JPH04101114U - power circuit - Google Patents

Abstract

(57) [Summary] [Purpose] A series regulator that uses a 3-terminal power supply IC and can output large currents, which reduces power consumption inside the power supply circuit and does not require adjustment of the output terminal voltage. The purpose is to provide [Structure] A power supply circuit according to the present invention uses a three-terminal power supply IC to control an output terminal voltage. Here, the voltage supplied to the power supply IC is supplied from a bias voltage different from the input terminal voltage. Therefore, the input terminal voltage may be the output terminal voltage plus the minimum input/output voltage at which the power transistor can operate. Therefore, a power supply circuit is constructed in which the power consumed inside the power supply circuit is small and the output terminal voltage does not need to be adjusted.

Description

[Detailed explanation of the idea]

0001 [Purpose of invention]

0002

[Industrial application field]

The power supply circuit according to the present invention relates to a control circuit for a series regulator.

0003

[Conventional technology]

Generally, a three-terminal power supply IC is used in a stabilized power supply circuit. This power supply I When using C, the number of parts in the power supply circuit is small and there is no need to adjust the circuit. There is a characteristic that. However, there are few power supply ICs that can output large currents. Therefore large current In order to output the It is necessary to add 10 to the circuit.

0004 The minimum required for transistor 10 and power supply IC 15 to operate in this circuit. The potential difference between the input and output is 2.5V for the power supply IC15, and the voltage difference between the transistor 1 3.2V is required, including the emitter-base voltage of 0.7V. Therefore, this The power consumption P of the power supply circuit is, when the current flowing through the circuit is I, P≧(2.5+0.7)×I=3.2×I becomes.

[0005] For example, if I=1A, the power consumption P of this power supply circuit is 3.2W. In this case, it is necessary to consider the maximum rating, maximum loss, etc. of the transistor 10. child Taking these into consideration, this transistor 10 must have large collector loss. stomach. It is also necessary to dissipate heat generated by collector losses. For this reason, large A heat sink is required. As a result, a power supply circuit that outputs a large current has a large configuration.

[0006] In addition, there is a power supply circuit that outputs a large current using a power supply control IC. However, when this control IC is used, it is necessary to adjust the output terminal voltage. Therefore Not suitable for mass production.

[0007] As described above, a power supply circuit that outputs a large current requires the minimum input input for each element to operate. The output potential difference is large. Therefore, the power consumed inside the power supply circuit increases. Yo It was a large configuration. On the other hand, when using a control IC, the output terminal voltage Adjustments are required. Therefore, it was not suitable for mass production.

[0008]

[Problem that the idea aims to solve]

As mentioned above, a power supply circuit that outputs a large current requires the minimum input/output that each element can operate with. The potential difference is large. Therefore, the power consumed inside the power supply circuit increases. Therefore It was a large configuration. On the other hand, when using a control IC, the output terminal voltage must be adjusted. is necessary. Therefore, it was not suitable for mass production.

[0009] Therefore, the power supply circuit according to the present invention is intended to eliminate the above problem. We provide a power supply circuit with low internal power consumption and no need to adjust the output terminal voltage. The porpose is to do.

0010 [Structure of the idea]

[0011]

[Means to solve the problem]

A collector is connected between the input terminal to which DC current is supplied and the output terminal connected to the load. a power transistor with a coupled vector-emitter path; coupled between a bias voltage source and the output terminal, and responsive to voltage changes at the output terminal. A 3-terminal power supply IC whose current flows changes depending on the The base of the power transistor changes according to the change in the current flowing through the three-terminal power supply IC. This circuit is equipped with a means to control the ground voltage and outputs a large current, but the internal consumption of this circuit This makes it possible to reduce power consumption.

0012

[Effect]

The power supply circuit according to the present invention uses a three-terminal power supply IC to control the output terminal voltage. . This means that the voltage supplied to the power supply IC is supplied from a bias voltage different from the input terminal voltage. I am providing. As a result, the input terminal voltage becomes the output terminal voltage, and the power transistor It is sufficient to add the minimum operable input/output voltage. Therefore, it is consumed inside the power supply circuit. A power supply circuit is constructed that consumes small amount of power and does not require adjustment of the output terminal voltage.

[0013]

【Example】

Hereinafter, a power supply circuit according to the present invention will be explained based on illustrated embodiments. FIG. 1 is a circuit diagram illustrating an embodiment of a power supply circuit according to the present invention. In FIG. 1, the input terminal to which a DC input voltage is supplied is a transistor 10 (NPN type) is connected to the collector terminal of the On the other hand, the emitter of this transistor 10 The voltage output from the terminal becomes the output terminal voltage of this power supply circuit. transistor 1 A resistor 12 is connected between the emitter and base of 0. Also, this base terminal is connected to a resistor 13. The other end of this resistor 13 is connected to a transistor 11 (PN P type) collector terminal is connected. At the emitter terminal of transistor 11 Bias voltage is connected. There is a resistor between the emitter and base of transistor 11. A resistor 14 is connected. The base terminal of the transistor 11 is connected to the power supply IC1. 5 input terminals are connected. The output terminal of the power supply IC 15 is connected to the output terminal of the transistor 10. Connected to emitter terminal. Also, the other terminal of the power supply IC15 is at the reference potential. Connected to the dots. Furthermore, a capacitor is connected between the input/output terminal of the power supply IC 15 and the reference potential point. sensors 16 and 17 are connected.

