JP2010110148A - Power supply device - Google Patents

Abstract

Provided is a power supply device capable of performing constant current control and constant voltage control, which can reduce the risk of increased cost while reducing power loss as compared with a conventional power supply device.
A power converter that is a switching power supply circuit, a voltage controller that generates a voltage control signal at a level corresponding to an output voltage Vo, and a current that generates a current control signal indicating a detection result of an output current Io. By adding the voltage obtained from the control unit 2 and the current control signal and the voltage control signal, the resistor 65 that generates the feedback voltage, and the comparison result between the feedback voltage generated by the resistor 65 and the reference voltage The switching control unit 4a generates a control signal to control the switching of the power conversion unit 5a so that the feedback voltage approaches the reference voltage, and outputs the control signal to the power conversion unit.
[Selection] Figure 1

Description

  The present invention relates to a power supply device capable of performing constant current control and constant voltage control.

  Conventionally, there is known a power supply device capable of performing constant current control for outputting a constant current and constant voltage control for outputting a constant voltage (see, for example, Patent Document 1). In the power supply device described in Patent Document 1, a constant current power supply circuit and a constant voltage power supply circuit are individually prepared, and the outputs are OR-coupled and output. This power supply device normally outputs a constant voltage by a constant voltage power supply circuit, and when the load side voltage reaches a predetermined voltage, the constant voltage power supply circuit is disconnected and a constant current power supply circuit outputs a constant current. It has become.

  In this power supply apparatus, the constant voltage power supply circuit is configured by an emitter follower system in which a Zener diode that determines an output voltage is connected to the base of an NPN transistor. The constant current power supply circuit is configured by a general constant current circuit that obtains a constant current that is double the hFE by controlling the base current of the transistor.

Output switching from the constant voltage power supply circuit to the constant current power supply circuit uses a comparator to compare the output voltage and the reference voltage, and when the output voltage exceeds the reference voltage, the semiconductor provided on the output side of the constant voltage power supply circuit This is achieved by opening the switch.
JP-A-2-219426

  However, the power supply device described in Patent Document 1 includes transistors arranged in series on the current output line to the load in both the constant voltage power supply circuit and the constant current power supply circuit. In particular, these transistors are not saturated. Since it is used in a region, there is a disadvantage that the power loss in the transistor is large.

  Here, a switching power supply circuit is known as an efficient power supply circuit with little power loss. However, if each of the constant voltage power supply circuit and the constant current power supply circuit described in Patent Document 1 is configured with a switching power supply circuit, the cost increases.

  An object of the present invention is to reduce the risk of increasing costs while reducing power loss in a power supply device capable of performing constant current control and constant voltage control as compared with the power supply device described in Patent Document 1. It is providing the power supply device which can be performed.

  A power supply apparatus according to the present invention includes a power conversion unit that outputs voltage and current corresponding to a control signal by turning on and off a switching element according to a predetermined control signal to switch input power, and the power A voltage control unit that detects an output voltage of the conversion unit and generates a voltage control signal at a level corresponding to the output voltage; and a current control signal that detects an output current of the power conversion unit and indicates a detection result of the output current A current control unit that generates a voltage, an addition unit that generates a feedback voltage by adding the voltage obtained from the current control signal and the voltage control signal, and a feedback voltage generated by the addition unit. The control signal is generated to control the switching of the power converter so that the feedback voltage approaches the reference voltage according to the comparison result with the reference voltage, and the power And a switching control unit for outputting to the section.

  According to this configuration, the power conversion unit outputs a voltage and a current according to the control signal by turning on and off the switching element. When the switching element is used in an on / off operation in this manner, the switching element operates in a saturation region, and therefore, power loss is reduced as compared with the case where the transistor is used in a non-saturation region as in the background art. Further, the voltage control unit generates a voltage control signal at a level corresponding to the output voltage of the power conversion unit, and the current control unit generates a current control signal indicating the output current detection result of the power conversion unit. Then, the voltage obtained from the current control signal and the voltage control signal are added by the adding unit, and this is fed back to the switching control unit as a feedback voltage. Further, a control signal is generated by the switching control unit to control switching of the power conversion unit so as to bring the feedback voltage closer to the reference voltage according to the comparison result between the feedback voltage and the reference voltage, and is output to the power conversion unit. The In this case, since the detection result of the output voltage and output current of the power converter is reflected in the feedback voltage, the switching of the power converter is controlled based on the feedback voltage. Since the control and the constant voltage control can be performed, it is possible to reduce the possibility of increasing the cost as compared with the case where two switching power supply circuits are provided for the constant current and the constant voltage.

