JP2007236047A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch the current supply capacity quickly by detecting the operation mode surely even if a load circuit does not supply a mode switch signal in a power supply system constituted by connecting a plurality of power supply circuits in parallel. <P>SOLUTION: The power supply system comprises a first power supply circuit 10, a second power supply circuit 20 having a current supply capacity smaller than that of the first power supply circuit and having such output characteristics as the output voltage drops when the output current exceeds a predetermined value, an output synthesizing circuit 30 for supplying at least one of the output voltage from the first power supply circuit and the output voltage from the second power supply circuit to the output terminal, a circuit 50 for detecting the output voltage supplied to the output terminal, and a mode switch circuit 60 for making a transition from a waiting mode to a normal operation mode by activating the first power supply circuit when the output voltage becomes smaller than a first set value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply system configured by connecting a plurality of power supply circuits in parallel, and in particular, configured by connecting a first power supply circuit for a normal operation mode and a second power supply circuit for a standby mode in parallel. It relates to the power system.

  In recent years, electronic devices having a standby mode are increasing for energy saving measures. In such an electronic device, in the standby mode, power consumption is reduced by reducing a current flowing in a circuit serving as a load of the power supply circuit.

  However, for example, when a power supply circuit such as a switching regulator is designed so that the power conversion efficiency increases when the load current is large, unnecessary current consumption occurs when the load current is small, and the power conversion efficiency is reduced. It gets smaller. Therefore, if current is supplied to the load circuit in the standby mode using a power supply circuit having sufficient current supply capability in the normal operation mode, the overall power consumption cannot be reduced much because of the current consumption in the power supply circuit. . Therefore, it is required for the power supply circuit to reduce power consumption in the standby mode.

  In the power supply circuit, in order to switch the operation between the normal operation mode and the standby mode, a mode switching signal is generally used. Therefore, the load circuit must supply a mode switching signal to the power supply system. On the other hand, in order to omit the supply of the mode switching signal, the operation mode of the load circuit is sensed by detecting the load current.

  However, when the operation of the power supply circuit is completely stopped in the standby mode, the detected load current becomes zero, and the power supply circuit and the load circuit cannot shift to the normal operation mode. Further, when the power supply voltage applied to the load circuit in the standby mode is smaller than that in the normal operation mode, there is a possibility that the operation of the load circuit may be hindered. Furthermore, when the load circuit includes a safety protection circuit, the safety protection circuit may operate as soon as the standby mode is shifted to the normal operation mode, and the operation of the load circuit may be stopped.

  In order to reduce the power consumption of the power supply circuit in the standby mode, the power supply system may be configured by connecting the first power supply circuit for the normal operation mode and the second power supply circuit for the standby mode in parallel. It has been broken. In such a power supply system, power consumption in the standby mode can be reduced by making the current supply capability of the second power supply circuit smaller than the current supply capability of the first power supply circuit.

  As a related technique, the following Patent Document 1 discloses a vehicle power supply system capable of reducing unnecessary dark current by performing highly efficient power supply. This power supply system converts an input DC input voltage into a DC output voltage lower than the DC input voltage and supplies it to a load, and a constant supply converter connected in parallel to the DC converter. A standby current supply converter that converts the output voltage to be supplied to the load, and a controller that switches and controls the driving of the constant supply converter and the standby current supply converter according to the load current flowing through the load and the DC input voltage. I have.

  In Patent Document 1, when the current detection sensor detects that the load current has dropped below a predetermined value, the controller stops driving the constant supply converter and starts driving the standby current supply converter. When the current detection sensor detects that the load current has increased to a predetermined value or more, the controller stops driving the standby current supply converter and starts driving the constant supply converter.

However, when shifting from the standby mode to the normal operation mode, since the impedance of the load circuit decreases, the output voltage of the power supply system also decreases, and an increase in the load current cannot be detected or the detection is delayed. There is a risk of As described above, when the operation mode of the load circuit is determined based only on the load current, there is a problem that malfunction or delay is likely to occur.
Japanese Patent Laying-Open No. 2004-201389 (1-2, page 5, FIG. 2)

  Accordingly, in view of the above points, the present invention provides a power supply system configured by connecting a plurality of power supply circuits in parallel, even if the load circuit does not supply a mode switching signal to the power supply system. It is an object of the present invention to detect the operation mode of a circuit with certainty and to quickly switch the current supply capability to a load circuit.

