JP5353374B2 - Time-sharing control power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inexpensive stable DC power supply which can dispense with a choke coil and a flywheel diode having a capacity corresponding to the choke coil and is low in loss. <P>SOLUTION: This time division control power supply includes a resonance transformer 13, having a primary winding 10 having a resonance circuit 9 and first and second secondary windings 11, 12; a first DC power supply circuit 14 connected to the first secondary winding 11; a second DC power supply circuit 15 connected to the second secondary winding 12; and a resonance frequency control part 16, which controls the frequency of the resonance circuit 9 according to a voltage generated at the second secondary winding 12. A smoothing capacitor 19, connected to the first secondary winding 11 via a rectification circuit 17 and a first switching element 18, is arranged at the first DC power supply circuit 14, in parallel with an output part of the first DC power supply circuit 14, and a switching period of the first switching element 18 is controlled by a time-division control circuit 20 according to a voltage of the smoothing capacitor 19, thus controlling the output of the first DC power supply circuit 14. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a time-division power source used for various electronic devices.

  Hereinafter, a conventional DC power supply will be described with reference to the drawings.

  FIG. 7 is a circuit diagram of a conventional DC power supply for display equipment. This display device DC power supply has a configuration including a first DC power supply unit 1 compatible with panel light emission and a second DC power supply unit 2 corresponding to driving of the control unit other than panel light emission. . In particular, in the first DC power supply unit 1, in order to stabilize the output voltage, the voltage obtained in the rectifying and smoothing circuit 3 is stepped down and stabilized by the DCDC converter 4 to extract the output voltage.

For example, Patent Document 1 is known as prior art document information relating to the invention of this application.
Japanese Unexamined Patent Publication No. 7-194115

  However, in order to obtain a stable output voltage in a conventional DC power supply, a large choke coil and a flywheel diode having a capacity corresponding to the large choke coil are required.

  For example, when the load of the second DC power supply unit 2 fluctuates, the voltage of the first DC power supply unit 1 may change in conjunction with the fluctuation. This factor is because both the first DC power supply unit 1 and the second DC power supply unit 2 are supplied with electric power from the same transformer 5. As a means for making this phenomenon difficult to manifest, A relatively high voltage with respect to the output voltage of the first DC power supply 1 is extracted from the rectifying / smoothing circuit 3 of one DC power supply unit 1, and the DCDC converter 4 controls the switching element 6 in accordance with load fluctuations. A stable output voltage was obtained by lowering the voltage.

  Accordingly, the choke coil 7 in the DCDC converter 4 and the flywheel diode 8 having a capacity corresponding to the choke coil 7 and the corresponding physical space are required. As a result, the power source is increased in size and the cost is increased accordingly. Another problem is that a large energy loss occurs in these devices.

  Therefore, the present invention eliminates the need for a choke coil and a flywheel diode having a capacity corresponding to the choke coil, reduces power loss, and obtains a compact, low-cost DC power supply.

  In order to achieve this object, a resonant transformer having a primary winding having a resonant circuit section and first and second secondary windings, and a first DC connected to the first secondary winding. Resonance frequency control for controlling the frequency of the resonance circuit unit in accordance with a power supply circuit, a second DC power supply circuit connected to the second secondary winding, and a voltage generated in the second secondary winding A smoothing capacitor connected to the first secondary winding via a rectifier circuit portion and a first switching element in the first DC power supply circuit. The output of the first DC power supply circuit is provided by connecting in parallel to the output unit, and controlling the switching of the switching element and the switching period by the time division control unit according to the voltage of the smoothing capacitor. It is characterized by controlling.

  According to the present invention, a choke coil and a flywheel diode having a capacity corresponding to the choke coil are not required, and it is possible to provide a DC power source that can be reduced in size and price and further reduced in power loss.

  Hereinafter, a time division control power supply according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a circuit diagram showing a configuration of a time division control power source in the first embodiment of the present invention.

  Here, the time-division control power supply includes a primary winding 10 that constitutes a part of the resonance circuit unit 9, a resonant transformer 13 having first and second secondary windings 11 and 12, and a first secondary winding. The first DC power supply circuit 14 connected to the winding 11 and the second DC power supply circuit 15 connected to the second secondary winding 12 are basic components.

