Static DC to AC power converter including separate high and low power converters

• US 5,452,197 A
• Filed: 02/04/1993
• Issued: 09/19/1995
• Est. Priority Date: 02/04/1993
• Status: Expired due to Term

• Current Assignee: Vanner, Inc. (Vanner Holdings, Inc.)
• Original Assignee: Vanner Weldon, Inc.
• Inventors: Rice, Milton W.
• Primary Examiner(s): Sterrett, Jeffrey L.
• Application Number:
  US08/013,309
• Time in Patent Office: 957 Days
• Field of Search: 363/17, 363/49, 363/65, 363/71, 363/98, 363/132
• US Class Current: 363/71
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode

Abstract

Disclosed is a DC-to-AC power converter (10) that includes a high power DC-to-AC converter (20) and a low power DC-to-AC converter (40). The low power DC-to-AC converter produces a continuous 120-volt AC signal until a load sense circuit (60) determines that a load (14) is drawing more than a predetermined level of power. The load sense circuit then transmits a load sense signal to a control circuit (80) that disables the low power DC-to-AC converter and enables the high power converter. As a result, the DC-to-AC power converter is able to start virtually any load while conserving the power of a DC source.

Claims

1. A DC-to-AC power converter for providing an AC output signal to a load from a DC voltage source, comprising:

a first, high power, DC-to-AC converter coupled to the DC voltage source for producing a first, high power, AC output signal;

a second, low power, DC-to-AC converter source for producing a second, low power, AC output signal, wherein the second, low power, DC-to-AC converter produces a continuous, low power, AC output signal even if no load is present;

switch means for connecting either the first, high power, AC output signal to the load or the second, low power, AC output signal to the load;

power monitoring means for monitoring power drawn by the load and for producing a signal if the load draws more than a predetermined level of power; and

control circuit means for receiving the signal from the power monitoring means, and for causing the switch means to disconnect the second, low power, AC output signal from the load and to connect the first, high power, AC output signal to the load when the control circuit means receives the signal from the power monitoring means.

2. The DC-to-AC power converter of claim 1, further comprising:

a pulse width modulation circuit that drives the first, high power, DC-to-AC converter to produce a high power 120-volt, 60 Hz AC output signal.

3. A DC-to-AC power converter for producing an AC signal from a DC voltage source, comprising:

a first DC-to-AC converter for producing a first AC signal, including;

(a) a first transformer having a primary winding and a secondary winding;

(b) first switch means connected to conduct current from the DC source to the primary winding of the first transformer;

(c) second switch means connected between the primary winding and a ground potential, said first and second switch means being located on opposite sides of the primary winding of the first transformer;

(d) third switch means connected to conduct current from the DC source to the primary winding of the first transformer;

(e) fourth switch means connected between the primary winding and a ground potential, wherein said third and fourth switch means are located on opposite sides of the primary winding; and

(f) pulse width modulation means for controlling the first, second, third and fourth switch means so that the first AC signal is produced on the secondary winding of the first transformer;

a second DC-to-AC converter for producing a second AC signal, including;

(g) a second transformer having a primary winding and a secondary winding;

(h) means for producing a first 60 Hz signal; and

(i) means for producing a second 60 Hz signal that is out of phase with the first 60 Hz signal, wherein the primary winding of the second transformer is connected to the means for producing the first 60 Hz signal and the means for producing the second 60 Hz signal, said means for producing a first 60 Hz signal and the means for producing a second 60 Hz signal being operable to conduct a current through the primary winding of the second transformer in alternate directions;

power monitoring means for producing a load sense signal when the level of power drawn by a load exceeds a predetermined threshold, including;

(j) a load sense transformer that produces a signal proportional to a level of power drawn by the load;

(k) a comparator for comparing the signal with a threshold value and for producing a load sense signal when the power drawn by the load exceeds the threshold value; and

(l) switching means that are responsive to the load sense signal for connecting the first AC signal to the load and disconnecting the second AC signal from the load when the comparator produces the load sense signal.

4. A method of providing a load with an AC voltage signal from a DC voltage source, comprising the steps of:

producing a low power AC voltage signal from the DC voltage source by;

(a) providing an input clocking signal to a first and a second flip-flop such that the first and the second flip-flop change states alternately in time; and

(b) connecting an output of the first and second flip-flop to a transformer to conduct a current through the transformer in alternate directions as the first and the second flip-flop change states;

(c) providing an input clocking signal to a first and second flip-flop such that the first and the second flip-flop change states alternately in time; and

(d) connecting an output of the first and second flip-flop to a transformer to conduct a current through the transformer in alternate directions as the first and the second flip-flop change states;

connecting the low power AC voltage signal to the load;

monitoring the level of power drawn by the load;

determining if the level of power drawn by the load exceeds a predetermined threshold; and

producing a high power AC voltage signal from the DC voltage source, disconnecting the low power AC voltage signal from the load and connecting the high power AC voltage signal to the load when the level of power drawn by the load exceeds the predetermined threshold.

5. A DC-to-AC power converter for providing an AC output signal to a load from a DC voltage source., comprising:

a first, high power, DC-to-AC converter coupled to the DC voltage source for producing a first, high power, AC output signal;

a second, low power, DC-to-AC converter source for producing a second, low power, AC output signal;

the second, low power, DC-to-AC converter comprising;

a transformer having a primary winding and a secondary winding;

means for producing a first 60 Hz signal;

means for producing a second 60 Hz signal that is out of phase with the first 60 Hz signal;

wherein the primary winding of the transformer is connected to the means for producing the first 60 Hz signal and the means for producing the second 60 Hz signal, said means for producing a first 60 Hz signal and said means for producing a second 60 Hz signal being operable to conduct a current through the primary winding in alternate directions;

switch means for connecting either the first, high power, AC output signal to the load or the second, low power, AC output signal to the load;

power monitoring means for monitoring power drawn by the load and for producing a signal if the load draws more than a predetermined level of power; and

control circuit means for receiving the signal from the power monitoring means, for causing the switch means to disconnect the second, low power, AC output signal from the load, and to connect the first, high power, AC output signal to the load when the control circuit means receives the signal from the power monitoring means.

6. The DC-to-AC power converter as in claim 5, wherein the means for producing the first and second 60 Hz signals comprise:

a first flip-flop connected to change states each time it receives a clock input;

a second flip-flop connected to change states each time it receives a clock input; and

means for providing out-of-phase clock inputs to the first and second flip-flops.

7. The DC-to-AC power converter as in claim 6, wherein the means for providing out-of-phase clock inputs to the first and second flip-flops comprise:

a source of a 120 Hz clocking signal;

means for producing an inverted 120 Hz clocking signal;

means for connecting the 120 Hz clocking signal to one of the first and second flip-flops; and

means for connecting the inverted 120 Hz clocking signal to the other of the first and second flip-flops.