JP2735202B2 - Switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a switching power supply device having an abnormal current detection function. 2. Description of the Related Art Conventionally, switching power supply devices have been widely used as power supply means for various electronic devices, and some of them have an abnormal current detection function. For this type of device, for example, 100A at + 24V output voltage
It is determined that the current is abnormal (overcurrent) when the current flows through the load. FIG. 10 is a diagram showing a configuration of a conventional switching power supply device. In the figure, 1 is a filter, 2 is a rectifier, 3 is a smoothing capacitor for smoothing the rectified voltage, 4 is a switching power transistor (hereinafter referred to as a transistor), 5 is a transistor that consumes energy stored in a transformer when the transistor 4 is off. 6A performs pulse width modulation control of transistor 4 and outputs (+ 5V, + 12V ... + 24V)
And 7 is a single-input / multi-output type transformer. The _{D 11, D 12, D 21} , D 22, D
n ₁ and Dn ₂ are rectifier diodes on the secondary side of the transformer 7 and C ₁ and C
₂ … Cn is a smoothing capacitor, L ₁ , L ₂ … Ln is a transistor 4
Coil to reduce the ripple voltage while reducing the peak value of the current flowing through the, R _1, R ₂ ... Rn are resistors for detecting current _{value, C F1, C F2 ... C} Fn is the load-side smoothing capacitor and R,
_F1 , R _F2 ... R _Fn indicate resistances on the load side. In this circuit, 100V AC passes through filter 1 and rectifier 2
When the full-wave rectification is performed, electric charges corresponding to about 140 V are accumulated in the capacitor 3. On the other hand, the operating voltage + V is applied to the control circuit 6A, and an on-pulse is applied to the base of the transistor 4 to turn on the transistor 4 to the control circuit 6A. At this time, the charge of the capacitor 3 is A → B → C → D → E
The current flows in the direction of → F → G → H →. Each output J, K... L on the secondary side of the transformer 7
Produces a voltage of the ratio of the primary: secondary winding, and the diodes D ₁₁ and D _11
21, ... Dn _1, current flows through the coil L _1, L ₂ ... Ln, load R _F1,
R _F2 ... R _F n. Here, the components of the ripple current are accumulated as charges in the capacitors C ₁ , C _2, ... Cn, and each outputs a DC voltage. When the transistor 4 is turned off, the exciting current C → D of the transformer 7 continues to flow as it is, and this energy and the energy stored in the leakage inductance are consumed by the snubber circuit 5. At this time, a back electromotive force is generated by the energy stored in the choke coil of each secondary circuit of the transformer 7, and the current flowing through each of the coils L ₁ , L ₂ . continues to flow through the _{D 12, D 22 ... Dn 2} , also R _F1, the ripple current leads to R _F2 ... R _F n is,
The capacitors C ₁ , C _2, ... Cn are stored as electric charges. When the voltage on the secondary side of the transformer 7 decreases, the pulse width of the ON time of the transistor 4 is increased by the pulse width control function of the control circuit 6A in order to increase the energy sent to the secondary side. Conversely, when the secondary voltage of the transformer 7 rises, the control circuit 6A reduces the pulse width of the on-time of the transistor 4. By this operation, the DC output on the secondary side is stabilized. When the stabilized DC output is output to M, Q, and U, current flows to each load. For example, in the case of + 5V, M → N → R _F1 → P → O → resistance R ₁
The street, a current flows to the capacitor C _1. At this time, the resistance R ₁
A voltage is generated at both ends a and b, and is input to the control circuit 6A. Similarly, in the case of outputs +12 V and +24 V, voltages at both ends C and D and both ends e and f are input to the control circuit 6A. For example, in the case of output + 24V, if overcurrent is considered at 100A, Rn = 0.01Ω, the voltage across Rn is 1V (100A
