JPS60125174A - Power source circuit - Google Patents

Abstract

PURPOSE:To prevent a rush current flow flowing to a circuit element which has a switching element and a feedback diode when regulating the output by controlling to lead or lag the phase of a load current in cooperation with the regulation of the ON duty of the switching element. CONSTITUTION:When a power source is turned ON, a full-bridge inverter is operated, and a discharge lamp L0 starts firing. When the value of a variable resistor R2 is gradually increased, the input voltage of the terminal 7 of an integrated circuit IC is raised, and the ON duty of a rectangular wave control signal from terminals 12, 13 is decreased. Accordingly, it becomes dimming state. The ON duty of transistors Tr1-Tr4 are controlled, the inductance value of a saturable inductance MAG is controlled to control the phase of a load current, and the rush currents of the transistors Tr1-Tr4 and diodes D1-D4 are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a power supply circuit used in a lighting device for a discharge lamp or the like.

[Background technology]

FIG. 1 shows a conventional example of a power supply circuit used as a discharge lamp lighting device, FIG. 2 (2) shows a time chart during full lighting, and FIG. 2(B) shows a time chart during dimming.

In Figure 1, E is an AC power supply, DB is a full-wave rectifier, and C
is a smoothing capacitor, island is a separately excited full bridge inverter, Lo is a discharge lamp as a load, L is an inductance, C is a capacitor, Tr is a transistor as a switching element, D is a diode to D4111. . Io, IO2 and ■. E□, voE2 are the collector currents of the transistors Tr1*T'2 and the collector-emitter voltages, I, I, DIDB-DOJ)0. The forward current of DB, (2) 5 is the load current, and (2) is the load voltage.

The transistors Tr, i are controlled on and off by a control circuit (not shown).

When Tr4 is on, transistor Tr2. A first state in which Tr is off and a second state in which transistors Tr2+Tr3 are off are alternately repeated. Transistor Tr engineering.

Tr4 performs the same operation, and transistors Tr2. T
r3 performs the same operation, the diode D and D4 perform the same operation, and the diode D2. Since D3 performs the same operation, in Fig. 2, transistor Tr + Tr2 and diode D are shown for transistors and diodes.

Only the operating waveform of D2 is representatively shown.

Separately excited full bridge inverters are well-known, and start the lamp by series resonance between an inductance L and a capacitor C. After lighting, the inductance L acts as a stabilizing element and allows a specified lamp current to flow.
It becomes a slow phase load.

When dimming, each transistor Tr −
This is done by controlling the on-duty of 'I'r4. When the on-duty of transistors Tr to Tr 4 is reduced during dimming, even if the load is a slow-phase load due to the inductance L et discharge lamp impedance, for example,
After current flows through the diodes D and D4, a section appears in which the transistors Tr2 and T are turned on, and a momentary power short circuit occurs due to the reverse recovery time τ of the diodes D and D4, and the transistor Tr2 and T are turned on.

A rush current momentarily flows through Tr4, diode D, and D4. Therefore, the first problem in the conventional example is that there is a risk of heat generation and even destruction of the circuit elements.

Such a problem occurs not only in an inverter having a separately excited full-bridge inverter as shown in the drawing, but also in an inverter having a switch element and a feedback diode.

[Purpose of the invention]

An object of the present invention is to provide a power supply circuit in which inrush current is suppressed from flowing into circuit elements including switch elements and feedback diodes when output adjustment is performed.

[Disclosure of the invention]

The power supply circuit of the present invention includes: an inverter with a switch element and a feedback diode connected to a DC or rectified power supply; a control circuit that controls on/off the switch element;
a load current phase variable element interposed between the output end of the inverter and the load; a means for adjusting the on-duty of the switching element; and a means for adjusting the on-duty of the switching element; and control means for controlling the phase of the load current to be advanced or delayed.

According to this configuration, when the on-duty of the switch element is adjusted to long or short during output adjustment, the phase variable element is controlled so that the load current phase automatically advances or lags accordingly, so the feedback Reverse recovery of the diode is suppressed, and therefore, the occurrence of short-circuiting of the instantaneous power source is also suppressed, and inrush current is also suppressed from flowing through the transistor and the feedback diode.

An embodiment of the present invention will be described based on FIGS. 3 and 4. FIG. 3 shows the basic circuit as a whole, and FIG. 4 shows a more specific circuit.

DB is a full-wave rectifier (diode bridge) connected to the AC power source E, and C□ is a smoothing capacitor connected to the output end of the rectifier DB, which together with the rectifier DB constitute a rectified power source.

Tr + Tr2 is the first transistor connected in series with the output terminal of the capacitor C□. A transistor as a second switch element, Tr3. The fourth transistor Tr4B is connected in parallel to the series circuit of Tr2, and the third transistor connected in series with each other is connected in parallel to the series circuit of Tr2. Transistor as a fourth switch element, D, D2. D3゜1) Each of the 4 digits is the first! 4 transistor Tr.

