JPS62169215A - Constant current controller - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a load by outputting a current lower than a prescribed current in the noncontrol state. CONSTITUTION:This controller consists of a switching element 10, its driving part 11, a transformer 20, a rectifying element 21, etc., and the turn-on/off operation time of the element 10 is controlled to adjust output voltage and current applied to a load 16. In this case,a reference voltage source 17 is provided in an inverted terminal (r) of an error amplifier 18 and a light receiving element 13 is provided in series between the switching element driving part 11 and the base of the element 10 to prevent a current larger than the prescribed current from being outputted in the non-control state. Thus, light emission of a light emitting element 19 is stopped by the error amplifier 18 if the potential difference of a current detecting resistance 14 is larger than that the reference voltage source 17. As the result, the light receiving element connected optically to this element 13 is turned off and the switching element 10, is turned off and a lower non-control output current is outputted to the load 16.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a constant current control device for a power supply.

(Prior art) Fig. 5 is a configuration diagram of a constant current device generally called a switching regulator, in which 1 is a switching element, 2 is a switching drive section, 3 is a transformer, 4 is a current detection section, and 5
6 is a control signal feedback section, 6 is a DC power supply, 7 is a rectifying element, 8 is a smoothing capacitor, and 9 is a load. This device adjusts the output voltage and current applied to the load 9 by controlling the on/off operation time of the switching cable 1 by the switching drive unit 2.6 Figure 6 shows a specific example of the device shown in Figure 5. It shows the configuration of 1
0 is the main transistor as a switching element, 1
1 is a switching drive unit, 12 is a DC power supply, 13 is a light receiving element, 14 is a current detection resistor, 15 is a smoothing capacitor, 16 is a load, 17 is a reference voltage source, 18 is an error amplifier,
19 is a light emitting element, 20 is a transformer, and 21 is a rectifier.

In such a device, first, the main transistor 10 is repeatedly turned on and off under the control of the switching drive unit 11 to intermittent the output of the DC power supply 12, and then supplies DC to the load 16 via the transformer 20 and the rectifier 21. Supplying output current. At this time, the potential difference across the current detection resistor 14 is proportional to the output current applied to the load 16, and when the potential difference across the current detection resistor 14 becomes larger than the reference voltage source 17, the error amplifier 18 causes the light emitting element 19 to emit light. . As a result, the light receiving element 13 optically coupled to the light emitting element 19 is turned on, acting to turn off the main transistor 10, and a substantially constant desired current is supplied to the load 16.

FIG. 7 shows the current waveform in the above case, and in an uncontrolled state, an uncontrolled current 23 larger than the expected current 22 is output, and the output current is detected by the current detection resistor 14. is higher than the desired current 22, the switching drive is performed via the light emitting element 19, light receiving element 13, etc. that constitute the control signal feedback section 5 (FIG. 5) so that the output current decreases to the desired current 22 based on that information. section 11 is controlled.

(Problem to be Solved by the Invention) However, in the above-described operation, when an uncontrolled state occurs due to poor feedback of the control signal, etc., the expected current 22 (
The uncontrolled current 23 higher than (Fig. 7) becomes the output current,
This has the disadvantage of damaging or destroying the connected load 16.

(Means for Solving the Problems) In order to eliminate the above-mentioned drawbacks, the present invention provides a constant current control device that outputs a current lower than the desired current when in an uncontrolled state. The configuration is such that the switching drive section is controlled through the control signal feedback section so that the detected output current of the detection section becomes approximately equal to the desired current.

(Function) With the above configuration, the present invention has the advantage that even if current control becomes impossible, the output current is lower than the expected current, so the connected load will not be destroyed.

(Example) Hereinafter, the present invention will be explained in detail by way of an example using the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. Reference numerals not explained below refer to the same reference numerals as those in FIG. 19
This is the starting capacitor for starting the light emission. As shown in the figure, the reference voltage source 17 is applied to the inverting terminal r of the error amplifier 18, the voltage detection output of the current detection resistor 14 is applied to the non-inverting terminal f, and the direction of the light emitting element 19 is determined by the output current. is provided in the direction in which it emits light under normal conditions and turns on the main transistor 10.

The present invention is configured in this way, and similarly to FIG. 6, the main transistor 10 is repeatedly turned on and off by the switching drive section 11 to intermittent the output of the DC power supply 12, and the main transistor 10 is connected to the load 16 via the transformer 20 and the rectifier 21. The desired current is supplied to the output current as the output current. At this time, the potential difference across the current detection resistor 14 is proportional to the current applied to the load 16, and the potential difference across the current detection resistor 14 is based on 4! voltage source 17
When it becomes larger than , the error amplifier 18 stops the light emitting element 19 from emitting light.

