JPH072012B2 - Switching power supply - Google Patents

Description

The present invention relates to a converter type switching power supply device in which input and output are insulated from each other, and more specifically, to a primary side circuit on two insulating metal substrates. And a switching power supply device in which a secondary circuit is mounted.

(B) Prior Art FIG. 5 shows a flyback type switching power supply circuit.

Switching power supply circuit shown is a primary winding and a secondary winding opposite polarity transformer T to insulate the input V _IN and the output V _OUT, switching transistor for controlling a current flowing from the input V _IN to the transformer T Or a switching element Q such as power MOSFET, a constant frequency of several + KHz,
A PWM circuit (60) that outputs a pulse whose duty is changed by a feedback signal to the control electrode of the switching element Q, a snubber circuit (66) for discharging energy accumulated in the leakage inductance of the transformer T, a switching element Q Current detector (64) that monitors the current of the device and protects against overcurrent, temperature detector (62) that prevents thermal runaway of the power supply circuit, diode D ₃ that rectifies and smoothes the output voltage of the transformer T, capacitor C ₂ , A voltage detector (68) for performing constant voltage control and overvoltage control of the output V _OUT , a photocoupler (70) for insulating and feeding back the output of the voltage detector (68), and the like.

Next, the operation of the switching power supply circuit configured as described above will be described.

When the output pulse of the PWM circuit (60) becomes high level and the switching element Q is turned on, a closed circuit of the input V _IN-the primary winding of the transformer T-the switching element Q is formed and the primary winding of the transformer T is formed. A current that linearly increases flows. At this time, the secondary winding output of the transformer T is a diode
Since the electric power is not transmitted through the transformer T because it is blocked by D _3, all the energy supplied to the primary winding is stored in the transformer T. Then, when the output pulse of the PWM circuit (60) becomes low level and the switching element Q is turned off, a counter electromotive force is generated in the primary winding, and the secondary winding output based on this counter electromotive force is output to the diode D ₃ It is charged into the capacitor C ₂ via and becomes the output V _OUT .

Since the switching power supply circuit that performs the above operation is highly efficient, it is possible to form a hybrid integrated circuit on an insulating substrate such as ceramics if it has a relatively small capacity, and it is necessary to reduce the size and weight of electric circuits these days. It is suitable as a power supply device for equipment. However, since an insulating substrate made of ceramics or the like has a low thermal conductivity, there is a problem in that a large-capacity switching power supply circuit that generates a large amount of heat cannot be formed into a hybrid integrated circuit.

(C) Problems to be Solved by the Invention On the other hand, when an insulating metal substrate is used as a substrate to make a switching power supply circuit into a hybrid integrated circuit, the heat radiation problem is solved Since the primary side circuit and the secondary side circuit of the circuit must not be formed on a single metal substrate, there is a problem that the manufacturing process becomes complicated. Moreover, when a plurality of insulating metal substrates are used, it is difficult to match the lead pitches derived from the respective insulating metal substrates. Furthermore, there is a problem that the number of leads for external connection increases.

Therefore, it is an object of the present invention to provide a switching power supply device capable of simplifying a circuit pattern forming process, an element mounting process, and the like, as well as those using a single substrate.

(D) Means for Solving the Problems The present invention has been made in view of the above problems, and a primary side circuit and a secondary side circuit of a switching power supply circuit are provided on first and second insulating metal substrates. The first and second insulating metal substrates are mounted in a special manner, and the first and second insulating metal substrates are coupled by a photocoupler for insulating and returning a voltage signal and an overvoltage signal from the secondary side circuit to the primary side circuit. It solves the problem of the insulation distance between the circuit and the secondary circuit and the problem in the manufacturing process.

(E) Action By connecting the first and second insulated metal boards, which have the primary circuit and the secondary circuit of the switching power supply circuit mounted specially, with a photo coupler, it becomes possible to treat them as an integrated metal board. It is possible to simplify the device mounting process, the lead fixing process, and the like as in the case of using a single substrate. Further, since the two metal substrates are coupled by the photocoupler, the number of leads for externally connecting the photocoupler is reduced, and the distance between the first and second insulating metal substrates can be set accurately.

(F) Example First, the outline of the outer shape and structure of the switching power supply device of the present invention will be described with reference to FIG. Since any converter type switching power supply circuit including the switching power supply circuit described in the description of the conventional example can be used for the switching power supply device of the present invention, the description of the circuit configuration will be omitted.

Referring to FIG. 4, the switching power supply device of the present invention includes two hybrid integrated circuit boards each having a primary side circuit and a secondary side circuit separated by an insulating transformer (not shown because they are externally connected) ( 20 (20) (20), leads (56) (58) derived from one peripheral edge of each of the two hybrid integrated circuit boards (20) (20), and two hybrid integrated circuit boards (20) (20) Are shown by a photocoupler (50) and a frame-shaped casing (10).

The two hybrid integrated circuit boards (20) (20) are arranged on the same plane with a predetermined distance therebetween, and their peripheral edges are fixed to the stepped portion of the casing (10) using an adhesive sheet or the like. The primary side and secondary side circuits of the switching power supply circuit mounted on the hybrid integrated circuit board (20) (20) are the hybrid integrated circuit board (20).
They are arranged in independent sealed spaces formed by the (20) and the casing (10), respectively, and the circuits and the transformer are coupled via the leads (56) (58). Further, the feedback of the voltage and the overvoltage signal from the secondary side circuit to the primary side circuit is performed by the photocoupler (50). The exposed region where the photocoupler (50) is arranged is sealed by a cover (not shown).

