JP2603966B2 - Switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a switching power supply device having a current detection function.

2. Description of the Related Art Conventionally, switching power supplies have been widely used as power supply means for various electronic devices, and some of them have a 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. 9 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 storing a voltage after rectification, 4 is a switching power transistor (hereinafter referred to as a transistor), and 5 is an intermittent transformer current when the transistor 4 is turned on and off. A snubber circuit that consumes the energy stored in the transformer when the transistor 4 is turned off, and 6A controls the pulse width modulation of the transistor 4 and outputs (+ 5V, + 5V)
A control unit for detecting an overcurrent of 12V... + 24V) is a single-input multiple-output transformer.

D ₁₁ , D ₁₂ , D ₂₁ , D ₂₂ , Dn ₁ , and Dn ₂ are _two of the transformers 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, an electric charge of about 140 V is accumulated in the capacitor 3.

On the other hand, the operating voltage + V is applied to the control unit 6A,
6A gives an ON pulse to the base of the transistor 4 to turn on the transistor 4.

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 current 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 drops, 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.

In the case of outputs + 12V and + 24V, the voltages at both ends C and D and both ends e and f are input to the control circuit 6A in the same manner.

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 considering overcurrent at 100A,
Even if the load generates heat or ignites in spots, no abnormality is detected.

(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 under such circumstances, and when an abnormality occurs in a load, the abnormality can be detected even if the current does not reach an overcurrent current, thereby avoiding the possibility of occurrence of a fire or the like. The purpose of the present invention is to provide a switching current device.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve this object, the present invention switches input DC to convert it to a desired voltage, rectifies and smoothes it, and supplies it to a predetermined load. In the switching power supply device configured as described above, current detection means for detecting a load current, storage means for previously storing data of a reference pattern of a change in the load current, and a current value detected by the current detection means A control means is provided for comparing the reference pattern of the change in the load current stored in the storage means on a time axis, and recognizing the occurrence of an abnormality when they do not match.

(Operation) In the switching power supply device of the present invention, the control means monitors not only the maximum current value but also the current value-time factor, and the load current changes in a normal pattern in the load operation. If the relationship between the current value and the time is a fixed pattern), it is regarded as normal. Otherwise, even if the current value is very small and does not reach the overcurrent value, it is regarded as abnormal.

(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 a configuration of one embodiment of the present invention, and portions common to FIG. 9 are denoted by common reference numerals.

In the figure, 1 is a filter, 2 is a rectifier, 3 is a smoothing capacitor for storing a voltage after rectification, 4 is a switching transistor, 5 is a transistor for turning on and off the transistor 4 and turning off and off the transistor 4. A snubber circuit that sometimes consumes the energy stored in the transformer, 6B controls the pulse width of the transistor 4 and detects the overcurrent of each output (+ 5V, + 12V ... + 24V), and 7 is a single-input multiple-output type. It is a transformer.

D ₁₁ D ₁₂ , D ₂₁ , D ₂₂ , Dn ₁ , Dn ₂ are rectifier diodes on the secondary side of the transformer 7, 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, an electric charge of about 140 V is accumulated in the capacitor 3.

On the other hand, the operating voltage + V is applied to the control unit 6B,
6B gives an ON pulse to the base of the transistor 4 to turn on the transistor 4.

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 current 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 abnormal part is the same as the circuit of FIG. 9, but the configuration of the control circuit is different in the circuit of this embodiment.

The control circuit 6B of the present embodiment has a driver 8 for applying a drive pulse to the base of the transistor 4, a pulse register 9 for holding the drive pulse, control data and a “reference current pattern” to be described later written in advance. ROM10
, A RAM 11 serving as a work area, and a microcomputer having an abnormal current monitoring function and a pulse width modulation function
12, a current register 13 for holding the load-side current value as binary data, an AD converter 14 for converting the load-side current to binary data, and a current switching circuit 15 to be described later. .

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 is a diagram showing a change in the load current of the +24 V output in the circuit of the present embodiment in a normal state, that is, a “reference current pattern” to be described later. The current is shown. Here, 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 for detecting the abnormal value by the control circuit 6B of the present embodiment.

In the control circuit 6B of the present embodiment, the voltage across a-b of the resistor _{R 1, R 2 ... Rn,} c-d, when e-f is inputted to the control circuit 6B, the microcomputer 12 is a current switching circuit 15 Operate and select any of ab, cd, ef, and AD
It is set as binary data in the current register 13 via the converter 14. This data is then transferred to the microcomputer 12
Read.

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, so that a change in the current value over time can be detected. is there.

Hereinafter, the operation of the microcomputer 12 of the control section 6B will be described with reference to the flowcharts of FIGS. 6 and 7.

