JPH04304160A - Dc power supply with battery backup function - Google Patents

Abstract

PURPOSE:To provide a power supply provided with battery backup function which can freely select the voltage of backup battery and can provide uninterruptible backup operation with low voltage fluctuation without sacrifice of conversion efficiency. CONSTITUTION:Power is fed from a commercial power supply 1 through a DC/DC converter for main power supply to a load 4 and a battery 5. Upon interruption of the commercial power supply 1, a power interruption detecting switch 7 switches the backup battery from the main power supply DC/DC converter 3 to the input side of a backup DC/DC converter 11 having output voltage being set lower than the input voltage of the DC/DC converter 3. At that time, a switching diode 12, being turned ON based on the relationship between the input and output voltages, drives the main power supply DC/DC converter 3 continuously.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device with a battery backup function that can continue supplying power from a battery when the commercial power supply is cut off.

0002

2. Description of the Related Art In DC load circuits, power is supplied by converting commercial frequency AC voltage into DC. By the way, in this case, in order to avoid a power transmission stop due to a power failure due to a power outage of the commercial frequency AC power supply, etc., and to ensure the reliability of load operation, a backup function using a battery is conventionally provided as shown in Fig. 2 or 3. BACKGROUND ART A power supply device is used to continue supplying power to a load using a battery. The example in Figure 2 is constant commercial input (1)
The output is rectified by the charger (6), and the resulting DC output drives the main power supply DC-DC converter (3) to obtain a DC output with the required voltage value, and then the load (4) supply to. At the same time, the backup battery (5) is constantly charged by the output of the charger (6).
The main power supply DC-DC converter (3) is driven from the backup battery (5) during commercial input interruption, and the load (4) is
). In addition, in the example of Fig. 3, the output of the constant frequency input (1) is rectified by the rectifier and smoothing circuit (2), and the DC output is used to convert the output to the main power supply DC-DC converter (
3) to convert the DC input into a DC output with a required voltage value, and supply power to the load (4). At the same time, the backup battery (5) is charged by the commercial input (1) via the charger (6), and when the commercial input (1) is cut off, a mechanical Switch (8) allows commercial input (1)
Instead, a backup inverter (DC-AC
In this method, the output of the converter (9) is connected to the AC side of the rectifying and smoothing circuit (2) to continue supplying power.

0003

[Problems to be Solved by the Invention] However, these conventional DC power supply devices with a battery backup function have the following problems. In other words, the system in Figure 2 allows the input of the DC-DC converter (3) to be connected to the commercial input (
There is an advantage that it is possible to switch from 1) to a backup battery (5). However, on the other hand, the voltage of the backup battery (5) is regulated by the output voltage of the rectifier and smoothing circuit (2). Therefore, the voltage of the backup battery (5) cannot be freely selected, resulting in a problem that the degree of freedom in design is reduced. Furthermore, the conversion efficiency during operation with commercial input is reduced. Further, in the method shown in Fig. 3, the backup battery (5) is constantly charged via the charger (6), and the backup battery (5)
The backup inverter (9) is driven by the output, and the AC output is supplied to the AC side of the rectifying and smoothing circuit (2). Therefore, there is a great advantage that the voltage of the battery (5) can be freely selected. However, on the other hand, the backup inverter (9) supplies power to the AC side of the smoothing rectifier circuit (2), which has a poor power factor, so the VA capacity and battery capacity of the backup inverter (9) are increased by the power factor. As a result, it becomes larger. In addition, in the system of FIG. 3, when the commercial input (1) is cut off, the mechanical changeover switch (8) requires time to switch. Therefore, during this time, the output voltage of the rectifying and smoothing circuit (2) becomes zero, and the main power supply DC-DC converter (3) becomes in a no-voltage state. Therefore, the main power supply DC-DC converter (3
) is difficult to switch to the backup inverter (9) without momentary interruption, and if this is attempted, there is a problem in that the switching circuit becomes extremely complex. In addition, if the switching time of the switch (8) is long, the voltage will drop significantly even if it does not become a no-voltage state due to the voltage holding effect of the smoothing capacitor forming the rectifier and smoothing circuit (2), so the backup inverter (9) A large potential difference is generated between the output voltage of the For this reason, there is a problem in that the electrical shock during backup is large and stability is lacking.

0004

[Object of the Invention] The present invention makes it possible to freely select the voltage of the backup battery while maintaining conversion efficiency equivalent to that of conventional devices, and at the same time, it is highly efficient, has no power outages, and is stable with little voltage fluctuation. The present invention aims to solve the problems of the conventional system by providing a compact power supply device with a battery backup function that can provide a backup operation.

