JPH07322616A - Dc-dc switching power supply device - Google Patents

Abstract

PURPOSE:To eliminate the mutual influence (interference) of output when a plurality of switching power supply circuits are provided and to reduce the circuit scale. CONSTITUTION:A common single PWM control circuit 10 is provided for two switching power supply circuits generating outputs(a) and (b). Two switching elements 2a and 2b are simultaneously turned on and are turned off individually according to each output voltage level. Therefore, the expansion of the power supply circuit does not increase the scale due to the single PWM control circuit. Also, all switching elements are fumed on simultaneously so that the on-pulse is synchronized, thus preventing the output from interfering one another.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC switching power supply device, and more particularly to a DC-DC switching power supply device which supplies various kinds of voltage outputs.
The present invention relates to a DC switching power supply device.

[0002]

2. Description of the Related Art Conventionally, as a first method of supplying power to a device which requires various kinds of power supply voltages, a method of obtaining a plurality of outputs by arranging a plurality of single output power supplies in parallel as shown in FIG. As a second method, a method of obtaining multiple outputs by using a single transformer with multiple outputs as shown in FIG. 9 is generally adopted.

With respect to the first method, the case where there are two types of output will be described with reference to FIG. In FIG. 8, an example of a conventional switching power supply is such that an input filter 1 having a DC power supply DC input supplied from the outside as an input, and an output of the input filter 1 is switched by a control signal from a pulse width (PWM) control circuit 10a. Switching element 2a
A transformer 3a having a rectangular wave pulse voltage output from the switching element 2a as a primary side input, and a pulse voltage output to the secondary side of the transformer 3a as an input, and a rectifier 4a for rectifying and smoothing into a DC voltage. And output filter 5
a and the output of the output filter 5a are input, and the pulse width of the control signal supplied to the switching element 2a so that the voltage value of the output of the output filter 5a becomes the required voltage value (period during which the switching element 2a is turned on). A first power supply circuit having a PWM control circuit 10a for changing

Further, similarly, an input filter 1b having a DC input as an input, a switching element 2b for switching the output of the input filter 1b by a control signal from the PWM control circuit 10b, and a rectangular wave output from the switching element 2b. The output of the output filter 5b and the rectifier 4b and the output filter 5b, which receives the pulse voltage output to the secondary side of the transformer 3b as the input, and the rectifier 4b that rectifies and smoothes the DC voltage, are output. A PWM control circuit 10b that changes the pulse width of the control signal supplied to the switching element 2b (the period during which the switching element 2b is turned on) so that the voltage value of the output of the output filter 5b becomes the required voltage value. A second power supply circuit having

The output of the output filter 5a is supplied to the load as a DC output a, and the output of the output filter 5b is supplied to the load as a DC output b. Since the switching elements 2a and 2b are repeatedly turned on and off at a cycle of several tens of KHz or more, a pulse voltage output is always obtained on the secondary side of the transformers 3a and 3b, and a stable DC voltage is rectified / smoothed to D.
It is obtained from C output a and DC output b.

Next, regarding the second method, the output type is 2
Two cases will be described with reference to FIG. FIG.
No. 18720 gazette, etc., and the input filter 1 which inputs DC input, the switching element 2 which switches the output of the input filter 1 by the control signal from the RWM control circuit 10, and the output from the switching element 2. A transformer 3 having a rectangular wave pulse voltage as a primary side input, a rectifier 4a for rectifying and smoothing a DC voltage as a pulse voltage output to the secondary side of the transformer 3 and an output filter 5a, and a transformer. The output voltage of the rectifier 4b and the output filter 5b of the output filter 5b that receives the pulse voltage output to the secondary side of the other system of 3
PWM for changing the pulse width of the control signal supplied to the switching element 2 (the period during which the switching element 2 is turned on) so that the output voltage value of the output filter 5b receives the DC voltage output from Control circuit 10
It is composed by.

The output of the output filter 5a is supplied to the load as a DC output a, and the output of the output filter 5b is supplied to the load as a DC output b. Also in this case, switching of the switching element 2 is repeated at a cycle of several tens of KHz or more, so that a pulse voltage output is always obtained on the secondary side of the transformer 3, and a rectified and smoothed stable DC voltage is obtained as the DC output b. can get. Also for the DC output a, a voltage proportional to the DC output b is output, so that the DC output is stable.

