DC-DC power converter including sensing means for providing an output when the reserve power of the converter falls below a predetermined amount for a given input voltage

Claim 2

A DC-DC (direct current to direct current) power conversion apparatus for use in a remote terminal of a telephone system which receives power from a voltage source located in a central office, wherein a substantial impedance exists between said power conversion apparatus and said central office, said power conversion apparatus comprising, in combination: a PWM (pulse-width modulator) apparatus having a variable duty cycle, said PWM apparatus including input voltage supply means for receiving power from said voltage source and supplying a DC input voltage, and converter output means for supplying a converted output voltage to a load; feedback control means, comprising a part of said PWM apparatus, for maintaining a given regulated DC output voltage at said converter output means over a range of load impedances by varying the duty cycle of said PWM apparatus; and detecting means, connected to said PWM apparatus, for supplying an output signal indicative of the reserve power available from said PWM apparatus, said reserve power output signal being derived as a function of the duty cycle of said PWM apparatus, said detecting means comprising: means for measuring the duty cycle of said PWM apparatus; and means for providing said reserve power output signal when the duty cycle of said PWM apparatus exceeds a threshold level indicating that an increase in the power received from said voltage source is required.

Claim 3

The power conversion apparatus as set forth in claim 1 wherein said means for measuring the duty cycle further includes means for comparing the duty cycle of said PWM apparatus with said threshold level, said threshold level representing a minimum reserve power threshold.

Claim 4

The power conversion apparatus as set forth in claim 2 wherein said reserve power output signal is provided by said threshold detector when the duty cycle of said PWM apparatus exceeds said minimum reserve power threshold thereby indicating that an increase in the power received from said voltage source is required.

Claim 5

A DC-DC (direct current to direct current) power conversion apparatus for use in a remote terminal of a telephone system which receives power from a voltage source located in a central office, wherein a substantial impedance exists between said power conversion apparatus and said central office, said power conversion apparatus comprising, in combination: a PWM (pulse-width modulator) apparatus having a variable duty cycle, said PWM apparatus including input voltage supply means for receiving power from said voltage source and supplying a DC input voltage, and converter output means for supplying a converted output voltage to a load; feedback control means, comprising a part of said PWM apparatus, for maintaining a given regulated DC output voltage at said converter output means over a range of input supply voltage by varying the duty cycle of said PWM apparatus; and detecting means, connected to said PWM apparatus, for supplying an output signal indicative of the reserve power available from said PWM apparatus, said reserve power output signal being derived as a function of the duty cycle of said PWM apparatus, said detecting means comprising: means for measuring the duty cycle of said PWM apparatus; and means for providing said reserve power output signal when the duty cycle of said PWM apparatus exceeds a threshold level indicating than an increase in the power received from said voltage source is required.

Claim 6

A DC-DC (direct current to direct current) power conversion apparatus for use in a remote terminal of a telephone system which receives power from a voltage source located in a central office, wherein a substantial impedance exists between said power conversion apparatus and said central office, said power conversion apparatus comprising, in combination: a PWM (pulse-width modulator) apparatus having a variable duty cycle, said PWM apparatus including input voltage supply means for receiving power from said voltage source and supplying a DC input voltage, and converter output means for supplying a converted output voltage to a load; feedback control means, comprising a part of said PWM apparatus, for maintaining a given regulated DC output voltage at said converter output means over a range of input supply voltage by varying the duty cycle of said PWM apparatus; and detecting means, connected to said PWM apparatus, for supplying an output signal indicative of the reserve power available from said PWM apparatus, said reserve power output signal being derived as a function of the duty cycle of said PWM apparatus, said detecting means comprising: means for measuring the duty cycle of said PWM apparatus; and means for providing said reserve power output signal when the duty cycle of said PWM apparatus exceeds a threshold level indicating than an increase in the power received from said voltage source is required.

Claim 7

The power conversion apparatus as set forth in claim 4 wherein said means for measuring the duty cycle further includes means for comparing the duty cycle of said PWM apparatus with said threshold level, said threshold level representing a minimum reserve power threshold.

