JPS5812031A - Self-oscillation type switching regulator - Google Patents

Abstract

PURPOSE:To protect a load and a regulator, by keeping the stop of oscillation of a switching element against a failure of a self-oscillation type switching regulator. CONSTITUTION:A time ranging from a time t=0 of application of AC voltage to a time t1 when a thyristor 15 of a start circuit 14 turns on, is set larger than a time when a switching transistor (TR)1 surely starts the oscillation. When the TR1 completely turns on and the increase in the collector current stops, an electromotive force of an input wiring 201 is inverted, a reverse bias is applied to the TR1, the TR1 is turned on and the oscillating operation is repeated. Since the thyristor 15 is turned on with a voltage across a capacitor 17, the oscillation stop of the TR1 can be kept in case of a failure of load circuit connected to an output winding 203.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-excited oscillation switching regulator that converts oscillation output to obtain an output voltage. IK is characterized by its reliable startup and safety during operation. In general, this type of switching regulator must be given a signal to turn on the switching element in order to start oscillation. The signal for turning on the engine is called the starting current.This starting current IIl!
When a transistor is used as the switching element,
It supplies that base. However, once this starting current starts oscillating, f! Even if the L cup is removed, it will not affect the oscillation operation. To start up such a switching regulator, conventionally, nine self-excited oscillation type switching regulators having the configurations shown in FIG. 3 are used.

These will be explained below.

Figure #11 is a schematic circuit diagram showing a self-excited oscillation type switching regulator that supplies a starting current as an initial current to the base of a switching transistor through an input DC voltage through a resistor. The configuration of this circuit is that an input DC voltage (1) generated from an AC power supply via a four-terminal rectifying element REC is passed through a smoothing capacitor C1, a switching transistor 1, and an input winding 201. Output winding 202. Drive @ 92
03 is wound through the iron core and connected to the next converter transformer 2,
It supplies nine signals to an oscillation circuit consisting of control path 3.
In order to start this switching transistor l, a resistor 4 is interposed between the positive electrode of the #I element REC and the base of the switching transistor l. line 2
The control circuit 3 that operates the 030 generated voltage and controls the oscillation period of the transistor l is provided.

In the operation of this circuit, the load short-circuit and converter
In the event of a circuit failure such as a short circuit or open circuit of the transformer 2, the output winding 20
The electromotive force (output voltage) of 2 jumps up and gradually decreases. In such a case, when the output voltage becomes abnormally high, the operation of control path 3 causes the switching transistor l to The on-time of the oscillation is lost, and although the oscillation stops once, it oscillates again, resulting in intermittent oscillation where the on-time of the state described above is lost.Also, if the output voltage decreases (due to negative ) The off-time of the switching transistor becomes extremely short.
In the case of the above-mentioned situation V, in which the oscillation is once stopped and then oscillated intermittently as described above, the switching transistor l is in a state where a constant base current is applied by the resistor 4. Even if oscillation stops due to the occurrence of an abnormal situation, it will start oscillating again when the road condition passes a certain operating point.This oscillation is nonlinear vibration. Since the transistor l operates in the linear region, there is a good chance that the maximum collector loss will occur and it will be destroyed.The self-oscillating switching regulator shown in Figure 2 is
In order to compensate for the shortcomings of the first cylinder, a capacitor Cm is installed between the positive electrode of the rectifying element REC and the resistor 4! Figure 1IX3 shows the AC input terminal PIP for the same purpose.
A resistor Rr is connected to the resistor 4 through a series of a diode DI and a capacitor TC', and a resistor Rr is interposed between the intersection of the diode D1 and the capacitor Cm' and the negative electrode of the rectifying element REC. Figures 2 and 3 with @
The co/capacitors C1 and CI' used in the circuit shown in FIG. 1 pass only the displacement current when the input tm voltage Vi rises and supplies an initial starting current to the switching transistor lK through the resistor 4 only when the power is turned on.

In such a circuit, the reason why the reliability of starting the capacitors C1 and Cm' becomes a problem is when the power is turned on (on).
If the switching regulator is continuously disconnected (off), depending on the timing, sufficient starting current may not be generated. As for the reliability of activation of capacitors c, , c, ', it is important to consider the specific number of capacitors Cm, Cm' and resistors 4 for operating conditions where the value of the AC power source changes over a wide range. The present invention has been made in view of the above-mentioned points, and aims to ensure operation reliability so that a sufficient starting current is generated and the output voltage is generated at the same time as the current is turned on. The purpose of this item is to provide a self-excited oscillation type switching regulator that prevents the supply of starting current to the switching element when the element oscillates, thereby retaining a potential oscillation stop function in preparation for circuit abnormalities. The invention will be explained based on the drawings. ◎The fourth garden is a circuit showing an embodiment of the invention. This is an operation explanatory diagram for explaining the operation, and the coordinates are 0 and 4g, where the vertical axis is voltage and the horizontal axis is time. Elements that are the same as conventional elements are given the same symbols. The AC input cam C is supplied from the terminal P*Pa by turning on a power switch (not shown), and generates an input DC voltage vl using a 4-terminal rectifier RBC. Is there a smooth condenser for the electrode, negative electrode, and O-sensor? C
t and a resistance u in parallel with this smoothing capacitor 7tCtK,
12. A switching transistor 10 pace is connected to the intersection of the resistor line and the mouth, and its collector and emitter are respectively connected to the rectifying element RE through the input winding 201.
However, the resistance value & of the resistor ν is set to be sufficiently larger than the resistance value R11 of the resistor 13, and the voltage between the base and emitter of the transistor 10 is
mm o 0 (V) K is configured so that it can be maintained.
'tfl:,, The output of the control circuit 3 which adjusts the switching time of the #i transistor l is supplied to the intersection of the resistors 12 and 13, and the adjustment operation of the control circuit 3 is performed by the control circuit 3. It is connected to Kushiro 3 and adjusted based on the feedback voltage applied to the tip PmK.

