JPS6062823A - Regenerative voltage clamping circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application and Prior Art The present invention relates to a regenerative voltage clamp circuit that bypasses overvoltage due to regenerative energy of an electric motor through a resistor.

When an electric motor is driven from an AC power source through a rectifier circuit, a gradually decreasing voltage is generated in the armature until the armature completely stops rotating when the electric motor is stopped. This regenerated energy at the time of stoppage is applied to the rectifier circuit, but since the rectifier circuit has unidirectional characteristics, there is no part to bypass the regenerated energy, and the voltage may rise above the rated voltage.

Since such overvoltage poses a problem in terms of withstand voltage of various parts, a structure shown in FIG. 1, which is disclosed in Japanese Patent Publication No. 58-29698, has been proposed. In the same figure, ■ is a transformer, RFC is a rectifier circuit, CMPL is a comparator with hysteresis function, C1 and C2 are capacitors,
R1-R4 are resistors, Dl is a diode, and Ql is a transistor. When DC current is supplied from the rectifier circuit REC to the load via the diode D1, the comparator CMP
Since a voltage of, for example, about 0.7 V is input to the forward side of the diode D1, the output of the comparator CMP becomes zero, and the transistor Q1 is in an off state.

When the voltage generated in an inductive load such as an electric motor exceeds the output voltage of the rectifier circuit RFC, a reverse voltage is applied to the diode D1, and this reverse voltage is applied to the comparator CM.
Since the output of the comparator CMP1 turns on the transistor Q1, the low resistance value resistor R
4, current caused by overvoltage can be bypassed and voltage rise can be suppressed.

However, in such a conventional circuit, a large current that flows to the load flows through the diode D1, so it is necessary to use a diode with a large allowable current. Also, comparator CM
A capacitor with a large capacity must be used as the capacitor C1 that creates the reference voltage of PI; a capacitor with a small capacity cannot provide sufficient smoothing because it is drawn into the load circuit, causing ripples and causing the comparator CMPI to malfunction. There was a risk that it would cause

Therefore, the conventional regenerative voltage clamp circuit requires a large space due to the above-mentioned diodes and capacitors, and is expensive. To provide a regenerative voltage clamp circuit which improves the above-mentioned drawbacks of the conventional technology and which reduces the capacitance of a capacitor and diode for detecting the above-mentioned overvoltage in a regenerative voltage clamp circuit that prevents overvoltage by bypassing the circuit, and is inexpensive and compact. The purpose is to

Structure of the Invention The present invention provides a circuit for rectifying an alternating current voltage in a rectifier circuit and supplying a direct current to a load such as a motor. A capacitor that is charged at a peak voltage, a comparator that compares the charging voltage of the capacitor with a positive potential of a load, and when the positive potential of the load exceeds the charging voltage of the capacitor, an output is output from the comparator. A regenerative voltage clamp circuit characterized by having a transistor that is turned on and a resistor connected in series with the transistor between output terminals.

Embodiment FIG. 2 is a circuit diagram of an embodiment of the present invention, in which REC is a rectifier circuit, CMP2 is a comparator with a hysteresis function, C2 is a transistor, C3 and C4 are capacitors, and D2
~D4 is a diode, and R5-R9 are resistors. One input of the comparator CMP2 has a rectifier circuit R connected to the load.
The positive side output of EC is input, and the peak voltage of the rectifier circuit RFC is obtained through diodes D2 to D4 and resistor R5, and the charging voltage of capacitor C3 charged with the peak voltage is input to the other side. . In addition, the comparator CM
The output of P2 is input to the base of transistor Q2.

When supplying current to the load from the AC power supply via the rectifier circuit RE, C, the capacitor c3 has dies A-D.
2-D3. A3 is charged to a constant voltage through resistor R5.
This charging voltage is applied to the other terminal of the comparator CMP2 and constitutes a reference voltage. And comparator CMP
Since the input impedance of C2 is very large, the current flowing through capacitor C3 and diodes D2 to D4 is small.

Therefore, the diodes D2 to D4 can be diodes with a small allowable current. Also, capacitor C3
Since there is no current drawn into the load circuit as in the conventional technology,
A small capacitor is sufficient.

Therefore, when the voltage generated in an inductive load such as an electric motor exceeds the charging voltage of the capacitor C3, that is, when the voltage input to one terminal of the comparator CMP2 exceeds the reference voltage input to the other terminal. , comparator CMP2
An output is output from the transistor Q2, which turns on the transistor Q2, bypasses the current that would cause an overvoltage due to the low resistance value R9, and suppresses the voltage rise.

Effects of the Invention As described above, the regenerative voltage clamp circuit of the present invention has the following effects:
The peak voltage of the rectifier circuit is taken out through a diode,
This peak voltage was rectified by a capacitor, and the charging voltage of this capacitor was input as the reference voltage of the comparator.

Therefore, since the input impedance of the comparator is very large, the current flowing through the capacitor is small, and the current flowing through the diode is also small. Also, since there is no draw into the load circuit, the capacitance of the capacitor is reduced. Furthermore, a diode with a very small allowable current can be used as the diode. Therefore, unlike conventional methods, there is no need for a diode with a large allowable current to pass the load current or a capacitor with a large capacity to smooth the output of the rectifier circuit and create a reference voltage, so the space can be reduced and the price can be reduced. An inexpensive regenerative voltage clamp circuit can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a conventional regenerative voltage clamp circuit, and FIG. 2 shows an embodiment of the regenerative voltage clamp circuit of the present invention. RFC... Rectifier circuit, R1-R9... Resistor, 01~
C4... Capacitor, Ql, Q2... Transistor, D1-D4... Diode, CMPl, CMP2.
...Comparator.

Claims (1)

[Claims] In a circuit that rectifies an alternating current voltage with a rectifier circuit and supplies direct current to a load such as a motor, a capacitor that obtains a peak voltage of the output voltage of the rectifier circuit through a diode and a resistor and is charged with the peak voltage; a comparator that compares the charging voltage of the capacitor with a positive potential of the load; a transistor that outputs an output from the comparator and is turned on when the positive potential of the load exceeds the charging voltage of the capacitor; A regenerative voltage clamp circuit comprising a transistor and a resistor connected in series between output terminals.