Dual voltage power supply

• US 5,412,308 A
• Filed: 03/15/1994
• Issued: 05/02/1995
• Est. Priority Date: 01/06/1994
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: HP Inc.
• Inventors: Brown, Preston D.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US08/214,088
• Time in Patent Office: 413 Days
• Field of Search: 323/265, 323/267, 323/268, 323/271, 323/282, 323/289, 323/222, 323/224, 323/266, 323/272, 363/71, 307/11, 307/18, 307/28, 307/43, 307/75
• US Class Current: 323/267
• CPC Class Codes: G05F 1/577 for plural loads
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A high efficiency power supply for producing two regulated output voltages (i.e. 3.3 and 5 volts) from an unregulated input voltage. The supply includes a 4-15 volt battery pack, a first (5.0 volt) output, a second (3.3 volt) output, and a ground. The positive terminal of the battery is connected directly to the second output. The 3.3 volt differential with ground is maintained by a voltage regulator that couples the negative terminal of the battery pack to ground (i.e. ground floats relative to the battery). A second voltage regulator couples the positive terminal of the battery pack to the first output, and maintains this first output at 5.0 volts relative to ground. This latter regulator is capable of boost operation, permitting a 5.0 volt output to be maintained even if the battery pack voltage is less than this value. Neither regulator includes a transformer, making the supply particularly well suited for use in miniaturized equipment, such as palmtop computers.

Claims

1. A power supply comprising:

first and second output terminals and a ground terminal, the first and second output terminals and a ground terminal, the first and second output terminals providing output voltages of V₁ and V₂, respectively;

an input voltage source providing an input voltage of V_in ;

first regulator means coupled between the input voltage source and the first output terminal for converting V_in to V₁, the first regulator means capable of providing an output voltage higher than Vin, and capable of providing an output voltage lower than Vin;

second regulator means coupled between the input voltage source, the second output terminal, and the ground terminal for converting V_in to V₂ ;

wherein neither the first nor second regulator means includes a transformer.

2. The power supply of claim 1 in which the first regulator means comprises a switching regulator.

3. The power supply of claim 2 which further includes an inductor and a diode serially interposed between the input voltage source and the first output terminal.

4. The power supply of claim 1 wherein the second regulator means includes a ground switch.

5. The power supply of claim 1 wherein neither the first nor second regulator means includes capacitive elements for transferring energy from the input voltage source to the first or second outputs.

6. The power supply of claim 1 having an efficiency greater than 80%.

7. The power supply of claim 1 wherein the second regulator means can produce an output voltage less than the input voltage provided by the input voltage source.

8. The power supply of claim 1 wherein the first and second regulator means include only one inductor each.

9. A power supply comprising:

first and second outputs providing output voltages of V₁ and V₂, respectively;

a input voltage source having a positive and negative terminal and providing an input voltage, Vin;

first and second voltage regulators, the second voltage regulator having first, second, and third terminals;

a ground terminal;

and a ground switch having first and second terminals, the first terminal being coupled to the negative terminal of the input voltage source;

the first voltage regulator being coupled to the positive and negative terminals of the input voltage source and the first output, the first voltage regulator capable of providing an output voltage higher than Vin, and capable of providing an output voltage lower than Vin;

the first terminal of the second voltage regulator being coupled to the positive terminal of the input voltage source and the second output;

the second terminal of the second voltage regulator being coupled to the second terminal of the ground switch;

and the third terminal of the second voltage regulator being coupled to the ground terminal;

wherein neither the first nor the second voltage regulator includes a transformer.

10. A method for providing two regulated outputs comprising:

providing an input voltage source with positive and negative terminals, first and second output terminals providing first and second output voltages, first and second voltage regulators without transformers, a ground, and a ground switch;

sensing the first output voltage from the first voltage regulator;

storing energy in the first voltage regulator;

maintaining the first output voltage at a first predetermined level that is higher than an input voltage provided by the input voltage source when the input voltage is less than the first predetermined level;

maintaining the first output voltage at the first predetermined level that is lower than an input voltage provided by the input voltage source when the input voltage is greater than the first predetermined level;

increasing the first output voltage by releasing the energy stored in the first voltage regulator if the first output voltage has dropped below the first predetermined level;

sensing the voltage at the second output terminal from the second voltage regulator;

storing energy in the second voltage regulator if the second output voltage has dropped below a second predetermined level by switching the ground switch and thereby coupling the negative terminal of the input voltage source to ground through the second voltage regulator; and

regulating the second output voltage by selectively storing and releasing energy in the second voltage regulator.

11. A power supply comprising:

first and second output terminals and a ground terminal, the first and second output terminals providing output voltages of V₁ and V₂, respectively;

an input voltage source providing an input voltage of V_in ;

first regulator means coupled between the input voltage source and the first output terminal for converting V_in to V₁, the first regulator means capable of providing an output voltage higher than Vin, and capable of providing an output voltage lower than Vin;

second regulator means coupled between the input voltage source, the second output terminal, and the ground terminal for converting V_in to V₂, the second regulator means coupled between the input voltage source and the ground terminal such that the input voltage source floats relative to the ground terminal;

wherein neither the first nor second regulator means includes a transformer.

12. The power supply of claim 11 wherein the input voltage source has a positive and negative terminal, the second regulator means coupled between the negative terminal and the ground terminal such that the voltage at the negative terminal of the input voltage source floats relative to the ground terminal.

13. The power supply of claim 12 wherein the second regulator means includes a ground switch, the ground switch coupled to the negative terminal.