JP2008042962A - Capacitor-charging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor-charging apparatus of simple circuitry which does not require two independent circuits for detecting both the average current level and the peak current that flow to the primary side of a transformer. <P>SOLUTION: A current is induced in the secondary winding of a transformer 7 by turning a DC current applied to the primary winding thereof on/off through a switching element 3, that current is smoothed and rectified and then supplied to a capacitor (not shown), thus charging the capacitor. In such a capacitor-charging apparatus, the DC current is generated by a power factor improving circuit 6, on/off control of the switching element 3 is performed at a PWM control section 11, and a current transformer, having the primary connected in series with the primary winding of the transformer 7 and the secondary connected with a CT circuit detection circuit section 1, is provided. The CT circuit detecting circuit section 1 extracts a voltage proportional to the average current flowing through the primary winding of the transformer 7, and a voltage proportional to the peak current flowing through the primary winding of the transformer 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a capacitor charging device that is optimal for storing electricity in a capacitor such as an electric double layer capacitor.

  The capacitor charger is provided with a constant power charging mode (CP mode: Constant Power mode) in addition to a constant voltage charging mode (CV mode: Constant Voltage mode) and a constant current charging mode (CC mode: Constant Current mode). In the initial stage of capacitor charging, charging is performed in a constant current charging mode (CC mode), charging is then performed in a constant power charging mode (CP mode), and constant voltage charging mode (CV mode) is near full charge. ), The capacitor can be charged efficiently.

In the capacitor charger as described above, PWM (Pulse Width Modulation) control is used by a switching converter or the like to ensure a stable power supply, and the desired charge control is performed by changing the pulse width. A constant voltage charging mode (CV mode), a constant current charging mode (CC mode), and a constant power charging mode (CP mode) are realized. In the switching converter, the DC power applied to the primary winding of the transformer is periodically turned on / off, the AC power induced in the secondary winding of the transformer is rectified and smoothed, and the DC power converted in voltage is supplied. Obtained as output power. The capacitor charging method and the charger as described above are disclosed in, for example, Non-Patent Document 1, Patent Document 1, and the like. FIG. 5 is a diagram showing a current waveform generated on the primary side of the transformer in the switching converter. As shown in the figure, the electric power for the period Ton in one cycle T is extracted on the secondary side of the transformer.
Okamura Ikuo, “Electric Double Layer Capacitor and Power Storage System”, published by Nikkan Kogyo Shimbun, September 30, 2005, 3rd edition, 1st edition, pages 135-137 JP-A-7-87668

  By the way, in order to realize the constant power charging mode (CP mode) with the switching converter, the current and voltage on the secondary side of the switching converter constituting the capacitor charger are detected, and these products are transferred to the primary side. In general, feedback control for feedback is performed. However, in the feedback control, (1) in the case of a relatively low voltage output, the stability is insufficient and constant power control is difficult, and (2) delay occurs. (3) There is a problem that the multiplier for obtaining the product of the current and voltage on the secondary side is expensive.

  Therefore, in the capacitor charger, it has been studied to realize a constant power charging mode (CP mode) only on the primary side without performing feedback control. Assuming that the efficiency of the switching converter is constant, if the control is performed so that the voltage is constant and the current is constant on the input side, the constant power charging mode ( CP mode). In order to secure a constant voltage condition on the input side, it is possible to provide a power factor correction (PFC) in the front stage of the charger. Therefore, the constant power charging mode (CP mode) can be realized without using feedback control if the control is performed so that the current is constant. To achieve this, the average current on the primary side is used. It becomes necessary to sense.

  On the other hand, an overcurrent protection function is known as one of the functions of a switching converter IC. In order to protect the primary side of the transformer used in the switching converter, the function of monitoring the peak current flowing through the primary side of the transformer and stopping the oscillation when an overcurrent is about to flow. It is. The cause of this overcurrent is the magnetic saturation phenomenon of the transformer core. When magnetic saturation of the transformer core occurs, the L component of the transformer disappears, and a short-circuit current flows on the primary side of the transformer where the impedance is lost. Such a short-circuit current becomes an overcurrent for the IC for the switching converter and leads to destruction of the IC. Therefore, the IC has the above-described overcurrent protection function. FIG. 6 is a diagram showing a current waveform generated on the primary side of the transformer when magnetic saturation of the core of the transformer occurs in the switching converter. In order to utilize the overcurrent protection function of the IC, it is necessary to detect the peak current flowing on the primary side as shown in the figure.

  In summary, the primary side of the switching converter detects the average current for realizing the constant power charging mode (CP mode) and the peak current for utilizing the overcurrent protection function of the IC. However, if these objective circuits are provided independently, there is a problem that the circuit configuration becomes complicated and costs increase.