  The switching control unit includes first, second, and third terminals, and when the feedback voltage input to the third terminal exceeds the reference voltage, the first terminal, the second terminal, A shunt regulator that increases a current flowing between the first terminal and the second terminal when the feedback voltage input to the third terminal is lower than the reference voltage. Preferably, the control signal is obtained according to a current flowing between the first terminal and the second terminal.

  According to this configuration, since the switching control unit can be configured using a general-purpose shunt regulator, it is easy to simplify the switching control unit.

  The switching control unit further includes a photocoupler, and the output voltage of the power conversion unit is applied to both ends of a series circuit of the input side of the photocoupler and the shunt regulator, and the output side of the photocoupler It is preferable that a current flowing through the terminal is used as the control signal.

  According to this configuration, since the power converter is insulated from the shunt regulator to which the feedback voltage reflecting the output voltage and current on the secondary side of the power converter is input, and the power converter, the power converter It becomes easy to insulate the primary side from the secondary side, and to constitute an insulation type power supply device.

  The voltage control unit is configured by applying the output voltage of the power conversion unit to both ends of a series circuit of first and second resistors, and the output voltage is divided by the first and second resistors. The voltage generated between the terminals of the second resistor is used as the voltage control signal, and the current control unit passes the current control signal through the second resistor and detects the current value of the current control signal. When the output current exceeds the target current value set in advance as the current value of the constant current output, the current value of the set current value set in advance is set, and when the output current is less than the target current value, The adder reduces the voltage that is generated when the current control signal flows through the second resistor to be superimposed on the voltage control signal at the second resistor. That The voltage generated is preferably set to the feedback voltage.

  According to this configuration, the voltage control signal is obtained by dividing the output voltage of the power converter by the first and second resistors. In addition, when the output current of the power converter exceeds the target current value of the constant current output, the current control unit sends a current control signal of the set current value to the second resistor, and the output current does not reach the target current value In this case, a current control signal having a current value less than the set current value is passed through the second resistor. If it does so, the voltage drop which arises in 2nd resistance according to a current control signal will be increased / decreased according to whether the output current of a power converter part exceeds a target electric current value. The voltage drop generated in the second resistor is superimposed on the voltage obtained as a voltage control signal in the second resistor, that is, added to obtain a feedback voltage. In this case, since the adder can be configured with a simple configuration using the second resistor, it is easy to reduce the cost of the adder.

  Further, when the target voltage preset as the voltage value of the constant voltage output is divided by the first and second resistors, the first voltage generated by the second resistor is the current control of the set current value. A signal is higher than a second voltage generated in the second resistor by flowing through the second resistor, the first voltage is equal to or higher than the reference voltage, and the second voltage is equal to or higher than the reference voltage. It is preferable that resistance values of the first and second resistors and the set current value are set.

  According to this configuration, when the output voltage of the power conversion unit reaches the target voltage of the constant voltage output, the first voltage obtained by dividing by the first and second resistors is the output current of the power conversion unit. The resistance value of the first and second resistors and the set current value are set so that the voltage becomes higher than the second voltage generated in the second resistor when the current exceeds the target current value of the constant current output. Then, when the power converter performs a constant current output operation according to the feedback of the output current value based on the current control signal, the load state changes and the output voltage of the power converter changes to the target voltage of the constant voltage output. Then, while the feedback voltage is an added value of the first voltage and the second voltage, the first voltage is higher than the second voltage. Therefore, the feedback amount of the output voltage value in the feedback voltage is greater than the output current. As a result of being larger than the feedback amount, the power converter can be made to perform a constant voltage output operation.

  The power conversion unit is a charging circuit for supplying a charging current to the secondary battery, and the target current is set to a current value when the secondary battery is charged with a constant current, The target voltage is preferably set to a full charge voltage of the secondary battery.

  According to this configuration, the secondary battery is charged with a constant current by causing the power conversion unit to perform a constant current output operation according to feedback of the output current value based on the current control signal. Then, the terminal voltage of the secondary battery, that is, the output voltage of the power conversion unit increases with charging, and when the full charge voltage of the secondary battery is reached, the first voltage becomes higher than the second voltage and the power conversion unit Switch to constant voltage output operation. Then, the secondary battery is charged at a constant voltage with a full charge voltage. Thereby, it becomes possible to charge a secondary battery by a constant current-constant voltage charge (CCCV charge) until it becomes a full charge.

  The second voltage generated in the second resistor when the current control signal of the set current value flows through the second resistor has a target voltage set in advance as a voltage value of a constant voltage output as the first and the second voltages. The first voltage generated by the second resistor when divided by the second resistor is higher than the first voltage, the first voltage is higher than the reference voltage, and the second voltage is higher than the reference voltage. The resistance values of the first and second resistors and the set current value may be set.

