JP2001275344A - Switching power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To finely discriminate failures in a switching power circuit. SOLUTION: The switching waveform of a switching transformer 30 is rectified and taken out by a switching waveform detection circuit 24 and inputted into a switching waveform monitor circuit 40A, where at least one of the period, duty, and peak value of the waveform is detected for the determination of normal or abnormal conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply circuit having a function of monitoring a switching waveform to determine an abnormality.

[0002]

2. Description of the Related Art A general switching power supply circuit is shown in FIG.
As shown in (1), the circuit comprises a primary circuit 10 that performs switching by inputting an AC voltage, and a secondary circuit 20 that rectifies and boosts the boosted AC voltage to obtain a DC output voltage. The switching circuit 30 connects the primary circuit 10 and the secondary circuit 20.

The switching transformer 30 includes a control unit 1
1 controls the switching. Reference numeral 12 denotes a snubber circuit that absorbs the back electromotive force generated in the switching transformer 30 and returns it to the input side.

In the secondary circuit 20, D1 is a rectifying diode, C1 is a smoothing capacitor, 21 is an output which detects an error between the output voltage and the target voltage by an operational amplifier and sends it to the control unit 11 as an output voltage control signal. Voltage error detector, 22
Is an output voltage excess detection unit that compares the output voltage and the upper limit voltage with a comparator and sends an operation stop signal to the control unit 11 when detecting an output voltage excess, and 23 compares the output voltage and the lower limit voltage with a comparator and determines whether the output voltage is too small. An output voltage under-detection unit that sends an operation stop signal to the control unit 11 upon detection.

When signals from the output voltage error detecting section 21, the output voltage excessive detecting section 22, and the output voltage under detecting section 23 are sent to the control section 11, the primary circuit 10 and the secondary circuit 20 are insulated. If necessary, a photocoupler or the like is used.

As described above, in a general switching power supply circuit, in addition to the function of controlling the output voltage to be constant, when the output voltage becomes too small or too large,
An output voltage excess detection unit 22 and an output voltage underdetection unit 23 are provided to protect the circuit, and a protection function is incorporated in the control unit 11 to prevent the semiconductor element from being burnt even with an excessive current. .

[0007]

However, only the protection function against such overvoltage, undervoltage, and overcurrent can detect minute abnormalities such as abnormal oscillation (ringing) and abnormalities of the snubber circuit 12. Did not.

An object of the present invention is to provide a switching power supply circuit having a function of monitoring a switching waveform in a switching transformer and determining even a small abnormality.

[0009]

According to a first aspect of the present invention, there is provided a primary circuit having a control unit for controlling switching of an AC input voltage, a switching transformer for receiving the switched voltage, and A secondary side circuit which takes out a voltage from the switching transformer, rectifies and smoothes the DC output voltage, and provides an output voltage error detection section in the secondary side circuit, and outputs an error signal detected by the output voltage error detection section. In a switching power supply circuit that controls the switching by inputting to the control circuit, a switching waveform detection circuit that rectifies and extracts a switching waveform of the switching transformer, and captures a switching waveform signal detected by the switching waveform detection circuit. Detects at least one of the waveform period, duty, and peak value Determines normal, and configured to include a switching waveform monitoring circuit outputting the determination result.

In a second aspect based on the first aspect, the switching waveform monitoring circuit stops the operation of the switching power supply circuit when the switching waveform monitoring circuit determines at least one abnormality of a cycle, a duty, and a peak value of the switching waveform. I made it.

According to a third aspect of the present invention, a plurality of switching power supply circuits are provided with the switching waveform detection circuit according to claim 1;
A switching waveform concentration monitoring circuit for intensively capturing a switching waveform signal output from each of the switching waveform detection circuits, wherein a period of a switching waveform of each switching power supply circuit in the switching waveform concentration monitoring circuit;
At least one of the duty and the peak value is detected to determine whether each switching power supply circuit is normal or abnormal, and the identification number of the switching power supply circuit determined to be abnormal and the content of the abnormality are output.

In a fourth aspect based on the third aspect, when the switching waveform centralized monitoring circuit determines an abnormality in one switching power supply circuit, the abnormal switching power supply circuit or all switching power supply circuits are stopped. I tried to make it.

