JP2006081235A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device having a compact and space-saving active dummy circuit composed of only a few inexpensive parts.
A power conversion unit connected to a load unit to generate a predetermined output voltage, a dummy load arranged in parallel with a voltage output of the power conversion unit, and a switching element for controlling on / off of power feeding to the dummy load, A power supply device comprising: a coupling portion having an attachment / detachment mechanism for connecting the power supply device and the load portion; and a load voltage detection terminal for monitoring an input voltage of the load portion on the switching element. It is characterized by that.
[Selection] Figure 1

Description

  The present invention relates to an active dummy circuit that suppresses an increase in output terminal voltage when a power supply device such as a switching regulator is at a light load.

  As a prior art relating to an example configuration of an active dummy circuit that suppresses an overvoltage state of an output voltage caused by load fluctuation in a power supply device, for example, there is the following document.

Japanese Utility Model Publication No. 5-62189 JP-A-9-265328 Actual Kaihei 11-262255

  Patent Document 1 includes a constant voltage circuit and an active dummy circuit on the secondary side of the DC / DC converter, and compares the reference voltage generated by the constant voltage circuit with the secondary output voltage to detect a light load. In some cases, the active dummy circuit is switched.

  Patent Document 2 is a power supply device configured with a voltage monitoring circuit and a dummy load circuit on the output side of a power conversion circuit, and uses a control voltage signal of an error amplifier used for output voltage stabilization for active dummy circuit control. The effect of reducing the number of parts is obtained.

  Patent Document 3 is a power supply device configured by a voltage monitoring circuit and a dummy load circuit on the output side of a power conversion circuit, and a choke transformer in series with an output current is provided in the voltage monitoring circuit. When a light load is detected by a decrease in electromotive force induced on the secondary side of the choke transformer, a forced dummy load current is generated by acting on the active dummy circuit.

  FIG. 3 shows a configuration example of an active dummy circuit corresponding to, for example, Patent Document 1 as a representative of these prior arts.

  FIG. 3 shows an example of use of an active dummy circuit in a circuit composed of four blocks: a power conversion unit, a voltage monitoring unit, an active dummy unit, and a load unit. The power conversion unit includes a transformer T, a transistor Q that drives the primary side of the transformer T, a diode D that is inserted on the secondary side of the transformer T, and a capacitor C.

  The voltage monitoring unit is represented in the figure by assuming that the current detection resistor Rs is 1, the current source Vref is 2, and the voltage comparison circuit is 3.

  The active dummy part is composed of a switching element 4, a dummy resistor Rd (5), and a base resistor Rb (6). The switching element 4 is connected to the determination signal S1 of the voltage comparison circuit 3 at the base using a PNP transistor. Moreover, the load part 10 is comprised by the load 8 couple | bonded with the output terminal of the power converter.

  Next, the operation of the active dummy circuit shown in FIG. 3 will be described.

  The current pulse driven on the primary side of the transformer T by switching the transistor Q generates a voltage having a ratio corresponding to the winding ratio of the transformer T on the secondary side of the transformer T, and the interaction between the diode D and the capacitor C Rectified. As a result, a predetermined voltage Vcc is output to the secondary side of the transformer T, that is, the output end of the power conversion unit.

  The load unit 10 connected to the output terminal of the power conversion unit includes a load 8 and is applied with a predetermined voltage Vcc. At this time, the current generated on the secondary side of the power converter and passing through the load 10 is indicated by a load current I. The load current I varies depending on the impedance value of the connected load unit 10.

  On the other hand, since the current detection resistor Rs (1) constituting the voltage monitoring unit is inserted in the path of the load current I, a voltage drop value Vrs proportional to the load current I appears at both ends thereof. The voltage comparison circuit 3 compares the voltage drop value Vrs with a current source Vref value that provides a predetermined reference voltage value.

  When the voltage drop value Vrs is Vrs <Vref, the voltage comparison circuit 3 outputs a level low signal as the determination signal S1. When the voltage drop value Vrs is Vrs> Vref, the voltage comparison circuit 3 outputs a level high signal as the determination signal S1.

  When level high is input to the determination signal S1, the switching element 4 constituting the active dummy portion is in an off state. For this reason, the switching element 4 is not conducted, and the dummy current Id does not flow through the dummy resistor Rd (5) on the collector side.

