JPH0191657A - Switching power unit - Google Patents

Abstract

PURPOSE:To eliminate the outbreak of fire and others by monitoring abnormal current of the load side by a controlling means not only with the maximum current value but also with the factor of current value - time. CONSTITUTION:AC 100V is full-wave rectified by a rectifier 2 through a filter 1, and stored in a condenser 3. A control section 6B provides a base of a transistor(Tr) with on-pulse, and turns it on. At this time, the output voltage is generated at each of secondary sides of a transistor 7 by charge of the con denser 3 and is supplied to the load RF. When a Tr4 is turned off, energy of the transistor 7 and energy stored into a leakage inductance are consumed at a snubber circuit 5. At this time, the controlling section 6B is provided with a driver 8 to give driving pulse to the base of Tr4, a pulse resistor 9, a ROM10, RAM11, a micro-computer 12, a current resistor 13, a AD converter 14 and a current switching circuit 15. Even the current value within the overcurrent value recognizes the current varying value of abnormal current by time elapsing, and detects the current variation other than a defied pattern.

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.

(Prior Art) Switching power supplies have been widely used as power supply means for various electronic devices, and some of them are equipped with an abnormal current detection function.

In this type of device, for example, at an output voltage of +24V, 10
When a current of 0 A flows through the load, it is determined that the current is overcurrent.

FIG. 9 is a diagram showing the configuration of a conventional switching power supply device.

In the figure, 1 is a filter, 2 is a rectifier, 3 is a smoothing capacitor that accumulates the voltage after rectification, 4 is a switching power transistor (hereinafter referred to as a transistor), and 5 is an intermittent current of the transformer by turning on and off the transistor 4. 6A is a snubber circuit that consumes the energy (i) accumulated in the transformer when transistor 4 is off, and 6A is a snubber circuit that controls pulse width modulation of transistor 4 and outputs each output (+5V
, +12V...+24■), and 7 is a single-input, multiple-output type transformer.

Also C++, D+2, D2+, D22) Dn+.

Dn2 is a rectifier diode on the secondary side of the transformer 7, C+,
C2-Cn are smoothing capacitors, Ll, 12...ln are coils that reduce the peak value of the current flowing through the transistor 4 and reduce the ripple voltage, R1, R2...
・Rn is a resistor for detecting current value, CF I N CF 2
...CFn is the smoothing capacitor on the load side, and the RF
I, RF2...RFn indicates resistance on the load side.

In this circuit, when AolooV passes through filter 1 and is full-wave rectified by rectifier 2, capacitor 3 has approximately 14
A charge of 0■ is accumulated.

On the other hand, the operating voltage +V is applied to the control section 6A, and the control section 6A applies an on-pulse to the base of the transistor 4 to turn on the transistor 4.

At this time, the charge of capacitor 3 is A→B-+C→D-+
A current flows in the direction of E-+F-+G-H→.

In addition, the respective outputs J, K, on the secondary side of the transformer 7...
A voltage with the ratio of the primary winding to the secondary winding is generated in L, and the diode D
+ +, D2 I, ”'Dn +, Dil 1-1, Ll
...A current flows through In, and the load RF + , RF 2.
...Reaches Rpn. Here, the ripple current components are accumulated as charges in the capacitors CI, C2, . . . , Cn, and each outputs a DC voltage of J5.

Furthermore, when the transistor 4 is turned off, the excitation current C->D of the transformer 7 tends to continue to flow, and this energy and the energy stored in the leakage inductance are consumed in the snubber circuit 5.

At this time, a back electromotive voltage is generated by the energy stored in the choke coils of each secondary circuit of the transformer 7, and the current flowing through each of the coils L1, Ll...in while the transistor 4 is on is transferred to the diode. D+2, D
22... continues to flow through Dn2, and also RF + ,
The ripple current reaching Rp2...RFn is stored as a charge in the capacitors CI, 'C2...Cn.