In a fifth aspect based on the first, second, third or fourth aspect, the determination of the peak value of the switching waveform is performed by determining whether the peak value is within a predetermined range between an upper limit and a lower limit. No, whether the value exceeded the upper limit, or whether the value fell below the lower limit.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a circuit diagram of a switching power supply circuit according to a first embodiment of the present invention. The same components as those in FIG. 9 are denoted by the same reference numerals. In the present embodiment, on the secondary side of the switching transformer 30, the switching waveform detection circuit 24 is configured by the voltage dividing resistors R1 and R2, the rectifying diode D2, and the protection constant voltage diode D3. A half-wave rectified switching waveform signal on the secondary side is detected. In the present embodiment, the primary-side circuit 10 includes the protection switch 13 that cuts off the input voltage.

40A inputs the switching waveform signal detected by the switching waveform detection circuit 24,
A switching waveform monitoring circuit that monitors the cycle, duty, and peak value of the voltage, and includes an A / D converter, a CPU,
It is constituted by a DSP (Digital Signal Processor) 41 having other circuits such as a memory (not shown). P1 is an input port of the switching waveform signal, PA1
Is an output port for sending a stop signal to the control unit 11 and the protection switch 13 when the switching waveform is detected as abnormal, and PB1 and PB2 are output ports for 2-bit normal / abnormal data.

FIG. 2 is a flowchart of a processing program of the DSP 41 of FIG. The switching waveform signal input from the port P1 is A / D converted, fetched and sequentially recorded (S1, S2). Then, when the waveform data is acquired for one cycle (S3), the cycle and the duty are determined by the time to the start point and the end point of the half-wave waveform, the end point of the previous half-wave waveform, and the time to the start point of the next half-wave waveform. And calculate (S
4) It is determined whether the value is within a predetermined range set in advance to determine whether the value is abnormal or normal (S5). If it is normal, it is further determined whether or not the peak value of the voltage is within a predetermined range set in advance (S6). If it is abnormal, it is determined whether or not the peak value abnormality is the tenth (S7). Then, at the tenth time, the content of the error (in this case, abnormal voltage peak value) is recorded in the internal memory (S8).
Further, a power-off signal is transmitted from the port PA1 to the control unit 11 (S9) to stop the switching operation of the switching transformer 30 and to shut off the protection switch 13.

On the other hand, if it is determined in step S5 that the cycle or duty is out of the predetermined range, it is determined whether or not the cycle or duty is the tenth time (S10).
Then, at the tenth time, the content of the error (in this case, the cycle or duty abnormality) is recorded in the internal memory (S8). Further, a power-off signal is sent from the port PA1 to the control unit 11 (S9), and the switching transformer 30 is turned off.
And the protection switch 13 is shut off.

After or simultaneously with the process of stopping the switching operation and shutting off the protection switch 13, the DSP 41 outputs 2-bit data indicating the above-mentioned normal / abnormal contents recorded in the internal memory from the ports PB1 and PB2. As shown in the lower left part of FIG.
The contents represented by 2-bit data of 1, PB2 are "period abnormality", "duty abnormality", "peak value abnormality", or "normal", and this data is used for display, management, and the like. .

As described above, in this embodiment, the rectifying switching waveform on the secondary side of the switching transformer 30 of the switching power supply circuit is taken into the switching waveform monitoring circuit 40A, and the cycle, duty, peak value, and the like are monitored. , It enables fine monitoring.

[Second Embodiment] FIG. 3 is a diagram showing a second embodiment of the present invention. The switching power supply circuit for generating the same or different output voltages shown in FIG.
,..., An shows a case in which n units (each having an identification number) are provided and are monitored intensively. However, each power supply circuit A1, A2,.
.., An do not include the switching waveform monitoring circuit 40A. The power supply circuits A1, A2,..., An have a common protection switch 13.

Reference numeral 40B denotes a centralized switching waveform monitoring circuit which individually captures switching waveform signals from the switching waveform detection circuits 24 of the power supply circuits A1, A2,..., An, and A / D converts each of them. From the CPU to the CPU. In the DSP 42,
P01, P02, ..., P0n are power supply circuits A1, A
, An, the input port of the switching waveform signal, and PA1 ′ is used to switch the protection switch 13 when the switching waveform of any one of the power supply circuits A1, A2,. An output port for sending a stop signal for shutting down, PB1 and PB2 are output ports for 2-bit normal / abnormal data, and PC1 and PC2 send data indicating an identification number of a specific power supply circuit in which an error has occurred. This is a 4-bit output port.