  When the low level is input to the determination signal S1, the switching element 4 constituting the active dummy portion is turned on. For this reason, the switching element 4 becomes conductive and the dummy current Id flows through the dummy resistor Rd (5) on the collector side.

  Therefore, when the load unit 10 varies and the load current I decreases from a predetermined value, the voltage drop value Vrs falls below the Vref value. As a result, the determination signal S1 becomes a level low output, and the switching element 4 is turned on.

  As a result, when the state of the load unit 10 varies and the load current I decreases below a predetermined value, the dummy current Id is supplied to the dummy resistor Rd (5) of the active dummy unit instead.

  That is, by compensating for the decrease in the load current I by the dummy current Id generated by the active dummy unit, the output on the secondary side of the power conversion unit is stabilized and the fluctuation of the voltage Vcc is suppressed.

  As described above, in the operation of a general active dummy circuit, at least three functional block units, that is, a power conversion unit, a voltage monitoring unit, and an active dummy unit are required for the connected load unit.

  However, as shown in the operation examples of the active dummy circuit shown in Patent Document 1 to Patent Document 3 described above, in addition to consuming a large area when mounting these components on a printed circuit board, There was a problem that the circuit was relatively complicated.

  Therefore, the problem to be solved by the present invention is to provide a power supply device including a compact and space-saving active dummy circuit which is constituted by only a few inexpensive parts.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
A power supply comprising: a power converter that is connected to a load unit to generate a predetermined output voltage; a dummy load that is arranged in parallel with the voltage output of the power converter; and a switching element that controls on / off of power supply to the dummy load In the apparatus, the switching element is provided with a load voltage detection terminal for monitoring an input voltage of the load section.

  The invention according to claim 2 is the power supply device according to claim 1, wherein the load voltage detection terminal is short-circuited with the power input terminal of the load portion when the connection portion is in the connected state.

  According to a third aspect of the present invention, in the power supply device according to the first and second aspects, the load voltage detection terminal is opened when the connecting portion is in a separated state.

  A fourth aspect of the present invention is the power supply apparatus according to the first aspect, wherein the switching element includes an emitter terminal, a collector terminal, and a base terminal.

  A fifth aspect of the present invention is the power supply apparatus according to the first to fourth aspects, wherein the load voltage detection terminal is connected to the base terminal.

  A sixth aspect of the present invention is the power supply apparatus according to the first to fifth aspects, wherein the dummy load portion is connected in series with the switching element.

According to a seventh aspect of the present invention, a power converter that is connected to a load unit and generates a predetermined output voltage, a dummy load that is arranged in parallel with the voltage output of the power converter, and on / off of power supply to the dummy load are controlled. A switching element that controls, and a switch that controls on / off of power feeding to the load unit,
In the power supply apparatus having the above-described configuration, the switching element is provided with a load voltage detection terminal for monitoring an input voltage of the load section.

  The invention according to claim 8 is the power supply device according to claim 7, wherein the load voltage detection terminal is short-circuited with the power input terminal of the load unit when the switch is set to power supply on, and when the power supply is set to off. It is characterized by being open.

  A ninth aspect of the present invention is the power supply apparatus according to the eighth aspect, wherein the switching element includes an emitter terminal, a collector terminal, and a base terminal.

  According to a tenth aspect of the present invention, in the power supply device according to the seventh to ninth aspects, the load voltage detection terminal is connected to the base terminal.

  An eleventh aspect of the present invention is the power supply apparatus according to any one of the seventh to tenth aspects, wherein the dummy load is connected in series with the switching element.

The present invention has the following effects.
According to the inventions of claims 1, 2, 3, 4, 5 and 6, conventionally, three functional blocks of a power conversion unit, a voltage monitoring unit and an active dummy unit are required as components for the load unit. By applying the present invention to the power supply apparatus, the active dummy circuit can be operated with a configuration including a power conversion unit, an active dummy unit, and a simple connection unit.

  According to the seventh, eighth, ninth, tenth and eleventh aspects of the present invention, there is provided a power supply apparatus that conventionally requires three functional blocks, ie, a power conversion unit, a voltage monitoring unit, and an active dummy unit, as components for the load unit. By applying the present invention, the active dummy circuit can be operated only by the power conversion unit and the active dummy unit.

