JPH03243139A - Power supply - Google Patents

Abstract

PURPOSE:To feed voltage stably by performing constant control of output voltage according to the output from means for amplifying the difference between the output voltage from a power supply and a reference voltage, and lowering the reference voltage when input voltage to the power supply drops below the lower control limit. CONSTITUTION:Voltage of a commercial power supply 1 is subjected to A/D conversion 2 in order to charge a battery 3 and further subjected to D/A conversion and voltage transformation 6 thus producing an AC voltage through an AC filter 7. A voltage reference circuit 21 produces a reference voltage based on a DC voltage detected through a DC voltage detecting circuit 22 and the reference voltage is provided to an error amplifier 13. Difference between the output voltage from an output voltage detecting circuit 11 and the reference voltage is then amplified 13 in order to control the modulation width of a PWM modulation circuit 15 and to control the inverter 5 through a gate amplifying circuit 16 thus producing a constant voltage. When power interruption endures for a long term and the battery voltage drops to the lower control limit, reference voltage to be outputted from the voltage reference circuit 21 is lowered and voltage control operation is continued.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a power supply device that supplies stable power even when the input power source or load fluctuates. The present invention relates to a power supply device that can supply a stable voltage without causing an abnormality such as an output overvoltage even when the input voltage is restored or the overload is released by preventing the voltage control limit from being reached.

(Prior Art) A typical example of a power supply device that supplies stable electric power is an uninterruptible power supply device that uses a storage battery as a power source to supply stable AC voltage even during an AC input power outage. Generally, this type of uninterruptible power supply is used as a power source for important loads such as computers and communication equipment, and is required to have little fluctuation in output voltage in response to fluctuations in AC input voltage and load. In order to make the backup time by the storage battery as long as possible, it is required that the control range be as wide as possible, corresponding to the voltage when the storage battery is discharged.

FIG. 4 is a block diagram showing an example of a conventional uninterruptible power supply. In the figure, 1 is the tube power supply (AC input power supply)
, 2 is a rectifier, 3 is a storage battery, 4 is a storage battery connection switch,
5 is an inverter, 6 is an inverter transformer, 7 is an AC filter that removes harmonic components from the output voltage of the inverter 5 and improves it to a sine wave voltage, 11 is an output voltage detection circuit, 12
13 is a voltage reference, 13 is an error amplification circuit that amplifies the deviation between the output of the output voltage detection circuit 11 and the voltage reference 12, 14 is an oscillator that serves as the output frequency reference of the inverter 5, and 15 is an output signal of the oscillator 14 and an error amplification circuit. 13 is a PWM control circuit which synthesizes the output signal of the PWM control circuit 15 to create a firing pattern of the switching elements constituting the inverter 5; and 16 is a gate amplifier circuit which amplifies the output signal of the PWM control circuit 15. That is, the switching elements of the inverter 5 are subjected to PWM control by 14 to 16, and the output voltage of the AC filter is controlled to match the voltage reference 12 by the output of the error amplification circuit 13.

In addition, when the voltage of the commercial power source 1 drops even momentarily, the storage battery connection switch 4 is made conductive and DC power is supplied from the storage battery 3 to the inverter 5 via the storage battery connection switch 4, and the DC voltage is varied by the output voltage control means of the inverter 5. By controlling the output voltage to a constant level, stable AC power can be continuously supplied.

(Problem to be Solved by the Invention) The voltage control range of the inverter 5 is selected so that the device can output the rated voltage even at the discharge end voltage of the storage battery 3, but the utilization rate of the switching elements constituting the inverter 5 is set high. Therefore, the voltage rating of the inverter transformer 6 is normally selected so that the output pulse width of the inverter 5 is maximum (corresponding to the output upper limit value of the error amplification circuit 13) at the end of discharge voltage of the storage battery 3.

As a result, when the storage battery 3 continues to be discharged due to a power outage in the commercial power supply 1 and the input voltage of the inverter 4 falls below the voltage control limit (linear control limit) corresponding to the discharge end voltage, the output of the error amplification circuit 13 decreases. It reaches the upper limit and enters the so-called saturation region and becomes uncontrollable.

In this state, when the commercial power supply 1 is restored and the input voltage of the inverter 5 is rapidly restored by the output of the rectifier 2, it will take a considerable amount of time for the voltage control to return from the saturation region to the linear control region. The maximum width state continues for a while, and as a result, the output voltage becomes overvoltage, which may damage the load-side equipment or detect overvoltage and cause the system to stop. Alternatively, depending on the rise of the input voltage recovery of the inverter 5, the output voltage of the inverter 5 becomes asymmetric between positive and negative, causing DC bias in the inverter transformer 6 (over-excitation of the inverter transformer 6 due to the output overvoltage of the inverter 5), which is the worst case scenario. , the device itself trips and stops due to the overcurrent of the inverter 5.

In addition, if the storage battery 3 is a battery with large internal inductance, such as an alkaline battery, the storage battery 3 may be short-circuited not only when recovering after a power outage of the commercial power source 1 but also when switching to the discharge mode of the storage battery 3 due to a power outage of the commercial power source 1. A voltage drop occurs over time, and when the voltage of the storage battery 3 is restored, a problem similar to the above may occur.

As described above, the configuration as shown in FIG. 4 has the above-mentioned problem in the recovery operation after the input voltage of the inverter 5 drops.

The present invention has been made in view of the above points, and it prevents the voltage control limit from reaching the voltage control limit even when the input voltage drops or overloads, and prevents abnormalities such as output overvoltage even when the input voltage is restored or when the overload is released. It is an object of the present invention to provide a power supply device that can supply a stable voltage without causing voltage problems.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention amplifies the deviation between the output voltage and the voltage reference in a power supply device that supplies stable power despite fluctuations in the input power source and load. amplifying means;
When the input voltage of the power supply device is lower than the lower limit value corresponding to the control limit of the control means, or the above-mentioned Means is provided for lowering the voltage reference when the output of the amplification means exceeds an upper limit value corresponding to the control limit of the control means.