  According to this configuration, when the output current of the power conversion unit exceeds the target current value of the constant current output, the second voltage generated by the current control signal having the set current value flowing through the second resistor is the power conversion unit. The resistance value of the first and second resistors and the set current so that the output voltage of the first and second resistors becomes higher than the first voltage obtained by dividing by the first and second resistors when the output voltage becomes the target voltage of the constant voltage output Value is set. According to this, when the power converter performs a constant voltage output operation according to the feedback of the output voltage value based on the voltage control signal, the load state changes and the output current of the power converter changes the target current value. When the current control signal having the set current value flows to the second resistor and the second voltage is generated, the feedback voltage becomes an added value of the first voltage and the second voltage, while the second voltage is the first voltage. Since it becomes higher than the voltage, the feedback amount of the output current value in the feedback voltage becomes larger than the feedback amount of the output voltage value. As a result, the power conversion unit can perform a constant current output operation.

  In addition, as the target current, it is preferable that a limiting current value for limiting an excessive increase in the output current of the power conversion unit is set.

  According to this configuration, when the power conversion unit performs a constant voltage output operation, for example, when the output current of the power conversion unit exceeds the limit current value due to an overload state, the power conversion unit outputs Since the constant current output operation with the current value as the limit current value is performed, it is possible to limit an excessive increase in the output current of the power conversion unit.

  In the power supply device having such a configuration, the power conversion unit outputs a voltage and a current corresponding to the control signal by turning on and off the switching element. When the switching element is used in an on / off operation in this manner, the switching element operates in a saturation region, and therefore, power loss is reduced as compared with the case where the transistor is used in a non-saturation region as in the background art. Further, the voltage control unit generates a voltage control signal at a level corresponding to the output voltage of the power conversion unit, and the current control unit generates a current control signal indicating the output current detection result of the power conversion unit. Then, the voltage obtained from the current control signal and the voltage control signal are added by the adding unit, and this is fed back to the switching control unit as a feedback voltage. Further, a control signal is generated by the switching control unit to control switching of the power conversion unit so as to bring the feedback voltage closer to the reference voltage according to the comparison result between the feedback voltage and the reference voltage, and is output to the power conversion unit. The In this case, since the detection result of the output voltage and output current of the power converter is reflected in the feedback voltage, the switching of the power converter is controlled based on the feedback voltage. Since the control and the constant voltage control can be performed, it is possible to reduce the possibility of increasing the cost as compared with the case where two switching power supply circuits are provided for the constant current and the constant voltage.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a circuit diagram showing an example of a configuration of a power supply device according to an embodiment of the present invention.

  FIG. 1 is a circuit diagram of an insulating power supply device 1a according to an embodiment of the present invention. 1 includes a current control unit 2, a voltage control unit 3, a switching control unit 4a, a power conversion unit 5a, an output capacitor 7, a + B terminal 81, a −B terminal 82, a V output terminal 83, and a G output. A terminal 84 is provided.

  The + B terminal 81 and the −B terminal 82 are connection terminals that receive power supply power input from the outside. The DC power supply voltage received by the + B terminal 81 and the −B terminal 82 is supplied to the power converter 5a. For example, a commercial AC power supply voltage may be supplied to the + B terminal 81 and the −B terminal 82. In this case, for example, a rectifier circuit or a smoothing circuit that rectifies the AC voltage received at the + B terminal 81 and the −B terminal 82 may be provided and converted to a DC voltage and then supplied to the power conversion unit 5a.

  The V output terminal 83 and the G output terminal 84 are connection terminals for outputting the current and voltage generated by the power supply device 1a to an external load. The output capacitor 7 is connected between the V output terminal 83 and the G output terminal 84.

  Various secondary batteries 6 such as a lithium ion secondary battery and a nickel hydride secondary battery are connected to the V output terminal 83 and the G output terminal 84 as external loads. In this case, the power supply device 1 a functions as a constant current-constant voltage charging device that charges the secondary battery 6.

  The configuration of the power conversion unit 5a will be described below. The power conversion unit 5a switches the input power in accordance with a control signal output from the switching control unit 4a via the photocoupler 31, thereby outputting a voltage and current corresponding to the control signal. It is a switching power supply circuit.

  The power conversion unit 5 a includes a power supply control circuit 11, an insulating transformer 21, a switching element 51, a phototransistor 31 a that is an output side of the photocoupler 31, and a diode 33. As the switching element 51, for example, a semiconductor switching element such as an FET (Field Effect Transistor) can be used.

