JP2551201Y2 - Switching power supply type charger - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply type charger which is particularly suitable for charging high performance sealed batteries and the like, which have been particularly widely used in recent years.

[0002]

2. Description of the Related Art FIG. 3 shows the charging characteristics of a typical battery.
Until t ₁ when the charge-up performs rapid charging, perform floating charge since it lowers the charging voltage to maintain a 100% state of charge of the battery. In the floating charging area, the rectifier normally supplies DC power to the load.However, when the load increases or during a power outage, the battery supplies power, so that a small charge current is always supplied to the battery to compensate for the self-discharge of the battery. I have to. Since the battery is repeatedly charged and discharged by a chemical reaction, the battery is affected by the ambient temperature, and a required battery voltage varies. In particular, in the floating charging region, it is necessary to perform charging in accordance with the temperature characteristics of the battery with respect to such a change in the ambient temperature. In the conventional charger, a thermistor is provided near the battery, and the temperature of the charging voltage is corrected by a change in resistance of the thermistor.

[0003]

[Problems to be Solved by the Invention] However, the temperature coefficient of the thermistor changes non-linearly with temperature change.
Since the temperature does not match the temperature characteristics of a battery with a linear negative temperature coefficient, accurate temperature correction is not performed, and there is a possibility that overcharging may occur or self-holding may occur and the battery may not be fully charged. There is a problem that the battery life is shortened. The present invention has been made in view of such a problem, and provides a switching power supply type charger that can perform temperature correction completely matching the temperature characteristics of the battery and can ensure the safety and long life of the battery. It is intended to provide.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a high frequency switching circuit which switches a DC voltage obtained by rectifying and smoothing an AC input voltage to form a high frequency pulse voltage. A power supply circuit that supplies a DC output voltage obtained by transforming the voltage to a required voltage by a high-frequency transformer and further rectifying and smoothing the load battery, and inverting and amplifying the difference by comparing a detected value of the output voltage with a comparison reference voltage. A constant-voltage / constant-current control circuit that performs constant-voltage control by outputting a switching pulse signal having a pulse width according to the value to the high-frequency switching circuit;
A temperature detection circuit that detects a change in the ambient temperature of the load battery as a voltage change due to a resistance change of a thermistor disposed near the load battery; and the constant voltage constant based on the detected temperature detected by the temperature detection circuit. By selecting one of a number of adjustment resistors connected in parallel to a voltage dividing resistor that determines a comparison reference voltage of the current control circuit, the comparison reference voltage of the constant voltage / constant current control circuit is linearly controlled with respect to a temperature change. And a comparison reference voltage control circuit.

[0005]

According to the above configuration, the comparison reference voltage control circuit includes:
When one of the adjustment resistors is selected based on the temperature detected by the temperature detection circuit, the combined resistance of the adjustment resistor and the voltage-dividing resistor becomes a new voltage-dividing resistor that determines the comparison reference voltage of the constant-voltage and constant-current control circuit. The reference voltage changes linearly with changes in temperature. When the comparison reference voltage decreases with respect to the detected value of the output voltage, the pulse width of the switching pulse signal output from the output terminal of the constant voltage / constant current control circuit decreases, and the output voltage decreases. When the comparison reference voltage increases, the pulse width of the switching pulse signal increases and the output voltage increases. In this way, the output voltage is linearly corrected for the temperature change.

[0006]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a switching power supply type charger according to the present invention. In the figure, 1 is an AC power supply, 2 and 3 are rectifying elements and smoothing capacitors for rectifying and smoothing an AC input voltage to obtain a DC voltage, respectively, and 4 is a high frequency switching circuit for switching the DC voltage. Of the primary side main circuit. The secondary-side main circuit of the high-frequency transformer 5 includes a high-frequency rectifier diode 6 and a smoothing circuit 7, and supplies a DC output voltage V ₀ to a load battery 8.

The midpoint between the output voltage detecting voltage dividing resistor 9 and the detecting resistor 10 connected to the output terminal to the load battery 8 is connected to the negative input terminal of the constant voltage / current control circuit 11. The constant-voltage / constant-current control circuit 11 supplies the reference voltage Vre
f, oscillator, switching regulator control I
It is a circuit including C (for example, type 494). The reference voltage Vref of the constant voltage / constant current control circuit 11 is connected to the negative sensing terminal (−S) via the resistors 12 and 13, and the negative sensing terminal is connected to the battery 8.
Is connected to the minus terminal inside. 16 for resistor 13
Number of adjusting resistors 14 _1, ..., 14 ₁₆ are connected in parallel, respectively, respectively, the adjustment resistor 14 _1, ..., the light emitting diodes 27 ₁ to be described later to 14 _16, ..., phototransistors forming a 27 ₁₆ a pair 15 _1, ..., 15 ₁₆ are connected in series. The midpoint between the resistors 12 and 13 is connected to the positive input terminal of the constant voltage / current control circuit 11. An output terminal of the constant voltage / constant current control circuit 11 is connected to a gate terminal of the high frequency switching circuit 4 via a drive transformer 16 and a gate drive circuit 17.

