Power holdup circuit
View Patent ↗A power holdup circuit including a monitoring circuit and a power holdup circuit. The monitoring circuit includes an average voltage comparator and an absolute voltage comparator which cooperate to detect a voltage drop in the voltage supplied by the power supply. The monitoring circuit also includes a timer to determine the time period of the voltage dropout. If a predetermined voltage dropout event occurs, the monitoring circuit generates a control signal to a switching component which activates a holdup power source. The holdup power source includes an energy storage device that stores energy to maintain the supply voltage during dropout periods.
1. A power holdup circuit for maintaining a voltage supplied by a power supply comprising:
a monitoring circuit, the monitoring circuit monitoring the power supply voltage to detect a power dropout condition;
a power switching circuit including:
an energy storage device, the energy storage device storing energy for maintaining the voltage supplied by the power supply;
a select circuit, the select circuit enabling the storage of energy in the energy storage device in a first mode of operation and enabling the release of energy stored in the energy storage device in a second mode of operation,
wherein the monitoring circuit generates a control signal for selecting the mode of operation of the select circuit in accordance with the energy supplied by the power supply, and wherein the monitoring circuit protects the power holdup circuit by selectively entering the first mode of operation in response to a power dropout condition.
2. The power holdup circuit of claim 1 wherein the monitoring circuit selects the second mode of operation in response to a power dropout condition and selects the first mode of operation if the power dropout condition exceeds a predetermined time period.
3. The power holdup circuit of claim 2 wherein the monitoring circuit selects the second mode of operation in response to a power dropout condition and selects the first mode of operation if the voltage drop during a power dropout condition exceeds a predetermined value.
4. The power holdup circuit of claim 1 wherein the monitoring circuit selects the second mode of operation in response to a power dropout condition and selects the first mode of operation if the voltage drop during a power dropout condition exceeds a predetermined value.
5. The power holdup circuit of claim 1 wherein the monitoring circuit further comprises:
a first circuit for comparing the power supply voltage relative to a reference voltage; and
a second circuit for comparing the power supply voltage to an average of the power supply voltage.
6. The power holdup circuit of claim 1 wherein the monitoring circuit selects the second mode of operation when the power supply voltage falls below the reference voltage and the power supply voltage falls below the average of the power supply voltage.
7. The power holdup circuit of claim 1 wherein the monitoring circuit further comprises a timer circuit, the timer circuit determining a duration of a power dropout, wherein the monitoring circuit selects the second mode of operation when the duration of the power dropout exceeds a predetermined time period.
8. The power holdup circuit of claim 1 wherein the power switching circuit further comprises a charge circuit for controlling the charging of the energy storage device.
9. The power holdup circuit of claim 8 further comprising a current limiting device in series with the energy storage device.
10. The power holdup circuit of claim 9 further comprising a switch in series with the current limiting device to enable charging during the first mode of operation.
11. The power holdup circuit of claim 8 wherein the charge circuit further comprises one of the group of a soft-start charger, a dedicated charger, and a main rectifier charger.
12. The power holdup circuit of claim 1 wherein the energy storage device comprises one of the group of a battery, an accumulator, a capacitor, and an electrochemical device.
13. The power holdup circuit of claim 1 wherein the select circuit includes one of the group of a thyristor, a silicon controlled rectifier, a FET, a MOSFET, an IGBT, and a bipolar transistor.
14. A power holdup circuit for maintaining an energy supplied by a power supply comprising:
a monitoring circuit, monitoring circuit monitoring the power supply voltage to detect a power dropout condition the monitoring circuit including:
a first circuit for comparing the power supply voltage relative to a reference voltage; and
a second circuit for comparing the power supply voltage to an average of the power supply voltage;
a power switching circuit including:
an energy storage device, the energy storage device storing energy for maintaining the voltage supplied by the power supply;
a select circuit, the select circuit enabling the storage of energy in the energy storage device in a first mode of operation and enabling the release of energy stored in the energy storage device in a second mode of operation,
wherein the monitoring circuit generates a control signal for selecting the mode of operation of the select circuit in accordance with the energy supplied by the power supply, and wherein the monitoring circuit protects the power holdup circuit by selectively entering the first mode of operation in response to a power dropout condition.
15. The power holdup circuit of claim 14 wherein the monitoring circuit selects the second mode of operation when the power supply voltage falls below the reference voltage and the power supply voltage falls below the average of the power supply voltage.
16. The power holdup circuit of claim 15 wherein the monitoring circuit selects the second mode of operation in response to a power dropout condition and selects the first mode of operation if the power dropout condition exceeds a predetermined time period.
17. The power holdup circuit of claim 16 wherein the monitoring circuit selects the second mode of operation in response to a power dropout condition and selects the first mode of operation if the voltage drop during a power dropout condition exceeds a predetermined value.
18. The power holdup circuit of claim 15 wherein the monitoring circuit selects the second mode of operation in response to a power dropout condition and selects the first mode of operation if the voltage drop during a power dropout condition exceeds a predetermined value.
19. The power holdup circuit of claim 14 wherein the monitoring circuit further comprises a timer circuit, the timer circuit determining a duration of a power dropout, wherein the monitoring circuit selects the second mode of operation when the duration of the power dropout exceeds a predetermined time period.
20. The power holdup circuit of claim 19 wherein the power switching circuit further comprises a charge circuit for controlling the charging of the energy storage device.
21. The power holdup circuit of claim 20 further comprising a current limiting device in series with the energy storage device.
22. The power holdup circuit of claim 21 further comprising a switch in series with the current limiting device to enable charging during the first mode of operation.
23. The power holdup circuit of claim 20 wherein the charge circuit further comprises one of the group of a soft-start charger, a dedicated charger, and a main rectifier charger.
24. The power holdup circuit of claim 14 wherein the energy storage device comprises one of the group of a battery, an accumulator, a capacitor, and an electrochemical device.
25. The power holdup circuit of claim 14 wherein the select circuit includes one of the group of a thyristor, a silicon controlled rectifier, a FET, a MOSFET, an IGBT, and a bipolar transistor.