JPS5810968A - switching power supply circuit - Google Patents

Abstract

PURPOSE:To surely synchronize even with a large control power, by cutting off a pulse width controlling transistor (TR) controlling a switching TR at a trigger signal period. CONSTITUTION:A TRQ1 is a transistor for switching output and a TRQ2 for pulse width control is connected between the emitter and base. A diode D10 cuts off the TRQ2 at the period of trigger signal and inserted between the anode side of a diode D5 and the TRQ2. The diode D10 zeroes a current i2 at triggering to flow a trigger current i1 to the base of the TRQ1 as it is, allowing to obtain sure synchronism with the small trigger current i1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-excited switching power supply circuit used as a power supply circuit for a television picture reception machine.

The purpose is to provide a device that can synchronize the switching frequency of a power supply circuit to a predetermined frequency with a smaller current than ever before.

Figure 1 is a basic circuit diagram of a conventional isolated self-excited switching regulator V-1, where 0) is the commercial power supply, T is the converter transformer, Q is the switching output transformer Nx, and (2
) is the load, in this case the horizontal deflection circuit of a TV receiver. The commercial power supply α) is rectified and smoothed by diodes D&-D4 and conductor tC1, and converted into a converter. ,
It is applied at the beginning of the windings P1 to P of the 〇-order windings. The output section causes self-excited oscillation to occur in the secondary windings B, ~B1 of the switching output transformer Tt0, and the secondary windings 51~S of the converter transformer Tt0.
, the pulse generated in the diode D- and the conductor-? C
4, the current is supplied to the load (2) and the horizontal deflection circuit starts operating. Furthermore, in the past, the horizontal deflection circuit's heavy duty voltage FBP was controlled by the trigger transformer T so that the generation of noise during switching occurred during the retrace period.
1 to the switching output F transistor Q10 base, and synchronizes the switching frequency with the horizontal frequency fuK. R1 is a starting resistance.

C, C capacitor, switching output transistor Q
When the collector current of the conductor C3 increases, the regeneration effect is likely to occur, and when the switching output transistor Q is on, one end of the conductor C3 connected to the resistor R8 is charged to have a positive polarity. , when off, the charge is discharged through the path of resistor R8 → secondary winding B, ~ bird → hoft side ground 0) → diode D.

This charging and discharging is repeated 6D, the starting current is the transformer T
, is a diode that prevents V iodine from being applied through the windings of . In addition, since the trigger pass voltage is applied from the cord V-cord V-ya V14), T) is necessary for insulation from the Hola) S/Car/(2) side.

Furthermore, the output voltage is stabilized by restricting the base current of the switching output transistor Q1. This essentially performs a pulse width modulation operation.

1 is a silane sFx for error amplification, Dv is a Zener diode for reference voltage, and R6 is a variable resistor IL for setting the output voltage.
Rle R4e Rle Rv is a resistor, and D is a diode.

F1~F, Hacompar-) In the secondary II line of Huns T1.

Provided for detecting fluctuations in output voltage, diode D
If the voltage after rectification and smoothing by , and conductor +C is -v1, then if the absolute value of 1 becomes small for some reason, then the voltage between the emitter pace of transistor Q is lower than 9. collector current decreases. In other words, the emitter current of transistor Q decreases,
Control is performed to increase the absolute value of -vl by widening the conduction period of the switching output transistor Q. The Kubasa, in which the absolute value of -V is opposite to the above, performs the opposite operation, and by stabilizing the potential of -vl in this way, the output voltage is kept stable.

When synchronization is applied in the above conventional circuit, the emitter current of the Nitofungister Qm is 1. Assuming that the current value that can be passed as 11 is 11, and the current value of the current 110 is 11, as shown in Fig. 2, I, < I, O
During period t, the emitter current is 1. is the trigger current 1. The current 11 flowing towards the switching output transistor q pace changes with i,=0. 1. >1. The trigger current image is the switching output transistor Q
The current t begins to flow to the pace of 1, and the switching transistor also turns on. As the power to control increases, the current value must be increased to stabilize the output voltage! , is large, and accordingly a large trigger current 11 is required. Furthermore, when the trigger current i1 is small, a pause occurs in which synchronization is not applied.

FIG. 3 shows an embodiment of the present invention that can avoid the problem described in L. Components having the same functions as those in FIG. The anode side of the diode D and the transistor l are connected so as to cut off the transistor I Qs during the signal period T (see FIG. 2).
With the diode interposed between the pace of Qm and the current value of 1. = 0, the trigger current 1t flows directly at the pace of the switching output IQ, and synchronization can be reliably achieved with a small trigger power supply.

In the above embodiment, the rigger signal is supplied (via the transformer T), but depending on the case, it may be configured to be connected to a capacitor or to be supplied directly.

The explanation will be given by taking as an example the case of synchronizing to the horizontal frequency fw, but the same applies to the case of synchronizing the curve to an integer number.

As described above, according to the present invention, the trigger current is applied to the pace of the switching output transistor and the pace of the transistor for controlling the path V path width of the pace current of the switching output transistor, and the path V path width is applied during the trigger signal period. It is configured to cut off the control F fungis.

Even when the control power becomes large, it is necessary to ensure synchronization with a small trigger current.

[Brief explanation of the drawing]

FIG. 2 is a diagram illustrating the operation of FIG. 1, and FIG. 3 is a diagram illustrating a switching regulator according to an embodiment of the present invention. T.--converter transistor, T8.--trigger shift, Q1.--switching output transistor, Q. ...Transistor [transistor for controlling path M path width]. D2. ...diode, 11-) rigger current agent
Yoshihiro Morimoto Figure 1, Figure 2

Claims (1)

[Claims] In a switching power supply circuit that is used for the power supply of a TV pilot aircraft and is triggered to synchronize the switching frequency to a frequency that is an integer multiple of the horizontal polarization shoulder number, the pace of the switcher output and the switching Output) The highest pace current without finless
9. A switching power supply circuit characterized in that the switching power supply circuit is configured to apply a trigger pulse to the pace of a tuning resistor (for width control) and to turn off the tuning resistor for width control during the trigger signal period.