On the other hand, a sub-circuit including an auxiliary high-frequency switching circuit 18 is connected to the smoothing capacitor 3 of the primary-side main circuit.
It is a secondary circuit. The auxiliary high-frequency transformer 19
The auxiliary constant voltage power supply circuit 20 is connected to the secondary side winding of the constant voltage power supply circuit 20. The constant voltage Vcc obtained by the auxiliary constant voltage power supply circuit 20 is supplied to each control circuit and is located near the load battery 8. The installed thermistor 21 and the thermistor 2
1 is supplied to a detection resistor 22 connected in series.
The midpoint between the thermistor 21 and the detection resistor 22 is connected to the A / D port of the microcomputer 23. The 4-bit output signal of the microcomputer 23 is input to the line recorder 24. Between the 16 output terminals a constant voltage Vcc line line recorder 24, the respective phototransistor 15 _{1-15 16}
Photocoupler 25 ₁ with, ..., the light emitting diode 27 ₁ constituting 25 _16, ..., 27 ₁₆ are connected

[0009] Incidentally, the microcomputer 23 and a line recorder 24 and photocoupler 25 _to 253 ₁₆ and the adjusting resistor 14 _{1-14 16,} the comparison reference applied to the positive input terminal of the constant-voltage constant-current control circuit 11 The reference voltage control circuit 28 controls the voltage. The photocouplers 25 _{1 to} 25 ₁₆ of this embodiment are used to protect the microcomputer 23 by insulating the main circuit side having a high battery voltage from the microcomputer 23 side. Therefore, when the battery voltage is low, direct connection is possible without using such a photocoupler.

In the switching power supply type charger having the above configuration, the commercial AC input voltage of the AC power supply 1 is rectified and smoothed by the rectifying element 2 and the smoothing capacitor 3 to be a DC voltage. It is switched to a high frequency pulse voltage. This high-frequency pulse voltage is transformed by the high-frequency transformer 5 into a voltage corresponding to the secondary-side load battery 8, converted into direct current by the high-frequency rectifier diode 6, and smoothed by the smoothing circuit 7 into a direct-current voltage with little ripple, thereby reducing the load. It is supplied to the battery 8.

The output voltage is detected as a voltage division between the voltage dividing resistor 9 and the detecting resistor 10 via the plus side sensing terminal (+ S), and is used as a detection signal for the constant voltage control. 11 is input to the minus input terminal. A comparison reference voltage obtained by dividing the reference voltage Vref by the resistors 12 and 13 is applied to the positive input terminal of the constant voltage / current control circuit 11. When the output voltage rises and the detection signal of the minus input terminal becomes higher than the comparison reference voltage of the plus input terminal, the constant voltage / current control circuit 11 acts as an inverting amplifier, and the pulse width of the switching pulse signal ( Ton). As a result, the switching pulse signal having a short pulse width is supplied to the drive transformer 1.
Since the voltage is output to the high-frequency switching circuit 4 via the gate drive circuit 6 and the gate drive circuit 17, the output voltage is reduced and maintained constant.

A change in the temperature around the load battery 8 appears as a change in resistance of the thermistor 21 arranged near the load battery 8. Assuming that the resistance value of the thermistor 21 is R _S and the resistance value of the detection resistor 22 is R 22, Vcc / (R _S 21
+ R22) flows through the thermistor 21, so that a resistance change of the thermistor 21 results in a change of the current. The change in the current of the thermistor 21 is detected as a voltage which is the product of the current and the detection resistor 22,
/ D port. Microcomputer 23
Has 16 levels of voltages corresponding to the resistance of the thermistor 21 input to the A / D port, and a table of thermistor temperatures and output signal patterns corresponding to these voltages in the memory. The output signal pattern is composed of 4 bits 00
There are 16 types from 00 to 1111.

Now, a certain voltage is applied to the microcomputer 2
When input to the A / D port 3, the microcomputer 23 outputs a 4-bit output signal corresponding to the voltage to the line recorder 24. The line recorder 24 is based on the output signal of the microcomputer 23, and the light emitting diodes 27 _{1 to} 27 ₁₆ of the ₁₆ photocouplers 25 _{1 to} 25 ₁₆ are provided.
_{One of 16} is selected to emit light. By this, the phototransistor 15 _{1-15 16} ON corresponding to the light emitting diodes 27 ₁ to 27 _16, one of the adjustment resistor 14 _{1-14 16} dividing resistors 13 of the phototransistor circuit is connected in parallel . As a result, the adjustment resistor 14 ₁
The combined resistance of any one of .about.14 _{16 and} the voltage dividing resistor 13 becomes a new voltage dividing resistor, and the comparison reference voltage applied to the plus side input terminal of the constant voltage / constant current control circuit 11 changes. When the comparison reference voltage decreases with respect to the detection input of the negative input terminal, the pulse width of the switching pulse signal output from the output terminal decreases, and the output voltage decreases. When the comparison reference voltage increases, the pulse width of the switching pulse signal increases and the output voltage increases.

