JPH0412792Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current feedback type transistor switching circuit, that is, a CT drive type transistor switching circuit.

In FIG. 1, which shows a conventional single-stone current feedback transistor DC stabilized power supply device, a DC power supply 1 includes a primary winding 3 of an output transformer 2, a feedback winding 5 of a current feedback transformer 4, that is, a CT. A switching transistor 6 is connected to the secondary winding 7 of the output transformer 2 through a rectifier circuit 8, and a load 9 is connected to the secondary winding 7 of the output transformer 2 through a rectifier circuit 8.
is connected between the base and emitter of the transistor 6, a capacitor 12 is connected in series with the on/off control winding 11 of the feedback transformer 4, and the winding 11
Power supply line +V is connected to the series circuit with capacitor 12 and capacitor 12.
Transistor 1 to selectively apply a voltage of
3 is connected to the winding 11 and the capacitor 1 to selectively form a discharge circuit for the capacitor 12.
A transistor 14 is connected in parallel to 2.
Reference numeral 15 denotes a control pulse generation circuit, which applies an on-drive pulse to the transistor 13 and an off-drive pulse to the transistor 14 in response to detection of the DC output voltage. 16 is a reset circuit for the transformer 2.

In the power supply circuit configured in this way, when the transistor 13 is turned on, a current flows through the winding 11 to charge the capacitor 12, and the voltage induced in the base drive winding 10 causes the switching transistor 6 to Turns on. When the switching transistor 6 is turned on, a collector current flows, which is fed back to the base by the transformer 4, thereby maintaining the conduction of the transistor 6. When turning off the transistor 6, one transistor 13 is kept off while the other transistor 14 is turned on to form a discharge circuit for the capacitor 12, thereby causing a current in the opposite direction. flows, generating a reverse voltage in the base drive winding 10 and turning off the transistor 6.

By the way, in order to turn on the transistor 6, it is sufficient to apply an on-pulse to the winding 11, taking only the rise time _tr into consideration. On the other hand, in order to turn off the transistor 6, an off pulse must be applied to the winding 11 in consideration of the accumulation time _tstg and the falling time _tf . However, since the on/off of the transistor 6 is controlled by charging and discharging the common capacitor 12, if the capacitance of the capacitor 12 is set large in order to increase the off-pulse width, the on-pulse width will inevitably increase. However, the disadvantage was that the drive power for on-control was wasted. Also,
Since the capacitor is connected in series with the winding 11, there is a problem in that it is difficult to obtain a steep rising pulse for turning on the transistor 6.

Therefore, an object of the present invention is to provide a current feedback transistor switching circuit that can reduce drive power loss.

To achieve the above object, the present invention includes a switching transistor, a feedback winding of a current feedback transformer connected in series with the transistor, and a transformer coupled to the feedback winding and between the base and emitter of the transistor. a connected base drive winding; an on-drive winding and an off-drive winding transformer-coupled to the base drive winding; an on-control pulse having a width corresponding to the on-period of the switching transistor; a control pulse generation circuit that generates an off control pulse having a width corresponding to the off period of the switching transistor; and a control pulse generation circuit that supplies the on drive winding with an on pulse for turning on the switching transistor. and a power supply terminal between the off-drive winding and the power supply terminal for supplying the off-drive winding with an off-pulse for turning off the switching transistor. a differential circuit including a connected off-pulse supplying transistor, a capacitor, and a resistor, and connected between a terminal for outputting the on-control pulse of the control pulse generation circuit and a base of the on-pulse supplying transistor;
an on-pulse width setting circuit configured to generate a pulse having a width shorter than the on-period in synchronization with the on-control pulse; and a differentiating circuit comprising a capacitor and a resistor, an off-pulse width that is connected between a terminal that outputs an off-control pulse and the base of the off-pulse supply transistor and is set to generate a pulse having a width shorter than the off-period in synchronization with the off-control pulse; The present invention relates to a current feedback transistor switching circuit consisting of a setting circuit and a setting circuit.

