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Wide output range with L6598D

VikramHCL
Associate II

Hi ST team,

We are going to use L6598D PWM controller (Half bridge topology) followed by PFC IC L4985B for our variable power supply design.

We need two models for variable (programable) power supply (Model 1 & Model 2) as below specifications. So, can we generate below mentioned wide output voltage from IC L6598D with Half bridge topology?

For Model 1 Vout: 3V-63V/5A (80W maximum with auto ranging)

For Model 2 Vout: 3V-23V/20A (80W maximum with auto ranging)

ST_HF bridge.jpg

 
 

Regards

Vikram

1 ACCEPTED SOLUTION

Accepted Solutions
Peter BENSCH
ST Employee

Welcome @VikramHCL, to the community!

Well, the L6598D in half‑bridge resonant topology could be used to realise a programmable 80W isolated supply for both models, provided the resonant tank, transformer and frequency range are carefully optimised for the required voltage and current ranges.

For Model 1 (3...63 V/5 A, 80W max) and Model 2 (3...23 V/20 A, 80W max), the feasibility depends mainly on the design of the LLC/resonant network, the transformer turns ratio and the allowed switching‑frequency span. In practice, such wide output‑voltage ranges might be achievable, but will require:

  • a transformer carefully designed to avoid core saturation and excessive copper loss at low output voltages and high currents,
  • appropriate current‑limit and power‑limit control across the whole range,
  • and careful selection of the operating frequency window to keep the converter within safe stress and acceptable efficiency

Just a note: at very low switching frequencies, that is well below the resonance frequency, and under high load, the converter operates outside optimal ZVS conditions, which leads to higher losses and thus significant stress on the half-bridge switches, effectively limiting the usable voltage range.

The discussion of such a design probably concerns only your specific case and goes far beyond the scope of a thread intended for the general public. For detailed questions about the exact implementation, you should therefore contact your local distributor and request support from their FAE resource.

Hope that helps?

Good luck!
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

View solution in original post

2 REPLIES 2
Peter BENSCH
ST Employee

Welcome @VikramHCL, to the community!

Well, the L6598D in half‑bridge resonant topology could be used to realise a programmable 80W isolated supply for both models, provided the resonant tank, transformer and frequency range are carefully optimised for the required voltage and current ranges.

For Model 1 (3...63 V/5 A, 80W max) and Model 2 (3...23 V/20 A, 80W max), the feasibility depends mainly on the design of the LLC/resonant network, the transformer turns ratio and the allowed switching‑frequency span. In practice, such wide output‑voltage ranges might be achievable, but will require:

  • a transformer carefully designed to avoid core saturation and excessive copper loss at low output voltages and high currents,
  • appropriate current‑limit and power‑limit control across the whole range,
  • and careful selection of the operating frequency window to keep the converter within safe stress and acceptable efficiency

Just a note: at very low switching frequencies, that is well below the resonance frequency, and under high load, the converter operates outside optimal ZVS conditions, which leads to higher losses and thus significant stress on the half-bridge switches, effectively limiting the usable voltage range.

The discussion of such a design probably concerns only your specific case and goes far beyond the scope of a thread intended for the general public. For detailed questions about the exact implementation, you should therefore contact your local distributor and request support from their FAE resource.

Hope that helps?

Good luck!
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
Peter BENSCH
ST Employee

One more addendum, because in this thread you basically asked for the same task, only with different output powers and different controllers: if by auto-ranging you mean that for each model both the output current is limited and the output power is limited by reducing the voltage in the latter case, then the output powers mentioned here can also be reached with L4985B + L6598D. However, and as mentioned before, the crucial points are design issues, not controller limits. Nevertheless, the summary still applies here.

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.