  In order to solve the above-described problem, a power supply system according to one aspect of the present invention includes a first power supply circuit having a first current supply capability and a second current supply capability smaller than the first current supply capability. A second power supply circuit having an output characteristic in which the output voltage decreases when the output current exceeds a predetermined value, and at least one of the output voltage of the first power supply circuit and the output voltage of the second power supply circuit. The output synthesis circuit that supplies one to the output terminal, the output voltage detection circuit that detects the output voltage supplied to the output terminal, and the output voltage supplied to the output terminal based on the detection result of the output voltage detection circuit And a mode switching circuit that shifts from the standby mode to the normal operation mode by activating the first power supply circuit when it becomes smaller than the set value of 1.

  According to the present invention, a second power supply circuit having a current supply capability smaller than that of the first power supply circuit and an output characteristic in which the output voltage decreases when the output current exceeds a predetermined value is supplied to the output terminal. By controlling the first and second power supply circuits based on the output voltage and the output current, the power supply system operates in the operation mode of the load circuit even if the load circuit does not supply a mode switching signal to the power supply system. Can be detected reliably, and the current supply capability to the load circuit can be switched quickly.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a block diagram showing the configuration of the power supply system according to the first embodiment of the present invention. This power supply system is configured by connecting in parallel two power supply circuits that input an AC voltage and output a DC voltage.

  As shown in FIG. 1, the power supply system includes a first power supply circuit 10 having a first current supply capability (for example, 24V, 10A), and a second current supply capability smaller than the first current supply capability. (For example, 24V, 1A), the second power supply circuit 20 having an output characteristic in which the output voltage decreases when the output current exceeds a predetermined value, the output voltage V1 of the first power supply circuit 10 and the second An output synthesis circuit 30 for supplying at least one of the output voltages V2 of the power supply circuit 20 to the output terminal, an output current detection circuit 40 for detecting the output current I supplied to the output terminal, and an output terminal. An output voltage detection circuit 50 for detecting the output voltage and a mode switching circuit 60 for switching between the standby mode and the normal operation mode.

In the present embodiment, switching power supply circuits are used as the first and second power supply circuits 10 and 20. The first power supply circuit 10 includes a power conversion circuit 11 such as a switching regulator, a converter or a PFC (power factor controller) circuit that performs a switching operation using a switching element such as a transistor, And a control circuit 12 that generates a drive signal S _D 1 for driving the switching element. Similarly, the second power supply circuit 20 generates a power conversion circuit 21 that performs a switching operation using a switching element such as a transistor, and a control that generates a drive signal S _D 2 for driving the switching element of the power conversion circuit 21. Circuit 22.

  FIG. 2 is a diagram illustrating a configuration example of the first and second power supply circuits illustrated in FIG. 1. This switching power supply circuit includes a rectifying / smoothing circuit 71 connected to AC voltage input terminals 1 and 2, a transformer 80 that boosts or steps down an AC voltage on the primary side, and outputs it to the secondary side, and a primary of the transformer A switching element 72 that is connected in series to the side winding 81 and flows a current to the primary winding of the transformer according to a pulsed drive signal, and a primary current that detects a current flowing to the primary winding 81 of the transformer And a detection circuit 73.

  Further, the switching power supply circuit includes a diode 91 that half-wave rectifies the voltage generated in the secondary winding 82 of the transformer, a capacitor 92 that smoothes the rectified voltage and supplies the rectified voltage to the output terminals 3 and 4; It has a secondary side voltage detection circuit 93 that detects the output voltage at the output terminals 3 and 4, and a control circuit 74 that sets the pulse width of the drive signal.

  The detection result of the secondary side voltage detection circuit 93 is transmitted to the control circuit 74 as an optical signal. Thereby, the detection result on the secondary side can be transmitted to the primary side while maintaining isolation between the primary side and the secondary side of the transformer 80.

  The rectifying / smoothing circuit 71 includes, for example, a diode bridge and a capacitor. The AC voltage applied between the input terminal 1 and the input terminal 2 is full-wave rectified by the diode bridge and smoothed by the capacitor.