  The resonance circuit unit 9 includes a resonance frequency control unit 16 that controls the frequency of the resonance circuit unit 9 in accordance with the voltage generated in the second secondary winding 12. The first DC power circuit 14 includes a first secondary winding 11 and a smoothing circuit connected in parallel with the output unit of the first DC power circuit 14 through a rectifier circuit unit 17 and a switching element 18. A capacitor 19 is provided. Further, the voltage of the smoothing capacitor 19 is detected and then input to the time division control circuit unit 20, and the switching element 18 is turned on and off by the PWM signal generated by the calculation in the time division control circuit unit 20. And the switching period are controlled. As a result, the output of the first DC power supply circuit 14 is controlled.

  According to the above configuration, by providing the first DC power supply circuit 14 with the time-sharing type output stabilization circuit, the choke coil and the flywheel diode are not required in the output portion of the first DC power supply circuit 14. This eliminates the need for an element that stores energy corresponding to the inductor, and enables the power supply circuit to be reduced in size and price. At the same time, it is possible to reduce the power loss generated in the inductor or the like.

  Hereinafter, the operation of the time-division control power supply will be described with reference to the circuit diagram of FIG. 2 and the timing charts of FIGS.

  First, in the time-division control power supply of FIG. 2, the second DC power supply in the time-division control power supply in a state where there is no load on the output V1 of the first DC power supply circuit 14, that is, the display panel is not being displayed. The voltage waveform in the second secondary winding 12 of the circuit 15 is shown in FIG. 3A, the resonance current waveform in the primary winding 10 is shown in FIG. 3B, and the PWM signal is generated in the PWM generation block 21 of the time division control circuit unit 20. 3C shows a voltage waveform in the timing capacitor 22 for generating the current, FIG. 3D shows a current waveform supplied to the smoothing capacitor 19 by switching the switching element 18, and the first DC power supply circuit 14. The voltage waveform of the output V1 is shown in FIG. Here, in order to stabilize the output V1, the current shown in FIG. 3D flows through the smoothing capacitor 19 shown in FIG. This current is smoothed by the smoothing capacitor 19 and then becomes the output V1 of the first DC power supply circuit 14 shown in FIG.

  In this case, since the first DC power supply circuit 14 is in an unloaded state and literally no power is consumed by the load, the supply of voltage to the output V1 of the first DC power supply circuit 14 also needs to be changed almost. The current supply time T1 in FIG. 3D is very short. That is, the ON time of the switching element 18 becomes the shortest when there is no load.

  In the embodiment shown here, the current waveform supplied to the smoothing capacitor 19 is generated by periodically performing the switching operation of the switching element 18 shown in FIG. This is for simplifying the explanation of the no-load state, and this waveform does not occur in a complete no-load state. In the complete no-load state, the clamped flat portion does not exist in the timing capacitor 22 shown in FIG. 3C, so there is no transmission of a PWM signal corresponding to the period of the flat portion. This is because there is also no current waveform supplied to the smoothing capacitor 19 by switching of the switching element 18 shown in 3 (d). That is, in this embodiment, the weak load state is described as a substitute for the no-load state.

  On the other hand, the voltage waveform at the second secondary winding 12 in the time-division control power supply in a state where a load is applied to the output V1 of the first DC power supply circuit 14 in FIG. 4 (a), FIG. 4 (b) shows the current waveform in the primary winding 10, FIG. 4 (c) shows the voltage waveform in the timing capacitor 22, and the current waveform supplied to the smoothing capacitor 19 by switching the switching element 18. 4 (d) and FIG. 4 (e) shows the waveforms at the respective locations of the output V1 of the first DC power supply circuit 14. FIG. Here, since there is a load on the output V1 shown in FIG. 2, the current shown in FIG. 4 (d) flows through the smoothing capacitor 19 shown in FIG.

  In this case, by detecting a decrease in the voltage of the smoothing capacitor 19, the voltage of the timing capacitor 22 rises in a short time in order to transmit the PWM signal in a long period, and this has the waveform shown in FIG. It becomes. A PWM signal is transmitted during the clamped flat portion of the waveform to turn on the switching element 18 shown in FIG. When the switching element 18 is ON, the current shown in FIG. 4D flows through the smoothing capacitor 19 shown in FIG. 2 with respect to the voltage from the rectifying unit 23. This current is smoothed by the smoothing capacitor 19 and then becomes the output V1 of the first DC power supply circuit 14 shown in FIG.

  Here, since the load is present in the first DC power supply circuit 14 shown in FIG. 2, the power consumption by the load is large, and the voltage supply to the output V1 of the first DC power supply circuit 14 is as follows. It is necessary to change it according to the load. Therefore, the current supply time T2 in FIG. 4D requires a relatively long time. That is, when the load is present, the ON time of the switching element 18 is longer than that when there is no load depending on the magnitude of the load. Here, during the period in which the switching element 18 is ON, the current waveform of the primary winding 10 is increased as compared with the broken line assuming a complete no-load state, as shown in FIG. 4B.

