JPS60121959A - Power source - Google Patents

Abstract

PURPOSE:To prevent the erroneous operation of a power source by connecting a smoothing circuit for smoothing the waveform of a signal voltage with a malfunction detector. CONSTITUTION:Even if a transistor 9 is conducted in an extremely short time width, it is absorbed to a smoothing circuit 31 not to operate an operational amplifier 6. In other words, no signal is outputted from the amplifier 6 even if a single spark discharge occurs. Accordingly, it does not stop the operation of a controller 5 nor operate for a signal of extremely short time width while providing a function of reliably detecting the malfunction at the secondary side.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a power supply device suitable for use in, for example, a charging device or a static elimination device of a copying machine.

Technical Background and Problems Conventionally, in this type of device, the output state of the secondary side is detected and the energization to the primary side is controlled by a control circuit. A tertiary winding is provided which can obtain an output with the same waveform as the secondary side, and the peak value of the signal from this tertiary winding is detected and used as a control signal.

That is, it operates to increase the output when the detected voltage decreases. Therefore, depending on such a control circuit, if the secondary side is short-circuited and the voltage drops, the operation of the circuit cannot be stopped.

For this reason, when the voltage on the secondary side decreases, -
A detection circuit that protects the circuit by stopping power supply to the next side is also provided separately from the above-mentioned detection circuit. However, the signal waveform obtained from the tertiary winding is as shown in Figure 2, and since the conventional detection circuit has high sensitivity, when the lowest voltage part Δ of the ripple current is deep, it appears as if the secondary voltage has decreased. It will malfunction in the same way as when you did it.

Therefore, there is an inconvenience that the circuit stops even though it is operating normally.

Purpose of the Invention The object of the present invention is to provide a power supply device having a function to protect circuits and equipment by stopping output when an abnormal state such as an output short circuit or spark discharge occurs on the secondary side. SUMMARY OF THE INVENTION The present invention provides a control circuit that controls the output of the secondary side and an abnormality detection circuit that stops the output when the secondary side voltage drops abnormally. Since a smoothing circuit is connected to smooth the waveform, the signal voltage is pulsating and the lowest voltage part is low, so that malfunctions caused by this can be prevented and abnormal conditions can be detected in a stable manner. This is what I did.

Embodiments of the Invention First, a primary winding 3 of a lance 2 and a transistor 4 serving as a switching device Ql are connected to a power supply l to form an inverter (A). A control circuit 5 is connected to these transistors 1 to 4, and to the input side of the control circuit 5, operational amplifiers 6 and 7, which serve as detection circuits and are indicated as OF1 and OF2, are connected.

Moreover, the electric current m 1 km l! A constant voltage circuit 8 is connected, and this constant voltage circuit 8 is connected to the emitter of a pnp type transistor 9 called C2 constituting the abnormality detection circuit, and is also connected to voltage dividing resistors 10° 11 called R+, R2. There is. One input of the operational amplifier 6.7 is connected to the connection midpoint of these voltage dividing resistors 10°11.

Next, each of the secondary windings 12 of the lances 1 to 2 has one
The output terminal 15 is connected via the rectifier T-13 and the capacitor 14 C1. Further, a current detection circuit 16 is connected to this secondary side. This current detection circuit wJ16 is connected to the other input side of the operational amplifier 7.

Thus, a tertiary winding 17 is wound around the transformer 2, which provides an output similar to the output waveform of the secondary winding 12. This tertiary winding 17 is connected to a smoothing circuit 21 consisting of a rectifying element 18 designated as D2, a resistor 19 designated as R3 and C2, and a capacitor 20. This smoothing circuit 2
1 is connected to voltage dividing resistors 22 and 23 of R4 and R5, and the voltage dividing resistors 22 and 23 are connected to the other input side of the operational amplifier 6 via a diode 24 D3. A high frequency bus capacitor 6a and a resistor 6b are connected to this input end and output side.

Further, the base of the transistor 9 is connected to the smoothing circuit 21 via a smoothing circuit (B) consisting of a resistor 25 of R6 and a capacitor 26 of C3. The collector of this 1-transistor 9 is connected to the other input side of the operational amplifier 6 via a resistor 27 of R7 and a diode 28 of D4.

However, a smoothing circuit 31 in which a resistor 29 of 'RR and a capacitor 30 of C4 are connected in parallel is connected to the midpoint of the connection between the resistor 27 and the diode 28.

