JP2017027139A - Regulator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively configure a regulator circuit while keeping an automatic return function.SOLUTION: A regulator circuit comprises: a regulator element Q01 inserted between a DC input terminal and a DC output terminal and controlling outputs by the control voltage applied to a control terminal; a constant voltage element ZD01 inserted between the control terminal and a ground of the regulator element; and a resistance element R01 for bias connected between the control terminal and an input-side terminal of the regulator element. An output voltage monitoring circuit 10 measures the potential difference between input/output terminals of the regulator element Q01, and generates and outputs an abnormality detection signal when the potential difference exceeds a prescribed value. When the abnormality detection signal is input, a control circuit 20 lowers a connection point potential between the control terminal and constant voltage element of the regulator element Q01 to block a conduction state of the regulator element.SELECTED DRAWING: Figure 1

Description

  The present invention is configured such that a regulator element for output control such as a transistor is inserted between a DC input terminal and a DC output terminal, and the control voltage of the regulator element is stabilized by a constant voltage element such as a Zener diode. Regulator circuit.

One conventional example of a regulator circuit used for controlling an internal circuit of a switching power supply device or for low power output is a regulator circuit Y having a circuit configuration as shown in FIG. 2, T _1p and T _1n are DC input terminals, T _2p and T _2n are DC output terminals, Q11 is a regulator element for output control (NPN type transistor), ZD11 is a Zener diode as a constant voltage element, R11 Is a bias resistance element, F11 is a fuse element (fuse resistance) that is blown by an overcurrent, A is a DC power source, and B is a load circuit. A DC power source A is connected between the input terminal T _1p on the high potential side and the input terminal T _1n on the low potential side, and a load is connected between the output terminal T _2p on the high potential side and the output terminal T _2n on the low potential side. Circuit B is connected. The collector of the regulator element Q11 is connected to the input terminal T _1p on the high potential side via the fuse element F11, and the emitter of the regulator element Q11 is connected to the output terminal T _2p on the high potential side. A biasing resistance element R11 is connected between the base (control terminal) and the collector of the regulator element Q11, the base of the regulator element Q11 is connected to the cathode of the Zener diode ZD11, and the anode of the Zener diode ZD11 is on the low potential side. The input terminal T _1n and the low potential side output terminal T _{2n are} connected. The fuse element F11 plays a role of protecting the regulator element Q11 from an overcurrent caused by an output voltage abnormality drop due to an output short circuit or the like.

  Upon activation, the current from the DC power source A flows into the Zener diode ZD11 via the fuse element F11 and the biasing resistance element R11, generating a constant potential (Zener voltage) at the cathode, and the base voltage reaches the operating voltage. Regulator element Q11 conducts and power is supplied to load circuit B. Since the base voltage (control voltage) of the regulator element Q11 is controlled to a constant value by the breakdown voltage (zener voltage) of the Zener diode ZD11, the output current Io flowing through the regulator element Q11 is maintained at a constant value, and the output voltage Vo is Stabilize. When an output voltage abnormality drop occurs due to an output short circuit or the like in the load circuit B, and an overcurrent flows through the main circuit of the fuse element F11 and the regulator element Q11, the fuse element F11 is blown, and the regulator element from the overcurrent due to the output voltage abnormality drop Protect Q11. When restarting after the abnormality in the load circuit B is resolved, the fuse element F11 is replaced. Note that a partially similar configuration is disclosed in Patent Document 1 for the regulator circuit Y of FIG.

JP-A-57-95179

  The conventional example described above has a problem that it cannot be restarted unless the fuse is replaced after the abnormality is resolved. Therefore, it is conceivable to use a PTC thermistor (positive characteristic thermistor) that does not require replacement in place of the fuse element. When the element temperature exceeds the specified value due to overcurrent, the resistance value increases rapidly due to tripping, limiting the circuit current to a very small value, and the element temperature decreases and returns to the original resistance value. There is no need to replace it like a fuse. Since the operation speed is moderately slow, it does not malfunction due to inrush current during hot plugging, and is highly safe.

  However, if a PTC thermistor is employed, the cost will be significantly increased compared to a fuse element, which is disadvantageous in terms of cost burden.

  The present invention has been made in view of such circumstances, and an object thereof is to construct a regulator circuit at low cost while maintaining the automatic return function.