  The primary winding 21a of the insulating transformer 21 and the switching element 51 are connected in series. One end on the primary winding 21 a side of the series circuit is connected to the + B terminal 81, and one end on the switching element 51 side is connected to the −B terminal 82.

  A control terminal, that is, a gate terminal of the switching element 51 is connected to the power supply control circuit 11. The phototransistor 31a on the output side of the photocoupler 31 is connected to the control signal input terminal of the power supply control circuit 11, and outputs a feedback signal (control signal) from the switching control unit 4a to the power supply control circuit 11.

  One end of the secondary winding 21b of the isolation transformer 21 is connected to the V output terminal 83 via the diode 33, and the other end of the secondary winding 21b is connected to the G output terminal 84 via the shunt resistor 61. Yes.

  The power supply control circuit 11 outputs a PWM (Pulse Width Modulation) control signal in which the pulse width (duty ratio) is changed according to the control signal output from the switching control unit 4 a via the photocoupler 31 to the gate of the switching element 51. To turn the switching element 51 on and off. Then, a direct current and a direct voltage corresponding to the control signal from the switching control unit 4a are generated by the power supply control circuit 11, the insulating transformer 21, the switching element 51, and the diode 33. Then, the direct current and the direct voltage are supplied to an external load such as the secondary battery 6 via the V output terminal 83 and the G output terminal 84.

  In the power conversion unit 5a configured in this manner, no transistor is provided in the current supply line to the load, and the switching element 51 is turned on and off in the saturation region. The power loss can be reduced as compared with the power supply apparatus.

  The configuration of the voltage control unit 3 will be described below. The voltage control unit 3 is configured by connecting a resistor 64 (first resistor) and a resistor 65 (second resistor) in series. Further, the resistor 64 in this series circuit is connected to the V output terminal 83, and the resistor 65 is connected to the connection point between the secondary winding 21 b and the shunt resistor 61. In this case, a voltage obtained by dividing the output voltage of the power converter 5a by the resistors 64 and 65 corresponds to a voltage control signal corresponding to the output voltage. A voltage at the connection point P1 of the resistors 64 and 65, that is, a voltage generated between both terminals of the resistor 65 is supplied as a feedback voltage Vbk to a reference terminal REF of a shunt regulator 71 described later in the switching control unit 4a.

  The configuration of the current control unit 2 will be described below. Both ends of the shunt resistor 61 are connected to the operational amplifier 42 via resistors 72 and 73, respectively. The operational amplifier 42 includes a negative feedback resistor 74 connected from the output terminal to the negative input terminal, and a speed-up capacitor 93 connected from the output terminal to the positive input terminal. The output terminal of the operational amplifier 42 is connected to the positive input terminal of the comparator 41.

  The resistors 73 and 74 have the same resistance value. The parallel combined resistance value of the resistors 73 and 74 is set to be equal to the resistance value of the resistor 72. Thus, a differential amplifier circuit having an amplification factor of 1 is configured. The voltage generated when the output current of the power conversion unit 5 a flows through the shunt resistor 61, that is, the voltage representing the output current of the power conversion unit 5 a is differentially amplified by the differential amplifier circuit using the operational amplifier 42. As a result, the noise component of the minute voltage signal generated in the shunt resistor 61 is removed and then output to the positive input terminal of the comparator 41.

  The resistors 66 and 67 are connected in series. In addition, the resistor 66 in this series circuit is connected to a circuit power source, and the resistor 67 is connected to a connection point between the secondary winding 21 b and the shunt resistor 61. Then, the power supply voltage VCC of the circuit power supply is divided by the series circuit of the resistors 66 and 67, and the divided voltage is applied to the negative input terminal of the comparator 41.

  Here, when the current of the target current value Icc, which is a current value when the power conversion unit 5a performs constant current output, flows through the shunt resistor 61, the voltage generated in the shunt resistor 61 and the power supply voltage VCC are converted into resistors 66, The voltage dividing ratio of the resistors 66 and 67 is set in advance so that the divided voltage when divided by 67 is equal. When the power supply device 1a is used as a charger for the secondary battery 6, the target current value Icc is a current value for constant current charging.

  The output terminal of the comparator 41 is connected to the negative input terminal via the speed-up capacitor 92. The output terminal of the comparator 41 is connected to the connection point P 1 of the resistors 64 and 65 via the diode 34.

  When the output voltage of the operational amplifier 42 exceeds the divided voltage of the resistors 66 and 67, that is, when the output current value detected by the shunt resistor 61 exceeds the target current value Icc, the comparator 41 is connected via the diode 34 to the resistance. A current control signal having a preset set current value Is is supplied to 65. Further, the comparator 41 reduces the current value of the current control signal to substantially zero when the output current value detected by the shunt resistor 61 is less than the target current value Icc. The set current value Is may be set, for example, according to the current driving capability of the comparator 41. For example, a resistor is connected to the output terminal of the comparator 41, and the set current value Is is adjusted by the resistance value. It may be.