  Also, here, the current waveform supplied to the smoothing capacitor 19 shown in FIG. 2 becomes the current waveform shown in FIG. 4 (d), and this is precisely the moment when the voltage of the timing capacitor 22 shown in FIG. If not captured, there is a large variation in the rise timing of the current waveform, and as a result, there is a possibility that the supply of voltage to the output V1 of the first DC power supply circuit 14 cannot be stabilized. . Therefore, it is necessary to accurately capture the moment when the voltage of the timing capacitor 22 drops.

  In addition to this, the resonant power supply operates as an operation frequency of several tens of kHz when the load is maximum, but changes to 300 kHz or more when the load is light.

  Therefore, it is possible to improve the stability of the output V1 by configuring a circuit that accurately responds to a change in the current of the timing capacitor with respect to an operation in which the load changes rapidly.

  Therefore, the timing capacitor 22 is accurately captured at the moment when the timing capacitor 22 descends, and after this is performed, the supply of the voltage to the output V1 of the first DC power supply circuit 14 is also accurately changed in response to the load. A detection circuit is provided. That is, by providing a synchronization detection circuit unit that obtains a synchronization signal synchronized with the resonance current of the resonance frequency control unit 16, and synchronizing the synchronization signal with charging / discharging of the timing capacitor 22 and switching of the switching element 18, This makes it possible to operate the split control power supply more accurately.

  Hereinafter, a synchronization detection circuit unit that detects a synchronization signal will be described.

  The current waveform of the primary winding 10 having the resonance circuit section 9 in each of the time-division control power sources for obtaining this synchronization signal is shown in FIG. 5A, the terminal S3 in the second secondary winding 12 shown in FIG. 5B and 5B, the voltage waveform of S5 is equal to or lower than the threshold voltage at the terminal S5 and the voltage detected by the first falling detection unit 25 when the voltage is lower than the threshold voltage at the terminal S3 shown in FIG. The waveform of the voltage detected by the second falling detection unit 26 is detected by the first falling detection unit 25 and the second falling detection unit 26 shown in FIGS. 5 (d) and (d '), the integrated waveform of the voltage detected by the first falling detector 25 shown in FIG. 2 and the integrated waveform of the voltage detected by the second falling detector 26 shown in FIG. FIG. 5E shows a voltage waveform obtained by ANDing the waveform with the operator 28.

  Here, the synchronization signals shown in FIGS. 5C, 5C, and 5E are both the current waveform in the primary winding 10 and the terminal S3 in the second secondary winding 12 shown in FIG. It is synchronized with the voltage waveform, and can be applied as a synchronization signal to any of them.

  Of course, the frequency of the synchronizing signal shown in FIG. 5 (e) changes according to the frequency of the primary winding 10 shown in FIG. Therefore, in particular, the synchronization signal shown in FIG. 5 (e) is obtained based on the integrated waveform of the voltages detected by the first falling detection unit 25 and the second falling detection unit 26 shown in FIG. From the above, it is possible to define the pulse width of the synchronization signal shown in FIG. 5E according to the time constant during integration. That is, by reducing the pulse width, application is possible even when the frequency of the primary winding 10 shown in FIG. 2 is very high.

  FIG. 6 shows a detailed circuit diagram in the block diagram of the time division control circuit 20. The voltage detected by the first falling detection unit 25 and the second falling detection unit 26 is converted by the integration circuit 27. This is a case where the synchronizing signal shown in FIG. Therefore, the time constant at the time of integration is determined by the load resistor R27 and the capacitor C27 of the integration circuit 27 shown in FIG.

  Here, the second secondary winding 12 is provided with a terminal S4 as a center tap of the terminals S3 and S5 at both ends, and by inverting the polarity of the terminal S3 and the terminal S5, a symmetrical amplitude around the terminal S4. The voltage waveforms shown in FIGS. 5 (b) and (b ′) can be obtained. Therefore, the integrated waveforms of substantially the same shape voltage with a phase shift of 180 degrees by the transistors Q5 and Q6 of the first falling detection unit 25 and the second falling detection unit 26 are shown in FIG. d ′) is obtained, and the AND operation of the two integrated waveforms is performed by the operator 28 to extract the synchronization signal shown in FIG. 5 (e).