  The present invention solves the above problems by taking the following measures.

The regulator circuit according to the present invention comprises:
A regulator element that is inserted between the DC input terminal and the DC output terminal and controls the output by a control voltage applied to the control terminal;
A constant voltage element inserted between the control terminal of the regulator element and the ground;
A regulator circuit comprising a biasing resistance element connected between a control terminal and an input side terminal of the regulator element,
further,
Measures the potential difference between the input side terminal and the output side terminal of the regulator element, and generates and outputs an abnormality detection signal when the potential difference exceeds a specified value due to a voltage abnormality drop of the output side terminal of the regulator element An output voltage monitoring circuit to
A control circuit that lowers a connection point potential between a control terminal of the regulator element and the constant voltage element to cut off a conduction state of the regulator element when an abnormality detection signal is input from the output voltage monitoring circuit; It is characterized by that.

  The regulator circuit of the present invention configured as described above has the following characteristics.

  According to this configuration, the output voltage monitoring circuit measures the potential difference between the input-side terminal and the output-side terminal of the regulator element, and the potential difference exceeds the specified value due to the abnormal voltage drop at the output-side terminal of the regulator element. Sometimes anomaly detection signal is generated and output. When the abnormality detection signal is input to the control circuit, the control circuit lowers the potential at the connection point between the control terminal of the regulator element and the constant voltage element to cut off the conduction state of the regulator element. Therefore, it is possible to maintain an automatic recovery function from an abnormal state without using a fuse element that needs to be replaced in order to recover from the abnormal state or a relatively expensive PTC thermistor. Moreover, since the voltage is not continuously lowered by the regulator element when the output is short-circuited, heat generation is small, and it is not necessary to attach a large heat sink.

  Furthermore, according to the present invention, there are the following advantageous effects. That is, when the power is turned on between the DC input terminals to start the regulator circuit, the current from the DC power supply flows to the constant voltage element through the bias resistance element, and the regulator element is operated to control the regulator element. A constant voltage is applied to the terminal to turn on the regulator element and start the regulator circuit.

  The output voltage monitoring circuit measures a potential difference between the input side terminal and the output side terminal of the regulator element, generates an abnormality detection signal when the potential difference exceeds a specified value, and outputs it to the control circuit.

  In the above configuration, the following aspect is preferable.

  The output voltage monitoring circuit includes two resistance elements connected in parallel between the input and output terminals of the regulator element and connected to each other in direct current, and a control terminal connected to a connection point between these resistance elements. The current terminal is connected to the input side terminal of the regulator element, and the second current terminal is preferably provided with an output voltage abnormality drop detection switching element that serves as an output terminal of the abnormality detection signal.

  The control circuit includes a bypass switching element bypassed between both ends of the constant voltage element, a control terminal of the bypass switching element, and an abnormality detection in the switching element for detecting an output voltage abnormality drop. A resistance element connected between a signal output terminal, a resistance element connected between a connection point between the resistance element and a control terminal of the bypass switching element, and a low-side terminal of the constant voltage element; The structure which has is preferable.

  As described above, according to the present invention, it is not necessary to use a conventionally required fuse element, and it is not necessary to replace the fuse element at the time of restart, and the burden is reduced in terms of cost and operation. Is done. In addition, it is not necessary to use a PTC thermistor which does not require replacement but has a problem of high cost.

The circuit diagram which shows the structure of the regulator circuit in the Example of this invention Circuit diagram showing configuration of regulator circuit in conventional example

  Hereinafter, embodiments of the regulator circuit of the present invention having the above configuration will be described in detail at the level of specific examples.

FIG. 1 is a circuit diagram showing a configuration of a regulator circuit in an embodiment of the present invention. In FIG. 1, A is a DC power supply, B is a load circuit, X is a regulator circuit, T _1p and T _1n are DC input terminals to which a DC voltage is input, and T _2p and T _2n are DC output terminals to which a DC voltage is output. , Q01 is a regulator element (NPN bipolar transistor) that generates a current according to the control voltage, ZD01 is a Zener diode as a constant voltage element, R01 is a biasing resistance element, 10 is an output voltage monitoring circuit, and 20 is a control Q02 is a PNP bipolar transistor (switching element for detecting abnormal output voltage), Q03 is an NPN bipolar transistor (switching element for bypass), and R02, R03, R04, and R05 are resistance elements.