[0014] Generally, the minimum potential difference between input and output that allows a power supply IC to operate is approximately 2.5V. Also The potential difference between the base and emitter of transistor 11 is about 0.7V. So bye The as voltage is the output terminal voltage plus 2.5V and 0.7V. on the other hand The operable potential difference between the emitter and collector of the transistor 10 is approximately 0.5 It is V. Therefore, the input terminal voltage should be 0.5V higher than the output terminal voltage. Become.

[0015] The bias current flowing into the power supply IC 15 is the base-emitter of the transistor 11. It is determined by the voltage between the two and the resistor 14. On the other hand, the voltage output from transistor 10 The current is determined by the base current flowing into this transistor 10. this base The current is limited by resistor 13. Note that the resistor 12 and capacitors 16 and 17 are used to stabilize the circuit. There is.

[0016] Next, the operation of this power supply circuit will be explained. When the output terminal voltage decreases, the power supply IC 15 increases the bias current. this The increase corresponds to an increase in the base current of the transistor 11. The transistor 11 is As the base current increases, the output current from the collector also increases. This output voltage The current flows through resistor 13 into the base of transistor 10. For this reason, the transition The base current of star 10 increases. This causes the emitter of transistor 10 to output current increases. Due to this increase in output current connected to the output side, fig. The voltage of the unindicated load increases.

[0017] Conversely, when the output terminal voltage increases, the bias current of power supply IC15 decreases. Do a little. Then, the transistor 10 output current decreases. Ultimately, the output terminal voltage is lowered. As described above, the power supply IC 15 controls the bias current according to the output terminal voltage. are doing. This keeps the output terminal voltage constant. Also, the transistor 10 The power consumption is determined by the emitter current of transistor 10 and the minimum operable value of transistor 10. It is determined by the product of the functional voltage. For example, the minimum operable voltage is 0.5V, and the emitter current is 1A. In this case, the power consumption is 0.5W, which is significantly smaller than the conventional circuit. Ru.

[0018] Next, another embodiment of the power supply circuit according to the present invention will be described. FIG. 2 is a circuit diagram showing another embodiment. In this diagram, the same components as in Figure 1 are marked with the same symbol.

[0019] This embodiment limits the base current of transistor 10 among the embodiments shown in FIG. The resistor 13 that was used is gone, and this part is short-circuited. Instead of this resistor 13 A circuit is provided to limit the base current of transistor 10. This circuit is It is composed of resistors 18 and 19 and a transistor 20 (PNP type).

[0020] One end of the resistor 19 and the emitter terminal of the transistor 20 are connected to a bias voltage. ing. The other end of the resistor 19 and one end of the resistor 18 are both connected to the transistor 11. connected to the transmitter terminal. The other end of the resistor 18 is the base of the transistor 20 connected to the terminal. And the collector terminal of transistor 20 is a transistor It is connected to the base terminal of 11.

[0021] The current flowing from the bias voltage side flows through the resistor 14, transistor 20, and resistor 19. The current is divided by Here, the current flowing from the bias voltage side increases for some reason. When the base current of the transistor 20 increases through the resistor 19 and the resistor 18, the base current of the transistor 20 increases. add This increases the collector current of transistor 20. Therefore, The emitter current of transistor 11 hardly increases. Therefore, the circuit in Figure 2 is as shown in Figure 1. The circuit operates in the same way as the circuit shown in .

[0022] As described above, according to the power supply circuit according to the present invention, the number of components is relatively small. The power consumption of transistors can be significantly reduced. This allows the power This means that the transistor has a smaller collector loss than conventional transistors. Therefore The heat sink may be small. Due to these reasons, the structure is smaller than the conventional one. can. Also, since no adjustment is required, it is suitable for mass production. In addition, heat to surrounding equipment is The impact can be reduced.

[0023]

[Effect of the idea]

As described above, the input terminal voltage is set lower than before, and the output terminal voltage is By controlling the voltage using a power supply IC, the power consumption of the power transistor can be kept low. be able to. For this reason, power transistors with low collector loss can be used. Wear. Furthermore, it becomes possible to downsize the heat sink. Due to these factors, compared to conventional It can be configured compactly. Also, since no adjustment is required, it is suitable for mass production.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional circuit.

[Explanation of symbols]

10, 11...transistor 12, 13, 14...Resistance 15...Power IC

Claims (1)

[Scope of utility model registration request] 1. A power transistor having a collector-emitter path coupled between an input terminal to which direct current is supplied and an output terminal connected to a load, and a power transistor coupled between a bias voltage source and the output terminal. A power supply circuit comprising: a three-terminal power supply IC in which a current flowing through the three-terminal power supply IC changes according to a change in voltage at an output terminal; and means for controlling a base voltage of the power transistor according to a change in the current flowing through the three-terminal power supply IC. .