Claims: We Claim:
1. A counterpoise circuit based arrangement for tight cross regulation, the arrangement comprising:
a primary stage circuit having an input power supply;
a transformer coupled to the primary stage circuit having a bias winding;
a counterpoise circuit connected to the bias winding of the transformer; and
a plurality of output circuit connected to secondary winding of the transformer.
2. The arrangement as claimed in claim 1, wherein the primary stage circuit comprises of:
an electromagnetic interference filter connected to the input power supply;
a start up circuit connected to the electromagnetic interference filter;
a diode rectifier and filter circuit connected to the counterpoise circuit;
a controller circuit receiving input from the filter and the start-up circuit; and
a switch controlled by the output from the controller.
3. The arrangement as claimed in claim 1, wherein each of the output circuit comprises of:
a diode rectifier connected to the transformer winding;
an output filter connected to diode rectifier; and
a low drop out regulator connected to the output filter.
4. The arrangement as claimed in claim 1, wherein the counterpoise circuit regulates the output voltage at plurality of outputs, subsequently decreasing clamp voltage of the switch.
5. The regulation as claimed in claim 4, wherein the output voltage of the arrangement is achieved by providing tight cross regulation at any load condition.
6. The regulation as claimed in claim 5, wherein the tight cross regulation is achieved by providing complete input voltage range by equal distribution of leakage energy.
7. The regulation as claimed in claim 5, wherein the load condition is achieved by at least one load combination selected from the list comprising of:
one output at minimum load and a plurality of outputs at maximum load;
one output at maximum load and a plurality of outputs at minimum load; and
at least one output at no-load and a plurality of outputs at varying load condition.

Bangalore NARENDRA BHATTA HL
20th March 2018 (INTELLOCOPIA IP SERVICES)
AGENT FOR APPLICANT
, Description:COUNTERPOISE CIRCUIT FOR TIGHT CROSS REGULATION

FIELD OF INVENTION
The invention generally relates to the field of power converters and particularly to multiple output converters.

BACKGROUND
Power converters, ac to ac, ac to dc and dc to dc are used to convert input power into desirable output power, to drive a load. In multiple output converters, two or more outputs deliver power which is converted from a single input source. These output voltage signals drive separate loads. In many applications, a single converter may have to provide multiple isolated output voltages. A traditional way of designing multiple-output converters is to use a multiple winding transformer. When there is variation in the input voltage received by the converter, it is desirable to control the converter output voltages using line regulation and also to provide some form of regulation for outputs.
The cross regulation issue is caused by variations of voltage drops across the rectifying devices and output filter inductors in the converter. The existing converters achieve tight cross regulation for conditioned loads, where one output is at full load and other outputs are at minimum load or vice versa. But, if one or more output is at no load and other outputs are at any load condition, then cross regulation is not achieved. Tight cross regulation is inhibited as a result of the leakage energy, developed from leakage inductance, passing to the output which are at no-load and low load, and increase in clamp voltage at the switch.

BRIEF DESCRIPTION OF DRAWINGS
So that the manner in which the recited features of the invention can be understood in detail, some of the embodiments are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
FIG.1 shows a block diagram of a counterpoise circuit for tight cross regulation, according to an embodiment of the invention.
FIG.2 shows a schematic diagram of a primary stage circuit of thecounterpoise circuit for tight cross regulation, according to an embodiment of the invention.