The present invention has the following effects.

(a) Since the on-pulse width setting circuit and the off-pulse width setting circuit are provided independently, the on-pulse width and the off-pulse width can be set to optimal values, and power loss in the drive circuit can be reduced.

(b) Since the on-pulse width setting circuit and the off-pulse width setting circuit have a differential circuit configuration consisting of a capacitor and a resistor, the on-pulse supply transistor and the off-pulse supply transistor are sufficiently driven to determine the start of the on-period and the beginning of the off-period. A sufficient current can flow through the on-drive winding and the off-drive winding. Thereby, switching loss of the switching transistor can be reduced.

(c) Since it has a feedback winding, it is not necessary to apply an on-drive winding with a width corresponding to the entire on-period; it is only necessary to apply an on-pulse to the on-drive winding at the beginning of the on-period; It is possible to reduce the power loss of the circuit for

Embodiments of the present invention will be described below with reference to FIGS. 2 to 4. However, in FIG. 2, the parts indicated by numerals 1 to 10 and 16 are substantially the same as those indicated by the same numerals in FIG. 1, so their explanation will be omitted.

In Figure 2, the error amplifier 1 for voltage detection
A voltage detection line 18 is coupled to one input terminal of 7, and a reference voltage source 19 is connected to the other input terminal. Therefore, a voltage corresponding to the difference between the output voltage and the reference voltage is obtained as a first control signal on the line 20 connected to the output terminal. In addition to the first control signal input from line 20 to the control pulse generation circuit 21 shown surrounded by a dotted line, a second control signal corresponding to the input voltage is input from the output line 23 of the input voltage detection circuit 22.

An input resistor 24 for determining the charging time constant is connected in series to the line 20 into which the second control signal proportional to the output voltage is input, and a triangular wave generating capacitor is connected between the output end of this resistor 24 and the ground line. 25 are connected. Further, the upper end of the capacitor 25 is connected to both the input line and the output line of a voltage comparator 26 having hysteresis, which is shown surrounded by a dotted line. Comparator 26 is comprised of an operational amplifier 27 and resistors 28, 29, 30, 31, and 32. The output terminal of the input resistor 24, that is, the upper end of the capacitor 25 is connected to the inverting input terminal of the operational amplifier 27, and the output terminal of the operational amplifier 27 is connected to the upper end of the capacitor 25 via the resistor 31. Therefore, an astable multivibrator is formed by the capacitor 25 and the comparator 26, and a triangular wave as illustrated in FIGS. 3A and 4A is generated on the triangular wave output line 33 connected to the upper end of the capacitor 25. can get.

34 is an on-drive voltage comparator composed of an operational amplifier, and its non-inverting input terminal is connected to a voltage dividing point formed by a resistor 35 and a resistor 36, and is also connected to the input voltage detection circuit 22 via a resistor 37. It is connected. Further, the inverting input terminal of the comparator 34 is coupled to the triangular wave output line 33. 38
is an off-drive voltage comparator composed of an operational amplifier, whose non-inverting input terminal is coupled to the triangular wave output line 33, and whose inverting input terminal is connected to the voltage dividing point between the resistors 35 and 36. , are connected to the input voltage detection circuit 22 via a resistor 37.

39 is an on-pulse width setting circuit, which includes a capacitor 41 connected in series to the output line 40 of the comparator 34 in the previous stage, and the output line 40 and the power supply line +
It consists of discharge resistors 42 and 43 connected between V and V. Note that the output terminal of the capacitor 41 is coupled to the base of the on-drive transistor 13. 4
4 is an off-pulse width setting circuit, which consists of a capacitor 46 connected in series to the output line 45 of the comparator 38 in the previous stage, and discharge resistors 47 and 48 connected between the output line 45 and the power supply line +V. Become. Note that the output terminal of the capacitor 46 is coupled to the base of the transistor 49. Further, the transistor 49 is Darlington connected to the second driving transistor 14 at the next stage. That is, its emitter is coupled to the base of the next stage transistor 14, and its collector is commonly connected to the next stage's collector. Also, its emitter and power line +V
A resistor 50 is connected between them.

