JPS61254072A - Circuit for controlling power source - Google Patents

Abstract

PURPOSE:To reduce the size, the weight and the cost by employing a circuit for controlling a power source formed on a chip with an output voltage controller and an AC signal generator to obtain a DC voltage. CONSTITUTION:A power source 101 of an electronic device has a circuit 100 for controlling a power source and a switching circuit 102 to obtain the desired voltage or constant-current output from a DC input voltage. In this case, a pulse-width modulation (PWM) controllers 105 and an AC voltage output unit 106 are provided in the circuit 100. Further, the both circuits are composed as integrated circuits (e.g., monolithic integrated circuits). Thus, the circuit 100 operates the circuit 102 by DC constant voltage output by a PWM control signal 103 output from the controller 105, and an AC output voltage 104 is output by an AC voltage output unit 106. The power source 101 is reduced in size and cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application] The present invention relates to a power supply control circuit for a power supply section of an electronic device such as a copying machine or a printer that requires a plurality of power supply voltages.

E Summary of the Disclosure" This specification and drawings describe a power supply control circuit for a power supply unit of an electronic device, etc., in which the power supply control circuit outputs a control signal for controlling a DC output voltage and an AC voltage signal. The present invention discloses a technology that contributes to downsizing and cost reduction of the power supply section.

[Prior Art J] In electronic devices, their power supply devices often require multiple output voltages 6 For example, copying machines, etc. 1 is a charger,
The developing device requires multiple DC high voltages and AC high voltages,
In order for them to operate stably, each output power source requires independent control. In this case, each conventional power supply control section is composed of so-called discrete elements, which are independent for each part, and the number of parts is large, slowing down miniaturization. Further, even if the control section is integrated circuit, the control output is limited to one system at most, making it difficult to downsize the power supply section.

[Problems to be Solved by the Invention] The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and provides a power supply control circuit that contributes to downsizing of the power supply section of electronic equipment and, ultimately, to lower costs. The challenge is to provide.

Measures for Solving Problem E] As one means for solving the above problem, for example, in the power supply unit 101 shown in FIG. 1, in order to obtain a desired constant voltage constant current output from the input DC voltage.

It has a power supply control circuit 100 and a so-called switching circuit 102 according to an embodiment of the present invention.

Inside the power supply control circuit 100, there is a pulse width modulation (PWM)
) A control circuit 105 and an AC voltage output section 106 are provided.

[Function] In the configuration shown in FIG. 141, the power supply control circuit 100
The switching circuit 102 is operated at a constant voltage by the PWM control signal 103 outputted by the PWM control circuit,
Further, an AC voltage output section 10B outputs an alternating current (AC) output voltage 104.

[Example] Hereinafter, a more specific example of the present invention will be described with reference to the accompanying drawings.

FIG. 2 shows a pie diagram of a power supply control circuit 100 as an example.
I made it into an IC using the Polar CBIPOLAR) process.
FIG. 2 is a configuration diagram of a circuit block of a chip monolithic IC. In addition, in the following drawings, the mark 0 represents the terminal of IC100, and in Fig. 2, it is an integrated circuit (hereinafter referred to as IC).
In addition to 100, the external circuit elements C~C3, C5~
C7, R1-R8 are added. To explain the IC 100, the number of terminals is 28, the 14th terminal is a ground terminal, and the 28th terminal is a power supply terminal.

IC100 is an AC converter that outputs AC voltage from terminal 27 using an ACC signal generator 1, a waveform shaping unit 2, and an AC output control unit 3.
It consists of a voltage output section (corresponding to 106 in FIG. 1) and a PWM control circuit for two systems of DC voltage and current control. Each of these circuits is independent and can operate in parallel. Therefore, a power supply control circuit consisting of only two PWM control circuits excluding the AC voltage output section is also possible. The operation of each part will be explained below in order.

<Outline of pwM control circuit) ? Since the PWM control circuits of the systems are the same, the following explanation will only be made for one circuit.The control for DC output voltage stabilization operation is performed by so-called PWM modulation, and the control circuit for this mainly consists of four elements. . That is, output control sections 5 and 15, pulse width control sections 9 and 19, oscillation circuits 10 and 20, PWM output section 11.21, and protection circuit 6
, 7°16.17, error amplifiers 8, 18, etc.