[0008]

In the conventional switching power supply of this type, in the method of arranging the single output power supplies in parallel like the first method, the switching frequencies of the switching power supplies are different from each other, so that the respective outputs are mutually different. Electromagnetic interference may occur, resulting in a large output ripple or adversely affecting the load.

Further, as disclosed in Japanese Utility Model Laid-Open No. 62-104581 and Japanese Patent Application Laid-Open No. 1-255469, even if the switching frequencies of the respective switching power supplies are synchronized to eliminate electromagnetic interference between the respective outputs. , For example, when three kinds of outputs are required, three single power supplies are required, and three PWM control circuits are required accordingly,
There is a drawback that the circuit configuration becomes large-scale.

Further, in the method of simultaneously obtaining various kinds of power supply voltage outputs from one transformer like the second method, when the capacity (power consumption) of the load device connected to a certain output fluctuates, There is a drawback that the power supply voltage of the other output fluctuates.

An object of the present invention is to provide a DC-DC switching power supply circuit capable of eliminating the influence of mutual output even when a plurality of switching power supply circuits are provided and suppressing an increase in circuit scale. .

[0012]

According to the present invention, a transformer, a switching element for turning on / off a voltage applied to the primary side of the transformer, and rectifying and smoothing an AC output induced on the secondary side of the transformer. A DC-DC switching device including first and second switching power supply circuits, each of which has a means for performing a rectifying and smoothing output voltage common to the first and second switching power supply circuits. Accordingly, there is provided control means for controlling the on / off state of each switching element of the first and second switching power supply circuits, and the control means generates an on timing for simultaneously turning on both switching elements. The off timing for turning off the corresponding switching element is determined according to the generation means and the corresponding rectified and smoothed output voltage. DC-DC switching power supply device which comprises a off-timing determining means is obtained.

[0013]

Operation: P common to a plurality of switching power supply circuits
A WM control circuit is provided, the switching elements of each switching circuit are turned on at the same time, and the off timing is controlled according to the output voltage level of each circuit, thereby eliminating interference between outputs and increasing the circuit scale. To prevent.

[0014]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 1 is a configuration diagram in the case of two types of outputs. In FIG. 1, an embodiment of the present invention is an input filter 1a which receives a DC power supply DC input supplied from the outside as an input.
A switching element 2a for switching the output of the input filter 1a by a control signal from the PWM control circuit 10; a transformer 3a for inputting a rectangular wave pulse voltage output from the switching element 2a to a primary side input; Input the pulse voltage output to the secondary side,
It has a first switching power supply circuit including a rectifier 4a that rectifies and smoothes a DC voltage and an output filter 5a.

Similarly, an input filter 1b having a DC input as an input, and an output of the input filter 1b as a PWM control circuit 1
A switching element 2b that switches according to a control signal from 0, and a transformer 3b that receives a rectangular wave pulse voltage output from the switching element 2b as a primary side input.
And a second switching power supply circuit composed of a rectifier 4b for rectifying and smoothing a DC voltage with a pulse voltage output to the secondary side of the transformer 3b as an input, and an output filter 5b.

Further, the outputs of the output filters 5a and 5b are independently input, and the outputs of the output filters 5a and 5b are supplied to the switching elements 2a and 2b so that the respective output voltages have the required voltage values. It is configured by a single PWM control circuit 10 that independently changes the pulse width of the signal (the period during which the switching elements 2a and 2b are turned on), and the output of the output filter 5a is the DC output a.
The output of the output filter 5b is supplied to the load side as a DC output b.

In FIG. 1, an nth switching power supply circuit may be provided as indicated by a dotted line, and in this case, the PWM control circuit 10 also controls on / off of the nth switching element.