  For this reason, the first effect brought about by the power supply device embodying the present invention is that the number of components is reduced and the mounting area of the printed circuit board is reduced. Further, it can be realized at a lower price than the conventional embodiment.

  The second effect is that the circuit is simple and simple, so that there are very few parameters to be considered at the time of design, such as part selection, constant determination, and temperature characteristic calculation. For this reason, the failure probability due to component deterioration is small and contributes to quality improvement, and also contributes to a significant reduction in work man-hours during design, maintenance operation, and operation tests at the time of shipment.

  The third effect is that no functional block equivalent to the voltage monitoring unit is required, so the load unit is disconnected on the secondary side even when the load unit is disconnected electrically or mechanically and the power supply unit is in no-load operation. Therefore, there is no need to take into account the situation such as the increase of the output voltage and the accompanying element destruction and the operation of the overvoltage protection circuit.

  As a fourth effect, when the load unit is electrically and mechanically connected and the power supply device returns to the load operation, the dummy current is forcibly turned off by directly acting on the active dummy unit. For this reason, the power consumed by the active dummy circuit during normal operation can be suppressed to a power consumption that is negligibly negligible in the base resistor Rb.

  Two embodiments of the power supply device having the above effects will be described with reference to the drawings.

  FIG. 1 is a configuration block diagram showing a first embodiment of a power supply device according to the present invention.

  FIG. 1 shows that the switching element 4 of the active dummy part does not operate when the power supply device of the first embodiment engages the connector 11 of the coupling part, and the dummy resistor Rd (5) does not consume any dummy power. The operation is explained.

  The power supply device of FIG. 1 includes an active dummy circuit and includes functional blocks of a power conversion unit, an active-dummy unit, and a connection unit. 1, components having the same symbols as those in FIG. 3 are components having the same function.

  The power conversion unit includes the same components as in FIG. 3, and includes a transformer T, a transistor Q that drives the primary side of the transformer T, a diode D that is inserted on the secondary side of the transformer T, and a capacitor C.

  The active dummy portion is composed of the same components as in FIG. 3 and the switching element 4 and the dummy resistor Rd are represented by 5. The switching element 4 uses a transistor and has a base portion connected to a load voltage detection terminal TP.

  Further, the base portion is connected to GND at the output end of the power conversion portion via a base resistor Rb. Moreover, the load part 10 is comprised with the load 8 electrically connected to the output terminal of the power converter part via the coupling part.

  The coupling portion is provided between the active dummy portion and the load portion, and is constituted by the connector 11 in the embodiment of FIG. The connector 11 includes a load voltage detection terminal TP in addition to the power supply Vcc and GND signal lines supplied to the load 8.

  The load voltage detection terminal TP is electrically connected to the Vcc signal line supplied to the load 8 in the load unit 10. Further, when the coupling portion is in the coupled state, it contacts the load voltage detection terminal TP described above.

  Further, the circuit components constituting the voltage monitoring unit required in the conventional example of FIG. 3 are not required in the example of the present invention of FIG.

  Next, the operation of the embodiment shown in FIG. 1 will be described.

  When the connector 11 is in the mating state, that is, in the coupling state, the power supply voltage Vcc supplied to the load 8 is also applied to the load voltage detection terminal TP. Since the connector 11 is in the mating state, the voltage Vcc is input to the load voltage detection terminal TP that contacts the load voltage detection terminal TP.

  At this time, in the switching element 4 constituting the active dummy portion, the switching element 4 is in an OFF state by being blocked by the potential barrier at the junction between the base and the emitter.

  That is, the power supply voltage Vcc is supplied to the emitter of the transistor of the switching element 4 constituting the active dummy part, while the load voltage detection terminal TP is connected to the base part of the switching element 4.

  For this reason, when the connector connector 11 is in the mating state, no potential difference is generated between the base and the emitter in the switching element 4, and therefore the dummy current Id does not flow through the dummy resistor Rd (5).

  On the other hand, when the connector 11 is in the separated state, that is, in the no-load state, the path of the voltage Vcc supplied to the load 8 is disconnected, and the load voltage detection terminal TP that is in contact with the load voltage detection terminal TP is electrically connected. An open state is entered.

