JPH02280668A - Power source - Google Patents

Abstract

PURPOSE:To improve fail-safe performance by additionally providing means for detecting stoppage of operation of a switching element, CONSTITUTION:An AC/DC converter performs full-wave rectification of AC input through a rectifying circuit 10 and provides the full-wave rectified output to a booster type chopper circuit 20. The chopper circuit 20 comprises a switching element Q1 to be turned ON/OFF through a PWH circuit 31, an inductor L1, a diode D1, and the like, and further provided with a control circuit comprising a VCA 32, a differential amplifier 33 and an error amplifier 35. A circuit 50 for detecting stoppage of operation of the switching element Q1 comprises a filter circuit 51 and a binary coding circuit 52. By such arrangement, improper operating condition is alarmed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a switching power supply device (AC/DC converter) that generates stable DC power from AC power.

(Prior Art) Recently, a power factor correction type AC/DC converter as shown in FIG. 2 has been developed. In FIG. 2, a sine wave AC input is full-wave rectified by a rectifier circuit 10 consisting of a diode bridge, and is input to a step-up chopper circuit 20, which will be described in detail below. The chopper circuit 20 includes a switching element Q1 that is turned on and off by a PWM (pulse width control) circuit 31 at a frequency sufficiently higher than that of the AC power supply, and an inductor L1 that is connected in series with the switching element Q1 between the output of the rectifier circuit 10. and a diode D1 and a capacitor C1 connected in series across the switching element Q1 so that current flows through the inductor L1 when the switching element Q1 is off. The capacitor C1 has a considerably large capacity, and a DC output that has been smoothed and voltage stabilized (described later) is taken out from both ends of the capacitor C1. Note that the capacitor C2 is a small capacitor for absorbing high frequency ripples, and is not essential to this device.

The signal of the output voltage v1 of the full-wave rectification of the rectifier circuit 10 is VCA
The signal is input to a differential amplifier 33 via a voltage controlled variable gain amplifier (C voltage controlled variable gain amplifier) 32. Inductor L1 of chopper circuit 20
Current 11 flowing through is detected by current transformer 34, and its low frequency component signal is input to differential amplifier 33. The PWM circuit 31 operates according to the differential output of the differential amplifier 33, and changes the drive pulse width (on time) of the switching element Q1 so that the differential output is minimized. Further, an error between the output voltage V2 of the chopper circuit 20 and the reference voltage VS is detected by the error amplifier 35, and this output becomes the control voltage of the VCA 32.

In the above configuration, the differential amplifier 33 compares the waveform of the human power V1 of the chopper circuit 20 and the waveform of the current 1 flowing through the inductor L1, and uses PWM so that the current waveform changes to follow the voltage waveform. The circuit 31 changes the on-time of the switching element Q1.

When the switching element Q1 is on, current flows from the rectifier circuit 10 to the inductor L1 through the switching element Q1, and energy is stored in the inductor L1. The current increase value during this on-period is proportional to the input voltage v1 and proportional to the on-time. When the switching element Q1 is turned off, a current due to the release of the energy stored therein is superimposed on the output of the rectifier circuit 10 and is supplied to the capacitor C1 side.

The pulse width control based on the comparison between the input voltage waveform and the current waveform of the inductor L1 works to shorten the on-time of the switching element Q1 as the input voltage V1 increases. Through this control, the change in the current waveform becomes approximately equal to the full-wave rectified waveform of the input voltage. In other words, when viewed from the AC input side, the input voltage and input current have almost the same waveform and there is no phase difference, resulting in almost the same state as if the negative current were a resistor. The above is the operation of the first control means.

Further, the second $ control means operates as follows.

The larger the output voltage v2 is than the reference voltage Vs, the more vcA32
The smaller the gain is, and the smaller v2 is than Vs, the more VC
The gain of A32 increases. This VCA 32 is a circuit through which the waveform signal of the input voltage in the first control means passes, and its gain becomes a basic parameter of the first control means. That is, if the output voltage (2) is too high, the on-time of the switching element Q1 is shortened, and on the other hand, when it is too low, the on-time is extended, which acts to bring the output voltage v2 closer to the reference voltage Vs.

As explained in detail above, in this type of power supply,
The input current changes almost following the AC input voltage, becoming almost a sine wave with no phase difference, and the relationship between voltage and current seen from the AC TS source side is almost the same as in the case of a resistive load (the power factor is improved). Therefore, unlike conventional capacitor input type rectifier circuits, large pulse currents do not flow intensively in a short period of time, and restrictions on the current withstand characteristics of circuit elements are relaxed, and various It is possible to reduce harmful noise.