  SUMMARY OF THE INVENTION The present invention solves the above-described problems. The invention according to claim 1 is directed to applying a direct current applied to the primary winding of the transformer to the secondary winding by turning on and off the switching element. In a capacitor charging device that induces a current, rectifies and smoothes the current, supplies the capacitor, and charges the capacitor, a power factor correction circuit that generates the DC current, a PMW control unit that performs on / off control of the switching element, A current transformer having a primary side connected in series with a primary winding of the transformer and a secondary side connected to a CT circuit detection circuit unit, wherein the primary side of the transformer is connected to the CT circuit detection circuit unit. A voltage proportional to the average current flowing in the side winding and a voltage proportional to the peak current flowing in the primary winding of the transformer are extracted.

  According to the present invention, since the peak current flowing on the primary side of the transformer can be detected simultaneously with the detection of the average current value flowing on the primary side of the transformer, both the average current value and the peak current can be detected. There is no need to provide two independent circuits, and the circuit configuration is simplified and the cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a capacitor charging apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a CT detection circuit unit, 2 is a current transformer (CT), 3 is a switching element, 4 is an AC power supply, 5 is a full-wave rectifier circuit, 6 is a power factor correction circuit (PFC), 7 is a transformer, 8 is a current detector, 9 is a voltage detector, 10 is a signal selector, 11 is a PMW controller, D1 is a diode, C1 and C2 are capacitors, and R is a resistor.

  For example, an AC power supply 4 that is a commercial power supply is rectified by a full-wave rectifier circuit 5 formed of a diode bridge, and then input to a power factor correction circuit (PFC) 6. The power factor is a value obtained by dividing the effective power by the apparent power, and is represented by W / (V × I). In the case of a direct current, it is always 1 and a power factor correction circuit is not required, but the AC power supply 4 generally includes a power factor correction circuit. This power factor correction circuit (PFC) 6 can be controlled so that Vin, which is the subsequent stage, becomes a constant voltage, and this Vin is applied to the primary winding of the transformer 7. The switching element 3 made of an FET or the like turns on / off the current flowing through the transformer 71 secondary winding and induces a switching signal on the secondary side of the transformer 7. In the switching converter used in the capacitor charging device of the present invention, the excitation energy is stored in the winding of the transformer when the switching element 3 is turned on, and the excitation energy is released when the switching element 3 is turned off. On the output side (secondary side of the transformer) of such a switching converter, the induced voltage is rectified and smoothed by the diode D1 and the capacitors C1 and C2, and a DC voltage is generated between the terminals TT ′ of the capacitor charging device. Supplied.

  The PMW control unit 11 controls on / off of the switching element 3 to control the output of the switching converter. The capacitor charging device of the present invention has three charging modes: a constant voltage charging mode (CV mode: Constant Voltage mode), a constant current charging mode (CC mode: Constant Current mode), and a constant power charging mode (CP mode: Constant Power mode). A signal from the voltage detection unit 9 when the constant voltage charging mode (CV mode) is entered, and a signal from the current detection unit 8 when the constant current charging mode (CC mode) is entered. In the power charging mode (CP mode), the average value signal from the CT detection circuit unit 1 is input to the PMW control unit 11 via the signal selection unit 10 and used. Further, the CT detection circuit unit 1 includes a circuit for detecting the peak current on the primary side of the transformer 7 so that no overcurrent flows on the primary side of the transformer. In order to protect the overcurrent on the primary side of the transformer 7, a peak current signal is input from the CT detection circuit unit 1 to the PMW control unit 11, and when the PMW control unit 11 is about to flow, Measures such as stopping switching of the switching element 3 are taken. Note that optical coupling can be used between the signal selection unit 10 and the current detection unit 8 and the voltage detection unit 9 in consideration of insulation between the primary side and the secondary side of the transformer.

  The current transformer (CT) 2 basically detects a current flowing through the primary side of the transformer 7. Therefore, the primary side of the current transformer 2 is connected in series with the primary side of the transformer 7 via the switching element 3 as shown in the figure, and the primary side of the current transformer 2 is connected to the CT detection circuit unit 1. . Based on the input from the current transformer (CT) 2, the CT detection circuit unit 1 outputs a signal proportional to the average current value flowing on the primary side of the transformer 7 and a signal proportional to the peak current value.

  Here, the constant power charging mode (CP mode) in the capacitor charging device of the present invention will be described. In FIG. 1, a capacitor (not shown) is connected between terminals T-T 'of the capacitor charging device and charged. The voltage of the capacitor charging device is Vout, the current flowing into the capacitor is Iout, and the power supplied to the capacitor is Pout. Further, the output voltage from the power factor correction circuit (PFC) 6 is Vin (this voltage is also a voltage input to the transformer 7), the current flowing into the transformer is Iin, and the power supplied to the transformer 7 is Pin.

  In order to realize a constant power charging mode (CP mode) in a charging device, a general method is to monitor Pout, that is, the product of Vout and Iout, and control by applying feedback so as to make it constant. However, in the capacitor charging device of the present invention, the feedback control is used only for the constant voltage charging mode (CV mode) and the constant current charging mode (CC mode), and is output for the constant power charging mode (CP mode). Control is performed without applying power feedback. The specific concept will be described.

