JP6219641B2 - Separately excited power supply - Google Patents

Description

  The present invention relates to a separately excited power source used in various electronic devices.

  Hereinafter, a conventional separately excited power supply will be described with reference to the drawings. FIG. 3 is a circuit block diagram showing the configuration of a conventional separately-excited power supply. The comparison control unit 1 performs a comparison operation between the signal from the control function unit 2 and the signal from the detection circuit 4 connected to the output terminal 3. The calculation result signal is output to the PWM signal generation unit 5. The PWM signal generation unit 5 performs a comparison operation between the signal output from the comparison control unit 1 and the signal from the oscillation circuit unit 6, and outputs the calculation result to the switching element 7 as a signal for switching control as a PWM signal. It is oscillating. Then, the switching element 7 and the transformer 8 output the voltage corresponding to the control by the PWM signal based on the instruction from the control function unit 2 to the output terminal 3 through the rectifier circuit unit 9, and from the output terminal 3 Electric power is supplied to the load 10.

  Here, as operations of the conventional separately-excited power supply, the calculation in the PWM signal generation unit 5, the PWM signal for controlling the switching element 7, and the voltage generated on the primary side of the transformer 8 are shown in FIGS. ) And (c) will be used to explain. Also, here, Vosc and Vcomp in FIG. 4A, Vpwm in FIG. 4B, and Vt1 in FIG. 4C are the output signal from the oscillation circuit unit 6 shown in FIG. This corresponds to the output signal, the PWM signal from the PWM signal generator 5, and the primary winding voltage of the transformer 8.

  As shown in FIGS. 4A, 4B, and 4C, the difference between Vosc and Vcomp is reflected as an on-duty that is the width of Vpwm, and Vt1 is generated by the switching operation corresponding to the on-duty time. Is done. The voltage Vt1 generated on the primary side of the transformer 8 shown in FIG. 3 is boosted to a magnification corresponding to the turns ratio of the transformer 8 and rectified to a DC voltage by the rectifier circuit unit 9, and is output from the output terminal 3 to the load 10 Electric power is supplied to the device at a predetermined voltage.

  For example, Patent Document 1 is known as prior art document information related to the invention of this application.

JP 2011-15557 A

  However, in the conventional separately-excited power source, the voltage appearing on the secondary side of the transformer 8 is a value obtained by multiplying Vp corresponding to the potential difference between the peak voltage Vp1 of the primary side voltage Vt1 and 0 (V) by the turn ratio. In other words, even if Vp is a minimum value, it becomes a voltage value corresponding to Vcc. Therefore, even if the voltage on the secondary side is also the minimum value, it is close to a value obtained by multiplying Vcc by the turn ratio.

  As a result, in the transformer 8 to which the above turns ratio is applied, it is not easy to suppress the voltage on the secondary side to a small value, and there is a problem that the variable range of the output voltage to the output terminal 3 becomes small. It was a thing.

  Therefore, the present invention aims to increase the variable range of the output voltage.

In order to achieve this object, an instruction control unit that issues a setting signal for setting an arbitrary output voltage, an output voltage detection unit that detects a voltage at an output terminal and issues a detection signal, and the setting signal A comparison control unit that compares the detection signal and generates a correction signal; a control signal generation unit that generates and transmits a control signal from the correction signal and a reference oscillation signal; and a switching element controlled by the control signal; , a transformer primary winding to the switching device is connected, said a separately-excited power supply with a rectifier unit connected between the transformer secondary winding and said output terminal, said control signal the generation unit generates the control signal by converting the voltage to current in terms of the reference oscillation signal is amplitude-modulated by said correction signal, the current operation of the switching element Controls I, the reference oscillation signal is controlled to a constant time flowing said control signal, said control signal has a reference interval, corresponding to the reference distance from the control signal of the last stops When the elapsed time has elapsed, the control signal generator compares the voltage of the primary winding with the DC power supply voltage feeding the primary winding, and the voltage of the primary winding is applied to the primary winding. When it is determined that the voltage is equal to the DC power supply voltage, the next control signal is supplied .

  According to the present invention, the potential difference generated on the primary side of the transformer can be set to an arbitrary value from a continuous value between a small value and a predetermined value. As a result, the variable range of the output voltage can be increased. It is something that can be done.