[0005]

[Means of the present invention for solving the problems] FIG. 1 is a block circuit diagram showing an embodiment of the present invention (the same reference numerals as in FIGS. 2 and 3 indicate equivalent parts), and the features of the present invention are as follows. The following points apply. That is, as shown in Figure 1, as in the past, the rectifier and smoothing circuit (2) is normally connected to the commercial input (1).
The main power supply DC-DC converter (3) is driven through the main power supply DC-DC converter (3) to supply power to the load (4). In addition, a power outage detection circuit (7) and a power outage detection switch (10) that turns off when the commercial input is interrupted are provided, and the output of the main power DC-DC converter (3) is constantly connected to the battery (5). is formed so that it is charged. On the other hand, a backup DC-DC converter (11) is provided which is driven by a battery (5) and constantly sends out an output, and the output is connected to a main power supply DC-DC converter (3).
) is provided with a switching diode (12) connected to. Furthermore, backup DC-DC converter (11
) is set so that the output voltage V2 of the rectifying and smoothing circuit (2) is lower than the output voltage V1 of the rectifying and smoothing circuit (2), and the diode (12) is configured so that it can maintain an off state at all times. The backup operation is performed as follows. That is, when the commercial input (1) is disconnected, the output voltage V1 of the rectifier and smoothing circuit (2) is lower than the output voltage V2 of the backup DC-DC converter (11), so the switching diode (
12) immediately turns on. For this reason, the output of the backup DC-DC converter (11), which is always in operation, is applied to the input side of the main power supply DC-DC converter (3) to perform backup, and when the commercial input (1) is disconnected, Power continues to be supplied to the load (4). On the other hand, when the commercial input (1) is disconnected, the power failure detection switch (10) activated by the power failure detection circuit (7) is turned off, causing the main power supply D
The output side of the C-DC converter (3) is disconnected from the backup battery (5) and the backup DC-DC converter (11), and the main power supply DC-D
The supply of charging current to the battery (5) by the C converter (3) and the supply of driving current to the backup DC-DC converter are stopped, and the backup DC-DC converter (11) is switched to an independent backup battery (
5). Therefore, commercial input (1)
Until recovery, backup power is stably supplied to the load (4) from the backup battery (5) without being affected by the output of the main power DC-DC converter (3).

[0006]

[Effects of the Invention] The present invention provides a battery (5) as described above.
The backup DC-DC converter (11) is driven, and its output is used as the input of the main power supply DC-DC converter. Therefore, the battery voltage can be freely selected. Also, backup DC-DC converter (11
) directly drives the main power supply DC-DC converter (3) without going through the rectifier and smoothing circuit (2). Therefore, the battery (
The AC output of the inverter (9) driven by
There is no need to consider a low power factor unlike the method of adding power to the alternating current side of the rectifying and smoothing circuit (2). Therefore, D for backup
The capacity of the C-DC converter (11) and battery (5) should be large enough as long as it can bear the sum of the power of the load (4) and the loss of the main power DC-DC converter (3). There is no. In addition, in the present invention, the backup DC
- Since the connection between the DC converter (11) and the input side of the main power supply DC-DC converter (3) is performed by turning on and off based on the potential relationship between the anode and cathode of the diode (12), it is possible to use a conventional switch. Compared to the conventional method, the backup DC-DC converter can be switched and connected more quickly when the commercial power input is cut off. Therefore, it is maintained by the smoothing capacitor of the rectifying and smoothing circuit (2),
Since the backup DC-DC converter (11) is connected in a state where the input voltage of the main power supply DC-DC converter (3) decreases little, backup is performed without momentary power interruption and with less voltage fluctuation. Furthermore, the circuit that constantly supplies power to the load (4), that is, the circuit that occupies most of the operating time, is composed of a rectifying and smoothing circuit (2) and a main power supply DC-DC converter (3), as in the past. There is no difference from the conventional circuit shown in FIGS. 2 and 3. Therefore, it is possible to provide a DC power supply device with a battery backup function that solves the problems of the conventional device while always maintaining the same conversion efficiency as before.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the present invention.

FIG. 2 is an explanatory diagram of a conventional device.

FIG. 3 is an explanatory diagram of a conventional device.

[Explanation of symbols]

(1) Commercial input (2) Rectifier smoothing circuit (3) Main power DC-DC converter (4) Load (5) Backup battery (6) Charger (7) Power outage detection circuit (8) Changeover switch (9) Backup inverter (10) Switch (11) Backup DC-DC converter (1
2) Switching diode

Claims (1)

[Claims] 1. A circuit for rectifying and smoothing a commercial input; a main power DC-DC converter for supplying power to a load using the output of this circuit; A battery that is disconnected from the main power DC-DC converter by a power failure detection switch when the input is cut off, and a backup DC-DC converter that uses the battery as a power source and sends out an output of a voltage lower than the output voltage of the rectifier and smoothing circuit. When the output voltage of this backup DC-DC converter exceeds the output voltage of the rectifier and smoothing circuit when the commercial input is cut off, it becomes conductive and the output of the backup DC-DC converter is converted to the main power supply DC-DC. A DC power supply device with a battery backup function, characterized by comprising a diode connected in the direction of supply to the input side of the converter.