JP2007236175A - Power supply, standby electric power circuit using the same, and charging circuit for storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply, where a depletion type junction FET (JFET) is used and an idling current is zero, and to provide a standby electric power circuit using the power supply and a charging circuit for storage batteries. <P>SOLUTION: The drain of the JFET Q1 is connected to the positive terminal of a DC power supply E as shown in Fig.1, a capacitor C1 is connected between the source of Q1 and the negative terminal (0 point) of E, and voltage, where a gate side is positive, is applied between the gate of Q1 and the 0 point, thus obtaining a power circuit of which the idling current is zero, and setting both the ends of C1 to be the power supply. Both the ends of C1 are connected to the power supply terminal of a control circuit SG as an auxiliary power supply EH. A load circuit RL and a MOS FET Q2 are connected in series between the positive and negative terminals of E from a positive side, and output OP of SG is connected to the gate of Q2 for turning on and off Q2, thus obtaining the standby electric power circuit having an idling current of zero. Fig. 3 and Fig. 4 are other embodiments, and a circuit is applied to an AC power supply. The RL is not connected to the MOSFET, and the storage battery is connected instead of the capacitor C1, thus obtaining the charging circuit for the storage battery. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a power source using a depletion type junction FET (hereinafter simply referred to as JFET), a standby power circuit using the power source, and a storage battery charging circuit.
The embodiments are all N-channel JFETs, but P-channel JFETs can also be used with simple circuit modifications. Since the concept of the charging operation of the capacitor used in the power supply circuit and the storage battery charging operation are the same, the description will focus on the power supply and the standby power circuit using the power supply, and the operation description of the storage battery charging circuit will be simplified.
The following confusing terms used in the specification are listed first to make sure.
(1) Input power supply: DC power supply (including pulsating power supply) connected to the input terminal of the power supply circuit.
(2) Power supply circuit: A circuit that takes the input power of (1) as an input and outputs the power of (3). In the circuit of FIG. 1, it is a portion of JFET Q1, capacitor C1, battery B, and resistor R1.
The storage battery charging circuit is basically the same as the power supply circuit, but the capacitor C1 is not necessarily connected.
(3) Power supply: Both ends of the capacitor C1 used in the power supply circuit of (2) are power supplies.
In the standby power circuit, this power source is an auxiliary power source for the control circuit.
In the storage battery charging circuit, this power supply terminal becomes the positive / negative terminal of the storage battery charging circuit.
(4) Output voltage: The voltage of the capacitor C1 of the power supply circuit of (3) is an output voltage, which is represented by Vc1.
The output voltage of the power supply circuit becomes an auxiliary power supply voltage in the standby power circuit.
In the storage battery charging circuit, it becomes the same value as the storage battery voltage Vt during charging.
(5) Output current: Current flowing out from the power source of (3).
The standby power circuit is a power supply current for the control circuit.
In the storage battery charging circuit, the storage battery charging current is obtained.

In recent large-scale power supply circuits, a switching regulator power supply circuit is often used.
Since standby power is small, much research and development has not been put in place, and the auxiliary power supply circuit used for standby power still uses a three-terminal regulator.
FIG. 5 is an example of a circuit using a three-terminal regulator as an auxiliary power source. If the three-terminal regulator of FIG. 5 is connected to the DC power source E, an idling current (current that is passed to generate an output voltage, which is called a bias current or a circuit current) at the zero point regardless of the presence or absence of the output current. This current flows regardless of the presence or absence of the output current) and consumes power. For example, if the voltage of the DC power supply E is 15 V and the idling current is 10 mA, the standby power of 150 mW is obtained even with only the idling current. In actual products that use a three-terminal regulator, there are many products with standby power in the range of several hundreds mW to several W, other than the above, including the excitation current of the transformer. Is several mW or less, and the ratio of standby power to required power is actually several hundred to several thousand times. In addition, 10% of all household power in Japan is standby power, and reduction of standby power is an essential issue in order to prevent global warming.
In the storage battery charging circuit, the battery to be charged is connected to the output of the 3-terminal regulator unit in FIG. 5, but charging is performed manually by monitoring the charging voltage in order to fully charge and not to overcharge. It is necessary to stop charging or automatically stop charging with a complicated circuit. Moreover, since the idling current flows also in the charger itself, there are many circuits that consume power even when the charged storage battery is not connected.
Magazine “Transistor Technology” CQ Publishing Co., Ltd., May 2000, P.I. 168-169, FIG. Magazine "Electronic Technology" Nikkan Kogyo Shimbun, March 1998, P.I. 2-3.

