JP4887847B2 - Power system - Google Patents

Description

  The present invention relates to a power supply system including a main power supply and a plurality of distributed power supplies connected to the main power supply, and in particular, switching noise of a switching power supply provided in the main power supply and a switching power supply provided in each of the distributed power supplies. The present invention relates to a technique for avoiding overlap with switching noise.

  A power supply configured to connect a plurality of distributed power supplies to a single power supply bus connected to a battery and supply an output of a switching power supply incorporated in each of the distributed power supplies to a load connected to the distributed power supplies A supply device has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-37482

  It is conceivable to provide a main power supply having a switching power supply instead of the battery. In this case, switching noise (hereinafter referred to as first switching noise) of a switching power supply provided in the main power supply is superimposed on the power supply bus. Further, switching noise (hereinafter referred to as second switching noise) of a switching power supply provided in the plurality of distributed power supplies wraps around the power bus.

  In this state, the first and second switching noises are not in a synchronized relationship, and the frequencies of both noises may change relatively. For this reason, there is a possibility that the generation timing of the first switching noise and that of the second switching noise coincide with each other on the power supply bus. In this case, the noise peak level becomes large and adversely affects peripheral circuit elements. May cause effects.

  Therefore, an object of the present invention is to provide switching noise of a switching power source provided in the main power source and each of the distributed power sources in a power source system including a main power source and a plurality of distributed power sources connected to the main power source. It is to avoid overlap with switching noise of the switching power supply.

In order to achieve the above object, the present invention provides a main power source having a first switching power source capable of changing a switching cycle to first and second switching cycles, and is connected to the main power source. A plurality of distributed power sources each having a second switching power source that operates based on an output of the power source, wherein each of the distributed power sources detects a switching noise generated by the first switching power source of the main power source . Based on the switching means, a switching period detecting means for detecting a switching period of the main power source, and determining whether the switching period of the main power source is the first switching period or the second switching period So that the switching cycle determination means and the switching cycle are the same as the switching cycle of the main power supply, One, and a power control means for controlling the second switching power supply as the switching cycle is started with a delay from the switching period of the main power supply, the difference of the magnitude of the delay in each distributed power I try to let them.

  The switching noise detection means may include detection means for detecting the switching noise and converting it into a corresponding pulse signal, and configured to detect the switching noise based on the pulse signal.

  For example, the switching noise detecting means is configured to measure a predetermined mask time after detection of the switching noise, and to detect the next switching noise after the time measurement of the mask time is completed.

It said main power source, Ru may comprise a modulating means for modulating, based the first switching frequency of the switching power supply to a predetermined communication data. Further, each of the distributed power supply based on the switching cycle is determined by the switching cycle determining unit, a data demodulation means for demodulating said communication data than the switching frequency of the modulated first switching power supply by the modulation means Can be provided. The communication data is used as command data for controlling each of the distributed power sources, for example.

According to the present invention, since the switching noise of the switching power supply provided in the main power supply and the switching noise of the switching power supply of each distributed power supply are distributed, the overlap of the former switching noise and the latter switching noise is avoided. As a result, an increase in the peak level of switching noise is prevented, and adverse effects on peripheral circuit elements due to the switching noise are suppressed.
In addition, since the switching timing of the switching power supply of the main power supply is synchronized with the switching timing of the switching power supply of each distributed power supply, the main power supply and each distributed power supply are switched using the switching noise of the switching power supply of the main power supply. When performing communication between the two, it is possible to avoid communication errors and achieve highly reliable communication.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a power supply system according to the present invention.
This power supply system includes a main power supply 10, a plurality of distributed power supplies 30 (30-1 and 30-2) connected to the main power supply 10 via a power supply line 20, and a host 40 (such as a microcomputer) that generates communication data. Consisting of). Note that an arbitrary number of two or more distributed power sources 30 can be provided.

  As shown in FIG. 2, the main power supply 10 includes a modulation control unit 11 and a switching power supply unit 12. The modulation control unit 11 modulates the switching frequency of the switching power supply unit 12 based on control data (communication data) given from the host 40.

The switching power supply unit 12 includes an oscillation unit 120 as illustrated in FIG. In the oscillating unit 120, for example, when the switches S _a1 and S _b1 are turned on, the capacitor C is charged via the resistor R _a1 , the switch S _a1 and one switching element (for example, P channel MOS) 123a. When the charging voltage of the capacitor C exceeds _a predetermined reference voltage Va, the comparator 121a sets the flip-flop 122. As a result, the one switching element 123a is turned off and the other switching element (for example, , N-channel MOS) 123b is turned on.