A DC power source A is connected between the high potential side DC input terminal T _1p and the low potential side DC input terminal T _1n in the regulator circuit X. The high potential side of the DC input terminals T _1p on the regulator element Q01 collector (input side terminal) is connected (node N01), the resistance element R01 for bias between the collector and the base (control terminal) of the regulator element Q01 is It is connected. The base of the regulator element Q01 is connected to the cathode (high side terminal) of the Zener diode ZD01, and the anode (low side terminal) of the Zener diode ZD01 is connected to the DC input terminal T _1n on the low potential side. The emitter of the regulator element Q01 (output side terminal) connected to the DC output terminal T _2p the high potential side (node N 02), the anode of the Zener diode ZD01 are connected to the DC output terminal T _2n on the low potential side. A load circuit B is connected between the output terminal T _2p on the high potential side and the output terminal T _2n on the low potential side.

  The output voltage monitoring circuit 10 includes a PNP transistor Q02 and two resistance elements R02 and R03. One end of the resistor element R02 is connected to the collector of the regulator element Q01, and one end of the resistor element R03 is connected to the emitter of the regulator element Q01. The other end of the resistor element R02 and the other end of the resistor element R03 are connected to each other, and the base (control terminal) of the PNP transistor Q02 is connected to the node N03 that is the connection point. The emitter (first current terminal) of the PNP transistor Q02 is connected to one end of the resistance element R02.

The control circuit 20 includes an NPN transistor Q03 and two resistance elements R04 and R05. One end of the resistor element R04 is connected to the collector (second current terminal) of the PNP transistor Q02 in the output voltage monitoring circuit 10. One end of the resistor element R05 is connected to the output terminal T _2n on the low potential side (the anode of the Zener diode ZD01). The other end of the resistor element R04 and the other end of the resistor element R05 are connected to each other, and the base (control terminal) of the NPN transistor Q03 is connected to the node N04 that is the connection point. The collector of the NPN transistor Q03 is connected to the cathode of the Zener diode ZD01, and the emitter of the NPN transistor Q03 is connected to the anode of the Zener diode ZD01.

  In the above configuration, the output voltage monitoring circuit 10 and the control circuit 20 have a role of protecting the regulator element Q01 from an overcurrent caused by an output voltage abnormality drop due to an output short circuit or the like in the load circuit B.

  Hereinafter, the operation of the regulator circuit X configured as described above will be described.

  First, the operation at startup will be described. When the power is turned on, the current from the DC power source A flows into the base of the regulator element Q01 via the biasing resistance element R01 for starting, and makes the regulator element Q01 conductive. The current that flows between the first and second current terminals of the regulator element Q01 is supplied to the load circuit B. Since the cathode potential of the Zener diode ZD01 is held at a constant voltage determined by the Zener voltage, the value of the current flowing through the regulator element Q01 is also held constant.

A slight current also flows through the series circuit of the resistance element R02 and the resistance element R03 in the output voltage monitoring circuit 10, but the voltage across the load circuit B, that is, the potential of the output terminal _T2p on the high potential side is high, and the potential of the node N03 is also high. _Therefore , the base-emitter voltage V _BE02 of the PNP transistor Q02 is kept at a level lower than the operating voltage, and the PNP transistor Q02 is kept off. Since the PNP transistor Q02 is in the off state, the NPN transistor Q03 in the control circuit 20 is also kept in the off state. Therefore, the Zener diode ZD01 is in an operating state, and its cathode is kept at the Zener voltage.

Next, the operation of the load circuit B when the potential on the output side is abnormally lowered due to a short circuit or the like will be described. When an abnormal output voltage drop occurs due to an output short circuit or the like, the potential at the node N02 (the connection point between the load circuit B, the emitter of the regulator element Q01 and the resistor element R03) is greatly reduced, and the collector- The emitter-to-emitter voltage V _CE01 rises (rises to near the output voltage V _DC1 of the DC power source A). Along with this, the current flowing through the series circuit of the resistance element R02 and the resistance element R03 increases, and the potential of the node N03 decreases. As a result, the base-emitter voltage V _BE02 of the PNP transistor Q02 increases and reaches the operating voltage, so that the PNP transistor Q02 becomes conductive.