Next, details of the configuration of the PWM control circuit 10 used in FIG. 1 will be described with reference to FIG.
The PWM control circuit 10 includes A / D converters 14 and 17 that receive DC outputs a and b, and buffers 15 and 18 that receive 8-bit digital signal outputs from the A / D converters 14 and 17, respectively. , Digital signal processor 12 (hereinafter referred to as DSP1) that receives the outputs of buffers 15 and 18 as input.
2), and a buffer 1 that outputs a signal for controlling the switching elements 2a and 2b using the output of the DSP 12 as an input.
3, an address decoder 16 for selecting a buffer among the buffers 13, 15 and 18 using a control signal from the DSP 12 as an input via an address bus.

Here, the DSP 12 performs the operation defined by the program, and this program is executed by the DSP 12
It is either built-in or stored in the external memory of the DSP 12. However, it is omitted from the configuration diagram here because there is no difference from general usage here.

Next, the operation of the PWM control circuit 10 and the DSP 1
The operation of the second program will be described. 3 to 6 are flowcharts of the program of the DSP 12, FIG. 3 is a main routine thereof, FIG. 4 is a timer 1 interrupt routine, FIG. 5 is a timer 2 interrupt routine, and FIG. 6 is a timer 3 interrupt routine.

FIG. 7 is a time chart of the waveforms of the control signals for the switching elements 2a and 2b and the execution routine of the DSP 12. Here, the timer interrupt is a general DSP.
This is a function that is generally used in, and when the time is set in advance, the program is executed, and the interrupt enabled state is set, the processing is automatically transferred to the timer interrupt routine when the set time elapses, and the timer interrupt routine is executed. When the process ends, the process of returning to the execution position of the original routine is performed.

In the present invention, three timer interrupts are used. The set time of the timer 1 interrupt indicates the period of one cycle of the switching operation, the set time of the timer 2 interrupt indicates the period in which the switching element 2a is turned on, and the set time of the timer 3 interrupt indicates the switching element 2
The period during which b is on is shown.

When the DSP 12 is turned on, it starts executing the program (step 101). Initialize the timer 1 interrupt time in the main routine (step 10
2) Then, the timer 2 and timer 3 interrupt times are initialized (step 103) (step 10).
4), enable timer 1 interrupt (step 10)
5). Here, the timer 1 interrupt time is 0.0001
Suppose you set it to seconds. Then, after 0.0001 seconds, the execution shifts to the timer 1 interrupt routine.

Timer 1 interrupt routine (step 20
In 1), first, “00000011 (2
8-bit data "base number" is output (step 2
02). Each bit from the lower bit to the upper bit of this 8-bit data specifies the switching element of the first to eighth switching power supplies, and indicates that the bit 1 is ON and the bit 0 is OFF. And As a result, the control signals for the switching elements 2a and 2b are both turned on.

Next, the DSP 12 fetches 8-bit data from the buffer 15 (step 203), compares the data with the data for DC output a preset in the program (step 205), and then from the buffer 15. If the captured data is larger (the voltage value of the DC output a is higher than the required voltage value), the time set value of the timer 2 interrupt is decremented by 1 (step 206),
On the contrary, if the data fetched from the buffer 15 is smaller (the voltage value of the DC output a is lower than the required voltage value), the time set value of the timer 2 interrupt is increased by 1 (step 207), and then the timer 2 is set. The interrupt is enabled (step 208).

Similarly, DSP 12 has buffers 18-8.
The bit data is fetched (step 204), and the data is compared with preset DC output b data (step 209). If the data fetched from the buffer 18 is larger (voltage of the DC output b) Value is higher than the required voltage value), the timer 3 interrupt time setting value is decremented by 1 (step 210). Conversely, if the data fetched from the buffer 18 is smaller (the DC output b voltage value is required). Lower than the voltage value to be set) and the time set value of the timer 3 interrupt is incremented by 1 (step 21
1) After that, the timer 3 interrupt is enabled (step 212), and execution is returned to the main routine (step 21).
3).

Next, the DSP 12 enters a waiting state for a timer 2 interrupt or a timer 3 interrupt. Here, it is assumed that a timer 2 interrupt has occurred. At this time, execution is timer 2
Move to interrupt routine (step 301), timer 2
In the interrupt routine, the lower 1 of 8 bits is stored in the buffer 13.
The data in which the bit is set to "0" is output (the second lower bit is not changed) (step 302), the switching element 2a is turned off, the timer 2 interrupt is prohibited (step 303), and the execution is returned to the main routine. (Step 30
4).