Thus, the charge of the capacitor C is discharged through the other switching element 123b, resistors R _b1 and switch S _b1. When the voltage of the capacitor C decreases to the reference voltage _Vb due to this discharge, the flip-flop 122 is reset by the comparator 121b, so that the one switching element 123a is turned on and the other switching element 123b is turned off. Thereafter, such an operation is repeated, and as a result, the oscillating unit 120 outputs a triangular wave as illustrated.

On the other hand, when the switches S _a2 and S _b2 are turned on, the resistors R _a2 and R _b2 are selected, and the same switching operation as described above is performed. In this embodiment, when the resistors R _a1 and R _b1 are selected, the switching frequency of the switching power supply unit 12 is set to f ₁ (for example, 1.2 MHz), and when the resistors R _a2 and R _b2 are selected. The switching frequency is set to f ₂ (for example, 1 MHz).

For example, when the control data “1”, “0”, and “1” are sequentially input, the modulation control unit 11 turns on the switches S _a1 and S _b1 of the switching power supply unit 12 for the data “1”. turns on the switch Sa2, S _b2 of the switching power supply unit 12 to the data "0". Therefore, in the oscillation unit 120, the switching frequency is modulated in the form of f ₁ → f ₂ → f ₁ in accordance with the change of control data “1” → “0” → “1”.

The drive circuit 124 includes an error amplifier (not shown) that compares the voltage of the power supply line 20 and the reference voltage V _ref , and compares an error signal that is an output of the error amplifier with a triangular wave output from the oscillation unit 120. A square wave (PWM (Pulse Width Modulation) pulse) as shown in FIG. 5A is generated.
The switching circuit 125 includes a switching element that is driven on / off at the frequency of the triangular wave by the PWM pulse. The switching element is provided between the output of the power supply line 50 and the switching circuit 125 supplies an input voltage V _in to the switching power supply unit 12. The switching circuit 125 is also provided with a diode or a synchronous transistor that commutates the output current.
The smoothing circuit 126 smoothes the output of the switching circuit 125 to form a predetermined DC voltage, and outputs this DC voltage to the power supply line 20.
Since the configuration and operation of the drive circuit 124, the switching circuit 125, and the smoothing circuit 126 are the same as those of a normal switching power supply, detailed description thereof will be omitted.

Since the switching elements in the switching circuit are switched by the square wave shown in FIG. 5A, switching noise as indicated by reference numerals N _mf and N _mr is superimposed on the output voltage of the smoothing circuit 126 in FIG. Will do. Since the switching noises N _mf and N _mr are respectively generated at the positions of the front edge and the rear edge of the square wave shown in FIG. 5A, the frequency corresponding to the switching frequency (f ₁ or f ₂ ) of the oscillation unit 120 is set. Have.
The voltage V _in supplied from the power supply line 50 shown in FIG. 3 is an output voltage of the battery 60 shown in FIG.

  As shown in FIG. 4, the distributed power supply 30 includes a detection circuit 31, a timer 32 register 33, a time comparison / determination circuit 34, a data demodulation circuit 35, a switching control circuit 36, and a switching power supply unit 37. The elements 31 to 37 are operated by the voltage of the power supply line 20 (output voltage of the main power supply 10) given through a regulator or the like (not shown).

  Switching noise (see FIG. 5D) superimposed on the DC voltage on the power supply line 20 is input to the detection circuit 31. The detection circuit 31 binarizes the switching noise after detecting the envelope. Accordingly, the detection circuit 31 outputs a pulse signal corresponding to the switching noise.

The timer 32 starts from the time when a pulse signal corresponding to the switching noise N _mf shown in FIG. 5D is input from the detection circuit 31, and the time division switching band shown in FIG. 5 (the main power supply 10 and the distributed power supply 30 are spaced apart from each other). Time corresponding to the period of time when the switching operation is sequentially started (the switching element is turned on) and the input / output dependent switching band (the main power supply 10 and the distributed power supply 30 are switched according to the set cycle, set voltage, load, etc. A time T _m (hereinafter referred to as “the period during which the operation is performed”) and a time corresponding to all or a part of the time corresponding to the switching inhibition band (the period during which the switching operation of the main power supply 10 and the distributed power supply 30 is prohibited). Time). Then, the output pulse signal of the detection circuit 31 at the time excluding the mask time is extracted as a pulse signal corresponding to the switching noise N _mf .

