JPH0435937Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a constant current power supply that performs constant current operation control by negatively feeding the load current to the primary side via a negative feedback resistor and detecting the voltage change in the negative feedback resistor. .

Conventionally, such a constant current power supply includes one shown in FIG. This constant current power supply 1 includes a DC power supply section 2
An output conversion circuit section 3 having a high-voltage transformer T is provided between the load R _L and the load R L, and a negative feedback path is provided to feed back the load current I _O of the load R _L on the secondary side of the high-voltage transformer T to the primary side. A negative feedback circuit section 4 including a resistor Rf and a comparison amplifier CP is provided. Note that 5 is a regulator that operates upon receiving the output of the negative feedback circuit section 4. In such a constant current power supply 1, for example, when the primary side DC power supply part 2 is grounded to the grounding part 6 and used for powering other circuits (not shown), the load current I _O
However, instead of flowing like the solid line A, it flows like the broken line B. Therefore, in this type of conventional constant current power supply, the primary side of the DC power supply section 2 etc. is connected to the grounding section 6.
It is possible to control the constant current to flow through the load R _L only when the load R It was not possible to control the constant current to flow through R _L.

An object of the present invention is to enable a constant current to always flow through a load on the secondary side without being affected by grounding of the primary side of a DC power supply unit or the like.

In order to achieve these objectives, this invention
An output conversion circuit section having a high-voltage transformer is provided between the DC power supply section and the load, and a negative feedback resistor and a negative feedback resistor are provided in the path that feeds back the load current flowing through the load on the secondary side of the high-voltage transformer to its primary side. , a constant current power supply comprising a negative feedback circuit section including a regulator connected to the primary side of the high voltage transformer or a comparator amplifier that controls an oscillation circuit based on the voltage change in the negative feedback resistor. A resistor is provided between the input section of the comparator amplifier and the ground section of the primary side of the DC power supply section, etc., and the winding start side of the secondary side of the high voltage transformer is connected between the input section of the comparator amplifier and the negative feedback resistor. By connecting between them, a path for negative feedback is formed.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 is a circuit diagram of this embodiment, and parts corresponding to those in FIG. 1 are given the same reference numerals. The constant current power supply 20 of this embodiment includes a DC power supply section 2, an output conversion circuit section 3, a negative feedback circuit section 4, and a regulator section 5. The output conversion circuit section 3 includes an oscillation transistor Tr ₂ , a high voltage transformer T, and a rectifier diode.
D ₁ , smoothing capacitor C ₁ , spark discharge prevention resistor
Including R ₁ and discharge resistor R ₂ . This output conversion circuit section 3 includes an oscillation transistor Tr ₂ and a high voltage transformer T.
It has an oscillation circuit such as collector tuning and emitter grounding made up of the primary coil _L1 and circuits not shown. This output conversion circuit section 3 also has the following features:
A high voltage output is obtained by a high voltage transformer T. This high-voltage output is then converted to a DC high-voltage output by a rectifier diode D ₁ and a smoothing capacitor C ₁ , and a spark discharge prevention resistor.
A DC voltage output is applied to the load R _L via R ₁ . The regulator 5 has a transistor Tr ₁ as a variable impedance element, and the negative feedback output of the negative feedback circuit section 4 is applied to the base of the transistor Tr ₁ .

The negative feedback circuit section 4 includes a comparison amplifier CP.
The comparison amplifier CP has positive and negative phase inputs +, - and an output connected to the regulator 5. The negative feedback circuit section 4 also includes a reference power supply Vs. A negative feedback resistor Rf is connected between the positive side of this reference power supply Vs and the positive phase side input section + of the comparison amplifier CP.
Further, the winding start side of the secondary side of the high-voltage transformer T is connected between the negative feedback resistor Rf and the positive-phase input section + of the comparison amplifier CP, thereby forming a negative feedback path. A voltage dividing resistor R ₃ is connected in parallel to this reference power supply Vs.
R ₄ is provided. The connection point X between the voltage dividing resistors R ₃ and R ₄ is connected to the negative phase side input section - of the comparator amplifier CP. In addition, in parallel to the series circuit of the reference power supply Vs and the negative feedback resistor Rf, there is a capacitor _C2 for absorbing voltage ripples, and a diode for voltage clamping to protect the comparator amplifier CP in the event of an output short circuit or spark discharge. D ₂ is connected.

In such a configuration, the negative feedback resistor Rf is
Positive phase side output section + of comparator amplifier CP and reference power supply Vs
It is connected to the ground section 6 of the DC power supply section 2, which is the primary side, via the ground section 6 of the DC power supply section 2, which is the primary side. Therefore,
Even if the negative terminal side of the DC power supply unit 2 is grounded to the grounding unit 6 in order to use it as a power source for another circuit (not shown), the load current I _O I flows through the load R _L as shown by solid lines E and F. After that, it can flow through the reference power supply Vs and the negative feedback resistor Rf of the negative feedback circuit section 4 and reach the winding start side of the secondary side of the high voltage transformer. Since the load current Io flows through the negative feedback resistor Rf, the negative feedback circuit section 4 can provide a negative feedback output to the regulator 5, and therefore can perform constant current operation.

This constant current operation will be explained in detail. First, when a drive signal is applied to the base of the oscillating transistor Tr ₂ at the same time as the DC power supply 2 is applied, a resonant waveform is generated at the collector of the transistor Tr ₂ , and a high voltage is applied to the secondary side via the high voltage transformer T. A resonant waveform is generated. This resonant waveform is rectified and smoothed by a rectifying diode D ₁ and a smoothing capacitor C ₁ into a high DC voltage. By this,
A load current Io flows through the load R _L to the load R _L , the reference power supply Vs, the negative feedback resistor Rf, and the beginning of the secondary winding of the high voltage transformer T, and is boosted and flows to the load R _L.