Note that 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 increases, the control circuit 6A reduces the pulse width of the on-time of the transistor 4. This action stabilizes the DC output on the secondary side.

Then, when the stabilized DC output is output to M, Q, and tJ, current flows to each load.

For example, in the case of +5V, M-+N-IRF+→P→O→
Current flows through the resistor R1 and into the capacitor C1. At this time, a voltage is generated across the ends a and b of the resistor R1, and the control circuit 6A
is input.

In the case of output +12V and +24V, both ends C1D
1 voltages at both ends e and f are input to the control circuit 6Δ.

For example, in the case of an output of +24V, assuming that 100A is not considered overcurrent, Rn = 0.01Ω, and the voltage across Rn is IV (100AX O, 01Ω-IV) (7
), the control circuit 6A detects an overcurrent.

By the way, in this type of device, for example, if the normal current is 20A at +24V, some abnormality will occur on the load side.
Even if the partial load current increases by 10Δ, the total current will only flow by 3OA.

Therefore, if 100Δ is considered to be overcurrent, no abnormality will be detected even if the load generates heat or ignites in spots.

(Problem to be solved by the invention) In this way, with conventional switching power supplies, even if an abnormality actually occurs in the load, it is not detected until the overcurrent current is reached, and in the case of R, a fire may occur. The problem was that I had something to do.

The present invention was developed under these circumstances, so that if an abnormality occurs in the load, it can be detected even if the overcurrent current has not been reached, thereby avoiding the risk of fire, etc. The purpose is to provide switching power supplies.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve this object, the present invention switches input DC to convert it into a desired voltage, rectifies and smoothes it, and supplies it to a predetermined load. A switching power supply device configured as follows: current detection means for detecting an output current to the load; storage means for storing in advance a pattern of normal current changes in the load as binary data;
The current value detected by the current detection means and the current value stored in the storage means are compared, the occurrence of an abnormality in the load is recognized from the difference between the two, and the switching operation is controlled according to the result of this recognition. This means that there is a means of controlling the distribution of goods.

(Function) In the switching power supply device of the present invention, the control means monitors the abnormal current on the zero load side not only by the maximum current value but also by the factor of current value - time, so that the change in load current is a pattern of normal load operation. (If the relationship between current value and time is a fixed pattern), it is considered normal; otherwise, even if the current value is very small and does not reach the overcurrent value, it is considered abnormal.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention,
Parts that are common to those in Figure 9 are marked with common numbers.

In the figure, 1 is a filter, 2 is a rectifier, 3 is a smoothing capacitor for accumulating the rectified voltage, 4 is a switching transistor, and 5 is a transistor that switches on and off the current of the transformer by turning on and off the transistor 4. 6B is a control unit that controls the pulse width modulation of the transistor 4 and detects the overcurrent of each output (+5■, +12v...+24v); 7 is a snubber circuit that consumes the energy stored in the transformer when it is off; This is a single-input, multiple-output type transformer.

Also C++, D+2, D2+, D22sDn+, Dn2
are the rectifier diodes on the secondary side of the transformer 7, C1, C2,
...Cn is a smoothing capacitor, L+, L2...l-n is a coil that reduces the peak value of the current flowing through the transistor 4 and also reduces the ripple voltage, R1, R2...
・Rn is a resistor for detecting current value, Cp + , CF 2
...CFn is the smoothing capacitor on the load side, and Rp
I, RF2...Rpn indicates resistance on the load side.

In this circuit, when AolooV passes through filter 1 and is full-wave rectified by rectifier 2, capacitor 3 has approximately 14
A charge of 0V is accumulated.

On the other hand, the operating voltage +V is applied to the control section 6B, and the control section 6B applies an on-pulse to the base of the transistor 4 to turn on the transistor 4.

At this time, the charge of capacitor 3 is A→B-+C→D-+
E-4F-) G → 1'' → flows as a current.