Here, since the shunt resistor 61 has a very small resistance value, the output voltage Vo between the V output terminal 83 and the G output terminal 84 is approximated as the output voltage of the power conversion unit 5a, and the resistance value of the resistor 64 is set as follows. When the resistance value of R ₆₄ and the resistor 65 is R ₆₅ , the voltage generated at the resistor 65, that is, the feedback voltage Vbk is obtained by the following equation (1).

Vbk = Vo × {R ₆₅ / (R ₆₄ + R ₆₅ )} + Is × R ₆₅ (1)
Here, it corresponds to _{Vo × {R 65 / (R} 64 + R 65)} is a voltage control signal, because the set current value Is × _{R 65} is equivalent to the voltage indicated by the current control signal, by the resistor 65, The voltage indicated by the current control signal and the voltage control signal are added to generate a feedback voltage Vbk.

On the other hand, when the output voltage of the operational amplifier 42 is less than the divided voltage of the resistors 66 and 67, that is, when the output current value detected by the shunt resistor 61 is less than the target current value Icc, the comparator 41 is turned off. When the comparator 41 is turned off, the current value of the current control signal decreases to zero, that is, the term of the set current value Is in the equation (1) becomes zero and the term of Is × R ₆₅ becomes zero. 1) becomes Vbk = Vo × {R ₆₅ / (R ₆₄ + R ₆₅ )}.

  Thus, the voltage generated by superimposing the voltage generated by the current control signal flowing through the resistor 65 on the voltage control signal is used as the feedback voltage Vbk, and a reference of a shunt regulator 71 (to be described later) in the switching control unit 4a. Applied to terminal REF. In this case, the resistor 65 corresponds to an example of an adding unit.

  The switching control unit 4a includes a resistor 68, a stabilization resistor 69, a filter resistor 70, a filter capacitor 90, a speed-up capacitor 91, an LED (Light Emitting Diode) 31b on the input side of the photocoupler 31, and a shunt regulator 71. Yes.

  The shunt regulator 71 is, for example, described in the HA1743H series data sheet (RENESAS HA1743H series shunt regulator RJJ03D0646-0300 (Previous: ADJ-204-074B) Rev. 3.00 2005.6.15) from Renesas Technology Corporation. Can be used.

  The shunt regulator 71 includes a cathode K (first terminal), an anode A (second terminal), and a reference terminal REF (third terminal). A feedback voltage Vbk input to the reference terminal REF is generated inside the shunt regulator 71. When the generated reference voltage Vref (for example, 2.5 V) is exceeded, the current flowing between the cathode K and the anode A is increased, and when the feedback voltage Vbk input to the reference terminal REF is lower than the reference voltage Vref, the cathode The current flowing between K and anode A is reduced.

  The resistor 68, the LED 31b, and the shunt regulator 71 are connected in series. The resistor 68 in this series circuit is connected to the V output terminal 83, and the anode A of the shunt regulator 71 is connected to the connection point between the secondary winding 21b and the shunt resistor 61.

  Here, when the feedback voltage Vbk given by the equation (1) exceeds the reference voltage Vref, the current flowing through the shunt regulator 71 increases, the LED 31b is turned on, and the phototransistor 31a is turned on. When the phototransistor 31a is turned on, the power supply control circuit 11 controls the switching (on / off duty) of the switching element 51 to reduce the power supplied to the load by the power conversion unit 5a. Then, the feedback voltage Vbk given by Equation (1) decreases and approaches the reference voltage Vref.

  Further, when the feedback voltage Vbk given by the expression (1) falls below the reference voltage Vref, the current flowing through the shunt regulator 71 decreases, the LED 31b is turned off, and the phototransistor 31a is turned off. When the phototransistor 31a is turned off, the power supply control circuit 11 controls the switching of the switching element 51 to increase the power that the power conversion unit 5a supplies to the load. Then, the feedback voltage Vbk given by Equation (1) rises and approaches the reference voltage Vref.

  That is, the switching control unit 4a controls the amount of power output from the power conversion unit 5a by the control signal via the photocoupler 31 so that the feedback voltage Vbk approaches the reference voltage Vref.

  The stabilization resistor 69 is connected in parallel with the LED 31b. The filter resistor 70 and the filter capacitor 90 are connected in series, and are connected between the cathode K that is the output terminal of the shunt regulator 71 and the reference terminal REF that is the input terminal. A speed-up capacitor 91 is also connected between the cathode K and the anode A of the shunt regulator 71.