Inputs to the output control section 5 are made to terminals 3 to 6 of the IC 100. The output control section 5 determines whether or not the pulse width control i9 can be operated. The third terminal is an input for so-called soft start, and is used to prevent excessive current from flowing into the switching circuit when the power is turned on. The time required for the soft start is determined by the time constants of R2, R3, and C2.

The protection circuits 6 and 7 are respectively circuits for shutting down the output when an overvoltage occurs or an overcurrent flows in the output. The other inputs of each of the protection circuits 6.7 are reference voltages generated within the IC 100, as described below.

The output remote control of the No. 4 terminal is externally controlled, and this signal can also directly determine whether or not the pulse width control section 9 operates.

As will be described later, the oscillation circuit 10 oscillates at a reference frequency determined by the time constants of external components 03 and R4, and the frequency is based on the pulse width determined by the output of the pulse width section W section 9. The output of the switching circuit is kept constant by changing according to the change in the on-time period.The pulse width control section 9 controls the difference between the monitor voltage of the DC output voltage of the switching circuit and the external reference voltage. The error voltage is amplified by the error amplifier 8, and the length of the above-mentioned "on time" is controlled by the error voltage. Therefore, PWM
The PWM output signal that is the output of the output section 11 (terminal 13) becomes an output signal whose "on time" becomes longer as the error amplification voltage becomes larger.

As described above, in this embodiment, the operation of the pulse width control section 9 and the oscillation circuit 10 takes the form of frequency variable pulse width modulation in which the ``off time'' is constant and the ``on time'' is variable. However, another method is also conceivable in which the frequency is constant and the so-called duty ratio of "on time" and "off time" is varied.

(Connection with switching circuit) Figure 3 shows how IC100 is connected to the switching circuit and DC
The zero line circuit that shows an example of a circuit that obtains a constant voltage is a so-called ringing choke converter ("on-off") method. Its operation will be explained. The PWM output signal (terminal 13) is output by the power amplifier 30. The input DC voltage is converted into single-phase AC by the inverter 40 according to the power amplified PWM output signal.
Furthermore, it is rectified by a diode 41, and a capacitor 42
This is to supply a desired constant DC voltage to the load. Voltage detection for constant voltage output control is performed by rectifying and smoothing the voltage stepped down by the secondary winding 44 of the transformer 45 using a diode 43° capacitor C1l, and inputting the resulting voltage to the No. 7 terminal. Inputting voltage to terminal 6 also serves as overvoltage detection.

In addition, overcurrent detection is performed by inputting the voltage generated between CIO and R10 to terminal 5. Note that the circuit example shown in 83@ is just an example, and is suitable for "on-off" type inverters and chopper type switching circuits. can also be easily applied.

(Pulse Width Modulation Operation) FIG. 4(1k) shows an example of the PWM control circuit (7) in the IC 100, and FIG. 4(b) is an example of its timing chart. First, the voltage-frequency conversion operation for PWM will be explained with reference to FIG. 4 (JL). Transistor Q2 forms a charging path to lamp circuit C3°R4;
On the other hand, Q3 forms a discharge path. Whether the lamp circuit charges or discharges depends on the on/off state of transistor Q1 (ie, the set state of latch 28). When latch 2B is reset (reset output Q/ is “1”)
], transistor Q1 is on, and therefore the lamp circuit is in a discharge state. Note that "/" in Q/ indicates negative logic, and when the latch 28 is set, it is in a charging state. The output of the lamp circuit (terminal 12) is VR50, which is the output of the level priority selection circuit 26 to be described later, and the comparator 2.
Assuming that VH, which is the input of 6, is 51, the condition for the reset output Q/ of the latch 28 to be 1'' is only if VH<VR in the comparator 26. In other words, if the latch 28 is set, the lamp circuit becomes a charging state, VR50 rises, and when V)l < VR, latch 2
8 resets and starts discharging.