The drive winding that drives the switching circuit 3 directly controls the base current of the switching transistor 10. Also, the output 1 [12G3 is outputted via a rectifying and smoothing circuit consisting of a diode D3 and a conductor ytcs. Terminals Pa and PsKII are connected to each other, and a load (not shown) is connected to them.Now, the relationship between the intersection of resistor 11 and resistor 1 of the starting resistance group - and the negative electrode of the regulator full element REC is as follows. A starting circuit 14, which is the main part of the present invention, is interposed. The starting circuit 14 has a configuration in which a resistor 16 and a capacitor are connected in parallel to the anode/dog terminal of the thyristor 15.
The voltage Ve across this capacitor 170 is connected to a series circuit of 17 and is configured to form a gate signal for a thyristor t, which will be described later.
1, the sum of the resistance values of the resistor 16 &t+R1・, and the parallel resistance value of the resistance value Itts of the resistor 1. The resistance value R1 of the resistor 11 is set so that it is charged immediately even after discharging.
1 is set sufficiently small.However, this resistance value Rs
t is set within the surge breakdown current rating of the thyristor 15. The gate of the thyristor 15 is connected to the negative electrode of the integer #1IIA through a resistor 18, and connected to the resistor #1I through a Zener diode. 16 and the connection intersection of capacitor 17 KI [Iil! ◎Therefore, the iris register 15 of this starting circuit 14 has a guiding shape 11.
1K, the configuration is such that the starting current that enters the resistor LaKm can be shunted to almost any starting circuit 14. In this case, the current flowing through the resistor 1lls is greater than the holding current of the thyristor 15. Also, the conduction state of this thyristor 15 is 111.
It is configured to turn on from when the distribution power switch is turned off to before the switching transistor l stops oscillating.This makes it possible to ensure that the power switch/gregiator starts up at 3'h'7. 0 The operation of the present invention having the above configuration will be explained below.0 First, regarding the reliability of startup as the main effect of the present invention, when the AC voltage is turned on at time t = OK$P in FIG. This is primarily guaranteed by setting the time τ at which the thyristor 15 of the starting circuit 14 turns on at time t11 to be larger than the time at which the switching thyristor l of the switch y regulator starts firing operation reliably.・The time during which this transistor l oscillates w4# is determined by the input DC voltage when the power is turned on.■1 is the starting resistor■,
A starting current 1 of 1,000 is applied to the base of the switching transistor 1 through u, and the resulting increase in collector current induces an output voltage of 11 [K] through the input winding 201, and this output voltage is the driver 19202. This is the time it takes for the voltage generated in the control circuit 3 to be applied to the base of the switching transistor 1. After this, the switching transistor lFi is completely turned on and the collector current increases. Since it stops, input volume! The electromotive force of 1201 is reversed, and a reverse bias is applied to the base of the switching transistor 10 through the same path as described above.@This reverse bias turns off the switching transistor lri, and thereafter this oscillation operation is repeated.0 Switching transistor 1 repeats the following operation and the starting voltage fL11 becomes unnecessary, so the thyristor rib is turned on by the voltage Ve across the capacitor 17 mentioned above.0 This causes the output voltage to turn on! 1203K It is possible to maintain the stoppage of oscillation of the switching transistor 1 in the event of a circuit abnormality due to am and disconnection of the connected load or other causes. FIG. 5 shows the input DC voltage Vi and the terminal voltage V of the capacitor 17 when such an action is performed by the starting circuit 14 consisting of the thyristor 15 and the capacitor 17.
The operation of this starting circuit 14 will be explained in detail below 0, which indicates the change in e. Input DC voltage viFi When the AC power source is turned on, it rises with the rising characteristic of #5A and charges the capacitor 17. Conan? 17 time constant τe
FiC (Rtt/ (Cs proverb + Rxs)), and when the voltage across both ends due to this time constant @ r c K becomes larger than the breakdown voltage VK of the Zener diode, the thyristor 15
can be turned on. To be precise, when the voltage Ve across the thyristor 15 is biased to a voltage equal to the sum of the breakdown voltage v1 and the gate triggerable voltage V of the thyristor 15, the thyristor 15 turns on. Expressing this time in a formula, time τ has elapsed from time t = 0 (when the power is turned on), and at 9 o'clock, we get 0 When the thyristor rib turns on, the starting current ■1 is almost the same as that of thyristor 15. Since the anode current fiK is included, the switching transistor l is connected through the resistor 12.
The electric current tIt flowing to the base of is zero. Therefore,
When this self-oscillation type switching regulator is in operation, the switching transistor 1 is connected to the thyristor 150.
The starting voltage RLs component #i will not flow to the 0 pace.
This is due to the short circuit of the load as mentioned above,
When the switching transistor l stops oscillating due to a circuit abnormality caused by a short-circuit or open-circuit of each winding of the converter transformer 2, it will no longer start oscillating on its own). O#1, which can protect the load and the switching regulator itself, discharges with a time constant CRI・? In order to return the voltage Vc across -O to its original value, set the value of the resistor 11 to a small value within the range allowed by the surge current rating of the thyristor 15, as described above. By charging the capacitor 17, when the power switch is turned off, the thyristor B can be turned on and off before the switching transistor l stops oscillating, and when the current switch is turned on again. Since the thyristor 15 is also off, the output voltage is reliably generated as described above. This secondarily guarantees the reliability of activation.

