Efficient switching in SMPS

Projectseminar on halfbridge power supplies
Tutor: M.Sc. Muhammad Bilal Saif
By Mitja Stachowiak
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Introduction

How to built a halfbridge?

Which topology to use?
... switching frequency?
... control strategy?

Having a look onto existing power supplies:

Efficiency

{x:'Pout', y:[['Hama', 'eff']]} {x:'Pout', y:[['Hama', 'eff'], ['HP_slim', 'eff']]}

Hama power supply

{ staticIndicators:{Iout:0.1}, x:'t', y:[['Transformer', 'Vsec']] } { staticIndicators:{Iout:0.2}, x:'t', y:[['Transformer', 'Vsec']] } { staticIndicators:{Iout:0.3}, x:'t', y:[['Transformer', 'Vsec']] } { staticIndicators:{Iout:1}, x:'t', y:[['Transformer', 'Vsec']] } { staticIndicators:{Iout:4}, x:'t', y:[['Transformer', 'Vsec']] }

HP power supply

{ staticIndicators:{Iout:0}, x:'t', y:[['HP', 'Vpri'], ['HP', 'Vsec1'], ['HP', 'Vsec2']] } { staticIndicators:{Iout:0.5}, x:'t', y:[['HP', 'Vpri'], ['HP', 'Vsec1'], ['HP', 'Vsec2']] } { staticIndicators:{Iout:2}, x:'t', y:[['HP', 'Vpri'], ['HP', 'Vsec1'], ['HP', 'Vsec2']] } { staticIndicators:{Iout:4}, x:'t', y:[['HP', 'Vpri'], ['HP', 'Vsec1'], ['HP', 'Vsec2']] }

Conclusion of measurements

Halfbridge topology with center tab transformer output and active rectifier
Frequency is 100 KHz ... 120 KHz
On-Off-Control is used for power saving
The voltage is controlled in the PFC

The transformer

Model: Deltatec MV-NBS9049

No datasheets by manufacturer
This part is not availlable on the market

Use a LCR-Meter to determine the parameters:

Halfbridge prototype

Halfbridge startup

{ staticIndicators:{Iout:0, Vin:20}, x:'t', y:[['begin', 'Is'], ['begin', 'Vp3'], ['begin', 'Vs1']] } { staticIndicators:{Iout:0.1, Vin:30}, x:'t', y:[['begin', 'Is'], ['begin', 'Vp3'], ['begin', 'Vs1']] } { staticIndicators:{Iout:0.1, Vin:30}, x:'t', y:[['firstOpt', 'Is'], ['firstOpt', 'Vp3'], ['firstOpt', 'Vs1']] } First optimization:

Ceramic Cap (1 µF) added between + and -
Better diodes at Transformer output
27 Ω added between gate and driver
50% duty cycle since now

{ staticIndicators:{Iout:0.0, Vin:50}, x:'t', y:[['firstOpt', 'Vp3'], ['firstOpt', 'Vs1'], ['firstOpt', 'Is']] } { staticIndicators:{Iout:0.0, Vin:50}, x:'t', y:[['firstOpt', 'Vp3'], ['firstOpt', 'Vs1'], ['firstOpt', 'Is'], ['firstOpt', 'Vgate_high'], ['firstOpt', 'Vgate_low']] } { staticIndicators:{Iout:0.0, Vin:80}, x:'t', y:[['secondOpt', 'Is'], ['secondOpt', 'Vgate_high'], ['secondOpt', 'Vgate_low'], ['secondOpt', 'Vp3']] } Second optimization:

Resistor Gate-Driver reduced to 12 Ω
Ceramic Cap (0.47 µF) added next to the driver
Bootstrap diode replaced with better model

{ staticIndicators:{Iout:0.0, Vin:160}, x:'t', y:[['secondOpt', 'Is'], ['secondOpt', 'Vgate_high'], ['secondOpt', 'Vgate_low'], ['secondOpt', 'Vp3']] } { staticIndicators:{Iout:2, Vin:200}, x:'t', y:[['secondOpt', 'Is'], ['secondOpt', 'Vgate_high'], ['secondOpt', 'Vgate_low'], ['secondOpt', 'Vp3']] }

Zero volatge switching

{ action : function () { document.getElementById('ZVS').src = 'images/ZVS_1.svg'; } } { action : function () { document.getElementById('ZVS').src = 'images/ZVS_2.svg'; } } { action : function () { document.getElementById('ZVS').src = 'images/ZVS_3.svg'; } }

{ staticIndicators:{f:120, Iout:0}, x:'t', y:[['Meas', 'Is'], ['Meas', 'Vp3'], ['Meas', 'Vs1'], ['Sim', 'Vp3'], ['Sim', 'Ip3']] } { staticIndicators:{f:120, Iout:2}, x:'t', y:[['Meas', 'Is'], ['Meas', 'Vp3'], ['Meas', 'Vs1'], ['Sim', 'Vp3'], ['Sim', 'Ip3']] } { staticIndicators:{f:120, Iout:4}, x:'t', y:[['Meas', 'Is'], ['Meas', 'Vp3'], ['Meas', 'Vs1'], ['Sim', 'Vp3'], ['Sim', 'Ip3']] }