  By taking out the synchronization signal shown in FIG. 5 (e) by the above method, the remote terminal 29 shown in FIG. 6 enters the panel light emission state, and the power supplied from the primary winding 10 in the transformer 13 is temporarily supplied to the panel. Even when the potential of the second DC power supply circuit 15, particularly the voltage of the second secondary winding 12, is concentrated on the first DC power supply circuit 14 that hits the light emission side, the polarity is reversed. Since it operates, it is possible to stably extract the synchronization signal.

  In addition, by using the timing pulse generation circuit 30c as the synchronization signal of FIG. 5E, a discharge signal for discharging the timing capacitor 22 in a short time is generated, and the control time of the timing capacitor 22 is more accurately determined by this discharge signal. It can be carried out. As a result, the time for generating the PWM signal can be more strictly defined, and the stable supply of the voltage to the output V1 of the first DC power supply circuit 14 by the time division control becomes possible.

   Further, as a method of obtaining a more stable output V1, the output of the first DC power supply circuit 14 (rated voltage of 75V) is, for example, the PWM output of the AND output of the operator 28 until the voltage reaches 60V in the process of increasing voltage. It is good to use as. That is, when the output V1 is equal to or less than a predetermined value, the output of the operator 28 is used as a PWM signal as means for obtaining a soft start. This is to suppress the duty of the PWM signal in order to prevent sudden supply of power, and the duty is preferably about 50%. When applied to the output V1 in the above range, the duty of the PWM signal is approximately 50%. However, when the duty is set strictly, the integration time of FIGS. 5D and 5D, that is, It can be easily adjusted by setting the constants of R27 and C27 shown in FIG.

  For example, in the state where the second DC power supply circuit 15 shown in FIG. 6 operates in the resonance power supply and the output voltage of the first DC power supply circuit 14 is not present, a sudden voltage immediately after the remote terminal 29 is turned ON. In order to increase, the timing capacitor 22 is continuously charged with the maximum current. As a result, the PWM signal for controlling the switching element 18 becomes close to a duty of 100%, and there is a fear that the switching is kept on substantially. It is a soft start to prevent it. In other words, it is close to the state where the first secondary winding 11 of the resonant transformer 13 is short-circuited, and may cause a decrease in the output of the secondary winding 11 against the purpose. Since the output of the secondary winding 12 is also extremely reduced and may affect the detection of the synchronization signal, the soft start circuits 30a and 30b and the generation of timing pulses are necessary to prevent the occurrence of these effects. By providing the circuit 30c together, it is possible to obtain a stable output V1 of the first DC power supply circuit 14.

  In addition, in order to avoid excessive concentration of power in the first DC power supply circuit 14, an OCL control circuit 31 that performs current limiting is provided in the time division control circuit 20 to control the output V1. The stable operation of the first DC power supply circuit 14 can be made possible. That is, a current limiting unit is provided. For example, the OCL control circuit 31 has the following configuration.

The detection resistor 32 of the first DC power supply circuit 14 detects the value of the current flowing through the first DC power supply circuit 14 as a voltage. At the same time, a bias circuit including the shunt regulator IC2 (for example, for 2.5 (V)), the transistor Q5, and the resistors 33, 34, and 35 is formed to generate a current limit value. Then, the same current as the constant current corresponding to the current limit value supplied by the bias circuit is passed through the resistor 36 by the current mirror Q11. Thus, a threshold voltage value obtained by converting the current limit value into a voltage is determined. Here, assuming that the resistance values of the resistor 35 and the resistor 36 are R35 and R36, the above current limit value is the constant current Ic.
Ic = 2.5 (V) / R35
Is obtained.

The threshold voltage value Vr flows the same current to the resistor 36 by the current mirror Q11.
Vr = Ic * R36
And replace Ic,
Vr = 2.5 (V) * (R36 / R35)
Can be obtained as

  Here, the voltage drop in the detection resistor 32 is equal to the voltage drop in the resistor 37, and the resistors 37 and 38 connected via the current mirror Q9 have the same current I37 and current I38, respectively. Value current will flow. The voltage generated in the resistor 38 pushes up the voltage of the resistor 40 connected to the base of the output control error amplifier Q15 via the temperature compensating transistor T1, the emitter follower T2, and the resistor 39 of the current mirror Q8. .

  That is, when the current value flowing through the first DC power supply circuit 14 exceeds the limit current value determined by the OCL control circuit 31, the base voltage V1 of the output control error amplifier Q15 increases, and the charging current to the timing capacitor 22 is increased. Is going to decrease. In other words, when the base voltage V1 generated by the currents I37 and I38 linked to the voltage drop of the detection resistor 32 reaches the threshold voltage value, the pulse width of the PWM signal becomes narrower and the ON time of the switching element 18 becomes shorter. The output V1 of the DC power supply circuit 14 is lowered. As a result, stable operation of the first DC power supply circuit 14 can be achieved.