Circuit block diagram of separately excited power source in the embodiment of the present invention Timing chart of separately excited power source in the embodiment of the present invention Circuit diagram of conventional separately excited power supply Timing chart of conventional separately excited power supply

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a circuit block diagram showing the configuration of a separately excited power source in the embodiment of the present invention. Here, an instruction control unit 11 that issues a setting signal for setting an arbitrary output voltage and an output voltage detection unit 13 that detects a voltage at the output terminal 12 and generates a detection signal are connected to the comparison control unit 14. Yes. Then, after comparing the setting signal and the detection signal, the comparison control unit 14 outputs the result as a comparison correction signal. Further, the control signal generator 15 generates and transmits a control signal from the comparison correction signal and the reference oscillation signal, and the switching operation of the switching element 16 is controlled by this control signal. A primary winding 18 of the transformer 17 is connected to the switching element 16, and an output terminal 12 is connected to a secondary winding 19 of the transformer 17 via a rectifier 20. Thereby, an arbitrary output voltage is selected or set from the instruction control unit 11, and the output voltage is stably supplied from the output terminal 12 to the load 21 in accordance with this instruction.

  Here, the control signal generator 15 modulates the amplitude of the reference oscillation signal by using the comparison correction signal. A signal after amplitude modulation is converted from a voltage to a current by the VI converter 15a to generate a control signal, and the switching operation of the switching element 16 is controlled by the current.

  With the above configuration and operation, the potential difference generated in the primary winding 18 of the transformer 17 can be freely selected from a wide range and set by controlling the switching state of the switching element 16. . This is because the switching operation of the switching element 16 is controlled by the base current Ib in the unsaturated region or in both the unsaturated region and the saturated region, so that the voltage value supplied from the Vcc to the primary winding 18 of the transformer 17. This is because it is possible to control so as to change the temperature precisely.

  This operation will be described in detail below with reference to FIGS. 1 and 2A to 2D. As operations in the above configuration, the reference oscillation signal Vosc of the control signal generation unit 15, the comparison correction signal Vcomp of the comparison control unit 14, the signal Vcont after amplitude modulation of the control signal generation unit 15, and the VI converted by the VI converter 15a The control signal Ib and the voltage Vt1 generated in the primary winding 18 of the transformer 17 will be described with reference to the timing charts of FIGS. 2 (a), (b), (c), and (d).

  First, the waveform of Vosc is a waveform of a voltage generated by the pulse oscillator 22 in the control signal generator 15. The pulse oscillator 22 supplies this Vosc to the base terminal 23 b of the oscillation switching element 23.

  Next, the waveform of Vcomp is a voltage generated by the comparator 24 in the comparison control unit 14. The voltage indicated by Vcomp corresponds to the difference between the voltage requested to be output by the instruction control unit 11 and the voltage of the output terminal 12 detected by the output voltage detection unit 13. In the example of the timing chart, the detected output voltage of the output terminal 12 becomes lower as compared to the output voltage required by the instruction control unit 11 as time progresses (goes to the right in the timing chart). It shows that.

  Further, the waveform of Vcont is a voltage obtained as a result of the control signal generation unit 15 inverting the pulse signal Vosc generated from the pulse oscillator 22 using the voltage Vcomp output from the comparison control unit 14 and modulating the amplitude thereof. It is. Here, the modulation operation in the control signal generation unit 15 supplies the signal of the pulse oscillator 22 to the base terminal 23b of the oscillation switching element 23 and the collector terminal 23c of the oscillation switching element 23 of the comparison control unit 14. By connecting to the output side, Vcont consisting of various pulses in which Vosc is inverted and amplitude is changed in accordance with Vcomp is generated.

  The waveform of Ib is a current obtained as a result of converting Vcont from voltage to current. Conversion from voltage to current is performed by a VI converter 15a provided in the control signal generation unit 15, and Ib is a switching element. 16 is supplied as a base current.

  Here, an FET may be applied as the switching element 16 by connecting a current detection element (not shown). However, by using a bipolar transistor which is a current control type, a base current in an unsaturated region is used. By flowing Ie corresponding to Ib continuously, the voltage of the primary winding 18 of the transformer 17 to which Vcc is supplied is changed. The waveform of Vt1 is this voltage generated in the primary winding 18, and the voltage of Vt1 is generated using Ie corresponding to the base current Ib continuously as described above, so the lower limit value of Vt1. Vb can be controlled by the base current Ib as an arbitrary value.

  In other words, by converting the primary voltage waveform into a primary current and further using the flyback voltage in the control by the base current as the primary current, the value of Vb is reduced from a value close to 0 (V) to Vcc. A value close to can be selected. In this embodiment, the case where the flyback voltage is used has been described. However, a forward voltage in the control by the base current may be used.

  In other words, this control method is one in which the switching element 16 is operated in the unsaturated region when the output voltage is on the low output side. For this reason, since the potential difference between Vp and Vb corresponding to the voltage generated in the primary winding 18 of the transformer 17 is very small when Vb is close to Vcc, Vb where the switching element 16 is in the saturation region is 0 ( It can be a range up to a large potential difference when V is close to V). Therefore, the ratio between the minimum value and the maximum value of the potential difference between Vp and Vb can be set as a large value.

