JPS605744Y2 - Insulation resistance tester - Google Patents

Description

[Detailed description of the invention] The present invention is a DC low voltage power supply circuit including a constant voltage circuit, and a DC low voltage power supply circuit including a constant voltage circuit.
- This relates to an insulation resistance meter composed of a DC converter and an indicator circuit using the direct polarization method, in which the base current compensator of the base current adjustment circuit in the blocking oscillation circuit that constitutes the primary side of the DC-DC converter includes: By providing a positive temperature coefficient thermistor whose resistance value changes in response to changes in ambient temperature, and accomplishing temperature compensation for the base current that drives the oscillation transistor in the blocking oscillation circuit, the output of the blocking oscillation circuit is adjusted to the ambient temperature. The purpose is to maintain the insulation resistance constant against changes and to reduce the error in the insulation resistance reading of the insulation resistance meter due to changes in ambient temperature.

Figure 1 shows the degree of variation in the secondary side output current (load current) of a DC-DC converter used in a conventional insulation resistance tester driven by a DC low-voltage power supply circuit with respect to changes in ambient temperature. DC-DC
:+ It becomes difficult to temperature compensate the output current (load current) of the inverter, and with an insulation resistance meter where the above output current (load current) is converted to an insulation resistance value by an indicator circuit, due to changes in ambient temperature, There were large errors in each insulation resistance reading.

The present invention has been devised to solve the above-mentioned conventional problems, and will be described below with reference to drawings showing embodiments thereof.

Figure 2 shows a block diagram of the circuit configuration of the insulation resistance tester. 1 is a DC low voltage power supply circuit including a constant voltage circuit, and 2 is a DC-DC circuit consisting of a blocking oscillation circuit, a booster circuit, and a voltage doubler rectifier circuit. Converter, 3 is an indicator circuit based on the direct polarization method, and 4 is a load.

Figure 3 shows a blocking oscillation circuit that constitutes the primary side of the DC-DC converter, which has a transformer that controls oscillation and boosting of the insulation resistance meter.This blocking oscillation circuit 5 drives the oscillation transistor Q□. Semi-fixed resistance V
A base current adjustment section 6 consisting of R1, two resistors R□,
A base current adjustment circuit constituted by a base current temperature compensator 7 in which R2 and a positive characteristic thermistor RT whose resistance value changes in response to changes in ambient temperature are connected in series and parallel, an oscillation transistor Q1, a base resistor R3, Emitter resistance R1
, a resonant capacitor C1, and an oscillation circuit consisting of a lance T that controls oscillation and boosting.

In the circuit shown in Figure 3, Vin=V1+v2...
-Constant regardless of temperature, the following relationship holds true: VB (base bias voltage) = ■2 Vto = (base-emitter voltage).

If the ambient temperature were to drop now, the base-emitter voltage VBE of the oscillation transistor Q1 would rise, and the base bias voltage V8 would decrease.

Therefore, the base current is difficult to flow (and DC-D
The output of the oscillation circuit on the primary side of the C converter 2 decreases.

Accordingly, the output current (load current) on the secondary side of the DC-DC converter 2 also decreases.

However, the base current temperature compensation section 7 of the base current adjustment circuit
Since the resistance value of the positive characteristic thermistor RT decreases as the ambient temperature decreases, the voltage V1 applied to the current adjustment circuit decreases, and due to the relationship V1 + V2 = Vin (constant), the voltage applied to the resonant capacitor C1 decreases. ■2 increases.

Accordingly, the bias voltage v8 at the base of the oscillation transistor Q increases.

In other words, even if the ambient temperature drops, the oscillation transistor Q1
The output of the blocking oscillation circuit 5 is always kept constant because the base current IB that drives the
As a result, the output current on the secondary side of the DC-DC converter 2 (
load current) can be prevented from decreasing due to a drop in ambient temperature.