Next, the manufacturing process of one embodiment will be described in order to clarify the characteristics of the present invention.

FIG. 1A is a plan view of a circuit board immediately before mounting a circuit component to form a hybrid integrated circuit board. Note that FIG. 1B is a sectional view taken along the line I-I.

As the metal substrate (20), a metal substrate having a thickness of 0.5 mm to 3 mm, such as aluminum, is used. As shown in FIG. 1A, the metal substrate (20) is punched into a rectangular shape together with a rectangular waste hole (24) in the center thereof. To be done.

When aluminum is used, an oxide film is formed by anodic oxidation treatment after this, and a laminate of a copper foil with a thickness of 18 μm to 35 μm and a polyimide-based or epoxy-based insulating resin layer (26) with a thickness of about 35 μm is formed. It is attached. Then, this copper foil is etched into a predetermined shape to form a circuit pattern (28), pads (30) (32) for external leads, and a photocoupler (50).
Pad (34), a pad (36) for a variable resistance element, etc. are formed. The variable resistance element connected to the pad (36) has a level setting for constant voltage control,
It is used for setting the overvoltage detection level or the overcurrent detection level, and can be arranged on any one or both of the circuit boards separated in a later step.

Referring to FIG. 2, a switching element (40), a PWM circuit (42), an overcurrent detection circuit (44), a diode (46), an overvoltage which constitute a switching power supply circuit on the circuit board completed as described above. Integrated circuits such as detection circuits (48),
Alternatively, elements such as resistors and capacitors are surface-mounted in a chip shape, and the photocoupler (50) is surface-mounted on the pad (34) so as to straddle a rectangular hole. Pads (30)
The leads (56) (58) are soldered and fixed to the (32), and further, predetermined electrodes and circuit patterns are connected by wire bonding.

In the illustrated embodiment, a hybrid integrated circuit board (20) (2) on which the primary side and secondary side circuits of a switching power supply circuit are mounted.
0) is mechanically connected by the bridge (22) and is integrally formed, so that the circuit element mounting step and the circuit pattern etching step described above are performed in the same manner as the processing of a single substrate. Not only that, since the pitch of each pad (30) (32) of the hybrid integrated circuit board (20) (20) to be separated in a later process can be set with high accuracy, each lead (56) (58) It becomes possible to perform fixing with a single lead frame.

Next, the hybrid integrated circuit board (20) on which the device mounting and the fixing of the leads (56) (58) are completed, the bridge (22) connecting the circuit boards on the left and right of the waste hole and the lead frame (54) are stamped and punched. Are removed by the process described above and completed as two hybrid integrated circuit boards bonded only by the photocoupler (50) (see FIG. 3). Since the distance between the two hybrid integrated circuit boards (20) and (20) is fixed by fixing the photocoupler (50), the board distance determined by perfect standards or the like can be guaranteed even in the subsequent steps.

(G) Effects of the Invention As described above, according to the present invention, (1) since an insulating metal substrate is used, the heat dissipation characteristics are good, and a large capacity switching power supply device can be accommodated.

(2) Although the safety standard is satisfied because the primary side circuit and the secondary side circuit of the switching power supply circuit are completely separated, etching is performed because the two insulating metal substrates are connected by the bridge. The mounting process and the like can be simplified to the same level as the single substrate processing.

(3) Since the two insulating metal substrates are coupled by the photocoupler, the number of leads for external connection of the photocoupler is reduced and the distance between the two insulating metal substrates is ensured.

(4) The insulating metal substrate shields noise radiated from the circuit elements or the internal wiring which form the switching power supply circuit.

[Brief description of drawings]

FIG. 1A is a plan view of a circuit board used in the embodiment,
FIG. B is a sectional view taken along the line I-I, FIG. 2A is a plan view of a hybrid integrated circuit board on which circuit elements are mounted, and FIG.
FIG. 3 is a plan view of the completed hybrid integrated circuit board, FIG. 4 is a perspective view of an embodiment, and FIG. 5 is a circuit diagram of a general switching power supply circuit. (10) …… Casing, (20) …… Hybrid integrated circuit board,
(22) …… Bridge, (24) …… Blank hole, (26) …… Insulating resin layer, (28) …… Circuit pattern, (30) (32) …… Lead pad.

Claims (4)

[Claims] 1. A switching element constituting a primary side circuit of a switching power supply circuit, a first insulating metal substrate on which a plurality of circuit elements such as a circuit for controlling the operation of the switching element are mounted, and a switching power supply circuit. Second mounting a plurality of circuit elements such as a diode and an overvoltage detection circuit that constitute a secondary circuit
Of an insulating metal substrate, a photocoupler for insulating and returning a voltage signal and an overvoltage signal from a secondary side circuit of a switching power supply circuit to a primary side circuit, and a switching power supply circuit mounted on the first and second insulating metal substrates. And a casing having a space for independently sealing the primary side circuit and the secondary side circuit, wherein the photocoupler separates and couples the first and second insulating metal substrates on the same plane at a predetermined interval. Switching power supply. 2. The switching power supply according to claim 1, wherein the first and second insulating metal substrates are formed by cutting a bridge of a single insulating metal substrate having a rectangular hole. apparatus. 3. The switching power supply device according to claim 2, wherein the width of the dead hole is set to a size that satisfies a required insulation standard. 4. Leads derived from the first and second insulating metal substrates are fixed to one peripheral edge thereof before the single insulating metal substrate is separated by cutting a bridge. Item 2. A switching power supply device according to item 2.