Table 1 summarizes the change of each part with respect to the thermistor temperature.

[Table 1] Thermistor Thermistor Microcomputer Photocoupler Parallel conversion with resistor 13 Temperature resistance Output signal ON Connected resistor Reference voltage t ₁ R ₁ 0000 27 ₁ 15 ₁ 14 ₁ V ₁ t ₂ R ₂ 0001 27 ₂ 15 ₂ 14 ₂ V _{2 t 3 R 3 0010 27 3 15} 3 14 3 V 3 t 4 R 4 0011 27 4 15 4 14 4 V 4 t 5 R 5 0100 27 5 15 5 14 5 V 5 t 6 R 6 0101 27 6 15 6 14 6 V ₆ t ₇ R _{7 0} 110 27 ₇ 15 ₇ 14 ₇ V ₇ t ₈ R _{8 11 11} 27 ₈ 15 ₈ 14 ₈ V ₈ t ₉ R ₉ 1000 27 ₉ 15 ₉ 14 ₉ V ₉ t ₁₀ R ₁₀ 1001 27 ₁₀ 15 ₁₀ 14 ₁₀ V ₁₀ t ₁₁ R _{11 10 10} 27 ₁₁ 15 ₁₁ 14 ₁₁ V ₁₁ t ₁₂ R _{12 10 11} 27 ₁₂ 15 ₁₂ 14 ₁₂ V ₁₂ t ₁₃ R ₁₃ 1100 27 ₁₃ 15 ₁₃ 14 ₁₃ V ₁₃ t ₁₄ R ₁₄ 110 127 ₁₄ 15 ₁₄ 1 _{14 V 14 t 15 R 15 1110} 27 15 15 15 14 15 V 15 t 16 R 16 1111 27 16 15 16 14 16 V 16

The resistance values of the adjusting resistors 14 _{1 to} 14 ₁₆ are selected in advance so that the comparison reference voltages V _{1 to} V ₁₆ change linearly with changes in the thermistor temperatures t _{1 to} t ₁₆ . . Therefore, when the thermistor temperature changes with a fixed value of Δt from t ₁ to t ₁₆ as shown in FIG. 2, the thermistor resistance changes exponentially nonlinearly from A to T as shown by A in FIG. However, the converted comparison reference voltage to the plus side input terminal of the constant voltage / constant current control circuit 11 changes linearly from A 'to T' as shown by A 'in FIG.
As a result, the comparison reference voltage could be changed linearly with respect to the temperature change, and voltage control completely matching the temperature characteristics of the battery could be performed.

[0016]

As is apparent from the above description, according to the present invention, the comparison reference voltage of the constant voltage / constant current control circuit is controlled linearly with respect to the temperature change by the comparison reference voltage control circuit. The temperature correction of the output voltage that completely matches the temperature characteristics of the battery is performed, there is no risk of overcharging or insufficient charging, and the battery can be made safe and have a long life.
The reliability of the battery can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a switching power supply type charger according to the present invention.

FIG. 2 is a diagram illustrating a temperature change of a thermistor resistance and a conversion reference voltage.

FIG. 3 is a diagram showing charging characteristics of a charger.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Rectifier element, 3 ... Smoothing circuit, 4 ... High frequency switching circuit, 5 ... High frequency transformer, 6 ... High frequency rectifier diode, 7 ... Smoothing circuit, 8 ... Load battery, 9 ... Division voltage for output voltage detection Resistance, 10 ... Detection resistance, 1
1 ... constant-voltage constant-current control circuit, 12, 13 ... reference voltage setting dividing resistors, 14 _{1-14 16} ... adjustment resistor, 21 ...
Thermistor, 22: detection resistor, 23: microcomputer, 24: line recorder,
25 _{1 to} 25 ₁₆ ... photocoupler, 28 ... comparison reference voltage control circuit.

Claims (1)

(57) [Scope of request for utility model registration] 1. A high-frequency switching circuit switches a DC voltage obtained by rectifying and smoothing an AC input voltage to form a high-frequency pulse voltage, transforms the high-frequency pulse voltage to a required voltage by a high-frequency transformer, and further performs rectification and smoothing. A power supply circuit for supplying a DC output voltage obtained by the above to a load battery; and a high-frequency switching circuit that compares a detected value of the output voltage with a comparison reference voltage and outputs a switching pulse signal having a pulse width corresponding to an inverted amplification value of the difference. A constant-voltage / constant-current control circuit that performs constant-voltage control by outputting the temperature to a load battery; and a temperature detection circuit that detects a change in the ambient temperature of the load battery as a voltage change due to a resistance change of a thermistor disposed near the load battery. A voltage dividing resistor that determines a comparison reference voltage of the constant voltage / current control circuit based on the temperature detected by the temperature detecting circuit. A comparison reference voltage control circuit that linearly controls the comparison reference voltage of the constant voltage / constant current control circuit with respect to a temperature change by selecting one of a large number of adjustment resistors connected in parallel to each other. A switching power supply type charger.