On the other hand, if the ambient temperature becomes high, the DC-DC controller
The output current (load current) on the secondary side of the D
Secondary side output current (load current) of C-DC converter 2
This can prevent an increase in ambient temperature due to a rise in ambient temperature.

Furthermore, when a heavy load is applied to the secondary side of the DC-DC converter 2, a larger output current (load current) flows to the secondary side than when the load is light, and fluctuations in the output current (load current) due to changes in ambient temperature also occur. Although it is larger than when the load is light, the DC-
Since the oscillation frequency of the blocking oscillation circuit 5 on the primary side of the DC converter 2 becomes low, the input impedance of the transformer T that controls oscillation and boosting becomes low, and as a result, the collector current Ic of the oscillation transistor Q1 in the blocking oscillation circuit 5 decreases. It becomes larger than when the load is light.

Accordingly, a large current flows through the base current adjustment circuit in the blocking oscillator circuit 5, and voltage fluctuations due to changes in the ambient temperature at the rain end of the base current temperature compensation section 7 of the base current adjustment circuit also become larger than when the load is light. Voltage fluctuations due to changes in ambient temperature of V□ applied to the base current adjustment circuit also increase.

Therefore, the above-mentioned V, +V2=Vin (-constant),
■8”V2 From the relationship with VB, oscillation transistor Q1
The bias voltage V[3 at the base of the oscillating transistor Q fluctuates significantly compared to light load due to changes in ambient temperature.
The base current that drives the blocking oscillator circuit 5 also changes to compensate for changes in the output current (load current) due to changes in ambient temperature compared to when the load is light, so the output of the blocking oscillator circuit 5 is always kept constant. It is possible to compensate for variations in the output current (load current) on the secondary side of the DC-DC converter 2 due to changes in ambient temperature.

Conversely, when a light load is applied to the secondary side of I) C-DC converter 2, the DC
- It is possible to compensate for variations in the output current (load current) on the secondary side of the DC converter 2 due to changes in ambient temperature.

In this way, any load force on the secondary side of the DC-DC-Y inverter can be compensated for by fluctuations in the output current (load current) due to changes in ambient temperature.

(Fig. 4) As described above, the insulation resistance meter of the present invention includes a base current adjustment section and a temperature compensation section for the base current in the Base-Smith current adjustment circuit of the oscillation transistor.
- Since the output current (load current) on the secondary side of the DC converter can be temperature-compensated, the error in each insulation resistance instruction value due to changes in ambient temperature becomes extremely small, and as a result, reliability can be improved.

[Brief explanation of drawings]

Figure 1 shows the DC-DC used in a conventional insulation resistance meter.
A graph showing the temperature characteristics of the output current (load current) on the secondary side of the converter, Fig. 2 is a block diagram of the circuit configuration of an insulation resistance meter showing an embodiment of the present invention, and Fig. 3 shows a DC diagram of the resistance meter. - A circuit diagram showing a blocking oscillator circuit on the primary side of the DC converter. FIG. 4 is a graph showing the temperature characteristics of the output current (load current) on the secondary side of the DC-DC converter of the present invention. 1...DC low voltage power supply circuit, 2...D
C-DC converter, 3... Indicator circuit, 5.
... Blocking oscillation circuit, 6 ... Base current adjustment section, 7 ... Temperature compensation section, R□, R2
...Resistor, RT...Positive characteristic thermistor, Q-type...Oscillation transistor.

Claims (1)

[Scope of utility model registration request] A DC-DC inverter has a DC low voltage power supply circuit including a constant voltage circuit, a transformer that controls oscillation and boosting, and the primary side of this transformer is composed of a blocking oscillation circuit mainly composed of oscillation transistors, and a direct polarization method. The base current adjustment circuit of the oscillation transistor of the blocking oscillation circuit includes a base current adjustment section consisting of a semi-fixed resistor, two resistors, and one positive characteristic thermistor connected in series and parallel. An insulation resistance tester with a temperature compensation section for the base current inserted in series.