  The transformer 80 includes a magnetic core 84, a primary side winding 81, a secondary side winding 82 wound around the core 84, and an auxiliary winding 83 for generating an internal power source. Yes. Here, if the number of turns of the primary side winding 81 is N1 and the number of turns of the secondary side winding 82 is N2, when there is no loss, the step-up ratio between the primary side and the secondary side is N2 / N1. A dot symbol attached to the transformer 80 indicates the polarity of the winding.

  Generally, in a switching power supply, as a power transmission method from the primary side to the secondary side of the transformer, a forward method in which power is transmitted from the primary side to the secondary side when the switching element is turned on, and the switching element is turned off. Sometimes there is a flyback system that transmits power from the primary side to the secondary side. The present invention can be applied to either of them, but in this embodiment, a flyback method will be described as an example.

  In the flyback type switching power supply as shown in FIG. 2, the primary side winding 81 and the secondary side winding 82 of the transformer have a reverse polarity relationship, and while the switching element is on, The primary side current of the transformer 80 increases, but the secondary side current does not flow because the secondary side of the transformer 80 is reverse-biased by a diode. The transformer 80 stores energy in the core 84 when the switching element is on.

  Next, when the switching element is turned off, the magnetic field tries to maintain the current, so that the voltage polarity of the transformer 80 is reversed and a current flows on the secondary side of the transformer 80. The secondary current of the transformer 80 flows to the capacitor 92 through the diode 91 connected in series, and the capacitor 82 is charged, thereby generating a DC output voltage between the output terminal 3 and the output terminal 4.

  FIG. 3 is a diagram showing output current-output voltage characteristics (secondary current-secondary voltage characteristics) of the second power supply circuit shown in FIG. The control circuit 74 shown in FIG. 2 determines whether or not the primary side current detected by the primary side detection circuit 73 has exceeded a threshold value. The pulse width of the drive signal is controlled so as to perform the voltage stabilization operation.

  As shown by an arrow (1) in FIG. 3, the secondary side current increases, the primary side current reaches the threshold value at point A, and the primary side current exceeds the threshold value. Then, the control circuit 74 keeps the pulse width of the drive signal constant and stops the constant voltage stabilization operation.

  Thereafter, the secondary side voltage does not become constant, and when the secondary side current increases according to the impedance state of the load circuit, the secondary side voltage gradually decreases as shown by an arrow (2) in FIG. Go. However, if the secondary side voltage is equal to or higher than the threshold value and the secondary side current is maintained even if the secondary side voltage decreases as between the points A and B, the switching power supply circuit Can be considered to be within the allowable operating range. For example, an inductive load is driven by a current, so that it can operate even if the power supply voltage drops somewhat.

  Referring to FIG. 1 again, the output synthesis circuit 30 includes a diode D1 to which the output voltage V1 of the first power supply circuit 10 is supplied and a diode D2 to which the output voltage V2 of the second power supply circuit 20 is supplied. Is done. The diodes D1 and D2 are connected to each other in a wired OR manner, and supply the higher one of the output voltage V1 of the first power supply circuit 10 and the output voltage V2 of the second power supply circuit 20 to the output terminal.

The output voltage detection circuit 50 compares the resistances R1 and R2 that divide the output voltage supplied to the output terminal and the detection potential V _DET 1 obtained by the voltage division with the reference potential V _REF 1, thereby providing the output terminal. And a comparator 51 that determines whether the supplied output voltage is larger or smaller than the first set value.

The output current detection circuit 40 includes a resistor R1 inserted between the output synthesis circuit 30 and the output terminal, a potential difference detection circuit 41 that detects a potential difference generated at both ends of the resistor R1, and a detection potential V of the potential difference detection circuit 41. Comparator 42 that compares _DET 2 with reference potential V _REF 2 and determines whether the output current supplied to the output terminal is larger or smaller than the second set value.

The mode switching circuit 60 includes, for example, an RS flip-flop 61 to which an output signal from the output current detection circuit 40 and an output signal from the output voltage detection circuit 50 are supplied. RS flip-flop 61, together with the signal supplied to the set terminal S when activated to a high level, and outputs the mode switching signal S _M of the high level from the non-inverting output terminal Q represents a normal operating mode, the inverting output and outputs an inverted mode switching signal S _M bar low level from the terminal Q bar. Further, the RS flip-flop 61, the signal supplied to the reset terminal R is activated to a high level, and outputs the mode switching signal S _M of the low level indicating the standby mode from the non-inverting output terminal Q, the inverting and outputs an inverted mode switching signal S _M bar high-level from the output terminal Q bar.

