JP5003035B2 - POL power supply circuit protection circuit - Google Patents

Description

The present invention relates to a protection circuit for a POL (Point of Load) power supply circuit, and in particular, a POL power supply in which a DC / DC converter arranged adjacent to a load end is mounted on a latest FPGA (Field Programmable Gate Array) mounted board. The present invention relates to a protection circuit for a POL power supply circuit that prevents an excessive POL power supply input voltage from being applied to a load at the time of failure.

  In recent years, in each package substrate of an electronic device, a voltage drop due to a pattern resistance or a parasitic inductance of a printed circuit board cannot be ignored with a decrease in voltage of an LSI (Large Scale Integrated Ci-rcuit). In addition, a malfunction may occur if the instantaneous power supply voltage drop or the subsequent voltage fluctuation (parasitic vibration) when the LSI consumption current rapidly increases, such as switching of the operation mode, is large.

  In order to cope with these problems, a distributed power supply system in which a DC / DC converter power supply is arranged in the immediate vicinity of a load such as an LSI, an FPGA (Field Pro-grammable Gate Array), a DSP (Digital Signal Processor), etc. has been adopted. It is becoming.

  An FPGA (Field Pro-grammable Gate Array) indicates an LSI that can be programmed by a user, and a DSP (Digital Signal Processor) indicates a microprocessor dedicated to digital signal processing.

  By using this power feeding method, the distance between the power source and the load can be shortened, and the influence of a voltage drop due to wiring or a transient voltage change due to wiring inductance can be reduced. Further, this idea of distributed power supply is further developed, and there is a method called POL (Point of Load) in which a DC / DC converter is arranged immediately on each device serving as a load, and a converter that realizes POL is a POL type DC / DC / DC converter. This is called a DC converter. When expressed in Japanese, POL has the image of “arranged adjacent to the load end”.

  There are two types of POL converters, a non-insulated type and an isolated type DC / DC converter. The DC / DC converter power source used here is required to be small and inexpensive, so a transformer or the like can be used. Non-insulated type DC / DC converter.

  As a problem when the non-insulated POL power supply is applied, there is a phenomenon in which the input voltage passes through the output as it is when the power supply circuit fails. As a result, a voltage exceeding the rating may be applied to various loads connected to the POL power output.

FIG. 3 is a protection circuit diagram of a conventional POL power supply circuit . In the figure, a fuse 3 and a thyristor 4 are inserted in the input section of the POL power supply circuit 1, and an output voltage detection section 5 is inserted between the output section of the POL power supply circuit 1 and the connected load. Further, the detection terminal of the output voltage detection unit 5 and the control terminal of the thyristor 4 are connected.

The operation of the protection circuit of the conventional POL power supply circuit having such a configuration is as follows. When the detection voltage of the output voltage detector 5 exceeds a certain value (overvoltage is detected), the H signal is input to the control terminal of the thyristor 4 and the thyristor 4 becomes conductive. Therefore, the fuse 3 is burned out because a large current flows between the GNDs via the thyristor 4 and the fuse 3 is blown. In this way, a configuration is adopted in which the input to the POL power supply circuit is cut off. (For example, refer to Patent Document 1).

  FIG. 4 is a circuit diagram of a conventional non-insulated DC / DC converter. In the figure, a rectifying switching S1 and a commutation switch S2 are connected in series between input terminals, and a choke coil L and a smoothing capacitor C are connected in series between SOURCE-DRAIN of the commutation switch S2. Yes.

  The operation of the conventional non-insulated DC / DC converter having such a configuration is as follows. By a switching signal (not shown) input to the gate of the rectifying switch S1, the rectifying switch S1 generates a pulse voltage by intermittently applying a DC input voltage, and a current flows through the choke coil L by this output, and the smoothing capacitor C is charged. Is done. The voltage appearing between the terminals of the smoothing capacitor C is the output voltage applied to the load. The on / off state of the rectifying switch S2 is inverted from that of the rectifying switch S1, and is complementarily turned on / off to perform a synchronous rectifying operation.

  The POL power supply circuit 1 shown in FIG. 3 has, for example, a method using a non-insulated DC / DC converter shown in FIG. 4, and a POL type non-insulated DC / DC converter that realizes POL, that is, a non-insulated POL power supply circuit. Is configured.

However, the conventional POL power supply protection circuit of FIG. 3 has the following problems.
(1) An input voltage is generated as an output voltage until the fuse is blown.
(2) Large rated fuses and thyristors with sufficient margin for steady-state current are required.
(3) When the input is cut off, an abnormal alarm cannot be generated.

