JPH0850148A - Servo motor controller main circuit DC voltage detector - Google Patents

Abstract

PURPOSE:To provide a simple and inexpensive device for detecting a precise main circuit DC voltage which is applicable to a serve motor control device by counting the time width of the rectangular wave output from a diode for halve-wave rectifying the output voltage of the secondary side coil of a pulse transformer. CONSTITUTION:A main circuit capacitor 2 has a main circuit DC voltage on both ends, and a pulse transformer 6 is switched by a switching circuit 7, whereby an output voltage VCC is provided. Since this output voltage is fed back by a feedback circuit 7 to change the switching duty, a fixed voltage can be regularly kept. For the waveform of the input voltage V2 of a counter 5, since the time width is contracted according to an increase in the main circuit DC voltage, when the load of the VCC is supposed to be constant, and reversely extended according to the decrease, the time width during one period is counted by the counter 5, and converted into a voltage by a microcomputer 4, whereby the main circuit DC voltage can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for insulating a power source from a main circuit DC power source by using a pulse transformer and obtaining a main circuit DC voltage from a switching ratio of an output of the pulse transformer.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing an embodiment of the prior art. 1 is a rectifier, 2 is a main circuit capacitor, 3 is a power transistor forming an inverter, 15 is an AC servomotor, 16 is an A / D converter, 9 is an isolator, and 4 is a microcomputer. According to this first conventional technique, the main circuit DC voltage across the main circuit capacitor 2 is
The D converter 16 converts the digital signal, and the isolator 9
It was isolated by and was detected by the microcomputer 4.

[0003]

However, this prior art has a problem that the A / D converter, the isolator, and the separate power supply for them are required, and the circuit becomes complicated and expensive. Therefore, it is an object of the present invention to provide a device that can be used in a simple and inexpensive servo motor control device and that detects an accurate main circuit DC voltage.

[0004]

In order to solve the above problems, the present invention relates to a main circuit DC voltage detecting device of a servo motor control device for detecting a DC voltage across a main circuit capacitor, wherein the main circuit capacitor is connected in parallel. A connected series circuit of the primary side coil of the pulse transformer and the switching circuit, a smoothing capacitor connected to the secondary side coil of the pulse transformer, and a feedback circuit for negatively feeding back the output voltage from the smoothing capacitor to the switching circuit. A diode for half-wave rectifying the output voltage of the secondary coil of the pulse transformer, a counter for counting the time width of the rectangular wave output from the diode, and a microcomputer for converting the count value of the counter into a voltage. It is characterized by having.

[0005]

By the above means, the main circuit DC voltage can be obtained only by the counter, so that it can be inexpensively detected with a simple circuit. Further, the main circuit DC voltage can be accurately detected and used for control.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of the present invention will be described below with reference to FIG. In FIG. 1, description of the same reference numerals as those in FIG. 3 is omitted. Reference numeral 5 is a counter, 6 is a pulse transformer, 7 is a switching circuit, and 8 is a power supply feedback circuit. 10,
Reference numerals 11, 12, 13 are diodes, and 14 is a capacitor. The operation of the circuit configured as above will be described. Both ends of the main circuit capacitor 2 are the main circuit DC voltage, and the switching circuit 7 switches the pulse transformer 6 to obtain the output voltage VCC. Since this output voltage is fed back by the feedback circuit 8 and the switching duty is changed, a constant voltage can be always maintained. That is, the feedback circuit 8 functions to reduce the switching duty of the switching circuit 7 when V ₁ increases. The secondary side of the pulse transformer 6 has a lower voltage than the primary side due to the winding ratio of the transformer, and the secondary side output voltage V ₁
Has a switching waveform as shown in FIG. The input voltage V ₂ of the counter 5 has a half-wave rectified waveform as shown in FIG. Assuming that the load of VCC is constant, the waveform of the input voltage V ₂ becomes T ₁ when the DC voltage of the main circuit becomes high.
Is shortened, and when it is lowered, it is extended. Therefore, if the time of T _{1 in} one cycle T is counted by the counter 5 and converted into a voltage by the microcomputer 4, the main circuit DC voltage can be detected. For example, when the main circuit DC voltage is 300V, VCC is +5
Assuming that V is T ₁ /T=0.5 and T = ₁₀ μs (switching frequency = 100 kHz) at this time, the main circuit DC voltage changes as follows. Main circuit DC voltage T ₁ 250V 5.83μs 300V 5.0μs 350V 4.17μs Therefore, the time of T ₁ is counted by the counter 5 and converted into a voltage. Assuming an 8-bit counter with a 24 MHz clock, 0 to about 6 in units of about 2.5V
It can detect up to about 00V.

[0007]

As described above, according to the present invention, without using an expensive A / D converter or isolator,
A simple circuit consisting only of a counter can detect the accurate DC voltage of the main circuit.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a specific embodiment of the present invention.

FIG. 2 (a) is a waveform of an output voltage V ₁ of the pulse transformer 6. (B) It is a waveform of the input voltage V ₂ of the counter 5.

FIG. 3 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 Rectifier 2 Main Circuit Capacitor 3 Power Transistor 4 Microcomputer 5 Counter 6,18 Pulse Transformer 7 Switching Circuit 8 Feedback Circuit 9 Isolator 10, 11, 12, 13 Diode 14 Capacitor 15 AC Servo Motor 16 A / D Converter 17 AND Circuit 19 Rectifier circuit

Claims (1)

[Claims] 1. A main circuit DC voltage detecting device for a servo motor control device for detecting a DC voltage across a main circuit capacitor, wherein a primary coil of a pulse transformer and a switching circuit connected in parallel to the main circuit capacitor are connected in series. Body, a smoothing capacitor connected to the secondary coil of the pulse transformer, a feedback circuit for negatively feeding back the output voltage from the smoothing capacitor to the switching circuit, and a half output voltage of the secondary coil of the pulse transformer. A main circuit of a servo motor control device comprising a diode for wave rectification, a counter for counting a time width of a rectangular wave output from the diode, and a microcomputer for converting a count value of the counter into a voltage. DC voltage detector.