  Next, the operation of the power supply system according to the present embodiment will be described with reference to FIGS. FIG. 4 is a waveform diagram for explaining the operation of the power supply system according to this embodiment. As shown in FIG. 4, first, in the standby mode, the first power supply circuit 10 is deactivated, and the output voltage V1 has a low value (for example, 0 V). Is activated, and its output voltage V2 has a high value (for example, 24V).

  Next, when the load circuit shifts from the standby mode to the normal operation mode and the load current increases, the output current I of the power supply system also increases. Accordingly, the output voltage V2 of the second power supply circuit 20 decreases, The output voltage supplied to the output terminal also decreases. When the output voltage supplied to the output terminal becomes smaller than the first set value, the output voltage of the output voltage detection circuit 50 is activated from the low level to the high level, and the RS flip-flop 61 of the mode switching circuit 60 is set. Is done.

As a result, the RS flip-flop 61 outputs a high level mode switching signal S _M and a low level inversion mode switching signal S _M bar. As a result, the first power supply circuit 10 is activated and its output voltage V1 becomes a high value (for example, 24V), the second power supply circuit 20 is deactivated, and its output voltage V2 becomes a low value ( For example, the power supply system shifts from the standby mode to the normal operation mode. In this way, the operation mode can be switched quickly. When switching the operation mode, it is desirable to suppress an excessive decrease in the output voltage so that the fluctuation range of the output voltage is within about 5%.

  Furthermore, when the load circuit shifts from the normal operation mode to the standby mode and the load current decreases, the output current I of the power supply system also decreases. When the output current supplied to the output terminal becomes smaller than the second set value, the output voltage of the output current detection circuit 40 is activated from low level to high level, and the RS flip-flop 61 of the mode switching circuit 60 is reset. Is done.

As a result, the RS flip-flop 61 outputs a low level mode switching signal S _M and a high level inversion mode switching signal S _M bar. As a result, the first power supply circuit 10 is deactivated and its output voltage V1 becomes a low value (for example, 0V), and the second power supply circuit 20 is activated and its output voltage V2 becomes a high value ( For example, the power supply system shifts from the normal operation mode to the standby mode.

  In the above description, the operation of the second power supply circuit 20 is stopped in the normal operation mode. However, the operation of the second power supply circuit 20 may be continued in the normal operation mode. In that case, by setting the output voltage V1 of the first power supply circuit 10 to a value higher than the output voltage V2 of the second power supply circuit 20, a current flows from the second power supply circuit 20 to the output terminal in the normal operation mode. No longer flows. Alternatively, by setting the output voltage V1 of the first power supply circuit 10 and the output voltage V2 of the second power supply circuit 20 to the same value, the first and second power supply circuits 10 and 20 are operated in parallel. Also good.

Next, a second embodiment of the present invention will be described.
FIG. 5 is a block diagram showing a configuration of a power supply system according to the second embodiment of the present invention.
In the second embodiment, a second power supply circuit 100 including a battery 101 and a resistor R4 is used instead of the second power supply circuit 20 shown in FIG. The other points are the same as in the first embodiment. When the internal resistance of the battery 101 is large, the resistor R4 can be omitted.

  In the power supply system configured as described above, when the load circuit shifts from the standby mode to the normal operation mode and the load current increases, the output current I of the power supply system also increases. The output voltage V2 decreases, and the output voltage supplied to the output terminal also decreases. As described in the first embodiment, when the output voltage supplied to the output terminal becomes smaller than the first set value, the output voltage of the output voltage detection circuit 50 is activated from the low level to the high level. Then, the RS flip-flop 61 of the mode switching circuit 60 is set.

Thus, RS flip-flop 61 outputs a mode switching signal S _M of the high level. As a result, the first power supply circuit 10 is activated and its output voltage V1 becomes a high value (for example, 24 V), and the power supply system also shifts from the standby mode to the normal operation mode.

  Even in the normal operation mode, the operation of the second power supply circuit 20 is not stopped, but by setting the output voltage V1 of the first power supply circuit 10 to a value higher than the output voltage V2 of the second power supply circuit 20, No current flows from the second power supply circuit 20 to the output terminal.