FIG. 4 is a flowchart of a processing program of the DSP 42 shown in FIG. The switching waveform signals input to the ports P01 to P0n are A / D converted, captured, and sequentially recorded (S11). Then, the processing of steps S2 to S8 shown in FIG. 2 or a processing similar thereto is performed for each switching waveform data of each power supply circuit (S121).
To S12n). As a result, when there is an abnormality in the switching waveform data of any of the power supply circuits (S1
3) The identification number of the abnormal power supply circuit and the type of abnormality are recorded (S14), and a signal for shutting off the protection switch 13 is output (S15).

As described above, in the present embodiment, a plurality of power supply circuits can be monitored simultaneously to identify a power supply circuit having an abnormal switching waveform, and the protection switch 13 can be shut off for protection.

Here, one protection switch 13 is used in common for a plurality of power supply circuits. However, like the power supply circuit shown in FIG. 1, each of the power supply circuits is provided with the protection switch 13. Only the protection switch 13 of a specific power supply circuit having an abnormal switching waveform may be turned off.

[Third Embodiment] FIG. 5 is a circuit diagram of a modification of the switching power supply circuit of the first embodiment described with reference to FIG. Although the switching power supply monitoring circuit 40A of the switching power supply circuit of FIG. 1 detects the peak value of the voltage by processing the switching waveform signal, the switching power supply monitoring circuit 40C of the present embodiment monitors the voltage inside and outside the DSP 43.

In FIG. 5, reference numeral 44 denotes a comparator which outputs "H" when the switching waveform signal level is higher than the upper limit voltage V1, and 45 denotes a comparator which outputs "H" when the switching waveform signal level is lower than the lower limit voltage V2. The outputs of the comparators 44 and 45 are ORed by the resistors R3 and R4 and input to the port P2 of the DSP 43. Therefore,
The voltage Vs of the switching waveform signal is V
"L" indicating normal when in the range of 2 <Vs <V1
However, otherwise, "H" indicating an abnormality is input.

FIG. 6 is a flowchart of a processing program of the DSP 43 of FIG. The same processes as those shown in FIG. 2 are denoted by the same reference numerals. S21 is a processing unit that captures data from the port P2, and determines whether or not the peak value of the voltage is abnormal based on the data captured here (S21).
6). However, this determination is made at the peak timing. Since the peak timing can be detected by the data of the switching waveform signal taken in from the port P1, if the data input from the port P2 at this timing is "L", it is determined that the data is normal, and if the data is "H", it is determined that the data is abnormal. Others are the same as the processing shown in FIG.

[Fourth Embodiment] FIG. 7 is a circuit diagram of another modification of the switching power supply circuit of the first embodiment described with reference to FIG. Although the switching power supply monitoring circuit 40A of the switching power supply circuit of FIG. 1 monitors three values of the cycle, the duty, and the peak value of the voltage, the switching power supply monitoring circuit 40D of the present embodiment monitors the voltage peak value among them. Monitors whether it is an undervoltage or an overvoltage.

Therefore, the outputs of the comparators 44 and 45 shown in FIG. 5 are individually taken into the ports P21 and P22 of the DSP 46. The output port of this DSP 46 is PB1
ＰPB3, as shown in the lower left part of FIG. 7, from the ports PB1, PB2, and PB3, “period abnormality”, “duty abnormality”, “peak value excessive”, “peak value excessive”, or “normal”. Is output. This data is used for display and management.

FIG. 8 is a flowchart of a processing program of the DSP 46 of FIG. The same processes as those shown in FIG. 2 are denoted by the same reference numerals. S31 is the port P21, P22
This is a processing unit that takes in data from the device, and determines whether the peak voltage is abnormal based on the data taken in here (S6). However, this determination is made at the peak timing, as described with reference to FIG. At this timing, if the data of the port P22 is “H”, it is determined that “the peak value is too large”, and if the data of the port P21 is “H”, it is determined that the “peak value is too small”. Others are the same as the processing shown in FIG.

