JPH0398107A - Voltage stabilizing circuit with overcurrent protection function - Google Patents

Abstract

PURPOSE:To reduce the thermal designing and packaging limitations by securing such a constitution where the control signal received from an overcurrent detection means does not effect a control element at all during a normal power supply action when no overcurrent is detected and the control signal received from an output voltage fluctuation detection means is supplied to the control element via a matching means. CONSTITUTION:An output voltage fluctuation detection means 101 outputs a control signal in accordance with the fluctuation component of the output voltage. An overcurrent detection means 102 outputs a control signal in accordance with detection of a load current higher than a prescribed level. A matching means 103 performs a matching operation to secure a wired OR between the control signals of both means 101 and 102. A control element 104 is inserted in series between an input DC power supply and a load and the both-end impedance of the element 104 changes in accordance with the control signal received from the means 103. Thus the output voltage is stabilized and an overcurrent is limited. As a result, since the hardware scale is reduced owing to a simple constitution of a single control element the packaging limitation is reduced. Furthermore the thermal designing limitation is also reduced.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a voltage stabilization circuit with overcurrent protection that limits the load current to a certain value or less when the load is short-circuited or overloaded. The purpose of this design is to reduce thermal design and mounting constraints by using a single element that can be used in common. overcurrent detection means for outputting a control signal according to current detection; matching means for matching to take a wired OR of each control signal output from the output voltage fluctuation detection means and the overcurrent detection means; The control element is inserted in series between the input DC power source and the load, the impedance at both ends thereof changes according to the control signal from the matching means, and the control element stabilizes the output voltage and limits overcurrent. do.

[Industrial application field]

The present invention relates to a voltage stabilizing circuit with overcurrent protection that limits the load current to a certain value or less in the event of a short circuit or overload of the load.

[Conventional technology]

Traditionally, systems that require limiting the load current to below a certain value to prevent load and power circuit failures include:
A circuit is employed in which the output voltage is first stabilized by a voltage stabilization circuit, and then power is supplied to the load via an overcurrent protection circuit.

FIG. 7 is a diagram showing a conventional circuit configuration for overcurrent protection and voltage stabilization.

In the figure, a voltage stabilizing circuit 720 detects and corrects fluctuations in the output voltage, and maintains the output voltage constant by controlling the power source 720.
The power supplied from 10 is output to the next stage overcurrent protection circuit. The overcurrent protection circuit 730 includes the voltage stabilization circuit 7
20 output to the load 740, and monitors the current of the load 740 to detect a short circuit or overload and limit the load current.

FIG. 8 is a connection diagram showing an example of a conventional overcurrent protection and voltage stabilization circuit.

In the figure, when the output voltage obtained at the emitter of transistor 825 increases, the base potential of transistor 823 increases by a predetermined value according to the voltage division ratio by resistors 821 and 822, and the impedance between the collector and emitter of transistor 823 increases. descend. Along with this, the base potential of the transistor 825, which is set by the resistor 824 and the transistor 823, decreases, and the impedance between the collector of the transistor 825 and the ivy increases, and fluctuations in the output voltage are reversely corrected and the output voltage increases. The voltage is stabilized.

In addition, in the overcurrent protection circuit 730, when the load current exceeds a certain value, a voltage drop proportional to the load current connected to the inverting input of the voltage comparator 833 (both ends of the resistor 835 connected in series with the load 740) ) becomes higher than the reference voltage at the non-inverting input of voltage comparator 833 (set by resistor 831 and Zener diode 832), and the output voltage of voltage comparator 833 drops to a predetermined value. do. Correspondingly, the base potential of the transistor 834 (set by the output of the voltage comparator 833 and the resistor 836) decreases, the impedance between the collector and the ivy increases, and the load current is limited.

[Problem to be solved by the invention]

By the way, the collector loss P, of the transistor 825 in such a conventional voltage stabilizing circuit is expressed as P,=(EV)·I. Here, E is the input voltage of the voltage stabilization circuit 720, ■ is the output voltage of the voltage stabilization circuit 720, and ■ is the load current.

Therefore, if the difference (E-V) between the supply voltage to the load 72!0 and the input voltage of the voltage stabilizing circuit 720 with overcurrent protection is large, or if the load current ■ is large, use a transistor with large collector loss as the transistor 825. is required, and the mechanical dimensions of the device also become large.

In addition, the transistor 8 in the conventional overcurrent protection circuit
The collector loss P2 of 34 is expressed as Pz=V'Is. Here, ■ is the output voltage of the voltage stabilization circuit 720, and ■3 is the current value when limited by the overcurrent protection circuit 730.