  And the voltage value in the case of making the power converter 5a perform a constant voltage output is preset as the target voltage value Vf. When the power supply device 1 a is used as a charger for the secondary battery 6, the target voltage value Vf is a voltage value for performing constant voltage charging and a fully charged voltage of the secondary battery 6.

Here, the resistance values R ₆₄ and R ₆₅ and the set current value Is are set in advance so as to satisfy the following expressions (2), (3), and (4).

Vf × {R ₆₅ / (R ₆₄ + R ₆₅ )} ≧ Vref (2)
Is × R ₆₅ ≧ Vref (3)
Vf × {R ₆₅ / (R ₆₄ + R ₆₅ )}> Is × R ₆₅ (4)
Next, the operation when the power supply device 1a is used as a charging device for the secondary battery 6 will be described. FIG. 2 is an explanatory diagram illustrating an example of changes in the output voltage Vo and the output current Io of the power supply device 1a when the secondary battery 6 is charged by the power supply device 1a.

  First, at timing T <b> 1, the power conversion unit 5 a causes the switching element 51 to perform a switching operation on the primary side power input between the + B terminal 81 and the −B terminal 82 according to a command from the power supply control circuit 11. Thus, the current flowing through the insulating transformer 21 is controlled to perform power conversion. The current and voltage thus obtained are output to the secondary battery 6 via the V output terminal 83 and the G output terminal 84.

Then, at the timing T1, since the secondary battery 6 is not yet charged, the terminal voltage of the secondary battery 6, that is, the output voltage Vo becomes a low voltage. Here, the terminal voltage before starting the charging of the secondary battery 6 is set to Vo = Vb ₀ .

Then, in the expression (1), the term Vo × {R ₆₅ / (R ₆₄ + R ₆₅ )} becomes a small value, so that the feedback voltage Vbk≈Is × R ₆₅ . Here, as described above, the switching control unit 4a controls the amount of power output from the power conversion unit 5a so that the feedback voltage Vbk approaches the reference voltage Vref. Since the set voltage value Is output from the current control unit 2 is mainly reflected in the feedback voltage Vbk, the power conversion unit 5a outputs the current of the target current value Icc set in the current control unit 2. Operates as a constant current power supply.

  Thereby, when the terminal voltage of the secondary battery 6 is low, the constant current charging of the target current value Icc is performed.

Thereafter, the secondary battery 6 terminal voltage of progressing the charging of the secondary battery 6, i.e., the output voltage Vo rises, the value of _{Vo × {R 65 / (R} 64 + R 65)} is Is × _{R 65} When the value is smaller than the value, constant current charging (constant current output) continues as a result of the dominant current control.

At time T2, when the output voltage Vo reaches the target voltage value Vf that is the fully charged voltage of the secondary battery 6, Vo × {R ₆₅ / (R ₆₄ + R ₆₅ )} as shown in Expression (4). value becomes larger than the value of is × R _65, results influence of the output voltage Vo at the feedback voltage Vbk is dominant, as described above, the switching control unit 4a is brought close to the feedback voltage Vbk in the reference voltage Vref In this way, the output current Io is reduced by controlling the amount of power output from the power converter 5a.

When the output current Io decreases and falls below the target current value Icc, the output current of the comparator 41 becomes zero, the term of Is × R ₆₅ in the equation (1) becomes zero, and the feedback voltage becomes more and more accelerated. The influence of the output voltage Vo at Vbk becomes dominant.

  Then, as a result of the power converter 5a being controlled substantially based only on the output voltage Vo, the output voltage is shifted to constant voltage charging (constant voltage output) that makes the target voltage value Vf constant. Since the target voltage value Vf is the full charge voltage of the secondary battery 6, the secondary battery 6 can be fully charged.

As described above, the power supply device 1a shown in FIG. 1 can perform constant current control and constant voltage control only by including one power conversion unit 5a that is a switching power supply circuit. Further, in the power supply device 1a, the resistance values R ₆₄ and R ₆₅ and the set current value Is are set so as to satisfy the expressions (2), (3), and (4), whereby the secondary battery is charged. It can be suitably used as a current-constant voltage (CCCV) charger.

Next, the operation when the power supply device 1a is used as a constant voltage power supply with an overcurrent protection function will be described. When the power supply device 1a is used as a constant voltage power supply with an overcurrent protection function, the resistance values R ₆₄ and R ₆₅ and the set current value Is satisfy Expressions (2) and (3) and the following Expression (5). Set as follows.