Further, due to the boosting action of the chopper circuit and the feedback control action of the output voltage by the second control means,
Even if the AC input voltage fluctuates or the voltage rank changes, the output voltage can be kept constant.

As a result, it becomes possible to easily construct a power supply device that does not require switching and is compatible with, for example, a 100 V AC power source to a 200 V AC power source.

(Problems to be Solved by the Invention) According to the power supply device having the above configuration, it is possible to handle a wide voltage range of the AC input power source without any adjustment. However, since the chopper circuit 20 is a step-up type, when the voltage peak value of the AC power source exceeds the specified output voltage V2, the on/off drive of the switching element Q1 stops, the switching element Q1 remains off, and the rectifier circuit 10, current flows intermittently to the output capacitor C1 through the inductor L1 and diode D1. This is the same operation as a conventional capacitor input type rectifier circuit, and even if the output voltage V2 is almost equal to the target voltage, this device has no power factor improvement effect, and the input current becomes a pulse current synchronized with the AC power supply. . Such a state is not a correct usage state of this device.

The present invention was made in view of the above-mentioned problems, and an object thereof is to provide a power supply device that can detect and notify an abnormal state in which the switching operation of the switching element in the chopper circuit stops. be.

(Means for Solving the Problems) Therefore, in the present invention, in the power supply device having the above-described configuration, a switching stop detection means is added that detects that the switching element is no longer driven on/off and generates a notification signal.

(Function) When the voltage of the AC power supply becomes larger than the output voltage target value, the switching element is fixed off by the action of the second control means described above. Then, the switching stop means detects this and issues a notification signal.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which a switching stop detection circuit 50 is added to the same power supply device as in FIG. 2. Since the configuration and operation of the power supply device itself have already been described in detail, the configuration and operation of the switching stop detection circuit 50 will be explained below.

Switching stop detection circuit 50 in the embodiment of FIG.
are an auxiliary secondary winding L2 attached to an inductor L1 in the chopper circuit 20, a filter circuit 51 that filters a high frequency signal induced in this secondary winding L2, and a filter circuit 51.
A binarization circuit 52 generates a notification signal when the output level of the output signal exceeds a predetermined threshold. Connected to the output side of the binarization circuit 52 are a light emitting diode lamp that lights up in response to the notification signal, a circuit that notifies other external circuits of an abnormality, and the like.

In the above configuration, when the switching element Q1 is turned on/off by the PWM circuit 31, a current with a high frequency component due to switching flows through the inductor L1 and the switching element Q1, and a high frequency signal is transmitted to the auxiliary secondary winding L2. induced. This high frequency signal is transmitted to the filter circuit 5.
1 to the binarization circuit 52, and when the switching element Q1 is in the switching operation, the signal is input to the binarization circuit 52.
2, the input exceeds the threshold and no notification signal is output.

When the switching of the switching element Q1 stops and is fixed off, no high frequency signal is induced in the auxiliary secondary winding L2, and the input of the binarization circuit 52 falls below the threshold, at which time a notification signal is output. .

Note that the means for detecting that the switching operation of the switching element Q1 has stopped is not limited to the above-described embodiment, and various configurations can be considered, and the present invention can be implemented with any configuration.

(Effects of the Invention) As explained in detail above, in the power supply device according to the present invention, in the configuration of the power factor correction method, a means for detecting the stoppage of operation of the switching element of the chopper circuit is added, so that the voltage of the AC power supply is If the power factor is too high and the power factor improvement effect of the device cannot be achieved in an inappropriate operating condition, this will be notified. Further improvement.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a power supply device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional power supply device. 10... Rectifier circuit 20... Chopper circuit 31... PWM circuit 50... Switching stop detection circuit Direct diagram ○ Fig. 2

Claims (1)

[Claims] A rectifier circuit that full-wave rectifies an AC power source to obtain a pulsating output; A switching element that is driven on/off at a sufficiently higher frequency than the AC power source; an inductor connected in series between the outputs, and a diode and a capacitor connected in series across the switching element such that current flows through the inductor when the switching element is off, and smoothed DC output from both ends of the capacitor. a chopper circuit for controlling the drive pulse width of the switching element so that the waveform of the low frequency component of the current flowing through the inductor or the switching element changes to follow the waveform of the output voltage of the rectifier circuit; a second control means for controlling the drive pulse width of the switching element so as to reduce an error between the output voltage of the chopper circuit and a reference voltage; and a second control means for controlling the driving pulse width of the switching element such that the switching element is no longer driven on/off. A power supply device comprising: a switching stop detection means that detects this and issues a notification signal;