SUMMARY OF THE INVENTION
One aspect of the invention provides a counterpoise circuit based arrangement for tight cross regulation of the output. The arrangement includes a primary stage circuit having an input voltage, a transformer coupled to the primary stage circuit having a bias winding, a counterpoise circuit connected to the bias winding of the transformer and a plurality of output circuit connected to secondary winding of the transformer.
The primary stage circuit includes a filter that is connected to input power supply, a start up circuit connected to the filter output, a diode rectifier and filter circuit connected to the counterpoise circuit, a controller circuit receiving input from the start-up circuit and bias winding. The primary stage circuit further includes a switch controlled by the output from the controller. The controller circuit is biased by the bias winding and the start-up circuit. The outputs are regulated by the switch indirectly with the controller.
The output circuit includes a diode rectifier connected to the transformer winding, an output filter connected to diode rectifier and a regulator connected to output filter.
The counterpoise circuit regulates the output voltage at plurality of outputs, subsequently decreasing clamp voltage of the switch. The output voltage of the arrangement is achieved by providing tight cross regulation at any load condition.
The arrangement provides tight cross regulation for complete input voltage range by equal distribution of leakage energy. The arrangement provides tightly cross regulated voltage for one output at minimum load and a plurality of outputs at maximum load, one output at maximum load and a plurality of outputs at minimum load and one or more output at no-load and a plurality of outputs at varying load condition.
DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the invention provide an arrangement to obtain tight cross regulated multiple-output for varying range of input power.
FIG.1 shows a block diagram of a counterpoise circuit for tight cross regulation, according to an embodiment of the invention.
The arrangement 100 comprises of a primary stage circuit 101, a transformer 102, a counterpoise circuit 104 and a plurality of output circuit 105.
The primary stage circuit 101 is connected to an input power supply 106. The input power supply 106 includes but is not limited to a DC source and a live bus. The transformer 102 is connected to the primary stage circuit 101. The transformer 102 includes a primary winding 107, a bias winding 103 on the primary side of the transformer 102 and a plurality of secondary winding 106 on the secondary side. The counterpoise circuit 104 is connected to the bias winding 103 of the transformer 102. The plurality of output circuit 105 is connected to the secondary winding 108 of the transformer 102.
The primary stage circuit 101 includes but is not limited to an input filter, a start up circuit, a rectifier, a controller circuit, a switch and resistors. The filter removes unwanted frequency components from input signal of the input power supply 106. The input signal is then fed to the primary winding 107 of the transformer 101 and the start up circuit. The filter described herein includes but is not limited to active and passive filters. The startup circuit limits the primary stage circuit 101 from an undesired operating point and also doesn’t interfere the circuit 101 once the desired operating point is reached. The operating point described herein is a point where supplying of the required voltage and current to startup circuit. In one example of the invention, 11V and 10mA are selected as the operating point. The rectifier provides a unidirectional signal. The controller circuit is configured to control the power supply to the transformer 102 through a switch. The switch includes but is not limited to transistors and switching circuit.
The bias winding 103 of the transformer 102 provides feedback to the controller circuit. The feedback obtained from the bias winding103 is then sent to counterpoise circuit 104.
The output circuit 105 includes but is not limited to a diode rectifier, an output filter and a regulator. The arrangement 100 includes a plurality of output circuits 105 and a plurality of tightly cross regulated output voltages by output terminals 109.
When additional voltage is developed across the bias winding 103 due to leakage energy, the bias winding 103 provides feedback to the controller circuit. The controller circuit generates minimum duty cycle due to increased voltage sensed by feedback. Simultaneously, the load is driven by the terminals 109. The counterpoise circuit 104 employed at bias winding 103 equally distributes leakage energy to the secondary winding 108, achieving tight cross regulation.
FIG.2 shows a schematic diagram of the primary stage circuit of the counterpoise circuit for tight cross regulation, according to an embodiment of the invention. The primary stage circuit 101 is connected to an input power supply 106. In one example of the invention, the input power supply 106 is a raw bus-live power supply. The primary stage circuit 101 includes an electromagnetic interference filter 202, hereinafter referred to as EMI filter 202, which is connected to the input power supply 106 through a fuse protection circuit 201, a start up circuit 203 connected to the EMI filter 202, a diode rectifier and filter circuit 204 connected to the counterpoise circuit 104, a pulse width modulation (PWM) controller circuit 206 receiving input from the EMI filter 202 and the start-up circuit 203. The primary stage circuit 101 further includes a MOSFET switch 207. The MOSFET switch 207 is controlled by the output from the PWM controller 206. The PWM controller circuit 206 is biased by bias voltage from the bias winding 103 together with the start-up circuit 203. The outputs 109 at the terminal are regulated by the MOSFET switch 207 indirectly with the PWM controller 206. For protection of the PWM controller circuit 206, an input under voltage protection circuit 205, a current monitor and an overcurrent protection circuit 207 are connected to the controller 206.
The counterpoise circuit 104 is connected to the diode rectifier and filter circuit through a series resistor 208.
In another embodiment of the invention, the counterpoise circuit 104 is provided on the secondary side of the transformer 102.
The counterpoise circuit 104 regulates the output voltage at plurality of outputs, subsequently decreasing clamp voltage of the switch. The output voltage of the arrangement is achieved by providing tight cross regulation at any load condition.
The arrangement provides tight cross regulation for complete input voltage range by equal distribution of leakage energy. The arrangement provides tightly cross regulated voltage for one output at minimum load and a plurality of outputs at maximum load, one output at maximum load and a plurality of outputs at minimum load and one or more output at no-load and a plurality of outputs at varying load condition.
For example, the tables shown depict the circuit for outputs: +3.5V/0.25A, -3.5V/0.01A, +15V/0.18A, +5V/0.9A, with and without the counterpoise circuit. The circuit with counterpoise circuit gives rated output voltage at +3.5V terminal at maximum, and remaining outputs at no load.

Without counterpoise circuit for outputs: +3.5V/0.25A, -3.5V/0.01A, +15V/0.18A, +5V/0.9A
Sl.No Load condition Rated output Voltage Output voltage
1 Condition-1: If +3.5V is maximum, remaining outputs are minimum +3.5 V/FL 3.506
-3.5V/ML -3.501
+15V/ML 15.048
+5V/ML 5.049
2 Condition-2: If +3.5V is maximum, remaining outputs are no load +3.5V/FL 3.13
-3.5V/FL -3.501
+15V/NL 15.048
+5V/NL 5.049

With counterpoise circuit for outputs: +3.5V/0.25A, -3.5V/0.01A, +15V/0.18A, +5V/0.9A
Sl.No Load condition Rated output Voltage Output voltage
1 Condition-1: If +3.5V is maximum, remaining outputs are minimum +3.5 V/FL 3.506
-3.5V/ML -3.501
+15V/ML 15.048
+5V/ML 5.049
2 Condition-2: If +3.5V is maximum, remaining outputs are no load +3.5V/FL 3.506
-3.5V/FL -3.501
+15V/NL 15.048
+5V/NL 5.049

The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.