A power supply and a standby power circuit using the power supply will be described. As shown in FIG. 5, a circuit example is considered in which the output voltage of the three-terminal regulator circuit is used as the power source of the control circuit SG used in the standby power circuit, and the MOSFET Q2 that is a switch is turned on / off by the output OP of SG. The standby power circuit needs to apply a voltage to the power supply terminal of the control circuit SG regardless of the output current of the three-terminal regulator. That is, the three-terminal regulator has to cause an idling current to flow in order to generate an output voltage, and the idling current becomes standby power.
Moreover, in the battery charging circuit, it is necessary to stop charging manually or automatically when charging is completed, but it is troublesome to stop manually, and it becomes a complicated and expensive circuit to make the circuit automatically stop, and the charged storage battery is connected Even if not, there is a problem that idling current flows and power is generated.
The present invention solves such problems.
In the power supply and standby power circuit, if there is output current from the power supply circuit, the current flows from the input power supply to the power supply circuit, but if the output current from the power supply circuit is zero, the inflow current from the input power supply is basically maintained while maintaining the output voltage. The goal is to zero.
The purpose of the storage battery charging circuit is to make charging automatically stop when the storage battery voltage exceeds a certain voltage, and to make the idling current zero.
As described above, although both circuits have a difference between a capacitor and a storage battery, the relationship between the gradual decrease of the charging current accompanying the gradual increase of the charging voltage and the concept of the idling current are exactly the same.

A power source and a standby power circuit using the power source will be described using a DC power source. Connect the drain of the JFET to the DC power supply positive terminal, connect the capacitor to the source of the JFET, connect the other terminal of the capacitor to the power supply negative terminal (0 point), and the gate side is positive between the zero point and the gate of the JFET Apply voltage. The capacitor charged in this circuit becomes the power source. Since this power supply has idling current ≈ zero, the power during idling is on the order of microwatts (μW) due to leakage current.
In the storage battery charging circuit, when the capacitor terminal of the circuit is a positive / negative terminal for charging the storage battery, the charging current gradually decreases as the storage battery voltage gradually increases, and eventually becomes zero.

The proposed power source is a power source suitable for a low power source, and is optimal for an auxiliary power source such as a standby power circuit.
In the storage battery charging circuit, the charging current gradually decreases as the storage battery voltage increases, and if the storage battery is charged to a certain voltage, the charging current becomes zero, so that the battery is not overcharged.
In both circuits, the idling current is basically zero.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

Prior to describing FIG. 1, FIG. 2 will be described. FIG. 2 shows a transfer characteristic that is a relationship between the gate-source voltage Vgs (negative value) and the drain current Id using the drain saturation current Idss of the JFET 2SK184 as a parameter, and Vgs at which Id becomes zero is the pinch-off voltage Vp ( Negative value). As apparent from FIG. 2, the pinch-off voltage Vp has a small absolute value at a low drain saturation current Idss, and the absolute value of Vp is large at a large Idss. Therefore, JFETs with large variations are often ranked by Idss. Structurally, the gate-drain is a PN junction, and in principle, the gate voltage can be higher than the drain voltage by about 0.7 V, but the drain current at that time is almost the drain saturation current.
Published by Masaomi Suzuki, “Design of transistor circuit”, CQ Publisher, July 20, 1994, 3rd edition. FIG. 2 shows p. 37. Transfer of FIG.