  Although the transformer 13 has the first and second secondary windings 11 and 12 as described above, although not shown, the first DC power circuit and the first secondary winding are connected to the first secondary winding of the transformer. Two DC power supply circuits may be connected, and a resonance frequency control unit that controls the frequency of the resonance circuit unit in accordance with a voltage generated in the second DC power supply circuit may be provided.

  In the first DC power supply circuit, a smoothing capacitor connected to the first secondary winding via the rectifier circuit portion and the first switching element is connected to the output portion of the first DC power supply circuit. The output of the first DC power supply circuit is controlled by controlling the switching of the first switching element and the switching period by the time division control unit according to the voltage of the smoothing capacitor. A time-sharing control power supply is also possible.

  Thereby, since the secondary side winding can be made one, the volume of the transformer can be suppressed small, and it is effective in reducing the cost. Of course, the output voltage can be stably supplied.

  The time-division control power supply of the present invention can be reduced in size and price, has an effect of stabilizing output, and is useful in various electronic devices.

1 is a first circuit diagram of a DC power supply according to an embodiment of the present invention. The 2nd circuit diagram of the direct-current power supply in one example of the present invention (A)-(e) 1st timing chart of DC power supply in one Example of this invention (A)-(e) 2nd timing chart of DC power supply in one Example of this invention (A)-(e) 3rd timing chart of DC power supply in one Example of this invention The 3rd circuit diagram of the direct-current power supply in one example of the present invention Circuit diagram of conventional DC power supply

DESCRIPTION OF SYMBOLS 9 Resonance circuit part 10 Primary winding 11 1st secondary winding 12 2nd secondary winding 13 Resonance transformer 14 1st DC power supply circuit 15 2nd DC power supply circuit 16 Resonance frequency control part 17 Rectifier circuit part DESCRIPTION OF SYMBOLS 18 Switching element 19 Smoothing capacitor 20 Time division control circuit part 21 PWM generation block 22 Timing capacitor 23 Rectification part 25 1st falling detection part 26 2nd falling detection part 27 Integration circuit 28 Operator 29 Remote terminal 30a Software Start circuit 30b Soft start circuit 30c Timing pulse generation circuit 31 OCL control circuit

Claims (7)

A resonant transformer having a primary winding having a resonant circuit and first and second secondary windings;
A first DC power supply circuit connected to the first secondary winding;
A second DC power supply circuit connected to the second secondary winding;
A resonance frequency control unit that controls the frequency of the resonance circuit unit according to a voltage generated in the second secondary winding;
The first DC power supply circuit includes a smoothing capacitor connected to the first secondary winding via a rectifier circuit portion and a first switching element with respect to the output portion of the first DC power supply circuit. Connected in parallel,
A time-division control power source that controls the output of the first DC power supply circuit by controlling the switching period of the first switching element by a time-division control circuit unit in accordance with the voltage of the smoothing capacitor. The time division control power supply according to claim 1, wherein the time division control unit includes a synchronization detection circuit unit, a soft start circuit unit, and a current limiting circuit unit. The time division control power supply according to claim 2, wherein the synchronization detection circuit unit generates a synchronization signal synchronized with the resonance frequency of the resonance circuit unit. The time-division control power supply according to claim 3, wherein the rising timing of the synchronizing signal and the rising timing of the resonance current are matched. The time division control power supply according to claim 2, wherein the soft start circuit unit drives the first switching element with a switching signal in which a time width of the synchronization signal is adjusted until an output voltage of the first DC power supply circuit reaches a specified value. . The current limiting circuit unit converts the output current of the first DC power supply circuit into a voltage,
The time division control power supply according to claim 2, wherein the synchronization signal of the time division control circuit unit is adjusted by a signal obtained by amplifying the voltage. A resonant transformer having a primary winding having a resonant circuit portion and a first secondary winding;
First and second DC power supply circuits connected to the first secondary winding;
A resonance frequency control unit that controls the frequency of the resonance circuit unit according to a voltage generated in the second DC power supply circuit;
The first DC power supply circuit includes a smoothing capacitor connected to the first secondary winding via a rectifier circuit portion and a first switching element with respect to the output portion of the first DC power supply circuit. Connected in parallel,
A time-division control power supply that controls the output of the first DC power supply circuit by controlling the switching period of the first switching element by a time-division control circuit in accordance with the voltage of the smoothing capacitor.

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