said clamping means comprises a diode.