  In the switching element 4, since the output voltage Vcc of the power converter is still applied to the emitter side, a potential difference of Vcc is generated between the open load voltage detection terminal TP and the base connected to the base. .

  As a result, in the switching element 4 constituting the active dummy portion, the base current Ib flows due to the potential difference generated between the base and the emitter.

  The base current Ib generated at this time is expressed by Ib = (Vcc−Vbe) / Rb, and the switching element 4 is turned on.

  Therefore, in the switching element 4 constituting the active dummy part, a voltage (Vcc-Vce) obtained by subtracting a voltage drop corresponding to the collector-emitter voltage Vce from the applied voltage Vcc of the emitter part is generated in the collector part, and the dummy resistor Rd Applied to both ends of (5).

  The dummy current Id generated at this time is expressed by Id = (Vcc−Vce) / Rd, and has an effect of consuming electric power with the dummy resistor Rd (5) instead of the load 8.

  That is, while the load unit is connected, while the load 8 is consuming the power generated by the power conversion unit, there is no power consumption by the dummy resistor Rd (5) which is a dummy load.

  On the other hand, while the load unit is separated and the load 8 does not consume the power generated by the power conversion unit, a predetermined voltage is applied to the dummy resistor Rd (5), which is a dummy load, and the dummy resistor Rd (5). Is consuming power instead of the load 8.

  FIG. 2 is a block diagram showing a configuration of a power supply device according to a second embodiment of the present invention.

  FIG. 2 shows an operation when the switching element 4 of the active dummy unit is activated when the power supply device of the second embodiment turns off the switch 13 and a predetermined dummy power is consumed by the dummy resistor Rd (5). Is explained.

  The power supply device of FIG. 2 which is Embodiment 2 is configured only by a power conversion unit and an active dummy unit in addition to the load unit 10. In FIG. 2, portions having the same symbols as those of the components in FIG. 1 are components having the same functions, and thus description thereof is omitted.

  The power supply device according to the second embodiment does not have the connector 11 corresponding to the coupling portion provided in the first embodiment. Instead, the load unit 10 includes a switch 13. That is, the second embodiment shows an example in which the power supply device and the load unit are operated without being separated while being combined as an integrated configuration.

  As the switch 13, a slide switch having a two-pole single-throw circuit is used in the embodiment shown in FIG. In the load unit 10, the supply line of the power supply voltage Vcc from the power supply unit and the connection line to the voltage detection terminal TP connected to the load 8 can be set to ON or OFF simultaneously.

Next, the operation of the power supply device according to the second embodiment will be described.
By adopting a two-pole single-throw circuit for the switch 13, the load voltage detection terminal TP is electrically connected to the power input terminal of the load 8 in the load unit 10 when the switch 13 is set to be on, and the switch 13 is off. When set, the input is opened.

  For this reason, when the switch 13 is in the ON state, the power supply device according to the second embodiment corresponds to a state when the connector 11 corresponding to the connecting portion is coupled to the power supply device according to the first embodiment.

  On the other hand, when the power switch 13 is in the OFF state, the power supply device according to the second embodiment corresponds to the state when the connector 11 of the connecting portion is separated in the first embodiment.

  In the first embodiment, the connector 11 is used as means for acting on the load voltage detection terminal TP provided in the switching element 4. On the other hand, in the second embodiment, an on / off function of the power switch 13 is used instead of the insertion / extraction operation of the connector 11.

  Therefore, the connector 11 of the first embodiment and the power switch 13 of the second embodiment have the same operation for switching the respective active dummy circuits.

  Moreover, when implementing the power supply device which has the characteristics of Example 1 and Example 2, the connector 11 and the power switch 13 are provided together. In such a power supply device, in addition to continuing the operation on the primary side, the power supply to the load 8 can be easily turned off and turned on while maintaining the engagement between the connector 11 and the load unit 10.

  For this reason, the electrical inspection of the load 8 is efficiently performed for confirming the operation such as the AC characteristics generated at the time of turning on / off the power, the transient phenomenon of Vcc, and the initialization sequence accompanying the power-on for a specific terminal of a specific device. Can be implemented.

  In other words, even if the load unit 10 has an operation test that involves turning off / on the power, it is easy to perform one-touch operation by simply turning the switch 13 on and off without detaching the troublesome connector 11. The load 8 can be turned off / on again.