  1 will be described with reference to FIG. FIG. 1 shows an embodiment according to claims 1 to 3 of the present invention, which is a DC power supply circuit. First, the power supply and standby power circuit will be described. The drain of JFET Q1 is connected to the positive terminal of DC power supply E, the black dot side of capacitor C1 is connected to the source of Q1, and the non-black dot side of C1 is connected to the zero point which is the negative terminal of E. Both ends of the capacitor C1 are connected to the power supply terminal of the control circuit SG. The negative terminal of battery B is connected to point 0, and the positive terminal of B is connected to the gate of JFET Q1 via resistor R1. Resistor R1 suppresses the current flowing out of B when the voltage of battery B is higher than the voltage of capacitor C1. Separately, the load circuit RL and the MOSFET Q2 are connected in series from the positive terminal between the positive and negative terminals of the DC power supply E, and the gate of Q2 is connected to the output OP of the control circuit SG. In this circuit, the JFET Q1, the capacitor C1, the resistor R1, and the battery B are power supply circuits, and both ends of C1 are the power supply for the control circuit SG and serve as the auxiliary power supply EH.

The operation of this circuit will be described on the assumption that the voltage of the DC power supply E is greater than a certain value. Depending on the difference between the voltage Vc1 of the capacitor C1 and the voltage Vb of the battery B, the operation is slightly different as follows.
The following description will be made with the capacitor C1. Since the capacitor charging operation and the storage battery charging operation are exactly the same as described above, the voltage Vc1 of the capacitor C1 is changed to the storage battery charging voltage Vt, and the charging current of the capacitor C1 is charged to the storage battery. If the current is replaced with the current, the description will be made as the storage battery charging operation as it is, so the description of the storage battery charging circuit will be omitted.
(Battery B voltage: Vb, capacitor C1 voltage: Vc1, Q1 gate-source voltage: Vgs, Q1 pinch-off voltage: Vp, Q1 drain current: Id, Q1 drain saturation current: Idss)
a. The drain current Id of Q1 when the output current of the power supply is zero will be described.
(At this time, the drain current Id of Q1 is the same value as the charging current of the capacitor C1)
(1). When 0 ≦ (Vb−Vc1), Vgs≈0, so Id≈Idss, and the capacitor C1 is charged with Idss.
(2). When Vp ≦ (Vb−Vc1) = Vgs ≦ 0, Id is based on Vgs according to FIG. 2, and the capacitor C1 is charged with Id.
Since (Id) is zero when (Vb−Vc1) = Vp, the standby power of the power supply circuit is also zero.
(3). (Vb−Vc1) <Vp does not hold, but if this is done for some reason, Id is zero, so the standby power of the power supply circuit is zero.
b. The voltage Vc1 of the capacitor C1 when the output current from the power supply and the drain current Id are stable at the same value will be described.
(4). When 0 ≦ the output current of the power supply circuit = Id ≦ Idss, Vc1 = (Vgs at the time of Vb−Id), but since Vgs is a negative value, Vc1 is an absolute value higher than Vb by Vgs.
(5). When Idss ≦ (output current of the power supply circuit), the output current is suppressed to Idss. At this time, Vc1 = Vb.
c. A summary of the output voltage of the power supply circuit in a stable state.
The output voltage OP (voltage Vc1 of the capacitor C1) of the power supply circuit is Vb ≦ Vc1 ≦ (Vb−Vp) as can be seen from the following (6) to (8).
(6). When output current = Idss: Vc1 = Vb
(7). When the output current is zero: Vc1 = (Vb−Vp)
(8). When output current = Id = Vc1 = (Vgs at Vb−Id)
(Vp and Vgs are negative values in the N-channel JFET as described above)
In the storage battery charging circuit, if the storage battery voltage Vt = (Vb−Vp) described in (7) is set, Vt will not be charged more than (Vb−Vp), and if Vt drops, the battery will be charged automatically. Be started.