[Other Embodiments] In each of the embodiments described above, the switching waveform detection circuit 24
May be incorporated in the primary circuit 10 of the switching transformer 30.

[0032]

As described above, according to the present invention, it is possible to detect an abnormality in a switching power supply circuit with respect to small items such as a cycle, a duty, and a peak voltage, thereby providing an advantage that a detailed diagnosis can be performed. . Also, multiple switching power supply circuits can be monitored centrally,
It is also possible to identify a power supply circuit having an abnormality and determine the type of the abnormality.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a switching power supply circuit according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a processing program of a DSP of a switching waveform monitoring circuit of the switching power supply circuit of FIG. 1;

FIG. 3 is a circuit diagram of a switching power supply circuit according to a second embodiment of the present invention.

4 is a flowchart of a processing program of a DSP of the switching waveform centralized monitoring circuit of the switching power supply circuit of FIG. 3;

FIG. 5 is a circuit diagram of a switching power supply circuit according to a third embodiment of the present invention.

6 is a flowchart of a processing program of a DSP of the switching waveform monitoring circuit of the switching power supply circuit of FIG. 5;

FIG. 7 is a circuit diagram of a switching power supply circuit according to a fourth embodiment of the present invention.

8 is a flowchart of a processing program of a DSP of the switching waveform monitoring circuit of the switching power supply circuit of FIG. 7;

FIG. 9 is a circuit diagram of a switching power supply circuit according to a conventional embodiment.

[Explanation of symbols]

10: primary side circuit, 11: control unit, 12: snubber circuit,
13: cutoff switch 20: secondary side circuit, 21: output voltage error detection unit, 22:
Output voltage excess detection section, 23: Output voltage excess detection section, 24:
Switching waveform detection circuit 30: Switching transformers 40A, 40C, 40D: Switching waveform monitoring circuit,
40B: switching waveform central monitoring circuit, 41, 42,
43, 46: DSP.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H730 AA20 BB21 BB57 BB81 CC01 EE02 EE07 FD01 FF09 XX03 XX11 XX12 XX13 XX23 XX32 XX33 XX36 XX37 XX42 XX50

Claims (5)

[Claims] 1. A primary circuit having a control unit for controlling switching of an AC input voltage, a switching transformer for taking in the switched voltage, and a secondary for taking out a voltage from the switching transformer and rectifying and smoothing to obtain a DC output voltage. A side circuit, and an output voltage error detection unit is provided in the secondary side circuit, and an error signal detected by the output voltage error detection unit is input to the control circuit to control the switching. A switching waveform detection circuit that rectifies and extracts a switching waveform of the switching transformer, and captures a switching waveform signal detected by the switching waveform detection circuit, and detects at least one of a cycle, a duty, and a peak value of the waveform to detect a normal state. / Waveform monitoring to judge abnormalities and output the judgment result A switching power supply circuit comprising a visual circuit. 2. The switching power supply circuit according to claim 1, wherein the switching waveform monitoring circuit stops the operation of the switching power supply circuit when it determines at least one of a period, a duty, and a peak value of the switching waveform. Switching power supply circuit. 3. A plurality of switching power supply circuits comprising the switching waveform detection circuit according to claim 1, and a switching waveform centralized monitoring circuit for intensively capturing switching waveform signals output from the respective switching waveform detection circuits,
The switching waveform centralized monitoring circuit detects at least one of a cycle, a duty, and a peak value of a switching waveform of each switching power supply circuit, and determines whether each switching power supply circuit is normal or abnormal. A switching power supply circuit for outputting an identification number of a circuit and details of the abnormality. 4. The switching power supply circuit according to claim 3, wherein when the switching waveform centralized monitoring circuit determines that one switching power supply circuit is abnormal, the abnormal switching power supply circuit or all switching power supply circuits are stopped. A switching power supply circuit. 5. The switching waveform according to claim 1, 2, 3, or 4, wherein the determination of the peak value of the switching waveform is performed by determining whether the peak value is within a range between a predetermined upper limit and a lower limit. A switching power supply circuit characterized in that the determination is made based on whether an upper limit value has been exceeded or a lower limit value has been exceeded.