Power supply system

• US 3,873,846 A
• Filed: 08/29/1973
• Issued: 03/25/1975
• Est. Priority Date: 09/07/1972
• Status: Expired due to Term

• Current Assignee: Nationsbank NA (Bank of America Corp.)
• Original Assignee: Fumio Otaki, Minoru Morio
• Inventors: Morio, Minoru, Otaki, Fumio
• Primary Examiner(s): Beha, Jr., William H.
• Application Number:
  US05/392,412
• Time in Patent Office: 573 Days
• Field of Search: 321/2,4,8R,27R,45S 307/11,22,23,29,38,64,66,72,73,80,82 315/27TD 178/DIG.11 320/57,59,60
• US Class Current: 307/23
• CPC Class Codes: H02M 1/10 Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from ac or dc
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop

Abstract

A DC power supply circuit of the switching or chopping type for converting a voltage from an AC power source or from a DC power source into a predetermined DC voltage and supplying the converted DC voltage to a load, comprises a converting transformer having first and second primary windings and a secondary winding and first and second switching circuits connected to the first and second primary windings, respectively, and being selectively operated for switching or chopping the voltage applied from the AC or DC power source to the respective primary winding thereby to produce a pulse voltage at the secondary winding of the converting transformer to which a rectifier circuit is connected. The converted DC voltage obtained at the output of the rectifier circuit is connected. The converted DC voltage obtained at the output of the rectifier circuit is compared with a reference voltage, and the switching circuits are controlled on the basis of such comparison for maintaining the converted DC voltage at a predetermined level.

Claims

1. A DC power supply circuit of the switching type comprising:

a. a transformer having a first primary winding, a second primary winding and a secondary winding;

b. a first series circuit connected to said first primary winding and including rectifier means and first switching means;

c. a first input terminal adapted to be connected to an AC power source for selectively supplying an input voltage to said first series circuit;

d. a second series circuit connected to said second primary winding and including second switching means;

e. a second input terminal adapted to be connected to a DC power source for selectively supplying an input voltage to said second series circuit;

f. driving means for supplying a switching signal to at least one of said first and second switching means to intermittently interrupt at least one of said first and second series circuits such that the current flowing through a corresponding one of said first and second primary windings is intermittently interrupted so as to induce a voltage across said secondary winding; and

g. output rectifier means connected to said secondary winding for rectifying said induced voltage and for producing an output DC voltage.

2. A power supply circuit according to claim 1 wherein said secondary winding is isolated from said first primary winding.

3. A power supply circuit according to claim 2 including drive transformer means for supplying said switching signal from said driving means to at least said one switching means.

4. A power supply circuit according to claim 1 wherein said second primary winding is formed from a portion of said secondary winding.

5. A power supply circuit according to claim 4 including selector switch means for selectively connecting one end of said secondary winding to ground when said AC power source is connected to said first input terminal and to said DC power source when said DC power source is connected to said second input terminal.

6. A power supply circuit according to claim 1 wherein said driving means comprises pulse duration modulator means responsive to said DC output voltage for generating switching pulses having a duration dependent upon the difference between said DC output voltage and a predetermined value and means for supplying the output of said pulse duration modulator means to said switching means to thereby vary the duration that said switching means is closed in accordance with said switching pulse duration for stabilizing said DC output voltage.

7. A power supply circuit according to claim 6 further comprising error amplifier means coupled to said output rectifier means for applying a control signal to said pulse duration modulator means proportional to the deviation of said DC output voltage from said predetermined value.

8. A power supply circuit according to claim 1 further including an auxiliary transformer having a primary winding connected in series with said first series circuit and a secondary winding coupled to said driving means, said auxiliary transformer being responsive to an initial application of AC voltage to said first series circuit to induce a transient voltage at said secondary winding thereof, said transient voltage being supplied to said driving means as an operating voltage.

9. A power supply circuit according to claim 1 wherein said driving means includes selector means for supplying said switching signal to said first switching means when said AC power source is connected to said first input terminal and to said second switching means when said DC power source is connected to said second input terminal.

10. A power supply circuit according to claim 4 furtheR including a diode for connecting one end of said second primary winding to ground.