Therefore, if the output voltage (1) of the voltage stabilization circuit 720 or the limited current value (I3) by the overcurrent protection circuit 730 is large, the transistor 834 is required to have a large collector loss, and the mechanical dimensions of the element also become large. .

In this way, in the conventional circuit structure, the operations of the transistors 825 and 834 used as control elements are similar, but they are required for each function, and as mentioned above, depending on the specifications of the power supply. Extremely high power was required, and there were constraints on thermal design and implementation.

An object of the present invention is to provide a voltage stabilization circuit with overcurrent protection that reduces constraints on thermal design and implementation by using a common control element for the voltage stabilization circuit and the overcurrent protection circuit as a single element. do.

[Means to solve the problem]

FIG. 1 is a block diagram of the principle of the present invention.

The output voltage fluctuation detection means 101 outputs a control signal according to the fluctuation amount of the output voltage.

The overcurrent detection means 102 outputs a control signal in response to detection of a load current equal to or greater than a predetermined value.

The matching means 103 performs matching to take a wired OR of each control signal output from the output voltage fluctuation detecting means 101 and the overcurrent detecting means 102.

The control element 104 is inserted in series between the input DC power source and the load, and the impedance at both ends thereof changes according to the control signal from the matching means 103, thereby stabilizing the output voltage and limiting overcurrent.

[For production]

According to the above structure, during normal power supply operation in which no overcurrent is detected, the control signal from the overcurrent detection means 102 has no effect on the control element 104, and the control signal from the output voltage fluctuation detection means 101 does not affect the control element 104. is supplied to the control element 104 via the matching means 103, and the output voltage is stabilized.

In addition, when overcurrent is detected, the overcurrent detection means 1
A control signal from 02 is supplied to control element 104 via matching means 103, and the load current is limited.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In the conventional circuit structure, the voltage stabilization circuit and overcurrent protection circuit were independent, but the control elements of each circuit are inserted in series with the load and are controlled by control signals given from each control signal generation circuit. They have the same function in that they control the impedance at both ends, and can be shared by unifying the peripheral circuits in functional blocks.

Therefore, the circuit structure adopted in this embodiment for unifying the peripheral circuits of each control element will be explained below.

FIG. 2 is a block diagram of the voltage stabilization circuit.

In the figure, a power supply 210 is connected to an input terminal of a voltage stabilization circuit, and is connected to a control voltage setting circuit 221, an output terminal, and a load 240 via a voltage control element 225.

The output of the control voltage setting circuit 221 and the reference voltage 228 are each connected to each input terminal of the control signal generation circuit 223, and the output of the control signal generation circuit 223 is connected to the control terminal of the voltage control element 225. Note that the reference voltage 22
Reference numeral 8 denotes a reference voltage source provided in this embodiment in order to unify the control signal generation circuit 223 with an overcurrent protection circuit to be described later.

FIG. 3 is a block diagram of the overcurrent protection circuit.

In the figure, a power supply 310 is connected to each input terminal of the overcurrent protection circuit, one of which is connected to an output terminal and a load 340 via a current control element 334. The other end of load 340 is connected to the other output terminal and control current setting circuit 335. The output of the control current setting circuit 335 and the reference voltage 331 are respectively connected to each input terminal of the control signal generation circuit 333, and the output of the control signal generation circuit 333 is connected to the control terminal of the current control element 334.

With such a configuration, it is possible to unify all functional blocks except for the control voltage setting circuit 221 and the control current setting circuit 335 shown in FIG. 2.

FIG. 4 is a diagram showing a configuration example of a voltage stabilizing circuit corresponding to FIG. 2.

In the figure, in correspondence with FIG. 2, the voltage control element 2
25 is an FET 425 and a resistor 424, and a control signal generation circuit 223 is a voltage comparator 423 and a transistor 426.
and resistor 427, reference voltage 228 is connected to resistor 428
and Zener diode 429, and control voltage setting circuit 221 corresponds to resistors 421 and 422, respectively.

In this voltage stabilizing circuit 420, in order to share the control element with the overcurrent protection circuit described later, the FE742 which is the control element
A control signal to the gate of 5 is given by the oven collector output of the transistor 426, and a voltage comparator 423 is used as a control signal generating circuit to perform voltage stabilization control only for positive fluctuations in the output voltage. .

FIG. 5 is a diagram showing a configuration example of an overcurrent protection circuit corresponding to FIG. 3.

In the figure, in correspondence with FIG. 3, the current control element 3
34 is a FET 534 and a resistor 536, and a control signal generation circuit 333 is a voltage comparator 533 and a transistor 537.
and resistor 538, reference voltage 331 is connected to resistor 531
and the Zener diode 532, and the control current setting circuit 335 corresponds to the resistor 535, respectively.