  As another prior art, in a non-insulated DC-DC converter, when the voltage between the terminals between the smoothing capacitors is compared with a predetermined reference voltage and it is detected that the voltage value between the terminals is equal to or higher than the reference voltage value, An invention of a circuit for protecting an overcurrent by outputting a drive signal to a commutation transistor is disclosed. (For example, refer to Patent Document 2).

This conventional technique also has the following problems.
(1) In order to directly turn on the commutation transistor Q1 in the non-insulated DC-DC converter, it is necessary to modify the existing non-insulated DC-DC converter.
(2) Since a short circuit state is formed between the output terminals via the choke coil, it takes some time to stop the generation of the non-insulated DC-DC converter output.
JP 2005-130593 A JP-A-11-187651

In order to solve the problems of the prior art, the present invention is provided with a mechanism for controlling connection / release of a POL power supply output and a load in accordance with the output voltage of the POL power supply. It is an object of the present invention to provide a protection circuit for a POL power supply circuit in which this voltage is not applied to a load even if it passes through.

The first invention for solving the above problems is the protection circuit of the POL power supply circuit supplying a power supply voltage to a load, a switch provided between the load and the output terminal of the POL conductive Minamotokai path, Control means for turning on or off the switch according to a comparison between an input voltage and an output voltage of the POL power supply circuit, and the control means has a positive bias voltage when the result of the comparison is within an allowable range. Is applied and is turned on, and when the result of the comparison is outside the allowable range, a positive bias voltage is not applied and the transistor circuit is turned off.

According to the first aspect of the present invention, a small and low-priced protection circuit can be configured, and a protection circuit for a POL power supply circuit that does not apply an abnormal voltage to a load can be provided.

The second invention is, in the protection circuit of the POL power supply circuit of the first invention, wherein the POL electrostatic Minamotokai path is a non-isolated DC / DC converter which does not incorporate the transformer.

A third invention is, in the protection circuit of the POL power supply circuit of the first invention, further comprising a comparing means for comparing the input voltage and the output voltage of the POL power supply circuit, the comparing means, a result of the comparison is acceptable range In the transistor circuit, a negative bias voltage is applied to be turned on, and when the comparison result is outside the allowable range, the negative bias voltage is not applied and the transistor circuit is turned off.

According to the third aspect of the invention, it is possible to provide a protection circuit for a POL power supply circuit that can reduce the size and cost of the package circuit.

According to a fourth aspect of the present invention, in the protection circuit for a POL power supply circuit according to the first aspect of the present invention, the switch is an overvoltage blocking transistor at a connection load end.

According to the fourth aspect of the invention, it is possible to provide a protection circuit for a POL power supply circuit that can reduce the size and cost of the package circuit.

According to a fifth invention, in the protection circuit for the POL power supply circuit according to the first invention, the control means is turned on when a positive bias voltage is applied within a permissible range of the comparison result of the comparison means . When the result is out of the allowable range, the transistor circuit is turned off without applying a positive bias voltage.

According to the fifth aspect of the invention, it is possible to provide a protection circuit for a POL power supply circuit that can reduce the size and cost of the package circuit.

As described above, according to the protection circuit for the POL power supply circuit of the present invention, it is not necessary to arrange a fuse having a larger capacity than necessary, a highly rated thyristor, or the like in the input section, thereby reducing the size and cost of the package circuit. be able to.

In the protection circuit of the conventional POL power supply circuit , the POL power supply input voltage is applied to the load circuit until the input section is disconnected. However, in the protection circuit of the POL power supply circuit of the present invention, the output value Is abnormal, the load circuit and the power circuit output are immediately disconnected, so that no abnormal voltage is applied to the load circuit.

Further, the protection circuit of the POL power supply circuit of the present invention is composed of several transistors, and since each transistor does not cause a large loss, it can be configured with a small size and a low price. Therefore, it is incorporated in the POL power supply circuit module. It is also possible easily.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a protection circuit diagram of a non-insulated POL power supply circuit according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a POL power supply circuit, which is composed of a POL type non-insulated DC / DC converter by the non-insulated DC / DC converter described in FIG. TR3 is a switching transistor inserted between the output of the POL power supply circuit 1 and the connection load to which the power supply voltage is supplied, and by applying ON / OFF switching, the output voltage of the POL power supply circuit 1 is applied to the connection load. Is not applied. TR1 and TR2 are transistors constituting a control circuit for controlling ON / OFF switching of TR3.

  TR3 (Pch type) is inserted between the output of the POL power supply circuit and the load to which the power supply voltage is supplied. When a negative bias voltage is applied between GATE and SOURCE of TR3 and SOURCE and DRAIN are turned ON (short circuit), a POL power supply output voltage is applied to the load. On the other hand, when this negative bias voltage is not applied, the SOURCE-DRAIN state is in an OFF (open) state, so that the connection load end is in a high impedance state and no voltage is applied.