Also, each output J1K on the secondary side of the transformer 7...
In this case, a voltage with the ratio of primary to secondary winding occurs, and the diode C
++, D2+, =-Dnl, coil L1, L2-In+
, : Current flows and reaches the load Rr+, RF2-...RpH. Here, the ripple current components are capacitors C1 and C2
. . . It is accumulated in Cn as a charge, and each outputs a DC voltage.

Also, when transistor 4 is turned off, transformer 7 is energized! ! The current C-+D tends to continue flowing as it is, and this energy and the energy stored in the leakage inductance are consumed in the snubber circuit 5.

At this time, the coils L1, L2 of each secondary circuit of the transformer 7
...A back electromotive force is generated by the energy stored in ln, and during the period when transistor 4 is on, coils I-+ and L2
...In continues to flow through the diodes D+ 2 , D22 . . . Dnz, and the ripple currents reaching the loads RF + , Rp 2 . ...is accumulated in Cn as a charge.

Note that 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 71m 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 11H when the transistor 4 is on. Due to this action, 2
The DC output on the next side is stabilized.

Then, when the stabilized DC output is output to M and QSU, current flows to each load.

The above portions are 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 this embodiment includes a driver 8 that applies a drive pulse to the base of the transistor 4, a pulse register 9 that holds the drive pulse, and control data and a "reference current pattern" to be described later written in advance. ROMl
0, a RAM II that serves as a work area, a microcomputer 12 that has an abnormal current monitoring function and a pulse width modulation function, a current register 13 that holds the current value on the load side as binary data, and a current register 13 that holds the current value on the load side as binary data. It includes an AD converter 14 that converts the data into binary data, and a current switching circuit 15, which will be described later.

FIG. 2 is a diagram showing an equivalent circuit on the load side of the +24V output voltage in FIG. 1.

The load Rrn includes a plurality of resistance components F1 and rF2, respectively.
...consisting of rFn.

For control power supplies and computer power supplies, these resistance elements F 1
, rF2... rFn are respectively logic board 1
equivalent to 1 sheet.

Figure 3 shows the normal voltage of 24V in the circuit of this embodiment.
It is a diagram showing a change in the zero-load current of the output, that is, a "reference current pattern" to be described later, in which the horizontal axis shows T (time) and the vertical axis shows the current.

Here, t is the time width, and ■ is the current value.

Further, FIG. 4 is a diagram showing a pattern of abnormal values of the load current of the same → 24V output, and FIG. 5 is a diagram for explaining the procedure for detecting this abnormal value by the control circuit 6B of this embodiment. be.

In the control circuit 6B of this embodiment, the resistors R1, Rz・”
The voltages a-b, c-d, and e-f across Rn are the control circuit 6B.
When the input is input, the micro combi coater 12 operates the current switching circuit 15 to select one of a-b, c-d, and e-f, and converts it into a binary value to the current register 13 via the AD converter 14. Set as data. The microcomputer 12 then reads this data.

That is, the microcomputer 12 calculates the current values of each D CjJj force (secondary side) as a7b, c-d, e-f, respectively.
This allows input as a voltage value between the current values and detect changes in the current value over time.

The operation of the microcomputer 12 of the control section 6B will be explained below according to the flowcharts of FIGS. 6 and 7.

In order to explain the operation in detail here, the change in the load current during normal operation at +24V output is shown in FIG.

In other words, normally 20A flows, and in pattern ■, l2
=3OA, and the current changes by a period tll or a period t12. In addition, in pattern ■, I3=90Δ, only period t2, and 1. =45△ and the current changes by 3.

Furthermore, there is also a case of pattern ■.

It is assumed that the patterns (2), (2), and (2) do not overlap, and that the current value changes in synchronization with the unit time t.

In FIG. 6, first, in step 21, the switching circuit 15
e and f of +24V are selected, and in step 22, AD conversion is performed and the digital value set in the current register 13 is read. Then, as steps 23 to 27, II=20A, 12=30Δ, I3=70A, I in FIG.
4 = 45 A, I 5 = 10 OA or more, read the current value again after 1 hour and find out whether it corresponds to one of the patterns ■, ■, ■, ■ in Figure 3, or deviates from these. Check for presence.