  That is, even if the value of Vp is not set to a large voltage value, the ratio between the minimum value and the maximum value of the potential difference between Vp and Vb can be set to a large value. Thereby, since the switching element 16 is not applied with an excessive voltage, the reliability of the switching element 16 can be maintained and improved, and the switching element 16 having various characteristics can be selected. Needless to say.

  Further, here, both the Vcont amplitude-modulated by the control signal generation unit 15 and the control signal Ib after VI conversion by the VI converter 15a are both voltages having a constant pulse width during the period in which the power supply is operating, It is a current signal. In these cases, the pulse width of the pulse oscillator 22 in the control signal generator 15 is defined in advance. This is because the operation of the pulse oscillator 22 is not restricted by operations and functions other than the pulse oscillator 22 due to feedback or the like, and is not necessary. Therefore, the operation of the pulse oscillator 22 itself is independent and does not change according to the detection signal from the output voltage detection unit 13. Therefore, the pulse oscillator 22 may be arranged either inside or outside the control signal generator 15 or the separately excited power source that is a power supply device. For example, an oscillator arranged in a set to which the power supply device is applied is arranged. A separately-excited power source may be operated by connecting as the pulse oscillator 22. As a result, the power supply device can be simplified and the cost can be reduced, and the pulse oscillator 22 does not require any adjustment when applied to the power supply device.

  Furthermore, a state in which excessive voltage is generated in the switching element 16 can be limited or suppressed by using a fixed pulse whose pulse width is defined in advance as a signal generated from the pulse oscillator 22 and fixing the time during which the base current Ib flows. can do.

  If the pulse width of Vosc, which is a signal generated from the pulse oscillator 22, is changed, the base current Ib corresponds to a period in which Vosc is LOW, and with the passage of time since Vosc becomes LOW. It will generally rise. Then, Vt1 shown in FIG. 2D varies according to the base current Ib. Here, the variation of Vt1 with respect to the base current Ib shown in FIG. 2C depends on the hfe value of the switching element 16 shown in FIG. That is, the relationship between Vt1 and the base current Ib varies due to variations in hfe values of the individual switching elements 16.

  In particular, when the hfe value is large and the base current Ib increases with time over a long period of time, the switching element 16 is controlled in a saturated state by the large base current Ib, and the primary winding 18 is controlled by the operation of the switching element 16. A situation occurs in which an abnormal high voltage is generated at the output terminal 12 based on the energy stored in. As a result, a great burden is placed on the switching element 16 and an adverse effect that the insulation on the secondary high-voltage part must be reinforced.

  On the other hand, when the pulse width of the signal generated from the pulse oscillator 22 is fixed, the time during which the base current Ib flows is limited to the time during which Vosc is LOW. Again, Vt1 varies according to the base current Ib, and the variation of Vt1 with respect to the base current Ib depends on the hfe value of the switching element 16. Accordingly, the relationship between Vt1 and the base current Ib also varies due to variations in hfe values of the individual switching elements 16.

  However, even if the hfe value of the switching element 16 is large toward the upper limit side and the base current Ib is a large value, the switching element 16 is controlled in a saturated state by the large base current Ib. The time for which the saturated state continues is limited. For this reason, the energy stored in the primary winding 18 by the operation of the switching element 16 is also limited. Then, fixing the time width on the LOW side of Vosc generated from the pulse oscillator 22 and fixing the time during which the base current Ib flows suppresses the generation of an abnormal high voltage at the output terminal 12. As a result, it is difficult to cause an adverse effect that a large load is applied to the switching element 16 and that the insulation against the high-voltage portion on the secondary side must be reinforced.

  Further, by fixing the time during which the base current Ib flows, the upper limit value of the output voltage is limited, whereby the transformer 17 can be appropriately designed. That is, similarly to the fact that the upper limit of the voltage applied to the switching element 16 can be roughly defined by the time during which the base current Ib flows, the upper limit value of the voltage applied to the transformer 17 can also be generally defined by the time during which the base current Ib flows. Therefore, if the transformer 17 having an appropriate magnetic saturation characteristic at the upper limit value of the voltage corresponding to the time during which the base current Ib flows is used, it is possible to operate the transformer 17 appropriately and to design the transformer 17 without waste. It also becomes. Alternatively, on the contrary, the pulse width may be set so as to correspond to the characteristics of the transformer 17 and the switching element 16.