Here, when the load current Io flowing through the load R _L increases, the load current Io flowing through the negative feedback resistor Rf also increases, so the potential difference between both ends of the negative feedback resistor Rf increases. Since the reference power supply Vs is a stable fixed voltage, when the potential difference of the negative feedback resistor Rf increases,
The potential at the positive phase side input section + of the comparator amplifier CP becomes low. The balanced state of this comparator amplifier CP is that the negative phase side input section - is Vs × {R ₃ / (R ₃ + R ₄ )}, and the positive phase side input section + is relative to the negative phase side input section -. The voltage has settled down to a slightly higher potential.

As for the operation of this comparison amplifier CP, when the potential of the positive-phase side input section + attempts to fall below the equilibrium state, it acts in the direction of lowering its output voltage. As the output voltage of the comparison amplifier CP decreases, the base voltage of the transistor _Tr1 of the regulator 5 decreases, and the voltage applied to the primary side of the transformer T decreases, thereby reducing the load _RL . The flowing load current Io becomes smaller and constant current operation is performed.

Furthermore, when the load current Io flowing through the load R _L changes in the direction of decreasing, the operation opposite to that described above will be performed. In addition, the potential EX at the connection point
is set to be lower than the potential EY at the connection point Y between the reference power supply Vs and the negative feedback resistor Rf. In this way, according to this embodiment, even if the DC power supply section 2 is grounded, constant current operation can be performed without being affected by this. Note that the above-mentioned resistor R _f may be replaced with a constant voltage diode.

FIG. 3 is a circuit diagram of another embodiment, and parts corresponding to those in FIG. 2 are given the same reference numerals. What should be noted in the constant current power supply 30 of this embodiment is that the regulator 5 is not provided and the negative feedback output of the negative feedback circuit section 4 is applied to the oscillation circuit section OS of the output conversion circuit section 3. This is what is happening. The oscillation circuit section OS drives the oscillation transistor Tr ₂ in response to its negative feedback output. Therefore, the oscillation transistor Tr ₂ oscillates in response to variations in the load current Io, and this induces a high voltage output in the secondary coil L ₂ of the high voltage transformer T to keep the load current Io constant. Ru. The rest of the configuration is similar to the circuit shown in FIG.

FIG. 4 is a circuit diagram of still another embodiment.
Portions corresponding to those in FIG. 3 are given the same reference numerals. Each of the embodiments shown in FIGS. 2 and 3 is of a type in which a positive output is given from the output conversion circuit section 3 to the load R _L. On the other hand, the embodiment shown in FIG. 4 is of a type in which a negative output is given to the load _RL . What should be noted about the constant current power supply 40 of this embodiment is that the reference power supply Vs is provided between the positive phase side input section + of the comparison amplifier CP of the negative feedback circuit section 4 and the ground section 6; A negative feedback resistor Rf is provided between the negative phase side input section - and the ground section 6. In this embodiment as well, the load current Io flows as shown, so constant current operation control can be performed regardless of whether or not the DC power supply section 2 is grounded. In this embodiment, the other configuration is the same as that in Fig. 2, except that a constant voltage diode D ₂ ' is provided as a clamping diode, and the direction of the rectifying diode D ₁ is reversed. .

FIG. 5 is a circuit diagram of yet another embodiment,
Portions corresponding to those in FIGS. 2 to 4 are given the same reference numerals. This embodiment is also of the negative output type as in FIG. 4. Constant current power supply 50 of this embodiment
3, the regulator 5 is not provided as in FIG. 3, and the negative feedback output of the negative feedback circuit section 4 is applied to the oscillation circuit section OS in the output conversion circuit section 3. The other configurations are the same as in FIG. 4.

As described above, according to the present invention, the negative feedback resistor is
It is provided between the input section of the comparator amplifier and the ground section of the primary side of a DC power supply section, etc., and the winding start side of the secondary side of the high voltage transformer is provided between the input section of the comparator amplifier and the negative feedback resistor. This connection forms a negative feedback path, so even if the primary side is grounded, such as when the DC power supply is used as a power source for other circuits, the negative feedback resistor will still carry the load current. Therefore, constant current operation control can be performed without being affected by the grounding of the primary side of the DC power supply unit or the like.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, and FIGS. 2 to 5 are diagrams showing each embodiment of the present invention. 20, 30, 40, 50...constant current power supply, 2...
...DC power supply section, 3...Output conversion circuit section, 4...Negative feedback circuit section, 5...Regulator section, 6...Grounding section, CP...Comparison amplifier, Rf...Negative feedback resistor, Io
...Load current, R _L ...Load.

Claims (1)

[Claims for Utility Model Registration] An output conversion circuit section having a high-voltage transformer is provided between the DC power supply section and the load, and the load current flowing through the load on the secondary side of the high-voltage transformer is negatively fed back to its primary side. The path includes a negative feedback circuit section including a negative feedback resistor and a comparison amplifier that controls a regulator or an oscillation circuit connected to the primary side of the high voltage transformer based on a voltage change in the negative feedback resistor. In the constant current power supply, a negative feedback resistor is provided between the input section of the comparator amplifier and the ground section of the primary side of the DC power supply section, etc., and the negative feedback path is connected to the beginning of the winding of the secondary side of the high voltage transformer. A constant current power supply, characterized in that the constant current power supply is formed by connecting the side of the comparator between the input section of the comparator amplifier and the negative feedback resistor.