JPS6015962B2 - Constant current power supply board current detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current detection circuit for a constant current power supply board for supplying power to a communication device, particularly to a plurality of repeaters from a distance.

Generally, a constant current supply board is used to supply DC power to distant repeaters in order to provide stable power regardless of the number of repeaters or cable loss. In recent years, there has been an increasing demand for higher current stability due to the demand for lower power consumption in repeaters, and at the same time, higher power efficiency and simpler circuits for power supply boards are also required.

In order to simplify the circuit configuration, the known power supply board does not directly detect the output DC current, but has a stabilization circuit that indirectly detects the output current inside the converter. The reality was that stability was poor.

A possible method to improve this current stability is to directly detect the output DC current and compare it with the reference voltage, but this method requires a dedicated power supply for the control circuit and has the disadvantage of complicating the circuit. There is. FIG. 1 shows a circuit diagram of a power supply board using a conventionally known DC-DC converter. In the diagram, reference number 1
, 1' are input terminals, reference numerals 2 and 2' are output terminals, and the input DC voltage is converted into AC by the inverter 4 and supplied to the load 3. Reference numerals 6 and 7 are the contacts of the relay 5. Normally, when current is flowing through the winding of the relay 5, the contacts 6 and 7 are closed and are self-maintained by the current supplied to the load 3. There is. The load 3 is an outdoor line in which a cable and a plurality of repeaters are connected in series, and when such a line is disconnected, the voltage output from the power supply panel becomes abnormally high. Relay 5 and its contacts 6 and 7 are used to cut off the line from the power supply board output when such high voltage occurs.
Switch 12 connected to terminals 8, 9 and 10, 11
and 13 are for closing the switch and making the contacts 6 and 7 of the relay 5 at the start of power supply. The output of the inverter 4 is converted into a necessary voltage by a transformer 14, then double-wave rectified by diodes 15 and 16, smoothed by a choke coil 17 and a capacitor 8, and converted into direct current.

To improve the stability of the output current, it is necessary to insert a resistor in series with the output circuit, detect the voltage drop caused by this resistor, and compare it with a reference voltage. The resistor 19 is used to detect this current, and the voltage detected by the resistor 19 is divided into necessary voltages by resistors 24, 26 and a variable resistor 25, and then compared with a reference fin pressure. The power source for the generation of the reference voltage and the comparison/amplifier circuit is obtained from the auxiliary winding of the transformer 14. The diode 20 rectifies the terminal voltage of the auxiliary winding, and the voltage at the terminal of the auxiliary winding is rectified by the capacitor 21 to be connected to the control circuit. It is used as a power source. The resistor 22 and the constant voltage diode 23 generate a reference voltage from this control circuit power supply, and the multiplier 27 similarly receives the control circuit power supply and compares the reference voltage with the detected voltage. An amplification signal of the difference between the reference voltage and the detected voltage is obtained at the output of the intensifier 27, and the operation of the inverter 4 is controlled so as to form the basis of an optical feedback loop.
The circuit connected in this manner acts to supply a constant current to the output, and maintains a constant current even when the impedance of the load 3 changes significantly. As a result, the voltage between the output terminals 2 and 2' changes due to fluctuations in the bowl 3, and therefore, the power supply voltage for the control circuit also changes over time and is also affected by fluctuations in the input voltage. In order for the control circuit to operate stably within the range of input voltage fluctuations and load rated fluctuations, the power supply voltage must also be stable. Therefore, it is generally necessary to use a stabilizing circuit, which increases the complexity of the circuit. This is unavoidable, and the power consumption in the control circuit increases due to the stabilization of the power supply voltage, resulting in a decrease in the power efficiency of the entire feeder board.

SUMMARY OF THE INVENTION An object of the present invention is to provide a current detection circuit which eliminates the above-mentioned drawbacks and which operates stably with a simple circuit configuration. Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows a first embodiment of the present invention, and parts given the same reference numerals as those in FIG. 1 have the same functions, so a description thereof will be omitted. In the circuit of the present invention, the voltage drop caused by the relay 5 is utilized, and a reference voltage is obtained by a constant voltage diode 101 and a resistor 102 and applied to one input terminal a of the multiplier 106.

Detection of the output current is similarly performed using the voltage drop of relay 5, and resistors 103 and 105 and variable resistor 1
04 divides the voltage of the relay 5, and a multiplier 106
is applied to the other input terminal b. Furthermore, the intensifier 10
6 is also obtained using the voltage drop of relay 5, and the positive power terminal c and negative power terminal d are respectively connected to relay 5.
connected to both ends. At the output terminal c of the multiplier 106, a DC voltage is obtained as an error multiplication signal obtained by comparing the current flowing through the relay 5 with a reference value, and the inverter 4 is controlled as a negative feedback loop. As a result,
The output current is stabilized, and even if the impedance of the load 3 changes significantly, the current flowing through the relay 5 remains stable. That is, even if the voltage between the output terminals 2 and 2' changes significantly, the operation of this circuit is not affected. As is clear from the above explanation, this circuit detects current, generates a reference voltage, and supplies power to the comparison/amplification circuit using the light drop of relay 5, and its operation is as follows: It is stable and unaffected by load, and the distribution structure is simple.

Furthermore, since a dedicated power supply circuit is not required, the power efficiency of the entire power supply panel is not significantly reduced. FIG. 3 shows another embodiment of the present invention, which is used particularly when high precision and stability of the output current are required.