Similarly, when the timer 3 interrupt is generated (step 401), data in which the lower 2nd bit of the buffer 13 is set to "0" is output (the lower 1st bit is not changed) (step 402), and switching is performed. The element 2b is turned off and the timer 3 interrupt is prohibited (step 40
3) Return execution to the main routine (step 404).

The switching operation is performed as described above, and this operation is performed every time the timer 1 interrupt is generated. Since the timer 1 interrupt is set to 0.0001 seconds now, this switching is performed at 10 KHz.

Each interrupt routine requires 100 instructions.
Since it can be configured with instructions or less, if the program execution speed of the DSP 12 is a standard 10000000 instructions / second, there is sufficient time margin even if it is operated at 10 KHz. Further, since the switching is always performed in synchronization with the timer 1 interrupt period, the interference noise generated in each output system due to the switching is reduced. Further, since the stabilizing operation is independently performed for each output system with respect to the power fluctuation of the load device, the load fluctuation of one output system does not affect the other output system.

Further, even if a load device of a certain output system has a short circuit failure, it is easy to add a function of detecting an abnormal decrease in the output voltage value and stopping the operation of only that output system. The above characteristics are effective as long as the number of output systems is n and n outputs (n is an arbitrary number) are within the operation range of the DSP 12, and when the number of output systems is increased, DS is added.
By adding a program to P12, it is possible to add more control circuit parts without newly adding them.

[0033]

As described above, according to the present invention,
Since only one PWM control circuit is used to independently control the pulse width for all outputs and each switching is performed in synchronization, the interference noise due to the switching generated in each output system is reduced.

Further, since the stabilizing operation is independently performed for each output system against the power fluctuation of the load device, the load fluctuation of one output system does not affect the other output system. Further, even if the load device of a certain output system has a short circuit failure, it is easy to add a function of detecting an abnormal decrease in the output voltage value and stopping the operation of only that output system. In addition, when the number of output systems is increased, it is possible to increase the number without adding a control circuit part by adding a DSP program.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a PWM control circuit 10 in the block of FIG.

3 is a flow chart of a main routine of the DSP 12 in the block of FIG.

FIG. 4 is a flow chart of a timer 1 interrupt routine of the DSP 12 as well.

FIG. 5 is a flow chart of a timer 2 interrupt routine of the DSP 12 as well.

FIG. 6 is a flow chart of a timer 3 interrupt routine of the DSP 12 as well.

FIG. 7 is a time chart showing the relationship between the PWM pulse and the execution routine of the DSP 12.

FIG. 8 is a block diagram showing an example of a conventional switching power supply device.

FIG. 9 is a block diagram showing another example of a conventional switching power supply device.

[Explanation of symbols]

 1a, 1b Input filter 2a, 2b Switching element 3a, 3b Transformer 4a, 4b Rectifier 5a, 5b Output filter 10 PWM control circuit 12 DSP 13, 15, 18 Buffer 14, 17 A / D converter 16 Address decoder

Claims (3)

[Claims] 1. A first and a transformer, each having a transformer, a switching element for turning on and off a voltage applied to a primary side of the transformer, and a means for rectifying and smoothing an AC output induced on a secondary side of the transformer. A DC-DC switching device including a second switching power supply circuit, wherein the first and second switching power supply circuits are provided in common and are provided in common in accordance with the rectified and smoothed output voltage. The switching power supply circuit has a control means for controlling an on / off state of each switching element, the control means generating an on timing for simultaneously turning on both switching elements, and a corresponding rectified and smoothed output voltage. And an off-timing determining means for determining off-timing for turning off the corresponding switching elements in accordance with the above. DC-DC switching power supply unit, characterized in that. 2. The off-timing determining means is configured to determine the off-timing of the corresponding switching element in accordance with each difference between the predetermined first and second reference values and the corresponding rectified and smoothed output voltage. The DC-DC switching power supply device according to claim 1, wherein 3. The D according to claim 2, wherein the first and second reference values and the rectified and smoothed output voltage are each processed as digital data.
C-DC switching power supply device.