JP2791128B2 - Power supply - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly to a power supply device in which respective outputs of output circuits respectively connected to outputs of a plurality of step-up transformers are connected in series to supply power to a load. It is.

2. Description of the Related Art Conventionally, a power supply device such as a DC / DC inverter that outputs a high voltage for a charger of a copying machine or the like has been known.
When this type of device is used, various values of high voltage may be required, and a method of forming a desired high voltage by combining the outputs of a plurality of inverter transformers in series is known.

In such a configuration, when the outputs of two or more transformers are superposed, conventionally, the withstand voltage between the primary and secondary of the inverter transformer used is set to be equal to or higher than the output voltage of the circuit.

[Problems to be Solved by the Invention] Generally, the withstand voltage specification between the primary and secondary is proportional to the cost of the transformer, and the higher the withstand voltage, the higher the manufacturing cost of the device. However, in the above-described conventional technology, when a high voltage is generated in a booster circuit by using an inverter transformer having a relatively low price and a low transformation ratio, and the voltage is similarly superimposed on a voltage generated by another transformer, the output is increased. Leakage and discharge could occur due to insufficient withstand voltage between the secondary and the secondary.

Therefore, if the withstand voltage of the transformer can be reduced without danger of discharging even at the same output voltage, an effect of cost reduction can be expected.

 An object of the present invention is to solve the above problems.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, the respective outputs of output circuits connected to the outputs of a plurality of step-up transformers are connected in series, and the input side of the step-up transformer is connected. In the power supply device for supplying a combined voltage of the output voltage from each output circuit to the load by controlling the reference voltage of the load, the reference potential of the load and the reference potential of the input of the step-up transformer are set to be equal to each other, and the power supply device is configured by each output circuit. One end of the series circuit is connected to the reference potential, the other end is connected to the input terminal of the load, and among the output circuits connected in series, the closer the output side to the load, the absolute value of the output voltage. high,
Further, a configuration is adopted in which the absolute value of the output voltage is set lower for a circuit closer to the reference potential.

[Operation] According to the above configuration, the potential on the output side of each step-up transformer can be minimized in any combination of output voltages. The required breakdown voltage can be reduced.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

First Embodiment FIG. 1 shows a first embodiment of the power supply device of the present invention.

In the figure, reference numerals T1 and T2 denote inverter transformers, which are switched by transistors Q1 and Q2, respectively. The bases of the transistors Q1 and Q2 are controlled by a predetermined switching pulse. When the base drive is stopped, the output of each inverter transformer is stopped. Although not shown here, it goes without saying that load current and voltage can be controlled as desired by providing a means for adjusting the waveform and frequency of the switching pulse of the transistors Q1 and Q2.

On the primary side of the inverter transformers T1, T2, the symbol R
1, R2 is a resistor to increase the switching speed. The resistors R3 and R4 form an integrator paired with the capacitors C1 and C2 when viewed from the inverter transformers T1 and T2, and connect the switching noise of the inverter transformers T1 and T2 to the middle point of the primary coils of the inverter transformers T1 and T2. Power supply line Vcc
Acts as a filter to prevent transmission to However, the resistance values of the resistors R3 and R4 are set so small that the voltage drop can be ignored. Diodes D1 and D2 are inverter transformers T1 and T2
Reset.

On the other hand, on the secondary side of the inverter transformer T1, the capacitors C2 to C5 and the diodes D3 to D6 constitute a half-wave quadruple voltage rectifier circuit. On the secondary side of the inverter transformer T2, the capacitor C7 and the diode D7 form a half-wave rectifier circuit.

Resistors R5 and R6 are connected to the rectified outputs in parallel with the line. Further, the + output of the inverter transformer T2 is grounded, the-output is connected to the-output of the inverter T1 via line 1, and power is supplied to the external load Z from the + side of the inverter transformer T1. That is, the secondary outputs of the inverter transformers T1 and T2 are connected in series.

The resistors R5 and R6 are internal load resistors that adjust the transformer output voltage when no load is applied and adjust the responsiveness of voltage rise and fall.