The operation of the entire circuit of FIG. 1 will be described as a power supply and standby power circuit. Since a voltage is applied to the gate of JFET Q1, the current of DC power source E flows through DC power source E-JFET Q1-capacitor C1-DC power source E to charge capacitor C1. The voltage charged in the capacitor C1 is applied to the power supply terminal of the control circuit SG as the auxiliary power supply EH, SG operates, and the SG output OP is applied to the gate of the MOSFET Q2. Although the output OP of the control circuit SG becomes high / low by the input IP, if OP is low, the MOSFET Q2 is turned off, so that no current flows through the load circuit RL. If the output OP is high, the MOSFET Q2 is turned on, so that current flows through the DC power supply E-load circuit RL-MOSFETQ2-DC power supply E, and the load circuit RL operates.
In this circuit, if an output current flows from the power supply circuit, a current flows from the DC power supply E to the power supply circuit. If the output current from the power supply circuit is zero, the idling current is zero as described in “0009” (2). Therefore, the current from E is zero and the standby power is zero. In the conventional standby power circuit, it was necessary to flow an idling current to generate a voltage regardless of the presence or absence of the output current from the power supply circuit. However, the idling current is zero when only the output voltage is generated. This is a point that is greatly different from the conventional standby power circuit. The voltage Vc1 (auxiliary power supply voltage) of the capacitor C1 varies somewhat depending on the power supply current of the control circuit SG, but as described above, the fluctuation range is equal to or less than the pinch-off voltage Vp.
The drain saturation current Idss of the JFET is generally 20 mA or less, but the output current can be increased if the JFETs are connected in parallel. In the parallel connection of a plurality of JFETs, the drain current Id is the sum of all Ids, and the pinch-off voltage Vp is the lowest Vp (absolute value is maximum). In order to reduce the fluctuation of the output voltage depending on the magnitude of the output current (decrease the absolute value of Vp), a JFET having a small drain saturation current Idss may be connected in parallel. In order to reduce the fluctuation of the output voltage due to the output current, the standby power increases slightly, but if a resistor is connected to the output terminal and a certain amount of current is allowed to flow constantly, the pinch-off voltage Vp is substantially reduced. . In FIG. 2, if Id = 1 mA is constantly applied to a JFET having a drain saturation current Idss = 6.5 mA, the pinch-off voltage Vp becomes −0.7 V → −0.4 V, and the voltage fluctuation range as the power supply circuit is 0 .7V → 0.4V. Instead of the battery B, a “several hundred MΩ resistor + zener diode” can be used. The Zener diode current at that time becomes a kind of idling current and the standby power increases, but the power is about several μW.
Regarding the storage battery charging circuit, the capacitor C1 described in the paragraphs “0008” to “0009” may be replaced with a storage battery, but this will be briefly described again. If a storage battery is connected to the output terminal of the power supply circuit, it can be used as a storage battery charging circuit. If the charging completion voltage of the storage battery = (Vb−Vp), the charging current gradually decreases as the storage battery voltage increases, and the charging current becomes zero when the storage battery voltage becomes (Vb−Vp). Since the charging is automatically started when the battery is lowered, the circuit is optimal for the use of the float that is used while charging the storage battery. As a single charger, overcharge can be prevented. Moreover, the idling current is zero. Note that the capacitor C1 is not always necessary when used as a charger. When considered as a charging circuit, only the power supply circuit within the dotted line is operated, and the circuit of the load circuit RL and MOSFET Q2 is unnecessary.