Since the VR50 is manually input to the driver 29, the PWM output signal that is the output of the driver 29 is °' i ”
The actual time is when VR50KVi>VDCHte. The timing at which the lamp circuit starts charging is determined by the comparator 27 as VL>VR, and since VL, which is the power of the comparator 27, is constant, the PWM output signal is
The time during which the temperature is O° is constant.

In this way, although the off time is constant, pulse width modulation is performed by varying the on time depending on the fluctuation of VH. The above operation will become clear from the timing chart of FIG. 4(b).

That is, V) I decreases (VHz in Figure 4 (b)) [increases (
If VH2)J is used, the wavelength of VH50 becomes shorter and longer, the on-time of the PWM output signal becomes shorter and longer, and the output voltage of the switching circuit decreases and increases.

Therefore, the level control of V)4 will be explained. Fourth
FIG. 2A shows a more specific block diagram of the output control unit 5° pulse width control unit 9 shown in FIG. The level priority selection circuit 25 that outputs vH selects the analog input with the lowest - accumulated voltage among the three analog inputs and outputs it as VJ4.

The three inputs are the output from the soft start section 24, the output from the error amplifier 8, and the pulse width remote control (terminal 10). As described above, the output of the error amplifier 8 is feedback because of the normal constant voltage output operation of the IC 100. The pulse width remote control of terminal 10 allows the upper limit of the on-time width of the pulse width to be forcibly controlled by applying an arbitrary voltage from the outside, and controls the output voltage of the IC 100 from the outside. It is. That is, voltage is supplied from the outside depending on the usage conditions of this IC. Therefore, when the error amplifier 8 performs normal operation, the terminal 10 is maintained at a predetermined voltage level. Further, if the voltage level of the terminal 10 is set to the lowest level, the operation of the IC 100 is stopped.

The soft start section 24 will be explained. There are two inputs to the soft start section 24, one of which is a signal from the terminal 3 that becomes "1" (or "O'") for a certain period of time during the soft start. When this signal is active, the soft start section 24 outputs a low level analog signal to the level priority selection circuit 25. As mentioned above, the level priority logic circuit 25 gives priority to the lowest level voltage and outputs it as vH, so at the time of soft start, even if there is another high level input voltage, this low level for soft start is given priority. .

Another input to the soft start section 24 is the output from the priority logic circuit 23.

The priority logic circuit 23 prioritizes and outputs the respective outputs from the protection circuit 6.7 and the external remote section 22. In the output remote section 22, the soft start section 24 turns on the output to the level priority selection circuit 25 based on the signal from the terminal 4.
10 F F is performed.

(Operation of protection circuit) An example of the protection circuit 6.7 is shown in FIG. VCH.

VaL (Vc H>Vc L), if the monitor output of the terminal 5 switching circuit is connected, the terminal 5
If the voltage exceeds vCH, 33 is reset and the amplifier 3
4 outputs low voltage. Therefore, VH decreases and the switching circuit stops operating. 1 When the original operation is stopped and the peak of terminal 5 becomes vcL, the comparator 32
3 is set and the error amplifier 8 outputs a high level. Even if the error amplifier 8 outputs a high level, the IC 100 restarts soft start, so the output (VH) of the level priority circuit 25 is suppressed low.

As explained above, a power supply control circuit equipped with two PWM control circuits makes it possible to downsize the power supply section of electronic equipment. It can be used as a power source.

(AC Voltage Output Unit) A power supply control circuit provided with the above PWM control circuit and further provided with an AC voltage output unit 10B as shown in FIG. 2 will be described. As shown in FIG. 2, the AC voltage output section is composed of an AC signal generation section 1, a waveform shaping section 2, and an AC output control section 3, and outputs an AC voltage from the 27th terminal.

The AC signal generator 1 generates a triangular wave (or sawtooth wave) using a ramp circuit (C1*Rz) similar to the oscillation circuit 10. The waveform shaping section 2 converts the triangular wave into a rectangular wave (or trapezoidal wave) or a SIN wave by polygonal line approximation. The AC output control section 3 drives and outputs a rectangular wave or a SIN wave. Other roles of the AC output control section 3 are a soft start function using the time constants of Ra and Ca through the 26th terminal, and external output control through the 24th terminal. Output square wave or SI
The N wave is boosted through a power amplification circuit (not shown) and can be used as, for example, an AC voltage for a developing device of a copying machine or an AC high voltage power source for developing bias.