× 0.01Ω = 1V), the control circuit 6A detects an overcurrent. By the way, in this type of device, for example, when the normal current is 20 A at +24 V, even if some abnormality occurs on the load side and the partial load current increases by 10 A, the total current flows only at 30 A. Therefore, when it is considered that the current is overcurrent at 100 A, no abnormality is detected even if the load generates heat or ignites in a spot manner. (Problems to be Solved by the Invention) As described above, in the conventional switching power supply device, even if an abnormality actually occurs in the load, it is not detected until the current reaches the overcurrent, and in the worst case, a fire occurs. There was a problem that there was. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a switching power supply device capable of detecting an abnormality in a load even if the current has not reached an overcurrent current. And [Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention connects a plurality of loads to a secondary side of a transformer and detects a current consumption consumed by each load. A switching power supply for controlling the switching operation on the primary side of the transformer by judging the state of the load, and a current value holding means for holding the value of the current consumption; And a plurality of selection control means which are sequentially selected at a certain cycle and held in the current value holding means, and a plurality of current patterns which are set in advance in time series and are used as a reference of the current consumption of each load are stored for each operation state. Current pattern storage means, and the value of the current consumption of the load at a time selected by the selection control means and held by the current value holding means, and stored in the current pattern storage means. And determining monitoring means a state of the load by comparing the current pattern as a reference for the current consumption of the load in Kino operating state, wherein by monitoring means in accordance with the load state of the determination result of the transformer 1
And control means for controlling the switching operation on the next side. (Operation) In the switching power supply of the present invention, the control unit monitors not only the maximum current value of the abnormal current of the load but also the current value-time factor, and outputs the output current or the load from the load. If the change in the return load current is a normal operation pattern (the relationship between the current value and time is a predetermined pattern), it is normal. Otherwise, it is abnormal even if the current value is very small and does not reach the overcurrent value. Regard it. (Example) Hereinafter, details of an example of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of one embodiment of the present invention, and the same reference numerals are given to parts common to FIG. In the figure, 1 is a filter, 2 is a rectifier, 3 is a smoothing capacitor for storing a rectified voltage, 4 is a switching transistor, 5 is a snubber circuit that consumes energy stored in a transformer when the transistor 4 is off, and 6B. Is a control circuit that performs pulse width modulation control of the transistor 4 and detects overcurrent of each output (+5 V, +12 V... +24 V), and 7 is a single-input multiple-output transformer. D ₁₁ , D ₁₂ , D ₂₁ , D ₂₂ , Dn ₁ , Dn ₂ are ₂ of the transformer 7
The rectifier diode on the secondary side, C ₁ , C ₂ … Cn are smoothing capacitors,
L ₁ , L ₂ ... Ln are coils that reduce the peak value of the current flowing through the transistor 4 and reduce the ripple voltage.
R _1, R ₂ ... Rn are resistors for detecting current value, the _{C F1, C F2 ... C F} n load side of the smoothing capacitor, and R _F1, is R _F2 ... R _F n indicates the load side resistance. In this circuit, 100V AC passes through filter 1 and rectifier 2
When the full-wave rectification is performed, electric charges corresponding to about 140 V are accumulated in the capacitor 3. On the other hand, the operating voltage + V is applied to the control circuit 6B, and the control circuit 6B gives an ON pulse to the base of the transistor 4,
The transistor 4 is turned on. At this time, the charge of the capacitor 3 is A → B → C → D → E
The current flows in the direction of → F → G → H →. Each output J, K... L on the secondary side of the transformer 7
Produces a voltage of the ratio of the primary: secondary winding, and the diodes D ₁₁ and D _11
21 … Dn ₁ , current flows through coils L ₁ , L ₂ … Ln, and loads R _F1 , R
_F2 … R _F n. Here, the components of the ripple current are accumulated as charges in the capacitors C ₁ , C _2, ... Cn, and each outputs a DC voltage. When the transistor 4 is turned off, the exciting current C → D of the transformer 7 continues to flow as it is, and this energy and the energy stored in the leakage inductance are consumed by the snubber circuit 5. At this time, the coils L ₁ , L ₂ ... Ln of the respective secondary circuits of the transformer 7