That is, when the current of the intensifier output changes, in the embodiment of FIG. 2, this current change becomes an error in the detected current, but the third
The circuit shown in the figure improves this point. In the embodiment shown in FIG. 3, the same reference numerals as those in FIG. 1 have the same functions, so a description thereof will be omitted.

This embodiment similarly utilizes the voltage drop caused by the relay 5, and a constant voltage source is obtained by a constant voltage diode 202 and a resistor 201.

The anode potential of the diode 202 is connected to the negative power supply terminal d of the multiplier 208 as a reference potential. resistance 2
03 and 204 are used to bias the reference voltage input terminal a of the multiplier 208 and to perform high-voltage current detection as described later. A voltage proportional to the output current is generated across the current detection resistor 19, and a voltage regulator diode 20
2 and the zener voltage is divided by resistors 205 and 207 and variable resistor 206 and guided to the other input terminal b of multiplier 208. The power supply terminal e of the multiplier 208 is connected to the cathode of the constant voltage diode 202, and the power flowing into the power supply terminal e of the multiplier 208 is connected to the cross current detection resistor 1.
It is obtained from the current passing through 9. The amount of change in the voltage drop bounded by the current detection resistor 19 is compared and multiplied by the input terminals a and b of the multiplier 208, and appears at the output terminal c.
The voltage generated at this power terminal controls the inverter 4 as a negative feedback loop, thereby controlling the voltage drop amount of the resistor 19 so as to offset the change. Now, if the gain of the negative feedback loop is sufficiently large, the potentials of input terminals a and b of the multiplier 208 will be equal, and the following relationship will hold true. k,
．． V2=k2(Vz+1.

・Rs) ...■From this.

= Sosa/K Yoko. ...■, and the output current is V
z, Rs, k, . It is stabilized to a value determined by k2.

Here, Vz: Zener voltage l of the voltage regulator diode 202
o: Output current Rs: resistance value k of current detection resistor 19,: voltage division ratio between a and d by resistors 203 and 204 k2: voltage division ratio between b and d by resistors 205 and 207 and variable resistor 206 This circuit is loop-controlled to keep the output current constant regardless of input voltage fluctuations and load impedance fluctuations, but when such external fluctuation factors are added, the output terminal of the multiplier 208 Naturally, the current supplied from c to the inverter 4 changes.

This change in current appears as a change in the current applied to the power supply terminal e of the multiplier 208, but the power to the multiplier 208 is obtained using the voltage drop of the relay 5, and the current is applied to the power terminal e of the multiplier 208. A change in the current is always read as a change in voltage drop across the detection resistor 19, and is led to the input terminal point b through the resistor 207 and the variable resistor 206. In this circuit, the only circuit that bypasses the sense resistor 19 is the connection to the resistor 207, and the input impedance of the multiplier 208 is usually high enough so that the resistance values of the resistors 205 and 207 are can be set to a sufficiently high value.

That is, the output current supplied to the load 3 can be accurately detected as a voltage drop across the detection resistor 19 without being affected by changes in the operating point of the multiplier 208. The feature of this embodiment is the second
As shown in the figure, the circuit configuration is simple because the voltage drop of relay 5 is used instead of providing a dedicated power supply circuit for generating the reference voltage and powering the multiplier. The goal is to not significantly reduce efficiency. In addition, in order to maintain the output current accurately regardless of fluctuations in output impedance, the voltage drop across relay 5 is stable even if the terminal voltage between output terminals 2 and 2' varies greatly, and the reference voltage and multiplier operation is not affected. In both of the above examples,
Although the winding resistance of the relay 5 is used, if there is an impedance element, such as a standard resistance for current measurement or a dummy load, which is always inserted in series with the output circuit, it can be used.

The present invention can be applied to constant current generation circuits other than DC-DC converters.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a current detection circuit of a secondary power supply board, and FIGS. 2 and 3 are circuit diagrams showing first and second embodiments of the present invention, respectively. In Figs. 2 and 3, 1, 1'...input terminals,
2, 2'... Output terminal, 8.9, 10, 11...
... Control terminal for starting power supply, 4 ... Inverter, 5 ... Relay, 6, 7 ... Contact of relay 5, 106, 208 ... Multiplier, 19, 102, 103, 104, 105, 201
,203,204,205,206,207...
・Resistance, 101, 202... Constant voltage diode. Multi-figure 2 Kanta-3

Claims (1)

[Scope of Claims] 1. An impedance element connected in series to an output circuit, a reference voltage generation circuit connected in parallel to the impedance element and generating a reference voltage in response to the voltage across the impedance element; a voltage dividing circuit that is connected in parallel to the impedance element and outputs a divided voltage obtained by dividing the voltage between both ends of the impedance element;
a comparison amplifier circuit, which is applied to an input terminal of the reference voltage, the divided voltage is applied to a second input terminal, and outputs a voltage proportional to the difference between the reference voltage and the divided voltage. Current detection circuit of current supply board. 2. A series connection circuit of an impedance element and a current detection element connected in series to the output circuit, and a reference voltage generation circuit connected in parallel to the impedance element and generating a reference voltage in response to the voltage across the impedance element. a voltage dividing circuit that is connected in parallel to the series-connected circuit and outputs a first divided voltage obtained by dividing the voltage across the series-connected circuit; and a voltage across the impedance element or the reference voltage. is the power supply voltage, the reference voltage or a second divided voltage obtained by dividing the reference voltage is applied to a first input terminal, the first divided voltage is applied to a second input terminal, and the reference voltage or A current detection circuit for a constant current power supply board, comprising: a comparison amplifier circuit that outputs a voltage proportional to the difference between a second divided voltage and the first divided voltage.