The on/off control winding 11 is configured with a center tap, and the lower half is used as the on drive winding 11a and the upper half as the off drive winding 11b, and the center tap is grounded. An on-drive transistor 13 is connected between one end of the on-drive winding 11a and the positive power supply line +V, and an on-drive transistor 13 is connected between one end of the on-drive winding 11a and the positive power line +V.
An off-drive transistor 14 is connected between one end of the power supply line and the positive power supply line +V.

Next, the operation of the circuit shown in FIG. 2 will be explained with reference to the waveforms shown in FIGS. 3 and 4.

Now, in the circuit of Fig. 2, the output voltage, that is, the first
Assuming that the control signal of is kept constant,
A triangular wave A having a constant period or frequency is obtained on the triangular wave output line 33 as shown in FIG. 3A, and this becomes one input of the comparators 34 and 38. Comparator 3
4 and 38, a second control signal proportional to the input voltage obtained by combining the voltage applied from the input voltage detection circuit 22 and the voltage obtained by dividing the power supply voltage +V by the resistor 35 and the resistor 36. enters. If the voltage level of this second control signal, which is proportional to the input voltage, is the solid line 23a in FIG.
The first comparator 34 compares the triangular wave A and the second control signal voltage, and the first comparator 34 outputs a low-level pulse width control having a pulse width of the on time T _ON shown in FIG. 3B. I get a signal. Also, from the second comparator 38, the output of the first comparator 34 and 180
A low level signal having a pulse width of off time T _OFF with a degree phase difference is obtained as shown in FIG. 3C.

On the other hand, if the input voltage changes as shown by the dotted line 23b in FIG. 3A, the outputs of the comparators 34 and 38 also change as shown by the dotted lines in FIGS. 3B and 3C. If the switching circuit is not of the current feedback type, the low level pulse width control signal shown in FIG. 3B may be used, for example, as the base signal of the switching transistor. However, since the switching circuit of this embodiment is configured as a current feedback type, the on-pulse width setting circuit 39 and the drive transistor 13
Accordingly, the on-pulse shown in FIG. 3D is generated at the rising edge of the pulse shown in FIG. 3B, while the off-pulse setting circuit 39 and the transistor 14
The off-pulse shown in FIG. 3E is generated at the rising edge of the pulse shown in FIG. 3C.

The on-pulse width setting circuit 39 consists of a capacitor 41 for determining the pulse and resistors 42 and 43 forming a discharge circuit for the capacitor 41. By adjusting the capacitance of the capacitor 41, the on-pulse width setting circuit 39 is set to be longer than the rise time t _r of the switching transistor 6. It is set to obtain an on-pulse with an on-pulse width of t ₁ to _{t 2} . On the other hand, the off-pulse width setting circuit 44 includes a capacitor 46 that determines the pulse width and a resistor 4 that forms this discharge circuit.
7 and 48, and is set to obtain an off-pulse with an off-pulse width _t5 to _t6 that is slightly longer than the sum of the accumulation time _tstg and fall time _tf of the switching transistor 6 by adjusting the capacitance of the capacitor 46. has been done.