The timer 32 also measures the generation cycle of the extracted pulse signal, that is, the generation cycle of the switching noise N _mf corresponding to the switching cycle of the main power supply 10. The switching cycle of the main power supply 10 is measured by counting clock signals during a period in which two pulse signals are extracted. Therefore, the timer 32 has a built-in clock signal generator and a counter that counts its output signal. The count value of the counter is written in the register 33 as information indicating the switching cycle of the main power supply 10.

The counter is reset when the count value is recorded in the register 33. Therefore, the register 33 is updated so that the latest switching cycle information is always recorded.
On the other hand, the timer 32 has a delay time Δti (CH1
The distributed power source 30-1 counts Δt1 and the CH2 distributed power source 30-1 counts Δt2), and outputs a timing end signal to the switching control circuit 36. The delay time Δt
1 and Δt2 are set to satisfy Δt1 <Δt2.

The time comparison / determination circuit 34 compares the count value recorded in the register 33 with a predetermined threshold, and the switching cycle of the main power supply 10 is T1 (= 1 / f ₁ ), T2 (= 1 / f ₂ ). It is determined which one. For example, data “1” is output when it is determined that the cycle is T1, and data “0” is output when it is determined that the cycle is T2.

  The data demodulating circuit 35 forms parallel data indicating one piece of communication data (for example, 1 byte data) based on the serial data given from the time comparison / determination circuit 34, and the parallel data is used as command data for the distributed power supply 30 ( The data is given to the switching control circuit 36 as data for commanding start, stop, output voltage switching, and the like. The communication data is recognized by collating the serial data with a plurality of predetermined one-byte data arrangement patterns. For example, when the serial data is “1” 1 “0”, certain communication data (command data) is recognized from the data arrangement pattern of each bit.

The switching control circuit 36 switches the switching power supply unit based on the time measurement end data of the delay time Δti given from the timer 32, the period data given from the time comparison determination circuit 34, and the command data given from the data demodulation circuit 35. 32 is controlled.
The switching power supply unit 37 has the same configuration as the switching power supply unit 12 shown in FIG.

Incidentally, the switching noise of the switching power supply unit 12 of the main power supply 10 is superimposed on the power supply line 20 connecting the main power supply 10 and the distributed power supply 30 as described above. On the other hand, when the switching power supply unit of the distributed power supplies 30-1 and 30-2 performs a switching operation, the switching noise generated by the operation is caused to pass through the circuit pattern of the distributed power supplies 30-1 and 30-2, particularly the ground pattern. It goes around the power supply line 20 (see FIG. 5D).
Instead of inputting the voltage V _{in of the} battery 60 (voltage on the power supply line 50) to the switching power supply unit 37 of the distributed power supply 30, the voltage of the power supply line 20 may be input. In this case, the switching noise of the distributed power supply 30 is directly superimposed on the power supply line 20.
When the switching noise of the switching power supply unit 37 that wraps around (or is superimposed on) the power supply line 20 overlaps with the switching noise of the main power supply 10, the noise peak level may increase and adversely affect peripheral circuit elements. There is.
In view of this, the power supply system according to the present embodiment avoids an overlap between the switching noise of the main power supply 10 and the switching noise of the distributed power supplies 30-1 and 30-2 in the power supply line 20. Operates to be distributed.

Hereinafter, the above operation will be described in detail.
In the power supply system of the present embodiment, the overlap of the switching noise is avoided by delaying the start point of the switching cycle of the distributed power source 30-i (i = 1 to n) with respect to the start point of the switching cycle of the main power source 10. To do.
As switching periods of the main power supply 10 and the distributed power supply 30, two types of T1 and T2 (T2> T1) are used.

Before starting the system, the switching power supply unit 12 of the main power supply 10 stops the switching operation, so that no DC voltage is output to the power supply line 20. For this reason, each of the distributed power supplies 30-1 and 30-2 connected to the power supply line 20 is in a non-power-feeding state and is suspended.
When the system is activated, activation command data (1 byte data composed of “0”) is output from the host 40 to the main power supply 10. Accordingly, the switching power supply unit 12 of the main power supply 10 switches at the switching cycle T1, and thus a DC voltage having a predetermined value in which the switching noise of the cycle T1 is superimposed on the power supply line 20 is output. FIG. 6A shows the switching operation of the main power supply 10 when the system is started.

  When the DC voltage is supplied to the distributed power supply 30-i (i = 1, 2), each of the components 31 to 35 performs the above-described operation. When the activation command data is input from the data demodulating circuit 35 to the switching control circuit 36 of the distributed power supply 30-i, the switching control circuit 36 controls the switching power supply unit 37 to start from the switching cycle of the main power supply 10. The switching power supply unit 37 is switched in the switching period T1 delayed by the delay time Δti.

