JPS6013473A - Power source starting circuit - Google Patents

Abstract

PURPOSE:To simplify the construction of a power source by enabling to couple a starting self-exciting output to a self-exciting output as a self-exciting output to be fed back to a switching transistor through a drive transformer. CONSTITUTION:A DC input of a DC input terminal 22 is applied through the primary winding 23A of an output transformer 23 to a switching transistor 24. The AC output generated at the secondary winding 23 of the transformer 23 is rectified and delivered to a DC output terminal 27. The DC output is applied as a drive input of a pulse width modulator 34, and a switching controlling switching transistor 35 is controlled by the output. A self-exciting oscillation system is formed of the transistor 24, the transformer 23, a resistor 31, a rectangular oscillator 33, a pulse width modulator 34, a transistor 35, a drive transistor 38, and the transistor 24. The DC input for starting the system is applied to the base of the transistor 24, and a series feedback circuit is formed at the secondary side of the transformer 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply starting circuit, and is particularly suitable for application to a switching power supply or converter that switches DC input.

[Background technology and its problems]

The first switching power supply or converter of this kind
There is one using a switching power supply circuit 1 as shown in the figure. This power supply circuit 1 supplies DC power supplied to a DC input terminal 2 to the collector of a transistor 4 as a switching element through a primary winding 3AY of an output transformer 3, and inputs DC power by turning on and off the transistor 4. An alternating current voltage is generated in the secondary winding 3B of the output transformer 3 by intermittently passing the voltage through the primary winding 3A.

This AC voltage is rectified by a rectifying element 5 and a capacitor 6 and sent to a DC output terminal 7 as a DC output S2.

The switching power supply circuit l has a rectangular wave oscillation circuit 10,
The rectangular wave output S3 is given to the pulse width modulation circuit 11 (2), and the duty ratio of the rectangular wave output S3 is set to the WH5 output S2.
The pulse output S4 is changed according to the change in pulse width, and this pulse output S4 is passed through the Y drive transformer 12 to the base of the switching transistor 40, which is turned on and off. - By performing a self-oscillation operation via the circuit 11, the output voltage S2''f can be obtained from the secondary side of the output transformer 3.

Note that the DC power supply S1 of the switching power supply circuit 1 is an AC power supply #
The AC power supplied to the I terminal 13 is connected to the bridge rectifier circuit 1.
4 and a capacitor 15, and the rectified signal is applied to the input terminal 2.

Here, the self-oscillation operation of the switching power supply circuit 1 shown in FIG. 1 is started by the starting circuit 16. The starting circuit 16 includes an AC power source 17, a rectifying element 18, and a capacitor 1.
9, the DC output S5' is converted into a DC output S5' and the DC output S5 is converted into a DC pulse width modulation circuit 11 and a rectangular wave oscillation circuit 10.
as an initial start-up input, thus power input terminal 13
When an AC input is applied to the circuit, a pulse output 84 is generated by operating the rectangular wave oscillation circuit 10 and the pulse width modulation circuit 11, whereas when no AC input is received, the circuit]0 and 11 is set in a non-operating state so that the pulse output S4 is not generated.

On the other hand, when using the starting circuit 11 having the configuration shown in FIG.
A comparatively large and heavy transformer 17 must be specially provided as the dynamic circuit 16, and this poses a problem in that a certain amount of heat is applied when trying to downsize the overall configuration.

An excellent conventional configuration is the +I+' structure shown in Figure 2. In the case of FIG. 2, as shown by attaching the same reference numerals to the parts corresponding to those in FIG. The pulse output S4 is given to the drive transformer 12 through the isolation transformer 21. In this case, the starting circuit 16 breaks the oscillation circuit Z3 which receives the DC human power S1 as a single drive signal through the resistor 22, and outputs a rectangular wave S6' generated by the starting standby oscillation circuit 7:3 to which AC input is applied. The switching transistor 4 is caused to start the switching operation of the transistor 4 at 44 via the drive transformer 12, thus obtaining a state in which the blood flow output S2 is sent to the output terminal 7.

In this way, the square wave oscillation circuit 1 of the switching power supply circuit 1
0 and the pulse width modulation circuit 11 are brought into a state of operation by the DC output S2, and thereafter the transistor 4 is operated by the pulse output S2.
The switching operation is performed by 4. In this state, the pulse output S4 is given to the oscillation stop circuit array connected to the secondary side of the isolation transformer 210, and the oscillation stop signal S7
to stop the oscillation circuit Z3, thus starting the starting circuit 1
Stop the operation of step 6.

In this way, in the case of Fig. 2, when pulling the switching power supply circuit 1 into the self-excited oscillation state, the oscillation circuit B of the starting circuit 16 first causes externally excited oscillation, and as a result, after the self-excited oscillation operation occurs, By stopping the passive oscillation system by the oscillation stop circuit U, the switching operation is performed only by the self-excited oscillation system of the switching power supply circuit 1. Let it continue (5').

ing. In this way, even in the configuration shown in FIG. 2, it is not only necessary to provide a relatively large and heavy insulating transformer 21 in order to make the switching power supply circuit 1 self-excited and oscillate. There is a problem that 24 must be provided.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and attempts to propose a much simpler configuration than conventional configurations as a starting circuit for inducing self-excited oscillation operation in a switching power supply circuit. It is something.