When the output of the comparator 34 becomes low level as shown in the period t ₁ to _{t 5} in FIG. 3B, since the comparator 34 is configured as a constant current drawing type,
The charging current of the capacitor 41 flows through the emitter/base of the transistor 13 and the capacitor 41, the transistor 13 is turned on, and the on-pulse determined by the capacitance _C1 of the capacitor 41 is applied to the on-drive winding 11a of the transformer 4. is applied to turn on the switching transistor 6. On the other hand, in the period _t5 to _t7 in FIG. 3, when the output of the second comparator 38 becomes low level and conversely, the output of the first comparator 34 becomes high level, The charge in the capacitor 41 of the on-pulse width setting circuit 39 is discharged by a circuit including resistors 42 and 43. In addition, in response to the low level output of the second comparator 38, a circuit including the power supply line +V, the emitter-base of the transistor 14, the emitter-base of the transistor 49, the capacitor 46, and the comparator 38 The capacitor 46 is charged. At this time, since the comparator 38 is configured as a constant current drawing type, the capacitor 46 is charged with a constant current, and the width of the on-pulse is determined by the capacitance C ₂ of the capacitor 46.
determined by. In addition, two transistors 1
4 and 49 are connected in a Darlington manner to increase the current amplification factor, it is possible to obtain a sufficient off-pulse in response to the charging waveform of the capacitor 46. The off pulse is the off drive winding 11 of the transformer 4.
When applied to b, transistor 6 is reverse biased and turned off.

Next, when the input voltage is constant and only the output voltage changes, as shown in FIG. 4A, the voltage level of the second control signal is kept constant as shown by the solid line 23a, and the output voltage Only the triangular wave A changes in response to the corresponding first control signal. That is, the period of the triangular wave of the astable multivibrator composed of the capacitor 25 and the comparator 26 changes as shown by the dotted line in FIG. To explain this in more detail, as the voltage of the first control signal on the line 20 increases in response to an increase in the output voltage, the charging voltage of the capacitor 25 rises faster. When this voltage becomes higher than the reference voltage of the operational amplifier 27, the output of the operational amplifier 27 is inverted to a low level, and the discharge circuit of the capacitor 25 is activated.
It is formed by a circuit consisting of a resistor 31 and an operational amplifier 27. By the way, since the operational amplifier 27 is configured as a constant current attraction type, it only allows a constant current to flow in when the output is reversed to a low level. If only the capacitor 25 is connected during the discharge period of the capacitor 25, the capacitor 25
is always discharged at a constant current, but the first control signal line 2 is connected to the output terminal of the operational amplifier 27.
0 is connected, and the voltage of this line 20 changes according to the output voltage, so that the combined current of the first control signal and the charging voltage of the capacitor 25 flows through the operational amplifier 2.
If the first control signal, that is, the output voltage is high, the current component based on this will inevitably increase, and conversely, the current component will flow into the output terminal of capacitor 2.
5 will be discharged less and the time taken to reach the low level trigger point of the hysteresis of comparator 26 will be longer. Therefore, the generation period of the triangular wave A becomes longer, and the switching transistor 6 is turned on/off.
The off period also changes from T ₁ to T ₂ . Note that since the intersection point between the triangular wave A and the second control signal indicated by the solid line 23a is set relatively above the triangular wave A, even if the period of the triangular wave A changes in response to the output voltage, the on-time T _po hardly changes, and off time T _pff changes mainly. As is clear from the above, when the output voltage changes, the switching frequency of the switching transistor 6 changes based on the change in the off time T _pff , resulting in control to keep the output voltage constant.

When both the input voltage and the output voltage change simultaneously, the control is a combination of those shown in FIGS. 3 and 4.

As is clear from the above, the apparatus of this embodiment has the following advantages.

(a) Since the on-pulse width setting circuit 39 and the off-pulse width setting circuit 40 are provided, and the width of the off-pulse is set larger than the on-pulse width, the drive current does not continue to flow more than necessary when turning on the switching transistor 6. control, and drive power loss can be reduced.

(b) Capacitors 41, 46 and windings 11a, 11b
Transistors 13 and 14 are interposed between the
Further, since a margin is provided for the current increase rate of the transistors 13 and 14, it is possible to obtain a steep waveform that allows the charging waveform of the capacitor to be ignored, and it is possible to increase the switching speed.