  That is, at the time of starting the system, as shown in FIGS. 6B and 6C, the first switching cycle of the distributed power supply 30-1 (CH-1) and the distributed power supply 30-2 (CH-2) ( T1) is delayed from the switching cycle of the main power supply 10 by time Δt1 and time Δt2, respectively.

Next, the case where the distributed power supply 30-i detects the switching noise of the main power supply 10 in the second and subsequent cycles will be described.
As shown in FIG. 9A, if the delay time Δti is Δti = Δti _min (= T2−T1), as shown in FIG. 9B, the distributed power source of CHi delayed by Δti _min is used. The end point of the switching cycle coincides with the end point of the switching cycle of the main power supply 10.

On the other hand, the relationship between the switching periods T1 and T2 and the delay time Δti
T1 + Δti>T2> T1 (1)
In such a case, the next switching noise of the main power supply 10 can always be detected before the switching cycle of the distributed power supply 30 ends. The operation rule of the distributed power supply 30 under this relationship is as follows.
When the distributed power source 30-i detects the switching noise of the main power source 10 in the second cycle and thereafter, the switching control circuit 36 determines the elapsed time from the previous switching noise given from the register 33 (the switching cycle of the main power source 10 is changed). The next switching period is determined to be T1 or T2. That is, when the elapsed time corresponds to the cycle T1, the next switching cycle is determined as T1, and when the elapsed time corresponds to the cycle T2, the next switching cycle is determined as T2.

When the next cycle is determined as T1, the next switching cycle is started with a delay of the delay time Δti from the time point when the switching noise of the main power supply 10 is detected (see FIGS. 7 and 8). In this case, even if the previous switching cycle has not ended after the delay time Δti has elapsed, the next switching cycle is forcibly started. This is because the main power supply 10 and the distributed power supply 30-i are not out of synchronization.
On the other hand, when the next switching cycle is determined as T2, the next cycle is started with the end of the current switching cycle (see FIGS. 7 and 8).
In addition, when the switching noise of the main power supply 10 cannot be detected, the switching operation of the switching power supply unit 37 is stopped. Thereafter, when switching noise is detected, the operation is resumed at the switching cycle T1 in the same manner as at startup.

Next, the relationship between the switching periods T1 and T2 and the delay time Δti is
T2> T1 + Δti> T1 (2)
The case where it is set as follows will be described. In this case, the next switching noise of the parent is not always detected before the switching cycle of the distributed power supply 30 ends. The operating rules of the distributed power supply 30-i under this relationship are as follows.

The operation at the time of starting the system is the same as when the relationship (1) is set. In the second and subsequent cycles, when the switching cycle of the main power supply 10 is T1, the distributed power supply 30-i performs the following operation.
a. When the next switching noise of the main power source 10 is detected before the switching cycle of the distributed power source 30-i is completed, the next switching cycle consisting of T1 is started when Δti time has elapsed from the detection time. In this case, even if the current switching cycle has not ended after the delay time Δti has elapsed, the next switching cycle is forcibly started. This is because the main power supply 10 and the distributed power supply 30-i are not out of synchronization.
b. If the next switching noise of the main power supply 10 cannot be detected by the end of the cycle of the distributed power supply 30-i, the next switching cycle consisting of T2 is started.

On the other hand, after the second cycle, when the switching cycle of the main power supply 10 is T2, the distributed power supply 30-i performs the following operation.
a. When the switching noise of the main power source 10 is detected only once during the switching cycle of the distributed power source 30-i, the next switching cycle consisting of T2 is started when the own switching cycle is completed.
b. When the switching noise of the main power source 10 is detected twice during the switching cycle of the distributed power source 30-i, the next switching cycle consisting of T1 is started when Δti time has elapsed from the second detection time. In this case, even if the current switching cycle has not ended after the delay time Δti has elapsed, the next switching cycle is forcibly started. This is because the main power supply 10 and the distributed power supply 30-i are not out of synchronization.
c. When the switching noise of the main power supply 10 cannot be detected even once during the switching cycle of the distributed power supply 30-i, the switching operation is stopped. Thereafter, when switching noise is detected, the operation is resumed at the switching cycle T1 in the same manner as at startup.