As a result, the light receiving element 13 optically coupled to the light emitting cable 19
is turned off, acting to turn off the main transistor 10, a desired current is extracted, and a constant output current is supplied to the load 16.

FIG. 2 shows the output current according to the configuration shown in FIG. 1, 25 is the expected current, and 26 is the uncontrolled current in the case of poor control, that is, when the light emitting element 19 does not emit light. According to the present invention, such a low uncontrolled current 26 is output when there is no control.

As described above, the present invention provides the reference voltage source 17 at the inverting terminal r of the error amplifier 18, and provides the light receiving element 13 in series between the switching drive section 11 and the base of the switching transistor 10. In the case of a failure in feedback of a control signal to, that is, when there is no control, a constant current power supply device is configured that does not output a current larger than the desired current.

FIG. 3 shows another embodiment of the present invention, and the explanations of the symbols refer to those of FIGS. 1 and 6.

This embodiment differs from that in FIG. 1 in that the direction of the light emitting element 19 and the inputs to the inverting terminal r and non-inverting terminal f of the error amplifier 18 are opposite to those in FIG. Similarly to the above case, the main transistor 10 is repeatedly turned on and off under the control of the switching drive unit 11 to intermittent the output of the DC power supply 12, and the desired current 25 is outputted to the load 16 via the transformer 20 and the rectifying element 21. (Figure 2). At this time, the potential difference across the current detection resistor 14 is proportional to the current applied to the load 16, and when the potential difference across the current detection resistor 14 becomes larger than the reference voltage source 17, the error amplifier 18 causes the light emitting element 19 to emit light. Stop.

As a result, the light receiving element 13 optically coupled to the light emitting element 19
is turned off, acting to turn off the main transistor 10, and the load 16 receives the desired current 25 as the output current.
(Fig. 2) is supplied.

Figure 4 shows the main part of the circuit configuration during large current control.
During large current control, a transistor 27 is provided between the base of the main transistor 10 and the switching drive section 11 instead of the light receiving element 13, and this is controlled by the light emitting element 13, thereby achieving constant current control of large current. It made it possible.

(Effects of the Invention) As is clear from the above description, the present invention provides a method for controlling the output current when a current control failure occurs in a constant current device.

To prevent the risk of the current rising above the intended value and destroying the load,
This effect can be easily avoided with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, FIG. 2 is an explanatory diagram of its output current, FIG. 3 is a diagram of the configuration of another embodiment of the present invention, and FIG. 4 is a diagram showing still another embodiment. Diagram showing the main part of the example, 5th
FIG. 6 is a block diagram showing the configuration of a conventional device, FIG. 6 is a specific configuration diagram thereof, and FIG. 7 is an explanatory diagram of its output current. 1... Switching element, 2, 11...
...Switching drive unit, 4...Current detection unit, 5...Control signal feedback unit, 9, 16...
...Load, 10...Main transistor, 1
3... Light receiving element, 14... Current detection resistor, 17... Reference voltage source, 18...
...Error amplifier, 19...Light emitting element,
22, 25... Expected current, 23, 26...
...Uncontrolled current, 24...Start-up capacitor. Figure 1 14-4 is shown in Figure 1 14-4. Zugamma Gunza 9 Disaster

Claims (3)

[Claims] (1) In a constant current control device comprising a current detection section for output current and a current control section for controlling the output current to a substantially constant predetermined current using the detected output, the current detection section A constant current control device, characterized in that when the current control section or the current control section malfunctions, the output current becomes lower than a required desired current. (2) An error amplifier that applies a reference voltage source for a predetermined current to an inverting terminal and a detection output of an output current to a non-inverting terminal, and when the detected output current becomes higher than the reference voltage source. When an abnormality in the current control section or an abnormality in the output current is detected by providing a light emitting element that emits light based on the output of the above error amplifier, and a light receiving element in which a starting capacitor optically coupled to the output of the light emitting element is added in parallel. 2. The constant current control device according to claim 1, wherein the switching transistor is controlled based on the output information of the light receiving element so that the output current is equal to or less than a predetermined current. (3) An error amplifier that applies a reference voltage source for a predetermined current to a non-inverting terminal and a detection output of an output current to an inverting terminal, and when the detected output current becomes higher than the reference voltage source. A light emitting element that emits light based on the output of the error amplifier, and a light receiving element in which a starting capacitor optically coupled to the output of the light emitting element is added in parallel are provided to detect an abnormality in the current control section or an abnormality in the output current. 2. The constant current control device according to claim 1, wherein the switching transistor is controlled based on the output information of the light receiving element so that the output current is equal to or less than a predetermined current.