1-chip monolithic IC with multiple pulse width control functions as described above (also equipped with an AC voltage output section)
We will explain how to mount the device and its peripheral elements on the board.

Peripheral components for the oscillation frequency of the monolithic IC, various time constant circuits such as soft start, and transistors (or rectifiers) of the switching circuit that drives the converter transformer used in high-voltage power supplies are mounted on a hard substrate such as a ceramic substrate. The thick membrane and chip components are attached to the substrate by glue flow soldering, and the monolithic IC is formed on the substrate using reflow soldering or wire bonding technology. Furthermore, heat dissipation characteristics can be improved by pasting a metal plate on the back side of a hard substrate such as a ceramic substrate.

E. Effects of the Invention As explained above, according to the present invention, by using a power supply control circuit in which an output voltage control circuit for obtaining a DC voltage and an AC signal generation part are configured on one chip as a power supply part. , it becomes possible to construct an extremely small, lightweight, and low-cost power supply device.

[Brief explanation of drawings]

ff Figure 11 is a diagram showing the principle configuration of the embodiment, and Figure 882 is a diagram showing the configuration of the power supply control circuit of the embodiment. Figure 3 is a circuit diagram when the power supply control circuit is applied to the ringing choke converter method. @Figure 4 (Ca) is a circuit diagram for explaining the operation of pulse width modulation. Figure 4 (b) is a timing chart of the circuit in Figure 4 (a). FIG. 5 is a circuit diagram of an example of a protection circuit. In the figure, 1... AC signal generation section, 2... Waveform shaping section,
3... AC output control section, 5.15... Output control section. 6.7, 16.17...protection circuit, 9 e, 19
... Pulse width control section, 10.20 ... Oscillation circuit, 1
1°21...PWM output section. Patent applicant: Canon Co., Ltd. Figure 2 Figure 4 (a) Figure 5

Claims (12)

[Claims] (1) It has a DC output voltage control signal generation section that generates a control signal for controlling the DC output voltage, and an AC voltage generation section that outputs an AC voltage, and the control signal generation section and the AC voltage generation section is a power supply control circuit characterized by being an integrated circuit. (2) The power supply control circuit according to claim 1, wherein the integrated circuit is a monolithic integrated circuit, a film integrated circuit, or a hybrid integrated circuit. (3) The power supply control circuit according to claim 1, wherein the DC output voltage control signal generating section controls the DC output voltage by pulse width modulation. (4) The power supply control circuit according to claim 1, characterized by having two systems of DC output voltage control signal generation sections. (5) A power supply control circuit according to claim 1, characterized in that the AC voltage generated by the AC voltage generator is supplied to an AC high-voltage power supply device for developing bias of, for example, an electronic copying machine or a printer. . (6) Claim 4, characterized in that the control signal generated by the DC output voltage control signal generator is supplied to, for example, a charger of an electronic copying machine/printer or a DC high-voltage power supply device for developing bias. power supply control circuit. (7) The power supply control according to claim 3, characterized in that the pulse width modulated control signal keeps the off time substantially constant while the on time varies in a range of approximately 0 to 50%. circuit. (8) The power supply control circuit according to claim 1, further comprising a protection circuit, an output voltage control circuit from outside the power supply control circuit, and a soft start circuit. (9) The power supply control circuit according to claim 8, wherein the output voltage control circuit is a limiter circuit that determines an upper limit. (10) The power supply control circuit according to claim 8, wherein the protection circuit has a hysteresis function for the input signal and a circuit for adjusting the cutoff time of the pulse width modulation output using an external element. . (11) It further includes a peripheral circuit element and a hard board such as a ceramic board for attaching the peripheral circuit element by, for example, reflow soldering technology or thick film printing technology, and the power supply control circuit is connected to the hard board using wires, for example. The power supply control circuit according to claim 2, which is implemented by bonding or the like. (12) The power supply control according to claim 11, wherein the hard substrate is formed by, for example, a bonded structure of a metal plate and a ceramic substrate, or an insulating member and a printed structure on a metal plate. circuit.