  The GATE electrode of TR1 (Pch type) is connected to the POL power supply output, and the SOURCE electrode is connected to the POL power supply input. When a negative bias voltage is applied to the GATE-SOURCE voltage, the SOURCE-DRAIN is turned ON (short circuit). When the GATE-SOURCE voltage is ON, the DRAIN voltage is high (substantially Vin), and when OFF, the low level (substantially GND potential) Become.

  The GATE electrode of TR2 (Nch type) is connected to the DRAIN electrode of TR1. The DRAIN electrode is connected to the GATE electrode of TR3, and ON / OFF of TR3 is controlled. The DRAIN potential of TR2 is low level (approximately GND potential) when ON, and is high level (approximately Vin) when OFF.

  FIG. 2 is a diagram showing changes in the potential of each transistor in the protection circuit 2 shown in FIG. 1, and shows a case where (a) the POL power supply circuit is normal and (b) a POL power supply circuit is abnormal. The operation of FIG. 1 will be described below with reference to FIG.

  During normal operation, a normal voltage Vp obtained by stepping down the input voltage Vin is generated at the output of the POL power supply circuit 1. Since Vp <Vin, a negative bias voltage is applied between GATE and SOURCE of TR1, and TR1 is turned on. Since the GATE potential of TR2 connected to the DRAIN electrode of TR1 becomes Vin and the GATE-SOURCE is in a positive bias state, TR2 is also in the ON state. The GATE potential of TR3 connected to the DRAIN electrode of TR2 is substantially the GND potential. Also, the SOURCE potential of TR3 becomes the output voltage Vp of the POL power supply, the GATE-SOURCE state is in a negative bias state, and TR3 is also in the ON state. Therefore, during normal operation of the POL power supply, the POL power supply output unit and the load are in a conductive state, and a voltage is applied to the load.

  When the POL power supply circuit is faulty, that is, when the input voltage Vin is generated at the output section of the POL power supply circuit, TR1 does not become ON because both the GATE potential and the SOURCE potential are Vin. Therefore, since the GATE potential is substantially the GND potential in TR2, a positive bias is not applied between GATE and SOURCE, and the TR2 does not turn on. That is, the drain potential of TR2 is approximately Vin. As a result, TR3 becomes both GATE and SOURCE potentials Vin, so that it is in an OFF state as in TR1 and TR2. Therefore, when the output voltage of the POL power supply circuit is Vin, the POL power supply output unit and the load are in a non-conductive state, the load end becomes high impedance, and application of an abnormal voltage value is avoided.

  INDUSTRIAL APPLICABILITY The present invention can be used in general electronic equipment such as a transmission / radio device mounted with a PKG (package) substrate provided with a POL power supply circuit (particularly, a non-insulated POL power supply circuit) in the immediate vicinity of a load circuit.

It is a protection circuit diagram of the POL power supply circuit in one Embodiment of this invention. FIG. 2 is a diagram showing a potential change of each transistor in the protection circuit of the POL power supply circuit shown in FIG. 1. It is a protection circuit diagram of a POL power supply circuit according to the prior art. It is a schematic circuit diagram of a non-insulated DC / DC converter.

Explanation of symbols

1 POL power supply circuit 2 protection circuit 3 fuse 4 thyristor 5 output voltage detector

Claims (4)

In the protection circuit of the POL power supply circuit that supplies the power supply voltage to the load,
A switch provided between the output terminal of the POL power supply circuit and the load;
Control means for turning on or off the switch according to a comparison between an input voltage and an output voltage of the POL power supply circuit;
When the comparison result is within an allowable range, the control means is applied with a positive bias voltage to be in an on state, and when the comparison result is outside the allowable range, the positive bias voltage is not applied and is in an off state. A protection circuit for a POL power supply circuit, wherein the protection circuit is a transistor circuit. The protection circuit of the POL power supply circuit according to claim 1,
The protection circuit for a POL power supply circuit, wherein the POL power supply circuit is a non-insulated DC / DC converter without a built-in transformer. The protection circuit of the POL power supply circuit according to claim 1,
Comparing means for comparing the input voltage and the output voltage of the POL power supply circuit,
The comparison means is a transistor circuit in which a negative bias voltage is applied when the comparison result is within an allowable range and is turned on, and when the comparison result is outside the allowable range, a negative bias voltage is not applied and the transistor circuit is turned off. POL power supply circuit protection circuit. The protection circuit of the POL power supply circuit according to claim 1,
A protection circuit for a POL power supply circuit, wherein the switch is a transistor for preventing an overvoltage at a connection load end.

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