Flow counter electromotive voltage is generated by the stored energy, the current flowing to the respective coils L _1, L ₂ ... Ln transistor 4 is in the ON period of, through the diode D _12, D ₂₂ ... Dn ₂ to Subsequently, also the load R _F1, the ripple current leads to R _F2 ... R _F n is stored as a charge in the capacitor C _1, C ₂ ... Cn. When the voltage on the secondary side of the transformer 7 decreases, the pulse width of the ON time of the transistor 4 is increased by the pulse width control function of the control circuit 6B in order to increase the energy sent to the secondary side. Conversely, when the secondary voltage of the transformer 7 increases, the control circuit 6B reduces the pulse width of the transistor 4 during the ON time. By this operation, the DC output on the secondary side is stabilized. When the stabilized DC output is output to M, Q, and U, current flows to each load. The above parts are the same as those of the circuit of FIG. 10, but the configuration of the control circuit is different in the circuit of this embodiment. The control circuit 6B includes a driver 8 that supplies a drive pulse to the base of the transistor 4, a drive pulse of the driver 8,
A pulse register 9 for holding data from the CPUs, a ROM 10 in which control data is written, a RAM 11 as current pattern storage means in which a “reference current pattern” described later is written and stored, A microcomputer having a monitoring function, a selection control function, and a pulse width modulation function
12, a current register 13 as current value holding means for holding the current value on the load side as binary data, an AD converter 14 for converting the load side current into binary data, and a current switching circuit to be described later. 15 and a switch 18 for sending a command to the microcomputer 12 via the pulse register 9. A control line 19 is connected to a bit 5 of the pulse register 9 via a pull-up resistor RP, and a control line 19 is connected to an operation voltage + V on the switch 18 side. Is connected to the control line 20. FIG. 2 is a diagram showing an equivalent circuit on the load side of the +24 V output voltage in FIG. Load R _F n are respectively configured plurality of resistance components r _F1, from r _F2 ... r _F n. In the control power supply and the computer power supply, these resistance components r _F1 and r _F
F2 ... r _F n corresponds to a single logic board, respectively. FIG. 3 shows +24 in the circuit of this embodiment in a normal state.
FIG. 7 is a diagram showing a change in the load current of the V output, that is, a “reference current pattern” to be stored in the RAM 11, wherein the horizontal axis represents T (time) and the vertical axis represents current. Where t
Indicates a time width, and I indicates a current value. FIG. 4 is a diagram showing a pattern of an abnormal value of the load current of +24 V output, and FIG. 5 is a diagram for explaining a procedure in which the control circuit 6B detects this abnormal value. In the control circuit 6B, the voltage a− across the resistors R ₁ , R ₂ .
When b, cd, and ef are input to the control circuit 6B, the microcomputer 12 operates the current switching circuit 15 and a-
One of b, cd and ef is selected and set as binary data in the current register 13 via the AD converter 14.
Then, the microcomputer 12 reads this data. That is, the microcomputer 12 inputs the current value of each DC output (secondary side) as a voltage value between a-b, cd, and ef, and detects a temporal change in the current value. is there. Hereinafter, the operation of the microcomputer 12 of the control circuit 6B will be described with reference to the flowcharts of FIGS. 6 and 7. Note that, to simplify the explanation of the operation, +24 V
The change of the load current in the output at the time of normal operation is as shown in FIG. That is, the current is usually 20 A, and the pattern has I ₂ = 3
In 0A, only for the period t ₁₁ current changes. In the pattern only period t ₂ in I ₃ = 70A, and I ₄ = 45A only period t ₃ to the current change. Further, there may be a pattern. It is assumed that the patterns do not overlap, and that the current value changes in synchronization with the unit time t. In FIG. 6, first, e and f of +24 V are selected by the switching circuit 15 as a step 21, and the digital value set in the current register 13 is read by performing an AD conversion as a step 22. The third view Step 23~27 I ₁ = 20A, I _{2
= 30A, I 3 = 70A,} I 4 = 45A, I 5 = if consistent with the 100A or any time t after again read the current value, respectively third
It is checked whether it corresponds to any of the patterns in the figure, or whether it is out of these. For example, if Yes in step 23, the pattern is compared with the pattern.