In this overcurrent protection circuit 530, in order to share the control element with the voltage stabilization circuit, the FET5 which is the control element is
A control signal to the gate of transistor 34 is provided by the open collector output of transistor 537.

The voltage stabilizing circuit with overcurrent protection of this embodiment is constructed as follows based on the voltage stabilizing circuit 420 shown in FIG. 4 and the overcurrent protection circuit 530 shown in FIG. 5.

FIG. 6 is a connection diagram of a voltage stabilizing circuit with overcurrent protection according to an embodiment of the present invention.

In the figure, the circuit that is shared in correspondence with FIGS. 4 and 5 is FET625 (FE7 in FIG. 4).
425, which corresponds to FET 534 in FIG.
Hereinafter, only the corresponding numbers in FIGS. 4 and 5 will be shown. ).

), resistor 624 (424, 536), resistor 627
(427, 538), resistor 630 (430, 550
) and Zener diode 631 (431, 551)
A constant voltage source and a resistor 62B (42
8, 53l) and Zener diode 629 (429
, 532).

In this embodiment, the collectors of transistors 626 and 637 are connected in parallel to the gate of the shared FET 625 via a resistor 627, but since the transistor 637 is off when no overcurrent is detected, there is no effect. The output voltage is stabilized solely by the control signal from transistor 626. Furthermore, when an overcurrent is detected, the transistor 637 is turned on, so no matter what output the transistor 626 outputs, the gate of the FET 625 is connected to the power supply ground via the resistor 627 and the collector and emitter of the transistor 637. .

With this configuration, the FET 625, which is a control element, and its peripheral circuits are shared, and the scale of the hardware is reduced.

Regarding the relationship between this embodiment and the principle block diagram of the present invention shown in FIG. ) is included in the output voltage fluctuation detection means 101, a resistor 635, a voltage comparator 633, and a reference voltage generation circuit (shared with the output voltage variation detection means 101) are included in the overcurrent detection means 102, and transistors 626, 637 are included in the overcurrent detection means 102. The resistor 627 corresponds to the matching means 103, and the FET 625 and the resistor 624 correspond to the control element 104.

〔Effect of the invention〕

As described above, according to the present invention, the voltage stabilizing circuit with overcurrent protection is configured by a single control element, and the scale of the hardware can be reduced. Therefore, restrictions on implementation can be reduced. Furthermore, if the specifications required for the power supply circuit require a control element with a large power dissipation (accompanying this, the mechanical dimensions of the element also become large), thermal design constraints can also be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of a voltage stabilization circuit, Fig. 3 is a block diagram of an overcurrent protection circuit, and Fig. 4 is a diagram showing an example of the structure of a voltage stabilization circuit. , Fig. 5 is a diagram showing a configuration example of an overcurrent protection circuit, Fig. 6 is a connection diagram of a voltage stabilizing circuit with overcurrent protection according to an embodiment of the present invention, and Fig. 7 is a diagram showing a conventional overcurrent protection circuit and a voltage stabilizing circuit with overcurrent protection. Figure 8 is a diagram showing a circuit configuration for voltage stabilization. FIG. 8 is a connection diagram showing an example of a conventional circuit for overcurrent protection and voltage stabilization. In the figure, 101 is an output voltage fluctuation detection means, 102 is an overcurrent detection means, 103 is a matching means, 104 is a control element, 210, 310, and 410 are power supplies, 221 is a control voltage setting circuit, and 223 and 333 are control signal generators. circuit, 225 is a voltage control element, 240, 340, 440, 540, 640 is a load, 33
1 is a reference voltage, 334 is a current control element, 335 is a control current setting circuit, 420 is a voltage stabilization circuit, 421, 422, 424, 427, 428, 531, 5
35, 536, 538, 550, 62l1622, 62
4, 627, 628, 630, 635 are resistors, 423, 533, 623, 633 are voltage comparators, 425
, '534, 625 are FETs, 426, 537, 626, 637 are transistors, 42
9, 532, 551, 629, and 631 are Zener diodes, 530 is an overcurrent protection circuit, and 600 is a voltage stabilization circuit with overcurrent protection. It is stable and B's block diagram is shown in Figure 2. 5 Figure

Claims (1)

[Claims] (1) Output voltage fluctuation detection means (101) that outputs a control signal according to the fluctuation of the output voltage, and overcurrent detection means (102) that outputs a control signal according to the detection of a load current of a predetermined value or more. , matching means (103) for matching to take a wired OR of each control signal output from the output voltage fluctuation detection means (101) and the overcurrent detection means (102);
and a control device that is inserted in series between the input DC power source and the load, and whose impedance changes depending on the control signal from the matching means (103) to stabilize the output voltage and limit overcurrent. A voltage stabilizing circuit with overcurrent protection, comprising: an element (104).