FIG. 3 shows an AC power supply circuit in an embodiment according to claims 1 to 3 of the present invention. Since the storage battery charging circuit conforms to the description of the first embodiment, it is omitted here. In this circuit, an anti-series circuit in which gates and sources of MOSFETs Q3 and Q4 are connected to each other is connected in series to an AC power supply AC and a load circuit RL. In the following explanation, the sources of the MOSFETs Q3 and Q4 are set to 0 points, the black dot side of the AC power supply AC is set to K point, the non-black dot side of AC is set to L point, and the connection point between the drain of Q4 and the load circuit RL is M point. And The resistor R2 and the gate of JFET Q1 are connected to the cathode of ZD of the parallel circuit of the Zener diode ZD with the capacitor c2 and the anode at the 0 point side from the 0 point side between the K point and the 0 point, and another terminal of R2 and Q1 Are connected to the cathode of the diode D1, and the anode of D1 is connected to the point K. Further, the capacitor C1 is connected between the source of the JFET Q1 and the zero point, both ends of C1 are connected to the power supply terminal of the control circuit SG, and the output OP of SG is connected to the gates of the MOSFETs Q3 and Q4. The parasitic diodes of MOSFETs Q3 and Q4 are diodes D3 and D4, respectively.
The operation will be described. If the black spot side of the AC power supply AC becomes positive, the AC current flows through the AC power supply AC-diode D1-resistor R2-zener diode ZD-diode D3-AC power supply AC to charge the capacitor C2 to the Zener voltage of ZD, The voltage is applied to the gate of JFET Q1. If the black dot side of the AC power supply AC becomes positive in this state, the AC current flows through the AC power supply AC-diode D1-JFETQ1-capacitor C1-diode D3-AC power supply AC to charge C1. The voltage of the capacitor C1 is applied to the power supply terminal of the control circuit SG as the auxiliary power supply EH, SG operates, and the SG output OP is applied to the gates of the MOSFETs Q3 and Q4. If the output voltage OP of the control circuit SG is low, the MOSFETs Q3 and Q4 are turned off, so that no current flows through the load circuit RL. If the output OP is high, the MOSFETs Q3 and Q4 are turned on, so that a current flows through the load circuit RL. If the black dot side of the AC power source AC is positive, the current flowing through the load circuit RL flows through the AC power source AC-load circuit RL-MOSFET Q4-diode D3-AC power source AC, and the current when the black dot side is negative is AC power source AC- The load circuit RL operates by flowing through the MOSFET Q3-diode D4-load circuit RL-AC power supply AC. Note that the current flowing through the parasitic diode when the MOSFET is on first flows through the channel portion from the source to the drain of the MOSFET, and also flows through the parasitic diode when the on-voltage exceeds the rising voltage of the parasitic diode. The AC power supply AC may not be a commercial frequency, and may be the secondary side of the transformer. Capacitor C2 makes the gate voltage of JFET Q1 DC.

FIG. 4 shows an embodiment according to claims 1 to 3 of the present invention, which is an AC power supply circuit different from FIG. Since the storage battery charging circuit conforms to the description of the first embodiment, it is omitted here.
In FIG. 4, an anti-series circuit in which the cathodes of the diodes D5 and D7 are connected between the points L and M in FIG. 3 and an anti-series circuit in which the anodes of the diodes D6 and D8 are connected are connected in parallel. The drain of MOSFET Q2 is connected to the cathode, and the source of Q2 is connected to the anodes of D6 and D8. The zero point of this circuit is the source of MOSFET Q2. Similarly to FIG. 3, capacitors C1 and C2, Zener diode ZD, resistor R2, diode D1, and JFET Q1 are connected between the K point and the 0 point, and both ends of C1 are connected to the power supply terminal of the control circuit SG. The output OP is connected to the gate of MOSFETQ2.
The operation will be described. The circuit is almost the same as the paragraph “0011” until both ends of the capacitor C1 are power supplies and the voltage of C1 is applied to the power supply terminal of the control circuit SG to operate SG. If the output OP of the control circuit SG is low, the MOSFET Q2 is turned off and no current flows through the load circuit RL. If the output OP is high, the MOSFET Q2 is turned on, and a current flows through the load circuit RL. If the black dot side of the AC power source AC is positive, the current flowing through the load circuit RL flows through the AC power source AC-load circuit RL-diode D7-MOSFET Q2-diode D6-AC power source AC, and the current when the black dot side is negative is AC The power supply AC-diode D5-MOSFET Q2-diode D8-load circuit RL-AC power supply AC flows and RL operates. The load circuit RL of FIG. 4 is for an AC circuit, but the RL can be connected between the cathodes of the diodes D5 and D7 and the drain of the MOSFET Q2 if the circuit RL operates even with a direct current. In that circuit, a plurality of series circuits of a load circuit and a MOSFET can be controlled by a plurality of control circuits.