Checked every time. Here current is longer than the period t ₁₁ in the pattern of FIG. 4 3
If the current continues to flow at 0A, it is abnormal.
B, c, 30A is YES in step 46 through step 41, 43 and 45 in response to two, the short time 30A than the period t ₁₁
Since it is abnormal at 20 A, it is NO at step 42 and NO at step 44 and is treated as abnormal. In the pattern shown in FIG. 3, YES is determined in step 24, and the current values are checked in steps 28 to 37. If all the current values are present, the process returns to step 48 with a normal return. Further steps
If any of 28 to 37 is NO, it is treated as abnormal. The pattern of FIG. 3 comprises steps 25, 38-40 and 48
Are compared. The pattern is determined to be YES at step 26, and the process goes to step 49. The pattern in Fig. 4 is a step
23 is not YES, processing is performed in steps 50 to 52, and each current value is compared with a normal pattern value prepared in advance in steps E, H, G, H, R, and N in FIG. If they match, the answer is NO in step 52 and the return is normal, but if the pattern is undefined (not prepared), the answer is YES in step 52 and the routine goes to step 49. The pattern in FIG. 5 is also NO in step 27, and steps 50 to 52 return to step 49. That is, the fifth
The figures, ヲ, ヲ, 、, カ, ヨ, and 、 do not match at the stage of comparing the current values. If an abnormality occurs in the processing in FIG. 6, the process proceeds to step 53 in the processing in FIG. 7, and energy is not supplied to the secondary side. Therefore, abnormal heat generation at the load R _F n is also eliminated. Note that various warning methods can be considered as the processing of step 54. For example, in step 53, the transistor 4 is continuously turned on and off, and in step 54, the operator is notified by some method, and the operator turns off the entire power supply device. In this embodiment, when the microcomputer 12 writes 0 to the LSB of the pulse register 9, the output of the driver 8 becomes 1
As a result, the transistor 4 is turned on, the driver 8 is turned to 0 when LSB = 1, and the transistor 4 is turned off. The microcomputer 12 controls the pulse width on time and stabilizes the secondary side output voltage. Control. In this embodiment, the steps in the description of FIG.
The current values are compared between 23 and 27.
When checking 30 A at 23, the value of 28 to 32 A is checked to correct the error at the time of conversion from the actual e and f voltages (FIG. 1) to the current register 13. Next, the “reference current pattern” stored in the RAM 11
Will be described. First, the case at the time of startup will be described. First, before turning on the main power supply AC100V of the power supply circuit, the operating voltage + V is supplied to the control circuit 6B to activate the control circuit 6B. Thereafter, AC100V is supplied to the power supply circuit. As a result, a current is output to the load side. Then, a change in the load current from the load is detected, and the pattern of the current change is stored in the RAM 11 as a “reference current pattern”. Next, the normal operation will be described. First, the power supply circuit is started by supplying AC100V, and the current is output to the load. Thereafter, data is output from the load CPU to bit 6 of the pulse register 9 of the control circuit 6B. As a result, the microcomputer 12 reads the data of bit 6, and if the data is "01" HEX, it is recognized that the data output following this data is the data of the current pattern. When the data is output, it is stored in the RAM 11. Next, a case where the data is manually stored in the normal state will be described. First, AC100V is supplied to the power supply circuit and activated. Then, the switch 16 is closed when a change in current is stored as a “reference current pattern”. As a result, the bit 5 of the pulse register 9 becomes “0” level, and the microcomputer 12 sets the “reference current pattern”
It is recognized that the pattern of the change of the current that is When the current change pattern is output,
Stored in the RAM 11. Next, comparison between the “reference current pattern” and the detected current change pattern will be described. For example, when there are a plurality of reference patterns such as a power-on pattern, a load startup pattern, a normal pattern, and a load change pattern, in each reference pattern,