Vf × {R ₆₅ / (R ₆₄ + R ₆₅ )} <Is × R ₆₅ (5)
Further, the voltage dividing ratio of the resistors 66 and 67 is set so that the target current value Icc becomes a limit current value for limiting an excessive increase in the output current of the power conversion unit 5a.

  As shown in FIG. 1, a load circuit 6 a is connected to the V output terminal 83 and the G output terminal 84 instead of the secondary battery 6. As the load circuit 6a, various load circuits such as a personal computer, a mobile phone, and a motor of an electric vehicle are assumed.

  FIG. 3 is an explanatory diagram showing an example of changes in the output voltage Vo and the output current Io of the power supply device 1a when the power supply device 1a shown in FIG. 1 is used as a constant voltage power supply with an overcurrent protection function.

  First, at timing T <b> 11, the power conversion unit 5 a causes the switching element 51 to perform a switching operation on the primary side power input between the + B terminal 81 and the −B terminal 82 according to a command from the power supply control circuit 11. Thus, the current flowing through the insulating transformer 21 is controlled to perform power conversion. The current and voltage thus obtained are output to the load circuit 6a via the V output terminal 83 and the G output terminal 84.

Then, at timing T11, if the load circuit 6a is normal, the current flowing through the load circuit 6a is less than the target current value Icc. Therefore, the output current Io is less than the target current value Icc, and the output current of the comparator 41 is zero. Thus, the term Is × R ₆₅ in the equation (1) becomes zero, and the feedback voltage Vbk = Vo × {R ₆₅ / (R ₆₄ + R ₆₅ )}.

  Then, as a result of controlling the power conversion unit 5a substantially based only on the output voltage Vo, a constant voltage output that makes the output voltage constant at the target voltage value Vf is executed. As described above, in the region where the constant voltage output is performed, the output voltage Vo is kept constant at the target voltage value Vf even if the output current Io varies due to the load variation.

Here, at the timing T12, the output current Io increases in the load circuit 6a due to, for example, an overload condition or a short circuit failure, and when the output current Io exceeds the target current value Icc, the output current of the comparator 41 becomes the set current. It becomes the value Is. Then, towards the term Is × _{R 65} from equation (5) is larger than _{Vf × {R 65 / (R} 64 + R 65)}, the specific gravity of the portion related to the current control in the formula (1) increases.

  Then, power conversion unit 5a operates as a constant current power source that outputs a current of target current value Icc set in current control unit 2. As a result, the output current Io is kept constant at the limited current value by the constant current operation, so that the possibility that the output current Io exceeds the limited current value and an overcurrent flows is reduced.

  In addition, although the example which used the insulation type switching power supply circuit was shown as the power conversion part 5a, as a power conversion part, not only an insulation type but a various switching power supply circuit can be used.

  FIG. 4 is a circuit diagram showing an example of a power supply device 1b using a power conversion unit 5b that is a non-insulated switching power supply circuit instead of the power conversion unit 5a. The power supply device 1b shown in FIG. 4 differs from the power supply device 1a in that a switching control unit 4b and a power conversion unit 5b are provided instead of the switching control unit 4a and the power conversion unit 5a. Since the other configuration is the same as that of the power supply device 1a, the description thereof will be omitted, and the characteristic points will be described below.

  The switching control unit 4b is different from the switching control unit 4a in that the resistor 68, the stabilization resistor 69, and the photocoupler 31 (LED 31b) are not provided, and the cathode K of the shunt regulator 71 is directly connected to the power supply control circuit 11. Different.

  The power converter 5b is different from the power converter 5a in that the insulating transformer 21 and the photocoupler 31 (phototransistor 31a) are not provided, but the coil 22 is provided. The + B terminal 81 is connected to the anode of the diode 33 via the coil 22, and the connection point between the coil 22 and the diode 33 is connected to the −B terminal 82 via the switching element 51. The -B terminal 82 is connected to the G output terminal 84 via the shunt resistor 61.

  The power supply control circuit 11 uses the current flowing through the shunt regulator 71 instead of the current flowing through the phototransistor 31a as a control signal. Thereby, the power supply device 1b operates similarly to the power supply device 1a.

  In addition, although the insulation type switching power supply circuit and the non-insulation type switching power supply circuit are illustrated as the power conversion units 5a and 5b one by one, the power conversion unit converts the converted power according to the control signal from the switching control unit. Any switching power supply circuit that can control the amount (voltage, current) can be used. For example, various switching power supply circuits such as a DC / DC converter can be used.

  The power supply device according to the present invention is a power supply device that needs to perform constant current control and constant voltage control, in particular, a power supply device used as a charging device for a secondary battery, or an output current value limited to a certain limit current or less. It is suitable as a power supply device having overcurrent protection.