Tr2 + Tr31 Feedback diode connected in parallel to Tr4, shown is a discharge lamp as a load, and C is a discharge lamp. A capacitor connects the filament at both ends of , L is a discharge lamp.

This is a current limiting element as a phase variable element connected in series to one of the filaments.

The four transistors Tr to Tr4 and the four feedback diodes D to D4 form a full bridge inverter. The middle point of the second diode D and D2 (the middle point of the first and second transistors Tr and Tr2),
Third. Between the fourth transistor Tr3° and the midpoint of Tr4 (the midpoint of the third and fourth diodes D3 and D4),
discharge light. , a load circuit consisting of a current limiting element of capacitor C9 is connected.

T is the transformer connected to the power supply E, DB is the full-wave rectifier (diode bridge) connected to the secondary side of the transformer T,
C2 is a smoothing capacitor connected to the output end of the rectifier DB, which together with the rectifier DB constitutes a rectified power supply. CC is a control circuit connected to this rectified power supply; Fourth
The transistor Tr + Tr 4 is turned on, and the second transistor Tr4 is turned on. A first state in which the third transistor Tra @ Tr3 is turned off; The fourth transistors Tr and Tr4 are turned off, and the second. Each transistor Tr~
A control signal is sent between the base and emitter of Tr 4.

That is, the secondary side of the pulse transformer PT connected to the output end of the control circuit CC is the first . The secondary of the pulse transformer PT2 (1111 is connected between the base and emitter of the fourth transistor Tr, Tr, a and separately connected to the output terminal of the control circuit CC)
It is connected between the base and emitter of Tr3.

CCC is a load current phase control circuit connected to the rectified power supply and control circuit CC, and its output side is connected to a current limiting element. This current phase control circuit CCC is configured to control the current limiting element so that the phase of the load current advances or lags depending on the length or shortness of the on-duty in conjunction with the adjustment of the on-duty of the transistors Tr-Tr4. has been done.

To explain more specifically with reference to FIG. 3, the control circuit CC
is an integrated circuit IC (μPD1042 manufactured by NEC @),
Resistor R6゜capacitor C6 connected to its ■ and ■ terminals
It consists of 0, which is the output terminal of the integrated circuit IC.
, ■ terminals are connected to pulse transformers PT and PT2, respectively, and alternately output rectangular wave control signals. ■The terminal is a terminal for adjusting the on-duty of the control signal from the terminal.It is connected to the midpoint of the series circuit of the resistor R connected to the rectifier power supply and the variable resistor R2, and the variable resistor The on-duty is adjusted by changing the input voltage by adjusting R2. The oscillation frequency of the control signal is determined by resistor R6 and capacitor C6.

The load current phase control circuit CCC is configured as follows. The base of the transistor Tr5 is connected to the middle point of the resistor R and the variable resistor R2 via the resistor R3, and the negative terminal of the rectifier power supply is connected to the base of the transistor Tr6 through the emitter Kl bias Zener diode DZ2. It is connected to. A series circuit of a resistor R4 and a reverse bias Zener diode D2□ is connected to a rectified power supply, and the midpoint thereof is connected to the base of a transistor Tr through a resistor R5. The transistor Tr6 has its collector connected to the positive terminal of the rectified power supply together with the collector of the transistor Tr7,
Its emitter is connected to the base of the transistor Tr. The emitter of the transistor Tr is connected to a parallel circuit consisting of a saturable inductance MAG, which is a current limiting element, and a capacitor C5.
A capacitor C4 connected to the base of r6 is connected to the negative terminal of the rectified power supply.

Next, the operation will be explained.

After turning on the power, due to the above reasons, the full bridge inverter ■. The discharge light is working. starts and lights up.

When variable resistor R2 = 0, the on-duty of the square wave control signal output from the 0.0 terminal is maximum, and the discharge lamp is turned on. All the lights will be lit and there will be a roar. At this time, transistor Tr 5
No base current flows through the resistors R4 and R4, which are in the off state.
Sufficient base current is supplied to the transistor T' 6 * Tr 7 through R5, and the transistor Trq enters the on state (saturation region), and the saturable inductance MAG
Since the control current flowing through becomes maximum, the inductance value of saturable inductance MAG becomes minimum.

On the other hand, as the value of the variable resistor R2 is gradually increased, the input voltage at the ■ terminal of the integrated circuit IC increases, and the on-duty of the square wave control signal from the ■ and ■ terminals decreases accordingly. This is a so-called dimming state. As stated in [Background technology], as the on-duty is reduced,
Transistor Tr engineering.

