Power-saving line interactive uninterruptible power system

[0001] The present invention relates to an uninterruptible power supply (UPS) system, and more particularly to an energy-saving line interactive UPS system.

2. Description of the Prior Art [0002] A conventional method and device for providing battery charging in a backup power supply system are described in US Patent No. 5,302,858, which can be briefly described as follows: The battery in the backup power supply system is charged when power from the main power supply system is available alternating by using the main transformer and main inverter. When AC power is available, AC voltage appears on the transformer's primary winding, which is connected to the inverter. The switches in the bridge inverter are connected for a relatively short time to the transformer's primary winding, causing the current to flow through the transformer's dissipation inductance to rapidly increase the load. When the switching devices are turned off, the leakage inductance induces voltage and the current continues to flow from the primary winding to the inverter through anti-parallel diodes, in the opposite direction to the base through the battery voltage, to the battery, thus landing the battery with the energy stored in the transformer inductance. The inverter reaches zero when the energy stored in the inductance is completely discharged. The cycle can be repeated by turning on the switches in the bridge inverter at 'periodic times', so that the current in the inverter can cyclically be zero, or by turning the switches back on when the inverter voltage reaches zero.

[0003] With reference to Fig. 4, a traditional line interactive UPS has a set of power switches (50), low frequency transformer (51), full bridge switching system (52), main controller (53), charge and discharge controller ( 54) and a rechargeable battery (55).

[0004] A set of power switches (50) is connected in series between an AC power source and a load and determines whether the AC power source provides power to the load.

[0005] The low frequency transformer (51) has two windings (511a, 511b). One of the windings (511a) is connected to the load and connected to an AC power source through a set of power switches (50).

[0006] The full bridge switching system (52) has two half-bridge switching systems (521, 522). Series-connected nodes of two half-bridge switching systems (521, 522) are connected to the second winding (511b) of the low-frequency transformer (51).

[0007] The main controller (53) is connected to a set of power switches (50).

[0008] The charge and discharge mode controller (54) is connected to the main controller (53) and to the full bridge switching system (52) and activates the full bridge switching system (52) to enter the charging or discharging mode according to the charging or discharging command from the main controller (53).

[0009] The battery (55) is connected to the full bridge switching system (52) and performs the charging process by the full bridge switching system (52).

[0010] Considering the above-mentioned line interactive UPS, the main controller (53) determines the status of the current AC supply and battery capacity (55) and sends a charge or discharge command to the charge and discharge mode controller (54). In addition, the charge and discharge mode controller (54) decides whether to start charging or discharging mode. When the AC power source normally supplies power, the main controller (53) controls a set of power switches (52) to turn on or off so that the AC power is directly directed to the load and low frequency transformer (51). If it is determined that the battery capacity (55) decreases during this period, the main controller (53) controls the full bridge switching system (52) through the charge and discharge mode controller (54) to convert the AC power supply to DC and charge the battery ( 55) until the battery is fully charged (55). However, upon detecting an irregularity or loss of AC power, the main controller (54) immediately turns off the set of power switches (50) and sends a discharge command to the charging and discharging mode controller (54). The charge and discharge mode controller (54) then activates the full bridge switching system (52) to convert the DC current stored in the battery (55) to AC and to provide AC power to the load to ensure uninterrupted power supply. Because the UPS is permanently connected to the load, it is called a line interactive UPS. Although this UPS arrangement ensures that the battery maintains its full capacity, battery charging is performed by conversion in the low-frequency transformer (51) and the full bridge switching system (52). As a result, the full capacity of the battery consumes more energy.

[0011] The present invention has the features set out in the appended claim 1.

[0012] The object of this invention is to provide an energy-saving line interactive UPS. When AC power is supplied normally, the high frequency charging loop is designed to charge the battery and maintain its full capacity. [0013] To achieve the above purpose, the energy-saving line interactive UPS has a set of power switches, low frequency transformer, H bridge, main controller, charging and discharging mode controller, battery and high frequency charging circuit.

[0014] The set of power switches is connected to an AC power input adapted to connect an AC source and determine if the AC power source is supplying energy to the load.

[0015] The low frequency transformer has two windings. One winding is adapted for connection with a load and for connection to an AC power source.

[0016] The full bridge switching system has two half bridges having series connected nodes connected to the second winding of the low frequency transformer.

[0017] The main controller is connected to a set of power switches.

[0018] The charging and discharging mode controller is connected to the main controller and the full bridge switching system and activates the full bridge switching system to enter the charging or discharging mode according to the charging or discharging command from the main controller.

[0019] The battery is connected to the full bridge switching system and performs charging and discharging through the full bridge switching system.

[0020] The high frequency charging circuit is connected between the AC power input and the battery and converts the AC power to DC to charge the battery.

[0021] When the AC power source normally supplies current, high frequency charging is started if it is detected that the battery capacity is not full. The DC output from the high frequency charging rectifier is converted into a DC voltage supply and supplied to charge the battery and maintain the battery's full capacity. Therefore, the line interactive UPS system according to the above invention can charge the battery without the intervention of a low-frequency transformer and a full bridge switching system, thanks to which it can effectively prevent additional energy consumption.