When the efficiency of the switching converter in the capacitor charger is η, the relationship between Pout and Pin is
Pout = η × Pin
Can be expressed as Under the assumption that η is constant, it can be seen that Pin = (Constant) can be used to set Pout = (Constant). As long as strict accuracy is not required in the constant power charging mode (CP mode), it can be assumed that η is constant in this way. Pin is
Pin = Vin × Iin
Since the power factor correction circuit (PFC) 6 can be controlled to be Vin = (Constant), in the capacitor charging device of the present invention, in order to set Pin = (Constant) As a result, it can be understood that control should be performed so that Iin = (Constant).

  In order to control to Iin = (Constant), it is necessary to monitor the average current value, not the instantaneous current value of Iin. In the capacitor charging device of the present invention, the CT detection circuit unit 1 extracts a signal proportional to the average current value of Iin based on the input from the current transformer (CT) 2.

  Next, the CT detection circuit unit of the capacitor charging device of the present invention will be described. FIG. 2 is a diagram showing a circuit configuration of the CT detection circuit unit of the capacitor charging apparatus according to the embodiment of the present invention. In FIG. 2, D2 and D3 are rectifying diodes, and C2 and C3 are peak hold capacitors. As shown in FIG. 2, let one terminal of the current transformer 2 be CT (+) and the other terminal be CT (-). Further, as shown in FIG. 2, terminals V (+), V (−), and COM2 are defined. Since a direct current component does not come out on the secondary side of the current transformer 2, an average voltage value on the secondary side of the current transformer 2 appears at the middle point COM2.

  FIG. 3 is a diagram showing a waveform of a current flowing on the primary side of the current transformer (CT) of the capacitor charging device of the present invention. Moreover, FIG. 4 is a figure which shows the voltage waveform between the terminals of CT detection circuit part of the capacitor charging device of this invention. On the secondary side of the current transformer 2, a current waveform similar to the current waveform flowing on the primary side can be observed. Since an average voltage value on the secondary side of the current transformer 2 appears in COM2, a voltage value proportional to the peak current of Iin is obtained from between the V (+)-V (−) terminals, and COM2-V ( -) A voltage value proportional to the average current value of Iin can be taken out between the terminals.

  A voltage value proportional to the peak current of Iin output from between the V (+)-V (−) terminals is input to the PMW control unit 11. In the PMW control unit 11, when this voltage value exceeds a certain value (that is, when Iin is an overcurrent), the switching element 3 is turned on and off to stop the primary of the transformer 7. Controls the peak current flowing on the side.

  On the other hand, a voltage value proportional to the average current value of Iin output from between the COM2-V (−) terminals is input to the PMW control unit 11 via the signal selection unit 10. The PMW control unit 11 performs a constant power operation based on the above-described principle by referring to this voltage value (that is, the average current value of Iin) in the constant power charging mode (CP mode). is there.

  Thus, in the capacitor charging device of the present invention, by using the current transformer 2 and the CT detection circuit unit 1, the primary side of the transformer 7 is detected simultaneously with the detection of the average current value flowing through the primary side of the transformer 7. It is also possible to detect the peak current flowing in the circuit, so there is no need to provide two independent circuits for detecting both the average current value and the peak current, and the circuit configuration is simplified and the cost can be reduced. Is.

It is a block diagram of the capacitor charging device which concerns on embodiment of this invention. It is a figure which shows the circuit structure of CT detection circuit part of the capacitor charging device which concerns on embodiment of this invention. It is a figure which shows the current waveform which flows into the primary side of the current transformer (CT) of the capacitor charging device of this invention. It is a figure which shows the voltage waveform between the terminals of CT detection circuit part of the capacitor charging device of this invention. It is a figure which shows the electric current waveform which generate | occur | produces on the primary side of the transformer in a switching converter. In a switching converter, it is a figure which shows the electric current waveform which generate | occur | produces on the transformer primary side at the time of the magnetic saturation of the core of a transformer generate | occur | producing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... CT detection circuit part, 2 ... Current transformer (CT), 3 ... Switching element, 4 ... AC power supply, 5 ... Full wave rectifier circuit, 6 ... Power factor improvement circuit (Power Factor Correction; PFC), 7 ... Transformer, 8 ... Current detection unit, 9 ... Voltage detection unit, 10 ... Signal selection unit, 11 ... PMW control unit

Claims (1)

In a capacitor charging device that charges a DC current applied to a primary winding of a transformer by inducing a current in a secondary winding by turning on and off the switching element, rectifying and smoothing the current, and supplying the capacitor to the capacitor.
A power factor correction circuit for generating the direct current;
A PMW controller that performs on / off control of the switching element;
A current transformer having a primary side connected in series with a primary side winding of the transformer and a secondary side connected to a CT circuit detection circuit unit;
In the CT circuit detection circuit unit, a voltage proportional to the average current flowing in the primary side winding of the transformer and a voltage proportional to the peak current flowing in the primary side winding of the transformer are extracted. Capacitor charging device.

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