For example, if the answer is Yes in step 23, the pattern is pattern (2), so it is checked every time t in steps 41 to 47.

If the current continues to flow for 30 A longer than tel during the period of pattern (■) in Figure 4, it is an abnormality, so steps 41, 43, and 45 are performed in accordance with A, C, C, and 2 in Figure 5. After that, 30A becomes YES in step 46, and since it is abnormal if 30Δ becomes 20Δ in a time shorter than the period tll, it becomes NO in step 42, NO in step 44, and it is treated as an abnormality.

In pattern ■ of FIG. 3, YES in step 24.

The current values are checked in steps 28 to 37, and if all current values are present, the process returns normally and goes to step 48. Further, if NO in any of steps 28 to 37, it is treated as an abnormality.

Pattern 3 of FIG. 3 is compared in steps 25.38-40 and 48. Also, for pattern (2), the result is YES in step 26, and the process goes to step 49.

Pattern ■ in FIG. 4 does not result in YES in steps 23 to 27, and is processed in steps 50 to 52.
Compare each current value with the normal pattern value prepared in advance for , ) pattern, the answer is YES in step 52 and the process goes to step 49.

For pattern (2) in FIG. 5, the result in step 27 is NO, and steps 50 to 52 return to step 49. In other words, in Figure 5, ru, wo, wa, force, yo, and yu do not match at the stage of comparing electric current fields.

If an abnormality occurs in the process shown in FIG. 6, the process goes to step 53 in FIG. 7, and energy 1 is sent to the secondary side! will no longer be supplied. Therefore, abnormal heat generation in the load RFn is also eliminated. Note that various warning methods can be considered for the process of step 54.

For example, in step 53, the transistor 4 is continuously turned on and off, and in step 54, if the operator is notified by some method, the operator turns off the power supply.

J3 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, turning on the transistor 4, and when LSB=1, the driver 8 becomes 0, turning off the transistor 4. The microcomputer 12 controls the pulse width on-time and stabilizes the secondary output voltage.

In this embodiment, steps 23 to 27 in the explanation of FIG.
For example, when checking 30Δ in step 23, check the values of 28 to 32A and check the actual 6, f? Errors during conversion from the 11f pressure (FIG. 1) to the current register 13 are corrected.

Thus, in this embodiment, even if the current value is within the overcurrent value, by recognizing the current change value of the abnormal current over time, and by detecting the current change other than the defined pattern, a power supply function that was not available in the past is possible. becomes.

In this example, an inquiry is explained in which the time change pattern of the load current during normal operation 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, the power supply Ambient temperature constantly changes1
I'm at No. Furthermore, when the power supply device is started immediately and after a certain period of time has elapsed, the internal temperature rises due to self-heating of the power supply device.

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" that should be initially written in ROMlo does not necessarily match the current pattern during normal operation.

Therefore, it is conceivable to extract the reference current pattern in the ROM10 to RΔM11 and modify it according to the external environment.

FIG. 8 is a diagram showing another embodiment of the present invention constructed from these circumstances.

In FIG. 8, parts that are the same as those in FIG. 1 are given the same reference numerals, and their explanations are omitted.

In the figure, 60 is a vin (input voltage) sensor,
Detects switching input voltage. Reference numeral 61 denotes a temperature sensor, which is provided at a location where changes in characteristics of transistors, transformers, chokes, capacitors, etc. whose overcurrent characteristics are likely to change depending on temperature are 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 taken into the register 65 via the AD converter 64. Further, the microcomputer 12 extracts the reference current pattern 1 from the ROM 10 to RΔM11.

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

In addition, in this embodiment, a PWM controller 1-roll circuit 66 is provided separately, and the "reference current pattern" is this PWM controller 1-roll circuit 66.
Using what is in the M control circuit 66 as it is, the load current pattern multiplied by 1!7 by the current detection of each resistor R1 to Rn is corrected based on the information from the PWM control circuit 6 circuit 6 internal vin sensor 60, and the ROM10 It can also be used as an inner pattern.