[Summary of the invention]

In order to achieve this object, in the present invention, at the time of initial startup when a power supply input arrives, a switching element is operated by the power supply input to form a startup self-excited output when energy is present in the drive transformer, and this startup self-excitation is generated. The excitation output is coupled to the signal line of the self-excited oscillation output obtained in steady state to the switching element, and the switching element is operated by this combined output.

〔Example〕

(6) Hereinafter, four embodiments of the power supply starting circuit according to the present invention will be described in detail with reference to the drawings. In FIG. 3, 21 indicates the switching power supply circuit as a whole, and the DC input Sll arriving at the DC input terminal η is passed through the primary winding 23A of the output transformer B to the switching transistor U as a switching element.
By turning on and off the transistor array, the secondary winding 23B of the output transformer B generates an AC output.

This AC output is rectified by a rectifying element and a capacitor and sent to a DC output terminal n as a DC output S12.

This DC output 812 is applied as a driving input to a pulse width modulation circuit which receives a rectangular wave oscillation circuit and its output 813 via a resistor 31 and a capacitor 32, and thus a pulse output 814 obtained by the pulse width modulation circuit. is given to the switching control transistor A. The DC output S12 obtained through the resistor 36 is applied to the control transistor A through the primary winding 38A of the drive transformer, and the transistor A turns on and off to turn the resistor 36 to the primary winding. 38A-) A switching control signal S15 is generated in the secondary winding m3sB of the drive transformer 38 by flowing on/off snow and dirt through the loop L2 of the land disk A-earth. This control signal S15 is applied to the base of the switching transistor array through a parallel circuit 7 including a diode 39 and a capacitor 40.

Thus, the switching transistor array - output transformer - resistor 31 - square wave oscillation circuit and pulse width modulation circuit 3
A self-oscillation system is formed through a loop of 4-transistor 35-drive transformer 38-switching transistor 3.

In addition to this configuration, as a starting circuit for the self-excited oscillation system, a DC power source 811 is connected to the base of the switching transistor array through the resistor 41, and is connected to the negative terminal of the secondary winding Z3B of the output transformer B and the drive transformer 1 of the drive transformer. The positive side ends of the next winding 38A are connected by a series feedback circuit including a capacitor 42 and a resistor 43.

In the configuration shown in FIG. 3, the switching power supply circuit 21 as a whole is in a stopped state before the DC input S11 is applied to the input terminal B.

When DC input Sll arrives in such a stopped state,
This is applied to the base of the switching transistor array through the resistor 41, thereby turning on the transistor 24. As a result, the first volume of Outkadrance Otsu! 1
Since current begins to flow from the negative pole side to the positive pole side in ljlBA, a voltage is generated that is positive on the negative pole side and negative on the positive pole side of the secondary winding Z4B, which causes the secondary winding 23B-capacitor 42-
The resistor 43-drive transformer flows, thereby generating a positive voltage at the positive end of the secondary winding 23A and a negative voltage at the negative end. Therefore, a voltage is generated in the secondary winding 38B of the drive transformer, which is positive at the positive end and negative at the negative end, and is applied to the base of the switching transistor array.

As a result, the collector current of the transistor U and hence the excitation current of the primary winding Z(A) grows rapidly, thus forming a positive feedback circuit.

As a result, the transistor string quickly becomes saturated and its collector current does not change, so the voltage generated in the primary winding Z3A and therefore the secondary winding Z3B of the output transformer B is reversed, and this causes the above-mentioned transformer B to be inverted. The current flowing through the feedback circuit of the capacitor 42 and resistor 43 between the secondary winding B of the transformer and the primary winding A of the transformer is reversed, and as a result, the voltage of the transformer's primary winding 38A and secondary winding 38B is reversed. By inverting, the switching transistor U is turned off.

When the transistor U turns off in this way, the current flowing through the output transistor 2AAK also becomes 0, and eventually returns to the initial state again, and the DC input 811 is applied to the base of the transistor string via the resistor 41, and the transistor string turns on. Return to state. Thus, the switching power supply circuit 21
is activated through a loop L1 including a capacitor 42 and a resistor 43, and enters a self-oscillation state, whereby a DC output 812 is sent to the output terminal n via the rectifying element 5 and the capacitor 26.

In this state, the DC output 812 is applied to the rectangular wave oscillation circuit 33 and the pulse width modulation circuit 34 via the resistor 31, and these circuits become operational.

In this state, the pulse output 814 turns on and off the switching control transistor 35Z, and at the time of the on operation, the resistor 36-drive transformer blade 2
Second best & 38A-) Run raster 35-earth loop L2
If the switching control current flows through or the transistor 35 is turned off from this state, this loop L2
current will no longer flow. Therefore, in the drive transformer, the current in the primary winding AK/l/-g L2 intermittently flows to generate a voltage that reverses the elasticity in the secondary winding 38B, and thereby the switching transistor 2
4 is turned on and off. In this case, when the transistor A is on, the switching transistor 24 is turned off, and when the transistor 35 is off, the switching transistor 24 is turned on.

