JPH0448110Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a power control device that detects power consumption in an element and controls the power consumption according to the detected value.

[Technical background of the invention]

Conventionally, a linear control element such as a transistor is inserted between a load and a power source, and the voltage, current, etc. supplied to the load are controlled by controlling the linear control element. Furthermore, if the power consumed by the linear control element is relatively large, it is necessary to control the power consumption within a certain range in order to protect the element. For this purpose, the voltage applied to the element and the current flowing through the element are detected and multiplied by a multiplier circuit to calculate the power consumption, and this value is controlled to be below a certain value.

For example, the maximum voltage applied to the element is
At 10V, the maximum current flowing through the device is 10A, and the maximum allowable power consumption is 50W. The graph of the operating region in this case is shown by diagonal lines in FIG. Therefore, in this case, the element is 50W
It is sufficient to have a heat dissipation capacity of . However, if for some reason there is a possibility that more than 50W of power will be consumed, in order to protect the element, the current and voltage will be detected and the power consumption will be calculated using a multiplier circuit so that the maximum value will be 50W. need to be controlled.

[Problems with background technology]

However, multiplication circuits generally have complex circuit configurations and are expensive. Further, in order to calculate power consumption in order to protect the above-mentioned elements, it is not necessary to have such precision as to use a multiplication circuit.

[Purpose of invention]

This idea was made in view of the above circumstances.
It is an object of the present invention to provide a constant power control device that has a simple configuration, can detect when the power consumption of an element has reached a certain level, and is inexpensive.

[Summary of the idea]

In other words, the present invention detects the voltage applied to the element and the current flowing through the element, obtains the algebraic sum of these detected values, and compares this value with a reference value corresponding to the target power to perform pseudo power control. It is characterized by carrying out the following.

[Example of idea]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and numeral 1 in the figure represents an input terminal. A DC power supply and a load (not shown) are connected in series between this input terminal and a reference potential indicated by ▽ in the figure. This input terminal 1 is also connected to a reference potential via a power control means 2 having an element 12, which controls the power consumed.

The control means 2 is a series circuit of an element 21, that is, a transistor, and a current detection resistor 22.

Reference numeral 3 denotes voltage detection means for detecting the voltage applied to the element 21, and the non-inverting input of the operational amplifier 31 is connected to the terminal 1.

4 is a current detection means, and a current detection resistor 22
The non-inverting and inverting inputs of an operational amplifier 41 are connected to both ends of the .

Reference numeral 5 denotes an adding means, which applies each detection output of the voltage detection means 3 and the current detection means 4 to the inverting input of the operational amplifier 51 via resistors 52 and 53, and adds the target power to the non-inverting input. A corresponding reference value Vref is provided from the power supply 54. Then, the output of the operational amplifier 51 is applied to the element control means 6 via the diode 55.

Reference numeral 6 denotes an element control means, which applies the control voltage Vc applied to the output of the addition means 5 and the control input terminal 7 to the non-inverting input of the operational amplifier 61, and applies the terminal voltage of the current detection resistor 22 to the non-inverting input. It will be done. The output of the operational amplifier 61 is then applied to the base of the transistor 21. Above control voltage Vc
corresponds to the target value of power to be consumed by the power control means 2.

With such a configuration, for example, the voltage E applied to input terminal 1 is 0 to 10V, and the current is I
is 0 to 10A, and the maximum allowable power consumption P
is 50W. Thus, in normal operation, only the power control means 2 and the element control means 6 are involved in the operation. The element control means 6 then controls the current I flowing through the transistor 21 so that the voltage between the terminals of the power supply detection resistor 22 becomes equal to the reference value Vref. Note that the addition means 5 determines that the sum of the detected values of the voltage detection means 3 and the current detection means 4 is the reference value.
The element control means 6 is controlled so as not to exceed Vref.

Therefore, when operating this circuit at the voltage E, current I, and power P mentioned above, the reference value for each detection value of the voltage detection means 3 and the current detection means 4 is
For example, the Vref relationship may be set as follows. That is, voltage/current detection means 3, 4
Assume that the output level is linearly proportional to the input level, and for a current I of 10A, the output is
10V, voltage E is 10V, output is 10V, and reference value Vref is 7.5V. and resistors 52, 53
are equal, and the voltage/current detection means 3,
Divide the output voltage of 4 into 1/2.

Therefore, when the current I is flowing 10A, if the voltage E is 5V or less, the voltage at the inverting input of the operational amplifier 51 is 7.5V or less, so the output of the adding means 5 has no effect.

When the voltage E becomes 5V or more, the voltage at the inverting input of the operational amplifier 51 tends to become 7.5V or more, so the element control means 6 is controlled by the output of the adding means 5, and the voltage E becomes higher. Accordingly, the current I is decreased. Voltage E and current I at this time
The relationship is E=15-I and is given by straight line B in Figure 2.

Similarly, if the voltage E is 10V and the current I is less than 5A, the voltage at the inverting input of the operational amplifier 51 is
Since the voltage is below 7.5V, the output of the adding means 5 has no effect.

Even if the control voltage Vc is increased to increase the current I to 5A or more, the voltage at the inverting input of the operational amplifier 51 tends to be 7.5V or more, so the output of the adding means 5 controls the element control means 6. control to prevent the current I from increasing.

Therefore, according to the above embodiment, control is performed such that the arithmetic sum of voltage E and current I is E+I=15, so that voltage E as shown by curve C in FIG.
The maximum error for constant power control where the product of and current I is constant E x I = 50 is when voltage E = 7.5V,
At this time, the current I is allowed to be 7.5A, so the power consumption is 7.5×7.5=56.25W.

Therefore, the error for 50W is 12.5%.
However, since semiconductor elements such as transistors are usually used with sufficient derating, an error of about 12.5% does not pose a problem.

Therefore, according to the above embodiment, pseudo constant power control can be performed.

Note that the present invention is not limited to the above-mentioned embodiments; for example, in the above-mentioned embodiments, control is mainly performed using current, but control may be performed mainly using voltage.

Further, although operational amplifiers are used as the voltage detection means 3 and the current detection means 4, they can be omitted if the impedance of the signal source is sufficiently low.

Further, by combining the values of the resistors 52 and 53 of the adding means 5 and the reference value Vref, pseudo constant power control of various characteristics can be performed.

Therefore, the device of the present invention is extremely effective when applied to devices that require linear control elements to consume large amounts of power, such as power supplies and electronic loads.

[Effect of idea]

As described above, according to the present invention, it is possible to provide a power control device that has an extremely simple configuration, is inexpensive, and is capable of controlling according to power consumption.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a diagram showing the operation of the circuit of the above embodiment in comparison with the operation of a conventional device.

Claims (1)

[Claims for Utility Model Registration] (1) A power control means having an element for controlling the power consumed, a voltage detection means for detecting the voltage applied to the element of the power control means, and a current flowing through the element. current detection means for detecting the voltage, addition means for obtaining an algebraic sum of the detection value of the voltage detection means and the detection value of the current detection means, and controlling power consumption in the element according to the addition output of the addition means. What is claimed is: 1. A power control device comprising an element control means. (2) Utility model registration The power control device according to claim 1, characterized in that the power control means is a transistor.