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

This output voltage is stabilized as is already done in general power supplies; for example, a +5V output voltage is detected and inputted to the PWM control circuit 66, where a drive pulse with a desired on-pulse width is generated. This means that it is input to transistor 4.

Note that the output of the PWM control circuit 66 and the control circuit 6C
The output of both is a pulse that turns on and off.
These outputs are input to an AND circuit 67.

Furthermore, since the clock of the control circuit 6C and the clock of the PWM control circuit 66 need to match in frequency and phase, they are connected by a CLOCK 5VnC line.

Note that there are cases where 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. The voltage detection signal may be obtained or may be output from one of the secondary windings, for example the +5V winding, for example from the anode side of the diode D++.

[Effects of the Invention] As explained above, in the switching power supply device 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 factor of current value - time, so that the change in the load current is not normal. If the load operation pattern is correct, it is normal; otherwise, the current value is so small that it cannot reach the overcurrent value. Since it is considered abnormal, there is no risk of fire or the like.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the 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 at J3 in the same embodiment device, and Fig. 3 is a “reference” circuit diagram in the same embodiment. 4 and 5 are diagrams illustrating abnormal current detection processing in the same embodiment, and FIGS. 6 and 7 are flowcharts illustrating the operation of the device of the embodiment, and FIGS. FIG. 8 is a circuit diagram showing the configuration of another embodiment of the present invention, and FIG. 9 is a circuit diagram showing an example of the configuration of a conventional switching power supply device. 1... Filter, 2... Rectifier, 3... Smoothing capacitor, 4... Switching 1 to transistor, 5...
・Snubber circuit, 6Δ~6C...control circuit, 7...transformer, 8...driver, 9...pulse register,
10... ROM, 11... RAM, 12... Microcomputer, 13... Rectification register, 1/l
, 62.64...A/D converter, 15...Current switching circuit, 60...Input voltage sensor, 61...Temperature sensor, 63...Par pressure register, 65...Temperature register , 66...PWM control circuit, 67...AN
D circuit. Applicant Toshiba Corporation Agent Patent Attorney Suyama Sa - Fn Confucian 2 Diagram

Claims (8)

[Claims] (1) In a switching power supply device configured to switch input DC to convert it to a desired voltage, rectify and smooth it, and supply it to a predetermined load, a current detection means for detecting an output current to the load; Comparing the current value detected by the current detection means with the current value stored in the storage means, the storage means stores in advance the pattern of normal current change in the load as binary data, and the current value detected by the current detection means is compared with the current value stored in the storage means. 1. A switching power supply device comprising: control means for recognizing the occurrence of an abnormality in the load based on a difference in the number of signals, and controlling the switching operation according to the recognition result. (2) The switching power supply device according to claim 1, wherein the control means controls the switching operation by pulse width modulation. (3) The switching power supply device according to claim 1, wherein the control means stops the switching operation at the time when the occurrence of an abnormality in the load is recognized. (4) The switching power supply according to claim 1, wherein the control means regularly compares the current value detected by the current detection means and the current value stored in the storage means every unit time. Device. (5) Claim 1, wherein the control means corrects the current value detected by the current detection means according to the voltage change of the input DC, and compares it with the current value stored in the storage means. Switching power supply as described. (6) Claim 1, wherein the control means corrects the current value stored in the storage means according to the voltage change of the input DC, and compares it with the current value detected by the current detection means. Switching power supply as described. (7) Claim 1, wherein the control means corrects the current value detected by the current detection means according to a temperature change in a predetermined part, and compares it with the current value stored in the storage means. Switching power supply as described. (8) Claim 1, wherein the control means corrects the current value stored in the storage means according to a temperature change in a predetermined region, and compares it with the current value detected by the current detection means. Switching power supply as described.