As described above, the present invention potentially has the function of maintaining the oscillation stop of the switching transistor 1, and the switching transistor l of the switching regulator.
However, it is possible to avoid the intermittent oscillation situation in which the oscillation temporarily stops in response to a load short circuit or a short circuit/discharge of the converter transformer, and then abnormally oscillates toward destruction.

Self-excited oscillation type switching regulator K with the above configuration
The strange explanation is that the switching transistor l has no choice but to stop oscillating on its own in the event of an abnormality such as a load short-circuit or open-circuit.
This is the ninth occurrence when the output voltage of , becomes an overvoltage, and a protection circuit is added to detect the overvoltage and protect the switching regulator from stopping the oscillation of the switching transistor l due to a circuit abnormality. Figure 6 shows such a protection circuit at the output terminal Pa P
s is a circuit diagram showing a self-excited oscillation type switching regulator. In other words, the configuration of FIG. , this protection path 21 has a resistor 9 at the anode of the thyristor SCR, and its gate is a Zener diode DZ.
Intersection point KI where voltage dividing resistors Rm and Rν are connected in series through
The acid bias resistance R on the gate is
・are connected and configured.

This protection circuit 21 detects that the output voltage of the output terminals Pa-Pg becomes an overvoltage, and short-circuits the output terminals P4-8.
This is because the divided voltage of P exceeds the breakdown voltage of the Zener diode Dx. This turns on the thyristor SCR and creates a load short-circuit condition. Therefore, the switching transistor l stops oscillating in this short-circuit condition , the protection circuit 21 Fi, which maintains this oscillation stopped state by the action of the starting circuit 14 of the present invention,
Since the load is short-circuited in all circuit abnormalities, it is possible to quickly operate and protect the circuit against open output winding 203, load short-circuit, etc. that may actually occur.

As described above, according to the present invention, the load and the regulator body can be safely maintained by maintaining the switching element's oscillation stop when the self-excited oscillation type switching regulator is malfunctioned, such as when the load is short-circuited or opened. This has the effect of allowing the output voltage to not rise due to the power switch being turned on and off at random.
It has the remarkable effect of eliminating fundamental malfunctions and guaranteeing extremely reliable startup.

[Brief explanation of drawings]

Figures 1 to 3 are schematic circuit diagrams showing a conventional self-oscillation switching regulator equipped with a starting resistor, Figure 4 is a circuit diagram showing an automatic oscillation switching regulator according to the present invention, and Figure 5 is a schematic circuit diagram showing a conventional self-oscillation switching regulator equipped with a starting resistor. An operation explanatory diagram for explaining the time required to erase the starting current for one hour of input DC voltage rise; FIG. 6 is a circuit diagram showing an example of the use of the present invention.

Claims (1)

[Claims] ■ A switching element that oscillates when a DC bias is applied when the power is turned on; a converter transformer that generates an output voltage by generating the oscillation output of the switching element; In a power supply device which is designed to promote oscillation of a switching element and is equipped with a resistor for electromotive force, a resistor connected in series is provided between a reference potential to which DC bias is supplied and which starts the switching element. and a starting circuit that is interposed between the connection intersection of the series-connected resistors and one of the reference potentials marked #, and short-circuits the connection intersection and one of the reference potentials marked # after oscillation of the switching element. A self-excited oscillation type switch y-dare gierator characterized by comprising: (2) The starting circuit is configured to turn off once the switching element stops oscillating by resetting the DC bias. (3) The self-oscillation type starting circuit according to claim 1 or 2, wherein the switching element stops oscillating when the load is short-circuited and maintains the short-circuited state. Switching regulator (2) The starting circuit has an anode connected to the connection intersection of the series ma and nine resistors, a cathode connected to one of the reference potentials, and a gate connected to the ml through a Zener diode.
The self-oscillation type % type % according to claims 1 to 3, which is constituted by a thyristor that is turned on by the voltage across the capacitor.