JPS6176018A - Switching system direct current power supply - 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] Industrial applications The present invention relates to a switching type DC power supply.

BACKGROUND OF THE INVENTION FIG. 2 shows a conventional switching DC power supply. The power supplied from the AC power supply 1 is rectified by the rectifier 2, and the content? The signal is smoothed by 3° and supplied to the primary winding 51 of the switching truss 7 connected in series with the switching element 4 such as an FIT. The pulse current generated in the secondary winding 52 of the transformer 50 by turning on and off the switching element 4 is rectified and smoothed by the filter circuit 6 consisting of diodes 61 and 62, an axle 63, and a capacitor 64, and is supplied to the load 7. Ru.

The voltage supplied to the load 7 is made constant by controlling the off-off ratio of the switching element 4. To control this, the constant voltage control circuit 8 fully controls the gate output pulse width of the pulse width sterilization circuit 9 according to the output voltage Eo, and the switching element 4 is turned on and off by the pulse output of the circuit 9. An automatic control circuit is provided for controlling. Resistance 101. diode 1
An excitation energy absorption circuit consisting of O2 and a condenser 103 [O absorbs the excitation energy of the transformer 6 when the switching element 4 is off. Ninth, to protect the switching element 4 etc. from an excessive current caused by a short circuit in the load 7, etc., the current flowing through the switching element 4 1. A current detector (for example, a shunt resistor) 11 that detects the entire current and a current limiting circuit that limits the current flowing through the switching element 4 so that the detected current does not exceed a certain value are provided, so that the current 11 exceeding the certain value flows. Then, the output of the current limiting circuit 12 limits the gate output pulse width of the pulse width control circuit 9, and the overcurrent limiting function limits the on/off of the switching element 4. It is possible to operate the switching element 4 etc. without damaging it.

Problems to be Solved by the Invention In the conventional configuration, the filter circuit capacitor 64 (
When an internal short circuit occurs in a capacitor (generally an aluminum electrolytic capacitor is used) due to a failure.

(1) The overcurrent limiting circuit (11 and 12) limits the current flowing through the switching element 4 to a certain value or less in the same way as when the load 7 is short-circuited, thereby allowing the switching operation to continue.

(2); When a short circuit occurs inside the capacitor 64, the overcurrent is limited and the current flows.1. A secondary current 1 corresponding to the current flows through the conductor f64.

(3) The current flowing through the capacitor 64 is significantly larger than its normal ripple current;
Flow 1. The flow concentrates at the internal short-circuit location of the connector 7te 64.

(4) Short circuit contact resistance r of capacitor 64 and flowing current 1. A power loss of 1 - occurs at the short-circuited portion; the internal temperature of the capacitor rises, and the explosion-proof valve in the capacitor diagram opens, causing a failure such as the electrolyte inside the capacitor being scattered.

(5)! Even after the solution scatters, the current continues to flow and the temperature continues to rise unless the short circuit is released.

(6) Eventually, the rise in temperature may lead to ignition and fire.

As described above, even though an overcurrent limiting function is provided, there is a risk that an internal short circuit or a decrease in internal impedance of the capacitor of the filter circuit may lead to damage to the capacitor or electrolyte scattering or ignition.

Means and operation for solving the problem The present invention includes a protection circuit that stops the switching operation of the switching element when the current flowing through the smoothing electrolytic capacitor of the filter circuit exceeds a predetermined historical limit value. As a result, capacitor abnormalities within the rated load range can be detected in the optical state as well, and when an electrolytic capacitor fails, the continuation of the failure state is interrupted by controlling the switching element to stop, thereby enabling early failure detection.

Example FIG. 1 is a circuit diagram showing one embodiment of the present invention.

The difference between this figure and Figure 2 is that the load is 1! A current detector 13 that detects L, a load t Ri t t and a capacitor/
The current that is the sum of the current of 64 1. Detecting current detector 14 and 5 cars t? The capacitor current 1tc (=1 - 1xt) is detected from the detection values of the R detectors 13 and 14, and this I
E current is load current 1. The current determining circuit 15 provides a command to the pulse width control circuit 9 to stop the operation of the switching element 4 (off state) when t is also large.

In this configuration, during normal operation, the load current is 1! except at the start of operation! The determination circuit 15 determines from both current detectors 13 and 14 that the capacitor current 1□0 is small compared to tK.
There is no output. When an abnormality occurs due to an internal failure of the capacitor 64, the current 1mc in the capacitor t1 becomes larger than the load current 1tt within the rated range regardless of the load weight, and the determination circuit 15 outputs a command to stop the operation of the switching element 4, and the capacitor Cut off the current to the 64 side. As a result, the operation is stopped before the malfunction of the condenser 64 causes the electrolyte to scatter or cause other circuit components to burn out.

In the embodiment, the output of the 1-judgment circuit 15 can also be used as a display command for a failure indicator (lamp or alarm buzzer) to clearly display the location of loading failure, thereby making repairs and inspections easier.

Nine, in the example, a capacitor current was added to the load current and this current! The case is shown in which the normality or abnormality of one current of the capacitor is determined according to the load/light/heavy condition by detecting the entire capacitor current from # and .

Another method may be to directly detect the current of the capacitor 64 (for example, by connecting a shunt resistor 't' to the capacitor) and perform a protection operation by detecting a certain value or more.

Effects of the Invention According to the present invention, capacitor 1! A protection circuit is installed that determines whether the current is normal or abnormal by detecting the current, and stops the switching element from operating. This has the effect of preventing the spread of failures.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a conventional circuit diagram. 4... Switching element, 5... Switching transformer/s, 6... Filter circuit, 64... Capacitor,
7...Load, 8...Voltage control circuit, 9...Pulse width control circuit. Ll... Current detector, 12... Current limiting circuit, 1
3, 14... Current detector, 15... Current determination circuit.

Claims (1)

[Claims] A switching method DC that supplies DC voltage to a series circuit of a switching transformer and a switching element, and supplies DC power to a load with an output voltage obtained by rectifying and smoothing the voltage on the secondary side of the switching transformer generated by switching of the switching element. A switching type DC power supply characterized in that the power supply includes a protection circuit that stops the switching operation of the switching element when the current flowing through the smoothing electrolytic capacitor exceeds a predetermined limit value.