JPS6353791B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching regulator multi-output sequence circuit.

The multiple outputs of the switching regulator include
Depending on the type of load, a power-on and power-off sequence is required, and this power-off sequence must be established even during a power outage. Therefore, conventionally, a switching regulator detects the AC input waveform and outputs a predetermined output from among the multiple outputs to a switching element.
A method is adopted in which the output is immediately turned off using a relay or the like, and other outputs are held by a holding means such as a capacitor. However, since this method detects a power outage by detecting the AC input waveform, the detection speed of a power outage is slow, and even if it detects a half wave of the AC input waveform,
This requires 10 msec (for 50 Hz), requires a large holding means with a longer holding time, and is further affected by the frequency and waveform distortion of the AC input.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-output sequence circuit for a switching regulator that eliminates the above-mentioned drawbacks, allows the function of the holding means to be reduced, and is unaffected by the frequency and waveform distortion of AC input. .

The present invention will be described below by way of examples with reference to the drawings.

As shown in FIG. 1, an AC voltage of 100V from a commercial power source is rectified by a rectifier circuit 1 and smoothed by a capacitor 2 to become a DC voltage. This DC voltage is interrupted by a transistor 3 and applied to the primary winding of a transformer 4, and the outputs of each secondary winding of the transformer 4 are rectified by diodes 5 to 8, respectively, to coils 9, 10 and capacitors 11, 12. The signal is smoothed by the output terminals 13 to 16 and supplied to each load.
The control circuit 17 compares the output voltage between the output terminals 13 and 14 with the reference voltage of the reference power supply 18, and amplifies the difference voltage. The drive circuit 19 has a pulse width corresponding to the output voltage of the control circuit 17 and a high frequency, for example, 20KHz.
This pulse generates a pulse of transformer 20,
It is applied between the base and emitter of the transistor 3 via the resistor 21. The on-time of the transistor 3 increases as the output voltage between the output terminals 13 and 14 decreases, and conversely decreases as the output voltage increases, so that the output voltages of the output terminals 13 to 16 are stabilized. The pulse width detection circuit 22 is the drive circuit 19
A power outage is detected by detecting that the output pulse width of the output pulse width exceeds a preset reference pulse width. This pulse width detection circuit 22 uses a well-known pulse extinction detection circuit, and the switching element 2
3 is turned on at the time of a power outage by the output signal of the pulse width detection circuit 22, short-circuiting between the output terminals 15 and 16, and turning off the output voltage. As the switching element 23, a thyristor having a hold function is used. At this time, the output voltage between the output terminals 13 and 14 is still held by the capacitor 2. FIG. 2 shows the off sequence of the output voltage A between the output terminals 13 and 14 and the output voltage B between the output terminals 15 and 16 during a power outage.

In this embodiment, the pulse width detection circuit 22 detects a power outage based on the 20 KHz pulse from the drive circuit 19, so the power outage detection speed is 400 times faster than in the case of detecting a half wave of a 50 Hz AC input using the conventional method. Therefore, the holding means 2 can be made smaller, and it is not affected by the frequency and waveform distortion of AC input. Moreover, the sequence of outputs A and B is established regardless of the magnitude of the voltage drop across the capacitor 2.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be similarly applied to switching regulators such as push-pull type and half-bridge type.

As described above, according to the present invention, an AC input is converted into a DC voltage, which is intermittently applied to a transformer using a switching element, and the multiple outputs of this transformer are converted into DC voltages and outputted from multiple output terminals. A switching regulator applies a high-frequency pulse having a pulse width corresponding to one of the voltages to the switching element, detects that the pulse width exceeds a preset value, and outputs the multi-output. Since a predetermined one of them is turned off by a switching element, the detection speed of a power outage is fast, the holding means can be reduced in size, and it is not affected by the frequency and waveform distortion of the AC input.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a timing chart of the same embodiment. 22... Pulse width detection circuit, 23... Thyristor.

Claims (1)

[Claims] 1. Convert AC input to DC voltage and apply it to a transformer intermittently using a switching element, convert the multiple outputs of this transformer to DC voltage, output from multiple output terminals, and respond to one of these multiple output voltages. A switching regulator that applies a pulse with a pulse width to the switching element includes a pulse width detection circuit that detects when the pulse width exceeds a preset value; A switching regulator multi-output sequence circuit comprising a switching element that shorts a predetermined one of a plurality of output terminals.