(c) When the input voltage changes, the voltage is adjusted by changing the on-time T _po , so the switching frequency does not change. Therefore, frequency changes are reduced, and the possibility of electronic equipment malfunctioning due to noise that is an integral multiple of the operating frequency is reduced. Note that the output voltage fluctuates due to fluctuations in the load 9, and the switching frequency changes, but if the switching frequency changes due to a light load, the current in the main circuit of the power supply device will be small. Therefore, the noise level is low and the possibility of malfunction is low. Furthermore, since it is an abnormal situation when the drooping overcurrent protection is activated, there is little possibility that it will cause a noise disturbance.

(d) Since the variable frequency oscillator is constituted by the astable multivibrator consisting of the capacitor 25 and the comparator 26, the frequency of the triangular wave can be relatively easily changed in accordance with the output voltage.

Although the embodiments have been described above, the present invention is not limited thereto and can be further modified. For example, the present invention is not limited to a single-transistor DC power supply, but can also be applied to a parallel inverter circuit in which switching transistors are connected to both ends of a transformer having a center tap, or a bridge inverter circuit. Furthermore, instead of providing the pair of comparators 34 and 38, for example, an inverted signal from one of the comparators 34 may be formed, thereby creating an off pulse. Alternatively, an off pulse may be generated in response to the high level period of one of the comparators 34. In addition, comparators 34 and 38
The low level output of the transistors 13 and 14 is used as a pulse width control signal, and the comparators 34 and 3 are configured to respond to the high level base signal.
8 to generate a high level output. Further, the first and second control signals may be any signals as long as they are equal to or proportional to the output voltage and the input voltage. Also, winding 1
1a and 11b may be independent instead of being in a center tap type.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional current feedback transistor DC stabilized power supply device, Fig. 2 is a circuit diagram of a power supply device according to an embodiment of the present invention, and Figs. 3 and 4 are A to A in Fig. 2. FIG. 3 is a waveform diagram showing the state of point F. FIG. In the symbols used in the drawings, 4 is a current feedback transformer, 5 is a current feedback winding, 6 is a switching transistor, 10 is a base drive winding, and 1 is a current feedback transformer.
1 is an on-off control winding, 11a is an on-drive winding,
11b is an off-drive winding, 13 and 14 are transistors, 21 is a control pulse generation circuit, 34 and 38 are voltage comparators, 39 is an on-pulse width setting circuit, 41 is a capacitor, and 44 is an off-pulse setting circuit.

Claims (1)

[Claims for Utility Model Registration] A switching transistor, a feedback winding of a current feedback transformer connected in series to the transistor, and a transformer coupled to the feedback winding and connected between the base and emitter of the transistor. a base drive winding; an on-drive winding and an off-drive winding transformer-coupled to the base drive winding; an on-control pulse having a width corresponding to the on-period of the switching transistor; a control pulse generation circuit that generates an OFF control pulse having a width corresponding to the OFF period of the switching transistor; an on-pulse supply transistor connected between the switching transistor and the switching transistor; and an on-pulse supply transistor connected between the off-drive winding and the power supply terminal for supplying the off-drive winding with an off-pulse for turning off the switching transistor. a differentiator circuit consisting of a transistor for supplying an off-pulse, a capacitor, and a resistor, which is connected between a terminal for outputting the on-control pulse of the control pulse generating circuit and a base of the transistor for supplying an on-pulse; The on-pulse width setting circuit is set to generate short-width pulses in synchronization with the on-control pulse, and the differentiating circuit includes a capacitor and a resistor.
connected between a terminal for outputting the OFF control pulse of the control pulse generation circuit and a base of the OFF pulse supply transistor, and configured to generate a pulse having a width shorter than the OFF period in synchronization with the OFF control pulse. A current feedback transistor switching circuit consisting of an off-pulse width setting circuit set to , and a current feedback transistor switching circuit.