IN THE DRAWING [0022]

Fig. 1 is a schematic diagram of an example line interactive UPS circuit;

Fig. 2 is a schematic diagram of an embodiment of a line interactive UPS circuit in accordance with the present invention;

Fig. 3A is a circuit diagram in the low current charging mode of Fig. 2;

Fig. 3B is a circuit diagram for the high current charging mode of Fig. 2;

Fig. 4 is a circuit diagram of a conventional line interactive UPS system.

[0023] With reference to Fig. 1, an example line interactive UPS system has a set of power switches (10), low frequency transformer (11), full bridge switching system (12), main controller (13), charge and discharge mode controller ( 14), battery (15) and high frequency charging circuit (16).

[0024] The power switch set (10) is connected to the AC power input terminal (AC IN). The AC inlet (AC IN) terminal is connected to an AC power source. A set of power switches (10) determines whether alternating current is supplied to the load (not shown). In this embodiment, one of the terminals of the power switch set (10) is connected to the AC input terminal (AC IN) and the other terminal (Vout) is connected to the load. In other words, the power switch set (10) is connected in series between the AC input (AC IN) terminal and the load.

[0025] The low frequency transformer (11) has two windings (111a, 111b). One winding (111a) is connected to the load and is connected to the AC power source through a set of power switches (10).

[0026] The full bridge switching system (12) has two half-bridge switching systems (121, 122). Series-connected nodes of two half-bridge switching systems (121, 122) are connected to the second winding (111b) of the low-frequency transformer (11).

[0027] The main controller (13) is connected to a set of power switches (10).

[0028] The charging and discharging mode controller (14) is connected to the main controller (13) and the full bridge switching system (12) and activates the full bridge switching system (12) in charging or discharging mode according to the charging or discharging command from the main controller (12).

[0029] The battery (15) is connected to the full bridge switching system (12) for charging or discharging through the full bridge switching system (12).

[0030] The high frequency charging circuit (16) is connected between the AC input terminal (AC) and the battery (15) to convert the AC to DC and charge the battery (15). In an embodiment, the high frequency charging circuit (16) has a rectifier (161) and a high frequency charger (162).

[0031] Said line interactive UPS mainly adds a high frequency charging circuit (16) between the AC input terminal and the battery (15). When the AC supply is working properly, the high frequency charging circuit (16) is activated when a reduced battery capacity is detected. The direct current output from the rectifier (161) is converted into direct current at the specified voltage and is supplied to the battery (15) to charge the battery (15) and maintain the full capacity of the battery (15). Hence, the line interactive UPS system charges the battery (15) without passing through the low frequency transformer (11) and the full bridge switching system (12) and thus avoids additional power consumption.

[0032] Referring to Fig. 2, the embodiment of the line interactive UPS according to the present invention is almost identical in construction except for the additional switch (17). The switch (17) is connected in series between the winding (111a) of the low-frequency transformer and the set of power switches (10), the switch (17) is controlled by the charging and discharging mode controller (14). With reference to Fig 3A, when the main controller (13) sends a signal indicating that the current battery capacity (15) is full to the charging and discharging mode controller (14), the charging and discharging mode controller (14) turns off the switch (17) to disconnecting the low frequency transformer (11) from AC power and charge. In this example, the switch (17) can be one of the relays: field effect transistor, triac, bipolar transistor.

[0033] Typically, the battery capacity slightly decreases over time from being fully charged. When such a slight decrease in battery capacity is detected, the main controller sends a low current charge command to the charge and discharge mode controller. The charge and discharge mode controller maintains the switch in the off state and disconnects the low frequency transformer from AC power and charge. Meanwhile, the high frequency charging circuit is activated to directly convert AC to DC to charge the battery.

[0034] With reference to Fig. 3B, the battery power (15) of the UPS is converted into an AC power source in the load in the event of a short AC power outage, and the battery capacity drops to a low state. The main controller (13) sends a high current charge command to the charge and discharge mode controller (14). The charge and discharge mode controller (14) maintains the switch (17) connected to the low-frequency transformer (11) with an AC power source and a charge. The AC power source performs rapid battery charging (15) with a high current by a low frequency transformer (11) and a full bridge switching system (12) until the battery (15) has fully charged.

[0035] In summary, because the normal AC power supply works for a longer time than the irregular power supply or no power supply, the present invention adds a high frequency charging circuit to avoid power loss caused by the adaptation of the low frequency transformer to charge the battery. Also, when normal AC power is detected, the low frequency transformer is disconnected from the AC power to avoid excessive power consumption. Considering the circuit structure, the UPS of the present invention consumes only 0.5W in normal AC operation, thereby achieving an energy saving effect.

[0036] Although numerous features and advantages of the present invention have been set forth in the above description, together with details of the structure and function of the invention, the description is only intended to illustrate the invention.

Cyber ​​Power Systems Inc. Proxy:

PL-PAT-2012-196

EP 2 290 785 B1