In such a configuration, a constant reference voltage is applied to the operational amplifier 6.7 by the constant voltage circuit 8 and the voltage dividing resistor 10.11, and the control circuit is controlled by the output of these operational amplifiers 6.7. 5 operates to control the conduction of transistor 4. By energizing the primary winding 3 of the transformer 2 in this way, a constant voltage, for example 4 kV to 8 kV at 20 kHz, is generated on the secondary side, and a voltage with a similar waveform is applied to the tertiary winding 17. also occurs. The output of the tertiary winding 17 has a waveform as shown in FIG. 2 after passing through the diode 18 and the smoothing circuit 21. Although this has a peak value of P, it still has properties as a pulsating flow. and.

A signal is applied to the operational amplifier 6 via the voltage dividing resistors 22 and 23 and the diode 24, thereby controlling the control circuit 5 in accordance with the increase or decrease in the peak value P to maintain a constant output state. When performing such control, it is preferable for detection control that the output voltage from the tertiary winding 17 be a pulsating current rather than completely smoothed. That is, if the capacitance of the capacitor 20 is made too large, the engine will be in an uncontrolled state until the capacitor 20 is charged at startup, resulting in a large output. For this reason, it is preferable that the capacitor 20 is not very large.

In addition, the current detection circuit 16 sends a signal to the operational amplifier 7,
When there is a current change due to load fluctuation, etc., output control is performed to maintain it constant.

Although the output from the smoothing circuit 21 is applied to the base of the 1-run risk 9 via the resistor 25, the voltage at this portion is normally high, so the transistor 9 does not become conductive. and.

W +1 C3>C2 Conditions have been set.

However, when there is an output short circuit or a spark discharge on the load side, the voltage on the output side of the resistor 25 decreases. If this voltage drop occurs, transistors 1 to 9 become conductive, and a high input voltage is applied to the operational amplifier 6 via the resistor 27 and diode 28.

As a result, the operation of the control circuit 5 is stopped and the energization of the primary winding 37\ is stopped. As a result, no output is output to the secondary side, so the circuit continues to be in a stopped state.

Therefore, in the output from the tertiary winding 17 shown in FIG. 2, it is quite possible that the level of the lowest voltage portion A is equal to or lower than the conduction voltage of the transistor 9.

However, the waveform to this lowest voltage portion is smoothed by the smoothing circuit (B) including the capacitor 26, and does not fall to the level shown in FIG.

Therefore, 1-run risk 9 is not turned on. Further, even if the transistor 9 becomes conductive for a very short time, it is absorbed by the smoothing circuit 31 and no operating voltage is applied to the operational amplifier 6. That is, even if there is a single spark discharge, no signal is output from the operational amplifier 6. Therefore, the operational amplifier 6 does not issue a signal to stop operation unless a signal that exceeds the buffering effect of the smoothing circuit 31 is given, so it has the function of reliably detecting abnormalities on the secondary side and is extremely short. It does not operate on time width signals.

Therefore, it is extremely stable.

In the above embodiment, the current detection circuit 16 performs constant current control during normal load operation,
Although the description has been given of a system in which constant voltage control is performed during no-load by voltage control using the tertiary winding 17, the implementation is not limited to such a system, and only constant voltage control may be performed.

Further, in place of the 1-run risk 9, another switching element that responds to the voltage value, such as a power switch, may be used.

Effects of the Invention As described above, the present invention detects the output state of the secondary side with the detection circuit, and controls the energization of the primary winding l\ based on this signal, and also controls the energization of the primary winding l\ based on this signal. The device is equipped with an abnormality detection circuit that stops energization of the negative side winding l\ when the voltage abnormally drops.Since the abnormality detection circuit is equipped with a smoothing circuit that smoothes the waveform of the signal voltage, the time width is extremely short. No operation is performed in response to a short voltage drop, thereby preventing malfunctions, thereby making it possible to perform stable abnormality detection.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, with FIG. 1 being a circuit diagram and FIG. 2 being a waveform diagram. 3...-Next winding, 5... Control circuit, 6... Operational amplifier (detection circuit), 9... 1-Run risk (abnormality detection circuit), 12... Secondary winding, 17...・Tertiary winding, 31・
Smoothing circuit applicant Toshiba Electric Materials Corporation

Claims (1)

[Claims] An inverter having a switching device for switching a DC voltage and an output transformer, a control circuit for controlling the switching device to control the output of the inverter, a detection winding provided on the output transformer, and a detection winding for the detection winding. a detection circuit that provides a detection signal obtained by rectifying the output to the control circuit; an abnormality detection circuit that responds to the detection signal of the detection circuit and causes the control circuit to turn off the switching device when the detection signal abnormally decreases; A power supply device comprising a smoothing circuit that smoothes and provides the detection signal to the detection circuit.