In each state, a pattern having a large current value is set, and the pattern of each mode is compared with the detected current change pattern. In addition, a “reference current pattern” for each lapse of time is stored, and a predetermined “reference current pattern” is selected at each time and compared with a detected current change pattern. Therefore, in the above-described embodiment, even when the current value is within the overcurrent value, the current change value of the abnormal current is recognized over time to detect a current change other than the current change pattern stored in the RAM. Thus, an unprecedented power supply function becomes possible. In this embodiment, a case is described in which the time change pattern of the load current in the normal state does not change due to the external environment of the power supply. However, in an actual power supply, the input voltage of the power supply, Temperature is constantly changing. In addition, the internal temperature increases due to self-heating of the power supply device immediately after the power supply device is started and after a certain time has elapsed. When the input voltage and the temperature of the components inside the power supply change in this way, the transient characteristics of the output voltage of the power supply and the overcurrent value at the time of overload change. Therefore, the “reference current pattern” written in the RAM 11 does not always match the current pattern during normal operation. Therefore, it is conceivable to correct the reference current pattern in the RAM 11 according to the external environment. FIG. 8 is a diagram showing another embodiment of the present invention constituted under such circumstances. In FIG. 8, portions common to FIG. 1 are denoted by common reference numerals, and description thereof is omitted. In the figure, reference numeral 60 denotes a Vin (input voltage) sensor, which detects an input voltage for switching. Reference numeral 61 denotes a temperature sensor, which is provided at a location where a characteristic change of a transistor, a transformer, a choke, a capacitor, or the like, in which the overcurrent characteristic is likely to change depending on the temperature, is detected. Then, the output of the Vin sensor 60 is taken into the register 63 via the AD converter 62, while the output of the temperature sensor 61 is read by the AD converter.
It is taken into the register 65 via 64. Then, by performing an operation between the registers 63 and 65, the reference current pattern is corrected in the RAM 11. Further, in this embodiment, a PWM control circuit 66 is separately provided, and the “reference current pattern” is the same as that in the PWM control circuit 66, and each of the resistors R _{1 to} Rn
The load current pattern obtained by the current detection may be corrected in the PWM control circuit 66 based on the information from the Vin sensor 60, and may be used as a pattern in the RAM 11. In the above-described embodiment, it is necessary to modulate the pulse width of the transistor 4 in order to stabilize the output voltage, which is the original power supply function, but this description is omitted. This output voltage stabilization is performed, for example, by detecting a +5 V output voltage and inputting it to a PWM control circuit 66, where a drive pulse having a desired on-pulse width is generated, as already performed by a general electrode. This means inputting to the transistor 4. The output of the PWM control circuit 66 and the output of the control circuit 6c are both ON / OFF pulses, and these outputs are input to the AND circuit 67. Furthermore, the clock of the control circuit 6c and the PWM control circuit 6
Because the frequency and phase must be matched with the clock of 6, it is connected by CLOCK Sync line. In some cases, it is desired to supply the drive voltage for the microcomputer 12 and its peripheral circuits from a secondary circuit that is insulated from the input voltage. In such a case, for example, a boosting winding is provided in the transformer 7 and the input may be obtained a voltage detection signal from any one of the secondary windings for example + 5V winding, for example, may be out of the anode side of the diode D _11. Further, in the above-described embodiment, the microcomputers 12 and the RAM 11 are provided in the control circuits 6B and 6C, respectively.