(Function) In a power supply device with such a configuration, before the voltage control limit is reached due to input voltage drop, overload, etc., it is detected that the input voltage lower limit or amplification means upper limit value corresponding to the control limit is exceeded. By lowering the voltage reference, operation is continued in the linear control region, thereby preventing abnormalities such as output overvoltage due to delay in control response when input voltage is restored or when overload is released.

(Example) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the same parts as those in FIG. 4 are given the same reference numerals, and the explanation thereof will be omitted, and only the different points will be described here. That is, in FIG. 1, 22 is the inverter 5.
A DC voltage detection circuit 22 detects that the input voltage (DC voltage Ed) has fallen below a lower limit value corresponding to the voltage control limit, and 22 normally outputs a constant voltage reference, and the detection output of the DC voltage detection circuit 22 This is a voltage reference circuit that lowers the voltage reference according to the voltage.

FIG. 2 is a characteristic diagram for explaining the operation of the voltage reference circuit 21. When the DC voltage Ed falls below the lower limit value Ed corresponding to the voltage control limit, the error is amplified according to the DC voltage Ed. It has a characteristic that lowers the voltage reference applied to the circuit 13.

Next, the operation of the power supply device configured as described above will be described.

When the DC voltage Ed is higher than the lower limit value Ed, the voltage reference output from the voltage reference circuit 21 is constant as shown in FIG. 2, and the output voltage is Controlled to match a fixed voltage reference.

On the other hand, when the discharge of the storage battery 3 continues due to a power outage in the commercial power supply 1 and the DC voltage Ed is about to drop below the lower limit value Ed, the DC voltage detection circuit 21 immediately detects the drop in the DC voltage Ed, and this detection signal The voltage reference circuit 22
As shown in the characteristic shown in FIG. 2, the voltage reference applied to the error amplification circuit 13 is lowered in accordance with the DC voltage Ed. As a result, the error amplifier circuit 13 and the PWM control circuit 15 operate to match the output voltage of the device to the reduced voltage standard, and continue operating in the linear control region without deviating from the voltage control limit (the output voltage of the device is However, there is no practical problem as long as it is within the allowable level of the load-side equipment).

Subsequently, when the commercial power supply 1 is restored and the DC voltage Ed exceeds the lower limit value Ed1 due to the output of the rectifier 2 and rapidly recovers,
The output of the voltage reference circuit 22 returns to a constant voltage, but since the voltage control was originally in the linear control region, it responded quickly and the output voltage simply returned to the original voltage and was stabilized without any abnormalities such as output overvoltage. Controlled by voltage.

In this way, in this embodiment, when the input voltage of the inverter 5 falls below the lower limit value corresponding to the voltage control limit, the voltage control is performed linearly by controlling the voltage reference to be lowered according to the input voltage. Since the operation continues in the control region, the voltage control system responds quickly even when the input voltage is subsequently restored, and the problem of abnormalities such as output overvoltage can be solved.

In the explanation of the conventional device shown in Fig. 4, we focus on the malfunction phenomenon during recovery after the input voltage drops, but the same malfunction also occurs when the overload is released when the voltage control limit is reached due to overload. A phenomenon is observed.

The other embodiment shown in FIG. 3 has a configuration that is effective against malfunctions occurring in these two modes. In the same figure, 31
1 is a voltage reference circuit similar to 21 in FIG. 1, and 32 is a level detection circuit configured to lower the output of the voltage reference circuit 31 when the output of the error amplifier circuit 13 exceeds an upper limit value corresponding to the voltage limit limit. By directly monitoring the output of the error amplifying circuit 13 and changing the voltage reference, it is possible to always operate in the linear control region.

In the above embodiment, an AC output power supply device using an inverter has been described, but the present invention is not limited to an AC output power supply device, and can also be applied to a DC output power supply device.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent the voltage control limit from reaching the voltage control limit even when the input voltage drops or overloads, and to prevent abnormalities such as output overvoltage from occurring even when the input voltage is restored or the overload is released. It is possible to provide a power supply that does not supply a stable voltage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a characteristic diagram for explaining the operation of the voltage reference circuit in the embodiment of FIG. 1, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a block diagram showing an example of the configuration of a conventional power supply device. 1... AC input power supply, 2... Rectifier, 3... Storage battery, 4... Storage battery connection switch, 5...
Inverter, 6... Inverter transformer, 7...
- AC filter, 11... Output voltage detection circuit, 13
...error amplification circuit, 14...oscillator, 15...
PWM control circuit, 16... gate amplifier circuit, 21.31
... Voltage reference circuit 522 ... DC voltage detection circuit, 3
2...Level detection circuit.

Claims (2)

[Claims] (1) In a power supply device that receives DC power or AC power as input and outputs stabilized DC voltage or AC voltage, an amplification means that amplifies the deviation between the output voltage and a voltage reference;
a control means for controlling the output voltage to be constant according to the output of the amplification means; and a control means for detecting an input voltage of a power supply device, and when the input voltage falls below a lower limit value corresponding to a control limit of the control means. A power supply device comprising means for lowering the voltage reference. (2) In a power supply device that receives DC power or AC power as input and outputs stabilized DC voltage or AC voltage, an amplifying means for amplifying the deviation between the output voltage and a voltage reference;
control means for controlling the output voltage to be constant according to the output of the amplification means; and a control means for detecting the output of the amplification means, and when the output level exceeds an upper limit value corresponding to the control limit of the control means; A power supply device comprising means for lowering a voltage reference.