  Furthermore, when the load circuit shifts from the normal operation mode to the standby mode and the load current decreases, the output current I of the power supply system also decreases. When the output current supplied to the output terminal becomes smaller than the second set value, the output voltage of the output current detection circuit 40 is activated from low level to high level, and the RS flip-flop 61 of the mode switching circuit 60 is reset. Is done.

Thus, RS flip-flop 61 outputs a mode switching signal S _M of the low level. As a result, the first power supply circuit 10 is deactivated, and the output voltage V1 becomes a low value (for example, 0 V), and the power supply system also shifts from the normal operation mode to the standby mode.

  The present invention can be used in a power supply system configured by connecting a plurality of power supply circuits in parallel.

It is a block diagram which shows the structure of the power supply system which concerns on the 1st Embodiment of this invention. It is a figure which shows the structural example of the 1st and 2nd power supply circuit shown in FIG. It is a figure which shows the output current-output voltage characteristic of the 2nd power supply circuit shown in FIG. It is a wave form diagram for demonstrating operation | movement of the power supply system which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the power supply system which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Input terminal 3, 4 Output terminal 10 1st power supply circuit 11, 21 Power conversion circuit 12, 22 Control circuit 20 2nd power supply circuit 30 Output composition circuit 40 Output current detection circuit 41 Potential difference detection circuit 42, 51 Comparator DESCRIPTION OF SYMBOLS 50 Output voltage detection circuit 60 Mode switching circuit 61 RS flip-flop 71 Rectification smoothing circuit 72 Switching element 73 Primary side current detection circuit 74 Control circuit 80 Transformer 81 Primary side winding 82 Secondary side winding 83 Auxiliary winding 84 Core 91 Diode 92 Capacitor 93 Secondary side voltage detection circuit R1 to R4 Resistor D1, D2 Diode

Claims (7)

A first power supply circuit having a first current supply capability;
A second power supply circuit having a second current supply capability smaller than the first current supply capability and having an output characteristic in which an output voltage decreases when the output current exceeds a predetermined value;
An output synthesis circuit for supplying at least one of an output voltage of the first power supply circuit and an output voltage of the second power supply circuit to an output terminal;
An output voltage detection circuit for detecting an output voltage supplied to the output terminal;
Based on the detection result of the output voltage detection circuit, when the output voltage supplied to the output terminal becomes smaller than the first set value, the first power supply circuit is activated to normally return from the standby mode. A mode switching circuit for shifting to an operation mode;
A power supply system comprising: An output current detection circuit for detecting an output current supplied to the output terminal;
The mode switching circuit deactivates the first power supply circuit when an output current supplied to the output terminal becomes smaller than a second set value based on a detection result of the output current detection circuit. The power supply system according to claim 1, wherein the power supply system shifts from the normal operation mode to the standby mode.   The power supply system according to claim 1, wherein the mode switching circuit activates the second power supply circuit in a standby mode and deactivates the second power supply circuit in a normal operation mode. The second power circuit is
A transformer having a primary winding and a secondary winding;
A switching element connected in series to the primary winding of the transformer, and for passing a current to the primary winding of the transformer in accordance with a pulsed drive signal;
A primary side detection circuit for detecting a current flowing in the primary side winding of the transformer;
A secondary circuit for rectifying and smoothing a voltage generated in the secondary winding of the transformer;
A secondary side detection circuit for detecting a voltage rectified and smoothed by the secondary side circuit;
A control circuit for controlling the current flowing in the primary winding of the transformer by setting a pulse width in the drive signal based on the detection result of the primary detection circuit and the detection result of the secondary detection circuit When,
The power supply system according to claim 1, comprising:   The power supply system according to claim 1, wherein the second power supply circuit includes a battery.   The output voltage detection circuit compares the potential obtained by dividing the output voltage supplied to the output terminal with a first reference potential, whereby the output voltage supplied to the output terminal is set to the first setting. The power supply system of any one of Claims 1-5 which determines whether it is larger or smaller than a value. The output current detection circuit compares a potential obtained by detecting a potential difference between both ends of a resistor inserted between the output synthesis circuit and the output terminal with a first reference potential, thereby the output terminal The power supply system of any one of Claims 1-6 which determines whether the output current supplied to is larger or smaller than a 2nd setting value.

Images