In the above configuration, when a switching pulse is applied to the bases of the transistors Q1 and Q2 and the boost ratios of the inverter transformers T1 and T2 are the same, a voltage obtained by multiplying Vcc by the boost ratio is induced on the secondary side. .

For example, if Vcc is 20 V and the boost ratio is 50, a voltage of 1000 V is induced on the secondary side of the transformer, the voltage V1 across the internal load resistor R5 is 4000 V, the voltage V2 across the resistor R6 is 1000 V, and the external load Z Is 4000-1000 = 3000
V.

When the switching pulse is applied only to the base of the transistor Q1, V1 = 4000V, V2 = 0V, and the output V0 is 4000V. When a switching pulse is applied only to the base of the transistor Q2, V1 = 0V, V2
= 1000V, and the output V0 becomes -1000V. However, it is assumed that the resistances R5 and R6 are sufficiently smaller than the external load Z.

In the above setting, the absolute value of the output voltage on the inverter transformer T1 side is set high, and the absolute value of the output voltage on the inverter transformer T2 side is set low. That is, the absolute value of the output voltage of the high-voltage output unit on the power supply line 11 side to the load is increased, and
The absolute value of the output voltage of the high voltage output unit near the ground side is set low. According to such an output voltage setting, as described below, at least the withstand voltage of the inverter transformer T1 on the power supply line 11 side to the load can be set low.

First, according to the above configuration, when only the inverter transformer T2 is driven, 1000V is induced in V2 and applied to the secondary coil of the inverter transformer T1 via the line 1. Therefore, since a potential difference of about 1000 V is generated between the primary coil and the secondary coil of the inverter transformer T1, the withstand voltage between the primary and secondary of the inverter transformer T1 needs to be at least 1000V.

On the other hand, when only the inverter transformer T1 is driven, V1
= 4000V is induced and applied to the external load resistance Z,
Since the secondary coil of the inverter transformer T2 is at the ground level, 4000 V is not required for the primary and secondary breakdown voltages in this operating state.

Therefore, the inverter transformer T1 only needs to have a withstand voltage between the primary and secondary coils that can withstand a voltage of 1000V, and the inverter transformer T2 also has a primary and secondary coil of 1000V in case both the inverter transformers T1 and T2 are driven. It can be seen that the secondary withstand voltage is sufficient.

To make this clearer, a different connection structure is shown in FIG. The order of the series connection of the secondary outputs of the inverter transformers T1 and T2 is reversed, one end of the inverter transformer T1 is grounded, and the output from the inverter transformer T2 is output to the external load resistor Z.

Since the configuration of the rectifier circuit on the secondary side of the inverter transformers T1 and T2 is the same as that in FIG. 1, in FIG. 2, the absolute value of the boosted output of the transformer T1 far from the output terminal (on the ground side) is larger. It is getting bigger. However, under the same input conditions as in the example of FIG. 1, the voltage applied to the external load resistance Z is equal to that of the example of FIG. That is, when the entire power supply is viewed, it is considered that the power supply has the same function.

Here, under the same conditions as in FIG.
Considering the case of driving only, V1 = 4000V is induced,
4000 V is applied to the external load resistor Z via the resistor R6. Therefore, 4000 V is applied to the secondary coil of the inverter transformer T2,
The withstand voltage between the secondary and the secondary must be at least 4000V.

Therefore, by using the configuration shown in FIG. 1 instead of the configuration shown in FIG. 2, the withstand voltage of the inverter transformer T1 can be greatly reduced from 4000 V conventionally required to 1000 V,
The manufacturing cost of the device can be reduced without danger such as leakage and discharge.

Second Embodiment FIG. 3 shows the configuration of a more generalized power supply device as a second embodiment of the present invention.

Here, three inverter transformers T1 to T3 are used, and each primary side is switched by a primary drive circuit 31 to 33. On the other hand, a booster rectifier circuit 41 to 43 is connected to each secondary side, and rectification is performed. The outputs are connected in series via resistors R11 to R13. Here, the boost rectifier circuit 41 is connected to the output side, and the boost rectifier circuit 43 is connected to the ground side.