  A current flows through the resistance elements R04 and R05 in the control circuit 20 through the PNP transistor Q02 conducted from the DC power source A, and the NPN transistor Q03 whose base potential is increased by the voltage drop at the resistance element R05 is conducted. As a result, both ends of the Zener diode ZD01 are bypassed, the base potential of the regulator element Q01 is greatly lowered to the ground level, and the regulator element Q01 is turned off. In this way, when an abnormal step-down occurs on the output side, the detection operation by the output voltage monitoring circuit 10 connected in parallel between the input and output terminals of the regulator element Q01, and the regulator circuit Q01 being turned off by the control circuit 20 based thereon By the operation, the regulator element Q01 can be protected from an abnormal output voltage drop due to an output short circuit or the like.

In the normal operation state, for example, the output voltage V _DC1 of the DC power supply A is 30 [V], the voltage V _R0 of the load circuit B is 23.4 [V], and the power loss in the regulator element Q01 is, for example, 5 [W Then, the load current I _{0 at} that time is
I ₀ = W / (V _DC1 −V _R0 ) = 5 / (30-23.4) ≈0.75 [A]
It becomes. If the operating point when the PNP transistor Q02 in the output voltage monitoring circuit 10 is turned on is 1 [V], the voltage across the resistance element R02 is in the range of 0.55 to 0.75 [V]. Is set to R02: R03 = 1: 25.

In a normal operation state, the potential difference between the nodes N01 to N02 is 30-23.4 = 6.6 [V]. By dividing this by 26, 6.6 / (1 + 25) ≈0.25 [V]. The voltage across the resistor element R02 is 0.25 [V], and the voltage across the resistor element R03 is 6.35 [V]. At this time, the potential of the node N03 is 29.75 [V]. The base-emitter voltage V _BE02 of the PNP transistor Q02 is 0.25 [V], which has not reached the operating voltage, so that the PNP transistor Q02 is kept off in the normal operating state. It will be.

Assume that an abnormal output voltage drop occurs due to an output short circuit or the like, and the potential of the node N02 drops to, for example, 1.0 [V]. The potential difference between the nodes N01 to N02 is 30−1.0 = 29.0 [V]. By dividing this by 26, 29.0 / (1 + 25) ≈1.1 [V]. The voltage across the resistor element R02 is 1.1 [V], and the voltage across the resistor element R03 is 27.5 [V]. At this time, the potential of the node N03 is 28.9 [V], and the potential is decreased by 0.85 [V] from 29.75 [V] in the normal operation state. That is, the base-emitter voltage V _BE02 of the PNP transistor Q02 is 1.1 [V], which reaches the operating voltage, so that the PNP transistor Q02 becomes conductive.

When changing the operating point, the resistance values R ₀₂ and R ₀₃ of the resistance elements R ₀₂ and R ₀₃ are calculated as follows.

The base-emitter voltage of the PNP transistor Q02 is V _BE02 and the base current is I
As _B02, resistance R ₀₂ of resistor element R02 is

Can be obtained as

Further, when the PNP transistor Q02 is in a conducting state, the maximum value of the base-emitter voltage V _BE02 is V _BEmax , the minimum variation of the resistance value of the resistance element R02 is R _02min , and the PNP transistor Q02 flows to the PNP transistor Q02. When the maximum value of the base current is I _Bmax , the resistance value R ₀₃ of the resistance element R ₀₃ is

Can be obtained as Here, 1 [V] is the potential of the node N02 when the PNP transistor Q02 is to be conducted.

(V _DC1 −V _BEmax ) is the potential of the node N03, (V _DC1 −V _BEmax −1) is the voltage across the resistor element R03, (V _BEmax / R _02min ) is the current flowing through the resistor element R02, and I _Bmax is the PNP type. The current flowing from the emitter of the transistor Q02 to the base, [(V _BEmax / R _02min ) + I _Bmax ], is the total current flowing through the resistance element R03. When these relationships are calculated by applying Ohm's law, the above equation (2) is obtained.