By the way, the data demodulating circuit 35 monitors communication data from the host 40 transmitted via the power supply line 20 during the switching operation as described above, and sends command data based on the communication data to the switching control circuit 36. Output. For example, when the command data instructs switching of the output voltage, the switching control circuit 36 changes the reference voltage V _ref (see FIG. 3) of the switching power supply unit 37 to change the switching power supply unit. 37 output voltage is switched.

As is clear from the above description of the operation, the delay time in the second and subsequent cycles is Δt1, Δ
It does not necessarily match t2. Therefore, the time division switching band is defined in consideration of the maximum delay time assumed in advance.
On the other hand, the input / output dependent switching band is set as follows. That is, when the host 40 outputs command data for changing the output voltage of the distributed power source 30-i, the switching power source 37 of the distributed power source 30-i changes the command data by changing the ON / OFF duty ratio in switching. The output voltage corresponding to is realized. Further, the distributed power source 30-i changes the duty ratio in order to maintain the target voltage when the output voltage fluctuates due to fluctuations in the load connected to the output. The change in the duty ratio causes a change in the rear edge of the signals shown in FIGS. 5B and 5C, in other words, a change in the generation time of the switching noise in FIG. 5D synchronized with the rear edge. The input / output dependent switching band is set in anticipation of changes in switching noise generation time.
The switching prohibition band is set for the purpose of ensuring a time region in which neither the switching power supply unit 12 of the main power supply 10 nor the switching power supply unit 37 of the distributed power supply 30 performs switching.

According to the power supply system according to the present embodiment that operates as described above, the switching noise of the switching power supply unit 12 provided in the main power supply 10 and the switching noise of the switching power supply 37 of each distributed power supply 30-i are distributed. The overlap of the former switching noise and the latter switching noise is avoided. As a result, an increase in the peak level of switching noise is prevented, and adverse effects on peripheral circuit elements due to the switching noise are suppressed.
Moreover, since the switching timing of the switching power supply unit 12 of the main power supply 10 and the switching timing of the switching power supply unit 37 of each distributed power supply are synchronized, the main power supply using the switching noise of the switching power supply of the main power supply and each Reliability of communication with the distributed power source is improved.

1 is a block diagram showing an embodiment of a power supply system according to the present invention. It is a block diagram which shows the structural example of a main power supply. It is a circuit diagram which shows the structural example of a switching power supply part. It is a block diagram which shows the structural example of a distributed power supply. It is a chart which shows the operation waveform and switching noise of the switching power supply of a main power supply and a distributed power supply. It is a chart which shows the switching period at the time of starting of a main power supply and each distributed power supply. It is a chart which shows an example of change of a switching cycle after starting of a main power supply and each distributed power supply. It is a chart which shows the other example of a change of a switching cycle after starting of a main power supply and each distributed power supply. It is a chart for demonstrating the relationship between a switching period and delay time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main power supply 11 Modulation control part 12 Switching power supply part 20 Power supply line 30-1, 30-2 Distributed power supply 31 Detection circuit 31
32 Timer 33 Register 34 Time Comparison Judgment Circuit 35 Data Demodulation Circuit 36 Switching Control Circuit 37 Switching Power Supply Unit

Claims (6)

A main power supply having a first switching power supply capable of changing the switching period to first and second switching periods;
A plurality of distributed power sources each having a second switching power source connected to the main power source and operating based on an output of the main power source, and each of the distributed power sources,
Switching noise detecting means for detecting switching noise generated by the first switching power supply of the main power supply;
Switching period detecting means for detecting a switching period of the main power source based on the switching noise;
Switching period determining means for determining whether the switching period of the main power source is the first switching period or the second switching period;
Power control means for controlling the second switching power supply so that the switching period becomes the same as the switching period of the main power supply, and the switching period is delayed from the switching period of the main power supply. With
A power supply system, wherein the magnitudes of the delays in the respective distributed power supplies are made different.   The switching noise detection means includes detection means for detecting the switching noise and converting it to a corresponding pulse signal, and configured to detect the switching noise based on the pulse signal. Item 2. The power supply system according to Item 1.   2. The switching noise detecting means is configured to time a predetermined mask time after detecting the switching noise, and to detect the next switching noise after the time measurement of the mask time is completed. The described power supply system. The distributed power supply system according to claim 1, wherein the main power supply includes modulation means for modulating the switching frequency of the first switching power supply based on predetermined communication data. Each of the distributed power sources includes data demodulating means for demodulating the communication data based on the switching frequency of the first switching power supply modulated by the modulating means based on the switching period determined by the switching period determining means. The power supply system according to claim 4. 6. The power supply system according to claim 4 or 5, wherein the communication data is command data for controlling each of the distributed power supplies.

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