It is a circuit diagram which shows an example of a structure of the power supply device which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the output voltage Vo of the power supply device at the time of charging a secondary battery with the power supply device shown in FIG. 1, and the change of the output current Io. It is explanatory drawing which shows an example of the output voltage Vo of a power supply device when using the power supply device shown in FIG. 1 as a constant voltage power supply with an overcurrent protection function, and the change of output current Io. It is a circuit diagram which shows the modification of the power supply device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Power supply device 2 Current control part 3 Voltage control part 4a, 4b Switching control part 5a, 5b Power conversion part 6 Secondary battery 6a Load circuit 11 Power supply control circuit 21 Insulation transformer 21a Primary winding 21b Secondary winding 22 Coil 31 Photocoupler 31a Phototransistor 31b LED
33, 34 Diode 41 Comparator 42 Operational amplifier 51 Switching element 61 Shunt resistor 64, 65, 66, 67, 68 Resistor 69 Stabilizing resistor 70 Filter resistor 71 Shunt regulator 72, 73 Resistor 74 Negative feedback resistor 81 + B terminal 82 -B terminal 83 V output terminal 84 G output terminal 90 Filter capacitor 91, 92, 93 Speed-up capacitor Icc Target current value Vf Target voltage value Io Output current Vo Output voltage Is Set current value Vref Reference voltage Vbk Feedback voltage

Claims (8)

A power converter that outputs a voltage and a current according to the control signal by switching the input power by turning on and off the switching element according to a predetermined control signal;
A voltage control unit that detects an output voltage of the power conversion unit and generates a voltage control signal at a level corresponding to the output voltage;
A current control unit that detects an output current of the power conversion unit and generates a current control signal indicating a detection result of the output current;
An adder that generates a feedback voltage by adding the voltage obtained from the current control signal and the voltage control signal;
In response to a comparison result between the feedback voltage generated by the adding unit and a preset reference voltage, the control signal is generated to control switching of the power conversion unit so that the feedback voltage approaches the reference voltage. And a switching control unit that outputs to the power conversion unit. The switching controller is
A first terminal, a second terminal, and a third terminal; when the feedback voltage input to the third terminal exceeds the reference voltage, the current flowing between the first terminal and the second terminal is increased. A shunt regulator configured to reduce a current flowing between the first terminal and the second terminal when the feedback voltage input to the third terminal is lower than the reference voltage.
The control signal is
The power supply device according to claim 1, wherein the power supply device is obtained according to a current flowing between the first terminal and the second terminal. The switching controller is
In addition, with a photocoupler,
The output voltage of the power converter is applied to both ends of a series circuit of the input side of the photocoupler and the shunt regulator,
The power supply device according to claim 2, wherein a current flowing through an output-side terminal of the photocoupler is used as the control signal. The voltage controller is
An output voltage of the power conversion unit is applied to both ends of a series circuit of first and second resistors, and the output voltage is divided by the first and second resistors to be connected between terminals of the second resistor. Is used as the voltage control signal,
The current controller is
The current control signal is passed through the second resistor, and the current value of the current control signal is preset when the detected output current exceeds a target current value preset as a current value of a constant current output. If the output current is less than the target current value, the current value of the set current value is reduced to a current value less than the set current value,
The adding unit is
The voltage generated when the voltage generated when the current control signal flows through the second resistor is superimposed on the voltage control signal in the second resistor is used as the feedback voltage. 4. The power supply device according to any one of items 3. When the target voltage preset as the voltage value of the constant voltage output is divided by the first and second resistors, the first voltage generated by the second resistor is the current control signal of the set current value. The first voltage is higher than the second voltage generated in the second resistor by flowing through the second resistor, the first voltage is equal to or higher than the reference voltage, and the second voltage is equal to or higher than the reference voltage. The power supply device according to claim 4, wherein resistance values of the first and second resistors and the set current value are set. The power conversion unit is a charging circuit for supplying a charging current to the secondary battery,
The target current is set to a current value when charging the secondary battery at a constant current,
The power supply device according to claim 5, wherein the target voltage is a fully charged voltage of the secondary battery. The second voltage generated in the second resistor when the current control signal of the set current value flows through the second resistor has the target voltage preset as the voltage value of the constant voltage output as the first and second voltages. The first voltage is higher than the first voltage generated by the second resistor when divided by a resistor, the first voltage is greater than or equal to the reference voltage, and the second voltage is greater than or equal to the reference voltage. The power supply device according to claim 4, wherein a resistance value of the second resistor and the set current value are set. As the target current,
The power supply device according to claim 7, wherein a limit current value for limiting an excessive increase in output current of the power conversion unit is set.

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