Early switched mode power supplies.

[Geordie McBoyne]

From the television engineers point of view the switched mode power supply employed in the 1969 BRC 3000 TV chassis was the first time such technology was introduced in domestic TV sets.
However, I'm sure SMPSUs were used in the electronics industry much earlier than 1969. Patents were taken out in the late 1950s.

From Wikipedia: https://en.wikipedia.org/wiki/Switched-m...ly#History

The attachment shows a switching power supply which employed the LM300 regulator IC, an inductor, and a 2N2905 transistor.

Geordie McBoyne.

[ppppenguin]

I used to own a bench PSU made by IE (International Electronics?) type DS 50 50 2 (I think). It had conventional mains transformer, then switching pre-regulators running at low frequency (10s or 100s of Hz, variable, you could hear them change frequency as the load changed) followed by linear post regulators. It was dual output, 0-50V 2A. There was also a single output version. The BBC used a lot of these. I know it dates from before 1974 but have no evidence as to how much earlier.

[chriswood]

I was wondering if the Mullard EHT unit used in the early 50s projection TVs would qualify as switch mode, it seems to have the essentials found in switch mode units.

Chris

[ppppenguin]

By that reckoning any energy recovery line output stage is a switchmode PSU.

If you want to draw the distinction between regulators and direct mains powered supplies that may be trickier. Any energy recovery line output stage running more or less directly off rectified mains would count as the latter. Whereas the IE DS 5050 I referred to earlier has SM regulators.

I don't know when computer makers turned to SMPS. They needed lots of amps at accurate and stable low voltages long before most of us.

[Geordie McBoyne]

I was wondering if the Mullard EHT unit used in the early 50s projection TVs would qualify as switch mode, it seems to have the essentials found in switch mode units.
Chris

In a sense I guess it is. The repetition rate of the pulses supplied to the voltage tripler diodes varies according to the beam current of the CRT, although I'm not sure if the pulse amplitude remains level.

In the BRC 3000 switched mode power supply line timebase pulses are supplied to a monostable and the mark space ratio of the chopper drive pulse depends on the current and voltage demands of the timebases. SMPSU supplies 55 to 63volts.

Geordie McBoyne.

[Nick]

From the television engineers point of view the switched mode power supply employed in the 1969 BRC 3000 TV chassis was the first time such technology was introduced in domestic TV sets.
However, I'm sure SMPSUs were used in the electronics industry much earlier than 1969.  Patents were taken out in the late 1950s.

Interesting article: https://www.xppower.com/resources/blog/h...plies-smps

[Exiled Yorkshireman]

The earliest SMPS I ever worked on as a field service engineer was in the HP 5830A gas chromatograph introduced in late 1973/early 1974. This was a fiendishly complex SMPS designed to supply all the voltages required by this very early processor-controlled computing GC. We were supposed to do component-level repair in the field on these, but I saw very few failures.

[Murphyv310]

There were valve SMPS back in the late 50s, funnily enough I read this last week.
I'll try to find the article and post it up.

https://www.xppower.com/resources/blog/h...plies-smps

[davetheresurrector]

The Hewlett Packard 740 DC Voltage Standard/Differential Voltmeter (1965) has a flyback-mode switcher that outputs 0-1000V at up to 25W power. Some germanium transistors, including the darlington pair switch, and some silicon.

The Remex RRS3300 paper tape reader (1970) has a buck-mode switcher controlled by an LM300 to provide +5V to logic and the quartz lamp that illuminates the read head. Later models went back to a linear regulator, ran the lamp on unregulated AC, and added brightness compensation.