  Next, the operation at the time of recovery will be described. When the abnormal drop state of the output voltage is eliminated, the voltage across the load circuit B is recovered and increased by the current flowing from the resistance elements R02 and R03 in the output voltage monitoring circuit 10 to the load circuit B, and the potential of the node N02 and hence the node N03 Since the potential increases and the base voltage of the PNP transistor Q02 increases, the PNP transistor Q02 is turned off. In conjunction with this, the NPN transistor Q03 in the control circuit 20 is also turned off, and the Zener diode ZD01 operates, whereby the base voltage of the regulator element Q01 rises to the operating voltage and the regulator element Q01 becomes conductive. That is, when the abnormal drop state of the output voltage is resolved, the regulator circuit X automatically returns, and it is not necessary to turn on the power as in the conventional example.

As described above, the regulator circuit X according to the present embodiment is activated when the power is turned on when the regulator element Q01, the PNP transistor Q02, and the NPN transistor Q03 are turned off. The regulator element Q01 flows to the Zener diode ZD01 via the starting bias resistance element R01, generates a Zener voltage V _ZD across the Zener diode ZD01, and raises the base voltage of the regulator element Q01 to the operating voltage. Conduct. In this operation, the resistive element R01 for starting bias, the Zener diode ZD01, and the regulator element Q01 are not affected by the capacitive element (if the load is capacitive, the regulator element Q01 When off, the capacitive load is charged via the resistance elements R02 and R03). Therefore, compared with the case where a capacitive element (delay element) is present in the regulator circuit, there is an advantage that the starting operation is quick.

  As described above, the regulator circuit X of the present embodiment has a sufficiently high operating speed when the output voltage abnormality is reduced due to an output short circuit or the like, and the regulator element Q01 is completely turned off. Therefore, it is not necessary to use a fuse element as in the conventional example, and naturally, part replacement such as replacement of the fuse element is unnecessary. Further, it is not necessary to use a relatively expensive PTC thermistor. Moreover, since the voltage is not continuously lowered by the regulator element Q01 when the output is short-circuited, heat generation is small, and it is not necessary to attach a large heat sink.

  The present invention relates to a regulator circuit used for controlling an internal circuit of a switching power supply device or for low power output, and a regulator element for output control such as a transistor is connected in series between a DC input terminal and a DC output terminal. In the regulator circuit configured to stabilize the control voltage of the regulator element with a constant voltage element such as a Zener diode, the circuit configuration is simplified, the cost is reduced, and an automatic recovery function is provided. It is useful as a technique to keep.

10 Output voltage monitoring circuit 20 Control circuit Q01 Regulator element (transistor)
Q02 Switching element (transistor) for detecting abnormal output voltage drop
Q03 Bypass switching element (transistor)
R01 Resistive element for bias X Regulator circuit ZD01 Constant voltage element (Zener diode)
T1p, T1n DC input terminal T2p, T2n DC output terminal

Claims (3)

A regulator element that is inserted between the DC input terminal and the DC output terminal and controls the output by a control voltage applied to the control terminal;
A constant voltage element inserted between the control terminal of the regulator element and the ground;
A regulator circuit comprising a biasing resistance element connected between a control terminal and an input side terminal of the regulator element,
further,
Measures the potential difference between the input side terminal and the output side terminal of the regulator element, and generates and outputs an abnormality detection signal when the potential difference exceeds a specified value due to a voltage abnormality drop of the output side terminal of the regulator element An output voltage monitoring circuit to
A control circuit that lowers a connection point potential between a control terminal of the regulator element and the constant voltage element to cut off a conduction state of the regulator element when an abnormality detection signal is input from the output voltage monitoring circuit; A regulator circuit characterized by that.   The output voltage monitoring circuit includes two resistance elements connected in parallel between the input and output terminals of the regulator element and connected to each other in direct current, and a control terminal connected to a connection point between the two resistance elements. The switching element for detecting an output voltage abnormality drop, wherein a current terminal is connected to an input side terminal of the regulator element, and a second current terminal is an output terminal of an abnormality detection signal. Regulator circuit.   The control circuit includes a bypass switching element bypassed between both ends of the constant voltage element, a control terminal of the bypass switching element, and an output of an abnormality detection signal in the output voltage abnormality drop detection switching element A resistive element connected between the terminal, and a resistive element connected between a connection point between the resistive element and the control terminal of the bypass switching element and the low-side terminal of the constant voltage element. The regulator circuit according to claim 2.

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