  For example, assuming that the load unit 10 is a mass-produced product before shipment, when performing inspection items that require power reconnection after connection with the power supply unit, the work process is shortened and labor and labor are greatly reduced. Bring effect.

  On the power supply device side, stable operation can be continued even when the load part is disconnected by the action of the active dummy circuit, and there is no restriction on the impedance value of the connected load part.

  That is, any variation in the impedance value of the load section viewed from the active dummy circuit is collected in the detection result of two states of the switching element open state (open) and conduction state (short) by the load detection terminal TP.

  For this reason, the active dummy circuit control function that operates the dummy resistor to stabilize the power on the primary side even in an operating environment where the load fluctuates significantly while the power supply device is continuously operated. To achieve with minimum parts.

  In the conventional example, on / off control of the dummy load, which requires a complicated voltage monitoring unit based on the operating current, the present invention adopts a connection that allows the base part of the switching element to function as a load voltage detection terminal, so that there is no load In this case, a predetermined voltage is forcibly applied to the dummy load.

  Furthermore, instead of the voltage monitoring unit that has been used in the past, the switching element has a simple and simple configuration that monitors the voltage applied to the load unit, so the control function of the active dummy circuit in the power supply device is low-cost and space-saving. / Provided with power saving.

  As a means for monitoring a decrease in the applied voltage of the load portion, the first embodiment includes a connector 11 having a detachable coupling portion, and the second embodiment includes a switch 13 in the load portion as an alternative to the coupling portion.

  As described above, according to the power supply apparatus embodying the present invention, it is possible to achieve control of an active dummy circuit that is inexpensive, compact, and simple with a configuration of minimum parts. In addition, the present invention can be widely applied to all switching power supplies with load fluctuations on the secondary side under the continuous operation conditions where the primary side control and the operation are not interrupted, and the effects can be enjoyed.

1 is a configuration block diagram illustrating an example of a first embodiment of a power supply device according to the present invention. It is a structure block diagram which shows an example of Example 2 of the power supply device which concerns on this invention. It is an example of 1 structure of the conventional active dummy circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current detection resistance 2 Current source 3 Voltage comparison circuit 4 Switching element 5 Dummy resistance 6 Base resistance 10 Load part 11 Connector 12 Load voltage detection terminal 13 Switch

Claims (11)

A power supply comprising: a power conversion unit connected to a load unit to generate a predetermined output voltage; a dummy load arranged in parallel with the voltage output of the power conversion unit; and a switching element for controlling on / off of power feeding to the dummy load In the device
A coupling portion having a detachable mechanism to connect between the power supply device and the load portion;
A load voltage detection terminal for monitoring an input voltage of the load unit in the switching element;
A power supply device characterized by comprising:   The power supply device according to claim 1, wherein the load voltage detection terminal is short-circuited with a power input terminal of the load unit when the connection unit is in a connected state.   3. The power supply device according to claim 1, wherein the load voltage detection terminal is opened when the connecting portion is in a separated state.   The power supply apparatus according to claim 1, wherein the switching element includes an emitter terminal, a collector terminal, and a base terminal.   5. The power supply device according to claim 1, wherein the load voltage detection terminal is connected to the base terminal. 6.     The power supply apparatus according to claim 1, wherein the dummy load unit is connected in series with the switching element. A power conversion unit that is connected to the load unit and generates a predetermined output voltage; a dummy load that is arranged in parallel with the voltage output of the power conversion unit; and a switching element that controls on / off of power feeding to the dummy load. In power supply,
A switch for controlling on / off of power feeding to the load section;
A load voltage detection terminal for monitoring an input voltage of the load unit in the switching element;
A power supply device characterized by comprising:   The power supply apparatus according to claim 7, wherein the load voltage detection terminal is short-circuited with a power input terminal of the load unit when the switch is set to supply power on, and is opened when the switch is set to supply power off.   The power supply device according to claim 7, wherein the switching element includes an emitter terminal, a collector terminal, and a base terminal.   The power supply apparatus according to any one of claims 7 to 9, wherein the load voltage detection terminal is connected to the base terminal. The power supply apparatus according to claim 7, wherein the dummy load is connected in series with the switching element.

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