Claim 8

The power conversion apparatus as set forth in claim 5 wherein said reserve power output signal is provided by said threshold detector when the duty cycle of said PWM apparatus exceeds said minimum reserve power threshold thereby indicating that an increase in the power received from said voltage source is required.

Claim 9

A discontinuous flyback power conversion apparatus for use in a remote terminal of a telephone system which receives power from a voltage source located in a central office, wherein a substantial impedance exists between said external voltage source and said power conversion apparatus, said power conversion apparatus comprising, in combination: DC (direct current) voltage supply means for receiving power from said voltage source and supplying an input signal which may vary in voltage amplitude; load impedance output means for connection to a load whose impedance may vary; a variable duty cycle PWM (pulse-width modulator) apparatus, connected between said DC voltage supply means and said load impedance output means and including control input means for supplying a converted input voltage to a load, said control input means including a power switching element for controlling the duty cycle of said PWM apparatus; feedback control means, connected to said control input means of said PWM apparatus, for maintaining a given regulated output voltage to said load impedance output means; and detecting means, connected to said PWM apparatus, for supplying an output signal indicative of the reserve power available from said power conversion apparatus, said reserve power output signal being determined as a function of the duty cycle of said PWM apparatus, said detecting means comprising: means for detecting an actual pulsed on-time of said power switching element and providing a signal indicative of the duration of said actual pulsed on-time; means for detecting a maximum available pulsed on-time of said power switching element and providing a signal indicative of the duration of said maximum available on-time; means for comparing said actual pulsed on-time with said maximum available pulsed on-time of said power switching element and providing a signal representing the difference therebetween in order to derive an unused pulsed on-time of said power switching element; means for converting said unused pulsed on-time signal to a voltage level; means for generating a stable reference voltage representing a minimum reserve power threshold; and a threshold detector for comparing said unused pulsed on-time voltage level with said stable reference voltage, said threshold detector supplying said reserve power output signal when said stable reference voltage is greater than said unused pulsed on-time voltage level thereby indicating that said minimum reserve power threshold has been exceeded and an increase in the power received from said voltage source is required.

Claim 10

A discontinuous flyback power conversion apparatus for use in a remote terminal of a telephone system which receives power from a voltage source located in a central office, wherein a substantial impedance exists between said external voltage source and said power conversion apparatus, said power conversion apparatus comprising, in combination: DC (direct current) voltage supply means for receiving power from said voltage source and supplying an input signal which may vary in voltage amplitude; load impedance output means for connection to a load whose impedance may vary; a variable duty cycle PWM (pulse-width modulator) apparatus, connected between said DC voltage supply means and said load impedance output means and including control input means for supplying a converted input voltage to a load, said control input means including a power switching element for controlling the duty cycle of said PWM apparatus; feedback control means, connected to said control input means of said PWM apparatus, for maintaining a given regulated output voltage to said load impedance output means; and detecting means, connected to said PWM apparatus, for supplying an output signal indicative of the reserve power available from said power conversion apparatus, said reserve power output signal being determined as a function of the duty cycle of said PWM apparatus, said detecting means comprising: means for detecting an actual pulsed on-time of said power switching element and providing a signal indicative of the duration of said actual pulsed on-time; means for detecting a maximum available pulsed on-time of said power switching element and providing a signal indicative of the duration of said maximum available on-time; means for comparing said actual pulsed on-time with said maximum available pulsed on-time of said power switching element and providing a signal representing the difference therebetween in order to derive an unused pulsed on-time of said power switching element; means for converting said unused pulsed on-time signal to a voltage level; means for generating a stable reference voltage representing a minimum reserve power threshold; and a threshold detector for comparing said unused pulsed on-time voltage level with said stable reference voltage, said threshold detector supplying said reserve power output signal when said stable reference voltage is greater than said unused pulsed on-time voltage level thereby indicating that said minimum reserve power threshold has been exceeded and an increase in the power received from said voltage source is required.