  FIG. 2 is an example of a standby power circuit in which the output voltage of a power supply circuit that uses a DC power supply as an input is used as a power supply for a control circuit in the first embodiment of the present invention.   The transfer characteristic of JFET is the relationship between the gate-source voltage Vgs and the drain current Id using the drain saturation current Idss as a parameter.   In the second embodiment of the present invention, an example of a standby power circuit using an output voltage of a power supply circuit with an AC power supply as an input as a power supply for a control circuit is shown.   In the third embodiment of the present invention, it is an example of a standby power circuit that uses an output voltage of a power supply circuit having an AC power supply as an input, which is different from that shown in FIG.   It is an example of a standby power circuit in which the output voltage of a three-terminal regulator is used as a power source for a control circuit in a conventional circuit.

Explanation of symbols

E DC power supply AC AC power supply B Battery EH Auxiliary power supply SG Control circuit IP Control circuit input OP Control circuit output RL Load circuit Q1 Depletion type junction FET (JFET)
Q2-Q4 MOSFET
D1-D8 Diode R1-R2 Resistor C1-C2 Capacitor Id JFET drain current Idss JFET drain saturation current Vgs JFET gate-source voltage Vp JFET pinch-off voltage Vb Battery voltage Vc1 Capacitor C1 voltage (auxiliary power supply voltage) )
Vt Charged battery voltage

Claims (3)

The power supply which uses the both ends of the capacitor | condenser of one power supply circuit selected from the following A group as a power supply terminal.
Group A a. Connect the drain of the depletion type N-channel JFET to the positive terminal of the DC power supply or pulsating power supply, connect the source of the JFET and the capacitor, and connect the other terminal of the capacitor and the negative terminal of the DC power supply or the pulsating power supply. A power supply circuit in which a positive voltage is applied to the gate of the JFET with reference to the negative terminal of the DC power supply or pulsating power supply.
b. Connect the drain of the depletion type P-channel JFET to the negative terminal of the DC power supply or pulsating power supply, connect the source of the JFET and the capacitor, and connect the other terminal of the capacitor and the positive terminal of the DC power supply or the pulsating power supply. A power supply circuit in which a negative voltage is applied to the gate of the JFET with reference to the positive terminal of the DC power supply or pulsating power supply.     A standby power circuit using the power source of claim 1 as a power source for a control circuit for controlling conduction of a main power switch circuit during standby. A storage battery charging circuit in which a charging positive terminal and a charging negative terminal of one power supply circuit selected from the following group A are used as storage battery connection terminals during charging.
Group A a. A drain terminal of a depletion type N-channel JFET is connected to a positive terminal of a DC power source or a pulsating current power source, the source of the JFET is used as a positive terminal for charging a charged storage battery, and a negative terminal of the DC power source or the pulsating current power source is a charged storage battery. A power supply circuit in which a positive voltage is applied to the gate of the JFET with reference to the negative terminal of the DC power supply or pulsating power supply as a negative terminal for charging.
b. The drain of a depletion type P-channel JFET is connected to the negative terminal of a DC power source or a pulsating current power source, the source of the JFET is used as a negative terminal for charging a charged storage battery, and the positive terminal of the DC power source or the pulsating current power source is a charged storage battery As a positive terminal for charging, a power supply circuit in which a negative voltage is applied to the gate of the JFET with reference to the positive terminal of the DC power supply or pulsating power supply.

Images