11. A DC power supply circuit of the switching type for supplying an electrical apparatus with a stabilized DC voltage of substantially constant amplitude in response to energization by an AC power input source or a DC power input source, comprising:

a transformer having a first primary winding, a second primary winding and a secondary winding;

a first series circuit connected to said first primary winding and including input rectifier means and first switching means;

first input means adapted to connect an AC power source to said first series circuit for supplying an AC voltage to said first series circuit;

a second series circuit connected to said second primary winding and including second switching means;

second input means adapted to connect a DC power source to said second series circuit for supplying a DC voltage to said second series circuit, said first and second input means being mutually exclusive in supplying the respective voltages to the respective series circuits;

pulse generating means operable at a frequency determined by the operation of said electrical apparatus for supplying switching signals of variable duration to at least one of said first and second switching means to thereby intermittently energize at least said one switching means for a corresponding duration and at said frequency such that current flows intermittently through the respective one of said first and second primary windings for substantially said duration;

output rectifier means connected to said transformer secondary winding for rectifying a voltage induced across said secondary winding and for generating an output DC supply voltage;

detecting means coupled to said output rectifier means for detecting the deviation of said output DC supply voltage from a predetermined value and for generating a control signal proportional to said deviation; and

means for applying said control signal to said pulse generating means so that said control signal determines said duration of said switching signals.

12. A power supply circuit in accordance with claim 11 wherein said first input means includes a first power switch connected to said first series circuit and first connector means coupled to said first power switch for being supplied with said AC power source.

13. A power supply circuit in accordance with claim 12 wherein said DC power source comprises a rechargeable battery connected to second connector means, and wherein said second input means comprises a second power switch connected to said second series circuit and further connected to said first connector means;

a DC selector switch assuming a normally closed state to connect said second connector means to said second power switch; and

means for coupling an external DC supply to said first connector means and for simultaneously opening said normally closed DC selector switch to thereby couple said external DC supply to said second power switch.

14. A power supply circuit in accordance with claim 11 wherein said pulse generating means includes amplifying means for receiving said switching signals;

and selector switch means coupled to said amplifying means and responsive to DC voltage applied to said second series circuit for connecting said amplifying means to said second switching means and responsive to the absence of DC voltage applied to said second series circuit for connecting said amplifying means to said first switching means.

15. A power supply circuit in accordance with claim 14 wherein said second primary winding consists of a portion of said secondary winding;

and wherein one end of said secondary winding is connected to said output rectifier means and the other end of said secondary winding is common to said second primary winding and is selectively coupled to ground by selective switching means such that said other end is coupled to ground when said AC power source is connected to said first series circuit and said other end is supplied with DC voltage when a DC power source is connected to said second series circuit.

16. A power supply circuit in accordance with claim 11 wherein said DC power source comprises a rechargeable battery and wherein said power supply system further includes charging means for recharging said battery when said AC power source is connected to said first series circuit.

17. A power supply circuit in accordance with claim 16 wherein said charging means comprises charging current rectifier means connected to a mid-tap of said transformer secondary winding for producing a DC charging current;

AC sensing means included in said first series circuit for detecting when said AC power source is connected to said first series circuit; and

selective coupling means responsive to said AC sensing means for coupling said DC charging current to said rechargeable battery.

18. A power supply circuit in accordance with claim 11 further including start-up means for temporarily supplying operating voltages to at least said pulse generating means and said detecting means when said AC power source or a DC power source is initially connected to said first or second series circuits, respectively.

19. A power supply circuit in accordance with claim 18 wherein said start-up means comprises an auxiliary transformer connected in said first series circuit and responsive to a transient voltage applied thereto when said AC power source is initially connected to said first series circuit;

transient voltage rectifier means for rectifying the voltage induced across said auxiliary transformer to a DC voltage;

means for supplying said last-mentioned DC voltage to at least said pulse generating means and said detecting means; and

means for preventing the application of said last-mentioned DC voltage to said output rectifier means.

20. A power supply circuit in accordance with claim 19 wherein said start-up means further comprises voltage limiting means having an input terminal connected to said second input means for detecting when a DC source is connected thereto, and an output terminal coupled to at least said pulse generating means and said detecting means, said voltage limiting means being conductive when a DC power source is initially connected to said second series circuit;

and means for rendering said voltage limiting means nonconductive when said output DC supply voltage reaches a substantally steady-state level.