Here, the output of the step-up rectifier circuit 41 of the inverter transformer T3 is V3, the output of the step-up rectifier circuit 42 of the inverter transformer T4 is V4, and the output of the step-up rectifier circuit 43 of the inverter transformer T5 is
V5. Each of the rectifier circuits 41 to 43 is composed of a voltage doubler rectifier circuit as shown in FIG. The configuration of the primary driving circuits 31 to 33 on the primary side is the same as that of FIG.

In such a configuration, more voltage values can be output by a combination of three high voltage outputs. For example, + 4000V, + 2000V, 0V, -2000V, -4000V
V3 = 4000V, V4 = -200
It can be realized by setting 0V, V5 = -2000V, controlling the primary drive circuits 31 to 33 to drive / non-drive, and combining these voltages.

In this way, among the transformer output circuits connected in series, the circuit closer to the output side has a higher absolute value of the output voltage, and
By setting the absolute value of the output voltage to be lower for a circuit closer to the ground side, the breakdown voltage between the primary and secondary of the transformer can be reduced as in the above-described embodiment. In the case of FIG. 3, all transformers having a withstand voltage of 2000 V can be used.

If the voltage is not set as described above in FIG. 3, as a method for obtaining the same power supply output, V3 = −2000V, V3
It is conceivable to configure the respective step-up rectifier circuits so that 4 = −2000V and V5 = + 4000V. In this configuration, the withstand voltage of the inverter transformers T3 and T4 must be 4000V as in the case of FIG. .

As described above, even when three transformer outputs are combined, of the transformer output circuits connected in series, the circuit closer to the output side has a higher absolute value of the output voltage, and the circuit closer to the ground side has a higher output voltage. By setting the absolute value to be low, a combination of withstand voltages having the lowest primary and secondary withstand voltages can be realized for each transformer, and a simple and inexpensive power supply device can be provided without danger such as leakage and discharge.

[Effects of the Invention] As is clear from the above, according to the present invention, the outputs of the output circuits connected to the outputs of the plurality of step-up transformers are connected in series to control the input side of the step-up transformer. In a power supply device for feeding a load with a composite voltage of output voltages from each output circuit, a reference potential of the load and a reference potential of the boost transformer input are set to be equal, and one end of a series circuit formed by each output circuit is connected. In addition to being connected to the reference potential, the other end is connected to the input terminal of the load, and among the output circuits connected in series, the closer the output side to the load, the higher the absolute value of the output voltage,
Since the circuit closer to the reference potential employs a configuration in which the absolute value of the output voltage is set lower, the potential on the output side of each booster transformer can be minimized in any combination of output voltages. The required withstand voltage between the primary and secondary (input / output) coils can be reduced, and there is no danger of leakage, discharge, etc. realizable.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a main part of a first embodiment of a power supply device according to the present invention, FIG. 2 is a circuit diagram showing an operation in the configuration of FIG. 1, and FIG. 3 is a second embodiment of the present invention. FIG. R1 to R6, R11 to R13, resistors D1 to D6, diodes Q1, Q2, transistors T1, T2, inverter transformer Z, external load resistors 31 to 33, primary drive circuit 41 to 43, step-up Rectifier circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Akiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Yoshimi Kuramochi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Shunichi Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-59-185120 (JP, A) JP-A-57-50757 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H02J 1/00 306

Claims (1)

(57) [Claims] An output circuit connected to an output of each of a plurality of step-up transformers is connected in series to control an input side of the step-up transformer so that a combined voltage of output voltages from the output circuits is applied to a load. In the power supply device for supplying power, the reference potential of the load is set equal to the reference potential of the input of the step-up transformer, and one end of a series circuit including each output circuit is connected to the reference potential, and the other end is connected to the load. Further, among the output circuits connected in series, a circuit closer to the output side to the load has a higher absolute value of the output voltage, and a circuit closer to the reference potential has a lower absolute value of the output voltage. A power supply device characterized by being set.