In this way, the switching power supply circuit 21 is a switching transistor, an output transistor? :3.The steady oscillation operation is continued by the self-excited oscillation system passing through the drive transformer 38 in a separate pulse width modulation circuit, so that the DC output S12 continues to be sent to the output terminal Ibara.

Even in this state, the secondary winding m? of the output transformer is passed through the circuit of the capacitor 42 and resistor 43 as described above regarding the loop L1. A Drive transformer section 1 from B
A current that turns on and off flows through the secondary winding 38A, but the power of the current flowing through this loop 22 is t loop L1 (resistor 36, primary winding 38A of the transformer blade, transistor 35
), the control output S15 generated in the secondary winding 38B of the drive transformer can be set to a value significantly smaller than the power of the current that is turned on and off through the loop L2, which has a large power. , will change depending on the off state, so the capacitor 42 and resistor 43'&
The result is that the control through loop L1 becomes ineffective.

Therefore, the switching power supply circuit 2J having the configuration shown in FIG. 3 starts by self-oscillating through the loop L1, and then enters this self-oscillating state when it self-oscillates through the loop L2 driven by the pulse width modulation circuit. As a result, the system is stable and can operate without the need for an isolation transformer or oscillation stop circuit, unlike the case of the Kagusu Nitsuana Junmai.

Furthermore, according to the configuration shown in FIG. 1, if the timing of switching the operating constant temperature given from the starting circuit 16 to the operating power supply given from the DC output S (2) is not precisely aligned, the switching voltage imitation circuit will be balanced at the time of this switching. In order to avoid this, it is inevitable that the configuration of the startup circuit 16 will be quite complicated in order to match the timing in practice, but according to the configuration shown in FIG. can be easily done.

FIG. 4 shows another embodiment of the present invention, in which the output line 314 is connected and the signal of this output line is directly supplied to the primary winding 38A of the drive transformer 38. There is. The secondary winding 38B of each drive transformer is connected to the base of the switching transistor 5 through a switch control transistor 53 and an isolation transformer 54, and further through a capacitor.

Even in the configuration shown in FIG. 4, at startup, the switching power supply circuit 21 performs a startup operation by the startup self-excitation output given to the drive transformer through the loop L1, and as a result, when a DC output S12 can be obtained, the pulse width modulation circuit It is possible to switch to a self-excited operation using the pulse W/force S14, thus obtaining the same effect as described above with respect to FIG.

FIG. 5 shows still another embodiment of the present invention, in which the starting self-excited oscillation generates a self-excited voltage by the tertiary winding 61 provided in the output transformer z3, and the entire self-excited output The structure is the same as that shown in FIG. 4 except that it is connected to the collector of the switching ink control transistor 53 via a resistor 62 and a capacitor 63. Even in this case, the same operation and effect as in the case of FIG. 4 can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the self-excited output for starting, which has relatively low power, is combined with the self-excited output during steady state to obtain the self-excited output that is fed back to the switching transistor through the drive transformer. Utilizing the difference in power between the self-excited output during startup and steady state, the self-excited output at low power is used to oscillate until the self-excited output during high power steady state is generated. If a steady self-excited output with a large power is formed as the device continues to operate, the steady self-excited output with a large power will cause oscillation, so it is necessary to provide an oscillation stop circuit as described above with reference to FIG. It can be lost. In addition, the timing of switching from the starting self-excited state to the steady self-exciting state is when the steady self-exciting output becomes large, so the timing of switching from the starting state to the steady state is changed as in the conventional i-mode shown in Fig. 1. There is no need to strictly synchronize
This greatly simplifies the structure of the starting circuit.

[Brief explanation of drawings]

Figures 1 and 2 are connection diagrams showing conventional power supply starting circuits;
FIG. 3 is a connection diagram showing a seventh embodiment of the power supply starting circuit according to the present invention, and FIGS. 4 and 5 are connection diagrams showing other embodiments of the present invention. 21... Switching room temperature circuit, O... Output transformer, U... Switching transistor, 5... Rectifying element, 33... Rectangular wave oscillation circuit, 34... - Pulse width modulation circuit, 35...・Transistor for switching control. Applicant's agent 1) Kei Hajime

Claims (1)

[Claims] A pulse-modulated pulse output is formed based on the secondary output of an output transformer driven by a switching element, and the pulse output is returned to the switching element via a drive transformer for self-excitation. In a power supply circuit configured to oscillate, wait for initial startup when a power input arrives, and compare it with the pulse output based on the secondary side output obtained at the output transformer by operating the switching element with the power input. forming a starting self-exciting output with small energy, and coupling this starting self-exciting output to the signal line of the drive transformer for the pulse output;
A power supply start-up circuit characterized in that the switching element is operated by the combined output. (1) ＾A?