Tr4, Tr2. A phenomenon occurs in which an inrush current flows through the transistor Tr3, but in order to prevent this phenomenon, the phase of the load current IL shown in Figure 2, Figure 51, in which the necessary parts are reproduced, is forced to delay the phase of the load current IL. Tr4
Or, for example, in the case of the transistor Tr, just make sure that no forward current flows through the diode D2 before the transistor Tr turns on, so that the load current IL crosses zero after the transistor Tr2 +''rr3 turns on. In this embodiment, such control is performed.That is, by decreasing the on-duty and delaying the phase of the load current, at the same time,
A waveform as shown in Fig. 5 can be obtained, and the diode D
It is possible to prevent inrush current due to the reverse recovery time of D4. Therefore, the on-duty of the transistors Tr to Tr4 is controlled, and the inductance value of the saturable inductance MAG is controlled to prevent rush currents from the transistors Tr to Tr4 and the diodes D□ to D4.

That is, when the value of the variable resistor R2 is zero, the on-duty is maximum (<50%), but at this time, the transistor Tr is OFF, and the base 'It a power is supplied to the transistors Tr6+Tr7- through the resistors R4 and R5. , the control current flowing through the saturable inductance MAG becomes maximum, and its inductance value becomes minimum, and the discharge lamp. becomes a so-called fully lit state.

On the other hand, if the value of variable resistor R2 is increased, the integrated circuit IC
The voltage at the ■ terminal increases, thereby @.

(2) The on-duty of the rectangular wave control signal from the terminal is reduced by m. At the same time, the base current of the transistor Tr s increases, the transistor Tr 5 starts conducting, the base potential of the transistor Tr 6 decreases, and the base current of the transistor Tr 61 'l' r7 decreases. The transistor '[rヮ operates in the unsaturated region.

Therefore, the control current of the saturable inductor 7MAG decreases, its inductance value increases, and the load current l
This acts to further delay the phase of L. As described above, by controlling the on-duty of the transistors 'lr~Tr4 and controlling the inductance value of the saturable inductance MAG, the phase of the load current is delayed, as shown in Figure 5 (13). For example, since current is prevented from flowing through the diode D2 before the transistor Tr is turned on and collector current flows, stable dimming lighting can be performed without inrush current flowing.

In addition, use a discharge lamp as shown in Figure 6. and inverter In are combined with transformer T2, and the electric current E is AC100 dC20
When selecting 0V, if the oscillation frequency is constant,
As shown in FIG. 7, by reducing the on-duty to 1/2 that of AC 100V when AC is 200V, it is possible to make the output of the coupling transformer a constant voltage and keep the output constant. Also, set the on-duty to ACvXvFI#.
The output can be made constant by setting it to 100/vx at Cioo v.

Furthermore, in the case of Figure 8, when the frequency is AC200V,
By making the IA at C100V and making the saturable inductance side chain twice that at AC100V1,
Discharge lamp as shown. The power supplied to the system can be kept constant. A
At CVxV, frequency is A 100/v at C100V
In X, the value of saturable inductance MAG is A C100
■When setting V to X/100, the power can be kept at a constant voltage. In the above case, capacitor C may be omitted.

〔Effect of the invention〕

According to this invention, when adjusting the output, it is possible to suppress the flow of rush current to the switch elements, feedback diodes, and other circuit elements that constitute the inverter, thereby extending the life of the inverter and improving the reliability of the equipment. There is.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram of the conventional example, Fig. 2 (2) is a time chart of waveforms of each part when all lights are on, ■ is a time chart of waveforms of each part when dimming, and Fig. 3 is a time chart of waveforms of each part when dimming. The electrical circuit diagram of one embodiment, the 4th figure is a more specific electrical circuit diagram,
(5) in Fig. 5 is a waveform time chart that reproduces the necessary parts of Fig. 2 (■), 0 is a time chart of the operating waveform of the embodiment, No. 6 and 1 is an electric circuit diagram of the application example, and Fig. 7 is FIG. 8 is a 1B circuit diagram of another application example, and FIG. 9 is a waveform diagram thereof. Tr ~l1lr4...transistor (switch element)
, D engineering ~ D4...Feedback diode, ■□...Inverter, CC...Control circuit, L...Current limiting element (phase variable element), MAG...Saturable inductance (phase variable element) , R2...Variable resistance (on-duty adjustment means), CCC...Load current phase control circuit (means) 4g +! "j! Σ U) ES:j3.:! 12 Figure 8 Figure 7 Figure 9

Claims (1)

[Claims] An inverter with a switching element and a feedback diode connected to a DC or rectified power source, a control circuit that controls on/off of the switching element, and a load current phase variable element inserted between the output end of the inverter and the load. a means for adjusting the on-duty of the switching element; and a control means for controlling the variable phase element so that the phase of the load current advances or lags depending on the length or shortness of the on-duty in conjunction with the on-duty adjustment. Equipped with power supply circuit.