In this case, in order to simplify the explanation of the operation, the change of the load current at the time of normal operation at +24 V output 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 or time period t ₁₂ current changes. In the pattern only period t ₂ in I ₃ = 90A, and the pattern change in current for a period t ₃ in I ₄ = 45A. 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, it is a pattern, and it is checked every time t in steps 41 to 47.

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 of FIG. 3, the answer is YES in step 24, the current values are checked in steps 28 to 37, and if there are all current values, the process returns to step 48 with a normal return. Step 28
If it is NO at ~ 37 somewhere, 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 and the transistor 4 is turned on.
Becomes 0, and the transistor 4 is turned off. The microcomputer 12 controls the pulse width on-time, and controls the stabilization of the secondary output voltage.

In the present embodiment, the current values are compared in steps 23 to 27 in the description of FIG.
Is checked, the value of 28 to 32 A is checked, and the error at the time of conversion from the actual e, f voltage (FIG. 1) to the current register 13 is corrected.

Thus, in the present embodiment, even if the current value is within the overcurrent value, by detecting the current change value of the abnormal current with the passage of time, it is possible to detect a current change other than the defined pattern, thereby enabling a power supply function that was not conventionally possible. Becomes

In this embodiment, the case where the time variation pattern of the normal load current does not change due to the external environment of the power supply is described. 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. For this reason, the “reference current pattern” to be initially written in the ROM 10 does not always match the current pattern during normal operation.

Therefore, it is conceivable to take out the reference current pattern in the ROM 10 to the RAM 11 and correct it according to the external environment.

FIG. 8 is a view 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. The microcomputer 12 reads the “reference current pattern” from the ROM 10
Out to RAM11.

By performing an operation between these registers 63 and 65, the reference current pattern is corrected in the RAM 11,
The corrected pattern is compared with the detected current pattern.

Also is provided separately from the PWM control circuit 66 in the present embodiment, the "pattern of current to be a reference" is directly used in the PWM control circuit 66, the resistors R ₁ ~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 the pattern in the ROM 10.

In this embodiment, it is necessary to modulate the pulse width of the transistor 4 in order to stabilize the output voltage, which is an original power supply function, but this description is omitted.

This output voltage is stabilized, for example, by detecting a + 5V output voltage and inputting it to the PWM control circuit 66, where a drive pulse having a desired on-pulse width is generated, as already performed by a general power supply. 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.

[Effect of the Invention] As described above, in the switching power supply of the present invention, the control means monitors the abnormal current on the load side not only by the maximum current value but also by the current value-time factor, and the change in the load current is normal. If it is a load operation pattern, it is considered normal, otherwise, the current value is very small and even if it does not reach the overcurrent value, it is regarded as abnormal, and there is no risk of fire or the like.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing an equivalent circuit of a load in the device according to the embodiment, and FIG. 4 and 5 are diagrams showing an abnormal current detection process in the embodiment, FIGS. 6 and 7 are flow charts showing the operation of the device in the embodiment, and FIG. FIG. 9 is a circuit diagram showing an example of the configuration of a conventional switching power supply device. 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 (8)

(57) [Claims] 1. A switching power supply device configured to switch an input direct current to convert it to a desired voltage, rectify and smooth and supply it to a load, and a current detecting means for detecting a load current; And comparing the load current detected by the current detection means with the reference pattern of the change in the load current stored in the storage means, wherein the storage means pre-stores the data of the reference pattern of the change in A switching power supply device, comprising: a control unit that recognizes occurrence of an abnormality when the switching power supply is not performed. 2. The switching power supply according to claim 1, wherein said control means controls the input DC switching operation by pulse width modulation. 3. The switching power supply device according to claim 1, wherein said control means stops said switching operation when it recognizes that an abnormality has occurred in said load. 4. The control means compares the load current detected by the current detection means with a reference pattern of a change in the load current stored in the storage means for each unit time, and 2. The switching power supply device according to claim 1, wherein when a mismatch is determined by comparing the times, the occurrence of an abnormality is recognized. 5. The control means corrects the load current detected by the current detection means according to the input DC voltage, and calculates the corrected load current and the load current stored in the storage means. 2. The switching power supply according to claim 1, wherein the switching power supply compares the reference pattern with the change. 6. The control means corrects the reference pattern of the change of the load current stored in the storage means in accordance with the voltage of the input DC. 2. The switching power supply device according to claim 1, wherein a comparison is made with a load current detected by the current detection means. 7. The control means corrects the load current detected by the current detection means in accordance with the temperature of a predetermined portion, and calculates the corrected load current and the load current stored in the storage means. 2. The switching power supply according to claim 1, wherein the switching power supply compares the reference pattern with the change. 8. The control means corrects the reference pattern of the change of the load current stored in the storage means according to the temperature of a predetermined portion. 2. The switching power supply according to claim 1, wherein the switching power supply is compared with a load current detected by the current detecting means.