  On the other hand, when the hfe value of the switching element 16 varies to the lower limit side, the voltage output from the output terminal 12 is naturally the lower limit side. However, as described above, When the value is on the upper limit side, the output voltage is also limited according to the time limit due to the time during which the base current Ib flows. From this, the ratio of the maximum output voltage when the hfe value is on the upper limit side to the maximum output voltage when the hfe value is on the lower limit side is a compressed value compared with the ratio of the hfe upper limit value to the hfe lower limit value. It becomes. That is, the variation in the maximum output voltage can be made smaller than the variation in the apparent hfe value. Further, regarding the lower limit side of the output voltage, since the switching element 16 is operated in the unsaturated region, control to a desired output voltage is possible regardless of whether the hfe value is on the upper limit side or the lower limit side. .

  Here, the description has been made of fixing the time during which the base current Ib flows by fixing the width on the LOW side of Vosc, which is a signal generated from the pulse oscillator 22. However, after fixing the width on each LOW side, The HIGH side width may be changed.

  For example, when the output voltage at the output terminal 12 or the voltage Vt1 generated in the primary winding 18 of the transformer 17 becomes a large value, if the pulse interval in each base current Ib becomes insufficient and narrows, Vt1 becomes the level of Vcc. Since the base current Ib starts to rise again before it decreases to Vt1, Vt1 suddenly shifts to Vb from a voltage value higher than Vcc. For this reason, the collector current of the switching element 16 increases and the power loss increases.

  Therefore, in order to stabilize Vt1, the oscillation control unit 15b provided in the control signal generation unit 15 first compares Vt1 and Vcc. The pulse oscillator 22 continues to be in a HIGH state and issues a signal until Vt1 decreases to the value of Vcc. Thus, the oscillation control unit 15b controls the pulse oscillator 22 so that the next base current Ib does not rise. Specifically, when Vt1 has already reached Vcc after the lapse of the reference time for the pulse oscillator 22 to emit the HIGH state, the HIGH state is terminated according to the reference time and the state shifts to the LOW state, which is a predetermined time. The base current Ib begins to flow. On the other hand, in a state where Vt1 is higher than Vcc after the reference time for the pulse oscillator 22 to emit a signal in the HIGH state, the pulse oscillator 22 remains in the HIGH state until Vt1 drops to the level of Vcc. The oscillation control unit 15b instructs to continue. In addition, when Vt1 drops to the level of Vcc, the pulse oscillator 22 shifts to the LOW state, and the oscillation controller 15b controls the pulse oscillator 22 so that the base current Ib starts to flow. In this way, the signal generated by the pulse oscillator 22 is synchronized with the timing at which Vt1 becomes a predetermined value.

  As a result, each base current Ib flows at an optimal timing so that Vt1 can be output at a stable value, and as a result, power loss accompanying an increase in the collector current of the switching element 16 can be suppressed. .

  As described above, in the separately excited power source of the present invention, by controlling the current of the switching element 16 to operate in the unsaturated region of the switching element 16, the control range of the output voltage is increased and the switching element 16 is controlled. It suppresses the applied excess voltage. In addition, by controlling the pulse signal for control to have a fixed pulse width, by limiting the saturation operation period, an excessive voltage applied to the switching element 16 is suppressed, and insulation in a portion where a secondary high voltage is applied It suppresses the deterioration of the property.

  The separately excited power source of the present invention has an effect that the variable range of the output voltage can be increased, and is useful in various electronic devices.

DESCRIPTION OF SYMBOLS 11 Instruction control part 12 Output terminal 13 Output voltage detection part 14 Comparison control part 15 Control signal generation part 15a VI converter 15b Oscillation control part 16 Switching element 17 Transformer 18 Primary winding 19 Secondary winding 20 Rectification part 21 Load 22 Pulse Oscillator 23 Switching element for oscillation 23b Base terminal 23c Collector terminal 24 Comparator

Claims (2)

An instruction control unit for issuing a setting signal for setting an arbitrary output voltage;
An output voltage detector that detects the voltage of the output terminal and issues a detection signal;
A comparison control unit that compares the setting signal and the detection signal to generate a correction signal;
A control signal generator for generating and transmitting a control signal from the correction signal and the reference oscillation signal;
A switching element controlled by the control signal;
A transformer having a primary winding connected to the switching element;
A rectifier connected between the secondary winding of the transformer and the output terminal ;
A separately-excited power source with
Wherein in the control signal generation unit generates the control signal by converting the voltage to current in terms of the reference oscillation signal is amplitude-modulated by said correction signal, and controlled by the current operation of the switching element,
The reference oscillation signal is controlled to make the time for which the control signal flows constant,
The control signal has a reference interval;
When the time corresponding to the reference interval has elapsed since the previous control signal stopped, the control signal generator compares the voltage of the primary winding with the DC power supply voltage supplied to the primary winding. When the voltage of the primary winding is determined to be equal to the DC power supply voltage to the primary winding, the next control signal is sent.
Separately-excited power supply characterized by this . The separately excited power source according to claim 1 , wherein the switching element is a bipolar transistor.

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