The data of the "reference current pattern" from the CPU is directly stored in the CPU. However, as shown in FIG. 9, a current measuring device 91 is connected between the power supply side 17 and the load side 16. Then, a measuring instrument 94 having a microcomputer 92 and a RAM 93 is connected to the CPU 95 on the load side 16 and the measuring instrument 94 measures and stores a “current pattern as a reference”, and stores the data of the stored current pattern. The load may be stored in the external storage device 96 and transmitted to the control circuits 6B and 6C in a predetermined period, or may be directly transmitted to the control circuits 6B and 6C in a predetermined period. In FIG. 9, FILT: smoothing circuit, SW: switching circuit, CT1, 2: current detector, T: transformer, RECT: rectifier circuit, DRIVE: driver, PWM: pulse width modulation circuit, AD1, 2: AD Converter, DA1: DA
Converter, CA: current amplifier, VA: voltage amplifier, VREF: reference voltage. 1 and 8 have the same functions as those in FIG. 1 and FIG. With this configuration, the control circuit on the power supply 17 side
The configuration of 6B and 6C can be simplified, and the measuring instrument 94
Is turned on, the "reference current pattern" on the power supply circuit and the load side can be reliably measured. In each of the above embodiments, for example, as shown in FIG.
It is configured so as to measure the pattern of current change from the voltage across R ₁ ~Rn, may be configured to measure the previous output current input to the load. For example, each resistor R _{1 to} Rn
Was connected between the coil L ₁ Ln and the respective load side terminals M, Q, and U, respectively, to measure the pattern of current change from the voltage at both ends of the resistors R ₁ ~Rn. [Effects of the Invention] As described above, in the switching power supply of the present invention, the control unit monitors not only the maximum current value of the abnormal current of the current supplied to the load, but also the current value-time factor. Is normal if the change is a normal operation pattern (the relationship between current value and time is a predetermined pattern), otherwise it is regarded as abnormal even if the current value is very small and does not reach the overcurrent value. Abnormality can be detected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a configuration of a switching power supply according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing an equivalent circuit of a load in the circuit of FIG. 1, and FIG. FIGS. 4A and 4B are diagrams for explaining a "reference current pattern" in the embodiment of FIG. 1, FIGS. 4 and 5 are diagrams showing an abnormal current detection process in the embodiment of FIG. 1, and FIGS. FIG. 6 is a flowchart showing the operation of the switching power supply of FIG. 1, FIG. 8 is a circuit diagram showing the configuration of a switching power supply of another embodiment of the present invention, and FIG. 9 is a diagram of another embodiment of the present invention. FIG. 10 is a block diagram showing a configuration of a switching power supply, and FIG. 10 is a circuit diagram showing an example of a configuration of a conventional switching power supply. DESCRIPTION OF SYMBOLS 1 ... Filter 2 ... Rectifier 3 ... Smoothing capacitor 4 ... Switching transistor 5 ... Snubber circuit 6A-6C ... Control circuit 7 ... Transformer 8 ... Driver 9 ... Pulse Register, 10… ROM, 11… RAM,
12 ... microcomputer, 13 ... rectifier resistor, 1
4, 62, 64: AD converter, 15: Current switching circuit, 60:
Input voltage sensor, 61: Temperature sensor, 63: Voltage register, 65: Temperature register, 66: PWM control circuit, 67: AND circuit.

Claims (1)

(57) [Claims] In a switching power supply device, a plurality of loads are connected to a secondary side of a transformer, a current consumption consumed by each load is detected, a state of the load is determined, and a switching operation of a primary side of the transformer is controlled. A current value holding means for holding a current value; a selection control means for sequentially selecting a consumption current detected for each load with a certain period and holding the current value holding means in the current value holding means; A current pattern storage unit in which a plurality of current patterns as a reference of the current consumption of each load are stored for each operation state; and The value of the current consumption is compared with the current pattern stored in the current pattern storage means and used as a reference of the current consumption of the load in the current operation state. A switching power supply comprising: a monitoring unit that determines a state of the load; and a control unit that controls the switching operation on the primary side of the transformer in accordance with a determination result of the load state by the monitoring unit. apparatus. 2. 2. The switching power supply device according to claim 1, wherein the current pattern storage means stores a current change pattern at the time of power activation as a reference current pattern. 3. 2. The switching power supply device according to claim 1, wherein the current pattern storage means stores a normal current change pattern as a reference current pattern. 4. The control means comprises an operation stopping means for stopping the switching operation on the primary side of the transformer when the state of at least one load is determined to be abnormal by the monitoring means. 2. The switching power supply device according to claim 1.